The International Journal of Oral & Maxillofacial Implants, 04/2005

Purpose: The overall goal of this project was to evaluate culture-expanded bone-marrow-derived mesenchymal stem cells (MSCs) for alveolar bone repair in terms of safety and potential efficacy. Materials and Methods: MSCs isolated from bone marrow aspirations were culture-expanded and cryopreserved. Thawed cells were incubated with 3.2 3 5-mm hydroxyapatite/tricalcium phosphate (HA/TCP) cylinders in a closed system containing 5 3 107 cells/mL. Cells alone, cell-free constructs, or cell-loaded constructs were rinsed in saline and implanted in extraction sockets in the mandibular second and fourth premolar sites of 14 beagle dogs. Acute reactions were evaluated histologically after 7 or 21 days, and bone formation was examined after 49 days. Results: Neither implanted MSC-related inflammation nor ectopic osteogenesis was observed. At 7 and 21 days, dil-labeled canine MSCs were found in more than 80% of the implant sites. Few canine MSCs were found in neighboring tissue. Mild inflammation present at 7 days diminished by 21 days. After 49 days, measured bone formation was 34%, 25%, and 35% for cell-loaded, cell-free, and untreated sockets, respectively (P .05). At 21 days, bone formation was evident in all sites. Wound dehiscence was a complication associated with cell exclusionary membranes and resulted in local inflammation. Discussion: The extraction model indicates the safety of MSCs implanted adherent to HA/TCP. Local bone repair occurred in the absence of nonspecific differentiation or migration with distant osteogenesis. Conclusions: An alveolar socket model may be an appropriate model for initial clinical investigation of MSC-mediated bone repair.

Purpose: Implant placement in the posterior maxilla may often be contraindicated because of insufficient bone volume and the presence of the maxillary sinus. In these situations, sinus floor lifting and grafting frequently have been proposed as the best treatment. The aim of this study was to compare histologically the use of 100% autogenous bone versus a combination of autogenous bone and cortico-cancellous pig bone for maxillary sinus augmentation. Materials and Methods: Eighteen patients requiring bilateral maxillary sinus augmentation were selected for this study. Bone for grafting was harvested from the iliac crest. Each patient received 100% autogenous bone in 1 randomly selected sinus (control side) and a 1:1 mixture of autogenous bone and corticocancellous pig bone particles in the contralateral sinus (test side). Five months after the augmentation procedure, bone biopsy specimens were taken at the time of implant placement. Results: No complications were observed during the surgical procedures; all patients healed uneventfully. No signs or symptoms of maxillary sinus disease were observed during the 5 months after surgery. No significant differences in bone percentages were observed in the bone biopsies from test and control sides. Discussion and Conclusion: It could be concluded from this study that corticocancellous pig bone particles can be successfully used in a 1:1 mixture with autogenous bone from the iliac crest for maxillary sinus augmentation in cases of severely atrophic maxilla.

Purpose: The purpose of this study was to assess the bone mineral density changes after bone regeneration therapy using xenogeneic demineralized freeze-dried bone graft (DFDBG) plus platelet-rich plasma (PRP) and DFDBG alone in 3-wall peri-implant defects in dogs. Materials and Methods: The mandibular premolars and molars of 9 adult hound dogs were removed surgically, and 90 sites were prepared for implant placement. Before implant placement, a total of 162 mesial and distal 3-wall peri-implant defects were surgically created. Defects were randomly assigned to three groups: DFDBG + PRP, DFDBG alone, and no treatment. Animals were sacrificed at 1, 2, and 3 months, and specimens were subjected to bone mineral density (BMD) and bone mineral content (BMC) analysis with a peripheral dual x-ray absorptiometry densitometer. Results: The effect of treatment on BMD and BMC differed significantly by month of sacrifice (P = .030 and P = .035 for the month-by-treatment interactions, respectively). BMD differed significantly between peri-implant defects treated with DFDBG alone and untreated defects at 3 months (mean BMD of 0.6667 for DFDBG alone versus 0.5606 for untreated defects; P .001). BMC also differed significantly between peri-implant defects treated with DFDBG alone and untreated defects at 3 months (mean BMC of 0.0276 for DFDBG alone versus 0.0236 for untreated defects; P = .001). No other pairwise comparison of the treatments within each month of sacrifice or at the overall treatment effect across all three months demonstrated significant differences. Discussion: PRP has been proposed as an autogenous source of growth factors, which may increase the speed and completeness of healing. This study did not demonstrate a significant improvement in BMD or BMC when PRP was combined with DFDBG. Defects where grafting material was used, either with or without PRP, did demonstrate slightly greater BMD and BMC than those left untreated. Conclusion: This study found that the addition of PRP to xenogeneic bone grafts did not significantly alter BMD or graft maturity levels in this animal model.

