This study was performed to investigate release of Ca ion from non-crystal calcium phosphate using the specimen which underwent heating at 800℃,1000℃, and 1100℃. The quantity of Ca ion and pH value was measured 1 day, 1 week, 2 weeks, 4 weeks and 8 weeks after immersion. The main results were as follows:
1. Non-crystal calcium phosphate showed the maximum amount of release for calcium ion.
2. Sintering of Hydroxyapatite at 1100℃ showed maximum amount of release for calcium ion.
3. By increasing the immersion, amount of Ca ion was decreased.
4. Relationship between amount of Ca ion and pH value was not clear.
5. Non-crystal calcium phosphate heated at 1000℃ and 1100℃ was identified as well-crystallized Hydroxyapatite.
6. Non-crystal calcium phosphate heated at 1000℃ and 1100℃ was observed as crystals on the surface of powder.
In order to know the influence of laboratory temperature on the properties of the quick-heating investments, the setting expansion, heat expansion roughness of mold and casting accuracy were measured at 16℃,23℃, and 30℃ under 60% humidity. Results were as follows:
1. With a rise in room temeperature, the setting expansion was increased.
2. With a rise in room temeperature, the heat expansion was decreased.
3. With a rise in room temeperature, the roughness of casting was increased.
4. With a rise in room temeperature, the surface of mold for dimple was increased.
5. With a rise in room temeperature, the casting shrinkage was decreased.
An electrochemical study was made on the relationship between superstructural metals,subjected to dissimilar pretreatment methods, and thermal sprayed coating Ti implant. As a result, the following findings were obtained.
1. The produced electrode potential can be classified as noble or less noble,depending on the types of metals used for superstructures type G (55% Au,26% Ag 10% Cu), type Pd (56% Ag, 20% Pd, 12% Au,11% Cu), type M (66% Ag,19% Sn,10% Zn) and type Ti, and their pretreatment methods.
2. Ti material is less nobel than the superstructural metals and shows a higher electrode potential.
3. The differences of the galvanic current values obtained,after the 264-hour metasurement, between the Ti implant thermal sprayed coating material and the superstructural metals are 14.03 mA/cm2 for type G, 2.53 mA/cm2 for type Pd, and 0.16 mA/cm2 for type M.
4. The galvanic current values of superstructural metals range from 0.02 to 14.12 mA/cm2.
5. The current-potential curve obtained by using cyclic voltammetry shows that the reactions of type G and Pd are reversible regardless of pretreatment.
6. Type M causes a reversible or irreversible reaction,revealing a complicated reaction.
7. Type Ti pretreated by the A method shows an irreversible reaction and type Ti pretreated by the B or C method shows a reversible reaction.
The purpose of this study was to evaluate methods available for estimating changes in various conditions of bone minerals and structure of mandible using X-ray image.
Four specific and conventional techniques were performed for determining bone density:
1. Specific instrument of bite-block for constant condition of X-ray films in clinical treatment.
2. Correcting contrast for bone loss on teeth against background noise on X-ray films using a control marker.
3. Detail images of X-ray density using a microscope.
4. Detail analysis using a computer system.
Specimens were collected from 26 cadavers (18 males, 8 females, 40～90 years old) which had no injuries to the alveolar bone. One hundred sixty-two X-ray films of other specimens were collected during clinical treatment.
Radiographic bone density on four types (type 1, dentious jaw; type 2, molar teeth loss; type 3, first molar or premolar teeth loss; type 4, edentulous jaw thick of jaw body; type 5, edentulous jaw, thin jaw body) were analyzed.
Type 1:The density of bone mineral was low in the alveolar crest bone, which showed irregularly arranged bundle-like bone matrices forming complex networks when soft X-ray instruments were used.The X-ray computer system showed that the level of density increased gradually to the inner region of the mandible.
Type 2: The density of bone mineral of alveolar crest bone was high, and numerous fine complex bone matrices formed networks in the upper basal bone around the mandibular canal. The levels of mineral density gradually increased from alveolar bone to the basal region of the mandible.
