Evaluation of marginal fit and microleakage of monolithic zirconia crowns cemented by bio-active and glass ionomer cements: In vitro study / Avaliação da adaptação marginal e microinfiltração de coroas monolíticas de zircônia cimentadas com cimentos bioativos e ionômero de vidro: estudo in vitro

Objective: to evaluate the marginal fit and microleakage of monolithic zirconia crowns cemented by bio-active cements (Ceramir) compared to that cemented with glass ionomer cement, and to evaluate the effect of thermocycling on marginal fit. Material and Methods: Twenty sound human molar teeth were prepared to receive monolithic zirconia crowns. Teeth were divided randomly into two equal groups according to the type of luting cement: Group I (glass ionomer cement) and group II (Ceramir cement). After cementation, the vertical marginal gap was assessed using stereomicroscope before and after thermocycling. Twenty equidistant measurement points were taken for each crown. Leakage assessment was carried out using Fuchsin dye penetration followed by digital photography under a stereomicroscope. Data were analyzed by Mann-Whitney U test to compare between the two luting cements. Wilcoxon signed-rank test was used to evaluate the effect of thermocycling on the marginal fit (P ≤ 0.05). Results: Whether before or after thermocycling, the results showed no significant difference between the marginal gap values of the two tested groups. For both groups, there was a significant increase in marginal gap values after thermocycling. Also, there was no significant difference between leakage scores of the two tested groups. Conclusion: Similarity in the physical properties and chemical composition of the two cements resulted in a nonsignificant effect on the vertical marginal fit and the extent of microleakage of translucent zirconia crowns. Thermocycling had a negative impact on the vertical marginal gap of the two tested luting agents. (AU)

Objetivo: avaliar a adapatação marginal e a microinfiltração de coroas monolíticas de zircônia cimentadas com cimentos bioativos (Ceramir) em comparação com o cimento de ionômero de vidro e avaliar o efeito da termociclagem na adaptação marginal. Material e Métodos: Vinte molares humanos sadios foram preparados para receber coroas monolíticas de zircônia. Os dentes foram divididos aleatoriamente em dois grupos iguais, de acordo com o tipo de cimento: Grupo I (cimento de ionômero de vidro) e grupo II (cimento Ceramir). Após a cimentação, a adaptação marginal vertical foi avaliada com estereomicroscópio antes e após a termociclagem. Vinte pontos de medição equidistantes foram obtidos para cada coroa. A avaliação da infiltração foi realizada utilizando a penetração do corante de fucsina, seguida de fotografia digital sob estereomicroscópio. Os dados foram analisados pelo teste de Mann-Whitney para comparação entre os dois cimentos. O teste de Wilcoxon foi usado para avaliar o efeito da termociclagem na adaptação marginal (P ≤ 0,05). Resultados: Antes ou depois da termociclagem, os resultados não mostraram diferença significativa entre os valores de fenda marginal dos dois grupos testados. Para ambos os grupos, houve um aumento significativo nos valores de fenda marginal após a termociclagem. Além disso, não houve diferença significativa entre os escores de infiltração dos dois grupos testados. Conclusão: A similaridade nas propriedades físicas e na composição química dos dois cimentos resultou em um efeito não significativo na adaptação marginal vertical e na extensão da microinfiltração de coroas translúcidas de zircônia. A termociclagem teve um impacto negativo na fenda marginal vertical dos dois agentes de cimentação testados. (AU)

In vitro evaluation of marginal fit of zirconia-reinforced lithium silicate laminate veneers at two thicknesses using different CAD/CAM systems / Avaliação in vitro do ajuste marginal de folheados laminados de silicato de lítio reforçados com zircônia em duas espessuras usando diferentes sistemas CAD / CAM