Purpose: Since natural dental arches usually form Monson or Spee occlusal curvatures among the posterior teeth, they tend to incline in mesial and lingual directions. The purpose of this study was to examine the biomechanical rationale for placing implants according to these curvatures in the mandibular posterior region. Materials and Methods: A 3-dimensional finite element model was created in which 2 implants were placed in the mandibular molar area. Stress distribution in the bone around the implants was analyzed under different distal implant inclinations. Results: Stress in the cervical area of the mesial and distal implants and the surrounding bone was higher when the implants were placed parallel to each other compared to when the distal implant was placed with a mesial or mesiolingual inclination. Discussion: The slightly smaller effect of a mesiolingual inclination compared to a mesial inclination can be explained by the large cantilever on the buccal side of the superstructure. Conclusion: Within the limitations of this study, it was suggested that there is a biomechanical rationale for placing implants in the posterior mandible area with a mesial inclination similar to that of natural teeth. It was also suggested that too much lingual inclination can put the implant at risk of overload.

Purpose: To assess histomorphometric parameters of dental implants placed in partially edentulous maxillae of minipigs. Materials and Methods: In 9 minipigs, 6 XiVE implants were placed on each side of the maxilla, either after implant site preparation by an osteotome technique or by spiral drills. The implants were restored with fixed provisional restorations and loaded either immediately or after healing periods of up to 5 months. After a loading period of 6 months, the animals were sacrificed and the implants were retrieved together with the adjacent bone. Histologic specimens were prepared and bone-to-implant contact (BIC) ratio, interthread bone area, and peri-implant bone area were determined. Results: An analysis of variance revealed that the BIC ratio on the palatal side was significantly influenced by the preparation technique of the implant site (P = .001) and by the healing period (P = .02). After implant site preparation by an osteotome technique, higher BIC values were achieved for implants that were loaded either immediately or after healing periods of 1 to 3 months. After healing periods of 4 to 5 months, implant site preparation with spiral drills showed slightly better results in regard to BIC. Interthread bone area and peri-implant bone area did not differ significantly statistically for the 2 implant placement techniques and the 3 healing periods. Discussion and Conclusion: After 6 months of functional loading in the maxilla, successful immediately loaded implants performed the same as implants subjected to an unloaded healing period prior to loading as far as histomorphometric data were concerned. Prospective randomized clinical studies should be carried out in humans to compare immediate loading to loading after an unloaded healing phase.

Purpose: The aim of the present study was to analyze the possible impact of clinical status, presence and severity of inflammation, and loading on nitric oxide (NO) metabolism around mandibular dental implants. Materials and Methods: A total of 34 implants in 17 patients, loaded either early (EL) or after a delay (DL), were classified according to the presence and severity of clinical inflammation in the peri-implant sites. Clinical parameters were recorded, peri-implant sulcular fluid (PISF) samples were obtained, and PISF nitrite levels were spectrophotometrically determined. Clinical measurements and nitrite analysis were repeated at 1, 3, 6, and 9 months postloading at available sites. Results: Compared to noninflamed sites, inflamed sites demonstrated higher mean total nitrite levels (P = .032) that tended to increase with the severity of inflammation at both EL and DL implants. At noninflamed sites, EL implants provided significantly higher PISF volume than DL implants (P = .001). At noninflamed sites, EL implants revealed higher total nitrite levels; on the contrary, at inflamed sites, DL implants revealed higher total nitrite levels. In general, nitrite levels demonstrated a pattern of decrease followed by an increase during follow-up. Discussion: Increased NO production with the presence and the severity of inflammation supports the contribution of NO in the peri-implant inflammatory process. Loading is also likely to have an impact on NO metabolism, which suggests a role for NO in remodeling and adaptation of bone around dental implants. Conclusion: Besides the presence of inflammation, the severity of inflammation and loading also seem to have an impact on NO metabolism around dental implants. (50 references)

