Influence of transmucosal height in abutments of single and multiple implant-supported prostheses: a non-linear three-dimensional finite element analysis.

The aim of this study was to analyze the influence of three different transmucosal heights of the abutments in single and multiple implant-supported prostheses through the finite element method. External hexagon implants, MicroUnit, and EsthetiCone abutments were scanned and placed in an edentulous maxillary model obtained from a tomography database. The simulations were divided into two groups: (1) one implant with 3.75 × 10 mm placed in the upper central incisor, simulating a single implant-supported fixed prosthesis with an EsthetiCone abutment; and (2) two implants with 3.75 × 10 mm placed in the upper lateral incisors with MicroUnit abutments, simulating a multiple implant-supported prosthesis. Subsequently, each group was subdivided into three models according to the transmucosal height (1, 2, and 3 mm). A static oblique load at an angle of 45 degrees to the long axis of the implant in palatal-buccal direction of 150 and 75 N was applied for multiple and single implant-supported prosthesis, respectively. The implants and abutments were assessed according to the equivalent Von Mises stress analyses while the bone and ceramics were analyzed through maximum and minimum principal stresses. The total deformation values increased in all models, while the transmucosal height was augmented. The transmucosal height of the abutments influences the stress values at the bone, ceramics, implants, and abutments of both the single and multiple implant-supported prostheses, with the transmucosal height of 1 mm showing the lowest stress values.

Assessment of the amount of residual sodium hypochlorite after chemical disinfection of heat-polymerized resins / Evaluación de la cantidad de hipoclorito de sodio residual después de la desinfección química de resina termo-polimerizadas

Aim To evaluate the release of sodium hypochlorite from three different commercial brands of heat-polymerized acrylic resin immersed in water and submitted to mechanical or chemical polishing after disinfection with hypochlorite at different concentrations. Material and methods Fifty-four disk-shaped specimens (n = 18) were made for each resin (Lucitone 550, QC-20, and Classico) and assigned to two groups according to the type of polishing. Specimens were divided in three sub-groups in relation to sodium hypochlorite concentration (1%, 2.5%, and 5.25%), and the groups were immersed for 10-min periods in each sodium hypochlorite concentration. The electrochemical method used for detecting the release of sodium hypochlorite in each specimen was the cyclic voltammetry. Results In the specimens of Clássico resin polished mechanically and immersed in 5.25% sodium hypochlorite, as well as Lucitone and QC-20 resins immersed in 2.5%, the amounts of disinfectant solution released in the four 15-min water exchanges were higher than the four 60-min exchanges. Conclusion There were differences in hypochlorite release from the three commercial brands of denture-base acrylic resins subjected to mechanical polishing. However, no hypochlorite release from the same resins was observed when they were subjected to chemical polishing.

Objetivo Evaluar la liberación de hipoclorito de sodio de 3 marcas comerciales diferentes de resinas termo-polimerizadas sumergidas en agua, y sometidas a pulido mecánico o químico después de la desinfección con hipoclorito a diferentes concentraciones. Material y métodos Cincuenta y cuatro especímenes en forma de disco (n = 18) fueron confeccionados para cada resina (Lucitone 550, QC-20 y Clássico) y asignados a 2 grupos de acuerdo con el tipo de pulido. Las muestras se dividieron en 3 subgrupos en relación con la concentración de hipoclorito de sodio (1, 2,5 y 5,25%), y los grupos se sumergieron durante períodos de 10 min en cada concentración de hipoclorito de sodio. El método electroquímico usado para la detección de la liberación de hipoclorito de sodio en cada espécimen fue a través de voltametría cíclica. Resultados En las muestras pulidas mecánicamente de resina Clássico inmerso en hipoclorito de sodio al 5,25%, así como en las resinas Lucitone y QC-20 inmersas a 2,5%, la cantidad de solución desinfectante liberada en los 4 intercambios de agua de 15 min fue superior a los 4 de 60 min. Conclusión Hubo diferencias en la liberación de hipoclorito de las 3 marcas comerciales de resinas acrílicas sometidas a pulido mecánico. Sin embargo, no se observó liberación de hipoclorito en las mismas resinas cuando se sometieron a pulido químico.

Three-Dimensional Finite Element Analysis of the Biomechanical Behaviors of Implants with Different Connections, Lengths, and Diameters Placed in the Maxillary Anterior Region.

