Do tooth-supported zirconia restorations present more technical failures related to fracture or loss of retention? Systematic review and meta-analysis.

OBJECTIVES: This systematic review was performed to determine the main cause of technical failure of tooth-supported zirconia crowns and fixed partial dentures (FPDs), categorizing them as fracture/chipping or loss of retention/decementation. MATERIALS AND METHODS: Electronic and manual searches were performed for randomized clinical trials, prospective clinical trials, and prospective cohort studies that reported the technical failure rates of zirconia restorations. The Cochrane Collaboration risk-of-bias tool and Newcastle-Ottawa scale were used to assess the quality of the studies. RESULTS: Fifty-two studies were included and most of them had unclear risk of bias. Considering all reported fractures/chipping, for veneered crowns with 1 to 3 years of follow-up, the relative risk (RR) of fracture in relation to loss or retention was 3.95 (95% CI 1.18-13.23; p = 0.03). For 4 to 6 years of follow-up, the RR was 5.44 (95% CI 1.41-20.92; p = 0.01). For veneered FPDs with 1 to 3 years of follow-up, the RR was 5.98 (95% CI 2.31-15.01; p = 0.0002). For 4 to 6 years of follow-up, the RR was 3.70 (95% CI 1.63-8.41; p = 0.002). For 7 years or more of follow-up, the RR was 3.45 (95% CI 1.84-6.46; p = 0.0001). When only framework fractures were considered, there were no significant differences for the RR in all follow-up periods (p > 0.05). CONCLUSIONS: Higher RR for fracture/chipping in relation to decementation for veneered zirconia crowns and FPDs at all follow-up times. For framework fractures, no difference was observed between the risk of failure of the restoration due to fracture or decementation. CLINICAL RELEVANCE: Zirconia crowns and FPDs showed relatively high success and survival rates. However, considering the technical failures, there is approximately four times higher chance of fracture/chipping than loss of retention for both single and multi-unit tooth-supported veneered zirconia restorations.

Demineralized human dentin matrix for alveolar ridge preservation using a volumetric and histologic analyses in rats.

The aim of this study was to evaluate a Demineralized Human Dentine Matrix (DHDM) as viable biomaterial for alveolar ridge preservation in a rat model. Wistar rats were submitted to the extraction of maxillary first molars bilaterally. Sockets were filled with biomaterials and divided into 4 experimental groups (n=5): blood clot, autogenous bone, bovine-derived xenograft (BDX) and DHDM. Animals were sacrificed at 7, 14 e 28 days. Microtomography (uCT) volumetric evaluation and qualitative histological analyses were performed. Results obtained through the uCT showed similar values between the DHDM and the other experimental groups. The histological evaluation demonstrated DHDM with an unspecific inflammatory process and bone neoformation with slow reabsorption of the material. This result indicates that DHDM implanted in rat sockets is biocompatible and reduces the alveolar ridge volume loss after tooth extraction.

Relationship between battery level and irradiance of light-curing units and their effects on the hardness of a bulk-fill composite resin.

Objectives: This study evaluated the relationship between the battery charge level and irradiance of light-emitting diode (LED) light-curing units (LCUs) and how these variables influence the Vickers hardness number (VHN) of a bulk-fill resin. Materials and Methods: Four LCUs were evaluated: Radii Plus (SDI), Radii-cal (SDI), Elipar Deep Cure (Filtek Bulk Fill, 3M Oral Care), and Poly Wireless (Kavo Kerr). Irradiance was measured using a radiometer every ten 20-second activations until the battery was discharged. Disks (4 mm thick) of a bulk-fill resin (Filtek Bulk Fill, 3M Oral Care) were prepared, and the VHN was determined on the top and bottom surfaces when light-cured with the LCUs with battery levels at 100%, 50% and 10%. Data were analyzed by 2-way analysis of variance, the Tukey's test, and Pearson correlations (α = 5%). Results: Elipar Deep Cure and Poly Wireless showed significant differences between the irradiance when the battery was fully charged versus discharged (10% battery level). Significant differences in irradiance were detected among all LCUs, within each battery condition tested. Hardness ratios below 80% were obtained for Radii-cal (10% battery level) and for Poly Wireless (50% and 10% battery levels). The battery level showed moderate and strong, but non-significant, positive correlations with the VHN and irradiance. Conclusions: Although the irradiance was different among LCUs, it decreased in half of the devices along with a reduction in battery level. In addition, the composite resin effectiveness of curing, measured by the hardness ratio, was reduced when the LCUs' battery was discharged.

Demineralized human dentin matrix for alveolar ridge preservation using a volumetric and histologic analyses in rats

Abstract The aim of this study was to evaluate a Demineralized Human Dentine Matrix (DHDM) as viable biomaterial for alveolar ridge preservation in a rat model. Wistar rats were submitted to the extraction of maxillary first molars bilaterally. Sockets were filled with biomaterials and divided into 4 experimental groups (n=5): blood clot, autogenous bone, bovine-derived xenograft (BDX) and DHDM. Animals were sacrificed at 7, 14 e 28 days. Microtomography (uCT) volumetric evaluation and qualitative histological analyses were performed. Results obtained through the uCT showed similar values between the DHDM and the other experimental groups. The histological evaluation demonstrated DHDM with an unspecific inflammatory process and bone neoformation with slow reabsorption of the material. This result indicates that DHDM implanted in rat sockets is biocompatible and reduces the alveolar ridge volume loss after tooth extraction.

Resumo O objetivo deste estudo foi avaliar a Matriz Dentinária Humana Desmineralizada (MDHD) como biomaterial viável para preservação do rebordo alveolar, no modelo em rato. Ratos Wistar foram submetidos à exodontias dos primeiros molares superiores bilateralmente. Os alvéolos foram preenchidos com biomateriais e divididos em 4 grupos experimentais (n=5): coágulo sanguíneo, osso autógeno, osso xenógeno de origem bovina e MDHD. Os animais foram sacrificados aos 7, 14 e 28 dias. Foram realizadas avaliações volumétricas por microtomografia (uCT) e análises histológicas qualitativas. Os resultados obtidos por meio do uCT mostraram valores semelhantes entre o MDHD e os demais grupos experimentais. A avaliação histológica demonstrou MDHD com processo inflamatório inespecífico e neoformação óssea com lenta reabsorção do material. Esse resultado indica que a MDHD implantada em alvéolo de rato é biocompatível e reduz a perda de volume do rebordo alveolar após extração dentária.