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1.
Medicine (Baltimore) ; 99(43): e22648, 2020 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-33120754

RESUMO

To analyze the stress distribution of the maxillary central incisor with oblique fracture, repaired by different methods, using 3-dimensional finite element analysis. From the biomechanical point of view, it is expected to provide a reference for clinical selection of restoration method which is more conducive to stress distribution and preservation of dental tissue as much as possible.Use cone beam CT and finite element software to establish the finite element models of the maxillary central incisor with oblique fracture, and then create models according to 5 repairing methods(A. fiber post-core-crown group; B. cast post-core-crown group; C.3 mm deep endocrown; D.4 mm deep endocrown; E.5 mm deep endocrown)after root canal treatment, and analyze the Von Mises equivalent stress and maximum principal stress distribution and peak value of each model.When the height of dentin ferrule was fixed, the value of the Von Mises equivalent stress and the maximum principal stress in residual tooth tissue: group A was the highest, and there was no significant difference in group B, C, D and E. And the stress distribution area of 5 groups were the same. In prosthodontic layer: group B was the highest, while group A was the lowest, and the stress peak slightly increased with the increase of depth in group C, D and E. And the 5 groups were with the same stress distribution area as well. In adhesive layer: group A was the highest, while group B was the lowest, and there was little difference among group C, D and E. Group A was concentrated in 1/3 of the post tip, while group B,C,D and E were concentrated in 1/3 of the post and the post tips.Complete and high enough dentin ferrule is a requirement for repairing heavily defected maxillary central incisor with fiber post-core crown and cast post-core crown. When the dentin ferrule is incomplete, the stress distribution of the endocrown is more excellent than post-core-crown. And the endocrown with a depth of 3 mm retainer may be the best repair method. As for post-core crown restoration, the cast post-core crown is more favorable for the uniform distribution of residual tooth tissue than the fiber post-core crown.


Assuntos
Coroas , Análise do Estresse Dentário/métodos , Incisivo/fisiologia , Resinas Compostas , Dentina/fisiologia , Análise de Elementos Finitos , Humanos , Técnica para Retentor Intrarradicular , Raiz Dentária
2.
PLoS One ; 15(2): e0229360, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32092128

RESUMO

This study evaluated the von Mises stress (MPa) and equivalent strain occurring around monolithic yttria-zirconia (Zir) implant using three clinically simulated finite element analysis (FEA) models for a missing maxillary central incisor. Two unidentified patients' cone-beam computed tomography (CBCT) datasets with and without right maxillary central incisor were used to create the FEA models. Three different FEA models were made with bone structures that represent a healed socket (HS), reduced bone width edentulous site (RB), and immediate extraction socket with graft (EG). A one-piece abutment-implant fixture mimicking Straumann Standard Plus tissue level RN 4.1 X 11.8mm, for titanium alloy (Ti) and Zir were modeled. 178 N oblique load and 200 N vertical load were used to simulate occlusal loading. Von Mises stress and equivalent strain values for around each implant model were measured. Within the HS and RB models the labial-cervical region in the cortical bone exhibited highest stress, with Zir having statistically significant lower stress-strain means than Ti in both labial and palatal aspects. For the EG model the labial-cervical area had no statistically significant difference between Ti and Zir; however, Zir performed better than Ti against the graft. FEA models suggest that Ti, a more elastic material than Zir, contributes to the transduction of more overall forces to the socket compared to Zir. Thus, compared to Ti implants, Zir implants may be less prone to peri-implant bone overloading and subsequent bone loss in high stress areas especially in the labial-cervical region of the cortical bone. Zir implants respond to occlusal loading differently than Ti implants. Zir implants may be more favorable in non-grafted edentulous or immediate extraction with grafting.


Assuntos
Implantes Dentários para Um Único Dente , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Zircônio/química , Fenômenos Biomecânicos , Simulação por Computador , Humanos , Incisivo/química , Teste de Materiais , Maxila/patologia , Estresse Mecânico , Ítrio/química
3.
Biomed Mater Eng ; 30(5-6): 541-558, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31903978

RESUMO

This study investigated the effect of three different parameters of a dental implant on stress and strain values in the peri-implant bone by finite element analysis. In this work, the effect of diameter, length and elastic modulus on the biomechanical behavior of a new dental implant was simulated using the finite element method. A three-dimensional model of a mandible segment corresponding to the premolar region and twelve dental implant models were obtained. Loads in three directions were distributed on the surface of the coronal area of the dental implants. The dental implant models were obtained in the FreeCAD 0.16 software and the simulations were made using the Abaqus/CAE software. In all cases, higher stress concentrations were obtained in the peri-implant cortical bone between 40.6 and 62.8 MPa, while the highest levels of strain were observed in the peri-implant trabecular bone between 0.002544 and 0.003873. In general, the highest von Mises equivalent stress values were observed in the peri-implant cortical bone. However, in this bone, both the maximum von Mises equivalent stress values and the von Mises strain are similar or inferior to those reported in different studies by finite element for other models of dental implants under immediate loading. Maximum von Mises strain values were observed in peri-implant trabecular bone. However, in this bone strains levels were obtained that maintain bone density or increase it. The effect of the three simulated variables (implant diameter, length, and elastic modulus) have a statistically significant influence on the von Mises equivalent stress and in von Mises strain values.


