Exam 1 - 123
Lines of Retzius
Concentric series of bands, on the enamel rods, represent incremental growth lines that extend at an acute angle from DEJ
Enamel pearls
Defects that occur during apposition and maturation stages of tooth development due to displacement of ameloblasts to root surface; this occurs more to maxillary molars
What makes the PDL?
Dental sac
Enamel cannot regrow but....
Dentin and cementum can
What begins to form once the inner enamel epithelium (IEE) has folded?
Dentin and enamel
What happens during root completion?
Dentin continues to form apically under enamel, eventually forming the root
As pulp gets smaller....
Dentin gets larger
Dentin is covered by enamel in the crown and cementum in the pulp and encloses the innermost pulp therefore
Dentin makes up the bulk of the tooth
Since enamel is translucent....
Dentin of the tooth gives the white enamel crown its underlying yellow hue
Which CEJ relationship would be at risk for dentinal hypersensitivity?
Gap between enamel and cementum, leaving dentin exposed
What will expose cementum?
Gingival recession
Systemic enamel dysplasia
Involves larger numbers of ameloblasts and may result from traumatic birth, systemic infections, nutritional deficiencies, or dental fluorosis
What happens to the dental lamina during the bell stage?
It breaks down and the enamel organ loses connection with the oral epithelium
As dentin continues to mature.....
It gradually increases in density
What is the dentition for a child between the age of 6-12?
Mixed dentition
Predentin is laid down in layers during the apposition stage... ________ from the DEJ
Moving away
Bell Stage
- 11th-12th week - Proliferation, differentiation, morphogenesis - Differentiation of enamel organ into bell shape with four cell types and dental papilla into two cell types
Initiation stage
- 6th-7th week - Induction - Ectoderm lining stomodeum gives rise to oral epithelium and then to dental lamina with its dental placodes; adjacent to deeper ectomesenchyme which is derived from neural crest cells - Both tissues are separated by basement membrane
Bud Stage
- 8th week - Proliferation - Growth of dental papilla into the bud shape that penetrates growing ectomesenchyme
Cap Stage
- 9th-10th week - Proliferation, differentiation, morphogenesis - Formation of tooth germ as enamel organ forms into cap shape that surrounds inside mass of dental papilla, with outside mass of dental sac, both from ectomesenchyme
Odontoma
- A benign neoplasm of odontogenic origin - Come from presence of epithelial pearls - Linked to tooth development
3rd molars (wisdom teeth) are removed to prevent what?
- A dentigerous cyst - First asymptomatic but if get larger can displace teeth, causing fracture and severe pain
Eruption cyst
- A dentigerous cyst that appears on a partially erupted tooth - Appears fluctuant, blue, vessicle-like gingival lesion
What type of restorative treatment would be need after a root canal?
- A permanent full coverage crown - Placed on treated natural crown to protect it from breaking and to prolong retention of tooth
What will a bud develop into?
- A tooth germ with it's associated supporting tissue during the next stage
Hyperdontia, Supernumerary teeth
- Abnormal initiation may result in the development of one or more extra teeth - Initiated from persisting dental placodes within dental lamina - Initiation stage
Contour Lines of Owens
- Adjoining parallel imbrication lines - Interruptions in dentin formation - Appears as dark bands - Most pronounced in Neonatal line
What could happen to a tooth after a root canal is preformed?
- Can be come dark and brittle, may break during mastication - Darkening is due to left over degradative products from pulpal necrosis with the death of the pulp tissue that were passed along the dentinal tubules
Irreversible Pulpitis
- Can cause a pulpal infection in the form of a periapical abscess or cyst in the surrounding periodontium, spreading through the apical foramen or any accessory canal (shows communication between pulp and surrounding tissue) - Pulp dies due to bacterial invasion - Must be surgically removed by pulpectomy - Spontaneous pain - Lasting minutes/hours
Lacuna
- Cementum "space" around the cementocyte - Body
As long as there are cementoblasts available...
- Cementum can resorb and regrow - Less susceptible to resorption than bone
Central Cells of Dental Papilla
- Central cell mass of dentin papilla - Will differentiate into pulp tissue
Pulp forms from....
