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1.
Braz. j. oral sci ; 20: e211632, jan.-dez. 2021. ilus
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1282550

RESUMO

Non-carious cervical lesions cause destructive dental disorders that actively contribute to the progressive loss of dental structure and the immediate need for dental treatment, due to their multiple symptoms and factors that produce them. Aim: The purpose of the study was to determine the relationship between extrinsic factors and non-carious cervical lesions in patients of the National Hospital Hipólito Unánue. Methods: The research was of a descriptive correlative type. The sample consisted of male and female patients between 18 and 65 years old, who attended the carielogy service of this hospital. For data collection, 2 questionnaires were used to estimate the values of the extrinsic factors that allowed us to obtain the necessary information on the variables to be studied. Spearman's Rho was applied to determine the relationship between the variable's study. Results: According to Spearman's Rho of 0.622, compared to p-0.000 <0.01. Between the variables studied; extrinsic factors and noncarious cervical lesions there is a moderate and significant positive correlation. Conclusion: Through this section it was possible to demonstrate the existing relationship between extrinsic variable factors and non-carious cervical lesions, therefore it was concluded that there is a moderate and significant positive correlation in the sample comprised by the patients of the Hospital in mention


Assuntos
Humanos , Masculino , Feminino , Abrasão Dentária , Erosão Dentária , Análise do Estresse Dentário , Dentina , Desgaste dos Dentes
2.
Dental Press J Orthod ; 26(4): e2119124, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34468559

RESUMO

OBJECTIVE: The aim of this experimental in vitro study was to evaluate whether dental bleaching performed before orthodontic treatment change the shear bond strength (SBS) of monocrystalline and polycrystalline esthetic brackets. METHODS: Sixty (60) bovine incisors teeth were used and randomly divided into the following six groups (n=10): SCP (without bleaching/polycrystalline brackets); SCM (without bleaching/monocrystalline brackets); 1CP (one bleaching session/polycrystalline brackets); 1CM (one bleaching session/monocrystalline brackets); 3CP (three bleaching sessions/polycrystalline brackets); and 3CM (three bleaching sessions/monocrystalline brackets). The brackets were bonded seven days after the bleaching sessions. The samples were submitted to the SBS test in a universal testing machine (Instron model 4411) at 1 mm/min crosshead speed. The two-way analysis of variance (ANOVA) and the Tukey tests were performed at a 5% level of significance. After the mechanical test, samples were evaluated to determine the adhesive remnant index (ARI). RESULTS: The SBS values were significantly higher for the monocrystalline brackets, when compared with the polycrystalline type (p< 0.0001), and significantly higher with three bleaching sessions than without bleaching (p< 0.0436). The ARI showed predominance of failures between the bracket and resin for all the groups (score 3). CONCLUSION: Three dental bleaching sessions increased the SBS values. Monocrystalline brackets showed higher SBS values than the polycrystalline type.


Assuntos
Colagem Dentária , Braquetes Ortodônticos , Clareamento Dental , Animais , Bovinos , Análise do Estresse Dentário , Estética Dentária , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento
3.
Dental Press J Orthod ; 26(4): e21203, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34468562

RESUMO

OBJECTIVE: In this study, simulations were performed by the finite element method (FEM) to determine the tension and displacement in mini-implants and in expander appliance during rapid maxillary expansion, by varying the number and location of the mini-implants. METHODS: For the computational simulation, a three-dimensional mesh was used for the maxilla, mini-implants and expander appliance. Comparisons were made on six different Mini-implant Assisted Rapid Palatal Expander (MARPE) configurations, by varying the amount and location of mini-implants. A closed suture was design and received two activations of 0.25 mm, and an open suture had a 0.5-mm aperture that received 20 activations, also of 0.25 mm. RESULTS: For the closed suture, the maximum displacement values in the mini-implants were between 0.253 and 0.280 mm, and stress was between 1,348.9 and 2,948.2 MPa; in the expander appliance, the displacement values were between 0.256 and 0.281 mm, and stress was between 738.52 and 1,207.6 MPa. For the open suture, the maximum displacement values in the mini-implants were between 2.57 and 2.79 mm, and stress was between 5,765.3 and 10,366 MPa; in the appliance, the maximum displacements was between 2.53 and 2.89 mm, and stress was between 4,859.7 and 9,157.4 MPa. CONCLUSIONS: There were higher stress concentrations in the mini-implant than in the expander arm. In the simulations with a configuration of three mini-implants, stress overload was observed in the isolated mini-implant. Displacements of the mini-implants and arms of the appliance were similar in all simulations.