PURPOSE: To evaluate the biomechanical behaviors of multiple implant-supported prostheses with different implant lengths, connections, locations, and restoration materials in the maxillary anterior region using three-dimensional finite element analysis. MATERIALS AND METHODS: A finite element model of a maxillary image was created from a tomography data bank. The simulations were executed in two types of models based on the treatment plan: (1) two implants with 4.0-mm diameters placed in the maxillary central incisors to simulate an implant-supported fixed prosthesis with four elements with a cantilever of both maxillary lateral incisors; (2) two implants with 3.75-mm diameters placed in the maxillary lateral incisors to simulate a conventional fixed prosthesis with four elements with pontics for maxillary central incisors. Subsequently, the models created were subdivided into eight subgroups according to implant length, connection type, and restoration material. A total static oblique load of 150 N was applied to the cingulum area of the palatal surfaces of the four incisors at an angle of 45 degrees to the long axis of the implant in the palatal-labial direction. Bone stresses were analyzed through maximum and minimum principal stresses and ductile material as implant, framework, and abutments were analyzed using von Mises stress criterion. RESULTS: Regardless of implant diameter and type of treatment, the 8.5-mm-long implants exhibited the lowest tensile and compressive stresses. Maximum and minimum principal stresses were identified in the cortical bone. The lowest von Mises equivalent stress values were identified in the metal-ceramic prostheses, with the exception of the cantilever prosthesis model with flat top connection. Conical cone implant models exhibited maximum von Mises equivalent stress in contact with the abutment. CONCLUSION: The lowest principal stresses in the peri-implant bone were observed in implants with conical cone connection and 8.5 mm in length. Also, in most cases, the models with metal-ceramic restorations exhibited better stress distributions.

Total deformation of multiple implant-supported prostheses through three-dimensional finite element analysis / Deformación total de prótesis múltiple implanto-soportadas a través de un análisis tridimensional por elementos finitos

The purpose of this study was to evaluate through finite element analysis (FEA) the total deformation or displacement as a whole system of multiple implant-supported prostheses in the maxillary anterior region with different implant's length, connection, location and restoration material. An edentulous anterior region of a hemi-maxilla model was used in finite element analysis. The simulations were divided in two groups according to treatment plan: 1) two implants were placed in the upper central incisors, simulating an implant-supported fixed prosthesis (acrylic resin and metal-ceramic) of four elements with cantilever of both upper lateral incisors; 2) two implants placed in the upper lateral incisors, simulating a conventional fixed prosthesis of four elements with both upper central incisors as pontic. Models with cantilever prosthesis in acrylic resin showed the highest values of total deformation, which were 17 times higher than those of metal-ceramic in the distal face of the lateral incisors, regardless of the type of implant connection. In conventional prostheses in acrylic resin, external hexagon connections had lower total deformation values compared with morse taper connection. Also, the implant length was found to have no effect on the values of total deformation. In conclusion, total deformation was substantially greater in all models with acrylic resin restorations.

El propósito de este estudio fue evaluar mediante análisis de elementos finitos (FEA) la deformación total o desplazamiento como un sistema completo de prótesis múltiples implanto-soportadas en la región anterior de la maxila con diferentes longitudes, conexiones y posiciones del implantes y variando el material de restauración. Se utlizó un modelo hemi-maxilar de una región anterior desdentada de un modelo para ser analizado por medio de elementos finitos. Las simulaciones fueron divididas en dos grupos de acuerdo con el plan de tratamiento: 1) dos implantes se colocaron en los incisivos centrales superiores, simulando una prótesis fija implanto-soportada (resina acrílica y metal-cerámica) de cuatro elementos con cantilever de ambos incisivos laterales superiores; 2) dos implantes colocados en los incisivos laterales superiores, simulando una prótesis fija convencional de cuatro elementos con los dos incisivos centrales superiores como póntico. Los modelos con prótesis en cantilever en resina acrílica mostraron los mayores valores de deformación total, siendo 17 veces mayor a los de metal-cerámica en la cara distal de los incisivos laterales, independientemente del tipo de conexión del implante. En las prótesis convencionales en resina acrílica, las conexiones hexagonales externas tenían valores deformación total más bajos en comparación con la conexión cono morse. También, se encontró que la longitud del implante no mostró ninguna influencia en los valores de la deformación total. En conclusión, la deformación total fue sustancialmente mayor en todos los modelos con restauraciones de resina acrílica.

