Prevalencia de cristales de colesterol en granulomas perirradiculares de origen endodóntico / Prevalence of cholesterol crystals in periradicular granulomas of endodontic origin

Resumen Objetivo Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para conectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos A partir de un modelo maestro que representa un maxilar desdentado con cuatro implantes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilladas al modelo maestro. Su desajuste inicial se analizó utilizando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un procedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructura metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significación fue establecido en p<0,05. Resultados El Grupo I tuvo un desajuste inicial de 97,30±13,81μm y el Grupo II de 98,53±11,24μm. Luego de la soldadura, el Grupo I registró 98,53±17,17μm, 1,23μm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61μm, 4,60μm por encima del original. Se analizaron mediante prueba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se observaron diferencias no significativas, p=0,41 y p=0,38 respectivamente. Conclusiones Bajo las condiciones de este estudio, se observó que los dos métodos de soldadura analizados fueron confiables para unir supraestructurasos metálicas sin que se afecte su ajuste final.

Abstract Aim Compare two conventional welding procedures using a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master model. Its initial mismatch was analyzed using a stereoscopic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statistically. The level of significance was established at p<0.05. Results Group I had an initial mismatch of 97.30 ±13.81μm, and Group II of 98.53±11.24μm. After welding, Group I registered 98.53±17.17μm, 1.23μm higher than the initial one. In Group II, 103.13±17.61μm was observed, 4.60μm above the original. They were analyzed using Student's t test; in both cases the result was p>0.05. When comparing groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions Under the conditions of this study, it was observed that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit.

Estudio in vitro del ajuste de supraestructuras pasivadas sobre implantes múltiples / In vitro study of the adjustment of passivated suprastructures on multiple implants

Resumen Objetivo Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para conectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos A partir de un modelo maestro que representa un maxilar desdentado con cuatro implantes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilladas al modelo maestro. Su desajuste inicial se analizó utilizando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un procedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructura metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significación fue establecido en p<0,05. Resultados El Grupo I tuvo un desajuste inicial de 97,30±13,81μm y el Grupo II de 98,53±11,24μm. Luego de la soldadura, el Grupo I registró 98,53±17,17μm, 1,23μm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61μm, 4,60μm por encima del original. Se analizaron mediante prueba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se observaron diferencias no significativas, p=0,41 y p=0,38 respectivamente. Conclusiones Bajo las condiciones de este estudio, se observó que los dos métodos de soldadura analizados fueron confiables para unir supraestructurasos metálicas sin que se afecte su ajuste final.

Abstract Aim Compare two conventional welding procedures using a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master model. Its initial mismatch was analyzed using a stereoscopic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statistically. The level of significance was established at p<0.05. Results Group I had an initial mismatch of 97.30 ±13.81μm, and Group II of 98.53±11.24μm. After welding, Group I registered 98.53±17.17μm, 1.23μm higher than the initial one. In Group II, 103.13±17.61μm was observed, 4.60μm above the original. They were analyzed using Student's t test; in both cases the result was p>0.05. When comparing groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions Under the conditions of this study, it was observed that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit.

Marginal and internal discrepancy of 3-unit fixed dental prostheses fabricated by subtractive and additive manufacturing / 대한치과보철학회지

PURPOSE: This study was to evaluate marginal and internal discrepancy of 3-unit fixed dental prostheses (FDP) fabricated by subtractive manufacturing and additive manufacturing.MATERIALS AND METHODS: 3-unit bridge abutments without the maxillary left second premolar were prepared (reference model) and the reference model scan data was obtained using an intraoral scanner. 3-unit fixed dental prostheses were fabricated in the following three ways: Milled 3-unit FDP (MIL), digital light processing (DLP) 3D printed 3-unit FDP (D3P), stereolithography apparatus (SLA) 3D printed 3-unit FDP (S3P). To evaluate the marginal/internal discrepancy and precision of the prosthesis, scan data were superimposed by the triple-scan protocol and the combinations calculator, respectively. Quantitative and qualitative analysis was performed using root mean square (RMS) value and color difference map in 3D analysis program (Geomagic control X). Statistical analysis was performed using the Kruskal-Wallis test (α=.05), Mann-Whitney U test and Bonferroni correction (α=.05/3=.017).RESULTS: The marginal discrepancy of S3P group was superior to MIL and D3P groups, and MIL and D3P groups were similar. The D3P and S3P groups showed better internal discrepancy than the MIL group, and there was no significant difference between the D3P and S3P groups. The precision was excellent in the order of MIL, S3P, and D3P groups.CONCLUSION: Within the limitation of this study, the 3-unit fixed dental prostheses fabricated by additive manufacturing showed better marginal and internal discrepancy than the those of fabricated by subtractive manufacturing, but the precision was poor.