Assuntos
Implantes Dentários , Técnica de Expansão Palatina , Análise do Estresse Dentário , Análise de Elementos Finitos , Maxila/cirurgia , Palato , Estresse Mecânico
4.
Stomatologiia (Mosk) ; 100(4): 83-87, 2021.
Artigo em Russo | MEDLINE | ID: mdl-34357734

RESUMO

OBJECTIVE: The objective of the study was to improve the strength properties polymer by modifying its basis with various materials. MATERIAL AND METHODS: A polymer in the form of a pink-colored plasticine mass with veins was studied, a quartz mesh «Quartz splint mesh¼ manufactured by RTD (France) and two metal gold-plated wire mesh (0.1 mm and 0.15 mm in diameter) manufactured by Renfert (Germany). Modified test specimens, 65×40×3.5 mm in size were covered with a lavsan film and at a slight pressure the material was rolled out with a glass cylinder flush with the frame. Curing was carried out in Fhotopress photopolymer (Aveyron, RF) under the 460-470 nm wavelength light for 6 minutes on each side. The plates were sawn with a mill in the form of strips 64×10×3.3 mm and kept in distilled water at 37 °C for 50 h before testing. The test of the reinforced samples was carried out with a middle and lower location of quartz and metal grids pre-treated with adhesive and subjected to a 4-point bending test. Bending strength, bending modulus, and fracture deformation were determined using a Zwick/Roell Z010 testing machine with a constant crosshead speed under loading (5±1) mm/min. The statistical significance of the influence of reinforcing elements on the performance of the basic physical and mechanical properties of the base material was determined using Student's t-test. RESULTS: The value of fracture toughness index K1 at the lower location of the quartz mesh was 3.72±0.43 MN/m1.5, which was 4.9 times significantly higher than K1 for the non-reinforced material (p=0.0001). CONCLUSION: The ability to achieve maximum material strength with the lower reinforcement method increases the functional usefulness of removable orthodontic and orthopedic structures with a basis of «Nolatek¼ light-cured material.


Assuntos
Vidro , Polímeros , Resinas Compostas , Análise do Estresse Dentário , Humanos , Teste de Materiais , Aparelhos Ortodônticos , Estresse Mecânico
5.
Stomatologiia (Mosk) ; 100(4): 132-136, 2021.
Artigo em Russo | MEDLINE | ID: mdl-34357742

RESUMO

The information about methods of surface preparation for dentures made from ceramic based on zirconium dioxide for better adhesive fixation is presented in the first part of this article. Micromechanical methods of preparation for cementation of the surface of a zirconia dental prosthesis are discussed in the first part of this article. The second part of the article provides an overview of scientific research on chemical methods for preparing a surface made of zirconia and the problem of the bond strength of polymer cement with a prepared surface made of zirconia.


Assuntos
Colagem Dentária , Cimentos de Resina , Cerâmica , Cimentos Dentários , Porcelana Dentária , Análise do Estresse Dentário , Humanos , Teste de Materiais , Propriedades de Superfície , Zircônio
6.
Am J Dent ; 34(4): 179-185, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34370908

RESUMO

PURPOSE: To compare the effect of the immediate dentin sealing (IDS) and resin cement type on fracture resistance of Class II mesio-occluso-distal (MOD) zirconia inlay restorations. METHODS: 90 Class II MOD cavities on freshly extracted human mandibular third molars, prepared with a high-speed handpiece, were divided into two groups: those with IDS (CR+) and without IDS (CR-). The CEREC system was used to prepare zirconia inlays from Katana super translucent multi-layered blocks. The inlays were cemented with one of three resin cements: RelyX Unicem 2 (RU), Multilink Automix (MA), or Super-Bond (SB). These specimens were stored in water at 37°C for 24 hours and exposed to 5,000 thermal cycles. A vertical load was applied with a metal sphere (Φ 6-mm) on a material testing system, with a crosshead speed of 0.5 mm/minute, until the specimen fractured. Fracture resistance was measured for each tooth, and the fractures were categorized according to Burke's classification. Statistical analyses were conducted using two-way ANOVA and Tukey's honest significant difference tests (P< 0.05). RESULTS: No significant differences in tooth fracture resistance were identified between the CR+ and CR- groups. The SB group had a significantly higher fracture resistance compared to that of the MA group. Fracture morphology showed many mode IV fractures in all groups. IDS did not affect tooth fracture resistance, although there was a significant difference in tooth fracture resistance for different resin cement types used with Class II MOD zirconia inlay restorations. CLINICAL SIGNIFICANCE: Zirconia inlay restorations provide excellent mechanical performance, morphology, and esthetic appearance. In vitro, zirconia inlays cemented with any luting resin cement restored tooth fracture resistance to levels similar to that of intact teeth. Fracture resistance varied among the different resin cements.


