• Journal of Technologic Dentistry
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• v.36 no.2
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• pp.75-81
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• 2014

Purpose: This study was to compare adaptations of lithium disilicate CAD/CAM crowns fabricated with different scanning systems. Methods: This study selected the mandibular right first molar as an abutment for experiments and produced 10 working models. Lithium disilicate crowns appropriate for each abutment were produced by using a CEREC$^{(R)}$ CAD/CAM system. The independent t-test was then used to compare and analyze the data obtained from the two groups(${\alpha}$=0.05). Results: Mean(SD) adaptation were $86.93(22.82){\mu}m$ for the InS group, $88.42(26.77){\mu}m$ for the ExS group. They were no statistically significant differences between groups for adaptation(p>0.05). Conclusion: Within the limitations of this study, the results suggest that the accuracy of all investigated optical scanner were satisfactory for clinical use. Further assessment and improvement of the lithium disilicate ceramic for the fabrication of FPDs is evidently still required.

• The Journal of Advanced Prosthodontics
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• v.12 no.3
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• pp.173-180
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• 2020

PURPOSE. This study compared digital (reference point matching) and replica methods for measuring marginal and internal fit of full coverage restorations. MATERIALS AND METHODS. A maxillary left first molar typodent was fixed on to an aluminum base and prepared to receive all-ceramic full coverage restoration. The model was scanned with an intraoral scanner (CEREC Omnicam, Sirona, York, PA, USA). Twelve crowns were fabricated from lithium disilicate blocks (IPS emax CAD, Ivoclar Vivadent) and then crystalized. Marginal and internal fit of each restoration was measured by two examiners using replica and a new digital three-dimensional technique. Reliability between the two methods and two examiners was assessed by correlation and Cronbach's Alpha coefficient (P<.05). A Bland-Altman assessment for agreement was used to compare the two methods. RESULTS. Bland-Altman assessment showed that the mean of difference for marginal, absolute marginal, and axial gap was respectively -1.04 ㎛, -41.9 ㎛, and -29.53 ㎛ with limit of agreement (LOA) between -37.26 to 35.18 ㎛ for marginal, -105.85 to 22.05 ㎛ for absolute marginal and -80.52 to 22.02 ㎛ for axial gap. Positive correlation for repeatability (P<.05) in determining marginal and internal gaps by the two examiners in both techniques was revealed. Reliability of both techniques in all sites of measurements was at least good (0.8 ≤ α < 0.9). CONCLUSION. Both measuring techniques appeared highly reliable for evaluating fit of fixed dental restorations, while reference point matching provided higher values in axial and absolute marginal gap assessment.

• Journal of Technologic Dentistry
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• v.45 no.1
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• pp.1-7
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• 2023

Purpose: To evaluate the marginal and internal fit of metal coping fabricated by a metal three-dimensional (3D) printer that uses selective laser melting (SLM). Methods: An extraoral scanner was used to scan a die of the prepared maxillary right first molar, and the coping was designed using computer-aided design software and saved as an stereo lithography (STL) file. Ten specimens were printed with an SLM-type metal 3D printer (SLM group), and 10 more specimens were fabricated by casting the castable patterns output generated by a digital light processing-type resin 3D printer (casting the 3D printed resin patterns [CRP] group). The fit was measured using the silicon replica technique, and 8 points (A to H) were set per specimen to measure the marginal (points A, H) and internal (points B~G) gaps. The differences among the groups were compared using the Mann-Whitney U-test (α=0.05). Results: The mean of marginal fit in the SLM group was 69.67±18.04 ㎛, while in the CRP group was 117.10±41.95 ㎛. The internal fit of the SLM group was 95.18±41.20 ㎛, and that of the CRP group was 86.35±32 ㎛. As a result of statistical analysis, there was a significant difference in marginal fit between the SLM and CRP groups (p<0.05); however, there was no significant difference in internal fit between the SLM group and the CRP group (p>0.05). Conclusion: The marginal and internal fit of SLM is within the clinically acceptable range, and it seems to be applicable in terms of fit.

