Biomedical subjects

N Natsuaki

Publications and source records attributed to N Natsuaki.

9 recordsLinked to original sources

PubMed2003

Visual observation of the dynamic flow of elastomer rubber impression material between the impression tray and oral mucosa while seating the impression tray.

The purpose of this study was to inspect visually, the dynamics of the impression flow at seating of the impression tray. The effects of the relief and the escape hole of the impression tray on the impression flow were also examined. Three types of the transparent impression tray (flat tray, relief tray and escape hole tray) were prepared. Transparent silicone polymer was put on the impression tray surface. Four drops of the dark blue silicone impression material was injected into the transparent silicone polymer on the impression tray. The impression tray was seated on the model of the denture-supporting mucosa. The movement of the four drops caused by the impression flow was visually recorded with the video camera and examined. The result for the flat tray showed that the impression material moved from inside to the outside. It was also shown that the speed of the moved impression material increased as the seating of the impression tray advanced. The results for the relief tray and the escape hole tray showed the effect of the relief and the escape hole prepared to the impression tray on the speed and the direction of the flow of the impression material.

Dental Impression Materials↗

PubMed2003

Finite element analysis of the effect of the bucco-lingual position of artificial posterior teeth under occlusal force on the denture supporting bone of the edentulous patient.

To improve the quality of the complete denture prosthesis, the bucco-lingual position of the artificial posterior teeth must be determined with consideration of the shape of the maxillary and mandibular residual ridge and the relationship between them. The arrangement of posterior artificial teeth should be considered not only for the denture stability but also for the avoidance of high pressure on the supporting structures. A two-dimensional finite element method program to investigate the statics for the contour of the complete denture and the residual ridge was developed. With this program, the effect of the bucco-lingual position of the artificial posterior teeth under occlusal force on the denture supporting bone could be investigated.

Bite Force↗

PubMed2003

Galvanic skin response of oral cancer patients during speech.

Severe speech difficulty is often caused after surgery of an oral cancer. Prosthetic treatment with a removable obturator prosthesis is generally provided for such patients. Although some speech ability is recovered with prosthetic treatment, patients sometimes complain of continued dissatisfaction with their speech. However, it is difficult to evaluate the dissatisfaction. Therefore, a new method for evaluation is desirable. In this study, such a new method using the galvanic skin response as the index for the dissatisfaction of the patient was developed, and its objectivity was investigated. Eleven patients with maxillary bone defects were selected. Prior to the evaluation, improvement of speech with the removable prosthesis was confirmed using the speech intelligibility test and the visual analogue scale. The electrical resistant value at pronunciation was measured with the measuring system composed with the apparatus (galvanic skin response (GSR) measuring apparatus), the personal computer program. The changes for the electrical resistant value after pronunciation were evaluated by calculating the decrease ratio at pronunciation [(the mean electrical resistance before pronunciation - the mean electrical resistance after pronunciation)/the mean electrical resistance before pronunciation]. This decrease ratio at pronunciation was defined as the index of the speech dissatisfaction of the subject. The mean values for the decrease ratio with prosthesis were significantly smaller than the values without prosthesis (P < 0.05). From the results of this study, it is suggested that the measurement of the electrical resistance change of the skin during speech could be a new method for evaluating the speech dissatisfaction of the post-oral-cancer patient.

Female↗

PubMed2001

Maintenance of condylar position using an occlusal splint after mechanical vibrating-traction of the TMJ.

Although adequate relief of excess mechanical loading to the joint has been accepted as one of the important treatment concepts in the orthopaedic field, a treatment method for the temporomandibular joint (TMJ) to relieve excess mechanical loading has not yet been established. This study aimed to clarify the effect of an occlusal splint on the maintenance of the distracted condylar position achieved by vibrating-traction method. Vibrating dynamic traction force was applied for 5 min to the right TMJ using vibrating-traction apparatus. A flat stabilization splint was adjusted to keep the mandibular position and the condylar displacement was evaluated for 6 h after the dynamic traction procedure. Mean vertical displacement of the mandibular right first molar immediately after the vibrating-traction for the six subjects was 156 microm (ranging from 141 to 179 microm). The calculated mean condylar displacement immediately after the traction was 480 mum and could be kept to be 381 mum even after 6 h by wearing the flat stabilization splint. From the results of this study, it was revealed that the mechanically tracted condylar position could be maintained by a flat occlusal splint. It was suggested that the vibrating-traction method followed by the provision of occlusal support might have a possibility to work as a mechanical relieving procedure for the TMJ.

Adult↗

PubMed2001

Effect of a thick palatal appliance on muscular symptoms in craniomandibular disorders: a preliminary study.

Several treatment modalities for myofascial pain dysfunction syndrome (MPD) are being used at present. However, from the standpoint of patients' quality of life, it would be reasonable to seek a more effective treatment modality. This study aimed to show clinical data of a preliminary study regarding the effect of a thick palatal appliance, designed to fill the palatal concavity with a thick resin base, on muscular symptoms in eighteen MPD patients. Shown here are the clinical results of two volunteer patients using palatal appliances of two different thicknesses. In this study, MPD patents were divided into the three following groups: 1. no-treatment group; 2. thick palatal appliance group; and 3. medication group. Based on the results of this study, it was suggested that the thick palatal appliance could bring about early improvement of MPD syndrome. It is suggested that the thickness of the palatal plate was an important factor in obtaining the clinical effect.

