DHG Test 2

The powder/water ratio for a maxillary preliminary impression in alginate on an adult is:

c. 3 scoops of powder to 3 measures of water.

This type of wax is def to obtain occlusal records

impression wax

Which of the following is a disadvantage of an impression obtained with HC?

lack of dimensional stability

• Impressions give a ___________ reproduction of these tissues

negative

The ___________ representation is the model that is created when gypsum is poured into the impression.

positive

Which type of stock tray would be selected and prepared to cover half of the arch?

quadrant

What is an alginate impression slightly contacts and exudes water, it is termed?

syneresis

Acid Etch:

· Acid etching is the use of acidic substance to prepare the tooths natural enamel for the application of an adhesive · The acid roughens the surface microscopically, increasing retention of a dental resin. · Etching of dental enamel with acid removed the smear layer and opens enamel tubules.

Cleaning of Appliances:

· Brush with an unused brush to clean or place in ultrasonic in a sealed plastic bag with cleaning solution. · Rinse well after cleaning

Protective Barriers

· Cover surface before opportunity for contamination · Barriers may be clear plastic wrap, bags, or tape · Used in combination with surface disinfection · Clean and disinfect surfaces at beginning of day then cover surfaces with barriers · Remove contaminated barriers between patients and replace with clean barriers so that disinfected surfaces remain uncontaminated

Hazard Communications:

· Employee right-to-know · Written program · Identify employees who may be exposed to hazardous chemicals and identify person responsible for program · Describes staff training and how chemicals are handled including the labeling and safety practices in the office. · Describes chemical emergency response to spills and exposures

Acetone and Alcohol:

· Flammable · Use in well ventilated area · Stored in tightly sealed containers

Peforations in trays

• Impression trays are often perforated This allows the alginate to flow through the holes when seated Creates mechanical retention of alginate to the tray

Exposure to chemicals

• Inhalation can cause direct damage to lungs • May be absorbed into circulatory system to organs • Skin Contact - Ingestion

Pattern Wax

• Inlay• Casting• Baseplate

What is a bloodborne pathogen?

• Microorganism in blood or other body fluids (OBF) that can cause disease or illness.Ex: Hepatitis B virus, Hepatitis C virus, HIV • Examples of body fluids - Blood - Semen - Vaginal secretions - Cerebrospinal fluid - Synovial fluid - Pleural fluid - Amniotic fluid - Saliva

Use of Impression Materials - Accuracy

• Need for accuracy may determine the type of material used. For study models a less accurate impression material can be used. For die casts a more accurate impression material must be used.

Disinfection of Appliances:

• Place appliance in zippered plastic bag containing acceptable disinfectant for the time required by the manufacturer • Thoroughly rinse as soon as it is removed from disinfectant • The disinfectants taste bad and can irritate tissues • Store appliance in a clean, zippered bag containing mouthwash and water or just water alone.

PPE eye protection

• Place side shields on glasses to protect against aerosol, splatter, projectiles, hazardous chemicals. • Patient should also wear safety goggles; if non-disposable then disinfect between patients Additional: Filtered eye protection when using curing light

Inelastic impression materials

• Plaster: Rarely used for impressions • Impression Compound (Dental Compound): composed of 40% resins, 7% waxes, 3% organic acids + 50% fillers • ZOE: Zinc oxide-eugenol paste; will be discussed in Cements

Risk of infectious diseases

• Precautions to protect against infectious diseases • The Standard for Occupational Exposure to Bloodborne Pathogens established by Occupational Safety and Health Administration (OSHA) • OSHA makes rules for employee safety in the workplace to prevent deaths, injuries and illnesses related to work.

Agar

• Reversible hydrocolloid, sets thermoplastically (physical reaction). • Exhibits hysteresis which is the property of a material to have two different temperatures for melting and solidifying. Water, for example, has one temperature for both. • Works well in wet environment

PPE

• Single use, nonsterile disposable exam gloves when you are likely to encounter blood or OBF o Assisting w/personal careo When obvious blood is present o Care giver has broken skino cleaning up spills (Blood or OBF) • Remove gloves prior to touching non-contaminated surfaces • Remove gloves after use and wash hands thoroughly

Disinfection by Spraying:

• Spray rinsed impression with acceptable disinfectant • Seal in a plastic bag for manufacturer's recommended time • Remove from sealed back • Rinse with water and shake to remove excess water Cleaning and Disinfection of Oral Appliances of Dentures:

Plastic Trays

➢Disposable and therefore easy for disinfection ➢Inexpensive ➢Do not support the impression material as well and can be distorted ➢Can be heated and adapted to patient's mouth

Custom Trays

➢Used when the most accurate impressions are needed ➢Made using a working model of the patient's mouth ➢Fabricated using acrylic or resin

When mixing alginate material:

Add the powder to the water

Managing Aerosol and Splatter

Aerosol and splatter in dentistry is inevitable, but we can take measures to decrease the presence of excess microorganisms. 1. Dental dam 2. High speed evacuator 3. Pre-treatment mouth rinse: These decrease the microorganisms intraorally for a short period of time. 4. Pre-treatment toothbrushing with ADA approved paste

Some hydrocolloids require extensive equipment. A water bath (called a storage bath) is used for which hydrocolloid material?