Assuntos
Cimentos de Resina , Fraturas dos Dentes , Resinas Compostas , Porcelana Dentária , Análise do Estresse Dentário , Dentina , Humanos , Restaurações Intracoronárias , Teste de Materiais , Zircônio
7.
Int J Oral Maxillofac Implants ; 36(4): 640-649, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34411203

RESUMO

PURPOSE: The aim of this study was to determine the effect of solid (one-piece) and two-piece abutments on the stress profile of narrow implants with marginal bone loss. MATERIALS AND METHODS: Solid and two-piece abutments were connected to a conical internal octagon-connection implant (3.3 mm in diameter, 10 mm in length) and restored with a single crown. Three-dimensional finite element analysis was used to simulate the stress distribution in implant models with different levels of marginal bone resorption (0, 1, 2, and 3 mm). The effect of the design variables under increased bone resorption scenarios, including abutment screw length and diameter, was assessed. Static loading was applied to determine the mechanical response of the implant and cortical and trabecular bone. RESULTS: Marginal bone resorption levels dominated the mechanical response under static loading conditions. A marginal bone loss of 3 mm significantly increased stress values in the implant vicinity and abutment screw. Both abutment designs displayed similar stress distribution in the surrounding bone, but lower stress values were observed in the implant body with two-piece abutments. The abutment screw length was more effective in the resultant stress, as the longer screws reduced the stress in the implants. CONCLUSION: Marginal bone resorption magnitude is the crucial parameter in biomechanics to determine the mechanical behavior. As bone loss increases, resultant stress around implants under mastication forces may lead to implant failure, regardless of abutment type.


Assuntos
Dente Suporte , Implantes Dentários , Fenômenos Biomecânicos , Projeto do Implante Dentário-Pivô , Implantes Dentários/efeitos adversos , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Estresse Mecânico
8.
Int J Oral Maxillofac Implants ; 36(4): e63-e71, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34411208

RESUMO

PURPOSE: This study aimed to investigate whether axial or radial functionally graded root analog implants can optimize the stress and strain distribution near the implant-bone interface in alveolar bone models under static loads using finite element analysis (FEA). MATERIALS AND METHODS: The 3D profile of the root analog implant was captured from a natural tooth in CBCT data. The implant was separated into different layers (3, 5, and 10 layers) to vary the Young modulus axially or radially. The variation in Young modulus was designed to be linear, exponential, or parabolic. Different occlusal loads were applied. The von Mises stress and strain were used to evaluate the system risk of failure. RESULTS: The difference in the numbers of layers had no significant effect on the alveolar bone. In the radial functionally graded implant models, the maximum von Mises stress of the alveolar bone decreased as the outer layer's elastic modulus increased; however, in the vertical functionally graded implants, this stress varied little. The maximum von Mises stress of the cancellous bone changed only slightly, from 2 to 5 MPa in all models. The maximum strain of the alveolar bone varied from 0.001478 mm to 0.003999 mm. Those FEA results were in line with previous findings. CONCLUSION: The functionally graded root analog implants show no significant biomechanical advantages over dense zirconia implants. Radial functionally graded root analog implants should optimize the peri-implant stresses and are biomechanically favorable for design.