Objective: The purpose of this in vitro study was to evaluate the marginal fit of laminate veneers made of zirconia-reinforced lithium silicate with two thicknesses using different CAD/CAM systems. Material and methods: 42 Laminate veneers milled from zirconia-reinforced lithium silicate were divided into three main groups according to milling machine used into: group X5, laminate veneers fabricated by inLab MCX5 milling machine; group CM, laminate veneers fabricated by Ceramill motion 2 milling machine; and group XL, laminate veneers fabricated by inLab MCXL milling machine. Each group was divided into two subgroups according to veneer thickness into: subgroup I, 0.5 mm thickness laminate veneers and subgroup II, 0.3 mm thickness laminate veneers. The marginal fit was measured using stereomicroscope. The results were tabulated and statistically analyzed using two-way ANOVA test followed by Tukey's post hoc test. Comparisons of main and simple effects were done utilizing Bonferroni correction. The significance level was set at (p ≤0.05) for all tests. Results: The mean( ± SD) highest marginal discrepancy was recorded in subgroup CMII at 85.45 ± 1.82 µm while the least mean marginal discrepancy was recorded in subgroup X5I (71.24 ± 2.64 µm). Conclusion: Both thicknesses(0.5 mm thickness and 0.3 mm thickness) and all tested CAD/CAM systems produced zirconia-reinforced lithium silicate laminate veneers with clinically acceptable marginal gaps; however, the closed CAD/CAM systems produced veneers with superior marginal fit than open systems at 0.3 mm thickness. The CAD/CAM system with the 5-axis milling machine produced the best marginal fit with 0.5 mm thickness. (AU)

Objetivo: O objetivo deste estudo in vitro foi avaliar a adaptação marginal de facetas laminadas de silicato de lítio reforçado com zircônia com duas espessuras, utilizando diferentes sistemas CAD / CAM. Material e métodos: 42 facetas laminadas fresadas a partir desilicato de lítio reforçado com zircônia foram divididos em três grupos principais de acordo com a fresadora usada em: grupo X5, facetas laminadas fabricados pela fresadora inLab MCX5; grupo CM, facetas laminadas fabricados por Ceramill motion 2; e grupo XL, facetas laminadas fabricados pelo inLab MCXL. Cada grupo foi dividido em dois subgrupos, de acordo com a espessura do laminado, em: subgrupo I, facetas laminadas com 0,5 mm de espessura e subgrupo II, facetas laminadas com espessura de 0,3 mm. A adaptação marginal foi medida usando estereomicroscópio. Os resultados foram tabulados e analisados estatisticamente usando o teste ANOVA de dois fatores seguido pelo teste post hoc de Tukey. Comparações dos efeitos principais e simples foram realizadas utilizando a correção de Bonferroni (P ≤ 0,05). Resultados: A maior discrepância marginal média ( ± DP) foi registrada no subgrupo CMII em 85,45 ± 1,82 µm, enquanto a menor discrepância marginal média foi registrada no subgrupo X5I 71,24 ± 2,64 µm. Conclusão: Ambas as espessuras (0,5 mm e 0,3 mm)e todos os sistemas CAD / CAM testados produziram facetas de laminado de silicato de lítio reforçadas com zircônia com lacunas clinicamente aceitáveis. No entanto, os sistemas CAD / CAM fechados produziam facetas com adaptação marginal superior aos sistemas abertos com 0,3 mm de espessura. O sistema CAD / CAM com a fresadora de 5 eixos produziu a melhor adaptação marginal com 0,5 mm de espessura (AU)

Effect of Finish Line Design and Cement Space Thickness on the Marginal Accuracy of Monolithic Zirconia Crowns / Efeito do desenho da linha de término e da espessura do espaço de cimento na precisão marginal de coroas monolíticas de zircônia

Objective: The purpose of this study was to evaluate the effect of finish line design and cement space thickness on the marginal accuracy of monolithic zirconia crowns. Materials and methods: Thirty crowns were fabricated from translucent zirconia (inCoris TZI) using Cerec in-Lab system and divided into three main groups (10 each) according to the finish line type of the die (knife-edge, chamfer, and shoulder). Every group was divided into two subgroups (5 each) according to cement space thickness (20 and50µm). Optical impressions were taken for the dies using the Cerec scanner and cement space was set twice for every finish line design; 20 and 50 µm. The completed crowns were cemented to the dies and the marginal gap was evaluated. The collected data was statistically analyzed using Mann-Whitney U test and Kruskal-Wallis test and the significance level was set at P ≤ 0.05. Results: Regarding the marginal gap; there was no statistically significant difference between different finish line designs or between different cement space thicknesses. Conclusion: Neither finish line design nor cement space thickness has an effect on the marginal gap of inCoris TZI crowns. (AU)

