Comparison of Peri‐Implant Soft Tissue Parameters and Crestal Bone Loss Around Immediately Loaded and Delayed Loaded Implants in Smokers and Non‐Smokers: 5‐Year Follow‐Up Results

Background: The aim of this study is to compare peri‐implant soft tissue parameters (plaque index [PI], bleeding on probing [BOP], and probing depth [PD] ≥4 mm) and crestal bone loss (CBL) around immediately loaded (IL) and delayed loaded (DL) implants in smokers and non‐smokers. Methods: Thirty‐one patients with IL implants (16 smokers and 15 non‐smokers) and 30 patients with DL implants (17 smokers and 13 non‐smokers) were included. Personal data regarding age, sex, and duration and daily frequency of smoking were gathered using a questionnaire. Peri‐implant PI, BOP, and PD ≥4 mm were recorded, and mesial and distal CBL was measured on standardized digital radiographs. Multiple group comparisons were performed using the Bonferroni post hoc test (P <0.05). Results: All implants replaced mandibular premolars or molars. Mean scores of PI (P <0.05) and PD ≥4 mm (P <0.05) were statistically significantly higher in smokers compared with non‐smokers in patients with IL and DL dental implants. The mean score of BOP (P <0.05) was statistically significantly higher in non‐smokers compared with smokers in both groups. CBL (P <0.05) was statistically significantly higher in smokers compared with non‐smokers in both groups. There was no statistically significant difference in PI, BOP, PD ≥4 mm, and total CBL among smokers with IL and DL implants. Conclusions: Tobacco smoking enhances peri‐implant soft tissue inflammation and CBL around IL and DL implants. Loading protocol did not show a significant effect on peri‐implant hard and soft tissue status in healthy smokers and non‐smokers.     

Influence of Implant Neck Surface and Placement Depth on Crestal Bone Changes Around Platform‐Switched Implants: A Clinical and Radiographic Study in Dogs

Background: The aim of this animal study is to analyze bone remodeling around platform‐switching (PS) implants with and without a machined (MACH) collar placed at different levels in relation to the crestal bone in a canine model. Methods: All mandibular premolars and first molars were extracted in five dogs. After 6 months, grit‐blasted acid‐etched (GBAE) PS implants with and without a MACH neck were randomly inserted in each hemimandible, positioning the implant‐abutment interface in either a supracrestal (+1.5 mm), equicrestal, or subcrestal (?1.5 mm) position, and healing abutments were connected. Implant abutments were dis/reconnected at 12, 14, 16, and 18 weeks after implant placement. After 6 months of healing, animals were sacrificed. Clinical parameters and periapical radiographs were registered on the day of implant placement, at 2 months, at every abutment dis/reconnection, and at sacrifice. Crestal bone changes were calculated and defined as the primary outcome variable. Results: When crestal bone changes from implant placement to 6 months were compared between MACH and GBAE groups, no significant differences were encountered except for implants placed in an equicrestal position (P = 0.04). However, multivariable regression analysis revealed no significant differences between MACH and GBAE implants placed in a supracrestal (β = ?0.08; P = 0.45), equicrestal (β = ?0.05; P = 0.50), or subcrestal (β = ?0.13; P = 0.19) position. Conclusion: Surface treatment of the implant neck had no significant influence on crestal bone changes around PS implants with and without a MACH collar.     

Efficacy of Using PDGF and Xenograft With or Without Collagen Membrane for Bone Regeneration Around Immediate Implants With Induced Dehiscence‐Type Defects: A Microcomputed Tomographic Study in Dogs

