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

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

Full mouth rehabilitation with vertical dimension increase in patient with severely worn out dentition: A case report / 대한치과보철학회지

Excessive teeth wear can lead to reduced chewing efficiency, occlusal plane collapse, and facial changes. Full mouth rehabilitation with a change in vertical dimension may cause pain in the temporomandibular joint, masticatory muscle and teeth, so an accurate diagnosis and treatment plan is required. In this case, a 69-year-old man had excessive teeth wear with a loss of posterior support. We evaluated the degree of adaptation to the increased vertical dimension with the removable occlusal splint and provisional restoration. We report this case because the treatment result has been functionally and aesthetically satisfactory by providing stable anterior guidance, proper posterior teeth disclusion, and even contact of all teeth in centric occlusion.

Implant-assisted removable partial denture using digital guide surgery in partially edentulous mandible: A case report / 대한치과보철학회지

Fixed implant prostheses or removable partial dentures are common treatment for partially dentulous patients. Recently, an implant-assisted removable partial denture (IARPD) has been introduced and is widely used. In the case of removable partial dentures using implant attachment and surveyed fixed prostheses, the consideration about parallelism of insertion path between implants and surveyed fixed prostheses is an important factor for success of IARPDs. In this case, she complained of discomfort while using the mandibular removable partial denture. Thus, an IARPD using implant surveyed fixed prostheses was fabricated.Thereafter, more implants were placed by a digital guide surgery to have the same insertion path as the existing surveyed fixed prostheses. Locator attachments were installed to the left and right premolar implants, and the left molar was able to obtain support of the removable partial denture with healing abutment. The clinical results were satisfactory on the aspect of aesthetic and masticatory function.

Full mouth rehabilitation with vertical dimension increase in patient with severely worn out dentition: A case report / 대한치과보철학회지

Excessive teeth wear can lead to reduced chewing efficiency, occlusal plane collapse, and facial changes. Full mouth rehabilitation with a change in vertical dimension may cause pain in the temporomandibular joint, masticatory muscle and teeth, so an accurate diagnosis and treatment plan is required. In this case, a 69-year-old man had excessive teeth wear with a loss of posterior support. We evaluated the degree of adaptation to the increased vertical dimension with the removable occlusal splint and provisional restoration. We report this case because the treatment result has been functionally and aesthetically satisfactory by providing stable anterior guidance, proper posterior teeth disclusion, and even contact of all teeth in centric occlusion.

Fabrication of dentures for a patient with unstable mandibular movements: A case report / 대한치과보철학회지

For patients with unstable mandibular movements and centric relation of the mandible due to long-term use of ill-fitting dentures, the successful fabrication of new dentures is challenging. Before fabrication new dentures, registration of centric relation is the critical point in such cases. In this case, treatment dentures with a flat occlusal table were used to stabilize mandibular movements and to register centric relation. In order to reflect the patient's jaw relation and vertical dimension obtained through the treatment dentures to the final denture, the treatment dentures were digitally duplicated, and impressions and jaw relations were obtained using the duplicated therapeutic dentures. The clinical results were satisfactory on the aspect of aesthetic and masticatory functioned.

Clinical accuracy of impression technique using digital superimposition ofcustomized abutment with subgingival margin: A case report / 대한치과보철학회지

Traditionally, gingival retraction has been performed to obtain customized abutment impressions with subgingival margins of the implant supported prosthesis. However, gingivalretraction may have side effects such as gingival recession and bleed, leading to an inaccurate impression. In order to prevent these problems, in this case, the new techniquehas been introduced; a customized abutment which is designed for superimposition is used. Before the connection of the abutment to the implant fixture, pre-scannedshape data are stored, and then the optical impression without gingival retraction is obtained after connecting to the fixture. The suprastructure is fabricated by superimposingthe two data. This technique showed the clinical efficacy of fabricating the implant supported prosthesis with subgingival margin, which satisfied the aesthetics, convenience,and clinically acceptable marginal and internal fit. (J Korean Acad Prosthodont 2020;58:169-75)

Effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fitness / 대한치과보철학회지

PURPOSE: To evaluate an effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fit through three-dimensional analysis. MATERIALS AND METHODS: Ten monolithic zirconia crowns were fabricated using titanium abutment model. Monolithic zirconia crowns were designed, milled, and sintered as a control group, and additional firing with coloring was performed as a test group. Three dimensional analysis were performed by using triple-scan protocol, and cross-section analysis on mesio-distal and disto-lingual section was evaluated to measure marginal and internal fitness. Then, three-dimensional surface difference on between two groups was evaluated (α=.05). RESULTS: There was statistically significant difference between the control group (32.0 ± 24.3 µm) and the test group (17.0 ± 10.8 µm) in the mesial axial wall (P < .02) and the control group (60.2 ± 24.3 µm) and the test group (71.8 ± 21.5 µm) in the distal axial wall (P < .01). There was no statistically significant difference at the remaining point. CONCLUSION: There was no statistical significance on the deviation of inner surface of crown according to firing number, and the results of both group were considered clinically acceptable.

