Reliability of light microscopy and a computer-assisted replica measurement technique for evaluating the fit of dental copings

Abstract The aim of this in vitro study was to assess the reliability of two measurement systems for evaluating the marginal and internal fit of dental copings. Material and Methods: Sixteen CAD/CAM titanium copings were produced for a prepared maxillary canine. To modify the CAD surface model using different parameters (data density; enlargement in different directions), varying fit was created. Five light-body silicone replicas representing the gap between the canine and the coping were made for each coping and for each measurement method: (1) light microscopy measurements (LMMs); and (2) computer-assisted measurements (CASMs) using an optical digitizing system. Two investigators independently measured the marginal and internal fit using both methods. The inter-rater reliability [intraclass correlation coefficient (ICC)] and agreement [Bland-Altman (bias) analyses]: mean of the differences (bias) between two measurements [the closer to zero the mean (bias) is, the higher the agreement between the two measurements] were calculated for several measurement points (marginal-distal, marginal-buccal, axial-buccal, incisal). For the LMM technique, one investigator repeated the measurements to determine repeatability (intra-rater reliability and agreement). Results: For inter-rater reliability, the ICC was 0.848-0.998 for LMMs and 0.945-0.999 for CASMs, depending on the measurement point. Bland-Altman bias was −15.7 to 3.5 μm for LMMs and −3.0 to 1.9 μm for CASMs. For LMMs, the marginal-distal and marginal-buccal measurement points showed the lowest ICC (0.848/0.978) and the highest bias (-15.7 μm/-7.6 μm). With the intra-rater reliability and agreement (repeatability) for LMMs, the ICC was 0.970-0.998 and bias was −1.3 to 2.3 μm. Conclusion: LMMs showed lower interrater reliability and agreement at the marginal measurement points than CASMs, which indicates a more subjective influence with LMMs at these measurement points. The values, however, were still clinically acceptable. LMMs showed very high intra-rater reliability and agreement for all measurement points, indicating high repeatability.

The marginal fit of lithium disilicate crowns: Press vs. CAD/CAM

Abstract: This study aimed to compare the vertical marginal gap of teeth restored with lithium disilicate crowns fabricated using CAD/CAM or by pressed ceramic approach. Twenty mandibular third molar teeth were collected after surgical extractions and prepared to receive full veneer crowns. Teeth were optically scanned and lithium disilicate blocks were used to fabricate crowns using CAD/CAM technique. Polyvinyl siloxane impressions of the prepared teeth were made and monolithic pressed lithium disilicate crowns were fabricated. The marginal gap was measured using optical microscope at 200× magnification (Keyence VHX-5000, Japan). Statistical analysis was performed using Wilcoxon test. The lithium disilicate pressed crowns had significantly smaller (p = 0.006) marginal gaps (38 ± 12 μm) than the lithium disilicate CAD/CAM crowns (45 ± 12 μm). This research indicates that lithium disilicate crowns fabricated with the press technique have measurably smaller marginal gaps compared with those fabricated with CAD/CAM technique within in vitro environments. The marginal gaps achieved by the crowns across all groups were within a clinically acceptable range.

Effect of software version and parameter settings on the marginal and internal adaptation of crowns fabricated with the CAD/CAM system

Objective This study investigated the marginal and internal adaptation of individual dental crowns fabricated using a CAD/CAM system (Sirona’s BlueCam), also evaluating the effect of the software version used, and the specific parameter settings in the adaptation of crowns.Material and Methods Forty digital impressions of a master model previously prepared were acquired using an intraoral scanner and divided into four groups based on the software version and on the spacer settings used. The versions 3.8 and 4.2 of the software were used, and the spacer parameter was set at either 40 μm or 80 μm. The marginal and internal fit of the crowns were measured using the replica technique, which uses a low viscosity silicone material that simulates the thickness of the cement layer. The data were analyzed using a Friedman two-way analysis of variance (ANOVA) and paired t-tests with significance level set at p<0.05.Results The two-way ANOVA analysis showed the software version (p<0.05) and the spacer parameter (p<0.05) significantly affected the crown adaptation. The crowns designed with the version 4.2 of the software showed a better fit than those designed with the version 3.8, particularly in the axial wall and in the inner margin. The spacer parameter was more accurately represented in the version 4.2 of the software than in the version 3.8. In addition, the use of the version 4.2 of the software combined with the spacer parameter set at 80 μm showed the least variation. On the other hand, the outer margin was not affected by the variables.Conclusion Compared to the version 3.8 of the software, the version 4.2 can be recommended for the fabrication of well-fitting crown restorations, and for the appropriate regulation of the spacer parameter.

