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Biomedical subjects

K Tsuga

Publications and source records attributed to K Tsuga.

At least 19 recordsLinked to original sources
PubMed2000

Creating a vertical stop for interocclusal records.

This article describes a method of making an accurate interocclusal record when the most distal tooth is an abutment of a fixed partial denture. The method uses conical stops, prepared in the enamel of the abutment or made of composite or a metal core covered with composite, to maintain the vertical dimension of occlusion and to act as a third point of reference for a stable occlusal relationship when occluding the definitive casts. This article also explains how to use the cones and how to make each variety.

Dental Abutments↗
PubMed2000

Immediate maxillary denture base extension for posterior palatal seal.

A procedure for extension of the maxillary denture base for development of a posterior palatal seal is described. The technique involves provisional extension with paraffin wax and adding direct relining resin supported by a silicone putty core. This simple, quick procedure achieves immediate recovery of retention for underextended maxillary dentures without additional laboratory procedures.

Dental Polishing↗
PubMed2000

A biomechanical effect of wide implant placement and offset placement of three implants in the posterior partially edentulous region.

To prevent loosening or fracture of screws retaining the prosthesis to the implants in the posterior partially edentulous region, the use of staggered buccal and lingual offset placement or wide implants is suggested. However, it is not known how this usage compensates for the torque produced by lateral occlusal forces. This study evaluated the effectiveness of offset placement of three implants and a wide implant placement at the most posterior site. Three-dimensional geometric analysis was used to calculate the tensile force applied to gold screws in clinical situations with buccal or lingual loading perpendicular to cuspal inclination (10 or 20 degrees ). Four variations of the placement of three implants (3.75 mm) are: (1) straight; (2) buccal offset of the second implant; (3) lingual offset of the second implant; (4) a wide implant (5 mm) placement at most posterior site. The offset placement did not always decrease tensile force at the gold screw, but wide implant placement and decrease in cuspal inclination did.

Bicuspid↗
PubMed2000

Evaluation of lower oesophageal sphincter pressure using endoscopic manometric sleeve assembly.

BACKGROUND: The purpose of this study was to establish a method to determine lower oesophageal sphincter (LOS) pressure using an endoscopic manometric sleeve assembly. METHODS: We used a 250-cm, three-lumen, 2.2-mm external diameter silicon catheter with a 3-cm sleeve sensor that was passed easily through the biopsy channel (2.8 mm diameter) of the gastroscope. Each lumen was perfused with distilled water using a low-compliance, pneumohydraulic capillary infusion system. Forty-seven healthy subjects and 35 patients with oesophageal disorders underwent study during routine diagnostic endoscopy. In 27 of the subjects, standard transnasal manometry with a three-lumen, 4.5-mm diameter polyvinyl catheter with a 5-cm sleeve sensor was also performed. RESULTS: Lower oesophageal sphincter pressure (LOS) was evaluated in all subjects (median pressure 16 mmHg, range 0-55 mmHg) for 6 min during routine endoscopic examination. The LOS pressure readings between standard and endoscopic manometry correlated well. The LOS pressure was significantly lower in healthy subjects with hiatal hernia than in those without hernia and was also significantly lower in patients with reflux oesophagitis than in healthy subjects. CONCLUSIONS: Endoscopic manometric sleeve assembly was used during routine endoscopic examination and was useful for easily determining LOS pressure. It could be used for evaluation of oesophageal motility disorders, thus avoiding the use of a more invasive and time-consuming method.

Case-Control Studies↗
PubMed1999

Dynamic viscoelastic properties of antimicrobial tissue conditioners containing silver-zeolite.

OBJECTIVES: The purpose of this study was to determine the effects of including the antimicrobial silver-zeolite (SZ) on the dynamic viscoelastic properties of various tissue conditioners. METHODS: The dynamic viscoelastic properties of five commercially available tissue conditioners: Visco-gel (VG), GC Soft-Liner (SL), FITT (FT), SR-Ivoseal (IV) and Shofu Tissue Conditioner (TC) containing SZ were evaluated after 1 and 28 days of water- and artificial saliva immersions with the use of complex modulus and loss tangent parameters. Values for these two parameters for each tissue conditioner were statistically analyzed by one- and two-way ANOVA and Bonferroni's test. RESULTS: Complex modulus and loss tangent values of TC were not significantly different among specimens containing 0, 2, 5 and 10 wt.%-SZ, respectively. In FT and TC containing 2 wt.%-SZ, these values were not significantly different between 1 and 28 days in both water- and saliva immersions. CONCLUSION: The results suggest that incorporating SZ does not affect TC's inherent dynamic viscoelastic properties, while the other tissue conditioners investigated may be found to have changed viscoelastic properties as a consequence of the inclusion of SZ.

Acrylic Resins↗
PubMed1999

The effectiveness of element downsizing on a three-dimensional finite element model of bone trabeculae in implant biomechanics.

