Harold R. Stanley

THE EFFECTS OF SURGICAL EXPOSURES OF DENTAL PULPS IN GERM-FREE AND CONVENTIONAL LABORATORY RATS.

Abstract The purpose of this study was to observe the pathologic changes resulting from untreated experimental pulp exposures in germ-free rats as compared with conventional rats with a normally complex microflora. The pulp tissues of these rats were exposed by drilling through the occlusal surface of the maxillary right first molar with a carbide round bur mounted in a jewelers spindle-topped hand mandrel. After varying postoperative time intervals (1 to 42 days), the animals were killed and the appropriate tissues were serially sectioned. By the eighth day, vital pulp tissue remained only in the apical half of the roots in the conventional animals. Complete pulpal necrosis with granulomas and abscess formation occurred in all older specimens. Evidence of repair was uniformly lacking. In contrast, no devitalized pulps, apical granulomas, or abscesses were found in the germ-free animals. Dentinal bridging began at 14 days and by 21 and 28 days was complete, regardless of the angle or severity of the exposure. These results, even in the face of gross food impactions, indicate that the presence or absence of a microbial flora is the major determinant in the healing of exposed rodent pulps.

FOCAL EPITHELIAL HYPERPLASIA: AN UNUSUAL ORAL MUCOSAL LESION FOUND IN INDIAN CHILDREN.

Abstract An unusual focal hyperplasia involving the oral epithelium has been described. The lesion developed in nineteen Indians, of whom fifteen were Navajo Indian children from the Gallup, New Mexico, area. Similar clinical lesions are described in other ethnic groups in the American Indian population. The chief morphologic change noted is an acanthosis of discrete segments of oral epithelium and a ductal hyperplasia with secondary retention phenomena involving the minor salivary glands underlying areas of epithelial change. No recognizable etiologic factor or factors have been identified, although a communicable agent is being considered. The possibility of a genetic basis for the lesion has been suggested.

The relationship of bacterial penetration and pulpal pathosis in carious teeth

Abstract This study was based on the histologic examination of forty-six virgin carious human teeth. In each specimen measurements were made of the distance between the deepest penetration of the bacteria and the pulpal tissue. The pulpal pathosis was graded according to the type of lesion and the amount of reparative dentine formation. Specimens in which the distance between the penetrating bacteria and the pulp, including the thickness of the reparative dentine, averaged 1.11 mm. or more revealed insignificant pathologic lesions. Specimens with no reparative dentine also presented only minimal pathosis or none at all. When the reparative dentine itself was invaded by the bacteria, however, pathosis of real consequence and of an irreversible nature was found.

The rate of tertiary (reparative) dentine formation in the human tooth

Abstract In view of the increased interest in the biologic potential of the human dental pulp, the rather misleading statements concerning the rate of tertiary (reparative) dentine formation indicate the necessity of establishing some guidelines for this process. A histologic study of 108 human teeth with Class V cavities prepared by high- and low-speed methods with and without coolants was carried out. Little evidence of tertiary dentine formation was apparent prior to the thirtieth post-operative day. The rate of formation was highest initially in the 27- to 48-day interval (3.5 μ per day); it decreased markedly after the forty-eighth day of the experimental period to 0.74 μ per day; and it decreased further to 0.23 μ in the 72- to 132-day period. The average rate for the total length of the study was 1.49 μ per active day. The factor of remaining dentine thickness by itself did not appear to effect tertiary dentine production. However, operative techniques inducing considerable trauma were capable of slightly increasing the production of tertiary dentine.

Ameloblastoma potential of follicular cysts

Abstract One hundred eight cases of ameloblastoma definitely associated with follicular cysts and/or impacted tooth follicles were compiled from a review of the literature and a study of unpublished cases. A marked reduction in the prevalence of such cases occurred after the age of 30. The evidence presented supports the hypothesis that the potential for forming an ameloblastoma is lost with the transition of odontogenic epithelium to squamous epithelium in impacted tooth follicles and/or follicular cysts as the patient grows older.

The relationship of coronal pulp stone formation to experimental operative procedures.

