Periodontal ligament

牙周韌帶

何坤炎副教授：高醫醫學大學何坤炎副教授：高醫醫學大學 口腔醫學院牙醫學系口腔醫學院牙醫學系07-312110107-3121101 轉 轉 7004 , 70297004 , 7029 kuyeho@kmu.edu.twkuyeho@kmu.edu.tw

學習目標：學習目標：• 牙周組織解剖結構及顯微結構• 牙周組織的進化與發展• 牙周組織的神經、血管• 牙周組織的功能

學習資源：學習資源：1. Ten Cate’s Oral histology. sixth edition, pp 241-2741. Ten Cate’s Oral histology. sixth edition, pp 241-2742. Rateitschak, Wolf, and Hassel: Color Atlas of Periodontology.2. Rateitschak, Wolf, and Hassel: Color Atlas of Periodontology. 1st edition, 19851st edition, 19853. Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 19784. Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p133 -140

Periodontium(牙周組織 )

Periodontal ligament Gingiva( 牙齦 )

Cementum ( 牙骨質 )

Alveolar bone ( 齒槽骨 )

Rateitschak, Wolf, and Hassel: Color Atlas of Rateitschak, Wolf, and Hassel: Color Atlas of Periodontology. 1st edition, 1985, p 1Periodontology. 1st edition, 1985, p 1

* It is attached to the dentine of the root by cementum and to the bone by alveolar bone. 牙周韌帶藉著牙骨質與牙本質附著 ,藉著 齒槽骨與骨頭附著 * It acts as adapting apparatus for support of the teeth during function 當行使功能時，作為適應的工具以支持牙齒

Periodontal ligamentPeriodontal ligament

1. PDL located between the cementum

and the periodontal surface of the

alveolar bone. 2. It surrounds the necks and roots of

teeth.

3. It is a fibrous connective tissue,

abundant with cellularity and

vascularity.

Ten Cate’s Oral histology. sixth edition, p 261,Fig.9-20Ten Cate’s Oral histology. sixth edition, p 261,Fig.9-20

• PDL contains a heterogeneous population of mesenchymal cells , when triggered appropriately, can differentiate toward an cementoblast or osteoblast phenotype, that can promote formation of bone and cementum

• Perivascular and endosteal fibroblasts when appropriately induced, have the capacity to form

PDL, cementum, and bone

• Compelling ( 令人信服的 ) evidence indicating that populations of cells within the PDL, during development and during regeneration, secrete factors that can regulate the extent of mineralization• Factors secreted by PDL fibroblasts may inhibit mineralization and prevent the fusion of tooth root with surrounding bone; for example, ankylosis

PDLPDL* It ranges in width from 0.15 to 0.38 mm, with thinnest

portion around middle third of the root( 最窄部分在 牙根中間 1/3 處 )* A progressive decrease with age* Tension and pressure site

From KMUH

Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p139, Fig. 11-18

Sharpey’s fibers Sharpey’s fibers (( 夏庇氏纖維夏庇氏纖維 ))These fibers are embedded in the cementum

and serve as an attachment for the tooth to

the surrounding bone.

夏庇氏纖維埋在牙骨質做為牙齒與周遭骨頭之附著

Sharpey’s fibers Sharpey’s fibers (( 夏庇氏纖維夏庇氏纖維 ))The principal fibers are more numerous but

smaller at their attachment to cementum

than at the alveolar bone

Evolution of PDLEvolution of PDL The central points of coordinated in the jaws is

the radical reconstruction of the mandible.1. In ancestral reptiles( 爬蟲類 )the teeth are ankylosed

( 連黏 ) to the bone. In mammals they are suspended ( 懸掛 ) in their sockets by ligaments.

2. The mandibular articulation is formed by a separated bone of mandible , articulare and quadratum.

Evolution of PDL (cont’) Evolution of PDL (cont’) 3. Dentary attains larger proportion of mandible →

finally forms mammalian mandible.

articulare → malleus ( 槌骨 ), quadratum →incus ( 砧骨 )

Dentary growing a condylar process, formed a new

temporomandibular joint ( 顳顎關節 )

Evolution of PDL (cont’)Evolution of PDL (cont’)4. In reptile, the growth of mandible is “suture ”

in mammal the cartilage of the condylar as the

most important growth site of the mandible.

