Tooth Tissues and Periodontium

dentinogenesis

process of dentin formation, occurs as part of odontogenesis

• begins during the bell stage

  • involves differentiation of dental papilla cells (odontoblasts to produce dentin)

dentin

origin: outer cells of dental papilla

composition: hydroxyapatite, collagen, water

process: secretion of collagenous matrix (predentin)

• mineralization—> dentin

dentin formation (produced by odontoblasts, continues while tooth is vital, can be stimulated by external factors, can rebuild)

mature dentin anatomy

70% inorganic- hydroxyapatite

20% organic- collagen

10% water

key features:

• forms bulk of tooth

• supports enamel and prevents fracture

• provides strength & flexibility

more dentin characteristics

yellow in color—> influences tooth shade (darkens if pulp becomes necrotic/dies)

DEJ

• scalloped interface with enamel

• increases surface area & bond strength

accessory canals (go laterally off to sides)

• additional openings besides apical foramen

• connect pulp to PDL

• pathway for infection spread and sensitivity

dentinal tubules & permeability

dentinal tubules run from DEJ —> pulp

• contain dentinal fluid (10% water)

• house odontoblastic processes

neural component- may contain afferent nerve fibers (sensory)

permeability- dentin is permeable due to tubules

• tubule density is higher closer to pulp- influences caries progression & sensitivity

types of dentin- placement

peritubular dentin- forms walls of dentinal tubules

• highly mineralized

intertubular dentin- between tubules

• less mineralized than peritubular

• forms BULK OF DENTIN

circumpulpal dentin- surrounds the pulp chamber, parallel to DEJ

• main structural dentin

• more mineralized than intertubular

types of dentin

primary dentin- forms before eruption (during tooth development)

• makes up BULK of tooth

secondary dentin- forms after eruption and deposited throughout life (responds to normal wear and tear)

• gradually reduces pulp chamber size

tertiary dentin (reparative/reactive)

• forms in response to stimuli (ex. caries/stress, stimulates odontoblasts to make tertiary dentin)

• protects pulp

types of dentin based on mineralization

2 phases of dentin formation:

• primary- maturation of pre-dentin

• secondary- crystal formation (mineral deposit)

2 types of mineralization

• globular- complete fusion of mineral crystals

  • fully mineralized

  • strong and dense structure

• interglobular- incomplete fusion of crystals

  • less mineralized

  • more porous and weaker

microscopic features of dentin

incremental lines:

• Imbrication lines of von Ebner (daily growth lines)

• Contour lines of Owen (accentuated lines due to stress/trauma)

• Neonatal line (mark of birth- seperates prenatal & postnatal dentin/enamel)

structural feature

• Granular layer of Tomes (located near CDJ and DEJ (root dentin)

  • hypomineralized, granular appearance

pulp

origin: dental papilla (mesenchymal, inner cells- mesoderm)

functions:

• support

• sensory (afferent)

• nutritive (nutrition supply only through pulp!!)

• protective

cells:

• undifferentiated mesenchymal cells

• fibroblasts

pulp anatomy

pulp horns- occlusal most extent of the pulp

coronal pulp- shadows tooth shape apical/occlusal dimish first

—> make up pulp chamber (crown)

radicular pulp- continuous with periapical tissue: tubular in shape

—> extends from neck to apex (root pulp)

apical foramen- opening at root apex, entry for nerve & blood supply

• connects pulp to periodontal tissues

• may have accessory foramina

microscopic features of pulp

fibroblasts (most common cell type in pulp): protein synthesis: collagen

odontoblasts: reside pre-dentin

undifferentiated mesenchymal cells (by pre-dentin)

pulp stones: mineralized mass of dentin (not common)

• free from chamber wall

• attached to chamber wall

• embedded- enclosed in dentin

odontoblastic layer- nearest to dentin (capable of 2 and 3 degree? formation)

cell-free zone- nerves and capillaries

cell-rich zone- rich in vasculature

pulpal core (core)- deepest; extensive vascular supply

—> work together to ensure tooth remains vital

pulp age changes (how teeth can die)

• less cells and organelles

• higher fibrosis (collagen fibers)

• vascular plaques lead to less blood flow—> atherosclerosis

• apical foramen narrowing/obliteration (deposits of cementum overtime)

clinical considerations

pulpitis

• pulpal hyperemia- follows restoration (swelling, is reversible)

• acute pulpitis- rapid onset (react to extreme hot/cold, irreversible)

• chronic pulpitis- “comes and goes”

• chronic hyperplastic pulp (pulp grows out of tooth, typically children)

• necrotic or gangrene pulp (dead pulp—> no pain or sensitivity)

more considerations

• size- chambers decrease with age

• accessory canals

• periodontal lesions (can lead to pulpitis)

• pulp caps: direct and indirect (root exposure)

• pulpotomy (removal of coronal pulp of vital tooth- can put filling in)

• pulpectomy aka RCT (remove all pulp- put in gutta percha)

• symptoms of pulpal disease (sensitive to hot (worse), when don’t feel anything—> dead)

  • sensitive to cold (initial dying of tooth or need adjustment), hot- might be dying

enamel

origin- inner enamel epithelium (ectoderm)

