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Biomedical subjects

M Ai

Publications and source records attributed to M Ai.

At least 37 records · Page 2Linked to original sources
PubMed2000

Influence of protrusive tooth contact on tapping point distribution.

This study investigated the influence of protrusive tooth contacts (tooth contacts during mandibular protrusion) on the tapping point distribution. Nine healthy subjects volunteered for this study and the protrusive tooth contact pattern, as well as the retrusive tooth contact pattern, was altered on four maxillary occlusal splints. The first splint was adjusted to make the sagittal incisal path of protrusion and retrusion equivalent to that of the natural dentition. The second and third splints had partial and complete elimination of the protrusive tooth contact, respectively. The fourth splint had complete elimination of both protrusive and retrusive tooth contacts. The subjects were asked to use each splint continuously for 1 week. The tapping point distribution was measured on the 7th day after insertion of each splint. The four experimental occlusal conditions were found to have a significant effect on the tapping point distribution. The complete elimination of the protrusive tooth contact caused an anterior tapping point location and an increase in the tapping point area. The former tendency was found to be independent of the presence of the retrusive tooth contact. In conclusion, it was suggested that the protrusive tooth contact plays a significant role in maintaining the consistency and stability of the tapping point.

Adult↗
PubMed2000

Relationship between hyperinsulinemia and remnant lipoprotein concentrations in patients with impaired glucose tolerance.

This study was performed to explore further the association between insulin resistance and plasma remnant lipoprotein (RLP) concentration. For this purpose we used the sum of the plasma insulin concentrations before and 30, 60, 90, 120, and 180 min after a 75-g oral glucose load (sigmaIRI) as a surrogate measure of insulin resistance in 61 subjects with impaired glucose tolerance. SigmaIRI was determined on 2 occasions, before and 16 weeks after initiation of a diet and exercise program. At baseline, sigmaIRI correlated with the sum of the plasma glucose concentrations in response to the 75-g oral glucose load (r = 0.26; P < 0.04) as well as plasma concentrations of triglyceride (r = 0.21; P = 0.09), RLP-cholesterol (r = 0.41; P < 0.001), and RLP-triglyceride (r = 0.46; P < 0.001). In contrast, neither total (r = 0.07) nor high density lipoprotein (HDL) cholesterol (r = 0.04) concentrations correlated with sigmaIRI. SigmaIRI was lower in 42 subjects following life-style intervention, associated with significant (P < 0.005) reductions in sigmaglucose, and fasting glucose, insulin, triglyceride, RLP-cholesterol, and RLP-triglyceride concentrations. However, none of these variables decreased in the 19 subjects whose sigmaIRI did not fall. Finally, the change in sigmaIRI following intervention with diet and exercise was significantly associated with differences in sigmaglucose (r = 0.63; P < 0.001) and fasting glucose (r = 0.26; P < 0.05), insulin (r = 0.79; P < 0.001), triglyceride (r = 0.29; P < 0.03), RLP-cholesterol (r = 0.71; P < 0.001), and RLP-triglyceride (r = 0.49; P < 0.001) concentrations. These results demonstrate that variations in concentrations of RLPs are highly correlated with changes in sigmaIRI, consistent with the possibilities that 1) RLP measurements are useful estimates of insulin resistance; and 2) an increase in RLP concentrations may provide the mechanistic link between insulin resistance and coronary heart disease.

Aged↗
PubMed1999

Infrared gold alloy brazing on titanium and Ti-6Al-4V alloy surfaces and its application to removable prosthodontics.

