• The Journal of Advanced Prosthodontics
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• v.7 no.6
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• pp.475-483
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• 2015

PURPOSE. The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS. The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS. Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION. The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.1
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• pp.100-109
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• 2022

Installation of dental implants at optimal angles and positions is critical in long-term stable implant-supported restorations. Surgery and prosthodontic procedures should be performed accurately as the treatment is planned. In this clinical case, Computer aided design and manufacturing technology was used not only to establish a precise surgical plan, but also to fabricate both provisional and definitive fixed prostheses. A surgical guide was designed to install the implants at proper positions for the definitive prostheses. The patient's esthetic information, which was necessary for the new provisional and definitive fixed prostheses, was obtained from the existing temporary dentures. Finally, the complete mouth fixed implant-supported rehabilitation using monolithic zirconia provided the patient with functionally and esthetically satisfactory prostheses.

• The Journal of Advanced Prosthodontics
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• v.15 no.6
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• pp.315-332
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• 2023

PURPOSE. This study aimed to investigate whether the accuracy of intraoral scanners is influenced by different scanning strategies in an in vitro setting, through a systematic review and meta-analysis. MATERIALS AND METHODS. This review was conducted in accordance with the PRISMA 2020 standard. The following PICOS approach was used: population, tooth impressions; intervention, the use of intraoral scanners with scanning strategies different from the manufacturer's instructions; control, the use of intraoral scanners following the manufacturers' requirements; outcome, accuracy of intraoral scanners; type of studies, in vitro. A comprehensive literature search was conducted across various databases including Embase, SciELO, PubMed, Scopus, and Web of Science. The inclusion criteria were based on in vitro studies that reported the accuracy of digital impressions using intraoral scanners. Analysis was performed using Review Manager software (version 5.3.5; Cochrane Collaboration, Copenhagen, Denmark). Global comparisons were made using a standardized mean difference based on random-effect models, with a significance level of α = 0.05. RESULTS. The meta-analysis included 15 articles. Digital impression accuracy significantly improved under dry conditions (P < 0.001). Moreover, trueness and precision were enhanced when artificial landmarks were used (P ≤ 0.02) and when an S-shaped pattern was followed (P ≤ 0.01). However, the type of light used did not have a significant impact on the accuracy of the digital intraoral scanners (P ≥ 0.16). CONCLUSION. The accuracy of digital intraoral scanners can be enhanced by employing scanning processes using artificial landmarks and digital impressions under dry conditions.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.88-96
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• 2017

Purpose: The purpose of this study is to assess the relationship between the time spent designing custom abutments and repeated learning using dental implant computer aided design (CAD) software. Materials and Methods: The design of customized abutments was performed four stages using the 3DS CAD software and the EXO CAD software, and measured repeatedly three times by each stage. Learning effect by repetition was presented with the learning curve, and the significance of the reduction in the total time and the time at each stage spent on designing was evaluated using the Friedman test and the Wilcoxon signed rank test. The difference in the design time between groups was analyzed using the repeated measure two-way ANOVA. Statistical analysis was performed using the SPSS statistics software (P < 0.05). Results: Repeated learning of the customized abutment design displayed a significant difference according to the number of repetition and the stage (P < 0.001). The difference in the time spent designing was found to be significant (P < 0.001), and that between the CAD software programs was also significant (P = 0.006). Conclusion: Repeated learning of CAD software shortened the time spent designing. While less design time on average was spent with the 3DS CAD than with the EXO CAD, the EXO CAD showed better results in terms of learning rate according to learning effect.

• The Journal of Advanced Prosthodontics
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• v.9 no.4
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• pp.239-243
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• 2017

PURPOSE. The purpose of this study is to compare single and three-unit metal frameworks that are produced by micro-stereolithography. MATERIALS AND METHODS. Silicone impressions of a selected molar and a premolar were used to make master abutments that were scanned into a stereolithography file. The file was processed with computer aided design software to create single and three-unit designs from which resin frameworks were created using micro-stereolithography. These resin frameworks were subjected to investment, burnout, and casting to fabricate single and three-unit metal ones that were measured under a digital microscope by using the silicone replica technique. The measurements were verified by means of the Mann-Whitney U test (${\alpha}=.05$). RESULTS. The marginal gap was $101.9{\pm}53.4{\mu}m$ for SM group and $104.3{\pm}62.9{\mu}m$ for TUM group. The measurement of non-pontics in a single metal framework was $93.6{\pm}43.9{\mu}m$, and that of non-pontics in a three-unit metal framework was $64.9{\pm}46.5{\mu}m$. The dimension of pontics in a single metal framework was $110.2{\pm}61.4{\mu}m$, and that of pontics in a three-unit metal framework was $143.7{\pm}51.8{\mu}m$. CONCLUSION. The marginal gap was smaller for the single metal framework than for the three-unit one, which requires further improvement before it can be used for clinical purposes.

