• The Journal of Korean Academy of Prosthodontics
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• v.60 no.2
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• pp.135-142
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• 2022

Purpose. This study aims to evaluate the combined effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns. Materials and methods. Seven nickel-chromium dies were generated from a 3D model of mandibular first molar using the digital scanner with the following geometries: 1.5 mm occlusal reduction, 1.0 mm deep chamfer. Based on the abutment model, Zirconia blocks (Luxen Zirconia) were selected to fabricate Sixty-three zirconia crowns with occlusal thicknesses of 0.3 mm, 0.5 mm, and 1.5 mm, and different axial thicknesses of 0.3 mm, 0.5 mm, and 1.0 mm. All crowns were cemented by resin cement. Next, the crowns were subjected to load-to-fracture test until fracture using an electronic universal testing machine. In addition, fracture patterns were observed with a scanning electron microscope (SEM). Two-way ANOVA and the Tuckey HSD test for post hoc analysis were used for statistical analysis (P < .05). Results. The mean values of fracture resistancerecorded was higher than the average biting force in the posterior region. The two-way ANOVA showed that the occlusal and axial thickness affected the fracture resistance significantly (P < .05). However, the effect of axial thickness on fracture resistance did not show a statistical difference when thicker than 0.5 mm. The observed failure modes were partial or complete fracture depending on the severity of crack propagation. Conclusion. Within the limitations of the present study, the CAD-CAM monolithic zirconia crown with extremely reduced thickness showed adequate fracture resistance to withstand occlusal load in molar regions. In addition, both occlusal and axial thickness affected the fracture resistance of the zirconia crown and showed different results as combined.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.150-157
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• 2016

PURPOSE. The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS. Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS. Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION. Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.36.1-36.8
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• 2019

Background: This study aims to examine the outcome of simultaneous maxillary sinus lifting, bone grafting, and vertical ridge augmentation through retrospective studies. Methods: From 2005 to 2010, patients with exhibited severe alveolar bone loss received simultaneous sinus lifting, bone grafting, and vertical ridge augmentations were selected. Fifteen patients who visited in Seoul National University Bundang Hospital were analyzed according to clinical records and radiography. Postoperative complications; success and survival rate of implants; complications of prosthesis; implant stability quotient (ISQ); vertical resorption of grafted bone after 1, 2, and 3 years after surgery; and final observation and marginal bone loss were evaluated. Results: The average age of the patients was 54.2 years. Among the 33 implants, six failed to survive and succeed, resulting in an 81.8% survival rate and an 81.8% success rate. Postoperative complications were characterized by eight cases of ecchymosis, four cases of exposure of the titanium mesh or membrane, three cases of periimplantitis, three cases of hematoma, two cases of sinusitis, two cases of fixture fracture, one case of bleeding, one case of numbness, one case of trismus, and one case of fixture loss. Prosthetic complications involved two instances of screw loosening, one case of abutment fracture, and one case of food impaction. Resorption of grafted bone material was 0.23 mm after 1 year, 0.47 mm after 2 years, 0.41 mm after 3 years, and 0.37 mm at the final observation. Loss of marginal bone was 0.12 mm after 1 year, and 0.20 mm at final observation. Conclusions: When sinus lifting, bone grafting, and vertical ridge augmentation were performed simultaneously, postoperative complications increased, and survival rates were lower. For positive long-term prognosis, it is recommended that a sufficient recovery period be needed before implant placement to ensure good bone formation, and implant placement be delayed.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.1
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• pp.46-52
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• 2017

Provisional restoration plays an important role in the process of restoration with fixed partial denture by providing protection and restoring function and esthetics of abutment tooth. This is especially true in patients requiring use of provisional prosthesis for a long term. However, such situations may lead to higher possibility of provisional prosthesis fracture, and if expected so, reinforcement of provisional prosthesis should be considered. In this article, a patient requiring prosthetic treatment with increase of vertical dimension of occlusion was introduced. Due to increased vertical dimension of occlusion, the provisional restoration was expected to withstand relatively larger amount of load during a relatively long observation period. In order to minimize possible occurrence of fracture, reinforcement of the provisional restoration was sought by insertion of cast-metal framework and by using bis-acryl resin. The reinforced provisional restoration showed satisfactory results during the observation period of 4 months.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.2
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• pp.144-150
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• 2017

Purpose: The aim of this in vitro study is to investigate load bearing capacity of esthetic abutments according to the type of material and wall thickness. Materials and methods: 70 specimens equally divided into seven groups according to their abutment wall thicknesses. The abutments prepared with titanium 0.5 mm wall thickness were used as a control group (Ti-0.5), whereas zirconia abutments and resin nano ceramic abutments with wall thickness 0.5 mm, 0.8 mm and 1.0 mm were prepared as test groups (Zir-0.5, Zir-0.8, Zir-1.0 and RNC-0.5, RNC-0.8, RNC-1.0). All specimens were tested in a universal testing machine to evaluate their resistance to fracture and all of them underwent thermo-cycling before loading test. Mean fracture values of the groups were measured and statistical analyses were made using two-way ANOVA. Results: Zir-1.0 showed the highest mean strength ($2,476.3{\pm}342.0N$) and Zir-0.8 ($1,518{\pm}347.9N$), Ti-0.5 ($1,041.8{\pm}237.2N$), Zir-0.5 ($631.4{\pm}149.0N$) were followed. The strengths of RNC groups were significantly lower compared to other two materials (RNC-1.0 $427.5{\pm}72.1$, RNC-0.8 $297.9{\pm}41.2$) and the strengths of all the test groups decreased as the thickness decreases (P < .01). RNC-0.5 ($127.4{\pm}35.3N$) abutments were weaker than all other groups (P < .05). Conclusion: All tested zirconia abutments have the potential to withstand the physiologic occlusal forces in anterior and posterior regions. In resin nano ceramic abutments, wall thickness more than 0.8 mm showed the possibility of withstanding the occlusal forces in anterior region.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.2
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• pp.125-137
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• 2003