Agar

reversible hydrocolloid

Agar

This is the most widely used irreversible hydrocolloid for preliminary impressions

Alginate

The best way to alter the setting time of alginate is:

Alter the temp of the water

An impression material should be mixed:

Always mix all dental products according to the manufacturer's instructions.

Addition Silicones

Most popular of non-aqueous elastomeric impression materials Used for crown and bridge procedures Clean and do not have an unpleasant taste or smell Addition silicones are the most accurate, stable and expensive of all impression materials. Also called vinyl polysiloxanes and polyvinylsiloxanes (PVS) Allow for more than one pour in gypsum stone

This type of wax is used to modify the shape of impression trays, cushion braces and to help in repairing fractured dentures.

Processing wax

Infection Protocol for Grinding or Polishing Dentures and Oral Appliances:

Prosthesis or Dental Appliance Chairside Adjustments Clean before disinfecting Rinse Disinfect Rinse Store in clean plastic zipped bag with mouthwash and water

Agar equipment

Requires special equipment which takes up a lot of room

Types of Hydrocolloid Impression Materials

Reversible Hydrocolloid• Example is agar• Undergoes a physical setting reaction Irreversible Hydrocolloid• Example is alginate• Undergoes a chemical setting reaction

The following is/are examples of aqueous elastomeric impression materials:

Reversible and Irreversible Hydrocolloids

Care of Finished Impression

Rinse impression again gently with water after appropriate disinfection time period; gently shake off excess water. Wrap with damp paper towel and place in sealed plastic bag. Place tray side down on a flat surface. • Pour impression with gypsum as soon as possible • If not poured immediately, 100% relative humidity for storage

Which of the following procdures should be followed after an alginate impression is removed from a patient's mouth?

Rinse the impression with tap water and spray with disinfectant.

Metal Trays

Stiff so provide the most accuracy and support ➢Reusable ➢More expensive ➢Require sterilization after every use. ➢Can not be adapted to patient's mouth

Composition of alginate powder

Supplied as powder and mixed with water Potassium alginate - carbohydrate powder that dissolves in water to form sol; derived from algae Inert filler - typically silica, which gives the mixed material body and helps prevent it being runny Other additives - such as reactors, retarders, colors, and flavors

Introduction to Elastomerics

There 4 commonly used types. They are named based on their polymerization chemistry .➢Polysulfide ➢Condensation Silicone ➢Polyether ➢Addition SiliconeHave similar, but not identical, mixing and handling properties Require adhesives to be painted on the tray, even if the tray is perforated

The powder/water ratio for a mandibular preliminary impression in alginate on an adult is:

2 scoops of powder to 2 measures of water.

The setting time for regular-set (or normal-set) alginate is _____________.

2 to 4.5 mins

Impression Waxes: Correction Waxes

Easy way to quickly correct areas in the mouth for impressions Can correct air bubbles or defects in stone models

Impression materials are categorized as either:

Elastic or Inelastic

Impression materials that have mechanical properties permitting considerable elastic deformation but that return to their original form are classified as:

Elastomeric

Impression materials that have mechanical properties permitting considerable elastic deformation but that return to their originial form are classified as:

Elastomeric

Pattern Waxes: Casting Waxes

Form wax pattern for metal framework of partials and full dentures.

List the four most common types of non-aqueous impression material.

Polysulfide, Condensation Silicone ,Polyether ,Addition Silicone

The two types of elastic impression materials are called:

The two types of elastic impression materials are aqueous elastomerics and inaqueous elastomerics.

Environmental Effects On the Alginate

Water-based material that will gain moisture from the environment - imbibition Can lose water to the environment - syneresis

Which type of tray is designed to fit a specific patient?

custom tray

All of the following statements are true about the "working time" of alginate material except one. Which one is the EXCEPTION?

d. Working time begins when the the impresion is seated.

Stock Trays

➢"Off the shelf" ➢Come in many different shapes and sizes ➢Specific trays for edentulous, partial edentulous, and mouths with all teeth ➢Can be metal or plastic

Disinfection by immersion is preferred over disinfection by spraying. The most important reason is because:

Constant contact of the spray with all surfaces of the impression can only be assured with immersion

When considering elastomeric materials

Dimensional stability - ability of material to keep its shape after it has been removed from the mouth Deformation - ability of material to resist permanent change by stresses during removal from the mouth Permanent deformation - material changes and will not regain its previous shape

Putty System

High viscosity material that is used with a low viscosity material -It enable the low viscosity material to be forces around the teeth -Two colored materials are scooped and then kneaded together -Do not use latex gloves - only nitrile or vinyl gloves

Use of Impression Materials - Elasticity

Impression materials are either flexible (elastic) or rigid (inelastic) upon removal from the mouth Mouths with teeth have undercuts and require elastic impression materials Edentulous mouths may use elastic or inelastic impression materials.