• Journal of Korean society of Dental Hygiene
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• v.9 no.2
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• pp.57-71
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• 2009

This study aims to investigate the stress factors of students in Dental Hygiene Department who will soon take the national examination, corresponding countermeasures and relationship of internal and external personality. On the basis of the results from investigation, this study will identify the methods to effectively cope with stress and to take the national examination with more positive thinking for the students and faculty members in Dental Hygiene Department, who have to pass the difficult test, the national examination. The structured questionnaires were given to junior students in Dental Hygiene Department in three colleges, to identify the stress factors, methods to deal with stress and A/B personality types. For the stress factor by field, the M college showed significantly higher stress about curriculum and assignment than the C college. In the stress factor analysis by item, the lack of information on national examination in the test area, all items in learning environment, a quantity of assignment that doesn't help the preparation of national examination in the assignment area, and lack of information on employment in job area demonstrated the significant difference(p<0.05). For the methods of subjects to deal with stress, several subcategories of long-term and short-term adaptation had significance. In case of the methods to deal with stress by personality type, B type in the short-term adaptation method in M college and A type in the long-term adaptation method in C college were significantly higher(p<0.05). As for the correlation between the population sociological features and stress factors by personality type, health status had the high correlation with test in the test area. In other areas, the travel hours to school showed the significant correlation. The higher the records were, the longer the travel hours were and the better the health status was, the higher the long-term adaptation method scores were. Moreover, the personality of A type showed the higher scores in the long-term adaptation method than that of B type. The health status and personality type showed the significant correlation(p<0.05). In conclusion, it is required to prevent any situations b identify the personality type and stress reasons of the students in Dental Hygiene Department who will take the national examination soon. The additional requirement is the continuing interest and counseling of faculty members to help students to cope with stress with positive attitude.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.444-450
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• 2014

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 ${\times}200$ 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 $155.93{\pm}33.98{\mu}m$ with Anatomical Occlusal preparation design having the least gap value of $139.23{\pm}30.85{\mu}m$ 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.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.536-541
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• 2015

The purpose of this study was to evaluate the marginal and internal gap of Cobalt (Co)-Chromium (Cr) sintering metal coping fabricated by dental computer-aided design/computer-aided manufacturing systems. Abutment tooth 46 of universal numbering system was selected for the study. Twenty Co-Cr metal copings of two groups were manufactured and scanned. Co-Cr cast metal copings (CCM) group of ten were fabricated using investment, burnout and casing after subtractive manufacturing of wax block. Also, Co-Cr sintering metal copings (CSM) group of ten were fabricated using sintering processing after subtractive manufacturing of Co-Cr soft metal bock. Marginal and internal gap of Co-Cr metal copings of twenty were measured by digital microscope (${\times}160$) with silicone replica technique. The data was analyzed from IBM SPSS Statistics ver. 22.0 Statistical software for Mann-Whitney U test (${\alpha}=0.05$). $Mean{\pm}standard$ deviation of marginal gap of CCM group was $90.12{\pm}61.73{\mu}m$ of CSM group was $60.17{\pm}24.83{\mu}m$. However, two groups was statistically not different (p>0.05). This study showed that CSM group was clinically acceptable adaptation.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.179-186
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• 2013

PURPOSE. One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. MATERIALS AND METHODS. The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (${\alpha}$=.05). RESULTS. In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). CONCLUSION. Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.210-217
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• 2016