Insertion Area in the Mandible Masticatory Muscles for use in Finite Element Analyses / Área de Inserción en la Mandíbula de los Músculos de Masticación para ser Utilizados en Análisis por Elementos Finitos

To validate the virtual finite element analysis (FEA) results, it is needed that the mathematical models take into account the insertion area. Thus, the aim of this study was to measure the insertion area of masticatory muscles in the mandible in human cadavers to be used in FEA. The insertion area of the masticatory mandible's muscles was measured on both sides of fifty human cadavers throughout digital photos and software. The insertion area of the masseter was 7.47(±0.41) cm2, the temporal (inner portion) was 3.05(±0.13) cm2, the temporal (outer portion) was 2.25(±0.28) cm2, the medial pterygoid was 2.2(±0.23) cm2, and the lateral pterygoid was 0.8(±0.05) cm2. In conclusion, there is enough data to be used for the finite element analysis.

Para validar los resultados virtuales de análisis por elementos finitos (FEA) es necesario que los modelos matemáticos consideren el área de inserción muscular. Así, el objetivo de este estudio fue medir el área de inserción en la mandíbula de los músculos de masticación en cadáveres humanos para ser utilizado en FEA. El área de inserción en la mandíbula de los músculos de masticación fue medida en ambos lados de cincuenta cadáveres humanos por medio de fotografías digitales y software. El área de inserción del músculo masetero fue 7,47(±0,41) cm2, la porción interna del músculo temporal fue de 3,05(±0,13) cm2 y su porción externa de 2,25(±0,28) cm2, para los músculos pterigoideo medial fue de 2,2(±0,23) cm2 y pterigoideo lateral 0,8(±0,05) cm2. En conclusión, los datos son suficientes para ser utilizados para análisis de elementos finitos.

Magnitude and distribution of stresses in composite resin and sound dentine interface with mechanical retentions.

BACKGROUND: Adhesive systems are constantly subjected to mechanical and chemical stresses that negatively impact the integrity and durability of the dentine-adhesive interface. Despite the lack of evidence to support or reject the clinical indication for mechanical retention, the potential further contribution of these preparations to the behavior of the composite resin-sound dentine bond has been rarely addressed. The authors evaluated by finite element analysis the effect of mechanical retention on the magnitude and distribution of stresses in a composite resin-sound dentin bonding interface when subjected to tensile and shear forces. MATERIAL AND METHODS: A three-dimensional model was created based on three cylindrical volumes representing the sound dentin, adhesive system, and composite resin. From this main model, two models were designed to simulate dentine bonding: 1) a model with no mechanical retention, which considered flat adhesion; and 2) a model with retention, which considered four hemispherical holes on the dentine surface. Both groups were subjected to linear static analysis under tensile and shear loading of 200N. RESULTS: At the model with retentions' bonding interface under tensile and shear loading, a concentration of Von Mises equivalent stress was observed within the retentions, with a reduction of those stresses on the bonding boundary surface. CONCLUSIONS: Additional mechanical retention increases the tensile strength of the sound dentin-composite resin bonding interface, promoting a decrease in the magnitude of the stresses and their redistribution under tensile and shear loading. Key words:Adhesion, composite resins, dentine, finite element analysis.

Platelet-rich fibrin application in dentistry: a literature review.

The development of bioactive surgical additives to regulate the inflammation and increase the speed of healing process is one of the great challenges in clinical research. In this sense, platelet rich fibrin (PRF) appears as a natural and satisfactory alternative with favorable results and low risks. The following review attempts to summarize the relevant literature regarding the technique of using PRF, focusing on its preparation, advantages, and disadvantages of using it in clinical applications. PRF alone or in combination with other biomaterials seems to have several advantages and indications both for medicine and dentistry, due it is a minimally invasive technique with low risks and satisfactory clinical results.

The influence of the connection, length and diameter of an implant on bone biomechanics.

BACKGROUND: Regardless of the multiple options of connections, diameters and heights for dental implants, the clinician should know the biomechanical behavior of the bone to plan the treatment according to the biological and anatomical conditions of each patient, without risk to the long-term treatment success. REVIEW: The following review attempts to summarize the relevant literature to establish guidelines for clinicians based on the scientific evidence regarding the influence by the implant's connection, diameter and length on the bone biomechanics. CONCLUSIONS: The length, diameter and connection of each implant have a degree of influence in bone biomechanics. Despite the influence of different implant connections, diameters and lengths on peri-implant bone stress and strain, these characteristics should remain within the physiological limits to avoid a pathological overload, bone resorption and consequent risk to the long-term success of implant-prosthetic treatment.

