Clinical performance of a conometric retention system for single implant restorations: 1-year analysis of a prospective multicenter study
Conventional screw- and cement-retained single implant restorations are associated with biological and technical complications. Friction-retained conometric concepts have been proposed as an alternative; however, clinical evidence for single crowns, particularly from prospective multicenter studies, remains limited. This study evaluated the 1-year clinical performance of a conometric retention system for implant-supported single crowns. This prospective multicenter study was conducted at nine clinical centers in Europe and North America. Subjects requiring single-tooth replacement in the maxilla or mandible received one implant restored with a prefabricated 5.9° conometric abutment and a titanium nitride–coated coping. All-ceramic crowns were extraorally bonded and seated without cement or screws. Radiographs were obtained at implant placement, delivery of the permanent restoration, and after 1 year. Primary outcomes were implant and prosthetic survival. Secondary outcomes included marginal bone level (MBL) changes, bleeding on probing, plaque, probing pocket depth, and complication rates. Descriptive statistics and confidence intervals were calculated. A total of 144 implants were included in the per-protocol analysis. Three implants failed after delivery of the permanent restoration, resulting in a 1-year implant survival rate of 96.7%. Of 131 restorations evaluated at 1 year, 4 showed irreversible loss of conometric retention and were classified as prosthetic failures. In total, 22 prosthetic complication events were recorded, including 18 reversible technical complications (12.5%) and 4 irreversible failures, corresponding to an overall complication rate of 15.3%. Mean MBL change was − 0.11 mm from implant placement to PR and − 0.02 mm from PR to 1 year. Within the limitations of this 1-year analysis, the investigated conometric retention system demonstrated high implant and prosthetic survival rates and limited marginal bone changes. However, a clinically relevant incidence of technical complications, including irreversible loss of conometric retention, was observed during the first year of function. These findings suggest that the conometric concept may require careful case selection and clinical monitoring. Long-term follow-up is required to further evaluate the clinical stability and prosthetic reliability of this retention concept over time. Trial registration: ClinicalTrials.gov, ID, NCT04063878, August 20, 2019.