Periimplant soft tissue health surrounding screw- and cement-retained implant crowns: A multi-center, 3-year prospective study

Periimplant soft tissue health surrounding screw- and cement-retained implant crowns: A multi-center, 3-year prospective study
Implant Dentistry: Volume 12(1) March 2003 p 102
Ng, Mavis Wu
Lippincott Williams & Wilkins, Inc.
Abstract:
Background.
Cement-retained implant crowns have become increasingly popular over screw-retained restorations because of their better mechanical and esthetic properties, greater cost-effectiveness, as well as ease of technique. Long-term effectiveness depends on their ability to maintain periimplant tissue health. Recent in vitro studies concluded that screw-retained crowns are superior based on the considerably smaller size of the marginal gap at the crown-implant interface. However, there have not been in vivo human studies documenting clinical relevance of such gap size discrepancy.
Purpose.
This study was to evaluate soft tissue conditions surrounding dental implants with screw- or cement-retained restorations during a 3-year follow up.
Methods.
In a multi-center, randomized, prospective study, 152 ITI Hollow Cylinder dental implants were placed in 80 patients in the maxillary anterior region. Fifty-nine implants (38.82%) were restored with cement-retained and 93 (61.18%) with screw-retained crowns. At the time of crown placement (loading), as well as 3, 6, 12, and 36 month postloading, modified plaque index (MPI), sulcus bleeding index (SBI), keratinized mucosa (KM), gingival level (GL), esthetics, and patient satisfaction were recorded. Student t test, ANOVA, correlation, and multivariate regression analyses were performed.
Results.
Cemented crowns showed no difference in MPI compared with screw-retained crowns except at 36-month postloading, where a higher MPI was shown in cemented crowns (P < 0.05). A higher mean SBI was shown in cemented crowns than screw-retained ones throughout the entire 3-year follow-up period except at 3-month postloading (P < 0.05). When compared with baseline levels, the mean MPI was stable for cemented crowns for up to 3 years; the mean MPI was also stable for screw-retained crowns for 12 months and improved at 36-month postloading. (P < 0.05). In terms of SBI, cemented crowns showed a rising score from baseline after 12-month post loading; however, the mean SBIs for screw-retained crowns were not different from baseline after 12-month post loading (P > 0.05). For both cement- and screw-retained crowns, KM and GL remained constant. Prophylaxis application correlated well with a lower MPI (P < 0.05). The SBI was positively influenced by prophylaxis, whereas it was negatively influenced by GL (P < 0.05). SBI also positively correlated with MPI (r = 0.49). In the evaluation of esthetics, practitioners favored cemented crowns (P < 0.05), whereas patients did not show a preference.
Conclusion.
Cemented crowns demonstrated significantly higher MPI and SBI scores at time points beyond 12-months and 6-months postloading, respectively. The difference in MPI was due to an improvement from the screw-retained group; cemented crowns maintained a stable MPI up to 3 years. SBI of cemented crowns increased at 1 and 3 years postloading, which contributed to the difference between the two different crown groups. No recession was observed in both groups. Patients were equally satisfied with the esthetic appearance of either type of restoration.