Purpose: To test the null hypothesis that there is no difference in failure rates between various root-formed osseointegrated dental implant systems after 5 years of loading. Materials and Methods: A search was conducted for all randomized controlled clinical trials (RCTs) comparing different implant systems with a follow-up of 5 years. The Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE, and EMBASE were searched. Several dental journals were also searched by hand. Written contacts were established with authors of the identified RCTs and with more than 55 oral implant manufacturers and personal contacts to identify unpublished RCTs. No language restriction was applied. The last electronic search was conducted on February 1, 2005. Screening of eligible studies, quality assessment, and data extraction were conducted in duplicate. Results were expressed as random effect models using weighted mean differences for continuous outcomes and relative risk for dichotomous outcomes with 95% confidence intervals. Results: Ten RCTs were identified. Four of these RCTs, reporting results from a total of 204 patients, were considered suitable for inclusion. Six different implant types were compared. On a per-patient rather than a per-implant basis, there were no statistically significant differences, with the exception of more marginal bone loss around early loaded Southern implants when compared to early loaded Steri-Oss implants (mean difference -0.35 mm; 95% CI -0.70 to -0.01). However, the difference disappeared in the meta-analysis. Discussion and Conclusions: There were no clinical differences among implant systems. However, these findings are based on only 4 RCTs with few participants. More RCTs should be conducted with larger patient samples.

Purpose: To guide treatment planning by analyzing the rates of dental implant failure to determine associated risk factors. Materials and Methods: All consecutively treated patients from January 1982 until January 2003 were included in a retrospective cohort study, as defined in the hierarchy of evidence for dental implant literature. Data regarding gender, age, implant location, bone quality, bone volume, and medical history were recorded. Correlations between these data and implant survival were calculated to establish relative risk (RR) ratios. Results: Increasing age was strongly associated with the risk of implant failure. Compared to patients younger than 40 years, patients in the 60-to-79 age group had a significantly higher risk of implant failure (RR = 2.24; P .05). Gender, hypertension, coronary artery disease, pulmonary disease, steroid therapy, chemotherapy, and not being on hormone replacement therapy for postmenopausal women were not associated with a significant increase in implant failure. Smoking (RR = 1.56), diabetes (RR = 2.75), head and neck radiation (RR = 2.73), and postmenopausal estrogen therapy (RR = 2.55) were correlated with a significantly increased failure rate. Overall, implant failure was 8.16% in the maxilla and 4.93% in the mandible (P .001). Discussion: Patients who were over age 60, smoked, had a history of diabetes or head and neck radiation, or were postmenopausal and on hormone replacement therapy experienced significantly increased implant failure compared with healthy patients. Conclusion: Overall, dental implant failure is low and there are no absolute contraindications to implant placement. Conditions that were found to be correlated with an increased risk of failure should be considered during treatment planning and factored into the informed consent process. (More than 50 references.)

Purpose: The aim of this study was to investigate the stress distribution in mandibular bone supporting a single or separate multiple implant-retained superstructures. Materials and Methods: Three-dimensional finite element models consisting of the mandibular bone, 8 implants, and 1 or more superstructures were created. Vertical and oblique loads were directed onto the occlusal areas of the superstructures to simulate the maximum intercuspal contacts and working contacts, such as the canine-protected and group function occlusion. Results: The unseparated 1-piece superstructure generated the lowest maximum equivalent stresses in the peri-implant bone, followed by the 2-piece superstructure separated at the midline. For the 3-piece superstructure, which was separated between the canine and the premolar, the maximum stress was lower when the canine on the working side was loaded than when the posterior teeth were loaded. Discussion: Separating the 1-piece superstructure into 2- to 4-piece superstructures increased the mechanical stress around supporting implants. Canine load on the working side is distributed well in 1-piece and 3-piece superstructures. Conclusion: Based on the results of this finite element model study, canine protected occlusion is recommended for 1-piece and 3-piece superstructures. The unseparated superstructure was more effective in relieving stress concentration in the edentulous mandibular bone than the separated superstructures.

