• Journal of Dental Rehabilitation and Applied Science
• /
• v.26 no.2
• /
• pp.121-143
• /
• 2010

To investigate the effect of implant types and bone resorption on the fracture characteristics. 4 types of Osstem$^{(R)}$Implant were chosen and classified into external parallel, internal parallel, external taper, internal taper groups. Finite elements analysis was conducted with ANSYS Multi Physics software. Fatigue fracture test was performed by connecting the mold to the dynamic load fatigue testing machine with maximum load of 600N and minimum load of 60N. The entire fatigue test was performed with frequency of 14Hz and fractured specimens were observed with Hitachi S-3000 H scanning electron microscope. The results were as follows: 1. In the fatigue test of 2 mm exposed implants group, Tapered type and external connected type had higher fatigue life. 2. In the fatigue test of 4 mm exposed implants group, Parallel type and external connected types had higher fatigue life. 3. The fracture patterns of all 4 mm exposed implant system appeared transversely near the dead space of the fixture. With a exposing level of 2 mm, all internally connected implant systems were fractured transversely at the platform of fixture facing the abutment. but externally connected ones were fractured at the fillet of abutment body and hexa of fixture or near the dead space of the fixture. 4. Many fatigue striations were observed near the crack initiation and propagation sites. The cleavage with facet or dimple fractures appeared at the final fracture sites. 5. Effective stress of buccal site with compressive stress is higher than that of lingual site with tensile stress, and effective stress acting on the fixture is higher than that of the abutment screw. Also, maximum effective stress acting on the parallel type fixtures is higher. It is careful to use the internal type implant system in posterior area.

• The korean journal of orthodontics
• /
• v.28 no.3 s.68
• /
• pp.379-389
• /
• 1998

The purpose of the present study was to evaluate the change of tooth mobility following orthodontic tooth movement. Six orthodontic patients which had been treated with edgewise appliance were used. Tooth mobility was measured with Periostest at the time of the removal of orthodontic appliance and 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24 weeks after appliance removal. Following results were obtained: 1. Tooth mobility upon the removal of orthodontic appliance showed individual variation while incisor showed greater mobility than the other teeth. 2. Tooth mobility showed continued decrease pattern until 24 weeks after appliance removal. 3. While maxillary incisors showed continued decrease pattern during the study period, the other teeth showed steep decline pattern during the first 12 weeks and gentle slope during the second 12 weeks. 4. The tooth mobility of the maxillary second premolar showed the most typical change in terms of the consistency of the decline. 5. There were no significant differences of tooth mobility between heavy- and light-contacted anterior teeth during experimental period. The results of the present study suggested that periodontal reorganization is not completed even in 24 weeks following orthodontic tooth movement.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.38 no.3
• /
• pp.138-149
• /
• 2022

The clinical applicability of ceramics can be increased by analyzing the causes of fractures after fracture testing of dental ceramics. Fractography to analyze the cause of fracture of dental ceramics is being widely applied with the development of imaging technologies such as scanning electron microscopy. Setting the experimental conditions is important for accurate interpretation. The fractured specimens should be stored and cleaned to avoid contamination, and metal pretreatment is required for better observation. Depending on the type of fracture, there are dimple rupture, cleavage, and decohesive rupture mainly observed in metals, and fatigue fractures and conchoidal fractures observed in ceramics. In order to reproduce fatigue fracture in the laboratory, which is the main cause of fracture of ceramics, a dynamic loading for observing slow crack growth is essential, and the load conditions and number of loads must be appropriately set. A typical characteristic of a fracture surface of ceramic is a hackle, and the causes of fracture vary depending on the shape of hackle. Fractography is a useful method for in-depth understanding of fractures of dental ceramics, so it is necessary to follow the exact experimental procedure and interpret the results with caution.

• The Journal of Korean Academy of Prosthodontics
• /
• v.50 no.3
• /
• pp.156-161
• /
• 2012

Purpose: This study was conducted to obtain difference in fracture strength according to the diameter of one-body O-ring-type of mini implant fixture, to determine the resistance of mini implant to masticatory pressure, and to examine whether overdenture using O-ring type mini implant is clinically usable to maxillary and mandibular edentulous patients. Materials and methods: For this study, 13 mm long one body O-ring-type mini implants of different diameters (2.0 mm, 2.5 mm and 3.0 mm) (Dentis, Daegu, Korea) were prepared, 5 for each diameter. The sample was placed at $30^{\circ}$ from the horizontal surface on the universal testing machine, and off-axis loading was applied until permanent deformation occurred and the load was taken as maximum compressive strength. The mean value of the 5 samples was calculated, and the compressive strength of implant fixture was compared according to diameter. In addition, we prepared 3 samples for each diameter, and applied loading equal to 80%, 60% and 40% of the compressive strength until fracture occurred. Then, we measured the cycle number on fracture and analyzed fatigue fracture for each diameter. Additionally, we measured the cycle number on fracture that occurred when a load of 43 N, which is the average masticatory force of complete denture, was applied. The difference on compressive strength between each group was tested statistically using one-way ANOVA test. Results: Compressive strength according to the diameter of mini implant was $101.5{\pm}14.6N$, $149{\pm}6.1N$ and $276.0{\pm}13.4N$, respectively, for diameters 2.0 mm, 2.5 mm and 3.0 mm. In the results of fatigue fracture test at 43 N, fracture did not occur until $2{\times}10^6$ cycles at diameter 2.0 mm, and until $5{\times}10^6$ cycles at 2.5 mm and 3.0 mm. Conclusion: Compressive strength increased significantly with increasing diameter of mini implant. In the results of fatigue fracture test conducted under the average masticatory force of complete denture, fracture did not occur at any of the three diameters. All of the three diameters are usable for supporting overdenture in maxillary and mandibular edentulous patients, but considering that the highest masticatory force of complete denture is 157 N, caution should be used in case diameter 2.0 mm or 2.5 mm is used.