Assuntos
Implantes Dentários , Fenômenos Biomecânicos , Simulação por Computador , Implantes Dentários/efeitos adversos , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Estresse Mecânico
9.
Int J Oral Maxillofac Implants ; 36(4): 723-729, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34411211

RESUMO

PURPOSE: To assess the impact of abutment angulation on loosening torque, torque loss, and percentage of torque loss in the prosthesis and abutment screws after aging of the implant-supported prosthesis. MATERIALS AND METHODS: Fifty epoxy maxillary casts with missing central, lateral, and canine teeth were used, and each cast received two implants. All casts were divided into five groups (n = 10): (1) both implants received straight abutments (0-0); (2) the central implant received a straight abutment and the canine implant received a 17.5-degree angled abutment (0-17.5); (3) the central implant received a straight abutment and the canine implant received a 35-degree angled abutment (0-35); (4) both implants received 17.5-degree angled abutments (17.5-17.5); and (5) both implants received 35-degree angled abutments (35-35). For each cast, a three-unit zirconia restoration was fabricated, and a torque meter was utilized to tighten the abutment screw (25 Ncm) and prosthesis screw (18 Ncm). The reverse torque value was recorded for each screw. All restorations were subjected to 3,500 thermal cycles between 5°C and 55°C and load cycled for 150,000 cycles with 50-N load. After the loosening torque was measured for each screw, the torque loss and percentage of torque loss were calculated. RESULTS: There was a statistically significant difference in the torque loss of the central prosthesis screw (P < .001) and canine prosthesis screw (P < .001) between study groups. The 35-35 group showed the highest percentage of torque loss, while the 0-0 group showed the lowest value. A significant difference was found regarding the torque loss of the central abutment screw (P < .001) and canine abutment screw (P < .001). The abutment screws of the 35-35 group showed the highest percentage of torque loss, while the 0-0 groups showed the lowest percentage of torque loss. CONCLUSION: Screw loosening of the prosthesis and abutment screws increases with increasing abutment angulation after aging. In the same fixed prosthesis, the torque loss in the prosthesis and abutment screws was higher in canine screws employing different angled abutments.


Assuntos
Projeto do Implante Dentário-Pivô , Implantes Dentários , Parafusos Ósseos , Dente Suporte , Prótese Dentária Fixada por Implante , Falha de Restauração Dentária , Análise do Estresse Dentário , Humanos , Torque
10.
Gen Dent ; 69(5): 62-66, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34424215

RESUMO

The aim of this study was to evaluate the influence of the geometry of the screwdriver-screw connection on the reverse torque of UCLA screws after repeated cycles of tightening and loosening in an implant-supported prosthesis. Thirty sets of external hex titanium implants, UCLA abutments, and UCLA abutment screws were divided into 3 experimental groups (n = 10). In the square group, the implant and UCLA abutment system were mounted in an upright position using a screw with a square screwdriver-screw connection. In the hexagonal group, the implant and UCLA abutment system were mounted in an upright position using a screw with a hexagonal screwdriver-screw connection. In the hexalobular group, the implant and UCLA abutment system were mounted at 70° using a dynamic UCLA abutment and screw with a hexalobular screwdriver-screw connection. Ten alternating torque-reverse torque cycles were applied to each screw using a screwdriver fixed at the end of a digital torque meter. The screws with a square connection resulted in less loss of reverse torque than the other types. Screws with a hexagonal connection showed a statistically significant loss of torque initially but remained constant for the remaining cycles. For the screws with a hexalobular connection, the loss of torque was greater, and substantial deformation of the plastic in the microstructure was noted. The screwdriver-screw connection geometry had a direct influence on the reverse torque of UCLA screws, and the initial reverse torque of the abutment screws with a square connection was greater than that of the hexagonal and hexalobular designs.


Assuntos
Dente Suporte , Implantes Dentários , Parafusos Ósseos , Análise do Estresse Dentário , Humanos , Torque
11.
Clin Oral Investig ; 25(10): 5595-5612, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34432138