Assuntos
Interface Osso-Implante , Implantes Dentários , Planejamento de Prótese Dentária , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Fenômenos Biomecânicos/fisiologia , Interface Osso-Implante/patologia , Interface Osso-Implante/fisiopatologia , Implantes Dentários/normas , Modelos Dentários , Módulo de Elasticidade , Humanos , Imageamento Tridimensional , Mandíbula/patologia , Mandíbula/fisiologia , Estresse Mecânico , Suporte de Carga/fisiologia
4.
Biomed Res Int ; 2019: 2041348, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31828093

RESUMO

The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on strain detected in all tested materials showing higher strain in samples with 2 mm thickness compared to 1 mm samples. Shrinkage strain values were the highest in Set PP samples indicated the possibility of undesirable de-bonding.


Assuntos
Cimentos Dentários/química , Resinas Acrílicas/química , Austrália , Resinas Compostas/química , Colagem Dentária/métodos , Análise do Estresse Dentário/métodos , Humanos , Teste de Materiais/métodos , Poliuretanos/química , Cimentos de Resina/química , Resistência à Tração
5.
Microsc Res Tech ; 82(12): 2049-2053, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31587442

RESUMO

Orthodontic brackets, specifically in their slots, are responsible for receiving active orthodontic forces and transferring them to the teeth to be moved. The presence of an altered slot or inaccurate dimensions can influence the mechanical relationship between the bracket and archwire, interfering with the biomechanics of tooth movement. The objective of this study was by comparing the accuracy of slot placement of upper right lateral incisor metal brackets for Bioprogressive Ricketts therapy from five trademarks. The following characteristics were evaluated: height, torque, and internal parallelism of the walls of the slot. The sample included 75 brackets, 15 each from the following trademarks: 3M Abzil, Forestadent, Morelli Rocky Mountain Orthodontics, and Tecnident. Images of the slot profiles were obtained through standardized techniques using scanning electron microscopy, measured by the AutoCAD 2017 software, and compared to Ricketts prescription, respecting standard deviation with the technical and tolerance parameters present in standard ISO 27020. The results indicated that most of the evaluated characteristics were in accordance with the standard parameters, considering the tolerance adopted. There were exceptions found to this pattern of precision in the 3M Abzil brackets with regard to torque variation, and the Morelli brackets in relation to height variation and parallelism between the walls of the slot. Considering the measured dimensional characteristics, the metal brackets used in Bioprogressive Ricketts therapy has satisfactory pattern accuracy; however, there are still some specific inaccuracies in brackets from certain brands that can require more attention during the detailing phase.


Assuntos
Análise do Estresse Dentário/métodos , Incisivo/fisiologia , Braquetes Ortodônticos , Ortodontia/métodos , Humanos , Teste de Materiais , Fios Ortodônticos , Aço Inoxidável , Estresse Mecânico , Propriedades de Superfície , Torque
6.
Am J Orthod Dentofacial Orthop ; 156(3): 326-336, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31474262

RESUMO

INTRODUCTION: Orthodontic mini-implants aid in the correction of distocclusions via direct anchorage (pull from mini-implant to teeth) and indirect anchorage (teeth pulled against other teeth anchored by the mini-implant). The aim of this study was to compare stress levels on the periodontal ligament (PDL) of maxillary buccal teeth in direct and indirect distalization against orthodontic mini-implants and accounting for individual variation in maxillary anatomy and biomechanical characteristics of the compact bone. METHODS: A 3D model of the maxilla containing the different components (teeth, PDL, trabecular and cortical bones) was generated from a computed tomographic scan. Cortical bone was divided into several areas according to previously defined zones. Bone stiffness and thickness data, obtained from 11 and 12 cadavers, respectively, were incorporated into the initial model to simulate the individual cortical bone variation at the different locations. Subsequently, a finite element analysis was used to simulate the distalization modalities. RESULTS: Stresses at the buccal, palatal, mesial, and distal surfaces were significantly different between adjacent teeth under stiffness but not thickness variation. In both distalization modalities, low or no significant correlations were found between stress values and corresponding cortical bone thicknesses. High significant and inverted correlations were observed at the first molar between stress amounts and cortical bone stiffness (direct modality: -0.68 < r < -0.72; indirect modality: -0.80 < r < -0.82; P <0.05). CONCLUSIONS: With the use of a novel finite element approach that integrated human data on variations in bone properties, findings suggested that cortical bone stiffness may influence tooth movement more than bone thickness. Significant clinical implications could be related to these findings.


