On failure of oral implants

Abstract: Introduction: Nowadays oral implant placement is an effective and predictable treatment modality for replacing missing teeth in both fully and partially edentulous patients. Despite the high implant survival and success rates, there is a general appreciation that some risk factors predispose individuals to more complications and implant failures and may result in lower implant survival and success rates. Determining the exact elements that are critical for osseointegration would be extremely useful. A better understanding of the factors associated with implant failure provide data for the planning of future studies, facilitate clinical decision-making, and may enhance implant success. Once identified, the risks can then be avoided, or an alternative intervention can be applied, implying in the least cost to produce a given level of effectiveness in oral rehabilitation. The general aim of the present thesis was to assess the impact of several factors on the failure of oral implants. Materials and Methods: The articles included in the present thesis consist of three types of studies. First, a general overview was performed in order to identify risk factors associated with the failure of oral implants (Study I). Then, a systematic review of the literature with meta-analyses was performed to analyze the influence of one risk factor (smoking) on the failure of oral implants, marginal bone loss (MBL), and postoperative infection around implants (Study II). The seven retrospective studies (Study III-IX) were based on all 2,670 patients provided with 10,096 implants, consecutively treated on a routine basis at one specialist clinic (Clinic for Prosthodontics, Centre of Dental Specialist Care, Malmö, Sweden - Folktandvården Skåne AB, Specialisttandvård Malmö) during the period from 1980 to 2014. The dental records of all patients ever treated with implants in this clinic were read in order to collect the data. The data were directly entered into a SPSS file (SPSS software, version 23, SPSS Inc., Chicago, USA) as the files were being read. Several anatomical-, patient-, health-, and implant-related factors were collected. The clinical studies included in the thesis focused on the association between implant failure and bruxism, the intake of proton pump inhibitors and of selective serotonin reuptake inhibitors and their relation to failure, the impact of different surgeons, and the number of early failures, cluster behavior of failures, and clinical and radiological outcomes of implants followed up for a minimum of 20 years. Besides descriptive statistics and tests for the comparison of 2 or of 3 or more independent and dependent groups of continuous and categorical data, survival analyses, logistic regression models, generalized estimating equation method, and multilevel mixed effects parametric survival analysis were performed, depending on the study. Results and Conclusions: After a systematic review of the literature, it may be suggested that the following situations may increase the implant failure rate: a low insertion torque of implants that are planned to be immediately or early loaded, inexperienced surgeons inserting the implants, implant insertion in the maxilla, implant insertion in the posterior region of the jaws, implants in heavy smokers, implant insertion in bone qualities type III and IV, implant insertion in places with small bone volumes, use of shorter length implants, greater number of implants placed per patient, lack of initial implant stability, use of cylindrical (non-threaded) implants and prosthetic rehabilitation with implant-supported overdentures. Moreover, it may be suggested that the following situations may be correlated with an increase in the implant failure rate but with a weaker association than the factors listed above: use of the non-submerged technique, immediate loading, implant insertion in fresh extraction sockets, smaller diameter implants. Some recently published studies suggest that modern, moderately rough implants may present with similar results irrespective if placed in maxillae, in smoking patients or using only short implants (Study I). The systematic review of the literature with meta-analyses suggested that the insertion of oral implants in smokers affects the implant failure rates, the incidence of postoperative infections, as well as the marginal bone loss (Study II). Smoking and the intake of antidepressants are suggested to be potentially influencing factors with respect to the occurrence of implant failures up to the second-stage surgery - abutment connection (Study III). Bruxism may significantly increase both the implant failure rate and the rate of mechanical and technical complications of implant-supported restorations (Study IV). The intake of proton pump inhibitors may be associated with an increased risk of oral implant failure (Study V), but not so the intake of selective serotonin reuptake inhibitors (Study VI). Different levels of failure incidence of oral implants could be observed depending on the individual surgeons, occasionally reaching significant levels. Although a direct causal relationship could not be ascertained, it is suggested that the surgeons’ technique, skills, and/or judgment may influence the oral implant survival rates (Study VII). A cluster pattern among patients with implant failure is highly probable. Shorter implants, turned implants, poor bone quality, younger patients, the intake of antidepressants and of proton pump inhibitors, smoking, and bruxism were identified as suggested potential factors exerting a statistically significant influence on the cluster behavior of dental implant failures (Study VIII). Most of the implant failures occur at the first years after implantation, regardless of a very long follow-up. Implants in different jaw locations, irradiation, and bruxism were the factors suggested to affect the survival of implants. Marginal bone loss can be insignificant in long term observations, but it may, nevertheless, be the cause of secondary failure of oral implants in some cases (Study IX).