Sex Identification Based on Tooth Crown Trait Analysis Among the Mongoloid Race

Abstract Objective: To determine whether anterior and posterior tooth crown traits exhibit sexual dimorphism and identify traits characteristic to the Mongoloid race, especially among the Indonesian population. Material and Methods: This study cross-sectional study analyzed 108 dental casts from 36 males and 72 females. The traits analyzed included winging, shoveling, double shoveling, canine mesial ridge, canine distal accessory ridge, hypocone, metaconule, Carabelli's cusp, protostylid, metaconulid, enteconulid, and hypoconulid. All tooth crown traits were scored based on the ASUDAS scoring system. Descriptive statistics were used to calculate the absolute and relative frequencies. The Chi-square tests was used to determine significant differences in anterior and posterior tooth crown traits between males and females. Level of significance was set at 5%. Results: None of the traits showed sexual dimorphism. Moreover, the most common traits among the Mongoloid race were hypocone (94.4%) and shoveling (86.1%). Conclusion: Although none of the traits exhibited sexual dimorphism, most of them had a higher incidence among females than males. Nonetheless, further research including adequate samples and a similar number of females and males, is needed, especially for population studies.

Comparison of Two Different Non-Radiographic Mixed Dentition Analysis

Objective: To evaluate the applicability of two different non-radiographic mixed dentition analysis in school going children of Aligarh district, India. Material and Methods: Mesiodistal dimension was measured on the dental casts of 120 school going children with electronic digital vernier caliper. The following inclusion criteria were adopted: presence of all fully erupted permanent teeth; no congenital craniofacial anomalies; no previous history of orthodontic treatment; and presence of intact dentition with no proximal caries, restoration, or age related attrition. Predicted values of canines and premolars were obtained from Moyer's at 75th percentile and Tanaka and Johnston mixed dentition analysis. Descriptive statistics were used to calculate the mean and standard deviation. Paired observations were compared by t­test. The level of significance was at p<0.001. Results: The mean difference between the predicted and the actual value of canines and premolars using Moyer's probability table at 75th percentile and Tanaka and Johnston regression equation were statistically significant. No significant differences were found between Moyer's analysis 75th percentile and Tanaka and Johnston mixed dentition analysis in both arch and sexes. Conclusion: These two non-radiographic mixed dentition analysis overestimated the mesiodistal width of canines and premolars.

Mini-implant selection protocol applied to MARPE

Abstract Introduction: Rapid maxillary expansion (RME) is the therapy of choice to correct skeletal transverse dimension in children and adolescents, associating orthopedic and dental effects. In an attempt to prevent the undesirable dentoalveolar effects and optimize the potential of skeletal expansion in individuals in advanced stages of skeletal maturation, the miniscrew-assisted rapid palatal expander (MARPE) was proposed by Lee et al. in 2010. Objective: This paper presents a systematized protocol for selection of miniscrews indicated for MARPE, by the evaluation of cone-beam computed tomographies (CBCT). Variables related with the bone and soft tissue thicknesses at the palatal regions of interest, as well as in relation to the fixation rings of miniscrews of the palatal expander are analyzed and discussed to provide better performance in the clinical practice.

Resumo Introdução: a expansão rápida da maxila (ERM) é a terapia de escolha para a correção da dimensão transversa esquelética em crianças e adolescentes, associando-se efeitos ortopédicos e dentários. Com a finalidade de prevenir os efeitos dentoalveolares indesejáveis e otimizar o potencial de expansão esquelética em indivíduos com estágios avançados de maturação esquelética, a técnica de expansão rápida da maxila assistida por mini-implantes (MARPE) foi proposta por Lee e colaboradores em 2010. Objetivo: o presente estudo apresenta um protocolo sistematizado para seleção de mini-implantes indicados para a MARPE, mediante avaliação de imagens de tomografia computadorizada de feixe cônico (TCFC). Variáveis relacionadas à espessura de tecido ósseo e tecido mole nas regiões de interesse do palato, bem como em relação ao anel de fixação dos mini-implantes do parafuso expansor, são analisadas e discutidas para proporcionar melhor desempenho na prática clínica.