The use of screw-retaind prosthesis on an osseointegrated implant is a popular treatment modality offering relative ease in the removal of the restoration. One of the complications associated with this modality is the loosening of the abutment and coping screws. Loosening of the screws results in patient dissatisfaction, frustration to the dentist and, if left untreated, component fracture. There are several factors which contribute to the loosening of implant components which can be controlled by the restorative dentist and lab technician. This article offers pratical solutions to minimize this clinical problem and describes the factors involved in maintaining a stable screw joint assembly. To avoid joint failure, adherence to specific clinical, as well as mechanical, parameters is critical. With respect to hardware, optimal tolerance and fit, minimal rotational play, best physical properties, a predictable interface, and optimal torque application are mandatory. In the clinical arena, optimal implant distribution; load in line with implant axis; optimal number, diameter, and length of implants; elimination of cantilevers; optimal prosthesis fit; and occlusal load control are equally important.

• The Journal of Advanced Prosthodontics
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• v.7 no.4
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• pp.329-337
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• 2015

PURPOSE. This retrospective study aims at the evaluation of implant-supported overdentures (IODs) supported by ceramo-galvanic double crowns (CGDCs: zirconia primary crowns + galvano-formed secondary crown). MATERIALS AND METHODS. In a private practice, 14 patients were restored with 18 IODs (mandible: 11, maxilla: 7) retained by CGDCs on 4 - 8 implants and annually evaluated for technical and/or biological failures/complications. RESULTS. One of the 86 inserted implants failed during the healing period (cumulative survival rate (CSR) implants: 98.8%). During the prosthetic functional period (mean: $5.9{\pm}2.2years$), 1 implant demonstrated an abutment fracture (CSR-abutments: 98.2%), and one case of peri-implantitis was detected. All IODs remained in function (CSR-denture: 100%). A total of 15 technical complications required interventions to maintain function (technical complication rate: 0.178 treatments/patients/year). CONCLUSION. Considering the small sample size, the use of CGDCs for the attachment of IODs is possible without an increased risk of technical complications. However, for a final evaluation, results from a larger cohort are required.

• Geomechanics and Engineering
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• v.20 no.6
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• pp.547-556
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• 2020

An understanding of the influence of MR (Magmatic Rock) thickness on the surrounding rock behaviors is essential for the prevention and management of dynamic disasters in coal mining. In this study, we used FLC3D to study the breaking and instability laws of surrounding rock with different MR thicknesses in terms of strata movement, stress and energy. The mechanism of dynamic disasters was revealed. The results show that the thicker the MR is, (1) the smaller the subsidence of the overlying strata is, but the subsidence span of the overlying strata become wider, and the corresponding displacement deformation value of the basin edge become smaller. (2) the slower the growth rate of abutment pressure in front of the working face is, but the peak value is smaller, and the influence range is larger. The peak value decreases rapidly after the breaking, and the stress concentration coefficient is maintained at about 1.31. (3) the slower the peak energy in front of coal wall, but the range of energy concentration increases (isoline "O" type energy circle). Finally, a case study was conducted to verify the disaster-causing mechanism. We anticipate that the research findings presented herein can assist in the control of dynamic hazards.

• The Journal of the Korean dental association
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• v.54 no.3
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• pp.198-205
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• 2016

The purpose of this paper was to investigate the significance of splinted and non-splinted implant-supported restorations with an internal connection for multiple consecutively missing teeth. Upon examination of the effects of fixture-abutment connection, the distribution of occlusal load was favorable in splinted implant-prosthesis with an external connection, but effect of strain distribution was not significant in splinted implant-prosthesis with an internal connection. In splinted implant-prostheses for short implants, strain distribution was not affected by the method of retention. For cement-retained prostheses, the effect of strain distribution due to splinting was not significant. In clinical studies, non-splinted prostheses with an internal connection for multiple consecutively missing teeth showed high survival rate, mild marginal bone loss, and stable periodontal condition. However, failure to achieve optimal proximal contact between single-unit prostheses may lead to food impaction, and veneer fracture may be inevitable when the framework provides inadequate support in the proximal region. In conclusion, splinted implant-prosthesis is not an indication in all cases, and clinical consideration of its use should be based on the patient's oral condition, such as location and number of implants, formation of proximal contact, canine guidance, existence of parafunctional habit, and oral hygiene, when multiple consecutively missing teeth are replaced by internal connection type implant.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.3
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• pp.239-243
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• 2020

When the marginal fit of fixed dental prosthesis decreases, biological and technical complications, such as plaque accumulation, periodontal disease, hypersensitivity, components fracture, cement loss, can happen. The complications affect the long-term success and survival of prostheses. This case report describes a clinical procedure to minimize the marginal gap of implant-supported screw-and-cement retained prosthesis by removing prosthesis-abutment complex and burnishing the interface area. The marginal gap was measured before and after the burnishing using a stereomicroscope and compared. This technique improves the marginal fit, thereby contributing the longevity of the prosthesis.