It has been our consensus opinion to start prosthetic treatment when a patient has lost his or her posterior molars (premolars) as soon as possible after the healing of the residual ridge by varioustypes of fixed, implant and mainly removable prostheses. This has been our so-called “Golden rule”in teaching our students and in our clinical practice for patients for many years. But it is also true thatmany prosthetic devices quickly fall into disuse after initial treatment due to various lesions such ascaries, periodontitis and the resorption of the residual ridges. In view of thesenegative aspects inwearing removable partial dentures, a group of researchers in the Netherlands came to advocate the“ Shortend dental arch (SDA)”; The Dentist need not provide the posterior occlusal support composedof two molars if the patient has sufficient occlusal support till the second premolar. This concept of SDA now prevails in Northwestern Europe and parts of the USA even at the educational level. Thispaper discusses the concept of SDA and analyzes the structure of it, the difference from the conventionalconcept of occlusal support and the possible risk, based on the first symposium on this problemheld in our Society in May 2003.Key wordsshortened dental arch (SDA), occlusal support, treatment modality, partial edentualism, prostheticintervention

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Literatures on the shortened dental arch (SDA) concept were reviewed. Clinical data demonstrated that the SDA is one option as a treatment goal in the majority of patients, meeting the requirement offunction, aesthetics, and stability. However, most of the data were obtained from limited types of SDA (OU: 3-5), in a rather small number of patients, and published by a certain research group.Future research is required with a large sample in a multi-center trial and with longitudinal design toimprove the scientific evidence.

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It is well known that implant treatment based on the concept of osseointegration is an effective option in contemporary dentistry. The original protocol of the Brånemark system recommends the shortened dental arch (SDA) in a totally edentulous jaw. Several Japanese patients were unsatisfied with thelack of second molars in terms of masticatory function and self-confidence. The author started theapplication combined with anterior and posterior fixtures even in the totally edentulous jaw in orderto restore second molars in 1985. There were thought to be some disadvantages of such applicationin the beginning, but these were verified by the long-term clinical cases to be imaginary. Furthermore, restoration with second molars brings functional and mental satisfaction to patients. Installation intomaxillary tuberosity, pterygoid process and/or palatine process has been done and shows excellentresults. This paper discuss several options of design of the superstructure, in order to avoid SDA thatis not acceptable for old-fashioned prosthodontists.

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Purpose: In the last two decades, the Shortened Dental Arch (SDA) concept has been introduced as a treatment strategy for posterior edentulous patients; i.e. there is no need to restore the missing partof the molar region. On the other hand, clinical experience suggests various possibilities for functionaldisturbance starting from instability of occlusion. The purpose of this study was to clarify whetherthe SDA concept applies to all posterior edentulous patients.
Study selection: Ten patients with unilaterally posterior missing teeth were enrolled in this study, anda multiple evaluation for SDA condition was applied to them. This evaluation consisted of anobjective evaluation (radiographic evaluation for temporomandibular joint and measurement ofcondylar displacements during maximum voluntary clenching) and a subjective evaluation (questionnaire).
Results: Abnormal radiographic appearances in the edentulous-side condyle were observed in 50% ofsubjects. Condylar displacements during clenching were significantly high in the edentulous-sidecondyle compared to that in the dentulous-side condyle. 40% of subjects showed a high level ofcomplaints for SDA conditions.
Conclusions: These results indicated the potential risks for the oral functions. We propose thatclinical guidelines be developed for deciding whether to adopt a “Wait and See” approach for the SDApatients without any positive treatment, or to start prosthetic intervention immediately.

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Patient: A case report of a 14-year-old girl complaining of an esthetic problem due to enamel hypoplasia is presented. Her father and grandmother showed the same problem in their teeth.Although none of the primary teeth had showed enamel hypoplastic status, all of her permanent teethhad a dark brown rough surface. The patient was referred to our clinic in January 1999 at thecompletion of permanent teeth eruption. Laminate veneers were set for the upper incisal and canineteeth to improve the esthetic problem, while composite resin fillings were appliedto the lower teeth forfinancial reasons. Seventeen months later, laminate veneers were set for the lowerincisal and canineteeth at the request of the patient. It has been 3 years since the laminate veneers were set, and noproblem has been found so far.
Discussion: Although gum recession is to be expected in a person of her age, her concern wasimprovement of the color and shape of the teeth. She understood the necessity of future treatmentagainst possible recession. For these reasons, our strategy gave priority to improving the estheticproblem over future gum recession.
Conclusions: The treatment with laminate veneers improved not only the esthetic problem but alsoquality of life associated with an inferiority complex due to unusual tooth color.Since few cases havebeen reported in terms of laminate veneers for enamel hypoplasia, long-term follow-up will be neededfor this patient.

