Er:YAG laser removal of zirconia crowns on titanium abutment of dental implants -- an in vitro study

Abstract

Background This research aimed to explore feasibility and the time required when erbium-doped yttrium aluminum garnet (Er:YAG) laser as a non-invasive treatment modality to retrieve different thicknesses of zirconia material bonded by two dental cements from titanium implant abutments. Methods prepared 40 titanium blocks (length: 20 mm, width: 10 mm, height: 10 mm) and square zirconia sheets (length: 10 mm) with different thicknesses (1 mm, 2 mm, 3 mm, and 4 mm) were 20 pieces each. Resin modified glass ionomer cement (RXL2; RelyX Luting 2, 3M ESPE, USA), and resin cement (CSAL; Clearfil SA luting, Kuraray, Japan) were used to bond zirconia sheet and titanium block. Specimens were kept in 100% humidity for 48 hours. Er:YAG laser was used to retrieve the zirconia sheet and recorded the time. Universal testing machine was used to measure the residual adhesion of the samples that did not retrieve after 5 minutes of laser irradiation. Shear bond strength (MPa) and the time data (s) were analyzed using Kruskal-Wallis Test. The bonding surface of the zirconia sheet was examined in a scanning electron microscopy (SEM). Results Within 5 minutes of laser irradiation, RXL2 group: 1 mm group all fell off, 2 mm group 3 specimens did not fall off, there was no statistical difference in the average time between the two groups; CSAL group: half of the 1 mm group fell off. Shear bond strength test results: there was no statistical difference between 1mm and 2mm in RXL2 group and 1mm in CSAL group, there was no statistical difference between 3mm in RXL2 group and 2mm in CSAL group, and there were significant differences statistically in comparison between any two groups in the rest. SEM inspection showed that the 1mm and 2mm adhesive surfaces had obvious fracture points caused by laser. Conclusion From this in vitro study, the following could be concluded:it is faster to remove zirconia crowns from titanium abutment when luted with RelyX Luting 2 compared to Clearfil SA luting, and as the thickness of the restoration increases, the time required for gradually increases gradually.