Full mouth rehabilitation of a patient with tooth wear and insufficient restorative space due to loss of posterior teeth support: a case report / 대한치과보철학회지

To rehabilitate a patient with inappropriate occlusion due to posterior support loss, it is necessary to achieve an appropriate occlusal vertical dimension and create prostheses that demonstrate stable occlusion at the centric relation for full mouth restoration. This case shows full mouth rehabilitation in a patient with missing posterior teeth and tooth wear, achieved through implant-supported prostheses and zirconia full-veneer crowns. To assess adaptation to the increased occlusal vertical dimension, an occlusal splint and temporary restorations were secured. By fabricating the definitive restorations based on the anterior guidance of the temporary restorations, stable occlusal rehabilitation was successfully achieved.

Development of a prototype simulator for dental education / 대한치과보철학회지

Purpose@#. The purpose of the study was to fabricate a prototype robotic simulator for dental education, to test whether it could simulate mandibular movements, and to assess the possibility of the stimulator responding to stimuli during dental practice. @*Materials and methods@#. A virtual simulator model was developed based on segmentation of the hard tissues using cone-beam computed tomography (CBCT) data. The simulator frame was 3D printed using polylactic acid (PLA) material, and dentiforms and silicone face skin were also inserted. Servo actuators were used to control the movements of the simulator, and the simulator’s response to dental stimuli was created by pressure and water level sensors.A water level test was performed to determine the specific threshold of the water level sensor. The mandibular movements and mandibular range of motion of the simulator were tested through computer simulation and the actual model. @*Results@#. The prototype robotic simulator consisted of an operational unit, an upper body with an electric device, a head with a temporomandibular joint (TMJ) and dentiforms. The TMJ of the simulator was capable of driving two degrees of freedom, implementing rotational and translational movements. In the water level test, the specific threshold of the water level sensor was 10.35 ml. The mandibular range of motion of the simulator was 50 mm in both computer simulation and the actual model. @*Conclusion@#. Although further advancements are still required to improve its efficiency and stability, the upper-body prototype simulator has the potential to be useful in dental practice education.

Influence of tongue pressure on the obturator prosthesis for soft palate defects: a 3D-FEA study

Purpose@#The purpose of the study was to analyze how swallowing tongue pressure affects the biomechanics of a velopharyngeal obturator prosthesis and compare its displacement across different occlusal rest positions. @*Materials and Methods@#A 3D geometric model consisting of the maxilla, teeth, soft palate, and a portion of the pharynx was developed based on the CBCT and MRI data.A defect was created by the resection of soft palate portion. Two experimental models were generated based on two different velopharyngeal obturator designs: one “with mesial occlusal rests” (Model 1) and the other with “distal occlusal rests” (Model 2). A pressure of 25 kPa was applied at the surface of the bulb of the obturator prosthesis opposite the base of the tongue to simulate tongue pressure during swallowing. The maximum von-Mises stress and displacement values of two types of obturator prostheses were analyzed and compared. @*Results@#The maximum von-Mises stress in the metal framework, located at the posterior palatal strap, was slightly higher in model 1 (64.9 MPa) than in model 2 (54.2 MPa). In both models, the acrylic resin obturator bulb exhibited a maximum stress value of 4.3 MPa. There was no significant difference in prosthesis displacement between the two models, with 31.3 µm for model 1 and 33.6 µm for model 2. @*Conclusion@#Swallowing tongue pressure had a minor impact on the biomechanics of a velopharyngeal obturator prosthesis, and distal occlusal rests showed a slightly better biomechanical response compared to mesial occlusal rests.

Full mouth rehabilitation in osteoporosis patient with loss of teeth and excessive wear / 대한치과보철학회지

Teeth wear with loss of posterior support often leads to symptoms such as irregular occlusal plane and excessive wear of anterior teeth. In such environment, establishing proper posterior support and harmonious anterior guidance and occlusal plane is recommended. In this case, the patient had excessively worn dentition with loss of posterior support, while denying surgical treatment due to her(his) history of osteoporosis, ibandronate injection, and risk of medication-related osteonecrosis of the jaw (MRONJ). To recover the vertical space needed for prosthetic restoration, full mouth rehabilitation with vertical dimension increase of remaining teeth was decided. Missing teeth in the posterior area were restored with mandibular removable partial denture. The treatment plan was determined through careful diagnosis, and every step of procedures including tooth preparation, provisional phase with the increased vertical dimension, and definitive prosthetic phase were carried out accordingly. Once the treatment was completed, the patient was satisfied functionally and esthetically. Periodic examination of oral hygiene, occlusal stability was conducted.

