Tord Lundgren

Bacterial Colonization of the Dental Implant Fixture-Abutment Interface: An In Vitro Study

BACKGROUND The geometry of the fixture-abutment interface (FAI) might influence the risk of bacterial invasion of the internal part of the implant. The aim of this study was to use an in vitro model to assess the potential risk for invasion of oral microorganisms into the FAI microgap of dental implants with different characteristics of the connection between the fixture and abutment. METHODS Thirty implants were divided into three groups (n = 10 per group) based on their microgap dynamics. Groups 1 and 2 were comprised of fixtures with internal Morse-taper connections that connected to standard abutments and the same abutments with a 0.5-mm groove modification, respectively. Group 3 was comprised of implants with a tri-channel internal connection. Fixtures and abutments were assembled and allowed to incubate in a bacterial solution of Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) and Porphyromonas gingivalis. Two standard abutments were either exposed to bacterial culture or left sterile to serve as positive and negative controls. After disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated, and allowed to culture under appropriate conditions. RESULTS Three of the 10 samples in group 1 developed one colony forming unit (CFU) for A. actinomycetemcomitans, whereas zero of 10 samples developed CFUs for P. gingivalis. Ten of 10 and nine of 10 samples from groups 2 and 3, respectively, developed multiple CFUs for A. actinomycetemcomitans and P. gingivalis. CONCLUSION This study indicated that differences in implant designs may affect the potential risk for invasion of oral microorganisms into the FAI microgap.

Bacterial Colonization of the Implant–Abutment Interface Using an In Vitro Dynamic Loading Model

BACKGROUND Previously, we demonstrated that the geometry of the fixture-abutment interface influences the risk of bacterial invasion into the internal part of the implant, although the contribution of loading on this invasion was not evaluated. The aim of the present study is to use an in vitro dynamic-loading model to assess the potential risk for invasion of oral microorganisms into the fixture-abutment interface microgap of dental implants with different fixture-abutment connection characteristics. METHODS Twenty-eight implants were divided into two groups (n = 14 per group) based on their microgap dynamics. Group 1 was comprised of fixtures with internal Morse-taper connection that connected to standard abutments. Group 2 was comprised of implants with a four-groove conical internal connection that connected to multibase abutments. The specimens were immersed in a bacterial solution of Escherichia coli and loaded with 500,000 cycles of 15 N in a wear simulator. After disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated, and cultured under appropriate conditions. The difference between loosening and tightening torque value was also measured. RESULTS One of the 14 samples in Group 1 and 12 of the 14 of samples in Group 2 developed multiple colony forming units for E. coli. Implants in Group 1 exhibited an increase in torque value in contrast to implants in Group 2, which exhibited a decrease. CONCLUSION This study indicates that differences in implant design may affect the potential risk for invasion of oral microorganisms into the fixture-abutment interface microgap under dynamic-loading conditions.

Crestal Bone Changes Around Implants With Reduced Abutment Diameter Placed Non-Submerged and at Subcrestal Positions: A 1-Year Radiographic Evaluation

BACKGROUND There is limited information about two-part implants placed in subcrestal positions. The aim of this study is to retrospectively evaluate the 1-year outcome of implants placed non-submerged and in a subcrestal position. METHODS Records of 50 consecutive partially edentulous patients restored with dental implants were reviewed. For each implant, radiographs from the surgical appointment were compared to those from the 1-year follow-up visit and evaluated regarding: 1) the degree of subcrestal positioning of the implant, 2) changes of marginal hard tissue height over time, and 3) if the marginal hard tissue could be detected on the implant platform at the follow-up visit. RESULTS The overall survival rate from baseline to the last recorded follow-up visit was 100%. At the surgery, the implants were placed, on average, 1.37 mm (mesial) and 1.28 mm (distal) subcrestally. The mean marginal loss of hard tissues was 0.11 +/- 0.30 mm. There were no statistical significant differences regarding the loss of marginal hard tissues between mesial and distal surfaces or the maxilla versus the mandible. There was no statistical significant correlation regarding the degree of subcrestal implant position and loss of marginal mineralized hard tissue (r = 0.15; P >0.05). The mineralized hard tissue on the implant shoulder was found in 69% of the implants at the 1-year follow-up visit. CONCLUSIONS The present study reported a minimal loss of mineralized hard tissue around dental implants placed non-submerged and at subcrestal positions. In addition, these implants had hard tissue healing that extended onto the implant shoulders on most of the observed implants.