- Central cells of dental papilla - During odontogenesis, when predentin forms around the dental papilla, the innermost tissue is considered pulp
Mesognathic facial profile
- Class I malocclusion - Slightly protruded jaw
Retrognathic facial profile
- Class II malocclusion - Jaw is majorly retruded
Prognathic facial profile
- Class III malocclusion - Jaw is majorly protruded - Prominent chin
Canaliculi
- Communicating projections extending out from lacuna - Cementocyte cytoplasmic extension - Extend out toward PDL - They DO NOT CONTAIN nerves, but help diffuse nutrients from the PDL
Treacher Collins Syndrome
- Complication of formation in NCC - Prevents proper dental development - NCC's do not migrate to proper areas - Initiation stage
Dental papilla
- Condensed mass of ectomesenchyme of tooth germ that produces dentin and pulp
Cellular Cementum
- Consists of the last layers of cementum deposited over the acellular cementum - Mostly in the apical one-third of each root - Formed faster than acellular - Contains cementocytes - Acts as a trap
Cell-free zone
- Contains fewer cells than odontoblastic layer - Nerve and capillary plexus located here
Cell-rich zone
- Contains increased density of cells compared with cell-free zone and more extensive vascular supply
Gross anatomy of Pulp
- Coronal pulp (located in crown of tooth): Chamber, Pulp horns - Radicular pulp (located in root): Canals, Apical foramen
Peritubular dentin
- Creates the wall of the dentinal tubule - Highly mineralized
Curve of Wilson
- Cross-arch curvature of the occlusal plane - Bucco-lingual dimension
Curve of Spee
- Curvature formed by the maxillary and mandibular arches in occlusion - Anterior/Posterior dimension
How is irreversible pulpitis treated?
- Dead pulp is removed - Gutta- Percha (inert radiopaque rubbery material) is placed within the pulp chamber, including each canal - AKA root Canal - Tooth is no longer vital because its nutritional source from the vascular pulpal tissue has been removed
The pits and fissures of enamel encourage growth of what?
- Decay - The arrangement of rods influences pattern and spread of decay
Intertubular dentin
- Dentin found between the tubules - Highly mineralized
As you get older...
- Dentin gets thicker - Pulp gets smaller
Dentinogenesis imperfecta
- Disturbance results in blue-gray or brown teeth with a rainbow like opalescent sheen - Enamel appears as usual but chips off because of a lack of support by the abnormal underlying dentin - Usually need a full coverage crown for esthetics and to prevent further attrition
The primary dentition develops during...
- Embryonic and fetal period of prenatal development
Mesenchyme
- Embryonic connective tissue for the rest of body is derived from mesoderm
What types of mature teeth tissue are NOT directly derived from NCC's?
- Enamel - Certain types of cementum
Continuing into the maturation phase...
- Enamel rods will grow in length - Enamel rods will grow away from the DEJ toward the outer surface of the tooth - Enamel rods will take on a wavy pattern
Apposition stage
- Enamel, dentin, and cementum are secreted in successive layers upon those already present - Induction continues to occur between the ectodermal tissue of the enamel organ and mesenchymal tissue of the dental papilla and dental sac
Sclerotic Dentin
- Evidence of chronic irritation - Response of body to protect itself
Hypercementosis
- Excessive production of cellular cementum, which mainly occurs at the apex or apices of the tooth - May be present on radiographs as a radiopaque (or lighter) mass at each root apex - Can result from: occlusal trauma, chronic periapical inflammation, Paget's disease (disrupts the replacement of old bone tissue with new bone tissue)
Dentin dysplasia
- Faulty development of dentin - Can result from an interference with the metabolic processes of the odontoblasts during dentinogenesis
Enamel dysplasia
- Faulty development of enamel
The permanent dentition develops during...
- Fetal period
Fusion
- Union of two adjacent tooth germs - May result from pressure in the region which leads to a broader falsely macrodontic tooth - Two separate and distinct pulp cavities with the resulting enamel, dentin, and pulp united - Cap stage
Two types of nerves associated with pulp...
- Unmyelinated nerves (70%) - Myelinated nerves (20-30%) - Mostly relay the sensation of pain (injuries to pulp)
What does the posterior progression of odontogenesis allow time for?
- Upper and lower jaws to grow and accommodate increased number of primary teeth - Larger primary molars - Overall larger permanent teeth
Apposition Stage
- Various times - Induction, proliferation - Dental tissue types secreted in successive layers as matrix
Maturation Stage
- Various times - Maturation - Dental tissue types fully mineralize to mature form
Globular dentin
- When complete crystalline fusion has occurred - Dentin will appear more uniform - Appear as lighter, rounded areas under a microscope
Does dentin receive stimuli?