Type 3: Complex networks were found in the alveolar bone oriented at right angles to the surface of the mandible. The level of density tivas low at 6 mm below the surface.
Type 4: Compacted mineral matrices were found in the alveolar crest. The level of density increased to 10 mm below the crest.
Type 5: The level of density was only high at the basal portion of the mandible.
The results suggested that the structure of the alveoler crest bone is related to the density of bone mineral in human mandible, and may provide useful information for implantation.
In this study the accuracy of distance measurements on the three-dimensional (3 D) image based on spiral X-ray computerized tomography (CT) were examined by using three fresh human cadaves. Comparative measurements were taken of the mandible removed from the cadaver by using caliper and reconstruted 3 D image (volume rendering) from CT slices. As a result, the variation between caliper and 3 DI measurements averased 0.361mm and incongruellce was 0.558%. In some cases, this means variation was smaller than the measuremtnts of mandible by using caliper. It was concluded that direct measurements on reconstructed 3 DI from data of the spiral CT are applicable to the clinical case.
Osseointegrated implant are popularly accepted by today's general dental professionals as a deficiency prosthetic treatment with high predictability. Osseointegration is defined as a condition in which the bone structure comes in direct contact with the fixture. However, since osseointegration has no mechanism to buffer impact, as in the case of a natural tooth, and the force applied is transmitted directly to the bone, it provides dynamic characteristics different from those of a natural tooth. Most clinicians have empirically taken precautions to guard against failure of osseointegration caused by external force by increasing the number of fixtures to be inserted or inserting as long a fixture as possible.However, few experimental studies have investigated and elucidated the differences in stability of the fixture under various stresses generated by differences in fixture length. Therefore, the dynamic effects of differences in fixture length on the mandible was investigated using a method for measuring the degree of strain on the bone surface.
In this case, a static load was applied to the implant superstructure of an experimental model fabricated by inserting the fixture in a dried human mandible, and the findings obtained are reported here.
Four Brånemark system implants® (available from Nobel Biocare Japan) were inserted between the right and left mental foramens of the mandibles in conformity with the generally practiced technique.Four fixtures were called R 1, R2, L1, and L2 from the right side.
The torque required for fixture insertion was 10.1±0.84 Ncm for the 7-mm fixture and 20.8±4.80 Ncm for the 15-mm fixture, and it was assumed that the latter could achieve strong fixation.
Validation was done for bone strain caused by the difference in the fixture major axis, and as a result, significant differences were observed in the alveolar parts and diaphysis corresponding to R 2 and L 1 when a load was applied to the median portion. When a load was applied to the left-side distal portion, significant differences were observed in the alveolar parts and diaphysis corresponding to L 1, L2, and R1. When a load was applied to the right-side distal portion, significant differences were observed in the alveolar parts and diaphysis corresponding to R 1, R 2, and L 2. Furthermore, in strains around the fixture head portion, significant difference was recognized.
Consequently, the results suggested it is desirable to use as long a fixture as possible whose top end reaches the compact bone to achieve strong fixation and to disperse stresses when fixtures are inserted.
The Video Overlay Monitoring System (VOLMS) superimposes vital signs from a monitor onto images for medical use. Image quality attained by the camera component as well as the recording and playback components of VOLMS was evaluated.
Based on the measurement using test charts, the resolution of a camera for an overall view of surgery and that of an intraoral camera were 320 to 350. While an object of 2.5 mm or larger could be identified at a distance of 70 cm in the overall view, an object of 90 micrometers or larger at a distance of 21 mm could be identified by the intraoral camera. The resolution of a still video recorder and that of a printer were 450 to 500. Due to VTR's low resolution of 270, the overall system resolution was decreased. Blue chroma of the intraoral camera was low and its luminance was generally high, which was no problem for clinical use. Both chroma and luminance of the recording and playback components were satisfactory. The standardized pictures of implant placement to superstructure setting clearly showed wound healing around the implant. In this care, any changes in vital signs suggestive of general infection were not observed even in the inflammation period.
