Dental caries and treatment characteristics in human twins reared apart.

The 'reared apart' model, eliminating the effect of common environmental factors, is used extensively in twins research. In this study, teeth present (TP), teeth present excluding third molars (TPX3), teeth restored (TR), teeth restored index (TRI), surfaces restored (SR), surfaces restored index (SRI) and surfaces restored or carious (SRCI), were compared in 46 monozygotic (MZ) twin pairs and 22 dizygotic (DZ) twin pairs separated during infancy and raised apart. The dental examination included charting, panoral and bitewing radiographs, study models and a questionnaire. Data were analysed using intraclass correlations (ICC) and analysis of variance (corrected for age and sex). For all characteristics, the MZ pairs showed greater within-pair similarity than DZ pairs. For MZ pairs, the ICC values for the dental characteristics were all statistically significant (p < 0.005): TP, 0.45; TPX3, 0.49; TR, 0.57; TRI, 0.61; SR, 0.46; SRI, 0.67; SRCI, 0.58. For DZ pairs, none of the ICC values reached statistical significance: TP, 0.04; TPX3, 0.11; TR, 0.30; TRI, 0.31; SR, 0.20; SRI, 0.17; SRCI, 0.26. Despite subjects being reared in different environments, receiving different diets and different dental professional care, the MZ findings demonstrated significant genetic variance (45-67%) for the number of teeth present, number of teeth and surfaces restored, and caries present; the DZ data supported this conclusion. These findings provide new evidence for a genetic contribution to dental caries.

Measurement of preventive resin restorations using computer profilometry.

The amount of extracoronal material placed when a tooth is restored with a preventive resin restoration (PRR) was quantitatively measured together with the projected area of each cavity preparation. Thirty-three patients (mean age 11 yrs, 6 mos) requiring a PRR on a lower first permanent molar were selected. Impressions of the teeth were made with polyvinylsiloxane before and after cavity preparation and then restored with P-50 and Concise sealant. Following occlusal adjustment, a third impression was taken. Replicas were digitized using computer profilometry. Computer images of occlusal surfaces were superimposed using a "goodness of fit" method. The volume of extracoronal material placed on all molar teeth (n = 33) was X = 6.52 +/- 2.9 mm3. The mean depth applied was X = 222.52 +/- 83.09 mu and the mean area of material applied over the entire tooth surface was X = 27.13 +/- 5.72 mm2. The cavity preparations occupied, on average 19.02 percent of the occlusal surface.

A retrospective cohort evaluation of preventive resin restorations.

This study measured the longevity and clinical success of preventive resin restorations (PRRs) placed in permanent teeth by multiple operators in the Pediatric Dentistry Clinic at the University of Minnesota. A retrospective chart audit identified patients who had one or more PRRs placed. Only restorations of the occlusal surfaces of the first or second permanent molars were included. Each patient was given a dental examination. On completion, the patient's chronological record of treatment was reviewed for the following information: experience of the operator, type of isolation used, bonding material, liner type, composite resin, and sealant type. Teeth were examined with a front surface dental mirror and a sharp No. 23 dental explorer. Evaluations were made according to criteria developed by Cvar and Ryge, but modified to include a sealant evaluation. Independent measurements were made by each of the two examiners and a consensus was obtained. One hundred restorations were examined in 64 patients. The mean duration of service was 27 +/- 13 months. Sealant was evaluated as alfa (complete) 26 per cent, bravo (incomplete/adequate) 48 per cent, charlie (incomplete/inadequate) 21 per cent and delta (lost) five per cent. Cavosurface discoloration was evaluated as alfa (none) 87 per cent, bravo (margin only) 12 per cent, and charlie (margin/proceeding toward pulp) one per cent. Anatomical form was evaluated as alfa (well contoured) 89 per cent, bravo (under contoured/dentin not exposed) 11 per cent. Marginal adaptation was evaluated as alfa (no visible crevice) 85 per cent, bravo (visible crevice/no dentin exposed) 12 per cent, charlie (visible crevice/dentin exposed) two per cent and delta (restoration missing) one per cent.(ABSTRACT TRUNCATED AT 250 WORDS)

A twin study of genetic variation in proportional radiographic alveolar bone height.

The purpose of this study was to estimate the genetic variance for alveolar bone height by means of the classic twin method and the study of monozygous twins reared apart. Panoramic radiographs were obtained from 120 pairs of adult twins (mean age = 40.4 years, S.D. = 10.4 years), for comparison of 62 pairs of monozygous twins reared together (MZT), 25 pairs of like-sexed dizygous twins reared together (DZT), and 33 pairs of monozygous twins reared apart (MZA). Mesial and distal bone heights were determined as a proportion of tooth length. A full-mouth bone score was computed for each twin by averaging these proportions from all measurable teeth. Between-pair (B) and within-pair (W) variances were computed for each twin group. The population variances (B + W) of the MZT and DZT twin groups were similar, which validated a basic assumption of the twin model. Intraclass correlations and heritability estimates were also computed for the reared-together and reared-apart twin groups. Boot-strap sampling was used to provide estimates and confidence limits for these values. The intraclass correlations for the twin groups were: MZT = 0.70, DZT = 0.52, and MZA = 0.55. The results of this study suggest that there is significant genetic variance in the population for proportional alveolar bone height.

