Guided bone regeneration (GBR) technique has been used widely with dental implants, however, the technique is still not fully established. Particularly, in humans, the minimum time to regenerate bone defects covered with a barrier membrane is still unknown. The purpose of this clinical study was to evaluate regenerated bone maturation with long-term indwelling of Gore-Tex^® membrane using X-ray CT imaging as well as conventional diagnostic means. A patient was a 25-year-old woman who had completely a fractured upper right central incisor caused by an accident. She accepted the treatment plan which included GBR and dental implant restoration. After membrane indwelling for five and 11 months, X-ray CT was taken under the same condition and subjected to image processing. The processed X-ray CT image clearly showed that the bone defect was still present even after ll-month membrane indwelling however, we clinically confirmed that solid bone-like tissue existed beneath the membrane. After the membrane was removed, ITI implant was placed and successfully functioned for over one year. It is suggested that the 11-month membrane indwelling period is clinically sufficient for bone maturation but not pathologically sufficient. Further investigation should be conducted to determine of the minimum time of membrane indwelling and develope a method for acceleration of regenerated bone maturation.

View full abstract

It is necessary for the edentulous maxillofacial patient to improve not only the physical function and appearance but also psychological recovery. A case of maxillofacial prosthesis using new material for obturator is reported. The patient is 70-year-old man who received surgical resection of the left maxilla, including orbita and upper half of the ramus of the mandible, to remove a squamous cell carcinoma. In the post-operation course, he visited our clinic to restore mastication, articulation and esthetics. A maxillary prosthesis with a hollow type obturator using light-cured resin type soft lining material was fabricated. To recover the left facial defect, the epithesis using foaming polyurethane was fabricated. 15 months have passed since completion of treatment, however, there was no tissue erosion or bleeding in the supporting area of the maxillary sinus. Physical function was considerably improved and the patient was pleased with his esthetics.

View full abstract

The purpose of this study was to evaluate and compare the mechanical properties, water sorption and solubility and shear bond strengths of eight commercially available luting agents to silver-palladiumcopper-gold (Ag-Pd-Cu-Au) dental alloy. Five adhesive resin cements, Bistite Resin Cement, Imperva Dual, Panavia EX, Panavia 21 and Super-Bond C & B and three conventional luting agents, zinc phosphate (Elite Cement 100), carboxylate (HY-bond Carbo Cement) and glass ionomer (Fuji Bond) were used. In general, resin cements except for Super-Bond C & B showed higher values of Knoop hardness and compressive, diametral and transverse strengths than conventional luting agents. Adhesive resin cements showed much less water sorption and solubility than ordinary cements. Adhesive luting agents maintained excellent bond strengths of approximately 27-37 MPa to Ag-Pd-Cu-Au alloy after 50, 000 thermocycles while alternately immersing the specimen in 4°C and 60°C water for one minute each. These results suggest that resip cements may be more clinically useful for cementing restorations than conventional luting agents.

View full abstract

OXILYZER^® is a device to obtain acidic electrolyzed water from tap water. It is known that acidic water (Aqua-oxidized water) has strong bactericidal effects. We have investigated the biological safety of Aqua-oxidized water for use in the intraoral area, and three tests, hemolysis test usingrabbit blood, cytotoxicity test and mutagenicity test, were performed.
The results were as follows:
I. Aqua-oxidized water had 75% hemolysis potential even under 0.85% NaCl conditions.
2. Aqua-oxidized water showed no inhibition of cell proliferation under 25% concentration. At 25-50% concentration it showed slight inhibition, but no significant differences were observed between Aquaoxidized water and distilled water. And no change in cell morphology was observed.
3. By Salmonella/microsome mutagenicity test, Aqua-oxidized water showed no mutagenicity.

View full abstract

After surgical correction of skeletal class III malocclusions, their morphological and functional changes are observed. The functional changes of mandibular movements were analyzed from a threedimensional standpoint in this study.
In regard to protrusion and lateral excursions, the range of motion of incisal and condylar points between intercuspal position and each occlusal border position was measured. In regard to maximum opening movement, amount of opening at incisal points and the range of motion of the condylar points was measured.
The results were as follows
1. The range of motion between intercuspal position and each occlusal border position increased after surgery for both incisal and condylar points. This is due to the stylomandibular ligament restricting each occlusal border position which moves backward by sagittal splitting osteotomy and to the correction of occlusal interferance during protrusion before surgery.
2. The amount of maximum opening in maximum opening movement showed little change, but the range of motion of the condylar path showed an increasing tendency after surgery. It is suggested that there is close relationship between the change of the range of motion of condylar points and the morphological change of the ramus.