Vertical and horizontal misfit analysis of 3-unit fdp fabricated with different techniques and cad/cam systems

Abstract The aim of this is was evaluate the vertical and horizontal marginal adaptation of 3-unit fixed partial denture frameworks fabricated using different techniques and CAD/CAM systems. A total of 40 framework specimens were fabricated and divided into four groups as follows: lost-wax casting (G1); lost-wax casting with welding (G2); extraoral optical scanning of models (3S/DWOS) (G3); intraoral optical scanning (Cerec Bluecam/Sirona) (G4). A reference model was used to simulate a fixed partial denture with three elements (with a central pontic). The frameworks of G1 and G2 were cast in nickel-chromium (NiCr) alloy, whereas those of G3 and G4 were milled in zirconia. In all groups, vertical and horizontal marginal adaptation (over-contour and under-contour) was evaluated using a three-dimensional optical microscope (Quick Scope, Mitutoyo). The results showed higher vertical marginal misfit in G1 than in the other groups (p<0.001). Regarding horizontal marginal misfit, higher over-contour values occurred in G3 than in the other groups (p<0.001). G3 did not show under-contour at all, whereas the other groups did not differ from each other in this regard (p>0.05). Within the limitations of this study, it can be concluded that lost-wax casting with welding is a viable alternative to the use of CAD/CAM systems to fabricate frameworks of three-unit FPDs, since the techniques yielded similar vertical misfit values. Extra-oral CAD/CAM systems showed the highest horizontal misfit (over-contour) compared to other groups.

Resumo O objetivo deste estudo foi avaliar a adaptação marginal vertical e horizontal de infraestruturas de prótese fixas de três elementos confeccionadas por diferentes técnicas e diferentes sistemas CAD/CAM. Um total de 40 infraestruturas foram confeccionadas e divididas em quatro grupos: fundição por cera perdida (G1); fundição por cera perdida com ponto de solda (G2); escaneamento óptico extraoral para escaneamento do modelo (3S/DWOS); escaneamento óptico intraoral (Cerec Bluecam/Sirona) (G4). Uma matriz metálica foi utilizada para simular uma prótese fixa de três elementos (com pôntico central). As infraestruturas do G1 e G2 foram fundidas em liga metálica de níquel-cromo (NiCr), enquanto que as infraestruturas de G3 e G4 foram fresadas em zircônia. Todos os grupos foram analisados quanto à adaptação marginal vertical e horizontal (sobrecontorno e subcontorno) em microscópio óptico tridimensional (Quick Scope, Mitutoyo). Os resultados apresentaram maiores valores de desadaptação marginal vertical no G1 comparados aos outros grupos (p<0,001). Em relação a desadaptação marginal horizontal, maiores valores de sobrecontorno foram observado no G3 em comparação com os demais grupos (p<0,001). Não foi observado valores de subcontorno para o G3, enquanto que os demais grupos não apresentaram diferença significante para o subcontorno (p> 0,05). Dentro das limitações do presente estudo, pode-se concluir que a técnica convencional após ponto de solda é uma alternativa viável para confecção de infraestruturas de próteses fixas de três elementos comparado ao uso de sistemas CAD/CAM, uma vez que as técnicas apresentaram valores de adaptação marginal vertical similares. Os sistemas CAD/CAM extraoral apresentou o maior desajuste horizontal (sobrecontorno) em comparação com outros grupos.

