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Biomedical subjects

H Yatani

Publications and source records attributed to H Yatani.

At least 37 records · Page 2Linked to original sources
PubMed1998

Etched-porcelain resin-bonded onlay technique for posterior teeth.

Remarkable advances in adhesive dentistry have made it possible to strongly bond porcelain to enamel and dentin. This evolution has dramatically changed restorative dentistry and has produced a new, highly esthetic, and strong restoration--etched-porcelain resin-bonded restorations. These restorations can be placed with confidence on posterior teeth. They are virtually indistinguishable from natural tooth structure and, thus, provide additional treatment alternatives for patients who desire natural-appearing posterior teeth. Etched-porcelain resin-bonded onlays on posterior teeth not only are an excellent restorative modality for moderately broken-down teeth but also may be used to bring caries-free teeth into occlusion. The latter can be an option for stabilizing occlusion for some patients with posterior open bite due to various causes. This article presents clinical and laboratory techniques for etched-porcelain resin-bonded onlays on posterior teeth.

Bicuspid↗
PubMed1998

Steric effects of N-acyl group in O-methacryloyl-N-acyl tyrosines on the adhesiveness of unetched human dentin.

We have prepared various O-methacryloyl-N-acyl tyrosines (MAATY) to reveal the relationship between molecular structure near carboxylic acid and adhesive strength of MAATY-HEMA type adhesive resin to unetched dentin. In this study, we attempted to change the steric hindrance effect without changing the HLB value, i.e., introducing an iso-acyl group instead of n-acyl group into MAATY. O-methacryloyl-N-ethylbutyryl tyrosine (MIHTY) showed significantly lower adhesive strength when compared with O-methacryloyl-N-hexanoyl tyrosine even though both MAATY have the same HLB value. The possible explanation of the significantly different adhesive strength was that the 2-ethylbutyryl group in MIHTY was bulky, resulting in inhibition of the hydrogen bonding of the carboxylic group. The HLB value is independent of the steric effect of molecular structure, and thus the steric factor should be taken into consideration for the explanation of different adhesive strengths within the adhesive monomers having the same HLB value but different molecular structures.

Adhesiveness↗
PubMed1998

The long-term effect of occlusal therapy on self-administered treatment outcomes of TMD.

Because of a lack of substantial scientific data, the efficacy of occlusal therapy for the management of temporomandibular disorders (TMD) is still controversial. Of a total of 1405 consecutive TMD patients examined over the last 10 years, 369 (26.3%) were determined to have completed treatment at least 1 year before the present survey. A sample questionnaire was mailed to each patient in this sample population. The questionnaire failed to reach 46 patients; of the 323 patients who received the questionnaire, 260 (80.5%) responded. The mean duration of time between their last visit and this survey was 3.7 years. The questionnaire elicited information on treatment outcomes, present treatment needs, and current signs and symptoms. Participants were divided into two treatment groups: (a) those who underwent some occlusal therapies (Phase II) following successful reversible therapies (Phase I) (20 men and 114 women); and (b) those who underwent reversible therapy only (33 men and 93 women). Participants were further differentially diagnosed into five diagnostic subgroups of TMD, based on the clinical examination at the initial visit, tomography, and, for some patients, magnetic resonance imaging. The subgroups included myalgia, arthralgia, anterior disc displacement with an without reduction, and osteoarthritis/osteoarthrosis. Only 12.3% of the total population surveyed reported lack of improvement to an acceptable level and further need for treatment. The remaining patients reported satisfactory results in the reduction of TMD symptomatology and no further need for treatment, because their symptoms had either disappeared or improved to an acceptable level. Regardless of treatment groups and diagnostic subgroups, the current subjective signs and symptoms were negligible in most patients, and mean mouth openings were in the normal range. No particular diagnostic subgroups seemed to have significantly better outcome following Phase II occlusal therapy. These results suggest that the majority of TMD signs and symptoms improve to an acceptable level with only reversible therapy, and the long-term value of additional occlusal therapy following reversible therapy is minimal. Therefore, permanent occlusion-changing therapies apparently are not generally needed to maintain TMD symptom reduction over time.

Activities of Daily Living↗
PubMed1997

The effect of occlusal appliances and clenching on the temporomandibular joint space.

It has been suggested that stabilization appliances and mandibular anterior repositioning appliances work by decompressing the temporomandibular joint. To indirectly test this assumption, tomograms of right temporomandibular joints of seven subjects were taken during comfortable closure and maximum clenching in maximum intercuspation and on the two types of occlusal appliances. Outlines of the condyle and the temporal fossa were automatically determined by an edge detection protocol. Upon comfortable closure, the anterior joint space dimension was reduced with stabilization appliances and mandibular anterior repositioning appliances. Upon maximum clenching, the minimum joint space dimension on stabilization appliances was equivalent to that seen in maximum intercuspation, while that on mandibular anterior repositioning appliances was substantially less (P < .05). Findings do not indicate that these appliances induce an increase in joint space during clenching.

