In Vitro Comparison of Internal and Marginal Adaptation between Printed and Milled Onlays.

STATEMENT OF PROBLEM: Nowadays, milling is still the gold standard for fabricating indirect restorations, but to overcome its disadvantages, there are alternatives, such as 3D printing. PURPOSE: This study aimed to compare the gaps between the prepared tooth and milled and printed onlays fabricated with the same CAD design. It also aimed to determine the gap reproducibility across onlays fabricated by 3D printing and milling. METHODS: A resin tooth was prepared for an onlay. After scanning the preparation, an onlay was designed with proprietary dental software. Next, 22 onlays were milled in a graphene-reinforced PMMA disc (Group 1), and 22 onlays were 3D-printed with a hybrid composite material (Group 2). After that, all fabricated restorations were scanned and superimposed on the scanned prepared resin tooth. Subsequently, a specific software was used to measure the margin, central, and intaglio-located gap between the milled or printed restoration and the preparation. Finally, measurements were compared with a multifactor analysis of variance. RESULTS: The results demonstrated that printed onlays (Group 2) adapted better to the prepared tooth than the milled ones (Group 1) (p < 0.05). The comparison of standard deviations showed the better gap reproducibility of printed onlays (p < 0.05). CONCLUSION: This study concluded that the printed onlays adapted significantly better to the prepared tooth than the milled onlays. Printed onlays also showed significantly better gap reproducibility.

Narrow diameter titanium-zirconium tissue-level implants supporting multi-unit FDPs in the anterior area: A 5-year prospective study.

BACKGROUND: Narrow diameter implants (NDIs) are used in cases of limited mesio-distal space, or if the alveolar ridge does not allow placement of a standard diameter implant. PURPOSE: The aim of this prospective case series study is to present the 5-year clinical-, radiological-, and patient-reported outcome measures (PROMs) of patients with partial edentulism in the anterior area of the jaws requiring the placement of two narrow diameter implants to support a 3- or 4-unit fixed partial denture (FPD). MATERIALS AND METHODS: Thirty partially edentulous patients missing 3 or 4 adjacent teeth in the anterior area of the jaws were included in the study. Two titanium-zirconium tissue-level NDIs were placed in each patient in healed anterior sites (60 implants). A conventional loading protocol was performed to provide a FPD. Implant survival, success, marginal bone-level changes (MBL), clinical parameters, buccal bone stability with CBCT, adverse events and PROMs were recorded. RESULTS: The survival and success rates for the implants were 100%. The mean MBL (±SD) after prosthesis delivery, and 5-year follow-up (mean 58.8 months; range: 36-60) was 0.12 ± 0.22 and 0.52 ± 0.46 mm, respectively. Decementation and screw loosening were the most frequent prosthetic complications, yielding a prosthetic survival and success rates of 100% and 80%, respectively. Patient satisfaction was high with a mean (±SD) score of 89.6 ± 15.1. CONCLUSIONS: The use of tissue-level titanium-zirconium NDIs supporting splinted multi-unit FPDs in the anterior area seems to be a safe and predictable treatment option after a 5-year follow-up period.

Fracture Resistance in Non-Vital Teeth: Absence of Interproximal Ferrule and Influence of Preparation Depth in CAD/CAM Endocrown Overlays-An In Vitro Study.

There is ample evidence to support the use of endocrowns to restore endodontic teeth. However, the influence of the position of the interproximal margins on fracture strength has not yet been studied. The aim was to determine the relationship between the apicocoronal position of the interproximal restorative margins and fracture resistance in nonvital teeth restored with CAD/CAM endocrown overlays. Forty extracted human maxillary premolars were prepared for endocrown overlay restorations without ferrule on the interproximal aspects and classified according to the position of the interproximal restoration margins in relation to the alveolar crest: 2 mm (group A), 1 mm (group B), 0.5 mm (group C), and 0 mm (group D). Fracture strength was measured using a universal testing machine applying a compressive force to the longitudinal tooth axis. Group A had a mean fracture resistance of 859.61 (±267.951) N, group B 1053.9 (±333.985) N, group C 1124.6 (±291.172) N, and group D 780.67 (±183.269) N, with statistical differences between groups. Group C had the highest values for fracture strength compared to the other groups (p < 0.05). The location of the interproximal margins appears to influence the fracture resistance of CAD/CAM endocrown overlays. A distance of 0.5 mm between the interproximal margin and the alveolar crest was associated with increased fracture resistance.

Fracture Resistance of Two Different Composite Resin CAD/CAM Crowns Bonded to Titanium Abutments.

PURPOSE: To determine the influence of thermal and mechanical cycling on fracture load and fracture pattern of resin nanoceramic crowns and polymer-infiltrated ceramic-network (PICN) crowns, both fabricated with CAD/CAM technology. MATERIALS AND METHODS: A total of 90 premolar crowns bonded to titanium abutments were divided into three groups of 30 crowns each: 30 resin nanoceramic crowns (LU); 30 PICN crowns (VE); and 30 metal-ceramic crowns (MC). The 30 specimens of each group were further divided into three subgroups of 10 each that underwent (1) no treatment, (2) thermocycling (2,000 cycles, 5°C to 55°C), and (3) thermocycling with subsequent mechanical cycling (120,000 cycles, 80 N, 2 Hz). The specimens were loaded to failure, and two-way ANOVA and chi-square test were used to determine differences in fracture resistance and pattern. RESULTS: Mechanical and thermal cycling significantly influenced the critical load to failure of the three materials; however, no significant differences were observed between the thermocycled materials and the materials that were thermocycled with subsequent mechanical cycling. The MC specimens experienced significantly higher fracture loads than those of the LU and VE specimens, which showed no differences from each other in fracture resistance. The fracture patterns showed chipping in MC crowns and partial or complete fracture in LU and VE crowns. The fracture pattern depended on the material and was unrelated to the type of treatment it underwent. CONCLUSION: All crowns showed adequate resistance to normal masticatory forces in the premolar area. The cyclic fatigue load negatively influenced all three materials.