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To measure post-gel shrinkage, elastic modulus, and flexural strength of orthodontic adhesives and to predict shrinkage stress using finite element analysis (FEA). The following 6 orthodontic adhesives were tested: Transbond XT (3M Unitek, Monrovia, Calif), Transbond Plus Color Change (3M Unitek), Greengloo (Ormco, Brea, Calif), Ortho Connect (GC America, Alsip, Ill), Trulock (RMO, Denver, Colo), GoTo (Reliance, Itasca, Ill). Post-gel shrinkage was measured using a biaxial strain gauge during light curing. Elastic modulus and flexural strength were measured with a 4-point bending test. Analysis of variance and Student-Newman-Keuls post hoc tests were used to compare the shrinkage, elastic modulus, and flexural strengths among the materials (α =.05). Shrinkage stresses caused by the post-gel shrinkage and elastic modulus values were calculated using a cross-sectional FEA of a metallic bracket bonded to an incisor. Properties were highly different among the adhesives (P ≤.0001). Transbond XT (0.38 ± 0.09 percent volumetric contraction) and GoTo (0.42 ± 0.05 percent volumetric contraction) had the lowest post-gel shrinkage; Transbond Plus Color Change had the highest (0.84 ± 0.08 percent volumetric contraction). OrthoConnect (6.8 ± 0.6 gigapascals) had the lowest elastic modulus; GoTo (28.3 ± 3.1 gigapascals) had the highest. Trulock (64.1 ± 8.2 megapascals) had the lowest flexural strength; Greengloo (139.1 ± 20.7 megapascals) had the highest. FEA showed that the highest shrinkage stresses were generated with Transbond Plus Color Change and the lowest with OrthoConnect. Post-gel shrinkage of orthodontic adhesives was comparable with restorative composites, which are known to create shrinkage stresses in restored teeth. FEA indicated that this shrinkage creates stresses in the adhesive and in the enamel around the brackets. [ABSTRACT FROM AUTHOR]

Objective: To evaluate adhesive performance in terms of debonding forces of precoated metal and ceramic brackets 4 years after expiration. Materials and Methods: Buccal and lingual surfaces of embedded extracted maxillary premolars were etched with 34% Tooth Conditioner Gel (Dentsply Caulk, Milford, Del), rinsed, and dried. Transbond MIP (3M Unitek, Monrovia, Calif) was applied prior to placing adhesive precoated brackets (APC II Victory stainless steel and APC Plus Clarity ceramic brackets, 3M Unitek). The preexpiration brackets had 29-35 months before, and the postexpiration brackets were 45-52 months past, their expiration dates. Sample size was 17-21 per group. Debonding forces were determined by subjecting the bonded brackets to a shear force in a universal testing machine. Debonding forces were compared using two-way ANOVA. Debonded surfaces were examined under a stereomicroscope to determine failure modes, which were compared using the chi-square test. Results: No statistically significant difference was found in debonding forces (P ?=? .8581) or failure modes (P ?=? .4538) between expired and unexpired brackets. Metal brackets required statistically significantly higher debonding forces than did ceramic brackets (P ?=? .0001). For both expired and unexpired brackets, failure modes were mostly cohesive in the adhesive layer for ceramic brackets, and mixed between adhesive and cohesive failure in the adhesive layer for metal brackets. Conclusions: Adhesive precoated brackets did not have any reduction in enamel-adhesion properties up to 4 years after their expiration date. Extended shelf life testing for precoated dental brackets may be worth considering. [ABSTRACT FROM AUTHOR]

Objective: To measure enamel surface changes after ceramic bracket debonding and after cleanup. Materials and Methods: Forty extracted teeth were scanned in three dimensions using an optical scanner (baseline). Two ceramic bracket systems were placed (19 metal-reinforced polycrystalline ceramic brackets; 21 monocrystalline ceramic brackets). Seven days later, brackets were debonded and teeth scanned (post-debond). Adhesive remnants and bracket fragments were recorded. Tooth surfaces were cleaned using a finishing carbide bur and scanned again (post-cleanup). Post-debond and post-cleanup scans were aligned with the baseline, and surface changes were quantified. Results were statistically compared using t-tests and Mann-Whitney tests (α = .05). Results: The depth of enamel loss (mean ± standard deviation) post-debond was 21 ± 8 μm and 33 μm and post-cleanup was 28 ± 14 μm and 18 ± 8 μm (P = .0191); the post-debond remnant thickness was 188 ± 113 μm and 120 ± 37 μm (P = .2381) and post-cleanup was 16 ± 5 μm and 15 μm for polycrystalline and monocrystalline ceramic brackets, respectively. The monocrystalline ceramic brackets predominantly left all adhesive on the tooth; the polycrystalline ceramic brackets were more likely to leave bracket fragments attached. Conclusion: Both systems allowed successful removal of the brackets with minimal enamel loss. However, the polycrystalline ceramic brackets left more fragments on the tooth, which complicated cleanup efforts. [ABSTRACT FROM AUTHOR]

Objective: To examine the effects of application of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) paste and microabrasion treatment on the regression of white spot lesions (WSLs)., Materials and Methods: Artificially-induced WSLs in bovine enamel were randomly assigned to one of four treatment groups: CPP-ACP paste only, microabrasion only, microabrasion and CPP-ACP, and a control. Samples were treated with each regimen twice daily for 2 weeks and stored in remineralizing solution between the treatments. Quantitative light-induced fluorescence was used to measure changes in fluorescence, which indicate changes in mineral content of WSLs immediately before (T1) and 2 weeks after treatment (T2). A two-within-subject factor analysis of variance was used to analyze the significance of any changes in mineral content of the lesions from T1 to T2., Results: There was a statistically significant (P < .05) gain in fluorescence associated with the microabrasion only, as well as the microabrasion and CPP-ACP treatments. The changes in fluorescence for the CPP-ACP treatment alone were not statistically significant (P  =  .40)., Conclusions: CPP-ACP paste alone does not significantly improve the fluorescence value (ie, the mineral content) of WSLs. Within the limitations of this in vitro study, microabrasion treatment with or without CPP-ACP improved the fluorescence and thus reduced WSLs.