A study on the Korean dental education system II: the need for integrated education system / 대한구강보건학회지

Objectives@#With the rapid changes in society, there are more arguments for redefining dental education system. This study aimed to review and analyze the problems in the current dental education system in Korea and then propose an integrated education system based on those findings. @*Methods@#A narrative review of the problems confronting the dental education system in Korea was carried out. Accordingly, full-text screening and specialists’ discussions were extracted from the review. The purpose of the review was to summarize the strengths and weaknesses of Korean dental education systems to offer perspectives on an integrated education system in accordance with the specialists’ opinions. @*Results@#The results revealed that the problems of the current dental education system were identified in clinical education, basic science, and humanities and social sciences. Dental schools should provide clinical education so that dental students can be exposed to the clinical environment at an early stage and perform patient-based clinical practice. It is also imperative to encourage participation in research programs to train dental scientists, as well as to reflect on courses that can adapt to changes brought about by new technologies. It is recommended that education opportunities for integrated humanities and social sciences be provided. @*Conclusions@#It will be critical in the future for dental schools to embrace a flexible education system from various perspectives. It is vital that dental schools play a role in developing students’ critical thinking, problem-solving, and decision-making skills. Finally, as part of an integrated education system, an improvement program should be devised.

A study on the Korean dental education system II: the need for integrated education system / 대한구강보건학회지

Objectives@#With the rapid changes in society, there are more arguments for redefining dental education system. This study aimed to review and analyze the problems in the current dental education system in Korea and then propose an integrated education system based on those findings. @*Methods@#A narrative review of the problems confronting the dental education system in Korea was carried out. Accordingly, full-text screening and specialists’ discussions were extracted from the review. The purpose of the review was to summarize the strengths and weaknesses of Korean dental education systems to offer perspectives on an integrated education system in accordance with the specialists’ opinions. @*Results@#The results revealed that the problems of the current dental education system were identified in clinical education, basic science, and humanities and social sciences. Dental schools should provide clinical education so that dental students can be exposed to the clinical environment at an early stage and perform patient-based clinical practice. It is also imperative to encourage participation in research programs to train dental scientists, as well as to reflect on courses that can adapt to changes brought about by new technologies. It is recommended that education opportunities for integrated humanities and social sciences be provided. @*Conclusions@#It will be critical in the future for dental schools to embrace a flexible education system from various perspectives. It is vital that dental schools play a role in developing students’ critical thinking, problem-solving, and decision-making skills. Finally, as part of an integrated education system, an improvement program should be devised.

Implant-assisted Removable Prosthetic Rehabilitation of a Patient with Crossed Occlusion

'Crossed occlusion’ is the condition in which occlusal intercuspation is lost when several teeth on upper and lower jaw remain. This report describes a clinical case in which a patient had two upper-left posterior teeth and two lowerright posterior teeth; typically known as left-right crossed occlusion. Considering the patient’s general condition and financial situation, the treatment plan included placement of two implants on each jaw against the remaining teeth using surgical guide. To find out the ideal position of implants, digital diagnostic wax-up was preceded by superimposing the cast and cone beam computed tomography image, which was aided with radiographic stents. The consequent surveyed implant bridge provided stable vertical stop for fabrication of the implant assisted removable partial dentures. The patient was satisfied with the functionality and esthetics of definitive prosthesis.

