30 June 2021

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Crestal or 1.5 mm subcrestal positioning of transmucosal dental implants with cemented or screw-retained crowns in posterior jaws: 4-month data from a single-centre randomised controlled trial

Authors: Carlo Barausse, Marco Esposito, Fabio Colombelli, Pierantonio Bellini, Jacopo Buti, Pietro Felice

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Objectives. To compare crestal versus 1.5 mm subcrestal positioning of single transmucosal dental implants and screw-retained versus cemented crowns.

Materials and methods. One hundred and sixty partially edentulous patients requiring one single implant-supported crown in the premolar/molar area were randomly allocated to four arms: crestal positioning and screw-retained crown (Group 1, 40 patients); crestal positioning and cement-retained crown (Group 2, 40 patients); 1.5 mm subcrestal positioning and screw-retained crown (Group 3, 40 patients); or 1.5 mm subcrestal positioning and cement-retained crown (Group 4, 40 patients) by a single operator. After an unloaded healing period of 3 months, definitive metal-ceramic crowns were delivered, and patients were followed up to 4 months after loading. Outcome measures were: crown and implant failures, complications, aesthetics assessed using the pink aesthetic score (PES), peri-implant marginal bone level changes and patient satisfaction, all recorded, when possible, by blinded assessors. 

Results. At four months post-loading, four patients dropped out (two from Group 1 and one each from Groups 2 and 3, respectively). Two implants each failed in Groups 2 and 4, but there were no statistically significant differences between groups (P = 1.000). Complications affected four patients from Group 1, one from Group 2, two from Group 3 and six from Group 4, but between-group differences were not statistically significant (P = 0.207). The mean pink aesthetic scores were 10.30 ± 2.13 (Group 1), 10.22 ± 2.76 (Group 2), 10.47 ± 2.96 (Group 3), and 10.51 ± 2.24 (Group 4), respectively, with no statistically significant differences between groups (P = 0.9541). Likewise, there were no statistically significant differences in peri-implant marginal bone loss at 4 months after loading between groups (P = 0.9011: -0.21 mm ± 0.28 for Group 1, -0.25 mm ± 0.27 for Group 2, -0.28 mm ± 0.57 for Group 3 and -0.24 mm ± 0.26 for Group 4). Furthermore, there were no differences in patient satisfaction in terms of either function (P = 0.400) or aesthetics (P = 1.000), and all patients would undergo the same intervention again.

Conclusions. No appreciable statistical or clinical differences were found between crestal or 1.5 mm subcrestal placement of transmucosal implants in posterior jaws or between rehabilitation with screw-retained or cement-retained crowns. However, longer follow-ups are required in order to formulate reliable clinical recommendations.