Correlation of Shear Bond Strength and Degree of Conversion in Conventional and Self-Adhesive Systems Used in Orthodontic Bonding Procedures

Abstract

(1) Background: Self-adhesive systems have been proposed for the orthodontic bonding with the intention to reduce the traditional three-component system. (2) Methods: The sample consisted of 32 extracted intact permanent premolars randomly divided into two groups (n = 16). In Group I the metal brackets were bonded with Transbond XT Primer and Transbond XT Paste. In Group II the metal brackets were bonded with GC Ortho connect. The resin was polymerized for 20 s from two directions (mesial and occlusal) using a Bluephase light-curing unit. The shear bond strength (SBS) was measured using a universal testing machine. Immediately after SBS testing, Raman microspectrometry was performed for each sample to calculate the degree of conversion (DC). (3) Results: There was no statistically significant difference in the SBS between the two groups. A significantly higher DC (p < 0.001) value was recorded in Group II, in which the brackets were bonded with GC. Very weak or no correlation (0.01) was recorded between SBS and DC in Group I and moderate positive correlation was recorded in Group II (0.33). (4) Conclusions: No difference was found in SBS between the conventional and two-step systems used in orthodontics. The two-step system demonstrated higher DC compared to the conventional system. There is a very weak or moderate correlation between DC and SBS.

Influence of the Bracket Material on the Post-Cure Degree of Conversion of Resin-Based Orthodontic Adhesive Systems

“…Higher filler content also limits the mobility of monomers and propagation of the polymerization reaction, resulting in a lower DC at the beginning [7,17], which consequently leads to a more extensive DC increase during the "dark" period [9]. Considering the large increase in DC values measured 1 day after polymerization for Enlight and Transbond XT in all groups, caution should be exercised when interpreting the results of other studies [6,8,10,[17][18][19]36] that measured the DC immediately after light curing. Generally, DC values measured within a period shorter than 1 day should be considered as gradually developing values, which are likely to vary depending on the time interval between the light curing and performing the measurement.…”

The Use of Lasers in Enhancing the Bond Strength of Orthodontic Brackets

“…The increased bond strength observed in the laser-assisted bonding group aligns with previous research suggesting that laser irradiation can modify enamel surface characteristics, promoting improved adhesive interactions. [ 1 2 ] Knösel et al . [ 2 ] reported that laser treatment could enhance the micromechanical retention of brackets on enamel surfaces, thereby contributing to higher bond strength values.…”

“…[ 1 2 ] Knösel et al . [ 2 ] reported that laser treatment could enhance the micromechanical retention of brackets on enamel surfaces, thereby contributing to higher bond strength values. The microstructural alterations induced by lasers might lead to increased surface roughness and higher energy for adhesive interlocking, resulting in stronger adhesive bonding.…”

“…[ 1 ] Lasers offer a precise and controlled means of modifying enamel surfaces, potentially enhancing the bond strength between brackets and teeth. [ 2 ] The application of laser energy to enamel can lead to microstructural changes that promote better adhesive interactions. [ 3 ] Moreover, lasers can aid in the removal of the smear layer and provide a cleaner enamel surface, which may positively impact the adhesive bonding process.…”

The Effect of Bonding Surface Design on Shear Bond Strength of 3D-Printed Orthodontic Attachments

“…The SBS of the samples was measured by a universal testing machine (K-21046, Walter + bia, Iohningen, Switzerland). The force was applied by a beveled flat-end metal rod at the attachment‒composite resin interface with 1 mm/min crosshead speed, parallel to the bonding surface [ 21 ].…”