Nicolas Elian

Screw loosening for standard and wide diameter implants in partially edentulous cases: 3- to 7-year longitudinal data.

Screw loosening is considered to be a common problem with both screw - retained and cemented implant restorations. A wider abutment platform, as well as using a torque driver to tighten specifically designed screws may help prevent this loosening. However, there has been no clinical study evaluating either of these. To longitudinally compare the frequency of screw loosening in standard diameter, (3.75 and 4.0 mm) implant supported prostheses to that of wide diameter, (5.0 and 6.0 mm) implant supported prostheses that were hand tightened, and to evaluate whether using a torque driver would minimize or prevent this problem, if screw loosening occurred. A total of 213 dental implants in 106 patients were included in this prospective longitudinal study. Of the implants 68 were wide diameter and 145 were standard diameter implants. Wide diameter implants showed 5.8% screw loosening, while standard diameter implants showed 14.5% screw loosening after insertion with only hand torquing. When these loose screws were tightened with a torque driver, there was no more loosening of screws. Within the limitations of this study, the wide diameter implants tested showed less screw loosening than the standard diameter implants when hand torqued. Additionally, within the scope of our study, using a torque driver to tighten the screws with the recommended force prevented this loosening from reoccurring in all cases.

Extraction Sockets and Implantation of Hydroxyapatites With Membrane Barriers A Histologic Study

The purpose of this pilot study was to investigate the effect on extraction socket healing when an absorbable hydroxyapatite (AH) and a nonabsorbable anorganic bovine bone mineral (ABB) covered with either an acellular dermal matrix allograft (ADMA) or expanded polytetrafluoroethylene (ePTFE) membrane barrier were left exposed to the oral cavity. Following tooth extraction, a total of 16 sockets in 15 patients with deficient buccal plates of ≥5 mm were randomly divided into 4 treatment groups: 1) AH covered with ADMA, 2) AH covered with an ePTFE membrane, 3) ABB covered with ADMA, and 4) ABB covered with an ePTFE membrane. Primary coverage was not attempted or obtained in any of the 16 treated sockets. Six to 8 months postextraction at the time of implant placement, histologic cores of the treatment sites were obtained. These cores were processed, stained with Stevenel’s blue/van Gieson’s picro fuchsin, and histomorphometrically analyzed. Vital bone, connective tissue and marrow, and residual graft particles were reported as a percentage of the total core. The mean vital bone was 34.5% (AH with ADMA), 41.7% (ABB with ADMA), 27.6% (ePTFE and AH), and 17.8% (ePTFE and ABB). The average percentage of vital bone in the 8 sockets covered with ADAMA was 38% compared with an average percentage vital bone of 22% in the 8 sockets covered with ePTFE membrane barriers. Because of the small number of specimens in the 4 groups, statistical analysis was not possible. However, in this pilot study, ADMA-covered sites resulted in more vital bone present 6 to 8 months postsocket treatment than obtained in the ePTFE-covered sites regardless of bone replacement materials used. Further research is warranted to see if these results show a similar difference in bone-to-implant contact after implant placement.

Effect of Interimplant Distance (2 and 3 mm) on the Height of Interimplant Bone Crest: A Histomorphometric Evaluation

BACKGROUND Implants restored according to a platform-switching concept (implant abutment interface with a reduced diameter relative to the implant platform diameter) present less crestal bone loss than implants restored with a standard protocol. When implants are placed adjacent to one another, this bone loss may combine through overlapping, thereby causing loss of the interproximal height of bone and papilla. The present study compares the effects of two interimplant distances (2 and 3 mm) on bone maintenance when bone-level implants with platform-switching are used. METHODS This study evaluates marginal bone level preservation and soft tissue quality around a bone-level implant after 2 months of healing in minipig mandibles. The primary objective is to evaluate histologically and histomorphometrically the affect that an implant design with a horizontally displaced implant-abutment junction has on the height of the crest of bone, between adjacent implants separated by two different distances. RESULTS Results show that the interproximal bone loss measured from the edge of the implant platform to the bone crest was not different for interimplant distances of 2 or 3 mm. The horizontal position of the bone relative to the microgap on platform level (horizontal component of crestal bone loss) was 0.31 ± 0.3 mm for the 2-mm interimplant distance and 0.57 ± 0.51 mm above the platform 8 weeks after implantation for the 3-mm interimplant distance. CONCLUSIONS This study shows that interimplant bone levels can be maintained at similar levels for 2- and 3-mm distances. The horizontally displaced implant-abutment junction provided for a more coronal position of the first point of bone-implant contact. The study reveals a smaller horizontal component at the crest of bone than has been reported for non-horizontally displaced implant-abutment junctions.

A two-stage full-arch ridge expansion technique: review of the literature and clinical guidelines.