RESUMO

OBJECTIVE: The aim of this study was to perform an integrative review on the layer thickness and microstructure of resin-matrix cements around custom-made or standard teeth root intracanal posts. MATERIALS AND METHODS: An electronic search was conducted on the PubMed using a combination of the following scientific terms: intraradicular post, root intracanal post, resin cement, thickness, adaptation, endodontic post, layer thickness, fit, shape, and endodontic core. The literature selection criteria accepted articles published in the English language, up to May 2021, involving in vitro analyses, meta-analyses, randomized controlled trials, and prospective cohort studies. RESULTS: The search identified 154 studies, of which 24 were considered relevant to this study. The selected studies provided important data considering cement layer thickness, tooth preparation, endodontic post, and type of resin-matrix cement. The anatomical variability of root canal systems, such as the oval- or C-shaped, represents a challenge in dental restoration with tooth root intracanal posts. The fitting of intracanal posts to different root regions is variable resulting in thick and irregular layers of resin-matrix cement. Defects like pores, micro-cracks, and micro-gaps were detected in the resin-matrix cement microstructure and represent spots of stress concentration and fracture. Custom-made tooth root intracanal posts provide a proper fitting and decrease the layer thickness of resin-matrix cement. CONCLUSIONS: In fact, the layer thickness of resin-matrix cements depends on the fitting of endodontic posts to tooth root canals. An increase of resin cement thickness causes the appearance of defects like pores, micro-cracks, and micro-gaps that can induce stress concentration and fractures at interfaces. CLINICAL RELEVANCE: The fitting of the endodontic post into the teeth root canal determine the layer thickness of the resin-matrix cement to establish an adequate retention. However, the increase in the thickness of the resin-matrix cement layer can lead to a high number of defects like pores or cracks and therefore decrease the strength of the interface.


Assuntos
Colagem Dentária , Técnica para Retentor Intrarradicular , Resinas Compostas , Cavidade Pulpar , Análise do Estresse Dentário , Humanos , Teste de Materiais , Estudos Prospectivos , Cimentos de Resina
12.
Beijing Da Xue Xue Bao Yi Xue Ban ; 53(4): 764-769, 2021 Aug 18.
Artigo em Chinês | MEDLINE | ID: mdl-34393242

RESUMO

OBJECTIVE: To evaluate the influence of base materials on stress distribution in endodontically treated maxillary premolars restored with endocrowns using three-dimensional finite element analysis. METHODS: A maxillary second premolar was scanned by Micro-CT and a three-dimensional finite element model of ceramic endocrown with 1 mm thickness of base was established. A model without base was also established as a negative control. Four kinds of conventional base materials with different elastic modulus were adopted: light cure glass ionomer(3M Vitrebond, 3 657 MPa), flowable composite resin(3M Filtek Z350XT Flowable Restorative, 7 300 MPa), high strength glass ionomer(GC Fuji Ⅸ, 13 130 MPa), and posterior composite resin(3M Filtek P60, 19 700 MPa). With a 200 N force loaded vertically and obliquely, the distribution and magnitude of stress in the tooth tissue and adhesive layer were investigated by three-dimensional finite element analysis. RESULTS: The maximum von Mises stress values(vertical/oblique) in dentin and adhesive layer were measured as follows: (1) no base material: 19.39/70.49 MPa in dentin and 6.97/17.97 MPa in adhesive layer; (2) light cure glass ionomer: 19.00/69.75 MPa in dentin and 6.87/16.30 MPa in adhesive layer; (3) flowable composite resin: 18.78/69.33 MPa in dentin and 6.79/16.17 MPa in adhesive layer; (4) high strength glass ionomer: 18.71/69.20 MPa in dentin and 6.74/16.07 MPa in adhesive layer; (5) posterior composite resin: 18.61/69.03 MPa in dentin and 6.70/16.01 MPa in adhesive layer. Under the same loading condition, models with different elastic moduli of base materials had similar stress distribution patterns. The von Mises stress of tooth tissue was mainly concentrated in the tooth cervix. Under oblique load, the regions where von Mises stress concentrated in were similar to those under a vertical load, but the values increased. The stress concentration in the tooth cervix was alleviated in models with base materials compared with the model without base material. The maximum von Mises stress in the tooth tissue and adhesive layer decreased when the elastic modulus of base materials increased and got close to that of dentin. CONCLUSION: The posterior composite resin of which the elastic moduli is high and close to that of dentin is recommended as base material for premolar endocrowns to alleviate the concentration of stress in tooth cervix and adhesive layer.


