A case of oral rehabilitation using implant fixed prosthesis (skeletal class III malocclusion patient) / 대한치과보철학회지

When the patient with class III malocclusion needs extensive oral rehabilitation due to multiple missing teeth, accurate diagnosis, and careful analysis, such as the patient’s occlusal relationship, facial changes, and evaluation of the temporomandibular joint are essential. Orthognathic surgery is often performed for aesthetic improvement, depending on the patient’s chief complaint. If it is not possible due to certain circumstances, partial aesthetic improvement can be achieved through minimal elevation of the vertical dimension. As this patient may have unexpected issues, such as temporomandibular joint disorder, oral habits like bruxism, and masticatory muscle tension, it was determined whether the patient could adjust to a reversible temporary removable partial denture. After this, the maxillary implant-supported fixed prostheses and the mandibular fixed prostheses were used to achieve stable posterior support and to partially improve the maxillary anterior esthetics. The patient was satisfied with the results both aesthetically and functionally. The prognosis is expected to be good if regular check-ups are conducted.

Enhanced Bone Formation by Rapidly Formed Bony Wall over the Bone Defect Using Dual Growth Factors

BACKGROUND@#In guided bone regeneration (GBR), there are various problems that occur in the bone defect after the wound healing period. This study aimed to investigate the enhancement of the osteogenic ability of the dual scaffold complex and identify the appropriate concentration of growth factors (GF) for new bone formation based on the novel GBR concept that is applying rapid bone forming GFs to the membrane outside of the bone defect. @*METHODS@#Four bone defects with a diameter of 8 mm were formed in the calvaria of New Zealand white rabbits each to perform GBR. Collagen membrane and biphasic calcium phosphate (BCP) were applied to the bone defects with the four different concetration of BMP-2 or FGF-2. After 2, 4, and 8 weeks of healing, histological, histomorphometric, and immunohistochemical analyses were conducted. @*RESULTS@#In the histological analysis, continuous forms of new bones were observed in the upper part of bone defect in the experimental groups, whereas no continuous forms were observed in the control group. In the histomorphometry, The group to which BMP-2 0.5 mg/ml and FGF-2 1.0 mg/ml was applied showed statistically significantly higher new bone formation. Also, the new bone formation according to the healing period was statistically significantly higher at 8 weeks than at 2, 4 weeks. @*CONCLUSION@#The novel GBR method in which BMP-2, newly proposed in this study, is applied to the membrane is effective for bone regeneration. In addition, the dual scaffold complex is quantitatively and qualitatively advantageous for bone regeneration and bone maintenance over time.

A prospective multicenter clinical study on the efficiency of detachable ball- and spring-retained implant prosthesis

PURPOSE@#This prospective clinical study was conducted to evaluate the clinical usefulness of the freely detachable zirconia ball- and spring-retained implant prosthesis (BSRP) through a comparative analysis of screw- and cement-retained implant prosthesis (SCRP). @*MATERIALS AND METHODS@#A multi-center, randomized, prospective clinical study evaluating the clinical usefulness of the detachable zirconia ball- and spring-retained implant prostheses was conducted. Sixty-four implant prostheses in 64 patients were examined. Periodic observational studies were conducted at 0, 3, 6, and 12 months after delivery of the implant prosthesis. Factors such as implant success rate, marginal bone resorption, periodontal pocket depth, plaque and bleeding index, and prosthetic complications were evaluated, respectively. @*RESULTS@#During the 1-year observation period, all implants survived without functional problems and clinical mobility, showing a 100% implant success rate. Marginal bone resorption was significantly higher in the SCRP group than in the BSRP group only at the time of implant prosthesis delivery (P = .043). In all observation periods, periodontal pocket depth was slightly higher in the BSRP group than in the SCRP group, but there was no significant difference (P > .05). The modified plaque index (mPI) scores of both groups were moderate. Higher ratio of a score 2 in modified sulcus bleeding index (mBI) was observed in the BSRP group in the 6- and 12-months observation. @*CONCLUSION@#Within the limitations of this study, the newly developed zirconia ball- and spring-retained implant prosthesis could be considered as an applicable and predictable treatment method along with the existing screw- and cement-retained prosthesis.