Assuntos
Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Técnicas de Movimentação Dentária/métodos , Fenômenos Biomecânicos , Parafusos Ósseos , Simulação por Computador , Implantes Dentários , Humanos , Imageamento Tridimensional/métodos , Maxila/anatomia & histologia , Maxila/diagnóstico por imagem , Modelos Anatômicos , Dente Molar , Procedimentos de Ancoragem Ortodôntica/instrumentação , Procedimentos de Ancoragem Ortodôntica/métodos , Desenho de Aparelho Ortodôntico , Ligamento Periodontal , Estresse Mecânico , Técnicas de Movimentação Dentária/instrumentação , Torção Mecânica
7.
J Mech Behav Biomed Mater ; 100: 103389, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31398693

RESUMO

The present study elucidates the mechanical performance of different designs of resin-bonded fixed dental prostheses made of lithium disilicate simulating masticatory loads of anterior or canine guidance. A three-dimensional model of maxilla was constructed containing central incisor and canine teeth, with edentulous space of the lateral incisor. Three designs of prosthesis were created: retained in central incisor (1-I), retained in canine (1-C) and fixed in both teeth (2-IC). The computational analysis was performed for load in canine and central incisor separately (100N, 45°). The tensile and shear stresses were calculated for the resin-bonded fixed dental prosthesis, bonding surface of each retainer and cement layer using 3D finite element analysis. The 20 highest stress values were analyzed using two-way ANOVA and post-hoc Tukey test, all with α = 5%. The computational analysis showed that 2-retainer resin-bonded fixed dental prosthesis presented the worst prognosis regardless of the mandibular movement. ANOVA showed that Mandibular movement*Retainer interaction influenced on the tensile and shear stresses values (p < 0.01). Higher stresses were observed in the connector region for all groups (13-82.2 MPa; 11-70.2 MPa). In order to reduce the stress concentration in the resin-bonded fixed dental prosthesis and the retainer made of lithium disilicate, the occlusion may serve as the selection criteria of the unitary abutment for better sustainability.


Assuntos
Porcelana Dentária/química , Prótese Dentária , Análise do Estresse Dentário/métodos , Imageamento Tridimensional/métodos , Aparelhos Ortodônticos Fixos , Resinas Sintéticas , Simulação por Computador , Dente Canino/fisiologia , Análise de Elementos Finitos , Humanos , Incisivo/fisiologia , Mandíbula/fisiologia , Teste de Materiais , Maxila , Prognóstico , Resistência ao Cisalhamento , Estresse Mecânico , Resistência à Tração , Dente/fisiologia
8.
J Dent ; 88: 103161, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31255639

RESUMO

OBJECTIVES: To evaluate the influence of bone type in terms of bone density and cortical bone thickness, on the stresses induced by two implants under compressive and oblique loads. METHODS: A numerical simulation technique based on the finite element method was applied. Two implant types (M-12 and Astra Tech) were introduced in a model matrix whose geometry was extracted from a real CBCT radiograph of the posterior mandibular region. The Young's module and Poisson's coefficient of the bone qualities described by Misch were calculated. Loads with amplitude of 400 N were exerted in two directions: compressive and 15° oblique to 5 mm above the uppermost part of the implant. RESULTS: The von Misses variant was analysed. Both implant types presented greater tension in the ​​cortical bone area than in the ​​trabecular bone region under compressive loading. For the oblique load condition, the stresses obtained in the cortical zone were significantly higher than those registered as a consequence of compressive loads in both implant types. CONCLUSIONS: Regardless of bone type, the M-12 implants presented lower tensions in the cortical bone than did the Astra implants. The tensions recorded for D3 and D4 bone types in the trabecular zone surrounding the M-12 implants were greater than those recorded for the Astra implants. CLINICAL SIGNIFICANCE: For both compressive and oblique loads, good mechanical behaviour was observed. The decrease in bone quality determines a worse stress distribution, and the cortical bone is overloaded. An efficient distribution of the forces may increase the implants' longevity.


Assuntos
Implantes Dentários , Prótese Dentária Fixada por Implante , Análise do Estresse Dentário/métodos , Mandíbula/diagnóstico por imagem , Simulação por Computador , Planejamento de Prótese Dentária , Módulo de Elasticidade , Análise de Elementos Finitos , Humanos , Estresse Mecânico
9.
Med Sci Monit ; 25: 3933-3940, 2019 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-31131833

RESUMO

BACKGROUND The purpose of this study was to assess the effect of different exposure levels of a dental implant's first thread on adjacent bone stress and strain using the finite element analysis method. MATERIAL AND METHODS Three-dimensional models of 2 threaded implants and abutments with a mandibular bone segment were constructed to represent the covered (C) and exposed models. In the exposed models, the implant was first placed in the bone, and rotated around its axis a quarter-turn each time to simulate 4 different levels of first thread exposure at the mid-lingual side: Upper Flank (UF), Thread Crest (TC), Lower Flank (LF), and Thread Root (TR) models. Oblique forces were applied and analysis was performed. RESULTS Maximum compressive stress magnitude and distribution varied according to the exposed thread profile. In the exposed group, peak stress ranged from 136 MPa to 197 MPa in TC and LF models, respectively, compared to 141 MPa in C model. In LF, UF, and C models, peak stress was observed at the mid-lingual side of the crestal region, while in TC and TR models, peak stress shifted distally in accordance with thread profile. However, alveolar bone volumes which exhibited compressive microstrain levels within the physiological loading and maintenance windows were relatively close in all models. CONCLUSIONS Results suggest that the exposed thread profile influences stress and strain outcomes in the adjacent bone; however, this influence is only limited to a small region around the exposed thread.


