Evaluation of the Success Criteria for Zirconia Dental Implants: A Four-Year Clinical and Radiological Study

Objectives. The aim was to evaluate survival and success rates, soft tissue health, and radiographic marginal bone loss (MBL) of zirconia implants placed in the esthetic and posterior areas of the jaws and in association with multiple or single implant restorations after at least 6 months of definitive restoration. Material and Methods. 35 one-piece zirconium implants were utilized for single or partially edentulous ridges rehabilitation. All implants received immediate temporary restorations and six months after surgery were definitively restored. Every 6 months after implant placement, a clinical-radiographic evaluation was performed. For each radiograph, the measurements of MBL were calculated. Results. The results showed that the mean MBL at 48-month followup was 1.631？mm. The mean MBL during the first year of loading was not more significant for implants placed in the first molar regions than for those positioned in other areas. Moreover, no differences in marginal bone level changes were revealed for multiple and single implants, whereas MBL in the first year was observed to be slightly greater for implants placed in the maxilla than for those placed in the mandible. Conclusion. Zirconia showed a good marginal bone preservation that could be correlated with one-piece morphology and characteristics of zirconia implants. 1. Introduction The use of endosseous implants achieves predictable results in terms of survival and success rates of oral rehabilitation [1]. More recently, greater interest is directed towards esthetics of the prosthetic rehabilitations. Successful esthetic results of dental implant placement require knowledge of essential biological concepts and skill in different surgical techniques [2]. Anyway, the surgical techniques or prosthetic [3] solutions by now proposed are not always sufficient to achieve long-term esthetic results; in fact, it was demonstrated that periimplant soft tissues tend to recede after positioning a definitive prosthetic restoration [4]. In order to avoid grayish transparency of titanium implants through soft tissues, ceramic materials were tested. All-ceramic dental implants were introduced in dental implantology as an alternative to titanium implants. Another reason to find an alternative material to titanium was sensibilization, possible release of metallic ions, and allergy to this material, as reported in some studies [5, 6]. Alumina was one of the first ceramic materials used but because of its hardness combined to a low flectural and fracture strength poor long-term results were achieved and this