Fuerza máxima de mordida en pacientes adultos mayores de origen mapuche y no mapuche portadores de prótesis parciales removibles clase I Kennedy / Maximum bite force in elderly Mapuche and non-Mapuche patients with Kennedy class I removable partial dentures

OBJETIVO Comparar la fuerza máxima de mordida (FMM) de los pacientes adultos mayores portadores de prótesis parciales removibles con extremo libre bilateral (clase I Kennedy) maxilar y mandibular, en individuos mapuches y no mapuches durante 2 períodos diferentes de medición. PACIENTES Y MÉTODOS Se dividió a 40 sujetos cuyas edades fluctuaban entre 60 y 80 años en 2 grupos de acuerdo con su origen étnico para medir su FMM en la región de molares a través de un dispositivo hidráulico. Los sujetos fueron instruidos para realizar 3 mordidas por lado lo más fuerte posible y el valor más alto fue considerado como fuerza máxima. Los datos fueron analizados por medio del test t de Student y prueba de Levene. RESULTADOS El género masculino presentó mayores valores de FMM (p < 0,05). Además, el grupo de individuos de etnia mapuche presentó mayores valores de FMM (p < 0,05). Se identificaron valores de FMM considerablemente mayores en el período de un mes posterior a la inserción de la nueva prótesis (p < 0,05). CONCLUSIONESLos mayores valores de FMM fueron observados en la etnia mapuche, en individuos de género masculino y un mes posterior a la inserción de ambas prótesis.

OBJECTIVE To compare the maximum bite force (FMM), in two different measurement periods, of mapuche and non-mapuche elderly patients with both maxillary and mandibular Kennedy class I removable partial dentures. PATIENTS AND METHODS A total of 40 subjects with ages ranging between 60 and 80 years were divided into 2 groups according to their ethnic origins to measure FMM in the molar region using a hydraulic device. The subjects were instructed to perform three bites with each side as hard as possible, and the highest value was considered as the maximum force. Data were analyzed by Student's t- test and Levene test. RESULTS Male gender showed higher FMM values (p < 0.05). The group of mapuche individuals showed the highest values of FMM (p < 0.05). Finally, considerably higher FMM values were identified at one-month period subsequent to the insertion of the new prosthesis (p < 0.05). CONCLUSIONS The highest FMM values were observed in patients of mapuche ethnic origin, in male patients, and at one-month period after both prostheses were inserted.

Radiographical and clinical evaluation of critical size defects in rabbit calvaria filled with allograft and autograft: a pilot study.

Regeneration of resorbed edentulous sites can be induced by bone grafts from the subject himself and/or by the use of biomaterials. At present, there has been an extensive search for biomaterials that are evaluated by artificially creating one or more critical defects. The aim of this work was to clinically and radiographically analyze bone formation by the use of some biomaterials in artificially created defects in the parietal bone of rabbits. Six rabbits were used, creating defects of 8 mm in diameter in parietal bones. One defect was maintained with coagulum only, and in others, freeze-dried bone allograft (FDBA), autologous bone, and a combination of autologous bone with FDBA respectively, were added. Animals were sacrificed at 15-90 days with 2 weeks interval each, and calvaria were analyzed macroscopically, measuring by digital caliper the lack of filling at the surface of defects, identifying limits at anteroposterior and coronal view, realizing a digital photograph register of their external surfaces. This was subsequently evaluated radiographically by occlusal film radiography used to quantify its density through software. In conclusion, autologous bone showed the best behavior, clinically as well as radiographically. However, FDBA is a good option as an alternative to autologous bone as its behavior was slightly lower over time. The combination of autologous bone and FDBA in the same defect showed results considerably inferior to grafts used separately. Low radiopacity and clear limits were observed through time for the control coagulum filled defect.

Ultraconservative fixed partial denture: esthetic and preservation of dental structure / Prótese parcial fixa ultraconservadora: estética com preservação de estrutura dental

The oral rehabilitation can be made with several ways with the objective to reestablish the masticatory function and the esthetic of the patient. The aim of this clinical case is to present a different type of fixed partial denture, as alternative option to the dental surgeon, showing particularities like indications, contraindications, advantages, disadvantages and technical procedures necessary to its fabrication. The sequential presentation of the realized procedures emphasized the unique aspects of the dental preparation, impression techniques, and cautions during metal structures and ceramic try-in procedures, and esthetic overlay on the metal with composite resin. As a result, it could be observed that the ultraconservative fixed partial denture required lesser removal dental structure, re-established the esthetic and the occlusion of the patient. Finally, it can be concluded that the ultraconservative fixed partial denture is a treatment option to be used in the small prosthetic space with success both mechanically and esthetically.

