The YUCD Student Clinical Case Presentation
The YUCD Student Clinical Case Presentation was held on October 14, 2022. All 65 6th grade students gave a poster presentation and 6 students were selected through preliminary examination to give an oral presentation. They shared their best clinical case review of the year with other students and faculty members, and had Q&A sessions. Considering the propriety of diagnosis, the result of the treatment and presentation skill, Ju-yeon Lee, who presented a case of maxillary and mandibular partial denture restoration in a patient with multiple dental caries, won the first prize.
The YUCD students are given the opportunity to perform actual patient treatments under the supervision of the professors in the Predoctoral Student Clinic, where international levels of infection control and quality control are being implemented. This annual event allows students to look back on the year and see how much they have grown.
The Opening Ceremony of the Department of Industrial Dentistry
The Grand Opening Ceremony of the Department of Industrial Dentistry was held on 13 December 2022. The Department of Industrial Dentistry was established with the vision of nurturing global talented individuals in the new industry field including Bio-Healthcare.
Through the establishment of the Department of Industrial Dentistry, the YUCD is expecting to strengthen the industry-academia-research cooperation by nurturing research manpower. Dental material and medical appliance companies can also take this opportunity to recruit qualified dental professionals with knowledge and innovative techniques.
We were honored by the presence of over 40 influential stakeholders in the dental industry. Yonsei University College of Dentistry marked an important milestone on its journey of challenge and innovation as a global leading university.
21st Yonsei Dental International Symposium
The 21st Yonsei Dental International Symposium was held on December 16, 2022. The symposium was divided into two sessions: Yonsei University College of Dentistry – Tohoku University Graduate School of Dentistry International Join Symposium and 7th Joint Symposium of College of Dentistry & College of Engineering.
Professor Kee-Joon Lee, the Dean of the Yonsei University College of Dentistry and professor Nobuhiro Takahashi, the Dean of the Tohoku University Graduate School of Dentistry opened the first session with welcome remarks. Three speakers from each university gave speeches on the topic of ‘Innovation and challenge of Geriatric dentistry.’ Attendees participated in an active discussion about effective and systematic care for the aged patients on the understanding of the biology of aging.
At the second session, two speakers from College of Dentistry and three speakers from College of Engineering gave speeches on the topic of ‘Digital integration of Dentistry and Engineering.’ The latest trends and concepts such as artificial intelligence, three-dimensional printing, new materials and bio-integrated electronics were introduced and demonstrated.
In addition, 80 student and resident researchers of the YUCD participated in an academic poster presentation to share their research achievements.
1. Anti-biofilm activity of chlorhexidine-releasing elastomerics against dental microcosm biofilms.
The prevalence of dental caries in orthodontic patients increases by 15 to 30% compared to before orthodontic treatment due to the pathogenic biofilm that accumulates around the orthodontic appliances. Dental caries in orthodontic patients commonly occurs around orthodontic appliances such as brackets attached to teeth, archwire, and elatomerics (Fig. 1). The research team led by professor Baek-Il Kim developed Chlorhexidine-releasing orthodontic elastomerics to reduce the incidence of dental caries by inhibiting the biofilm formation around the orthodontic brackets. They patented the invention that allows chlorhexidine, known as the most effective antibacterial substance in the oral cavity, to be continuously released from the elastomerics (patent number KR101591587B1). They evaluated the cariogenic pathogenicity of the biofilms non-invasively using a quantitative light-induced (QLF) system, and confirmed that the red fluorescence intensity indicating cariogenic pathogenicity exhibited 23% lower from the chlorhexidine-releasing elastomerics (CRE)-treated biofilm compared to the control group (Fig. 2). In addition, the live/dead cell ratio of the CRE-treated biofilm decreased by 27% compared to the control group (Fig. 3). This study confirmed the possibility of clinical application that chlorhexidine-coated elastomers can effectively prevent dental caries during orthodontic treatment. This study was published in the prominent international dental journal 'Journal of Dentistry (impact factor 4.991)' in July 2022.
Abstract
Objective: To evaluate the anti-biofilm activity of chlorhexidine-releasing elastomerics (CRE) developed to prevent biofilm-related diseases in orthodontic patients, using dental microcosm biofilms.
