Changes in Peri-implant Marginal Bone Level by Jaw Location: A Systematic Review and Meta-Analysis of 4970 Implants

The purpose of this study was to evaluate the current evidence on marginal bone-level changes (ΔMBL) around internal connection implants with fixed prostheses by jaw location over time. An electronic literature search for ΔMBL (change in marginal bone level) was conducted in 6 databases. The data from the included manuscripts were categorized by jaw sextant of the implants and duration of follow-up (<2 years, 2-5 years, and >5 years). Meta-analyses were performed on groups with at least 5 studies. A total of 1270 records were screened. Full-text review of 413 papers resulted in a total of 46 studies (representing 2259 patients with 4970 implants) included for quantitative synthesis and analysis. The ΔMBL was summarized at 2 time intervals with the following results: <2 years (anterior maxilla = 0.393 mm [95% confidence interval {CI}, 0.172, 0.613], posterior maxilla = 0.468 mm [95% CI, 0.288, 0.648], and posterior mandible 0.559 mm [95% CI, 0.397, 0.72]), 2 to 5 years (anterior maxilla = 0.683 mm [95% CI, 0.224, 1.142], posterior maxilla = 0.645 mm [95% CI, 0.42, 0.87], and posterior mandible 0.563 mm [95% CI, 0.278, 0.849]). There were insufficient studies in the anterior mandible and with follow-up data over 5 years for quantitative synthesis. Within the limitations of this study, location within the maxillary and mandibular jaws does not seem to influence ΔMBL around internal connection bone level implants with fixed restorations. Although there may be a tendency for greater initial remodeling in the posterior mandible followed by long-term stability, additional studies are needed to evaluate this further.

Influence of Periodontal Status and Prosthetic Treatment on Survival and Success Rates in Implant Therapy: A 5-Year Retrospective Follow-Up Study

The objective of the present study was to evaluate the 5-year outcome of dental implant therapy and assess the survival, success, and biological and technical complications. A periodontal and prosthetic-oriented evaluation was conducted on the variables that can influence the long-term predictability of implant therapy. A total of 615 patients and 1427 dental implants from a private clinic (MedArtis Dent, Cluj-Napoca, Romania) were enrolled in the study. The study was a longitudinal cohort with data collected retrospectively from physical/digital dental records in combination with a cross-sectional clinical/radiological examination. Results showed that periodontal diagnosis at baseline had a significant impact on the marginal bone loss prediction. Data showed that the cylindrical implant with an internal 45° medium taper connection experienced a higher rate of bone resorption compared to the tapered implant with the 5° internal connection. Screw-retained restorations and overdentures showed a statistical decrease in the marginal bone level height when compared to the cemented restorations. Data from our study suggest that not only is there a powerful association between recall visits and the rate of complications in dental implant treatment, but a lack of professional maintenance predicts a higher bone level loss during the 5-year interval.

Marginal Bone Maintenance and Different Prosthetic Emergence Angles: A 3-Year Retrospective Study

The aim of the present retrospective study was to assess marginal bone changes around implants restored with different prosthetic emergence profile angles. Patients were treated with implants supporting fixed dentures and were followed for 3 years. Marginal bone levels (MBL) measured at the prosthesis installation (t0) and at the 3-year follow-up visit (t1) were considered. The MBL change from t0 to t1 was investigated. Two groups were considered: Group 1 for restorations with an angle between implant axis and prosthetic emergence profile >30°, and Group 2 for those with an angle ≤30°, respectively. Moreover, peri-implant soft tissue parameters, such as the modified bleeding index (MBI) and plaque index (PI) were assessed. Seventy-four patients were included in the analysis and a total of 312 implants were examined. The mean EA in groups 1 and 2 was 45 ± 4 and 22 ± 7 degrees, respectively. The mean marginal bone level change (MBL change) of 0.06 ± 0.09 mm and 0.06 ± 0.10 mm were, respectively, in groups 1 and 2. The difference in the MBL change between the two groups was not statistically significant (p = 0.969). The MBL change does not seem to be influenced by the emergence angle for implants with a stable internal conical connection and platform-switching of the abutment diameter.