A reabilitação oral pode ser realizada de diversas formas com o intuito de restabelecer a função mastigatória e a estética do paciente. Este caso clínico tem o objetivo de apresentar um tipo diferente de prótese parcial fixa, como opção alternativa para o cirurgião-dentista, mostrando suas particularidades quanto à indicação, contraindicação, vantagens, desvantagens e procedimentos necessários à sua elaboração. A apresentação sequencial dos procedimentos realizados ressaltou os aspectos únicos do preparo dental, da técnica de moldagem, dos cuidados a serem observados na prova da estrutura metálica, na prova da cerâmica, dos aspectos diferenciais na cimentação e do recobrimento estético da estrutura metálica com resina composta. Como resultado pode-se observar que a prótese ultraconservadora exigiu menor desgaste estrutural dos dentes pilares, restabeleceu a estética e a oclusão do indivíduo. Diante disso, pode-se concluir que a prótese parcial fixa ultraconservadora é uma opção de tratamento a ser utilizada em pequenos espaços protéticos com sucesso mecânico e estético.

Evaluation of composite reinforcement on the fracture resistance of teeth with unsupported cusps / Evaluación del reforzamiento con resina compuesta sobre la resistencia a la fractura de dientes con cúspides sin soporte

This study evaluated the fracture resistance of maxillary premolars with wide Mesial-Occlusal-Distal (MOD) cavity preparations and unsupported cusps restored by four ways, compared with intact teeth. Thirty five human teeth were divided into five groups: control (G1 - intact teeth) and four experimental groups of MOD-prepared teeth: with buccal (B) and lingual (L) cusps reinforced with composite (Z-250) and restored with silver amalgam (Permite C) (G2); teeth with B and L cusps reinforced and linked with composite (P-60) and restored with silver amalgam (Permite C) (G3); teeth restored with composite (Z-250) by incremental fill technique (G4); and teeth with B and L cusps reinforced and linked with composite (P-60) and restored with composite (Z-250) by incremental fill technique (G5). After thermal cycling (500 cycles, 5°C to 55°C), fracture resistance was tested in a universal testing machine. Statistical analysis of the results (ANOVA) revealed no significant difference (p>0.5) among the groups (G1=157.78Kgf, G2=183.99Kgf, G3=152.53Kgf, G4=182.61Kgf and G5=155.96Kgf). Visual analysis of the teeth tested showed predominance of oblique failure pattern. The four types of restoration evaluated provide fracture resistance with values equivalent to intact teeth in MOD-prepared intact teeth with parallel walls and composite-reinforced cusps

Se evaluó la resistencia a la fractura de los premolares maxilares con preparaciones amplias de cavidades Mesio-Ocluso-Distal (MOD) y cúspides sin soporte restauradas por medio de cuatro formas, en comparación con dientes intactos. Treinta y cinco dientes humanos se dividieron en cinco grupos: control (G1 - dientes intactos) y cuatro grupos experimentales preparados con cavidades MOD: con cúspides bucales (B) y linguales (L) reforzadas con resina compuesta (Z-250) y restaurada con amalgama de plata (Permite C) (G2); dientes concúspides B y L reforzadas y unidas con composite (P-60) y restaurado con amalgama de plata (Permite C) (G3); dientes restaurados con composite (Z-250) a través de la técnica incremental (G4), y dientes con cúspides B y L reforzadas y unidas con resina compuesta (P-60) y restauradas con composite (Z-250) mediante la técnica incremental (G5). Después del ciclado térmico (500 ciclos, 5°C a 55°C), la resistencia a la fractura fue probada en una máquina de ensayo universal. El análisis estadístico de los resultados (ANOVA) no reveló diferencias significativas (p> 0,5) entre los grupos (G1 = 157,78 Kgf, G2 = 183,99 Kgf, G3 = 152,53 Kgf, G4 = 182,61 Kgf y G5 = 155,96 Kgf). El análisis visual de los dientes probados mostró un predominio de patrón de falla oblicua. Los cuatro tipos de restauración evaluados proporcionaron resistencia a fractura con valores equivalentes a los dientes intactos con preparaciones MOD, paredes paralelas y cúspides reforzadas con resina compuesta

Tensile and Flexural Strength of Commercially Pure Titanium Submitted to Laser and Tungsten Inert Gas Welds

