Comparison of bond strength between lingual and buccal surfaces on young premolars

Enamel Surface Roughness after Lingual Bracket Debonding: An In Vitro Study

The aim of the present study was to quantitatively assess changes in enamel roughness parameters before and after lingual bracket debonding. The lingual surface of 25 sound premolars extracted for orthodontic reasons was studied by 3D optical interferometric profilometry before and after debonding of lingual brackets following enamel finishing (with fine diamond) and polishing (with 12- and 20-fluted carbide burs). The roughness parameters tested were the amplitude parameters Sa and Sz, the hybrid parameter Sdr, and the functional parameters Sc and Sv. The parameter differences (after debonding-reference) were calculated, and statistical analysis was performed via a Wilcoxon signed-rank test. Statistically significantly higher values were observed in all the surface roughness parameters of enamel surfaces after finishing and polishing, with the mostly affected parameter being the Sdr. Under the conditions of the present study, the finishing and polishing instruments used after debonding of lingual noncustomized brackets created a surface texture rougher than the control in all the tested roughness parameters.

Avaliação da resistência ao cisalhamento de braquetes da técnica lingual colados sobre superfície cerâmica

OBJETIVO: avaliar a resistência ao cisalhamento de braquetes metálicos (American Orthodontics) utilizados na técnica lingual, colados em facetas de cerâmica. MÉTODOS: foram utilizados 40 corpos de prova divididos em quatro grupos de 10, de acordo com o material de colagem e do preparo da porcelana: Grupo I -resina Sondhi Rapid-Set e ácido fluorídrico; Grupo II -resina Sondhi Rapid-Set e óxido de alumínio; Grupo III -resina Transbond XT e ácido fluorídrico; e Grupo IV -resina Transbond XT e óxido de alumínio. Previamente à colagem, os braquetes foram preparados com base de resina de carga pesada (Z-250) e as facetas de cerâmica receberam aplicação de silano. O teste de cisalhamento foi realizado por uma máquina de ensaios Kratos à uma velocidade de 0,5mm/min. RESULTADOS: os resultados obtidos foram analisados estatisticamente através do teste de Tukey (p<0,05) e demonstraram diferença significativa entre os grupos I (2,77MPa) e IV (6,00MPa), e entre os grupos III (3,33MPa) e IV. CONCLUSÕES: concluiu-se que a colagem de braquetes da técnica lingual em superfície de cerâmica foi mais resistente ao cisalhamento com o uso de óxido de alumínio associado às duas resinas utilizadas neste estudo, porém a resina Transbond XT apresentou maior resistência que a Sondhi Rapid-Set.

Bonding properties of newly erupted and mature premolars

INTRODUCTION

The purpose of this study was to determine whether there were differences in bond strength between mature and newly erupted teeth when using both conventional and self-etching primer techniques for bonding orthodontic appliances. The nature of adhesive bond failure among the groups was also compared by using the adhesive remnant index (ARI).

METHODS

Premolars were collected, randomly divided, and bonded with either the conventional or the self-etching technique. Brackets were debonded on a testing machine with a shear-testing device. Bond strengths were compared with ANOVA and the Weibull analysis.

RESULTS

There were no statistically significant differences in bond strength values between the conventional etching and the self-etching primer groups or between newly erupted and mature teeth. ARI scores differed between mature and newly erupted teeth. Newly erupted teeth had more adhesive failures, and mature teeth had more cohesive bond failures at the enamel-composite resin interface.

CONCLUSIONS

Based on these results, bond strength does not appear to be affected by the posteruptive enamel maturation process.

Effects of buccal versus lingual surfaces, enamel conditioning procedures and storage duration on brackets debonding characteristics

OBJECTIVES

To determine the influence of two enamel conditioning techniques on buccal and lingual tooth surfaces at two different times on debonding strength and tooth damage.

METHODS

The study included 50 premolars. Buccal and lingual surfaces of 10 teeth were scanned using SEM before (N=4) and after enamel conditioning by either acid etching or sandblasting prior to acid etching (N=6) for their morphology. The remaining 40 teeth were divided into 2 equal groups, differing in enamel conditioning prior to metallic bracket bonding on the buccal and lingual surfaces. Each group was equally subdivided into short-term (48h) or long-term (12m) water storage. Debonding strength was measured followed by SEM and EDAX for adhesive remnant index (ARI) and calcium remnant index (CRI) left on bracket bases. ANOVA with repeated measures was applied to the results.

RESULTS

The buccal enamel was rougher than the lingual one. The surface morphology after the two types of conditioning showed a different pattern. A significantly higher debonding strength was needed to debond the buccal brackets compared to the lingual ones (p<0.05). A significantly higher ARI (p<0.002) and higher CRI (p<0.005) were found in the lingual surface compared with the buccal. No differences were found in debonding strength ARI or CRI regarding the different conditioning or storage duration.

CONCLUSIONS

Lingual bonding leads to higher ARI and CRI than buccal bonding. Sandblasting prior to etching does not improve bonding strength for lingual or buccal bonding.