Influence of finish line design on the marginal fit of nonprecious metal alloy coping fabricated by 3D printing, milling and casting using CAD-CAM / 대한치과보철학회지

Purpose@#The purpose of this study was to examine the correlation between the finish line designs and the marginal adaptation of nonprecious metal alloy coping produced by different digital manufacturing methods. @*Materials and methods@#Nonprecious metal alloy copings were made respectively from each master model with three different methods; SLS, milling and casting by computer aided design and computer aided manufacturing (CAD-CAM). Twelve copings were made by each method resulting in 72 copings in total. The measurement was conducted at 40 determined reference points along the circumferential margin with the confocal laser scanning microscope at magnification ×150. @*Results@#Mean values of marginal gap of laser sintered copings were 11.8 ± 7.4 μm for deep chamfer margin and 6.3 ± 3.5 μm for rounded shoulder margin and the difference between them was statistically significant (P < .0001). Mean values of marginal gap of casted copings were 18.8 ± 20.2 μm for deep chamfer margin and 33 ± 20.5 μm for rounded shoulder margin and the difference between them was significant (P = .0004). Conclusion: Within the limitation of this study, the following conclusions were drawn. 1. The variation of finish line design influences the marginal adaptation of laser sintered metal coping and casted metal coping. 2. Laser sintered copings with rounded shoulder margin had better marginal fit than deep chamfer margin. 3. Casted copings with deep chamfer margin had better marginal fit than rounded shoulder margin. 4. According to the manufacturing method, SLS system showed the best marginal fit among three different methods. Casting and milling method followed that in order.

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.

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.

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

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.

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.

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

PURPOSE: The aim of this study is to evaluate the effectiveness of MnO₂-diatom microbubbler (DM) on the surface of prosthetic materials as a mouthwash by comparing the biofilm removal effect with those previously used as a mouthwash in dental clinic.MATERIALS AND METHODS: DM was fabricated by doping manganese dioxide nanosheets to the diatom cylinder surface. Scanning electron microscopy (SEM) was used to observe the morphology of DM and to analyze the composition of doped MnO₂. Stereomicroscope was used to observe the reaction of DM in 3% hydrogen peroxide. Non-precious metal alloys, zirconia and resin specimens were prepared to evaluate the effect of biofilm removal on the surface of prosthetic materials. And then Streptococcus mutans and Porphyromonas gingivalis biofilms were formed on the specimens. When 3% hydrogen peroxide solution and DM were treated on the biofilms, the decontamination effect was compared with chlorhexidine gluconate and 3% hydrogen peroxide solution by crystal violet staining.RESULTS: Manganese dioxide was found on the surface of the diatom cylinder, and it was found to produce bubble of oxygen gas when added to 3% hydrogen peroxide. For all materials used in the experiments, biofilms of the DM-treated groups got effectively removed compared to the groups used with chlorhexidine gluconate or 3% hydrogen peroxide alone.CONCLUSION: MnO₂-diatom microbubbler can remove bacterial membranes on the surface of prosthetic materials more effectively than conventional mouthwashes.

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 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.

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.

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.

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.

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.

Therapeutic outcomes of methotrexate injection in unruptured interstitial pregnancy

OBJECTIVE: To examine the therapeutic outcomes of methotrexate (MTX) in the treatment of unruptured interstitial pregnancy. METHODS: We reviewed the medical records of patients who were diagnosed with interstitial pregnancy and received MTX as first-line treatment between January 2003 and July 2014 at CHA Gangnam Medical Center. The treatment success rates and subsequent pregnancy outcomes were examined. RESULTS: Ninety-seven patients were diagnosed with interstitial pregnancy between January 2003 and July 2014. Of them, 38 initially received MTX treatment. The diagnosis was made at a median of 6+3 weeks (5+0 to 11+3 weeks). Thirty patients received a systemic MTX injection, while the other 8 received a local MTX injection. Systemic treatment composed of an 8-day alternating MTX regimen, single-dose regimen, or high-dose regimen (100 mg/m2 + 200 mg/m2 intravenously over 12 hours). The local injection consisted of a direct MTX injection into the gestational sac with or without systemic MTX injection. Twenty-one patients (55.3%) were successfully treated with MTX. However, MTX therapy failed in 17 patients (44.7%), who required surgery. Mode of MTX treatment was the only predictive variable of MTX treatment success (P=0.039). Treatment success was seen in 7 of 8 patients (87.5%) in the local MTX group vs. 14 of 30 patients (46.7%) in the systemic MTX group. After treatment, 13 patients attempted a successive pregnancy; of them, 10 patients had a confirmed clinical pregnancy and healthy live birth. CONCLUSION: Combined MTX treatment including a local injection might be an initial approach to the treatment of interstitial pregnancy.

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.

Prosthetic rehabilitation of partially edentulous patient after maxillectomy: A case report / 대한치과보철학회지

Patients undergone partial maxillectomy experience post-operative masticatory, phonetic, and swallowing difficulties. They also encounter social and psychological challenges due to changes in their facial appearances. Thus, functional and esthetic recovery through maxillofacial prosthesis becomes significant for these patients. The objective of an appropriate obturator is to restore palate and improve phonetic and swallowing ability by separating the oral cavity, nasal cavity, maxillary sinus, and nasopharynx. In this case report, an obturator was fabricated for a patient who had partial resection from the maxillary posterior region to the pharynx due to squamous cell carcinoma. The purpose of this case study is to describe the results because the patient was successfully improved both functionally and esthetically.

Factors that affect the bite force measurement

Mastication is the process to help digestion by chewing or grinding food. Masticatory system consists of maxilla, mandible, temporomandibular joints, ligaments, dentitions, and musculatures. Assessing the bite force can be one of the methods to estimate the masticatory system. Bite force is influenced by facial morphology, age, sex, periodontal status, temporomandibular joint disorder and dental condition, and so forth. In general, higher maximum bite force is seen in those who have a square-shaped face and in male rather than female. In addition, bite force tends to be increased by age 20, maintained constantly until age 40 - 50, and then decreased. Periodontal disease is known as a causative factor for decreased bite force while temporomandibular disorder (TMD) remains controversial as to whether it affects the force. The status of teeth is considered as an important factor to determine the maximum bite force.

Anti-inflammatory and antioxidant effects of umbelliferone in chronic alcohol-fed rats

BACKGROUND/OBJECTIVES: Inflammation is associated with various types of acute and chronic alcohol liver diseases. In this study, we examined whether umbelliferone (7-hydroxycoumarin, UF) ameliorates chronic alcohol-induced liver damage by modulating inflammatory response and the antioxidant system. METHODS: Rats were fed a Liber-Decarli liquid diet containing 5% alcohol with or without UF (0.05 g/L) for 8 weeks, while normal rats received an isocaloric carbohydrate liquid diet. RESULTS: Chronic alcohol intake significantly increased serum tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 levels and decreased interleukin 10 level; however, UF supplementation reversed the cytokines related to liver damage. UF significantly suppressed hepatic lipopolysaccharide binding protein, toll-like receptor 4 (TLR4), nuclear factor kappa B, and TNF-alpha gene expression increases in response to chronic alcohol intake. Masson's trichrome staining revealed that UF improved mild hepatic fibrosis caused by alcohol, and UF also significantly increased the mRNA expressions and activities of superoxide dismutase and catalase in liver, and thus, decreased lipid peroxide and mitochondrial hydrogen peroxide levels. CONCLUSIONS: The findings of this study indicate that UF protects against alcohol-induced liver damage by inhibiting the TLR4 signaling pathway and activating the antioxidant system.