Effects of image and education on the precision of the measurement method for evaluating prosthesis misfit

Mai, Hang-Nga,Lee, Kyeong Eun,Ha, Jung-Hong,Lee, Du-Hyeong Elsevier 2018 The Journal of prosthetic dentistry Vol.119 No.4

<P><B>Abstract</B></P> <P><B>Statement of problem</B></P> <P>Various methods for measuring prosthesis misfit have been suggested. Although the cross-sectional images between the crown and abutment are used to evaluate the misfit, the effects of the image and the observer’s knowledge on the precision of measurement are unknown.</P> <P><B>Purpose</B></P> <P>The purpose of this in vitro study was to investigate the effects of the image and of education on the precision of prosthesis misfit measurement methods using inter- and intraobserver variability analyses.</P> <P><B>Material and methods</B></P> <P>The cross-sectional images in the margin were obtained using the computer-aided replica technique (CART), silicone replica technique (RT), and sectioning technique (ST). Twenty-five observers measured the absolute marginal discrepancy values in the images obtained from each group 4 times at an interval of 2 weeks; the observers went through different education sessions regarding the selection of the measurement points. The precision of measurement was determined and compared using the likelihood-ratio test statistic (α=.05) and the intraclass correlation coefficient with the linear mixed-effects model.</P> <P><B>Results</B></P> <P>The CART group exhibited the smallest deviations in the measurement variations, followed by the ST and RT groups (<I>P</I><.001). Additional education on misfit measurements generally decreased the deviation values in all the groups, but without any significant differences.</P> <P><B>Conclusions</B></P> <P>The cross-sectional image obtained from the measurement methods and education on the evaluation method affected the precision of the prosthesis misfit measurement. Digital methods might be a useful tool to significantly enhance the precision of the measurements.</P>

Effects of different finishing/polishing protocols and systems for monolithic zirconia on surface topography, phase transformation, and biofilm formation

Hang-Nga Mai,Su-Hyung Hong,Sung-Hun Kim,Du-Hyeong Lee 대한치과보철학회 2019 The Journal of Advanced Prosthodontics Vol.11 No.2

PURPOSE. The purpose of this study was to evaluate the effects of various protocols and systems for finishing and polishing monolithic zirconia on surface topography, phase transformation, and bacterial adhesion. MATERIALS AND METHODS. Three hundred monolithic zirconia specimens were fabricated and then treated with three finishing and polishing systems (Jota [JO], Meisinger [ME], and Edenta [ED]) using four surface treatment protocols: coarse finishing alone (C); coarse finishing and medium polishing (CM); coarse finishing and fine polishing (CF); and coarse finishing, medium polishing, and fine polishing (CMF). Surface roughness, crystal phase transformation, and bacterial adhesion were evaluated using atomic force microscopy, X-ray diffraction, and streptococcal biofilm formation assay, respectively. One-way and two-way analysis of variance with Tukey post hoc tests were used to analyze the results (α=.05). RESULTS. In this study, the surface treatment protocols and systems had significant effects on the resulting roughness. The CMF protocol produced the lowest roughness values, followed by CM and CF. Use of the JO system produced the lowest roughness values and the smallest biofilm mass, while the ME system produced the smallest partial transformation ratio. The ED group exhibited the highest roughness values, biofilm mass, and partial transformation ratio. CONCLUSION. Stepwise surface treatment of monolithic zirconia, combined with careful polishing system selection, is essential to obtaining optimal microstructural and biological surface results.

Verification of a computer-aided replica technique for evaluating prosthesis adaptation using statistical agreement analysis

Hang Nga Mai,이경은,이규복,정승미,이석재,이청희,안서영,이두형 대한치과보철학회 2017 The Journal of Advanced Prosthodontics Vol.9 No.5

PURPOSE. The purpose of this study was to evaluate the reliability of computer-aided replica technique (CART) by calculating its agreement with the replica technique (RT), using statistical agreement analysis. MATERIALS AND METHODS. A prepared metal die and a metal crown were fabricated. The gap between the restoration and abutment was replicated using silicone indicator paste (n = 25). Gap measurements differed in the control (RT) and experimental (CART) groups. In the RT group, the silicone replica was manually sectioned, and the marginal and occlusal gaps were measured using a microscope. In the CART group, the gap was digitized using optical scanning and image superimposition, and the gaps were measured using a software program. The agreement between the measurement techniques was evaluated by using the 95% Bland-Altman limits of agreement and concordance correlation coefficients (CCC). The least acceptable CCC was 0.90. RESULTS. The RT and CART groups showed linear association, with a strong positive correlation in gap measurements, but without significant differences. The 95% limits of agreement between the paired gap measurements were 3.84% and 7.08% of the mean. The lower 95% confidence limits of CCC were 0.9676 and 0.9188 for the marginal and occlusal gap measurements, respectively, and the values were greater than the allowed limit. CONCLUSION. The CART is a reliable digital approach for evaluating the fit accuracy of fixed dental prostheses.