Accuracy of Bite Registration Using Intraoral Scanner Based on Data Trimming Strategy for Fremitus Teeth

Purpose@#This study aimed to evaluate the accuracy of bite registration using intraoral scanner based on data trimming strategy for fremitus teeth. @*Materials and Methods@#A reference model was designed by Medit Model Builder software (MEDIT Corp., Seoul). Tooth number 24 and 25 were separated as dies and tooth number 26 was prepared for full-coverage crown. Those were printed using a 3D printer (NextDent 5100). The scanning procedure was performed by a single trained operator with one intraoral scanner (i700; MEDIT Corp.). The scanning groups were divided as follows: group 1 (G1), no fremitus; group 2 (G2), 0.5 mm buccal fremitus in the maxillary left first and second premolar; and group 3 (G3), 1.5 mm buccal fremitus in the maxillary left first and second premolar. Each group was scanned 10 times and were analyzed using the reference model data. Surface-based occlusal clearance was analyzed at the prepared tooth to evaluate accuracy.Result: Mean values of control group (G1) were 1.587±0.021 mm. G2 showed similar values to those from the control group (1.580±0.024 mm before trimming strategy and 1.588±0.052 mm after trimming strategy). G3 showed significantly greater values (1.627±0.025 mm before trimming strategy and 1.590±0.024 mm after trimming strategy) and the differences were found between trimming strategy (P=0.004). @*Conclusion@#Bite trimming strategy for fremitus teeth is a reliable technique to reduce inaccuracies caused by the mobility at maximum intercuspation.

Evaluation of Mechanical Properties of Threedimensional Printed Flexible Denture Resin according to Post-polymerization Conditions: A Pilot Study

Purpose@#The purpose of this study was to evaluate whether three-dimensional (3D)-printed flexible denture resin has suitable mechanical properties for use as a thermoplastic denture base resin material. @*Materials and Methods@#A total of 96 specimens were prepared using the 3D printed flexible denture resin (Flexible Denture). Specimens were designed in CAD software (Tinkercad) and printed through a digital light-processing 3D printer (Asiga MAX UV). Post-polymerization process was conducted according to air exposure or glycerin immersion at 35°C or 60°C and for 30 or 60 minutes. The maximum flexural strength, elastic modulus, 0.2% offset yield strength, and Vickers hardness of 3D-printed flexible denture resin were assessed.Result: The maximum flexural strength ranged from 64.46±2.03 to 84.25±4.32 MPa, the 0.2% offset yield strength ranged from 35.28±1.05 to 46.13±2.33 MPa, the elastic modulus ranged from 1,764.70±64.66 to 2,179.16±140.01 MPa, and the Vickers hardness ranged from 7.01±0.40 to 11.45±0.69 kg/mm2 . @*Conclusion@#Within the limits of the present study, the maximum flexural strength, 0.2% offset yield strength, elastic modulus, and Vickers hardness are sufficient for clinical use under the post-polymerization conditions of 60°C at 60 minutes with or without glycerin precipitation.

Dental students’ clinical confidence in denture treatment after clinical experiences / 대한치과보철학회지

