dental materials

Describe how filler affect the properties of composites

:Fillers can improve mechanical properties. They can interact with cement in several ways; to improve particle packing and give the fresh concrete other properties, and even to reduce the amount of cement in concrete without loss of strength.

Describe the particle shapes in lathe-cut, admix, and spherical alloys, and discuss their effects on the amalgam

:Shape of the particle determines handling characteristics. Spherical alloy: Produced by spraying (atomizing) a mist of molten alloy into an inert gas and are formed as the atomized droplets cool. Spherical particles require less mercury to wet them and set faster. Admix: Mixture of lathe-cut and spherical particles Also referred to as "blended" or "dispersed". Lathe-cut: Are formed by shaving fine particles off an ingot (block) of the alloy using a lathe (machine). Particles are sifted to separate them into fine and ultrafine particles.

What is a 'composite'?

A 'composite' is a mixture of two or more materials. The properties of this combination of materials are greater than each of the materials alone. The materials are not soluble in one another.

Explain the role of mercury in dental amalgam:

Wets the silver alloy powder creating a 'plastic' mass. Increased mercury weakens final product. Inadequate mercury results in a mix that contains voids.

Describe the factors that determine successful adhesion, including wettability, viscosity, film thickness, and surface characteristics:

Wetting: The degree to which a liquid adhesive is able to spread over the surface of a tooth and restorative material Based on the liquid's contact angle with the tooth material. The lower the contact angle the better the liquid adhesive spreads onto the surface of the tooth. Viscosity: Surface roughness will increase the wetting of the surface by the liquid •This ability may be hindered or enhanced by the viscosity of the material - the ability of a liquid material to flow •Materials with high viscosity are thicker and do not flow well, therefore may not be effective in wetting the area. Film thickness is the minimal thickness obtainable by a layer of a material - particularly important in working with dental cements. When seating a crown - if the film thickness of the cement is too great, it may keep the crown from seating completely. Surface characteristics: Cleanliness of a surface, moisture contamination, surface texture - surface irregularities may prevent complete wetting, surface energy of the restoration and tooth - determines the attraction of their atoms. Liquids spread over high surface energy surfaces better.

What are benefits of dental implants?

When implants are used in place of a fixed bridge, tooth structure is preserved because abutments do not have to be prepared, The individual implant units are easier to keep clean than a fixed bridge - gingiva stays healthier, Preserve bone in both ridge height and width (prevents atrophy of bone when a tooth has been extracted), and Implant supported denture - comfort, biting, chewing and speaking are improved when compared to traditional dentures.

Differentiate between negative and positive reproduction:

An impression is taken - the negative reproduction. Impression is filled with gypsum material (powder that is mixed with water). Once hardened - positive reproduction

Describe "wet" dentin bonding:

bonding to dentin that is kept moist after acid etching to facilitate penetration of bonding resins into etched dentin-etch tooth and rinse it but not complete drying.

Identify and discuss the factors that affect the rate and efficiency of abrasion

size, irregularity, and hardness of particles, Number of particles that contact the surface being abraded, and Speed and pressure of the abrasive. Rate of abrasion: Also dependent on the surface being abraded. Enamel is much more resistant to abrasion than softer cementum. The size, irregularity and hardness of the abrasive particle determine the depth of the scratches in the material being abraded (the amount of material being removed). Coarse pumice consisting of larger and coarser particles will remove more material than fine pumice

Explain the differences between reversible colloids and irreversible colloids

Agar hydrocolloid (reversible hydrocolloid): Thermal change takes product from sol to gel and back again (reversible!) . Highly accurate impressions. Must be poured immediately. Not generally used because of difficult manipulation and extra equipment. Works well in a moist environment Alginate hydrocolloid (irreversible hydrocolloid): Commonly known as 'alginate'. Setting reaction is chemical and NOT reversible (Sol - gel ONLY). Many uses that include study models, diagnostic casts, preliminary impressions, opposing arch impressions, and fabrication of various types of custom trays and mouthguards. Reasonably accurate material but not suitable for uses that require high degrees of accuracy (Crowns and bridges).

Define and discuss the properties of elastic impression material

Materials that can be stretched and bent without exhibiting permanent deformation Materials that return to their original form after being stretched or bent Materials that demonstrate these properties are considered 'elastic' Are used to record intraoral structures through the process of taking an impression These impressions are often used for fabrication of indirect restorations Accuracy of the indirect restoration is largely dependent on the properties of the impression material Flexibility - easier to remove from mouth Elastic recovery - set impression must be sufficiently elastic to return to its original dimension, without distortion, when removed from the mouth

Describe the different types of elastomers and discuss the uses, advantages and disadvantages of each

Polysulfides: Commonly known as 'rubber base'. Oldest of the elastomers. Least expensive of the elastomers. Dimensional stability. More stable than hydrocolloid but less than other elastomers. Accuracy. More accurate than alginate. Not as accurate as other elastomers. Setting Reaction: Supplied as two pastes. 1:1 ratio. Base/Catalyst: Base contains sulfur and Catalyst is lead dioxide or peroxide. Sulfur reacts with oxygen in the lead dioxide or peroxide to begin the polymerization reaction. Disadvantages: Objectionable odor (sulfur). Objectionable taste. Messy to clean up. Virtually impossible to clean out of fabric. Silicon: Condensation- Easy to mix. No unpleasant odor or taste. Supplied in two tubes. Base and Catalyst. 1:1 ratio. Base is dimethylsiloxane. Catalyst is stannous octoate. Silica is used as a filler. Material sets in 5-7 minutes. Improvement over polysulfide. Major disadvantage was in the ethyl alcohol by-product that required immediate pouring of the impression. This material has largely been replaced by addition silicone materials. Available in light, medium and heavy body as well as putty form. Silica is used as a filler material. Bite registration material also available. Popular for use in an automix gun. Various setting times also available Polyether: Very accurate impression material. More hydrophilic than other elastomers - can tolerate some water. Supplied as light, medium and heavy body material. Base material is a polyether. Catalyst is a sulfonic acid. Resulting material is a stable rubber. Catalyst material is very irritating to skin and mucous membrane (due to the acid content). Therefore, thorough mixing of the base and catalyst is necessary to avoid irritation. Mixing machines and automix guns. Stiffest (least flexible) of the elastomers. Can be difficult to remove from the mouth in undercut areas. Need at least 4mm of thickness to help improve the flexibility.Very accurate, Somewhat hydrophilic, High dimensional stability, Low permanent deformation. Short working time and setting time, compared with other elastomers, Sensitive to temperature and moisture; increasing either will shorten working/setting time, Must not be immersed in water or disinfecting solutions.

Define alginate impression materials and explain their composition

immersed in an appropriate disinfectant for up to 30 minutes without distorting. Lowest tear strength. Two major active ingredients: Potassium alginate or sodium alginate and Calcium sulfate dihydrate

Explain the chemical reaction that occurs in alginate impression material

transformed from a sol to a gel state when set. Mixing alginate powder with water creates sol. calcium sulfate dihydrate reacts with sodium alginate to form calcium alginate. This chemical reaction causes sol to gel and Occurs rapidly.

List the two major categories of elastic impression material•

-Hydrocolloids: Reversible and Irreversible Elastomers: Polysulfide, Silicone, Polyether

Define what a dental impression is and its purpose

A dental impression is a negative imprint of hard (teeth) and soft tissues in the mouth from which a positive reproduction (or cast - model) can be formed. Records the negative space surrounding the teeth by imprinting of those tissues into the impression material. Makes replicas of oral structures used to construct restorations or appliances

Discuss the requirements necessary for a consumer product to qualify for the ADA Seal of Acceptance:

A product submission must include data from clinical and/or laboratory studies that demonstrate safety and efficacy according to product category requirements developed by the ADA Council on Scientific Affairs. The consultants represent all fields relevant to evaluating dental products, including dental materials, microbiology, pharmacology, toxicology and chemistry. Only after a product has demonstrated its safety and efficacy will the ADA Council on Scientific Affairs award the Seal.

What is Kaolin?

A soft white clay mineral and Essential ingredient in the manufacture of porcelain

Define elasticity and give an example of when elasticity is desirable in dental procedures:

Ability of a material to recover its shape completely after deformation from an applied force. Not all materials return to their original shape when the force is removed. Materials that do not return to their original shape have exceeded their elastic limit. Elasticity is important for impression materials and orthodontics.

