The choice of statistic methods and interpretation of these results are annoying issues to accomplish clinical epidemiologic researches. Especially beginners who have less experience in conducting clinical studies would often feel difficulty due to the mental hurdle of these statistical procedures. However, the major principles of clinical epidemiological research were setting of hypothesis and study design, thus predictor variables, outcome variables and related statistical methods would be automatically determined after decision of these steps.
In this article, the essential knowledge to start clinical study such as various type of variables, selection of statistical procedures was reviewed following the previous review article that mainly focused on study designs.

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Purpose: The aim of this research was to obtain an objective grasp of the surface properties of titanium castings which are polished using a titanium polishing method developed by our university.
Methods: The specimens were cast conventionally using commercially pure (CP) titanium (Grade 3, T-alloy H, GC). The cast surfaces were polished using two methods; a conventional procedure for mirror surfaces and a modified procedure consisting of minimal grinding foracceptable fit of the inner surface. The center line average roughness (Ra) wasmeasured, and then qualitative analysis and map analysis were performed using Electron Probe X-ray Microanalysis. In addition, map and line analysis on sections of the as-cast titanium specimens was performed, and the Vickers hardness of the surface was measured. As controls, Au-Pt alloy and Co-Cr alloy specimens were analyzed.
Results: The Ra on the titanium inner surface was 1.52 μm, which was approximately four times higher than that on the mirror surface, and approximately two times higher than that for the Au-Pt alloy and Co-Cr alloy. The qualitative analysis of the titanium mirror surface detected elements such as C, Si, and Al as well as the ingot element. In addition, P was also detected on the titanium inner surface. The Vickers hardness was highest on the outermost surface layer, which decreased remarkably until a depth of 100-150 μm.
Conclusions: It was considered that the mirror surface formed by the titanium polishing method in our university obtained a level equivalent to that of precious metals. However, a reaction layer and elements derived from the investment material remained in the titanium inner surface.

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Purpose: In daily clinics, appropriate examination of thebuccolingual residual ridge shape is critical for complete denture treatment. To clarify the possibility of establishing standards for improving the reproducibility of objective evaluations, the relationship between conventional subjective evaluation by several dentists and objective evaluation by model measurement was evaluated.
Methods: The right and left first molar regions in study models (100 sets) of edentulous maxillas and mandibles were evaluated.
Subjective evaluation using a four-grade scale (U shaped, U-V shaped, V shaped, flat) was performed by sixteen dentists (eight with less than 3 years of clinical experience, eight with more than 7 years of clinical experience).
Objective evaluation (breadth of the residual ridge) was performed with digital vernier calipers. The relationship between objective evaluation and subjective evaluation was studied.
Discrimination values for objective evaluation were determined at changeover points for each rate of subjective evaluation.
In addition, we studied agreement between subjective evaluation and objective evaluation as determined by the discrimination values.
Results: Marked variation was noted in subjective evaluation depending on the individual and number of years of clinical experience. Discrimination values were obtained from subjective evaluation by the dentists with more than 7 years of clinical experience: for the maxilla, “V” and “U-V” were 7 mm and “U-V” and “U” were 9 mm; for the mandible, “V” and “U-V” were 5 mm and “U-V” and “U” were 7 mm. Agreement of the subjective evaluation based on these discrimination values was extremely low regardless of the individual's clinical experience.
Conclusions: Reproducibility of subjective evaluation of the residual ridge shape was low. Thus, we need to establish a reproducible and more universally effective evaluation method of residual ridge examination.

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Purpose: The purpose of this study was to examine reliability, construct validity and convergent validity of a pilot questionnaire, aimed to measure the intention of edentulous individuals to wear dentures, in a multi-center investigation.
Methods: Three hundred and eighteen patients who visited the Nihon University Dental Hospital at Matsudo and surrounding private dental clinics participated in this multi-center investigation by using a pilot questionnaire developed earlier from a qualitative study. Factor analysis was used to examine construction of questionnaire items. Internal consistency and construct validity were examined by Cronbach's alpha of each factor. Pearson's correlation coefficient was used to examine convergent validity by analyzing the correlation between intention to wear dentures and total score of the final questionnaire.
Results: As a result of factor analysis followed by analysis of internal consistency, four components were chosen to construct the final questionnaire: sensation, unpleasant matter, general state, and human interaction, resulting in Cronbach's alpha ranging from 0.59 to 0.91. A positive correlation was found between intention to wear dentures and total sum score of the final questionnaire. A significant correlation was found between intention to wear upper dentures and maxillary and mandibular partial denture wearer (r=0.30), intention to wear lower dentures and single maxillary denture wearer (r=0.28), maxillary and mandibular partial denture wearer (0.33), maxillary and mandibular complete denture wearer (r=0.30).
Conclusions: The final questionnaire constructed from 37 items covering four components was verified to be a valid and reliable clinical measure to grasp the intention of edentulous individuals to wear dentures.