PURPOSE: This study investigated the area size of the flow of a gold braze alloy on commercially pure titanium and Ti-6Al-4V alloy plates, and elemental composition at the interface was determined. In the second part of this study, the tensile strengths of titanium plates brazed using a gold alloy were investigated. MATERIALS AND METHODS: Chips of Type IV gold alloy and silver braze alloys were melted onto commercially pure titanium and Ti-6Al-4V surfaces in a dental infrared radiation unit. Flow area of each braze alloy was measured using a digital image analyzer. Tensile specimens (n = 5) were also prepared by infrared brazing using the braze alloys. Five specimens for each combination of the two titanium plates and the two braze alloys were subjected to tensile loading using a Universal testing machine. Electronprobe microanalysis of x-rays at cross-section of the brazed joints to determine elemental composition across the interface, as well as scanning electron microscopic observation at the fracture surfaces, were also conducted. RESULTS: The braze alloys flowed well and spread over the Ti and Ti-6Al-4V plates. Braze alloy type significantly influenced flow, and the gold alloy flowed less on the titanium materials. The mean tensile strengths of Ti and Ti-6Al-4V plates brazed using the gold braze alloy were 219 MPa and 417 MPa, respectively. The fracture surfaces of Ti-6Al-4V specimens with the gold braze alloy exhibited typical ductile behavior. Ti with the same braze alloy showed brittle surfaces. A greater concentration of Cu was found at the Ti with gold braze interface. CONCLUSION: The flow and the tensile strength of the gold alloy coating on titanium surface by means of an infrared brazing is adequate for dental use.

Alloys↗
PubMed1999

What types of occlusal factors play a role in temporomandibular disorders...? A literature review.

Recent studies and literature reviews of temporomandibular disorders (TMD) do not strongly support the role of occlusal etiologic factors. For this paper we collected and classified studies dealing with occlusion as a contributing factor to TMD through reviews, and discussions of these difficulties and possible solutions. Related articles from 275 papers covering nearly the past twenty years were selected from a prosthetic point of view and reviewed. The validity and reliability of occlusal examinations, however, are questionable since the epidemiological studies dealt with numerous varied subjects. Although occlusal relationships, such as overbite, non-working side interferences, and discrepancy between the intercuspal position and the retruded contact position, have often been considered as contributing factors of TMD, there is no consistency among even those studies that support such an occlusal factor. A project should be initiated to create a revised, precise and practical method to determine the occlusal contact and to categorize an occlusal contact scheme. To detect whether the patients' occlusal scheme works traumatically or not should be an important part of the occlusal examination. That is, the frequency and duration of tooth contact on the occlusal scheme should be studied.

Adolescent↗
PubMed1998

The influence of some demographic and clinical variables on psychosomatic traits of patients requesting replacement removable partial dentures.

The purpose of this study was to investigate the influence of some demographic and clinical variables on psychosomatic traits of the patients who visited the prosthodontic section of the Dental Hospital at Tokyo Medical and Dental University for replacement of their removable partial dentures (RPDs). Sixty-six patients with 50 maxillary and 44 mandibular RPDs completed the psychological measurements concerning their dentures using visual analogue scales (VAS). Female patients rated significantly lower satisfaction with the comfort of their dentures than males. Younger patients expressed less satisfaction with the aesthetics of their dentures than the older patients. The period of wearing the present denture significantly correlated with psychological measures of pain, comfort, and general satisfaction, suggesting that this clinical variable may be an important factor. There was no significant correlation between the patients' general satisfaction with dentures and the retention/stability scores assessed by the examiner.

Adult↗
PubMed1997

A short-term clinical follow-up study of superplastic titanium alloy for major connectors of removable partial dentures.

STATEMENT OF PROBLEM: Superplastic forming of Ti-6A1-4V alloy has been used in the fabrication of a removable denture framework. The method provides the titanium alloy denture framework with excellent physical properties not seen in cast titanium prostheses. PURPOSE: This study describes the technical procedure for fabricating removable dentures with this type of framework and evaluates clinical applications of the dentures in short-term follow-up periods from 6 months to 3 years. RESULTS: Results of this study demonstrated that the dentures functioned well and did not cause any major clinical difficulties. The patients have expressed satisfaction with the dentures at regular recall appointments. CONCLUSION: The clinical observations suggest that this method is suitable for fabricating titanium alloy removable dentures.

Acrylic Resins↗
PubMed1997

An optical system for measuring inclination and area of occlusal facets.

