Accelerated Aging Effects on Surface Hardness and Roughness of Lingual Retainer Adhesives

Abstract

Objective: To test the null hypothesis that accelerated aging has no effect on the surface microhardness and roughness of two light-cured lingual retainer adhesives. Materials and Methods: Ten samples of light-cured materials, Transbond Lingual Retainer (3M Unitek) and Light Cure Retainer (Reliance) were cured with a halogen light for 40 seconds. Vickers hardness and surface roughness were measured before and after accelerated aging of 300 hours in a weathering tester. Differences between mean values were analyzed for statistical significance using a t-test. The level of statistical significance was set at P Ͻ .05. Results:The mean Vickers hardness of Transbond Lingual Retainer was 62.8 Ϯ 3.5 and 79.6 Ϯ 4.9 before and after aging, respectively. The mean Vickers hardness of Light Cure Retainer was 40.3 Ϯ 2.6 and 58.3 Ϯ 4.3 before and after aging, respectively. Differences in both groups were statistically significant (P Ͻ .001). Following aging, mean surface roughness was changed from 0.039 m to 0.121 m and from 0.021 m to 0.031 m for Transbond Lingual Retainer and Light Cure Retainer, respectively. The roughening of Transbond Lingual Retainer with aging was statistically significant (P Ͻ .05), while the change in the surface roughness of Light Cure Retainer was not (P Ͼ .05). Conclusions: Accelerated aging significantly increased the surface microhardness of both lightcured retainer adhesives tested. It also significantly increased the surface roughness of the Transbond Lingual Retainer.

Mechanical properties of contemporary orthodontic adhesives used for lingual fixed retention

“…TBLR showed the highest HV values, which were higher than the values presented in dental literature [16,19]. TBXT showed identical HV values as those provided by Iijima et al [12] and close to those provided by Uysal et al [20].…”

“…Three of the products tested (TBLR, TBXT, BPA-FR) showed positive results as orthodontic adhesives. TBLR has been developed specifically for bonding lingual retainers and is used extensively in clinical practices and recent experimental studies, commonly as the control adhesive [16,19,21,23]. TBXT is an orthodontic bonding adhesive resin used mostly for brackets but has been occasionally used for the construction of fixed retainers in the laboratory setting [5,22,23].…”

“…Therefore, material hardness [19], wear resistance and water absorption [20,24] are among the critical mechanical properties for the longevity of fixed retainers under intra-oral conditions. In addition, fixed retainer adhesives are more vulnerable to aging mechanisms as they remain in the oral cavity for longer periods than the bracket adhesives [1,16].…”

Effects of thermocycling on the degree of cure of two lingual retainer composites

“…Moreover, extended working time enhances accurate wire placement and minimizes product waste 1) . While these excellent handling properties are both desirable and important, the degree of cure (DC) is also another very important factor for lingual retainer adhesives.…”

“…Photoactivated, resin-based composites (PARBCs) have become the material of choice for bonding lingual retainers today, as they offer ease of application and optimal handling characteristics to allow the clinician to shape and finish the adhesive around the lingual retainer wire for maximum patient comfort 1) . Moreover, extended working time enhances accurate wire placement and minimizes product waste 1) .…”