Shear Bond Strength of Hydrophilic and Conventional Orthodontic Primers Under Dry and Saliva‑Contaminated Conditions: An In‑Vitro Study

Aim Moisture contamination during orthodontic bonding can adversely affect bracket adhesion, particularly when conventional hydrophobic primers are used. This in‑vitro study aimed to compare the shear bond strength (SBS) and adhesive remnant index (ARI) of a hydrophilic primer (Bracepaste MTP) with those of a conventional primer (Transbond XT) and a moisture‑insensitive primer (Transbond MIP) under dry and saliva‑contaminated conditions.MethodsEighty extracted human premolars obtained from patients undergoing orthodontic treatment were randomly allocated using a computer‑generated randomization method into four groups (n = ۲۰): Group A, Transbond XT under dry conditions; Group B, Bracepaste MTP under dry conditions; Group C, Transbond MIP under moist conditions; and Group D, Bracepaste MTP under moist conditions. Following etching with ۳۷% phosphoric acid, primers were applied according to manufacturers’ instructions. Artificial saliva contamination was performed in the moist groups before primer application. Stainless steel premolar brackets were bonded using Bracepaste adhesive and light‑cured with an LED curing unit. Specimens were stored in artificial saliva for ۲۴ hours before SBS testing using a universal testing machine at a crosshead speed of ۱ mm/min. ARI scores were evaluated under a stereomicroscope at ×۱۰ magnification by a blinded examiner. Data were analyzed using one‑way ANOVA, Tukey post‑hoc test, and Chi‑square test (α = ۰.۰۵).ResultsSignificant differences in SBS values were observed among the groups (P < ۰.۰۰۱). Group A demonstrated the highest mean SBS (۱۳.۹۳ ± ۲.۲۳ MPa), which was significantly greater than Groups B, C, and D (P < ۰.۰۰۱). No statistically significant differences were found among Groups B (۱۱.۰۹ ± ۰.۹۳ MPa), C (۱۰.۹۶ ± ۱.۰۴ MPa), and D (۱۰.۷۱ ± ۱.۰۲ MPa) (P > ۰.۰۵). All groups demonstrated clinically acceptable bond strengths. ARI score distributions showed no statistically significant differences among groups (P = ۰.۶۲۷), with score ۱ being the most frequent finding.Conclusion Conventional Transbond XT primer exhibited superior bond strength under dry conditions. Moisture contamination reduced SBS values in all tested systems; however, Bracepaste MTP maintained clinically acceptable bond strength under both dry and moist conditions, comparable to Transbond MIP. Within the limitations of this in‑vitro study, Bracepaste MTP may be considered a suitable alternative for orthodontic bonding in situations where moisture control is difficult. Further in‑vivo studies incorporating thermocycling and long‑term aging are recommended.

کلیدواژه ها:

Bonding ، moisture tolerance ، orthodontic primer ، saliva contamination ، Shear Bond Strength