Background: Use of collagen membrane (CM) with xenograft and recombinant human platelet‐derived growth factor (rhPDGF) in guided bone regeneration (GBR) is debatable. The aim of this microcomputed tomographic experiment was to assess the efficacy of using PDGF and xenograft (with or without CM) for GBR around immediate implants with dehiscence defects. Methods: Ten beagle dogs underwent atraumatic bilateral second and fourth premolar extractions from both arches. A standardized dehiscence defect (6 × 3 mm) was created on the buccal bone and immediate implants were placed in distal sockets in each site. Animals were randomly divided into three groups: 1) group 1, xenograft with rhPDGF was placed and covered with CM; 2) group 2, xenograft with rhPDGF was placed over the defects; and 3) group 3, four immediate implants were associated with dehiscence (controls). After 16 weeks, animals were sacrificed and jaw segments were assessed for buccal bone thickness (BBT), buccal bone volume (BBV), vertical bone height (VBH), and bone‐to‐implant contact (BIC) using microcomputed tomography. Results: BBT was higher in group 2 (1.533 ± 0.89 mm) than group 1 (0.745 ± 0.322 mm) (P <0.001) and group 3 (0.257 ± 0.232 mm) (P <0.05). BBV was higher in group 2 (67.87 ± 19.83 mm³) than group 1 (42.47 ± 6.78 mm³) (P <0.05) and group 3 (19.12 ± 4.06 mm³) (P <0.001). VBH was higher in group 2 (6.36 ± 1.37 mm) than group 3 (0.00 ± 0.00 mm) (P <0.001). VBH was higher in group 1 (3.91 ± 2.68 mm) than group 3 (0.00 ± 0.00 mm) (P <0.05). BIC was higher in group 2 (67.25% ± 13.42%) than group 1 (36.25% ± 12.78%) (P <0.05) and group 3 (30.25% ± 7.27%) (P <0.01). Conclusion: GBR around immediate implants with dehiscence defects using PDGF and xenograft alone resulted in higher BBT, BBV, VBH, and BIC than when performed in combination with CM.     

Reconstruction of Severely Atrophied Alveolar Ridges with Calvarial Onlay Bone Grafts and Dental Implants

Objective: Severely atrophied alveolar ridges are most commonly reconstructed with free autologous bone grafts from the iliac crest. The use of these grafts, however, is frequently associated with bone resorption as possible late complication after implant surgery and prosthetic loading. Other donor sites, especially intraoral donor sites, show limited availability. The aim of this present study was to evaluate the clinical and radiographical outcome of alveolar ridge reconstruction with bone from the calvarium and subsequent implant rehabilitation. Patients and Methods: Reconstruction was performed by using calvarial split grafts in case of severe and complex alveolar ridge defects induced by trauma or bone atrophy. Fifteen patients were treated at 19 different intraoral recipient sites (15 sites in the maxilla, four in the mandible). Autologous block grafts were used for combined vertical and horizontal grafting. After a 3‐month healing period, patients received dental implants. A total of 99 dental implants (OsseoSpeed?, Astra Tech AB, Mölndal, Sweden) were inserted and left to heal in a submerged position for 3 months before the prosthetic implant‐based rehabilitation was performed. Results: No donor site complications occurred during or after surgery. At the intraoral recipient sites two infections occurred, leading to partial loss of the grafts. Implant placement, however, was possible in all cases. Two of 99 implants were lost in two patients prior to prosthetic loading. Patients were followed up clinically and radiographically for an average observation period of 28 months. Implant survival rate and success rates were 97.85 and 95.7%, respectively, and a minimal marginal bone loss was documented. Discussion: The low morbidity at the donor sites and the good marginal bone stability in the reconstructed regions indicate that calvarial bone grafts represent a viable treatment alternative to grafts from the iliac crest.     

Occurrence of Progressive Bone Loss Around Anodized Surface Implants and Resorbable Blasting Media Implants: A Retrospective Cohort Study

Background: This study evaluates occurrence of progressive bone loss (PBL) around implants with different implant surfaces. Methods: Retrospective examination of 2,517 implants was performed in 903 patients, including 1,147 anodized‐surface implants in 454 patients and 1,370 resorbable blasting media (RBM)‐surface implants in 449 patients, which were placed from January 2006 to December 2010. Through regular check‐up radiographs and records, presence of PBL (up to >50% of fixture length) was investigated. Implant removal for any reason was regarded a failure. Results: In total, 2,186 implants (979 anodized implants and 1,207 RBM implants) in 793 patients were included in this study. PBL was more frequently observed among anodized implants (n = 36 in 21 patients; 4%) than among RBM implants (n = 19 in 14 patients; 2%), and this difference was statistically significant (P <0.001). Occurrence of PBL was significantly influenced by surface modification and implant diameter (odds ratio [OR] of anodized surface = 4.40, 95% confidence interval [CI] = 1.78 to 10.89, P = 0.001; OR of wide implants = 9.62, 95% CI = 1.13 to 81.68, P = 0.038; determined by mixed‐effects logistic regression analysis with random patient effect). However, total survival rate was significantly influenced by implant diameter and not by surface modification (P = 0.019), although effect of implant diameter was observed to be significant on anodized implants (P = 0.030). Conclusion: Implant surface modification and implant diameter are significantly associated with occurrence of PBL.     