Ridge expansion techniques have been acknowledged to offer several advantages in the correction of ridge deformities. The expanded defect heals in a similar manner to an extraction socket. In selected cases patients can wear their dentures after surgery. Secondary surgical sites are not a prerequisite, and simultaneous implant placement can be achieved during ridge expansion. The limitation of this technique lies in its inability to create bone vertically. Therefore, it is not indicated for the correction of vertical defects. The application of the split ridge expansion technique has been reported in the literature as it pertains to partially edentulous deficient ridges. The purpose of this article was to present the application of the split ridge expansion technique in the fully edentulous maxilla and discuss the distinction between the immediate or one-stage approach and the delayed or two-stage approach. Histologic results are discussed. Two case reports demonstrate the results that can be obtained with this technique.

Unexpected return of sensation following 4.5 years of paresthesia: case report.

Neural damage leads to a transient or persistent alteration, depending on the severity or type of injury sustained. During the last decade, many investigators reported on paresthesia related to dental implants. In this case report, the patient had presented repeatedly with swelling and suppuration, showing typical signs of peri-implantitis. In addition, the implant was placed in proximity to the mental foramen and possibly had traumatized the mental nerve because the patient had had an altered sensation on his left side for the past 4.5 years. After removal of the implant, a significant diminishing of the paresthesia had occurred, described by the patient as a 40% improvement. Further improvement occurred at 6 and 9 months. In this case report, the findings differ from the current literature in that the return of sensation occurred following a prolonged state of paresthesia. This report documents 2 unique findings. First, an area of persistent paresthesia significantly improved 50 months after the initial injury, upon the removal of the offending implant. Second, the placement of another implant in the same vicinity did not result in recurrent paresthesia.

Radiological and micro‐computed tomography analysis of the bone at dental implants inserted 2, 3 and 4 mm apart in a minipig model with platform switching incorporated

BACKGROUND The purpose of this study was to assess the effect of inter-implant distance on interproximal bone utilizing platform switching. Analysis of interproximal bone usually depends on traditional two-dimensional radiographic assessment. Although there has been increased reliability of current techniques, there has been an inability to track bone level changes over time and in three dimensions. Micro-CT has provided three-dimensional imaging that can be used in conjunction with traditional two-dimensional radiographic techniques. METHODS This study was performed on 24 female minipigs. Twelve animals received three implants with an inter-implant distance of 3 mm on one side of the mandible and another three implants on the contra-lateral side, where the implants were placed 2 mm apart creating a split mouth design. Twelve other animals received three implants with an inter-implant distance of 3 mm on one side of the mandible and another three implants on the contra-lateral side, where the implants were placed 4 mm apart creating a split mouth design too. The quantitative evaluation was performed comparatively on radiographs taken at t 0 (immediately after implantation) and at t 8 weeks (after termination). The samples were scanned by micro-computed tomography (μCT) to quantify the first bone to implant contact (fBIC) and bone volume/total volume (BV/TV). Mixed model regressions using the nonparametric Brunner-Langer method were used to determine the effect of inter-implant distance on the measured outcomes. RESULTS The change in bone level was determined using radiography and its mean was 0.05 mm for an inter-implant distance of 3 and 0.00 mm for a 2 mm distance (P = 0.7268). The mean of this outcome was 0.18 mm for the 3 mm and for 4 mm inter-implant distance (P = 0.9500). Micro-computed tomography showed that the fBIC was always located above the reference, 0.27 and 0.20 mm for the comparison of 2-3 mm (P = 0.4622) and 0.49 and 0.34 mm for the inter-implant distance of 3 and 4 mm (P = 0.1699). BV/TV inside the defined parallelepipedic masks reached 82.38% for the 2 mm inter-implant distance and 85.00% for 3 mm, P = 0.8432. For the comparison of the 3-4 mm inter-implant distance, the means were 84.69% and 84.38%, respectively, P = 0.8401. Non-inferiority tests for the smaller inter-implant distances for both comparisons showed similar differences and similar tolerance ranges. CONCLUSION The effect of a smaller interproximal distances between implants on bone level, fBIC and BV/TV assessed by two convergent investigation methods, radiology and μCT, was similar to that of larger distances. Implants can potentially be placed 2 mm apart instead of 3 mm and 3 mm apart instead of 4 mm when platform switching is utilized. Further research with a conventional platform is warranted.

A Histomorphometric Comparison of Bio-Oss Alone Versus Bio-Oss and Platelet-Derived Growth Factor for Sinus Augmentation: A Postsurgical Assessment

