Photoelastic Analysis of Cemented or Screwed Implant-Supported Prostheses With Different Prostheses Connections

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

Photoelastic Stress Analysis of Different Attachment Systems on Implant-Retained and Conventional Palatal Obturator Prostheses

Background: Considering that an increasing number of patients are victims of mutilator surgical resections, these studies are important for treatment success of rehabilitation of patients presenting oronasal communication.Purpose: The aim of this study was to assess the stress distribution through photoelasticity in palatal obturator prostheses with different attachment systems for implants.Methods: Two photoelastic models were obtained from an experimental maxillary model presenting an oronasal communication. One model was fabricated without implant, and the other with 2 implants 10 mm in length inserted in the left crest. Four colorless palatal obturator prostheses were fabricated. One prosthesis presented no attachment system, whereas the remaining prostheses were adapted to 3 attachment systems. The assembly was positioned in a circular polariscope for application of axial load.Results: The results were based on photographic records of stress in the photoelastic model submitted to loading. The records revealed higher stress concentration on the bar-clip system followed by the O'ring/bar-clip and O'ring systems, respectively. A homogeneous stress distribution was observed on the photoelastic model with the mucous-supported prosthesis.Conclusions: The attachment systems generated different characteristics of stress distribution that was concentrated surrounding the implants. The bar-clip system exhibited the highest stress concentration on the alveolar crest.

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)

Photoelastic Analysis of Stress Distribution in Oral Rehabilitation

The purpose of this study was to present a literature review about photoelasticity, a laboratory method for evaluation of implants prosthesis behavior. Fixed or removable prostheses function as levers on supporting teeth, allowing forces to cause tooth movement if not carefully planned. Hence, during treatment planning, the dentist must be aware of the biomechanics involved and prevent movement of supporting teeth, decreasing lever-type forces generated by these prosthesis. Photoelastic analysis has great applicability in restorative dentistry as it allows prediction and minimization of biomechanical critical points through modifications in treatment planning.

Photoelastic Analysis of Implant-Retained and Conventional Obturator Prostheses With Different Attachment Systems and Soft Relining

Complete and partial loss of maxillary bone may jeopardize oral physiology and generate complications as oral-sinus-nasal communication. Palatal obturator prostheses are a treatment alternative for rehabilitation of these patients. The aim of this study was to assess stress distribution, through photoelasticity, on palatal obturator prostheses associated with different attachment systems (o'ring, bar clip, and o'ring/bar clip) of implants and submitted to relining. Two photoelastic models were fabricated according to an experimental maxillary model with oral-sinus-nasal communication. One model did not present implants, whereas the other included 2 implants with 13.0 mm in length in the left ridge. Four colorless maxillary obturator prostheses were fabricated and relined with soft silicone. One of these prostheses presented no attachment system, whereas the remaining prostheses included attachment systems adapted to the implants. The assembly (model/attachment system/prosthesis) was positioned in a circular polariscope during loading with 100 N at 10 mm/s. The results were based on observation during the experiment and photographic records of stress on the photoelastic model. The bar clip system exhibited the highest stress concentration followed by o'ring/bar clip and o'ring systems. The attachment systems presented different stress distribution with greater concentration surrounding the implants and homogenous stress distribution on the photoelastic model without implants. The highest concentration of fringes occurred, in ascending order, with o'ring, o'ring/bar clip, and bar clip systems.

Photoelastic analysis to compare implant-retained and conventional obturator dentures

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

Photoelastic analysis of forces generated by T-loop springs made with stainless steel or titanium-molybdenum alloy

Introduction: The purpose of this study was to use photoelastic analysis to compare the system of forces generated by retraction T-loop springs made with stainless steel and titanium-molybdenum alloy (TMA) (Ormco, Glendora, Calif) with photoelastic analysis. Methods: Three photoelastic models were used to evaluate retraction T-loop springs with the same preactivations in 2 groups. In group 1, the loop was constructed with a stainless steel wire, and 2 helicoids were incorporated on top of the T-loop; in group 2, it was made with TMA and no helicoids. Results: Upon using the qualitative analysis of the fringe order in the photoelastic model, it was observed that the magnitude of force generated by the springs in group 1 was significantly higher than that in group 2. However, both had symmetry for the active and reactive units related to the system of force. Conclusions: Both springs had the same mechanical characteristics. TMA springs showed lower force levels. (Am J Orthod Dentofacial Orthop 2011;140:e123-e128)

Photoelastic comparison of single tooth implant-abutment-bone of platform switching vs conventional implant designs

