• Journal of Korean Dental Science
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• v.12 no.1
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• pp.13-19
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• 2019

Purpose: The aim of this study was to compare the flexural strength of provisional fixed dental prostheses which was three-dimensional (3D) printed by several build directions. Materials and Methods: A metal jig with two abutment teeth and pontic space in the middle was fabricated. This jig was scanned with a desktop scanner and provisional restoration was designed on dental computer-aided design program. On the preprocessing software, the build angles of the restorations were arranged at $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$ and support was added and resultant structure was sliced to a thickness of $100{\mu}m$. Processed restorations were printed with digital light processing type 3D printer using poly methyl meta acrylate-based resin. After washing and post-curing, compressive loading was applied at a speed of 1 mm/min on a metal jig fixed to a universal testing machine. The maximum pressure at which fracture occurred was measured. For the statistical analysis, build direction was set as the independent variable and fracture strength as the dependent variable. One-way analysis of variance and Tukey's post hoc analysis was conducted to compare fracture strength among groups (${\alpha}=0.05$). Result: The mean flexural strength of provisional restoration 3D printed with the build direction of $0^{\circ}$ was $1,053{\pm}168N$; it was $1,183{\pm}188N$ at $30^{\circ}$, $1,178{\pm}81N$ at $45^{\circ}$, $1,166{\pm}133N$ at $60^{\circ}$, and $949{\pm}170N$ at $90^{\circ}$. The group with a build direction of $90^{\circ}$ showed significantly lower flexural strength than other groups (P<0.05). The flexural strength was significantly higher when the build direction was $30^{\circ}$ than when it was $90^{\circ}$ (P<0.01). Conclusion: Among the build directions $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$ set for 3D printing of fixed dental prosthesis, an orientation of $30^{\circ}$ is recommended as an effective build direction for 3D printing.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.4
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• pp.484-514
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• 1994

Cantilever bridge is widely used by mny clinicians, but its worst mechanical character, so called Class I lever system, makes dentists hesitate to restore the missing tooth with it. Therefore it is important to study stress of the cantilever bridge. In this study, two models of cantilever bridges that restores the missing mandibular second molar with two abutment teeth were constructed. One model was a type of cantilever bridge supported by a normal alveolar bone, the other one was supported by an alveolar bone resorbed to its 1/3 of root length. Maximum bite force(550N) and funtional maximum bite force(300N) were vertically applied to the distal end of the pontic, distal 1/3, and distal half of the pontic. And each force was also applied to centric occlusal contacts as a distributed force. Total 16 loading cases were compared and analyzed with 3-dimensional finite element method. The results were as follows: 1. The stress was concentrated on the joint of the pontic and the retainer, grooves, and distal cervical margin of the posterior retainer. 2. In case of maximum bite force(550N) at the end of the pontic, the risk of fracture at the joint of the pontic and the retainer was high. 3. In case of distributed force in centric occlusion and functional maximum bite force(300N), the stresses were less than the yield strength of the type VI gold for any loading cases. 4. In case of alveolar bone resorption, the occlusal force to the cantilever pontic caused more stress on the root apex and less stress on the alveolar crest region of the distal surface of the posterior abutment. 5. In case of alveolar bone resorption, the displacement was larger than that of normal alveolar bone in all loading cases.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.2
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• pp.140-145
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• 2024

Removable partial denture wearers are exposed to the risks that remaining teeth get damaged by caries, attritions, erosion, and fracture. In the case of damaged abutment tooth which should fit to Removable partial denture (RPD), the fabrication of surveyed crown is followed by the making of RPD. However, making new denture takes a long time, and needs several processes and costs. Also, patients should get used to new denture. If other abutment teeth and edentulous ridges provide the existing denture with support, retention, and stability, use of existing denture is considered clinically acceptable. In this situation, fabricating retrofit crowns to an existing removable partial denture makes patient use existing denture, cuts costs, and reduces discomfort. In this case, severely worn teeth were restored using monolithic zirconia crown which fit to an existing removable partial denture by CAD-CAM. Moreover, support, retention, and stability of the denture were improved, and both doctor and patient were satisfied with the result.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.24 no.2
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• pp.101-121
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• 2015