Effects of cementless fixation of implant prosthesis: A finite element study

PURPOSE: A novel retentive type of implant prosthesis that does not require the use of cement or screw holes has been introduced; however, there are few reports examining the biomechanical aspects of this novel implant. This study aimed to evaluate the biomechanical features of cementless fixation (CLF) implant prostheses.MATERIALS AND METHODS: The test groups of three variations of CLF implant prostheses and a control group of conventional cement-retained (CR) prosthesis were designed three-dimensionally for finite element analysis. The test groups were divided according to the abutment shape and the relining strategy on the inner surface of the implant crown as follows; resin-air hole-full (RAF), resin-air hole (RA), and resin-no air hole (RNA). The von Mises stress and principal stress were used to evaluate the stress values and distributions of the implant components. Contact open values were calculated to analyze the gap formation of the contact surfaces at the abutment-resin and abutment-implant interfaces. The micro-strain values were evaluated for the surrounding bone.RESULTS: Values reflecting the maximum stress on the abutment were as follows (in MPa): RAF, 25.6; RA, 23.4; RNA, 20.0; and CR, 15.8. The value of gap formation was measured from 0.88 to 1.19 µm at the abutmentresin interface and 24.4 to 24.7 µm at the abutment-implant interface. The strain distribution was similar in all cases.CONCLUSION: CLF had no disadvantages in terms of the biomechanical features compared with conventional CR implant prosthesis and could be successfully applied for implant prosthesis.

Stress analysis of mandibular implant overdenture with locator and bar/clip attachment: Comparative study with differences in the denture base length

PURPOSE: The design of the attachment must provide an optimum stress distribution around the implant. In this study, for implant overdentures with a bar/clip attachment or a locator attachment, the stress transmitted to the implant in accordance with the change in the denture base length and the vertical pressure was measured and analyzed. MATERIALS AND METHODS: Test model was created with epoxy resin. The strain gauges made a tight contact with implant surfaces. A universal testing machine was used to exert a vertical pressure on the mandibular implant overdenture and the strain rate of the implants was measured. RESULTS: Means and standard deviations of the maximum micro-deformation rates were determined. 1) Locator attachment: The implants on the working side generally showed higher strain than those on the non-working side. Tensile force was observed on the mesial surface of the implant on the working side, and the compressive force was applied to the buccal surface and on the surfaces of the implant on the non-working side. 2) Bar/clip attachment: The implants on the both non-working and working sides showed high strain; all surfaces except the mesial surface of the implant on the non-working side showed a compressive force. CONCLUSION: To minimize the strain on implants in mandibular implant overdentures, the attachment of the implant should be carefully selected and the denture base should be extended as much as possible.

Bone Regeneration in the Extraction Socket Filled with Atelocollagen: Histological and Radiographic Study in Beagle Dogs

PURPOSE: Alveolar bone develops with tooth eruption and is absorbed following tooth extraction. Various ridge preservation techniques have sought to prevent ridge atrophy, with no superior technique evident. Collagen has a long history as a biocompatible material. Its usefulness and safety have been amply verified. The related compound, atelocollagen, is also safe and displays reduced antigenicity since telopeptides are not present. MATERIALS AND METHODS: The current study evaluated whether the Rapiderm® atelocollagen plug (Dalim Tissen, Seoul, Korea) improves tissue healing of extraction sockets and assessed the sequential pattern of bone regeneration using histology and microcomputed tomography in six beagle dogs. To assess the change of extraction socket, hard tissues were examined 2, 4, 6, and 8 weeks after tooth extraction. RESULT: The experimental groups showed better bone fill with slow remodeling process compared to the control groups although there was no statistical difference between groups. CONCLUSION: The atelocollagen seems to have a tendency to slow bone remodeling in the early phase of healing period and maintain remodeling capacity until late phase of remodeling. Also, use of atelocollagen increased the bone-to-tissue ratio compared to healing of untreated extraction socket.

Fabrication of a CAD/CAM monolithic zirconia crown to fit an existing partial removable dental prosthesis

Fabricating a surveyed prosthesis beneath an existing partial removable dental prosthesis (PRDP) is a challenging and time-consuming procedure. The computer-aided design/computer-assisted manufacturing (CAD/CAM) technology was applied to fabricate a retrofitted, surveyed zirconia prosthesis to an existing PRDP. CAD/CAM technology enabled precise and easy replication of the contour of the planned surveyed crown on the existing abutment tooth. This technology ensured excellent adaptation and fit of newly fabricated crown to the existing PRDP with minimal adjustments. In this case report, a seventy-year-old male patient presented with fractured existing surveyed crown. Because the existing PRDP was serviceable, new crown was fabricated to the existing PRDP.