View full abstract

Tooth carving practice is the most fundamental training for students of dental technician training schools to learn the morphology of teeth.
Various tooth carving techniques have been advocated, but students should be trained in techniques that are easy to understand, simple, and less likely to cause accidental cut injuries.
In this study, after guidance manuals of the design mode technique our school adopted (A), Obana's dessin mode technique (B), and direct carving method (C) were explained and demonstrated to students, 10 consecutive tooth carving tasks were assigned. By evaluating the skill acquired by the students from the overall viewpoint and dimensional errors in comparison with the standard model, the following results were obtained.
1. The variance of regression between the number of repetitions of tooth carving assignment and the evaluation point of the product was highly significant in all 3 techniques. The gradient of the regression curve was 0.19, 0.13, and 0.08 in the techniques A, B, and C, respectively, being greatest in technique A.
2. The variance of regression between the number of repetitions of tooth carving assignment and the absolute value of the dimensional errors of the product was significant in technique A, highly significant in technique B, but was not significant at the 5% level in technique C. The gradient of the regression curve was similar for techniques A and B, being -0.032 and -0.034, respectively.
3. Dimensional errors at various sites showed a nearly normal distribution in all techniques at the first assignment.
4. The variance of regression between the number of repetitions of tooth carving assignment and the rate of dimensional errors, which were within ±10% of the standard dimensions, was highly significant in techniques A and B but was not significant at the 5% level in technique C. The gradient of the regression curve was 2.19 in techniques A and 2.51 in technique B, being slightly greater in the latter.

View full abstract

This report shows the superiority of the long period curing at a low temperature, 24 hours at 70°C, in comparison with the result from the previous report, part I 90 minutes at 70°C-boiled 30 minutes, by using the same materials and methods.
The results were as follows:
1. The strain in the specimen produced the tensile strain during processing, and this tensile strain slightly decreased with the lapse of time.
2. The amount of contraction from completion of processing to deflasking was 70% as compared with the result of 90 minutes at 70°C-boiled 30 minutes in the curing cycle.
3. It was defined that the difference of amount of contraction between the long curing period and lowtemperature and 90 minutes at 70°C-boiled 30 minutes in the curing cycle was due to the difference of temperature in final stage of processing.
4. The amount of contraction in each curing cycle showed a significant difference by storage in 37°C water for 7 days.

View full abstract

The bonding and fracture strengths between denture base materials and rebasing materials were examined in two different models (the standard specimens and the bite plate models). The polysulfone (PSF) and polymethylmethacrylate (PMMA) were used as denture base materials and rebasing materials respectively.
The results were as follows:
1. PSF joined with PMMA well in the tensile tests, and PSF had a higher bonding strength than PMMA.
2. When PSF was used as the rebasing material in the bite plate model, the fracture strength of the bite plate model was increased.
3. When PSF rebased PMMA, the fracture strength of the bite plate model decreased and the mechanical strength of PSF was lost.
4. When the bite plate model rebased PSF at the palate, the crack line was short.
5. The thickness of the bonding surface needed to be at least 1.8 mm, when PSF was used as the rebasing material.
6. In comparison with PMMA, PSF was more effecive in thick models.

View full abstract

Various types of artificial teeth have been developed for the denture. Anatomic teeth are generally used for masticatory ability, while nonanatomic teeth are used for denture stability, however which type is more suitable has not been decided yet. The purpose of this study was to examine the influence of the difference in occlusal configuration of lingualized occlusion. The experimental dentures of lingualized occlusion were made using anatomic teeth (30°) and nonanatomic teeth (blade teeth for lingualized occlusion). Four types of test foods were selected, and the food crushing effect and the influence of load variation to the denture were examinated.
The results were as follows:
1. Maximum vertical force
For all test foods, the average of maximum vertical force of the blade teeth was weaker than the 30° teeth, and a statistically significant difference was observed.
2. Maximum horizontal force
A difference was observed in the average of maximum horizontal force in various directions.
3. The crushing effect of the blade teeth was the most effective for hard food crushing.
4. It became clear from the above results, that the blade teeth had an effect on masticatory efficiency, the denture stability and the reduction of bearing stress of surviving tissue.

