Bone Adaptation Induced by Non-Passively Fitting Implant Superstructures: A Randomized Clinical Trial

Area of Science:

• Dental Implantology
• Biomaterials Science
• Biomechanics

Background:

• Passive fit of implant-supported restorations is crucial for long-term success.
• Achieving perfect passive fit can be technically demanding.
• Misfit can induce stress at the implant-bone interface.

Purpose of the Study:

• To evaluate if misfit strain in implant restorations decreases over time.
• To compare changes in prosthesis-induced bone strain between restorations with different initial fit levels.
• To test the null hypotheses regarding strain reduction and differences in bone strain changes.

Main Methods:

• A randomized clinical trial involving 20 edentulous sites restored with screw-retained fixed prostheses.
• Restorations were either cast as one piece (misfit) or assembled intraorally (fit).
• Strain gauge measurements were taken in vitro and in vivo over 6 months.

Main Results:

• No reduction in misfit strain was observed in vitro.
• Initial strain levels differed significantly between fit and misfit groups.
• In vivo, both fit and misfit restorations showed strain reduction, with no significant difference in percentage reduction between groups.

Conclusions:

• Bone adaptation around dental implants can decrease misfit strain in non-passively fitting prostheses over a 6-month period.
• Passive fit may not be as critical for maintaining osseointegration as previously assumed.
• Further research with longer observation periods and diverse patient populations is warranted.