This study evaluated the tensile and flexural strength of tungsten inert gas (TIG) welds in specimens made of commercially pure titanium (CP Ti) compared with laser welds. Sixty cylindrical specimens (2 mm diameter x 55 mm thick) were randomly assigned to 3 groups for each test (n=10): no welding (control), TIG welding (10 V, 36 A, 8 s) and Nd:YAG laser welding (380 V, 8 ms). The specimens were radiographed and subjected to tensile and flexural strength tests at a crosshead speed of 1.0 mm/min using a load cell of 500 kgf applied on the welded interface or at the middle point of the non-welded specimens. Tensile strength data were analyzed by ANOVA and Tukey's test, and flexural strength data by the Kruskal-Wallis test (α=0.05). Non-welded specimens presented significantly higher tensile strength (control=605.84±19.83) (p=0.015) and flexural strength (control=1908.75) (p=0.000) than TIG- and laser-welded ones. There were no significant differences (p>0.05) between the welding types for neither the tensile strength test (TIG=514.90±37.76; laser=515.85±62.07) nor the flexural strength test (TIG=1559.66; laser=1621.64). As far as tensile and flexural strengths are concerned, TIG was similar to laser and could be suitable to replace laser welding in implant-supported rehabilitations.

Este estudo avaliou a resistência à tração e à flexão de soldas feitas com gás inerte de tungstênio (TIG) em amostras de titânio comercialmente puro (Ti CP) em comparação com a solda a laser. Sessenta amostras cilíndricas (diâmetro de 2 mm e espessura de 55 mm) foram distribuídas aleatoriamente em três grupos para cada ensaio (n=10): sem solda (controle), solda TIG (10V, 36A, 8 s) e solda com laser de Nd:YAG (380 V, 8 ms). As amostras foram radiografadas e submetidas aos testes de resistência à tração e à flexão em máquina de ensaios mecânicos à velocidade de 1mm/min com célula de carga de 500 kgf aplicada na interface soldada ou no ponto médio das amostras controle. Os dados de resistência à tração foram analisados estatisticamente por ANOVA e teste de Tukey e os dados de resistência à flexão pelo teste de Kruskal-Wallis (α=0,05). Espécimes não-soldados apresentaram resistência à tração (controle=605,84±19,83) (p=0,015) e resistência à flexão (controle=1908,75) (p=0,000) significantemente maiores que os solados com TIG ou laser. Não houve diferença estatisticamente significante (p>0.05) entre os tipos de solda no teste de resistência à tração (TIG=514,90±37,76; laser=515,85±62,07) nem no teste de resistência à flexão (TIG=1559,66; laser=1621,64). As resistências à tração e à flexão foram similares quando as amostras foram soldadas com TIG e a laser.

Tensile and flexural strength of commercially pure titanium submitted to laser and tungsten inert gas welds.

This study evaluated the tensile and flexural strength of tungsten inert gas (TIG) welds in specimens made of commercially pure titanium (CP Ti) compared with laser welds. Sixty cylindrical specimens (2 mm diameter x 55 mm thick) were randomly assigned to 3 groups for each test (n=10): no welding (control), TIG welding (10 V, 36 A, 8 s) and Nd:YAG laser welding (380 V, 8 ms). The specimens were radiographed and subjected to tensile and flexural strength tests at a crosshead speed of 1.0 mm/min using a load cell of 500 kgf applied on the welded interface or at the middle point of the non-welded specimens. Tensile strength data were analyzed by ANOVA and Tukey's test, and flexural strength data by the Kruskal-Wallis test (α=0.05). Non-welded specimens presented significantly higher tensile strength (control=605.84 ± 19.83) (p=0.015) and flexural strength (control=1908.75) (p=0.000) than TIG- and laser-welded ones. There were no significant differences (p>0.05) between the welding types for neither the tensile strength test (TIG=514.90 ± 37.76; laser=515.85 ± 62.07) nor the flexural strength test (TIG=1559.66; laser=1621.64). As far as tensile and flexural strengths are concerned, TIG was similar to laser and could be suitable to replace laser welding in implant-supported rehabilitations.

Evaluation of the flexural strength and elastic modulus of resins used for temporary restorations reinforced with particulate glass fibre.