Adult↗

PubMed2000

Comparative study of the temporomandibular joint space in maximum intercuspation and canine edge-to-edge positions in deep bite and non-deep bite subjects.

In order to study the relationship between morphological properties of the TMJ and the mathematically predicted force distribution in the TMJ, the geometric distribution of the joint space on top of the condylar surfaces was evaluated. Seven deep bite subjects and seven non-deep bite subjects were used, and the joint space in the maximum intercuspation and canine edge-to-edge positions was analysed in each group. Standardized images of the TMJ were taken with computed tomography (CT) using a mandible positioner. The comparative ratio of joint space (CRJS) between the maximum intercuspation and the canine edge-to-edge positions was calculated and summarized on the map of the mean morphological outline of the condyle. On the balancing-side condyle, the CRJS of small value was distributed mainly on the anterior edge of the condyle in the non-deep bite group, whereas, in the deep bite group, it was distributed on the centre of the condyle. On the working-side condyle, the small CRJS was distributed around the lateral pole of the condyle in the non-deep bite group, whereas, in the deep bite group, it was found around the posterior part of the condyle. The distribution pattern of CRJS on the upper surface of the condyle in the non-deep bite group was consistent with the results of previous studies on mathematical simulation of TMJ loading. From the results of this study, it was suggested that the distribution of mechanical loading on the TMJ in the eccentric mandibular position would be highly affected by the comparative ratio of joint space. As the comparative ratio of joint space would be highly affected by the condylar position, the analysis of the morphology of the TMJ in relation to mechanical joint loading, in a future investigation, should be carried out on specific mandibular positions in relation to the function of the TMJ to be studied.

Adult↗

PubMed2000

Vibrating-traction method for mechanical joint distraction.

Mechanical static traction has been adopted as one of the treatment procedures for joint diseases and fractures. The effect of mechanical vibration on the mechanical traction of the temporomandibular joint was studied in six human subjects. A mechanical traction force of 2000 gf was applied as a dynamic traction force with mechanical vibration or as a static traction force. The dynamic traction force with vibration was applied for 5 min to the right temporomandibular joint using a vibrating-traction apparatus which generated mechanical vibrations of 1000, 3000 or 4000 Hz. Application of a static traction force for 5 min was used as a control condition. Vertical condylar displacement was mathematically evaluated from the deviation of the mandible using Eddy current displacement sensors which were attached to the maxillary dental arch. Among the three vibration frequencies, 3000 Hz resulted in the maximum vertical condylar displacement for all six subjects, showing the mean condylar displacement of 668+/-242 microm. In contrast, vibrations of 1000 and 4000 Hz showed a smaller traction effect. Application of the static traction force for 5 min resulted in a mean vertical condylar displacement of 5.7+/-4.9 microm, showing almost no traction effect to the joint. From the results of this study, it was revealed that vibrating traction could distract a joint more effectively than could static traction and that the traction force necessary for effective vibrating traction was less than that for static traction.

Adult↗

PubMed1999

New telescopic crown design for removable partial dentures.

STATEMENT OF PROBLEM: Special technical skills and experiences are required to fabricate a telescopic crown to provide adequate retention with precise frictional retention ("conus friction force") between coping and telescope. It is also difficult to control clinically alterations of retentive forces after prolonged usage. PURPOSE: This study examined an innovative telescopic crown system for removable partial dentures that can be fabricated without special technical skill or experience and readily adjusted retentive forces. The retention of telescopic crowns was investigated after repeated insertion/separation tests. MATERIAL AND METHODS: Ten telescopic crowns were constructed to evaluate retentive forces. Each telescopic crown was adjusted to provide a retentive force of approximately 9.8 N. Each telescopic crown was then subjected to 10,000 insertion/separation cycles, and retentive force of each telescopic crown was recorded initially and after every 1,000 cycles. The retentive force of each telescopic crown was re-adjusted after these measurements to provide a retentive force of approximately 9.8 N. The retentive force was recorded a second time after each 1,000 insertion/separation cycles up to 10,000 cycles. RESULTS: Retention of the telescopic crowns gradually diminished, depending on the number of insertion/separation cycles. The mean retentive force after 10,000 insertion/separation cycles was over 2 N. All 10 telescopic crowns were re-adjusted to exert a retentive force of 9.8 N after the initial 10,000 cycles, and the retentive force also diminished on the second 10,000 cycles. CONCLUSIONS: Reduction of retention was dependent on insertion/separation cycles. This new telescopic crown with reduced retention could be easily readjusted. Readjusted retentive forces were at least equivalent to the initial retention.

Analysis of Variance↗

PubMed1999

Relationship between anterior guidance and mesiodistal inclination of lower incisor in human subject with or without TMJ noise.

The relationship between anterior guidance and the mesiodistal inclination of the lower incisors relative to the existence of temporomandibular joint (TMJ) noise was investigated. One hundred and thirty-four individuals, 21 to 40 years of age (mean age 23.8; 104 men and 30 women), were examined. A highly significant correlation was observed between the mean lower-incisor inclination and the difference in steepness between the right and left anterior guidances in the subject group showing TMJ noise (P<0.001), whereas no significant correlation was observed in the group without TMJ noise.

Adult↗