5. In reptile, the growth of mandiblar body in height occurs in mandibular sutures where in mammals is occurred by growth at the free margins of the alveolar process.

Development of PDLDevelopment of PDL* The cells of the dental follicle give origin to f

ibroblasts of the developing PDL.

The formation of PDL occurs after the cells o

f Hertwing’s epithelial root sheath (HERS) ha

ve separated, forming the epithelial rests of

Malassez.

Development of PDLDevelopment of PDLA. Epithelial root sheathB. Undifferentiated mesenchyme of dental papillaC. Dental follicleD. OdontoblastsE. Epithelial restsF. CementoblastsG. Developing alveolar boneH. Developing cementumJ. Developing PDL

Berkovitz BK , Holland GR, Moxham BJ.: Color atlas &

textbook of oral anatomy. 1978, p170 Fig. 443

Cells of PDLCells of PDL* It divided into various categories: A. Synthetic cells: 1. fibroblasts 2. osteoblasts 3. cementoblasts

B. Resorptive cells: 1. fibroclasts 2. osteoclasts 3. cementoclasts

C. Progenitor( 原始細胞 )D. Epithelial rests of Malassez

E. Other: 1. mast cells 2. macrophages

Synthetic cells(Synthetic cells( 合成細胞合成細胞 )) * Synthesizing proteins for secretion

1. a large open-faced or vesicular ( 胞狀的 ) nucleus

containing prominent nucleoli ( 核仁 )

2. cytoplasm---hematoxyphilic---interaction of

RNA with acid hematin in H&E stain

3. clear, unstained Golgi membrane

FibroblastsFibroblasts (( 成纖維細胞成纖維細胞 )) * They are surrounded by fibers and ground substance and orientated parallel to the orientated bundles of collagen fibers

Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p138 Fig. 11-16

Osteoblasts Osteoblasts (( 造骨細胞造骨細胞 ))* Covering the periodontal surface

of the alveolar bone constitute

modified periosteum

Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p117, Fig. 302

CementoblastsCementoblasts(( 造牙骨質細胞造牙骨質細胞 ))* Similar to the distribution of osteoblasts o

n the bone surface

Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral a

natomy. 1978, p117 Fig. 300, 301

OsteoclastsOsteoclasts(( 破骨細胞破骨細胞 ))* Large and multinucleated, or small

and mononuclear ( 大而多核巨細胞 )* The characteristic multinucleated giant

cells exhibit eosinophilic cytoplasm.

* It occupy in Howship’s lacunae,

or surround the end of a bone spicule

in light microscope.

Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p149 Fig.12.16

* Osteoclasts are seen regularly in normal functioning PDL, in which the cell play an art in removal and deposition of bone that constitutes its remodeling ( 重塑形 )* Characteristic folds is termed ruffled or stri

ated border. It disappears in inactive osteoclasts

Osteoclasts (cont’)Osteoclasts (cont’)

• Resorption occurs in :

stage 1: demineralization at the bone margin

stage 2: disintegration ( 不結合 ) of the

exposed organic matrix

Cementoclasts Cementoclasts (( 破牙骨質細胞破牙骨質細胞 ))A. In PDL but undergo

continual deposition during life.

B. The cells located in Howship’s lacunae and the surface of the cementum.

From KMUH

Progenitor cellsProgenitor cells

* Undifferentiated and have the capacity to

undergo mitotic division( 有絲分裂 )* Stimulated appropriately, they undergo division

and one of the daughter cells differentiated into

a functional type of connective tissue cell

Epithelial rests of Malassez Epithelial rests of Malassez 1. Remnants of the epitheli

um of HERS

2. Network, strands, tubules rapid proliferation to pro

duce cyst ( 囊腫 ) and

tumors

Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p118 Fig. 304,305

Extracellular substanceExtracellular substance* Fibers: collagen ( 膠原纖維 ) oxytalan ( 抗酸纖維 )* Ground substance: Proteoglycans ( 酸性黏多醣 ) Glycoproteins( 醣蛋白 )

Ground substanceGround substance(( 基質基質 )) of the PDL of the PDL1. It is occupied the space between the cells

fibers, bloods and nerves

2. Comprises two major groups

1) proteoglycans or

acid mucopolysaccharides( 酸性黏多醣 )

2) glycoproteins( 醣蛋白 )

Fibers of the PDLFibers of the PDL

Many of collagen fibers are gathered together

to form bundles, each bundle or principal fiber

having a diameter of about 5µm, though smaller

bundles may be seen.

