JOURNAL OF PROSTHETIC DENTISTRY THE

Vol. 100 No. 3      SEPTEMBER - 2008

ISSN: 0022-3913      UBIC: 171

SUMMARY

Statement of problem.The osseointegration or fibrous encapsulation of immediately loaded dental implants depends on the extent of implant micromovement. The impact of acrylic resin or metal-reinforced acrylic resin provisional restorations on this movement is currently unknown. Purpose: the purpose of this study was to isolate and measure the effect of provisional restoration type on the vertical displacement of adjacent implants under load at 2 locations. Material and methods. Vertical loads ranging from 10-200 N were applied to polymethyl methacrylate resin (n=56) or metal-reinforced acrylic resin provisional restorations (n=56) supported by 4 implants inserted into homogenous artificial bone in a "u-shaped" alignment. Provisional restorations were first loaded in the anterior segment where the provisional restoration was supported by a mesial and distal implant, followed by loading on an extension 8 mm distal to the last implant. Vertical displacement of the 2 implants nearest the load application was measured and recorded using an optical image correlation technique based on photogrammetric principles. Data were subjected to a nonparametric multivariate analysis (generalized Wilcoxon test) and a Mann-Whitney test with a 2-tailed P value (α=.05). Results. There was no significant difference in the vertical implant displacement of the 2 provisional restoration groups when they were loaded in the anterior segment. However, when loads were applied to the distal cantilever, metal reinforcement resulted in less vertical displacement of the next-to-last implant. The mean vertical displacement of the next-to-last implant when supporting an acrylic resin provisional restoration increased from 20 µm ±3 µm (pooled loads of 10-50 N) to 130 µm ±21 µm (pooled loads of 160-200 N), while the vertical displacement of the implant when retaining a metal-reinforced acrylic resin provisional restoration increased from 10 µm ±2 µm to 69 µm ±13 µm under the same loads (P ≥.001). A significant difference over load stages (z=-3.22, P<.001) was observed. Conclusions. The choice of material used for a provisional restoration significantly influences the vertical displacement of implants placed in artificial bone. When loads are applied to distal cantilevers, load distribution with metal reinforcement seems more favorable than with unreinforced acrylic resin. (J Prosthet Dent 2008;100:173-182)

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