Define abrasion, finishing, polishing and cleaning

Abrasion: A material composed of particles that are hard enough and sharp enough to cut or scratch a softer material when rubbed across its surface Finishing: A procedure used to reduce excess restorative material to develop appropriate occlusion and contour; this is usually done with rotary cutting instruments. Finishing removes surface blemishes and produces a smooth surface. Finishing requires the hardest appropriate material except at the margin of the restoration, where tooth structure may be affected. Polishing: A procedure that produces a shiny, smooth surface by eliminating fine scratches, minor surface imperfections, and surface stains using mild abrasives frequently found in the form of pastes or compounds. Polishing produces little change in the surface. May have to be repeated periodically during the life of the restoration Cleaning: Procedure that is primarily meant to remove soft deposit from the surface of restoratives and tooth structures. Polishing and cleaning are done to remove surface stains and soft deposits from the clinical crowns and exposed root surfaces of teeth after hard deposits are removed. Aside from abrasives, there are also chemical cleaning products that are primarily used for removable appliances. Cleaning requires materials with Mohs hardness no greater than or equal to that of the substrate

Define dimensional stability, tear strength, and permanent deformation

Accuracy - must closely adapt to and flow over the surface of the tooth preparation and tissues - the material will flow if it has low viscosity and there is pressure on the material as the tray is seated Tear resistance - prevent tearing during removal of tray from mouth Dimensional stability - The set material must remain dimensionally stable after the impression is removed

Explain the difference between 'addition polymerization' and 'condensation polymerization'

Addition Polymerization: Similar to composites. Short chain, low-molecular weight monomers join in a chain reaction. Monomers create a stable rubber compound . Condensation: Also a chain reaction like addition polymerization. A stable rubber compound is produced. Unlike addition polymerization, a by-product is also produced. Usually water or ethyl alcohol

Discuss the advantages and disadvantages of amalgam as a restorative material:

Advantages: Can withstand high chewing forces. Biocompatible. Easy to manipulate. Very durable and wear resistant. Relatively inexpensive. Alternative for cusp replacement when patient cannot afford a crown Disadvantage: Not an esthetic material. May require more tooth structure removal to retain the restoration. Cannot chew on it immediately after placement. Possible temperature sensitivity after placement. Possible galvanic reaction with other metals in the mouth. Requires mercury hygiene measures with scrap material.

List the advantages and disadvantages of ceramic restorations:

Advantages: No underlying metal substructure, Biocompatibility, Wear resistance, Stain resistance, Ability to precisely place contacts and contours of the restoration, and Excellent esthetics. Disadvantage: Brittleness - can lead to fractures, Wear of the opposing enamel or restoration, Difficulty or inability to repair them in the mouth, The need for two appointments, and Difficulty of polishing them in the mouth.

Define and discuss agar impression material

Agar is an aqueous impression material used for recording maximum details; for example, as in the production of dies for fixed restorations. Agar is also known as a reversible hydrocolloidal impression material. It gives good detail reproduction than any other material.

Discuss why it is necessary that the allied oral health practitioner have an understanding of dental materials for the delivery of dental care:

Aid in the delivery of quality patient care. Ex: Proper placement of sealants can help prevent dental caries. Leads to success or failure of the material. Hygienist may or may not be involved in the placement of restorations, but they play a significant role in the maintenance of restorations and in educating the patient. Proper identification is important so that we do not mistake them for dental caries and to properly maintain the materials. This includes proper use of instruments, polishing agents, fluorides, near or at dental restoration. Or use of any substance or material for dental materials. Discuss the characteristics and properties of one dental material as compared to another. Describe steps involved in the fabrication of a certain type of restoration and home care regimens. Patients will be asking the hygienist the questions.

Explain mini-implants and their uses:

Also called narrow-body, Smaller in diameter, Minimally invasive - flap is usually not needed, Less costly, Can be placed in sites where the available bone would be inadequate for conventional implants, Stabilize denture, Sites with minimal bone, Replace teeth with narrow roots (lower incisors).

Compare the strength of amalgam with that of composite resin or glass ionomer cement:

Amalgam: One of the strongest direct restorative materials and Able to resist biting force repeatedly over long periods of time. Stronger in compression than composites or glass ionomers. Tensile strength and shear strength are relatively weak. Restorations made of amalgam rely on their bulk to resist breaking

Discuss polishing during oral prophylaxis for amalgam, composite, gold alloys, and ceramics restorations and implants

Amalgam: Use rubber cups or bristle brushes and prophy paste, Helps reduce tarnish and corrosion, and Helps to prolong life of the restoration. Composites: Traditional prophy paste should be avoided - excessive wear, Use aluminum oxide polishing paste, and Staining at margins may represent microleakage - cannot be polished away. Gold Alloys and Ceramics: Resistant to stain, Do not use regular prophy paste, and Specialty pastes are available that contain microfine particles that are not harmful for polishing veneers and crowns (can also just use toothpaste) .Implants: Must be careful to not abrade the surface, Use non abrasive cleaning paste or tin oxide, and Air polishing with glycine powder.

Define amalgamation / trituration:

Amalgamation is the reaction of the alloy with the mercury as it is mixed. The freshly mixed amalgam has a putty-like consistency that can be packed into the cavity preparation. Mixture gradually becomes firmer. During the first part of this firming phase, the amalgam can be carved to the anatomic shape of the tooth. Once it reaches its initial set, it can no longer be carved - but is not fully reacted. Takes up to 24 hours for most amalgams to gain their maximal strength.

List and compare the agencies responsible for setting standards and specifications of dental materials:

American Dental Association (ADA)-creates guidelines for testing products to help inform consumers of safety and efficacy of products and is a voluntary program. Food and Drug Administration (FDA)- this is for consumer protection and products must meet safety requirements, is a nonvoluntary program. International Agencies: International Dental Federation (IDF) and International Standards Organization (ISO)- these are for standards at the international level, companies must comply with quality management, and companies are audited to ensure their compliance with standards. These agencies regulate the products that can be used.

Describe the sequence of the two-stage surgical procedure:

Approximately 3 months later - the implant is uncovered, cover crew is removed, and healing abutment is place. After a few weeks, the crown impression procedure can begin

Define and discuss margination

Before finishing or polishing an amalgam or composite restoration, the clinician should check the integrity of the cavosurface margins for overhanging margins and deficiencies. Margination: the process of removing restoration prematurities to bring the restoration flush with the cavosurface tooth structure. May vary from removal of flash to removal of overhangs. Overhang margins collect microorganisms that contribute to periodontal disease and caries, prevent efficient use of dental floss and increases inflammation.

Describe reinforced ceramics:

Because the porcelains were prone to fracture, stronger ceramic materials were developed. The most common of these stronger glass-based ceramics are: Leucite Disilicate Ceramics and Lithium Disilicate Ceramics. Has more than tripled their fracture resistance.

Explain Image-Guided Implant planning and surgery and the benefits:

Before the introduction of cone beam computed tomography (CBCT) most surgeons relied on their clinical examination and two-dimensional radiographs. Panoramic radiographs magnify dental structures by about 25% - increased risk of errors . BCT - provides very accurate three-dimensional images, Can accurately assess, Density of bone, Thickness and height of the ridge at the planned implant site, Location of nerves and major blood vessels, Maxillary sinuses. Treatment planning software can import CBCT images, allowing the surgeon and restorative dentist to plan for the implant placement surgery, Type of implant, Proper diameter and length of implants, Proper position.

Describe the reaction stages a material undergoes to acquire its final stage:

Before the material reaches its ultimate solid state, the process goes through stages: The manipulation stage - includes the mixing time and working time. The reaction stage - the initial set and final set times. Mixing time is the length of time the dental auxiliary has to bring the components together into a homogeneous mix. Working time is the time permitted to manipulate the material in the mouth. Initial set time begins when the material no longer can be manipulated in the mouth. Final set time occurs when the material has reached its ultimate state.

Explain the physical properties of composites, including biocompatibility, strength, wear, polymerization shrinkage, thermal conductivity, coefficient of thermal expansion, elastic modulus, water sorption and radiopacity.

Biocompatibility: Dentin must be sealed to avoid chemical irritation of the pulp and Polished composites are well tolerated. Strength: Larger particles have increase tensile strength and compression strength. Wear: Composites wear faster than amalgams, Composites with a low volume of filler particles wear away faster than more highly filled composites, and Wear rate is beginning to approach that of amalgam. Polymerization Shrinkage: Shrinkage that occurs when the composite is cured, Resin matrix tends to shrink away from the cavity walls, and Can contribute to sensitivity, microleakage, staining at the margins and recurrent decay. Reducing the Effects of Polymerization Shrinkage: The greater the resin content of the composite - the greater the shrinkage, Increase filler particles - decrease shrinkage, and Placing the restoration in increments and curing each layer helps to reduce shrinkage. Thermal conductivity: Rate at which heat flows through a material and Composites are similar to natural tooth. Coefficient of thermal expansion: the greater the filler content the lower the CTE and In general, composites have a much higher CTE than natural tooth - can result in debonding and leakage of restoration. Elastic Modulus: Refers to the stiffness of the material and it's resistance to deformation, Stiffer materials have a higher elastic modulus, In composite restoratives the elastic modulus is determined by the amount of filler, and More filler = more stiffness. Water Sorption: Defined as the ability to absorb moisture, Resin matrix absorbs water from the oral cavity over time, This softens the matrix and degrades the restoration slowly and gradually, and The greater the percentage of resin matrix the more likely that water sorption will occur. Radiopacity: Metals are added to the filler to make the restoration more opaque when viewed on radiographs, Older composites do not have any of these additives and might appear radiolucent on radiographs , and Clinician may have a difficult time determining whether there are recurrent caries around radiolucent composites

Characteristics of the "perfect dental material" are:

Biocompatible, bond permanently to tooth structure, esthetic, and useful in repairing or regenerating missing tissues

Describe the long-term clinical requirements of therapeutic and restorative materials:

Biocompatible, durable, non-reactive under acid or alkaline conditions, compatible with other materials, and esthetically acceptable. Also able to be okay in conditions that are moist, produce stress, and that have different temperatures or acid levels.