Purpose: The aim of this study was to evaluate the marginal and internal adaptation of monolithic zirconia restoration made without physical model by digital intraoral scanner. Materials and methods: A prospective clinical trial was performed on 11 restorations as a pilot study. The monolithic zirconia restorations were fabricated after digital intraoral impression taking by intraoral scanner (TRIOS, 3shape, Copenhagen, Denmark), computer-aided designing, and milling manufacturing process. Completed zirconia crowns were tried in the patients' mouth and a replica technique was used to acquire the crown-abutment replica. The absolute marginal discrepancy, marginal gap, and internal gap of axial, line angle, and occlusal part were measured after sectioning the replica in the mesiodistal and buccolingual direction. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U test (${\alpha}=.05$). Results: From the adaptation analysis by replica, the statistically significant difference was not found between mesiodistal and buccolingual sections (P>.05), but there was significant difference among the measurement location (P<.01). The amount of absolute marginal discrepancy was larger than those of marginal gap and internal gap (P<.01). Conclusion: Within the limitations of this study, the adaptation accuracy of model-free monolithic zirconia restoration fabricated by intraoral scanner exhibited clinically acceptable result. However, the margin of zirconia crown showed tendency of overcontour and cautious clinical application and follow up is necessary.

• Journal of dental hygiene science
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• v.12 no.4
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• pp.368-374
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• 2012

Dental CAD (computer-aided design)/CAM (computer-aided manufacturing) systems facilitate the use of zirconia core for all-ceramic crown. The purpose of this study was to evaluate the marginal and internal fit of zirconia core fabricated using a dental CAD/CAM system and to compare the fit of metal cores by a conventional method. Ten identical cases of single coping study models (abutment of teeth 11) were manufactured and scanned. Ten zirconia cores were fabricated using dental CAD/CAM system. An experienced dental technician fabricated 10 samples of metal cores for the control group using the lost wax technique. Marginal and internal fit was measured by the silicone replica technique. Fit was measured with magnification of 160 using a digital Microscope. Margin, rounded chamfer, axial wall and incisal fits were measured for comparison. T-test of independent sample for statistical analysis was executed with SPSS 12.0 for Windows (SPSS Inc., Chicago, IL, USA) (${\alpha}$=0.05). The mean (SD) for marginal, rounded chamfer, axial wall and incisal were: $97.0\;(25.3){\mu}m$, $104.0\;(22.0){\mu}m$, $59.6\;(21.4){\mu}m$ and $124.8\;(33.3){\mu}m$ for the zirconia core group, and $785.2\;(18.4){\mu}m$, $83.8\;(15.1){\mu}m$, $42.7\;(9.6){\mu}m$ and $83.4\;(14.4){\mu}m$ for the metal core group. T-test showed significant differences between groups for margin (p<.001), rounded chamfer (p<.001), axial wall (p<.001) and incisal (p<.001). But zirconia core group observed that the marginal and internal fit values in the present study were within clinically acceptable range.

• Imaging Science in Dentistry
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• v.52 no.3
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• pp.303-308
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• 2022

Purpose: This technical report aims to describe and detail the use of micro-computed tomography for a reliable evaluation of the bulk-fill composite/tooth interface. Materials and Methods: Bulk-fill composite restorations in tooth cavities were scanned using micro-computed tomography to obtain qualitatively and quantitatively valuable information. Two-dimensional information was processed using specific algorithms, and ultimately a 3-dimensional (3D) specimen reconstruction was generated. The 3D rendering allowed the visualization of voids inside bulk-fill composite materials and provided quantitative measurements. The 3D analysis software VG Studio MAX was used to perform image analysis and assess gap formation within the tooth-restoration interface. In particular, to evaluate internal adaptation, the Defect Analysis addon module of VG Studio Max was used. Results: The data, obtained with the processing software, highlighted the presence and the shape of gaps in different colours, representing the volume of porosity within a chromatic scale in which each colour quantitatively represents a well-defined volume. Conclusion: Micro-computed tomography makes it possible to obtain several quantitative parameters, providing fundamental information on defect shape and complexity. However, this technique has the limit of not discriminating materials without radiopacity and with low or no filler content, such as dental adhesives, and hence, they are difficult to visualise through software reconstruction.