Clinical Factors Influencing Removal of the Cement Excess in Implant-Supported Restorations.

Background: The depth of the cementation margin has an influence on the amount of cement remnants around implants. However, the role of other clinical factors is still not clarified.

Purpose: The aim of the study was to evaluate the correlation between undetected cement and (i) location of the implant, (ii) implant diameter, and (iii) undercut.

Materials And Methods: Sixty-five patients were treated with single metal-ceramic restorations on implants. The undercut between the restoration and the tissue was measured. After cementation, the restoration-abutment unit was unscrewed. All quadrants of the specimens were photographed and analyzed. The ratio between total restoration area/peri-implant tissue area and area of cement remnants was calculated in pixels. Significance was set to 0.05.

Results: Sixty-five metal-ceramic restorations were placed on 65 implants (39 molars, 22 premolars, 4 anteriors; 21 implants had a diameter of 3.5 mm, 34 of 4.0 mm, 10 of 5.0 mm). An undercut of 1 mm was found in 118 sites, 2 mm in 96 sites, and 3 mm in 46. The percentages of soft tissue and restoration, respectively, covered by cement were as follows: molars 4% and 7%; premolars 3.8% and 7.3%; anteriors 3% and 3.4%; 3.5 mm diameter 3.3% and 7.4%; 4.0 mm 7.7% and 7.7%; 5.0 mm 3.9% and 2.1%; 1-mm undercut 3.5% and 5.4%; 2-mm 4% and 8.1%; 3-mm 4.8% and 8.4%. The relationship between amount of cement remnants and implant location was insignificant (p > 0.05) for both soft tissue and the specimen, but significant relationships with amount of cement remnants were found for diameter (p = 0.026 for soft tissue, p = 0.600 for specimen) and undercut (p = 0.004 for soft tissue, p = 0.046 for specimen).

Conclusion: If cemented crown restoration is desired, undercuts should be reduced to a minimum for better removal of cement excess, irrespective of the diameter and location of the implants in the mouth.