Use of Impression Materials - Flow

Impression materials come in many different viscosities • Examples (from low viscosity to high) are light-bodied, medium-body, heavy- body, and putty • Light bodied impression material are used with an injection syringe and placed directly on the tooth to achieve the most accurate detail. • Putty materials are the thickest impression materials. They are used when it is important to prevent running or dripping of the impression material.

Alginate-Uses

Impressions to be poured to make: • study models• opposing arch impressions • articulation• athletic trays

Which of the following materials is an example of an aqueous elastomeric?

Irreversible HC

Why use Elastomerics?

More stable than hydrocolloids More expensive than hydrocolloids As a group, non-aqueous elastomerics are strong, flexible, dimensionally stable, and accurate.

About Alginates:

*Always follow manufacturer's instructions Setting time is dependent on type of alginate, water temperature. Strength depends upon thoroughness of mix and rate of deformation. Alginate should set completely before removal from the mouth. Accuracy is best when stored at 100% humidity for no longer than a 1⁄2 hour to 1 hour.

Repairs/ Adjustments of Dentures or Appliances

- Clean and disinfect before sending to the lab for adjustments - Clean and disinfect in the lab before returning to the dental office - Disinfection of Items Used - All items that encounter oral tissues or touch objects that encounter oral tissues must be heat sterilized. - Includes items such as metal impression trays, burs, rag wheels, disks, metal spatulas, etc.

Hazard vs Risk

- Hazard- something that can harm - Risk - probability of harm - Safety - probability of no harm

Office and Lab Housekeeping:

- No eating, drinking, make-up, or lip balm application, removing or applying contacts where patients are treated, in the dental lab, or in sterilization area. - No food or beverage storage where dental products or hazardous or infectious materials are stored - All infectious wastes disposed according to local, state, federal regulations.

Types of Impression Trays

- Stock - Custom -Special use Tray

Standard Precautions

-Every person should be treated as though they have an infectious disease. -PPE and protective barriers will inhibit transmission of the infection from chemical or physical hazards -Hand washing -Facial Masks/Shields -Eye protection -Protective gowns -Sterilization/Disinfection/Managing Splatter -Safe Handling and Appropriate Waste Disposal -Proper cleaning of contaminated areas -Managing aerosols and splatter

Techniques of mixing elastomerics

-Paste system -Automix system - Mixing unit system -Putty system

Bite Registration

-Produce a reproduction of a patients bite

Condensation SIlicones

-Second non-aqueous elastomeric developed for dentistry -Based on silicone rubber Hydrophobic -Cleaner materials to use than polysulfides, but it is hard to pour models without voids -Must be poured as quickly as possible Not as popular as other similar products

Polyethers

-Working time and setting time are shorter than polysulfides -Very stiff and set quickly - usually use a disposable, plastic tray -Also very clean material but have unpleasant tasteVery accurate and easy to pour with gypsum products -Higher cost Impregum is the most popular polyether productSingle viscosity

What is used to ensure that alginate material has mechanical retention to the impression trays?

. Perforations in the tray

Study models are used by:

. as reference in orthodontic cases. b. to show size, shape and position of teeth. c. as an aid in treatment plans

The typical mixing time for alginate is _____________.

1 min

The typical mixing time for alginate is ___________. and the setting time for regular-set alginate materials is ______________.

1 minute; 3 to 4 minutes

The setting time for fast-set alginate is ____________.

1 to 2 minutes

Aqueous Elastomeric Impression Materials

1. Reversible Hydrocolloid 2. Irreversible Hydrocolloid

Alginate Types:

Available in two setting types. Setting refers to the working time and the setting time. Fast Set: gels in 1 to 2 min. after beginning of mix • Normal Set: gels in 2 to 41⁄2 min. after beginning of mix

Processing Waxes: Sticky Waxes

Becomes sticky when heated, Used to attach fractured parts of dentures and holding two pieces together of an oral appliance until they can be repaired.

Special Tray Examples

Bite Registrations - help relate upper and lower models properly Triple Tray - used with dual- arch or closed-mouth impression technique ❖Tray is loaded on both the top and bottom ❖Seated on the arch with the prepared tooth ❖Patient then closes their teeth together ❖Captures an impression of the prepared tooth, the opposing teeth, and the bite registration all at the same time.

Alginate impression material is:

Easy to use.

Processing Waxes: Boxing Waxes

Boxes in the impression tray to assist in model preparation.

A triple tray used with the dual-arch or closed-mouth impression technique. It is:

Captures an impression of the prepared tooth, the opposing teeth, and the bite registration all at the same time

Which wax is considered a pattern wax?

Casting

All but one of the following steps must be performed when disinfecting a removable dental appliance before making laboratory adjustments. Which one is the EXCEPTION?

Clean ultrasonically by placing the appliance directly into the solution in the ultrasonic unit holding tank

Important points

Clean up ASAP or wait until set Most of these impression materials are hydrophobic hydro = "water"; phobic = "hating" They will not flow in areas of moisture so must have a dry field for the impression.