The purpose of this study was to assess vital bone formation at 4 to 5 months and 7 to 9 months following sinus augmentation with anorganic bovine bone matrix (ABBM) with and without recombinant human platelet-derived growth factor (rhPDGF). Twenty-four subjects received bilateral sinus elevation surgery with ABBM on one side and ABBM and rhPDGF on the contralateral side. Twelve patients had core sampling at 4 to 5 months and 12 patients at 7 to 9 months postoperatively. In subjects with cores taken at 4 to 5 months, mean vital bone, connective tissue, and residual graft were 11.8%, 54.1%, and 33.6%, respectively, with ABBM alone. Cores of sinuses filled with ABBM and rhPDGF showed mean 21.1% vital bone, 51.4% connective tissue, and 24.8% residual graft. Paired t test showed a statistically significant difference in vital bone. In cores taken at 7 to 9 months, the values for ABBM alone and ABBM + rhPDGF were 21.4% vs 19.5% vital bone, 28.4% vs 44.2% connective tissue, and 40.3% residual graft vs 35.5%. There was no statistically significant difference in vital bone at 7 to 9 months after surgery. Test and control groups showed clinically acceptable levels of vital bone both at 4 to 5 months and 7 to 9 months postsurgery. However, vital bone formation was significantly greater in the 4- to 5-month sections of ABBM + rhPDGF vs the Bio-Oss alone. In the 7- to 9-month specimens, this difference disappeared. More rapid formation of vital bone with the addition of rhPDGF may allow for earlier implant placement.

The use of a xenogeneic collagen matrix at the time of implant placement to increase the volume of buccal soft tissue.

The purpose of this study was to evaluate the efficacy of Mucograft (MG; a porcine-derived purified collagen membrane) to increase the thickness and height of the buccal soft tissue when placed at the time of implant placement in patients with thin or deficient keratinized tissue (KT). The primary endpoint of the study was the change in thickness and height of the buccal KT. Secondary endpoints included stability of the midbuccal soft tissue level; clinician rating of color, texture, and contour of treatment site; probing pocket depths (PPDs); assessment of satisfaction outcome; and patient assessment of pain/discomfort. Thirty-two patients were enrolled and 31 patients completed the study. There were no statistically significant (SS) differences between the MG and control groups for height measures. There was no SS difference for KT thickness (P = .117) between the groups at the final measurement (3 months postsurgery). However, there was an SS difference (P = .009) in favor of the MG group when comparing the difference in presurgical KT thickness to that 3 months postsurgery. Thus, MG was successful (compared to the control) in increasing the buccal KT. There were no SS differences between the groups for any of the other endpoints, including color, texture, contour, and pain assessment at any visit or successful outcome between the treatment group and the control. More cases and longer follow-up of implants placed with MG are needed to verify the results of this randomized prospective study.

A Restoratively Driven Ridge Categorization, as Determined by Incorporating Ideal Restorative Positions on Radiographic Templates Utilizing Computed Tomography Scan Analysis

BACKGROUND The introduction of implants into the field of dentistry has revolutionized the way we evaluate edentulous ridges. In an attempt to evaluate the deficient edentulous ridge, numerous classification systems have been proposed. Each of these classification systems implements a different approach for evaluating and planning treatment for the ridge deficiency. PURPOSE The purpose of the present investigation was to propose a restoratively driven ridge categorization (RDRC) for horizontal ridge deformities based on an ideal implant position as determined through implant simulation, utilizing computed tomography (CT) scan images. MATERIALS AND METHODS Radiographic templates were developed to capture the ideal restorative tooth position. Measurements were performed using CT scan software in a cross-sectional view and by virtual placement of a parallel-sided implant with a 3.25-mm diameter. RESULTS Edentulous ridges were divided into five groupings: Group I, simulated implants with at least 2 mm of facial bone, accounted for 19.4% of ridges; Group II, simulated implant completely surrounded by bone, with less than 2 mm of facial plate thickness, accounted for 10.4% of ridges; Group III, wherein dehiscences are detected but no fenestrations are present, accounted for 33.3% of ridges; Group IV, wherein fenestrations are detected but no dehiscence is present, accounted for 6.3% of ridges; and Group V, wherein both dehiscences and fenestrations are present, accounted for 30.6% of ridges. CONCLUSION The use of RDRC indicates that a high number of cases in the maxillary anterior area would require augmentation procedures in order to achieve ideal implant placement and restoration.

Effect of 3- and 4-mm interimplant distances on the height of interimplant bone crest: a histomorphometric evaluation measured on bone level dental implants in minipig.

Purpose: To analyze crestal bone loss changes that may affect the gingival height around an implant and bone loss in interproximal areas. When implants are placed adjacent to one another, interimplant bone loss around 1 implant may combine with the implant bone loss around the adjacent implant to affect the crestal bone loss interproximally. Materials and Methods: The primary objective of this study was to evaluate histologically and histomorphometrically the effect that this implant design with a horizontally displaced implant-abutment junction has on the height of the crest of bone, between adjacent implants separated by 2 different distances: 4 mm and 3 mm. A secondary objective was to evaluate the percentage of bone-to-implant contact, interproximal soft tissue height, location of the junctional epithelium, and length of connective tissue contact to abutment and/or implant, for the 2 different distances. Results: Results showed that the interproximal bone loss measured from the edge of the implant platform to the bone crest was not different for interimplant distances of 4 or 3 mm. In addition, the secondary objective parameters also demonstrated similar results between the 2 interimplant distances. Conclusion: This study showed that interimplant bone levels can usually be maintained at similar levels for 4- and 3-mm distances during at least 2 months.