Toxicity testing of four silver nanoparticle-coated dental castings in 3-D LO2 cell cultures / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

To address the controversial issue of the toxicity of dental alloys and silver nanoparticles in medical applications, an in vivo-like LO2 3-D model was constructed within polyvinylidene fluoride hollow fiber materials to mimic the microenvironment of liver tissue. The use of microscopy methods and the measurement of liver-specific functions optimized the model for best cell performances and also proved the superiority of the 3-D LO2 model when compared with the traditional monolayer model. Toxicity tests were conducted using the newly constructed model, finding that four dental castings coated with silver nanoparticles were toxic to human hepatocytes after cell viability assays. In general, the toxicity of both the castings and the coated silver nanoparticles aggravated as time increased, yet the nanoparticles attenuated the general toxicity by preventing metal ion release, especially at high concentrations.

Exploring a new method for superimposition of pre-treatment and post-treatment mandibular digital dental casts in adults / 北京大学学报(医学版)

OBJECTIVE@#To explore a cone beam computed tomography (CBCT)-independent method for mandibular digital dental cast superimposition to evaluate three-dimensional (3D) mandibular tooth movement after orthodontic treatment in adults, and to evaluate the accuracy of this method.@*METHODS@#Fifteen post-extraction orthodontic treatment adults from the Department of Orthodontics, Peking University School and Hospital of Stomatology were included. All the patients had four first premolars extracted, and were treated with straight wire appliance. The pre- and post-treatment plaster dental casts and craniofacial CBCT scans were obtained. The plaster dental casts were transferred to digital dental casts by 3D laser scanning, and lateral cephalograms were created from the craniofacial CBCT scans by orthogonal projection. The lateral cephalogram-based mandibular digital dental cast superimposition was achieved by sequential maxillary dental cast superimposition registered on the palatal stable region, occlusal transfer, and adjustment of mandibular rotation and translation obtained from lateral cephalogram superimposition. The accuracy of the lateral cephalogram-based mandibular digital dental cast superimposition method was evaluated with the CBCT-based mandibular digital dental cast superimposition method as the standard reference. After mandibular digital dental cast superimposition using both methods, 3D coordinate system was established, and 3D displacements of the lower bilateral first molars, canines and central incisors were measured. Differences between the two superimposition methods in tooth displacement measurements were assessed using the paired t-test with the level of statistical significance set at P<0.05.@*RESULTS@#No significant differences were found between the lateral cephalogram-based and CBCT-based mandibular digital dental cast superimposition methods in 3D displacements of the lower first molars, and sagittal and vertical displacements of the canines and central incisors; transverse displacements of the canines and central incisors differed by (0.3±0.5) mm with statistical significance.@*CONCLUSION@#The lateral cephalogram-based mandibular digital dental cast superimposition method has the similar accuracy as the CBCT-based mandibular digital dental cast superimposition method in 3D evaluation of mandibular orthodontic tooth displacement, except for minor differences for the transverse displacements of anterior teeth. This method is applicable to adult patients with conventional orthodontic treatment records, especially the previous precious orthodontic data in the absence of CBCT scans.

Compensatory Class III malocclusion treatment associated with mandibular canine extractions

ABSTRACT Skeletal Class III malocclusions are ideally treated with orthodontic-surgical approaches. However, if there are no significant soft tissue implications and the patient does not want to undergo orthognatic surgery, other treatment options may be considered. The current case report describes a compensatory alternative for Class III malocclusion treatment, by means of mandibular canine extractions. This treatment alternative provided facial profile and occlusal improvement, which remains stable seven years posttreatment.

RESUMO As más oclusões esqueléticas de Classe III são idealmente tratadas com intervenções ortodôntico-cirúrgicas. Contudo, se não existirem implicações estéticas faciais e se o paciente não desejar se submeter à cirurgia ortognática, outras opções de tratamento podem ser consideradas. O presente caso clínico descreve um tratamento compensatório alternativo para a má oclusão de Classe III, com extrações de caninos inferiores. Esse tratamento alternativo propiciou melhoras no perfil facial e na oclusão, que permaneceu estável após sete anos da sua finalização.