Mixing of Non-Aqueous Elastomeric Materials

Come in two pastes which are different colors All (except for putty) are mixed together like polysulfides Instead of manually mixing, many are supplied in double-barreled cartridges which are placed in an "automix" gun The automix gun forces the two pastes together and out through a spiral-shaped baffle tip Working times and setting times vary according to manufacturer

Hazard Communications Employee Training:

Employee Training for: • Every new employee hired• New chemicals introduced into the office • Once a year and record kept for 5 years Training should include: • The use of hazardous chemicals• All safety practices• Required PPE• Safe handling and disposal methods Hazard Communications - SDS Sheets - SDS for every chemical - Inventory of hazardous chemicals - Proper labeling

A common use for impressions might be to:

Fabricate a crown or bridge.

Alginate material reproduces very fine details in casts. It is the preferred material to use when pouring up die casts.

False

All impression materials are compatible with all model materials. Because there are so many impression options, understanding the reason for the impression is not important.

False

Plastic trays can be sterilized and reused on different patients.

False

Normally non-aqueous elastomeric impressions are used for preliminary impressions and hydrocolloid materials are used for final impressions.

False Normally hydrocolloid impressions are used for preliminary impressions and non-aqueous elastomeric materials are used for final impressions.

Aqueous Elastomeric Impression materials are also known as hydrocolloids. "Hydro-" means gelatin and "Colloid-" means water

False Aqueous Elastomeric Impression materials are also known as hydrocolloids. "Hydro-" means water and "Colloid-" means gelatinous substance.

Alginate has three setting types - very slow setting, slow setting, and medium setting alginate.

False-Alginate has two setting types - normal and fast-setting alginate.

Is is preferable to remove alginate impression right before that completely set

False: Alginate impressions should not be removed from the mouth until they have completely set.

Alginate is one of the most expensive impression materials, and it records very fine details.

False: Alginate is one of the least expensive impression materials, but it does notrecord very fine details.

Normal set alginate will set within one min in the mouth

False: Fast Set: gels in 1 to 2 min. after beginning of mix Normal Set: gels in 2 to 4½ min. after beginning of mix

Some qualities of a metal tray are (more than one answer may be correct):

Feedback: Metal trays are a good choice for impressions. They are stiff and support the impression material, providing the most accuracy and stability. They can be reused once they are sterilized. Most trays are perforated which allows for mechanical retention of impression material. Unfortunately metal trays can not be adapted to fit every mouth and sometimes they will not work on certain patients.

Non-Aqueous Elastomeric Impression Materials: Final Impressions

Final impression materials are used to take impressions needed for pouring accurate working casts. The impression materials most commonly used are non-aqueous elastomerics. These impression materials are also known as or elastomers.

Polysulfides

First non-aqueous elastomeric developed for dentistry Often called "rubber base" materials Supplied as two pastes in tubes - catalyst is usually dark brown; the base is usually white Two pastes are dispensed in equal lengths on a paper mixing pad and a spatula is used to mix the two pastes together. Mixed material is loaded into a tray

What impression material will the dentist apply directly to a prepared tooth for a final impression for a crown?

Light Bodied material For a final impression of a crown preparation, a light-bodied material will be applied directly to the tooth which was prepared for the crown. This is because light-bodied material has a low-viscosity and records very fine detail. Putty and heavy-bodied material may be used in combination with light-bodied material to give the impression support and it forces the light-bodied material around the tooth or teeth of interest. Alginate would not be used for a final impression.

Viscosities of Addition Silicones

Light body ,Medium body Heavy body ,Monophase, Putty

List the five types of viscosities seen in addition silicon materials:

Light body, Medium body, Heavy body, Monophase, Putty

List two things to do to help decrease gagging during impressions.

Make sure the mix is not to thin Work with patient of stress reduction protocol

Properties of Dental Wax

Melting Range: Not a melting point Flow: Movement of wax as it approaches the melting range; distortion occurs at relatively low temperatures due to flow. Thermal Expansion: Waxes have high coefficient of thermal expansion. They expand when there is an increase in temperature and contract when there is a decrease. Uniform cooling is important. Strength: Easily deformed (very weak) Abrasion resistance: Low

The most hazardous form of mercury encountered in a dental office is:

Mercury Vapor

Stock impression trays are made of the following material:

Metal and plastic

Impression Tray Materials

Metal or Plastic

Properties of polysulfides

Much more accurate than alginate Can be used to take impressions needing finite detail such as crowns, inlays, and bridges. Today are sometimes used for final impressions for dentures. Least accurate of the non-aqueous elastomeric impression materials Should be poured within several hours after mixing Recommend to use with custom tray "Disagreeable" smell and tasteCan stain clothing Longest working time of any elastomeric impression material (4-6 minutes) Longest setting time. Must stay in the mouth for 10-15 minutes. Hydrophilic but only used for a single pourUse with full denture impressions

Exposure Control Plan:

Must be written -Includes all steps for each dental procedure performed to prevent exposure to blood-borne pathogens. -Includes protocol to follow if exposure to blood-borne pathogens occurs -Must be updated annually Employees must be familiar with this plan and review it annually

An impression is a _______________ reproduction of the patient's mouth.