OBJECTIVE: The flexural strength and the elastic modulus of acrylic resins, Dencor, Duralay and Trim Plus II, were evaluated with and without the addition of silanised glass fibre. MATERIALS AND METHODS: To evaluate the flexural strength and elastic modulus, 60 test specimens were fabricated with the addition of 10% ground silanised glass fibres for the experimental group, and 60 without the incorporation of fibres, for the control group, with 20 test specimens being made of each commercial brand of resin (Dencor, Duralay and Trim Plus II) for the control group and experimental group. After the test specimens had been completed, the flexural strength and elastic modulus tests were performed in a universal testing device, using the three-point bending test. For the specimens without fibres the One-Way Analysis of Variance and the complementary Tukey test were used, and for those with fibres it was not normal, so that the non-parametric Mann-Whitney test was applied. RESULTS: For the flexural strength test, there was no statistical difference (p > 0.05) between each commercial brand of resin without fibres [Duralay 84.32(±8.54), Trim plus 85.39(±6.74), Dencor 96.70(±6.52)] and with fibres (Duralay 87.18, Trim plus 88.33, Dencor 98.10). However, for the elastic modulus, there was statistical difference (p > 0.01) between each commercial brand of resin without fibres [Duralay 2380.64 (±168.60), Trim plus 2740.37(±311.74), Dencor 2595.42(±261.22)] and with fibres (Duralay 3750.42, Trim plus 3188.80, Dencor 3400.75). CONCLUSION: The result showed that the incorporation of fibre did not interfere in the flexural strength values, but it increased the values for the elastic modulus.

Glutaraldehyde release from heat-polymerized acrylic resins after disinfection and chemical and mechanical polishing.

This study evaluated the release of glutaraldehyde from heat-polymerized acrylic resins subjected to disinfection followed by chemical and mechanical polishing. Ninety disc-shaped specimens (15 x 4 mm), 30 per resin (Lucitone 550, QC-20 and Classico), were made and assigned to 2 groups according to the type of polishing. One side of each specimen was not polished and the other was either mechanically (n = 45) or chemically (n = 45) polished, and immersed in water at 50 °C for 1 h to allow the release of intrinsic substances and then kept in distilled water for 7 days. The specimens were disinfected by immersion in 2% glutaraldehyde for 10 min. After this period, 3 specimens from each group were immersed in water for 15, 30, 60, 120 and 240 min. For the 15-, 30-, 60-min immersions, 4 water exchanges were done at the end of period. High performance liquid chromatography (HPLC) was used to detect and quantify the glutaraldehyde released after each period. Data were analyzed statistically by two-way ANOVA and multiple comparisons were done by Tukey's and Scheffé's tests (α = 0.05). No glutaraldehyde release was observed from the specimens with chemical polishing at any of the immersion periods, while the mechanically polished specimens released glutaraldehyde. In the groups with water exchanges, Lucitone released more disinfectant in the 15-min period (0.040 µg/mL), Classico in the 30-min (0.021 µg/mL) and 60-min (0.018 µg/mL) periods, and QC-20 the same amount (-1.760 µg/mL) in all periods. In the groups without water exchanges, Lucitone released the highest amount of disinfectant (-1.370 µg/mL), differing significantly from QC-20 (0022 g/mL) and Classico (0019 g/mL), which were similar. The findings of this showed that chemically polished specimens from the 3 resin brands did not release glutaraldehyde after different periods of immersion, while glutaraldehyde release was observed from the mechanically polished specimens, especially from those made of Lucitone resin.

Evaluation of anodic behavior of commercially pure titanium in tungsten inert gas and laser welds.

PURPOSE: This study evaluated the resistance to corrosion in welds made with Tungsten Inert Gas (TIG) in specimens made of commercially pure titanium (cp Ti) in comparison with laser welds. MATERIALS AND METHODS: A total of 15 circular specimens (10-mm diameter, 2-mm thick) were fabricated and divided into two groups: control group-cp Ti specimens (n = 5); experimental group-cp Ti specimens welded with TIG (n = 5) and with laser (n = 5). They were polished mechanically, washed with isopropyl alcohol, and dried with a drier. In the anodic potentiodynamic polarization assay, measurements were taken using a potentiostat/galvanostat in addition to CorrWare software for data acquisition and CorrView for data visualization and treatment. Three curves were made for each working electrode. Corrosion potential values were statistically analyzed by the Student's t-test. RESULTS: Statistical analysis showed that corrosion potentials and passive current densities of specimens welded with TIG are similar to those of the control group, and had lower values than laser welding. TIG welding provided higher resistance to corrosion than laser welding. CONCLUSION: Control specimens welded with TIG were more resistant to local corrosion initiation and propagation than those with laser welding, indicating a higher rate of formation and growth of passive film thickness on the surfaces of these alloys than on specimens welded with laser, making it more difficult for corrosion to occur.

