MADI- OA lecture 7

Enamel: radiographically

Enamel appears more radiopaque (or brighter/whiter) than dentin and pulp

-96% mineralized

Mature enamel- 5 biological components

-crystalline

-avascular

-no nerves

-not renewable

-dynamic

Mature enamel- 6 physical components

-anatomical crown

-hard, esthetic surface

-bluish-white/ yellow-white

-permanent= translucent, primary= opaque

-varies in thickness

-radiopaque

Enamel composition (6)

majority calcium hydroxyapatite

-carbonate

-magnesium

-potassium

-sodium

-fluoride

Tomes' process- enamel (3)

-histologic processes on ameloblasts

-have a picket fence microscopic structure

-responsible for the way the enamel matrix is laid down

Enamel apposition (4)

-tomes process

-begin on incisal portion of future crown

-overlapping waves of apposition

-move cervically

What 2 proteins are involved in enamel apposition

amelogenins and enamelins

Ameloblasts

responsible for production and maturation of enamel matrix

have tomes processes on the ends

Apposition

stage of tooth development where hard tissue matrix (like enamel, dentin, and cementum) is secreted layer by layer by specialized cells

What is the microscopic structure of histologic landmarks on an ameloblast?

Picket fence structure

What causes deepened occlusal pits and grooves? (3)

-created when ameloblasts back into one another during apposition and affect their nutritional support

-incomplete maturation of enamel matrix

-caries, may need sealants

When does maturation of enamel matrix occur

during the maturation stage

completes mineralization

Maturation of enamel matrix (2)

-reduced enamel epithelium (REE) fuse with epithelium, canal forms, then eruption

-post eruptive maturation occurs due deposition of minerals from saliva into enamel

What do ameloblasts do during the maturation stage?

Ameloblasts move from production to actively transporting proteins and minerals.

2 histological features of enamel

-enamel rods

-lines of retzius

Enamel rods (4)

-crystalline structure of enamel

-perpendicular to DEJ

- variable lengths, slightly curved

-arrangement of enamel is determined by each ameloblasts tomes' processes

What feature contributes to the hardness of enamel

interlocking of enamel rods

What determines crown shape

enamel knot

What determines the variations in structural arrangement of enamel?

Each ameloblast's Tomes' processes

What is the structure of most rods in relation to the enamel?

extend the width of the enamel from the DEJ to the outer enamel surface

How does the DEJ between enamel and dentin appear

scalloped on a crown

What is one function of the DEJ?

It prevents fractures

Where is the DEJ most pronounced

-most pronounced in the coronal region, where occlusal forces are the greatest

Lines of retzius (3)

-incremental lines

-bands traverse the enamel rods in cross striations

-concentric rings

What 2 features are associated with lines of retzius

perikymata and neonatal line

Perikymata grooves (3)

-more prominent on the cervical region on facial surface

-horizontal grooves on enamel surface (wave like)

-reflect growth pattern of enamel

-correspond to Lines of Retzius

What causes perikymata grooves to smooth over time

abrasion and chemical wear

Neonatal lines (4)

-accentuated dark line of retzius

-occurs at time of birth

-found in all primary crowns and in larger cusps of permanent first molars

-can only really see on teeth developing in utero

3 microscopic features of enamel must be taken into consideration:

-hardness vs strength of enamel

-acid etching

-enamel is dynamic

Remineralization of enamel

mimics post-eruptive maturation

Enamel hardness

moderate level of hardness

-4x harder than dentin

Acid-etched enamel

temporarily demineralizes the surface

blue etch on teeth before filling to improve mechanical bonding

Dynamic properties of enamel

-fluorides and calcium/ phosphate ions contribute to remineralization and also demineralization

-remineralization of enamel mimics post-eruptive maturation

Dentin-pulp complex (2)

-make up the inner parts of the tooth

-shared developmental background, proximity, and interdependence

Dentin properties (6)

-crystalline (less hard then enamel- 70%)

-mainly calcium hydroxyapatite

-covered by enamel in crown and cementum in root

-protect pulp

-yellow/white

-tensile strength

Dentin radiographically

more radiolucent than enamel because it is less dense

more dense than pulp (more radiopaque than pulp)

What has the least density of the three dental tissues

pulp- appears most radiolucent

Apposition of dentin matrix

ameloblasts induce odontoblasts to produce pre-dentin in layers (matrix) then dentin