Methods: Elastomerics coated with one of two solutions (CRE 1 and 2) were attached to bovine enamel specimens. Uncoated elastomerics were used for negative (distilled water [DW]) and positive (0.1% chlorhexidine [CHX]) control groups. After saliva inoculation on the surface of the specimen for biofilm formation, DW and CRE groups were treated with DW, and the positive control group was treated with CHX twice a day for 5 min. After 7 days of biofilm formation, colony-forming units (CFUs, total and aciduric bacteria), red/green (R/G) ratio, biofilm thickness, live/dead cell ratio, and bacterial morphology in the biofilms were evaluated. Enamel demineralization was evaluated by fluorescence loss (ΔF).
Results: The CFUs of total and aciduric bacteria and R/G ratios in the CRE groups were significantly lower than those in the DW group with a reduction by 13%, 13%, and 19%, respectively (p < 0.05). The CFUs of total bacteria was significantly lower in the CRE groups than in the 0.1% CHX group (p < 0.05). Among the CRE groups, only CRE 1 exhibited a significantly reduced biofilm thickness of 54% compared to the DW group (p < 0.05) and apparent changes in bacterial morphology. ΔF in the CRE groups was significantly higher by 36% compared to that in the DW group (p < 0.05).
Conclusions: CREs exhibited anti-biofilm and demineralization-inhibiting effect. Particularly, CRE 1 using dichloromethane as the solvent was most effective against biofilms.
Clinical significance: Chlorhexidine-releasing elastomerics exhibited increased anti-biofilm and demineralization-inhibiting effect compared to 0.1% chlorhexidine mouthwash. Therefore, it is possible to prevent biofilm-related diseases simply and effectively by applying chlorhexidine-releasing elastomerics to orthodontic patients.
2. Homogeneity of dental curing unit beam profile and its effect on microhardness of dental composites with varying thicknesses
The light curing unit (LCU) is dental clinics' most frequently and widely used instrument. Unfortunately, there have been reports that the beam from the LCU is not uniform. However, some problems were found in the papers reporting the beam's inhomogeneity. Therefore, this study was conducted to analyze the effect of controlling factors to evaluate the inhomogeneity and to present the correct evaluation method. In addition, a study was conducted to determine whether the curing light's inhomogeneity affects the polymerization of the light-curing composite resin. This study confirmed that the inhomogeneity of the LCU was measured differently by several factors. Therefore, it was newly suggested that a standardized evaluation method that can control these factors is needed. In addition, it was also newly confirmed that the effect of such inhomogeneity on the polymerization of the light-curing composite resins was limited only when the composite resin was 4 mm or thicker. This article was published in ‘Dental Materials (impact factor 5.687).’
Abstract
Objectives: The dental curing unit (DCU) has been reported to emit inhomogeneous light. However, there are no studies on which elements could affect the inhomogeneity of DCUs. This study aimed to analyze the effect of attenuating factors such as the aperture of the lens or neutral density (ND) filters on the DCU's beam profile and evaluate the effect of DCU's inhomogeneous beam profile on the microhardness distribution on composite resin specimens with different thicknesses.
Methods: Radiant emittance and spectrum of eight DCUs were investigated with and without ND filters using different optical density (OD) values. Beam profiles of eight DCUs were photographed while increasing the OD values of the ND filter. The change in the beam profile while changing the f-number of the aperture and the OD value of the ND filters were recorded. The Vickers microhardness of Filtek Z350XT and SDR cured by Bluephase Style 20i with 1, 2, 3, and 4 mm specimens of nine points on each surface was measured.
Results: Irradiance and spectrum of DCUs uniformly decreased after attenuation by the ND filters. The beam profile of the DCUs blurred when the f-number of the aperture was higher. The microhardness of Filtek Z350XT showed differences between the central and peripheral areas, and between the points under violet LED and the center on the bottom surface of the 4 mm specimen. The microhardness of the SDR did not show any differences.
Significance: The inhomogeneity of the beam profile can be affected by attenuation conditions. DCU's inhomogeneous beam profile may have different effects on the composites depending on the thicknesses and types of composite resin used.