Resistência à tração uniaxial de copings fundidos e cimentados sobre munhões cone-morse com diferentes diâmetros e alturas / Uniaxial tensile strength of cast cemented copings for cone-morse prosthetic implant abutments with different diameters and heights

Objetivo: avaliar a resistência à tração de copings fundidos cimentados sobre pilares cone-morse com diferentes alturas e diâmetros. Material e métodos: quatro grupos (G1: 3,5 mm x 4 mm; G2: 3,5 mm x 6 mm; G3: 4,5 mm x 4 mm; e G4: 4,5 mm x 6 mm) com cinco amostras cada tiveram seus copings encerados, fundidos (liga de Ni-Cr) e cimentados (Panavia F, carga de 6 Kfg durante cinco minutos) sobre os respectivos pilares já torqueados com 25 Ncm. Depois, as amostras foram imersas em água destilada a 37oC ± 2oC durante 24 horas e submetidas ao ensaio de tração até soltura das restaurações. Os dados obtidos foram analisados estatisticamente quanto ao atendimento das pressuposições de normalidade e de homogeneidade de variância, pelos testes de Shapiro-Wilk, Levene e Anova dois critérios (α=5%). Resultados: os valores (média ± desvio-padrão) de resistência à tração (em Newtons) foram: G1: 108,9 ± 37,2; G2: 168,6 ± 43,9; G3: 143,4 ± 57,1; G4: 236,8 ± 52,2. Não houve interação estatisticamente significativa entre as variáveis diâmetro e altura (p=0,446). Ao se comparar os valores de resistência à tração, notou-se efeitos estatisticamente significativos entre o diâmetro (p=0,030) e a altura (p=0,003) dos munhões cone-morse. Munhões com 4,5 mm de diâmetro proporcionaram resistência à tração significativamente superior àquela obtida na condição em que foram empregados munhões com 3,5 mm, tanto nas condições 4 mm quanto 6 mm de altura. A resistência à tração foi aumentada (37%) com munhões 4,5 mm comparados aos munhões 3,5 mm. A resistência à tração foi aumentada (60,7%) com a altura de 6 mm, comparada à altura de 4 mm. Conclusão: pilares para implantes cone-morse com maiores dimensões proporcionam maior segurança e estabilidade às coroas cimentadas sobre implantes.

Objective: to evaluate the tensile strength of cemented copings on cone-morse abutments with different heights and diameters. Material and methods: four groups (G1: 3.5 mm x 4 mm; G2: 3.5 mm x 6 mm; G3: 4.5 mm x 4 mm; and G4: 4.5 mm x 6 mm) with five samples each had their waxed copings and cast in Ni-Cr alloy, being cemented (Panavia F, 6 Kgf-load, 5 minutes) on their respective already torqued abutments (25 Ncm). Then, samples were immersed in distilled water (37oC ± 2oC) for 24 hours and subjected to the tensile test until restorations being separated. The data obtained were analyzed statistically for normality and homogeneity of variances by the Shapiro-Wilk and Levene tests. Comparisons were made using the 2-way Anova test (α=5%). Results: the values (mean ± standard deviation) of tensile strength (in Newtons) were: G1: 108.9 ± 37.2; G2: 168.6 ± 43.9; G3: 143.4 ± 57.1; G4: 236.8 ± 52.2. There was no statistically significant interaction between the variables diameter and height (p=0.446). When comparing values of tensile strength, we observed statistically significant effects for diameter (p=0.030) and height (p=0.003). Abutments with a 4.5 mm diameter provide significantly higher tensile strength to those obtained with 3.5 mm in both 4 mm and 6 mm height conditions. The tensile strength was increased (37%) for the 4.5 mm compared to the 3.5 mm condition. The tensile strength was increased (60.7%) with a height of 6 mm, compared to height of 4 mm. Conclusion: abutments for cone-morse implants with larger dimensions provide greater safety and stability for cemented crowns.