What does the resin matrix contain?

Bisphenol A & Glycidylmethacrylate - Bis-GMA or Urethane Dimethacrylate - UDMA

Explain the differences between bonding to enamel and bonding to dentin:

Bonding to enamel alone is simpler than bonding to dentin-etching of enamel creates a high-energy, low tension surface that makes the surface easier to wet. Low viscosity resin penetrates spaces on & between enamel rods created by acid etching. Dentin bonding is not as strong as enamel - dentin closer to the pulp has more fluid and more tubules that are difficult to bond to. Enamel must be completely dried, dentin is left moist or wet. Wet dentin require use of a primer.

Explain the hardness tests used in dentistry Knoop Hardness Test also known as KHN:

Can be used to test most dental materials. Test by using a diamond - tipped tool; length of indentation is measured. Ability of materials to resist indentation. Mohs Scale of Hardness: Ranks materials by their relative abrasion resistance and Ability to resist being scratched

Explain what an alloy is:

Mixture of two or more metals. Pure metals typically lack strength. Combination of metals allows for maximizing characteristics that are useful in dental restoratives. Many alloys used in dentistry. Used in direct and indirect restorations.

Explain the rationale for the use of plastic/titanium instruments for cleaning titanium implants:

Care must be taken to not damage the surface of implants. If polishing is deemed necessary - tin oxide or other nonabrasive polishing paste (toothpaste). No air polishing. USS can be used WITH an implant tip (plastic coating or sleeve) and on low power.

List factors in proper maintenance of all-ceramic restorations:

Care should be taken when working around crowns. Select fluoride products that are not acidic - acidulated fluoride products can etch crown surface. Occlusal guards should be recommended for patients who grind teeth or have edge-to-edge bites- Restorations made entirely from Zirconia would be the exception.

Describe the thermal properties of ceramics:

Ceramic materials act as insulators in that they do not conduct heat or cold readily. They will however, expand and contract when subjected to temperature changes (Coefficient of thermal expansion). The higher the CTE, the more the ceramic expands or contracts with temp changes. This is important when two materials are bonded together. The two materials must have compatible CTEs - otherwise, they may fracture.

Discuss the similarities and differences among chemical-cured, light-cured, and dual-cured composite resins:

Chemical Cure Composite (Self-cure): Initiator-benzoyl peroxide (Base). Activator -tertiary amine (Catalyst). Each paste in a two-paste system contains the resin and filler and One paste contains the initiator and one paste contains the activator. Light-Cured Composite: Light is the activator. Accelerator is a tertiary amine. Both the initiator and accelerator are present in the composite material. Dual cured: Same initiators and activators as light-cure and chemical cure. Chemical reaction begins with mixing. Chemical reaction is slow. Light activation speeds the set. Chemical reaction will complete the polymerization process in areas not reached by the light.

Describe the chemical and physical nature of gypsum products:

Chemical Properties: The mineral gypsum is a dihydrate of calcium sulfate. The manufacturer heats the dihydrate, which causes it to lose water. It is then ground to produce a powdered hemihydrate - calcination. When we get the hemihydrate in office - we mixed it with water - get a viscous product capable of flowing. Once the chemical reaction is complete - the hemihydrate is converted back to a dihydrate and becomes a solid mass again. The by-product of the chemical reaction is heat. Exothermic reaction. The amount of water required to mix with the calcium sulfate hemihydrate is greater than the amount required for the chemical reaction - allows material to flow. Excess water evaporates on setting Physical Properties: Related to heating process during manufacture. Different methods of heating produce different types of particles. Size, shape and porosity determines specific use of the gypsum product. Larger porous particles yield weaker final product.

Describe porcelain-metal restorations (PFMs) and how they are made:

Combining porcelain with metal (PFM - porcelain-fused-to-metal) substructure increases strength and durability in the final restoration. Metal internal core with an esthetic covering. Low fusing porcelain is used first and is layered onto the metal substructure. Metal substructure is also called the 'coping'. Porcelain chemically fuses to the surface oxides as the two materials are heated together. Durable bond is formed. Created in layers: First layer is opaque so that the metal oxide color is blocked, Subsequent layers mimic the tooth shade, Incisal portions are made more translucent, and Porcelain and metal oxides chemically fuse together and mechanically interlock.

describe non-glass-based ceramics:

Composed of simple or complex oxides and No glassy matrix. Includes: Alumina and Zirconia

List the components of compomers:

Composite resins that have been modified with polyacid, Contains methacrylate groups for cross-linking (like composite), Material has an acid/base setting reaction like GI, Light activation chemicals are included, and Filler particles are glass

List and give examples of the four types of biting forces and the tooth structures most ideally suited to them:

Compression Force: Force applied to compress or squeeze an object-crushing biting force. Posterior teeth are ideally suited for this type of force. Large occlusal surface and multirooted base are well suited to resist a crushing force. Tensile Force: Force applied in opposite directions to stretch an object or pull it apart. When biting forces are used to stretch a material the teeth are exerting tensile force. Shearing Force: Force applied when two surfaces slide against each other in opposite directions. When the maxillary and mandibular incisors are used for cutting. Torsion or Torque: Twisting force that has tensile and compressive forces. This force is more descriptive of normal masticatory events. When we chew, we combine both compressive and tensile forces.

Explain the role of the gamma-2 phase in corrosion of amalgam:

Copper reacts with tin to keep it from being available for the gamma-2 phase. The - low-copper amalgams had much more corrosion because of the chemical reaction of tin and mercury. High-copper amalgams do not have a gamma-2 phase and are superior in their clinical performance. Reduced corrosion. Increase strength and reduced marginal breakdown.

Describe crowns, bridges, inlays and onlays:

Crowns: Used to restore teeth when a substantial amount of tooth structure is missing, Encircle and support remaining tooth structure, and Cemented in place. Bridges: Replaces a lost tooth or teeth, Each pontic tooth is supported by an actual tooth at each end (the abutment crown), and Cemented into place. Inlay: Replaces a lost tooth or teeth, Each pontic tooth is supported by an actual tooth at each end (the abutment crown), and Cemented into place. Onlay: Indirect Restoration - made outside the mouth in one solid piece that fits the specific size and shape of the preparation, Cemented in place, and Involves 1 or more of the cusps.

What is the study of dental materials?

Deals with the properties and proper manipulation of materials used by the dental team.

Define density and explain the relationship of density, volume, and crystalline structure:

Density: A measure of the weight a material has compared with its volume. Measure of the compactness of matter, or how much mass is squeezed into a given space. As a material becomes more dense, less air or spacing is seen between atoms. density is the measure of the weight of the material compared with its volume. As volume decreases, density increases. Close spacing of the crystalline structure gives the greatest density.

Describe alumina porcelain:

Developed in 1965 to enhance the fracture resistance compared with conventional feldspathic porcelain and Glassy type of porcelain that is half aluminum oxide in a melted glass (silica) matrix. Developed as an alternative to the PFM crown and Had very high flexural strength - about three times that of the glass-based materials.

Explain diagnostic cast, working cast, and dies

Diagnostic cast: Also called study models, Used to plan treatment and observe the oral structures of the mouth, Orthodontists use study models extensively as they plan and treat the alignment of the teeth. Working cast: Also called working models, Used to fabricate appliances such as an orthodontic retainer, bleaching trays, mouthguards or a removable prosthesis such as a partial or full denture Dies: Replicas of individual teeth or groups of teeth and are used to fabricate crowns and bridges

List and discuss the different types of materials that can be used in abrasion

Diamond: Hardest substance known - 10 on the Mohs hardness scale, Will abrade any substance , Usually bonded in varying degrees of coarseness to rotary cutting shanks and disks, Diamond paste is used for polishing composites and porcelains Tungsten Carbide Finishing Burs: Very hard, Varied shapes and designs, Used to cut preparations or to finish composite restorations. Silicon Carbide: Synthetic abrasive, Mohs' 9-10, Primarily supplied as coated finishing discs Aluminum Oxide: Synthetic abrasive, 9 on the Mohs' scale, Powder form used in air abrasion, Bonded and coated rotary discs, Used to smooth enamel or to finish metal alloys and ceramic materials. Sand: Natural abrasive composed of quartz and silica, 7 on the Mohs' scale, Coated discs and handheld strips Silicon Dioxide: Mohs' 6-7, Prophy paste, Rubberized cups and points used for finishing and polishing composite restorations Pumice: Volcanic silica, Extremely fine - Mohs' 6, Prophy paste, Used to polish tooth structure, amalgam and acrylic bases Rouge: Iron Oxide, Mohs' 5-6, Used to polish precious and semiprecious metal alloys in the lab, Not used intraorally Tin Oxide: Extremely fine, Final polishing agent for enamel and restorations, Powder mixed with water or glycerin Calcium Carbonate: Chalk, Mild abrasive - Mohs' 3, Prophy paste and dentifrice , Used to polish teeth, metal restorations and plastic materials Sodium Bicarbonate: Very low Mohs - 2.5, Cleaning agent in toothpaste and in air polishing Potassium and Sodium: Very low Mohs - .04-.05, Nonabrasive - used in toothpaste and desensitizing agents

Define ductility and malleability:

Ductility: The amount of dimensional change a solid can withstand without breaking - ability of an object to be pulled or stretched under tension without rupture. Materials with poor ductility are classified as brittle - these materials are much weaker when subjected to tensile force than to compressive force. Malleability: The ability to be compressed and formed into a thin sheet without rupture. Gold is very ductile with good malleability.