Assuntos
Implantes Dentários/efeitos adversos , Análise do Estresse Dentário/métodos , Fenômenos Biomecânicos/fisiologia , Simulação por Computador , Planejamento de Prótese Dentária , Módulo de Elasticidade , Análise de Elementos Finitos , Mandíbula/fisiologia , Software , Estresse Mecânico
10.
J. oral res. (Impresa) ; 8(2): 108-115, abr. 30, 2019. ilus, tab, graf
Artigo em Inglês | LILACS | ID: biblio-1145301

RESUMO

Statement of problem : fracture of endodontically treated teeth is reduced by the use of a post with ferrule, but the effect of different ferrule configurations and dowel materials is not clear. Purpose: to evaluate the effect of ferrules with different configurations and heights on the stress of endodontically treated teeth restored with three different post and dowel materials. Materials and Methods: fifteen models of maxillary central incisors restored with porcelain fused to metal crowns were obtained using pro engineer software. the models were divided into three groups, each consisting of five models with ferrule heights of 0mm, 2mm, 4mm, 2mm with oblique fracture, 4mm with oblique fracture, the models under group GFR were restored with fiberglass reinforced post (GFR) and composite core build-up, group NiCr with a custom cast post metal alloy (NiCr), and group Zr with zirconia post (Zr) and composite core build-up. an oblique load of 100N and 150N at an angle of 135 degrees was applied to the palatal surface of the tooth, a vertical load of 100N and 150N at an angle of 90 degrees was applied to the incisal tip of the tooth. The maximum principal stress and the von mises stress was calculated for the remaining tooth structure and post apex using the finite element analysis (FEA) software. Results: the maximum von misses stress was observed in the apex of the post (p<0.05). Group Zr showed the highest mean stress (6.39Mpa) followed by group NiCr (5.65Mpa). There was a significant difference between post and between NiCr and Zr post for 2mm and 4mm ferrule height, while for 0mm ferrule there was a significant difference between the GFR and NiCr groups (p<0.05). Under oblique load, the maximum mean stress was observed in remaining tooth structures while for vertical load, it was observed at the apex of the post. Regarding ferrule heights, there were significant differences between 0mm-2mm, and 0mm-4mm uniform ferrule in post apex in the case of NiCr posts (p<0.05). Absence of ferrule resulted in higher stress for the NiCr group. Conclusion: higher loads that led to fracture were observed only at the apex of the post. Zirconia posts (group Zr) had higher fracture loads, whereas absence of ferrule resulted in higher fracture load with custom cast posts (group NiCr). Fracture thresholds were high on the remaining tooth structure for all the dowel systems especially for composite core build up irrespective of ferrule height and configuration. Clinical implications: appropriate selection of post and dowel materials in different configurations of ferrule heights ensures clinical success.


Indicación del problema: la fractura de los dientes tratados endodónticamente se reduce mediante el uso de un poste con férula, pero el efecto de diferentes configuraciones de férula y materiales de clavija no está claro. Propósito: evaluar el efecto de los casquillos con diferentes configuraciones y alturas sobre el estrés de los dientes tratados endodónticamente restaurados con tres materiales diferentes de postes y tacos. materiales y métodos: quince modelos de incisivos centrales superiores restaurados con porcelana fundida a coronas de metal se obtuvieron con el software Pro Engineer. Los modelos se dividieron en tres grupos, cada uno de los cuales consta de cinco modelos con alturas de casquillo de 0mm, 2mm, 4mm, 2mm con fractura oblicua, 4mm con fractura oblicua. los modelos del grupo GFR fueron restaurados con poste reforzado con fibra de vidrio (GFR) y acumulación de núcleo compuesto, grupo nicr con una aleación de metal de poste fundido personalizado (NiCr) y grupo Zr con poste de zirconia (Zr) y acumulación de núcleo compuesto. se aplicó una carga oblicua de 100N y 150N en un ángulo de 135º a la superficie palatina del diente. se aplicó una carga vertical de 100N y 150N en un ángulo de 90º a la punta incisal del diente. la tensión principal máxima y la tensión de von mises se calcularon para la estructura dental restante y después del vértice utilizando el software de análisis de elementos finitos (FEA). Resultados: el estrés máximo de von falta se observó en el vértice de la publicación (p<0.05). El grupo Zr mostró el mayor estrés medio (6.39Mpa) seguido del grupo NiCr (5.65Mpa). Hubo una diferencia significativa entre la publicación NiCr y Zr para la altura de la férula de 2mm y 4mm, mientras que para la férula de 0mm hubo una diferencia significativa entre los grupos GFR y NiCr (p<0,05), bajo la carga oblicua, la tensión media máxima en las estructuras dentales restantes, mientras que para la carga vertical, se observó en el vértice del poste. En cuanto a las alturas de la férula, hubo diferencias significativas entre la férula uniforme de 0mm-2mm y de 0mm-4mm en el post-apex en el caso de los postes de NiCr (p<0.05), la ausencia de férula dio como resultado un mayor estrés para el grupo NiCr. Conclusión: las cargas más altas que llevaron a la fractura se observaron solo en el vértice del poste; Los postes de zirconia (grupo Zr) tuvieron mayores cargas de fractura, mientras que la ausencia de férula dio como resultado una mayor carga de fractura con postes moldeados personalizados (NiCr de grupo). Los umbrales de fractura fueron altos en la estructura dental restante para todos los sistemas de clavijas, especialmente para la acumulación de núcleos compuestos independientemente de la altura y configuración de la férula. Implicaciones clínicas: la selección adecuada de materiales de postes y tacos en diferentes configuraciones de alturas de férulas asegura el éxito clínico.


