Comparison of fit accuracy and torque maintenance of zirconia and titanium abutments for internal tri-channel and external-hex implant connections

Abstract

PURPOSEThis in vitro study aimed to evaluate the effect of implant connection design (external vs. internal) on the fit discrepancy and torque loss of zirconia and titanium abutments.MATERIALS AND METHODSTwo regular platform dental implants, one with external connection (Brånemark, Nobel Biocare AB) and the other with internal connection (Noble Replace, Nobel Biocare AB), were selected. Seven titanium and seven customized zirconia abutments were used for each connection design. Measurements of geometry, marginal discrepancy, and rotational freedom were done using video measuring machine. To measure the torque loss, each abutment was torqued to 35 Ncm and then opened by means of a digital torque wrench. Data were analyzed with two-way ANOVA and t-test at α=0.05 of significance.RESULTSThere were significant differences in the geometrical measurements and rotational freedom between abutments of two connection groups (P<.001). Also, the results showed significant differences between titanium abutments of internal and external connection implants in terms of rotational freedom (P<.001). Not only customized internal abutments but also customized external abutments did not have the exact geometry of prefabricated abutments (P<.001). However, neither connection type (P=.15) nor abutment material (P=.38) affected torque loss.CONCLUSIONAbutments with internal connection showed less rotational freedom. However, better marginal fit was observed in externally connected abutments. Also, customized abutments with either connection could not duplicate the exact geometry of their corresponding prefabricated abutment. However, neither abutment connection nor material affected torque loss values.

Mechanism of and factors associated with the loosening of the implant abutment screw: A review

“…As Vigolo et al have pointed out, the porcelain abutment manufactured by computer‐aided design/computer‐aided manufacturing (CAD/CAM) has lower precision than the titanium abutment and has larger degree of rotational freedom, although without significant difference and the rotational freedom of all the specimens was less than 3°. Comparing the prefabricated titanium abutment with the customized zirconia abutment, the latter is inferior to the former in terms of the precision, degree of rotational freedom, and torque loss; hence, it is more prone to the instability of the implant‐abutment connection …”

“…Comparing the prefabricated titanium abutment with the customized zirconia abutment, the latter is inferior to the former in terms of the precision, degree of rotational freedom, and torque loss; hence, it is more prone to the instability of the implant-abutment connection. 80,81 Along with the entrance of CAD/CAM and third-party prosthetic components into the clinic, concern about the non-original abutments is raised. Park et al 82 compared the torque loss of four abutment groups.…”

Avaliação de diferentes pilares para implantes dentários com conexão interna do tipo Tri-channel

“…A literatura traz que o afrouxamento, seja ele do pilar protético ou da retenção da prótese, é o problema mais frequentemente relacionado às reabilitações implantossuportadas (Sailer et al, 2009;Diez et al, 2012;Jorge et al, 2013;Siadat et al, 2017).…”

“…Acredita-se que a perda de torque esteja associada a "pré-carga" e ao efeito de "acomodação" (settling effect), onde pré-carga é a tensão gerada no parafuso após o aperto, o que é necessário para manter os componentes juntos, e o settling effect é o assentamento que é proporcionado pelo achatamento das micro-rugosidades das superfícies de contato do metal após o aperto do parafuso, o qual reduz a força de fixação que mantém os componentes juntos (Siadat et al, 2017;Gehrke et al, 2017;Kim et al, 2014;Kano et al, 2006). Ainda, segundo Hecker et al (2006), a falta de ajuste entre os componentes pode contribuir para a perda de pré-carga nos parafusos.…”

“…A literatura não apresenta consenso quanto ao valor de afrouxamento de parafusos após carregamento cíclico, havendo relatos que vão desde 2% até 50% em diferentes tipos de conexões e pilares (Siadat et al, 2017;Diez et al, 2012;Barbosa et al, 2011;Siamons et al, 2002).…”