Explain implant failures and long-term success of implants:

Early failure is usually due to failure of the bone to integrate with the implant. Due to poor surgical technique, infection of the implant site, poor quality of bone, or too-soon placement of loading forces on the implant. Failure of the implant that occurs after the initial integration is often caused by bacterial infection extending from the peri-implant tissues into the bone (peri-implantitis), or overloading of the implant during function leading to loss of the supporting bone. Long term success: Implant - bone integration (Osseointegration). Implant components are kept cleanSurrounding gingiva is maintained in a healthy state. Forces on the implant are not excessive.

Describe the effects of acid etching on enamel and dentin:

Enamel: Removes a small portion of the tooth surface, reduces enamel rods and opens porosities among them, etch applied for 10-30 seconds, area must be rinsed thoroughly after etching, dry thoroughly with air to reveal a characteristic frosty appearance. Etched enamel is a high-energy surface that allows penetration of the resin to form strong resin tags, contamination must be avoided, re-etching must be done if etched surface is contaminated. Dentin: Higher water content than enamel, cutting dentin with a high-speed handpiece and dental bur creates a 'smear layer', smear layer occludes dentin tubules and won't rinse off, acid etching for 10 seconds, then rinsing, removes smear layer, self-etch systems 'modify' the smear layer and incorporate it into the bonding agent.

Describe the sequence of the one-stage surgical procedure:

Exposing the bone at the chosen placement site with a surgical flap, A hole (called an osteotomy) is drilled in the bone at low speed, A series of burs will be used - starting with a small-diameter and increasing to the size of the implant, The implant is either lightly tapped or screwed into place, An acrylic resin surgical guide (called a stent) is made ahead of time with holes drilled through it at the same angulation at which the implant should be positioned, After the implant fixture is placed in the bone, a cover screw is placed into the opening at the top of the fixture, The surgical flap is repositioned and sutured closed over the implant.

What is gypsum?

Gypsum is a mineral widely found in nature that has been used for making dental cast since 1756. Gypsum products are made from gypsum rock. Gypsum rock is mined, ground into a fine powder, and then processed by heating to form a variety of products

What is feldspar and feldspathic porcelain?

Feldspar: A group of minerals that make up 60% of the earth's crust, A common raw material in the production of ceramics, and Materials that contain feldspar are 'feldspathic'. Feldspathic porcelain: Until recently were the most commonly used dental ceramic material, Porcelain particles were fused at high temps to form a type of glass, Metal oxides were added to create different shades of porcelain. And Feldspathic porcelains were used in conjunction with cast metal substructures to create PFM crowns.

Describe the use of compomers:

Filler glass may contain fluoride, Fluoride release is much less than with GI, Generally compomer is suitable for only Class III and V restorations, and Must be used with bonding agents (unlike GI).

What are the two most common reasons composites fail?

Fracture of the restoration and Recurrent caries

Describe the composition of Hybrid Ionomers and their uses, advantages and disadvantages:

HEMA (hydroxyethyl methacrylate) added, Some properties of composite and many properties of traditional GI, Resin improves strength, polishability, esthetics, and wear resistance and Less soluble than traditional GI.

Who developed an acceptable amalgam formula

GV black

Describe the clinical significance of galvanism and how it can be prevented:

Galvanism: The phenomenon of electric current being transmitted between two dissimilar metals. The current may result in stimulation to the pulp, called galvanic shock. We see this amalgam restorations. The salts of the saliva facilitate the movement of electrical current from one type of metal to another. Can change the type of dental material used to reduce shock and be very gentle in scaling with metal instruments.

Explain the three different phases of the amalgam reaction:

Gamma phase: First phase. The silver alloy phase. It is the strongest phase and has the least corrosion. Gamma 1 Phase: Second phase. Consisting of mercury reacting with the silver. Strong and corrosion resistant, although not as resistant as the gamma phase. Gamma 2 Phase: Third phase. Consists of the reaction of mercury with tin. Weak and corrodes readily Tin is used to control the rate of set of the amalgam.

Define 'colloid'

Glue like material, one substance suspended in another

Compare hand mixing and automixing:

Hand mixing: Viscosity can be varied, Volume of material can be varied, No extra equipment needed, Less expensive, Can mix shades if necessary. Mix may be inconsistent, Less convenient, More cleanup Automixing: Consistent mix, Can vary the volume of the material, Convenient, Less cleanup, Unable to vary the viscosity of the mix, Requires additional equipment, Cannot blend shades, More expensive

Describe glass-based ceramics:

Have silica as a main component and Have glassy matric. Includes: Porcelains, Feldspathic porcelains, Leucite-reinforced ceramics, Lithium disilicate ceramics.

What is added to filler particles for radiopacity?

Heavy metal ions are added- boron, barium, zirconium, zinc

What is the coupling agent?

Heavy metal ions are added. Helps the filler particles adhere (stick) to the matrix.

Describe resin hybrid ceramics:

Hybrid resin nanoceramic materials: Combine desirable properties of both composite resin and nanosized ceramic particles. Easy to mill and polish to a high shine. Tough, durable restorations that are not abrasive to the opposing teeth. Relatively new - long-term clinical studies are not yet available on their clinical performance.

Explain the difference between a hydrophobic and a hydrophilic impression material and give an example of both

Hydrophilic: the types of impression materials that are considered hydrophilic are those that have good surface-wetting characteristics. polyether impression material Hydrophobic: impression materials need a dry field to get the best results. Hydrophilic impression material can be mixed with water, hydrophobic impression material will lose surface detail because it can't mix with moisture.

Explain initial and final set of gypsum:

INITIAL SET time -should not be removed from mold. Regular set= 8-16 from beginning of mix Final set: Point at which material can be handled but it has minimal hardness and resistance to abrasion. Exothermic reaction is complete. Model is cool to touch. Recommended to wait 45 minutes to 1 hour before separating impression. Gypsum continue to harden for 24 hours. Should not wait more than 1 hour to separate impression and cast. Detrimental effect on the surface characteristics of the cast. Alginate will absorb water from the surface of the cast producing a weaker, more porous surface

Define imbibition and syneresis and explain how they affect dental impressions

Imbibition: The act of absorbing (uptake) moisture. Too much water causing 'swelling' of the impression Syneresis: Process of contraction of the alginate that squeezes out some liquid. Loss of moisture. Impression shrinks

compare the one-stage, two-stage and immediate surgical procedures:

Immediate-Placement Surgical Procedure: When the implant procedure involves the extraction of a tooth, some clinicians place the implant fixture at the time of extraction directly into the new socket. An artificial bone material can be placed in the socket to aid the growth of new bone into the socket and to help stabilize the fixture. Higher rate of failure. One-Stage: Performed just as with the two-stage procedure - difference is, a cover screw is not placed at the top of the fixture and it is not covered with the gingival flap. Instead, the healing abutment is placed and the gingiva is positioned around the abutment. Increasing in popularity - no second surgery. Best when the patients restorative needs are not complicated. Research has shown that there is no difference in survival of the implant between the one-stage and the two-stage

List the indications and contraindications for dental implants:

Implant Indications: Replace a single tooth, Replace several teeth, Replace all teeth, and Prevents atrophic edentulous mandible. Implant Contraindications: Patients with medical conditions that make them poor candidates for surgery (advanced cardiovascular or respiratory disease), Patients with systemic disease that affect connective tissues and healing (diabetes), Patients inability to maintain effective plaque control, Patients who have recently taken bisphosphonates - risk of delayed bone healing and bone infection, Patients with compromised immune systems, and Smoking.

Describe the composition of glass ionomer restoratives and their uses, advantages and disadvantages:

Introduced in the early 1970s. Self-cured, tooth-colored, fluoride-releasing materials. Bond to tooth without an additional bonding agent. Polyacrylic acid and glass. Acid/Base reaction when the material sets. Advantages: Chemically bond to enamel and dentin, Releases fluoride, Take up fluoride to act as a fluoride reservoir, Reduced microleakage on dentin, Reduced postoperative sensitivity , Biocompatible, and Expand and contract similar to tooth structure (CTE). Disadvantages- High wear rate, Too weak for stress-bearing restorations (occlusal surfaces and incisal edges of permanent teeth), Less esthetic (more opaque) than composites, Cannot polish as well as composite - surface roughness, and Initially sensitive to water loss or uptake.