Comparative evaluation of marginal adaptation between nanocomposites and microhybrid composites exposed to two light cure units.

Background: Recent advances in resin adhesives and restorative materials, as well as an increased demand for esthetics, have lead to the introduction of newer resin-based composites like nanocomposites and light-curing units like light emitting diodes (LEDs). Aim: The present study was conducted to evaluate the effect of conventional quartz tungsten halogen (QTH) curing unit and blue LED on marginal adaptation of microhybrid composite (Filtek Z250) and nanocomposite (Filtek Z350) resins. Materials and Methods: Eighty Class V cavities were prepared on, extracted human premolars and were divided into four groups of 20 each. The four groups were designed according to the restorative resin and light cure unit used microhybrid/QTH, nanocomposites/QTH, microhybrid/LED and nanocomposites/LED. After thermocycling and immersion in 2% Basic Fuschin dye solution, the teeth were sectioned and dye penetration was observed under a stereomicroscope at 20X magnification. Statistical Analysis: All the samples were scored and results were analyzed using the "Kruskal Wallis and Mann Whitney tests" with "Wilcoxone correction." Results: The results revealed least microleakage in microhybrid composites exposed to QTH and maximum in nanocomposites exposed to LED. Conclusion: Microhybrid composites exhibited lesser microleakage than nanocomposite resins.

Radiographic analysis of root canal fillings: influence of two sealers on the perception of voids

The aim of this ex vivo was to investigate if two radiopaque root canal sealers with different formulations would influence the radiographic perception of root canal fillings. The root canals of 48 extracted maxillary canines were prepared and randomly assigned to 3 groups of 16 specimens each. In each group, the root canals were filled by lateral condensation of gutta-percha and one of the tested sealers: Endométhasone, Sealer 26, or a non-radiopaque sealer. A through-and-through void was simulated in half of the specimens from each group (n=8). The buccolingual radiographic images obtained were randomly interpreted for voids existence by a radiologist and an endodontist. The differences in sensitivity and specificity between groups and examiners were compared using, respectively, Fisher's Exact and McNemar tests at 5 percent significance level. Both radiopaque sealers caused a significant decrease in sensitivity at the coronal part of fillings. The use of Endométhasone increased specificity values for both coronal and apical portions of the root canal fillings. In conclusion, the tested sealers influenced the radiographic perceptions of laterally condensed root canal fillings in a different way.

O propósito deste estudo ex vivo foi investigar se dois cimentos obturadores de fórmulas diferentes influenciariam a percepção radiográfica de obturações de canais radiculares. Os canais radiculares de 48 caninos superiores extraídos foram preparados e divididos em 3 grupos. Em cada grupo os canais foram preenchidos através da condensação lateral da guta-percha e de um dos cimentos testados (Endométhasone, Sealer 26 e cimento não-radiopaco), e um defeito de ponta a ponta foi simulado em metade dos espécimes de cada grupo (n=8). As imagens radiográficas vestíbulo-linguais obtidas foram aleatoriamente interpretadas quanto à existência de defeitos por um radiologista e um endodontista. As diferenças em sensibilidade e especificidade entre os grupos e examinadores foram comparadas respectivamente usando-se os testes Exato de Fisher e McNemar ajustados ao nível de significância de 5 por cento. Ambos os cimentos radiopacos ocasionaram uma redução significativa da sensibilidade na parte cervical das obturações. O uso do Endométhasone aumentou os valores de especificidade para as porções cervical e apical das obturações dos canais radiculares. Concluiu-se que os cimentos testados influenciaram de maneira distinta a percepção radiográfica de obturações endodônticas executadas com condensação lateral.

Comparison of resin push-out strength to root dentin of bovine- and human-teeth.

Aim : To compare the push-out strength of bovine- and human-root dentin and, thus, evaluate the suitability of bovine-root dentin to substitute human-root dentin for bond strength testing. Materials and Methods : Ten single-rooted human-teeth and ten bovine incisors were prepared using a #3 bur of a fiber post system (12 mm long). The posts were duplicated with resin cement (Duolink). The root canals were treated with All Bond 2 adhesive system and the resin posts were cemented using Duolink. The specimens were cut perpendicular to their long axis, yielding disc-specimens with 1.5 mm thickness, which were submitted to a push-out test (1 mm/min). Ten bond strength values per group (n = 10) were used for statistical analysis (Student t test, a =.05). Results : Statistically significant differences were found for the bond strength values between bovine- (4.1 ± 1.3 MPa) and human-root dentin (8.6 ± 5.7 MPa) (P =.0001). Conclusion : The push-out strengths of bovine- and human-root dentin were statistically different.