Declaração do problema: A necessidade de um método minimamente invasivo de preparação de coroa única é inevitável, principalmente com dentes enfraquecidos e com alta probabilidade de irritação pulpar. Portanto, é necessária uma restauração durável e adaptada, com preparação menos invasiva da linha de término. Objetivo: O objetivo deste estudo foi avaliar o efeito do design da linha de término e da espessura do espaço de cimento na precisão marginal das coroas monolíticas de zircônia. Material e Métodos: Trinta coroas foram fabricadas a partir de zircônia translúcida (inCoris TZI) usando o sistema Cerec em laboratório, e divididas em três grupos principais (n = 10), de acordo com o tipo de linha de término da matriz (lâmina, chanfro e ombro). Cada grupo foi dividido em dois subgrupos (5 cada), de acordo com a espessura do espaço do cimento (20 e 50 µm). Impressões ópticas foram obtidas para as matrizes usando o scanner Cerec e o espaço de cimento foi definido duas vezes para cada projeto de linha de chegada: 20 e 50 µm. As coroas confeccionadas foram cimentadas nos moldes e a diferença marginal foi avaliada. Os dados coletados foram analisados estatisticamente pelo teste U de Mann-Whitney e Kruskal-Wallis e o nível de significância foi estabelecido em P ≤ 0,05. Resultados: Em relação ao gap marginal não houve diferença estatisticamente significante entre diferentes projetos de linha de acabamento ou entre diferentes espessuras de espaço de cimento. Conclusão: nem o design da linha de término, nem a espessura do espaço de cimento afetam a folga marginal das coroas inCoris TZI. (AU)

Adaptación de cofias metálicas confeccionadas con dos técnicas: cera pérdida colado por centrifugación convencional e inducción / Adaptation of metallic copings made with two techniques: loss wax cast conventional centrifugation and induction

Nuevas técnicas nos están permitiendo migrar de la técnica de cera perdida colado por centrifugado convencional (CPCC) a técnicas como la cera perdida colado por inducción (CPCI). Objetivos: Comparar la discrepancia marginal e interna de cofias unitarias de aleación Cobalto-Cromo (Co-Cr) sobre una línea de terminación chamfer, confeccionadas con dos técnicas: CPCC y CPCI, determinando cual técnica tuvo mejor adaptación marginal e interna. Material y Métodos: Se fabricaron13 cofias metálicas unitarias de aleación Co-Cr para cada técnica a evaluar. Se utilizó la réplica de silicona para evaluar las discrepancias marginales e internas, cada muestra fue seccionada en cruz en sentido vestíbulo-palatino y en sentido mesio-distal, luego con un estéreomicroscopio se evaluó la zona cervical, axial y oclusal. Resultados: Se evaluó los supuestos de normalidad con la prueba de Shapiro-Wilk. Los análisis estadísticos fueron la prueba t de Student y U Mann-Whitney. La CPCI obtuvo una menor discrepancia marginal e interna en comparación con la CPC pero no se encontró diferencias estadísticamente significativas (p>0,05) entre ambas técnicas. Conclusiones: Aunque en la mayoría de los puntos de evaluación las cofias realizadas mediante la CPCI presento mejores valores de adaptación marginal e interna en comparación con la CPCC estos resultados sólo son valores descriptivos que no fueron concluyentes, ya que en la mayoría de los puntos evaluados no existió diferencia estadísticamente significativa (p>0,05). Observamos que la mayoría de los valores de ambas técnicas se encuentran dentro del rango clínicamente aceptable.

New techniques are allowing us to migrate from the technique of lost wax cast by conventional centrifugation (CPCC) to techniques such as lost wax cast by induction (CPCI). Objectives: To compare the marginal and internal discrepancy of cobalt-chromium (Co-Cr) alloy unit copes on a chamfer termination line, made with two techniques: CPCC and CPCI, determining which technique had better marginal and internal adaptation. Material and Methods: 13 Co-Cr alloy unit copings were fabricated for each technique to be evaluated. Silicon replication was used to evaluate the marginal and internal discrepancies. Each sample was cross-sectioned in the vestibular-palatine and mesio-distal directions, then the cervical, axial and occlusal zones were evaluated with a stereomicroscope. Results: 13 unitary Co-Cr alloy metal cops were manufactured for each technique to be evaluated. The silicone replica was used to evaluate the marginal and internal discrepancies, each sample was cross-sectioned in the vestibulo-palatal direction and in the mesio-distal sense, then with a stereomicroscope, the cervical, axial and occlusal areas were evaluated. Conclusions: The assumptions of normality were evaluated with the Shapiro-Wilk test. The statistical analyzes were Student s t test and U Mann-Whitney test. The CPCI obtained a lower marginal and internal discrepancy compared to the CPC, but no statistically significant differences were found (p >0.05) between both techniques. Conclusions: Although in most of the evaluation points the copings made by the CPCI presented better values of marginal and internal adaptation compared to the CPCC, these results are only descriptive values that were not conclusive, since in most of the evaluated points there was no statistically significant difference (p >0.05). We observed that most of the values of both techniques are within the clinically acceptable range.

