Chapter 2 Periodontium /Periodontal Tissues （牙周组织）

Introduction The gingiva（牙龈） The periodontal ligament（牙周膜） The alveolar process (牙槽突)

The Gingiva located around the necks of teeth keratinized epithelium(角化上皮) function during mastication

The periodontal ligament suspend the tooth in the socket provide a cushion against occlusal forces provide a delicate sense of touch and pressure carry oxygen and nutrition

The alveolar process the bony extension of the mandible & maxilla provide the necessary support for the teeth an attachment for periodontal ligament fibers compensate for tooth movement

Cementum an attachment for periodontal ligament fibers provide compensation for occlusal wear protect the sensitive dentin

Objective Histologic structures and function of the periodontal tissues the gingiva the periodontal ligament the alveolar bone

Part I Gingiva

Introduction Position: around the necks of teeth Color: pink

Surface Anatomy The free gingiva(游离龈) The attached gingiva(附着龈) Interdental papilla Free gingiva Attached gingiva The free gingiva(游离龈) The attached gingiva(附着龈) The interdental papilla(牙间乳头)

Free Gingiva Boundaries Coronally: the gingival margin Apically: the free gingival groove, 1.0~1.5mm (游离龈沟，GG)

Free Gingiva Gingival sulcus(龈沟) : 0.5~3mm Gingiva sulcus Gingiva sulcus Gingival sulcus(龈沟) : 0.5~3mm coronally: the gingival margin bottomly: the junctional epithelium the inner margin: the tooth surface the outer surface: sulcular epithelium

Attached Gingiva Position: between the free gingiva & the alveolar mucosa the free gingiva: the free gingival groove the alveolar mucosa: mucogingival junction

Stipple orange peel appearance the absence: an initial sign of pathology

Interdental Papilla Position: on the inter-proximal areas of the crowns on the labial and lingual surfaces Shape: wedge-shaped

The col interproximal to the vestibular and oral cavity surfaces of the interdental papilla a concave area anteriorly: like a pyramid posteriorly: be flattened plaque and calculus form: sign of inflammation

Histological Structure The surface epithelium Lamina propria rete epithelium ridges

The surface epithelium the margin of the gingiva the sulcular epithelium the epithelium attachment stratified squamous epithelium

keratinized, parakeratinized, or nonkeratinized

Gingival epithelium: % of cases Surface cell Stratum granulosum nucleus Keratinized 15 No Present Nonkeratinized 10 Yes None Parakeratinized 75 Partially None

pigment granules: basal layer, melanocyte

The sulcular epithelium thin lack keratinization

The col thin nonkeratinized extensions into the underlying connective tissue

The junctional epithelium Definition: a seal between the epithelium and the tooth, thin

Characteristics the basement membrane is smooth

a smaller tonofilament-to-cytoplasmic ratio desmosomes is four times less - molecules of high molecular weight can migrate into the surface rough endoplasmic reticulum & Golgi apparatus are highly developed - protein synthesis & glycosylation.

the attachment: cuticle & hemidesmosome attachment plaque tonofilaments lamina lucida and lamina densa cellular fibrils

high rate of cell turn over: the attachment between epithelium and tooth is dynamic

disturbance of the epithelial attachment: deepen of the gingival sulcus, form periodontal pocket

the relation between the gingiva and the tooth: changes constantly by age 20 or 30 year old: enamel 40 year old or later: cementoenamel junction Elderly: cementum

Lamina Propria The gingiva fibers

dentogingival group: the cervical cementum - the lamina propria alveologingival group: the alveolar crest - the lamina propria circular group: circle the tooth dentoperiosteal group: the cementum - the periosteum of the alveolar bone transseptal group: the cementum - the cementum of the neighboring teeth

elastic fibers: the walls of larger blood vessels fibroblasts, macrophages, lymphocytes and plasma cells.

Vascularity and Nerves highly vascular: the branches of the alveolar arteries

well innervated: touch endings, temperature and pain receptors

Summary The free gingiva. The attached gingiva, and the interdental papilla The free gingiva groove: separate the free and attached gingiva The mucogingival junction: separate the gingiva and the alveolar mucosa

The gingival epithelium : keratinized

The epithelial attachment: cuticle, hemidesmosome

Lamina propria: fiber groups - dentogingival, alveolar gingival, circular, dentoperiosteal, and transseptal No submucosa

Highly vascular and well innervated

Periodontal Ligament

Introduction The terms: periodontal ligament / periodontal membrane

Position: between the cementum and the alveolar bone proper Thickness: 0.15~0.38mm, the thinnest part - the midroot

The collagen fiber bundles Highly cellular Rich nerve and blood supply.

Histological Structure dense connective tissue composed of fibers, cells, and stroma

Fibers Principal fibers the bundles of collagenous fibers between the cementum and alveolar bone proper

Sharpey’s fibers: the embedded portions of principal fibers

Space fibers the loose connective tissue between the principal fiber bundles contain the blood vessels, lymphatics, and nerves

The groups of the principal fiber bundles the alveolar crest fibers the horizontal fibers the oblique fibers the apical fibers the interradicular fibers

Principal Fibers Group name Location of attachment. Function Principal Fibers Group name Location of attachment Function Alveolar crest Cervical root to alveolar crest of Resist vertical and alveolar bone proper intrusive force Horizontal Midroot to adjacent alveolar Resist horizontal bone proper and tipping force Oblique Apical one third of root to Resist vertical and adjacent alveolar bone proper intrusive force Apical Apex of root to fundic alveolar Resist vertical forces bone proper Interradicular Between roots to alveolar bone Resist vertical and proper lateral movement

Oxytalan fibers transmission electron microscopic observation fine fibers

the special stains part of the support system of the principal fibers.

Summary Position: between the root surface and the alveolar bone proper Thickness: fairly constant

Principal fibers Alveolar crest Horizontal Oblique Apical Interradicular

Oxytalan fibers: fine fibers aid in the support of the ligament

Next Class Hour The cells, vascular, lymphatic, and neural supply of periodontal ligament The histological structure of alveolar bone

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