The shear bond strength of orthodontic bracket base shapes to human enamel, an in vitro study
Bibliographic record
Abstract
Introduction: There is a growing demand for esthetic appliances during orthodontic treatment, with a specific interest in WildSmiles shaped brackets amongst children and adolescents. Bond failure of brackets over the course of orthodontic treatment can result in increased treatment time, increased overhead costs, and feelings of frustration for the patient and practitioner. Objective: The purpose of this study was to the evaluate the effect of orthodontic bracket base shape on shear bond strength (SBS) to human enamel, in vitro, at two time points, as well as the nature of debonding fractures using the Adhesive Remnant Index (ARI). Methods: Orthodontic brackets with different shaped bases (flower, heart, rectangular) were bonded to 120 extracted human third molars. SBS was measured using a Servohydraulic Test System at 24 hours and 2 months after initial bonding. ARI scores were evaluated under 10x magnification to assess the amount of resin left on the tooth. Results: The control bracket with a rectangular base shape had the highest mean SBS (26.78 ± 8.19 MPa), and significantly differed from flower (17.19 ± 4.45 MPa) and heart (18.86 ± 3.50 MPa) base shapes (p < 0.001). The mean SBS of flower and heart shaped brackets did not differ considerably from each other (p > 0.05). The mean SBS between debond times at 24 hours (21.50 ± 7.46 MPa) and 2 months (20.38 ± 6.69 MPa) were not statistically significant (p > 0.05). Analysis of ARI scores showed a significant difference between Flower-24 hours vs Heart- 2 months (p=0.039), Flower-24 hours vs Heart- 24 hours (p=0.004), and Control-2 months vs Heart-24 hours (p=0.015). The heart shaped bracket had a greater proportion of adhesive bond failures at the enamel-resin interface. Conclusion: Bracket base shape has an effect on SBS, with the rectangular base shape having a higher mean SBS compared to flower and heart base shapes. All bracket shapes had bond strengths above the clinically acceptable range of 6-8 MPa, and thus may provide adequate SBS in a clinical situation. Variations in ARI scores occurred based on bracket shape and were of a mixed adhesive-cohesive nature.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".