Comparison between Early Loaded Single Implants with Internal Conical Connection or Implants with Transmucosal Neck Design: A Non-Randomized Controlled Trial with 1-Year Clinical, Aesthetics, and Radiographic Evaluation

To evaluate the implant and prosthetic of two implants with different surfaces and neck design. Enrolled patients received bone level, 12° conical connection implants (Nobel Parallel, Nobel Biocare; NOBEL group) with anodized surface (TiUnite) and roughness of 1.35 μm, or transmucosal implant system (Prama, Sweden and Martina; PRAMA group) with convergent collar, ZIrTi surface, and roughness 1.4–1.7 μm. Both implants were made of pure grade IV titanium, with similar diameter and length, chosen according to the dentistry department availability and patient’s request. After early prosthesis delivery, patients were filled for at least one year. Outcome measures were: implant and prosthetic survival and success rates, physiological marginal bone remodeling, periodontal parameters and pink esthetic score (PES). Results: Fifteen patients were allocated and treated in each group. At the one-year follow-up, three patients dropped out, one in the NOBEL group and two in the PRAMA group. During the entire time of investigation, all implants survived and the prostheses were successful. No statistically significant differences were found in term of marginal bone loss, periodontal parameters, and aesthetics (p > 0.05). Conclusion: With the limitations of the present study, both implant systems showed successful clinical results. Finally, many other clinical and surgical variables may influenced marginal bone levels, implant survival, and periodontal parameters. More homogenous clinical trials with larger samples are needed to confirm these preliminary conclusions.

The effect of implant-abutment connections on peri-implant bone levels around single implants in the aesthetic zone: A systematic review and a meta-analysis

Objective

To systematically review literature about the effect of different implant‐abutment interface designs on peri‐implant bone level changes, implant loss and mid‐buccal mucosa changes around single implants in the anterior maxilla. Reviewing three connection configurations: Platform switched conical (PS‐conical); Platform switched parallel (PS‐parallel); Platform matched parallel (PM‐parallel).

Methods

A detailed search was carried out in Pubmed, EMBASE, Cochrane, Scopus, Open Gray and African journals Online (until December 1, 2020) and was restricted to clinical prospective studies of at least 1 year and with at least 10 human participants. A meta regression analysis was carried out primarily on the pooled peri‐implant bone level changes followed by implant loss and mid‐buccal mucosa level change. Risk of bias was assessed with RoB 2.0 and ROBINS‐I. The manuscript complied with the PRISMA guidelines and was registered in the PROSPERO database (ID: 225092).

Results

A total of 5513 hits gave 44 eligible articles for the analyses. Bone level change did not differ significantly between the two platform switched connections; their bone loss scores were significantly lower than PM‐connection. The PS‐conical connections have significantly lower implant losses than the PM connection. Mid‐buccal mucosa level change was comparable between the three connection configurations. Moderate to high risk of bias was detected in the included studies.

Conclusions

The performance of PS‐conical and PS‐parallel connection configurations both favored bone loss scores compared to the PM‐parallel connection configuration. All three demonstrated mid‐buccal mucosa changes that were small and did not differ significantly amongst the groups.

Clinical and radiographic performance of self-locking conical connection implants in the posterior mandible: Five-year results of a two-centre prospective study

OBJECTIVE

This prospective study aims to assess the 5-year clinical performance of implants with internal conical connection and platform-switched abutments in the posterior mandible.

MATERIAL AND METHODS

Healthy adults missing at least two teeth in the posterior mandible and with a natural tooth mesial to the implant site received two or three adjacent implants. After a transmucosal healing period single crown restorations were cemented on platform-switched abutments. Changes in marginal bone levels were investigated in standardized periapical radiographs from surgery and loading (baseline) to 60-months post-loading.