Shear bond strength of self-etch and total-etch bonding systems at different dentin depths

The purpose of this study was to evaluate the dentin shear bond strength of four adhesive systems (Adper Single Bond 2, Adper Prompt L-Pop, Magic Bond DE and Self Etch Bond) in regards to buccal and lingual surfaces and dentin depth. Forty extracted third molars had roots removed and crowns bisected in the mesiodistal direction. The buccal and lingual surfaces were fixed in a PVC/acrylic resin ring and were divided into buccal and lingual groups assigned to each selected adhesive. The same specimens prepared for the evaluation of superficial dentin shear resistance were used to evaluate the different depths of dentin. The specimens were identified and abraded at depths of 0.5, 1.0, 1.5 and 2.0 mm. Each depth was evaluated by ISO TR 11405 using an EMIC-2000 machine regulated at 0.5 mm/min with a 200 Kgf load cell. We performed statistical analyses on the results (ANOVA, Tukey and Scheffé tests). Data revealed statistical differences (p < 0.01) in the adhesive and depth variation as well as adhesive/depth interactions. The Adper Single Bond 2 demonstrated the highest mean values of shear bond strength. The Prompt L-Pop product, a self-etching adhesive, revealed higher mean values compared with Magic Bond DE and Self Etch Bond adhesives, a total and self-etching adhesive respectively. It may be concluded that the shear bond strength of dentin is dependent on material (adhesive system), substrate depth and adhesive/depth interaction.

Shear bond strength of self-etch and total-etch bonding systems at different dentin depths.

The purpose of this study was to evaluate the dentin shear bond strength of four adhesive systems (Adper Single Bond 2, Adper Prompt L-Pop, Magic Bond DE and Self Etch Bond) in regards to buccal and lingual surfaces and dentin depth. Forty extracted third molars had roots removed and crowns bisected in the mesiodistal direction. The buccal and lingual surfaces were fixed in a PVC/acrylic resin ring and were divided into buccal and lingual groups assigned to each selected adhesive. The same specimens prepared for the evaluation of superficial dentin shear resistance were used to evaluate the different depths of dentin. The specimens were identified and abraded at depths of 0.5, 1.0, 1.5 and 2.0 mm. Each depth was evaluated by ISO TR 11405 using an EMIC-2000 machine regulated at 0.5 mm/min with a 200 Kgf load cell. We performed statistical analyses on the results (ANOVA, Tukey and Scheffé tests). Data revealed statistical differences (p < 0.01) in the adhesive and depth variation as well as adhesive/depth interactions. The Adper Single Bond 2 demonstrated the highest mean values of shear bond strength. The Prompt L-Pop product, a self-etching adhesive, revealed higher mean values compared with Magic Bond DE and Self Etch Bond adhesives, a total and self-etching adhesive respectively. It may be concluded that the shear bond strength of dentin is dependent on material (adhesive system), substrate depth and adhesive/depth interaction.

Evaluation of the efficacy of chemical disinfectants for disinfection of heat-polymerised acrylic resin.

OBJECTIVE: This study evaluated the efficacy of disinfectants on the internal aspect of heat-polymerised acrylic resin contaminated with microbial strains. BACKGROUND: Dentures absorb oral fluids and become contaminated by different microorganisms. METHODS: Two hundred and fifty rectangular specimens were made of heat-polymerised acrylic resin, and then divided into five groups corresponding to the microbial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, S. mutans and Enterococcus faecalis). After contamination, the specimens were immersed in 1 and 2% sodium hypochlorite and 2% glutaraldehyde for periods of 5, 10 and 15 min. The specimens were placed into tubes containing different broths and incubated at 35°C and then visually analysed. Turbidity in the medium indicated microbial growth. The Fisher's exact test was used in the analysis of the results. RESULTS: The strain E. faecalis was the most resistant to the disinfectant solutions, and among them, glutaraldehyde was more effective than 2 and 1% hypochlorite for disinfection for 5 min; in the 10-min period there were no differences between the disinfectants. In 15 min of immersion, 1% hypochlorite and glutaraldehyde were more effective than 2% hypochlorite. CONCLUSIONS: Disinfection for 10 min with 1% hypochlorite and glutaraldehyde is effective in disinfecting the internal aspect of heat-polymerised acrylic resin.