Periodontal parameters around porous-coated dental implants after 3 to 4 years supporting overdentures

Evaluation of Stress Distribution and Force in External Hexagonal Implant: A 3-D Finite Element Analysis

Purpose: To analyze the stress distribution and the direction of force in external hexagonal implant with crown in three different angulations. Materials and Methods: A total of 60 samples of geometric models were used to analyze von Mises stress and direction of force with 0-, 5-, and 10-degree lingual tilt. Von Mises stress and force distribution were evaluated at nodes of hard bone, and finite element analysis was performed using ANSYS 12.1 software. For calculating stress distribution and force, we categorized and labeled the groups as Implant A1, Implant A2, and Implant A3, and Implant B1, Implant B2, and Implant B3 with 0-, 5-, and 10-degree lingual inclinations, respectively. Inter- and intra-group comparisons were performed using ANOVA test. A p-value of ≤0.05 was considered statistically significant. Results: In all the three models, overall maximum stress was found in implant model A3 on the implant surface (86.61), and minimum was found on model A1 in hard bone (26.21). In all the three models, the direction of force along three planes was maximum in DX (0.01025) and minimum along DZ (0.002) direction with model B1. Conclusion: Maximum von Mises stress and the direction of force in axial direction was found at the maximum with the implant of 10 degrees angulation. Thus, it was evident that tilting of an implant influences the stress concentration and force in external hex implants.

Stress distribution patterns of implant supported overdentures-analog versus finite element analysis: A comparative in-vitro study

Aims and Objectives:

The aim of this study was to asses & compare the load transfer characteristics of Ball/O-ring and Bar/Clip attachment systems in implant supported overdentures using analog and finite element analysis models.

Methodology:

For the analog part of the study, castable bar was used for the bar and clip attachment and a metallic housing with a rubber O-ring component was used for the ball/O-ring attachment. The stress on the implant surface was measured using the strain-gauge technique. For the finite element analysis, the model were fabricated and load applications were done in a similar manner as in analog study.

Results:

The difference between both the attachment systems was found to be statistically significant (P<0.001).

Conclusion:

Ball/O-ring attachment system transmitted lesser amount of stresses to the implants on the non-loading side, as compared to the Bar-Clip attachment system. When overall stress distribution is compared, the Bar-Clip attachment seems to perform better than the Ball/O-ring attachment, because the force was distributed better.

Peri-implant conditions around sintered porous-surfaced (SPS) implants. A 36-month prospective cohort study

OBJECTIVES

The specific aim of this study was to assess sintered porous-surfaced (SPS) implant system from a biological point of view, through a prospective study of the health status and the evolution of the peri-implant tissues over time and analysis of the changes observed in the various peri-implant parameters.

MATERIAL AND METHODS

Hundred and fifty-one patients were treated consecutively from 2005 to 2007 using 280 SPS implants, which were restored with a single crown or a partial fixed denture. To accurately monitor the health and biological evolution of peri-implant soft and hard tissues, a number of clinical parameters were adopted, such as the modified Plaque Index (mPI), the modified sulcus Bleeding Index (mBI), Peri-implant Probing Depth (PPD), and Crestal Bone Level (CBL). Clinical and radiographic examinations were scheduled over a 36-month follow-up of functional loading according to a well-established protocol generally applied to determine implant success rates and Peri-implant Bone Loss (PBL). Statistical analysis was used to determine any significant differences or correlations (P = 0.05).

RESULTS

A total of 259 SPS implants in 136 patients were followed up for 36 months. According to Buser's success criteria, the overall implant-based success rate was 98.1% and the mean PBL was 0.48 ± 0.29 mm. MBI and mPI mean values showed statistically significant differences between baseline and follow-up analyses (P < 0.001). No statistically significant differences in mean PPD values were found between baseline and control analyses (P = 0.060).

CONCLUSION

This prospective cohort study revealed that the biological behavior of SPS implant system was characterized by high tissue stability during the observation period, both as regards soft and hard tissues. In particular, the crestal bone remodeling pattern was very similar to that reported in other studies, confirming that the bone loss around SPS implants, at least at 36 months, seems to be predictable.

Force transfer and stress distribution in an implant-supported overdenture retained with a hader bar attachment: a finite element analysis

Background and Objectives. A key factor for the long-term function of a dental implant is the manner in which stresses are transferred to the surrounding bone. The effect of adding a stiffener to the tissue side of the Hader bar helps to reduce the transmission of the stresses to the alveolar bone. But the ideal thickness of the stiffener to be attached to the bar is a subject of much debate. This study aims to analyze the force transfer and stress distribution of an implant-supported overdenture with a Hader bar attachment. The stiffener of the bar attachments was varied and the stress distribution to the bone around the implant was studied. Methods. A CT scan of edentulous mandible was used and three models with 1, 2, and 3 mm thick stiffeners were created and subjected to loads of emulating the masticatory forces. These different models were analyzed by the Finite Element Software (Ansys, Version 8.0) using von Mises stress analysis. Results. The results showed that the maximum stress concentration was seen in the neck of the implant for models A and B. In model C the maximum stress concentration was in the bar attachment making it the model with the best stress distribution, as far as implant failures are concerned. Conclusion. The implant with Hader bar attachment with a 3 mm stiffener is the best in terms of stress distribution, where the stress is concentrated at the bar and stiffener regions.