View full abstract

AuCu-3 wt%Ga alloy bridges with age-hardenable characteristics at intraoral temperature were prepared to evaluate the dimensional change, hardness and surface roughness induced by phase transformation. Distortion behavior due to dimensional changes was determined by measuring the clearance formed between the inner surface of a crown and the metal mold. Phase transformation produced remarkable hardening over a few days by annealing at 37°C, and resulted in linear contraction of 0.04% and roughening of the alloy surface. Contraction ceased in about 3 days. Surface roughness was attributed to surface-relief effect relieving the internal coherent strains which originated in the ordering of AuCu. Bond strengths of an adhesive resin to AuCu-3 wt%Ga alloy and a Type IV gold alloy designed for resin-bonded restorations were also investigated in vitro with the use of two different metal primers. Disk specimens were cast in the alloys. The specimens were primed with either a vinyl-thiol primer or a thiophosphate primer, then bonded with an adhesive resin initiated with a tri-n-butyl borane derivative. AuCu-3 wt%Ga alloy exhibited higher bond strength than Type IV gold alloy with the use of metal primers after 20, 000 thermocycles.

View full abstract

Various kinds of dowel and cores of the patients were examined at the Tsurumi University Dental Clinic during from February to June 1993.
The results were as follows:
1. Plastic materials, having composite resin, decreased from 28% of the previous report to 8% and cast metal dowel and cores increased from 68% to 92%.
2. In cast dowel and cores, Ag-Pd-Cu-Au alloy indicated almost the same frequency, 87%, however, Ag-Pd-Cu-Au alloy decreased from 14% of the previous report to 2%. On the other hand castable ceramic appeared.
3. In plastic materials, composite resin decreased remarkably, from 91% to 44%, and dental cements increased from 9% to 53%.
4. In both anterior and posterior teeth, condition of remaining tooth structure was worse in the present examination than in the previous report.
5. In luting cements for dowel and cores, zinc phosphate cement decreased remarkably and glass polyalkenoate cement increased from 26% to 49%.

View full abstract

A strong earthquake occurred in the southwest area of Hokkaido on July 12, in 1993. Immediately after the earthquake, Okushiri Island, which is near the seismic center, was seriously damaged by a seismic sea wave and a large fire. Edentulous and partially edentulous patients who lost their dentures during the emergency evacuation were treated. Information through questionnaires about dental problems were obtained at the time of the disaster.
The results were as follows:
1. Eating was the most serious problem for persons who lost their dentures.
2. The menu and cooking methods of emergency relief foods were not considered suitable for persons who wore dentures and/or lost their dentures.
3. The results of questionnaires proved that the general public has little knowledge about dentures and/or denture wearers.
4. At the time of a disaster dentists must join as a member of the medical relief team to relieve dental problems or to secure masticatory function when long-term evacuation is predicted.
5. By 3-month follow-up, the dentures constructed and inserted by our team were found to be functioning satisfactorally and our prosthodontic approach was confirmed to be useful.

View full abstract

The purpose of the study was to investigate the relationship between the shape of screw-type titanium dental implants and bone formation. Implants were installed in experimental animals under simulated clinical conditions, and microvascular casts were prepared utilizing the plastic injection method described by Ohta, et al. Then, three-dimensional chronological changes in the microvasculature and bone formation during the bone healing process in the peri-implant tissues were observed using scanning electron and light microscopes.
New bone formation around the implant began in the body and proceeded towards the apical portion, while little change was observed around the flange during the experimental period. Newly formed blood capillaries were observed along the threads surrounding the body of the implant, and later, the implant was surrounded by new bone. Around the apical portion, the vertical cutout was filled with new bone at a relatively early stage.
These results suggest that the shape of the threaded implant is suitable for gaining initial stabilization, receiving occlusal loads, and resisting rotation.