Occlusal facets are regarded as an individual record of occlusal contacts that result from various mandibular movements. Analysing characteristics of the facets is important for the functional assessment of the stomatognathic system. A new system which quantifies such characteristics optically has been developed. This system is composed of optical devices, a graphic image-processor, a set of stages for mounting and positioning the model and laser indicators of the measuring point. The system enables the inclination and area of each facet and its location to be measured and its processed image displayed on the graphic monitor.

Computer Graphics↗
PubMed1997

All-cast-titanium removable partial denture for a patient with a severely reduced interarch distance: a case report.

A patient had a maxillary posterior edentulous area and severely reduced interarch distance that precluded the use of a conventional removable partial denture. An all-cast-titanium denture base and occlusal surface was designed to fabricate a removable denture to restore the edentulous area. Titanium was cast in a centrifugal casting machine with electric are melting design. The desirable characteristics of titanium, such as favorable mechanical properties, low density, and comparatively low cost, make this metal particularly effective and suitable for construction of an all-cast-metal denture base with a metal occlusal surface.

Adult↗
PubMed1996

Application of a newly developed 3-D deformation measurement system to prosthetic dentistry.

A new system for measuring three-dimensional deformation has been developed. The main components of the system are a fixed TV camera and vertically scanning projectors. The advantages of the system are: (1) since there is no mechanical contact between the object and the sensing unit, hardness and form of the object do not have to be considered; (2) the system does not need any precise geometry except for the reproducibility of the vertical scanning stage; (3) the time required for one measurements is extremely short; and (4) the system is not expensive. From the basic experiments for testing accuracy, this system has about +/- 30 microns range deviation against 1000 microns deformation of the object. The system has been applied to investigate the influence of various impression procedures for a removable partial denture on the displacement of the simulated soft mucosal tissue. It is revealed that deformation forms are expressed precisely. Our results suggest that this measurement system is quite useful for research in dentistry and that it could be widely applied.

Biomechanical Phenomena↗
PubMed1996

Influence of experimental occlusal discrepancy on masticatory muscle activity during clenching.

The influence of the experimental occlusal discrepancy on masticatory muscle activity was investigated on 12 subjects. Specially designed occlusal interferences were fabricated and various occlusal states were simulated with their aid. Subjects were asked to carry out eccentric clenching efforts and electromyographic activity of the masseter plus the anterior and posterior temporal muscles was measured. When compared with clenching on the unaltered natural dentition, clenching on the experimental interferences resulted in distinct patterns in the jaw elevator muscles, and the most characteristic change was observed when clenching effort was exerted on the experimental non-working side interference. Electromyographic activity in the anterior and posterior temporal muscles was decreased on the working side and increased on the non-working side and originally unilateral activity pattern with clear dominance on the working side was altered to a bilateral pattern, while that of the masseter muscles remained uninfluenced. Resultant bilateral activity in the anterior and posterior temporal muscles is thought to cause a superior movement of the working side condyle and an inferior movement of the non-working side condyle.

Adult↗
PubMed1995

[Clinical observation of posterior chamber lens implantation in children].

Extracapsular cataract extraction with posterior chamber intraocular lens (IOL) implantation was performed on 22 eyes of 16 patients with congenital or traumatic cataract and with ages ranging from 4 to 7 years old. The periods of follow-up were 1-2 years with a mean, 18 months. The postoperative reaction was mild, no untoward complications occurred in the remote follow-up and the postoperative visual acuities recovered well. The youngest age of IOL implantation, the choice of diopter of refraction and the management of intra- and post-operative complications were discussed.

Age Factors↗
PubMed1993

A new method for measuring nocturnal tooth contacts.

A new portable system for measuring nocturnal tooth contacts has been devised. This system was suitable for patients to take home and record tooth contacts by themselves. A micro photo sensor using optical fibres was applied to detect tooth contacts. The sensor and the target were accurately fixed to opposed molars, respectively on the same side, with removable metal attachments. Patients were instructed to set the attachment to their tooth each experimental night. In the present study, data was assembled for four or five nights in three subjects who were free of masticatory pain and dysfunction. Each subject showed an individual tooth contact pattern. It is suggested that this new system is useful and convenient for measuring nocturnal tooth contacts.