Influence of Implant Surface Topography and Loading Condition on Stress Distribution in Bone Around Implants: A Comparative 3D FEA

A three-dimensional Finite Element Method was used to study the influence of porous coated surface topography of an implant on stress and strain distribution pattern in the cortical and cancellous bone during axial and non-axial loading. Two implants, one with porous surface topography and one with smooth surface were embedded in separate geometric models of posterior mandibular region which was generated using a CT scan data. Material properties and boundary conditions were applied. Load of 100 and 50 N were applied on to the abutment from axial and non-axial directions respectively. Porous surface topography appeared to distribute stress in a more uniform pattern around the implant with near absence of stress in the apical region of implant. Smooth surfaced implant showed high punching stress at the apex of the implant. The porous coated interface was considered to simulate the shock absorbing behavior of periodontal ligament of natural dentition. Maximum amount of stress concentration was observed in the cortical bone which plays a major role in the dissipation of the stress.

Study of Biomechanics of Porous Coated Root Form Implant Using Overdenture Attachment: A 3D FEA

The purpose of this article is to do a three-dimensional finite element stress analysis, in relation to root form implant supported by overdenture attachment, during axial and non-axial loading. Two porous coated Titanium-aluminum-vanadium (Ti-6Al-4V) implants with overdenture abutment were embedded in both simple and 3D model of interforaminal region of mandible. The material properties of tissue ingrowth bonded interface were calculated considering Iso-Strain condition. The masticatory forces: axial load of 35 N, a horizontal load of 10 N, and an oblique load of 120 N, was applied for the two qualities of cancellous bone. It implied that porous topography of the implant led to optimal stress transfer at the tissue ingrowth bonded interface and insignificant punching stress at the apex than a smooth surface implant. The inferior bone quality was deformed even under physiologic loads and showed wider stress pattern. Simulated implant abutment to implant bone interface stress may be significantly affected by the quality of the bone and the surface topography of the implant. The interface is affected to a lesser extent by the prosthetic material properties. Threedimensional anatomical model was more close to reality than the geometry of much simpler altered models.

Implant-retained mandibular overdentures: A comparative pilot study of immediate loading versus delayed loading after two years

STATEMENT OF PROBLEM

Treatment options for an increasing number of completely edentulous patients using fixed restorations may be limited due to anatomical or financial constraints.

PURPOSE

The purpose of this pilot study was to compare immediate loading versus conventional delayed loading of implants placed for the retention of mandibular overdentures.

MATERIAL AND METHODS

Twenty-six subjects each received 3 implants placed in the symphysis area which were connected with a gold bar. In the experimental group (n=17), the 3 splinted implants were loaded 2 days after surgery; in the control group (n=9), the 3 implants were loaded 3 months after surgery using a conventional 2-stage approach. Recall appointments were scheduled every 3 months during the 2-year follow-up. The following clinical parameters were included and assessed: health of periimplant soft tissues using the bleeding index (BI), plaque index (PI), periimplant probing depth (PIPD), periimplant bone resorption as measured on panoramic radiographs, and implant stability using resonance frequency analysis (RFA). The Mann-Whitney test (alpha=.05) was used to compare each parameter in the 2 groups.

RESULTS

After 2 years, no implant failure was recorded in either group. No significant difference was found between the 2 groups after 2 years with regard to BI (P=.33), PI (P=.81), PIPD (P=.61), periimplant bone resorption (P=.32), or RFA (P=.06). After 1 year, periimplant bone loss (P=.05) and PIPD (P=.005) were increased in the control group.

CONCLUSIONS

Immediate loading of 3 splinted implants retaining a mandibular overdenture shortens treatment time for prosthesis insertion and shows, after 2 years, results comparable with the delayed approach.

Le Fort I osteotomy with interpositional bone grafts and delayed oral implants for the rehabilitation of extremely atrophied maxillae: a 1?9-year clinical follow-up study on humans

AIM

The purpose of this clinical follow-up study was to report the clinical outcome of osseointegrated implants placed in extremely atrophied edentulous maxillae after Le Fort I osteotomy and interpositional autogenous iliac bone grafts.