Zirconia polycrystalline (Y-TZP) showed better mechanical properties and superior resistance to fracture than other conventional dental ceramics. Zirconia-based ceramics have been successfully introduced into the clinic to fabricate fixed dental prostheses (FDPs), along with a dental computer-aided/computer-aided manufacturing (CAD/CAM) system. It has been clinically available as an alternative to the metal framework for fixed dental prostheses (FDPs). The most frequent clinical complication with zirconia-based FDPs was chipping of the veneering porcelain that was affected by many factors. Another option was full-contour zirconia FDPs using high translucent zirconia. Full-contour zirconia FDPs has many clinical advantages but it caused concern about the wear of antagonist enamel, because the hardness of Y-TZP was over double that of porcelain. However, many articles demonstrates that highly polished zirconia yielded lower antagonist wear compared with porcelains. In this article (1) advantages of full zirconia restorations, (2) clinical applications of zirconia restorations, (3) abutment preparation, (4) surface finish of zirconia restoration and antagonist enamel wear, (5) bond of zirconia with resin-based luting agents, (6) communication in clinical & lab.procedures for full zirconia restorations are reviewed.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.286-290
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• 2016

Recently, flexible removable prosthesis with thermoplastic resin clasp has increasingly become popular. In comparison with conventionally used acrylic resin, thermoplastic resin has lower flexural strength and elastic modulus. Thus, flexible removable prosthesis has low risk of fracture, so denture base can be made thin and light, increasing patient comfort. Also, it can passively sit at tooth undercut during rest, so abutment teeth need minimum or no preparation. In this case report, a 44 year old female patient with mild velopharyngeal insufficiency was treated with a palatal lift prosthesis made of polyester thermoplastic resin. Since the patient had no missing tooth and desired conservative treatment, the flexible removable prosthesis provided relatively satisfactory results.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.4
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• pp.384-390
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• 2018

Hybrid telescopic double crown have ever been good treatment option for patient with periodontally unfavorable few remaining teeth for successful prognosis. Tooth and implant combined telescopic double crown can be used for improving retention and support for denture with strategically placed implants on edentulous ridge. In this case, an 55-year-old female patient had chronic periodontitis with few remaining teeth on maxilla and fixed partial prosthodontics on mandible. Treatment of hybrid telescopic double crown with friction pin lasted 9.5 years only with natural teeth. After 9.5 years, additional implants was installed due to fracture of cast-posted abutment teeth. After implantation, tooth and implant combined double crown had fabricated. Through re-treatment, no complications of new denture has been found during 2 years follow up. This case presents fair prognosis of tooth and implant combined double crown denture in periodontally unfavorable condition.

• Journal of Periodontal and Implant Science
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• v.50 no.2
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• pp.97-105
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• 2020

Purpose: The present retrospective clinical study aimed to evaluate and compare the clinical and radiographic parameters, complications, and satisfaction in patients who received fixed prostheses supported by narrow-diameter implants (NDIs) in the anterior and posterior jaw. Methods: Patients aged ≥30 years who had NDI-supported fixed prostheses in the anterior or posterior region of either jaw for at least 2 years were included. Complications such as chipping of the crown; loosening or fracture of the screw, crown abutment, or implant; and loss of retention were recorded. Clinical peri-implant outcomes and crestal bone loss (CBL) were measured. A questionnaire was used to record responses regarding the aesthetics and function of the fixed restorations. Analysis of variance was used to assess the significance of between-group mean comparisons. The log-rank test was performed to analyze the influence of location and prosthesis type on technical complications. Results: Seventy-one patients (mean age: 39.6 years) provided informed consent with a mean follow-up duration of 53 months. Only bleeding on probing showed a statistically significant difference between NDIs in the anterior and posterior regions. The complication rate for NDIs in the posterior region was significantly higher than that for NDIs in the anterior region (P=0.041). For NDIs, CBL was significantly higher around splinted crowns than single crowns (P=0.022). Overall mean patient satisfaction was 10.34±3.65 on a visual analogue scale. Conclusions: NDIs in the anterior and posterior jaws functioned equally well in terms of periimplant soft and hard tissue health and offered acceptable patient satisfaction and reasonable complication rates.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.280-289
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• 2013