Clinical estimation of a diagnostic stent for mandibular implant using a multimodal radiography system has been shown.The purpose of this study was to estimate the availability in a cross-section of the mandible by tracing on a panoramic tomogram for evaluation of edentulous mandible and the effect of inclined positioning for measurement of the mandible. The reference markers were placed on the phantom for indicating X-ray beam to compare panoramic radiograph with panoramic tomogram.
The edentulous mandible was cut in the incisor,premolar, and molar regions to be 3 pieces and fixed to the mandibular positioner by resin. The metal tube was placed in each region vertical to the crest of the mandibular corpus. Subsequently, the mandible on the mandibular positioner was tilted up to 0° (standard position in our method), 5°,10° and 15°. The cross-sectional tomographic image of four angles was obtained by AZ 3000 to determine the width and the length of the alveolar process about three sections.
It was possible to direct X-ray beam using the metal tube for multimodal radiography.
The shape of each section (incisor, premolar, and molar) could be determined by the metal tube on the cross-sectional tomographic image. When the angle of mandibular positioner was tilted over 10°, the width and length of the alveolar process became significantly inaccurate by the paired t-test (p＜0.05). The results suggested that our method using the mandibular positioner and metal tubes was useful to obtain the information of morphometry in edentulous mandible.
The purpose of this study was to coat thin stable calcium phosphates on titanium substrates using a discharging method in an electrolyte. A titanium plate was connected to the cathode with a platinum anode in phosphoric acid and citric acid solution with oversaturated tri-calcium phosphate powder using a pulsed battery and was treated under discharging. The surface of titanium plates was coated by a calcium phosphate layer with treatment. The surface and the sectioned surface of the coated titanium plates were observed by SEM.
The coated layer was also analyzed by EDX, X-ray diffractory (XRD) analysis, and IR analysis. SEM observation on the sectioned surface revealed that the coated layer with a thickness of 5-10 μm adhered to the mother metal tightly. The results indicated that the composition of the coated layer was hydroxyapatite when the electrolyte contained 2 wt% phosphoric acid with citric acid. On the other hand, that of the coated layer was β-TCP when the electrolyte contained 4 wt% phosphoric acid with citric acid.
Therefore, thin stable calcium phosphate coating without secondary components on titanium could be obtained by discharging in an electrolyte when adjusting the composition and content of the electrolyte.
The purpose of this study was to morphologically and histomorphometrically evaluate the osseointegration between regenerated bone and dental implants. Following a four-month healing period after tooth extraction of beagle mandible, e-PTFE membranes were placed over the standardized defects. Subsequently, five different bone-filling materials were randomly placed under the membranes. The materials used were autogenous bone graft, demineralized freeze-dried bone powder of dog origin, bovine inorganic xenograft, beta-tricalcium phosphate, collagen-fleece, and membrane alone as a control. Following a healing period of six months, non-submerged implants with a titanium plasma coated surface were inserted in the sites. Three months after implant placement, the specimens were histologically analyzed in the non-decalcified sections.
On the radiographic measurement of defect sites in the beagle's mandibles at the ridge augmentation, recovery of bone height by GBR in DFDBA, auto-bone and TCP graft sites was much better than in the control, collagen and Bio-Oss® graft sites with statistically significant differences.
No statistically significant differences were revealed in direct bone contact rate between the six groups. The percentages of Bio-Oss® remnants demonstrated higher rates than the other four materials three months after implantation. The results suggested that implants could achieve good bone contact with regenerated bone in defects filled with a variety of bone filling materials.
The purpose of this study is to measure electrode potential of porous-surfaced endosseous dental implants in the human mouth. The electrode potentials of porous-surfaced dental implants in the mouth of patients were measured in conjunction with a platinum micro-probe.
Number of patients were of 22, ranging from 34～68 years.
The electrode potentials of 47 porous-surfaced endosseous dental implants were within the range of 0～-200mV (AgCl) and were not influenced by the stage of implantation (0～54 months after connection of the superstructures).
Comparison of the electrode potentials of the implants between male and female, time durations after the superstructures connection showed no excessive change in the patterns of distribution.