NEGATIVE

Selection of Impression Material

Not all impression materials are compatible with all model materials Wide variety of impression materials are available • Understanding the reason for the impression will help to determine the type of impression materials needed.

Infectious Diseases

Nothing is completely safe ➢ Wash hands, cover our nose and mouth when sneeze, masks

Mandibular Impression Process :Part 1

Operator should be standing in 7 o'clock position if right-handed and 5 o'clock if left-handed. The dental chair should be raised for easy access to the patient. • Adjust the headrest so that the occlusal plane is parallel to the floor. • Using a 2x2 gauze or the air syringe. Dry the patient's teeth as thoroughly as possible to remove excess saliva. Ask patient to open his or her mouth. Using the index finger or one hand, retract the patient's cheek. With the other hand, rub a small amount of alginate material over the occlusal and interproximal surfaces of the mandibular teeth. *This reduces air bubbles* • Grasp the handle of the impression tray so that the tray faces downward. • Rotate the tray into the mouth by using the front of the tray to retract the near cheek and your free hand to retract the far cheek. • Grasp the handle of the impression tray so that the tray faces downward. • Rotate the tray into the mouth by using the front of the tray to retract the near cheek and your free hand to retract the far cheek. Once the tray is inserted, straighten it so that the tray handle is in line with the patient's midface. Note the position of the anterior teeth in relation to the tray.

List the four techniques used for mixing non-aqueous elastomeric materials.

Paste system, Auto mix system ,Mixing unit system, Putty system

This type of wax is used to fabricate wax patterns of crowns, bridges, and inlays, to build contours of a denture, and to hold denture teeth in position.

Pattern wax

Tray selection impacts the support of the material and the accuracy.

TRUE

Preliminary Impressions

Taken to create a reproduction of the teeth or oral tissues Examples of use: Study models and working casts

When taking a maxillary impression, a right-handed operator should be standing in which position?

The 11:00 position gives the right-handed operator the best access for a maxillary impression

When taking a maxillary impression, a left-handed operator should be standing in which position?

The 1:00 position gives the left-handed operator the best access for a maxillary impression.

When taking a mandibular impression, a left-handed operator should be standing in which position?

The 5:00 position gives the left-handed operator the best access for a mandibular impression.

When taking a mandibular impression, a right-handed operator should be standing in which position?

The 7:00 position gives the right-handed operator the best access for a mandibular impression.

Why is it necessary to "Fluff" alginate before scooping it out of the container?

The dental assistant fluffs the alginate to make sure it hasn't settle which could make measuring inaccurate

If a patient would like their denture polished, the denture is first cleaned and disinfected before polishing. The rag wheel used for polishing appliances and dentures can be left on the lathe and only needs to be sterilized once a week.

The first sentence is true; the second sentence is false. Rag wheels should be sterilized after each use, and a new, sterilized rag wheel should be used with each patient's denture. The denture is first cleaned and disinfected before it is polished.

With alginate, the mandibular tray is loaded in 3 increments. The maxillary tray is loaded in 1 increment.

The first statement is false; the second statement is true. With alginate, the mandibular tray is loaded in 2 increments. The maxillary tray is loaded in 1 increment.

Addition silicones are the most popular type of non-aqueous elastomeric impression materials. The reason is because they do not cost very much

The first statement is true; the second statement is false. Addition silicone impression materials are the most popular non-aqueous elastomeric impression material, but they are also the most expensive. The ease of use and the excellent characteristics and properties is the reason for their popularity.

Maxillary Impression Process

The operator should be standing in 11 o'clock position if right-handed and 1 o'clock if left-handed. The dental chair should be raised for easy access to the patient. Adjust the headrest so that the occlusal plane is parallel to the floor. Using a 2x2 gauze or the air syringe. Dry the patient's teeth as thoroughly as possible to remove excess saliva. • Ask patient to open his or her mouth. Using the index finger or one hand, retract the patient's cheek. • With the other hand, rub a small amount of alginate material over the occlusal and interproximal surfaces of the maxillary teeth. *This reduces air bubbles* • Grasp the handle of the impression tray so that the tray faces upward. • Rotate the tray slightly to the side to begin to place the tray into the patient's mouth. Use the front of the tray to retract the near cheek and your free hand to retract the far cheek. • Once the tray is inserted, straighten it so that thetray handle is in line with the patient's midface. • Note the position of the anterior teeth in relation to the tray. • Begin to apply light and even pressure upward until resistance is felt. • Seat the tray in the posterior region, and then seat it in the anterior, allowing the alginate to flow over the molars. Retract the patient's upper lip as the tray is seated. This allows excess alginate and air to be expressed and minimizes bubbles. Excess alginate will also flow through the perforations. Massage and gently pull the patient's cheeks to release air and to capture the vestibule of the maxillary arch. Instruct the patient to breathe normally through his or her nose and to lean slightly forward. Keep the tray in place until alginate is completely set.

Why wold you select a fast set alginate when taking a preliminary impression?

The patient has a strong gag reflex

List the four things discussed to use when assessing the proper fit of an impression tray.