Assuntos
Humanos , Técnica para Retentor Intrarradicular/instrumentação , Análise do Estresse Dentário/métodos , Incisivo/fisiologia , Modelos Biológicos , Estresse Mecânico , Fraturas dos Dentes , Simulação por Computador , Planejamento de Prótese Dentária , Desenho Assistido por Computador , Materiais Dentários/química , Maxila/fisiologia
11.
Indian J Dent Res ; 30(1): 97-101, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30900665

RESUMO

Background: Progressive attachment loss around the teeth because of periodontal disease can result in increased tooth mobility. This adversely affects patient's comfort, function, and esthetics. Periodontal splinting helps in accomplishing stability by redistributing the functional and parafunctional forces. There are various materials that have been used for periodontal splinting. Fiber-reinforced composite, composite resin, and metal-reinforced composite are often used as splinting materials for periodontally compromised teeth. In our study, a comparison was done among these materials for their ability to distribute the stresses at different bone levels in mobile lower incisors splinted together with canines. Materials and Methods: Five patients of age group 25-50 years with Grade 2 and 3 mobile incisors having 40% or more bone loss and firm canines with optimal bone support were selected. From the computed tomography scan of each patient, three models were developed demonstrating splinting of mandibular incisors and canines with metal-reinforced composite, fiber-reinforced composite, and composite resin. So in total, 15 models were developed and each one of them was subjected to vertical and transverse loads of 150 N. Pattern of stress distribution was observed in these models using three-dimensional finite element analysis. Results: After splinting, the stress on the canine increased when bone levels around incisors decreased while stress on incisors reduced. Conclusion: Tested splinting materials were successful in stress distribution, and metal-reinforced composite was found to be better than the other splinting materials.


Assuntos
Resinas Acrílicas , Resinas Compostas , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Teste de Materiais/métodos , Metais , Doenças Periodontais/complicações , Contenções Periodontais , Poliuretanos , Estresse Mecânico , Mobilidade Dentária/etiologia , Mobilidade Dentária/terapia , Adulto , Dente Canino , Feminino , Humanos , Incisivo , Masculino , Mandíbula , Pessoa de Meia-Idade , Radiografia Dentária , Tomografia Computadorizada por Raios X , Mobilidade Dentária/diagnóstico por imagem
12.
Microsc Res Tech ; 82(7): 1032-1040, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30866096

RESUMO

The aim of this in-vitro study was to evaluate microtensile bond strength (µTBS) of two different self-adhesive composites (SACs) on the permanent dentin by applying five different universal adhesive systems. In this study, two different SACs [Vertise Flow (VF), Fusio Liquid Dentin (FLD)] and five different bonding systems [Clearfil Universal Bond Quick (CUB), Single Bond Universal (SBU), All Bond Universal (ABU), Prime Bond Universal (PBU), Futurabond U (FBU)] were used. A total of 22 groups were created in which SACs were applied without adhesive and with five different universal bonding agents in total-etch (TE) and self-etch (SE) modes. Two hundred and forty test sticks were obtained using 48 healthy human molar teeth in total with groups having 10 samples each. The µTBS test was applied to each sample in the Universal test device and the data obtained were analyzed statistically by variance analysis and Tukey HSD test. In addition, the resin-dentin interface and fractures modes in the groups were examined by SEM. Upon examining the µTBS results, the highest values were seen in the use of SBU adhesive in TE mode in VF group, while the lowest values were seen in the FLD control group. The difference between the control and experimental groups was found statistically significant (p < .05). Upon comparing the control groups with each other, it was seen that VF group had higher µTBS values than FLD group and the difference between the groups was found statistically significant (p < .05). The µTBS results and SEM images of the study showed that the use of SACs with universal adhesive systems provides a more effective bond strength.