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.

Comparison of the marginal fit of milled yttrium stabilized zirconium dioxide crowns obtained by scanning silicone impressions and by scanning stone replicas

PURPOSE: To determine the discrepancy in monolithic zirconium dioxide crowns made with computer-aided design and computer-aided manufacturing (CAD/CAM) systems by comparing scans of silicone impressions and of master casts. MATERIALS AND METHODS: From a Cr-Co master die of a first upper left molar, 30 silicone impressions were taken. The 30 silicone impressions were scanned with the laboratory scanner, thus obtaining 30 milled monolithic yttrium stabilized zirconium dioxide (YSZD) crowns (the silicone group). They were poured and the working models were scanned, obtaining 30 milled monolithic yttrium stabilized zirconium dioxide (YSZD) crowns (the plaster group). Three predetermined points were analyzed in each side of the crown (Mesial, Distal ,Vestibular and Palatal), and the marginal fit was evaluated with SEM (×600). The response variable is the discrepancy from the master model. A repeated measures ANOVA with two within subject factors was performed to study significance of main factors and interaction. RESULTS: Mean marginal discrepancy was 22.42±35.65 µm in the silicone group and 8.94±14.69 µm in the plaster group. The statistical analysis showed significant differences between the two groups and also among the four aspects. Interaction was also significant (P=.02). CONCLUSION: The mean marginal fit values of the two groups were within the clinically acceptable values. Significant differences were found between the groups according to the aspects studied. Various factors influenced the accuracy of digitizing, such as the design, the geometry, and the preparation guidance, as well as the texture, roughness and the color of the scanned material.

Marginal and Internal Adaptation of Zirconia Crowns: A Comparative Study of Assessment Methods

Abstract Marginal and internal adaptation is critical for the success of indirect restorations. New imaging systems make it possible to evaluate these parameters with precision and non-destructively. This study evaluated the marginal and internal adaptation of zirconia copings fabricated with two different systems using both silicone replica and microcomputed tomography (micro-CT) assessment methods. A metal master model, representing a preparation for an all-ceramic full crown, was digitally scanned and polycrystalline zirconia copings were fabricated with either Ceramill Zi (Amann-Girrbach) or inCoris Zi (Dentslpy-Sirona), n=10. For each coping, marginal and internal gaps were evaluated by silicone replica and micro-CT assessment methods. Four assessment points of each replica cross-section and micro-CT image were evaluated using imaging software: marginal gap (MG), axial wall (AW), axio-occlusal angle (AO) and mid-occlusal wall (MO). Data were statistically analyzed by factorial ANOVA and Tukey test (a=0.05). There was no statistically significant difference between the methods for MG and AW. For AO, there were significant differences between methods for Amann copings, while for Dentsply-Sirona copings similar values were observed. For MO, both methods presented statistically significant differences. A positive correlation was observed determined by the two assessment methods for MG values. In conclusion, the assessment method influenced the evaluation of marginal and internal adaptation of zirconia copings. Micro-CT showed lower marginal and internal gap values when compared to the silicone replica technique, although the difference was not always statistically significant. Marginal gap and axial wall assessment points showed the lower gap values, regardless of ceramic system and assessment method used.