Among 9 mm length implant group, 1 mm smooth coronal region group showed base values than 2 mm smooth coronal region group. The electrode potentials of fixtures toward base values according to remove the superstructures.
This indicate electrode potentials of fixtures suppress the corrosion of Pd-Au-Ag alloy.
In postoperative diagnostic imaging of dental implant treatment, intraoral radiography is most frequently used. However, bone resorption on the buccal or lingual side of a dental implant may not be evaluated using this technique. Tomography can detect bone resorption surrouding the dental implant.
The purpose of this study was to assess the usefulness of cross-sectional tomography using a panoramic machine in postoperative diagnostic imaging of dental implants.
Six patients were examined in this study.Panoramic radiography and cross-sectional radiography were performed in the sites of 15 dental implants.
Bone resorption surrounding the dental implant was evaluated in each radiograph.
Then obstructive shadows from the neighboring dental implants were observed in cross-sectional tomograms. Moreover, the treatment outcome of the dental implants with bone resorption was investigated.
The results were as follows:
Bone resorption was observed in 7 of 15 sites by panoramic radiography. On cross-sectional tomograms, bone resorption could be evaluated buccolingually. Moreover, bone resorption was noted on only cross-sectional tomography at two dental implant sites.
Although the images of objective dental implants on cross-sectional tomography were superimposed obstructive shadows from neighboring dental implants in 12 of 15 dental implant sites, they did not seriousiy impede the diagnoses.
In the anterior region, all obstructive shadows were located on the lingual side of the objective dental implant.
Six of 9 dental implants with bone resorption on radiography were removed after diagnostic imaging.
In conclusion, it is believed that cross-sectional tomography using a panoramic machine is useful in the postoperative diagnostic imaging of dental implant treatment.
In prophylaxis of postoperative infection, an air-cleaner was used to remove air-contaminant bacteria and fungi in the operating room during dental implant surgery. In general, next to Coagulasenegative staphylococci, the most frequent isolate, Corynebacterium species was isolated in the operatmg room.
When an air-cleaner was used during the operation, the bacteria and fungi were considerably decreased, especially fungi decreased below the detectable level. To the results indicated that application of an air-cleaner was decreased air-contaminant microbes in the operating room for the dental implant surgery.
The treatment room of the dental clinic were usually polluted by bacterial aerosols and flouting dust such as impression powder, dental plaster, dental metal,and tooth scrapings. It is very important to remove these factors of infectious materials in order to protect the staffs and patients from infection in the dental clinic.
In this study, the bactericidal effects of the extract from the natural plants(ICES ®) were investisated. The results were as follows:
1. The treatment room of the dental clinic surveyed in this study was polluted all times with many kinds of bacteria.
2. Bactericidal effects of the extract from natural plants (ICES ®) was observed in the treatment room of the dental clinic.
The results suggested that the extract from natural plants (ICES ®) may be useful for the prevention of infection in the dental clinic.
A clinicostatistical study was made on the first stage of surgery of dental implants in 204 cases with intravenous sedation during the past 3 years at the general dental office in order to analyze the effectiveness of Midazolam intravenous sedation with analgesic Butorphanol.
The results were as follows:
1. Male patients were 59 cases (28.9%) and female 145 cases (71.1%). Age distribution was fifties 33.3% and forties 30.9%. Mean age was 52.0±11.0 years.
2. Preoperative complications were hypertension 25 cases and diabetes 12 cases. The prevaｌence rate of general diseases was 32.4%.
3. Dental implantation was devided into 3 blocks in the mandible and maxilla, and each jaw also divided into premolar-molar and incisor regions. The 1 block group consisted of 81 cases, mean 2.1 dental implants, mean operation time 54.3 minutes, 2 blocks group was 66 cases, mean 4.0 dental implants, mean operation time 92.0 minutes, and more than 3 blocks group was 57 cases, mean 6.0 dental implants, mean operation time 115.6 minutes.
4. The administration dose of Midazolam after injection of 1 mg of analgesic Butorphanol was 2.10 mg±1.39 (0.028mg/kg) of 1 block group, 2.69 mg±1.69 (0.041 mg/kg) of 2 blocks group, and 3.85 mg±2.21 (0.055 mg/kg) of more than 3 blocks group. The mean dose of Midazolam was increased accompanied with increase of the number of operation blocks. The hemodynamics and respiratory condition during implantation were stable in each block group.
