Endosseous dental implant fractures an analysis of 21 cases

Implant fracture is an infrequent cause of implant failure. The present study evaluates 21 fractured implants, with an analysis of patient age and sex, the type, length and diameter of the implant, positioning in the dental arch, the type of prosthetic rehabilitation involved, the number of abutments and pontics, the presence or absence of distal extensions or cantilevers, and loading time to fracture. Implant fracture was more common in males than in females (15:4), and the mean patient age was 56.9 years. Most cases (n = 19) corresponded to implant-supported fixed prostheses - 16 with cantilevers of different lengths- while only two fractured implants were supporting overdentures instead of fixed prostheses. The great majority of fractured implants (80.9%) were located in the molar and premolar regions, and most fractured within 3-4 years after loading. It is important to know and apply the measures required to prevent implant fracture, and to seek the best individualized solution for each case - though complete implant removal is usually the treatment of choice

Digital image correlation analysis of the load transfer by implant-supported restorations

This study compared splinted and non-splinted implant-supported prosthesis with and without a distal proximal contact using a digital image correlation method. An epoxy resin model was made with acrylic resin replicas of a mandibular first premolar and second molar and with threaded implants replacing the second premolar and first molar. Splinted and non-splinted metal-ceramic screw-retained crowns were fabricated and loaded with and without the presence of the second molar. A single-camera measuring system was used to record the in-plane deformation on the model surface at a frequency of 1.0 Hz under a load from 0 to 250 N. The images were then analyzed with specialist software to determine the direct (horizontal) and shear strains along the model. Not splinting the crowns resulted in higher stress transfer to the supporting implants when the second molar replica was absent. The presence of a second molar and an effective interproximal contact contributed to lower stress transfer to the supporting structures even for non-splinted restorations. Shear strains were higher in the region between the molars when the second molar was absent, regardless of splinting. The opposite was found for the region between the implants, which had higher shear strain values when the second molar was present. When an effective distal contact is absent, non-splinted implant-supported restorations introduce higher direct strains to the supporting structures under loading. Shear strains appear to be dependent also on the region within the model, with different regions showing different trends in strain changes in the absence of an effective distal contact. (C) 2011 Elsevier Ltd. All rights reserved.

Planning for Immediate Loading of Implant-Supported Prostheses: Literature Review

The aim of this study was to present the factors that influence planning for immediate loading of implants through a literature review for treatment success. Research was conducted in the PubMed database including the key words immediate implant loading, implant-supported prostheses, and implant planning for studies published from 2000 to 2011. Forty-eight articles were used in this review to describe the indications and counterindications, presurgical planning, and technologies available for planning of this treatment alternative.

Passivity Versus Unilateral Angular Misfit: Evaluation of Stress Distribution on Implant-Supported Single Crowns: Three-Dimensional Finite Element Analysis

The aim of this study was to evaluate the effect of unilateral angular misfit of 100 Km on stress distribution of implant-supported single crowns with ceramic veneering and gold framework by three-dimensional finite element analysis. Two three-dimensional models representing a maxillary section of premolar region were constructed: group 1 (control)-crown completely adapted to the implant and group 2-crown with unilateral angular misfit of 100 Km. A vertical force of 100 N was applied on 2 centric points of the crown. The von Mises stress was used as an analysis criterion. The stress values and distribution in the main maps (204.4 MPa for group 1 and 205.0 MPa for group 2) and in the other structures (aesthetic veneering, framework, retention screw, implant, and bone tissue) were similar for both groups. The highest stress values were observed between the first and second threads of the retention screw. Considering the bone tissue, the highest stress values were exhibited in the peri-implant cortical bone. The unilateral angular misfit of 100 Km did not influence the stress distribution on the implant-supported prosthesis under static loading.

Obturator for Rehabilitation of Cleft Palate With Implant-Supported Retention System

Objective: Surgical reconstruction and prosthetic obturation are alternatives for the treatment of cleft in the soft palate.Design: The present case reports the rehabilitation of a patient presenting cleft palate with obturator prosthesis associated with implant-supported retention system.Conclusions: The use of ball attachment system improved speech, masticatory efficiency, swallowing, and social behavior of the patient.

Photoelastic Analysis of Biomechanical Behavior of Single and Multiple Fixed Partial Prostheses With Different Prosthetic Connections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Machined and plastic copings in three-element prostheses with different types of implant-abutment joints: a strain gauge comparative analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strain Gauge Analysis of the Effect of Porcelain Firing Simulation on the Prosthetic Misfit of Implant-Supported Frameworks

Objectives: This study investigated the effect of porcelain firing on the misfit of implant-supported frameworks and analyzed the influence of preheat treatment on the dimensional alterations.Materials and Methods: Four external-hex cylindrical implants were placed in polyurethane block. Ten frameworks of screw-retained implant-supported prostheses were cast in Pd-Ag using 2 procedures: (1) control group (CG, n = 5): cast in segments and laser welded; and test group (TG, n = 5): cast in segments, preheated, and laser welded. All samples were subjected to firing to simulate porcelain veneering firing. Strain gauges were bonded around the implants, and microstrain values (mu epsilon = 10(-6)epsilon) were recorded after welding (M1), oxidation cycle (M2), and glaze firing (M3). Data were statistically analyzed (2-way analysis of variance, Bonferroni, alpha = 0.05).Results: The microstrain value in the CG at M3 (475.2 mu epsilon) was significantly different from the values observed at M1 (355.6 mu epsilon) and M2 (413.9 mu epsilon). The values at M2 and M3 in the CG were not statistically different. Microstrain values recorded at different moments (M1: 361.6 mu epsilon/M2: 335.3 mu epsilon/M3: 307.2 mu epsilon) did not show significant difference.Conclusions: The framework misfit deteriorates during firing cycles of porcelain veneering. Metal distortion after porcelain veneering could be controlled by preheat treatment. (Implant Dent 2012;21:225-229)