Comparative clinical study of the marginal discrepancy of fixed dental prosthesis fabricated by the milling-sintering method using a presintered alloy

PURPOSE: The present study was designed to examine the clinical fit of fixed dental prosthesis fabricated by the milling-sintering method using a presintered cobalt-chromium alloy. MATERIALS AND METHODS: Two single metal-ceramic crowns were fabricated via milling-sintering method and casting method in each of the twelve consecutive patients who required an implant-supported fixed prosthesis. In the milling-sintering method, the prosthetic coping was designed in computer software, and the design was converted to a non-precious alloy coping using milling and post-sintering process. In the casting method, the conventional manual fabrication process was applied. The absolute marginal discrepancy of the prostheses was evaluated intraorally using the triple-scan technique. Statistical analysis was conducted using Mann-Whitney U test (α=.05). RESULTS: Eight patients (66.7%) showed a lower marginal discrepancy of the prostheses made using the milling-sintering method than that of the prosthesis made by the casting method. Statistically, the misfit of the prosthesis fabricated using the milling-sintering method was not significantly different from that fabricated using the casting method (P=.782). There was no tendency between the amount of marginal discrepancy and the measurement point. CONCLUSION: The overall marginal fit of prosthesis fabricated by milling-sintering using a presintered alloy was comparable to that of the prosthesis fabricated by the conventional casting method in clinical use.

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.

Precision of the milled full-arch framework fabricated using pre-sintered soft alloy: A pilot study

PURPOSE: This study aimed to evaluate the marginal discrepancy of full-arch frameworks in implant-supported prostheses fabricated using pre-sintered soft alloy (PSA). MATERIALS AND METHODS: Full-arch metal frameworks were fabricated on the edentulous implant model using casting alloy (CA), fully-sintered hard alloy (FHA), and PSA (n = 4 in each group). To evaluate the misfit of the framework to the abutments, the absolute marginal discrepancy (AMD) values of the frameworks were measured in cross-sectional images that had been drawn as part of the triple-scan protocol. The AMD values were compared among the tested alloy groups using the Kruskal-Wallis test, with a post hoc Mann-Whitney U test (α=.05). RESULTS: The FHA and PSA groups showed lower marginal discrepancies than the CA group (P < .001). However, the FHA group did not differ significantly from the PSA group. CONCLUSION: Soft alloy milling is comparable to hard alloy milling, and it is more precise than casting in terms of the marginal fit of implant-supported, full-arch prostheses.

Comparación de la precisión marginal de cofias de zirconia entre los sistemas CAD/CAM Cerec InLab (Sirona ® ), CAD/CAM Zirkonzahn (Zirkonzahn ® ) y sistema pantográfico Zirkograph 025 ECO (Zirkonzahn ® ) / Comparison of marginal fit of zirconia copings manufactured with the use of two CAD/CAM systems Cerec InLab (Sirona ® ) CAD/CAM Zirkonzahn (Zirkonzahn ® ) and Zirkograph 025 ECO pantographic system (manual milling system) (Zirkonzahn ® )

