Photoelastic Analysis of Stress Distribution With Different Implant Systems

The aim of this study was to evaluate stress distribution with different implant systems through photoelasticity. Five models were fabricated with photoelastic resin PL-2. Each model was composed of a block of photoelastic resin (10 x 40 x 45 mm) with an implant and a healing abutment: model 1, internal hexagon implant (4.0 X 10 mm; Conect AR, Conexao, Sao Paulo, Brazil); model 2, Morse taper/internal octagon implant (4.1 x 10 mm; Standard, Straumann ITI, Andover, Mass); model 3, Morse taper implant (4.0 x 10 mm; AR Morse, Conexao); model 4, locking taper implant (4.0 x 11 mm; Bicon, Boston, Mass); model 5, external hexagon implant (4.0 x 10 mm; Master Screw, Conexao). Axial and oblique load (45) of 150 N were applied by a universal testing machine (EMIC-DL 3000), and a circular polariscope was used to visualize the stress. The results were photographed and analyzed qualitatively using Adobe Photoshop software. For the axial load, the greatest stress concentration was exhibited in the cervical and apical thirds. However, the highest number of isochromatic fringes was observed in the implant apex and in the cervical adjacent to the load direction in all models for the oblique load. Model 2 (Morse taper, internal octagon, Straumann ITI) presented the lowest stress concentration, while model 5 (external hexagon, Master Screw, Conexao) exhibited the greatest stress. It was concluded that Morse taper implants presented a more favorable stress distribution among the test groups. The external hexagon implant showed the highest stress concentration. Oblique load generated the highest stress in all models analyzed.

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.

Torque Stability of Different Abutment Screws Submitted to Mechanical Cycling

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

Microstrain Around Dental Implants Supporting Fixed Partial Prostheses Under Axial and Non-Axial Loading Conditions, In Vitro Strain Gauge Analysis

The current study used strain gauge analysis to perform an in vitro evaluation of the effect of axial and non-axial loading on implant-supported fixed partial prostheses, varying the implant placement configurations and the loading points. Three internal hexagon implants were embedded in the center of each polyurethane block with in-line and offset placements. Microunit abutments were connected to the implants using a torque of 20 N.cm, and plastic prosthetic cylinders were screwed onto the abutments, which received standard patterns cast in Co-Cr alloy (n = 10). Four strain gauges (SGs) were bonded onto the surfaces of the blocks, tangentially to the implants: SG 01 mesially to implant 1, SG 02 and SG 03 mesially and distally to implant 2, respectively, and SG 04 distally to implant 3. Each metallic structure was screwed onto the abutments using a 10-N.cm torque, and axial and non-axial loads of 30 kg were applied at 5 predetermined points. The data obtained from the strain gauge analyses were analyzed statistically through the repeated measures analysis of variance and the Tukey test, with a conventional level of significance of P < 0.05. The results showed a statistically significant difference for the loading point (P = 0.0001), with point E (nonaxial) generating the highest microstrain (327.67 mu epsilon) and point A (axial) generating the smallest microstrain (208.93 mu epsilon). No statistically significant difference was found for implant placement configuration (P = 0.856). It was concluded that the offset implant placement did not reduce the magnitude of microstrain around the implants under axial and non-axial loading conditions, although loading location did influence this magnitude.

Implant-retained finger prosthesis with modified retention system

Background: Amputations affect both the physical and the psychological aspects of an individual, causing significant impact on self-esteem. The main causes of finger amputations are work-related accidents with dangerous machinery, road traffic accidents, and animal bites, as well as systemic diseases such as diabetes. This report aims to describe a simple technique for fabrication of implant-retained finger prosthesis with a modified base of the retention system.Case Description and Methods: The O-Ring retention system was used with a modified hexagon-shaped base and a metallic capsule adapted to the acrylic resin to attach the prosthesis to the implant.Findings and Outcomes: The prosthesis was made with silicone, and after osseointegration, it was installed without complications, leading to a patient satisfied with the end result and encouraged to return to social life.