Comparative Study of the Fit Accuracy of Full-Arch Bar Frameworks Fabricated with Different Presintered Cobalt-Chromium Alloys

Mai, Hang-Nga,Kwon, Tae-Yub,Hong, Min-Ho,Lee, Du-Hyeong Hindawi 2018 BioMed research international Vol.2018 No.-

<P><B>Purpose</B></P><P> This study was to measure the geometric discrepancies that occur during the sintering contraction of presintered Co-Cr alloys in a full-arch bar framework and to compare the variations between alloys from different manufacturers.</P><P><B> Materials and Methods</B></P><P> Eighteen implant-supported full-arch bar frameworks were fabricated through a soft-machining process using presintered Co-Cr alloy blocks: Ceramill Sintron (CS), Soft Metal (SM), and Sintermetall (SML) (n=6 for each group). The sintered frameworks were digitized using a structured light scanner, and the scan images were superimposed on the reference design. The geometric discrepancies of the sintered frameworks were three-dimensionally analyzed for horizontal, angular, and internal discrepancies. Kruskal-Wallis and Mann–Whitney U tests were used to compare the discrepancies among the groups (<I>α</I>=.05).</P><P><B> Results</B></P><P> Significant differences were found in the geometric discrepancy measurements among the groups. The CS group showed larger horizontal and angular discrepancies, followed by the SM and SML groups<I> (P</I><.001). The root mean square (RMS) values for internal discrepancy were not statistically different among the groups (<I>P</I>=.778).</P><P><B> Conclusion</B></P><P> The geometric discrepancies of full-arch bar frameworks fabricated using the soft-machining process were affected by accuracies in sintering contraction of presintered alloys.</P>

Three-dimensional morphometric analysis of facial units in virtual smiling facial images with different smile expressions

Hang Nga Mai,타우 타우 윈,Minh Son Tong,이청희,이규복,김소연,이현우,이두형 대한치과보철학회 2023 The Journal of Advanced Prosthodontics Vol.15 No.1

PURPOSE. Accuracy of image matching between resting and smiling facial models is affected by the stability of the reference surfaces. This study aimed to investigate the morphometric variations in subdivided facial units during resting, posed and spontaneous smiling. MATERIALS AND METHODS. The posed and spontaneous smiling faces of 33 adults were digitized and registered to the resting faces. The morphological changes of subdivided facial units at the forehead (upper and lower central, upper and lower lateral, and temple), nasal (dorsum, tip, lateral wall, and alar lobules), and chin (central and lateral) regions were assessed by measuring the 3D mesh deviations between the smiling and resting facial models. The one-way analysis of variance, Duncan post hoc tests, and Student’s t-test were used to determine the differences among the groups (α = .05). RESULTS. The smallest morphometric changes were observed at the upper and central forehead and nasal dorsum; meanwhile, the largest deviation was found at the nasal alar lobules in both the posed and spontaneous smiles (P < .001). The spontaneous smile generally resulted in larger facial unit changes than the posed smile, and significant difference was observed at the alar lobules, central chin, and lateral chin units (P < .001). CONCLUSION. The upper and central forehead and nasal dorsum are reliable areas for image matching between resting and smiling 3D facial images. The central chin area can be considered an additional reference area for posed smiles; however, special cautions should be taken when selecting this area as references for spontaneous smiles.

Verification of a computer-aided replica technique for evaluating prosthesis adaptation using statistical agreement analysis

Mai, Hang-Nga,Lee, Kyeong Eun,Lee, Kyu-Bok,Jeong, Seung-Mi,Lee, Seok-Jae,Lee, Cheong-Hee,An, Seo-Young,Lee, Du-Hyeong The Korean Academy of Prosthodonitics 2017 The Journal of Advanced Prosthodontics Vol.9 No.5