Objetivo: Comparar la precisión marginal de cofias de zirconia elaboradas empleando dos sistemas CAD/CAM Cerec InLab (Sirona®) y Zirkonzahn (Zirkonzahn®) y un sistema pantográfi co Zirkograph 025 ECO (Zirkonzahn®). Material y métodos: Se elaboró un muñón maestro de Cr-Co con preparación para corona de zirconia de un premolar superior. Se fabricaron 10 cofias de zirconia por grupo siguiendo los parámetros de cada sistema. El grupo control consistió en 10 cofias metálicas. Se ejecutó una técnica de réplica, utilizando polivinilsiloxano elite HD+ (Zhermack®). Mediante observación estereomicroscópica con aumento de 50x, se determinó en micras la discrepancia marginal absoluta y el espesor marginal de un punto por cara de cada cofia. El análisis estadístico se ejecutó con el software IBM SPSS®. Para comparar los datos obtenidos se realizó el test t. Resultados: La discrepancia marginal absoluta media y el espesor marginal fue 92.14 ± 38.59 y 78.62 ± 31.33 μm para el sistema CAD/CAM Cerec InLab (Sirona®), 38.71 ± 12.62 y 36.91 ± 13.56 μm para el sistema CAD/CAM Zirkonzahn (Zirkonzahn®), 77.92 ± 38.01 y 69.42 ± 33.23 μm para el sistema pantográfico Zirkograph 025 ECO (Zirkonzahn®) y 44.11 ± 15.36 y 43.74 ± 15.70 μm para el grupo control. Existieron diferencias estadísticamente significativas entre los sistemas Cerec InLab (Sirona®) y Zirkograph 025 ECO (Zirkonzahn®) en comparación con el grupo control para la discrepancia marginal absoluta y el espesor marginal. No existieron diferencias estadísticamente significativas entre los sistemas CAD/CAM Zirkonzahn (Zirkonzahn®) y el grupo control. El nivel de significancia fue p > 0.001. Conclusiones: El sistema más preciso fue CAD/CAM Zirkonzahn (Zirkonzahn®). El sistema que mostró menor precisión marginal fue Cerec InLab (Sirona®).

Objective: To compare marginal fit of zirconia copings manufactured following two different systems: CAD/CAM Cerec InLab (Sirona®) and Zirkonzahn (Zirkonzahn®) as well as a Zirkograph 025 ECO (Zirkonzahn®) pantograph system. Material and methods: A master Cr-Co model stump was manufactured; it was prepared for the zirconia crown of an upper premolar. Ten zirconia copings were manufactured for each group following manufacturer¿s instructions. Control group consisted on ten metallic copings. A replication technique was followed using elite HD+ polyvinyl siloxane (Zhermack®). Measurements were taken using a stereomicroscope at 50x magnification so as to obtain marginal width in microns and thus determine absolute marginal discrepancy of each coping. Statistical analysis was conducted using IBM SPSS® software. T-test study was conducted in order to compare obtained data. Results: Mean marginal absolute discrepancy and marginal width were as follows: 92.14 ± 38.59 and 78.62 ± 31.33 μm for Cerec InLab (Sirona®) CAD/CAM system, 38.71 ± 12.62 and 36.91 ± 13.56 μm for Zirkonzahn (Zirkonzahn®) CAD/CAM system, 77.92 ± 38.01 and 69.42 ± 33.23 μm for Zirkograph 025 ECO (Zirkonzahn®) pantograph system. Control group made of metal copings exhibited 44.11 ± 15.36 and 43.74 ± 15.70 μm. With respect to absolute marginal discrepancy and marginal width, significant differences were observed when comparing Cerec InLab (Sirona®) and Zirkograph 025 ECO (Zirkonzahn®) with control group. Nevertheless, no significant differences were observed between Zirkonzahn (Zirkonzahn®) CAD/CAM system and the control group. Overall level of statistical significance was p > 0.001. Conclusions: Zirkonzahn® CAD/CAM system was the most accurate system of all. CAD/CAM Cerec InLab system (Sirona®) proved to be the less precise system.

Marginal and internal discrepancies of zirconia copings: Effects of milling system and finish line design.

Context: Discrepancies at the abutment/crown interface can affect the longevity of zirconia restorations. Aim: The aim was to evaluate the marginal and internal discrepancies (MD and ID) of zirconia copings manufactured by two milling systems with different finish lines. Materials and Methods: Three aluminum‑master‑dies (h = 5.5 mm; Ø =7.5 mm; 6°), with different finish lines (large chamfer [LC]; tilted chamfer [TC]; rounded shoulder [RS]) were fabricated. Twenty impressions were made from each master die and poured. Sixty zirconia copings were manufactured and divided according to the factors “finish line” and “milling system” (n = 10): CADLC = Computer‑aided design/computer‑aided manufacturing (CAD/ CAM) + LC; CADTC = CAD/CAM + TC; CADRS = CAD/CAM + RS; MADLC = manually aided design/manually aided manufacturing (MAD/MAM) + LC; MADTC = MAD/MAM + TC; and MADRS = MAD/MAM + RS. For MD analysis, each coping was fixed, and the distance between the external edges of the coping and the edge of the cervical preparation was measured (50 points). Using the same copings, the ID of each coping was evaluated, by the replica technique, at 12 points equally distributed among the regions (n = 10): Ray (R), axial (A), and occlusal (Occl). The measurements were performed by optical microscopy (×250). The data (μm) were subjected to parametric and non‑parametric statistical analyses. Results: For the MAD/MAM system, the “finish line” (P = 0.0001) affected significantly the MD median values (μm): LC = 251.80a, RS = 68.40a and TC = 8.10b (Dunn’s test). For the CAD/CAM system, the median MD values (μm) were not affected by the factor “finish line” (P = 0.4037): LC = 0.82a, RS = 0.52a, and TC = 0.89a. For the ID, it was observed interaction between the finish line types and the region (P = 0.0001) and between region and milling system (P = 0.0031) (RM‑ANOVA). Conclusions: The CAD/CAM system presented lower MD values, regardless the finish line. However, the MAD/MAM system showed ID values smaller than those of CAD/CAM.