View full abstract

The influence of the occlusal vertical dimension on the muscle fiber conduction velocity (MFCV) and muscle fatigue was studied in the human temporal and masseter muscle in six healthy subjects (22-30years old). Occlusal vertical dimension was changed from the intercuspal position (ICP) to the maximum bite-raising position (21.0mm) by applying three different occlusal splints along the habitual opening-closing movement path. Muscle fatigue was developed until the subject stopped contracting the muscle at each occlusal vertical dimension. The EMG responses were evoked by electrical stimulation of the skin at the mandibular notch. The EMG signals were detected using a surface linear electrode array having seven contacts placed on the muscle fibers. The MFCV was calculated from the time delay between adjacent EMG signals.
The results were as follows:
1. The MFCV was increased with increment of the contraction level but decreased with increment of the occlusal vertical dimension.
2. The MFCV was decreased with muscle fatigue at each occlusal vertical dimension.
3. The endurance time was decreased with increment of the occlusal vertical dimension. The results indicate that occlusal vertical dimension is an important parameter for the propagation velocity of action potentials and for the development of static muscle fatigue.

View full abstract

The effect of the variation of the curvature of the cast circumferential clasp arm on clasp stiffness and stress was evaluated using three-dimensional finite element analysis.The results were as follows:
1. The curvature of the clasp arm under the condition of different lengths affected stiffness and stress.
1) The clasp arm using a non-tapered pattern with a small curvature showed less stiffness and lower stress than the arm with a large curvature.
2) The clasp arms using the original patterns, which were established from our previous study (taper 0.8, T/W ratio: 1/2 or 1/3), showed constant stiffness and low stress instead of change of curvature.
3) The clasp arm using Rapid flex pattern with large curvature showed lower stress than the arm with a small curvature.
2. The clasp arm with an adequate curvature in the condition of the same length showed low stress. This seemed to be the effect of torsion elasticity which was regarded to distribute the stress in the clasp arm.

View full abstract

The aim of this study was to investigate the influences of the color of abutments on IPS Empress' crowns.
IPS Empress^® ceramic disc specimens, metal disc abutment specimens (type IV gold and gold- silver - palladium alloy) and porcelain disc abutment specimens (A 1, A 2, A 3, A 3.5 and A 4) were used to investigate the influence of the color of abutment specimens on ceramic specimens.
The color of ceramic specimens was measured with a small area colorimeter and evaluated by the CIE L^*a^*b^* color system.
The results were as follows:
1. Both metal and porcelain abutment specimens influenced the color of ceramic specimens with a uniform thickness (1.0 mm) and different colors.
2. The colorimetric influences of abutment specimens were decreased with the increase in thickness of ceramic specimens.
3. Metal abutment specimens were brighter and more yellow than porcelain abutments.

View full abstract

An immediate obtainment of osseointegration would shortened the initial anchorage period of implant within bone and setting time of the final superstructure. Application of pulsing electromagnetic fields (PEMFs) as a method for increasing the rate of osseointegration has been considered. PEMFs have been demonstrated to promote the proliferation and differentiation of osteoblast-like clone MC3T3-E1 cells.
Recently, the immunohistochemical staining technique having Brd U or PCNA has been used as markers to study the proliferation dynamics of S-phase cells or late G, to S-phase cells. In this study, cell proliferation was examined in the experimental group having PEMFs-stimulation and in the control group lacking stimulation by immunohistochemical staining technique using Brd U and PCNA monoclonal antibodies. Brd Ulabeling and PCNA- positive indices were respectively calculated and compared. Further, alkaline phosphatase activity was investigated as a marker for cell differentiation of MC3T3-E1 cells by using a histochemical staining technique.
The results suggested that the Brd U-labeling index and PCNA-labeling index distinctly increased in the experimental group (P<0.001). Cells in the S-phase and late G, to S-phases were 1.8 times and 1.6 times higher, respectively, than control. Alkaline phosphatase staining was stronger in the experimental group than in the control group.

View full abstract

In order to evaluate masticatory function especially crushability, the method of evaluation of masticatory crushed particles was determined by applying discriminant analysis. As in our previous study, after 10 masticatory strokes, the crushed particles remaining on a 10 mesh sieve were measured by using a digital photograph analyzer. In the previous study, particle size distribution was divided subjectively into three patterns, and it was hard to evaluate the masticatory function of denture wearers, because most of them were included in the poor mastication group. Thus discriminant analysis was performed for objective evaluation of particle distribution.
1. From 50 samples of two groups (most efficient group and medium group), the discriminant analysis was carried out and discriminant function was calculated, respectively.
2. The score of discriminant function was calculated from all samples, and this value represented the grade of crushing of particles.
3. By using this value of crushability, it was possible to compare mastication with removable partial denture and without denture. Though affected by the consciousness of the patient, the value of crushability was improved by wearing denture.

