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 F_max. All specimens were examined under a stereomicroscope to determine the failure mode. Results: The median F_initial 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 F_max 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 F_initial (KW: p = 0.0024) and for F_max (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 (F_initial) and for complete fracture of the restoration (F_max). Keywords: abutment interface, dental materials, failure mode, fracture load, lithium disilicate, polymer infiltrated ceramic network, prosthetic dentistry, restorative material, thermomechanical aging

Phenotype modification therapy has emerged as one of the main treatment objectives of periodontal plastic surgery. However, long-term data on the stability of gingival thickness gains are not available. This study examined the kinetics of mucosal thickness gain as a measure of phenotype modification therapy following treatment of multiple gingival recession defects with vestibular incision subperiosteal tunnel access (VISTA). Six patients with 14 recession type (RT) II teeth were treated using VISTA and subepithelial connective tissue grafts (SCTG). Scanned images of study casts at pre- and postoperative periods (6 to 66 months) were digitally superimposed for quantitative evaluation of soft tissue dimensional changes. Mucosal thickness gains ranged from 1.0 ± 0.7 mm (1 mm apical to cement-enamel junction [CEJ]) to 1.4 ± 0.4 mm (5 mm apical to CEJ). The gingival thickness gains remained relatively stable, with thickness gains at 66 months of 0.5 ± 0.8, 0.9 ± 0.6, 1.1 ± 0.6, 1.0 ± 0.4, and 1.2 ± 0.6 mm at 1, 2, 3, 4 and 5 mm apical to the CEJ, respectively. Treatment of multiple gingival recession defects with VISTA and SCTG led to stable gingival thickness gains and shows promise as a strategy for phenotype modification therapy.