Influence of Screw Channel Angulation on the Fracture Resistance of Zirconia Abutments: An In Vitro Study

Abstract

Purpose The aim of this study was to investigate the effect of implant screw channel angulation on the fracture resistance of zirconia abutments without artificial aging. Materials and Methods Ten implant replicas were embedded in a jig of autopolymerizing acrylic resin. Using a surveyor and a metallic platform, the implant replicas were mounted centrally and with an angulation of 30°. A maxillary left central incisor crown was fabricated from pattern resin and scanned. The digital design of a monolithic zirconia implant abutment‐crown was completed using a 3D imaging software. For all specimens of this group (ASC25), the screw channel was positioned at 25° to the lingual. Following fabrication, the samples were attached onto the embedded implant replicas and manually torqued to 35 Ncm as recommended by the manufacturer. The monolithic zirconia implant abutment‐crowns were mounted in a metallic platform, positioned perpendicular to the indenter, and subjected to loading until failure. Crosshead speed was set at 0.5 mm/min for the universal testing machine. Data from a similar in vitro study where straight zirconia custom abutments (ASC0) were subjected to static load until failure was used as a control group. An unpaired Student's t‐test was used to determine if fracture resistance based on load at failure and maximum load in each group were significantly different from each other (ASC25 vs ASC0). Statistical significance level was inferred at p ≤ 0.05 Results Group ASC25 fractured at a mean (SD) load of 215.49 (47.10) N and a mean (SD) maximum load of 420.50 (17.18) N. Group ASC0 fractured at a mean (SD) load of 534.04 (133.77) N and a mean (SD) maximum load of 762.69 (109.59) N. The difference was statistically significant for both mean load and mean maximum load at failure (p ≤ 0.05). The survival rate of 0° zirconia abutments was significantly higher than that of 25° ASC zirconia abutments. Conclusions Within the limitations of this in vitro study the mean fracture load was significantly higher in the group with a straight channel angulation.

Mechanical Factors Implicated in Zirconia Implant Fracture Placed within the Anterior Region—A Systematic Review

“…The quality and risk of bias assessments for the three articles included in the review were carried out using the appraisal tool created by JBI SUMARI [ 19 , 23 ], and findings are presented in Table 1 and Table 2 . The study by Roehling et al [ 21 ] was deemed to have low bias, while articles from Scherrer et al [ 15 , 22 ] and Paolantoni et al [ 20 ] were found to have a high level of bias. The level of bias for each article was determined by the JBI SUMARI appraisal tool [ 23 ].…”

“…Evolution in ceramic manufacturing technology has led to significant and predictable improvements in the characteristic of dental materials. Recently, the focus has shifted towards additive manufacturing techniques for fabrication of customized root-form zirconia implants utilizing a combination of stereolithography and digital light processing [ 15 , 30 ]. However, further in vitro and clinical research is essential to confirm its suitability for root-form dental implant manufacture.…”

“…Despite the fracture resistance of zirconia implants in in vitro studies being widely reported, there is a distinct lack of data derived from in vivo specifically human studies. Furthermore, Garcia-Hammaker et al highlighted that the variability of in vitro study designs makes it difficult to have a consensus on the fracture strength and to correlate it to clinical circumstances [ 15 ]. As such, limitations on zirconia’s intended use in the clinical environment still exist, due to a lack of long-term clinical evidence of two-piece zirconia implants, as the technology has only been recently developed.…”

The Application of Angulated Screw-Channels in Metal-Free, Implant-Supported Restorations: A Retrospective Survival Analysis

“…The main concern regarding this fixation system is the reduced preload that can be applied to the retentive screw; this might lead to a higher rate of loosening of the restoration, especially in the posterior region [23]. Their application in zirconia abutments also showed a higher rate of abutment fracture [20].…”

“…ASCs can be applied to Porcelain Fused to Metal and, thanks to novel computeraided design and computer-aided manufacturing (CAD-CAM) systems, to Zirconia based restorations, both monolithic (completely made in zirconia, and then superficially colored [18]) and veneered (where a cutback is added in the design phase to provide space for subsequent veneering with ceramic [19]) [20].…”