Discuss the factors that interfere with good bonding:

Isolation and soft tissue management are important- saliva and blood are contaminants, astringents (used to control bleeding) can interfere with bonding, eugenol-containing temporary cements can interfere with bonding, wait 1-2 weeks after use of a whitening agent before doing a bonding procedure, recently applied topical fluoride can cause a drop in bond strength.

Explain the significance of the smear layer:

It is derived from: cut tooth debris, plaque, pellicle, saliva, blood. Isolation of the tooth helps prevent sources other than tooth debris, may interfere with bonding, must be removed or modified. Tenacious surface layer of debris resulting from cutting the tooth during cavity preparation; made up of fine particles of cut tooth structure

Explain the importance of detection of restorations and methods for detection:

It is important to detect restorations so you know exactly how to go about treating the patient and be sure to cause no damage. Obvious identification, difficult identification, tactile evaluation, visual evaluation, and radiographic evaluation

Explain why inelastic materials are not used, or seldom used, today

Largely replaced by elastomers. Composed of calcium hemihydrate. After impression set, it was scored with a knife or bur, broken and removed from the mouth.... Then reassembled in the lab with glue or wax

Discuss the adverse effects of microleakage at restoration margins:

Leads to decay under the restoration, sensitivity of the tooth, percolation can lead to sensitivity, staining of margins, and recurrent caries.

Explain the manufacturing process of gypsum products and how this affects their physical characteristics:

MINED- AS SOLID -dihydrate of calcium sulfate HEAT- the dihydrate to which causes a loss of water and GROUND- into a hemihydrate known as calcination ADD WATER- viscous product is produced to allow flowing COMPLETE- hemihydrate is converted back to dihydrate and becomes a sold mass CHEMICAL REACTION causes exothermic reaction during this process Excess water evaporates and mass of interlocking gypsum craystals is prduced - amount and size of the air voids remaining are directly related to the final hardness , strength and resistance to abrasion of the final product ----Calcination.

Describe the various types of composite resin restorative materials, and discuss the advantages, and disadvantages, of each type:

Macrofilled Composite (<1970): First generation of composites, 10-100 micron particle size, Large particle size yielded a rough final surface, Difficult to polish to a smooth finish, and No longer widely used. Microfilled Composite (Late 1970s): Developed to overcome the problems of macrofilled composites, Smaller filler particles, and Weaker than macrofilled composites but more natural looking restorations due to ability to polish the materia. Hybrid Composites (1980s): Contain macrofillers and microfillers (Range from .1 to 3 microns), Microfillers fill in the spaces around the larger macrofill particles, 70-80% filler by weight, Versatile because of high strength and polishability, and Anterior or posterior restorations. Microhybrids: Mix of small particles (.5 to 3 μm (micrometer) and microfine particles (.04 μm), High filler content (70%), and Microfine particles fill in the spaces between small particles. Nanohybrids: Microhybrids that contain nanosized particles, Particle size ranges from .005 to .020 μm, Increased fillers mean decreased resin, Decreased resin means less polymerization shrinkage (1% overall), Polishable to a high shine and able to retain their shine, and Wear resistant and strong - can be used in both anterior and posterior

Define biocompatibility and discuss why requirements for biocompatibility may fluctuate:

Material must not impede or adversely affect living tissue and should interact to the benefit of the patient. It may fluctuate because every person's mouth is different, people are allergic to some materials, what is best for anterior teeth might not be the right choice for posterior teeth.

List the materials needed to take an alginate impression

Maxillary and mandibular tray, mixing bowl, spatula, water measuring cup, alginate powder and scoop.

Describe the process used to achieve mechanical, chemical adhesion, or bonding retention:

Mechanical Retention involves the use of undercuts or other projections into which the material is locked in place. Once the material is hardened in place, it is retained through this design. Can no longer be used when significant amounts of tooth structure is removed. Chemical adhesion: The adhesives used in dentistry are commonly called dental cements. Dental cement retains the restoration by chemically and/or mechanically connecting the two surfaces. Bonding is the term also commonly used when describing the retention of materials. Bonding of materials occurs when the tooth surface is prepared with an acid-etch technique to create microscopic pores in enamel and dentin. A fluid bonding material is then allowed to flow into these pores and mechanically lock into the tooth structure. This technique offers several advantages in producing retention. Requires less removal of tooth structure because no undercuts are necessary. Produces a stronger retentive force between tooth and restoration. Seals the margins of the restoration to prevent the seepage of bacteria and fluids.

Explain the procedure for mixing and handling gypsum products to create casts:

Mixed in a flexible rubber bowl with a broad spatula. The mixing process is called spatulation. The measured amount of water is placed into the mixing bowl and the powder slowly sifted into the water within 30 seconds-Even wetting of the powder particles takes place and clumps are avoided -Minimizes amount of incorporated air into the mix - less voids in final product = stronger final product. Then, vigorously wipe the mix against the sides of the bowl to force out air and ensure wetting of all the powder particles. Mix until a smooth, homogeneous mix with a glossy surface. One-minute mixing time •Mixing for >2 minutes will accelerate setting time and increase expansion •Use of the dental vibrator removes air bubbles incorporated during the mix -Air bubbles cause voids in final product

Explain the factors that affect the setting time, setting expansion and strength of gypsum products:

Mixing for increased time will increase setting expansion and decrease setting time. Water Powder ratios are most important to maintain proper setting expansion rates. 0.30% plaster and 0.10% Stone. increase in temp will accelerate but using water over 100 degrees will retard setting at all and no reaction will take place

Explain Polymerization and Cross-Linking of polymers:

Monomers are short chain, low molecular weight molecules, Polymers are long chain, high molecular weight molecules, and Chain reaction. Free Radicals are created (Highly charged particles with unpaired electrons). Monomers have C=C bonds. Free radicals break one of the C=C bonds to form a single bond and another free radical. That free radical causes the same reaction with another monomer. Cross-Linking of Polymer Chains: Polymer chains have small groups of atoms hanging off their sides. When side groups of adjacent polymer chains share electrons, they form covalent bonds that link the chains together. Cross-linking of polymers produces a much stronger, stiffer material

Describe PFM crown failures:

Most porcelain failures result from small cracks that occur when porcelain is put under occlusal loading. The cracks spread over time until the porcelain fails. The bond at the metal oxide layer may also be inadequate and cause porcelain failure. Coefficient of thermal expansion of the porcelain and the metal need to be compatible to avoid fracture.

Define the types of bone grafting and the indications for bone grafting:

Needed when the proposed implant site lacks an adequate amount and quality of bone, Increase the width or height of bone, Place bone where the maxillary sinus extends too close to the alveolar ridge, Prevent implant from perforating the sinus - can also do what's called a Sinus Lift or reposition of the floor of the sinus Autografts: Harvested from the patient's own body, Typical sites: back of the lower jaw, chin, hip or shin, Large tori can also be used, Very effective - contains the patient's own bone marrow with cells that can promote bone growth and healing Allografts: Human bone taken from donors, The bone is washed and sterilized, Eliminates concerns of transmitting disease from the donor to the recipient Xenografts: Obtained from animals, usually cows, Bovine bone is very similar in structure to human bone - works well for grafting, Processed to make it sterile and biocompatible, only the mineral components are used, and it acts as a matrix or filler around which new bone grows Alloplasts: Synthetic materials that stimulate new bone growth, Commonly composed of calcium phosphate or hydroxylapatite, Often the material is mixed with the patient's bone marrow or with growth factors to stimulate bone activity.

Describe the advantages and disadvantages of digital impressions

No need for impression material, trays, adhesive, disinfectants, pouring impressions or packaging impressions for transport to the lab. Clinician can view preparation magnified on a computer monitor - helps eliminate errors. Images can be transmitted instantly. As accurate if not more than traditional impressions. For the patient: Process is easier - particularly for patients with strong gag reflexes or tori and Time for complete restoration to return from lab is shorter. Significant cost ($12,000-35,000), Labs charge a fee for processing digital images

List and explain the purposes of the other components that can be present in dental amalgam:

Other elements are allowed in lesser amounts (copper 10-30% and zinc 0-2%). Copper: Functions similar to silver in low Cu amalgam. In high Cu amalgams copper functions to eliminate the tin-mercury (gamma 2) phase. Results in increased strength and corrosion resistance. Zinc: Reduces oxidation and Improves life expectancy of the restoration

Discuss the effect of mixing time on the strength and manipulation of amalgam:

Overtriturated Amalgam: Too wet, crumbles, maybe hot (started setting before out of the capsule). Difficult to condense. Shortened working time - sets too quickly. Results in a weaker restoration that will corrode more readily. Undertritirated: Dry, grainy, crumbly appearance. Sets too quickly. Does not condense well. Weaker restoration because the components have not totally mixed. Proper Trituration: Satin appearance, Smooth surface, Cohesive mass, Plastic feel, Easy to condense , and Proper working time.