Comparación de la adaptación cervical de casquetes metálicos con o sin refuerzo / Comparison of cervical adaptation of metal caps with or without reinforcement

La permanencia y éxito actual de las coronas metalocerámicas como medio de rehabilitación del paciente, nos indica que no es una simple moda dentro de la odontología, sino que constituye una alternativa de solución de diferentes situaciones clínicas que se presentan día a día, pensando en la falencia con la que tropezamos. Teniendo en cuenta que el éxito o el fracaso de nuestras restauraciones metalocerámicas dependen en gran porcentaje de la adaptación de la misma a la superficie dentaria preparada, es importante considerar la problemática más frecuente, que es la línea gap o espacio existente entre la restauración coronaria (corona total) y la preparación dentaria, y su repercusión en la clínica. El objetivo del trabajo fue comparar la adaptación cervical de los casquetes metálicos con y sin refuerzo, además se verificó si las características en el diseño inciden en la adaptación cervical. El estudio fue de tipo experimental "In Vitro", para lo cual se confeccionó un troquel metálico a partir de un diente natural sano, tallado, según las instrucciones de la técnica de la silueta, para recibir una corona metalocerámica; en el laboratorio, sobre el mismo se confeccionaron los casquetes con o sin refuerzo, o los cuerpos de prueba. En ello se hicieron las mediciones. El desajuste cervical se midió con un miscroscopio óptico comparador de la marca Nikon, las lecturas fueron realizadas en la cara proximal, en vestibular y lingual de cada cuerpo de prueba y troquel (12 puntos de medición, totalizando 24 mediciones). En el resultado se constata que hubo un diferencia estadísticamente significativa entre el factor material con o sin refuerzo (p≤ 0,05) y no así por el factor caras y la interacción material (con o sin refuerzo) por caras. Teniendo en cuenta el factor caras, las medidas en un punto de adaptación marginal fueron mesial (87,6) distal (69) vestibular (58.6) los que sí tenían....

Análise in vitro do selamento marginal apical de duas técnicas de obturações de canais radiculares associadas a dois tipos de cones mestres / In vitro evaluation of apical leakage of two root canal obturation technique and two different masters points

O objetivo deste estudo foi avaliar a capacidade seladora, no sentido ápico-cervical, da obturação de canais radiculares realizada pelas técnicas: da Compressão Hidráulica Vertical com cone acessório e Compactação Lateral, variando nesta, o tipo de cone principal. Foram utilizados 45 dentes, divididos em 3 grupos com 15 elementos cada. Grupo 1: Compactação Lateral, utilizando-se como cone principal (cone mestre) um cone de guta-percha padronizado (conicidade 0,02) com o mesmo calibre do último instrumento utilizado no preparo apical do canal radicular. Grupo 2: Compactação Lateral, utilizando-se como cone principal (cone mestre) um cone acessório tipo M (medium), calibrando em uma régua calibradora. Grupo 3: técnica da Compressão Hidráulica Vertical, utilizando como cone principal (cone mestre) um cone acessório tipo M (medium) também calibrado em uma régua calibradora. A qualidade do selamento proporcionada pela obturação foi avaliada pela leitura linear efetivada por computação gráfica, da quantidade de penetração de soro fetal bovino em azul de metileno a 1%. Os resultados obtidos demonstraram não haver diferença significativa entre os três grupos.

Adaptación y filtración marginal de incrustaciones de cerámica inyectada y cerómero / Adaptation and marginal leakage of injected ceramics and ceromer inlays

Esta investigación comparó la adaptación cavitaria de incrustaciones confeccionadas con dos tipos de materiales: uno cerámico, la porcelana inyectada IPS Empress, y otro de base orgánica, el cerómero Targis. Se efectuaron tallados sobre molares seleccionados previamente y mantenidos en solución fisiológica a baja temperatura. Sobre ellos se prepararon cavidades MOD con paredes divergentes, ángulos redondeados y profundidades y espesores estandarizados. Se confeccionaron diez incrustaciones de porcelana inyectada y diez de cerómero, que se adhirieron con resinas de curado dual siguiendo estrictamente las indicaciones proporcionadas por el fabricante. Una vez fijadas a sus respectivas preparaciones se sometió a las piezas a un proceso de termociclado en solución de fucsina básica, con posterior inclusión en resina epoxi. Se cortaron los tacos obtenidos en sentido longitudinal y así se evaluó, mediante la utilización de un microscopio metalográfico, la adaptación cavitaria de las restauraciones en tres zonas predeterminadas, a 100 aumentos de magnificación. La filtración marginal fue evaluada con un microscopio óptico de 14 aumentos. No se observó diferencia estadísticamente significativa en la adaptación general entre las muestras de porcelana inyectada y las de cerómero, siendo de 91,25um (DS 35,48) el promedio de la brecha hallada en las primeras, y de 63,51um (DS26,21) el hallado en las segundas. No se observó filtración marginal alguna en la zona oclusal de la totalidad de las muestras, tanto en la interfase diente/resina de fijación como en la interfase resina de fijación/incrustación. A nivel proximal, sólo 5 especímenes mostraron filtración en la interfase diente/resina de fijación, pero ninguna lo hizo en la interfase resina de fijación/incrustación

