The healing capacity of mechanically exposed and bacterially contaminated dental pulps was assessed in monkeys after capping with 2 commercial Ca(OH)2 containing compounds. One hundred eighty teeth in 7 monkeys were employed, 45 as untreated controls and 135 as treated exposures. Class V buccal cavity preparations resulting in pulpal exposure were prepared, left open to the oral cavity for 0, 1, 24 h or 7 days and employed as controls, or debrided, capped, restored with amalgam and left undisturbed for 5 weeks as treated exposures. Zero and 1 h untreated exposures presented damage from the mechanical trauma only, whereas 24 h and 7 day pulp wounds exhibited pronounced infiltrations of polymorphonuclear and mononuclear leukocytes. In addition, the 7 day exposures demonstrated several teeth with partial and total necrosis. Treated 0, 1 and 24 h exposures demonstrated wound healing, minimal pulp tissue inflammation, reorganization of soft tissue and formation of new hard tissue at the exposure site in 86 of 99 teeth. Treated 7 day exposures healed less frequently, showing signs of dentin bridging in 15 of 27 teeth. This study indicated that mechanically exposed and orally contaminated dental pulps in monkeys have a high capacity to resolve inflammation and initiate healing with new dentin formation at the exposure site when treated as described.

The results from this study showed a variety of pulpal responses to various calcium hydroxide materials when placed directly on the dental pulp. Two of the materials proved to be more successful at stimulating reparative dentin bridging and healing of the underlying pulp tissue. The remainder of the pulp capping agents were ineffective at healing the pulp and forming a reparative dentin bridge. When teeth were capped with these other agents, the pulp showed necrosis and chronic inflammation.

The purpose of this investigation was to study the nerves in mouse molar teeth during their development to observe their distribution and their relationship to the odontoblast and its process. The specimens were first assessed by light microscopy using silver staining techniques. It was found that by nine days after birth, major nerves appeared in the pulp organ and extended to the basal region of the odontoblasts. At 15 days, a subodontoblastic neural plexus had developed, and by 25 days, isolated nerves penetrated into the predentin of the pulpal horns. From 25-70 days, a highly organized subodontoblastic plexus was apparent with branches extending into the odontoblastic layer, predentin and inner dentin.Ultrastructural study revealed small, nonmyelinated nerves at the basal region of the odontoblasts by nine days. Both myelinated and small, nonmyelinated nerves appeared in the subodontoblastic plexus. Small nerves closely associated with the odontoblastic process were found within the predentinal tubules by 25 days. These processes contained occasional mitochondria, numerous microvesicles and small dark granules. From 35-50 days of age, similar nerves which exhibited alternate constrictions and dilations along their lengths were found in the tubules of circumpulpal dentin. By 60 days, both Schwann cell covered and naked axons appeared among the odontoblasts, and by 70 days Schwann cell covered axons appeared in predentin.The pattern of development of pulpal nerves has been observed by light microscopy in silver impregnated sections of teeth by Arwill ('58), Fearnhead ('57, '61), Kubota et al. ('60) and Bernick ('59a). Arwill ('58) utilized both silver and iron trioxyhematoxylin staining and observed no nerve fibers in developing dentin of 13-32 week old human fetuses nor in mineralized dentin of erupted human permanent teeth. A few nerve fibers were observed in predentin of the erupted teeth, but such fibers did not appear intratubular in location. Fearnhead ('57) reported that the subodontoblastic nerve plexus did not appear until root formation was nearly complete, and that innervation of coronal dentin followed only after the tooth had been in functional occlusion for several years.Occasional nerve fibers in the predentin of human teeth have been reported by Fearnhead ('57, '61), Rapp et al. ('57 ('59b, '64). Fearnhead ('57) noted that small intratubular nerves about 0.2 in diameter extended through the predentin and into the dentin for a short distance. In no instance were such nerves found to traverse the entire thickness of the dentin or terminate near the dentino-enamel junction. On the other hand, Stella and Fuentes ('65) reported intratubular nerves which terminated in the peripheral dentin. However they used iron hematoxylin which is a nonspecific stain for neural elements.More recently, the increased magnification and resolution of the electron microscope have yielded further information concerning intradentinal nerves. Frank ('68b) identified intratubular nonmyeli- nated nerve fibers appr...