Desajuste vertical entre implante de hexágono interno e pilares Ucla totalmente calcináveis e com base de CoCr após a fundição pelo processo convencional / Vertical misfit between internal hexagon implants and Ucla burnout and CoCr prefabricated base abutments after conventional casting procedures

Objetivo: avaliar, por meio de um microdurômetro, o grau de desajuste na adaptação de pilares Ucla em implantes. Material e métodos: foram utilizados dez implantes de hexágono interno de plataforma regular, e seus respectivos componentes protéticos do tipo Ucla com antirrotacional, como seguem: dez pilares Ucla totalmente calcináveis e dez pilares Ucla com base de CoCr. Todos os pilares Ucla foram fundidos pelo mesmo laboratório de prótese e pelo mesmo processo laboratorial. Cada implante recebeu apenas dois pilares, que foram anexados por meio de um parafuso de titânio quadrado utilizando-se torque de 30 Ncm com torquímetro manual. Cada conjunto implante/pilar recebeu quatro marcações aleatórias em torno da circunferência, na qual foram feitas as medições do espaço existente entre as peças utilizando uma lupa estereoscópica de 100 vezes de aumento. Resultados: os resultados obtidos mostraram diferenças significativas entre os grupos submetidos ao teste Mann-Whitney (p < 0,05). Conclusão: o pilar Ucla com base de CoCr apresentou menor desajuste marginal vertical, quando comparado ao pilar Ucla totalmente calcinável, após o processo de fundição nos implantes de hexágono interno.

Objective: to evaluate, using a microhardness device, the misfit between Ucla abutments and internal hex implants. Material and methods: 10 internal hex implants received 10 Ucla burnout and 10 Ucla abutments with CoCr collar. All the abutments were cast in the same laboratory and under the same protocol. A square-head titanium screw was tightened to a 30 Ncm using a manual wrench. Each abutment/implant set receive four random markings around its perimeter. A stereoscopic lens was used to investigate the misfi t at 100 magnification. Results: there was a statistically significant difference between tested abutments (Mann-Whitney p < 0.05). Conclusion: the Ucla abutment with the CoCr collar presented less vertica misfit values after casting for internal hex dental implants.

Fixa metálica

Com o passar do tempo e o avanço tecnológico, certas técnicas ou etapas na confecção de próteses convencionais foram perdidas. O crescente uso do CAD/CAM, conciliado a falta de tempo, fez com que algumas etapas importantes do processo fossem esquecidas, como, por exemplo, como realizar uma estrutura metálica proporcional à cerâmica aplicada sobre ela.

As time passed and technology advanced, certain techniques or stages of conventional prostheses manufacturing were lost. The increasing use of CAD/CAM combined with lack of time caused some important stages of the process to be forgotten, such as how to make a metal structure proportional to the ceramic appllied to it.

Porosidades de fundição e suas causas / Porosities casting and their causes

A técnica moderna de fundição laboratorial permite um maior controle das ligas metálicas se comparada aos processos utilizados antigamente. O processo de fundição apresenta muitas variáveis e exige experiência. Durante a transformação de fase do resfriamento, o metal sofre várias modificações, praticamente todas as porosidades são geradas na passagem do estado líquido da liga para o sólido. O ideal é compreender os conceitos da metalurgia que influenciam o aparecimento de porosidades e não apenas decorar as indicações.

Reinforcement of provisional restoration with cast metal framework: A case report / 대한치과보철학회지

Provisional restoration plays an important role in the process of restoration with fixed partial denture by providing protection and restoring function and esthetics of abutment tooth. This is especially true in patients requiring use of provisional prosthesis for a long term. However, such situations may lead to higher possibility of provisional prosthesis fracture, and if expected so, reinforcement of provisional prosthesis should be considered. In this article, a patient requiring prosthetic treatment with increase of vertical dimension of occlusion was introduced. Due to increased vertical dimension of occlusion, the provisional restoration was expected to withstand relatively larger amount of load during a relatively long observation period. In order to minimize possible occurrence of fracture, reinforcement of the provisional restoration was sought by insertion of cast-metal framework and by using bis-acryl resin. The reinforced provisional restoration showed satisfactory results during the observation period of 4 months.