RESULTS

Twenty-four patients received 52 implants. Bone remodelling took place between surgery and loading (mean:-0.5, SD:±0.4 mm). From loading to 60 months, there was a mean bone change of 0.27 (SD:±0.47 mm) which stabilized 24 months after prosthesis delivery (mean:0.2, SD:±0.46 mm). 71.7% of all implants presented bone preservation at 60 months irrespective of the initial insertion depth. Two implants were lost after 5 years and the success rate was 95.1%. Patient enquiry revealed high satisfaction.

CONCLUSION

Internal conical connection implants with platform-switched abutments presented a high success rate and preservation of marginal bone levels at the implant shoulder after 5 years of loading.

Peri-Implant Behavior of Tissue Level Dental Implants with a Convergent Neck

Introduction: The aim of this retrospective study was to analyze the radiographic peri-implant bone loss of bone level implants and tissue level implants with a convergent neck in screw-retained single crowns and in screw-retained fixed partial prostheses, after two years of functional loading. Materials and methods: The sample was divided into two groups according to their type: Group I: supracrestal implants with convergent transmucosal neck; Group II: crestal implants. In each group we distinguish two subgroups according to the type of prosthetic restoration: single crowns and a three-piece fixed partial prosthesis on two implants. To quantify bone loss, parallelized periapical radiographs were analyzed at the time of implant placement and after two years of functional load. Results: A total of 120 implants were placed in 53 patients. After statistical analysis it was observed that for each type of implant bone loss was 0.97 ± 0.91 mm for bone level and 0.31 ± 0.48 mm for tissue level. No significant differences were found regarding the type of prosthesis and the location (maxilla or mandible) of the implants. Conclusions: Tissue level implants with a convergent transepithelial neck exhibit less peri-implant bone loss than bone level implants regardless of the type of prosthesis.

Regenerative periodontal surgery and orthodontic tooth movement in stage IV periodontitis: A retrospective practice-based cohort study

AIM

Evaluation of the effectiveness of regenerative treatment of intra-bony defects in combination with consecutive orthodontic tooth movements in stage IV periodontitis.

MATERIAL AND METHODS

A total of 526 intra-bony defects in 48 patients were analysed after regenerative therapy using collagen-deproteinized bovine bone mineral with or without collagen membrane or enamel matrix derivative followed by orthodontic tooth movement initiated 3 months after surgery. Changes in radiographic bone levels (BL) and probing pocket depths (PPD) were evaluated after 1 year and up to 4 years.

RESULTS

Tooth loss amounted to 0.57%. Mean BL gain was 4.67 mm (±2.5 mm) after 1 year and 4.85 mm (±2.55 mm) after up to 4 years. Mean PPD was significantly reduced from 6.00 mm (±2.09 mm) at baseline to 3.45 mm (±1.2 mm) after 1 year, and to 3.12 mm (±1.36 mm) after 2-4 years. Pocket closure (PPD ≤4 mm) was accomplished in 87% of all defects. Adjunctive antibiotic therapy did not show any statistically significant impact on treatment outcomes.

CONCLUSIONS

Within the limits of this retrospective study design, the findings suggest that the combination of regenerative treatment and consecutive orthodontic tooth movements resulted in favourable results up to 4 years.

Peri-implant marginal bone loss reduction with platform-switching components: 5-Year post-loading results of an equivalence randomized clinical trial

AIM

To compare the clinical performance and marginal bone levels of implants restored with platform-switching (PS) or platform-matching (PM) abutments.

MATERIALS AND METHODS

Adult patients missing two or more adjacent teeth in the posterior mandible received 2-4 CAMLOG SCREW-LINE implants and were randomly allocated to the PM or PS group, receiving the corresponding prosthetic components from surgery onwards. Implants were conventionally loaded with single cemented crowns. Patients were followed annually for 5 years. Outcome measures were marginal bone level changes, implant survival, performance of the prosthetic components and clinical parameters plaque index, sulcus bleeding index and pocket probing depth.

