Dental pulp （牙髓） 何坤炎副教授：高醫醫學大學 口腔醫學院牙醫學系 07-3121101轉 7004 , 7029 kuyeho@kmu.edu.tw

學習目標： 學習資源： pulp的解剖結構 pulp的的組織結構 pulp的功能 pulp的退行性變化 Ten Cate’s Oral histology. sixth edition, pp 397-416 Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, pp105-122

Anatomy of the pulp * Human has 20 primary It consists of soft connective tissue, vascular, lymphatic, and nervous tissue * Human has 20 primary and 32 permanent in each respective dentition Total volume for permanent teeth is about 0.38 ml Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p106, Fig.9.1

Pulp * Coronal portion--- pulp chamber occupies the crown of the tooth and resembles the shape the outer surface of crown dentin * Radicular portion--- root canal --- Apical foramen --- Accessory canal (Incidence: 33 % permanent teeth) Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p107, Fig.9.2

Coronal pulp --- pulp chamber Coronal pulp --- pulp chamber * Pulp horn, pulp extend into cusp, No of these horns depends on cuspal number * With age, coronal pulp decreases in size owing to continued dentine formation, progresses faster on the floor than other wall Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p107, Fig.9.2

Radicular pulp * Continuous with the periapical Root canal extend from cervical to apex of the root, tapered and conical * Continuous with the periapical tissue through apical foramen * Become smaller with age owing to continued dentinogenesis, smaller also due to apical cementum deposition Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p107, Fig.9.3

Apical foramen is the pulp opening to periodontium Opening varies in size from 0.3 to 0.6 mm, slightly larger in maxillary than in mandibular teeth 2. Generally is centrically located in the newly formed root apex but become more eccentrically located with age, and functional influence

Apical foramen 3. Sometimes apical opening is found on the lateral side of the apex 4.Tooth tipped apex deviate in the opposite direction Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p108, Fig.9.4

Development In earliest stage: the future papilla cause the oral epithelium to invaginate and form enamel organs Dental papilla further control the forming enamel organs to be an incisor or molar * Pulp is initially called dental papilla, after dentin forms: pulp * 8th week of embryonic life Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p110, Fig.9.7

Histology of the pulp 1. Large nerve trunk &blood vessel in the central 2. Peripherally: odontogenic region cell-free zone (Weil’s) cell-rich zone Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p109, Fig.9.5

Histology of the pulp Cell-free zone (Weil’s): area of mobilization and replacement of odontoblasts Cell-rich zone: composed principally of fibroblasts and undifferentiated mesenchymal cells * During early dentinogenesis, many young collagen fibers in this zone OD CRZ CFZ From KMU

Odontoblast 5-7 m in diameter, 25-40 m in length Near pulp-predentin junction, cytoplasma is devoid of organelles, at this clear zone cell constricts to 3-4 m, where the cell process enters the predentinal tubule Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p109, Fig.9.5

Odontoblast process into mineralized dentin, contains filaments and microtubes through its length to DEJ Recent information indicate it extends through DEJ into enamel as spindles Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p111, Fig.9.8

The form and arrangement of the cell bodies of odontoblasts are not uniform throughout the pulp Highly columnar in crown, Low cuboidal in middle of root, Flat and spindle close to the apex

Ground substance (jell-like tissue) Components of pulp Ground substance (jell-like tissue) 1) Proteoglycans or acid mucopolysaccharides (酸性黏多醣) 2) Glycoproteins (醣蛋白) Alternation in composition caused by age or disease, interfere with this function, producing metabolic changes, reduced cellular function, and irregularities in mineral deposition

Fibroblast: stain deeply with basic dyes, and cytoplasm is lighter stained appears homogeneous, typical stellate and extensive process Function in collagen formation and protein synthesis * Also ingesting and degrading collagen when approximate stimulated Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p112, Fig.9.12

Fibroblasts Characterized by their functional state, young pulp actively producing matrix and collagen, star shape, have multiple process with ovoid nucleus Abundant RER and mitochondria Old pulp--- fiber increase, smaller and spindle-shaped with few organelles Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p112, Fig.9.13

Collagen and fine fibers in pulp Collagen bundles: cross-sections at 64 nm intervals, range in length 10-100 m or more Fine collagen fibrils: argyrophilic fibers, originate from pulp fibroblasts  formation of predentin

Both type I and III collagen approximate (55:45) in the pulp remain constant from beginning of tooth development to tooth maturity Type I probably produced by odontoblast, type III by pulp fibroblasts

Young pulp fibers are relatively sparse If pulp is irritated, fibers may accumulate rapidly, older pulp contain more collagen of both bundle and diffuse type * The greatest concentration of collagen seen in most apical portion of the pulp Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p114, Fig.9.17

Histiocyte or macrophage irregularly shaped with short blunt process. Smaller, more rounded, and darker staining than fibroblast, and exhibits granular cytoplasm. * Disclosed by trypan blue (intravital dyes), aggregation of vesicles, phagocytized dense irregular bodies

Vascularity Peripheral plexus Vessels arising from external carotids to superior or inferior alveolar arteries. Thin-walled arteries and arterioles enter apical canal and pursue a direct route up to coronal area Central core Peripheral plexus Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p115, Fig.9.18, 19

