Mechanical properties of contemporary orthodontic adhesives used for lingual fixed retention

Abstract

OBJECTIVE The aim of the present study was to test the mechanical properties of different adhesives used in orthodontics for fixed retainers and to investigate their possible interrelations. MA-TERIALS AND METHODS Specimens of six different adhesive resins were prepared: Transbond XT, Transbond LR and an experimental BPA-free orthodontic adhesive, as well as IPS Empress Direct (IPS-ED), ZNano and Accolade. The mechanical properties tested were Martens hardness (HM), indentation modulus (EIT), the ratio of elastic to total work, commonly known as elastic index ( IT) and Vickers hardness (HV). These properties were determined using instrumented indentation testing according to ISO 14577-2002. The results of the aforementioned properties were statistically compared with one-way ANOVA-test and Student-Newman-Keuls multiple comparison test at a=0.05, while possible correlations among the properties tested were analyzed by Pearson correlation. RESULTS Significant differences were identified among all the materials tested for HM, with Transbond LR presenting the highest value. This resin presented the highest EIT too. Significant EIT differences were identified among the materials and only ZNano and IPS-ED showed no significant differences for this property. Transbond LR and ZNano showed higher HV values. ZNano demonstrated the highest elastic index. Pearson analysis showed a strong positive correlation between HM and EIT (0.970), HM and HV (0.837), and EIT and HV (0.695), while a weak negative correlation was found between EIT and elastic index (-0.505). CONCLUSIONS The materials tested demonstrated significant differences in their mechanical properties, and thus differences in their clinical performance are anticipated. Abstract Objective: The aim of the present study was to test the mechanical properties of different adhesives used in orthodontics for fixed retainers and to investigate their possible interrelations. Materials and methods: Specimens of six different adhesive resins were prepared: Transbond XT, Transbond LR and an experimental BPA-free orthodontic adhesive, as well as IPS Empress Direct (IPS-ED), ZNano and Accolade. The mechanical properties tested were Martens hardness (HM), indentation modulus (E IT ), the ratio of elastic to total work, commonly known as elastic index (η IT ) and Vickers hardness (HV). These properties were determined using instrumented indentation testing according to ISO 14577-2002. The results of the aforementioned properties were statistically compared with one-way ANOVA-test and Student-Newman-Keuls multiple comparison test at a = 0.05, while possible correlations among the properties tested were analyzed by Pearson correlation. Results: Significant differences were identified among all the materials tested for HM, with Transbond LR presenting the highest value. This resin presented the highest E IT too. Significant E IT differences were identified among the materials and only ZNano and IPS-ED showed no significant differences for this property. Transbond LR and ZNa...

Creep, Hardness, and Elastic Modulus of Lingual Fixed Retainers Adhesives

“…Although HM (also known as universal hardness) is supposedly independent of several limitations of traditional hardness techniques [22], there are limited previously published data of materials tested. Available HM data exists only for products TL (695 N/mm 2 ) and TX (568 N/mm 2 ) in a previous research [6], both of them close to the experimental findings of this study. The E IT was found in accordance to the data provided by the manufacturer for BP (13.7 GPa) [23].…”

“…The results for GA are similar to the data provided by the manufacturer (7.9 GPa) [24] and a previous study after testing in three point bending [19]. The moduli of FT and TL were also found close to previously reported values (FT 5.2 GPa [13]), (TL 17.3 GPa [6,25]) after IIT. The same is true for E IT for TX (15.0 GPa [6]), a value close to one provided by the manufacturer (16.4 GPa [23]) and the value of 14.3 GPa calculated after three point bending [16].…”

“…The moduli of FT and TL were also found close to previously reported values (FT 5.2 GPa [13]), (TL 17.3 GPa [6,25]) after IIT. The same is true for E IT for TX (15.0 GPa [6]), a value close to one provided by the manufacturer (16.4 GPa [23]) and the value of 14.3 GPa calculated after three point bending [16]. All materials tested showed modulus of elasticity greater than 1.5 GPa, which is the threshold according to ISO 20795-2 for orthodontic base polymers.…”

“…Orthodontists use specific orthodontic adhesives for brackets bonding and fix retainers. However common restorative [1,2], flowable composites [3,4], as well as resin composites for universal use [5,6], have been reported for the production of lingual fixed retainers.…”

“…Despite the fact that the mechanical properties of adhesives have been tested by experimental and retrieval analysis studies [6,10,11,12,13], there is currently no information on the time-dependent properties of orthodontic adhesives. However, adhesive resins in both aforementioned applications undergo static forces over the whole time of intraoral service.…”