RESULTS

Thirty-three patients received 72 implants in the PM group, and thirty-five patients received 74 implants in the PS group. Sixty patients attended the final appointment, 31 had received PS components and 29 had received PM components with 65 and 63 implants, respectively. Global survival rate was 96.6% with no differences between groups (p = 0.647). After 5 years of functional loading, PS restored implants presented 0.23mm (95% CI: [0.03, 0.43], p = 0.025) lower marginal bone level changes. The two groups were declared non-equivalent.

CONCLUSION

Patients requiring implant supported restorations in healed bounded or free end edentulous gaps of the mandible benefit from the use of PS components in terms of peri-implant marginal bone level maintenance, though it may not be clinically noticeable.

Subcrestal placement of dental implants with an internal conical connection of 0.5 mm versus 1.5 mm: Three-year after loading results of a multicentre within-person randomised controlled trial

PURPOSE

To evaluate whether there are some clinical benefits by placing single dental implants either 0.5 mm or 1.5 mm subcrestally in healed bone crests.

MATERIALS AND METHODS

Sixty partially edentulous patients requiring two single implant-supported crowns had both sites randomly allocated either to 0.5-mm or 1.5-mm subcrestal implant placement according to a split-mouth design at six centres and submerged in aesthetic areas or non-submerged in non-aesthetic areas for 3 months. Provisional acrylic crowns were delivered and were replaced after 2 months by definitive metal-ceramic crowns. Patients were followed to 3 years after loading. Outcome measures were: crown and implant failures, complications, aesthetics assessed using the pink aesthetic score (PES), peri-implant marginal bone level changes and patient preference, recorded by blinded assessors.

RESULTS

One patient dropped out. One patient lost both implants for infection at impression taking. Seven complications affected seven patients of the 0.5-mm group and four complications affected four patients of the 1.5-mm subcrestal group. Three patients had complications at both implants. There were no statistically significant differences for complications between group (OR = 4; 95% CI: 0.45 to 35.79; P (McNemar test) = 0.375). At delivery of definitive crowns, 2 months after loading, the mean PES was 11.22 ± 1.91 and 11.12 ± 1.59 for the 0.5- and 1.5-mm groups, respectively. At 1 year after loading, the mean PES was 12.09 ± 1.66 and 12.10 ± 1.52 for the 0.5- and 1.5-mm groups, respectively. At 3 years after loading, the mean PES was 11.99 ± 1.94 and 12.19 ± 1.78 for the 0.5- and 1.5-mm groups, respectively. There were no statistically significant differences between the two groups at 2 months (P = 0.626), at 1 year (P = 0.920) or at 3 years (P = 0.296). One year after loading, patients of the 0.5-mm group lost on average 0.21 ± 0.51 mm and those of the 1.5-mm group 0.11 ± 0.36 mm, the difference being not statistically significant (difference = 0.10 mm; 95% CI: -0.01 to 0.20; P = 0.078). Three years after loading, patients of the 0.5-mm group lost on average 0.34 ± 0.87 mm and those of the 1.5-mm group 0.19 ± 0.54 mm, the difference being statistically significant (difference = 0.15 mm; 95% CI: 0.00 to 0.30; P = 0.046). Patients did not prefer any depth of the implant placement over the other. There were no differences in outcomes between centres.

CONCLUSIONS

No appreciable clinical differences were noticed when placing implants 0.5 mm or 1.5 mm subcrestally; therefore clinicians can do as they prefer.

Peri-implant tissue healing at implants with different designs and placement protocols: An experimental study in dogs

OBJECTIVES

To compare the peri-implant tissue response to subcrestal or crestal placement of implants with or without "platform-switched" implant/abutment connections.

MATERIAL AND METHODS

On each side of the mandible in six Labrador dogs, two "platform-switched" (PS) implants and two implants with matching implant/abutment diameters (PM) were placed in a crestal or a 1.5 mm subcrestal position. Sulcus formers/abutments were connected, baseline radiographs obtained and the distance between the abutment-fixture junction (A/F) and the marginal bone level (B) was determined. Five months later, radiographic and clinical examinations were repeated and biopsies were obtained and processed for histological analysis.

