Wear of ceramic ballattachments retaining an overdenture: a controlled trial

“Objectives:” Loss of retention due to wear of the retentive mechanism is a common clinical problem of implant-retained overdentures. The purpose of this controlled clinical study was to compare the wear of ceramic ballattachments with that of titanium ballattachments after 1 year in clinical function in patients with an implant-retained mandibular overdenture.

“Methods:” Forty patients, each presenting with two interforaminal implants, have been divided into 2 groups. Patients of group 1 (test group) received two ceramic (ruby) ballattachments; patients of group 2 (control group) received two titanium grade 5 ballattachments. The dimensions of all attachments and matrices were measured optically before insertion and after one year in clinical function with an accuracy of 1 micron.

“Results:” A significantly higher wear of the ballattachments was registered in group 2 (3.4 ± 6.9 µm) as compared to group 1, which showed no wear (Wilcoxon p-value ≤0.05). Also the wear of matrices differed significantly between the two groups (Wilcoxon p-value: ≤0.05): 2.7 ± 4.1 µm in group 1 vs. 5.8 ± 4.7 µm in group 2. No correlation was found between ballattachment wear and matrix wear (Spearman rank test: ³0.05 for both groups). A noticeable drop-out rate of 30% due to mechanical failures of the ceramic attachments was observed in group 1.

“Conclusion:” Ceramic ballattachments showed an excellent wear resistance. However, its clinical use cannot be recommended yet due to a high mechanical failure rate. Hence, titanium ballattachments remain the clinical standard for implant-retained overdentures.