96% inorganic / 4% organic + water

hyrdoxyapatote crystals

non collagen proteins between crystals

• non-vital, avascular !!!!

primary enamel- more opaque—> whiter

maturation of enamel

enamel formation

• apposition (protein matrix)

• maturation (mineralization)

ameloblasts (form enamel)

• post-eruptive: dynamic (environmental influence) —> fluoride can help to strengthen enamel that is left, but it is nonvital

mature enamel

• Tomes process- cell extension (preeruption)

• four ameloblasts to 1 rod

• extend from DEJ to surface

(most mineralized at tip of tooth)

microscopic features of mature enamel

• DEJ: scalloped

• Striae of Retzius: Neonatal line (can show due to stress at birth)

• Enamel Spindles: odontoblastic processes become mineralized in enamel (during formation- in cusp tips)

• Enamel Tufts: deepest 1/3; not as mineralized (DEj into enamel- similar to Tomes)

• Enamel lamella: narrow and longer. partially calcified (DEJ to enamel)

enamel defects/disturbances

• genetic dysplasia—> affects all teeth

• febrille illness—> incremental defects (lines) (when children have fever- form ring around teeth)

• tetracycline—> discoloration- yellow/gray

• fluoride > 2 ppm—> fluorosis (white or brown discoloration)

• hypoplasia (not enough enamel) vs hypocalcification (didn’t mineralize well)

• Turner’s tooth—> trauma to primary tooth (disruption in reduced enamel epithelium causing localized absorption)

enamel clinical considerations

enamel (clinical)

• no repair after eruption

• fluoride: topical / systemic

• bonding (etch—> micro-retention)

wear

• attrition—> tooth to tooth

• abrasion—> external/mechanical (cervical 1/3, clenching & grinding can also cause because of flexion—> sensitivity—> if deep enough, can die)

• erosion—> chemical (typically 6 & 11 linguals- bellemic or acid reflex “sucking on lemons”)

periodontium

hard/soft tissues which support the tooth in relation to the alveolar bone

• alveolar bone

• PDL

• cementum

• tooth

• gingiva

cementum

in healthy patients- not visible; anchors PDL (receives nutrition from PDL)

• thickest at the apex; thinnest at CEJ

• AVASCULAR: no innervation

• can form throughout life, like pulp

• pale, dull yellow

• grainy feel (for instrumentation)

• 65% mineralized

development of cementum

origin- dental sac

• forms after HERS disintegration

• cells—> cementoblasts

• cementoid—> mineralized cementum

PDL and cementum

PDL—> collagen ligament (from tooth to bone)

cementocytes- entrapped cementoblasts

CEJ patterns:

• 60% overlap

• 30% meet

• 10% gao

cementum

• repair—> apposition (PDL cementoblasts)

• types: acellular (less cellular on outside, everywhere besides apex & furcation) and cellular (apex & furcation)

alveolar bone

alveolar bone-

• VASCULAR- 60% mineralized, rapid remodeling

types:

• alveolar bone proper (alveolar process)—> socket lining (lamina dura)

• cortical bone—> outer plates

• trabecular bone—> spongy support

PDL functions and cells

functions: attachment, sensory, nutritional, “shock absorber, functions in visual grooves”

cells of PDL:

• fibroblasts

• cementoblasts

• osteoclasts/osteoblasts

• odontoblasts

• Epithelial rests of Malassez (following disintegration of HERS)

PDL fiber groups

collagen fibers (Sharpey’s fibers)

distribute occlusal forces- embedded into cementum

alveolar group

• alveolar crest

• horizontal

• oblique (MOST IMPORTANT)

• apical

• interradicular

transseptal (interdental ligament)- tooth to tooth (mesiodistal to cervical 1/3 of tooth?)

gingival fibers

• support marginal gingiva

• maintain tooth- gingival seal

types:

• circular (sinches gums, goes around entire tooth)

• dentogingival (tooth to gingiva- most extensive

• alveologingival (bone to gingiva)

• dentoperiosteal (tooth to bone)

soft tissue landmarks

• marginal gingival (free- what you probe into)

• attached gingiva (keratinized, tough)

• alveolar mucosa (nonkeratinized)

• mucogingival junction (between attached & unattached- alv mucosa)

• papilla

dental curvatures

functions of dental curvatures (HOC)

• stabilize arch

• prevent disease (from bacteria invasion)

• disperse occlusal forces (all teeth are different)

• protect soft tissues (help periodontium)

improper curvatures

consequences of improper alignment

• premature tooth loss

• periodontal problems

• occlusal discrepancies (ex. bruxism- grinding)

proximal contact areas

• adjacent tooth surfaces that touch

• size gets bigger towards posterior

contact locations

anterior

• incisal 1/3

• centered F-L

posterior

• middle 1/3

• buccal to center

importance of contacts

• prevent food impaction

• stabilize arch (want the teeth to be touching)

• synergy of stabilization

improper contacts

• gingivitis (reversible inflammation)

• tooth movement/occlusal trauma

• bone & muscular changes

• damage to support structures

embrasures (formed by proximal spaces)

• v-shaped spaces

• space and shape (occlusal & apical)

functions of embrasures

• spillway for escape of food

• reduces occlusal trauma

• self-cleansing

• protects gingiva

• reflects tooth form