Assuntos
Colagem Dentária/métodos , Cimentos Dentários/química , Adesivos Dentinários/química , Resinas Sintéticas/análise , Resinas Compostas , Análise do Estresse Dentário/métodos , Humanos , Microscopia Eletrônica de Varredura , Dente Molar , Resistência à Tração
13.
Eur Rev Med Pharmacol Sci ; 23(5): 1855-1863, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30915727

RESUMO

OBJECTIVE: Fiber-reinforced composites (FRC) because of high strength and a low mass can be widely applied in many fields of dentistry. MATERIALS AND METHODS: The types of fibers commonly used in dentistry with the description of physicochemical properties of the reinforcing phase and polymer resin, are specified. The influence of the method of fiber positioning in the sample, their diameter, length and shape of fibers visible in cross-section on the strength of the FRC material, are underlined. The work also paid attention to the volume of the material that occurs as a result of the absorption of water from the oral environment and changes in bonding between matrix and fiber. RESULTS: The clinical procedures and a description of failures that may possibly happen in the oral cavity presented in the work, confirm that they allow fabrication of minimally invasive, lightweight, durable and biocompatible materials. At the moment, the only material group that can be used by direct technique to reach high load-bearing capacity restorations is FRC. CONCLUSIONS: Long-term treatment effectiveness makes FRCs an alternative to prosthetic restorations whose retention is obtained only as a result of mechanically interlocking to the abutment tooth. The use of FRCs in clinical dentistry is part of value-based medicine.


Assuntos
Resinas Compostas/química , Análise do Estresse Dentário/métodos , Odontologia/métodos , Polímeros/química , Humanos , Teste de Materiais , Propriedades de Superfície , Água/química
14.
Biomed Res Int ; 2019: 3126931, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30805363

RESUMO

Objective: The aim of this study is to evaluate the effects of different fiber insertion techniques and thermomechanical aging on the fracture resistance of endodontically treated mandibular premolar teeth restored using bulk-fill composites. Materials and Methods: Eighty human mandibular premolar teeth were randomly divided into eight groups: Group IN, Group BF, Group PRF1, Group PRF2, Group IN-TMA, Group BF-TMA, Group PRF1-TMA ,and Group PRF2-TMA. Group IN (intact) and Group IN-TMA (intact but subjected to thermomechanical aging) served as control groups. In the other six groups, endodontic treatment was performed and standardized mesio-occluso-distal (MOD) cavities were prepared. In BF, PRF1, and PRF2, the cavities were restored with bulk-fill composite only, bulk-fill/Ribbond, and bulk-fill/additional Ribbond, respectively. In BF-TMA, PRF1-TMA, and PRF2-TMA, the teeth were subjected to thermomechanical aging after the restorations. All of the teeth were fractured on the universal testing machine. Fracture surfaces were analyzed with a stereomicroscope. Results: Control groups showed significantly higher fracture strengths than tested groups (P<0.05). No statistically significant difference was observed among the tested groups (P>0.05). Most of the favorable fractures were seen in PRF1, PRF2, and PRF2-TMA. Most of the unfavorable fractures were seen in BF-TMA. Conclusions: Although fiber insertion with different techniques did not increase the fracture strength of teeth restored with bulk-fill composites, it increased the favorable fracture modes. Thermomechanical aging did not change the fracture strength of the groups.


Assuntos
Resinas Compostas/uso terapêutico , Materiais Dentários/uso terapêutico , Resistência à Flexão/efeitos dos fármacos , Fraturas dos Dentes/terapia , Viscosidade/efeitos dos fármacos , Preparo da Cavidade Dentária/métodos , Restauração Dentária Permanente/métodos , Análise do Estresse Dentário/métodos , Humanos , Teste de Materiais/métodos , Polietilenos/uso terapêutico , Dente não Vital/terapia
15.
Biomed Res Int ; 2019: 2196519, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30719440

RESUMO

Objectives: The aim of this study was to evaluate the influence of ferule and the post type on the fracture strength and stress distribution in premolars. Materials and Methods: Forty human mandibular premolars were decoronated, allocated in four groups, and restored as follows: CPC-NF: cast post-and-core and absence of ferule; CPC-F: cast post-and-core and presence of ferule; FPC-NF: glass-fiber posts and absence of ferule; FPC-F: glass-fiber posts and presence of ferule. The fracture strength (FS) and failure patterns were evaluated. Finite element analysis (FEA) evaluated the stress distribution. Results: FS did not differ between CPCs and FPC either in presence or in absence of ferule. The presence of ferule increased FS with both post types. Mean values of FS for ferule groups were higher than functional or parafunctional loads reported in literature, which was not the case for FPC-NF when compared to parafunctional loads. FEA with a functional load showed slightly higher compressive stresses in dentin in the group CPC-NF, which was much lower than the compressive strength of dentin. Lower percentage of catastrophic failures was observed in nonferule groups irrespective of post type, which was explained by the stress concentration in the cervical root region when FEA with the FS load was simulated. Conclusion: Ferule effect was shown to be more important than post type in the analysis. Both posts showed potential to withstand functional loads irrespective of presence of ferule. However, the mean FS was lower than parafunctional loads for FPC in the absence of ferule.


