Background The purpose of this study is to investigate the performance and fracture resistance of different resin-matrix ceramic materials for use in implant-supported single crowns with respect to the abutment design (crown thickness: 1 mm, 2 and 3 mm). Methods Forty-eight abutments and crowns were fabricated on implants in the right lower first molar. Two resin-matrix ceramic materials for dental crowns were selected for study: (1) a glass-ceramic in a resin interpenetrating matrix (Vita Enamic, Vita, Germany) and (2) a resin-based composite with nanoparticle ceramic filler (Lava Ultimate, 3 M ESPE, USA). Three types of abutments were designed: 1 mm thick crown + custom titanium abutment, 2 mm thick crown + custom titanium abutment and 3 mm thick crown + prefabricated titanium abutment. The experiment was divided into 6 groups (n = 8) according to the crown materials and abutment designs. After 10,000 thermocycles, fracture resistance was measured using a universal testing machine. The statistical significance of differences between various groups were analysed with ANOVA followed by a post hoc Tukey’s honestly significant difference test. The surfaces of the fractured specimens were examined with scanning electron microscopy (SEM). Results Two-way ANOVA revealed that the abutment design (F = 28.44, P = 1.52 × 10− 8<0.001) and the crown materials (F = 4.37, P = 0.043 < 0.05) had a significant effect on the fracture resistance of implant crown restoration. The Lava Ultimate-2 mm group showed the highest fracture resistance of 2222.74 ± 320.36 N, and the Vita Enamic-3 mm group showed the lowest fracture resistance of 1204.96 ± 130.50 N. Most of the 1 and 2 mm groups had partial crown fractures that could be repaired directly with resin, while the 3 mm group had longitudinal fracture of the crown, and the crowns were detached from the abutments. Conclusion Based on the in vitro data of this study, the fracture resistance of the 2 mm thick resin-matrix ceramic crown design was higher than that of the 1 and 3 mm groups. The 2 mm thick resin-matrix ceramic crown and personalized abutment are an option to replace zirconia for implant crown restoration.

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 80 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 (RelyX Luting 2; RXL) and resin cement (Clearfil SA luting; CSL) were used to bond zirconia sheet and titanium block. Specimens were kept in 100% humidity for 48 h. 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 min of laser irradiation. Shear bond strength (MPa) and the time data (s) were analyzed using Kruskal–Wallis Test. The bonding surface and the irradiation surface of the zirconia sheet was examined with the scanning electron microscopy (SEM). Results Within 5 min of laser irradiation, RXL group: 1 mm group all fell off, 2 mm group had 3 specimens did not fall off, there was no statistical difference in the average time between the two groups; CSL group: half of the 1 mm group fell off. Shear bond strength test results: there was no statistical difference between 1 and 2 mm in RXL group and 1 mm in CSL group, there was no statistical difference between 3 mm in RXL group and 2 mm in CSL group, and there were significant differences statistically in comparison between any two groups in the rest. SEM inspection showed that the bonding surface and the irradiation surface of the zirconia sheet had changes. Conclusion In this vitro study, the following could be concluded: it is faster to remove zirconia crowns with thickness less than 2 mm from titanium abutment when luted with RelyX Luting 2 compared to Clearfil SA luting.

Background: The purpose of this study is to investigate the performance and fracture resistance of different resin-matrix ceramics materials as implant-supported single crowns with respect to the abutment design (crown thickness: 1 mm, 2mm and 3 mm). Methods: Forty-eight aboutments and crowns were fabricated on implants right lower first molar simulating. Two resin-matrix ceramics materials for dental crowns were selected for study, (1)glass-ceramic in a resin interpenetrating matrix (Vita Enamic, Vita, Germany) and (2) resin-based composite with nanoparticle ceramic filler (Lava Ultimate, 3M ESPE, USA). The abutment is designed into the following three types: 1 mm thickness crown + custom titanium abutment, 2 mm thickness crown + custom titanium abutment and 3 mm crown + prefabricated titanium abutment. The experiment was divided into 6 groups (n=8) according to the crown materials and the abutment designs. After 10,000 thermocycling, fracture resistance was measured using a universal testing machine. The statistical differences in various groups were analyzed with ANOVA test followed by a post hoc Tukey’s honestly significant difference test. The surface of the fractured specimen was examined with the scanning electron microscopy (SEM). Results: 2-way ANOVA revealed that the factor of the abutment designs (F=28.44，P=1.52x10-8<0.001) and the crown materials (F=4.37，P=0.043<0.05) had a significant effect on the fracture resistance of implant crown restoration. The Lava Ultimate-2 mm group showed the highest fracture resistance of 2222.74±320.36 N, and the Vita Enamic-3 mm group showed the lowest fracture resistance of 1204.96±130.50 N. Most of the 1 mm and 2 mm groups had partial crown fracture that could be repaired directly with resin, while the 3 mm group had longitudinal fracture of the crown, and the crown was detached from the abutment. Conclusion: Based on the in vitro data of this study, the fracture resistance of the 2 mm thick resin-matrix ceramics crown design is higher than that of the 1 mm and 3 mm groups. The 2 mm thick resin-matrix ceramics crown and personalized abutment are an option to replace zirconia as an implant crown restoration.

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.