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

Abstract

Angulated screw channels (ASC) allow the clinician to reposition the access hole of screw-retained restorations, improving the design of the rehabilitation and the esthetic outcome. Few clinical studies are available on the efficacy of these restorations, especially at longer follow-ups and with a large number of subjects. The objective of this study was therefore to retrospectively evaluate patients rehabilitated with screw-retained restorations using ASC. The time of delivery and their adherence to the maintenance program was obtained, as well as the characteristics of the restoration and of the patient’s occlusion; a Kaplan–Meier survival curve was then built to investigate the success rate of these restorations and the effects of several variables were evaluated with a Cox model. A total of 105 subjects and 162 implants were enrolled in this study; after 42 months a success rate (92%) similar to what is reported for conventional screw-retained restorations was encountered. Monolithic zirconia restorations (n = 52) had a higher success rate (95%) when compared to partially veneered restorations (n = 53), which suffered a higher number of complications (90%). The other variables had no statistically significant effect. Implant supported prostheses adopting ASC provide a favorable outcome both in the posterior and anterior regions and can therefore be adopted to treat cases where the implant angulation is unfavorable for a conventional screw-retained prosthesis.

Influence of straight versus angulated screw channel titanium bases on failure loads of two‐piece ceramic and titanium implants restored with screw‐retained monolithic crowns: An in‐vitro study

“…Recent evidence suggests that angulated abutments might be associated with higher mechanical complications due to off‐axis loading and inferior preload on the abutment screw; this may result in premature screw loosening, followed by fracture and restoration failure (Hein et al, 2021; Hotinski & Dudley, 2019; Opler et al, 2020). However, clinical trials have reported high survival rates of 92%–96% for ASC reconstructions on titanium implants up to 3 years, with only a few technical complications (Di Fiore et al, 2023; Lv et al, 2021; Rella et al, 2021).…”

“…To overcome poor esthetic results due to an access hole on the vestibular surface, the concept of angulated screw channels (ASCs) for titanium implants was introduced in 2015 (Garcia‐Gazaui et al, 2015; Pitman et al, 2022; Rella et al, 2021). Depending on the system, ASCs allow an axis correction of up to 25° and shift of the screw‐access hole to the more favorable palatal position (Edmondson et al, 2022; Rella et al, 2021). A recent cone‐beam computed tomography study compared the prevalence of screw‐retained reconstructions with straight versus angulated abutments in the anterior maxilla (Edmondson et al, 2022).…”

Effect of internal connection type and screw channel angle on the screw stability of anterior implant‐supported zirconia crowns

“…Screw-retained implant-supported prostheses have the advantage of retrievability along with the elimination of residual cement that could lead to peri-implant diseases (Rella et al, 2021). However, placing an implant in an ideal position to locate the screw access channel in a nonvisible area may not be possible in some clinical conditions such as limited bone volume (Rasaie et al, 2022).…”

“…Recently, a new IAC system called TorcFit (Straumann AG), which offers an alternative to regular IAC of the same brand (CrossFit; Straumann AG) was introduced. Even though there are studies on angled screw channel system (Drew et al, 2020; Garcia‐Hammaker et al, 2021; Goldberg et al, 2019; Hu et al, 2019; Mulla et al, 2021; Rasaie et al, 2022; Rella et al, 2021; Swamidass et al, 2021), no study has ever investigated how this recently introduced IAC performs when restored with angled screw channel abutments. Therefore, the present study aimed to evaluate the effect of screw channel angle on the long‐term screw stability of this new IAC (TorcFit (TF)) and to compare it with that of the conventional IAC of the same brand (CrossFit (CF)), in which stable RTVs were demonstrated (Srimurugan‐Thayanithi et al, 2023).…”