-LIFETIME PRODUCTION (odontoblasts remain along outer pulpal wall)

When does dentin maturation occur

soon after growth

calcium hydroxyapatite crystals expand and fuse, forming dentin

Dentinal Tubules

-long hollow microscopic channels

-extend to outer pulpal wall

-direction of the tubule reflects the pathway of the odontoblast during appositional growth of pre-dentin and dentin

3 components of dentinal tubule

Dental fluid (protection)

Odontoblastic process (secretion)

Sensory axons (pain sensation)

3 ways to classify types of mature dentin

1. relationship to tubules

2. relationship to DEJ and pulp

3. time of formation

Dentin classification- relationship to tubules (2)

-peritubular dentin: creates wall of tubule, highly mineralized

-intertubular dentin: between tubules, less mineralized (stretching and pulling)

Dentin classification- relationship to DEJ and pulp (2)

-mantle dentin: first pre-dentin to for and mature in the tooth, near the DEJ and under enamel

-circumpulpal dentin: deep to mantle dentin around outer wall of pulp, mature after mantle dentin

Dentin classification- time of formation (3)

-primary: formed before completion of apical foramen of the root

-secondary: formed after completion of apical foramen

-tertiary: formed quickly in response to localized injury to exposed dentin

2 histological features of dentin

incremental lines of von ebner and contour lines of owen

Incremental Lines of Von Ebner (4)

-90 degrees to dentinal tubules

-appear as fine lines in dentin

-growth lines of dentin

-represent daily dentin formation by odontoblasts

Contour lines of Owen (4)

-accentuated imbrication lines of von ebner

-represent a disturbance in body metabolism that effects dentin formation

-appear as a series of dark bands

-most prominent is neonatal line

What is the most pronounced line of Owen?

The neonatal line.

Dentin clinical implications

-pathologies like caries, hypersensitivity, hard tissue loss

-changes with age

Dentinal Caries

-tooth decay

-dentinal tubules serve as an entry mechanism for cariogenic microorganisms

-carious process in dentin moves more rapidly

What is dentinal hypersensitivity? (3)

-tooth pain which is sharp in character and of short duration, usually arising from exposed/open dentin surfaces

-can be exposed from caries, cavity prep, recession, tooth wear

-also caused by microscopic anatomy of the tooth

What can cause dentin surfaces to be exposed?

Caries, cavity preparation, gingival recession, and tooth wear.

Dental hypersensitivity instrumentation

Protective layers of both cementum and dentin can be inadvertently removed with scaling/instrumentation

Hydrodynamic theory (2)

-sensitivity due to changes in dentinal fluid

-stimulation of the exposed dentinal tubules causes changes in dentinal fluid, which is transmitted to the nerve associated with the odontoblast cell bodies in pulp tissue

Hydrodynamic theory- sensitivity caused by (3)

evaporation and loss of dentinal fluid

movement of the fluid

ionic changes in the fluid

Attrition

hard tissue loss due to tooth-to-tooth contact (mastication or parafunctional habits)

Clinical signs of attrition (4)

-matching wear on occlusal surfaces

-shiny wear facets on amalgam

-enamel and dentin wear

-possible fractures

Erosion

loss through chemical means not involving bacteria (bulimia, gastric reflux, acidic drinks)

Clinical signs of erosion (7)

-broad concavities within smooth surface enamel

-cupping of occlusal surfaces with dentin exposure

-increased incisal translucency

-wear may be on non-occluding surfaces****

-raised, shiny amalagam restorations

-preservation of enamel cuff in gingival crevice

-pulp exposure and loss off surface enamel in primary teeth

Abrasion

loss through friction through toothbrushing and/or abrasive toothpaste

Clinical signs of abrasion (3)

-usually at the facial cervical area

-lesions more wide than deep

-canines commonly affected

Abfraction

possible loss through tensile and compressive forces during parafunctional habits

Clinical signs of abfraction (3)

-facial and/or lingual cervical areas

-deep, narrow, v-shaped notch

-commonly affects single teeth with occlusal loads

Caries

loss through chemical means by cariogenic bacteria

Clinical signs of caries (3)

-all surfaces can be affected; occlusal more common (pits & grooves)

