Comparative Analysis of the Stability of Prosthetic Screws under Cyclic Loading in Implant Prosthodontics: An In Vitro Study

Santo Catapano,Marco Montanari,Massimo Corsalini,Mattia Ferrari,Francesco Grande,Nicola Mobilio

doi:10.3390/app11020622

Santo Catapano, Marco Montanari + Show 4 more

Open Access

https://doi.org/10.3390/app11020622

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Abstract

Background: To compare the loss of preload in absence of loading and after a fixed number of cyclic loadings on 7-mm distal cantilever in two different connection systems using all-on-four prosthetic model. Methods: Two equal models of an edentulous mandible rehabilitated with all-on-four technique with two types of abutment system (MUA and OT-Bridge) supporting a hybrid prosthesis, were used. Initial torque values of the prosthetic fixing screw, after ten minutes from initial screw tightening and after 400,000 repeated loadings were registered using a mechanical torque gauge. Differences between initial and final torque values were reported for each anchoring system and the two systems were finally compared. Results: No statistically significant differences regarding the loss of preload between MUA and OT-Bridge system were found after 400,000 cyclic loadings; however, in MUA system it was found between anterior and posterior implant screws. A significant difference in preload loss was found only for MUA system comparing the initial screw torque to that measured after 10 min from the tightening in absence of cyclic loadings. Conclusions: Within the limits of the present study, MUA and OT-Bridge may be considered reliable prosthetic anchoring systems able to tolerate repeated cyclic occlusal loads on distal cantilever in all-on-four rehabilitation model without any significant loss of preload in screw tightening.

Highlights

In the last few decades, the screw-retained prosthesis on implants has become increasingly common for the rehabilitation of the totally edentulous patients [1,2,3]
According to the literature the loss of preload is influenced by several factors [17,27,28], including the type of material used for the fabrication of the abutment and the connecting screw, the fixture geometry connection, the type of prosthesis, the shape of the abutment screw head and the implant screwing method [18,19,20,24,32,33,34,35]
In the MUA system used, both the abutment and connecting screw are composed of grade 4 commercially pure titanium while the OT-Bridge system has a titanium nitride coating the low-profile attachment with an anodized titanium anchoring screw

Summary

Introduction

In the last few decades, the screw-retained prosthesis on implants has become increasingly common for the rehabilitation of the totally edentulous patients [1,2,3]. The All-On-Four technique for the rehabilitation of completely edentulous mandibles, initially proposed by Malo et al [8] is nowadays used by several clinicians [9,10,11] in order to reach the correct masticatory and speech functions, as well as an optimal prosthetic support, and to re-establish an acceptable situation for the patient [12] In these type of implant-supported rehabilitation, intermediate components between implant fixtures and prosthetic framework are used in order to correct implant misalignment and to achieve a passive fit of the framework. For this technique, one of the most used anchoring systems is the Multi-Unit-Abutment (MUA), which consists of straight or angulated components of different heights that move the implant internal connection to a conical external connection. The occlusal stress is moved from the implant screw to the multi-unit abutment screw, that is smaller than the first one and may be the weak point in case of prosthetic complications

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Conclusion