Marginal fit at cylinder-abutment interface before and after overcasting procedure

Area of Science:

• Dental Materials Science
• Prosthodontics
• Biomaterials Engineering

Background:

• Accurate marginal fit of prosthetic components is crucial for the longevity of dental implant restorations.
• Overcasting procedures can potentially alter the fit between the abutment and prosthetic cylinder.
• Evaluating different materials and screw torques is essential to optimize implant restoration outcomes.

Purpose of the Study:

• To measure the marginal fit at the cylinder-abutment interface before and after the overcasting procedure.
• To compare the marginal fit of gold (Group I) and Ni-Cr-Be (Group II) premachined cylinders.
• To assess the influence of different screw types (gold and titanium) and torque values (10Ncm and 20Ncm) on marginal fit.

Main Methods:

• Hexagonal implants with Estheticone-like abutments were used.
• Premachined gold and Ni-Cr-Be cylinders were tested with gold and titanium screws at 10Ncm and 20Ncm torque.
• Marginal fit was measured using a light microscope at the abutment-cylinder interface before and after overcasting with Ag-Pd or Ni-Cr-Be alloys.
• Statistical analysis included Paired t Test for intragroup and intergroup differences.

Main Results:

• Marginal misfit increased for Ni-Cr-Be cylinders after overcasting, though remained within acceptable limits.
• Gold cylinders combined with gold or titanium screws demonstrated the most effective reduction in marginal misfit.
• Neither gold nor titanium screws improved the marginal fit of Ni-Cr-Be cylinders post-overcasting.
• A 20Ncm torque generally improved marginal fit but carries a higher risk of prosthesis failure.

Conclusions:

• Ni-Cr-Be cylinders exhibit higher marginal misfit post-overcasting compared to gold cylinders, but are still acceptable for single-tooth implant restorations.
• Gold cylinders with either gold or titanium screws provide superior marginal fit, minimizing potential complications.
• The choice of screw type does not enhance the marginal fit of Ni-Cr-Be cylinders after the overcasting process.
• While higher torque improves fit, its clinical application should be cautious due to potential risks to prosthesis integrity.