The influence of the emergence profile on the amount of undetected cement excess after delivery of cement-retained implant reconstructions

ObjectiveTo test whether or not one of two emergence profile designs (concave or convex) is superior to the other in terms of remaining cement following cementation of reconstructions on individualized abutments and careful cement removal. Materials and methodsA central incisor with a single implant-supported reconstruction was selected as a model. Six types of abutments (n=10) with two different emergence profile designs (concave (CC) and convex (CV)) and three crown-abutment margin depths (epimucosal, 1.5mm submucosal, 3mm submucosal) were fabricated through a CAD/CAM procedure. Lithium disilicate reinforced ceramic crowns were cemented with chemically polymerized resin cement. A blinded investigator attempted to remove all cement excess. Thereafter, the entire reconstruction was unscrewed and analyzed for the overall amount and the depth of cement excess. Kruskal-Wallis and Mann-Whitney tests were used to investigate differences between groups. When more than two groups were compared between each other, a Bonferroni correction of the P value was performed. ResultsConcave abutments presented significantly more cement remnants than CV abutments when the entire abutment area of the epimucosal margin groups was evaluated (CC0mm: mean 2.31mm(2) (SD 0.99) vs. CV0mm: mean 1.57mm(2) (SD 0.55); P=0.043). A statistically significant increase in remnants was detected when the crown-abutment margin was located more submucosally for every abutment studied (0mm vs. 1.5mm: P<0.000, 0mm vs 3mm: P<0.000, 1.5mm vs. 3mm: P<0.000). The buccal quadrant demonstrated the least, whereas the oral and interdental quadrants showed the greatest amount of cement excess. ConclusionsConcave emergence profile abutments and deep crown-abutment margin positions increased the risk of cement excess. Oral and interdental areas are more prone to cement remnants than other surface areas.