- Yes it receives fluid and nerve stimulis in the dentinal tubules that comes from pulp
Does the oral epithelium contain two horseshoe shaped bands?
- Yes, at the surface of the stomodeum - One band for each future dental arch
Cementoblasts make cementum...
- inital soft matrix is called cementoid - eventually matures
Openbite
Anterior teeth do not occlude
Amelogenesis
Appositional growth of enamel matrix
Adult dentition starts when?
Around 12 years of age and continues on
How do calcium hydroxyapatite crystal form in collagen fibers?
As globules
When does odontogenesis begin?
Begins between the 6th and 7th week of prenatal development during the embryonic period
- Occurs for the primary dentition between the 11th-12th week of prenatal development - Characterized by continuation of ongoing processes of proliferation, differentiation, and morphogenesis
Bell stage
Group Function
Multiple contact relations between the maxillary and mandibular teeth in lateral movements on the working side whereby simultaneous contact of several teeth acts as a group to distribute occlusal forces.
Does enamel have nerve supply?
No, it is avascular
Does odontogenesis have clear and beginning end points between stages?
No, just a continuous process
After differentiation and repolarization...
Odontoblasts begin dentinogenesis
Dentigerous cyst
Odontogenic cyst that forms from the REE after the crown has completely formed and matured
How would you fix improper eruption of teeth?
Orthodontics
What do fibroblasts along the alveolar bone differentiate into?
Osteoblasts of the future lamina dura
Enamel lamellae
Partially mineralized vertical sheets of enamel matrix that extend from the DEJ near the tooth's cervix to the outer occlusal surface
Maturation stage
Reached when matrices of the hard dental tissue types subsequently fully mineralize to their correct levels
Pulp horns will eventually
Recede with age
When enamel is in a healthy state it can only be removed by...
Rotary cutting instruments or rough files
Predentin then does???
Surrounds the odontoblastic processes > which develop into dentinal tubules
Dentin is avascular
TRUE
T or F: The teeth have the longest developmental period of any set of organs in the body
TRUE
T or F: Dentin has great tensile strength
TRUE, provides an elastic basis for the more brittle enamel
End-to-End bite
Teeth occlude on incisal edges of maxillary and mandibular teeth
Staining of a tooth structure due to antibiotics is usually due to what...
Tetracycline
Canine Guidance
The beneficial overlapping of canines that causes posterior teeth to separate during movements of the mandible from right to left
What happens with the root is 2/3 developed?
The crown forms first and then will erupt
Hunter-Schreger bands
The crystals in the enamel rod groups bend to the right or left at a slightly different angle than do adjacent groups, increasing the enamel's strength
Relative Microdontia
The dentition can appear smaller by being within a large set of jaws
Dentinoenamel junction (DEJ)
The inner junction between the dentin and enamel
Underbite
The mandibular arch extends forward beyond the maxillary arch
Overjet
The maxillary arch horizontally overlaps mandibular arch
Overbite
The maxillary arch vertically overlaps mandibular arch
Class II Division I malocclusion
The maxillary incisors protrude facially from the mandibular incisors causing a severe overbite
What happens during repolarization?
The nucleus in each cell moves away from the center of the cell to the position farthest away from the basement membrane that separates the enamel organ from the dental papilla
After the IEE differentiates into preameloblasts....
The outer cells of the dental papilla are lined up and induced to differentiate into odontoblasts
Where do odontoblasts originally come from?
The outer cells of the dental papilla in the apposition stage
When newly exposed dentin on the crown turns various shades of yellow and appears rougher, what is happening?
The outer layers of enamel are being lost with aging
What is odontogenesis?
The process of tooth development
Centric Occlusion
The voluntary position of the dentition that allows the maximum contact when the teeth occlude
Pulp and dentin have a similar background because...
They are both derived from the dental papilla of the tooth germ
What can dental pulp stem cells turn into?
They can transform into fibroblasts or odontoblasts if either cell population is reduced after injury
Where do blood vessels enter into the pulp?
Through apical foramen
Enamel matrix is secreted from
Tomes Process
What is the enamel matrix secreted from?
Tomes process, an angled distal part of each ameloblast that faces the fully disintegrated basement membrane
Ankyloglossia
Tongue-tie; a defect of the tongue characterized by a short, thick frenulum
The enamel organ, dental papilla, and dental sac all form what?
