Purpose: Along with the reform of dental education for students, the program of pre-clinical practice in prosthetic treatment for edentulous patients was improved in 2006. The purpose of this study was to assess the educational effects of the new program of pre-clinical practice in comparison with the old program.
Materials and Methods: The subjects of the study were 4th-year students during the period of 2005 to 2007. After pre-clinical practice in complete denture treatment was completed, the questionnaire was carried out. The questions were as follows: 1) Do you think you will be able to carry out the treatment or operation for a patient in the clinical training? 2) Was the pre-clinical practice useful as a supplement to lectures? Although laboratory techniques were the main contents of pre-clinical practice in complete denture treatment in 2005, clinical skills took precedence in 2006. Moreover, both the clinical skill and the laboratory technique were programmed in 2007.
Results: In 6 items regarding clinical skills, the number of students who answered “I think I will be able to carry out the treatment or operation” or “pre-clinical practice was useful as a supplement to lectures” increased year by year. Moreover, in 23 items regarding pre-clinical practice, there were significant differences in researched two years.
Conclusion: It was suggested that the new program of pre-clinical practice in complete denture treatment was useful for acquirement of knowledge and technique.

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Purpose: Electroformed coping has a high adaptability and biocompatibility. Olympus Castable Ceramics (OCC), which is applied on castings using the lost wax technique, resembles tooth substance and also is biocompatible. Prior to developing new crown restorations using these characteristics to obtain a reinforced mechanical interlocking force between the sandblast gold frame and OCC, the effect of different thicknesses of reinforcement was analyzed using the coping fabricated by Galvano forming.
Methods: To evaluate interlocking force, the reinforced effect of OCC was examined for three thicknesses of gold frame: 150, 250 and 350 μm, which were then compared with the value of single OCC.
Results: In the three-point flexural strength test, only the sandblasted and 250-μm gold frame specimen showed a significant high value. Observing and analyzing the fractured and exfoliated surface, the sandblasted gold foil surface showed a rough texture which easily exerts an interlocking force but no chemical bonding effect.
Conclusion: Chemical bonding could not be expected and mechanical surface treatment of the gold frame is essential for reinforcement for both materials. The sandblasted 250-μm thick gold frame proved to be the most effective.

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Purpose: Using the QFD method, this study investigated the prioritisation of criteria used for the selection of artificial teeth. The study compared the approach of dentists and dental technicians and the prioritisation of different workplaces.
Methods: A preliminary questionnaire was prepared to determine what criteria were used in selecting artificial teeth. A questionnaire was then prepared based on the 19 criteria for selecting artificial teeth determined by the preliminary survey. This survey was conducted according to the VAS method.Participants were asked to prioritise the relative importance of the 19 selectional criteria determined by the preliminary survey. The participants consisted of 40 dentists (19 university dentists: 21 dentists in private practice) and 27 dental technicians (15 university technicians: 12 technicians in private practice).
Results: For anterior teeth, the prioritisation of the selectional criteria was very similar among all groups. There were differences with regards to the prioritisation of selectional criteria for posterior teeth.University dentists and technicians had only a few selectional criteria whose proritisation correlated. However, both dentists and technicians in private practice had many criteria whose priority correlated. When principal component analysis is conducted, the contribution ratio of main component 2 was 60% for dentists. Main component 3 had the highest contribution ratio for technicians, an explanation of which is possible.
Conclusion: There was no clear difference in the prioritisation of selectional criteria between dentists and technicians, or between workplaces for anterior teeth. With respects to posterior teeth, university dentists and dental technicians placed a greater priority on the accuracy of occlusion, whereas dentists and dental technicians in private practice put a higher priority on natural sensation. University dentists and dental technicians showed various tendencies with respects to the prioritisation of selectional criteria. Dentists and dental technicians in private practice require artificial teeth which are stable and are in harmony with the patient's natural teeth.