More validity of finite element analysis in implant biomechanics requires element downsizing. However, excess downsizing needs computer memory and calculation time. To investigate the effectiveness of element downsizing on the construction of a three-dimensional finite element bone trabeculae model, with different element sizes (600, 300, 150 and 75 microm) models were constructed and stress induced by vertical 10 N loading was analysed. The difference in von Mises stress values between the models with 600 and 300 microm element sizes was larger than that between 300 and 150 microm. On the other hand, no clear difference of stress values was detected among the models with 300, 150 and 75 microm element sizes. Downsizing of elements from 600 to 300 microm is suggested to be effective in the construction of a three-dimensional finite element bone trabeculae model for possible saving of computer memory and calculation time in the laboratory.

Biomechanical Phenomena↗
PubMed1999

Finite element analysis of the effect of vertical curvature on half-oval cast clasps.

High stresses in half-oval cast clasps are the main causes of deformation or fracture. A vertical curvature in clasps is said to be effective in reducing stress. However, such claims lack scientific basis. The purpose of the present study was to evaluate stress and stiffness in a three-dimensional (3D) finite element analysis (FEA) model of clasps with different vertical curvatures, cross-sectional forms and tapers, and to clarify the effect of vertical curvature on the half-oval cast clasp. Circumferential clasp arms for the mandibular second premolar were analysed by 3D FEA. The clasp arms were approximated by curved cantilever beams with a half-oval cross-section around a cylinder. The radius of curvature was set at 4 mm and the angle subtended by the clasp arm was 120 degrees. The clasp tip was set at a point 2 mm lower than the base. In the 'No-taper' half-oval clasp arm, stress increased and stiffness decreased with the increase in vertical curvature. In the shape of a preformed wax pattern (thickness/width = 0.80, tip/base = 0.70), stress and stiffness decreased slightly. In an 'Original' form (thickness/width = 0.33, tip/base = 0.80), vertical curvature had a very slight effect on stress and stiffness, and stress was the lowest. These findings suggest the superiority of the 'Original' form, with less stress and no effect of vertical curvature.

Dental Casting Technique↗
PubMed1999

The effectiveness of a new algorithm on a three-dimensional finite element model construction of bone trabeculae in implant biomechanics.

More validity of finite element analysis (FEA) in implant biomechanics requires element downsizing. However, excess downsizing needs computer memory and calculation time. To evaluate the effectiveness of a new algorithm established for more valid FEA model construction without downsizing, three-dimensional FEA bone trabeculae models with different element sizes (300, 150 and 75 micron) were constructed. Four algorithms of stepwise (1 to 4 ranks) assignment of Young's modulus accorded with bone volume in the individual cubic element was used and then stress distribution against vertical loading was analysed. The model with 300 micron element size, with 4 ranks of Young's moduli accorded with bone volume in each element presented similar stress distribution to the model with the 75 micron element size. These results show that the new algorithm was effective, and the use of the 300 micron element for bone trabeculae representation was proposed, without critical changes in stress values and for possible savings on computer memory and calculation time in the laboratory.

Algorithms↗
PubMed1998

Evaluation of the colorectal wall in normal subjects and patients with ulcerative colitis using an ultrasonic catheter probe.

BACKGROUND: Ulcerative colitis is usually evaluated by barium enema and colonoscopy, methods of imaging that are limited to the mucosal surface. Endoscopic ultrasonography (EUS) is the best modality for the evaluation of transmural changes in the bowel wall. We therefore evaluated the colorectal wall in normal control subjects and patients with ulcerative colitis using an ultrasonic catheter probe. METHODS: Endoscopic ultrasound with a catheter probe was performed on 36 normal control subjects (36 examinations) and 72 patients (111 examinations) with documented ulcerative colitis. RESULTS: In normal control subjects, the total wall, mucosa, submucosa, and muscularis propria were significantly thicker in the rectum than in the colon. There was no significant difference in the thickness of the colon and rectum among different age groups or between men and women. In ulcerative colitis, we classified the boundary of each layer into three patterns (smooth, irregular, and blurred) and then classified the wall into six types. In Matts grade 2 and 3 ulcerative colitis lesions, the total wall and each layer were significantly thicker than lower grade lesions and normal control subjects. For grade 1 and most of the grade 2 lesions, the boundary of each layer was smooth. In some of the grade 3 lesions, the mucosa-submucosa and submucosa-muscularis propria layer borders were abnormal. In all grade 4 cases, the mucosa-submucosa boundary was blurred. There was some correlation between the Matts grade and EUS findings except for Matts grade 3 lesions which had various EUS patterns. CONCLUSION: Endoscopic ultrasound with a catheter probe is a useful modality for the transmural assessment of the colorectal wall and, when used in conjunction with the many clinical and endoscopic parameters currently available, may contribute to the diagnosis and treatment of ulcerative colitis.

Adult↗
PubMed1998

A method for quantifying complete denture quality.

