Long-Term Prosthetic Aftercare of Two- vs. Four-Ball Attachment Implant-Supported Mandibular Overdentures

Little is reported about the prosthetic aftercare of implant-supported mandibular overdentures regarding the number of implants placed. The purpose of this study was to evaluate the prosthetic aftercare among edentulous patients restored with two vs. four mandibular implant-retained overdentures (MISOD). Forty-six consecutive edentulous patients treated by a new MISOD were retrospectively studied. Twenty-five patients had two-ball attachment MISOD (Group A), and 21 had four-ball attachment MISOD (Group B). The total amount of aftercare visits was recorded, as well as the type of treatments required (pressure sore spots relief, attachment liner replacement due to loss of retention, and metal ball attachment replacement due to wear). The mean follow-up duration was 93 +/- 57 months (range 9-246 months). None of the implants was lost. There were significantly more visits for pressure sore spots relief in Group A vs. Group B (6.2 +/- 2 in group A and 4.09 +/- 1.54 in group B, p < 0.0001). Differences in the other two tested parameters (number of visits for liner replacement (2.3 +/- 1.84 in group A and 2.4 +/- 1.63 in group B) and attachment replacement (2.36 +/- 1.85 in group A vs. 2.48 +/- 1.63 in group B) yielded a non-significant outcome (p = 0.814 for liner replacement and p = 1.000 for attachment replacement). The use of four-ball attachments in MISOD was more beneficial than two-ball attachments with regards to the aftercare of pressure sore spots. The number of implants did not influence the mechanical wear.