The relative impact of local and endogenous patient-related factors on implant failure up to the abutment stage

Abstract: The aim of the present study was to assess the influence of endogenous and local factors on the occurrence of implant failure up to the abutment stage. The study comprised a group of 399 consecutive patients, which represented the total of patients who had been treated from 1995 to 1997 (with a total of 1263 Brånemark Brån-system^® implants) at the Department of Periodontology of the University Hospital, Catholic University Leuven. For each patient, the medical history was carefully examined. Data collection and analysis were mainly focused on endogenous factors such as hypertension, osteoporosis, hypo- or hyperthyroid function, chemotherapy, diabetes type I or II, Crohn's disease, some local factors (e.g. bone quality, reason for tooth loss) and breach of sterility during surgery. The reason for tooth loss, smoking habits, radiotherapy and other local bone factors (bone quality and quantity) were also recorded. Implant failures were recorded up to the abutment connection. The present study indicated a success rate until this stage of 97.8%. General factors such as heavy smoking, chemotherapy plus poor bone quality increased implant failure rate. Radiotherapy, limited bone volume and claustrophobia, which led to breaching the strict preoperative rules of asepsis, appeared to be the most relevant local factors for early implant failures.     

Influence of Tapered and External Hexagon Connections on Bone Stresses Around Tilted Dental Implants: Three‐Dimensional Finite Element Method With Statistical Analysis

Background: The purpose of this study is to analyze the tension distribution on bone tissue around implants with different angulations (0°, 17°, and 30°) and connections (external hexagon and tapered) through the use of three‐dimensional finite element and statistical analyses. Methods: Twelve different configurations of three‐dimensional finite element models, including three inclinations of the implants (0°, 17°, and 30°), two connections (an external hexagon and a tapered), and two load applications (axial and oblique), were simulated. The maximum principal stress values for cortical bone were measured at the mesial, distal, buccal, and lingual regions around the implant for each analyzed situation, totaling 48 groups. Loads of 200 and 100 N were applied at the occlusal surface in the axial and oblique directions, respectively. Maximum principal stress values were measured at the bone crest and statistically analyzed using analysis of variance. Stress patterns in the bone tissue around the implant were analyzed qualitatively. Results: The results demonstrated that under the oblique loading process, the external hexagon connection showed significantly higher stress concentrations in the bone tissue (P <0.05) compared with the tapered connection. Moreover, the buccal and mesial regions of the cortical bone concentrated significantly higher stress (P <0.005) to the external hexagon implant type. Under the oblique loading direction, the increased external hexagon implant angulation induced a significantly higher stress concentration (P = 0.045). Conclusions: The study results show that: 1) the oblique load was more damaging to bone tissue, mainly when associated with external hexagon implants; and 2) there was a higher stress concentration on the buccal region in comparison to all other regions under oblique load.     

In vivo performance of zirconia and titanium implants: a histomorphometric study in mini pig maxillae

