Survival and failure modes: platform‐switching for internal and external hexagon cemented fixed dental prostheses

Abstract

This study evaluated the probability of survival (reliability) of platform-switched fixed dental prostheses (FDPs) cemented on different implant-abutment connection designs. Eighty-four-three-unit FDPs (molar pontic) were cemented on abutments connected to two implants of external or internal hexagon connection. Four groups (n = 21 each) were established: external hexagon connection and regular platform (ERC); external hexagon connection and switched platform (ESC); internal hexagon and regular platform (IRC); and internal hexagon and switched platform (ISC). Prostheses were subjected to step-stress accelerated life testing in water. Weibull curves and probability of survival for a mission of 100,000 cycles at 400 N (two-sided 90% CI) were calculated. The beta values of 0.22, 0.48, 0.50, and 1.25 for groups ERC, ESC, IRC, and ISC, respectively, indicated a limited role of fatigue in damage accumulation, except for group ISC. Survival decreased for both platform-switched groups (ESC: 74%, and ISC: 59%) compared with the regular matching platform counterparts (ERC: 95%, and IRC: 98%). Characteristic strength was higher only for ERC compared with ESC, but not different between internal connections. Failures chiefly involved the abutment screw. Platform switching decreased the probability of survival of FDPs on both external and internal connections. The absence in loss of characteristic strength observed in internal hexagon connections favor their use compared with platform-switched external hexagon connections.

Biomechanical performance of three fiberglass post cementation techniques: Imaging, <i>in vitro</i>, and <i>in silico</i> analysis

“…In addition to the thicker cement layer in the CFL, which makes it more prone to void formation because of the large amount of resinous material [21,22], there is more polymerization shrinkage. This is especially true in the cervical and middle thirds, which may explain the greater gap formation in the cementation line and consequent reduction in the contact area between the resin cement and root dentin [23,24]. Thus, although some studies suggest that increasing the thickness of the resin cement around FGP is not detrimental to post installation performance and bond strength [25], the opposite was observed in the present study.…”

Do short implants have similar survival rates compared to standard implants in posterior single crown?: A systematic review and meta‐analysis

“…[86][87][88] The two types of surface treatment used in the included studies provided excellent bone-to-implant contact, contributing to the longevity of implant stability on function, 89 90 Laboratory studies have shown higher stress in the coronal part of the implant and on its abutment, with consequent more fatigue when using implants with external hexagon with switching platform than implants with regular external hexagon, but with no difference between regular internal hexagon connections implants and internal hexagon connections implants with switching platform. 91,92 In this present review, prosthetic failure was only reported in the study by Pohl et al 71 This good result may be related to the fact that all included studies used implants with internal connection and switching platform: the study by Rossi et al 40 used implants with internal octagon connection and the other three studies 39,70,71 used implants with internal hexagon connections.…”

“…Our review presents a limitation regarding this evaluation because only two studies40,71 reported information about crown-to-implant ratio. Laboratory studies have shown higher stress in the coronal part of the implant and on its abutment, with consequent more fatigue when using implants with external hexagon with switching platform than implants with regular external hexagon, but with no difference between regular internal hexagon connections implants and internal hexagon connections implants with switching platform 91,92. 80,81 The four studies included in this review presented excellent surface treatments that favored rapid bone healing and surface increase by their developed porosity.…”

Annual review of selected scientific literature: Report of the committee on scientific investigation of the American Academy of Restorative Dentistry

“…From a mechanical perspective, the implant-abutment connection design and its relative horizontal interface geometry have been implicated as a possible factor in short-and long-term complication rates influencing soft and hard tissue health. To assess this issue in greater detail, Anshieta et al 205 evaluated survival/failure modes of 3-unit ISFPDs with external hexagon-platform matched or switched geometry compared with internal connection platformmatched or switched geometry. Authors hypothesized that no differences in survival/failure modes would be identified considering the "splinted" nature of ISFDPs in this in vitro protocol.…”