Severe Angle Class III skeletal malocclusion associated to mandibular prognathism: orthodontic-surgical treatment

ABSTRACT The present case report describes the orthodontic treatment of a young adult patient (18y / 1m), Class III skeletal malocclusion, with mandibular prognathism and significant dental compensation. The canine relation was Class III, incisors with tendency to crossbite and open bite, moderate inferior crowding, and concave profile. Skeletal correction of malocclusion, facial profile harmony with satisfactory labial relationship, correction of tooth compensation and normal occlusal relationship were obtained with orthodontic treatment associated to orthognathic surgery. This case was presented to the Brazilian Board of Orthodontics and Facial Orthopedics (BBO), as part of the requirements to become a BBO diplomate.

RESUMO O presente caso clínico descreve o tratamento ortodôntico de um paciente com 18 anos e 1 mês de idade, portador de má oclusão esquelética de Classe III, com prognatismo mandibular e significativa compensação dentária. A relação entre caninos era de Classe III, incisivos com tendência à mordida cruzada e mordida aberta, moderado apinhamento inferior, além de perfil côncavo. A correção esquelética da má oclusão; a harmonia do perfil facial, com relação labial satisfatória; correção da compensação dentária e relação oclusal normal foram obtidas com o tratamento ortodôntico associado à cirurgia ortognática. Esse caso foi apresentado à Diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), como parte dos requisitos para a obtenção do título de Diplomado pelo BBO.

Marginal and internal fit of zirconia copings obtained using different digital scanning methods

Abstract The objective of this study was to evaluate the marginal and internal fit of zirconia copings obtained with different digital scanning methods. A human mandibular first molar was set in a typodont with its adjacent and antagonist teeth and prepared for an all-ceramic crown. Digital impressions were made using an intraoral scanner (3Shape). Polyvinyl siloxane impressions and Type IV gypsum models were also obtained and scanned with a benchtop laboratory scanner (3Shape D700). Ten zirconia copings were fabricated for each group using CAD-CAM technology. The marginal and internal fit of the zirconia copings was assessed by the silicone replica technique. Four sections of each replica were obtained, and each section was evaluated at four points: marginal gap (MG), axial wall (AW), axio-occlusal edge (AO) and centro-occlusal wall (CO), using an image analyzing software. The data were submitted to one-way ANOVA and Tukey's test (α = 0.05). They showed statistically significant differences for MG, AO and CO. Regarding MG, intraoral scanning showed lower gap values, whereas gypsum model scanning showed higher gap values. Regarding AO and CO, intraoral digital scanning showed lower gap values. Polyvinyl siloxane impression scanning and gypsum model scanning showed higher gap values and were statistically similar. It can be concluded that intraoral digital scanning provided a lower mean gap value, in comparison with conventional impressions and gypsum casts scanned with a standard benchtop laboratory scanner.

Comparison of digital models generated from three-dimensional optical scanner and cone beam computed tomography

PURPOSE: The objective of this study was to compare the accuracy of digital models from 3 dimentional (3D) optical scanner and cone beam computed tomography (CBCT). MATERIALS AND METHODS: We obtained digital models from 11 pairs of stone casts using a 3D optical scanner and a CBCT, and compared the accuracy of the models. RESULTS: The error range of average positive distance was 0.059 - 0.117 mm and negative distance was 0.066 - 0.146 mm. Statistically (P < 0.05), average positive distance was larger than 70 µm and shorter than 100 µm, and that of negative distance was larger than 100 µm and shorter than 120 µm. CONCLUSION: We concluded that the accuracy of digital models generated from CBCT is not appropriate to make final prostheses. However, it may be acceptable for provisional restorations and orthodontic diagnoses with respect to the accuracy of the digitalization.

