Original study - ZZI 02/2016

The influence of various implant types on peri-implant bone loss – a retrospective radiological evaluation

Background: Preserving marginal bone is crucial for good esthetic and functional results with implant-supported prosthetic restorations. However, several authors have reported remodeling of crestal bone and bone loss during the early stages following implant placement.

Objective: The objective of the present retrospective study was to review marginal peri-implant bone loss using radiographs collected by a dental oral surgery practice over a period of up to 17 3/4 years. It was hypothesized that no difference in bone loss would be found between the various dental implant types. The influence of implant-specific design features, prosthetic restorations, and the implant/abutment connection were investigated.

Materials and Methods: In this retrospective study, post-operative and follow-up radiographs of patients who had received implants in a private oral and maxillofacial practice over a 17 3/4-year period were digitized. Peri-implant bone-level changes were measured, and descriptive statistics computed.

Results: The study included 569 patients ranging in age from 14.8 to 84.4 years who received a total of 1434 implants, of which 173 images (12.1 %) were excluded because of lack of follow-up radiographs. A total of 3613 radiographs were taken of the remaining 1261 implants, which included 506 from Astra Tech Dental (40.1 %), 558 from Camlog (44.3 %), and 197 from DENTSPLY Friadent (15.6 %). The measurements were distributed evenly among upper and lower jaws. Marginal bone loss decreased markedly after the first 2 years, and significantly (p < 0.05) more bone loss was found in the upper jaw (mean = 0.91 mm, SD = ± 1.37) than in the lower jaw (mean = 0.79 mm, SD = ± 1.60). Bone cavities were smallest at single-tooth sites (mean = 0.74 mm, SD = ± 1.39) and in edentulous lower jaws. They were significantly greater (p < 0.05) around implants supporting bridges (mean = 0.96 mm, SD = ± 1.54). Short and thin implants induced less bone loss than long and thick ones (p < 0.05). Implants that had been placed in augmented areas incurred more bone loss overall than others during the course of observation, but the type of augmentation was crucial. Examination of the individual implant types revealed the most significant differences (p < 0.05). Regardless of the type of load, superstructure, augmentation or location, Camlog implants exhibited the largest bone cavities (mean = 1.25 mm, SD = ± 1.49), followed by DENTSPLY Friadent implants (mean = 1.16 mm, SD = ± 1.69), and Astra Tech dental implants (mean = 0.18 mm, SD = ± 1.07).

Conclusion: The implant/abutment connector geometry appeared to significantly influence the progression of bone loss.

Keywords: peri-implant; marginal bone; bone level; bone loss

Cite as: Knöfler W, Wostratzky M, Schmenger K: The influence of various implant types on peri-implant bone loss – a retrospective radiological evaluation. Z Zahnärztl Implantol 2016; 32: 114–129

DOI 10.3238/ZZI.2016.0114–0129

Introduction

An adequate amount of local bone ensures firm retention of the implants together with the superstructures they support and contributes to esthetic success by supporting the soft tissue. Particularly during the early stages following implant placement, the crestal bone is subjected to considerable remodeling processes due to restoration of the biologic width [8, 13]. According to the criteria for successful implant outcomes published by Albrektsson und Zarb [1] and modified [2, 30], 1.5 mm bone loss in the first year and 0.2 mm during subsequent years is considered acceptable. However, given the continued development of implant systems, the question arises as to whether these criteria still apply today [3].

In the ongoing discussion about factors impacting the peri-implant bone level [15], the most important influences include those specific to the implant system [9, 22], the surgical procedures and treatments, the types of prosthetic restoration [23], the moment in time at which restoration is carried out, localization of the implant site and patient-specific influences [28]. The specific factors for every implant system include parameters such as implant length and diameter [4, 24], the implant shape, whether the system includes one or two-piece implants and the implant/abutment connector geometry [12]. The roughness of the implant surface, the type of coating and distance between the implant/abutment connection and bone may be of significance [6, 7, 25, 27]. Particularly with two-piece implants, the connection between the implant and the abutment determines the future situation of the peri-implant bone. One-piece implants with bar-borne coverdentures were shown to cause less bone resorption than two-piece systems. Bone loss due to surgical exposure and placement of the superstructure was also observed [19].

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