Tooth germ
Torsoversion
Tooth is rotated or turned (mesial or distal)
Supraversion
Tooth protrudes excessively into the oral cavity
Linguoversion
Tooth tipped toward tongue
Buccoversion
Tooth tipped towards cheek
Labioversion
Tooth tipped towards lips
T or F : The initial enamel is only partially mineralized
True
Disintegration of HERS allows....
Undifferentiated cells of the dental sac to come into contact with the newly formed surface of root dentin, inducing cells to become cementoblasts
How does the tooth bud develop during the cap stage?
Unequal parts of growth in the bud, leading to formation of a three-dimensional cap shape overlying the ectomesenchyme that is still attached superiorly to the dental lamina
How does root dentin become exposed?
When the thin layer of cementum is lost due to gingival recession with its lower margin of the free gingiva crest
Can dentin heal itself?
Yes
Can enamel undergo mineralization changes once it has matured?
Yes
Do mandibular teeth usually erupt before maxillary?
Yes
Can darkening of the clinical crown occur when pulp is infected or dies?
Yes the dentin will discolor and can lead to darkening of the crown
If a patient is starting to get their 3rd molars...
You can assume their age is probably between 18-21 give or take a few months
Teeth associated with microdontia?
maxillary lateral incisors (peg lateral), permanent third molar (peg molar)
Enamel matrix is fully mineralized at what percent?
96% in the maturation stage
Microdontia
Abnormally small teeth, occurs during bud stage
Basement Membrane
Acellular structure that separates the oral epithelium and the ectomesenchyme within the stomodeum
Class I Malocclusion
- Mesiobuccal cusp of the maxillary first molar occludes with the mesiobuccal groove of the mandibular first molar - Due to crowding, irregular spacing, or mesial drift as dentition ages
Why is enamel only confined to the anatomic crown?
Ameloblasts are not differentiated in the root area
Enamel Spindles
- Microscopic feature present in mature enamel as short dentinal tubules near DEJ - Noted beneath the cusps and incisal ridges or tips of the teeth - Result from odontoblasts that crossed the basement membrane before it mineralized into the DEJ
Primary dentition occurs when
6 months - 6 years
1st molars erupt around what age?
6 years
Active eruption
Actual vertical movement of the tooth
Occlusal plane
Formed by the biting surfaces of the upper and lower teeth with jaws closed
When does the apical foramen form?
After the crown erupts into the oral cavity
What obstacles do pulp stones present?
- May block access to canal - Can easily be removed with a dental bur
Abfraction
- May have loss through tensile and compressive forces during tooth flexure with parafunctional habits - Can affect both facial and lingual cervical regions - Deep and narrow V-shaped notch - Commonly affects single teeth that have occlusal loads
Acellular Cementum
- First layers of cementum laid down along dentin - NO cementocytes -AKA primary cementum - Covers entire outer surface of each root with more layers covering the cervical one-third near the CEJ - Width never changes over time
Dental Placodes
- First signaling centers of the tooth
Accessory canals
- Form when Hertwig epithelial root sheath (HERS) encounters a blood vessel during formation - Root structure then forms around vessel, allowing for the forming of the canal - Extra openings from the pulp to the periodontal ligament - AKA lateral canals because they are usually located on the lateral surfaces of the roots of some teeth
Secondary dentin
- Formed after completion of apical foramen - Formed more slowly; less mineralized than primary - Continues to form throughout life of the tooth
Primary dentin
- Formed before completion of apical foramen - Formed more rapidly; more mineralized than secondary
Tertiary dentin
- Formed quickly as a result of localized injury to exposed dentin - Forms underneath exposed dentinal tubules along the outer pulpal wall in attempt to seal off the injured area - Injury could be due to caries, cavity preparation, attrition, or gingival recession - Irregular course of tubules
Cemental spurs
- Found at or near the CEJ - Symmetrical spheres of cementum attached to the cemental root surface, similar to enamel pearls - Can result from irregular deposition of cementum on the root and may be noted on radiographs
How does cementum form?
- From the dental sac - Forms on the root dentin after the disintegration of Hertwig epithelial root sheath (HERS)
What happens to the oral epithelium during the latter part of the seventh week?