Resumo A adaptação marginal e interna é fundamental para o sucesso das restaurações indiretas e novos sistemas de imagem permitem avaliar esses parâmetros de maneira não-destrutiva e com precisão. Este estudo avaliou a adaptação marginal e interna de copings de zircônia fabricados com dois sistemas diferentes, utilizando as técnicas da réplica em silicone e micro-CT. Um modelo-mestre de metal, representando um preparo para uma coroa totalmente cerâmica foi digitalizado e copings de zirconia policristalina (Ceramill Zi, Amann Girrbach e inCoris Zi, Dentslpy Sirona, n=10) foram fabricados. Para cada coping, a adaptação marginal e interna foi avaliada pelas técnicas da réplica em silicone e micro-CT. Foram avaliados quatro pontos de cada seção transversal e imagem de micro-CT: adaptação marginal (MG), parede axial (AW), ângulo axial-oclusal (AO) e parede centro-oclusal (MO) utilizando um software de imagem. Os dados foram analisados estatisticamente por ANOVA e teste de Tukey (a=0,05). Não houve diferença estatisticamente significativa entre as duas técnicas para MG e AW. Para AO, houve diferenças significativas entre as técnicas para copings da Amann, enquanto que para copings da Dentsply Sirona foram observados valores semelhantes. Para o MO, ambas as técnicas apresentaram diferenças estatisticamente significativas. Observou-se uma correlação positiva entre os valores de adaptação determinados pelas duas técnicas. O método de avaliação influenciou a avaliação da adaptação marginal e interna de copings de zircônia. Pode-se concluir que a micro-CT mostrou menores valores de adaptação marginal e interna quando comparado com a técnica de réplica em silicone. Os pontos de avaliação da margem e da parede axial mostraram os menores valores de adaptação, independente do sistema cerâmico e da técnica de avaliação utilizados.

In vitro evaluation methods on adaptation of fixed dental prosthesis

Clinically, the fit of fixed prosthesis is an essential element for successful restoration. The fit of prosthesis is largely classified into marginal fit and internal fit, and various methods to assess these have been introduced including microscopic margin measurement, cross-sectional measurement, silicone replica technique, 3-dimensional scanning data superposition, weight technique and micro CT scanning. Thus, this study is aimed at proposing a more convenient and accurate measurement method of fits in a digital environment by comparatively analyzing the advantages and disadvantages of each known method based on existing literature.

Influence of Convergence Angle and Cement Space on Margin and Internal Adaptation of CAD/CAM All-ceramic Crowns / 中国医科大学学报

Objective To study the influence of the convergence angle and cement space on the fit of CAD/CAM all-ceramic crowns.Methods The PMMA resin was produced in two groups,group A (2 degrees) and group B (4 degrees),30 in each group,and each group was divided into 3 sub-groups A 1,A2,A3;or B 1,B2,B3.Each subgroup included 10 patients with a CAD/CAM all-ceramic crown with PMMA resin generation type,but the cement space was 40 μm,60 μm,or 80 μm.The internal clearance edge of the double color silicone rubber impression reproduction technology of the all-ceramic crown was observed under the microscope.Analysis Micro-image software was used to measure the edge gap,and the resulting data were analyzed using SPSS 20.0 software.Results When the cement space is the same,the difference between 2 degrees and 4 degrees was statistically significant.Conclusion The fit is the best when the cement space is 60 μm and the convergence angle space is 4 degrees.

Evaluation of effects of porcelain firing on the marginal fit changes of porcelain­ fused-to- metal crown fabricated utilizing two different margin designs and two commercially available base metal alloys

Aim: To find the marginal fit of the porcelain fused to metal crowns by two different margin designs (shoulder and chamfer) and two commercially available base metal alloys. Material and Methods: Tooth preparation of first central incisor for porcelain-fused-to-metal crown with shoulder margin and second incisor for porcelain-fused-to-metal crown with chamfer margin was done. Wax pattern of the same was prepared. Impression of both prepared ivorine incisors was made by light body impression material and poured with pattern resin. Both the patterns were invested and casted with cobalt chromium alloy for making master dies. Two wax patterns of unprepared central incisors were fabricated, one with shoulder margin and another with chamfer margin. These patterns were then cut back to the size of the coping. Four rings were invested. In each ring ten patterns, five with shoulder margin and five with deep chamfer margin were sprued together to ensure that each group would pass through the same investing and casting procedure, followed by ceramic firing and measurement. Results: Marginal fit change or marginal discrepancy (before and after firing) between the groups was highly significant. Conclusions: Veneered crowns exhibited highly significant marginal distortion than non- veneered copings after porcelain firing. Shoulder margin is better in minimizing marginal discrepancy compared to deep chamfer margin. Marginal discrepancy is less when cerabond base metal alloy is used with shoulder margin as compared to commend base metal alloy used for shoulder margin.

