Analysis of stress distribution in full-arch fixed mandibular prosthesis with structures made with the CAD/CAM technology and with the conventional technique: evaluation through photoelastic and strain gauge analysis

Author(s)

Rodrigo Antonio de Medeiros

• Document type: Doctoral Thesis
• Press: Araçatuba. 2017-01-23.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araçatuba
• Defense date: 2016-12-12
• Advisor: Marcelo Coelho Goiato

Abstract

This study aimed to evaluate the stress distribution in full-arch fixed mandibular prosthesis (Branemärk type) with infrastructure made of different materials and techniques, and under compressive force, through photoelastic and strain gauge analysis. A photoelastic cast of an edentulous jaw was fabricated and received five external hexagon implants (4x11mm) between the mental foramen. The groups were divided into: Group I - Nickel-Chrome fused infrastructure with acrylic resin occlusal coating; Group II - Nickel-Chrome fused infrastructure with ceramic occlusal coating; Group III - Yttria-stabilized zirconia fused infrastructure with ceramic coating. First, the photoelastic analysis was performed and later the strain gauge analysis. A force of 70 N was applied by using a testing machine (EMIC) in the region of the most anterior implant, between incisors, and in the center of the first molar on each side. The images were analyzed by a blinded evaluator through images and by using Adobe Photoshop CS6, according to the number of high intensity fringes in each group. Regarding the strain gauge analysis, the stress measure was performed in two distinct regions. For the first region, two resistance strain gauges were placed horizontally in the mesial and distal regions of the five implants, directly on the marginal ridge of the photoelastic cast. For the second region, the photoelastic resin was removed on the buccal and lingual surfaces of each implant, leaving 1 mm of intact resin, where the strain gauges were placed vertically. The same compression tests described above were carried out. Data were submitted to two-way ANOVA and to the Tukey post-hoc test with 5% level of significance. The results of both methods showed lower stress values for Group I, when compared to other groups. It can be concluded that when rigid materials are used for infrastructure fabrication, the esthetic coating influences the load generated on the marginal bone around the implant. The ceramic coating showed less satisfactory results. (AU)

• FAPESP's process: 14/11605-3 - Stress distribution in a mandibular implant-supported prosthesis with implant bridge manufacturing in CAD/CAM and by conventional techinique: photoelastic stress and strain-gauge analysis
• Grantee: Rodrigo Antonio de Medeiros
• Support Opportunities: Scholarships in Brazil - Doctorate