Objectives: To compare the bone tissue response to surface‐modified zirconia (ZrO₂) and titanium implants. Methods: Cylindrical low‐pressure injection moulded zirconia (ZrO₂) implants were produced with an acid‐etched surface. Titanium implants with identical shape, sandblasted and acid‐etched surface (SLA) served as controls. Eighteen adult miniature pigs received both implant types in the maxilla 6 months after extraction of the canines and incisors. The animals were euthanized after 4, 8 and 12 weeks and 16 zirconia and 18 titanium implants with the surrounding tissue were retrieved, embedded in methylmethacrylate and stained with Giemsa–Eosin. The stained sections were digitized and histomorphometrically analysed with regard to peri‐implant bone density (bone volume/total volume) and bone–implant contact (BIC) ratio. Statistical analysis was performed using Mann–Whitney' U‐test. Results: Histomorphometrical analysis showed direct osseous integration for both materials. ZrO₂ implants revealed mean peri‐implant bone density values of 60.4% (SD ± 9.9) at 4 weeks, 65.4% (SD ± 13.8) at 8 weeks, and 63.3% (SD ± 21.5) at 12 weeks after implantation, whereas Ti‐SLA implants demonstrated mean values of 61.1% (SD ± 6.2), 63.6% (SD ± 6.8) and 68.2% (SD ± 5.8) at corresponding time intervals. Concerning the BIC ratio, the mean values for ZrO₂ ranged between 67.1% (SD ± 21.1) and 70% (SD ± 14.5) and for Ti‐SLA between 64.7% (SD ± 9.4) and 83.7% (SD ± 10.3). For the two parameters investigated, no significant differences between both types of implants could be detected at any time point. Conclusion: The results indicate that there was no difference in osseointegration between ZrO₂ implants and Ti‐SLA controls regarding peri‐implant bone density and BIC ratio. To cite this article :
Gahlert M, Roehling S, Sprecher CM, Kniha H, Milz S, Bormann K. In vivo performance of zirconia and titanium implants: a histomorphometric study in mini pig maxillae.
Clin. Oral Impl. Res. 23 , 2012; 281–286.
doi: 10.1111/j.1600‐0501.2011.02157.x     

Bone tissue formation adjacent to implants placed in fresh extraction sockets: an experimental study in dogs

OBJECTIVE: To study the healing of marginal defects that occurred at implants placed in a healed ridge or in fresh extraction sockets. MATERIAL AND METHODS: Six dogs were used. The right side of the mandible was used in the first part of the study. The first, second premolars and first molars were extracted. After 3 months of healing the bone was prepared for implant installation in these premolar and molar sites. The marginal 5 mm of each recipient site was widened with a conical drill. Following implant installation a gap of varying dimension occurred around the titanium rod (artificial defect (A) sites). At this interval the third and fourth premolars were extracted and implants were installed in the distal socket of the two teeth (natural defect (N) sites). The flaps were sutured to allow non-submerged healing. After 2 months, the procedures were repeated in the left side. Two months later the animals were euthanized, and biopsies were obtained and prepared for histological examination. RESULTS: The length of the zone of de novo'bone-to-implant contact' in the defect region was longer at the A sites than at the N sites both at the 2- and the 4-month interval. Further, while after 4 months of healing the marginal bone crest at the A sites was located close to the abutment/fixture junction, at the N sites a marked reduction of the height of the bone crest was documented. Hence, most A site defects became completely resolved whereas healing of the N site defects was incomplete. CONCLUSION: The process of bone modeling and remodeling at an implant placed in a fresh extraction socket differs from the resolution of marginal defects that may occur following implant installation in a healed ridge.     

Outcomes of Dental Implants in Osteoporotic Patients. A Literature Review

Purpose: This article reviews available data on the outcome of dental implants in osteoporotic patients.
Materials and Methods: A search was performed in PubMed and completed in July 2007. The keywords "dental AND implants AND osteoporosis,""dental AND implants AND age,""dental AND implants AND gender," and "dental AND implants AND bone AND quality," with no limitations for language or year of publication, resulted in 82, 598, 94, and 541 articles, respectively. After abstract scanning (in case of doubt the article was read), 39 nonreview articles studying dental implant outcomes in osteoporotic/osteopenic subjects remained for our review. The bibliographies of the 39 articles were also inspected, but no additional studies were identified.
Results: Thirteen of 16 animal studies found lower osseointegration rates in osteoporotic/osteopenic bone than in normal bone. Six in nine clinical reports mention success. Eight of 12 studies in humans support the applicability of dental implants in osteoporotic patients.
Conclusions: There are no data to contraindicate the use of dental implants in osteoporotic patients; however, a proper adjustment of the surgical technique and a longer healing period may be considered in order to achieve osseointegration. Data on the use of biphosphonates in osteoporotic patients and implant outcomes are very limited, and no conclusions can be drawn. In addition, large prospective studies investigating the long-term success of dental implants in osteoporotic individuals are required.