James K. Avery

Histological Considerations of Direct Pulp Capping Agents

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.

H 3-HRP Analysis of the Nerve Supply to Primate Teeth

Sensory, sympathetic and parasympathetic ganglia located in the head and neck of rhesus monkeys were histologically examined after injection of H3-HRP into the right mandibular premolars and molars. The results showed positive labeling of ganglionic cell bodies located in the ipsilateral trigeminal, superior cervical, and otic ganglia, plus the ipsilateral mesencephalic nucleus of the trigeminal nerve.

The effects of combined nerve resection and cavity preparation and restoration on response dentine formation in rabbit incisors.

Abstract This study was carried out to determine the effects of nerve resection and cavity preparation with restoration (CPR) on the formation of response dentine in continually developing rabbit incisor teeth. Resections of the inferior alveolar nerve (IAN) and/or the superior cervical ganglion (SCG) were performed on the right side of 42 adult New Zealand rabbits. Fifteen days were allowed for neural degeneration, after which uniform CPR were placed in both resected and adjacent normal incisors. Half of the operated animals were killed 14 days after CPR placement and the second half, 35 days after. Both radiographic and histological evidence revealed a dramatic increase in dentine deposition following IAN and IAN-SCG with CPR both 14 and 35 days after cavity preparation. The pulps of these neural-resected and CPR incisors were small and limited to the growing end of the tooth. Most of the newly formed dentine appeared regular and without defects; however, the dentine found at the apex was distorted with the appearance of osteodentine. At 14 and 35 days after CPR, the SCG-resected incisors showed no more response dentine formation than adjacent non-resected teeth. Radiographic and histologic appearance of CPR treated incisors indicated they were comparable in size and morphology to the controls.

Structural elements of the young normal human pulp

Abstract The structural elements of the young normal dental pulp are fibrocytes and numerous small blood vessels. Structural organization of this organ is evident as the teeth reach functional occlusion. Larger-diameter vessels appear more centrally located, and fine capillaries appear among the odontoblasts. Fibroblasts then appear, and associated collagen fibers are evident throughout the pulp. Gradually the peripheral zone of the pulp organizes into cell-free, cell-rich zones, and a parietal layer of nerves is evident. Ultrastructural evidence of myelinated and nonmyelinated nerves is seen in the pulp, and neural terminations are noted in the tubules of predentine.

Ultrastructure of Intradentinal Nerves After Resection of the Inferior Alveolar Nerve in Mice

Intradentinal nerves in humans have been described by light microscopic techniques by Fearnhead (J Anat 91:267-277, 1957), Rapp, Avery, and Rector (I Canad Dent .Assn 23: 447-453, 1957), Arwill (Trans R Sch Dceit 3:1-88, 1958), and Bernick (J Dent RJs 43:406-411, 1969). Ultrastructure of intradentinal nerves has been reported by Frank (Den1line and Pulp, N. B. B. SYMONS (ed), 1968. pp 115-145). Although the presence of nerves in predentin and in calcified dentin has been established, the origin of these nerves has remained in doubt. Fearnhead (Proc Roy Soc Med 54:877884, 1961) found no intradentinal nerves in a monkey after resection of the infeiior alveolar nerve. However, there is no ultrastructural evidence to date to clarify whether the nerves present in predentin or circLimpulpal dentin ate from the inferior alveolar or sympathetic nerves. The present observations are from first molars of mature white mice (50 days) in which the inferior alveolar nerve was resected by the inframandibuilar approach on the right side; the teeth of the left side served as controls. Verification of resection was established by gross dissection at the time of killing. At 21 days after resection, the teeth were fixed in 1.33% osmic acid in s-collidine buffer at 4 C for two hours, dehydrated through graded alcohols and propylene oxide, embedded in Epon 812, sectioned at 500 to 800 A, and viewed with an electron microscope.: Nerve fibers from both the control and resected teeth were selected for comparison from similar locations, namely at the odontoblastic-predentinal border at a cuspal tip. Small unmyelinated nerve fibers from the normal side located just inside the predentin from the odontoblast exhibited a central axon that contained a mitochondrion, several large vesicles, and cross-sectioned neurofilaments. The axon was surrounded completely by a Schwann cell (Fig 1). The nerve fiber from the resected side also was a small unmyelinated nerve located at the odontoblastic-predentinal border. The nerve exhibited an axon that appeared badly shrunken and degenerated and that contained a large dark body and apparent remnants of a mitochondrion, but no vesicles (Fig 2). The Schwann cell surrounding the degen-

FUSION CAPABILITY OF RAT EMBRYONIC EXTRA-ORAL TISSUE IN VITRO

Abstract Epithelial mesenchymal interaction in the fusion process was studied by the means of fusing different extremities of a 15 day 16 hr rat foetus. The extremities used were the hands, feet, and tails, which at this stage of embryologic development appear to have a similar type of epithelial covering but differ markedly in the degree of specialization of the underlying mesenchyme. Two hands from one embryo were placed in palm to palm contact and grown under organ culture conditions for 72 hr with ten pairs of hands making up the experimental group. Ten pairs of feet made up the second experimental group with two feet from the same embryo being placed in sole to sole contact and grown under organ culture conditions. The third experimental group consisted of ten pairs of tails from littermate embryos and were placed side by side and cultured for 72 hr. In all three experimental groups, fusion with epithelial breakdown occurred though to different extents. It was noted that the degree of mesenchymal penetration across the interrupted epithelial barrier was related to the extent of specialization of the mesenchymal tissue. The greater the degree of specialization of the mesenchyme the less was the intermingling with the mesenchyme of the opposite member. The most specialized extremity the hand, also showed the lowest incidence of the fusion process progressing as far as the epithelial breakdown stage.

