Comparative Study of the Shear Bond Strengths and Bracket Failure Rates of Two Orthodontic Adhesive Systems

Abstract Objective: To evaluate and compare the shear bond strengths (SBS) and bracket failure rates (BFR) of orthodontic brackets bonded with Light Cure adhesive against those bonded with Self Cure adhesive. Material and Methods: The study had in vitro and in vivo parts. In the in vitro part to determine SBS of Light Bond(LB)(R) and Rely.a.Bond(RB)(R) adhesives used in bonding brackets to 88 extracted teeth, each adhesive type was used to bond 44 brackets. The clinical study was conducted to determine the BFR of the LB(R) and RB(R) adhesives by bonding 256 teeth using each adhesive type. A standardized bonding procedure was followed in both the in vitro and in vivo parts of the study. Data were analyzed using frequency, percentage, mean, independent t-test, chi-square, and Pearson Correlation statistics. A p-value of ≤ 0.05 was considered significant. SPSS version 21.0 was used to analyze the data generated. Results: There was a significantly higher mean SBS 10.6MPa for LB(R) adhesive than the 7.0MPa of the RB(R) adhesive. In the in vivo study, (LB)(R) had a greater but not significant BFR of 9.0% than RB(R) (8.0%). No significant relationship existed between the SBS of either adhesive type (as determined in vitro) and their BFR in vivo. Conclusion: Higher SBS of LB(R) did not translate to less BFR in the clinic, nor did a lower SBS of RB(R) translate to more BFR in the clinic (AU).

Perception of dental midline deviation amongst dental professionals and lay people

Objective: This study was conducted to evaluate the perception of midline coincidence as a determining factor in smile aesthetics. Methods: A single of a female smile was intentionally altered with a software program (Adobe Photoshop, CS5. 1990-2010, Adobe system incorporated). The alteration involved shifting the upper midline by 0.5mm to the left in four variations. These altered images were then rated by two groups, 30 in each group, the professionals and the lay persons using a visual analogue scale. Results: There was a statistically significant difference between the professionals and the laypeople in the perception of midline coincidence as a factor in assessing smile aesthetics, (p=0.038, T=2.1). Conclusion: The orthodontists, general dentists, other professionals and the laypersons detected specific dental aesthetic discrepancies at varying levels of deviation

Relationship between Two Indices in the Assessment of Orthodontic Treatment Complexity and Need.

Objective: To determine the relationship between the Index of Complexity, Outcome and Need (ICON) and Dental Aesthetic Index (DAI) in the assessment of orthodontic treatment complexity and need. Methods: A cross-sectional study was carried out. Pre-treatment dental casts of 150 consecutive patients from Lagos, Nigeria were assessed using the ICON and the DAI criteria. One investigator assessed all the models. In addition to descriptive statistics, the relationship between the ICON and DAI was examined by using non-parametric correlations (Spearman Rank Order and Pearson’s Product Moment Correlation Coefficient. Results: Forty-five (30%) of the subjects were classified by both ICON and DAI as having no treatment need. Of the 25(16.7%) that ICON classified as having difficult / very difficult complexity grades, 19(12.7%) of them were classified as having handicapping malocclusions by DAI standards. There was a significant correlation between DAI and ICON with regard to treatment need (p = 0.000). Also, there was a very statistically significant correlation between the ICON complexity grades and the DAI severity levels of malocclusion (p = 0.000). In general, both indices exhibited highly significant positive correlations (r = 0.600; p = 0.000). Conclusion: Both indices were generally in agreement on both aspects of orthodontic provision assessed. This suggests that both ICON and DAI can be used in the assessment of these facets of orthodontic care.