Stress distribution in implant-supported prosthesis with external and internal implant-abutment connections

Objective. This study aimed to investigate the stress distribution in screwed implant-supported prostheses with different implant-abutment connections by using a photoelastic analysis. Materials and methods. Four photoelastic models were fabricated in PL-2 resin and divided according to the implant-abutment connection (external hexagon (EH) and Morse taper (MT) implants (3.75 × 11.5 mm)) and the number crowns (single and 3-unit piece). Models were positioned in a circular polariscope and 100-N axial and oblique (45) loading were applied in the occlusal surface of the crowns by using a universal testing machine. The stresses were photographically recorded and qualitatively analyzed using software (Adobe Photoshop). Results. Under axial loading, the MT implants exhibited a lower number of fringes for single-unit crowns than EH implants, whereas for a 3-unit piece the MT implants showed a higher number of fringes vs EH implants. The oblique loading increased the number of fringes for all groups. Conclusion. In conclusion, the MT implant-abutment connection reduced the amount of stress in single-unit crowns, for 3-unit piece crowns the amount of stress was lower using an external hexagon connection. The stress pattern was similar for all groups. Oblique loading promoted a higher stress concentration than axial loading. © Informa Healthcare.

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)

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.

The influence of bone quality on the biomechanical behavior of full-arch implant-supported fixed prostheses

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

The Role of Implant/Abutment System on Torque Maintenance of Retention Screws and Vertical Misfit of Implant-Supported Crowns Before and After Mechanical Cycling

Purpose: This study aimed to evaluate the role of the implant/abutment system on torque maintenance of titanium retention screws and the vertical misfit of screw-retained implant-supported crowns before and after mechanical cycling. Materials and Methods: Three groups were studied: morse taper implants with conical abutments (MTC group), external-hexagon implants with conical abutments (EHC group), and external-hexagon implants with UCLA abutments (EHU group). Metallic crowns casted in cobalt-chromium alloy were used (n = 10). Retention screws received insertion torque and, after 3 minutes, initial detorque was measured. Crowns were retightened and submitted to cyclic loading testing under oblique loading (30 degrees) of 130 +/- 10 N at 2 Hz of frequency, totaling 1 x 10(6) cycles. After cycling, final detorque was measured. Vertical misfit was measured using a stereomicroscope. Data were analyzed by analysis of variance, Tukey test, and Pearson correlation test (P < .05). Results: All detorque values were lower than the insertion torque both before and after mechanical cycling. No statistically significant difference was observed among groups before mechanical cycling. After mechanical cycling, a statistically significantly lower loss of detorque was verified in the MTC group in comparison to the EHC group. Significantly lower vertical misfit values were noted after mechanical cycling but there was no difference among groups. There was no significant correlation between detorque values and vertical misfit. Conclusions: All groups presented a significant decrease of torque before and after mechanical cycling. The morse taper connection promoted the highest torque maintenance. Mechanical cycling reduced the vertical misfit of all groups, although no significant correlation between vertical misfit and torque loss was found.

The role of superstructure material on the stress distribution in mandibular full-arch implant-supported fixed dentures. A CT-based 3D-FEA

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

Effect of Abutment Screw Surface Treatment on Reliability of Implant-Supported Crowns

Purpose: To evaluate and compare the reliability of implant-supported single crowns cemented onto abutments retained with coated (C) or noncoated (NC) screws and onto platform-switched abutments with coated screws. Materials and Methods: Fifty-four implants (DT Implant 4-mm Standard Platform, Intra-Lock International) were divided into three groups (n = 18 each) as follows: matching-platform abutments secured with noncoated abutment screws (MNC); matching-platform abutments tightened with coated abutment screws (MC); and switched-platform abutments secured with coated abutment screws (SC). Screws were characterized by scanning electron microscopy and x-ray photoelectron spectroscopy (XPS). The specimens were subjected to step-stress accelerated life testing. Use-level probability Weibull curves and reliability for 100,000 cycles at 200 N and 300 N (90% two-sided confidence intervals) were calculated. Polarized light and scanning electron microscopes were used for fractographic analysis. Results: Scanning electron microscopy revealed differences in surface texture; noncoated screws presented the typical machining grooves texture, whereas coated screws presented a plastically deformed surface layer. XPS revealed the same base components for both screws, with the exception of higher degrees of silicon in the SiO2 form for the coated samples. For 100,000 cycles at 300 N, reliability values were 0.06 (0.01 to 0.16), 0.25 (0.09 to 0.45), and 0.25 (0.08 to 0.45), for MNC, MC, and SC, respectively. The most common failure mechanism for MNC was fracture of the abutment screw, followed by bending, or its fracture, along with fracture of the abutment or implant. Coated abutment screws most commonly fractured along with the abutment, irrespective of abutment type. Conclusion: Reliability was higher for both groups with the coated screw than with the uncoated screw. Failure modes differed between coated and uncoated groups.

Non-linear 3D finite element analysis of full-arch implant-supported fixed dentures

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

Photoelastic stress analysis of splinted and unitary implant-supported prostheses

The aim of this study was to evaluate the effects that splinting and different lengths of implants have on the stress distribution in implant-supported prostheses by photoelastic analysis. A total of five photoelastic resin models were made with different proposed situations, and 400 load applications were performed for the analysis. Compared with the unitary prosthesis, the splinted implant-supported prosthesis acted favorably in the distribution of stresses and strains to the implant (p < 0.001). The increase in length was a significant factor in the stress distribution (p < 0.05) and, ultimately, the overall reduction in stress. It was concluded that the splinted implant-supported prosthesis behaved better biomechanically compared with the unitary prosthesis.