Three-dimensional finite element analysis of buccally cantilevered implant-supported prostheses in a severely resorbed mandible

Purpose@#The aim of the study was to compare the lingualized implant placement creating a buccal cantilever with prosthetic-driven implant placement exhibiting excessive crown-to-implant ratio. @*Materials and Methods@#Based on patient’s CT scan data, two finite element models were created. Both models were composed of the severely resorbed posterior mandible with first premolar and second molar and missing second premolar and first molar, a twounit prosthesis supported by two implants. The differences were in implants position and crown-to-implant ratio; lingualized implants creating lingually overcontoured prosthesis (Model CP2) and prosthetic-driven implants creating an excessive crown-to-implant ratio (Model PD2). A screw preload of 466.4 N and a buccal occlusal load of 262 N were applied. The contacts between the implant components were set to a frictional contact with a friction coefficient of 0.3. The maximum von Mises stress and strain and maximum equivalent plastic strain were analyzed and compared, as well as volumes of the materials under specified stress and strain ranges. @*Results@#The results revealed that the highest maximum von Mises stress in each model was 1091 MPa for CP2 and 1085 MPa for PD2. In the cortical bone, CP2 showed a lower peak stress and a similar peak strain. Besides, volume calculation confirmed that CP2 presented lower volumes undergoing stress and strain. The stresses in implant components were slightly lower in value in PD2. However, CP2 exhibited a noticeably higher plastic strain. @*CONCLUSION@# Prosthetic-driven implant placement might biomechanically be more advantageous than bone quantity-based implant placement that creates a buccal cantilever

Comparison of two computerized occlusal analysis systems for indicating occlusal contacts

PURPOSE@#. The purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts. @*MATERIALS AND METHODS@#. Twenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar’s test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control. @*RESULTS@#. No statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%. @*CONCLUSION@#. Accura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.

Erratum: The biofilm removal effect of MnO2-diatom microbubbler fromthe dental prosthetic surfaces: In vitro study / 대한치과보철학회지

The article ‘The biofilm removal effect of MnO2-diatom microbubbler from the dental prosthetic surfaces: In vitro study’ authored by Eun-Hyuk Lee,Yongbeom Seo, Ho-Bum Kwon, Young-Jun Yim, Hyunjoon Kong, Myung-Joo Kim, published in April issue [Vol 58, No 1] of The Journal of KoreanAcademy of Prosthodontics (2020), has an erratum.The author names were mistakenly given as Ho-Bum Kwon, Young-Jun Yim. It should be corrected as Ho‐Beom Kwon, Young‐Jun Lim. The Journal ofKorean Academy of Prosthodontics apologizes to the readers for this error.

Comparison of the outcomes of three-dimensional finite element analysis under arbitrary and realistic occlusal loading conditions in mandibular posterior region

Purpose@#The purpose of this study was to compare the biomechanical outcome in the mandibular posterior region between two different loading conditions by finite element analysis. @*Materials and Methods@#The mandibular posterior teeth model and the implant model were generated for the study. And 2 different types of loading conditions were provided: Arbitrary occlusion and natural occlusion obtained from the digital occlusal analyzer, Accura (Accura, Dmetec Co. Ltd., Seoul, Korea). Total load of 100 N was evenly distributed over arbitrary occlusion points, and 100 N load was differentially distributed over natural occlusion points according to Accura data. The biomechanical outcome was evaluated by the finite element analysis software. @*Results@#The result of finite element analysis showed considerable difference in both von Mises stress pattern and displacement under different loading conditions. @*Conclusion@#In finite element analysis, it is recommended to simulate a realistic occlusal loading pattern that is based on accurate measurement.

An assessment of accuracy of half-guided implant surgery using implant surgical guide: A case report / 대한치과보철학회지

Nowadays, dental implant is one of the widely used treatment options for edentulous patients. Recently, a method of improving the accuracy of implant surgery using an implant surgical guide has been introduced and widely used in order to accurately place the implant in a proper position. Full-guided and half-guided implant surgery can be distinguished according to the level of surgical guide application during the implant surgery. It is true that full-guided implant surgery exhibits higher accuracy, but half-guided implant surgery is often performed in a clinical situation due to the factors such as the circumstances of the operation. A partially edentulous patient who lost teeth due to tooth fracture and periodontal disease was treated using implant and fixed prosthesis. Half-guided implant surgery was performed using an implant surgical guide during implant surgery, the accuracy of implant placement was analyzed.