The tray needs to be able to extend facially to include all teeth as well as musculature and vestibule. The tray also needs to extend distally to approximately 2 to 3 mm beyond the last tooth in the arch. This includes the retromolar area in the mandibular arch. The operators needs to allow 2-3 mm depth of alginate beyond the occlusal surface and incisal edge. For accuracy, the alginate must be tightly adapted to the tray. If alginate pulls away from tray after set, distortion will occur. The tray ultimately needs to be comfortable to the patient.

By OSHA mandate, the dental care provider must wear appropriate PPE (gloves, mask, eye protection, and clothing) during patient care involving contact with blood and saliva. This PPE should be worn only in the clinical treatment area.

True

Custom impressions produce the most accurate reproduction of the teeth and oral tissues. They are used to create casts for fabricating indirect restorations and full or partial dentures.

True

Custom trays are made on a model of the patient's arch. Therefore, to make a custom tray, an impression with a stock tray is needed to be completed first.

True

Hands should be washed before putting on and after removing gloves. If not visibly soiled and for nonsurgical procedures, hands may be cleaned by applying an alcohol-based solution and rubbing the hands for 15 seconds until the agent is dry.

True

Immediately after an impression is taken, it must be rinsed under running water to remove saliva or blood. This step is essential before the impression can be disinfected.

True

Several chemicals used in the dental office penetrate latex gloves. Information on the proper protective gloves may be found in the SDS.

True

Surface disinfection occurs after an intermediate-level disinfectant is sprayed onto a surface and allowed to air dry. Disinfection, however, is not effective unless that surface is first cleaned properly.

True

The alginate impression should be poured up as soon as possible or stored for a limited time in 100% relative humidity.

True

The setting time of alginate depends on the water temp and type of alginate

True

When using alginate impressions, all models and casts should be only poured in gypsum products.

True

Processing Waxes: Utility Waxes

Used to modify the shape of impression trays and cushion braces

Impression Waxes: Bite Registration

Useful to obtain occlusal records

Final Impressions

Usually taken by the dentist and are used to produce the most accurate reproduction of the teeth and oral tissues. Examples of use: Creating casts for fabricating indirect restorations and full or partial dentures

The disadvantages of using hydrocolloid materials is that:

Water easily evaporates if left in open air for too long Impression will shrink if left out too long The contract slightly after setting = syneresis Impression materials absorb water and swell (imbibition) which is important when disinfecting

loading mandibular tray

Wipe alginate mix into one mass on the inside of the bowl Gather half of the mix onto the spatula and wipe alginate into one side of the mandibular tray from the lingual. Press material to base of tray. Gather the remaining half of the alginate in the bowl onto the spatula; then load the other side of the tray in the same way. From anterior to posterior, smooth the alginate by wiping a moistened finger along the surface, beveling material toward the posterior.

Loading Maxillary tray

Wipe alginate mix into one mass on the inside of the bowl The maxillary tray is loaded in one increment. Gather all the mix onto the spatula and wipe alginate to fill the tray from the posterior. Place the bulk of the material in the anterior palatal portion of the tray. Moisten fingertips with tap water and smooth the surface of the alginate.

All of the following statements are true about the working time of alginate except for one. Which one is the EXCEPTION?

Working time begins when the impression is seated.

The following are ideal or desirable characteristics for impression materials (more than one answer may be correct):

a. Easy to manipulate b. Minimal equipment required d. Reasonable cost e. Biocompatibility g. Pleasant taste and smell h. Low stability and accuracy

alginate powder is composed of:

a. Potassium alginate b. Inert filler (usually silica) c. Additives such as reactors, retarders, colors, and flavors

The following are impressions that can be taken during a dental procedure

a. Preliminary Impressions b. Final Impressions c. Bite Registrations

The goal(s) of infection control when handling and disinfecting impressions, dentures, and appliances is/are to:

a. Protect the patient from microorganisms obtained from the laboratory b. Protect the laboratory personnel from the patient and any illness that could be transmitted. c. Protect laboratory equipment from contamination

The brown paste used in rubber base is called the

accelerator

The impression material that can be changed back and forth from gel to sol to gel to sol to gel is:

agar

The organic substance of irreversible HC material is:

algae

The material that changes from sol to a gel by chemical reaction is:

alginate

Which sets by gelation only?

alginate

Which delivery system for impressions mixes the impression material for you, ensuring that it is thoroughly mixed?

automix system

Inelastic impression materials are very flexible. Examples of inelastic impression materials are plaster, impression compound, and ZOE.

b. The first statement is false; the second statement is true.

Which wax is considered a Impression Wax

bite registration

Which type of impression type is used to provide a replica of the occlusal relationships of the teeth?

bite registrations

Which wax is considered a processing wax?

box

SDS

· Manufacturers usually send a Safety Date Sheet (SDS) with products which meet definitions of hazardous materials. · Formerly known as Materials Safety Data Sheets (MSDS) Lists the following information: • Product identification • Hazardous ingredients (not all ingredients) • Composition/information on ingredients • First Aid measures • Fire/explosive hazard data • Accidental release measures (spill/leak clean up) Lists the following information: • Handling and Storage • Exposure Control/PPE • Physical & Chemical Characteristics • Stability & Reactivity data • Toxicology Info (Health hazard data) • Special precautions (ecological info e.g. environmental) • Disposal Info There should be an SDS sheet on file for all hazardous products in the dental office. Dental personnel should know where the SDS sheets are stored.