Adult↗
PubMed1993

[Development of a handy dental surveyor].

A small portable surveyor, easy to use, was newly devised. The surveyor is essentially a parallelometer, an instrument used for determining the relative parallelism of two or more surfaces of the teeth or other parts of the dental cast. The characteristic structures of this instrument is as follows: The vertical standard is directly connected to the cast table with a universal joint, different from the others, and it can be tilted in any given degree to the table. The vertical sliding spindle can move freely parallel to the standard with the two horizontal arms, and it carries pencil leads of 0.9mm phi inside just as a mechanical pencil in structure. The accuracy of this surveyor is thought to be equal to that of the conventional ones in ordinary use.

Dental Casting Technique↗
PubMed1992

Tenderness on palpation and occlusal abnormalities in temporomandibular dysfunction.

Tenderness on palpation indicates objective painful symptoms. This study investigated the tenderness of the temporomandibular joint, muscles and their relation to occlusion in patients with temporomandibular dysfunction. Two hundred ten patients were examined; 96% had tenderness and 80% of cases of tenderness were diagnosed as occlusally related. The average number of tender areas was 5.4 per patient, despite the contribution of occlusion. Tenderness was observed most frequently in the lateral pterygoid muscle, followed by the insertion of temporal muscle. There was no correlation of temporomandibular joint tenderness to muscle tenderness, while tenderness of certain muscles to each other was correlated. Differences were related to the state of occlusion in the number of tender areas, to the ratio to tenderness of elevator muscles to horizontally acting muscles, and to the frequency of unilateral tenderness. The association of muscle tenderness and occlusion was suggested.

Adolescent↗
PubMed1991

Tooth contact patterns in patients with temporomandibular dysfunction.

The occlusal tooth contact patterns in patients with temporomandibular dysfunction and normal subjects were studied under a range of conditions using a newly devised radiotelemetry system. The patterns in the patient group were completely different from those in the control group. During rest or work, the patients showed higher values for total number and time of tooth contacts, as well as several contacts of extended duration. Moreover, many of the tooth contacts during swallowing were plural contacts in the patient group. These results suggest that patients with temporomandibular dysfunction exhibit increased tonus of jaw-closing muscles, which is probably due to occlusal disharmonies and psychological stress.

Adult↗
PubMed1991

Development of sealed cup yoke type dental magnetic attachment.

The purpose of this study was to develop a small cup type yoke magnetic attachment sealed from oral fluid. The magnetic device forms a closed circuit between the magnet, yokes, and keeper. A 3.2 mm phi x 1.4 mm SmCO5 magnet was put into a cup yoke of 447J1 stainless steel and covered by 447J1 stainless steel disk yoke with a 316L stainless steel ring. To protect the magnet from corrosion, the connection was sealed by laser welding. The optimum dimensions were figured out by a finite element method. The performance of the magnetic attachment was investigated. As a result, a magnet device 4.4 mm in diameter and 2.1 mm in height was developed. The breakaway retention when the keeper touched it was 341 gf on average.

Dental Stress Analysis↗
PubMed1991

[Newly devised subcutaneous needle electrodes for EMG recording].

Subcutaneous needle electrodes made of stainless steel were newly devised for ease of handling and perfect insulation. This needle (phi 0.20 mm) is used for acupuncture. The electrodes had the capability to record the EMG activity easily from a certain muscle. Then, the EMG activities of the masseter muscle were recorded with both these needle electrodes and surface electrodes and the results were compared. 1. Insertion of the electrodes into the subcutaneous tissue was easily performed because of the application of the acupuncture needle and their lightness of 0.2g was effective in fixing the electrodes on the skin without causing any tension. 2. After the insertion of the needle electrodes, the impedance showed below 5 kohm immediately, and the EMG recordings during biting could be simply achieved with great stability. 3. The action potential from the needle electrodes was less than that from the surface ones. The former reacted more sensitively to the change in the distance between the electrodes, compared with the latter.

Action Potentials↗