Abstract The purpose of this study was to determine whether or not the degree of pulp response elicited by cutting procedures and restorative materials was capable of increasing the incidence of pulp stone nidi and pulp stones. Four hundred seventy teeth were divided into eight separate groups according to their post-operative extraction time interval and examined histologically. The results suggest that there is some correlation between the incidence of pulp stone or nidus formation and an increase in postoperative extraction time interval. However, no significant correlation appeared to exist between formation of pulp stones or nidi and age of the patient, sex, thickness of remaining dentine beneath the cavity preparation, preparation time, or the traumatic potential of the operative procedure. Nidi and stones were most commonly seen perivascularly. In some instances, calcific formations could be seen in the lumina of vessels; in others, the vessel walls themselves were calcified but fresh blood cells could be seen in the lumina. A schematic diagram is presented to incorporate several hypotheses found in the literature and, at the same time, emphasize that thrombi formation and/or vascular-wall injury are possible mechanisms which may lead to the eventual formation of pulp stones.

The exposed germ-free pulp: Effects of topical corticosteroid medication and restoration

Abstract The dental pulps of germ-free and conventional Sprague-Dawley rats were surgically exposed and treated with corticosteroid and obtundent drugs and were either sealed by means of a temporary cement or left exposed to the oral environment. The results showed that, regardless of medication or closure, the pulps of conventional animals degenerated, whereas the pulps of germ-free animals healed uneventfully as substantiated by the formation of a reparative dentine bridge. The application of the steroid formula immediately following pulpal exposure was neither helpful nor harmful.

The cyclic phenomenon of periodontitis

Abstract Based on microscopic sections of eighteen human jaws, the constancy of seven measured distances, limited by anatomic and pathologic landmarks within the periodontium, was determined and their relationship to local pathologic factors was tested. The type of tooth, type of tooth surface (mesial or distal), and the presence of an approximating tooth had no effect on the mean lengths of the distances. Of the measurements made, the distance from the bottom of the calculus to the alveolar crest was found to be the most constant, having a mean length of 1.97 mm. and a coefficient of variation of 33.16 per cent. The length of the epithelial attachment was found to be the most variable structure of the periodontium. By analyzing the incidence of local pathologic factors in relation to each other, it was found that the degree of inflammation of the lamina propria and the degree of ulceration of the marginal epithelium could be predicted from the shape of the supragingival calculus; also, that the degree of ulceration of the crevicular epithelium could be predicted by the shape of subgingival calculus. One local pathologic factor, subgingival calculus, had an effect on three of the distances: (1) bottom of calculus to the bottom of the epithelial attachment, (2) bottom of calculus to the alveolar crest, and (3) bottom of calculus to deepest level of inflammatory cells. The mean lengths of these distances were greater in relation to scaly subgingival calculus than to nodular subgingival calculus. From these results a hypothesis is advanced that the alternating formation of scaly and nodular calculus on the tooth surface represents a cycle, which can be broken down into the following stages: 1. Stage I. Gradual breakdown of papillary structure. 1.1. Phase 1. Scaly calculus formation. 1.2. Phase 2. Nodular calculus formation. 2. Stage II. Severance of papillary structure. 3. Stage III. Recovery with rebuilding of a new papillary structure.

ORAL TUMORS INDUCED BY POLYOMA VIRUS IN MICE.

Abstract This report has described the histopathologic features of tumors appearing in oral, dental, and related tissues of mice inoculated at birth with polyoma virus. A total of seventy tumors were found in eleven mouse heads that were serially sectioned. The tumors apparently arose from gingival epithelium, nasal mucosa, accessory salivary glands, and osseous tissue. The tumors arising within the incisal and molar areas presented several characteristics of human ameloblastoma. The hypothesis is put forth that this type of tumor represents one type of ameloblastoma for this species (Mus musculus).

Reparative dentin formation resulting from cavity preparation

Abstract Thirteen different operative techniques were compared. The production of reparative dentin was evaluated with each technique and correlated with a previous study on extended or burn lesions produced by the same techniques. It was experimentally found that the Densco 300,000 r.p.m. air-water spray—No. 35 carbide bur technique, or a similar instrument, provided all the cutting efficiency of a high speed instrument without producing extended or burn lesions and caused the highest incidence of reparative dentin formation. But since the incidence of reparative dentin is so low with the above technique (33.3 per cent) and the biologic variation so great as to which teeth will be so inclined to produce reparative dentin, it is not practical for dentists to wait for reparative dentin to form. The reasonable procedure is to apply an adequate liner to the exposed dentinal tubules before cementation. It was also found that, other than the remaining dentin thickness value and the operative technique, no other factors influenced the reparative dentin formation (in specimens examined thirty days or longer postoperatively).