A pilot study of root position in orthodontic diagnosis model set-up / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the importance of root information in diagnosis set-up by constructing three-dimensional (3D) digital models with individual anatomic roots.</p><p><b>METHODS</b>Pretreatment cone-beam CT (CBCT) and laser scanning data were collected from two patients (extraction and non-extraction each) with skeletal Class I malocclusion. Threshold segmentation of the CBCT was performed to generate a 3D digital model which has individually isolated tooth. This model and the scan model were superimposed to generate an integrated model (Mo) composed of high-resolution surface scan crowns sutured to the CBCT roots. Pretreatment dentition plaster model were made into set-up model. The diagnosis model set-up was performed successively by three orthodontists and one senior orthodontic technician. Set-up model scan of each patient after tooth alignment was obtained. The isolated composite teeth were individually superimposed onto the set-up model surface scan to creat set-up model (Ma, Mb, Mc, Md) containing root position. These isolated composite teeth were also superimposed onto the posttreatment surface scan depicting the posttreatment model (M). In order to observe whether diagnosis model set-up would cause exposure of the root, Ma-Md were compared with Mo, which showed the true positions of alveolus. In order to validate the accuracy of the expected root position setup, Ma-Md were compared with the true root position represented by M. Color displacement maps generated to measure the discrepancies of root positions.</p><p><b>RESULTS</b>Nonparallel and exposure of the root was found in all setup models. Color displacement maps through molar superimpositions showed maximum differences of 8.79 mm for the maxillary teeth and 9.96 mm for the mandibular teeth.</p><p><b>CONCLUSIONS</b>Diagnosis model set-up based only on crown can not absolutely ensure the good alignment of roots without root exposure. It is necessary to construct the integrated model including root for diagnosis during tooth arrangement process.</p>

Capacidad de sellado de tres agentes cementantes para restauraciones coronarias indirectas / Sealing ability of three luting agents used for cementation of indirect coronal restorations

Objetivo: comparar ex vivo, por medio de un modelo de filtración bacteriana, la capacidad de sellado de un ionómero vítreo modificado con resinas, de un ionómero vítreo convencional y de un cemento de fosfato de cinc, utilizados para la cementación de coronas coladas (AU). Materiales y métodos: un total de 30 premolares humanos sanos, extraídos, fueron preparados de forma estandarizada para recibir una corona metálica con terminación en chamfer sobre dentina. Se realizaron impresiones, se vaciaron en densita tipo IV, se enceraron y se colaron en aleación de oro tipo III. Luego fueron separadas al azar en tres grupos de 10 (n=10) especímenes cada uno. Las coronas del grupo 1 fueron cementadas con Rely-X Luting Plus (3M/ESPE); y las del grupo 2, con Ketac-Cem (3m/ESPE); y las del grupo 3 (control), con el cemento de fosfato de cinc Harvard Cement (Harvard Debtal International GmbH, Hoppengarten, Alemania). Todos los especímenes fueron termociclados. Posteriormente, la superficie metálica oclusal fue reducida 1 mm hasta exponer la dentina, y las muestras se esterilizaron en autoclave. El proceso de filtración se realizó por medio de un sistema de doble cámara con medio de cultivo. El medio de la cámara superior se inoculó con E. faecalis y el sistema fue incubado durante 60 días. En la cámara inferior, la filtración bacteriana se controló diariamente. Los datos registrados fueron analizados por medio de las pruebas de Kaplan-Meyer y de Fischer, con un nivel de significación de P<0,05. Resultados: el tiempo de supervivencia para Rely-X Luting Plus no pudo ser estimado, ya que fue superior a los 60 días, tiempo máximo de duración de la experiencia. Para Ketac-Cem fue de 60 días, con un intervalo de confianza (95 por ciento) de 29,6-90,4. Y para Harvard Cement fue de 40 días, con un intervalo de confianza de 32,6-47,4. Las diferencias entre los grupos fueron estadísticamente significativas. Conclusión: Rely-X Plus demostró una capacidad de sellado superior.

Evaluation of the marginal fit of metal copings fabricated on three different marginal designs using conventional and accelerated casting techniques: An in vitro study.