RESULTS

The radiographic analysis showed that marginal bone level changes occurred during the first observation period (13 weeks). PS-implants showed minor marginal bone level alterations during the full observation period (20 weeks), regardless of placement depth. For PM-implants, placement had a significant impact on bone level changes; crestal placement resulted in a mean bone loss of 0.4 mm and subcrestal placement in a 1.5 mm bone loss. The histometric measurements resulted in a distance A/F-B of 0.6 and 0.0 mm for PS implants, placed in a crestal or subcrestal position, respectively. The corresponding distance at PM-implants was 1.5 mm irrespective of placement protocol. The peri-implant mucosa was thicker at subcrestally placed implants as compared to a crestal placement.

CONCLUSIONS

Bone remodeling occurred within the early healing phase. During the full 20 weeks of observation, PS-implants demonstrated significantly less crestal bone loss compared to PM-implants.

Adapting the vertical position of implants with a conical connection in relation to soft tissue thickness prevents early implant surface exposure: A 2-year prospective intra-subject comparison

AIM

To evaluate the effect of soft tissue thickness on bone remodelling and to investigate whether implant surface exposure can be avoided by adapting the vertical implant position in relation to the soft tissue thickness.

MATERIALS AND METHODS

Twenty-five patients received two non-splinted implants supporting an overdenture in the mandible. Soft tissue thickness was measured using bone sounding and ultrasonically. One implant was installed equicrestally (control), and the vertical position of the second implant was adapted to the site-specific soft tissue thickness (test). Crestal bone levels were determined on digital peri-apical radiographs and compared with baseline (implant placement).

RESULTS

Twenty-five patients were consecutively treated. No implants failed during the follow-up. A significant correlation was observed between soft tissue thickness and bone level alterations after 6 months (ultrasound ICC = 0.610; bone sounding ICC = 0.641) with inferior bone levels for equicrestal implants when thin tissues are present. Subcrestal implants showed significantly better bone levels after 6-month (n = 24, 0.04 mm versus 0.72 mm; p < .001), 1-year (n = 24, 0.03 mm versus 0.77 mm; p < .001) and 2-year follow-up (n = 24, 0.04 mm versus 0.73 mm; p < .001).

CONCLUSION

Initial bone remodelling was affected by soft tissue thickness. Anticipating biologic width re-establishment by adapting the vertical position of the implant seemed highly successful to avoid implant surface exposure.

1-year results from a split-mouth randomised controlled pilot trial comparing implants with 0.75 mm of machined collar placed at bone level or supracrestally

PURPOSE

The present study evaluated the hypothesis that implants inserted at bone level or supracrestally have different outcomes in single tooth replacements against the alternative hypothesis of no difference.

MATERIALS AND METHODS

This study was designed as a randomised, split-mouth, controlled pilot trial. Ten patients, each missing two bicuspids or molars, were treated with 20 implants featuring 0.75 mm of machined collar. Each patient randomly received one implant inserted at bone level (BL) and one inserted 0.75 mm to 1 mm above the alveolar crest (SC), measured with a periodontal probe during surgery. All the implants were inserted into healed healthy bone with an insertion torque ranging between 35 Ncm and 45 Ncm. Both implants were loaded with screw-retained acrylic-resin temporary crowns 3 months after implant insertion and 3 months later with screw-retained zirconia-ceramic definitive crowns. Outcome measures were implant/crown failures, biological and prosthetic complications, radiographic marginal bone level changes (MBL), probing pocket depth (PPD) and bleeding on probing (BOP). Clinical data were collected at baseline (implant insertion) and 1 year after implant placement (9 months after initial loading).

RESULTS

After 1 year of follow-up, no patients dropped out, no implants failed, and no complications occurred. The mean MBL at the 1-year follow-up was 0.28 ± 0.21 mm in the SC group and 0.93 ± 0.37 mm in the BL group. While the difference in MBL was statistically significant between the two treatment groups (difference 0.65 ± 0.34; 95% CI = 0.59 to 1.01; P = 0.0001), the soft-tissue parameters were not statistically different. The mean PPD was 2.63 ± 2.4 in the SC group and 2.40 ± 0.70 in the BL group (P = 0.419) and mean BOP was 0.50 ± 0.71 in the SC group and 0.40 ± 0.70 in the BL group (P = 0.754).

