Purpose: To evaluate the effect of misfit at implant-level fixed partial dentures (ILFPDs) and marginal bone support on the generation of implant cracks. Materials and Methods: This in vitro study included a mechanical fatigue test and finite element analysis. A mechanical cycling loading test was performed using 16 experimental models, each consisting of two parallel implants subdivided into four groups based on the misfit and the supporting bone condition. The framework, firmly seated at implants, was dynamically loaded vertically with a force of 1,600/160 N and 15 Hz for 1 × 106 cycles. Optical microscope, scanning electron microscope (SEM), and computed tomography three-dimensional (CT-3D) analyses were performed to detect impairments. Finite element models, representing the setups in the mechanical fatigue test, were used to represent the fatigue life. Results: None of the mechanical components presented distortion or fracture at the macroscopic level during the test. In a microscopy evaluation, the fatigue test revealed scratches visible in the inner part of the conical portion of the implants regardless of the groups. SEM and CT-3D analysis revealed one implant from the misfit/no bone loss group with a microfracture in the inner part of the conical interface. The simulated effective stress levels in the coronal body were higher in the misfit groups compared with the no misfit groups. The misfit groups presented effective stress levels, above 375 MPa, that penetrated the entire wall thickness. The no bone loss group presented an effective stress level above 375 MPa along its axial direction. In the no misfit group, the area presenting effective stress levels above 375 MPa in the conical connection was larger for the bone loss group compared with the no bone loss group. Conclusion: This study confirmed that implant fracture is an unlikely adverse event. A clear pattern of effective distribution greater than fatigue limit stresses could be noticed when the misfit was present. The dynamic load simulation demonstrated that the crack is more likely to occur when implants are fully supported by marginal bone compared with a bone loss scenario. Within the limitations of this study, it is speculated that marginal bone loss might follow the appearance of an undetected crack. Further research is needed to develop safe clinical protocols with regard to ILFPD.

Background: Screw‐retained fixed partial dentures (FPD) have shown a lower incidence of biologic complications and an easier retrievability compared with cemented FPD. Purpose: To compare the marginal bone loss at conical connection implant restored with a screw retained cobalt‐chrome FPD in an implant‐level (IL) or an abutment‐level (AL) setup. Materials and Methods: Patients with at least two adjacent missing teeth were randomly allocated to be restored with IL or AL FPD. Periapical radiographs and clinical examination were taken at implant placement, prosthetic connection, 6 and 12 months to evaluate marginal bone loss (MBL), and soft tissue conditions. Complications were used to calculate prognostic indexes. Results: Fifty patients were treated with 50 FPD supported by 119 implants. The difference of MBL between the IL and AL groups was statistically significant (P = 0.003). At 1 year, MBL was 0.086 ± 0.313 mm and 0.005 ± 0.222 mm in the IL and AL groups, respectively. The presence of BoP increased with time in IL, whereas it decreased in AL group (P < 0.001). A minor complication was encounted in one FPD. Conclusions: A low grade of MBL was present after 1 year. IL showed greater amount of MBL and soft tissue inflammation indexes than AL. In FPD, AL may be a safer procedure than IL setup in order to preserve a healthy periimplant tissue.

OBJECTIVES: This RCT compares marginal bone level (MBL) change and the clinical parameters after a 3-year function in maxillary implant-supported fixed complete dentures (FCDs) treated with four-implants(4-I) or 6-implants(6-I).

MATERIAL AND METHOD: Three centres treated 56 patients with 280 implants allocated to the 4-I or 6-I group. Radiographic and clinical examinations were performed. The primary outcome was to investigate MBL change between the groups.

RESULTS: Implant survival rates were 100% and 99% in the 4-I and 6-I groups, respectively. Considering the clustering effects, the MBL change was not significantly different between the groups over the 3-year follow-up. The MBL in the 4-I group was 0.30±0.50mm at baseline, 0.24±0.31mm at 1-year and 0.24±0.38mm at 3-year. In the 6-I group, MBL was 0.14±0.32mm at baseline, 0.16±0.35mm at 1-year and 0.12±0.26 mm at 3-year. There was a statistically significant difference between the groups at BL and 3Y. No significant differences between the groups were reported for clinical parameters at each time point as well as in between the visits. The technical and biological complications rates were 1.6% and 6.0%, respectively. Prosthetic complications affected 25 FCDs (47.2%).

CONCLUSION: MBL change revealed a stable condition in the 3-year period in the two groups. Few technical and biological complications occurred apart from the chipping/fracture of the prosthetic teeth. Four-implant is a feasible solution if the rehabilitation is oriented towards the most cost-effective treatment and towards avoiding bone augmentation procedures. Clinicians have to consider the potential required visits for prosthetic maintenance.

OBJECTIVES: This observational clinical study evaluated the patient satisfaction and the clinical outcomes of edentulous arches rehabilitated with overdentures retained by CAD-CAM milled titanium bars. MATERIALS AND METHODS: Edentulous patients were treated with a full-arch removable overdenture anchored on two milled bars based on a friction retention system. Patient satisfaction was tested using the validated Oral Health Impact Profile (OHIP-14) questionnaire at the pre- and post-treatment visits, up to two years after prosthesis delivery (possible score range: 0-56. Best: 0). The prosthodontist satisfaction was also assessed through a designed questionnaire (best possible range 0-4. Best:0). Radiographic and clinical examinations were performed at baseline and after 2 years of function. Implant and prostheses complications were recorded. RESULTS: Forty (25 mandible) edentulous patients, mean age 69 +/- 9.5 (SD) (52% males, 10% smokers), were treated with a total of 185 implants. The mean difference between pre- and post-treatment OHIP-14 score was 20.6 +/- 8.0 (P < 0.0001) showing a high level of satisfaction for aesthetics, functional and psychological outcomes. This perception was not influenced by patient's age or gender. The clinicians' mean score was 3.4 +/- 4.0. There was a marginal bone level (MBL) gain of 0.02 +/- 0.22 mm between the two time points. Minor complications were reported in five patients. CONCLUSIONS: This procedure may lead to satisfaction regarding aesthetics and mastication function. One of the most relevant aspects is the versatility, which allows selection of the most suitable treatment option according to patient needs. The prosthodontist satisfaction questionnaire showed that this procedure met the clinical expectations.