Mateus Bertolini Fernandes dos Santos

Effect of framework material and vertical misfit on stress distribution in implant-supported partial prosthesis under load application: 3-D finite element analysis

Abstract Objective. This study evaluated the influence of framework material and vertical misfit on stress created in an implant-supported partial prosthesis under load application. Materials and methods. The posterior part of a severely reabsorbed jaw with a fixed partial prosthesis above two osseointegrated titanium implants at the place of the second premolar and second molar was modeled using SolidWorks 2010 software. Finite element models were obtained by importing the solid model into an ANSYS Workbench 11 simulation. The models were divided into 15 groups according to their prosthetic framework material (type IV gold alloy, silver-palladium alloy, commercially pure titanium, cobalt-chromium alloy or zirconia) and vertical misfit level (10 µm, 50 µm and 100 µm). After settlement of the prosthesis with the closure of the misfit, simultaneous loads of 110 N vertical and 15 N horizontal were applied on the occlusal and lingual faces of each tooth, respectively. The data was evaluated using Maximum Principal Stress (framework, porcelain veneer and bone tissue) and a von Mises Stress (retention screw) provided by the software. Results. As a result, stiffer frameworks presented higher stress concentrations; however, these frameworks led to lower stresses in the porcelain veneer, the retention screw (faced to 10 µm and 50 µm of the misfit) and the peri-implant bone tissues. Conclusion. The increase in the vertical misfit resulted in stress values increasing in all of the prosthetic structures and peri-implant bone tissues. The framework material and vertical misfit level presented a relevant influence on the stresses for all of the structures evaluated.

Effects of Horizontal Misfit and Bar Framework Material on the Stress Distribution of an Overdenture-Retaining Bar System: A 3D Finite Element Analysis

PURPOSE To evaluate the influence of horizontal misfit change and bar framework material on the distribution of static stresses in an overdenture-retaining bar system using finite element (FE) analysis. MATERIALS AND METHODS A 3D FE model was created including two titanium implants and a bar framework placed in the anterior part of a severely resorbed jaw. The model set was exported to mechanical simulation software, where horizontal displacement (10, 50, 100, and 200 μm) was applied simulating the settling of the framework, which suffered shrinkage during laboratory procedures. Four bar materials (gold alloy, silver-palladium alloy, commercially pure titanium, and cobalt-chromium alloy) were also simulated in the analysis using 50 μm as the horizontal misfit. Data were qualitatively evaluated using von Mises stress, given by the software. RESULTS The misfit amplification presented a great increase in the stress levels in the inferior region of the bar, screw-retaining neck, cervical and medium third of the implant, and cortical bone tissue surrounding the implant. The higher stiffness of the bar presented a considerable increase in the stress levels in the bar framework only. CONCLUSION The levels of static stresses seem to be closely linked with horizontal misfit, such that its amplification caused increased levels of stress in the structures of the overdenture-retaining bar system. On the other hand, the stiffness of the bar framework presented a lower effect on the static stress levels.

Incidence of sleep bruxism among children in Itanhandu, Brazil

PurposeSleep bruxism (SB) in children may be related to headaches and causes extensive damage of primary teeth. This paper evaluates the incidence of SB in children from Itanhandu, MG, Brazil.MethodsThe presence of teeth wear facets was verified through clinical examinations on a sample of children, whose parents answered a questionnaire about their children’s behavior and habits. Analysis of variance and chi-square tests (p = 0.05) were applied to identify possible correlations between the presence of SB and the parents’ responses to the questionnaire.ResultsThe sample comprised of 170 children, 51.76% (n = 88) of which were girls, while the average age was 4.37 (±1.69) years. A total of 15.29% (n = 26) had been diagnosed as bruxers, 46.47% displayed restless behavior, and only 10% used medication. The average duration of breastfeeding was 4.4 (±0.25) months. A positive correlation was found between restless behavior and the presence of SB (p < 0.001). No correlation was found between SB and medication (p = 0.573), or between the duration of breastfeeding and restless behavior (p = 0.102), SB (p = 0.565) and medication (p = 0.794).ConclusionRestless behavior was positively correlated with SB, although no correlation was found between SB and medication or duration of breastfeeding.