CONCLUSIONS

The smooth-collar implants inserted supracrestally showed 0.7 mm less radiographic marginal bone loss compared with implants inserted at the bone level 9 months after loading.

Effectiveness of enamel matrix derivative on the clinical and microbiological outcomes following surgical regenerative treatment of peri-implantitis. A randomized controlled trial

OBJECTIVE

This randomized clinical trial aimed at comparing radiological, clinical and microbial effects of surgical treatment of peri-implantitis alone or in combination with enamel matrix derivative (EMD).

METHODS

Twenty-six subjects were treated with open flap debridement and decontamination of the implant surfaces with gauze and saline preceding adjunctive EMD or no EMD. Bone level (BL) change was primary outcome and secondary outcomes were changes in pocket depth (PD), plaque, pus, bleeding and the microbiota of the peri-implant biofilm analyzed by the Human Oral Microbe Identification Microarray over a time period of 12 months.

RESULTS

In multivariate modelling, increased marginal BL at implant site was significantly associated with EMD, the number of osseous walls in the peri-implant bone defect and a Gram+/aerobic microbial flora, whereas reduced BL was associated with a Gram-/anaerobic microbial flora and presence of bleeding and pus, with a cross-validated predictive capacity (Q(2) ) of 36.4%. Similar, but statistically non-significant, trends were seen for BL, PD, plaque, pus and bleeding in univariate analysis.

CONCLUSION

Adjunctive EMD to surgical treatment of peri-implantitis was associated with prevalence of Gram+/aerobic bacteria during the follow-up period and increased marginal BL 12 months after treatment.

Effect of platform switching on crestal bone levels around implants in the posterior mandible: 3 years results from a multicentre randomized clinical trial

Objective

Evaluation of differences in the clinical performance and crestal bone levels between implants restored with single crowns with platform‐matched or platform‐switched abutments after 3 years.

Material and Methods

The study enrolled adult patients missing two or more adjacent teeth in the posterior mandible with natural teeth mesial to the implant site. Randomization followed open‐flap implant insertion and the corresponding matching or switching healing abutments placed at surgery. Conventional loading was made with cemented crowns. Clinical follow‐up took place annually after loading up to 3 years. Bone level changes were measured in standardized radiographs as the variation in crestal bone from one evaluation to the next.

Results

Sixty‐three patients with a total of 135 implants (66 platform matching, 69 platform switching) were analysed. From surgery to 36 months, mean bone loss was 0.28 ± 0.56 mm for the platform‐switching group and 0.68 ± 0.64 mm for the platform‐matching group. A statistically significant difference was found between groups (p = 0.002) with an estimate of 0.39 mm (0.15–0.64, 95% CI) in favour of platform switching.

Conclusions

After 3 years, platform‐switching restorations showed a significant effect in the preservation of marginal bone levels compared to platform‐matching restorations.

Radiographic evaluation of conical tapered platform-switched implants in the posterior mandible: 1-year results of a two-center prospective study

OBJECTIVE

Long-term success of dental implants depends on healthy peri-implant soft tissues and adequate bone levels. This prospective study aims to assess bone level changes around implants with internal conical connection and platform-switching abutments in the posterior mandible.

MATERIAL AND METHODS

Adult patients missing at least two teeth in the posterior mandible and with a natural tooth mesial to the implant site received two or three adjacent internal conical connection implants. After a minimum transmucosal healing period of 8 weeks, single crown restorations were cemented over platform-switching abutments. Changes in marginal bone levels were measured in standardized periapical radiographs from surgery and loading (baseline) to 12 months post-loading.