PPE: Face Masks/ Shields

· Must be worn during any treatment that splatter or aerosol is created · Change mask for each patient because outer surface becomes contaminated · May need to change during treatment if mask becomes wet from exhaled air · Standard face masks protect from 95% of small particles · Face shield protects from splatter but not aerosol

Disinfections of Impressions:

· Once impression is taken and removed from the oral cavity, gently rinse with water and shake to remove excess water. · Techniques for disinfection ❖Immersion ❖Spraying with appropriate disinfectant · After disinfection, pour the impression or send impression to the dental lab • May be placed in a sealed bag containing appropriate disinfectant • Time is specified by the manufacturer of the disinfectant • Remove, shake, and pour impression or send to the lab • NOT for alginate

physical injuries

· Trips, slips, spills · Lifting · Lathes · Model trimmers · Burns, cuts, fire · Electrical hazards · Hearing protection · Respiratory hazards · Skin hazards

Mercury Safety: up

· Work in well ventilated space · Avoid direct skin contact, wear gloves · Store in unbreakable, tightly sealed containers · Store away from heat · Salvage amalgam scrap in a closed container · Clean up spilled mercury with a mercury clean up kit Precautions when handling: 1. Handle according to manufacturer's instructions 2. Avoid skin contact 3. Minimize chemical vapor 4. Close containers tightly 5. No eating, drinking, or smoking in lab 6. Wear protective eyewear, gowns, and masks 7. Follow proper cleanup procedures. 8. Dispose in accordance with SDS instructions and federal, state, and local regulations.

Semi-critical instruments

· ➢Heat sterilization or chemical liquid sterilization · ➢These are high level disinfectants · ➢Heat sterilization is preferred · ➢Chemical liquids such as glutaraldehyde, hydrogen peroxide, or peracetic acid may be used · ➢Radiology film holders, shade guides, mouth props - items which contact but do not penetrate mucous membranes

Important things about mixing alginate

• Alginate is fluffed because the material tends to settle possibly making measuring inaccurate. • Mixing order is important. Adding powder to water ensures the powder particles are wet evenly. If the order is reversed, the chemical reaction starts to quickly causing some particles setting faster than others. • Alginate should be mixed completely. Inadequate mixing causes the mix to contain air bubbles and gives it a grainy texture.

PPE: Handwashing

• Before non-surgical procedures, prior to placing gloves, and after removal of gloves • Wash (preferably with antimicrobial soap) for at least 15 seconds, rinse, and dry • Alternative: 60%-95% alcohol-based ethyl alcohol products that are rubbed into the hands for at least 15 seconds until dry ➢ NO VISIBLE contamination or hands not soiled otherwise

Impression

• Bite Registration • Correction Wax

Utility gloves

• Both OSHA and CDC indicate that utility gloves should be worn when processing contaminated instruments and performing housekeeping duties and tasks involving chemicals. • Heavy duty utility gloves offer significant protection against both percutaneous injury and chemical exposure.

Processing wax

• Boxing• Utility• Sticky Wax

Overgloves

• By slipping on the overgloves duringa patient's treatment, the healthcare worker is free to touch anything in the work area where the patient is being treated without contaminating other objects. • They can be removed, and the operator can return to the patient still wearing the tight-fitting patient gloves • Overgloves maintain the protective barrier desired without having to deglove.

Evaluating Mandibular Impressions

• Centered over incisors with peripheral roll • Should not be "overseated" • No tears or voids • Frena • Mucobuccal Attachments • Retromolar Pads • Tongue space present • Mylohyoid Ridge • All existing teeth in the arch or quadrant

Evaluating Maxillary Impressions

• Centered over incisors with peripheral roll • Should not be "overseated" • No tears or voids • Frena • Mucobuccal Attachments • Incisive Papilla • Hard Palate • Tuberosities • All existing teeth in the arch or quadrant

properties of alginate

• Ease of manipulation • Minimum equipment needed• Flexible impressions • Low cost • Model and die material restricted to gypsum • Least accurate of all impression materials; will not record fine detail

Mercury (Hg)

• Form used in dentistry and in dental amalgam is intermetallic compound with low or no toxicity • Metallic or elemental mercury can vaporize - risk of being inhaled • As a liquid mercury can be absorbed through skin • Chronic Hg toxicity affects central nervous system causing muscle tremors, irritability, mouth inflammation, decreased kidney function

Special Use tray types

• Full Arch• Quadrant• Section (Anterior or Poster) • Sideless

PPE:Attire

• High neck, cover arms, length that covers street clothes • Disposable or reusable • OSHA mandates no contaminated reusable attire can be laundered at home • Should only be worn in the clinical area

Impression Material Systems

• Impression materials are always mixed to make a thick paste or liquid. • Loaded into an impression tray, placed in a patient's mouth, and seated onto the oral tissues of interest. • The tray functions as a carrier and stabilizes the impression material.