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Purpose: We aimed to know the most effective surface treatment in repair restoration of light cured type of the high filler containing indirect composites.
Method: Indirect composite specimens (2×2×12.5mm) were made of Artglass (AE, AD) and Gradia (GE, GD). Specimens (2×2×25mm) for the bending bond strength test were made of indirect composite specimens and repair resins such as Charisma or Unifil S for the direct method and AE or GE for the indirect method. All resins were polymerized according to the manufacturer's instructions. Four kinds of surface treatments to the bonding surface were used as follows: no treatment (NT), silane treatment (S), bonding treatment (B), silane+bonding treatment (SB).Bending bond strength was determined by the three-point bending test after 24 hours storage in distilled water (37°C).
Results: In the direct method, significantly higher bending bond strength was recognized in SB for AE and in SB for AD, GE and in SB and B for GD (one-way ANOVA, p<0.05). On the other hand, in the indirect method, significantly higher bending bond strength was recognized in SB and S for AE, in SB for AD, in SB, S and B for GE and GD. SEM observation of the adhesion surface after bonding test showed adhesive failure in NT and cohesive failure in SB, S and B.
Conclusions: SB were effective surface treatments in both direct and indirect repair restorations of AE. SB, S and B were effective surface treatments in indirect repair restorations of GE.

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Purpose: This study compared masticatory ability between dentulous subjects and denture wearers in the elderly measured by multiple evaluation methods.
Methods: The subjects were all elderly, with 23 dentulous subjects and 23 denture wearers. The evaluation methods of both groups were measurements of masticatory ability by the biting of artificial capsules, maximal occlusal force using the Occlusal Force-meter ^®, occlusal force and occlusal contact area using the Dental Prescale ^®, and a questionnaire on difficulty in eating 35 kinds of food.
Results: The average values of masticatory ability of the dentulous and denture-wearing groups on the habitual side measured by artificial capsules were 8.41×10-²J and 1.53×10-²J respectively. There was no statistical significance between habitual and non-habitual sides of both groups. The average values of maximal occlusal force on the habitual side on the posterior teeth region measured by the Occlusal Force-meter ^® were 418.91 N and 74.67 N respectively. There was also no statistical significance between habitual and non-habitual sides of both groups. The average values of occlusal force measured by the Dental Prescale ^® were 286.35 N and 21.09 N respectively. The average values of occlusal contact area measured by the Dental Prescale ^® were 48.32 mm² and 3.36 mm² respectively.The average scores measured by the questionnaire on eating 35 kinds of food were 95.63 and 68.19 respectively.
Conclusions: The dentulous group received a higher score than the denture-wearing group in all masticatory ability tests. The results showed that the dentulous group had 6.2 times to 14.4 times the masticatory performance compared to the denture-wearing group in the objective tests (artificial capsules, Occlusal Force-meter^®), Dental Prescale ^®, and in the subjective test (questionnaire about eating foods), the results showed that the dentulous group had a 1.4 times higher score than the denture-wearing group.

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Purpose: The present study reviewed information obtained by conventional methods for analyzing condylar movement, and investigated the merits of 4-dimensional analysis compared to conventionalmethods.
Methods: Numerous studies have already reported on conventional methods for volunteers orpatients. The aim of this study was to describe the characteristics of each method. A patient withtemporomandibular dysfunction was therefore selected as the subject of this study. Mandibularmovement was recorded using a 6-degree-of-freedom jaw-tracking device, and the incisal and condylarpoints and bilateral first molars were selected as points of analysis. The skull and mandible werereconstructed from a computed tomography (CT) dataset into 3-dimensional images, and mandibularmovement data were applied to these images (4-dimensional analysis).
Results and Discussion: Large amounts of information were obtainable by analyzing mandibularmovements using conventional methods. Stick figures comprising the occlusal plane connected tobilateral condylar points were useful for understanding mandibular movements as a whole. Inaddition, condylar movements on the working side that are actually very difficult to record wereclarified by describing the movements of anatomical condylar points. Relationships between anatomicalstructures and mandibular movements were elucidated using 4-dimensional analysis. This methodtherefore seems useful for diagnosing and treating patients with or without temporomandibulardisorders.
Conclusions: Conventional methods provide sufficient information to grasp the conditions of thetemporomandibular joint, but 4-dimensional analysis offers opportunities not available with othermethods.

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Purpose: This experiment observed the conditions existing in the resting mandibular frontal-lingua alveolar mucosa, and the conditions under pressurization using a laser-Doppler blood flowmeter.
Methods: A special splint was used for the measurement of blood flow. Eighteen measuring pointswere set up at the lingual alveolar mucosa between the right and left canines. The area of pressurizationdivided the upper and lower alveolar mucosa into three. There were 4 conditions of pressurization: 3 positions, upper pressurization which pressurized only the upper part, downward pressurizationon 2 positions, and lower pressurization which pressurized only the lower part. The mucosal thicknessof the measuring points were measured by SDM (Schleimhaut-Dicken-Meβ).
Results: Though no difference was found laterally, there was a difference between the upper andlower parts. The blood flow in the floor of the oral cavity was about 1.8 times that in the gingivalmargin division. Thus, the blood flow in the floor of the oral cavity increased whenever pressure wasapplied to any part of the lingual alveolar mucosa. The average mucosal thickness of the 18 positionswas 0.83 mm.
Conclusions: The blood flow in the lingual alveolar mucosa showed no difference laterally at rest, butthere was a difference between the upper and lower parts in that the lower parts received a greateramount of blood flow and the blood flow in the upper parts was more sensitive to the pressure.