Assuntos
Força Compressiva/fisiologia , Resistência à Flexão/fisiologia , Vidro/química , Fraturas dos Dentes/fisiopatologia , Dente Pré-Molar/fisiopatologia , Resinas Compostas/química , Materiais Dentários/química , Falha de Restauração Dentária , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Humanos , Teste de Materiais/métodos , Cimentos de Resina/química , Estresse Mecânico
16.
Int J Oral Maxillofac Implants ; 34(1): 25-30, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30695084

RESUMO

PURPOSE: To investigate the optimal degree of convergence of the abutment with which the bond strength achieved by the pre-bonding method is comparable with that in direct bonding with a conventional degree of convergence. MATERIALS AND METHODS: Abutments with 5.5-mm diameter, 5-mm height, 0.5-mm shoulder width, and three kinds of degrees of convergence (2, 4, and 6 degrees) were first designed by digital modeling. Their corresponding inner crowns were also modeled, and a gap of 40 µm was kept between the abutment and the inner crown. Thirty abutments and 30 inner crowns were then lathed out from a titanium plate (10 sets per degree of convergence). Six groups were defined in this study, according to the different degrees of convergence and bonding methods (direct bonding, pre-bonding) (n = 10 sets). The samples handled with direct bonding would be cleaned for reuse in tests with pre-bonding. Temporary cement was used as an adhesive, and the bond strength was tested in each set of samples. The comparison among the results was performed by the Kruskal-Wallis test. RESULTS: The mean values of bond strength with direct bonding methods were 349.39 ± 65.75 N, 316.49 ± 54.22 N, and 277.49 ± 56.96 N, and with pre-bonding methods were 279.35 ± 48.58 N, 227.97 ± 26.72 N, and 154.6 ± 23.03 N, respectively (2, 4, and 6 degrees). No statistical difference was found among the values in direct bonding groups and, in pre-bonding groups, only the comparison between 2 and 6 degrees of convergence showed statistical significance (P = .000). Between different bonding methods, statistical differences were shown in abutments with 4 and 6 degrees of convergence (P = .006, P = .000), respectively. The bond strength with pre-bonding methods and 2 degrees of convergence showed no significant difference from that with direct bonding and 6 degrees of convergence. CONCLUSION: The bond strength was inversely proportional to the degree of convergence, and the bond strength of pre-bonding was lower than that of direct bonding with the same degree of convergence. When using the pre-bonding method, the bond strength between the abutment and inner crown with 2 degrees of convergence could be comparable with using the direct bonding method and abutments with conventional degrees of convergence.


Assuntos
Dente Suporte , Colagem Dentária , Cimentos Dentários/química , Análise do Estresse Dentário/métodos , Coroas , Cimentos de Ionômeros de Vidro , Humanos , Teste de Materiais , Titânio/química
17.
J Prosthodont Res ; 63(2): 227-231, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30651211

RESUMO

PURPOSE: Clinical failures of teeth restored with post-and-core are critical issues for the survival of teeth and maintenance of oral functions. A tooth with post-and-core restoration is a complex structure. Cement adhesion is believed to be the weakest component, and breakage in this component leads to changes in stress distribution in the complex structure. The tested hypothesis was that cement breaking processes of prosthetic treated teeth were affected by elastic properties of post-and-cores. METHODS: Finite element analysis focused on sequential adhesion failure between the dentin and cement; the penalty function method was used to analyze stress during each stage of bonding conditions. Failure patterns of adhesion and stress distribution within dentin under load of different materials of post-and-core was observed. RESULTS: Although, an initial failure of cement was observed at the palatal crown margin regardless of the material. Different patterns of adhesion failure between dentin and post-and-cores were observed by different elastic properties of post-and-cores. Stress concentration was observed at the corresponding areas of interface between adhesion failure and continued elements using both post-and-cores. CONCLUSIONS: Using failure criteria for cement adhesion, sequential changes of adhesion failure between dentin and post-and-cores were observed. Local stress concentrations leading to severe destruction of dentin were caused by not only materials of post-and-cores but their adhesive conditions to dentin. Nonlinear finite element analysis (FEA) using complex structure model which deals with alterations of interfacial condition between components could provide the simulation for the clinical failure of teeth restored with post-and-cores.


Assuntos
Colagem Dentária , Cimentos Dentários , Dentina , Módulo de Elasticidade , Técnica para Retentor Intrarradicular , Coroas , Modelos Dentários , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Humanos , Incisivo , Maxila , Estresse Mecânico , Resistência à Tração , Dente não Vital
18.
Am J Orthod Dentofacial Orthop ; 155(1): 98-107, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30591174