Purpose: This study evaluated the stability of implants in 51 patients following a clinical protocol of immediate functional loading. The stability during the first 3 months following implant placement was assessed according to bone type, implant location, and patient gender. Materials and Methods: Twenty-two male and 29 female patients were treated with 344 Brånemark System implants placed in edentulous bone or extraction sites and put into functional loading using the Teeth in a Day protocol. Each implant was tested for primary stability with resonance frequency analysis (RFA) at the time of implant placement, and RFA was performed at examinations 30, 60, and 90 days following surgery. Results: The analysis was based on the 276 implants that were successfully measured using RFA at all postoperative intervals. The clinical implant survival rate was 98.5% for the total population. RFA showed a decrease in bone-implant stability in the first month after implant placement from 70.35 ± 0.5 to 66.38 ± 0.50, followed by increases in stability in the second and third months (68.01 ± 0.50 and 68.82 ± 0.49, respectively), suggesting a process of adaptive bone remodeling around the implant. In general, lower initial stabilities were seen in softer bone types, in the posterior portions of the jaw compared to anterior areas, and in the female population. Discussion and Conclusion: The results of this study suggest an immediate loading protocol should have an undisturbed period of healing for the first 2 months following implant placement. The determination of "predictor" stability levels for different clinical conditions were based on multiple splinted implants, allowing a larger surface area to withstand the distribution of the load. The most significant "predictor" values from a surgical and prosthodontic perspective are those determined in soft bone, in reduced bone, or in areas where lever arms are created as a result of long spans between the implants. (More than 50 references.

Purpose: Bone grafting to repair osseous defects is widely used in dentistry, but little information on how to predict the clinical survival of grafted bone is currently available. As an initial step toward the establishment of formal criteria for predicting the clinical outcome of oral bone grafts, this pilot study sought to determine the relevance of adverse clinical and radiographic parameters as predictor variables for graft survival. Materials and Methods: Eighty patients presenting with a variety of clinical conditions were treated with 83 oral bone grafts. Alloplastic, allogenic, and/or autogenous materials were used with or without barrier membranes. During follow-up appointments at 1 week, 1 month, 3 months, 6 months, 1 year, and 2 years after grafting, a series of clinical and radiographic parameters were used to evaluate the degree of graft integration. The data were then analyzed to determine the prediction accuracy of each variable in relation to the results of the graft. Results: The findings of this clinical study suggest that the variables of (1) graft type, (2) inflammation, (3) infection, (4) fistula, (5) graft exposure, (6) pain, and (7) radiolucency were good indices for predicting graft survival, especially with cumulative data. Discussion: The quality of the prognostic indices appeared to be good and should be further investigated for future applications. Conclusions: The cumulative index, with a sensitivity of 88.9% and a specificity of 93.8%, was the best predictor of clinical outcome. The 1-month and 3-month indices were similar.

Purpose: To compare marginal implant bone loss (MBL), survival, and radiographic evidence of success of dental implants among smokers and nonsmokers. Materials and Methods: Consecutive records of 161 patients (aged 23 to 89 years, mean 57 years) treated with a total of 646 implants between the years 1995 and 1998 were examined. Patients were divided into 3 groups: nonsmokers, moderate smokers, and heavy smokers. Tobacco exposure was calculated by cigarettes per day and by pack-years. Follow-up ranged from 1 to 7 years (mean 3.8 years). Postoperative panoramic radiographs obtained before implant exposure and annually thereafter were analyzed for MBL changes. The influence of smoking and other variables on MBL was analyzed at all implant sites. Results: Generally, smokers had more MBL than nonsmokers (0.153 ± 0.092 mm and 0.047 ± 0.048 mm, respectively; P .001). When each jaw was examined separately, smoking had a greater effect on MBL in the maxilla than in the mandible (0.158 ± 0.171 mm versus 0.146 ± 0.158 mm, respectively; P .001). Furthermore, in the maxilla, heavy smokers had the greatest amount of MBL (0.1897 ± 0.1825 mm), followed by moderate smokers (0.123 ± 0.156 mm) and nonsmokers (0.0460 ± 0.070 mm) (P .001). In the mandible, there was no distinction between heavy and moderate smokers, and both had greater MBL than nonsmokers (P .001). Only 3 of the 646 implants failed; the cumulative survival rate was 99.5%. Overall radiographic success rate was 93.2%. Nonsmokers had a higher radiographic success rate (97.1%) than smokers (87.8%) (P .001). Conclusions: This study demonstrated a relationship between MBL and smoking habits. A higher incidence of MBL was found in the smoking group, and this was more pronounced in the maxilla.