Purpose@#The purpose of this study is to investigate dental students’ self-perception of clinical care ability after a denture treatment experience. @*Materials and methods@#Of the 58 fourth-year students at the dental school in 2019, 50 students completed the questionnaire concerning their denture treatment session, including treatment planning and pre-prosthetic treatment (4 questions), clinical and laboratory procedures (20 questions), and students’ opinions on clinical denture education (4 questions). Each question was answered on a five-point scale, of which points four and five, “agree” and “strongly agree” respectively, were classified as positive responses while points one and two, “disagree” and “strongly disagree” respectively, were classified as negative. @*Results@#All the items on clinical and laboratory procedures received a positive response rate of over 60%, and the overall self-perception of the students appeared to be positive. However, the questions on the ability to perform denture treatment independently after graduation received only 48% of positive answer. Those on patient management, explanations of denture precautions, customized tray production, boxing, and work model production were answered with the highest positive response rate whereas those on treatment planning, final impression acquisition, and surveying, were the lowest in each session. @*Conclusion@#The dental students with experience in denture treatment generally have a positive opinion of their clinical care ability, but further education may be necessary to improve their ability to treat their patients independently.

Finite element analysis of the effect of novel Lock Screw system preventing abutment screw loosening

PURPOSE: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. MATERIALS AND METHODS: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. RESULTS: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. CONCLUSION: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

The use of implant surveyed fixed prosthesis for removable partial denture with a few unilateral remaining teeth: A case report / 대한치과보철학회지

As implant can be covered by National Health Insurance Service (NHIS), it was increased the interest in the removable partial denture (RPD) with the surveyed fixed prosthesis supported by implant fixture. To achieve predictable result, it needs the prudent implant planning by basic principles of RPD and patient's residual ridge. This 67 years old age male had a few unilateral remaining teeth, and hoped the treatment covered by NHIS. As using CAD software, the position of implant is planned with regarding to occlusal table of provisional denture, basic principles of RPD, and resorbed residual ridge. The definitive prostheses can ensure the stability and retention of removable prosthesis. When planning implant fixed prostheses, the digital technique was utilized to consider basic principle of RPD and resorbed residual ridge. As a result, it provided satisfactory prostheses.

Use of digital scan data for evaluation of edentulous ridge relationship: A case report for removable prosthesis with unilateral cross bite / 대한치과보철학회지

After the teeth were extracted, maxillary and mandibular alveolar ridges show the opposite resorption pattern and as a result, the mandibular arch is enlarged than maxillary arch relatively. In this situation, we should evaluate both alveolar ridge relationship and arrange the artificial teeth properly for stability of removable prosthesis. This case is a 77 years old male patient who wishes to make removable prosthesis and has atrophic alveolar ridge. By use of model scanner and CAD software, the angle between interalveolar crest line and occlusal plane was easily measured. Depending on the measurement, the artificial teeth are arranged in unilateral cross bite and after completion, patient was satisfied with the denture which showed proper stability, retention, support.

A new minimally invasive guided endodontic microsurgery by cone beam computed tomography and 3-dimensional printing technology

Endodontic microsurgery is defined as the treatment performed on the root apices of an infected tooth, which was unresolved with conventional root canal therapy. Recently, the advanced technology in 3-dimensional model reconstruction based on computed tomography such as cone beam computed tomography has opened a new avenue in application of personalized, accurate diagnosis and has been increasingly used in the field of dentistry. Nevertheless, direct intra-oral localization of root apex based on the 3-dimensional information is extremely difficult and significant amount of bone removal is inevitable when freehand surgical procedure was employed. Moreover, gingival flap and alveolar bone fenestration are usually required, which leads to prolonged time of surgery, thereby increasing the chance of trauma as well as the risk of infection. The purpose of this case report is to present endodontic microsurgery using the guide template that can accurately target the position of apex for the treatment of an anterior tooth with calcified canal which was untreatable with conventional root canal therapy and unable to track the position of the apex due to the absence of fistula.

Interalveolar ridge crest relation analysis and rehabilitation of edentulous patient using dental CAD software: A case report / 대한치과보철학회지

As the number of elderly population increases, the proportion of edentulous patients is increasing, and the demand for traditional dentures will also increase. Arranging the artificial teeth according to the relationship and shape of the upper and lower alveolar ridge is an important factor increasing the stability of the denture. This case is a 79 year old female patient who wishes to make denture covered by national health insurance for psychological and economical reasons. With the alveolar bone severely atrophic, the dental CAD software was used for accurate diagnosis and the posterior teeth were arranged in a cross bite according to the interalveolar crest line angle by the program. After completion, the denture showed adequate stability and maintenance in periodic examinations and treatment, and the patient also expressed high satisfaction.