Crestal Bone–Level Changes Around Implants Placed in Post-Extraction Sockets Augmented With Demineralized Freeze-Dried Bone Allograft: A Retrospective Radiographic Study

BACKGROUND There is limited information regarding marginal crestal bone–level changes around implants placed in post-extraction sockets augmented with demineralized freeze-dried bone allograft (DFDBA). The aim of this study was to retrospectively compare bone-level changes around implants placed in post-extraction sockets augmented with DFDBA to implants placed in native bone. METHODS Records of 30 consecutive patients treated with dental implants placed in post-extraction sockets augmented with DFDBA and 30 consecutive patients with implants placed in native bone were reviewed. For each implant, the radiographs from the surgical appointment were compared to those from the last follow-up visit and evaluated regarding changes of marginal bone level over time. RESULTS The overall survival rate from baseline to the last follow-up visit was 100% for both groups. The mean marginal bone loss was 0.15 mm for both groups for a mean follow-up time of 12 months. There were no significant differences regarding the percentage of implants and implant surfaces demonstrating marginal bone loss. CONCLUSION The present study indicates implants placed in post-extraction sockets augmented with DFDBA exhibited minimal marginal bone loss similar to implants placed in native bone.

Retrospective evaluation of crestal bone changes around implants with reduced abutment diameter placed non-submerged and at subcrestal positions: the effect of bone grafting at implant placement.

BACKGROUND There is limited information regarding the effect of grafting of the osteotomy after subcrestal implant placement. The primary aim of this study is to retrospectively evaluate the effect of bone grafting of the defect between the bone crest and the coronal aspect of implants with reduced abutment diameter placed non-submerged and at subcrestal positions. METHODS Records of 50 consecutive patients treated with subcrestally placed dental implants grafted with a xenograft (Group A) and 50 consecutive patients with subcrestally placed dental implants without any grafting material (Group B) were reviewed. For each implant, the radiographs after placement were compared to images from the last follow-up visit and evaluated regarding the following: 1) degree of subcrestal positioning of the implant, 2) changes of marginal hard-tissue height over time, and 3) whether marginal hard-tissue could be detected on the implant platform at the follow-up visit. RESULTS The mean marginal loss of hard tissues was 0.11 ± 0.30 mm for Group A and 0.08 ± 0.22 mm for Group B. Sixty-nine percent of the implants in Group A and 77% of the implants in Group B demonstrated hard tissue on the implant platform. There were no statistically significant differences between the groups regarding marginal peri-implant hard-tissue loss. CONCLUSION The present study fails to demonstrate that grafting of the remaining osseous wound defect between the bone crest and the coronal aspect of the implant has a positive effect on marginal peri-implant hard-tissue changes.

Placement of implants with platform-switched Morse taper connections with the implant-abutment interface at different levels in relation to the alveolar crest: a short-term (1-year) randomized prospective controlled clinical trial.

PURPOSE This study sought to prospectively evaluate changes in marginal bone levels and soft tissue dimensions around platform-switched, Morse taper-connection implants placed with the implant-abutment interface (IAI) at different positions in relation to the alveolar crest. MATERIALS AND METHODS Thirty patients in need of single-tooth rehabilitations were randomly assigned to three groups based on the position of the IAI in relation to the alveolar crest at the time of implant placement. Implants in groups 0, 1, and 2 (n = 10 in each group) were placed at the bone level or 1 mm and 2 mm below the buccal aspect of the alveolar crest, respectively. Four months later, the implants were restored with crowns. Clinical parameters were recorded at 4 and 12 months, and marginal bone levels were assessed radiographically at placement, 4 months, and 12 months. RESULTS Mean marginal bone loss below the implant platform in group 0 implants was 0.18 ± 0.27 mm at 4 months and 0.27 ± 0.45 mm at 12 months. All implants in groups 1 and 2 exhibited no marginal bone loss below the implant platform, since the first bone-to-implant contact was located at or above the implant margin. At 12 months, implants in groups 1 and 2 exhibited greater mean bone loss above the implant platform compared to implants in group 0, but the differences were not statistically significant (group 0, 0.64 ± 0.49 mm; group 1, 0.81 ± 0.31 mm; group 2, 1.20 ± 0.68 mm). Implants in groups 1 and 2 exhibited a statistically significantly higher percentage of implant surfaces with bone on the implant platform compared to group 0 implants (90% versus 35%). CONCLUSIONS In the present study, differences in peri-implant bone responses existed for implants placed with the IAI at different locations in relation to the alveolar crest.

Immediate loading of implants placed with the osteotome technique: one-year prospective case series.

BACKGROUND There is limited information regarding marginal bone-level changes around immediately loaded implants placed with the osteotome technique. The aim of this case series is to prospectively evaluate the clinical and radiographic outcome of immediately loaded implants placed with the osteotome technique over a 12-month period. METHODS Eighteen patients in need of oral prosthetic rehabilitation that included single implant placement in positions #4 to #13 and/or #20 to #29 participated in this prospective trial. A modified implant installation procedure with an under preparation of the implant bed using the osteotome technique and immediate loading of the implant was performed. Clinical examinations were performed at 2 weeks, 6 months, and 12 months of follow-up. Radiographic examinations were performed at implant installation and at the 6- and 12-month follow-up visits. RESULTS One implant failed to integrate and was removed at 3 months after implant installation. Four of 20 implants had insertion torque value >35 Ncm. The mean marginal bone loss was -0.09 mm at the 6-month and -0.19 mm at the 12-month follow-up visits. CONCLUSION The present case series indicates that implants placed with the osteotome technique and immediately loaded did not demonstrate a high insertion torque and exhibited minimal marginal bone loss.