Purpose: The aim of this prospective study was to determine the incidence of neurosensory disturbance and the cumulative survival and success rates of ITI solid-screw implants placed in conjunction with an inferior alveolar nerve (IAN) transposition technique. Materials and Methods: 46 ITI implants were placed in 15 patients following transposition of the IAN. In 4 patients nerve transpositioning was performed bilaterally, so a total of 19 IAN mobilization surgeries were performed. Neurosensory dysfunction was objectively evaluated by using light touch (LT), pain (PT), and 2-point discrimination (2-DT) tests. In addition, patients were asked to answer a short questionnaire to investigate individual feelings of discomfort and advantages related to this surgical technique. The mean follow-up period was 49.1 months (range, 12 to 78 months). Results: The cumulative implant survival and success rates were 95.7% and 90.5%, respectively. Only 2 implants were lost. Neurosensory disturbance (ie, disturbance registered by the LT, PT, and 2-DT tests) was experienced in 4 of 19 cases. However, at the time of data analysis (12 to 78 months after surgery), all patients indicated that they would go through the surgery again. Discussion: The IAN transposition technique, when used in the severely atrophied posterior mandible, allowed placement of implants with adequate length and good initial stabilization. All patients felt that they had received significant benefits from their new prostheses. Conclusion: Based on the results of the present study, it can be concluded that lateral nerve transposition can be used as a surgical procedure to enable ITI implant placement in the severely resorbed posterior mandible. (More than 50 references.)

In restoring periodontally involved hopeless teeth, implant treatment has been widely used with combinations of various grafting techniques or guided bone regeneration. Instead of traditional surgical procedures, forced tooth eruption may be used successfully for implant site development. In this case, the authors orthodontically erupted a hopeless central incisor with an angular bony defect. Subsequently, they placed an implant immediately after tooth extraction and immediately loaded it with a temporary resin restoration.

A mandibular overdenture supported by 2 or 4 endosseous implants has been proven to be a reliable treatment modality for patients suffering from conventional denture problems. However, fabrication of an implant-retained mesostructure to support an overdenture is not possible in all cases. Malpositioning of implants is a common cause of failure in such cases. A case is presented in which a ball attachment caused pain and severe swelling of the floor of the mouth because of the lingual inclination of an endosseous implant. The lingual inclination of the implant was corrected by a segmental osteotomy. Six weeks later, prosthodontic treatment began, and the resultant overdenture supported by a Dolder bar was quite acceptable for the patient.

An implant was removed 6 months after restoration because of peri-implant pathosis. The implant had been placed adjacent to the mandibular right second premolar and close to a periapical lesion of the endodontically treated adjacent first premolar. Along with removal of the failed implant and an apicoectomy of the problem tooth, guided bone regeneration was used to restore the alveolar ridge defect at the site of the failed implant. A replacement implant was placed 6 months later and successfully restored after healing.

Purpose: Following tooth extraction, wound healing is characterized by remodeling and resorption of the alveolar bone at the extraction site. This produces reduction in ridge volume. Medical-grade calcium sulfate hemihydrate (MGCSH) has been proposed as a graft material for extraction sockets to minimize the reduction in ridge volume. The aim of this study was to investigate the influence of MGCSH on the histopathologic pattern of intrasocket regenerated bone and to evaluate histologically the healed MGCSH-grafted extraction socket site at 3 months postextraction. Materials and Methods: MGCSH was grafted in a fresh human extraction socket, and at 3 months a cylindric tissue specimen, 2.5 mm in diameter, was trephined from the previously grafted site and an implant was placed. Non-decalcified specimens were sectioned at a horizontal plane and stained for histologic and histomorphometric evaluation. Results: The mean trabecular area was 58.6% ± 9.2% in the coronal sections, 58.1% ± 6.2% in the middle sections, and 58.3% ± 7.8% in the apical sections. The differences in mean trabecular area between sections were not statistically significant. Discussion: It is significant that the MGCSH underwent complete resorption and replacement by newly formed bone because the most important negative attribute of other graft materials is the resorption time. Moreover, calcium sulfate shows great potential for guided bone regeneration in surgical sites. Conclusion: MGCSH seems to be an acceptable graft material for extraction socket bone regeneration because it is completely resorbable and allows new trabecular bone arrangement in a limited 3-month period.