Full-mouth rehabilitation with vertical dimension increase and computer tomography guided implant surgery in patient with excessive worn dentition and multiple loss of tooth / 대한치과보철학회지

Excessive wear causes many complications when untreated, so that accurate diagnosis, analysis and predictive treatment plan should be made, and through evaluation of vertical dimension and stepwise treatment, a stable inter-arch relationship can be set. For the long-term success of implant treatment, ideal position and angle of implant is important, and its importance increases especially in multiple implant cases. Therefore, thorough diagnosis and planning, accurate surgery and prosthodontic procedures are significant. In this case, a 68-year-old male patient with a loss of vertical dimension due to multiple tooth loss and overall tooth wear was planned with systematic analyses from the pre-treatment stage to rehabilitate vertical dimension. Full-mouth fixed rehabilitation with computer tomography guided implant surgery was performed to the newly set vertical dimension and attained satisfactory outcomes both functionally and esthetically.

Full mouth rehabilitation in a patient with reduced vertical dimension due to numerous tooth loss and excessie worn dentition: A case report / 대한치과보철학회지

As digital dentistry technology is being developed, it is being used in various ways. This case covers how digital dentistry technology is being applied on the treatment of patients with loss of vertical dimension due to worn dentition and multiple loss of teeth. The loss of vertical dimension was carefully assessed and recovered, and implants were placed with surgical guides, designed considering the final restoration. The movement of the mandibular was measured with the electronic instrument for recording mandibular movement. Wax-up process was done with Naturgemäße Aufwachs-Technik (N.A.T.) and Natural functional reconstruction (N.F.R.). It was scanned, and the provisional restoration was fabricated using Computer-Aided-Design/Computer-Aided-Manufacturing (CAD/CAM) technology, and the adjustment process was done at the clinic to meet with the satisfaction both functionally and esthetically, and then, using double scanning and CAD/CAM technology, it was carried out as a final restoration. As a result, the patient obtained satisfying results, utilizing the benefits of digital dentistry technology and traditional methods.

A study on the Korean dental education system / 대한구강보건학회지

OBJECTIVES: This study aimed to propose criteria for evaluating the validity of dental education systems in Korea and suggest future directions for their improvement. METHODS: We looked into dental educational institutions and derived criteria for analysis and comparison of dental education systems in Korea. Using analytical methods, we compared the strengths and weaknesses of each education system, and suggested core areas of improvement. RESULTS: Considering the demands placed on the Korean dental education sector, it is desirable to have an integrated education system that includes the preliminary and main courses, comprehensive training linking the basic medicine and clinical practice, and complete career guidance. CONCLUSIONS: A good dental education system is one that meets the educational goals set by a dental school. If the goal is to train a student to be a good dental practitioner, a 2+4 or 4+4 system is recommended, while a 3+4 model is more suitable when the objective is to train students to be researchers.

Three-dimensional finite element analysis of the splinted implant prosthesis in a reconstructed mandible

PURPOSE: The purpose of this study was to analyze the effects of the splinted implant prosthesis in a reconstructed mandible using three-dimensional finite element analysis. MATERIALS AND METHODS: Three-dimensional finite element models were generated from a patient's computed tomography data. The patient had undergone partial resection of the mandible that covered the area from the left canine to the right condyle. The mandible was reconstructed using a fibula bone graft and dental implants. The left mandibular premolars and molars remained intact. Three types of models were created. The implant-supported prosthesis was splinted and segmented into two or three pieces. Each of these models was further subcategorized into two situations to compare the stress distribution around normal teeth and implants. Oblique loading of 300 N was applied on both sides of the mandible unilaterally. The maximum von Mises stress and displacement of the models were analyzed. RESULTS: The stress distribution of the natural mandible was more uniform than that of the reconstructed fibula. When the loading was applied to the implant prosthesis of reconstructed fibula, stress was concentrated at the cortical bone around the neck of the implants. The three-piece prosthesis model showed less uniform stress distribution compared to the others. Displacement of the components was positively correlated with the distance from areas of muscle attachment. The three-piece prosthesis model showed the greatest displacement. CONCLUSION: The splinted implant prosthesis showed a more favorable stress distribution and less displacement than the separated models in the reconstructed mandible.