Impact of Replacing Conventional Complete Dentures with Implant-Supported Fixed Complete Dentures

The aim of this study was to assess the impact of replacing conventional mandibular complete dentures with implant-supported fixed complete dentures (ISFDs) on the oral health related quality of life (OHOOL) of edentulous patients and on the associated kinesiographic parameters. The patients had their complete dentures replaced by ISFDs and were assessed after 1, 2, 3, 6, and 12 months. An improvement of general OHQOL was observed 2 months after treatment with ISFDs. Kinesiographic recordings revealed significant mandibular vertical and horizontal opening increases and a greater vertical intrusion of the maxillary complete dentures during clenching after the treatment with ISFD.

Implant-supported rehabilitation after treatment of atrophic mandibular fractures: report of two cases

Objective The objective of this article is to present options of rehabilitation with dental implants in two cases of severely atrophic mandibles (<10 mm) after rigid internal fixation of fractures. Patients and method Two patients who sustained fractures in severely atrophic mandibles with less than 10 mm of bone height were treated by open reduction and internal fixation through a transcervical access. Internal fixation was obtained with 2.4-mm locking reconstruction plates. The first patient presented satisfactory bone height at the area between the mental foramens and after 2 years, received flapless guided implants in the anterior mandible and an immediate protocol prosthesis. The second patient received a tent pole iliac crest autogenous graft after 2 years of fracture treatment and immediate implants. After 5 months, a protocol prosthesis was installed in the second patient. Results In both cases, the internal fixation followed AO principles for load-bearing osteosynthesis. Both prosthetic devices were Branemark protocol prosthesis. The mandibular reconstruction plates were not removed. Both patients are rehabilitated without complications and satisfied with esthetic and functional results. Conclusion With the current techniques of internal fixation, grafting, and guided implants, the treatment of atrophic mandible fractures can achieve very good results, which were previously not possible.

Forced orthodontic eruption for augmentation of soft and hard tissue prior to implant placement

Forced orthodontic eruption (FOE) is a non-surgical treatment option that allows modifying the osseous and gingival topography. The aim of this article is to present a clinical case of a FOE, which resulted in an improvement of the amount of available bone and soft-tissues for implant site development. Patient was referred for treatment of mobility and unesthetic appearance of their maxillary incisors. Clinical and radiographic examination revealed inflamed gingival tissue, horizontal and vertical tooth mobility and interproximal angular bone defects. It was chosen a multidisciplinary treatment approach using FOE, tooth extraction, and immediate implant placement to achieve better esthetic results. The use of FOE, in periodontally compromised teeth, promoted the formation of a new bone and soft-tissue in a coronal direction, without additional surgical procedures, enabling an esthetic, and functional implant-supported restoration.

Quality of life and satisfaction of patients wearing implant-supported fixed partial denture: a cross-sectional survey of patients from Aracatuba city, Brazil

ObjectivesThe aim of this study was to evaluate the quality of life and satisfaction of patients wearing implant-supported fixed partial dentures.Materials &methodsA total of 106 patients were selected and submitted to clinical examination and collection of the demographic data for evaluation of the implant-supported fixed dentures conditions. All participants agreed to answer to the Oral Health Impact Profile (OHIP-EDENT) questionnaire and another questionnaire about satisfaction with the implant-supported prostheses. The patients were classified into the following three groups for statistical analysis: patients wearing splinted implant-supported prosthesis (E), patients wearing single implant-supported prosthesis (U), and patients wearing single implant-supported prosthesis associated with splinted prosthesis (E+U). Kruskal-Wallis test was used to compare the answers between the groups, and a logistic regression model was measured to verify the relation between variables of the patients and the questionaries'items.ResultsThere were significant differences among groups (P=0.006) for discomfort during surgery itself of the satisfaction questionnaire. The marital status, groups, and hygiene condition were significant mainly for physical pain item.ConclusionsIt was concluded that the patients presented high level of satisfaction and quality of life for the most of the items evaluated as well as the groups showed similar results.

Axial loads on implant-supported partial fixed prostheses for external and internal hex connections and machined and plastic copings: strain gauge analysis

The aim of this in vitro study was to use strain gauge (SG) analysis to compare the effects of the implant-abutment joint, the coping, and the location of load on strain distribution in the bone around implants supporting 3-unit fixed partial prostheses. Three external hexagon (EH) implants and 3 internal hexagon (IH) implants were inserted into 2 polyurethane blocks. Microunit abutments were screwed onto their respective implant groups. Machined cobalt-chromium copings and plastic copings were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in a cobalt-chromium alloy (n = 5): group 1 = EH/machined. group 2 = EH/plastic, group 3 = IH/machined, and group 4 = IH/plastic. Four SGs were bonded onto the surface of the block tangentially to the implants. Each metallic structure was screwed onto the abutments and an axial load of 30 kg was applied at 5 predetermined points. The magnitude of microstrain on each SG was recorded in units of microstrain (mu epsilon). The data were analyzed using 3-factor repeated measures analysis of variance and a Tukey test (alpha = 0.05). The results showed statistically significant differences for the type of implant-abutment joint, loading point, and interaction at the implant-abutment joint/loading point. The IH connection showed higher microstrain values than the EH connection. It was concluded that the type of coping did not interfere in the magnitude of microstrain, but the implant/abutment joint and axial loading location influenced this magnitude.

Three-dimensional finite element analysis of anterior single implant-supported prostheses with different bone anchorages

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