View full abstract

To assist in developing a “normal” electromyographic (EMG) envelope, various amplitude normalization procedures for surface EMG signals have been used to reduce the inter- and intrasubject variability of collected data. The effect of two normalization methods (normalization to mean ensemble average: NME, and peak ensemble average: NPE) on intersubject variability and reproducibility of surface EMG profiles from masticatory muscles during unilateral gum chewing was examined. The EMG profiles for anterior temporal (Ta), posterior temporal (Tp), masseter (M) and anterior belly of digastric (Da) muscles on chewing side from 5 asymptomatic dentate subjects were made on 3 different sessions. Coefficients of variation and intraclass correlation coefficients, ICC (3, 1), were used to assess the variability and reproducibility. Each normalization procedure reduced the intersubject variability of unnormalized EMG profiles for Ta, Tp and M. NME procedure provided lower intersubject variability for Da. Reproducibility of unnormalized profiles for Ta, Tp and M was significantly improved by the two procedures. The NME procedure on Da was more reproducible than the NPE procedure. These results showed that phasic characteristics of muscular activity influenced the outcome of amplitude normalization. These methods used. were reliable and reproducible for measuring phasic muscle activity of masticatory muscles during gum chewing.

View full abstract

The purpose of this study was to compare the physical of properties three low exothermic type self-curing hard denture relining materials (TR, CT, KL) with those of a conventional type (RR). Surface roughness, color difference, knoop hardness, water sorption, detail reproducibility, internal porosity, fluidity, temperature change during polymerization, transverse strength and adhesive strength for denture base resin was investigated.
TR, CT and KL showed greater fluidity than RR. Fluidity of TR and RR was influenced by environmental temperature.
Maximum temperature was proportionate to the thickness of specimens. TR, CT and KL showed a low maximum temperature during polymerization at 37°C more than RR. There were no notable differences in the maximum temperature during polymerization at 22°C.
The time to reach the maximum temperature during polymerization at 22°C, especially for KL and RR, was longer than that during polymerization at 37°C. The time to reach the maximum temperature was not proportionate to the thickness of specimens.
TR and CT showed higher values than RR in transverse strength and adhesive strength as a denture base resin.

View full abstract

In order to apply super-elastic Titanium-Nickel alloy to castclasps, retention forces and deformation degrees of Ti-Ni alloy castclasps were investigated in comparison with those of conventional cobaltchromium alloy in this study.
In the setting-removing test, retention forces of castclasps and their changes during the test were measured with Akers type clasps and I bar type clasps with the tooth model. Two directions for settingremoving were tested. One is the designed direction and the other is the 30 degrees declined one. The retention forces of Ti-Ni castclasps changed very little in both setting-removing directions. In case of Co-Cr castclasps, the retention forces decreased obviously in both directions.
In the bending test, deformation of Ti-Ni alloy and Co-Cr alloy were measured. Deformation of Ti-Ni alloy also changed very little after 1.0 mm and 3.0 mm displacement. However, Co-Cr alloy was greatly deformed in both 1.0 mm and 3.0 mm displacement.
Considering from these results, Ti-Ni alloy having the superelasticity could be a promising dental material for castclasps in prosthodontics

View full abstract

Restoration of discolored teeth to a more natural color provides the patient with not only a harmonious oral appearance, but also a feeling of self-esteem and psycological satisfaction. Porcelain laminate veneer crowns, which do not require much tooth reduction, have drawn much attention as a type of prosthesis which is capable of restoring discolored teeth while maintaining its original occlusion. However, due to the thinness of the laminate veneer crowns, it is difficult to hide the original color of the tooth abutment while giving it a semi-transparent natural appearance. Thus a more objective method of evaluating the color of discolored teeth by using a non-contact type spectrophotometer was undertaken, and the measured color was evaluated in terms of the CIELab system, Munsell system, and a new index involving color depth which will be referred to as the Rabe θ value.
Results indicated that it is possible to identify the color of teeth using the Rabe θ value, and that color variation between those teeth having natural tooth color to those having discoloration are clearly distinguishable by means of this index. Futhermore, by measuring the Rabe θ value of a tooth before and after placement of a porcelain laminate veneer crown, it was possible to determine the absolute color value of the tooth itself.

View full abstract