Prosthetic rehabilitation of a bone defect with a teeth-implant supported, removable partial denture

The use of teeth-implant, mucosa-supported removable dentures for rehabilitation of partially edentulous patients involves highly complex biomechanical aspects. This type of prosthesis associates 3 kinds of support that react differently to the functional and parafunctional forces developed in the oral cavity. Although the construction of removable partial dentures may seem paradoxical when osseointegrated implants are placed, in some cases, this option is an excellent alternative to solve difficulties related to the anatomic, biologic, psychomotor, and financial conditions of the patient. This article reports on a case in which a teeth-implant, mucosa-supported removable partial denture was the option of choice for a patient with financial and anatomic limitations, having a large structural loss of the residual alveolar ridge caused by trauma by a gunshot injury at the mandible. The 5-year follow-up did not reveal any type of biomechanical or functional problem. Copyright © 2006 by Lippincott Williams and Wilkins.

Evaluation of a two-step pouring technique for implant-supported prostheses impression

The aim of this study was to evaluate the efficacy of a pouring technique for implant-supported prostheses impressions. A metallic matrix (control group) with two implants positioned at 90 and 65 degrees was fabricated. The matrix was submitted to the direct transfer impression technique. In group CP (conventional pouring - n = 10), casts were obtained by the conventional pouring technique. In group EP (experimental pouring - n = 10), the analogs were embraced with latex tubes before the first pouring and then submitted to a second pouring. Vertical misfit and implants/analogs inclinations were evaluated. Data were analyzed by analysis of variance and Tukey's test (p < .05). Results demonstrated significant difference (p < .05) between control and experimental groups for misfit measurement in perpendicular implant/analog and between control group and group EP in leaning implant/analog. Considering inclination, there were significant differences (p < .05) between control and experimental groups for leaning analogs. Independently of the pouring technique, perpendicular implants produced more accurate casts.

Effect of unilateral misfit on preload of retention screws of implant-supported prostheses submitted to mechanical cycling

Purpose: The aim of this study was to evaluate the effect of different levels of unilateral angular misfit on preload maintenance of retention screws of single implant-supported prostheses submitted to mechanical cycling. Materials and methods: Premachined UCLA abutments were cast with cobalt-chromium alloy to obtain 48 crowns divided into four groups (n=12). The crowns presented no misfit in Group A (control group) and unilateral misfits of 50μm, 100μm and 200μm in the groups B, C and D, respectively. The crowns were attached to external hexagon implants with a titanium retention screw with torque of 30N/cm. Oblique loading of 130N at 2Hz was applied on each replica, totalizing 5×104 and 1×106cycles. Detorque values were measured initially and after each cycling period. Data were evaluated by analysis of variance and Tukey's HSD test (p<0.05). Results: All groups presented reduced initial detorque values (p< 0.05) in comparison to the insertion torque (30. ± 0.5. N/cm) and Group A (25.18. N/cm) exhibited the lowest reduction. After mechanical cycling, all groups presented detorque values from 19.5. N/cm to 22.38. N/cm and the mechanical cycling did not statistically influence the detorque values regardless the misfit level of the replicas. Conclusion: The unilateral misfit influenced the preload maintenance only before mechanical cycling. The mechanical cycling did not influence the torque reduction. © 2010 Japan Prosthodontic Society.

Influence of Abutment Type and Esthetic Veneering on Preload Maintenance of Abutment Screw of Implant-Supported Crowns

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Tilted and Short Implants Supporting Fixed Prosthesis in an Atrophic Maxilla: A 3D-FEA Biomechanical Evaluation

Purpose: This study compared the biomechanical behavior of tilted long implant and vertical short implants to support fixed prosthesis in an atrophic maxilla. Materials and Methods: The maxilla model was built based on a tomographic image of the patient. Implant models were based on micro-computer tomography imaging of implants. The different configurations considered were M4S, four vertical anterior implants; M4T, two mesial vertical implants and two distal tilted (45°) implants in the anterior region of the maxilla; and M6S, four vertical anterior implants and two vertical posterior implants. Numerical simulation was carried out under bilateral 150N loads applied in the cantilever region in axial (L1) and oblique (45°) (L2) direction. Bone was analyzed using the maximum and minimum principal stress (σmax and σmin), and von Mises stress (σvM) assessments. Implants were analyzed using the σvM. Results: The higher σmax was observed at: M4T, followed by M6S/L1, M6S/L2, M4S/L2, and M4S/L1 and the higher σvM: M4T/L1, M4T/L2 and M4S/L2, M6S/L2, M4S/L1, and M6S/L1. Conclusions: The presence of distal tilted (all-on-four) and distal short implants (all-on-six) resulted in higher stresses in both situations in the maxillary bone in comparison to the presence of vertical implants (all-on-four). © 2013 Wiley Periodicals, Inc.

Five-year follow-up of modified implant-supported overdenture in an iliac crest autograft failure: Clinical report

The treatment of extensive pathologic lesions in the jaw, most of the time, can generate rehabilitation problems to the patient. The solid ameloblastoma is a locally invasive odontogenic tumor with a high recurrence rate. Its treatment is aggressive and accomplished through resection with safety margin. The criterion standard for reconstruction is autogenous bone, but it can provide a high degree of resorption, causing inconvenience to the patient because of lack of rehabilitative option. This study aimed to describe a patient with ameloblastoma treated through resection and reconstruction with autogenous bone graft, in which, after an extensive resorption of the graft was made, a modified bar was applied to support a prosthetic implant overdenture. Copyright © 2013 by Mutaz B. Habal, MD.