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Purpose: This study compared the reliability levels of the saliva-based bacterial counts assessed by commercially available caries risk tests, Dentocult^® and CRT^® systems.
Methods: Thirty-five healthy adult subjects (mean age 24.8±1.98, mean DMFT 9.4±4.6) were selected from the sixth-grade students (70 students in total) in Okayama University Dental School. At an interval of 10 minutes, stimulated saliva samples were taken twice and incubated to evaluate salivary Streptococcus mutans (SM) and Lactobacilli (LB) counts in each system. Salivary bacterial counts were scored into four classes by five calibrated examiners with the aid of an estimation guide for each system. Based on these scores, the intra- and inter-examiner reliability levels were estimated by using a weighted kappa index.
Results: Mean kappa indexes for intra-examiner reliability were 0.71, 0. 80, 0.86 and 0.54 (Dentocult SM, CRT^®SM, Dentocult^® LB and CRT^® LB, respectively) and mean kappa indexes for interexaminer reliabilities were 0.57, 0.75, 0.72 and 0.44 (Dentocult^® SM, CRT^® SM, Dentocult^® LB and CRT^® LB, respectively). After data reduction selecting a median value among the five examiner estimates, kappa indexes for the reliability of each microbial assessment were calculated as 0.51, 0.92, 0.83 and 0.79 (Dentocult^® SM, Dentocult^® LB, CRT^® SM and CRT^® LB, respectively).
Conclusions: These results suggested that both systems had sufficient reliability for assessment of salivary bacterial counts in adult human subjects. Even with a simpler incubation schedule, the CRT^® system has the same level of clinically acceptable reliability as the Dentocult^® system.

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Purpose: The purpose of this study was to develop a new jaw tracking system with six-degree-offreedom, which had a simpler structure and eary operation.
Materials and Methods: 3 SPACE^®FASTRAK^®(Polhemus Inc.) was used to construct a new jaw tracking system. This system consists of a transmitter, two sensors, a system electronics unit, and a personal computer. Two sensors are fixed on the labial surface of upper and lower incisors by using a resin splint. When the transmitter and the sensor were positioned 300 mm apart, total measurement errors were revealed to be minimum and these values for distance and for angle were less than 100μm and 0.2 degree, respectively.
Discussion: Comparing the system with other jaw tracking systems on the market, the advantages of the system are: 1) since the sensor is small and lightweight, this apparatus causes minimum interference to the subject during measurement; 2) the mandibular movement can be reproduced as a movie on the CRT just after completing the measurement; 3) the kinematic axis can be automatically searched by using an original software.
Conclusions: A newly designed measurement system with six-degree-of-freedom was developed based on a low-frequency magnetic transducing technology. Both the hardware and software of the system showed good performance and high accuracy.

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Purpose: This study examined whether coating the keeper in a magnetic attachment system with a layer of gold can ensure cast-joining to a Ag-Pd casting alloy containing 12% Au without a gap.
Methods: A commercially available gold-coated keeper and experimental keepers with or without gold coating were used. The experimental keepers were specially fabricated from soft magnetic stainless steel that was identical to that used for a commercially available gold-coated keeper; they were then coated with a layer of gold (4 or 10μm thick). A commercial Ag-Pd alloy containing 12% Au was used for cast-joining. Each keeper with a wax rod was invested, and the wax pattern was burned out at 700°C. The Ag-Pd alloy containing 12% Au was then cast according to conventional laboratory procedures. The tensile cast-joint strength of the specimens was measured using a universal testing machine in air at room temperature. Also, the cross sections of the cast-joined specimens were examined by electron probe microanalysis.
Results: The joint strength test showed that all the gold-coated specimens, including the commercially available gold-coated keepers, had significantly greater cast-joint strength than those without gold coating. A gradual decrease was observed in the concentration of gold from the layer of gold on the keeper to the Ag-Pd alloy containing 12% Au surface. Close contact between the cast alloy-without the presence of an oxide layer- and the surface of the keeper was seen at the cast-joined interface area in the specimens made with gold-coated keepers.
Conclusions: The presence of the gold layer seems to minimize the formation of oxide films on the keeper during the casting process. This may be the main reason for an increase in the cast-joined strength of the gold-coated keepers to the cast alloy used.

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