Influence of crown-to-implant ratio of short vs long implants on implant stability and marginal bone loss in the mandibular single molar implant

PURPOSE: The purpose of this randomized clinical trial is to determine whether implant length and the crown-to-implant (C/I) ratio influence implant stability and peri-implant marginal bone loss (MBL). MATERIALS AND METHODS: 46 patients with single tooth missing in the posterior molar region of the mandible were included in this study. 19 implants (CMI IS-III active® long implant) of 5.0 mm diameter and 10 mm length were installed for the control group, while 27 implants (CMI IS-III active® short implant) of 5.5 mm diameter and 6.6, 7.3 or 8.5 mm length were placed for the experimental group. Each implant was inserted and immediately loaded using the digitally pre-fabricated surgical template and provisional restoration. The CAD-CAM monolithic zirconia crown was fabricated at 3 months after the surgery as a definitive restoration. The ISQ value and the MBL was measured at 48 weeks after the surgery. The correlation between the C/I ratio, MBL, and secondary implant stability was analyzed. RESULTS: Successful results in terms of ISQ and MBL were achieved with both groups. There was no significant difference between the groups in terms of ISQ values and MBL at 48 weeks after the surgery (P > 0.05). No significant correlation was found between the C/I ratio and secondary stability as well as the C/I ratio and the MBL (P > 0.05). CONCLUSION: The influence of C/I ratio in both groups was not shown on the stability nor the marginal bone loss in implants supporting single crown of the mandible. Short implant could be a preferable alternative option in the reduced bone height mandible under the limited condition despite its higher C/I ratio.

Three-dimensional finite element analysis of platform switched implant

PURPOSE: The purpose of this study was to analyze the influence of the platform switching concept on an implant system and peri-implant bone using three-dimensional finite element analysis. MATERIALS AND METHODS: Two three-dimensional finite element models for wide platform and platform switching were created. In the wide platform model, a wide platform abutment was connected to a wide platform implant. In the platform switching model, the wide platform abutment of the wide platform model was replaced by a regular platform abutment. A contact condition was set between the implant components. A vertical load of 300 N was applied to the crown. The maximum von Mises stress values and displacements of the two models were compared to analyze the biomechanical behavior of the models. RESULTS: In the two models, the stress was mainly concentrated at the bottom of the abutment and the top surface of the implant in both models. However, the von Mises stress values were much higher in the platform switching model in most of the components, except for the bone. The highest von Mises values and stress distribution pattern of the bone were similar in the two models. The components of the platform switching model showed greater displacement than those of the wide platform model. CONCLUSION: Due to the stress concentration generated in the implant and the prosthodontic components of the platform switched implant, the mechanical complications might occur when platform switching concept is used.

Implant supported prosthetic rehabilitation of severely atrophic mandible with fixed detachable prosthesis / 대한치과보철학회지

Implant supported prostheses have improved the quality of lives of totally edentulous patients. However, there are some limitations on the number of implants related to the residual bone level or the economic concern and so on. In this situation, applying fixed detachable prosthesis with bilateral cantilevers can be considered. This clinical report describes implant supported prosthetic rehabilitation of a patient with severe bone resorption. The patient was satisfied and felt comfortable with upper complete denture and lower fixed detachable prosthesis.

Immediate loading of mandibular single implant by using surgical guide and modeless digital prosthesis: a case report

In this case report, immediate loading of an implant-supported single-tooth prosthesis through complete digital workflow. A patient presented for restoration of missing a single tooth in the mandibular first molar. The digital impression was made with intraoral scanner and implant was placed using surgical guide pre-fabricated with pre-operative computed tomography (CT) and scan data. After 1 week later, prefabricated customized abutment and provisional restoration were connected for immediate loading. After 8 weeks later, abutment level impression was taken by intraoral scanner. At 3 months later from implant installation, monolithic zirconia crown were fabricated. This clinical report presents satisfying result in accuracy and patient satisfaction. A completely modeless digital procedure met expectations regarding precision, esthetics, and functionality.