PATIENTS AND METHODS

In a 10-year period (1995-2004), 39 patients, 18 males and 21 females, aged from 32 to 76 years, presenting with severely atrophied edentulous maxillae were treated with Le Fort I osteotomy and interpositional iliac bone grafts. Four to 8 months after the reconstructive procedure, 281 osseointegrated implants were placed in the reconstructed maxillae. Four to 8 months afterwards, abutments were connected and the prosthetic rehabilitation started. The mean follow-up period of implants after the start of prosthetic loading was 45.9 months (range: 12-108 months).

RESULTS

The reconstructive procedure was successful in 38 of 39 patients. In one patient, partial loss of the inlay graft occurred before implant placement. Six patients (42 implants) dropped out of the study. Fifteen implants were removed during the follow-up period, due to loss of integration. Thirty-two implants, although integrated, presented with peri-implant bone-level changes higher than those proposed for successful implants. Cumulative survival and success rates of implants were 94.5% and 82.9%, respectively.

CONCLUSION

Results from this study showed that Le Fort I osteotomy with interpositional bone grafts followed by delayed implant placement is an acceptable means to rehabilitate edentulous patients affected by extremely atrophied edentulous maxillae. Survival rates of implants are consistent with those related to implants placed in native, non-reconstructed bone. Conversely, the success rate of implants resulted to be lower as compared with those obtained for implants placed in native bone.

Quality and quantity of bone following alveolar distraction osteogenesis in the human mandible

PURPOSE

The purpose of this prospective study on humans were to evaluate (a) the clinical outcome of alveolar distraction osteogenesis for the correction of vertically deficient edentulous mandibular ridges, (b) the clinical outcome of dental implants placed in the distracted areas, and (c) the quality and quantity of the bone that had formed in the distraction gap.

MATERIAL AND METHODS

Seven patients presenting vertically deficient edentulous ridges were treated by means of distraction osteogenesis with an intraoral alveolar distractor. Approximately 3 months after consolidation of the distracted segments, 20 ITI solid screw SLA implants were placed in the distracted areas. Three to 4 months later, abutments were connected and prosthetic loading of the implants started. During implant site preparation, bone biopsies were taken at the implant sites with trephine burrs for histologic and histometric analyses.

RESULTS

The mean follow-up after the initial prosthetic loading was 18 months (range 12-24 months). The mean bone gain obtained at the end of distraction was 7 mm (range 5-9 mm). The cumulative success rate of implants 2 years after the onset of prosthetic loading was 95%, whereas the survival rate of implants was 100%. The newly formed bone consisted of woven bone reinforced by parallel-fibered bone with bone marrow spaces between the bone trabeculae. The bone area fraction in the distraction region ranged from 21.6% to 57.8% (38.5+/-11.7%).

DISCUSSION AND CONCLUSIONS

Results from this study showed that (a) distraction osteogenesis is a reliable technique for the correction of vertically deficient edentulous ridges, (b) the regenerated bone withstood the functional demands of implant loading, (c) survival and success rates of implants placed in the distracted areas were consistent with those of implants placed in native bone, and (d) there is sufficient bone volume and maturity in the distracted region for primary stability of the implant.

Alveolar distraction osteogenesis vs. vertical guided bone regeneration for the correction of vertically deficient edentulous ridges: A 1-3-year prospective study on humans

The purpose of this prospective study was to compare vertical guided bone regeneration (GBR) and vertical distraction osteogenesis (DO) for their ability in correcting vertically deficient alveolar ridges and their ability in maintaining over time the vertical bone gain obtained before and after implant placement. Eleven patients (group 1) were treated by means of vertical GBR with autogenous bone and e-PTFE membranes, while 10 patients (group 2) were treated by means of DO. In group 1, six patients received implants at the time of GBR (subgroup 1A), while five patients had implants placed at the time of membrane removal (subgroup 1B). In group 2, implants were placed at the time of distraction device removal. A total of 25 implants were placed in group 1 and 34 implants were placed in group 2 patients. Three to 5 months after implant placement, patients were rehabilitated with implant-borne dental prostheses. The following parameters were evaluated: (a) bone resorption of the regenerated ridges before and after implant placement; (b) peri-implant clinical parameters 1, 2, and 3 years after prosthetic loading of implants; (c) survival and success rates of implants. Bone resorption values before and after implant placement were significantly higher in group 1. The results suggested that both techniques may improve the deficit of vertically resorbed edentulous ridges, although distraction osteogenesis seems to be more predictable as far as the long-term prognosis of vertical bone gain is concerned. Implant survival rates as well as peri-implant clinical parameters do not differ significantly between the two groups, whereas the success rate of implants placed in group 2 patients was higher than that obtained in group 1 patients.

