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This study examines cellular differences between undemineralized and demineralized tooth sections. The material comprised unerupted and partly erupted third molars. After fixation for 24 h, 10- to 15-microns ground sections were prepared from half of the tooth, using a cutting-grinding system. The sections were compared with demineralized routine sections from the other half of the tooth. Undemineralized sections showed a better capacity for preserving the tissue integration. Especially between the odontoblast layer and the predentin a low frequency of disjunctions or tears were noted. At this level of examination fixation quality and vacuole frequency (intra-cellular spaces) did not show any differences between the two methods.

This study examines ameloblasts and odontoblasts in relation to mineralizing enamel and dentin in thin undemineralized tooth sections from unerupted and partly erupted human third molars. The material comprised 12 freshly removed third molars. After fixation for 24 h the specimens were dehydrated and embedded in hydroxyethylmethacrylate. Undemineralized sections 10-15 microns thick were prepared with a cutting-grinding system, and radiomicrographs were taken. Postsecretory ameloblasts were seen in different morphologic stages ranging from ruffle- and smooth-ended ameloblasts to cuboidal and squamous cells adhering to incomplete and fully mineralized enamel. The former occurred in the most coronal tooth part, whereas the latter were seen cervically. It was not possible to identify systematic modulation cycles as seen in postsecretory rat incisor ameloblasts. The well-defined subodontoblastic region with cell-free and cell-rich layers was established before tooth eruption. The function of the subodontoblastic region is not fully understood, but our findings suggest that the establishment of the region plays a role in maintaining the specific odontoblast phenotype in the coronal region possibly linked to progressive dentin mineralization.

The present study examines early enamel surface alterations taking place when active carious lesions enter an arrested stage. Orthodontic bands with a standardized space for plaque accumulation were used to produce incipient carious lesions on the buccal surface of all four first premolars of four young adolescents. The premolars were to be extracted for orthodontic reasons. After 4 weeks of local cariogenic challenge, all teeth were debanded. In each patient one tooth was extracted at the time of debanding. The remaining premolars were extracted 1, 2, and 3 weeks after re-exposure to the oral environment. No fluoride was added during the entire test period, and the patients were told to maintain usual oral hygiene. Scanning electron microscope examination of the experimental surface areas disclosed a gradual wearing away of the outermost crystals during the 3 weeks of observation. This was associated with a leveling off of surface irregularities and the development of a multitude of scratches. The observed attrition of the porous surface in the lesion area indicates that functional wear and toothbrushing were responsible for the arrestment by disturbance and removal of bacterial deposits.

A survey has been made of the reasons for placement and replacement of 6052 amalgam restorations in Denmark. In patients more than 16 years of age 48% of all restorations were made because of primary caries, and 52% were replacements of failed restorations. In primary teeth 64% and in permanent teeth of children 83% of the restorations were made because of primary caries. The reasons for replacement of restorations were dependent on dentition, age of the patient, and type of restoration. Secondary caries was the most frequent reason for replacement of failed restorations in permanent teeth, comprising a third of all replacements. Marginal discrepancies and bulk fracture of fillings were the other two major reasons. In primary teeth fracture and loss of fillings were the two major reasons for replacement of amalgam restorations, whereas secondary caries caused less than a quarter of all restorations to be replaced. The age of the restorations replaced ranged from 0 to 38 years, and half of the restorations replaced in permanent teeth of adults were less than 7 years old. A shorter longevity of failed restorations was noted in primary teeth and permanent teeth of children.

The aim of this review has been to suggest that future fluoride preventive programs should be based on what is at present known about the possible cariostatic mechanisms of fluoride. The relative role of enamel fluoride in caries prevention has become increasingly questioned during the last two decades. No significant relationship has been demonstrated between caries experience of the individual and fluoride content of the enamel. Furthermore, the fluoride content in surface enamel between teeth developed in low and "optimal" fluoride areas is too small to explain any significant effect on dissolution rate of the enamel. As the major explanation for the cariostatic effect of fluoride must therefore be sought in its local effect on the oral environment, the possible effects on plaque colonization, composition and metabolic activities are discussed. The effect of even low concentrations of fluoride in the liquid phase on enamel dissolution is described, and it is concluded that the major cariostatic effect of water fluoridation, fluoride tooth paste and mouth rinses can probably be ascribed to regular increases in fluoride ion activity in the oral fluids. The effect of high concentrations of topical fluoride solutions is thought to be a result of a slow dissolution of calcium fluoride deposited in initial caries lesions, whereby an increased fluoride ion concentration is maintained locally for longer periods of time. Finally, the clinical consequences of these considerations are described.

The effect of controlled oral hygiene was studied in 40 patients treated with immediate complete overdentures in one or both jaws. Before prosthetic treatment conservative periodontal treatment was conducted with intensive instruction and motivation in oral hygiene care. Caries and periodontal status were recorded before and 2-4 weeks (day 0), 6 months, and 12 months after prosthetic treatment. However, the patients were seen more frequently for motivation and professional tooth cleaning. The material included 44 overdentures with a total of 92 abutments, with 1-4 abutments in each jaw. Before treatment the overall mean plaque index score was 1.43 +/- 0.68 and the overall mean gingival index score 1.57 +/- 0.53, and on day 0 and after 6 and 12 months the overall mean PlI score was 0.33-0.65 and the overall mean GI score 0.67-0.97. Adjacent to the abutments there was a significant reduction of the PlI and the GI scores from before treatment to day 0 and from day 0 to 6 months after prosthetic treatment (P less than 0.001). There was a significant reduction of pocket depth from day 0 to 6 months and from 6 to 12 months (P less than 0.01). The results of this study have shown that it is possible to maintain teeth as abutments for overdentures in patients with an initial poor dental status.

Normal and fluorotic primary and permanent teeth were demineralized in 10% EDTA at pH 7 for varying periods of time up to 4 weeks. The fluorotic teeth initially dissolved at a much slower rate than non-fluorotic specimens and appeared to contain more organic material. After almost complete removal of the outer enamel a soft organic layer remained on the dentin surface. This consisted of a fine fibrillar mesh and some more dense material. After four weeks much of the organic material had disappeared leaving only a thin membrane on the dentin surface.