Diagnostic accuracy of impression-free digital models.

INTRODUCTION: Impression-free techniques might eliminate the potential shortcomings of digital dental models. Chairside scanners offer the advantage of obtaining digital dental models directly from the patient without the need for dental impressions. The aim of this study was to evaluate the accuracy of 3-dimensional digital models acquired from a chairside intraoral scanner compared with both manual and cone-beam computed tomography measurements of the same dental anatomy. METHODS: The study sample comprised 60 dry skulls. Each skull had the maxillary and mandibular arches scanned with a Cadent iTero scanner (Align Technology, San Jose, Calif) and had a cone-beam computed tomography scan taken with a CS 9300 unit (Carestream Health, Atlanta, Ga). Linear measurements in all 3 dimensions of the space in each dental arch together with tooth-size arch-length analysis for both the maxillary and mandibular arches were carried out manually on the dry skulls with calipers and digitally on the scanned 3-dimensional models and cone-beam computed tomography images. Intraclass correlation (ICC) analysis was performed for all variables tested in the study groups, with the manual measurements on the dry skulls as the gold standard. The Bland-Altman analysis was also applied to the data to graphically display the agreement of the diagnostic measurements obtained from these methods. RESULTS: Measurements from the iTero models demonstrated near-perfect agreement (ICC, 0.91-0.99) with the caliper measurements. Cone-beam computed tomography measurements had moderate to high levels of agreement (ICC, 0.65-0.99) compared with the caliper measurements. CONCLUSIONS: Direct digital acquisition of the dental arches with a chairside scanner provided almost 1-to-1 diagnostic information of the investigated anatomy and was superior to the cone-beam computed tomography measurements.

Shear bond strengths of a selenium containing and a conventional light cured adhesive for orthodontic bonding.

BACKGROUND: The objectives of this study were to evaluate the debonding strength and mode of failure of a selenium containing adhesive compared to an established orthodontic adhesive. MATERIALS AND METHODS: One hundred sixty bovine mandibular incisors were allocated to eight groups: steel and clear brackets were bonded with either selenium containing adhesive (Group 1: SeLect Defense) or a conventional light-cured adhesive (Group 2:Transbond XT) to measure debond strength and the adhesive remnant index was used to assess the location of bond failure. Data was evaluated using a three-way analysis of variance and Fisher's PLSD multiple comparisons test for mean debond strengths. RESULTS: Group 2 debond strengths were greater than that of Group 1 with the steel and clear brackets. Group 1 debond strengths were greater with clear than with steel brackets at both time points. Both adhesives demonstrated increased debond strengths from zero to 24 hours and the clear brackets exhibited a greater ARI than steel after debonding. Comparisons of debond strength means among adhesives, brackets, and times were all statistically significant. CONCLUSIONS/DISCUSSION: All debond strengths were within a clinically acceptable range according to previous literature. SeLect Defense may be desirable due to its potential for preventing white spot lesions despite the reduced strength compared to Transbond XT.

Bond strength comparison of color-change adhesives for orthodontic bonding using a self-etching primer.

BACKGROUND: The purpose of this study was to compare the shear bond strengths of two color-change adhesives with a commonly used conventional light-cure adhesive while using a self-etching primer, and to compare any changes in shear bond strengths over time. METHODS: One hundred and eighty extracted bovine incisors were randomly divided into nine groups of 20 teeth each. The teeth were prepared with a self-etching primer (Transbond™ Plus) Metal lower incisor brackets were bonded directly to each tooth with two different color-change adhesives (TransbondPlus and Grengloo™) and a control (Transbond XT). The teeth were debonded at three different time points (15 minutes, 24 hours, 1 week) using an Instron at 1.0 mm/min. The teeth that were to be debonded at 24 hours and 1 week were stored in distilled water at 37°C to simulate the oral environment. The data were analyzed by two-way analysis of variance and with Fisher's protected least-significant difference multiple comparisons test at the P < 0.05 level of significance. Adhesive remnant index (ARI) scores were calculated for each debonded tooth. RESULTS: Transbond Plus at 1 week had the highest mean shear bond strength (14.7 mPa). Grengloo tested at 24 hours had the lowest mean shear bond strength (11.3 mPa). The mean shear bond strengths for the remaining seven groups had a range of 12-14.5 mPa. Grengloo had >80% samples presenting with an ARI score of 1 at all times. Interestingly, both Transbond groups had ARI scores of 3 in more than 50% of their samples. CONCLUSION: Time had no significant effect on the mean shear bond strength of Transbond XT, Grengloo, or Transbond Plus adhesive.