A case of full mouth rehabilitation with orthodontic treatment in patient with extensive tooth erosion and wear using monolithic zirconia prostheses / 대한치과보철학회지

Extensive dental erosion and wear will cause serious loss of function and aesthetics in the mouth. In order to recover this condition, careful analysis of the patient's bite relationship is required. In particular, a treatment plan should be established considering the possibility of reproduction of the vertical dimension and centric relation, and appropriateness of the occlusal plane and anterior guidance. Also, the choice of prosthetic materials is an important consideration in patients with severe wear. In this case, patients with overall wear and erosion on tooth was established anterior guidance by orthodontic treatment and fully restored with monolithic zirconia, without increasing vertical dimension.

Occupational Burden of Asbestos-Related Diseases in Korea, 1998–2013: Asbestosis, Mesothelioma, Lung Cancer, Laryngeal Cancer, and Ovarian Cancer

BACKGROUND: Asbestos exposure causes asbestos-related diseases (ARDs) including asbestosis, malignant mesothelioma, lung cancer, laryngeal cancer, and ovarian cancer. Although Korea used substantial amounts of asbestos in the past, no study has focused on its occupational burden of disease (OBD). Therefore, this study aimed to determine the OBDs of ARDs in Korea. METHODS: The CARcinogen Exposure (CAREX) database was used to determine the proportion of exposed population. Relative risks for lung cancer, laryngeal cancer, and ovarian cancer were used to determine the population-attributable fraction. Data for deaths caused by ARDs during 1998–2013 were obtained from the World Health Organization mortality database. The potential years of life lost (PYLL) and annual average PYLL (APYLL) indicated OBDs. RESULTS: In Korea, the number of ARD-attributable deaths and PYLL due to all ARDs during 1998–2013 were 4,492 and 71,763.7, respectively. The number of attributable deaths and PYLL due to asbestosis, malignant mesothelioma, lung cancer, laryngeal cancer, and ovarian cancer were 37 and 554.2, 808 and 15,877.0, 3,256 and 47,375.9, 120 and 1,605.5, and 271 and 6,331.1, respectively; additionally, the APYLL were 15.0, 19.7, 14.6, 13.4, and 23.4, respectively, and the average age at death was 70.4, 62.6, 69.1, 69.9, and 61.8, respectively. Our study showed that although the use of asbestos has ceased in Korea, the incidence of ARDs tends to increase. CONCLUSION: Therefore, efforts to reduce future OBDs of ARDs, including early detection and proper management of ARDs, are needed in Korea.

A Study on Prevalence and Risk Factors for Varicose Veins in Nurses at a University Hospital

BACKGROUND: Lower-limb varicose veins (VVs) are common and known to have a higher prevalence among people who work in occupations requiring prolonged standing. In the Republic of Korea, however, VV-related occupational factors have seldom been examined. This study was conducted to assess the prevalence of VVs among nurses, an occupational group considered to be at high risk of VVs, and determine the occupational risk factors of prolonged standing. METHODS: Between March and August 2014, a questionnaire survey coupled with Doppler ultrasonography was conducted on the nurses working at a university hospital. RESULTS: A total of 414 nurses participated in the survey and diagnostic testing. From the survey analysis and test results, the prevalence of VVs in nurses was estimated to be 16.18%. Significant factors for venous reflux were age [odds ratio (OR) = 1.06, 95% confidence interval (CI) = 1.03–1.10], pregnancy (OR = 2.15, 95% CI = 1.17–3.94), and delivery (OR = 2.02, 95% CI = 1.08–3.78). The statistical significance of these factors was verified after risk adjustment for sociodemographic factors (OR = 3.40, 95% CI = 1.27–9.09). CONCLUSION: Factors significantly associated with venous reflux were increasing age and prolonged working hours (≥ 4 hours) in a standing position (OR = 2.80, 95% CI = 1.08–7.25), even after risk adjustment for sociodemographic factors. This study is significant in that an objective diagnosis of VVs preceded the analysis of the risk factors for VV incidence, thus verifying objectively that VVs are associated with occupations requiring prolonged hours of working in a standing position.

