• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.3
• /
• pp.352-362
• /
• 2005

Statement of problem. Accurate impression is essential to success of implant prostheses. But there have been few studies about the accuracy of fixture-level impression techniques in internal connection implant systems. Purpose. The purpose of this study was to compare the accuracy of two fixture-level impression techniques in two conditions (parallel and divergent) and to assess the effect of tightening sequences and forces on stresses generated on superstructures in internal connection implant system (Astra Tech). Material and methods. Two metal master frameworks made from two abutments (Cast-to Abutment ST) each and a corresponding, passively fitting, dental stone master cast with four fixture replicas (Fixture Replica ST) were fabricated. Ten dental stone casts for each impression techniques (direct unsplinted & splinted technique) were made with vinyl polysiloxane impressions from the master cast. Strain gauges for each framework were fixed midway between abutments to measure the degree of framework deformation on each stone cast. Pairs of strain gauges placed opposite each other constituted one channel (half Wheatstone bridge) to read deformation in four directions (superior, inferior, anterior, and posterior). Deformation data were analyzed using one-way ANOVA and the Tukey test at the .01 level of significance. And the effect of tightening sequences (right-to-left and left-to-right) and forces (10 Ncm and 20 Ncm) were assessed with ten stone casts made from parallel condition by the splinted technique. Deformation data were analyzed using paired t-test at the .01 level of significance. Conclusions. Within the limitations of this study, the following conclusions could be drawn. 1. Frameworks bent toward the inferior side on all casts made by both direct unsplinted and splinted impression techniques in both parallel and divergent conditions. 2. There was no statistically significant difference of accuracy between the direct unsplinted and splinted impression techniques in both parallel and divergent conditions (P>.01). 3. There was no statistically significant difference of stress according to screw tightening sequences in casts made by the splinted impression technique in parallel condition (P>.01). 4. Greater tightening force resulted in greater stress in casts made by the splinted impression technique in parallel condition (P<.01).

• The Journal of Korean Academy of Prosthodontics
• /
• v.41 no.4
• /
• pp.421-439
• /
• 2003

Statement of problem : It is difficult to obtain a good titanium casting body using the traditional sprue design because of high melting point of Ti, and the low fluidity and high reactivity of molten Ti. Purpose : A new sprue design for titanium casting bodies needs more trial and error. In order to decrease the number of trial and error, computer simulation(MAGMASOFT, Magmasoft Giessereitechnologie GmbH, Achen, Germany) was used to optimize sprue design in U-shaped implant superstructures. Material and method : Five kinds of sprue were examined for the design of the sprue former for titanium casting: Sprue design A(sprue length 4 mm, rectangular shape, 4 sprues), Sprue design B(sprue length 4 mm. round shape. radius 2 mm, 7 sprues), Sprue design C (sprue length 2 mm, round shape, radius 2 mm, 7 sprues). Sprue design D (sprue length 2 mm, cone shape, large radius 3mm. small radius 2mm, 7 sprues), and Sprue design E( sprue length 2 mm. one unit channel shape). Sprue design F(sprue length 2mm, one unit channel shape) was also examined for the design of the customized sprue former in the Biotan system(Schutz Dental Gmbh, Germany). The casting bodies were taken in Sprue design A, Sprue design D, Sprue design E, and Sprue design F in the Biotan casting system. The numerically predicted defects were compared with the experimental dental castings by the radiographic and sectional view observations. Results : 1. According to the result of computer simulation, turbulence during mold filling was decreased in the sequence of Sprue design F, Sprue design E, Sprue design D, Sprue design C, Sprue design B, and Sprue design A. 2. The calculated solidification time contours indicate that hot spot was moved from the casting body to the sprue button in the sequence of Sprue design A, Sprue design B, Sprue design C, Sprue design D, and Sprue design E. The filling pattern of Sprue design F was similar to that of Sprue design E. 3 The predicted filling pattern shows that less turbulence was found in the customized sprue former than in the standard sprue former. 4. According to the results of the radiographic and cross sectional observations, casting defects less than 1mm were found at the center of a casting body with Sprue design E and Sprue design F. However, larger casting defects of 4mm were found in a casting with Sprue design A. 5. The predicted casting porosity was similar to that of the real casting. Conclusion : One unit channel-type and customized sprue former can be recommended. Further research and developement of various sprue designs using computer simulation in necessary to optimize casting design, in order to reduce the formation of casting defects in implant titanuim super-structures.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.22 no.4
• /
• pp.329-340
• /
• 2006