Objectives: The maintenance and stability of peri-implantar soft tissue seem to be related to the crestal bone around the implant platform and different implant designs connections might affect this phenomenon. The aim of this study was to evaluate by photoelastic analysis the stress distribution in the cervical and apical site of implant-abutment interface of conventional implant joints (external hex, internal hex and cone morse) and compare to the novel platform switching design. Materials and methods: It was fabricated photoelastic models using five different implant-abutment connection, one set of external hex (Alvim Ti, Neodent, Curitiba, Brazil), one set of internal hex (Full Osseotite, Biomet 3i, Florida, USA), one cone morse set (Alvim CM, Neodent, Curitiba, Brazil), and two sets of internal hex plus platform switching concept (Alvim II Plus, Neodent, Curitiba, Brazil) (Certain Prevail, Biomet 3i, Florida, USA). These models were submitted to two compressive loads, axial from 20 kgf (load I) and another (load II), inclined 45° from 10 kgf. During the qualitative analysis, digital pictures were taken from a polariscope, for each load situation. For the quantitative analyses in both situations of load, the medium, minimum and maximum in MPa values of shear strain were determined in the cervical and apical site. The Kruskal-Wallis test was used to compare the results between the different systems and between cervical and apical site were compared using Mann-Whitney U test. Results: The results from qualitative analysis showed less concentration of strain in the cervical area to the internal hex plus platform switching (Certain Prevail), in both situation of load. The same results were get in the quantitative analysis, showing less stress concentrations around the implant Certain Prevail with internal hex plus the novel design (17.9 MPa to load I and 29.5 MPa to load II), however, without statistical significant difference between the systems. Conclusion: The minor stress concentration strongly suggest the use of platform switching design as a manner to prevent bone loss around the implant-abutment platform. Clinical Significance: From the result of this study its possible to make clinical decision for implant system which provides implant components with platform switching characteristics.

Photoelastic analysis of the influence of residual ridge inclination in conjugated class i mandibular prostheses with different attachment systems

Objectives: The aim of this study was to evaluate the stress distribution in mandibular free-end removable partial dentures (RPD) associated with FPD in the abutment teeth considering different inclinations of the residual ridge: (1) horizontal and (2) distal descending ridges and two designs of free-end RPD with different attachment systems were tested: (1) clasp and (2) system ERA. Methods. Axial loads (100 N) were applied on the teeth of the RPD. The images were recorded and the stress distribution was evaluated through photoelastic fringes. Results. In general, the distal descending ridge presented more photoelastic fringes in the region of the roots of the abutment teeth while the horizontal ridge exhibited higher compression in the base of the prosthesis. In the horizontal ridge, the denture with clasp presented more favourable stress distribution than the denture with the system ERA. In the distal descending ridge, the denture with the system ERA relieved the region of the abutment teeth and overloaded the residual ridge. Conclusion: The horizontal ridge presented more favourable performance; the dentures with clasp exhibited better performance for both ridges evaluated; the denture with the system ERA presented better results in the distal descending ridge. © 2013 Informa Healthcare.

Stress analysis in oral obturator prostheses: Imaging photoelastic

Maxillary defects resulting from cancer, trauma, and congenital malformation affect the chewing efficiency and retention of dentures in these patients. The use of implant-retained palatal obturator dentures has improved the self-esteem and quality of life of several subjects. We evaluate the stress distribution of implant-retained palatal obturator dentures with different attachment systems by using the photoelastic analysis images. Two photoelastic models of the maxilla with oral-sinus-nasal communication were fabricated. One model received three implants on the left side of the alveolar ridge (incisive, canine, and first molar regions) and the other did not receive implants. Afterwards, a conventional palatal obturator denture (control) and two implant-retained palatal obturator dentures with different attachment systems (O-ring; bar-clip) were constructed. Models were placed in a circular polariscope and a 100-N axial load was applied in three different regions (incisive, canine, and first molar regions) by using a universal testing machine. The results were photographed and analyzed qualitatively using a software (Adobe Photoshop). The bar-clip system exhibited the highest stress concentration followed by the O-ring system and conventional denture (control). Images generated by the photoelastic method help in the oral rehabilitator planning. © 2013 SPIE.

Stress analysis in oral obturator prostheses over parallel and tilted implants: photoelastic imaging

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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.

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.

Stress analysis in oral obturator prostheses, part II: photoelastic imaging

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stress distribution around osseointegrated implants with different internal-cone connections: photoelastic and finite element analysis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)