- Grows deeper - Penetrating the ectomesenchyme - Induced to produce an adjoining layer > the dental lamina
Imbrication Lines of Von Ebner
- Growth rings in dentin - Correspond to Lines of Retzius in enamel - Show the incremental nature of dentin during apposition stage - Run at 90 degree to the dentinal tubules
Enamel Tufts
- Hypocalcified or uncalcified areas of enamel at the DEJ
Pulpitis
- Inflammation of pulp - Can be caused by mechanical or chemical injury due to cavity preparation, extensive caries - Can result in extreme pain from the pressure as the inflammatory edema (swelling) presses on the afferent nerves contained in the pulp
Inner enamel epithelium
- Innermost tall columnar cells of enamel organ - Will differentiate into ameloblasts that form enamel matrix
Pulp
- Innermost tissue of the tooth - Connective tissue with all the components of a tissue: intercellular substance, tissue fluid cells, lymphatics, vascular system, nerves, and fibers
How does dentin pick up tooth stains?
- It remains exposed - More porous and permeable than intact enamel - Becomes more yellow or even brown to black
Anodontia
- Lack of initiation within the dental placode within the dental lamina - Results in the absence of a single tooth, multiple teeth, or an entire dentition - Initiation stage
Pulp chamber
- Large mass of contained pulp - Shape of each pulp chamber corresponds directly to the overall shape of the tooth - Individualized for every tooth
What happens when ameloblast move away from the DEJ?
- Lay down enamel rod extending from DEJ to outer edge of crown surface
Circumpulpal dentin
- Layer around outer palpal wall - Dentin formed after mantle dentin
Reduced enamel epithelium (REE)
- Layers of flattened cells overlying enamel surface from compressed enamel organ - When formation of the REE occurs for a primary tooth, it can then being to erupt into the oral cavity
Odontoblastic layer
- Lines outer pulpal wall and consists of cell bodies of odontoblasts, which may form secondary dentin, causing cell bodies to realign themselves - Cell bodies of afferent axons from dentinal tubules located between cell bodies of odontoblasts
Erosion
- Loss through chemical means (via acid) NOT involving bacteria - Broad concavities within smooth surface enamel - Cupping of occlusal surface (or incisal grooving) with dentin exposure (with possible dentinal hypersensitivity) - Increased incisal translucency - Wear on nonmasticatory surfaces (exact location depends on acid and intake type) - Raised and shiny amalgam restorations - Preservation of enamel cuff in gingival crevice - Pulp exposure and loss of surface characteristics of enamel in primary teeth
Caries
- Loss through chemical means (via acid) from cariogenic bacteria by way of dental biofilm - All surfaces can be affected - Occlusal surfaces more commonly affected, especially in pits and grooves - May have rapid progression of interproximal smooth surface lesions if progress goes unchecked - Cervical lesions sometimes secondary to other forms of hard tissue loss or gingival recession
Abrasion
- Loss through friction from toothbrushing/and or toothpaste - Usually located at facial cervical regions - Lesions more wide than deep - Canines commonly affected because of tooth position
Attrition
- Loss through tooth-to-tooth contact from mastication with aging or more severely with parafunctional habits - Matching wear on masticatory surfaces - Shiny facets on amalgam contacts - Enamel and dentin wear at the same rate - May have fracture of cusps or restorations
Certain regions of the dentition that are at an increased risk for supernumerary teeth?
- Maxillary central incisors - Distal to maxillary third molars - Premolar region
Class II Division II malocclusion
- Maxillary central incisors are either upright or retruded - Maxillary lateral incisors are either tipped labially or overlap the maxillary central incisors
Normal contacts of posterior teeth
- Maxillary palatal cusps contact the fossa of the mandibular posterior teeth - Mandibular buccal cusps contact the fossa of the maxillary posterior teeth
Pulp stones
- Mineralized masses of dentin complete with dentinal tubules and odontoblastic processes - Can be free or unattached to the outer pulpal wall - Can be attached to dentin at the dentin-pulp interface - "Stalactites" growing into pulp
Cementicles
- Mineralized spherical bodies of cementum found either attached to the cemental root surface or lying free in the PDL - Form from appositional growth of cementum around cellular debris in the PDL - Possibly as a result of microtrauma to Sharpey fibers
Stratum intermedium
- More inner compressed layer of flat to cuboidal cells - Supports production of enamel matrix - Cells show high alkaline phosphatase enzyme activity that is important for enamel mineralization
Stellate reticulum
- More outer star-shaped cell in many layers, forming network within enamel organ - Supports production of enamel matrix - Undergoes shrinkage as intercellular fluid is utilized for nutrition; space is then utilized by forming enamel
Mesial Drift
- Natural movement of teeth over time toward midline of the oral cavity - Can be caused by tooth taken out too early - Tooth distal to the missing tooth will migrate mesially - Will see large apical foramen on xray
Components of Cementum
- No nerve supply - Avascular (without blood vessels) - Receives its nutrition through its own cell from the surrounding PDL - Can form throughout the life of the tooth
Nonsuccedaneous teeth
- No primary predecessors - Permanent molars
What is the course of action if occlusal trauma is found?
