Clear aligner attachment removal techniques – an in vitro comparison of removal time residual composite, enamel surface characteristics, enamel loss, and material cost

Abstract

Abstract Introduction: At the completion of traditional orthodontic therapy, the brackets and residual adhesive must be removed. The adhesive removal is not only a time-consuming procedure but can also produce iatrogenic effects to the enamel. Bracket adhesive removal has been thoroughly studied in the literature, commonly utilizing extracted human teeth as a close alternative to in vivo studies. Studies posit that the low speed (LS) fine carbide bur continues to be the most popular method for bracket adhesive removal.1–4 An increasingly popular alternative therapy, clear aligner therapy (CAT), utilizes clear aligners (CA’s) to generate orthodontic tooth movement in adolescent and adult patients.5 As an esthetic alternative to brackets, CAT utilizes tooth-colored composite resin attachments on the facial surfaces of the patient’s teeth to aid in robust tooth movements.6 Differing from traditional metal bracket adhesive, CA attachment removal can be more challenging and time consuming, as the attachments contain a larger volume of resin to remove.1,7,8 Only one PubMed study can currently be found devoted to the removal of CA attachments, in which only two removal modalities were evaluated.1 Additionally, no studies have been completed to evaluate the material cost associated with attachment removal. Aim: To identify the most ideal method of CA attachment removal between five modalities in terms of removal time, residual composite, enamel surface characteristics, enamel loss, and material cost. Methods: Fifty-five extracted human premolar teeth were collected for this in vitro benchtop study. The teeth were randomly assigned into one group of five control teeth, and five equal groups of 10 teeth: Groups A, B, C, D, and E. Each tooth was mounted into an individual acrylic mold. A 3.5x1x2 mm CA composite resin attachment was bonded to the buccal surface of the 50 teeth assigned to Groups A-E at the center of the clinical crown.9 No procedure was done to the control teeth. A single operator removed the attachments utilizing a different removal modality assigned to each group. Group A attachments were removed with a high speed (HS) cylindrical fine carbide bur, Group B with a LS cylindrical fine carbide bur, Group C with a HS fine diamond bur, Group D with a LS round carbide bur, and Group E with an adhesive removing pliers. The mean results of the removals were compared between Modality A-E according to: removal time, residual composite, enamel surface characteristics, enamel loss, and material cost. Outcome measure results were summarized using means with 95% confidence intervals presented by group. The one-way analysis of variance was performed for comparison of means between groups, and Tukey’s method was conducted to adjust for multiple comparisons. A p-value of less than 0.05 was considered statistically significant. Intra-rater reliability of residual composite and enamel surface characteristics scores were summarized using the intraclass correlation coefficient after a two-week washout period. Results: Removal time: Group E resulted in the fastest mean removal time at 17.8 seconds, while Groups D and B had the slowest mean times at 57.2 and 64.9 seconds, respectively. Residual composite: Pairwise comparisons found no statistical difference between Groups A-D, where Groups B-D had the lowest mean residual composite. Group E had the highest residual composite and thus was the least effective for complete composite removal. Enamel surface characteristics: Pairwise comparisons found no statistical difference between Groups A, B, D, and E, where Group A had the lowest surface scratching, followed by Group B, E, and then. Group C had a statistically significantly higher mean surface scratching, indicating it produced the worst surface roughness between groups. Enamel surface loss: Pairwise comparisons found no statistical difference between Groups A, B, D, and E, where Group E had the least mean average surface and total area surface loss of 9.83 microns and 39.2 microns, respectively. Group C had the highest mean average surface and total area surface loss of 44.28 and 174.5 microns, respectively. Material cost: Group E had the highest initial cost, at $176.04 per plier. Group D was the most economical initial option, at $2.80 per bur. Conclusions: Removal of CA attachments produces changes to the enamel surface. Judicious placement and removal of attachments is strongly recommended. No single removal modality produced the best results for every category studied. Therefore, modality selection must be decided based on practitioner priorities.