Comparison of micro CT and cross-section technique for evaluation of marginal and internal fit of lithium disilicate crowns / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate the adaptation of lithium disilicate crowns fabricated by CAD-CAM (computer aided design-computer aided manufacturing) and heat-press technique to compare two different measurement methods in assessing fit of the ceramic crowns: micro CT and cross-section technique. MATERIALS AND METHODS: A prepared typodont mandibular molar for ceramic crown was duplicated and ten dies were produced by milling the PMMA (polymethylmethacrylate) resin. Ten vinyl polysiloxane impressions were made and stone casts were produced. Five dies were used for IPS e.max Press crowns with heat-press technique. The other five dies were used for IPS e.max CAD crowns with CAD-CAM technique. Ten lithium disilicate crowns were cemented on the resin dies using zinc phosphate cement with finger pressure. The marginal and internal fits in central buccolingual plane were evaluated using a micro CT. Then the specimens were embedded and cross-sectioned and the marginal and internal fits were measured using scanning electronic microscope. The two measurement methods and two manufacturing methods were compared using Mann-Whitney U test (SPSS 22.0). RESULTS: The marginal and internal fit values using micro CT and cross-section technique were similar, showing no significant differences. There were no significant differences in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique. CONCLUSION: Both micro CT and cross-section technique were acceptable methods in the evaluation of marginal and internal fit of lithium disilicate crown. There was no difference in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique except occlusal fit.

Study on methodology for the assessment of internal and marginal adaptation on fixed dental prosthesis

This article is to review various methods used to investigate internal and marginal adaptation of fixed dental prostheses, and to summarize a merit, worth, and limitation of each method, using some results of previous studies. The methods of measuring internal and marginal gap are divided into two categories in this study; in vivo and in vitro. In vivo methods are clinical evaluations, including exploration, radiography, and impression technique. In vitro methods are laboratory evaluations such as direct view, cross-sectioning, and silicone replica technique using microscope. Measuring by micro computed tomography (CT) or profilometer is also in vitro methods. In recent years, the development of scanning systems is able to analyze 3-dimensional internal and marginal space in detail. As measuring and analyzing technology become more advanced, the ability to thoroughly examine crown adaptation is becoming both simpler and more efficient.

An experimental study on the fit of Co-Cr basal crowns fabricated by different technology / 实用口腔医学杂志

Objective:To compare the fit of Co-Cr basal crowns fabricated by three kinds of technology. Methods:18 laser cured resin dies were divided into A, B and C groups(n=6) randomly. Co-Cr basal crowns of group A, B and C were made by traditional casting technology, CAD/CAM cutting metal technology and direct metal laser sintering technology( DMLS) respectively. The crowns were cemented to the corresponding dies and the basal crowns and dies were embedded in methyl acrylic. The thickness of the cement layer of the samples was measured under a stero microscope. Data were analyzed with SPSS13. 0 statistical software. Results:Marginal gap of group A, B and C was (66.08 ±3.90) μm, (29.21 ±3.31) μm and (24.96 ±2.99) μm respectively(P0. 05). Conclusion:DMLS technology may make the best marginal fit, CAD/CAM and DMLS technology may pro-duce better internal fit. The marginal fit and the internal fit of the crowns prepared by the 3 methods can meet the clinical requirements.

Influence of polyurethane resin dies on the fit and adaptation of full veneer crowns.

Context: Polyurethane resin is a possible alternative to type IV dental stone for fabrication of indirect restorations however its dimensional accuracy is questionable. Aim: The aim was to investigate the dimensional accuracy of silica filled polyurethane resin die material by evaluating the marginal fit and adaptation of indirect gold castings. Settings and Design: Experimental, in vitro study. Materials and Methods: Totally 40 copper plated replicas of a nickel chrome master die analogous to a veneer gold crown preparation were made and impressions recorded using polyvinylsiloxane material. Twenty impressions were poured in type IV dental stone (control group (Vel‑mix, Kerr, UK) and the remaining (n = 20) in silica filled polyurethane die material (test group) (Alpha Die MF, CA, USA). Gold castings were fabricated for each die using standardized techniques. The castings were seated on their respective copper plated dies, embedded in resin and sectioned. The specimens were analyzed by measuring marginal opening and the area beneath the casting at a ×63 magnification and using image analysis software. Statistical Analysis Used: Data were analyzed using a Student’s t‑test. Results: No significant difference was observed between the experimental groups (P > 0.05). The mean marginal opening for type IV, dental stone and polyurethane resin, was 57 ± 22.6 μm and 63.47 ± 27.1 μm, respectively. Stone displayed a smaller area beneath the casting (31581 ± 16297 μm2) as compared to polyurethane resin (35003 ± 23039 μm2). Conclusions: The fit and adaptation of indirect gold castings made on polyurethane and type IV dental stone dies were comparable.