Ten-year results of a prospective study using porous-surfaced dental implants and a mandibular overdenture

BACKGROUND

Numerous investigators have used osseointegrated dental implants as retention for mandibular overdentures, but few have reported 10-year outcomes or incorporated carefully standardized radiographs to document crestal bone loss.

PURPOSE

The purpose of this study was to use a prospective clinical trial design to assess the performance of short sintered porous-surfaced dental implants with a mandibular complete overdenture when all patients in the trial had undergone 10 years of continuous function.

MATERIALS AND METHODS

Fifty-two fully edentulous patients, most with advanced alveolar ridge resorption, each received three free-standing Endopore implants (7-10 mm in length, mean length, 8.7 mm; Innova Corporation, Toronto, ON, Canada) in the mandibular symphysis region. After 10 weeks of submerged healing, these implants were used to support an overdenture. Carefully standardized radiographs, using a customized stainless steel filmholder attached to each implant and the x-ray tube, were collected at baseline, 3 months, 6 months, yearly to 5 years, and then again at 7and 10 years.

RESULTS

Life table analysis revealed a 10-year implant survival of 92.7% and a mean annual bone loss after year 1 of 0.03 mm.

CONCLUSION

Short free-standing dental implants with a sintered porous surface used for implant fixation are a predictable and effective means of retaining a mandibular overdenture in patients with advanced mandibular ridge resorption.

Immediate loading of Brånemark implants: a 24-month follow-up of a comparative prospective pilot study between mandibular overdentures supported by Conical transmucosal and standard MK II implants

BACKGROUND

The purpose of this prospective study is to compare the long-term outcome of immediately loaded implant-retained mandibular overdentures supported by four screw-type one-piece transmucosal implants with that of four screw-type two-piece implants inserted in the interforaminal area of the mandible and rigidly connected by a U-shaped curved

MATERIALS AND METHODS

A prospective pilot study was conducted with 10 patients receiving an implant-supported overdenture in the mandible. The patients were randomly assigned to two groups. In the control group (five patients), four standard Brånemark implants (MK II; Nobel Biocare AB, Gothenburg, Sweden), 3.75 mm large and at least 10 mm long, were sited anterior to the mental foramina, and four standard abutments (Nobel Biocare AB) for bar construction were immediately screwed to the implants. In the test group (five patients), four conical transmucosal implants (Nobel Biocare AB), 3.75 mm large and at least 9 mm long in the threaded part, were sited anterior to the mental foramina. Immediately after implant placement, a U-shaped gold or titanium bar was fabricated and implants were immediately loaded (within 24 h) in both groups with an implant-retained overdenture. The patients were followed up for a minimum of 24 months. Implants were evaluated at the time of immediate loading and at 12 and 24 months after prosthetic loading, with the following parameters: modified plaque index (MPI), modified bleeding index (MBI), and probing depth (PD). Periimplant bone resorption was evaluated on panoramic radiographs taken 12 and 24 months after the beginning of prosthetic loading.

RESULTS

No significant differences were found between the two groups with regard to MPI, MBI, PD, and periimplant bone resorption at 12 and 24 months. The cumulative success rate of implants according to the criteria proposed by Albrektsson and colleagues was 100% in both groups after 2 years of functional loading.

CONCLUSIONS

Results from this study demonstrated that the success rate for immediately loaded mandibular implants is similar to that obtained in cases of delayed loading and that there are no significant differences between results with two-piece implants and one-piece transmucosal implants.

A role for surface topography in creating and maintaining bone at titanium endosseous implants

STATEMENT OF PROBLEM

A variety of claims are made regarding the effects of surface topography on implant osseointegration. Many in vivo and in vitro experimental observations have key limitations in their interpretations.

PURPOSE

This review considers the major claims made concerning the effects of commercially pure (cp) titanium implant surface topography on osseointegration. Important findings of consensus are highlighted, and existing controversies are revealed.

MATERIAL AND METHODS

This review considers many of the research publications listed in MEDLINE and presented in biomedical research publications and textbooks.

RESULTS

Implant surface topography is not well defined in the marketplace or consistently reported among experimental studies. Many in vitro evaluations are not predictive of or correlated with in vivo outcomes. In some culture models, increased surface topography positively affects pro-osteogenic cellular activities. Animal models reveal modest increases in bone-to-implant contact and increases in the biomechanical interlock of the implant with bone for implants of increased surface topography. Existing information fails to define increased surface topography as a risk factor for peri-implant inflammation.

CONCLUSION

Increased cp titanium implant surface topography improves the bone-to-implant contact and the mechanical properties of the enhanced interface. Growing clinical evidence for increased bone-to-implant contact at altered cp titanium implants confirms the temporally limited observations made in preclinical studies. In the absence of controlled comparative clinical trials, the aggregate experimental evidence supports the use of cp titanium implants with increased surface topography.