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Purpose: The gingival line is very important for esthetic appearance. This paper describes a new prosthetic technique, the biological tissue adaptation (BTA) technique, to align the gingival line, without orthodontic treatment or surgical crown lengthening which require flap surgery and ostectomy, and maintains a healthy gingiva without rebounding over the long term.
Technique: The gingivectomy is performed with an electrocautery knife at the position of the gingival line taking into consideration both esthetic appearance and biologic width. In principle, the abutment tooth margin is prepared on the same line as the performed gingival line. In forming the prosthesis, the margin should be perpendicular at the surface of the tooth with the same thickness as the wounded gingival tissue. In other words, the shape of the prosthesis is overhanging the gingival tissue.
Discussion: All 17 cases maintained healthy gingiva without rebounding or other major complications. This appeared to be because the biologic width was reestablished in three dimensions, and plaque accumulation and bacterial invasion can be prevented, because the gingival tissue adapts tightly to the margin of the prosthesis-formed overhang. In addition, the immune system may be superior because the bloodstream is not compromised due to the thick gingival margin, thus the periodontal surroundings biologically seemed to be preserved better.
Conclusion: The BTA technique has many advantages as a prosthetic technique in order to align the gingival line, and can maintain a healthy and esthetic gingiva over the long term.

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Patient: A 66-year-old female complained denture mobility and poor mastication. She had edentulous maxillar and the nearly edentulous mandible with extruded right canine and two remaining roots. Denture stabilizer had been incorrectly accumulated in layers to the maxillary denture. As results of examination, the patient was diagnosed with masticatory disorders due to maxillary denture mobility caused by the extruded mandiblar right canine. The maxillary complete denture, in which occlusal contact in the anterior tooth area was avoided, and a mandibular overdenture were placed. Questionnaires regarding masticable foods were used to evaluate the treatment effects.
Discussion: It was considered that masticatory disorders were occurred due to the patient's long-term misuse of denture stabilizer to increase the mobility of the maxillary denture raised by the mandibular canine.
Conclusion: Denture retention and stability were achieved by establishing appropriate denture base morphology, occlusal height, mandibular position, artificial teeth arrangement, and molar occlusal contact.

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Patient: An edentulous female complained of masticatory dysfunction. The mandibular residual ridge was observed severe resorption. The case was diagnosed as decreasing the occlusal vertical dimension and losing the retention and stability of mandibular complete denture. The occlusal vertical dimention was increased in new denture, and the position of artificial tooth arrangement and shape of the polished surface were determined using the flange technique.
Discussion: The border movement of mandible had expanded on gothic arch tracing and the mandible position changed to postero-inferio position compared to that before treatment by analysis of lateral cephalograms, due to an increase in the occlusal vertical dimention. It was considered that masticatory dysfunction was improved by gaining the retention and stability of mandibular complete denture.
Conclusion: Fabrication of a new denture with an appropriate occlusal vertical dimension and using the flange technique achieved a favorable prognosis in this case.

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Patient: A 39-year-old woman complained of tooth mobility and pain caused by root resorption in the upper left central incisor. The tooth was extracted by preserving as much of the periodontal tissue in the tooth cervix as possible. Implant placement was performed, and approximately five months later, an all-ceramic crown was set.
Discussion: We were able to create an ideal gingival emergence profile by taking an impression of the extracted tooth and incorporating the morphology of natural teeth into the provisional restoration, which enabled the prevention of gingival recession. In addition, the use of zirconia abutment onto which pink porcelain was sintered also contributed to the favorable outcome as it gave consideration to aesthetics from the perspective of gingival permeability.
Conclusion: We were able to prevent gingival recession which is commonly seen following placement of implant prosthesis in thin scalloped gingiva, and an aesthetically favorable outcome was obtained.

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Patient: An 85-year-old male with edentulous jaw developed dysmasesis and dysphagia after ostectomy of the mandibular border for a tumor of the mouth floor and immediate reconstruction with the cervical flap. An implant-supported fixed prosthesis and a palatal augmentation prosthesis(PAP) were fitted in the mandible and maxillary, respectively.
Discussion: The anatomical form of the mandible was damaged by tumor resection and the lower lip turned towards the tongue; therefore, a fixed upper structure was used for the mandible. Maxillary PAP installation supported the oral stage of swallowing, which was disturbed by expansion of the oral cavity proper with an increased height of articulation. Sufficient contact pressure for swallowing was obtained between the tongue and palate.
Conclusion: A patient with edentulous jaw after resection of an oral-floor tumor showed improved masticatory and deglutitive functions after installation of an implant-supported fixed prosthesis in the mandible and a PAP in the maxillary.

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