Statement of problem: Damping of the peak force transmitted to implants has been reported by in vitro studies using impact forces on resin-veneered superstructures. Theoretical assumptions suggest that use of acrylic resin for the occlusal surfaces of a prosthesis would protect the connection between implant and bone. Therefore, the relationship between prosthesis materials and the force transmitted through the implant system also needs to be investigated under conditions that resemble the intraoral mechanical environment. Purpose: The purpose of this study was to analyze the fracture strength and modes of temporary prosthesis when a flange or occlusally extended structure were connected on the top of the abutment. Material and method: Modified abutments of winged and bulk design were made by casting the desired wax pattern which is made on the UCLA type plastic cylinder. Temporary crowns were made using templates on the modified abutments, and its fracture toughness and strain were compared to the traditional temporary prosthesis. To evaluate the effect of aging, 5.000 times of thermocycling were performed, and their result was compared to the 24hours specimen result. Results: The following conclusions were drawn from this study: 1. In the fracture toughness test, temporary crown's fracture line located next to the screw hole while modified designs with metal support showed fracture line on the metal and its propagation along the metal-resin interface. 2. Wing and bulk structure didn't show significant difference in the fracture toughness (p>0.05), but wing structure showed stress concentration on the screw hole area compared to bulk structure which showed even stress distribution. 3. In the fracture toughness test after thermocycling, wing and bulk structure showed increased or similar results in metal supported area while off-metal area and temporary crown showed decreased results. 4. In the strain measurement after thermocycling, its value increased in the temporary and bulk structure. However, wing structure showed decreased value in the loading point while increased value in the screw hole area. Conclusion: Wing type design showed compatible result to the bulk type that its application with composite resin prosthesis to the implant dentistry is considered promising.

• Journal of Korean Dental Science
• /
• v.3 no.1
• /
• pp.25-31
• /
• 2010

This study sought to evaluate the effect of the type of grafts used in sinus lifting. A review of literature through MEDLINE search covering the period 1980 ~ 2006 was performed. After screening, this study was narrowed down to 2,452 patients receiving sinus lift grafts wherein 7,151 implants were placed. In this study, the types of grafts used in sinus augmentation were autogenous bone, allogenic bone, corticocancellous block bone, and various alloplastic materials. The success rate varied from 69% to 100% depending on the graft material type. The highest success rate was reported for the autogenous bone, with high success rates recorded for the most part in most studies.

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.4
• /
• pp.385-393
• /
• 2009

Statement of problem: High stress concentration on the crestal cortical bone has been regraded as a major etiologic factor jeopardizing long term stability of endosseous implants. Purpose: To investigate if the design characteristics of crestal module, i.e. internal type, external type, and submerged type, affect stress distribution on the crestal cortical bone. Material and methods: A cylindrical shaped implant, 4.3 mm in diameter and 10 mm in length, with 3 different crestal modules, i.e. internal type, external type, and submerged type, were analysed. An axisymmetric scheme was used for finite elment formulation. A vertical load of 50 N and an oblique load of 50N acting at $45^{\circ}$ with the implant's long axis was applied. The peak crestal bone stress acting at the intersection of implant and crestal bone was compared. Results: Under vertical load, the crestal bone stress was high in the order of internal, external, and submerged types. Under the oblique loading condition, it was in the order of internal, submerged, and external types. Conclusion: Crestal module design was found to affect the level of the crestal bone stresses although the actual amount was not significant.

