The ratio of hydroxyapatite (HAP) to calcium hydrogenphosphate (CHP) in 4 commercial dentifrices, which are denoted to contain HAP and CHP, were calculated from the Ca/P molar ratio obtained from energy-dispersive X-ray microanalysis. The ratios of HAP to CHP in the commercial dentifrices were [0.22 to 0.78], [0.23 to 0.77], [0.25 to 0.75], and [0.47 to 0.53], respectively. From our previous in-vitro studies on brushing of human enamel with commercial dentifrices containing HAP and CHP [0.23 to 0.77], and containing CHP but no HAP [0 to 1.00], we suggest that a larger amount of HAP in dentifrice shows a stronger abrasivity, though the HAP is indicated as an active ingredient not but an abrasive.

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The authors have conducted a turvey to obtain possible causal factors explaining the difficulties in dental treatment of psychiatric patients. The subjects were 53 psychiatric patients who had been treated during the period from Sep. '97 to Oct. '97 in the outpatients or inpatients unit in Karasuyama Hospital Showa University School of Medicine. The authors obtained the following observations of these patients on a first-come, first-served basis.
This survey showed the following aspects of dental treatment ; At intake time, unclear chief complaints, unclear verbalization and unidentified complaints were found. In diagnostic time, the difficulties that the authors found were the elevation of the threshold of patients' perceived pain, patients' general indifference, the degenerated ability of verbal expression and poor oral hygiene. In treatment time, difficulty of patients' opening mouths, difficulty of breathing through nostrils, involuntary movement, occlusion anomaly, negative attitude toward treatment and patients' delusion and fears were observed. In addition, for the difficult points of the oral hygiene, dry mouth, periodontal disease, gingival hyperplasia and deposit of dental calculus could be listed.
Through this survey, possible solutions of difficulties in dental treatment for the patients with mental illness have become more clear. Regarding intake and diagnostic time, it was useful to take enough time to treat and to get patients' information from their families and care takers in order to deal with the difficulties written above. In diagnostic time, the authors found that the majority of the problems found in the dental office could be solved when authors had patients take proper postures. It was, however, often necessary to use mouth gags and restraining belts.

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The patient (17 years old, male) with the missing of maxillary anterior teeth was referred from Prosthodontic Department at Showa University Dental Hospital. The temporary denture was used as the initial orthodontic anchorage and combined orthodontic treatment with the temporary denture and partial bracket system was performed from the beginning of active treatment. The treatment was then continued with multi-bracket system after removal of the denture. The space of 5 missing teeth at the beginning of orthodontic treatment closed into the 2-teeth-space at retention and the functional occlusion was fairly obtained thereafter. However, the mechanics used for the patient was complicated by using both the removable appliance and the fixed brackets ; and the cooperation of the patient had been required continuously. There-fore, the duration of active orthodontic treatment was prolonged.

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Long-term orthodontic treatment and observation have been required often for the patients with anterior crossbite associated with the unexpected growth of the maxilla and mandible. For these patients, two-stage orthodontic treatment has been routinely performed, the treatment of the mixed dentition for the first stage procedure and the treatment after the puberal growth spurt for the second stage procedure. The result and the stability of the first stage treatment affect the difficulties and duration of the second stage treatment.
In this report, we have treated a skeletal class 3 patient with anterior crossbite and crowding, impacting the canine and morphological anomalies of the teeth for 14 years and 6 months. The active orthodontic treatment was initiated at 8 years 8 months of age.
From this treatment, we experienced unpredictable manners of the mandibular growth and development during the post-puberal period. This treatment suggests that to be succeeding the skeletal class 3 treatment need the patient's cooperation and the management of occlusion during post-puberal period at the long-term orthodontic treatment.

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In the case of prosthetic treatment for missing teeth of a patient with severe disturbance of the mouth opening (trismus), we can almost never place an impression tray and a bite plate to the mouth. Therefore, we must treat the patient with a modified technique.
When we applied the silicone bite-impression technique that had been developed for a crown and a bridge, our treatment was successful.
A preliminary impression to make an individual custom tray was taken using the silicone bite-impression technique without a tray. An individual custom tray was made only at the alveolar ridge of the missing teeth. The opposite teeth registrations were made with a selfcuring resin on the occlusal table of the individual custom tray.
A final impression was taken with the silicone bite-impression technique using the individual custom tray. A functional impression of the alveolar ridge was taken using the individual custom tray and the injection type silicone impression material. An anatomical impression of the teeth was taken with the putty and the injection type silicone impression material.
Since the impression and the bite were accurately taken using our modified silicone biteimpression technique, the removable partial denture could be made and placed to the mouth of the patient with severe disturbance of the mouth opening.

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