RESULTS

Twenty-four patients received 52 implants. Bone remodeling took place between surgery and loading (-0.53 ± 0.40 mm). From loading to 12 months, there was a mean bone gain of 0.12 ± 0.42 mm which occurred mainly in the first 6 months after prosthesis delivery (0.11 ± 0.36 mm) and stabilized afterward. A total of 71.7% of all implants presented bone preservation or gain. No implant was lost at 1 year and the success rate was 100%. Patient inquiry revealed high satisfaction.

CONCLUSION

Internal conical connection implants with platform-switching abutments presented high success rate and enhancement or preservation of marginal bone levels after 1 year of loading.

Fresh-Socket Implants of Different Collar Length: Clinical Evaluation in the Aesthetic Zone

BACKGROUND

The aim of this clinical study was to compare clinical evaluations of implants in the aesthetic zone with smooth collars of different length.

MATERIALS AND METHODS

Sixty-six patients requiring extractions of one, two, or three teeth in the aesthetic zone of the maxilla were enrolled in this study. Ninety-four implants were positioned and were loaded immediately after tooth extraction. Forty-seven implants with a short smooth collar of 0.5 mm (SCI) and 47 implants with a long smooth collar of 1.8 mm (LCI) were utilized in this study and were placed using a nonsubmerged approach. Clinical (gingival index, modified plaque index, modified bleeding index, probing depth, gingival recession) and intraoral digital radiographic parameters were measured at baseline and after 6, 12, 24, and 36 months of healing to evaluate crestal bone loss levels over time.

RESULTS

After a follow-up period of 36 months, a survival rate of 100% was reported. The SCI group showed a mean bone loss of 1.07 ± 0.38 mm at 12 months and 1.09 ± 0.38 mm at 36 months. The LCI group showed a mean bone loss of 0.46 ± 0.14 mm at 12 months and 0.53 ± 0.12 mm at 36 months. After the 36-month follow-up period, both groups showed stable bone levels over time. Statistically significant differences were found between groups (p < .05). No statistically significant differences were found between SCI and LCI groups with regard to clinical parameters over time.

CONCLUSIONS

This study revealed significant differences in radiographically observed marginal bone loss between the two types of implant with different smooth-collar lengths, but no differences in gingival vestibular margin outcome were observed.

Ongoing Crestal Bone Loss around Implants Subjected to Computer-Guided Flapless Surgery and Immediate Loading Using the All-on-4® Concept

BACKGROUND

The All-on-4(®) concept is widely applied for full-arch rehabilitations, using two tilted and two axially loaded implants in order to overcome anatomical constraints.

PURPOSE

The aim of this study was to assess the survival and individual success of implants immediately loaded with an All-on-4 full-arch screw-retained prosthetic bridge in fully edentulous mandibles or maxillae over up to 3 years.

MATERIALS AND METHODS

In total, 20 patients with atrophic jaws (9 maxillae, 11 mandibles) were treated with computer-guided flapless surgery and immediately provided with a provisional bridge. The final prosthesis was delivered after 6 months. In total, 80 TiUnite(™) Brånemark implants were placed. Radiographs were taken after surgery and 1 and 3 years later.

RESULTS

A 3-year survival rate of 100% was seen for all implants, both in lower and in upper jaw. None of the temporary or definite prostheses were lost over the follow-up period of 3 years. After 1 year, the mean bone loss was 1.13 mm (SD 0.94; range -0.1 to 3.8), and after 3 years, it was 1.61 mm (SD 1.40; range 0 to 5). The mean bone loss between the 1-year and 3-year follow-ups was 0.48 mm (SD 0.66; range -1.2 to 3.6). This difference was statistically significant (p < .001), indicative of ongoing bone loss. Twenty-six percent of the implants had bone loss above 1.5 mm after 1 year, but after 3 years, 30% of the implants had already lost more than 1.9 mm.

CONCLUSION

The implant and prosthetic survival was 100%, and patients benefited from the All-on-4 treatment. However, unacceptable ongoing bone loss was seen in 49.2% of the patients; this may be a warning sign for future problems and needs clinical attention. Overloading and surgery-related aspects need to be investigated as potential explanations.