• The Journal of the Korean dental association
• /
• v.55 no.2
• /
• pp.128-138
• /
• 2017

Objective: The aim is to evaluate the potential of the mesiodens through the comparative inorganic analysis of 3rd molar teeth prior to clinical study. Material and methods: The extracted mesiodens and the 3rd molar teeth were prepared. The teeth are prepared as in the process of the autogenous tooth bone graft. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis was performed for inorganic analysis. Results: Rough and porous surfaces were observed in all materials in SEM analysis. Ca/P ratio of mesiodens was 1.55 and the 3rd molar was 1.22 in EDS analysis. XRD analysis shows that the 3 main peaks position were similar. This means that the graft materials are very similar to that of the crystallinity. Conclusions: The mesiodens and the 3rd molar teeth are very similar to the inorganic component. These results provide the reasonable rationale that mesiodens can be used as autogenous tooth bone graft in a clinic.

• Journal of Periodontal and Implant Science
• /
• v.27 no.1
• /
• pp.45-59
• /
• 1997

Platelet-derived growth factor(PDGF) has been shown to play an important role in periodontal regeneration. The purpose of the present study was to examine the distribution of PDGF in experimentally created periodontal intrabony defects after flap surgery with various bone graft materials. Six healthy mongrel dogs were used in this study. Three-wall bony defects were created in maxillary and mandibular premolars, inflammation induced by wire ligation and injection of impression material into the defects. Eight weeks later, the experimental lesions thus obtained were treated by plain flap surgery(control group), flap surgery plus autogenous bone graft(autogenous bone group), flap surgery plus Biocoral graft(Biocoral group), or flap surgery plus bioglass graft(bioglass group), which were randomly assigned to the defects. After 4, H, and 12 weeks postoperatively, 2 dogs were sacrificed at each time and 1he specimens were taken for histological examinations and immunohistochemical examinations for PDGF. In the control defects the amount of new bone formation was minimal. In the autogenous bone and Biocoral group new bone was deposited around implanted particles and the amount of new bone was increased with time. A large number of bioglass particles exibited a central excabation and bone formation could be observed in the central excabation as well as around the particles. The expression of PDGF was low in the control group. The expression of PDGF in Biocoral group was increased at 1, H week, but decreased at 12 week. The increased PDGF expression in autogenous bone and bioglass group was maintained to the end of the experiment.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.32 no.2
• /
• pp.154-161
• /
• 2010

Many edentulous posterior maxilla are found to be compromised by alveolar resorption and increased pneumatization of the sinus. One of the surgical procedures to overcome this anatomical limitation is sinus floor elevation with bone graft, which is reported as more appropriate and more successful procedure. Commonly, if the residual bone height is over 5mm, sinus floor elevation is operated through transcrestal approach using osteotome technique. But, it is possible for patients to feel discomfort during operation and dizziness after operation while malleting, sinus floor elevation, using osteotome technique. Some instruments and methods has been used to overcome these problems and use more easily. The aim of this study is to compare between the surgical procedure of sinus floor elevation using Hatch reamer technique and that of sinus floor elevation using osteotome technique. From 2004 Feb to 2007 Oct, we investigate patients (osteotome group: 72, Hatch reamer group: 70) who were given implant surgery with sinus floor elevation (osteotome group: 92, Hatch reamer group: 98). We analysed gender, age, residual bone height, amount of sinus floor elevation, used graft material, total success rate, failure rate by residual bone height and implant type and discomfort during operation, etc. The results obtained were as follows. 1. In the amount of sinus elevation was osteotome group was $3.85{\pm}1.02\;mm$ and Hatch reamer group was $3.93{\pm}1.38\;mm$. There was no statistically significant difference between the two groups (P > 0.05). 2. At the total success rate, osteotome group was 92.4% and Hatch reamer group was 94.9%. There was no statistically significant difference between the two groups (P > 0.05). 3. On the discomfort during the operation by using numerical rating scale, osteotome group was $2.87{\pm}0.83$ and Hatch reamer group was $1.12{\pm}0.64$. There was statistically significant difference between the two groups (P < 0.05). The Hatch reamer group clinical results was similar to osteotome group and we thought that Hatch reamer technique can overcome the faults of osteotome technique.