Characteristics of occupational musculoskeletal disorders of five sectors in service industry between 2004 and 2013

BACKGROUND: ‘Work related musculoskeletal disorders (WRMSDs)' have been mostly reported in the manufacturing industry but recently the occurrence of industrial injuries has been constantly increasing in the service industry. This research is going to analyze the data about workers' compensation for WRMSDs in five different service sectors and identify characteristics of occupations with the highest approved occupations. METHODS: According to the data released from the Korea Worker's Compensation & Welfare Service, the overview of 12,730 cases of workers' compensation for WRMSDs in five service sectors from 2004 to 2013 is going to be analyzed and the source data is going to be classified by the Korean Standard Classification of Occupations to select the top five occupations that have the highest number of approval. RESULTS: After selecting each five occupations from the service sector that have work related musculoskeletal disorders, the result showed that the occupation with the highest number of approval in the health and social care sector were the early childhood educators, cooks in the school canteens in education services sector, garbage collectors in the sanitation and similar services sector, deliverymen in wholesale and retail, consumer goods repair and building cleaners in general management businesses such as those in building maintenance. The major event observed in the top five occupations was the overexertion and reaction as a cause of WRMSDs. The day when the WRMSDs mostly occurred was on Monday and the most likely time was 10 am. The median days away from work and lost working days are 29–90 days and 0–50 days respectively. The difference in each occupation was observed in year of service, age, and gender. CONCLUSIONS: 83.21% of the approved cases of workers' compensation for WRMSDs occurred in the top 25 occupations in all of the five service sectors, which meant that the approval of workers' compensation is concentrated in specific occupations. This research is going to suggest preventive measures for work related musculoskeletal disorders in the service industry and to help prioritize the preventive measures. TRIAL REGISTRATION: Not applicable.

Eight-year follow-up of two different removable prostheses using six implants in maxillary edentulous patients / 대한치과보철학회지

An implant-supported fixed dental prosthesis (ISFDP) or an implant-supported overdenture (IOD) are good options when treating a completely edentulous jaw opposing natural teeth. However, an ISFDP for a full arch requires sufficient bone quality and quantity, which limits its application. Meanwhile, using an ISFDP as an abutment of a removable partial denture has been considered recently. This clinical report discusses the treatments applied to two patients with edentulous maxillas and opposing natural teeth: one was treated with an IOD and the other was treated with an ISFDP and removable partial denture. Follow-up and management were performed for 8 years.

Fabrication of immediate complete denture using Campagna tray technique / 대한치과보철학회지

An immediate complete denture is considered as restoration for lost natural teeth, which is fabricated following the extraction of the remaining teeth. Current esthetics and function can be retained by using immediate denture without edentulous period. However, the major disadvantages of immediate denture relate to the difficulties associated with taking accurate definitive impression and predicting the results of immediate denture. In this case report, the Campagna tray technique was used to take the final impression in a 49-year-old male patient presented with all remaining teeth diagnosed as hopeless teeth. Surgical templates were used for alveoloplasty after extraction. The immediate complete dentures were then delivered. The clinical assessments of immediate dentures showed good esthetic and functional outcomes. The patient showed high level of satisfaction.