3. Harmonization of robust radiomic features in the submandibular gland using multi-ultrasound systems: a preliminary study
The ultrasonography system is a specialized diagnostic tool for soft tissue diseases including the sialadenitis, and has the advantage of being able to examine the state change of tissues in real time with high resolution without ionizing radiation. For ultrasonography diagnostic system, many researchers have devoted to standardize the diagnostic protocols since ultrasonography is highly dependent on the operator and the examining center. The research team of oral and maxillofacial radiology in Yonsei University college of dentistry paid attention to establish a “standardized” and “quantifiable” techniques in ultrasound diagnostic system. The research team further step-up from simple extracting quantifiable pattern from the ultrasonography, to have standardized the discrepancy between different ultrasound systems through a machine learning-based method. The results of this research was published in December 2022 in ‘Dentomaxillofacial Radiology (impact factor 3.525)’, an international scientific journal of the dental diagnostic imaging field.
Abstract
Objective: This study aimed to identify robust radiomic features in multiultrasonography of the submandibular gland and normalize the interdevice discrepancies by applying a machine-learning-based harmonization method.
Methods: Ultrasonographic images of normal submandibular gland of young healthy adults, aged between 20 and 40 years, were selected from two different devices. In a total of 30 images, the region of interest was determined along the border of gland parenchyma, and 103 radiomic features were extracted using A-VIEW. The coefficient of variation (CV) was obtained for individual features, and the features showing CV less than 10% were selected. For the selected features, the interdevice discrepancy was normalized using machine-learning method, called the ComBat harmonization. Median differences of the features between the two scanners, before and after harmonization, were compared using Mann–Whitney U-test; confidence interval of 95%.
Results: Among total 103 radiomic features, 17 features were selected as robust, showing CV less than 10% in both scanners. All values of selected features, except two, showed a statistical difference between the two devices. After applying the ComBat harmonization method, the median and distribution of the 16 features were harmonized to show no significant difference between the two scanners (p > 0.05). One feature remained different (p ≤ 0.05).
Conclusion: On ultrasonographic examination, robust radiomic features for normal submandibular gland were obtained and interdevice normalization was efficiently conducted using ComBat harmonization. Our findings would be useful for multidevices or multicenter studies based on clinical ultrasonographic imaging data to improve the accuracy of the overall diagnostic model.
4. Comparing Free-Flap Reconstruction After Robot-Assisted Neck Dissection via a Retroauricular Approach and a Traditional Transcervical Approach: Single-Surgeon Experiences of 90 Consecutive Cases
It is essential to immediately reconstruct the large defects after massive tumor ablation in the oral and maxillofacial region for recovery of aesthetics and function. Recent trends include applying minimally invasive approaches, such as robot-assisted neck surgery via retroauricular approach for microvascular free flap reconstructions. However, it has been considered as an approach with limitations and a relatively low success rate compared to the conventional approach in a small number of patients (n=5, 7, 50). Professor Dongwook Kim’s team reported that cases using this approach showed the same reconstruction time and hospitalization days as the conventional approach, and the reconstruction for advanced stage and salvage operation, which were considered relative contraindications in previous studies, were also possible. This is the result of the highest success rate in the largest number of patients compared to previous studies (n=90, 100%, 98.3%). This study was published in the international scientific journal ‘Annals of Surgical Oncology (impact factor 4.339)’ in December 2022.
Abstract
Background: Predominant traditional approaches for most patients who have advanced-stage oral cancer with transcervical incision lines left irreversible scars. To address this, surgeons have continuously refined minimally invasive surgery (MIS) techniques, including robot-assisted neck surgeries. This article introduces and discusses the feasibility, versatility, and availability of free-flap reconstruction via the retroauricular approach (RA), considered difficult to date.
Methods: This study retrospectively analyzed 90 consecutive patients who had free-flap reconstruction performed by a single surgeon (D.K.) in the Department of Oral and Maxillofacial Surgery, Yonsei University, from March 2021 to April 2022. The type of defects and flaps, hospitalization days, total operation time, and type of vessels and anastomoses were compared statistically.
Results: The type of vessels used did not differ between the RA and the transcervical approach (TA) groups, nor in duration of hospital stays. Likewise, the total reconstruction time did not differ significantly between the TA group (240 min) and the RA group (245 min) (p = 0.756). However, the total operation time was about 1 h less in the TA group, a statistically significant difference (TA group [593 ± 152 min] vs. RA group [655 ± 117 min]; p = 0.044). All flaps were successful in the RA group, whereas one flap in the TA group led to a total loss (TA group [98.3%] vs. RA group [100.0%]; p = 1.000).
Conclusions: Even for patients with advanced oral cancer who require massive tumor ablation, it is feasible to obtain an aesthetic and functional surgical outcome by performing free-flap reconstruction via the retroauricular approach.