Periimplantitis and soft-tissue defects of dental implants: A pilot study on the fixing of the suprastructure as a possible factor affecting aetiology

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Inflammatory destruction of the periimplant bone (periimplantitis) is the most common reason for late implant loss. For implants supporting cemented suprastructures, a possible reason is the presence of undetected excess cement in the periimplant soft tissue, especially when standard abutments are used, when the cement gap is subgingival. Individual abutments might not face this problem, because the cement cap can be constructed so it is cleanable, but no data are yet available. This pilot-study will be conducted on 20 patients, comparing standard and individual abutments. The primary endpoint of the pilot study is to quantify undetected excess cement on standard and individual abutments and in the soft tissue around the implants with implant-supported single crowns after two weeks within an exploratory examination. For each abutment, 4 measurement points will be examined (buccal, lingual, distal, mesial). Position and distribution of the ratios of cement-free surface and surface with undetected excess cement will be shown as mean and standard deviation and displayed as box-plots. In addition, the periimplant soft tissue will be examined for volumetric changes or signs of inflammation, and cases of loss of retention will also be documented. All working steps in fabrication of the implant-supported single crowns will be performed by one dentist and one dental technician only. To avoid bias, randomization will be performed and all investigations in the study will be performed by two calibrated investigators who did not participate in the dental treatment at any time. The Institute of Medical Biometry and Informatics (IMBI) of the University of Heidelberg will be involved in the study from planning to statistical analysis. The aetiology of periimplantitis is numerous and mostly unknown, and the incidence is increasing drastically. This pilot study will enable calculation of sample size for a main study, which will be a multicentre study performed at the Universities of Frankfurt and Heidelberg, and within the existing practice network also, to emphasize the clinical relevance of this investigation. The purpose of the main study will be to formulate recommendations for treatment which enable undetected excess cement in the peri-implant soft tissue, a possible aetiological factor of periimplantitis, to be avoided.