Assuntos
Resinas Compostas , Colo do Dente , Dente Pré-Molar , Cerâmica , Análise do Estresse Dentário , Dentina , Análise de Elementos Finitos , Humanos , Teste de Materiais , Estresse Mecânico , Microtomografia por Raio-X
13.
J Contemp Dent Pract ; 22(6): 605-609, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34393114

RESUMO

AIM AND OBJECTIVE: The present study compared the frictional forces of three types of self-ligating lingual appliances. MATERIALS AND METHODS: The lingual appliances (2D, Forestadent; Alias, Ormco; and Clippy L, Tomy International) consisted of a self-ligating bracket (second premolar) and two self-ligating tubes (first and second molars) bonded to a stainless steel jig and attached to a "drawing-friction tester." Full-size and non-full-size stainless steel archwires were tested, and the static and kinetic friction acting on six lingual appliance/wire combinations was estimated (n = 5). Three-dimensional micro-computed tomography (micro-CT) analysis of each premolar bracket was performed. The frictional forces were compared between the bracket/wire combinations using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS: The Alias and Clippy L bracket/wire combinations had greater contact between the wire surfaces and bracket slots compared to the 2D bracket/wire combination. For all lingual appliances, the static and kinetic frictional forces were significantly higher for the full-size than non-full-size archwire. The 2D bracket, which had a wider outer wing, had less frictional force than the other appliances. The Alias, which had a narrower outer wing, had a significantly lower frictional force than the Clippy L. CONCLUSIONS: Frictional force was significantly higher for heavier full-size bracket/archwire combinations than for non-full-size archwires. The 2D bracket had lower frictional force due to its archwire-holding mechanism. The outer wing width may influence the frictional resistance. CLINICAL SIGNIFICANCE: The frictional forces of self-ligating lingual appliances vary, and bracket design and archwire size may influence the frictional performance.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Fricção , Humanos , Teste de Materiais , Desenho de Aparelho Ortodôntico , Aço Inoxidável , Titânio , Microtomografia por Raio-X
14.
J Indian Soc Pedod Prev Dent ; 39(2): 178-182, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34341238

RESUMO

Introduction: The primary function of corono-radicular post is to provide retention for the core and to reinforce and to replace the remaining coronal tooth structure. There is considerable controversy regarding optimal choice of the material. An ideal post system should exhibit fracture resistance higher than the average masticatory forces. Finite elemental analysis (FEA) method facilitates precise analysis of the distribution and magnitude of stresses at any point of complex and irregular structures. Thus, this FEA study has been undertaken to evaluate the fracture stress distribution patterns in three fiber posts, viz., carbon, glass fiber, and everStick with an FEA. Materials and Methods: The FE stress analysis was performed with the FE software program (CATIA). Three two-dimensional FEA models of central incisor were simulated, and elastic moduli and Poisson's ratio of all the materials were fed to the software. For all the models, a 200 N vertical force was applied on the lingual surface of the tooth at an angle of 45°. Stress concentration and distribution were evaluated and noted down for all the models. To evaluate the stresses within the restored tooth, the modified von Mises failure criterion was used. The equivalent stresses found in the tested models were compared with the tensile strength of the respective materials. Contact stresses in the luting cement-dentin interface were calculated. Results: Finite element method revealed that maximum stress concentration was at the point of stress application. The stress value was highest in carbon fiber post followed by glass fiber post and least stresses found in everStick post. Maximum stress was observed at the labial surfaces of crown. However, the stress values and distribution were more homogenous in everStick post. Conclusion: The present findings suggest that everStick post has uniform stress distribution within tooth structure.


Assuntos
Técnica para Retentor Intrarradicular , Resinas Compostas , Coroas , Materiais Dentários , Análise do Estresse Dentário , Dentina , Análise de Elementos Finitos , Vidro , Humanos , Estresse Mecânico
15.
J Endod ; 47(9): 1496-1500, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34237385

RESUMO

INTRODUCTION: The aim of this study was to investigate the fracture resistance of endodontically treated and restored permanent mandibular molars with minimally invasive access cavities subjected to thermocycling and dynamic loading. METHODS: Forty first and second mandibular molars were randomly assigned to 4 groups (n = 10/group) as follows: group 1, control (intact teeth); group 2, traditional access cavity (TradAC); group 3, conservative access cavity (ConsAC); and group 4, truss access cavity (TrecAC). After endodontic treatment, teeth were restored with SDR core (Dentsply Caulk, Milford, DE) and subjected to thermocycling followed by dynamic and static loading with a multiaxial fatigue testing machine (Instron, Canton, MA). The maximum load to fracture and pattern of failure (restorable/unrestorable) were recorded. Data were evaluated with analysis of variance and the Tukey post hoc test for multiple comparisons. RESULTS: Fracture resistance of the samples in the control group were higher than those in the experimental groups (P < .005). TradAC exhibited the least resistance to fracture (P < .005). There was no statistically significant difference in the fracture resistance of ConsAC and TrecAC (P = .361) Unrestorable fractures were more frequent in the TradAC group compared with all other groups. CONCLUSIONS: Mandibular molars with ConsAC and TrecAC exhibited superior fracture resistance compared with TradAC. TradAC had the highest number of unrestorable fractures.