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In 9 healthy dentate and 8 complete denture wearers, the hardness and adhesiveness of bolus after chewing in swallowing threshold was measured by the creepmeter.The number of chewing stroke until swallowing threshold was also counted in order to investigate the relationship between character of bolus and masticatory function. Masticatory performance of each subject was measured by the sieving method suggested by Kapur et al.
The results obtained are as follows.
1. As to the hardness of bolus after chewing in swallowing threshold, there was no significant difference between 9 healthy dentate and 8 complete denture wearers (P>0.05).
2. As to the number of chewing stroke, there was significant difference between 9 healthy dentate and 8 complete denture wearers (P<0.01).
3. In complete denture wearers, it seems that lower masticatory performance was compensated by increasing of number of chewing stroke until swallowing.
4. In 9 healthy dentate and 8 complete denture wearers, there was negative correlation between masticatory performance and number of chewing stroke until swallowing.
Form these results, it was suggested that the number of chewing stroke is useful as the parameter to evaluate masticatory function in complete denture wearers.

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Purpose: Optical properties of the incisal edge of natural teeth were investigated in terms of translucency and shade of color, and compared with optical properties of the dental ceramic system, and the relation between the translucency and hue was analyzed.
Methods: Using a multi-spectra camera system (MSC-2000), incisal edge areas of the spectro-reflectance of 175 natural teeth and 66 types of shade guides, and 25 incisal ceramic samples selected from 4 types of ceramics were measured under conditions of free-standing (no background), black background, and white background, to calculate L^*, a^*, b^*, C^*, and Translucency Parameter (TP). From the coloring numbers obtained, L^*, a^*, b^*, C^*, and TP in incisal edges of natural teeth, those of shade guides, and incisal ceramics were compared to evaluate the relationships between TP and L^*, a^*, or b^*.
Results: Compared with incisal edges of natural teeth, the value for L^* was low in that of shade guides, and the value for C^* was low in incisal ceramics. The values for a^* and b^* were distributed in a narrow range in shade guides and incisal ceramics. No correlations were noted between TP and L^*, a^*, or b^* in incisal edges of natural teeth and those of shade guides. Incisal ceramics showed a correlation between TP and L^*, and no correlations were noted between TP and a^* or b^*.
Conclusion: The shade of color in the incisal edges of natural teeth was widely distributed in both brightness and chroma, and translucency was higher in each shade tub than in incisal edges of natural teeth. In incisal edges of natural teeth and each shade tub, translucency and hue were mutually independent factors.

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Purpose: We designed a method of making a coping for the all-ceramic crown by firing porcelain of infiltrated Al203. This method does not need any particular apparatus or refractory cast, and can be completed in a very short sintering time. We investigated the possibility of clinical application.
Methods: Materials of the coping were two kinds of alumina with different diameter, glass powder for infiltration, lithium silicate glass and ammonium silicate. We investigated the crystal structure by XRD and the fractured surface by SEM, and measured the amount of marginal space after sintering and glass infiltration when the coping was returned to the master cast.
Results: Time necessary for completing coping by this method was about 4 hours. The coping was cornposed of alumina. Ammonium silicate was changed into glass by sintering, and the space between alumina particles was decreased by sintering. Furthermore, it disappeared by glass infiltration completely. The marginal space was 46-114 μm after sintering and 84-161 μm after glass infiltration.
Conclusions: This method of making a coping is very easy and quick, and the amount of marginal space is clinically allowable.

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Patient: In addition to crown and bridge detachments, a patient suffered from masticatory dysfunction and discomfort resulting from poor-fitting dentures. Masticatory dysfunction was resolved by the use of provisional dentures and re-adjustment of existing dentures. Treatment was initiated from the mandible where changes before and after the treatment were less significant. After confirming a good fit for the lower denture, treatment of the maxilla was started. Crowns with hard resin facings were fabricated, and the connectors and retainers for the partial denture were re-designed to eliminate the cause of discomfort.
Discussion: Efforts centered on attaining optimal retainers and connectors that would relieve the patient's discomfort. We implemented a step-by-step treatment plan while continually monitoring the patient's satisfaction, which contributed to the success of the treatment.
Conclusion: Partial dentures have some design allowance to accommodate requirements specific to each individual patient. Optimally designed partial dentures was proven to deliver high patient satisfaction.