Evaluation of marginal fit of 2 CAD-CAM anatomic contour zirconia crown systems and lithium disilicate glass-ceramic crown

PURPOSE: This study was to evaluate the marginal fit of two CAD-CAM anatomic contour zirconia crown systems compared to lithium disilicate glass-ceramic crowns. MATERIALS AND METHODS: Shoulder and deep chamfer margin were formed on each acrylic resin tooth model of a maxillary first premolar. Two CAD-CAM systems (Prettau(R)Zirconia and ZENOSTAR(R)ZR translucent) and lithium disilicate glass ceramic (IPS e.max(R)press) crowns were made (n=16). Each crown was bonded to stone dies with resin cement (Rely X Unicem). Marginal gap and absolute marginal discrepancy of crowns were measured using a light microscope equipped with a digital camera (Leica DFC295) magnified by a factor of 100. Two-way analysis of variance (ANOVA) and post-hoc Tukey's HSD test were conducted to analyze the significance of crown marginal fit regarding the finish line configuration and the fabrication system. RESULTS: The mean marginal gap of lithium disilicate glass ceramic crowns (IPS e.max(R)press) was significantly lower than that of the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia) (P<.05). Both fabrication systems and finish line configurations significantly influenced the absolute marginal discrepancy (P<.05). CONCLUSION: The lithium disilicate glass ceramic crown (IPS e.max(R)press) had significantly smaller marginal gap than the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia). In terms of absolute marginal discrepancy, the CAD-CAM anatomic contour zirconia crown system (ZENOSTAR(R)ZR translucent) had under-extended margin, whereas the CAD-CAM anatomic contour zirconia crown system (Prettau(R)Zirconia) and lithium disilicate glass ceramic crowns (IPS e.max(R)press) had overextended margins.

The effect of various veneering techniques on the marginal fit of zirconia copings

PURPOSE: This study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques). MATERIALS AND METHODS: Thirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (alpha=.05). RESULTS: Marginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group (63.06 microm) was higher than press-over (50.64 microm) and CAD-on (51.50 microm) veneered groups (P<.001). CONCLUSION: Three veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CAD-on techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.

Gap comparison between single crown and three-unit bridge zirconia substructures

PURPOSE: To compare marginal and internal gaps of zirconia substructure of single crowns with those of three-unit fixed dental prostheses. MATERIALS AND METHODS: Standardized Co-Cr alloy simulated second premolar and second molar abutments were fabricated and subsequently duplicated into type-III dental stone for working casts. After that, all zirconia substructures were made using Lava(TM) system. Marginal and internal gaps were measured in 2 planes (mesial-distal plane and buccal-palatal plane) at 5 locations: marginal opening (MO), chamfer area (CA), axial wall (AW), cusp tip (CT) and mid-occlusal (OA) using Replica technique. RESULTS: There were significant differences between gaps at all locations. The mean +/- SD of marginal gap in premolar was 43.6 +/- 0.4 microm and 46.5 +/- 0.5 microm for single crown and 3-unit bridge substructure respectively. For molar substructure the mean +/- SD of marginal gap was 48.5 +/- 0.4 microm and 52.6 +/- 0.4 microm for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was 150.5 +/- 0.5 microm and 154.5 +/- 0.4 microm for single and 3-unit bridge premolar substructures respectively and 146.5 +/- 0.4 microm and 211.5 +/- 0.4 microm for single and 3-unit bridge molar substructure respectively. CONCLUSION: Independent-samples t-test showed significant differences of gap in zirconia substructure between single crowns and three-unit bridge (P<.001). Therefore, the span length has the effect on the fit of zirconia substructure that is fabricated using CAD/CAM technique especially at the occlusal area.