- Occlusal guard (biteguard) - To be worn at night when patient will usually grind or clench tooth prevent tooth-on-tooth wear
How will permanent teeth move to erupt?
- Occlusally - Resorbs primary tooth root - Loosens the primary tooth
Bud Stage
- Occurs at the beginning of the 8th week of prenatal development - Named for an extensive proliferation of the dental placodes into buds, with these three-dimensional oval masses penetrating into the surrounding ectomesenchyme
Passive eruption
- Occurs with aging - Gingival tissue recedes, uncovering the clinical root and increasing the size of the clinical crown - No actual tooth movement takes place
Structure of pulp
- Odontoblastic layer - Cell-free layer - Cell-rich layer - Pulpal core (center of pulp chamber) - Listed outer > inner
Cells present in pulp
- Odontoblasts - Fibroblasts - Nerves - White blood cells - Dental pulp stem cells
Reversible pulpitis
- Only coronal portion of the pulpal tissue (immediately adjacent to caries) has signs of inflammation - Has stimulus - Brief pain (seconds) - Can treat the carious exposed or indirect exposed pulp tissue with a pulp cap (pulpotomy - root canal for primary teeth); permanent restoration is then completed over area to prevent any infection - Occurs in children mostly
Interglobular dentin
- Only primary mineralization has occurred within the predentin and the globules of dentin do not fuse completely - Slightly less mineralized - Frequently found under DEJ - Appears as dark spots or arcs under a microscope
Apical foramen
- Opening from the pulp into the surrounding PDL near each apex of the tooth - If more than one is present, largest = apical foramen; second one = accessory foramina - Opening is surround by cementum - Permits arteries, veins, lymphatics, and nerves to enter and exit the pulp from the PDL; allows the tooth to remain vital - Last part of tooth to form - Allows communication between the pulp and PDL
Outer enamel epithelium (OEE)
- Outer cuboidal cells of enamel organ - Serves as protective barrier for enamel organ - Nutritional supply for rest of enamel organ during enamel production
Four different types of cells within the enamel organ
- Outer enamel epithelium - Stellate reticulum - Stratum intermedium - Inner enamel epithelium
Outer cells of dental papilla
- Outer layer of cells of dental papilla nearest inner enamel epithelium (IEE) of enamel organ - Basement membrane is between outer layer and inner enamel epithelium - Will differentiate into odontoblasts that form dentin matrix
Mantle dentin
- Outermost layer near DEJ underneath enamel - First dentin formed
Ankylosis
- Periodontal ligament fuses with alveolar bone - Common in primary molars - Tooth will stop erupting - Will not be in plane of occlusion
6-12 rule of eruption
- Permanent teeth - By 6 years should have 1st permanent tooth - By age 12, all permanent teeth should be erupted
Succedaneous teeth
- Permanent teeth with primary predecessors - Anterior teeth and premolars
7-11 rule of eruption
- Primary teeth - By 7 months usually there is the first primary tooth - By age 11 most primary teeth are exfoliated
Neonatal Line
- Pronounced incremental line of Retzius, marks trauma experienced by ameloblasts during birth - Illustrating the sensitivity of the ameloblasts as they form enamel matrix
Nasymth's Membrane
- Reduced enamel epithelium fuses with oral epithelium - Sticks on tooth as it erupts - Can be removed with scaler or polish
Process of Eruption
- Reduced enamel epithelium has to fuse with the oral epithelium - Reduced enamel epithelium then disintegrates the central part of the fused tissue, leaving a protective epithelial lined eruption tunnel for the tooth to erupt through the surrounding oral epithelium into the oral cavity - Coronal part of fused epithelial tissue peels off the crown, leaving the cervical part still attached to the neck of the tooth, like a banana being peeled - Fused tissues remains near the CEJ after the tooth erupts then serves as the initial junctional epithelium of the tooth surface, creating a seal between the tissue and tooth surface
Usually a dentist would repair occlusal trauma by
- Replacing broken fillings - Replacing teeth - Extensive crown work
Enamel hypoplasia
- Results from a reduction in the quantity of enamel matrix due to factors that interfere with enamel matrix formation - Teeth appear with pitting and grooves in the enamel surface or in the development of horizontal lines across the enamel of the crown - Occurs during apposition or maturation stages