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Patient: A 73-years-old male complained of food stuffing for at anterior tooth and aesthetic disturbance. The diagnosis was stagnation of food which occurred to 3/3 secondary caries and aesthetic disturbance caused by non-conformity of the margin. After extraction of135, an immediate denture (5+5) was inserted. In addition, 3 was extruded by removal the partial denture as an anchorage.
Discussion: The clasp of the upper first molar was broken three years after prosthetic treatment. After that, there has been no specific trouble.
Conclusion: Removal of the partial denture was used as an anchorage to apply the orthodontic extrusion method over the maxillary left side canine. Through this method, we were able to perform conservative procedures for the treatment of the deep caries lesion observed on this tooth. Once the extrusion was completed, we could restore this tooth through prosthetic treatment. Long term good results were achieved.

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Patient: A 56-year-old female with bilateral distal extension missing in the mandible after severe periodontal abscess in the left submandibular area. A chief complaint was masticatory dysfunction. Insertion of a removable partial denture was considered in terms of its retention and its effect on periodontal disease with the goal of recovery of masticatory function.
Discussion: After installing removable partial denture, the surface area of a gummy-jelly bolus increased 2, 090 mm² after 30 chewing strokes, indicating sufficient masticatory performance. Moreover, four years subsequent to treatment, the surface area had increased to 2, 700 mm² and thus the masticatory performance had been retained well.
Conclusion: The masticatory performance of a patient with the bilateral distal extension missing in the mandible was improved and retained using a removable partial denture.

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Patient: The patient was a 63-year-old edentulous female with complaints of soreness of the underlying mucosa and masticatory disturbance. Both maxillary and mandibular alveolar ridges inclined anteriorly, and the anterior half of the maxillary alveolar ridge was flabby. After partial resection of the flabby ridge in the bilateral premolar regions, oral condition could be kept functionally stable with a set of dentures with a cross-bite arrangement of artificial molars. Although another set of dentures was needed seven years later because of aesthetic problems, the prognosis remains favorable eight and a half years after treatment.
Discussion: In this case, the cross-bite arrangement was quite effective in stabilizing the dentures. The patient did not complain of difficulties with speech or any other problems that were expected.
Conclusion: In this case, partial resection of the flabby ridge and cross-bite arrangement of artificial molars were effective for a favorable prognosis.

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Patient: A 21-year-old female patient with masticatory and esthetic problems due to injury visited our dental hospital. The patient was diagnosed as full dislocation of the maxillary incisor teeth, and laceration of the lips. Implant rehabilitation was therefore performed for esthetic and functionary recovery.
Discussion: After prosthodontic treatment, chipping of the maxilla incisor teeth restored with porcelain by premature contact and extrusion of the mandibular incisor teeth can be prevented by occlusal adjustment during periodical recall.
Conclusion: The patient was satisfied with the implant treatment, and implant rehabilitation is useful for treating a missing maxillary incisor due to injury and problem teeth in a crown root ratio by orthodontic treatment.

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Patient: The patient was a 62-year-old man with both missing teeth and teeth that needed to be extracted. His major complaint involved problems of aesthetic and masticatory function. After the maxillary anterior teeth were extracted, fixed and removable partial dentures were delivered for the maxillary and mandibular jaws, respectively. This clinical report describes the effectiveness of this patient's prosthetic rehabilitation and maintenance for 10 years.
Discussion: Using provisional restorations and treatment dentures, definitive prostheses could be well designed. Long-term satisfactory progress would be achieved since he properly managed his oral health and a fixed prosthesis was delivered to the maxillary anterior. However, various problems may arise in the future due to aging.
Conclusion: The collapse of occlusion was prevented by appropriate prosthetic rehabilitation for 10 years.

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Patient: A 55-year-old male visited our dental hospital with the chief complaint of having lost his ability to chew properly and inadequate anterior esthetics. This case report presents the result of occlusal reconstruction. The final prosthesis was restored in February 2001. A good prognosis was obtained during 5 years.
Discussion: Occlusal reconstruction using stabilized condylar position enabled the complicated oral situation to be improved functionally and esthetically. Furthermore, orthodontic treatment and periodontal surgery ensured hygiene and achieved highly esthetic restorations.
Conclusion: When occlusal reconstruction is needed, orthodontic treatment and periodontal surgery are necessary to improve esthetics and malocclusion prior to a prosthodontic approach.

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