Por qué se retrae el margen gingival de las restauraciones y cómo prevenirlo? / Why does the gingival margin of restorations retracts and how to prevent it?

Una situación por demás desagradable en las consultas de mantenimiento o de control es cuando se observa la visibilidad del margen de las coronas provocadas por la retracción de la encía. No cabe duda que el mayor empeño fue empleado para ocultar dicha terminación, ubicando adecuadamente el margen de la preparación, sin embargo, el defecto por demás frecuente se produce. Veamos qué maniobras, qué situaciones se deben evitar o qué acciones se deben realizar para que a largo plazo no se produzca la tan temida retracción. Podemos enumerar las posibles causas: 1- Comenzar la toma de impresión con la encía inflamada. 2- Lesión periodontal a causa de la placa bacteriana. 3- Maniobras operatorias incorrectas. a) Ubicación inadecuada del margen gingival. b) Invasión del espacio biológico. c) Incorrecta toma de impresión. 4- Apresuramiento en la toma de las impresiones. 5- Uso incorrecto de los elementos de higiene. 6- Anatomía ósea subyacente que predispone a los cambios de posición del margen gingival

Accuracy and porosity of denture bases submitted to two polymerization cycles.

In this study was verified accuracy and porosity of denture bases submitted to double cycles of polymerization. Thirty-Six master casts were made in dental stone from the impression of the metal die. They were divided in three groups. Denture bases of conventional acrylic resin were made on the casts of the groups I (GI-control) and II (GII), polymerized in water bath during 9 hours at 73 degrees C, and specific resin for microwave polymerization were made on the casts of the group III (GIII) and cured at 500 W during 3 minutes. Accuracy was verified by the weight of a impression material put between the denture base and cast die under load of 2 Kg. Afterwards, all the denture bases were relined by addition method and those of the group I and II were relined with the same material and polymerization technic. The denture bases of the group II were filled with the same resin, however cured in microwave oven with 500 W during 3 minutes. Accuracy was reevaluated. The porosity was verified by the immersion of the specimens in a solution of permanent black ink and the pores were counted through a stereo light microscope under magnification of 6.3 x. The average and standard deviation obtained for accuracy before and after the relining were respectively: GI: 0.63 +/- 0.02 - 0.66 +/- 0.03; GII: 0.63 +/- 0.03 - 0.68 +/- 0.03: GIII: 0.58 +/- 0.02 - 0.80 +/- 0.05. There was a significant difference (p < 0.05 as tested by Tukey) only for the group III. The average and standard deviation for porosity before and after the relining were respectively: GI: 8.33 +/- 0.63 - 9.25 +/- 0.85; GII: 8.17 +/- 0.98 - 10.08 +/- 1.63: GIII: 5.41 +/- 0.78 - 6.58 +/- 1.02. There was a significant difference (p < 0.05) for the group III before relining. The conclusion is that after relining, the conventional resin cured by water bath or microwaves energy showed a better adaptation, and the highest number of pores.

Avaliaçäo "in vitro" da qualidade do vedamento marginal cérvico-apical de alguns agentes cimentantes utilizados na fixaçäo de um retentor intra-radicular pré-fabricado (CYTCO) / Avaliation \"in vitro\" of cervic apical marginal sealing capacity of the agents cimentation in root canal fixation of pre-manufactured pin

Neste estudo avaliou-se a capacidade de vedar o canal radicular com o retentor intra-radicular Cytco(Mailleffer) fixado com cimentos de óxido fosfato de zinco, ionômero de vidro ou policarboxilato. Observou-se que nenhum dos cimentos testatos foram capazes de vedar o canal radicular hermética e tridimensionalmente em toda a extensäo preenchida pelo retentor intra-radicular, e que em 80 por cento dos espécimes a infiltraçäo marginal cérvico-apical foi superior ao comprimento do aparato protético utilizado. Analisados estatisticamente os resultados observou-se näo haver diferenças significantes para Ó 0,05