Comparison of Shear Bond Strength of Aligner Attachments using various Types of Composites

Abstract

BACKGROUND: The field of orthodontics has witnessed major advancements with the introduction of clear aligner therapy as an alternative to traditional fixed
appliances. Initially, conventional braces—comprising metal brackets and wires—were the primary method for correcting malocclusions. These systems, though
effective, often caused aesthetic concerns and oral discomfort. The evolution of digital technology and 3D imaging in the late 1990s led to the creation of clear
aligners, which offered a more aesthetic, removable, and comfortable option for patients. Composite dislodgement in aligner therapy refers to the accidental
detachment of composite attachments bonded to teeth, which aid in achieving precise tooth movements. These attachments enhance the grip and control of aligners,
allowing effective force application. AIM: This study aims to analyse the shear bond strength of various types of composites for the long term performance of the
composite attachments. MATERIALS AND METHODS: The study was conducted in Saveetha Dental College and Hospitals, Chennai, India. 15 extracted teeth
were considered as samples for the study and were divided into 5 groups containing 3 teeth each. 5 variants of composite resins were selected of the same brand
and assigned to each of the groups. Aligner attachments of size 3mm x 3mm were bonded in each h teeth on the buccal surface. Shear bond strength was calculated
using a 1mm knife. Results were evaluated. RESULTS AND DISCUSSION: Group 1 composites (Bulk fill injectible) showed the highest compressive stress
compared to others and a huge variation was seen in Bulk filled orthodontic composite. Maximum shear bond strength was also seen in group 1, with force bearing
of 215.49N. Studies indicate that bracket debonding rates vary widely, ranging from 3% to 34% depending on factors such as adhesive type, bracket design, patient
compliance, and treatment protocols. CONCLUSION: Among the materials tested, the Shofu Beautifil Injectable Bulk Fill Fluoride-Releasing Composite (Group
1) demonstrated the highest mean shear bond strength, indicating superior adhesion to enamel surfaces. This suggests that its combination of bulk-fill formulation,
fluoride release, and balanced filler loading provides improved mechanical stability and bond integrity. The Beautifil Flow 03 (intermediate viscosity) also exhibited
favorable bond strength, highlighting that medium-viscosity flowable composites can offer a good compromise between adaptability and resistance to
dislodgement. In contrast, low-viscosity composites (Beautifil Flow 02) recorded the lowest bond strength values, suggesting limited suitability for situations
demanding higher mechanical retention.