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.

Marginal fidelity of zirconia core using MAD/MAM system / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate the fit of zirconia core using MAD/MAM system comparing to that of conventional metal-ceramic and CAD/CAM system. MATERIALS AND METHODS: Duplicating the prepared resin tooth, 50 improved stone dies were fabricated. These dies are classified as a group of 5 to create the core. The groups were composed of metal-ceramic, Cercon(R), Ceramill(R), Rainbow(TM), and Zirkonzhan(R). Each core was cemented to stone die, and then, absolute marginal discrepancy was measured with microscope at a magnification of x50. Statistical analysis was done with one-way ANOVA test and Tukey's HSD test. RESULTS: The mean absolute marginal discrepancy for metal-ceramic was 51.97 +/- 23.38 micrometer, for Cercon(R) was 62.16 +/- 25.88 micrometer, for Ceramill(R) was 67.64 +/- 40.38 micrometer, for Rainbow(TM) was 125.07 +/- 42.19 micrometer, and for Zirkonzhan(R) was 105 +/- 44.61 micrometer. CONCLUSION: 1. Fit of margin was identified as in the order of metal-ceramic, Cercon(R), Ceramill(R), Zirkonzhan(R), and Rainbow(TM). 2. Absolute marginal discrepancy of the zirconia core that designed by MAD/MAM system had significant differences in order of Ceramill(R), Zirkonzhan(R), and Rainbow(TM). 3. The mean absolute marginal discrepancy between Cercon(R) and Ceramill(R) did not show significant differences.

A comparison of the fidelity of various zirconia-based all-ceramic crowns fabricated with CAD/CAM systems / 대한치과보철학회지

STATEMENT OF PROBLEM: The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems there is a need to evaluate the quality levels of these new fabrication techniques. PURPOSE: This study is to evaluate the crown fidelity (absolute marginal discrepancy and internal gap) of various zirconia-based all-ceramic crowns fabricated with different CAD/CAM (computer-assisted design/computer-assisted manufacturing) systems and conventional cast metal-ceramic crowns. MATERIAL AND METHODS: A resin tooth of lower right second premolar was prepared. After an impression was taken, one metal master die was made. Then 40 impressions of metal master dies were taken for working dies. 10 crowns per each system were fabricated using 40 working dies. Metal-ceramic crowns were cast by using the conventional method, and Procera, Lava, and Cerec inLab crowns were fabricated with their own CAD/CAM manufactruing procedures. The vertical marginal discrepancies and internal gaps of each crown groups were measured on a metal master die without a luting agent. The results were statistically analyzed using the one-way ANOVA and Tukey's HSD test. RESULTS: 1. Vertical marginal discrepancies were 50.6 +/- 13.9 micrometer for metal-ceramic crowns, 62.3 +/- 15.7 micrometer for Procera crowns, 45.3 +/- 7.9 micrometer for Lava crowns, and 71.2 +/- 2.0 micrometer for Cerec inLab crowns. 2. The Internal gaps were 52.6 +/- 10.1 micrometer for metal-ceramic crowns, 161.7 +/- 18.5 micrometer for Procera crowns, 63.0 +/- 10.2 micrometer for Lava crowns, and 73.7 +/- 10.7 micrometer for Cerec inLab crowns. CONCLUSION: 1. The vertical marginal discrepancies of, 4 crown groups were all within the clinically acceptable range (120 micrometer). 2. The internal gaps of LAVA, Cerec inlab, and metal-ceramic crowns were within clinically acceptable range except Procera crown (140 micrometer).