Environmental health centers for asbestos and their health impact surveys and activities

In 2009, Korea banned the import, transport, and use of asbestos, and the Asbestos Injury Relief Act (AIRA) was promulgated in 2011. Two environmental health centers for asbestos (EHCA), including Pusan National University Yangsan Hospital (PNUYH) and SoonChunHyang University Cheonan Hospital (SCHUCH), were adapted to find environmental asbestos-related diseases (ARDs) and to support the purposes of AIRA. EHCA conducted a health impact survey (HIS) on persons who resided or reside near asbestos factories or mines. A total of 13,433 persons have taken screening examinations in PNUYH EHCA, and 623 persons (4.6%) have had secondary examinations. Of the 21,014 persons who had screening examinations in SCHUCH EHCA, 2490 persons (11.8%) had secondary examinations. Some of those who tested positive for ARDs through HISs filed applications for the asbestos victims’ medical pocketbook (AVMP). Approximately 116 and 612 persons received AVMPs as a result of PNUYH and SCHUCH examinees, respectively. EHCAs have conducted HISs, public relations, and education for asbestos victims, ordinary citizens, and physicians. As HISs are based on voluntary participation, they does not monitor high-risk groups. Active surveillance focusing on high-risk groups has been blocked by the personal information protection act. Although important work has been performed in finding environmental asbestos victims and increasing public awareness on asbestos, it is necessary to improve the current system and registration.

Comparison of crown designs of different dental occupational groups, using CAD-CAM / 대한치과보철학회지

PURPOSE: Increasing use of computer aided design-computer aided manufacturing (CAD-CAM) system and number of design software made design of restoration easy and quick. Outcome of restoration has been dependent on dental technician's wax up proficiency, dentists can design restoration for themselves now. This study aims to investigate the outcome of restoration designs, according to handling skill of CAD-CAM design tool. MATERIALS AND METHODS: A patient's mandibular right 1st molar was prepared. After taking impression, stone model was made, scanned the stone model with 3 shape intra-oral scanner, stereolithography (STL) file was extracted. With 3shape dental designer, one dental technician with more than 5 years work experience (designer 0) and three dental technicians with less than 2years work experience (designer 1, 2, 3-group DT) and 4 1st year residents (designer 4, 5, 6, 7-group RT) designed gold crown on the same STL file. Designed crown's MD (mesio-distal) and BL (bucco-lingual) diameter, height of crown, inter-cuspal distance, number of occlusal contact points were compared. Statistical analysis was carried out, test of normality within each group, using independent t-test. Number of contact points were compared, using Wilcoxon signed-rank test. RESULTS: There was no significant difference between group DT and group RT. Number of contact points also resulted in no significant difference. CONCLUSION: The outcome of each designed crowns showed no statistical differences, in values which can be expressed as numbers. Subjective factors were different. With increasing proficiency in handling designing software, fabrication of restorations according to each designer's occlusal concept can be made easy.

Risk assessment of gastric cancer associated with asbestosis: a case report

BACKGROUND: The International Agency for Research on Cancer classifies asbestos as belonging to Carcinogen Group 2A for gastric cancer. We herein report a case of gastric cancer associated with asbestosis and describe the work-related and risk assessments of asbestos exposure for gastric cancer. CASE PRESENTATION: The 66-year-old male patient in our case worked in asbestos spinning factories. His level of cumulated asbestos fiber exposure was estimated to be 38.0-71.0 f-yr/cc. Thus, the Excess Life Cancer Risk for lung cancer associated with asbestos exposure was 9,648x10-5, almost 9,600 times the value recommended by the United States of America Environmental Protection Agency (1 x 10-5). The relative risk of developing lung cancer for this patient was more than 25 f-yr/cc, a well-known criterion for doubling the risk of lung cancer. CONCLUSION: The patient's exposure to high-dose asbestos was sufficient to increase his risk of gastric cancer because as the risk of lung cancer increased, the risk of gastric cancer was due to increase as well. Therefore, occupational asbestos fiber exposure might be associated with gastric cancer in this case.