List the uses for elastic impression materials

Partial and full dentures, crown and bridge cases, implants, any procedure that requires an accurate representation of structures in the mouth

Describe the assessment that should be done for dental implants at the hygiene visit

Patient Education, Oral hygiene instructions, Prophylaxis, Care must be taken to not damage the surface of implants, Plastic or titanium instruments, Without proper maintenance, the risk of implant failure greatly increases. At one time probing was not recommended for fear of damaging the epithelial cuff around the implant. HOWEVER, the current consensus is to perform gentle probing at maintenance visits - light touch and plastic probe. Sites with increased probing depths, exudate and bleeding should be recorded. Check implants for mobility-An implant that has integrated with the bone should not be mobile, Patient may complain that the implant is loose - may just be a component of the implant such as a retention screw (making the implant crown loose), If the actual implant is loose, there should be some radiographic findings of bone loss.

List the patient and operator factors that contribute to composite failure:

Patient: Poor diet, Poor oral hygiene, and Bruxism. Operator: Poor cavity preparation, Inadequate isolation, Over/under etching, Improper rinsing and drying of the tooth, Poor placement technique, Open proximal contact, Overheating the pulp, and Inadequate curing of the bonding agent or composite.

Explain who the Father of Modern Dentistry is and what he is known for:

Pierre Fauchard and devoted a portion of his book, The Surgeon-Dentist, published in 1728, to denture technique of connecting the maxillary and mandibular pieces with a spring.

Describe the purpose of the sinus lift procedure:

Place bone where the maxillary sinus extends too close to the alveolar ridge. Prevent implant from perforating the sinus - can also do what's called a Sinus Lift or reposition of the floor of the sinus

List the rationales for selection of ceramic materials:

Porcelain: Used more for anterior teeth, Used to make porcelain veneers and serve well once they are bonded to the enamel and used in low-stress areas, Risk of fracture is higher if they are bonded to dentin, and Prone to fracture if used in posterior teeth. Leucite-Reinforced Ceramics: Work well for inlays, onlays, thicker veneers, and anterior crowns if they are bonded and Not strong enough to hold up as posterior crowns. Lithium Disilicate: Has twice the strength and fracture toughness and has enough translucency that is can be used in the anterior and posterior part of the mouth and Can be used for three-unit bridges from premolars to the anteriors. Alumina and Zirconia: Very strong materials, Opaque - not esthetic for use in the anterior part of the mouth, Alumina show an increased risk of fracture when used for molar crowns - should be limited to anterior and premolars, Zirconia is a suitable alternative for PFM crowns - good for bruxers, and Zirconia can be used for cores for three-unit bridges and for implant abutments in the anterior smile zone.

Describe the three basic types of impressions

Preliminary, final, bite registration

Differentiate between therapeutic, preventative and restorative materials:

Preventative: directed toward preventing the occurrence of oral disease and promoting oral health. Ex-fluorides. Restorative: Applies to any filling, inlay, crown, bridge, implant or partial or complete denture that restores or replaces lost tooth structure, teeth or oral tissues. Maybe used for short term (temporary crowns, cements) or for long term use (permanent restorations, prosthetic, implant and orthodontic appliances). Therapeutic: Used in the treatment of disease and include materials such as medicated bases or topical treatments for periodontal disease.

Explain primary consistency and secondary consistency:

Primary consistency (luting consistency): Thin mix to the consistency of honey, Must flow easily to be effective luting cement. Secondary consistency: Addition of powder - increases strength, Thick, putty-like, Used as bases and restorations

Explain all the uses of dental cement:

Pulpal Protection: Pulp can be irritated by- Caries, Chemicals in restoratives, Thermal Conduction, Too little dentin. Cavity Varnish-Acts as a protective barrier between preparation and restoration, Varnish - solutions of natural resins (copal) or synthetic resins dissolved in a solvent, applied in two or three layers, Seals dentinal tubules, Reduces microleakage, Today's dentin bonding agents have largely replaced the use of varnish. Luting and Bonding: Cementing of two components together through adhesion, May be permanent or temporary, Example: Cementation of indirect restorations (crowns). Cements are placed in two categories- Luting cements , Bonding (or adhesive) cements. Cementing of two components together through adhesion, May be permanent or temporary. Example: Cementation of indirect restorations (crowns). Cements are placed in two categories : Luting cements and Bonding (or adhesive) cements. Achieve retention by filling the interface between the restoration and the tooth Bonding (adhesive) Cements: Stronger than luting cements, Fill the interface and provide micromechanical retention between the tooth and the resin-based cement and restorative materials, Stronger than luting cements, Fill the interface and provide micromechanical retention between the tooth and the resin-based cement and restorative material Restorations: Reconstruction of tooth structure- Permanent, Intermediate , Temporary/Provisional Surgical Dressings: Acts as a 'band-aid', Provide protection and support for the surgical site, patient comfort and to control bleeding, Mechanically retained in place by gently forcing the material into the embrasure space and under the contact , Acts as a 'band-aid'Provide protection and support for the surgic

Explain why finishing and polishing of restorations is done and the goals and benefits

Purpose: Improves esthetics, Improves tissue health, and Increases the longevity of the restorative material. Goal: Remove excess material. Smooth roughened surfaces. Produce an esthetically pleasing appearance with minimal trauma to hard and soft tissues. Removes marginal irregularities. Defines anatomic contours and occlusion. Removes the surface roughness of restorations. Produces a mirror-like surface luster.

What are filler particles?

Quartz, Glass, Silica, and Ceramic

Discuss the factors that aid in clinical identification of restorations

Radiographs: The shades of gray between the extremes of radiolucency and radiopacity aid in identifying tooth structures and materials, Composites, glass ionomers and ceramic materials are more radiopaque than Enamel, and Amalgam, gold and metals are VERY radiopaque. Visual appearance: Tooth enamel is the only natural material in the oral cavity that is translucent to visible light, Dentin has more color (yellow) and is much more opaque, Considerable efforts have been made to develop tooth-colored restorative materials that transfer light in a manner similar to that of tooth structures, and Ceramic materials and resins can be very difficult to visually detect. Surface smoothness: Exposed tooth surfaces in the oral cavity should feel smooth. A smooth surface is free of irregularities, The Explorer glides freely over surfaces and changes in contour and will not meet resistance, and Less plaque and debris accumulate on smooth surfaces. Sound and touch: When the explorer passes over the surface, it transmits two distinct sensations to the hygienist. Smooth: example - enamel. Rough: example - worn composite restoration. Sound: The tine (sharp point) of the explorer is silent on smooth enamel but scratchy or noisy on rough tooth surfaces, worn composite restorations, and residual orthodontic bonding resin, Produces a "ping" sound .Location: Location can make the identification of tooth-colored restorations difficult and Utilize radiographs and transillumination with the mouth mirror.

What are Giomers?

Relatively new hybrid restorative material. Name is derived from the words "glass ionomer" and "composite" - has desirable properties of each. Release fluoride but less of it and at a slower rate than glass ionomers. Can be recharged with fluoride from toothpaste or mouth rinse to act as fluoride reservoir.

Explain what a digital impression is

Removes many of the requirements and pitfalls of traditional impressions and is a CAD/CAM system

List the three major ingredients in composite resin:

Resin matrix, Filler particles, and Coupling agent.

Discuss the uses of inelastic impression materials

Rigid material used for making impressions primarily related to denture construction, Among the oldest materials in dentistry, Limited to use on edentulous arches

Explain and compare the two types of implant crown retention:

Screw-Retained Crowns: Implant crown is attached to the implant fixture by a small screw, Crowns are retrievable so that the implant fixture or abutment can be evaluated or a repair can be made, Screws may become loose and come out. Cement-Retained Implant Crowns: Crown is cemented to abutment, Permanent cement - crown is not retrievable, Provisional cement - retrievability is possible, Downside is that they may come off unexpectedly.

List and explain the types of endosseous implants:

Screws: Can be placed in smaller sockets and transmit biting force efficiently to the bone, Most Common. Cylinders: Cylindrical shape without screw threads and can be placed easily in the jawbone, Do not show sufficient primary stability because of smaller surface area, so suitable for 2 stage method (covered later). Blades: In the form of plates and can be used in cases with relatively narrow bone width.

List and explain the purposes of the main components in dental amalgam:

Silver-based alloy in a powder form. Mixed with mercury...a liquid metal. Amalgamation is the reaction of the alloy with the mercury as it is mixed. Must be predominately silver 40-70% adds strength, increases corrosion resistance and Setting expansion. Tin 12-30%, causes setting contraction, decreases corrosion resistance, and decreases strength.

Define stress, strain, and ultimate strength:

Stress: The amount of force exerted from within an object. Strain: the amount of change that the force has produced. If the stress within the object cannot resist the force, distortion or deformation occurs and the object is considered strained.