Vascularity subdivide to form an extensive vascular capillary Arteriole in coronal portion of pulp they divide and subdivide to form an extensive vascular capillary network, U-looping is seen, this anatomical configuration is thought to be related to regulation of blood flow Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p115, Fig.9.19

* Pulpal blood flow is most rapid than areas of the body Arterioles is 0.3 -1 mm/second Venules is 0.15 mm/second Capillaries about 0.08 mm/second * Pulpal pressure is among the highest of the body

Blood vessels Tunica intima --- squamous or cuboid endothelial cells surrounded by closely associated basal lamina Tunica media --- 1-3 layers of smooth muscle cells, occasionally endothelial cell wall in contact with muscle cells this is termed a “myoendothelial junction” Tunica adventitia --- made up of a few collagen fibers forming a loose network around the large arteries

Veins and venules 1. 100-150 m in diameter, larger than arteries 2. Tunica adventitia lacking or appear as fibroblast 3. Endothelial cells more flattened 4. In central region of root pulp

Capillary appears as “endothelium - lined” tubules (8-10 m), nuclei may be lobulated and cytoplasma projections into luminal surface * Fenestrated capillaries may involved in rapid transport of metabolites, for predentinal matrix formation, and calcification of dentin

Nerves 1. Most nerves are myelinated 2. Mediate the sensation of pain caused by external stimuli 3. Non-myelinated nerves closed to blood vessels, sympathetic in nature, vasoconstriction 4. Parietal layer of nerve--- plexus of Raschkow Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p116, Fig.9.21

5. Nerve ending close to odontoblast plasma membrane separated only by 200 Å cleft 6. Most of nerve endings in odontoblast are sensory afferents and sympathetic from superior cervical ganglion Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p117, Fig.9.23

Pulp tissue nerve fibers 1. A fibers fast conducting, diameter 1-6 m , for early stage of damage in dentin to sense the pain, for sharp, localized pain 2. Aβ fibers 1%, 6-12 m 3. C fibers--- nonmyelinated, 0.4-1.2 m, dull and diffuse pain

Most of nerve fibers and endings are found in pulp horns Sensory response in pulp can distinguish among thermal, mechanical and tactile *Raschkows nerve plexus and free nerve ending of unmyelinated axons in predentin and dentin layer

Functions of the pulp 1. Initiative (inductive) 2. Formative 3. Protective 4. Nutritive 5. Reparative

Functions of the pulp 1. Inductive---induce oral epithelium differentiate into dental lamina and enamel organ formation, and becoming a particular type of tooth 2. Formative---odontoblast develop organic matrix and function in its calcification, dentin is formed

Functions of the pulp 3. Nutritive- nourishes dentin through odontoblast and their process, and by blood vascular system 4. Protective---sensory nerves responds with pain to all stimulus Sympathetic---reflux, control circulation of blood vessel

Functions of the pulp 5. Defensive or reparative--- producing reparative dentin and mineralizing any affected dentinal tubules Macrophage and PMN aid in the process of repair Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p119, Fig.9.26

Functions of the pulp Provide vitality to teeth with its cells, blood vessels, and nerve Endodontic treated tooth function without pain but lost its protective mechanism that the pulp nerve provide

Regressive Changes * Cell changes --- aging pulp are characterized by fewer cells, decrease in size and number of various cytoplasmic organelles, less perinuclear cytoplasma, and possess long, thin cytoplasmic processes

Regressive Changes * Fibrosis -- accumulation of diffuse fibrillar components and bundles of collagen fiber Collagen increase is noted in medial and adventitial layers of blood vessels Any external trauma usually cause localized fibrosis and scarring effect

Regressive Changes * Vascular changes --- outer diameter of vessels walls becomes greater as collagen fibers increase in the medial and adventitial layers * Calcification in the walls of blood vessels is found in the region near apical foramen

Pulp stone <denticle> Classification: Structure---true, false denticle and diffuse calcification More than 60 y/o of age ♣ Incidence and size of pulp stones increase with age Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p120, Fig.9.28

Pain conduction– three mechanisms 1. Dentin contains nerve ending and directly innervated 2. Odontoblasts acts as a receptor and are coupled to nerve in the pulp 3. Receptors are in the pulp and are stimulated by fluid movement through the dentinal tube Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p118, Fig.9.25

Pain conduction--Hydrodynamic theory Stimulation causes odontoblasts and their processes to move contact with nerve endings in the predentin and pulp. * It results in mechanoreceptors receiving the impulse that conduct pain response to central nerve system Avery JK. Essentials of oral histology and embryology A clinical approach. 1992, p118, Fig.9.25

Clinical considerations 1 Clinical considerations 1. Nonvital tooth becomes brittle and is subject to fractures 2. Aging pulp chamber become smaller, due to excessive dentin formation  difficult to locate root canal 3. Accessory canals--- deep periodontal pocket may cause inflammation of dental pulp

結論 ♣ The vitality of dentin-pulp complex plays an important role in maintenance of a functional dentition, and maintaining tooth vitality while focusing particularly on the cell of pulp. ♣ Preservation of the vitality of pulp during operative procedures is the most important challenges to clinical dentist