Effect of anatomic, semi-anatomic and non-anatomic occlusal surface tooth preparations on the adaptation of zirconia copings

PURPOSE: To compare the accuracy of marginal and internal adaptation of zirconia (Zr) copings fabricated on anatomic (A), semi-anatomic (SA) and non-anatomic (NA) occlusal surface preparations. MATERIALS AND METHODS: 45 extracted bicuspid teeth were prepared for receiving zirconia crowns, with different occlusal preparation designs A=15, SA=15 & NA=15. The Zr copings were fabricated by using CAD4DENT, CAD/CAM. The copings were adjusted, cemented and were cross sectioned centrally from buccal cusp tip to lingual cusp tip into mesial and distal halves. The copings were examined under electron microscope at x200 magnification and the measurements were recorded at 9 predetermined areas in micrometers. RESULTS: Overall mean gap values for the three groups was found to be 155.93+/-33.98 microm with Anatomical Occlusal preparation design having the least gap value of 139.23+/-30.85 microm showing the best adaptation among the groups. Post Hoc Tukey's test showed a statistically significant difference (P=.007) between the means of gap for A & NA preparation designs. Measurements recorded at 9 predetermined points showed variations for the three groups. CONCLUSION: Anatomical occlusal preparation designs resulted in better marginal and internal adaptation of Zr copings. There is a considerable variation between the measured marginal and internal gap values for the Zr copings fabricated by the (CAD4DENT-CAD/CAM). This variation may be associated with the lack of standardization of the preparation of teeth, computerized designing of the coping for each tooth, cement used, uniform pressure application during the cementation of the copings, sectioning of the copings and the microscopic measurements.

Marginal fit of anterior 3-unit fixed partial zirconia restorations using different CAD/CAM systems

PURPOSE: Few studies have investigated the marginal accuracy of 3-unit zirconia fixed partial dentures (FPDs) fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) system. The purpose of this study was to compare the marginal fit of zirconia FPDs made using two CAD/CAM systems with that of metal-ceramic FPDs. MATERIALS AND METHODS: Artificial resin maxillary central and lateral incisors were prepared for 3-unit FPDs and fixed in yellow stone. This model was duplicated to epoxy resin die. On the resin die, 15 three-unit FPDs were fabricated per group (45 in total): Group A, zirconia 3-unit FPDs made with the Everest system; Group B, zirconia 3-unit FPDs made with the Lava system; and Group C, metal-ceramic 3-unit FPDs. They were cemented to resin dies with resin cement. After removal of pontic, each retainer was separated and observed under a microscope (Presize 440C). Marginal gaps of experimental groups were analyzed using one-way ANOVA and Duncan test. RESULTS: Mean marginal gaps of 3-unit FPDs were 60.46 microm for the Everest group, 78.71 microm for the Lava group, and 81.32 microm for the metal-ceramic group. The Everest group demonstrated significantly smaller marginal gap than the Lava and the metal-ceramic groups (P.05). CONCLUSION: The marginal gaps of anterior 3-unit zirconia FPD differed according to CAD/CAM systems, but still fell within clinically acceptable ranges compared with conventional metal-ceramic restoration.

A study on the marginal fit of CAD/CAM 3-unit bridges / 대한치과보철학회지

PURPOSE: The purpose of this study was to assess the marginal fit of three-unit bridges produced using LAVA CAD/CAM (computer-aided design/computer-aided manufacturing) system and conventional PFG in vitro. MATERIALS AND METHODS: #11, 13 resin teeth were prepared on dentiform, then duplicated. Twenty resin models were fabricated, ten for PFG 3-unit bridges and ten for LAVA 3-unit bridges. Each bridge was cemented on the resin model. Marginal discrepancy was measured with stereoscopic microscope (Nikon DS-Fi 1, Nikon, Japan) at a magnification of x75. Independent t-test was done for the statistical analysis. RESULTS: The mean marginal discrepancy values and standard deviations of the PFG bridges was 97.1 +/- 18.7 microm for incisors, 76.6 +/- 21.8 microm for canines; that of the LAVA bridges was 90.4 +/- 26.7 microm for incisor, 110.2 +/- 30.2 microm for canines. The mean marginal discrepancy between PFG and LAVA for incisor did not show significant difference (P>.05). But for canine, the mean marginal discrepancy of PFG bridges was smaller than that of LAVA bridges (P<.05). CONCLUSION: The LAVA CAD/CAM 3-unit bridges and the PFG 3-unit bridges showed clinically acceptable marginal discrepancy.