Fissure sealant wear at 30 months: new evaluation criteria.

The volume, depth and area of fissure sealant wear at 30 months is reported. Eighteen premolar teeth were included in the study. The teeth were sealed (Concise, White Sealant, 3M Dental Products Div., St Paul, MN, USA) and an impression taken, yielding a baseline record. Subsequent impressions were taken at 6 months and 30 months. Epoxy replicas were made from all impressions and the occlusal surface of each replica was digitized using a displacement stylus and programmable retrieval system. A goodness-of-fit routine was used to compare the digitized replicas and quantify wear. At 30 months, there was a mean sealant volume loss of 0.43 +/- 0.24 mm3 (mean of the maximum depth loss = 221.8 +/- 115.1 microns; mean area loss = 0.62 +/- 0.15 mm2) for all teeth. A new parameter, the Occlusal Stability Ratio (OSR), is discussed which describes the relationship between sealant area and sealant volume.

Quantitative changes in fissure sealant six months after placement.

Earlier studies have reported extensive volumetric loss of fissure sealant shortly after placement. To determine the volume of fissure sealant lost at six months, we used a servohydraulic profilometric apparatus in combination with computer graphics. Twenty-two premolar teeth were selected, and baseline silicone impressions were made of each tooth. The teeth were sealed and the occlusion adjusted where necessary. Impressions were made immediately of sealed teeth and again at six months. Epoxy replicas were made from all impressions, and their surfaces digitized by sequential profilometry. Using a three-dimensional root mean square (RMS) goodness-of-fit computer program, before sealant, after sealant, and six months after sealant computer-graphic images were superimposed. The volume of sealant lost after six months for all premolar teeth was X = 0.23 mm3 (maxillary second premolar: N = 9, X = 0.29 mm3; maxillary first premolar: N = 5, X = 0.27 mm3; mandibular second premolar: N = 4, X = 0.20 mm3; mandibular first premolar: N = 4, X = 0.08 mm3). The volume differences between tooth groups were not significant as measured by analysis of variance (ANOVA). These volumes represented a 13.99% loss of applied sealant for all premolars (maxillary second premolar: 19.72%; maxillary first premolar: 15.37%; mandibular second premolar: 8.46%; mandibular first premolar: 6.37%). The area of wear and the depth of wear also were measured.

Measurement of fissure sealant surface area by computer.

The amount of occlusal surface area covered when fissure sealant is applied to a tooth has not been previously reported. This study measured the occlusal surface area and sealant surface area using a computer-driven profilometric system. Twenty-two recently erupted, caries-free premolars were used. The mean occlusal area for all premolars was 34.34 mm2 +/- 4.42 mm2. The mean surface area of applied sealant for all teeth was 8.06 mm2 +/- 1.67 mm2, and the mean percentage of occlusal surface area covered by sealant was 23.97% +/- 5.02%. The occlusal surface area of mandibular first premolars was significantly smaller than that of the other premolar groups. However, this difference was not reflected in the area of sealant applied to premolars or in the percentage of occlusal surface covered by sealant. Mandibular first premolars required the same amount of coverage as the other tooth groups.

Assessment of recovery from nitrous oxide-oxygen sedation using neuropsychometry.

This study measured changes in adult performance following prolonged exposure (90 minutes) to nitrous oxide at psychosedative levels. Using a repeated-measures randomized blind design, experimenters exposed 12 subjects to four treatment combinations. These included: room air for 90 minutes (baseline); 100% oxygen for 90 minutes; nitrous oxide-oxygen sedation for 90 minutes followed by 100% oxygen for 2 minutes; and 90 minutes of nitrous oxide-oxygen sedation followed by 10 minutes of 100% oxygen. Following each treatment, participants were asked to perform six standard neuropsychological tests together with a rating scale measurement where subjects self-evaluated their respective levels of alertness. The tests were: digit span; digit symbol; paced auditory serial addition; controlled word association; letter cancellation; and grooved pegboard. Two-way analysis of variance revealed significant differences between mean scores for treatments on only two tests, grooved pegboard (P less than 0.05) and controlled word association (P less than 0.05). There was also a significant difference in mean scores obtained for the rating scale (P less than 0.001). These findings indicate that psychomotor performance and verbal fluency were affected by prolonged exposure to nitrous oxide even after recovery periods. No impairment of vigilance, immediate memory, or mental tracking could be detected as measured by the other tests. Subjective reports by the subjects accurately reflected their underlying impaired status.