The purpose of this study was to investigate the fracture resistance of re-attached coronal fragments of teeth using different materials and tooth preparations. Seventy-two recently extracted bovine incisors were selected. Eight incisors were maintained without any preparation as a control group. The incisal third of the other teeth was sectioned using a diamond saw. In one group (n = 32), a 2-mm bevel was prepared, whereas in the second group no preparation was made (n = 32). The specimens (beveled and non-beveled) were divided in four groups (n = 8) and re-attached with the following materials: a dual-cured resin cement RelyX ARC (RX); a chemically cured composite Bisfil 2B (B2); a light-cured composite Z250 (Z2); and a one-bottle adhesive Single Bond (SB). The bevel region was restored with adhesive and composite. All materials were used according to manufacturer's directions. A light-curing unit was used to polymerize the materials. Specimens were stored in saline solution for 72 h. De-bonding procedures were performed in a testing machine with cross-head speed of 0.6 mm min(-1). The load was applied in the incisal third. The resistance to fracture for control group was 70 (7) kg. The fracture resistance for non-beveled and beveled specimens were: SB, 3.3 (2.4) and 17.0 (4.1); RX, 11.5 (3.0) and 16.3 (3.1); Z2, 14.4 (4.2) and 20.5 (1.7); and B2, 19.5 (3.5) and 32.5 (7.4) kg. Analysis of variance (anova) and Fisher's protected least significant difference (PLSD) test disclosed significant influence for materials and cavity designs (P = 0.001). The highest failure loads were obtained with the B2 group and then with the Z2 with either bevel or non-bevel. RX produced lower failure loads than the restorative composites. The lowest failure load was obtained with SB in the non-beveled group. No technique studied was able to attain the fracture resistance of the control group and both materials and tooth preparation influenced the fracture resistance.

Total color difference in relation to the lightest tab, followed by the tab division into an adequate number of groups, is recommended as a possible and universally applicable mode of tab arrangement in dental color standards.

The aim of this study was to examine the accuracy of dental faculty members' utilization of diagnostic codes and resulting treatment planning based on radiographic interproximal tooth radiolucencies. In 2015, 50 full-time and part-time general dentistry faculty members at one U.S. dental school were shown a sequence of 15 bitewing radiographs; one interproximal radiolucency was highlighted on each bitewing. For each radiographic lesion, participants were asked to choose the most appropriate diagnostic code (from a concise list of five codes, corresponding to lesion progression to outer/inner halves of enamel and outer/middle/pulpal thirds of dentin), acute treatment (attempt to arrest/remineralize non-invasively, operative intervention, or no treatment), and level of confidence in choices. Diagnostic and treatment choices of participants were compared to "gold standard" correct responses, as determined by expert radiology and operative faculty members, respectively. The majority of the participants selected the correct diagnostic code for lesions in the outer one-third of dentin (p<0.0001) and the pulpal one-third of dentin (p<0.0001). For lesions in the outer and inner halves of enamel and the middle one-third of dentin, the correct rates were moderate. However, the majority of the participants chose correct treatments on all types of lesions (correct rate 63.6-100%). Faculty members' confidence in their responses was generally high for all lesions, all above 90%. Diagnostic codes were appropriately assigned by participants for the very deepest lesions, but they were not assigned accurately for more incipient lesions (limited to enamel). Paradoxically, treatment choices were generally correct, regardless of diagnostic choices. Further calibration is needed to improve faculty use and teaching of diagnostic codes.

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