Principal fPrincipal fibers of the PDLibers of the PDL1. Alveolar crest group(齒槽向組 )

2. Horizontal group(水平組 )

3. Oblique group (斜向組 )

4. Apical group (根尖組 )

5. Interradicular group

(根間組 )

Ten Cate’s Oral histology. sixth edition, p 266, Fig.9-25ATen Cate’s Oral histology. sixth edition, p 266, Fig.9-25A

Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p134 Table 11-1

Interstitial space Interstitial space (( 裂縫間隙裂縫間隙 )) Contain a network of blood vessels, nerves, ly

mphatics, also a network of

finer fibers interlace (交錯 )

and support the dense

collagen bundles

Avery JK. Essentials of oral histology and embryology A clinical

approach. 1992, p133 Fig. 11-2B

Interstitial spaceInterstitial space

Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p137 Fig. 11- 13, 11-14

OxytalanOxytalan(( 抗酸纖維抗酸纖維 ))1. They are immature elastic fibers （彈性纖

維）2. Run in an axial direction, one end embedded

in cementum and the other often in the wall

of a blood vessel.

3. Function in supporting the blood vessel and collagen fibers

OxytalanOxytalan(( 抗酸纖維抗酸纖維 ))

Berkovitz BK , Holland GR, Moxham BJ.: Color atlas & textbook of oral anatomy. 1978, p115 Fig. 294Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p133 Fig. 11-3

Structure of PDLStructure of PDL

A. Blood vessels

1. from apical vessels

2. from intra-alveolar vessels

3. from gingival vessels

* 在齒槽骨端較牙骨質端多* 在韌帶之尖端及頸部有 豐富血管網

NervesNerves 2. Two types of nerve fibers : 1) Large and myelinated( 髓鞘 ), have

knob- like ( 節瘤狀的 )endings

2) Small and may not be myelinated, and

end in branch

3) The larger fiber appear to be concerned

with touch and the small one with pain

Berkovitz BK , Holland GR, Moxham BJ.: Color atlas &

textbook of oral anatomy. 1978, p119 Fig. 306B

Functions of the PDLFunctions of the PDL * Supportive

• During mastication the compressed PDL provides support for the loaded tooth. 咀嚼時被壓縮的牙周韌帶提供牙齒的支持

• Collagen fibers and ground substance act as a cushion for the displaced tooth. 膠原纖維及基質作為位移牙齒之襯墊

Functions of the PDLFunctions of the PDL * Supportive

• Pressure of blood vessels provides a hydraulic mechanism for support of the tooth. 血管的壓力提供支持牙齒的水力學機轉

* Nutritive

Blood vessel provide anabolites and remove the

catabolites

Functions of the PDL (cont’)Functions of the PDL (cont’)

* Sensory

Through nerve supply, it can detect the most

delicate forces to the tooth and very light

displacement of the tooth, and protects the

tissue from the effects of excessively

vigorous masticatory movement.

Functions of the PDL (cont’)Functions of the PDL (cont’)

* Homeostatic （恆定）1. The cell of the periodontal ligament have a capacit

y to resorb and synthesize extracellular substance of the connective tissue of the ligament.

2. If homeostatic mechanism are upset will result in ankylosis bone and tooth

3. If the balance between synthesis and resorption is disturbed, the quality of the tissue will be change.

Homeostatic (cont’)Homeostatic (cont’)

4. If loss of homeostasis function, much of

extracellular substances of the ligament is lost,

the width of the periodontal space is decreased.

Clinical considerationsClinical considerations

1. The thickness of PDL seems to be maintained by the functional movement of the tooth2. Thin in functionless and embedded teeth wide in teeth that are under excessive occlusal stresses3. Pulp inflammation apical granuloma ( 肉芽腫 ) or cyst ( 囊腫 )

結論結論1. PDL provides an attachment for the tooth to bone

of the jaw while permitting the teeth to withstand

the considerable forces of mastication

2. The balance between formation and maintenance

of mineralized tissue versus soft connective tissue

of PDL require finely regulated control over cells

in the local area.