PURPOSE. The purpose of this study was to evaluate the reliability of computer-aided replica technique (CART) by calculating its agreement with the replica technique (RT), using statistical agreement analysis. MATERIALS AND METHODS. A prepared metal die and a metal crown were fabricated. The gap between the restoration and abutment was replicated using silicone indicator paste (n = 25). Gap measurements differed in the control (RT) and experimental (CART) groups. In the RT group, the silicone replica was manually sectioned, and the marginal and occlusal gaps were measured using a microscope. In the CART group, the gap was digitized using optical scanning and image superimposition, and the gaps were measured using a software program. The agreement between the measurement techniques was evaluated by using the 95% Bland-Altman limits of agreement and concordance correlation coefficients (CCC). The least acceptable CCC was 0.90. RESULTS. The RT and CART groups showed linear association, with a strong positive correlation in gap measurements, but without significant differences. The 95% limits of agreement between the paired gap measurements were 3.84% and 7.08% of the mean. The lower 95% confidence limits of CCC were 0.9676 and 0.9188 for the marginal and occlusal gap measurements, respectively, and the values were greater than the allowed limit. CONCLUSION. The CART is a reliable digital approach for evaluating the fit accuracy of fixed dental prostheses.

Perfluoroalkyl substances (PFASs) in seawater samples from the Yellow Sea and the East China Sea around Jeju Island, Korea

NGUYEN THI NGA,SEONGMIN CHO,MAI DUC HUNG,HYEONSEO CHO 환경독성보건학회 2022 한국독성학회 심포지움 및 학술발표회 Vol.2022 No.5

제주 해역 해수 및 해저퇴적물 중 과불화화합물(PFASs) 분포

Nguyen Thi Nga,Mai Duc Hung,조성민(Seongmin Cho),조현서(Hyeonseo Cho) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.10

지난 수 십년동안, PFASs 는 화장품, 카펫, 가죽, 음식포장, 소방 물품 등을 포함한 많은 실제 응용 분야에서 널리 사용되어 왔다. 이 물질들은 건강에 미치는 영향, 생태독성 잠재력, 생물 축적, 환경 지속성과 관련된 많은 논란을 받아왔다. 본 연구는 2020년 7월에 한국 제주 해역에서 표층 44 정점과 퇴적물 31 정점을 채취하여 PFASs 오염 정도와 공간적 분포를 파악하였다. 분석 결과 긴 고리로 구성된 고분자 PFASs가 짧은 고리로 구성된 저분자 PFASs 보다 해수와 퇴적물에서 풍부하게 나타났다. 또한 모든 검체에서 PFOA가 지배적인 PFAS로 검출되었다. 해수에서 PFAS의 농도는 2.95 to 9.28 (ng/L)이며 침전물은 0.11 to 1.00(ng/dry wt)의 범위를 보였다. 본 연구의 결과를 다른 해수 내 PFASs 결과와 비교하였다. Over the past few decades, Perfluoroalkyl substances (PFASs) have become ubiquitous in plenty of real-world applications including (cosmetics, carpets, leathers, food packages, fire-fighting forms, and so on). The substances have received many controversies concerning health effects, ecotoxicological potential, bioaccumulation, and being environmentally persistent. Forty-four surface seawater and thirty-one sediment samples were collected from Jeju sea area, Korea, in July 2020. Accordingly, we intensively analyzed the samples to understand contamination levels and their spatial distribution. The analyzed results indicate that long-chain PFASs were more abundant than short-chain PFASs in seawater and sediment environments. In addition, PFOA was also detected as the dominant PFASs in all samples. Concentration of PFASs in water ranges from 2.95 to 9.28 (ng/L), while in sediment from 0.11 to 1.00 (ng/dry wt). Comparing the PFAS in seawater of this study with several previous reports can observe that these are similar in concentration.

