Comparison between complete denture and implant-retained overdenture: effect of different mucosa thickness and resiliency on stress distribution

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

Effect of monomer treatment and polymerisation methods on the bond strength of resin teeth to denture base material

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

Effect of methyl methacrylate monomer on bond strength of denture base resin to acrylic teeth

Bond failures at the acrylic teeth and denture base resin interface are still a common clinical problem in prosthodontics. The effect of methyl methacrylate (MMA) monomer on the bond strength of three types of denture base resins (Acron MC, Lucitone 550 and QC-20) to two types of acrylic teeth (Biotone and Trilux) was evaluated. Twenty specimens were produced for each denture base resin/acrylic tooth combination and were randomly divided into control (acrylic teeth received no surface treatment) and experimental groups (MMA was applied to the surface of the acrylic teeth for 180 s) and were submitted to shear tests (1 mm/mm). Data (MPa) were analyzed using three-way ANOVA/Student's test (alpha = 0.05). MMA increased the bond strength of Lucitone denture base resins and decreased the bond strength of QC-20. No difference was detected for the bond strength of Acron MC base resin after treatment with MMA. (C) 2008 Elsevier Ltd. All rights reserved.

Evaluation of the Bond Strength of Denture Base Resins to Acrylic Resin Teeth: Effect of Thermocycling

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

Comparison of stress distribution between complete denture and implant-retained overdenture-2D FEA

The aim of this study was to compare the stress distribution induced by posterior functional loads on conventional complete dentures and implant-retained overdentures with different attachment systems using a two-dimentional Finite Element Analysis (FEA-2D). Three models representative of edentulous mandible were constructed on AutoCAD software; Group A (control), a model of edentulous mandible supporting a complete denture; Group B, a model of edentulous mandible supporting an overdenture over two splinted implants connected with the bar-clip system; Group C, a model of edentuluos mandible supporting an overdenture over two unsplinted impants with the O-ring system. Evaluation was conducted on Ansys software, with a vertical force of 100 N applied on the mandibular left first molar. When the stress was evaluated in supporting tissues, groups B (51.0 MPa) and C (52.6 MPa) demonstrated higher stress values than group A (10.1 MPa). Within the limits of this study, it may be conclued that the use of an attachment system increased stress values; furthermore, the use of splinted implants associated with the bar-clip attachment system favoured a lower stress distribution over the supporting tissue than the unsplinted implants with an O-ring abutment to retain the manibular overdenture.

Hyperbaric oxygen therapy treatment for the fixation of implant prosthesis in oncology patients irradiated

doi: 10.1111/j.1741-2358.2012.00636.x Hyperbaric oxygen therapy treatment for the fixation of implant prosthesis in oncology patients irradiated Objectives: This study aimed to present a clinical report of an irradiated oncologic patient who underwent hyperbaric oxygen therapy to be rehabilitated with implant-supported prosthesis. Materials and Methods: A 67-year-old man was admitted at Oral Oncology Center (FOA-UNESP) presenting a lesion on the mouth floor. After clinical evaluation, incisional biopsy and histopathological exam, a grade II squamous cell carcinoma was diagnosed. The patient was subjected to surgery to remove the lesion and partial glossectomy. Afterwards, the radiotherapy, in the left/right cervicofacial area of the supraclavicular fossa, was conducted. After 3 years of the surgery, the patient was submitted to hyperbaric oxygen therapy. Then, four implants were installed in patients mandible. Five months later, an upper conventional complete denture and lower full-arch implant-supported prosthesis were fabricated. Conclusion: The treatment resulted in several benefits such as improving his chewing efficiency, swallowing and speech, less denture trauma on the mucosa and improving his self-esteem.

Finite Element Analysis to Compare Complete Denture and Implant-Retained Overdentures With Different Attachment Systems

This finite element analysis compared stress distribution on complete dentures and implant-retained overdentures with different attachment systems. Four models of edentulous mandible were constructed: group A (control), complete denture; group B, overdenture retained by 2 splinted implants with bar-clip system; group C, overdenture retained by 2 unsplinted implants with o'ring system; and group D, overdenture retained by 2 splinted implants with bar-clip and 2 distally placed o'ring system. Evaluation was performed on Ansys software, with 100-N vertical load applied on central incisive teeth. The lowest maximum general stress value (in megapascal) was observed in group A (64.305) followed by groups C (119.006), D (258.650), and B (349.873). The same trend occurred it) supporting tissues with the highest stress value for cortical bone. Unsplinted implants associated with the o'ring attachment system showed the lowest maximum stress values among all overdenture groups. Furthermore, o'ring system also improved stress distribution when associated with bar-clip system.

Effect of different repair techniques on the accuracy of repositioning the fractured denture base

Objective:This study investigated the efficacy of different techniques for the union of fragments of a denture before repair and on the accuracy of the reposition.Materials and methods:For this study, 20 maxillary dentures made with Lucitone 550 heat-cured resin were used. Points were determined with a scanner on the cusp of the teeth, as a measurement of the segments. After digitisation, each model was exported to the AUTOCAD R 14 program and two-dimensional measurements of the distances between the marked points were made. After the initial analysis, the dentures were fractured into two segments using an impact test machine. For the repair, maxillary dentures were divided into two groups; in the first, the repair was carried out using Kerr's sticky wax and in the second group, Super Bonder was used to join the fragments, with subsequent inclusion of DENTSPLY((R)) Repair Material resin. After the repair, the points of the maxillary dentures were measured again. The numerical values obtained were tabulated to compare the measurements before fracture and after the repair. For statistical analysis, analysis of variance was employed, using a single factor and double factor, followed by the Tukey test with a reliability of 95%.Results:The results demonstrated a statistically significant difference between the materials used to join the dentures for repair, where the dentures were joined with sticky wax presented a larger variation in the distances between the points.Conclusion:The variation in distances between the points is influenced by the agent of repair.

