Evaluation of Shear Bond Strength of Metal Orthodontic Brackets to Composite Using Different Surface Conditioning Methods
Author(s): Ola Ali Mahmood*, Mehdi Abdulhadi Mehdi and Asseel Yousif Rashid
Abstract
Introduction: The rise of adult patient looking for orthodontic treatment that more likely to have existing restoration leads to increase in bonding of brackets to composite restoration. To ensure clinically optimum bond strength of brackets to composite, researchers are comparing and evaluating several surface treatment approaches.
Aims: The study's purpose is to assess the effect of different mechanical surface conditioning approaches (no preparation, diamond bur grinding, sandblasting with Al2O3, Er, Cr; YSGG laser irradiation) on Shear Bond Strength (SBS) of stainless steel orthodontic brackets to composite restoration.
Materials and methods: In this in vitro study 48 Composite discs were constructed (D=10 mm, H=4 mm). The samples were divided into two groups (n=24), one group underwent thermocycling (5000 cycle), then each group subdivided into four subgroups (n=6) according to the surface conditioning method (no-preparation, diamond bur, sandblasting with Al2O3, and Er, Cr: YSGG laser irradiation). After the brackets have been bonded to the composite discs, SBS of all the samples measured in a universal testing machine. Data was analyzed using one way ANOVA and post-hoc test. The samples were then examined at a magnification of x10 under a stereomicroscope to evaluate their failure mode and Adhesive Remnant Index (ARI). Kruskal-wallis test was used to compare ARI scores.
Results: No significant difference in shear bond strength between the composite control groups. However, significant difference in SBS values in the aged composite groups was recorded; the laser group values (10.81 MPa) were the highest among the tested groups. The no preparation aged group (2.95 MPa) has had the lowest SBS. ARI scores showed no significant difference among all groups (P>0.05). Sandblasting and grinding group mostly showed ARI score 2 and 3, however, score 0 and 1 were predominant in the no preparation and laser groups.
Conclusions: Diamond bur grinding, sandblasting with aluminum oxide and Er; Cr: YSGG laser irradiation of composite surface yields clinically acceptable outcomes in terms of shear bond strength and ARI values, bond strength with no preparation of composite surface was below the clinically acceptable range.