The value of original components

Dr Pantelis Petrakakis, freelance journalist and dentist, Düsseldorf MDT
Dr Nina Rätscho, BEGO Implant Systems, Bremen

Abstract

The long-term success of implant treatment depends on many biological, mechanical and patient-related factors. One aspect of the mechanical factors is the fit of the individual components in the implant system. A well-coordinated implant system strives for the highest possible accuracy of fit of the system components so as not to jeopardize the longevity of the implantprosthodontic reconstruction.

Prosthodontic components from third-party vendors or external suppliers, known as copycats, are being advertised more and more often. The question this raises is whether these cheaper and supposedly identical third-party components are comparable to the original components of the implant system, in terms of quality and safety.

The interface between the implant and the prosthodontic abutment is a sensitive area that could be affected by components that are supposedly identical but not fitting perfectly. For this reason the validity and supposedly comparable usability of the third-party components must be critically scrutinized.

The use of non-implant components in an implantprosthodontic restoration can result in mating inaccuracies and technical problems (Fig. 2). Micromovements between implant and prosthodontics can cause major problems, both in materials and in the biological field. Thus, the use of third-party components causes larger micro-movements than when using original components. The results of a recent in vitro study show that an oblique load with an acting force of 200 N, causes an average gap formation at the implant-prosthodontic interface which is up to three times higher if third-party components are used instead of the original components (BERBERI et al., 2016).

Another special feature are custom-made abutments. In a systematic review, mean vertical gaps between 50 and 160 μm could be identified (LALITHAMMA et al., 2014, PEREIRA et al., 2017). Cervical discrepancies of 70 μm (BAE et al., 2017) and up to 100 μm (PEREIRA et al., 2017) are considered clinically acceptable. Other authors point out that there is a lack of a clear, agreed definition of tolerances in the fit between the implant and the superstructure (ABDUO & JUDGE, 2014, KANO et al., 2007, MORAIS ALVES DA CUNHA et al., 2012).

A special role is played by the prefabricated, clearly oversized blanks, so-called pre-milled blanks or preface abutments. If manufactured by the implant manufacturer, these components have the original connection point to the implant. After the scan and design process, these abutments are clamped by standardized workpiece holders in milling machines, which are usually provided by the laboratory, and customized according to the clinical situation, while the original connection to the implant remains unaffected.

In a laboratory study conducted by GIGANDET et al. (2014), implants from three different manufacturers were supplied with the original abutments. Wax-up abutments were fabricated on one of the implant systems and then scanned with the respective scanning system of the other two implant systems and milled individually milled with titanium grade V using CAD / CAM technique. The abutments made using CAD / CAM technique differed greatly in the design of the interface between implant and abutment and showed a higher mean rotational latitude. The authors concluded that the poorer fit leads to a higher risk of implant and abutment fractures and recommended the use of native abutments.

An in vitro study confirms the results of this study. By combining individually milled abutments of a third-party supplier with different implants, significantly higher clefts could be observed in the implantprosthodontic interface than when using original abutments (de MORAIS ALVES DA CUNHA et al., 2012).

In another in vitro study, major differences in fit and inaccuracies of fit were observed between titanium abutments of different manufacturers, when fitted on the same implant (MATTHEOS et al., 2017).

SUI et al. (2014) reported that in the implant-andabutment system, the preferred site of a fatigue fracture depends on the material properties of the components. If the material properties of implant and abutment are the same, fatigue fractures are more likely to be observed in the area of the screw, while if the material properties differ, the respective susceptibility to fracture of the material is decisive. Thus, individual abutments made of zirconium oxide that do not match perfectly, if fitted on titanium implants, the micro-movements did not lead to fractures of the prosthesis screws, but rather to an increased susceptibility to fractures in the area of the abutments.

The information about the nature of the implantprosthodontic connection and the resulting micromovements due to inaccuracies of fit and their biological effects given in the scientific literature is partly contradictory.

The results of a recent systematic review show that heavy stresses are transmitted to the bones if the fits of the abutments are inadequate However, contrary to expectations, these unsuitable conditions of stress and the marginal gap formation do not have biological consequences such as crestal bone loss and / or a negative influence on the osseointegration of the implants. In fact, technical complications such as fractures of the prosthesis screw were observed (KATSOULIS et al., 2017).

In addition to an inadequate stress transfer to the crestal bone, another problem that arises as a result of fit inaccuracies at the implant-prosthodontic connection site is the bacterial colonization of the micro-gap and this can lead to biological complications.