This study compared the effects of external hex, internal octagon, and internal Morse taper implant—abutment connections on the peri-implant bone level before and after the occlusal loading of dental implants.
Periapical radiographs of implants 63 patients placed between and were collected, digitized, standardized, and classified into groups based on the type of implant—abutment connection. These radiographs were then analyzed with image-processing software to measure the peri-implant crestal bone change during the healing phase 4 months after implant placement and at loading phases 1 and 2 3 and 6 months after occlusal loading, respectively.
A generalized estimating equation method was employed for statistical analysis. The amount of peri-implant crestal bone change differed significantly among all time—phase pairs for all 3 types of implant—abutment connection, being greater in the healing phase than in loading phase 1 or 2.
However, the peri-implant crestal bone change did not differ significantly among the 3 types of implant—abutment connections during the healing phase, loading phase 1, or loading phase 2. This retrospective clinical study reveals that the design of the implant—abutment connection appears to have no significant impact on short-term peri-implant crestal bone change. Dental implants have been widely accepted as a predictable and reliable tool for dental reconstruction, but it is still necessary to ensure that the height of the peri-implant crestal bone is maintained Buser et al.
Albrektsson et al. The type of implant—abutment connection Quirynen et al.
Astrand et al. However, the volume of crestal bone lost was small between baseline and follow-ups at 1, 3, and 5 years and did not differ significantly between internal and external hex implants.
Weng et al. Peri-implant bone height at 3 months after abutment connection changed least for epicrestal placement of implants with an internal taper implant—abutment connection. The literature Maeda et al. Nishioka et al. They found that peri-implant bone strain varied significantly with the type of implant—abutment connection.
Finite element analyses predict that the stress distribution in peri-implant bone differs with the type of implant—abutment connection Maeda et al. Chu et al.
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Only a few studies Engquist et al. Therefore, the aim of the present study was to determine if peri-implant crestal bone—level alterations at different time phases may depend on the type of implant—abutment connection. This study also examined peri-implant crestal bone changes between the healing phase and the loading phases 3 and 6 months. This retrospective study analyzed periapical radiographs obtained from patients receiving dental implant treatment at the Department of Dentistry, China Medical University Hospital, from to Because the type of the superstructure Sadowsky, ; Heckmann et al.
The diameters and lengths of the implants were also limited to 4 to 5 mm and 10 to 12 mm, respectively. Implants that supported overdentures, implants with cantilevered fixed partial dentures, and the implants opposing removable partial or complete dentures were excluded.
Additionally, cases with implant failure and severe bone loss due to peri-implantitis were excluded to avoid large error values. All implants were placed at healed edentulous ridges at least 2 months after tooth extraction, and a standard healing protocol was followed which lasted 4 and 6 months for the mandible and maxilla, respectively. The implants were embedded at the crestal bone level with cover screws to facilitate healing, followed by the connection of abutments 3 to 6 months thereafter.
After the connection of impression copings, a periapical radiograph perpendicular to the occlusal plane was taken with a cone indicator Cone Indicator III, Hanshin Technical Laboratory, Nishinomiya, Japan.
These periapical radiographs were used to check that the impression copings had been seated completely; they also served as baseline data of the peri-implant crestal bone level. The impressions were made with a transfer technique 3 weeks after healing during the second stage, and the prosthesis was delivered at least 5 weeks after the second stage.
All prostheses were cemented to the abutments, which were then connected in the delivery appointments. Detailed information about the implants and patients are given in Table 1. The time intervals for measurement were designated as T0, T1, T2, and T3, where T0 represents the day of implant placement; T1, the day when the prosthesis was delivered after approximately 4 months of implant placement and the start of occlusal loading; T2, approximately 3 months after the start of implant loading; and T3, 6 months after the start of implant loading.
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Any changes in the height of the peri-implant crestal bone were observed during the healing phase i. Such changes in the peri-implant bone level during the healing phases would indicate bone changes during the healing time of the implant.
The changes in the peri-implant bone levels during loading phases 1 and 2 demonstrate bone changes that occurred approximately 3 and 6 months after occlusal loading, respectively. Standard radiographing protocols were followed at each recall visit i.
A Retrospective Study of Implant–Abutment Connections on Crestal Bone Level
The Figure shows the reference points for measurements. The bone—implant contact point was the first contact point between the bone and the implant.
The vertical bone gap VBG was the vertical distance between the implant—abutment junction and the bone—implant contact point. Differences in the VBG measured at various times were used to quantify the changes in the peri-implant bone level Appendix Table.
SPSS 18 was used for statistical analyses. Linear regression models based on generalized estimating equations GEEs; Zeger and Liang, were used to analyze the differences in the mean values of the mesial and distal peri-implant bone changes for the 3 implant—abutment connection types during the 3 time phases. This model considered the correlations of within-subject repeated measures. Robust sandwich estimators were used to compute standard errors, and an exchangeable working correlation matrix was used to model patients clustering within the 3 time phases for the GEEs.
