Aim: To evaluate the fracture load and the type of failure of two different monolithic restorative materials bonded to standardized titanium bases and fabricated by two different procedures regarding the bonding-interface. Materials-Methods: All screw-retained implant-crown specimens (n=40), subjected to fatigue by thermomechanical loading, differed in the restorative material (lithium disilicate-LDS or polymer infiltrated ceramic network (PICN), referred to as “hybrid ceramic”-HYC) and the interface type between the restorative material and the titanium base abutment (prefabricated ex-factory or produced during the CAM-milling procedure). This resulted in the following groups (n=10/group): (1) LDS-M: lithium disilicate crown with a CAM-milled interface, (2) LDS-P: lithium disilicate crown with a prefabricated interface, (3) HYC-M: PICN crown with a CAM-milled interface and (4) HYC-P: PICN crown with a prefabricated interface. Aged specimens underwent static fracture load testing. The load (N) at which the initial crack occurred was denoted as Finitial, and the maximal load (N) at which the restorations fractured as Fmax. All specimens were examined under a stereomicroscope to determine the failure mode. Results: The median Finitial values were 180 N for LDS-M, 343 N for LDS-P, 340 N for HYC-M and 190 N for HYC-P. The median Fmax values were1822 N for LDS-M, 2039 N for LDS-P, 1454 N for HYC-M and 1581 N for HYC-P. The intergroup differences were significant for Finitial (KW: p = 0.0024) and for Fmax (KW: p = 0.0010). The failure types also showed differences between the restorative groups. Conclusion: The choice of restorative material had a stronger influence on the fracture load than the abutment interface workflow. Lithium disilicate showed the highest load for initial crack appearance (Finitial) and for complete fracture of the restoration (Fmax). Keywords: abutment interface, dental materials, failure mode, fracture load, lithium disilicate, polymer infiltrated ceramic network, prosthetic dentistry, restorative material, thermomechanical aging

Purpose: To investigate the effect of aging on the morphology of the interface between monolithic implant crowns and standardized titanium base abutments. Materials and Methods: Four groups of hybrid abutment crowns differing in restorative material (lithium disilicate [LD] or polymer-infiltrated ceramic network [PICN]) and in fabrication procedure of the interfacial zone for luting to a titanium abutment (milled during CAD/ CAM procedure [M] or prefabricated [P]) were formed: LDS-M, LDS-P, PICN-M, and PICN-P (n = 10 each). The morphology of the crown-abutment interface was examined before and after artificial aging using scanning electron microscopy. The total gap length per specimen was measured at both time points, and intergroup (Kruskal-Wallis [KW]) plus pairwise (Wilcoxon Mann-Whitney [WMW]) comparisons were performed (α = .05). Results: Before aging, statistically significant differences in gap length were identified among groups (KW: P = .0369) for PICN-P > LDS-P (WMW: P = .0496) and LDS-M > LDS-P (WMW: P = .0060). The effect of aging among the groups, expressed as an increment of total gap length, was 50% in LDS-M, 30% in LDS-P, 20% in PICN-M, and 30% in PICN-P. After aging, the statistically significant differences in gap length identified among groups (KW: P = .0048) were for PICN-P > LDS-P (WMW: P = .0134); LDS-M > PICN-M (WMW: P = .0204); PICN-P > PICN-M (WMW: P = .0486); and LDS-M > LDS-P (P = .0022). However, comparison of the difference in gap length from before to after aging among the groups was not statistically significant (KW: P = .3549). Conclusion: The cementation interfaces of CAD/CAM crowns on standardized titanium base abutments demonstrated a high percentage of gaps before and after thermomechanical loading. The composition of the restorative material and the nature of the interface influenced the interfacial gap dimension.

This study sought to evaluate gingival volume changes following root coverage with the vestibular incision subperiosteal tunnel access (VISTA) procedure. Pre- and postoperative surface scans of 21 patients (154 teeth) treated with VISTA using various graft materials were digitally superimposed to quantify volumetric changes. A linear gingival thickness gain of approximately 1 mm and volumetric gain of 5.47 mm3 were achieved. A negative correlation was found between linear thickness gain and root prominence. The thickness achieved was not different with various graft materials. Since gingival thickness has been identified as an important predictor of periodontal root coverage, the methodology described in the present study, along with the identification of predictors of outcome, has important therapeutic implications.