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.

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.

Immediate Loading of Narrow Diameter Implants at the Mandibular Incisor Area Using Full Digital Flow: A Case Report

This case report describes the immediate loading of narrow diameter implants in the mandibular incisor area using full-digital flow. The 3-dimensional position of the implants was planned using digital software, and the corresponding surgical template was fabricated. The implants were inserted immediately after extraction and on the same day, the interim abutment and bridge were placed. At 8 weeks after surgery, the stability of the implants was measured and a digital impression was made using a scan body. Customized titanium abutments and a cementtype full zirconia bridge were delivered. At 36 weeks’ follow-up, no clinical or radiographic complications were detected, and the patient was satisfied with the results.

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.

A review on the accuracy assessment methods of 3-dimensional digital dental models

The aim of this article was to review various methods used to evaluate the accuracy of digital dental models. When evaluating the accuracy of digital models, the errors can be reduced by educating examiners and using artificial landmarks. The accuracy evaluation methods of digital dental models are divided into linear measurement, 2-dimensional cross-sectional analysis, and 3-dimensional best fit measurement. As the technology of scanners develops, many studies have been conducted to compare the accuracy of digital impression and conventional impression. According to improvement of scan technologies and development of 3-dimensional model analysis software, the ability to evaluate the accuracy of digital models is becoming more efficient. In this article, we describe the methods for evaluating the accuracy of a digital model and investigate effective accuracy analysis methods for each situation.

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.

Bone healing dynamics associated with 3 implants with different surfaces: histologic and histomorphometric analyses in dogs

PURPOSE: This study evaluated differences in bone healing and remodeling among 3 implants with different surfaces: sandblasting and large-grit acid etching (SLA; IS-III Active®), SLA with hydroxyapatite nanocoating (IS-III Bioactive®), and SLA stored in sodium chloride solution (SLActive®). METHODS: The mandibular second, third, and fourth premolars of 9 dogs were extracted. After 4 weeks, 9 dogs with edentulous alveolar ridges underwent surgical placement of 3 implants bilaterally and were allowed to heal for 2, 4, or 12 weeks. Histologic and histomorphometric analyses were performed on 54 stained slides based on the following parameters: vertical marginal bone loss at the buccal and lingual aspects of the implant (b-MBL and l-MBL, respectively), mineralized bone-to-implant contact (mBIC), osteoid-to-implant contact (OIC), total bone-to-implant contact (tBIC), mineralized bone area fraction occupied (mBAFO), osteoid area fraction occupied (OAFO), and total bone area fraction occupied (tBAFO) in the threads of the region of interest. Two-way analysis of variance (3 types of implant surface×3 healing time periods) and additional analyses for simple effects were performed. RESULTS: Statistically significant differences were observed across the implant surfaces for OIC, mBIC, tBIC, OAFO, and tBAFO. Statistically significant differences were observed over time for l-MBL, mBIC, tBIC, mBAFO, and tBAFO. In addition, an interaction effect between the implant surface and the healing time period was observed for mBIC, tBIC, and mBAFO. CONCLUSIONS: Our results suggest that implant surface wettability facilitates bone healing dynamics, which could be attributed to the improvement of early osseointegration. In addition, osteoblasts might become more activated with the use of HA-coated surface implants than with hydrophobic surface implants in the remodeling phase.

A comparison of the accuracy of intraoral scanners using an intraoral environment simulator

PURPOSE: The aim of this study was to design an intraoral environment simulator and to assess the accuracy of two intraoral scanners using the simulator. MATERIALS AND METHODS: A box-shaped intraoral environment simulator was designed to simulate two specific intraoral environments. The cast was scanned 10 times by Identica Blue (MEDIT, Seoul, South Korea), TRIOS (3Shape, Copenhagen, Denmark), and CS3500 (Carestream Dental, Georgia, USA) scanners in the two simulated groups. The distances between the left and right canines (D3), first molars (D6), second molars (D7), and the left canine and left second molar (D37) were measured. The distance data were analyzed by the Kruskal-Wallis test. RESULTS: The differences in intraoral environments were not statistically significant (P>.05). Between intraoral scanners, statistically significant differences (P < .05) were revealed by the Kruskal-Wallis test with regard to D3 and D6. CONCLUSION: No difference due to the intraoral environment was revealed. The simulator will contribute to the higher accuracy of intraoral scanners in the future.

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.

Comparative study on quality of scanned images from varying materials and surface conditions of standardized model for dental scanner evaluation

PURPOSE: The purpose of this study is to evaluate the image acquisition ability of intraoral scanners by analyzing the comprehensiveness of scanned images from standardized model, and to identify problems of the model. MATERIALS AND METHODS: Cast models and 3D-printed models were prepared according to international standards set by ISO12836 and ANSI/ADA no. 132, which were then scanned by model scanner and two different intraoral scanners (TRIOS3 and CS3500). The image acquisition performance of the scanners was classified into three grades, and the study was repeated with varying surface conditions of the models. RESULTS: Model scanner produced the most accurate images in all models. Meanwhile, CS3500 showed good image reproducibility for angled structures and TRIOS3 showed good image reproducibility for rounded structures. As for model ingredients, improved plaster model best reproduced scan images regardless of the type of scanner used. When limited to 3D-printed model, powdered surface condition resulted in higher image quality. CONCLUSION: When scanning structures beyond FOV (field of view) in standardized models (following ISO12836 and ANSI/ADA 132), lack of reference points to help distinguish different faces confuses the scanning and matching process, resulting in inaccurate display of images. These results imply the need to develop a new standard model not confined to simple pattern repetition and symmetric structure.

Erratum: Comparative study on quality of scanned images from varying materials and surface conditions of standardized model for dental scanner evaluation

No abstract available.

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.

Questionnaire survey for the clinical trial participants who experienced both digital and conventional impression

PURPOSE: The aim of this study was to assess the patients' perception, acceptance, and preference of the difference between a conventional impression and digital impression through questionnaire survey. MATERIALS AND METHODS: Thirteen (6 male, 7 female) subjects who experienced both digital and conventional impression at the same day were enrolled in this study. Conventional impression were taken with polyvinylsiloxane and digital impression were performed using a newly developed intra-oral scanner. Immediately after the two impressions were made, a survey was conducted with the standardized questionnaires consisting of the following three categories; 1) general dental treatment 2) satisfaction of conventional impression 3) satisfaction of digital impression. The perceived source of satisfaction was evaluated using Likert scale. The distribution of the answers was assessed by percentages and statistical analyses were performed with the paired t-test, and P < 0.05 was considered significant. RESULTS: There were significant differences of the overall satisfaction between two impression methods (P < 0.05). Digital impression showed high satisfaction in less shortness of breath and odor to participants compared to conventional impression. The use of an oral scanner resulted in a discomfort of TMJ due to prolonged mouth opening and in lower score of the scanner tip size. CONCLUSION: It was confirmed that the preference for the digital impression using intraoral scanner is higher than the conventional impression. Most survey participants said they would recommend the digital impression to others and said they preferred it for future prosthetic treatment.

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.