Assuntos
Cárie Dentária , Fraturas dos Dentes , Dente não Vital , Resinas Compostas , Análise do Estresse Dentário , Humanos , Mandíbula , Dente Molar/cirurgia
16.
Head Face Med ; 17(1): 24, 2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-34233698

RESUMO

BACKGROUND: Determine the exact slot dimension of a sample of a MBT prescription stainless steel conventional brackets from different manufacturers to compare the actual values with the nominal ones declared by the manufacturers and to verify the compliance with tolerance limits given by the ISO 27020:2019. Different batches from each manufacturer were evaluated to determine whether or not they are different in size. In addition, the geometry of the slot walls was assessed. METHODS: 360 stainless steel preadjusted orthodontic brackets of 12 different manufacturers were assessed. All brackets had a nominal slot size of 0.022 by 0.028 inches, belonged to the right upper central incisor, and were fabricated with the metal injection molding technique (MIM). For each manufacturer, three different manufacturing batches were evaluated. Brackets were coded using a single-blind design. RESULTS: All bracket systems in the study group except one displayed a statistically significant difference with the nominal declared value, although only four of the systems did not comply with the tolerance limits established by the ISO 27020:2019. In most of the systems, the slot height was oversized when compared to the nominal one. A significant interbatch variability was found in most of the evaluated systems. Most of the brackets walls were divergent. CONCLUSIONS: The dimensional accuracy of commercially available metal brackets is not guaranteed. The respect for the norm should be enforced as well as the quality controls along the manufacturing process since orthodontic brackets are a precision medical device.


Assuntos
Braquetes Ortodônticos , Análise do Estresse Dentário , Humanos , Teste de Materiais , Desenho de Aparelho Ortodôntico , Fios Ortodônticos , Método Simples-Cego , Aço Inoxidável
17.
J Contemp Dent Pract ; 22(3): 219-223, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34210918

RESUMO

AIM AND OBJECTIVE: This study aims to evaluate the effect of different resin cements on the bond strength (BS) of custom-made glass fiber posts (GFPs) using the push-out test. MATERIALS AND METHODS: Twenty-four uniradicular bovine teeth were selected. The crowns were sectioned at the cementoenamel junction, and the root canals were treated. The post spaces of the teeth were prepared to a length of 12 mm to receive a GFP. The specimens were randomly assigned to three experimental groups (n = 8), according to the resin cement used to fix the GFPs: RelyX U200 (U200), Allcem Core (ACC), and Allcem Dual (ACD). Each specimen was sectioned into six slices per root third (cervical, middle, and apical), which were subjected to the push-out test. BS values were calculated and compared using the Kruskal-Wallis and Friedman tests. RESULTS: There were significant differences in the middle third, according to the resin cement type used (p < 0.05). ACD showed lower BS values (p < 0.05). Significant differences were observed for ACD among the thirds of the slices, with the lowest values also observed for the middle third (p < 0.05). CONCLUSION: The present study shows that ACC and U200 showed higher BS values compared with ACD, and were also less influenced by the depth of the root dentin. CLINICAL SIGNIFICANCE: The restoration of endodontically treated teeth is a challenge in dentistry, and, in most cases, will require installation of fiberglass pins. In this respect, several types of resin cements are indicated for cementation of these pins; for this reason, their adhesiveness must be adequately investigated. Conventional cements and self-adhesive cements have shown satisfactory performance in cementing the custom-made GFPs, thereby making these cements satisfactory clinical choices. The present study suggests that ACD had lower performance than the other two cements evaluated.


