A 6-Year Randomized Controlled Trial on Different Implant Designs in Maxillary Overdenture Patients.

Area of Science:

• Dental Implantology
• Periodontology
• Biomaterials Science

Background:

• Crestal bone remodeling around dental implants is a concern.
• Microthreads and platform-shifting connections are proposed to mitigate bone loss.
• Long-term studies with controlled variables are limited.

Purpose of the Study:

• To evaluate the long-term effects of implant neck design (microthreaded vs. non-microthreaded) and abutment connection type (internal conical vs. external flat-to-flat) on crestal bone remodeling and peri-implant health.
• To report the clinical outcomes of bar-retained maxillary overdentures supported by four implants after at least six years of function.

Main Methods:

• A randomized controlled trial involving 25 patients receiving maxillary overdentures supported by four implants.
• Each patient received four implants with distinct designs: internal connection/microthreads (IMT), internal connection/no microthreads (INMT), external connection/microthreads (EMT), and external connection/no microthreads (ENMT).
• Crestal bone loss (CBL), plaque score (PS), bleeding on probing (BoP), and probing pocket depth (PPD) were assessed at one and six years post-placement.

Main Results:

• After six years, mean crestal bone loss was 0.37 mm (SD: 0.61).
• No statistically significant differences in CBL were found between the four implant designs over time.
• Neither microthreads nor connection type significantly affected CBL, PPD, BoP, or PS at the six-year follow-up.

Conclusions:

• Four-implant supported maxillary overdentures demonstrate high implant and prosthetic survival rates with stable crestal bone after six years.
• The presence of microthreads and the type of implant-abutment connection have a limited influence on peri-implant crestal bone loss.
• Peri-implant health indicators suggest the absence of peri-implantitis in the study cohort.