Enamel hypocalcification
- Results in reduction in the quality of the enamel maturation due to factors that interfere with enamel mineralization and maturation - Teeth appear opaque, yellower, or even browner within because of intrinsic staining of enamel
Pulp defensive mechanisms
- Sclerotic dentin - Pulpitis - Reversible pulpitis - Irresversible pulpitis
Exfoliation
- Shedding of primary tooth - Will get loose over time because of resorption - Coronal movement of the succedaneous tooth resorbs primary tooth root
Gemination
- Single tooth germ tries unsuccessfully to divide into two tooth germs by invagination - Results in large single-rooted tooth with a common enlarged pulp cavity - Cap stage - Occurs in anterior teeth in either dentition; mostly within primary dentition
Enamel tubercles
- Small rounded enamel extensions forming extra cusps - Located on crown - Cap stage - Noted on occlusal surface of permanent molars (especially third molars) - May present as a lingual extension on the cingulum of permanent maxillary anterior teeth (especially laterals and canines)
Pulp horns
- Smaller extension of coronal pulp into the cusps of posterior teeth - Especially prominent in permanent under the buccal cusp of premolars; in primary dentition under the mesiobuccal cusp of molars - NOT found on anterior teeth
Wear facets
- Smooth, flat surface contacts - Will notice wear on dentition
Functions of pulp
- Supports odontoblastic activity (dentin formation) - Defensive function (immune cells) - Nutritive function (blood vessels) - Sensory function (nerves)
Amelogenesis imperfecta
- Teeth have very thin enamel that chips off or have no enamel at all - Crowns are yellow because they are mostly composed of softer dentin that undergoes extreme attrition - Usually need a full coverage crown for esthetics and to prevent further attrition
What is dentinogenesis?
- The appositional growth of dentin matrix, or predentin, laying it down on their side of the now disintegrating membrane - Odontoblasts start their synthetic and secretory activity usually before enamel matrix production begins - Explains why dentin layer is slightly thicker in a developing tooth
Centric stops
- The contact points where the teeth will touch between the two arches - Maxillary posterior lingual will touch mandibular buccal and central pits for posterior - Maxillary anterior lingual will be touching the mandibular incisal edge
The proper migration of NCC's is essential for ???
- The development of the head and the neck as well as the teeth
Dens in Dente
- The enamel organ may abnormally invaginate by growth into the dental papilla - Permanent maxillary incisors - Cap stage
Enamel is...
- The hardest tissue in the body - Nonrenewable - Non-vital
After the formation of the IEE in the bell-shaped enamel organ...
- The innermost cells grow even more columnar as they elongate and differentiate into preameloblasts, lining along the basement membrane
Class III Malocclusion
- The mesiobuccal cusp of the maxillary first molar occluding (by more than the width of a premolar) DISTAL to the mesiobuccal groove of the mandibular first molar
Class II Malocclusion
- The mesiobuccal cusp of the maxillary first molar occluding (by more than the width of a premolar) MESIAL to the mesiobuccal groove of the mandibular first molar
The oral epithelium comes from what during initiation?
- The outer part of the ectoderm
How can coronal dentin become exposed?
- Through attrition - Certain enamel dysplasias - On incisal ridges of anterior teeth when trauma causes it to become chipped or worn
Enamel pearl
- Tooth enamel on root surface - Cap stage
Dental Sac
- Tooth germ part consisting of ectomesenchyme surrounding outside of enamel organ - Forms cementum, periodontal ligament, alveolar process
Infraversion
- Tooth is not in plane of occlusion - Not erupted fully
Ectomesenchyme
- Type of mesenchyme - Derived from neural crest cells (NCC) that have migrated to the region
Sclerotic dentin
- Type of tertiary dentin - Associated with localized injury - Noted in increased amounts as tooth ages - Odontoblastic processes die and leave the dentinal tubules vacant
Concresence
- Union of the root structure of two or more teeth through cementum only - Excess cementum deposition on one or more teeth after eruption - Caused by traumatic injury or crowding during apposition or maturation stages - Can complicate extractions and endodontic therapy
4 ameloblasts create...