A comparison of the fidelity between various cores fabricated with CAD/CAM systems / 대한치과보철학회지

STATEMENT OF PROBLEM: Recently, various all-ceramic crowns fabricated with CAD/CAM systems have come into wide use in dental clinic. However, there are only few domestic studies on CAD/CAM restorations. PURPOSE: Purpose of this study was to compare the fidelity (absolute marginal discrepancy and internal gap) between various cores fabricated with different CAD/CAM systems (Procera system, Lava system, Cerec inLab system) and conventional metal cast core. MATERIALS AND METHODS: 10 cores per each system were fabricated. The absolute marginal discrepancies were measured using measuring microscope and digital counter. The internal gaps were calculated using a silicone paste. The results were statistically analyzed using the one-way ANOVA test and Tukey's HSD test. RESULTS: Within the limits of this study the results were as follows. 1. The absolute marginal discrepancies were 32.5+/-3.7 micrometer for metal cast core, 72.2+/-7.0 micrometer for Procera core, 40.8+/-5.4 micrometer for Lava core, and 55.3+/-8.7 micrometer for Cerec inLab core. The internal gaps were 38.4+/-5.7 micrometer for metal cast core, 71.4+/-5.3 micrometer for Procera core, 45.9+/-7.3 micrometer for Lava core, and 51.8+/-6.2 micrometer for Cerec inLab core. 2. The fidelity of metal cast core showed the smallest gaps, followed by Lava core, Cerec inLab core, and Procera core. CONCLUSION: The fidelities of 4 core groups were all within the clinically acceptable range (120 micrometer).

The fit of zirconia core fabricated with CAD/CAM system / 대한치과보철학회지

STATEMENT OF PROBLEM: The use of zirconia prostheses fabricated with CAD/CAM system is on an increasing trend in dentistry. However, evaluation of the fit related to internal relief and marginal reproducibility of zirconia has not been reported. PURPOSE: This study was to evaluate the fit related to internal relief and marginal reproducibility of zirconia core fabricated with CAD/CAM system. Materials and methods: The evaluation was based on 30 zirconia cores and 5 IPS-Empress2 cores. Zirconia cores were fabricated in different conditions of internal relief(0, 10, 20, 30, 40 and 50 micrometer), and IPS-Empress2 cores were fabricated in accordance with the manufacturer's instructions. Before cementation, the marginal discrepancies of cores were measured on metal die. And then, each core was cemented to stone die, embedded in an acrylic resin and sectioned in two planes(mesiodistally and labiopalatally). The internal gaps were measured at the margin and axial surface. Measurements for the marginal discrepancies, the internal marginal gaps and the internal axial gaps were performed under a measuring microscope(Compact measuring microscope STM5; Olympus, Japan) at a magnification of *100. In addition, the marginal configurations of metal die, zirconia core and IPS-Empress2 core were examined with SEM(S-2700, Hitachi, Japan). RESULTS: Within the limits of this study the results were as follows. 1. Compared with IPS-Empress2 cores, the marginal discrepancies of zirconia cores had no significant differences, the internal marginal gaps were statistically smaller and the internal axial gaps were statistically larger in each condition of internal relief. 2. The marginal discrepancies and the internal marginal gaps of zirconia cores had no significant differences related to the conditions of internal relief(P>0.05). 3. The internal axial gaps of zirconia cores with 0.20micrometer for internal relief were significantly larger than that with 50micrometer(P<0.0001). 4. SEM micrographs showed favorable marginal reproducibility of zirconia core and smooth texture on the milling surface. CONCLUSION: The marginal discrepancy and the internal gaps of zirconia core were clinically acceptable and the milling surface was showed smooth texture. For fabrication of the durable esthetic restoration, further investigations on complex design of core, milling accuracy, compatability of enamel porcelain and porcelain firing seems to be needed.

A STUDY ON THE ACCURACY OF THE IMPRESSION BODY ACCORDING TO MATERIALS AND FORMS OF THE INDIVIDUAL TOOTH TRAY / 대한치과보철학회지

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth' s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin, Futar' occlusion, Blu-mousse) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by X-PLAN360d to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference. 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less mar ginal discrepancy than groups with 0.5mm-marginal-vent-space(p<0.05). In summary, these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.

A STUDY ON THE ACCURACY OF THE IMPRESSION BODY ACCORDING TO MATERIALS AND FORMS OF THE INDIVIDUAL TOOTH TRAY / 대한치과보철학회지

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth' s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin, Futar' occlusion, Blu-mousse) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by X-PLAN360d to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference. 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less mar ginal discrepancy than groups with 0.5mm-marginal-vent-space(p<0.05). In summary, these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.