Explain the fabrication of all-ceramic restorations including slip-cast, heat-pressing, sintering and computer assisted machining:

Slip cast: Ceramic powder is mixed with water to form 'slip'. Slip is pressed into a die and the mass is fired to create a porous ceramic core. This core is then infiltrated with molten glass to which conventional porcelains can be added. Heat pressing: Also called 'injection-molding'. Similar to the 'lost-wax' technique used for casting an alloy restoration. Ceramic material is pressed into the mold. High temperature and pressure are used. Sintering: Ceramic particles are heated to the point that they melt and fuse to adjacent particles at their border. Process is done in a vacuum in order to reduce porosity of the final product. Feldspathic porcelain is often used for the sintering process. Computer assisted machining: Various preprocessed ceramic materials are available in blocks for use with CAD/CAM (Computer-Aided Design/Computer-Aided Machining) technology. An optical (digital) impression of the prepared tooth is made and either used in the dental office or transmitted to the dental laboratory.

Define sol and gel

Sol: Liquid in which colloidal particles are suspended; by cooling or a chemical reaction, it can change into a gel Gel: a semisolid state in which colloidal particles form a framework that traps liquid (jell-O)

Describe the three forms of matter and give a defining characteristic of each:

Solid: Primary atomic bonds hold solids together, giving them strength and stability. The most stable have a regular crystalline structure with molecules in a regular spaced pattern. If molecules are arranged in a random form with no regular pattern, the solid is less stable and is called amorphous. Liquid: Molecules in a liquid state are not confined to patterns; they can flow. The movement of a liquid will depend on the characteristics of the liquid and the surface on which it is placed. The viscosity of a liquid is its resistance to flow. Gas: a substance or matter in a state in which it will expand freely to fill the whole of a container, having no fixed shape (unlike a solid) and no fixed volume (unlike a liquid).

Describe the effects of moisture and acidity on dental materials:

Some materials have the undesirable characteristic of water sorption - the ability to absorb moisture; may result in staining or slight enlargement of the material. Metals suffer from the effects of moisture and acidity, except for noble metals - such as gold and platinum. Corrosion: The deterioration or dissolution of the metal in response to a chemical attack (acid), or in an electrochemical reaction with other metals because of the moisture and acid present in the oral environment. Metals such as steel cannot be used in the oral cavity because the metal breaks down in the wet environment, becoming iron oxide (rust). When steel is coated first with a barrier to corrosive components, the barrier gives steel its stainless quality. Dental amalgams are particularly susceptible to corrosion - causing marginal breakdown and discoloration of tooth structures. Corrosion begins with surface tarnish discoloration due to oxidation of the metal's surface.

Describe the basic steps of bonding:

Step 1- proper tooth preparation: essential to achieving a strong bond, plaque and debris must be removed, slurry of pumice, thorough rinsing, tooth must be isolated with a rubber dam. Step 2- acid etching: Acid removes mineral from the surface to create porosities in the tooth (a 'high energy' surface). Increases the ability of liquids to wet the tooth surface. Orthophosphoric Acid-10%-38% solution. Liquid or gel - Liquids are brushed on and gels dispensed with special syringe and needle. Coloring agents are added so that it is easy to tell the etch from the tooth. Step 3- Application of the bonding agent: bonding agents contain two components: Primer and Adhesive. Some current systems are a single-step which simplifies the bonding process. Primer and adhesive are combined in a single component- some also contain the etch. Step 4- depends: Upon what procedure is being done. A composite resin restorative material may be used for a filling. A resin cement may be used to place an indirect restoration- Crown, veneer, inlay or bridge.

Describe the steps for subperiosteal implants:

Step 1: impression of bone. This type of implant is useful for a patient with an atrophic edentulous mandible—severe bone loss, The gums are opened and an impression of the bone is made in order to make the frame. placing frame: The gums are cut open to insert frame over jaw bone and then sutured back together Step 3: placement of tooth. After gums have grown back together and over the frame, place the tooth or teeth onto the implant posts/abutments

Explain the following properties and behaviors of gypsum products - strength, dimensional accuracy, solubility, and reproduction of detail:

Strength and Hardness: Factors that affect strength also affect hardness. Particle shape and Particle porosity. Dimensional accuracy: All gypsum products experience some setting expansion. Related to the growth of crystals as they join. Occurs only during set. Most expansion with plaster (.3%) Least with die stone (.1%)Prevented by strict water/powder ratio. Solubility: Set gypsum is not highly soluble in water. More porosity of material - more solubility. Models shouldn't be soaked for long periods. Anatomic portion should never be soaked. Reproduction of detail: Compatibility of impression material and gypsum material can influence reproduction of detail. Gypsum flows best when there is compatible wetting. Contamination of an impression (blood, food debris or saliva) will affect the surface detail. The greater the porosity of the final gypsum product, the less surface detail is produced. Even products that have the least amount of porosity have microscopic surface irregularities.

Describe zirconia ceramics:

Strongest ceramic materials currently used in dentistry, Have the highest flexural strength and fracture toughness, Twice as strong as the alumina-based ceramics, and Can be used in the anterior and posterior parts of the mouth for single-unit crowns or as cores for three-unit bridge.

List and explain the three possible reasons for adhesive failure:

Structural Failure- Tooth breaks. Adhesive Failure-Tooth and adhesive separate. Cohesive Failure- internal failure of the adhesive layer

Explain and compare the two main types of implants:

Subperiosteal (on the bone): Placed on top of the jaw with metal framework posts protruding through the gum to hold the prostheses, Used for patients who are unable to wear conventional dentures and who have minimal bone height, Fit directly over the remaining bone under the gum tissue. Endosseous/Endosteal(in the bone): Surgically placed INTO the jaw bone, Most common type, Generally used as an alternative for patients with bridges or removable dentures. 3 categories: Screws, Cylinders, Blades.

What is dental cement?

Substances that are placed in the mouth as a viscous liquid and subsequently set to a hard mas. Hard, brittle materials. Powdered oxide or glass mixed with a liquid.

Discuss finishing and polishing procedures

Sufficient amounts of material are removed to reproduce the anatomic contours of the restoration/prosthesis, Finer and finer cuts are then made into the material with diminishing abrasive agents until it takes on a smooth, shiny, mirror-like surface. Care must be taken to consider the anatomic form of the tooth, The finished and polished restoration should have a smooth, continuous line flush with the tooth surface, Contours of teeth must be recreated and should not be flattened or overly rounded

Define creep, corrosion, and tarnish:

Tarnish: An oxidation that attacks the surface of the amalgam and extends slightly below the surface. Results from contact with oxygen, chlorides, and sulfides in the mouth. Dark, dull appearance. It is not very destructive to the amalgam. The rougher the surface, the more it tends to tarnish. Polishing reduces tarnishDone 24 hours later (time for amalgam to fully set). Excessive heat during polishing can cause a release of mercury that results in a mercury-rich surface that will corrode more readily and deteriorate at the surface. Corrosion: Deterioration of a metal due to chemical attack or electrochemical reaction. Can be a chemical reaction between amalgam and substances in food or saliva. Can occur when two dissimilar metals interact in a solution containing electrolytes (saliva). Can also occur within the amalgam due to interaction of metal components. Weakens amalgam over time and can cause staining of adjacent dentinal tubules. This type of corrosion has been greatly reduced by high Cu alloy. Creep: Gradual change in shape of the restorationResults from compression force. Associated with gamma-2 phase seen with low-copper alloys and results in deterioration of the margins. High-copper alloys exhibit far less creep and have superior marginal integrity.

Explain what a high-noble alloy is:

The ADA classifies dental casting alloys according to their noble metal content and divides them into three categories. High-noble alloys - must contain at least 60% by weight noble alloys, of which gold must account for at least 40%. Do not tarnish or corrode very readily in the oral environment. Gold is the most corrosion resistant of the noble metals - has been used in dentistry for centuries. Gold use in dentistry is declining - high cost.

Explain osseointegration:

The attachment of molecules, fibers, cells and tissues to the implant. It is dependent on material biocompatibility, implant surface, bone, surgical technique, healing conditions and biting forces.

Define polymerization:

The chemical reaction that occurs when monomers join together to form polymers.

Describe tooth color in terms of hue, value, and chroma:

Three components of color. Hue - is the dominant color of the wavelength detected. Chroma - refers to the intensity or strength of the color. Value - how light or dark the color is.

Describe glazing:

The final firing of the porcelain at fusing temperature will create a surface glaze. Glazing creates a dense, shiny, smooth surface. Translucent 'overglaze' may also be used during this process. Porcelain stains may be added to the final glaze that mimic surface irregularities of the tooth.

Discuss the qualities of the oral environment that make it challenging for long-term clinical performance of dental materials:

The oral cavity is always in contact with moisture in the form of foods, saliva, and blood. It is changing pH levels constantly throughout the day and for different durations of time. Also encounters fluctuating temperatures.

Define hardness and describe how hardness contributes to abrasion resistance:

The resistance of a solid to penetration. Used to define a materials resistance to wear and abrasion. The hardness of a dental structure or material determines the extent to which it is scratched by an abrasive material. Enamel and porcelain are more resistant to being scratched than are cementum and dentin.

Discuss the safety of amalgam as a restorative material:

The safety has been called into question in recent years - studies have concluded that amalgam is safe for human use. However, a combination of concerns by patients about its safely and its lack of esthetics has prompted many patients to request tooth-colored restorative material.