STATEMENT OF PROBLEM: Reproducible and quantitative clinical evaluation of complete denture prostheses is of great importance for preoperative diagnosis, treatment planning, and assessment of quality of denture treatment. PURPOSE: This study attempted (1) to clarify the degree of contribution each clinical factor made to the general assessment of experienced prosthodontists to complete denture prostheses, and (2) to develop a method for quantitative assessment of complete denture quality. METHODS: Sixteen clinical factors with a three-grade scale were used to evaluate complete denture prostheses in 320 patients. The general assessment of the dentures was conducted with a 10-point scale. The contribution of each grade of the 16 factors to the general assessment level was determined by a multiple regression analysis. RESULTS: Seven factors were highly correlated to the general assessment. On the basis of these significant contributions, a complete denture scoring method was established followed by the calculation of the category scores of these factors and conversion of the total sum of each category score to an integer number between 0 and 100. The resultant quantification score was closely correlated with the general assessment of the denture. CONCLUSION: An evaluation protocol used for scoring of complete dentures was developed based on the scientifically analyzed knowledge of experienced prosthodontists.

Aged↗
PubMed1998

Self-assessed masticatory ability in relation to maximal bite force and dental state in 80-year-old subjects.

By means of a questionnaire, clinical examination and force recordings, the relationships between self-assessed masticatory ability, dental state and bite force were studied in 160 80-year-old persons, 74 men and 86 women. The subjects were in general satisfied with their masticatory ability and 70% had no problems, while 6% reported three or more problems with mastication. Half of the subjects were dentate without removable prostheses and almost one-third had 20 or more natural teeth. The edentulous persons (about one-fifth of all) reported more problems related to mastication than the other dentition groups. The maximal bite force varied much and exhibited a significant correlation to the number of remaining teeth and dental state. The self-assessed masticatory ability was only weakly correlated with dental state and bite force. It was concluded that many subjects with few or no remaining teeth and/or removable dentures had only few complaints of impaired masticatory function and showed a good adaptation to an impaired dental status and small maximal bite force.

Adaptation, Physiological↗
PubMed1998

Post-impression preparation to prevent fracture to isolated abutments with extensive bone loss in master casts.

A post-impression preparation technique can be used for preventing fracture of isolated abutments in master casts with extensive bone loss. This technique involves using a sharp knife to trim the impression obliquely at the clinical cervical line, creating a 1- to 2-mm-width bevel, followed by the insertion of a dowel pin into the abutment for reinforcement. This technique enlarges the abutments' diameter at the clinical cervical line and increases the resistance to breakage without altering the shape of critical areas.

Alveolar Bone Loss↗
PubMed1997

Sex difference of electromyogram of masticatory muscles and mandibular movement during chewing of food.

The aim of this study was to investigate whether there were sex differences in the electromyograms (EMG) of the masticatory muscles and in the mandibular movement of young adults when chewing food. Twenty subjects with normal dentitions were selected. The 11 test foods selected were all easily available in Japan. The results showed firstly that although there were no significant differences of chewing frequency between males and females, females chew food more slowly with less masticatory force and narrower mouth opening width than males; and secondly it appears that the chewing function in females is lower than in males.

Adult↗
PubMed1996

Associations between self-assessed masticatory ability and some general health factors in a Swedish population.

OBJECTIVES: The aims of this study were 1) to describe changes in self-assessed masticatory ability over a 14 year period (1975-89); and 2) to describe associations between self-assessed masticatory ability and age, dental state and some other background factors in a sample of the Swedish population in 1988/89. DESIGN: The Swedish National Central Bureau of Statistics investigates annually the living conditions of the Swedish population by means of interviews by trained persons. The data were analysed by means of stepwise logistic regression and calculation of adjusted relative risks. SUBJECTS: In the investigation in 1988/89, 12,901 people above 16 years of age participated and the response rate was 80%. RESULTS: In comparison between the investigations, the prevalence of reported impairment was lower in 1988/89 than in 1975 and 1980/81. Prevalence of reported impairment of chewing ability increased with ageing from 2% in young adults (16-34 years old) to 44% in older elderly (> 85 years old). In most age groups, edentulous people reported the highest prevalence, and dentate people the lowest. Relative risks for impaired masticatory ability, independent of age, gender and dental state, were higher for people in rural areas, with low income and living single, as well as for those with skeletal, gastrointestinal, psychiatric and tumour diseases. In the elderly, results from the logistic regression showed that some disability and psychosocial factors were also associated with masticatory ability. CONCLUSIONS: The results indicated that there was a group of elderly people who reported several functional and health problems including impaired masticatory ability.

Adolescent↗
PubMed1993

Reproducibility of tooth tapping rhythm in young and elderly dentate subjects.

The reproducibility of tooth tapping frequencies was measured in young and elderly dentate subjects. Six rates of tapping, i.e. 40, 60, 90, 120, 160 and 200 times per min, were practised to the accompaniment of a metronome for 15 s before recording. After a 15-s break, subjects were asked to reproduce the same rate of tapping without metronome accompaniment, and these movements were recorded. It was determined that the young subjects regulated tooth tapping frequencies by controlling velocity of mandibular movement. On the other hand, the elderly subjects regulated tooth tapping frequency by controlling opening width.

Adult↗