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

Abstract

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

“…Each assembly (prosthesis/photoelastic model with and without attachment systems) was positioned in a circular polariscope adapted to a universal testing machine (EMIC DL 3000, São Paulo, SP, Brazil). The assembly was placed into a glass with mineral oil to minimize the refraction of white light, 20,21,23 thereby, facilitating the photoelastic observation (Photoflood 500 W-GE Lighting General Eletric, Cleverland, Ohio, USA) that uniformly focuses on the recipient with the photoelastic model. Thus, a load of 100 N at 10 mm∕s was applied in the first molar region of each obturator denture.…”

“…Then, four obturator dentures were fitted to the photoelastic models with and without attachment systems and the other four dentures were directly relined with soft silicone (Sofreliner, Tokuyama Dental Corporation, Tokyo, Japan) in the region of oral-sinus-nasal communication under a load of 12.5 N and immersed in distilled water at 37 AE 2°C until the material set as recommended by the manufacturer 22 and then fitted to the photoelastic models. 20,21 A conventional obturator denture (mucosa-supported) was fabricated for group I (with no attachment system), while the other three obturator dentures were associated with different attachment systems: bar-clip associated to distally placed O-rings (group II), O-ring (group III), and bar-clip (group IV) (Neodent, Curitiba, Paraná, Brazil). The groups V, VI, VII, and VIII followed the same sequence but the dentures were relined with Sofreliner silicone.…”

“…Squared transfer copings were attached to the implants and splinted with a dental floss scaffold covered by self-polymerized acrylic resin [19][20][21] (Duralay Reliance Dental, MFG Co Worth, IC, USA) to obtain the photoelastic model II.…”

“…The groups V, VI, VII, and VIII followed the same sequence but the dentures were relined with Sofreliner silicone. 21 The obturator dentures were fabricated with colorless heat-polymerized resin and artificial teeth with 20 deg of cusp inclination. 20,21 The welding technique with burner (NP Solder, New Delhi, India) was used to obtain the bar-clip attachment system and to avoid stress in the photoelastic model II.…”

“…According to Prado Ribeiro et al 21 the effectiveness of lining materials is attributed to its viscoelastic properties and is mainly related to the flexibility of the material, which improves absorption and redistribution of the energy generated by occlusal forces. 30 It is known that the lower the hardness of such material, the greater the capacity to absorb and distribute energy produced by the forces of mastication during denture function.…”