Influence of different mucosal resiliency and denture reline on stress distribution in peri-implant bone tissue during osseointegration. A three-dimensional finite element analysis

OBJECTIVE The aim of this study was to evaluate the influence of mucosal properties and relining material on the stress distribution in peri-implant bone tissue during masticatory function with a conventional complete denture during the healing period through finite element analysis. MATERIALS AND METHODS Three-dimensional models of a severely resorbed mandible with two recently placed implants in the anterior region were created and divided into the following situations: (i) conventional complete denture and (ii) relined denture with soft lining material. The mucosal tissue properties were divided into soft, resilient and hard. The models were exported to mechanical simulation software; two simulations were carried out with a load at the lower right canine (35 N) and the lower right first molar (50 N). Data were qualitatively evaluated using Maximum Principal Stress, in MPa, given by the software. RESULTS All models showed stress concentrations in the cortical bone corresponding to the cervical part of the implant. The mucosal properties influenced the stress in peri-implant bone tissue showing a different performance according to the denture base material. The simulations with relined dentures showed lower values of stress concentration than conventional ones. CONCLUSIONS It seems that the mucosal properties and denture reline have a high influence on the stress distribution in the peri-implant bone during the healing period.

Sleep bruxism associated with obstructive sleep apnea syndrome in children.

AIMS Sleep bruxism (SB) and obstructive sleep apnea syndrome (OSAS) are often observed in children and may have several health implications. The aim of this paper is to evaluate their prevalence and to test for possible associations between these two conditions. METHODOLOGY The sample consisted of 496 children randomly selected among the preschoolers of Taubaté, Brazil; 249 (50·2%) were boys and 247 (49·8%) were girls. Diagnoses of SB and OSAS were made by clinical examinations and questionnaires filled out by the childrens parents in a cross-sectional design. Analysis of variance and Chi-square tests were applied to verify possible association among the variables in question. RESULTS The average age was 4·49 years (SD: ±1·04 years). A total of 25·6% were diagnosed with SB, while 4·83% were diagnosed with OSAS, and only 2·82% presented both conditions. A statistical association was found between SB and OSAS (P<0·001; Chi-square test): 11·03% of subjects with SB also presented with OSAS, and 97·18% of subjects without SB did not present with OSAS. No association was found among childrens gender and age and the presence of SB or OSAS. CONCLUSIONS Within the limits of this study, SB was associated with OSAS.

Influence of different soft liners on stress distribution in peri-implant bone tissue during healing period. A 3D finite element analysis.

The aim of this study was to evaluate the stress distribution in the bone adjacent to submerged implants during masticatory function in conventional complete dentures with different soft liners through finite element analysis. Three-dimensional models of a severely resorbed mandible with 2 and 4 submerged implants in the anterior region were created and divided into the following situations: (1) conventional complete dentures (control group); and conventional complete dentures with different soft liner materials, (2) Coe-Comfort, (3) Softliner, and (4) Molteno Hard. The models were exported to mechanical simulation software and 2 simulations were done with the load in the inferior right canine (35 N) and the inferior right first molar (50 N). The data were qualitatively evaluated using the maximum principal stress and microstrain values given by the software. The use of soft liners provides decreased levels of stress and microstrains in peri-implant bone when the load was applied to canine teeth. Considering all of the values obtained in this study, the use of softer materials is the most suitable for use during the period of osseointegration.

Stress analysis of different configurations of 3 implants to support a fixed prosthesis in an edentulous jaw

This studys aim was to evaluate the stress distribution in a mandibular implant-supported prosthesis and peri-implant bone considering implant quantity, diameter and position using linear 3-D finite element analysis. Models of an anterior jaw comprised 4 groups according to implant quantity, diameter, and position: control group C, 5 regular implants; R, 3 regular implants; W, 3 wide implants; and DTR, 3 regular implants with the distal ones tilted 30° distally. The cantilever was loaded with an axial load of 50 N. Data was evaluated using von Mises stress on implants and maximum principal stress and microstrain on the bone. The W group showed the lowest value of maximum principal stress in peri-implant bone of the loaded side (4.64 MPa) when compared to C (5.27 MPa), DTR (5.94 MPa), and R (11.12 MPa). Lower stress values in the loaded implants were observed in the experimental groups when compared to the C group. However, the unloaded implants presented opposite results. All the screws of the W group presented lower stress values when compared to the C group. However, the R and DTR groups presented an increase in stress values with the exception of the loaded screw. A reduction in the number of implants associated with wider implants reduced the stress in the bone and prosthetic components.