Histopathologic evaluation of the effects of new polycarboxylate cements on monkey pulps

Abstract Standard-depth cavities and pulp exposures were prepared in seventy-five rhesus monkey teeth. Four experimental zinc polycarboxylate cements and a control, zinc oxide-eugenol, were placed in randomly selected teeth of both arches and evaluated after 1, 3, and 8 weeks. The pulpal response beneath the sixty standard-depth cavities showed that all the experimental polycarboxylate cements and the control elicited mild reactions. The histologic response of the pulp in these teeth included slight disruption of the odontogenic zone, infiltration of few inflammatory cells, and minimal amounts of response dentin. In the fifteen teeth with exposed pulps, the pulpal response was moderate, characterized by a localized necrotic layer adjacent to the polycarboxylate cement walled off by a thin fibrous zone, and slight inflammation pulpal to the fibrosis.

Ultrastructure of Capillaries in the Odontoblastic Layer

Terminal extensions of subodontoblastic capillaries have been observed histologically among odontoblasts in coronal pulp in a variety of species, including man. James (J Anat 89:54749, 1955), Adams (I Dent Res 38:968-78, 1959), Klingsberg et al (J Dent Res 38:419, 1959), Adams (Arch Oral Biol 7:773-774, 1962), and Jesson (Atda Odontol Scand 25: 491-523, 1967) observed capillaries at varying depths among odontoblasts, but not in contact with the predentinal surface. This study was carried out to clarify the ultr:astructural relationships of terminal capillaries in the odontoblastic layer of coronal pulp. Present observations are from 70 first molars in functional occlusion in 35 white mice (30 to 60 days old). The teeth were extracted and fixed 1.33% osmic acid in s-collidine buffer at 4 C for two hours, dehydrated through graded ethanol and propylene oxide, embedded in Epon 812, sectioned at 500 to 800 A, stained with uranyl acetate, and viewed with an electron microscope. The capillaries were located at varying depths within the odontoblastic layer and frequently were close to the predentinal surface in the pulpal horns (Fig I). In older teeth (50 to 60 days), the capillaries seemed closer to the predentin than in the younger molars (30 to 40 days). The ultrastructure of the terminal capillaries revealed an endothelial-lined channel with a lumen slightly larger than one red blood cell (Fig 1). The wall of the endothelial cell was thin with an irregular-shaped nucleus. Intracytoplasmic structures included several elements of rough endoplasmic ricticulum, occasional small, round mitochondria, and frequent pinocytotic microvesicles. Along the more flattened side of the capillary opposite the nucleus occasional pores or fenestrations appeared in the endothelial cell wall (Fig 2). A continuous basement lamina enclosed the periphery of the capillary and separated the endothelial cell wall from the thin extensions of the pericytes or adjacent odontoblasts. The terminal capillaries were not encircled completely by the processes of the pericytes and were classified as A-l-alpha capillaries (BENNETT ET AL, Am J Physiol 196: 381-90, 1959). Fenestrations of the terminal capillaries among odontoblasts appeared in the region of the endothelial cell wall not enclosed by pericytes (Fig 2); this left only the basal lamina separating the capillary pores from adjacent odontoblasts. This arrangement allows

Differential Binding of 14C-Cortisone in Fetal, Placental, and Maternal Liver Tissue in A/Jax and C57BL Mice

When 14C-cortisone was given to pregnant A/Jax and C57BL mice, the concentration of radioactivity firmly bound to fetal tissue was significantly higher in A/Jax mice than in C57BL mice. Differences in the binding of cortisone to tissue proteins may explain the differential incidences of cleft palate in A/Jax and C57BL mice.

Demonstration of Cholinesterase in Teeth

Human teeth have been studied by treatment with copper thio-choline, the method developed by Koelle for demonstrating activity of both specific and nonspecific cholinesterases. Freshly extracted teeth were collected and immediately sectioned on a cutting machine designed for calcified tissues. One series of teeth was sectioned sufficiently thin for microscopic study. Another series of teeth was bisected to expose the pulp chambers to the reagents. These teeth were divided into 5 experimental groups. The first group was treated with 10-6M di-isopropylfluorophosphate (DFP) for 30 min at 37°C and then incubated with acetylthiocholine (AThCh) for 16 to 20 hr at 37°C in order to reveal the sites of activity of the specific enzyme, AChEase. The second group was incubated in a substrate of butyrylthiocholine (BuThCh) for 12 to 16 hr at 37°C to indicate the sites of the nonspecific ChEase. The third group was incubated in AThCh for 16 to 20 hr at 37°C without previous treatment by an inhibitor in order to reveal ...