Guliz Aktas

Comparison of implant versus tooth-supported zirconia-based single crowns in a split-mouth design: a 4-year clinical follow-up study

ObjectivesThis study aims to evaluate the 4-year clinical performance of tooth versus implant-supported single-unit zirconia crowns (LAVA™) placed on posterior region.Materials and methodsTwenty-four patients (10 men and 14 women) who had received 48 single crowns (24 implant-supported and 24 tooth-supported) from January 2007 to December 2009, were included. California Dental Association (CDA) quality assessment system, plaque and gingival index scores were used to evaluate the performance of the crowns at baseline and at all follow-up examinations.ResultsDuring the follow-up period, no fracture of zirconia coping has occurred. Major complication was chipping in three patients that required a new crown fabrication. Except for the failure ones, all crowns in both groups were rated as satisfactory at the follow-up examinations based on the CDA quality assessment criteria. There were no statistically significant differences between tooth and implant-supported crowns in terms of periodontal parameters.ConclusionsThe present 4-year follow-up clinical study demonstrates that single-unit tooth- and implant-supported zirconia crowns have similar prosthetic and periodontal outcomes.Clinical relevanceSingle-unit implant or tooth-supported zirconia crowns may be considered acceptable treatment modalities for restoration of either missing or compromised posterior teeth

Mechanical Failure of Endocrowns Manufactured with Different Ceramic Materials: An In Vitro Biomechanical Study.

PURPOSE To evaluate the effect of different silica-based ceramic materials on the mechanical failure behavior of endocrowns used in the restoration of endodontically treated mandibular molar teeth. MATERIALS AND METHODS Thirty-six intact mandibular molar teeth extracted because of a loss of periodontal support received root canal treatment. The teeth were prepared with a central cavity to support the endocrowns, replacing the occlusal surface with mesial-lingual-distal walls. Data acquisition of the prepared tooth surfaces was carried out digitally with a powder-free intraoral scanner. Restoration designs were completed on manufactured restorations from three silicate ceramics: alumina-silicate (control), zirconia-reinforced (Zr-R), and polymer-infiltrated (P-I). Following adhesive cementation, endocrowns were subjected to thermal aging, and then, each specimen was obliquely loaded to record the fracture strength and define the mechanical failure. For the failure definition, the fracture type characteristics were identified, and further analytic measurements were made on the fractured tooth and ceramic structure. RESULTS Load-to-fracture failure did not differ significantly, and the calculated mean values were 1035.08 N, 1058.33 N, and 1025.00 N for control, Zr-R, and P-I groups, respectively; however, the stiffness of the restoration-tooth complex was significantly higher than that in both test groups. No statistically significant correlation was established in paired comparisons of the failure strength, restorative stiffness, and fractured tooth distance parameters. The failure mode for teeth restored with zirconia-reinforced glass ceramics was identified as non-restorable. The resin interface in the control and P-I groups presented similar adhesive failure behavior. CONCLUSION Mechanical failure of endocrown restorations does not significantly differ for silica-based ceramics modified either with zirconia or polymer.

Effect of manufacturing techniques on the marginal and internal fit of cobalt-chromium implant-supported multiunit frameworks

Statement of problem. Subtractive and additive computer‐aided design and computer‐aided manufacturing (CAD‐CAM) systems have been used in the fabrication of cobalt‐chromium (Co‐Cr) long‐span restorations. However, the accuracy of fit of multiunit frameworks is unclear. Purpose. The purpose of this in vitro study was to compare the marginal and internal fit of implant‐supported, cement‐retained 3‐unit, 4‐unit, and 5‐unit Co‐Cr metal frameworks fabricated by the lost wax (LW), CAD‐CAM milling, and selective laser melting (SLM) techniques. Material and methods. A total of 90 Co‐Cr metal frameworks were fabricated for 3‐unit, 4‐unit, or 5‐unit implant‐supported cement‐retained restorations on stock abutments with 3 different manufacturing technique subgroups (LW, CAD‐CAM milling, and SLM). The silicone replica technique was used to evaluate the marginal and internal discrepancy values. By using a light microscope at ×45 magnification and a digital measurement program, the thickness of the silicone layer was measured at 16 reference points on each abutment for a total of 3360 measurements. The effect of manufacturing techniques and number of units (groups) on discrepancy values was evaluated using a full factorial ANOVA model. Group and manufacturing technique effects were analyzed separately by 1‐way ANOVA in case of significant interactions. Pairwise comparisons were evaluated using the Tukey post hoc test (&agr;=.05). Results. The mean marginal discrepancy of 3‐unit frameworks showed no statistically significant differences in the LW (35 &mgr;m) and SLM (25 &mgr;m) techniques; however, the frameworks manufactured by CAD‐CAM milling (68 &mgr;m) had the highest marginal discrepancy values (P<.001). The mean marginal discrepancy values were 40 &mgr;m (LW), 33 &mgr;m (CAD‐CAM milling), and 25 &mgr;m (SLM) for 4‐unit frameworks, and no significant differences were found among the manufacturing techniques. For 5‐unit frameworks, CAD‐CAM milling techniques had the widest mean marginal discrepancy values (85 &mgr;m), and copings manufactured by the LW technique had the lowest mean marginal discrepancy values (36 &mgr;m). For all manufacturing techniques, axial discrepancy values were not affected with respect to the unit number (P=.526). The highest internal discrepancy values were measured at the occlusal area in all groups. Conclusions. CAD‐CAM milling had the poorest marginal fit values for 5‐unit frameworks, whereas the LW technique demonstrated the best results. Unit number had no significant influence on the marginal and internal fit of the LW manufactured frameworks.

Effect of timing for core preparation, luting cement type and root level on adhesion of fiber posts to intraradicular dentin

Abstract This study assessed the effect of timing of core preparation and luting cement on adhesion of fiber-reinforced composite (FRC) posts on different levels of intraradicular dentin when cemented with either conventional dual-polymerized or self-adhesive resin cement. Single-rooted human teeth (N = 80) were endodontically treated and randomly divided into 2 groups (n = 40) according to resin cement: (a) Conventional dual resin cement (Variolink II, V) or (b) Self-adhesive resin cement (RelyX U200, R). They were further divided into two subgroups according to timing of core preparation (n = 20): (a) immediate (i) or (b) delayed (d). FRC posts (Cytec Blanco) were cemented and the roots were sliced into discs at the coronal, middle, and apical levels. Push-out tests were then performed in a Universal Testing Machine (1 mm/min). Data (MPa) were analyzed using three-way ANOVA and Tukey’s tests considering the factors ‘core preparation time’, ‘luting cement’, and ‘root level’ (α = 0.05). Type of luting cement (p < 0.001), time of core preparation (p < 0.001), and root level (p < 0.001) significantly affected the bond strength results. R cement was more significantly affected by core preparation time (Ri: 2.91 ± 1.1; Rd: 4.83 ± 1.68) compared to V cement (Vi: 2.92 ± 1.63; Vd: 2.65 ± 1.6) (p < 0.05). Coronal region demonstrated significantly higher bond strength values than those of middle and apical third in all groups (coronal: 4 ± 1.9; middle: 3.1 ± 1.4; apical: 2.4 ± 1.1) (p < 0.05). Adhesive failure between cement and dentin was the most frequent (64%) followed by adhesive failure between cement and post (18%). Delayed core preparation can improve bond strength of FRC posts to intraradicular dentin when cemented with self-adhesive cement compared to conventional dual-polymerized resin cement.