Purpose: Composite denture teeth have superior physical properties to acrylic resin teeth in terms of greater hardness and abrasive resistance. However, surface staining is still a major problems associated with composite denture teeth. The purpose of this study was to clarify the relation between surface roughness and surface staining of artificial teeth.
Materials and Methods: Three different composite denture teeth and two acrylic denture teeth were evaluated. Each artificial tooth was placed on a paraffin wax block. Half of the specimens were formed using a gas torch, and the others were not formed using a gas torch. Then, investing, packing and processing heat curing resin was carried out. After cooling, the specimens were polished with rough brush-polishing, soft brush-polishing and buff-polishing with a laboratory lathe. A control group consisting of five teeth was placed on self-curing resin without polishing. The roughness values (Ra and RzJIS) of each specimen were measured using a laser microscope. The color difference values (ΔE^*ab) of specimens were measured before and after immersion in tea solution for seven days using a spectrophotometer. The roughness value data were statistically analyzed by Dunnett's test, and t's test for a comparison between forming and not forming. Color difference data were similarly analyzed by Dunnett's test and t's test. Color difference values were analyzed by Tukey's HSD test as a comparison between different artificial teeth.
Results: Each of the artificial teeth showed various changes in Ra and RzJis with polishing, but it could not be established how far polishing influences the roughness values of artificial teeth. There was no significant difference in the color difference values by polishing and burning, except for one composite denture tooth.
Conclusion: Within the limitations of this study, polishing and forming using a gas torch have no effect on the staining of composite denture teeth.

View full abstract

Periodontal disease increases the risk of cardiac diseases, leading us to suppose that oral health affects the general condition. However, there are few reports where the general condition was evaluated with a simple objective method for comparative examination with the oral cavity.
On the other hand, it has been clarified both that arteriosclerosis progresses prior to the onset of cardiac disease and also that sclerosis of the aorta precedes sclerosis of the cerebroartery or coronary artery. Thus, in the present study we retrospectively examined the relationship between the remaining teeth and arterial stiffness to find out correlations of the oral cavity with the general condition. This was achieved by interpreting the arterial stiffness as an indicator of the general condition.
The subjects were 140 oral surgery patients (male: female=83: 57, 61.3±9.0 years old, Body Mass Index 23.2±3.4 [mean±SD]) without a history of cerebrovascular disorder and heart disease. They were subjected to digital panoramic radiography and a clinical examination. To evaluate the oral cavity, we examined the number of remaining teeth on the panoramic radiograph and the ratio of the number of the teeth with a crown-root ratio of higher than 1: 1 on alveolar osteoid images, to the number of remaining teeth.
Brachial-ankle pulse wave velocity (baPWV) and cardio-ankle vascular index (CAVI) were used as indices of arterial stiffness. With each of these parameters, higher values indicate stiffer vascular walls.
The following were revealed by examining correlations between the dental condition and the arterial stiffness parameters:
1) The number of remaining teeth was negatively correlated with both baPWV and CAVI; the lower the number of remaining teeth, the higher the baPWV (r=-0.29, P=0.0003) and CAVI (r=-0.33, P<0.0001).
2) The ratio of the number of teeth with a crown-root ratio of higher than 1: 1 to the number of remaining teeth positively correlated with both baPWV and CAVI ; the higher the rate of alveolar bone resorption, the higher the baPWV (r=0.22, P=0.0106) and CAVI (r=0.31, P=0.0002).
Thus, both the number of remaining teeth and the status of alveolar bone resorption correlated with baPWV and CAVI, suggesting that a reduced number of remaining teeth or the progress of alveolar bone resorption increases arterial stiffness.

View full abstract

Objectives:
In order to develop a simplified chair-side method for evaluating saliva biomechanics with high reproducibility, a newly developed "capillary tube method" and the conventional laboratory technique were compared.
Methods:
The most suitable capillary tubes and measuring conditions were determined by comparing seven types of capillary tube. The suction height was measured (every 5 seconds for 60 seconds) for two types of artificial saliva (100% and 50% salivert^®) and purified water (control).
For the experiment, 11 types of artificial saliva comprising various organic and inorganic ingredients were used. The suction height was measured (every 5 seconds for 30 seconds) with two types of capillary tube. As for conventional laboratory measurements, spinability was evaluated with a thread-forming property meter (NEVA METER^®) and viscosity was evaluated with an ultrasonic viscometer (VISCOSTICK^®).
The correlation coefficients for the relationships among "suction height", "spinability" and "viscosity" were then analyzed.
Results:
Two types of capillary tube (∅ 0.26 mm and ∅0.93 mm) were the most sensitive to the changes in the biomechanical characteristics of artificial saliva. The differences in suction height were most marked at 15 seconds.
The concentration of organic ingredients correlated negatively with "suction height" and correlated positively with "spinnability" and "viscosity". Weaker correlations were seen for inorganic ingredients. There was a significantly negative relationship between "suction height" and "viscosity" (P<0.01).
Conclusion:
Suitable conditions for the newly developed method were identified. The results suggest that this novel chair-side method may be used in place of viscosity measurement.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

There are a few reports of ultrasound examination of the effects of the palatal augmentation prosthesis (PAP) for postoperative oral-phalyngeal cancer patients. The aim of this study was to clarify lingual movements during swallowing with ultrasonography and to evaluate the effect of wearing the PAP on the oral functions of oral cancer patients.
Subjects and Methods:
The subjects were two patients who had been treated at the Rehabilitation Clinic for Speech and Swallowing Disorders in The Nippon Dental University Hospital. Case one was a 47 year-old-man who had a defect due to an operation for mouth flour cancer. He had been wearing a PAP to compensate for the defect for 1 1/2 years. Case two was a 77 year-old-woman who had a defect due to an operation for gingival cancer in the right side of the mandible. She had been wearing a PAP to compensate for the defect for 2 1/2 years. Lingual surface movements were quantified by measuring the grooving on the coronal sections during swallowing by ultrasonography (Nemio 17, SSA-550A, Toshiba Medical Co., Tokyo Japan) with and without PAP. The assessment items were 1) the depth of central grooving of the lingual surface movement during swallowing, 2) the duration of central grooving of the lingual surface movement during swallowing, and 3) the total duration of the lingual surface movement from ingestion to swallowing. The assessment parameters of swallowing difficulty were a questionnaire and a syllable-identification test. The differences between the with and without PAP results were analyzed by the Wilcoxon rank sum test. Results and discussion:
The results of the present study showed that the duration of central grooving of the lingual surface movement during swallowing showed increases in both patients by ultrasonography (p<0.05).
Moreover, we investigated feeling and speech intelligibility. The PAP improved these.
It was considered that as consequences of recovery of oral deficits shape due to an operation for oral cancer, the change of central grooving of the lingual surface movements during swallowing were influenced. In fact, wearing the PAP helped to redress lingual pressure by lingual movement.
This study showed that wearing the PAP was effective for support of lingual movement during swallowing. In addition, it seemed that we might apply ultrasonography as a PAP evaluation index.

View full abstract