Bacterial Colonization of the Implant-Abutment Interface (IAI) of Dental Implants with a Sloped Marginal Design: An in-vitro Study.

PURPOSE The aim of this study is to utilize an in vitro dynamic loading model to assess the potential risk of bacterial invasion into the Implant Abutment Interface (IAI) microgap of dental implants with sloped marginal design. MATERIALS AND METHODS Forty implants were divided into two groups (n = 20 per group) based on implant marginal design. Group 1 was comprised of implants with Morse-taper connection and conventional marginal design that connected to titanium abutments. Group 2 was comprised of implants with Morse-taper connection and sloped marginal design that connected to titanium abutments. The specimens were immersed in a bacterial solution of E. coli and loaded with 500,000 cycles of 160N using a chewing simulator. Following disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated and cultured under appropriate conditions. RESULTS Ten out of twenty implants of Group 1 and eight out of twenty implants of Group 2 had IAI microgaps colonized by E. Coli. There was not a statistically significant difference in the mean number of E. Coli CFU detected between implants of Group 1 (mean 19.2, SD 23.6) and Group 2 (mean 12.5, SD18.9) (p > .05). CONCLUSIONS The present study demonstrated that implants with a sloped marginal design exhibited similar risk for bacterial invasion into the IAI microgap under in vitro dynamic loading conditions compared to implants with conventional marginal design.

Cone beam computed tomographic evaluation of implants with platform-switched Morse taper connection with the implant-abutment interface at different levels in relation to the alveolar crest.

PURPOSE The aim of this study was to evaluate marginal bone levels, with cone beam computed tomography, on the buccal and lingual aspects of implants placed with the implant-abutment interface (IAI) at different positions in relation to the alveolar crest. MATERIALS AND METHODS Thirty patients in need of single-tooth rehabilitation were randomly assigned to three groups based on the position of the IAI in relation to the buccal aspect of the alveolar crest at the time of implant placement. Patients in groups 0, 1, and 2 had their implants placed level with the buccal crest or 1 or 2 mm apical to the buccal aspect of the alveolar crest, respectively. The implants were restored with screw-retained single crowns after 4 months. Marginal bone levels on the buccal and lingual aspects of the implants were evaluated at 12 months after implant placement. RESULTS All groups of implants demonstrated significantly different crestal positions. Group 2 implants maintained the greatest subcrestal position (1.33 ± 0.86 mm) compared to the implants of group 0 (-0.04 ± 0.18 mm) and group 1 (0.34 ± 0.44 mm). There were no differences between groups in the level of the first bone-to-implant contact relative to the implant platform. Implants of group 0 exhibited less buccal bone remodeling (-0.08 ± 0.25 mm) compared to group 1 (-0.65 ± 0.45 mm) and group 2 (-0.85 ± 0.75 mm) implants. For groups 1 and 2 implants, there was a significant negative correlation between buccal wall thickness following the osteotomy and the amount of buccal bone remodeling. CONCLUSION In this study, different responses were seen in the buccal and lingual peri-implant bone for implants with platform-switched Morse taper connections placed with the IAI at different locations in relation to the alveolar crest.

Abutment Disconnection/Reconnection Affects Peri-implant Marginal Bone Levels: A Meta-Analysis

PURPOSE Preclinical and clinical studies have shown that marginal bone loss can be secondary to repeated disconnection and reconnection of abutments that affect the peri-implant mucosal seal. The aim of this systematic review and meta-analysis was to evaluate the impact of abutment disconnections/reconnections on peri-implant marginal bone level changes. MATERIALS AND METHODS To address this question, two reviewers independently performed an electronic search of three major databases up to October 2015 complemented by manual searches. Eligible articles were selected on the basis of prespecified inclusion and exclusion criteria after a two-phase search strategy and assessed for risk of bias. A random-effects meta-analysis was performed for marginal bone loss. RESULTS The authors initially identified 392 titles and abstracts. After evaluation, seven controlled clinical studies were included. Qualitative assessment of the articles revealed a trend toward protective marginal bone level preservation for implants with final abutment placement (FAP) at the time of implant placement compared with implants for which there were multiple abutment placements (MAP). The FAP group exhibited a marginal bone level change ranging from 0.08 to 0.34 mm, whereas the MAP group exhibited a marginal bone level change ranging from 0.09 to 0.55 mm. Meta-analysis of the seven studies reporting on 396 implants showed significantly greater bone loss in cases of multiple abutment disconnections/reconnections. The weighted mean difference in marginal bone loss was 0.19 mm (95% confidence interval, 0.06-0.32 mm), favoring bone preservation in the FAP group. CONCLUSION Within the limitations of this meta-analysis, abutment disconnection and reconnection significantly affected peri-implant marginal bone levels. These findings pave the way for revisiting current restorative protocols at the restorative treatment planning stage to prevent incipient marginal bone loss.