Distribuição das tensões em próteses protocolo mandibulares com diferentes extensões de cantilever e material de revestimento oclusal

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

A MICROSTRAIN COMPARISON OF PASSIVELY FITTING SCREW-RETAINED AND CEMENTED TITANIUM FRAMEWORKS

Statement of problem. An imprecise fit between frameworks and supporting dental implants in loaded protocols increases the strain transferred to the periimplant bone, which may impair healing or generate microgaps.Purpose. The purpose of this study was to investigate the microstrain between premachined 1-piece screw-retained frameworks (group STF) and screw-retained frameworks fabricated by cementing titanium cylinders to the prefabricated framework (group CTF). This procedure was developed to correct the misfit between frameworks and loaded implants.Material and methods. Four internal hexagon cylindrical implants were placed 10 mm apart in a polyurethane block by using the surgical guides of the corresponding implant system. Previously fabricated titanium frameworks (n=10) were divided into 2 groups. In group STF, prefabricated machined frameworks were used (n=5), and, in group CTF, the frameworks were fabricated by using a passive fit procedure, which was developed to correct the misfit between the cast titanium frameworks and supporting dental implants (n=5). Both groups were screw-retained under torque control (10 Ncm). Six strain gauges were placed on the upper surface of the polyurethane block, and 3 strain measurements were recorded for each framework. Data were analyzed with the Student t test (alpha=.05).Results. The mean microstrain values between the framework and the implants were significantly higher for group STF (2517 me) than for group CTF (844 me) (P<.05).Conclusions. Complete-arch implant frameworks designed for load application and fabricated by using the passive fit procedure decreased the strain between the frameworks and implants more than 1 piece prefabricated machined frameworks.

BIOMECHANICAL BEHAVIOR OF THE SYSTEM PROSTHESIS/DENTAL IMPLANT: ANALYSIS BY THE PHOTOELASTICITY METHOD

One of the main reasons for the failure in dental implant treatments is the overload, which can cause bone resorption and later, the osseointegration loss in the implant. Therefore, the aim of this study was to analyze the tension generated around dental implants in the rehabilitation of three mandible posterior teeth, varying the connection type, the disposal, and the quantity of implants. The photoelasticity method was used in order to accomplish it. Through photoelasticity, the quantity and localization of the tensions around the implants in the different studied groups were compared (three straight line implants, three offset placement implants, two implants with a mesial cantilever, and two implants with a pontic). The results showed that the tension quantity and disposition around the dental implants of the connection external hexagon and internal hexagon were similar in all groups. In the group where the cantilever was used, an increase of the tension around the implant, adjacent to the cantilever, was observed. From the results it is concluded that the type of connection used in this study did not influence the tension quantity and distribution around the implants; however, the prosthetic configuration with the cantilever use, led to an increase of the tension around the implant, adjacent to the cantilever.

Extensometria: estudo das microdeformações ao redor de três implantes de hexágono interno, com posicionamento linear, sob a influência da fundição de coifas plásticas e usinadas

The objective of this in vitro study was quantify the micro strain development around the internal hexagon implants, varying the type of prosthetic coping. For This reason, three implants of internal hexagon were inserted into one polyurethane block in line placement. Microunit abutments were screwed onto the implants. Tangentially the implants were bonded the strain gauges, two to the center implant. Ten structures, each one containing three copings were cast in Co-Cr alloy, that were divided into groups in the first group, plastic copings were used, and in the second group machined copings were used. The superstructure’s occlusal screws were tightened onto Microunit abutments with 10 Ncm torque, the magnitude of micro strain was recorded. The mean values of each strain gauge of each plastic copings were 363,37 ± 237,66 and the machined copings were 338,12 ± 223,01. The data were analyzed statistically by t- Student test. No statistically significant difference was found between the prosthetic copings (p= 0,867). It was concluded that to internal hexagon implants in line placement, the type of copings presented similar magnitude of micro strain after prosthetic occlusal screw was tightened

Análise das microdeformações geradas ao redor de implantes de hexágono externo sob a aplicação de cargas verticais em pilares microunit retos e angulados

Pós-graduação em Odontologia Restauradora - ICT

Efeito do recobrimento de filmes de carbono tipo diamante depositados a plasma na manutenção do torque de parafusos protéticos

Pós-graduação em Odontologia Restauradora - ICT

Infiltração bacteriana nas interfaces entre implantes e pilares: efeito do desenho das conexões protéticas

Pós-graduação em Odontologia Restauradora - ICT

Influência de diferentes superfícies de implantes unitários com geometria do tipo hexágono externo, Platform Switching e Cone-Morse em osso tipo III e IV: estudo pelo método dos elementos finitos tridimensionais

Pós-graduação em Odontologia - FOA

Análise das tensões em próteses implantossuportadas esplintadas, variando a localização dos implantes, pôntico e cantilever: estudo pelo método dos elementos finitos tridimensionais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Carbono tipo diamante em componentes de implantes dentários: avaliação das propriedades antimicrobianas e de adesão de Escherichia coli

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)