• The Journal of Korean Academy of Prosthodontics
• /
• v.46 no.3
• /
• pp.255-260
• /
• 2008

STATEMENT OF PROBLEM: Preparation of implant beds with lasers is considered a safe and reliable method, but the accuracy of this technique has not been examined. PURPOSE: The purpose of this study was to evaluate the accuracy and effectiveness of implant bed preparation using an Er,Cr:YSGG laser. MATERIAL AND METHODS: An Er,Cr:YSGG laser was applied to pig rib bone. The laser was employed at a 5.75 W power setting, 30 Hz/sec pulse repetition, and 70 ${\mu}s$ pulse duration with 50 % water and 60% air spray. According to laser tips the groups were divided as follows; Group 1: paralleled - shaped sapphire tip (0.6 mm${\Phi}$), Group 2: paralleled - shaped zirconia tip (0.6 mm${\Phi}$), Group 3: tapered sapphire tip (0.4 mm${\Phi}$). The Er,Cr:YSGG laser tip was separated by 1 mm from the bone and applied for 15 seconds in a non-contact mode. After the application, the bone was sectioned for specimens. Histologic measurements were determined by computerized morphometry. The length of the prepared bone surface was measured and the width of the entrance was measured. The results were analyzed with one-way ANOVA (P<0.05). RESULTS: The prepared length of group 3 was longer than that of group 2. The prepared bone width was larger than the width of the laser tip in every group. Additional bone removal was observed adjacent to the prepared area and displayed an irregular surface. CONCLUSION & DISCUSSION: Different cutting effects were observed according to the laser tip, emphasizing the importance of proper tip selection in the clinical setting. This preliminary study supported the existence of hydrokinetic effects.

• Journal of Periodontal and Implant Science
• /
• v.27 no.2
• /
• pp.329-346
• /
• 1997

Dental implants have been developed for enhancement of osseointegration. Biocompatibility, bone affinity and surface characteristics of dental implants are very important factors for osseointegration. The aim of the present study was to determine the cytotoxicity and the bone affinity of titanium phosphide(Ti-P) implant material. The Ti-P surface was obtained by vacuum sintering of titanium within compacted hydroxyapatite powder. The composition and the chemical change of the surface were determined by Auger electron spectroscopy. The in vitro cytotoxicity was evaluated by the viability of the bone cells and macrophages obtained from chicken embryo and rat,s peritonium, respectively. For the comparative evaluation, 316L stainless steel, commercially pure titanium and Ti-P materials, prepared in size of 1O.0mm in diameter and 5.0mm in height, were immersed separately in bone cells and macrophages for 10 days. For the evaluation of the in vivo bone affinity, 316L stainless steel, commercially pure titanium and Ti-P materials, prepared in size of 5.0mm in diameter and 10.0mm in length, were implanted after drilling in diameter 5.5mm in femurs of 2 dogs weighing 10Kg more or less. Six weeks after implantation the specimens were prepared for histopathological examination and were observed under light microscope. In comparison of in vitro bone cell viability, Ti-P and commercially pure titanium groups were not significantly different from control group (p>O.1), but 316L stainless steel group was significantly lower than control group(p<0.05). There was no statistical difference in the viability of macrophages between 3 different groups and control group(p>O.l). In comparison of in vivo study, 316L stainless steel and commercially pure titanium showed fibrous encapsulation, but Ti-P showed remarkable new bone formation without any fibrous tissue. The results demonstrate that Ti-P has favorable biocompatibility and bone affinity, and suggest that dental implants with Ti-P surface may enhance osseointegration.