Assuntos
Colagem Dentária , Técnica para Retentor Intrarradicular , Animais , Bovinos , Cavidade Pulpar , Análise do Estresse Dentário , Dentina , Vidro , Teste de Materiais , Cimentos de Resina
18.
Dent Mater ; 37(9): 1425-1436, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34330519

RESUMO

OBJECTVE: Several pre-cementation procedures have been advocated to enhance adhesion between zirconia and resin-based cement. There is, however, limited documentation on how these pre-treatments affect the strength of zirconia crowns as most tests are performed on discs or bars. The aim was to assess the effect of pre-cementation procedures on fracture mode, fracture strength and cement retention on zirconia. METHODS: Two dental zirconia materials with different yttria content were assessed (<4 and>5 mol%). Both discs (n = 45) and crown-shaped specimens (n = 30) of the two materials were pretreated with either air-abrasion or hot-etching with KHF2 and compared with untreated controls with regards to surface roughness, crystallography, wettability, cement adhesion and fracture strength. RESULTS AND SIGNIFICANCE: Air-abrasion improves adhesion and strength of zirconia with moderate yttria content (<4 mol%). Acid etching with heated KHF2 showed the best effect on strength and cement retention on zirconia with higher yttria content (>5 mol%). Application of KHF2 was, however, complicated on crown-shaped specimens. Pre-treatment and cementation protocols should be optimized for different dental zirconias to improve both strength and retention.


Assuntos
Cimentação , Colagem Dentária , Cerâmica , Corrosão Dentária , Análise do Estresse Dentário , Teste de Materiais , Cimentos de Resina , Propriedades de Superfície , Ítrio , Zircônio
19.
J Mech Behav Biomed Mater ; 122: 104653, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34229172

RESUMO

PURPOSE: The purpose of this finite element analysis (FEA) was to evaluate the effect of specific retention biomaterials with different elastic modulus on the biomechanical response to the axial and off-axial biting loads of a mandibular midline single implant-supported overdenture (SIO) model. METHODS: Five 3-dimensional (3D) finite element models of an edentulous mandible with SIO were designed as follows: model M with a titanium retentive element for ball attachment, model P with a PEEK retentive element, model S with a silicone resilient liner retentive element, model T with a thermoplastic acrylic resin retentive element made from a CAD-CAM material, and model A with a polyacetal resin retentive element. Posterior bilateral vertical load (PV) at the 1st molar areas and anterior oblique load (AO) at the incisal edge of the mandibular central incisors at a 30-degree angle of 100 N were applied. Stress values were recorded. RESULTS: Stress values were higher for all models under (AO) loading than under (PV) loading. Model M recorded the highest stress values on the implant, its components, cortical, and cancellous bone under both loading conditions. Under (AO) loading condition, the ball abutment von Mises stress value in model S was almost 7 times lower than that of model M (19 and 130 MPa respectively) and the other 3 models (P, T, and A) (119, 121, and 120 MPa respectively). However, model S recorded the highest value of denture base stress at the attachment area. CONCLUSIONS: The elastic modulus of retention materials can affect stresses generated on the implant overdenture components and supporting structures.


Assuntos
Implantes Dentários , Revestimento de Dentadura , Materiais Biocompatíveis , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Mandíbula , Estresse Mecânico
20.
J Mech Behav Biomed Mater ; 122: 104655, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34246080

RESUMO

The aim of the present laboratory study was to mechanically characterize the interface between two dental resin-based composite (RBC) increments, and to investigate if elevated temperatures have an influence on the quality of the interface mimicking clinical filling procedure. Four RBCs (CLEARFIL MAJESTY™ Posterior, Kuraray (CMP)/Filtek™ Supreme XTE, 3M (FSX)/Grandio®SO, VOCO (GSO)/VisCalor® bulk, VOCO (VCB)) were tested with a fracture toughness test using Chevron notched beams (KI,CNB) at 23, 37 and 54 °C. KI,CNB specimens (3 × 4x25mm) with a V-shaped notch at the incremental interface were loaded until failure in a 4-point bending set-up. Failure modes were characterized using light microscopy, microstructural interface was analyzed using SEM. Statistical analysis was performed using Kolmogorov-Smirnoff test, two-way ANOVA and Tukey Post-Hoc test (p = 0.05). Mean KI,CNB ranged between 0.73 ±0.14 MPam0.5 (VCB, 23 °C) and 1.11 ± 0.11 MPam0.5 (FSX, 23 °C). The tested conventional highly filled RBCs presented fracture toughness at the incremental interface comparable to the cohesive strength of the bulk materials. VCB showed reduced interfacial fracture toughness at 23 and 37 °C, but performed well at elevated temperature of 54 °C.


Assuntos
Resinas Compostas , Análise do Estresse Dentário , Humanos , Teste de Materiais , Propriedades de Superfície , Temperatura
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