Adult↗
PubMed1997

Long-term follow-up study on drop-out TMD patients with self-administered questionnaires.

Although patient attrition might be a serious threat to the validity of treatment-outcome studies on temporomandibular disorders (TMD), studies on TMD patient attrition are scarce. Of the 1405 consecutive TMD patients examined in a recent 10-year period, 367 (26.1%) drop-out patients or patients identified with a control group were sampled. A mailed questionnaire failed to reach 41 patients, and 203 (62.3%) were returned. The questionnaire elicited information on reasons for dropping out, changes in symptoms, treatment received in other clinics after dropping out, present treatment needs, and current signs and symptoms. Dropouts were divided into two groups: (1) those who failed to show up for their first scheduled appointment after the clinical examination; (2) those who failed to complete treatment. A group of patients who were judged by the examiner not to need treatment were included as a control group. The main reasons for dropping out were environmental obstacles, perceived improvement of the disease, and dissatisfaction with services. Only 21.7% considered themselves to be in need of treatment, and only 10.3% had visited other clinics after dropping out. Only 8.9% complained of the continued aggravation of symptoms, whereas 57.6% reported improvement. In addition, pain, dysfunction, and daily activity limitation tended to improve with time, although temporomandibular joint noise tended to persist. These results suggest that TMD signs and symptoms tend to decrease in patients after dropping out, and that the natural fluctuation of TMD signs and symptoms should be taken into consideration when treating TMD.

Adolescent↗
PubMed1996

Temporomandibular disorders in the adult population of Okayama City, Japan.

In order to discover the prevalence of signs and symptoms of temporomandibular disorders (TMD) in Japan, and the difference in the prevalence among various sex and age groups in the Japanese population, 672 individuals (304 males and 368 females, age range 20-92 years) were selected randomly in Okayama City, Japan, and were investigated by means of questionnaires and clinical examinations. The reported frequency of symptoms was: TMJ sounds 24%, facial-TMJ-jaw pain 11%, headache 27%, teeth clenching 30%, and grinding 34%. The percent frequency of the following signs was: impaired mouth opening 5%, clicking 46%, reciprocal clicking 20%, crepitus 19%, TMJ tenderness 6%, and masticatory muscle tenderness 21%. The subjects with TMJ clicking were more frequently females than males. TMD signs and symptoms were found to be common in all age groups, but they were fewer in the older than in the younger age group. The younger-aged subjects with clicking appeared with significant frequency, whereas crepitus was populated with significant frequency by the oldest age group.

Adult↗
PubMed1989

[Microbeading resin-bonded retainers. 1. Tensile bond strengths and durability].

With the development of adhesive luting resins that adheres both dental alloys and tooth enamel has been widely used the resin-bonded fixed partial denture recently. Since we experienced, however, that the metal retainers without mechanical retention such as channels were often dislodged with metal interface failure, the more durable bonding between a luting resin and a metal has been desired. This study was undertaken to investigate the effect of microbeading onto the adherent metal surface on the tensile adhesive strength between an adhesive luting resin and a dental alloy. Maxgold equivalent to Type IV gold and Panavia EX were used as an adherent metal and a luting resin, respectively. The following conclusions were drawn: 1. Microbeading on the adherent metal surface made no contribution to an increase of the tensile adhesive strength, unless the adherent surface treatment was achieved. However, once 50 microns alumina blasting and tin plating were achieved on the microbeaded metal surface, the tensile adhesive strength was significantly increased. 2. Taking into account the fabrication technique and the tensile adhesive strength, the optimum diameter of microbeads seems to be 150 microns. 3. In the result of various accelerative durability tests (invasion tests in 70 and 100 degrees C water, thermal cycling between 4 and 60 degrees C water), the durability of 150 microns microbeaded metal surface on which 50 microns alumina blasting and tin plating were achieved was much better than that of the smooth metal surface.

Dental Alloys↗
PubMed1989

[Adherent surface treatment that improve the shear bond strength of calcium metaphosphate glass-ceramic (CMP)].

