Shuji Ohkawa

Changes in retention of various telescope crown assemblies over long-term use

An investigation was done on the effect of crown height, angle (one-half taper) and number of removals on the retention of telescope crowns. Assemblies of inner and outer crowns were constructed on master dies. Crown heights of 4 mm, 5 mm, and 6 mm were used. Cone angles of 0, 2, 4, and 6 degrees were used for each of the three heights. The inner crowns were fixed to the dies with an adhesive agent. the outer crowns were set over them and placed in a clamp. Separation forces were tested with an Instron machine (Instron Corp., Canton, Mass.). They were measured initially and after numerous 100 insertion/separation cycles up to 1000 cycles and numerous 500 insertion/separation cycles up to 10,000 cycles. The results demonstrated that the cone angle of the inner crown was more important than its height for maximum retention. Retention is rapidly lost after the cone angle exceeds 2 degrees. It was also shown that an accessory device is necessary to maintain retention capabilities after long-term use.

A new telescopic crown system using a soldered horizontal pin for removable partial dentures

Clinical and laboratory procedures used in a new telescopic system for removable partial dentures are discussed. This system uses 2-degree tapered inner and outer crowns with a horizontal pin soldered into the outer crown. The pin is easily adjusted to monitor the level of retention for the telescopic crown after long-term use of dentures.

A New Protocol for Diagnosis and Treatment of TM Disorders.

A new protocol for classifying of TM disorders was developed in order to classify the types of TM disorders followed by the criteria of Japanese Society for Temporomandibular Joint.This protocol consists of following several characteristics.1. It may be possible to shorten filling up time because of a filling up way of systematic procedure and selecting minimum items.2. It may be possible to classify TM disorders quickly because an instruction for filling up and a table for classifying the type of TM disorders are attached.3. It may be easy to evaluate the process of change of symptoms.4. It attaches a table of examination for finding differential diagnosis of TM disorders.5. It may be possible to fill up the results for various examinations of jaw function.6. It may be possible to use the construction of data base for the protocol for TM disorders by Japanese Society of Stomatognathic Function.

Application of multi valiable analysis on diagnosis of TM disorder patients.

In order to establish a diagnostic system for temporomandibular (TM) disorder patients, data were collected on the mandibular border movement at incisal point from TM disorder patients and analized by multi valiable analysis comparing with data from the subjects with no TM disorder symptom.Seven parameters were identified as useful ones for the discrimination between TM disorder group and control group. With these parameters, 71% of TM disorder group and 91% of control group were correctly discriminated, respectively.These findings suggest that application of multi valiable analysis may be useful for a diagnosis of TM disorder patients.

[A clinical study of patients with mandibular dysfunction. II. The effect of full-coverage occlusal splint therapy].

The clinical effect of full coverage occlusal splint during 13 weeks insertion was investigated in 30 mandibular dysfunction patients with two or more symptoms of temporomandibular joint (TMJ) pain, TMJ sounds and limitation of mandibular movement followed by no organic change in the TMJ, who were reported in part 1 of this study.A remarkable effect of occlusal splint was obtained and 86.7% of the 30 patients were improved totally. Especially, the symptoms, TMJ pain and shoulder stiffness were much improved, but less effective was seen to buccal pain and temporal headache. The period of producing the effect of occlusal splint was different to each symptom, but no change was seen after 10 weeks in any symptoms.These results clearly show the effect of full coverage occlusal splint for mandibular dysfunction patients and useful suggestion of occlusal splint therapy to this disease was obtained.