5. There was remarkable amnesia during the operation and some postoperative pain and swelling. There were no serious complications. There has been no falling and removal of dental implants.
It is concluded that the effectiveness of Midazolam intravenous sedation with Butorphanol was remarkably high in dental implants operation.
Clinical application of an implant as well as a prosthetic appliance with conventional denture is being established in patients with loss of multiple mandibular. Teeth there are two applications which are a method with bone-anchored bridge and another method with overdenture by supporting with a few number of implants.
The comparison among various attachments used for overdenture by supporting with a small number of implants are conducted and some findings are reported.
Questionnaires presented to the members of this study group included the following.
1. The distribution of age and sexuality of patients
2. The kinds and types of attachments (bar attachment, conus crowns, magnetic attachment, O-ring,etc.), and the frequency of use
3. The results with age of each attachment
4. The contents of the trouble cases in each attachment
5. The prognostic results by the relationship of occlusion in each attachment
6. The results by the supporting style of a bar attachment
These subjects were mainly studied by using long-term patients as controls,and preferable methods were discussed.
Long-term persistence of mandibular overdenture was highly observed even if it was supported with a small number of implants, suggesting an effective method with high predictability.
Clinical analysis of 24 patients who had removed dental implant due to failure at the department of Oral and Maxillofacial Surgery, Asahi University School of Dentistry from June 1983 through July 1998 was reported. They had been treated dental implant therapy at other clinics.
The results were as follows:
1. Twenty-four patients were 15 males and 9 females aged 17 to 74 years.
2. Thirty-five implants had been removed from 24 patients.Those implants included 20 plate type, 10 cylinder type,and 5 pin type implants. The superstructures of implants were connected to natural teeth in 26 cases and individual implants in 9 cases. Only 2 implants in this study were osseointegration implants.
3. The most (19 cases) of reasons to remove were mobility of implants and/or fibrous tissue with surrounding inflammation. Other reasons were maxillary sinusitis (2 cases), paralysis of the inferior alveolar nerve (2 cases), and severe sensitivity (1 case).
4. Nine patients in this study have systemic diseases.
This report describes the uprighting of severely impacted lower second molars using implants as an orthodontic anchorage. At first, the mandibular third molars were extracted. Four months after extraction, the implants were placed in the retromolar area about 5 mm distal to the mandibular third molar regions under local anesthesia and intravenous sedation. The impacted second molars were surgically exposed and lingual buttons were bonded to the occlusal surface of the teeth. The impacted teeth were brought into the oral cavity with elastics orthodontically. The treatment time for completely uprighting the lower right impacted second molar was 4 months and that of the left one was 7 months.This uprighting technique did not adversely affect other teeth and/or dental arches as an orthodontic anchorage. Therefore, it is inferred that this technique could be an effective way to upright the impacted lower second molars.
Successful prothodontic treatment is one of the important factors for long-term implantological success. In addressing the subject of implant prothodontics, one must consider not only the occlusal conditions but also the materials of the superstructures.
Recently, castable ceramics has been introduced as biocompatible restorative materials. In particular, β-Ca(PO3)2, which is stable in H2O and acid, possesses similar physical features to tooth enamel. Thus, in the present study, color matching, strength, bone conditions of periimplant tissues, and influence on the oral environment when calcium phosphate derived castable ceramics crowns are used as a superstructures of implant were assessed. The results were as follows:
1. Color matching
Color matching of castable ceramics to natural tooth is better than those of metal and thermosetting resin.
No crack was found in the castable ceramics crowns during the observation period.
3. Influence on antagonist
Antagonistic tooth did not have any clinical changes after constructing superstructures using castable ceramics.
4. Bone resorption
No bone resorption was observed after cementing superstructures using castable ceramics.
The results suggested that the calcium phosphate derived castable ceramics crown may be preferable to other materials as a superstructure of dental implant.