Human primary teeth in the stages of late root formation, mot completion and root resorption were impregnated with silver to allow study of the distribution of nerves in the pulp.Neural trunks composed of many individual, myelinated nerve fibers enter the apical foramen of primary teeth and pass in a coronal direction, often in close association with blood vessels. Neural trunks in the crowns of the teeth divide into smaller branches, which divide further into myelinated nerve fibers, which become interwoven to form the parietal layer (plexus of Raschkow). An occasional unmyelinated fiber leaves this zone and passes into the odontoblastic layer of cells where it appears to terminate with no specialized ending apparent. No nerves were seen to enter the predentin or dentin.As primary teeth begin to undergo root resorption, degenerative changes such as thickenings, varicosities and fragmentation appear in the nerves. The quantity of neural tissue also decreases. The greater the amount of resorption, the greater are the degenerative changes. In teeth in which the roots are almost completely resorbed, only a small number of nerves remain.The pattern of distribution of nerves in primary teeth is observed to be similar to that of permanent teeth. The density of the innervation of the primary teeth, however, is not found to be as great as that of permanent teeth.The innervation of human primary teeth has received little attention when compared to similar research on permanent teeth. The lack of interest in the distribution of pulpal nerves in the primary dentition may result from the belief that the pulps are similar to those of permanent teeth or that primary teeth are not a lasting component of the oral cavity. Clinicians have long been aware of a lower sensitivity to pain in primary teeth than in permanent teeth which may be due to differences in number and/or distribution of their neural components. Another area in which information is lacking involves changes in the neural tissue of the primary teeth during the period of root resorption (and exfoliation). The present investigation is concerned, therefore, with the distribution of nerves in primary teeth during stages of root formation, root completion, and root resorption.Bradlaw ('36) studied neural degenerative changes in both human and animal primary teeth using a variety of silver impregnation techniques. He observed these changes to occur prior to exfoliation in some teeth but not in others. Mohuiddin ('50) studied the primary and permanent teeth of the cat by means of both the Romanes' and Bielschowsky silver methods. The permanent and nonresorbing primary teeth exhibited patterns of innervation similar to those observed for human permanent teeth by Rapp, Avery and Rector ('51). All of these investigators observed neural fibers within the pulp to form arborizations or a parietal layer (plexus of Raschkow) adjacent to the dentin and then terminate between or among the odontoblasts. A few nerves were found in the predentin and dentin, but none were obse...

Ixmor)ucTIoT\-Tlie rather extensive litei-ature dealiiig with observations 011 tooth a i d ciiariiel includes 110 systematic study of tliiii wctioiis of undecalcified developing tooth by electron microscopp. The present work reports on such ail investigation, the ai.ca studied being the labial aspect of the basal id of tlic liaiiistei. lowei. incisor. Tlic lower incisor was selected for. stntlp since it is cwiitiiinously grom7ing and therefore allows exaiiiiiiatioii of all stages of developnieiit in the same tooth.It, large size nialres it coiir~eriieiit to work with. An excellent dewriptioii of tlic development, calcification, aiid eruption of the rat iiicisor together with a review of the literature has 1)ccii given hy Fai-ris ant1 Griffith ( '49).Deiztiue. Tliere exists, in the literature, coiisiilerable disagreement as to tlie i i a t u r~ of the pi'otoplasmic extension of tlie odontoblast, " Toriics' film-. " Rodcclwr ( '22) gave an exteiisivc s u n v y of tlie 1itei.atni~ aiid conclucled the odontohlast cxtcnsion to be a tubulai-strnctiire. Other investigators such as Orban ('49) and Soyes, Schour and Noyes ('42) have expressed tlic opinion that Tonics ' fibers a1.c "solid " cytoplasmic esteiisioiis of the odontoblast. * This p l x r is 1):iscd iii 1)ai t on \ro1 k perfornicd iiiiclci (*ontinct \I it11 the 1'1iitedStates Atomic Eiieig? Coiiiiiiissioii a t the Unirersitv of liocliestei, Atomic Energy Pioject, Rocliester, New P o l k . 1)ep:ti t m t~n t of lixdiation Biology, The l'iiircrsity of Rochcster School of Ile(11ciiic and Dciitietiy, liocliestei, Tzcw York. r)e+art~i~ent of a4ii:itoniy and Di\isioii of 1)ciital liesearcli, l'lic I'niversity of 12oc.llester School of 3lctlir1nc and Deiitistiy, 13orlrc.ster 20, S e w 3rorlc. 109