Influence of post-thickness and material on the fracture strength of teeth with reduced coronal structure.

Purpose: To evaluate the fracture strength of endodontically treated teeth with reduced coronal structure reinforced with glass-fiber posts and cast posts and core (nickel–chromium alloy) with different thickness. Materials and Methods: Forty maxillary central incisors were sectioned at 1 mm of the cementoenamel junction and endodontically treated. The teeth were divided into four groups (n = 10) and restored with cast post and core and glass-fiber posts with diameters of 1.5 mm and 1.1 mm. The fracture strength was evaluated using a Universal Testing Machine (Instron 1144) at 45° of angulation. The results were submitted to analysis of variance two-way and Tukeys test (P < 0.05). The failure mode was also evaluated. Results: Cast post and core were statistically superior to the glass-fiber posts with the self-post diameter (P = 0.001). When the self-post material was considered, no significant difference was observed between the two post-diameters (P = 0.749). The glass-fiber post-groups presented more fractures in the cervical third than the cast post and core groups. Conclusion: Teeth restored with cast post and cores present higher fracture strength than those reinforced with glass-fiber posts. An increased post-thickness does not increase the fracture strength. Glass-fiber posts lead to less severe fractures.

Influence of different metal flask systems on tooth displacement in complete upper dentures

OBJECTIVE  To verify the occurrence of tooth displacement in dentures processed by moist hot-polymerisation using traditional and experimental metal flask systems. MATERIALS AND METHODS   Waxed complete dentures were randomly assigned to three groups (n = 10), including traditional (TF) and experimental flasks (DF and HHF). Metal pins were placed at the incisal edge of maxillary central incisors (I), buccal cusp of first premolars (P) and mesiobuccal cusp of second molars (M). Transversal (I-I, P-P and M-M) and anteroposterior (LI-LM and RI-RM) distances were measured before and after denture processing using an optical microscope. The dentures were processed by hot water curing cycle (9 h/74 °C). Collected data were analysed by anova, Paired Students t-test and Holm-Sidak method (p < 0.05). RESULTS   All measured distances demonstrated contraction after polymerisation, except for LI-LM in TF and RI-RM in DF and HHF. Statistically significant differences were found between the distances P-P for DF and HHF, and M-M for all groups. Comparison among flask systems revealed statistically significant difference in the P-P distance for the TF and HHF. CONCLUSION   Different flask systems did not cause variation in tooth displacement during denture processing, with the exception of P-P distances for the TF and HHF. There is no evidence that different metal flask systems would promote tooth displacement of clinical significance.

Effect of bar cross-section geometry on stress distribution in overdenture-retaining system simulating horizontal misfit and bone loss

This study evaluated the influence of cross-section geometry of the bar framework on the distribution of static stresses in an overdenture-retaining bar system simulating horizontal misfit and bone loss. Three-dimensional FE models were created including two titanium implants and three cross-section geometries (circular, ovoid or Hader) of bar framework placed in the anterior part of a severely resorbed jaw. One model with 1.4-mm vertical loss of the peri-implant tissue was also created. The models set were exported to mechanical simulation software, where horizontal displacement (10, 50 or 100 μm) was applied simulating the settling of the framework, which suffered shrinkage during the laboratory procedures. The bar material used for the bar framework was a cobalt--chromium alloy. For evaluation of bone loss effect, only the 50-μm horizontal misfit was simulated. Data were qualitatively and quantitatively evaluated using von Mises stress for the mechanical part and maximum principal stress and μ-strain for peri-implant bone tissue given by the software. Stresses were concentrated along the bar and in the join between the bar and cylinder. In the peri-implant bone tissue, the μ-strain was higher in the cervical third. Higher stress levels and μ-strain were found for the models using the Hader bar. The bone loss simulated presented considerable increase on maximum principal stresses and μ-strain in the peri-implant bone tissue. In addition, for the amplification of the horizontal misfit, the higher complexity of the bar cross-section geometry and bone loss increases the levels of static stresses in the peri-implant bone tissue.