• Journal of Periodontal and Implant Science
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• v.53 no.5
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• pp.388-401
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• 2023

Purpose: This study investigated the accuracy of free-hand implant surgery performed by an experienced operator compared to static guided implant surgery performed by an inexperienced operator on an anterior maxillary dental model arch. Methods: A maxillary dental model with missing teeth (No. 11, 22, and 23) was used for this in vitro study. An intraoral scan was performed on the model, with the resulting digital impression exported as a stereolithography file. Next, a cone-beam computed tomography (CBCT) scan was performed, with the resulting image exported as a Digital Imaging and Communications in Medicine file. Both files were imported into the RealGUIDE 5.0 dental implant planning software. Active Bio implants were selected to place into the model. A single stereolithographic 3-dimensional surgical guide was printed for all cases. Ten clinicians, divided into 2 groups, placed a total of 60 implants in 20 acrylic resin maxillary models. Due to the small sample size, the Mann-Whitney test was used to analyze mean values in the 2 groups. Statistical analyses were performed using SAS version 9.4. Results: The accuracy of implant placement using a surgical guide was significantly higher than that of free-hand implantation. The mean difference between the planned and actual implant positions at the apex was 0.68 mm for the experienced group using the free-hand technique and 0.14 mm for the non-experienced group using the surgical guide technique (P=0.019). At the top of the implant, the mean difference was 1.04 mm for the experienced group using the free-hand technique and 0.52 mm for the non-experienced group using the surgical guide technique (P=0.044). Conclusions: The data from this study will provide valuable insights for future studies, since in vitro studies should be conducted extensively in advance of retrospective or prospective studies to avoid burdening patients unnecessarily.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.4
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• pp.444-450
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• 2017

Prosthetic decision-making is complex because of various factors, and involves a combination of the individual dentist's interpretation of the objective clinical data and his or her interaction with the patient. Increasing therapeutic options and emerging outcome data demand the constant re-evaluation of our decision-making process. In this case, fixed prosthetic restorations were selected as a treatment method to reconstruct the occlusal plane of a patient with disharmonious occlusal plane. And the occlusal plane was re-established by establishing a treatment plan through diagnostic wax-up. Provisional restorations obtained by continuous re-evaluation for a sufficient period of time was replicated to definitive restorations using CAD/CAM technology. The results were satisfactory when they were observed through clinical follow-up for 3 months after the end of treatment.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.243-253
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• 2009

This report described a technique utilizing a computer-aided design (CAD) /computer-aided machining (CAM) - guided surgical implant placement and prefabricated fixed complete denture for an immediately loaded restoration. A patient with an edentulous maxilla and mandible received 6 implants in maxilla and 6 implants in the mandible using CAD/CAM surgical templates. Prefabricated provisional maxillary and mandibular implant supported fixed prostheses were connected immediately after implant installation. Provisional prostheses were evaluated for aesthetics, function during 6 months. Definitive prostheses were fabricated.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.2
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• pp.166-172
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• 2018

In case of the treatment of maxillary anterior teeth, it should be taken into account the proper morphology, arrangement and color satisfying patient's esthetic demands. For this purpose, facial composition, dentofacial composition, dental composition and dentogingival composition should be considered making diagnosis and treatment plan in an esthetic point of view. In adjustable temporary crown state, careful evaluation and correction of the esthetic and functional aspect were performed, and the definite restoration was reproduced using double scan.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.1
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• pp.79-87
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• 2017

The open bite malocclusion is a common clinical entity and has multifactorial causes. Development of effective treatment plan and management is dependent on proper diagnosis. The skeletal open bite patient requires a coordinated orthodontic and orthognathic surgical approach to achieve stable occlusion, acceptable esthetics, and improved function. But in case of open bite with severely decayed dentition, restoration in the entire dentition is necessary. Using the facial analysis and diagnostic wax-up, the most effective treatment was prosthetic rehabilitation. The provisional restorations were fabricated to satisfy esthetic and functional requirements, which result in the uniformly distributed occlusal force, anterior and canine guidance. The inter-arch relationship, labio-dental harmony, and the soft tissue aspect, which is important to estimate the longevity were evaluated. Definitive restorations of monolithic zirconia were made by replicating provisional restorations by using the latest CAD/CAM technology. They were delivered to the patient and clinical follow-up observation was satisfactory.