RESUMO

INTRODUCTION: Many factors influence the force changes of clear aligners. The purpose of this study was to identify the various factors that influence the force changes generated by polyethylene terephthalate glycol-modified (PET-G) materials. Therefore, a force measurement system based on a flexible thin-film pressure sensor was established. METHODS: A series of clear aligners with 2 material properties and different activations at the maxillary central incisor, maxillary second premolar, and maxillary permanent first molar was designed and fabricated. The first material was conventional PET-G; the second material was modified PET-G with a higher modulus of elasticity and greater abrasion resistance. Several models, including teeth and aligners, were produced. Then, a force change detection device, including a thin-film pressure sensor, a signal acquisition circuit board, and a computer, was applied to measure changes in the forces delivered by the conventional and modified PET-G materials with increased frequencies of appliance removal. Finally, the forces were repeatedly measured to detect the force changes over 48 hours. RESULTS: The forces of both materials decreased similarly over time. These forces also decreased when the aligner removal frequency increased, but the forces decreased differently. The modified PET-G, with a higher modulus of elasticity and greater abrasion resistance, showed a more stable and lower force change than did the conventional PET-G. CONCLUSIONS: The forces delivered by both materials were within the orthodontic force range. Force changes were apparent when the appliance removal frequency increased. Compared with the conventional material, the modified PET-G material showed better stability. Therefore, the modified PET-G is a promising and applicable material with advantages for both orthodontists and patients.


Assuntos
Análise do Estresse Dentário/instrumentação , Aparelhos Ortodônticos Removíveis , Polietilenoglicóis , Análise do Estresse Dentário/métodos , Elasticidade , Humanos , Teste de Materiais , Desenho de Aparelho Ortodôntico , Polietilenotereftalatos , Estresse Mecânico , Fatores de Tempo
19.
Comput Math Methods Med ; 2019: 8074096, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31933678

RESUMO

Purpose: To evaluate the effects of different placements of mesial implants and different angles of distant implants in maxillary edentulous jaws on the stress on the implant and the surrounding bone tissue under dynamic loading. Materials and Methods: Cone beam computed tomography was used to acquire images of maxillary edentulous jaws. Using Mimics 17.0, Geomagic, and Unigraphics NX8.5 software, three-dimensional models were established: two mesial implants were placed vertically in the anterior region of the maxilla (bilateral central incisor, lateral incisor, and canine), and two distant implants were placed obliquely in the bilateral second premolar area at different inclined angles (15°, 30°, and 45°). The established models were designated I-IX. The models were subjected to dynamic load using Abaqus 6.12, with the working side posterior teeth loading of 150 N and simulation cycle of 0.875 s. Results: During the second to fourth phases of the mastication cycle, the stress was mainly concentrated on the neck of the distal implant. The stress of the distal implants was greater than that of mesial implants. Stress levels peaked in the third stage of the cycle. The stress of the distal cortical bone of distal implant of Model I reached the maximum of 183.437 MPa. The stress of the distal cortical bone and cancellous bone of distal implant of Model VIII represented the minima (62.989 MPa and 17.186 MPa, respectively). Conclusions: Our models showed optimal stress reductions when the mesial implants were located in the canine region and the distal implants tilted 30°.


Assuntos
Implantes Dentários , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Imageamento Tridimensional/métodos , Arcada Edêntula/diagnóstico por imagem , Idoso , Tomografia Computadorizada de Feixe Cônico , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Mastigação , Maxila/diagnóstico por imagem , Pessoa de Meia-Idade , Pressão , Estresse Mecânico , Dente
20.
J Prosthodont ; 28(2): e666-e674, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29143403

RESUMO

PURPOSE: To evaluate the effect of distal implant inclination on axial and nonaxial retentive forces of different Locator attachments used to retain mandibular overdentures. MATERIALS AND METHODS: Four duplicate mandibular edentulous acrylic models received 2 implants in the canine areas with 0°, 5°, 10°, and 20° distal inclinations. Experimental overdentures were connected to the implants with Locator extra light retention (Le), Locator light retention (Ll), and Locator medium retention (Lm). For the 20° model, extended range Locator extra-light retention (Lee) and Locator medium retention (Lem) were used. Axial and nonaxial (anterior, posterior, lateral) retentive forces were measured initially and after 540 cycles of denture insertion and removal. Three-way mixed ANOVA was used to analyze axial and nonaxial retentive forces RESULTS: After wear simulation, 20° angulation showed the highest axial retention for Le and Ll while 5° showed the highest retention for Lm; 0° and 5° showed the highest anterior and posterior retention for Lm; 20° showed the highest lateral retention for Le and Ll. For all implant inclinations, Lm showed the highest axial and nonaxial retention, and Le and Lee showed the lowest retention for 10° and 20° inclined implants, respectively. CONCLUSIONS: Axial and nonaxial retention of Locator attachments for implant-retained overdentures are significantly affected by the degree of distal implant inclination and the type of nylon inserts. Lm is recommended to retain overdentures when implants have 5° or 10° distal inclination, and Le and Ll are recommended with 20° inclination to maintain high axial and nonaxial retention after wear.


Assuntos
Prótese Dentária Fixada por Implante , Revestimento de Dentadura , Prótese Dentária Fixada por Implante/métodos , Análise do Estresse Dentário/instrumentação , Análise do Estresse Dentário/métodos , Planejamento de Dentadura , Retenção de Dentadura/métodos , Humanos , Técnicas In Vitro , Mandíbula
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