The Wald chi-square test was then used to determine whether the regression coefficient was zero; nonzero values indicated statistically significant differences in peri-implant crestal bone change between the various implant—abutment connection designs and time phases. The Bonferroni test was used for the post hoc test. Table 2 lists the peri-implant crestal bone changes for the 3 implant—abutment connection types external hex, internal octagon, and internal Morse taper during the 3 time phases healing phase, loading phase 1, and loading phase 2.
This study used the GEE method to conduct an overall test to determine whether the changes in height of the peri-implant bone differed between any 2 groups comprising the 3 implant—abutment connection types and 3 time phases. Three common commercially available implants with different types of implant—abutment connections external hex, internal octagon, and internal Morse taper systems were studied for their effects on the peri-implant crestal bone change during the first year after implantation.
The mean changes of the peri-implant crestal bone were less than 1 mm in the first year for all implants. Crestal bone changes that occurred between the placement of implants and 6 months after loading were all well within the success criteria proposed by Albrektsson et al. These findings are similar to those of Enkling and colleagues , who found that peri-implant crestal bone change was slightly greater during the healing phase than after the implants were loaded.
Several factors could hypothetically induce changes in crestal bone, including surgical trauma, occlusal overload, peri-implantitis, the microgap, the biological width, and the implant crest module used Oh et al.
The factor tested in the current study was the connection of the healing abutment in the second stage. Changes in crestal bone before occlusal loading are most likely to result from surgical trauma to the bone surrounding the implant when a heading abutment is connected in the second stage of surgery.
It is well recognized that crestal bone resorption during the first year should be less than 1. The biological width was significantly greater for 2-piece implants than for 1-piece implants in the study of Hermann et al.
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Lazzara and Porter reported that a concept of platform switching could bring the inflammatory cells infiltration, which would reduce the peri-implant crestal bone change. Subsequent studies have supported the advantages of platform-switching designs Pontes et al. However, our study and those of others Veis et al.
One of the limitations of the present study was the small sample size, which was due to the application of the strict inclusion criteria of implant-retained single or splinted crowns and to implant diameter and length falling within the ranges of 4 to 5 mm and 10 to 12 mm, respectively.
Future studies should increase the number of samples and extend the follow-up period. Even though a standardized radiographing procedure was applied in the present study to minimize errors in the obtained periapical radiographs, individual custom-made holders were not used throughout the study.
Additionally, the effect of the biological width between implant and abutment on the surrounding bone level was not examined. Some researchers have indicated that peri-implant bone level can be influenced by the biological width and that this dimension varies with the implant design Hermann et al. Future investigations should perform randomized controlled clinical trials with custom-made perpendicular holders and test the effects of connection type between implant and abutment on peri-implant bone level to determine if the biological width around implants exerts significant effects on bone change.
Within the limitations of this study, the following conclusions can be drawn: First, the level of peri-implant crestal bone does not differ significantly during either the healing phase or the loading phases among 3 different implant—abutment connection designs external hex, internal octagon, and internal Morse taper. Second, the level of peri-implant crestal bone changes significantly with the time interval healing phase, loading phase 1, and loading phase 2 , with it being slightly greater before the application of occlusal loading.
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J Dent Res. Author information Copyright and License information Disclaimer. This article has been cited by other articles in PMC. Abstract This study compared the effects of external hex, internal octagon, and internal Morse taper implant—abutment connections on the peri-implant bone level before and after the occlusal loading of dental implants. Keywords: internal octagon, internal Morse taper, peri-implant crestal bone change dental implant—abutment design, radiology, alveolar bone loss.
Introduction Dental implants have been widely accepted as a predictable and reliable tool for dental reconstruction, but it is still necessary to ensure that the height of the peri-implant crestal bone is maintained Buser et al.
Table 1. Characterization of the Implant—Abutment Connections. Open in a separate window.
Table 2. Table 3. Discussion Three common commercially available implants with different types of implant—abutment connections external hex, internal octagon, and internal Morse taper systems were studied for their effects on the peri-implant crestal bone change during the first year after implantation.
Conclusions Within the limitations of this study, the following conclusions can be drawn: First, the level of peri-implant crestal bone does not differ significantly during either the healing phase or the loading phases among 3 different implant—abutment connection designs external hex, internal octagon, and internal Morse taper.
References Abrahamsson I, Berglundh T. Effects of different impalnt surfaces and designs on marginal bone-level alternations: a review. The long-term efficacy of currently used dental implants: a review and proposed criteria of success. Influence of various implant platform configurations on peri-implant tissue dimensions: an experimental study in dog. Long-term stability of osseointegrated implants in augmented bone: a 5-year prospective study in partially edentulous patients.
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Influences of internal tapered abutment designs on bone stresses around a dental implant: three-dimensional finite element method with statistical evaluation. Evaluation of the Periotest as a diagnostic tool for dental implants.
Effect of platform switching on peri-implant bone levels: a randomized clinical trial. Overdenture attachment selection and the loading of implant and denture-bearing area: part 2. A methodical study using five types of attachment. Biologic width around one- and two-piece titanium implants.
Influence of forces on peri-implant bone. The effect of internal versus external abutment connection modes on crestal bone changes around dental implants: a radiographic analysis.
Platform switching: a new concept in implant dentistry for controlling postrestorative crestal bone levels.