In this study we examined the shearing adhesive strength between a calcium metaphosphate glass-ceramic (CMP) and various luting materials. Two usual luting cement-zinc phosphate cement (Elite Cement 100), glass-ionomer cement (Fuji ionomer cement Type I) and three adhesive luting resin-Super Bond C & B, Panavia EX and a tentative luting resin were used as the material. We also examined the effect of three adherent surface treatments--50 microns Almina blasting, hydrofluoride etching, and sodium hydroxide etching--on the adhesive strength of the two adhesive resin, Panavia EX and the tentative luting resin, to CMP. The following conclusion were drawn: 1. The adhesive strength to CMP surface polished with #600 emery paper was higher in order of Super Bond C & B, a tentative luting resin, Panavia EX, Fuji ionomer cement Type I and Elite Cement 100. 2. Sodium hydroxide etching was the most effective for the adhesion between the adhesive luting resin and CMP among the above four adherent surface treatments. 3. Irrespective of the etching time, the stimulation of sodium hydroxide bath by supersonic waves gave an additional increase to the adhesive strength. 4. Under the stimulation by supersonic waves, increasing sodium hydroxide concentration tends to increase the adhesive strength, whereas it is little affected by the etching time within three minutes. The maximum was obtained with concentration in four or five normal (4 or 5 N) sodium hydroxide.

Calcium Phosphates↗
PubMed1989

[Evaluation of the effectiveness of ion exchange on strengthening of dental porcelain].

This study evaluated the effectiveness of ion exchange on strengthening of porcelain used in metal ceramic. The paste for ion exchange was painted directly on the porcelain surface, dried, and heated at 450 degrees C in the porcelain furnace. The bending strength of porcelain test samples (6.5 x 1.5 x 20 mm), the compressive strength of porcelain-fused-to-metal (PFM) crowns, which were cemented on the metal dies of upper central incisor by an adhesive luting resin 'Panavia EX', and the color change of porcelain test samples (phi 10 x 4 mm) were measured before and after ion exchange. The conclusions were: 1. It was confirmed by X-ray analysis that the compressive stress layer generated by ion exchange for 30 minutes was 150-200 microns in thickness. However, further elongation of time of ion exchange elicited no significant argumentation in the strength. 2. 34 or 57 percent increase of the mean compressive strength of PFM crowns was observed after ion exchange for 30 minutes when the load was applied in the direction of 45 degrees lingually to the tooth long axis or of the tooth long axis, respectively. 3. No significant decrease was found when parts of the incisal edge or the lingual surface of PFM crowns which were strengthened by ion exchange for 30 minutes were reduced by 200 microns. 4. There was so slight difference in the color of dental porcelain before and after ion exchange that the influence seemed to be negligible in its clinical application.

Dental Porcelain↗
PubMed1989

[Effect of zinc iontophoresis on sealing of dentinal tubules by a new handy electolytic applicator].

The authors devised a new handy apparatus for iontophoresis in order to prevent pulp irritation caused by tooth reduction. This study was intended to observe the ability of the device. 8% zinc chloride solution was iontophoresed in the dentin of extracted human and bovine teeth by the device. Then, the dye and microbial invasion tests were carried out to investigate how effectively it could seal the dentinal tubules. The following conclusions were drawn: 1. By the zinc iontophoresis, the zinc briefly penetrated into the deep portion of the dentin. 2. The zinc iontophoresis by using the new device showed enough ability to decrease the coloring and bacterial invasion into the dentin, although all of the dentinal tubules were not sealed. 3. The tensile strengths of an adhesive luting resin 'Panavia EX' to the bovine dentin decreased significantly by the zinc iontophoresis. This phenomenon could be partly due to the lack of resin tag formation into the dentinal tubules.

Animals↗
PubMed1989

[Influence of luting materials on marginal fitness and tensile strength of full veneer crowns. Comparison between conventional dental cements and adhesive luting resins].

The ability of luting materials to minimize the marginal opening during the cementing process is an important factor in preventing recurrent caries and gingival inflammatory response. The newly developed adhesive resins may have the possibility to achieve better retention and to minimize the microleakage at the tooth/restoration interface since they have the ability to adhere both dental alloy and tooth structure. The purpose of this study is to compare the marginal fit and tensile strength of full veneer crowns cemented by two adhesive resins--Panavia EX and Super-Bond C&B--with those cemented by three usual luting materials-zinc phosphate cement, polycarboxylate cement, and glass-ionomer cement--. The results were summarized as follows: 1. Panavia EX provided the most excellent marginal fit, whereas Super bond C&B the worst. 2. There was no significant difference in marginal fit between the shoulder and the chamfer configuration in every luting material examined. 3. The tensile strength of full veneer crowns cemented by the two resins was approximately 4-5 times as large as that cemented by other three luting materials. 4. The results show that Panavia EX was superior to other four materials in that it had the highest tensile strength and the least marginal opening at the crown/abutment interface.

Acrylic Resins↗