Introduction: Abundant resources and techniques have been used for complete coverage crown fabrication. Conventional investing and casting procedures for phosphate-bonded investments require a 2- to 4-h procedure before completion. Accelerated casting techniques have been used, but may not result in castings with matching marginal accuracy. Aims and Objectives: The study measured the marginal gap and determined the clinical acceptability of single cast copings invested in a phosphate-bonded investment with the use of conventional and accelerated methods. Materials and Methods: One hundred and twenty cast coping samples were fabricated using conventional and accelerated methods, with three finish lines: Chamfer, shoulder and shoulder with bevel. Sixty copings were prepared with each technique. Each coping was examined with a stereomicroscope at four predetermined sites and measurements of marginal gaps were documented for each. Statistical Analysis: A master chart was prepared for all the data and was analyzed using Statistical Package for the Social Sciences version. Evidence of marginal gap was then evaluated by t-test. Analysis of variance and Post-hoc analysis were used to compare two groups as well as to make comparisons between three subgroups . Results: Measurements recorded showed no statistically significant difference between conventional and accelerated groups. Conclusion: Among the three marginal designs studied, shoulder with bevel showed the best marginal fit with conventional as well as accelerated casting techniques. Accelerated casting technique could be a vital alternative to the time-consuming conventional casting technique. The marginal fit between the two casting techniques showed no statistical difference.

Strain gauges's analysis on implant-retained prosthesis' cast accuracy.

Introduction: A proper cast is essential for a successful rehabilitation with implant prostheses, in order to produce better structures and induce less strain on the implants. Aims: The aim of this study was to evaluate the precision of four different mold filling techniques and verify an accurate methodology to evaluate these techniques. Materials and Methods: A total of 40 casts were obtained from a metallic matrix simulating three unit implant-retained prostheses. The molds were filled using four different techniques in four groups (n = 10): Group 1 - Single-portion filling technique; Group 2 - Two-step filling technique; Group 3 - Latex cylinder technique; Group 4 - Joining the implant analogs previously to the mold filling. A titanium framework was obtained and used as a reference to evaluate the marginal misfit and tension forces in each cast. Vertical misfit was measured with an optical microscope with an increase of 120 times following the single-screw test protocol. Strain was quantified using strain gauges. Data were analyzed using one-way ANOVA (Tukey's test) (α =0.05). The correlation between strain and vertical misfit was evaluated by Pearson test. Results: The misfit values did not present statistical difference (P = 0.979), while the strain results showed statistical difference between Groups 3 and 4 (P = 0.027). Conclusions: The splinting technique was considered to be as efficient as the conventional technique. The strain gauge methodology was accurate for strain measurements and cast distortion evaluation. There was no correlation between strain and marginal misfit.

Effect of veneering material on the deformation suffered by implant-supported fixed prosthesis framework

Knowing how stresses are dissipated on the fixed implant-supported complex allows adequate treatment planning and better choice of the materials used for prosthesis fabrication. Objectives: The aim of this study was to evaluate the deformation suffered by cantilevered implant-supported fixed prostheses frameworks cast in silver-palladium alloy and coated with two occlusal veneering materials: acrylic resin or porcelain. Material and Methods: Two strain gauges were bonded to the inferior surface of the silver-palladium framework and two other were bonded to the occlusal surface of the prosthesis framework covered with ceramic and acrylic resin on each of its two halves. The framework was fixed to a metallic master model and a 35.2 N compression force was applied to the cantilever at 10, 15 and 20 mm from the most distal implant. The measurements of deformation by compression and tension were obtained. The statistical 2-way ANOVA test was used for individual analysis of the experiment variables and the Tukey test was used for the interrelation between all the variables (material and distance of force application). Results: The results showed that both variables had influence on the studied factors (deformation by compression and tension). Conclusion: The ceramic coating provided greater rigidity to the assembly and therefore less distortion compared with the uncoated framework and with the resin-coated framework. The cantilever arm length also influenced the prosthesis rigidity, causing higher deformation the farther the load was applied from the last implant. .