Comparison of peri-implant submucosal microbiota in arches with zirconia or titanium implant-supported fixed complete dental prostheses: a study protocol for a randomized controlled trial

BACKGROUND: The success rate of implant-supported prostheses for edentulous patients is relatively high. However, the incidence of biological complications, especially peri-implant mucositis and peri-implantitis, increases yearly after the placement of prostheses. The accumulation of pathogenic bacteria adjacent to a prosthesis is the main cause of biological complications. Titanium, one of the classical materials for implant-supported prostheses, performs well in terms of biocompatibility and ease of maintenance, but is still susceptible to biofilm formation. Zirconia, which has emerged as an appealing substitute, not only has comparable properties, but presents different surface properties that influence the adherence of oral bacteria. However, evidence of a direct effect on oral flora is limited. Therefore, the aim of the present study was to assess the effects of material properties on biofilm formation and composition. METHODS: The proposed study is designed as a 5-year randomized controlled trial. We plan to enroll 44 edentulous (mandible) patients seeking full-arch, fixed, implant-supported prostheses. The participants will be randomly allocated to one of two groups: group 1, in which the participants will receive zirconia frameworks with ceramic veneering, or group 2, in which the participants will receive titanium frameworks with acrylic resin veneering. Ten follow-up examinations will be completed by the end of this 5-year trial. Mucosal conditions around the implants will be recorded every 6 months after restoration. Peri-implant submucosal plaque will be collected at each reexamination, and bacteria flora analysis will be performed with 16S rRNA gene sequencing technology in order to compare differences in microbial diversity between groups. One week before each visit, periodontal maintenance will be arranged. Each participant will receive an X-ray examination every 12 months as a key index to evaluate the marginal bone level around the implants. DISCUSSION: The current study aims to explore the oral microbiology of patients following dental restoration with zirconia ceramic frameworks or titanium frameworks. The features of the microbiota and the mucosal condition around the two different materials will be evaluated and compared to determine whether zirconia is an appropriate material for fixed implant-supported prostheses for edentulous patients. TRIAL REGISTRATION: International Clinical Trials Registry Platform (ICTRP) ChiCTR2000029470. Registered on 2 February 2020. http://www.chictr.org.cn/searchproj.aspx?