Define Shelf Life:

The shelf life of a material refers to the deterioration and change in quality of a material over time

Describe microleakage and how the results of this process can lead to recurrent decay and postoperative sensitivity:

The surface between the walls of the tooth structure (preparation) and the restoration is called the interface. If the interface is not sealed, there may be a space - fluids and microorganisms can penetrate between tooth structure and restorative material. This seepage is called microleakage and is responsible for much of recurrent decay, marginal staining, and postoperative sensitivity.

Define viscosity and thixotropic materials and describe the clinical significance of each:

The viscosity of a liquid is its resistance to flow. Thixotropic fluids are liquids that flow more easily under mechanical forces. Thixotropy is the property exhibited by certain materials of becoming fluid when stirred or shaken and returning to the semisolid state upon standing. Fluoride, gels, impression materials, and polishing pastes all have these qualities. It is significant for the materials to act in his way so they can properly do their jobs. For example, fluoride gel needs to be semi solid to stay in the tray but be liquid like to coat the entire tooth.

Define thermal conductivity and thermal expansion and contraction:

Thermal Conductivity - the rate at which heat flows through a material over time. Enamel and dentin are poor thermal conductors, whereas metals are excellent conductors. Gold is one of the best thermal conductors, cements are poor. Poor conductors can be used as restorations or as insulators. With few exceptions, all forms of matter expand when they are heated and contract when cooled, resulting in dimensional change. We need materials that have expansion and contraction similar enough to tooth structures to maintain them within the preparation. Excessive expansion may result in fractures. Excessive contraction may result in leakage of fluids and bacteria into the open gaps.

Describe porcelain veneers and their uses:

Thin layers of esthetic materials that are bonded to the fronts of teeth (like press-on nails). Used to lighten the color of teeth, cover stains or defects, close diastemas, or reshape crooked teeth so they appear to be in proper alignment. Bonded to the teeth with resin cements, using the acid-etch technique, and a resin bonding agent. Most commonly used materials: Directly placed composite resin restorative material and Indirectly placed porcelain/ceramic. Also called 'porcelain laminates' and are More durable than composite veneers.

List and describe the implant materials:

Titanium: Titanium and titanium alloys are the metals most commonly used because of their favorable biocompatibility with oral tissues, Light weight, corrosion-resistant, Great osseointegration. Ceramics and other various materials: Other materials that have been used are ceramics, composites, vitreous carbon, polymers and a variety of metals including gold - limited success, Zirconia ceramics are much stronger and hold up better than older ceramics, Ceramic implants will integrate with the bone more intimately than titanium, however, they have not been used long enough to compare their clinical longevity

Compare total-etch and self-etch bonding techniques:

Total Etch' systems: Very durable bonds, increased possibility of post-operative sensitivity, technique sensitive. Self-Etch systems have the etchant combined with other components of the bonding agent, simplifies the process, less post-operative sensitivity.

Describe the optical properties of ceramics, including translucency, reflectance, opacity and vitality:

Translucency: Allow light to pass through the surface and into the body of the material; some of the light is reflected back out . Glass-based ceramic materials are more translucent than nonglass ceramics - mimic enamel better. Reflectance: The surface of a ceramic material may reflect light that hits it. How much light is reflected is influenced by the surface polish and basic structure of the material. Opacity: Opaque ceramic materials do not allow light to pass through them, Nonglass ceramic materials are the most opaque, and Least esthetic. Vitality: Glass-based ceramic crowns have a more lifelike appearance (vitality) than PFM crowns, They emit light in the visible wave spectrum when ultraviolet light hits them, They are opalescent because they take on a bluish tinge when light reflects off them, and an orange-yellow tinge when light passes through them.

List the factors that contribute to tooth sensitivity after bonding:

Trapped air in dentinal tubules from over-drying, over-etching dentin causes inadequate seal that leaves tubules open, composite resins poorly placed causing leakage, less post-operative sensitivity with self-etch systems.

List and explain the gypsum products and their most appropriate uses:

Type I: Impression Plaster-Rarely used• Type II: Model Plaster (white): Heated in open vats, 115 degrees, Irregularly shaped particles, Beta (β) hemihydrate, Porous, Creates white model plaster, Durable but weak compared to stone categories, Used for diagnostic casts/study models, Least costly. •Type III: Dental Stone (Yellow):Heated at higher temperature, Heated under pressure, Uniformly shaped particles - requires less water, Alpha (α)hemihydrate, Less porous than model plaster, Usually yellow or 'buff' colored, 2.5 times stronger than plaster, Moderately expensive. •Type IV: High-Strength Dental Stone: Produced at pressures higher than those for stone, Subjected to additional grinding, Creates a denser more high-strength stone, Even more regularity to particle shape, Less water required for mixing, Used for working casts and dies, Fabricating wax patterns for cast restorations, Hard, abrasive-resistant surface is necessary to resist the abrasion of sharp instruments used to carve wax on dies, Almost 2 times stronger than type III. •Type V: High-Strength High-Expansion Dental Stone: Also referred to as gypsum-based investment, Addition of silica improves the material's resistance to heat and is the reason the material has increased thermal expansion - needed to compensate for the greater casting shrinkage of the newer base metals used for dental castings, Material is able to withstand very high heat and stress produced during the casting process, Blue or green color, Most costly of all gypsum products.

Define mixing time and working time

Working time: The elapsed time between start of the mix and seating in the mouth. Shorter the working time, the faster it must be mixed and seated. Regular set alginate: 2-3 minutes. Fast set alginate: 1.25-2 minutes

Explain, and compare, the various types of cements (zinc oxide-eugenol cement,zinc phosphate,zinc polycarboxylate, glass ionomer,hybrid glass ionomer, resin-based):

Zinc Oxide-Eugenol Cement (ZOE): Traditional cement used widely for many years, Powder-liquid and paste-paste systems (base/catalyst), Used for temporary cementations and temporary restoration, May be used for intermediate restoration with addition of resin fillers, Traditional cement used widely for many years , Powder-liquid and paste-paste systems (base/catalyst), Used for temporary cementations and temporary restoration, May be used for intermediate restoration with addition of resin fillers. Zinc Phosphate: Oldest of the cements, Long history of clinical success, Not as widely used today , Powder/liquid system, Permanent luting agent, at secondary consistency is a high-strength base, Oldest of the cements, Long history of clinical success, Not as widely used today, Powder/liquid system , Permanent luting agent , At secondary consistency is a high-strength base Zinc Polycarboxylate: First cements to have an adhesive bond to tooth structures (chemical adhesion), Used primarily for final cementation of indirect restorations, At secondary consistency suitable for high-strength bases, Usually called 'polycarboxylate' Glass Ionomer Cements: Introduced in the 1960s, They continue to evolve and are among the most versatile cements in dentistry, Chemically bond to both enamel and dentin, Release fluoride to reduce secondary caries formation, Introduced in the 1960s, They continue to evolve and are among the most versatile cements in dentistry, Chemically bond to both enamel and dentin , Release fluoride to reduce secondary caries formation Hybrid Glass Ionomer: Also called 'resin-modified' glass ionomer, Resin improves bond strength, compressive strength, and tensile strength of the material, Resin is hydroxyethylmethacrylate (HEMA), Decreased solubility—Virtually insoluble in oral fluidsExcellent film thickness, Also called 'resin-modified' glass ionomer, Resin improves bond strength, compressive strength, and tensile strength of the material, Resin is hydroxyethylmethacrylate (HEMA), Decreased solubility—Virtually insoluble in oral fluids, Excellent film thickness, Fluoride release essentially the same as traditional GI, Some setting expansion: Not recommended for permanent luting of ceramic restorations and Less sensitivity post-operatively than traditional glass ionomer Resin-Based Cements: Composite resin, Adhesive resin, Compomer, Essentially modified composite restorative materials that are used for cementation purposes, Strongest, and least soluble, of all the cements. Three types of curing mechanisms: Chemically cured, Light cured, Dual cured

Describe the advantages of high-copper amalgams over low-copper amalgams:

eliminates the tin mercury phase.

List and describe the implant components:

implant Fixture (post), Implant abutment, and Implant Crown (bridge/protheses).

What is the "amalgam war"?

in the mid-1800s, the Society of Dental Surgeons did not want to use shaving from silver coins because the high mercury content was making people sick and tried to pass a law where amalgam was not to be used.

Define brittleness and discuss how this property applies to restorative dental materials:

the hardness, the likelihood of breaking or cracking of material. ceramics and composites are described as brittle because they will sustain little strain before they fracture.

Relate stiffness and proportional limit, and describe how these properties apply to restorative dental materials:

the stiffness of a material is measured by Young's elastic modulus. Stiffer materials have higher modulus - Enamel has a high modulus. Restorative materials should have a modulus that is comparable with tooth structure. Proportional limit is the greatest stress a structure can withstand without permanent deformation. These both apply to dental materials because they need to be stiff, but the proportional limit needs to be known to choose the best material for the patients situation. They both work together.