Objective: Currently, minimal invasive approaches combining less invasive finish line preparations and reduced ceramic thickness are required. The aim of this study was to evaluate the fracture resistance of two ceramic systems fabricated with two preparation designs using CAD/CAM standardization technology. Materials and methods: Forty intact human maxillary premolars were divided into two main groups according to the preparation technique. Group H (Horizontal): teeth with shoulder finish line and group V (Vertical): teeth with feather edge. Each main group was subdivided randomly into two subgroups according to the material used. Group CD (Celtra Duo) zirconia-reinforced glass ceramics and group K (KATANA) monolithic zirconia. CAD/CAM was used for standardization of natural teeth preparation. After cementation using self-adhesive resin cement, all specimens were subjected to 5000 thermal cycles and then were loaded until fracture. Failure types were evaluated using Stereomicroscopy and Scanning Electron Microscopy (SEM). Results: Nonsignificant; the higher mean value was recorded with VCD group (482.5 ± 103.8 N) and VK group (1347.6 ± 177.4 N) vs HCD group (471 ± 107.6 N) and HK group (1255.6 ± 121.3 N). SEM findings showed that fractures occurred mainly at the occlusal side of the crowns. Conclusions: Vertical preparation showed a promising alternative to horizontal preparation. Moreover, both Celtra Duo and KATANA crowns can be used in premolar area with 0.5 mm margin thickness. Clinical significance: Zirconia-reinforced glass ceramic and monolithic zirconia crowns may not necessitate the preparation of invasive finish lines as the type of finish line did not impair the strength after aging conditions

Objectives Large part of the tooth is required to be removed during crown preparation. A minimally invasive method for preparing single crowns is required to increase the durability of teeth. The aim of this study was to evaluate the clinical performance of two ceramic systems fabricated with minimally invasive vertical preparation. Materials and methods Forty endodontically treated maxillary premolars were prepared with vertical preparation and received temporary crowns for a period of 21 days. Twenty zirconia-reinforced lithium silicate (Celtra Duo HT, Dentsply Sirona, Germany) and 20 monolithic high translucency zirconia (Katana HT, Kuarary Noritake, Japan) crowns were fabricated by CAD/CAM and cemented with dual-polymerizing luting resin. The crowns were evaluated clinically and radiographically for 36 months following modified FDI criteria. Statistical analysis was conducted with t Student test (Cochran Q). Results Over the follow-up period, there was no need to replace any of the study’s crowns. The overall survival rate of the 40 crowns was 100% according to the Kaplan–Meier survival method. The clinical quality of all crowns and the patient’s satisfaction were high. No caries was detected and no adverse soft tissue reactions around the crowns were observed. Periodontal probing depth was reported to be increased at mesial and distal sites more than the facial one in the 36-month follow-up with no statistically significant difference between both materials (P = 0.186). Conclusions Zirconia and zirconia-reinforced lithium silicate could be used as a material for restoration of teeth prepared with vertical preparation technique. Both ceramic materials achieved good esthetic results, promotes healthy and stable soft tissues with no mechanical complications after 3 years of clinical evaluation. Clinical relevance Monolithic high translucency zirconia and zirconia-reinforced lithium silicate ceramics can be used for the restorations of minimal invasive vertical preparation in premolar area with 0.5 mm margin thickness.

Objective To assess the clinical outcome of three esthetic implant‐supported crown systems fabricated with semi‐digital workflow and their influence on the clinical outcome of dental implants. Material and Methods A total of 30 participants had received dental implants restoring missing maxillary first/second premolars. After 6 weeks, customized zirconia abutments were early loaded. Two months later, the definitive crowns were fabricated using semi‐digital workflow and cemented. According to the crown material, 3 groups were randomly allocated; group (Z): ultrahigh‐translucent monolithic zirconia, group (C): resin‐matrix ceramic and group (P): polyetherketoneketone veneered with light‐cured composite resin. Clinical outcomes including the survival and success rates were evaluated at baseline, 6, 12, 18, and 24 months. Results The survival rate for all studied groups was 100%, while their success rate was 100% for group (Z) and 90% for group (C) and group (P). Based on the functional implant prosthodontic score, a statistically significant difference was detected between group (Z) and group (P) (p < 0.001) as well as between group (C) and group (P) (p = 0.01). Conclusions The zirconia group had the most favorable clinical behavior, while the polyetherketoneketone had the least. All crown systems had comparable success rates with similar values of the peri‐implant marginal bone loss. Clinical Significance Using semi‐digital workflow, ultrahigh‐translucent monolithic zirconia, resin‐matrix ceramic and polyetherketoneketone veneered with light‐cured composite resin can be considered as favorable implant‐supported crowns. The implant‐supported crown system based on polyetherketoneketone veneered with light‐cured composite resin is counted as a promising esthetic and restorative option.

This study aimed to evaluate vertical and horizontal alveolar bone changes after immediate implant placement in the mandibular posterior region combined with ridge preservation and socket sealing with custom healing abutments. Material and methods: eighteen immediately placed implants were inserted in sockets of mandibular molar and the space around the implants was filled with Allograft bone material. Socket was sealed with custom healing abutment. Radiographic evaluation of vertical and horizontal alveolar bone changes were performed on CBCT images taken immediately after implant placement (T0), six months (T6) and 12 months (T12). The following distances were measured around the four implants surfaces; 1) P-BIC; from implant platform to the first bone contact, 2) P-T; vertical distance between implant platform and alveolar bone crest, 3) OBS; from buccal and lingual border of bone to the implant surface at the level of the implant platform (OBS0), 2 mm (OBS2), and 4 mm (OBS4) apical to implant platform. Results:The highest bone loss at P-BIC and P-T distances was noted with distal surface, followed by mesial surface, the lowest was noted was buccal/lingual surfaces. At T6 and T12, Buccal surface recorded significant higher OBS0 bone loss than lingual surface. Conclusion:Immediate implant placement in the mandibular posterior region combined with ridge preservation and socket sealing with custom healing abutments and delayed loading protocol is a successful treatment and associated with acceptable vertical and horizontal bone loss around implants after one year follow-up.

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