1 enamel rod
Three CEJ relationships:
1) Cementum may overlap (15%) 2) Cementum may meet end-to-end (52%) 3) Gap between enamel and cementum, leaving dentin exposed (33%)
How many buds will each arch of the primary dentition have?
10 - maxillary 10 - mandibular (20 all together for 20 future primary teeth)
What do you think the age of a child would be who has 1st molars, mixed dentition, and their 2nd molars are beginning to erupt?
12-13
3rd molars usually complete eruption by?
21 years of age
Which teeth will start to erupt around 12 years of age?
2nd molars
Tomes Process is....
A projection of the basal or secretory end of each ameloblast that faces the DEJ.
Mature cementum is composed of 65% of inorganic or mineralized what?
Calcium hydroxyapatite
Occurs for the primary dentition between the 9th-10th week of prenatal development, during the fetal period
Cap stage
The immature enamel matrix is initially composed of
Carbohydrates, proteins, and only a small amount of calcium
What can dentinal tubule serve as an entry way for?
Cariogenic microorganisms as the carious process begins to extend from the enamel to form dentinal caries
Entrapped cementoblasts will mature into..
Cementocytes
Problems with premature loss of teeth
Creates occlusal problems
When are pulp stones formed?
During tooth development and also later as pulp ages and may be due to microtrauma
When teeth are in centric occlusion...
Each tooth of one arch is in occlusion with two others in the opposing arch (except for the mandibular central incisors and maxillary third molars)
All teeth develop from what?
Ectoderm and ectomesenchyme (derived from NCC's)
From 0-6 months, a baby is...
Edentulous No teeth
What does the enamel organ produce?
Enamel on the outer surface of the crown of the tooth
Centric Relation
End point of closure of mandible in which the mandible is in most retruded position
How would you deal with impactions?
Extract the tooth
What creates the fibers of the PDL?
Fibroblasts in the dental sac
How is the crown pattern of the tooth developed?
Folding of the inner enamel epithelium (IEE)
Dental fluorosis
Hypomineralization occurs due to an excess systemic fluoride level
What do fibroblasts in the PDL differentiate into?
If located along the root, they differentiate into cementoblasts
Impactions are caused by
Improper permanent tooth position from lack of space
Tongue thrust
Incorrect positioning of tongue during swallowing and/or during rest posture
How does the dental lamina form?
Initially in the midline for both arches and progresses posteriorly
At the 10th week of prenatal development....
Initiation is occurring for the anterior teeth of the permanent dentition and then later for the the premolars of the permanent dentition
Mature dentin is made up of 70% of??
Inorganic calcium hydroxyapatite
During maturation phase, what do ameloblasts replace organic carbohydrates with?
Inorganic hydroxyapatite crystals
What do arrest and reversal lines represent in cementum?
Layers reflecting resorption and regrowth
How will the permanent succedaneous tooth erupt?
Lingual to the root(s) of its primary predecessors if the primary tooth has not been fully shed
Mouth breathing/Lip incompetence
Lips open at rest due to inability to breathe through nose or it has become a habit
Parulis (gum boil)
Localized collection of pus in the gingival soft tissue
Pulpal core
Located in center of pulp chamber, similar to cell rich-zone with many cells and extensive vascular supply
Abnormally large teeth, occurs during bud stage
Macrodontia
Initial teeth for both dentitions develop in what order?
Mandibular anterior region > maxillary anterior region > posterior regions
Normal contacts of anterior teeth
Mandibular incisal edges contact the cingulum of the maxillary incisors
Crossbite
Mandibular teeth are positioned facially to maxillary teeth
Where are pulp stones commonly found?
Maxillary molars
Local Enamel Dysplasia
May result from trauma or infection occurring to a small group of ameloblasts
The disintegration of the basement membrane after the formation of predentin allows....
Preameloblasts to contact the newly formed predentin which induces the preameloblasts to differentiate into ameloblasts
What is differentiation?
Preameloblasts will induce dental papilla cells to differentiate into dentin-forming cells (odontoblasts) and then will themselves differentiate into cells that secrete enamel (ameloblasts)
In dentinogenesis, what do odontoblasts lay down?
Predentin
Mature dentin comes from what?
Predentin
Collagen fibers from the PDL that are partially inserted into the outer surface of the cementum at 90 degrees or perpendicular
Sharpey fibers
Premature tooth loss can be maintained by
Space maintainers
