The effects of provisional resin cements on the color and retentive strength of all-ceramic restorations cemented on customized zirconia abutments

Abstract

This study aimed to evaluate the effects of two types of provisional resin cements on the color and retentive strength of two different all-ceramic restorations cemented onto customized zirconia abutments. Forty-two crowns were made of monolithic zirconia and lithium disilicate ceramics (n = 21 per group) and cemented on customized zirconia abutments by using two provisional resin cements of TempBond Clear and Implantlink Semi, and TempBond serving as the control (n = 7 per cement subgroup). The specimens' color was measured before and after cementation and after thermocycling. The color difference was calculated by using CIEDE2000 formula (ΔE00). The tensile force was applied to assess the retentive strength. Kruskal-Wallis, Dunn's post-hoc, and Mann-Whitney non-parametric tests were used to compare ΔE00(1) and ΔE00(2) and two-way ANOVA followed by one-way ANOVA and Tukey's HSD post hoc test and T-test were used to compare retentive strength between subgroups. In the lithium disilicate group, ΔE00 of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi cements subgroup (P = 0.001). But, in the monolithic zirconia group, ΔE00 of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi (P = 0.020) and TempBond Clear cements (P = 0.007). In the monolithic zirconia group, the control subgroup (TempBond) was significantly more retentive than TempBond Clear (P = 0.003) and Implantlink Semi cement (P = 0.001). However, in the lithium disilicate group, Implantlink Semi cement was significantly more retentive than TempBond Clear (P = 0.019) and TempBond (control) (P = 0.001). The final color of both restorations was significantly affected by the provisional resin cement type. The retentive strength was influenced by both the type of cement and ceramic.

Fig 1. Milled customized zirconia abutment superstructure.

A: buccal surface, B: proximal surface, C: lingual surface. The bonding surface of the titanium implant insert (ZrGEN; AnyOne; model: AAOIPR4525; Megagen, South Korea) was abraded with 50-μm aluminum oxide particles at a 10-mm distance for 10 seconds (0.4 MPa). The inner surface of zirconia abutment superstructures was also subjected to airborne particle abrasion with 30-μm silica-coated aluminum oxide (Rocatec Soft; 3M ESPE, USA).

Fig 2. A full contour right maxillary central incisor crown with a projection on its incisal edge.

A: buccal surface, B: proximal surface, C: lingual surface. Forty-two ceramic crowns (n = 21 per group) were fabricated with either ultrahigh-translucent monolithic zirconia in A2 shade (ZIRAE; SHT Preshaded Zirconia Block, Nanjing Zirae Advanced Material Co, China) by using a laboratory milling machine (Cori Tec 340i; Imes-Icore GmbH, Germany) or high-translucent lithium disilicate ceramic in A2 shade (IPS e.max Press; Ivoclar Vivadent, Germany). For making lithium disilicate crowns, wax patterns were prepared by a 3D printer (Solidscape D76+; Solidscape, USA) based on the previously CAD-designed shape and dimensions. The wax patterns were sprued, invested, burned out; and lithium disilicate was pressed into the burned-out molds.

Fig 3. Mean and standard deviation of ΔE₀₀(1) and ΔE₀₀(2).

Fig 4. The mean and standard deviation of retentive strength of cements as a function of the type of restorations.

Concerning the effect of ceramic restoration, the mean retention was significantly different between the two ceramic types only when cemented with TempBond (P<0.001) and Implantlink Semi cement (P = 0.004); that is, the mean retentive strength of TempBond was significantly higher in monolithic zirconia restorations; while in lithium disilicate, Implantlink Semi was more retentive (Table 6).