Removable partial denture for oral function recovery of partial edentulous patients is a complicated treatment because the dentist should consider both hard tissue and soft tissue. Removable partial denture produced without consideration of precise design for each component and rotation of denture may cause fracture, deformation or loss of abutment teeth. In case of failure to achieve a proper denture, the reason of failure should be analyzed and the result must be applied to later RPD cases. Finding the solutions through the failed denture cases will help patients use their dentures more comfortably and keep their sound residual teeth and tissue longer.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.354-358
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• 2000

Tetragonal (t)-ZrO2/Al2O3 composites doped with Y2O3, Nb2O5, and Fe2O3 ((Y, Nb, Fe)-TZP/Al2O3) were prepared over the range containing Fe2O3 from 0.1 to 0.5 mol% with 0.1 mol% intervals to evaluate the effect of Fe2O3 addition on chromaticity, hydrothermal stability, and mechanical property of the composites. After autoclaving for 20 h at 18$0^{\circ}C$ under 3.5 MPa water vapor pressure, no tlongrightarrowm phase transformation was observed probably due to the preferential solid solubility of Fe2O3 in Al2O3, the presence of the rigid Al2O3 particles, and the inherent phase stability of (Y, Nb)-TZP. The optimized strength and the fracture toughness of the composite were 700 MPa and 8.5 MPa.m1/2, respectively, when 0.1 mol% Fe2O3 was added. The composites have shown a gradual color change from a slightly white ivory to a pale yellowish brown with increasing the Fe2O3 concentration.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.241-251
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• 2010

This study aims at contributing to the restorative dentistry by examining results in the vertical load test of four different low invasive fixed partial dentures. Based on a hypothesis on the right upper first molar is missing, three units of FPDs were made for the second premolar and the second molar abutment. that is, twelve metal dies and FPDs were made for resin bonded FPD and Two Key Bridges and Human Bridge without occlusal rest and Human Bridge with occlusal rest. By using universal test machine, the numerical maximum value were recorded during the vertical load test of each FPDs after the bonding process treated by Maxcem which is resin cement. The failure process and its result of prosthesis were also observed. The maximum load was 7,295 N, 4,729 N, 2,190 N, 3,073 N from groups of resin bonded FPD, Two Key Bridge, Human Bridge without occlusal rest and Human Bridge with occlusal rest respectively. There was a statistical significance among the groups of resin bonded FPD, Two Key Bridge and Human Brides. However, there was no significant difference between Human Bridge without occlusal rest and Human Bridge with occlusal rest. Regarding the failure of prosthesis, the groups of Resin Bonded FPD and Two Key Bridge showed that one of the abutment teeth in the both side of retention part was highly failed earlier than the other one (83.2% and 66.6% respectively). While, Human Bridge without occlusal rest and Human Bridge with occlusal rest showed high percentage of failure in the abutment teeth in the both side of retention part at the same time (91.6% and 58.3% respectively). This study demonstrates that the group of Human Bridges has low resistance to the vertical loads of low invasive FPDs in comparison with the groups of resin bonded FPD and Two Key Bridge. Nevertheless, the maximum occlusal load of the restorative position, resistance to diverse restoration failure, amount of tooth reduction and patients' cooperation should be considered when they are applied in the clinic in order to choose an appropriate restoration for each patient.