발치 후 지르코니아 보철물 제작에서 최적의 연조직 적합 형성을 위한 디지털 치료 증례

마이항나,이두형,Mai, Hang Nga,Lee, Du-Hyeong 대한치과보철학회 2020 대한치과보철학회지 Vol.58 No.3

Conventionally, when a zirconia fixed dental restoration is planned, the interim restoration is made manually and the final restoration is fabricated by the silicone impression taking at the prosthodontic stage. This conventional workflow does not provide direct relation between interim and final restorations. Moreover, the predictability of the final restoration could be low. Nowadays, the CAD/CAM based restoration fabrication and related digital techniques are developed and being applied in dentistry in multiple ways. This case report introduces a digital workflow for fabricating an optimal gingival adaptation and predictability of monolithic zirconia restoration by using CAD/CAM interim restoration, intra oral scan, and image superimposition technique in a case that required tooth extraction. 발치 후 고정성 지르코니아 보철물을 제작하는 경우 통상적으로 임시레진 보철물을 수작업으로 제작하고 보철단계에서 인상채득하여 최종 보철물을 제작한다. 이러한 전통적인 방식은 임시보철물과 최종 보철물 사이의 연계가 부족하고 결과의 심미적 기능적 예측성이 낮을 수 있다. 현재 CAD/CAM 방식의 보철물 제작과 관련 디지털 기술이 발전하여 진료에서 다양하게 활용되고 있다. 본 증례에서 발치 후 고정성 단일구조 지르코니아 보철물을 계획하는 경우 CAD/CAM 방식 임시보철물, 발치와 치유 후의 구내스캔, 컴퓨터 영상중첩술을 이용하여 최적의 가공치 적합도를 가지며 치료의 결과 예측도가 향상된 디지털 방식을 소개하고자 한다.

Effects of different surface finishing protocols for zirconia on surface roughness and bacterial biofilm formation

Du-Hyeong Lee,Hang-Nga Mai,Phyu Pwint Thant,Su-Hyung Hong,Jaewon Kim,Seung-Mi Jeong,Keun-Woo Lee 대한치과보철학회 2019 The Journal of Advanced Prosthodontics Vol.11 No.1

PURPOSE. Surface finishing of a zirconia restoration is essential after clinical adjustment. Herein, we investigated the effects of a surface finishing protocol for monolithic zirconia on final roughness and bacterial adherence. MATERIALS AND METHODS. Forty-eight disk-shaped monolithic zirconia specimens were fabricated and divided into four groups (n = 12) based on initial surface treatment, finishing, and polishing protocols: diamond bur+polishing bur (DP group), diamond bur+stone grinding bur+polishing bur (DSP group), no diamond bur+polishing bur (NP group), and no diamond bur+stone grinding bur+polishing bur (NSP group). Initial and final surface roughness was measured with a profilometer, and shown using scanning electron microscope. Bacterial adhesion was evaluated by quantifying Streptococcus mutans in the biofilm. Kruskal–Wallis and Mann-Whitney U tests were used to compare results among groups, and two-way analysis of variance was used to evaluate the effects of grinding burs on final roughness (α=.05). RESULTS. The DP group had the highest final Ra value, followed by the DSP, NP, and NSP groups. Use of the stone grinding bur as a coarsefinishing step significantly decreased final Ra values when a diamond bur was used (P<.001). Omission of the stone grinding bur increased biofilm formation on specimen surfaces. Combining a stone grinding bur with silicone polishing burs produced the smallest final biofilm values, regardless of the use of a diamond bur in initial surface treatment. CONCLUSION. Coarse finishing of monolithic zirconia with a stone grinding bur significantly decreased final Ra values and bacterial biofilm formation when surfaces had been roughened by a diamond bur. [ J Adv Prosthodont 2019;11:41-7] PURPOSE. Surface finishing of a zirconia restoration is essential after clinical adjustment. Herein, we investigated the effects of a surface finishing protocol for monolithic zirconia on final roughness and bacterial adherence. MATERIALS AND METHODS. Forty-eight disk-shaped monolithic zirconia specimens were fabricated and divided into four groups (n = 12) based on initial surface treatment, finishing, and polishing protocols: diamond bur+polishing bur (DP group), diamond bur+stone grinding bur+polishing bur (DSP group), no diamond bur+polishing bur (NP group), and no diamond bur+stone grinding bur+polishing bur (NSP group). Initial and final surface roughness was measured with a profilometer, and shown using scanning electron microscope. Bacterial adhesion was evaluated by quantifying Streptococcus mutans in the biofilm. Kruskal–Wallis and Mann-Whitney U tests were used to compare results among groups, and two-way analysis of variance was used to evaluate the effects of grinding burs on final roughness (α=.05). RESULTS. The DP group had the highest final Ra value, followed by the DSP, NP, and NSP groups. Use of the stone grinding bur as a coarsefinishing step significantly decreased final Ra values when a diamond bur was used (P<.001). Omission of the stone grinding bur increased biofilm formation on specimen surfaces. Combining a stone grinding bur with silicone polishing burs produced the smallest final biofilm values, regardless of the use of a diamond bur in initial surface treatment. CONCLUSION. Coarse finishing of monolithic zirconia with a stone grinding bur significantly decreased final Ra values and bacterial biofilm formation when surfaces had been roughened by a diamond bur. [ J Adv Prosthodont 2019;11:41-7]