-possibly rapid progression of interproximal lesions if unchecked

-cervical lesions sometimes secondary to other forms of HT loss and recession

Dental changes with age (5)

-narrowing of dentinal tubules

-in some cases, mineralization causes complete destruction

of dentinal tubules

-decreased ability of pulp to react to stimuli

-dentin exposure

-in few cases, idiopathic internal or external resorption

2 types of idiopathic resorption

Internal and External

Internal idiopathic resorption

-if the original site of the resorption starts in the pulp

-results from a chronic pulpitis

external idiopathic resorption

-if the original site is the external surface of tooth

-may be due to injury

3 properties of pulp

-innermost soft tissue of the soft tooth

-connective tissue

-similar background to dentin- both derived from dental papilla of the tooth germ

Pulp radiograph

Pulp appears radiolucent (less dense, bc its CT)

4 functions of pulp

Supportive

Sensory

Nutritive

Protective

How is pulp supportive

maintenance and continued formation of dentin (by way of odontoblasts)

How is pulp sensory

extremes in temperature, pressure, or trauma to the dentin or pulp are perceived as pain

How is pulp nutritive

pulp keeps the organic components of the surrounding mineralized tissue supplied with moisture and nutrients

How is pulp protective

increases coverage of the pulp by forming secondary or reparative dentin, and creates more dentin when needed (injury to pulp)

Pulp tissue divisions (2)

coronal pulp

radicular pulp

Pulp chamber

-large mass of pulp contained here

-shape corresponds directly to the overall shape of the tooth

-2 divisions

Coronal pulp

located in the crown of the tooth

-smaller extensions of coronal pulp into the cusps form the pulp horns

What teeth are pulp horns located on

only posterior teeth

Radicular pulp

-the portion located in the root area of the tooth

-also called the pulp canal/root canal

Apical foramen of the pulp

-opening in the root from the pulp into the surrounding PDL near each apex

-allows the entry and exit of arteries, veins, lymphatic, nerves

-surrounded by cementum

-makes the tooth vital

-last to form

What happens when Hertwig epithelial root sheath encounters a blood vessel?

Root structure forms around the blood vessel, creating the accessory canal.

Accessory canals of pulp

-extra opening from the pulp to the PDL

-form when hertwig epithelial root sheath (HERS) encounters a blood vessel during root formation

-teeth can have a variable number of canals

What are the components of connective tissue?

Intercellular substance, tissue fluid, lymphatics, vascular system, nerves, and fibers

Histological features of pulp

connective tissue and nervous tissue

Pulp connective tissue

-intercellular substance, tissue fluid, lymphatics, vascular system, nerves, and fibers

-reflects external form of enamel

-cells: fibroblasts and odontoblasts

Pulp nerve tissue

-myelinated: neurons located in dentinal tubules in dentin

-unmyelinated: associated with blood vessels, originate from V2 and V3 branches of trigeminal nerve

5 clinical considerations of pulp

-pulpitis

-pulp testing

-RCT

-pulp stones

-aging and the pulp

Pulpitis

-inflammation when the pulp is injured by cavity prep, extensive caries, or traumatic injury

-can later cause pulpal infection in the form of periapical abscess

Periapical abscess

in the surrounding periodontium, spreading through the apical foramen, or possibly an accessory canal

Pulp testing

-clinical and diagnostic aid used in dentistry to help establish health of the dental pulp

-tooth varies in response to pain-producing stimuli

-ice test and electric pulp test

3 results of pulp testing

-reversible pulpitis

-irreversible pulpitis

-necrotic pulp

Reversible pulpitis (2)

-quick, sharp hypersensitive response to thermal stimulus

-subsides with removal of stimulus (1-2 secs)

Irreversible pulpitis (2)

-indicated by lingering response to cold temperatures

-may give spontaneous pain without stimulation or may be asymptomatic

Necrotic pulp (2)

-indicated by asymptomatic

-nonvital tooth that does not respond to any stimuli

What does RCT stand for in dentistry?

Root Canal Therapy

RCT (4)

-pulp is removed, tooth is no longer vital

-an inert radiopaque material (gutta-percha) is placed within pulp chamber

-tooth may darken, become brittle, and break during mastication due to leftover degradative products from pulpal necrosis

-infection cause pulp to leak

What material is placed within the pulp chamber during endodontic therapy?

Gutta-percha