Instruments Sterilization and Surface Disinfection:

• Sterilization is a validated process that destroys all forms of microbial life. The term is intended to convey an absolute meaning, although the probability of the presence of pathogenic and other organisms can never be reduced to zero. • Disinfection defines a process that is less lethal than sterilization. Disinfection destroys some, but not all recognized pathogens, and it does not predictably eliminate bacterial spores

Alginate Handling Guidelines:

• Store in cool, dry place • Keep container lid on tightly • Use masks and safety glasses to protect against dust fumes.

Hydrocolloid Impression Materials

• These materials change from a liquid state to gel • The phases are called Sol - the liquid or suspension phase where the materials are mixed together Gel - the semisolid, rubbery phase • The setting process of a sol becoming a gel is called gelation

Infection Control

• Universal Precautions - Practice of avoiding contact with blood and other body fluids (OBF) by wearing gloves, goggles, etc. This term has been replaced with • Standard Precautions: Precautions designed to prevent transmission of bloodborne pathogens and other body fluid pathogens by considering that all patients and materials are potentially infectious

Pattern Waxes: Baseplate Waxes

• Used to build contours of a denture and hold denture teeth in position. • Also used for spacers and bite registration.

Use of Impression Trays

• Used to carry impression material to the mouth• Handle is used to remove tray from mouth• Impression trays are made in all different shapes and sizes• Tray selection impacts the support of the material and the accuracy.

Pattern Waxes: Inlay Waxes

• Used to fabricate wax patterns of crowns, bridges, and inlays• Wax is melted, added to die, and carved into a tooth structure to match the existing dentition • Then it is invested, heated, melted away, and liquid metal fills the space the wax has left

Impression Materials

• Used to make replicas of teeth and other oral tissues • Purpose is to record the dimensions of the oral tissues and their spatial relationships to fabricate a model of the mouth.

Mandibular Impression Process: Part 2

• Using the index fingers of both hands, gently press the tray downward over the teeth until resistance is felt. • The patient's lip and cheek should lap over the tray, allowing the excess alginate to fill the periphery. • Excess alginate will also flow through the perforations. Massage the patient's cheeks to release air and to capture the vestibule of the mandibular arch. Ask the patient to raise their tongue to the roof of their mouth and move it from side to side. Then have the patient gently close their mouth to relax the tongue and cheek muscles. Instruct the patient to breath normally through his or her nose. Keep the tray in place until alginate is completely set.

Disposable Items

• Usually made from inexpensive materials such as plastics • Designed for one-time use and discarded. • Saliva ejector, evacuation tip, air water syringe, treatment gloves, gowns, surface covers, face mask, syringe needles • NEVER reuse disposable items

Cleaning and Disinfecting:

• Visible soil on instruments interferes with microbial inactivation during sterilization and disinfection processes. • Cleaning is the removal of visible soil and is typically accomplished using water and a detergent or an enzymatic product to remove contaminants. • Detergents are compounds with both hydrophilic and lipophilic parts - the term "soap" is often used to refer to such products. • An acceptable surface disinfectant must be tuberculocidal and kill both hydrophilic and lipophilic viruses

Disadvantages of Hydrocolloids ( due to high water content)

• Water easily evaporates if left in open air for too long • Impression will shrink if left out too long• Contract slightly after setting = syneresis • Impression materials also absorb water and swell (imbibition) which is important when disinfecting

Acid Etch material safety:

• Wear protective gloves and clothing and use eye and face protection. • If swallowed, rinse mouth with water • In case of skin or eye contact - rinse with large amount of running water

Advantages of Hydrocolloids ( due to high water content)

• Wet tooth surface that is contaminated by oral fluids• Traps fewer bubbles because they will absorb some liquid • Easy to pour with gypsum products• Hydrophilic - meaning "water loving"

Custom Tray uses:

• full dentures • some removable partial dentures • indirect restorative procedures (crowns, bridges, implants, etc.)

The advantages of using hydrocolloid are the following:

•are able to wet tooth surface that is contaminated by oral fluids •trap fewer bubbles because they will absorb some liquid •are easy to pour with gypsum products •are h ydrophilic - meaning "water loving"

Non-Critical

➢ Items that do not contact mucous membranes but are touched or contaminated during dental treatment ➢ Use intermediate level disinfectants registered with the EPA such as hydrogen peroxide, citric acid, iodophors, quaternaries, sodium hypochlorite, sodium bromide, and chlorine ➢ Dental unit, dental chair, switches, handles, tube heads, plaster bowls, and spatulas

Level: Critical

➢ Sterilized in steam, dry heat, or saturated chemical vapor ➢ Items that may touch or penetrate mucous membrane or skin ➢ Instruments, burs, handpieces ➢ Stored in sterile wraps and unwrap just before use

Physical Hazard

➢ Training with equipment, education of risks, placement, proper cleaning, and maintenance • Chemicals Hazards ➢ Employee training, MSDS, inventories, disposal methods, properly stored and labels

emergencies

➢ Written procedures to manage and handle emergencies