Quality of life and stimulus perception in patients' rehabilitated with complete denture

The objective of this study was to evaluate and correlate quality of life (QoL), and stimulus perception of complete denture users, before and after the insertion of new prostheses. We selected 60 patients using bimaxillary complete conventional dentures who needed to replace their prostheses. During anamnesis, we collected demographic data and applied the Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT) questionnaire and stimulus perception questionnaire (PERCEPTION). Before installation of new prostheses, the patients responded to OHIP-EDENT questionnaire, and on the day of installation, they responded to PERCEPTION questionnaire. At the patients 3-month follow-up, we re-administered the OHIP-EDENT and PERCEPTION questionnaires. The Wilcoxon and MacNemar tests were used to compare patient responses between the time points analysed. Most of the OHIP-EDENT items showed a highly significant impact of the new prostheses on oral health (P = 0.003). The PERCEPTION questionnaire data indicated that the patients experienced significant improvements (P < 0.05) in terms of their sensations with the new prostheses. Cross-lagged data analysis did not show any causality between the OHIP-EDENT and PERCEPTION questionnaires (ZPF test, P = 0.772). We concluded that the treatment was effective with respect to the patients QoL and their adaptation to the new prostheses.

Analysis of Masticatory Cycle Efficiency in Complete Denture Wearers

Purpose: This study assessed masticatory efficiency and duration of the masticatory cycle in 14 asymptomatic patients with severe bone resorption. All patients had worn complete dentures for over 10 years. Recall visits were scheduled at 5 months and 1 year after receiving new dentures.Materials and Methods: Fourteen patients were evaluated in this study. The Research Diagnostic Criteria questionnaire and tests of the efficiency and duration of the masticatory cycle were performed with artificial food before, 5 months after, and 1 year after new dentures were delivered. Masticatory efficiency was assessed using a sieve system; artificial food was ground for 35 masticatory cycles and monitored by the operator.Results: Masticatory efficiency at 5 months was significantly improved for the 0.42-mm mesh. An improvement in masticatory efficiency and a reduction in mastication time were observed with the new dentures after 1 year.Conclusion: The results of this study indicated that 5 months did not allow enough time to demonstrate improved muscular capacity and ability after receiving new dentures. After 1 year, the duration of the masticatory cycle was reduced, and masticatory efficiency was significantly improved.

Effect of Flasking and Polymerization Techniques on Tooth Movement in Complete Denture Processing

Purpose: The purpose of this study was to compare the artificial tooth positional changes following the flasking and polymerization of complete dentures by a combination of two flasking methods and two polymerization techniques using computer graphic measurements.Materials and Methods: Four groups of waxed complete dentures (n = 10) were invested and polymerized using the following techniques: (1) adding a second investment layer of gypsum and conventional water bath polymerization (Control), (2) adding a second investment layer of gypsum and polymerization with microwave energy (Gyp-micro), (3) adding a second investment layer of silicone (Zetalabor) and conventional polymerization (Silwater), and (4) adding a second investment layer of silicone and polymerization with microwave energy (Silmicro). For each specimen, six segments of interdental distances (A to F) were measured to determine the artificial tooth positions in the waxed and polymerized stages using software program AutoCad R14. The mean values of the changes were statistically compared by univariate ANOVA with Tukey post-hoc test at 5% significance.Results: There were no significant differences among the four groups, except for segment D of the Silmicro group (-0.004 +/- 0.032 cm) in relation to the Gypwater group (0.044 +/- 0.031 cm) (p < 0.05), which presented, repectively, expansion and shrinkage after polymerization.Conclusions: Within the limitations of this study, it was concluded that although the differences were not statistically significant, the use of a silicone investment layer when flasking complete dentures resulted in the least positional changes of the artificial teeth regardless of the polymerization technique.

Bond strength of denture teeth to acrylic resin: effect of thermocycling and polymerisation methods

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

Influence of Different Base Thicknesses on Maxillary Complete Denture Processing: Linear and Angular Graphic Analysis on the Movement of Artificial Teeth

Objective: The purpose of this study was to compare the dental movement that occurs during the processing of maxillary complete dentures with 3 different base thicknesses, using 2 investment methods, and microwave polymerization.Methods: A sample of 42 denture models was randomly divided into 6 groups (n = 7), with base thicknesses of 1.25, 2.50, and 3.75 mm and gypsum or silicone flask investment. Points were demarcated on the distal surface of the second molars and on the back of the gypsum cast at the alveolar ridge level to allow linear and angular measurement using AutoCAD software. The data were subjected to analysis of variance with double factor, Tukey test and Fisher (post hoc).Results: Angular analysis of the varying methods and their interactions generated a statistical difference (P = 0.023) when the magnitudes of molar inclination were compared. Tooth movement was greater for thin-based prostheses, 1.25 mm (-0.234), versus thick 3.75 mm (0.2395), with antagonistic behavior. Prosthesis investment with silicone (0.053) showed greater vertical change compared with the gypsum investment (0.032). There was a difference between the point of analysis, demonstrating that the changes were not symmetric.Conclusions: All groups evaluated showed change in the position of artificial teeth after processing. The complete denture with a thin base (1.25 mm) and silicone investment showed the worst results, whereas intermediate thickness (2.50 mm) was demonstrated to be ideal for the denture base.

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)

All-Ceramic Crowns Over Single Implant Zircon Abutment. Influence of Young's Modulus on Mechanics

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