Many morphological studies of cell attachment or surface interaction between titanium and host cells have been carried out. However, these studies did not examine mRNA expression of the cells. Therefore, this study utilized the marker enzymes of cells and the expression of mRNAs in order to evaluate the initial attachment of osteoblastic cells on titanium plates which have different surface micromorphologies.
In this study, the in vitro early cellular responses of osteoblast-like cells (MC3T3-E1) were observed on titanium surfaces with different micromorphologies. Titanium plates were prepared with either a rough or a smooth surface morphology, and the circumference of the titanium plates was covered by a silicone tube for cultivating a fixed number of cells. Alkaline phosphatase (ALP) and lactic dehydrogenase (LDH) were used as marker enzymes. The mRNA expressions of ALP and osteopontine (OPN) were also investigated using reverse transcription-polymerase chain reaction (RT-PCR) analysis.
Significantly higher levels of cellular attachment were found on the rough surface than on the smooth one. In addition, ALP and LDH activity of cultured cells on the rough-surface titanium plates were higher than those on the smooth-surface ones.The mRNA expressions of ALP and OPN of cultured cells on the rough-surface titanium plates were enhanced compared with those on the smooth surface plates.
These findings demonstrate that surface roughness alters osteoblast-like cell proliferation, differentiation, and matrix production in vitro. The results also suggest that surface micromorphologies influence the cellular responses of osteoblast-like cells, although further quantitative analyses are required.
Titanium materials, due to their excellent biocompatibility and other properties, are increasingly utilized in the dental field. In general, although metallic materials including titanium materials are relatively difficult to machine, most of the machining problems can be solved by metal injection molding. Using this technique, a feasibility study was conducted for fabricating titanium implant by sintering pure titanium powders. The following conclusions were obtained.
1. The tensile strength of titanium bars which were produced by metal injection molding was equivalent to those of JIS Specification Grade 4 materials.
2. There were no significant differences in Ti dissolution amount in lactic acid solution between commercially pure titanium and titanium prepared by metal injection molding.
3. Microstructural observation revealed that there were internal pores in the injection-molded samples.
4. Further improvements to reduce internal porosity and enhance toughness are required.
Spherical-shaped hydroxyapatite particles (Ca/P of more than 1.7) were heat-treated at 800℃, 900℃, and 1,000℃ for 60 and 300 minutes. The effects of these heat treatments on x-ray diffraction pattern, dissolved amount of Ca and P ions after 5-week immersion in a physiological saline solution, and pH value of HAP were investigated. The following conclusions were obtained.
1. The pH value of HAP changed from 7.6 to 11 after heating. The increment was larger with higher heating temperature. With longer heating time, the pH value increased. The pH value decreased by prolonging the immersion time in the physiological saline solution.
2. The dissolution amount of Ca ion from heat treated HAP particles was higher than that from the un-treated HAP particles.
3. The dissolution amount of P ion from the untreated HAP was higher than that from the heat treated HAP particles, whereas the dissolution amount tended to decrease by increasing the heat treatment temperature.
4. X-ray diffraction patterns identified CaO peaks from HAP particles heated at 1,000℃ for both 60 and 300 minutes. These diffracted CaO peaks disappeared from HAP which was immersed in the physiological saline solution for 5 weeks.
A type of apatite cement, Biopex® could come into contact with either only a little or a lot of body fluid in clinical cases when used for the reconstruction of bone defect. Therefore, in the present study, effects of hardening environment on the conversion and the mechanical strength of Biopex® were studied with respect to humidity, in order to understand the detailed behaviour of Biopex®. We found a slower conversion of Biopex® to apatite in an incubator kept at 37℃ and 100% relative humidity, a circumstance simulating only a little body fluid, than in saline at 37℃, simulating a lot of body fluid. The mechanical strength of Biopex® increased with time, reaching a maximum value approximately at 1-2 weeks regardless of the hardening environment with the Biopex® employed in this study. However, the mechanical strength of Biopex® kept in an incubator showed higher values (p＜0.05) when compared with Biopex® was immersed in saline solution.
We concluded, therefore that the regulation of the hardening environment is important to realize faster conversion and/or obtain a monolith with a higher mechanical strength.
Hydroxyapatite (HA) coated implant is clinically significant and some kinds of these implants are now being used in the clinical scene.
We already examined an ultra-thin HA coated implant using the thermal decomposition method in a pathological study, and acquired good results. In the second study, we embedded implants of ultra-thin HA layered type (HA-type) and pure titanium type (Ti-type) in the femur of rabbits, and compared the bone contact ratio surrounding the implants.
1. Measurements of the thickness of the bone for every point of the HA-type and Ti-type in both groups showed an upward tendency with time within the same type. In a comparison of the same point of the HA-type and Ti-type, the direction of the HA-type showed a higher value than the Ti-type in many cases.
2. When the bone contact ratio at each point was compared, in all weeks the direction of the HA-type showed a higher value than the Ti-type. Moreover, a significant difference was found among both at 2, 4, and 8 weeks. However, no significant difference was found at 12 and 24 weeks.
As the ultra-thin HA coated implant using the thermal decomposition method could bond with a new bone at an early stage, and could achieve initial fixation quickly, we consider that it is useful in clinical settings.
This study investigated clinical results after autogenous bone grafting to clarify the usefulness of the maneuver. The subjects were 27 males and 32 females, of ages from 14 to 65 years, averaging 31.4 years, at the bone graft. They had undergone repair of cleft palate, augmentation of the alveolar ridge, or elevation of the maxillary sinus floor. The donor sites were the ilium and/or jaws.
The following results were obtained
1. There were no major complications, although some patients had experienced wound dehiscence, infection, or paresthesia around the donor or recipient sites postoperatively.
2. The planned treatment could be performed in 93.2% of the patients.
The investigation of the patients that received implant placement after bone grafting revealed:
1. Greater gain of bone height was possible with the ilium compared with the jaws.
2. The increase of bone height was the maximum in cleft patients and the minimum in augmented patients.
3. The length of the implants installed at the grafted sites was longer than 13 mm in almost all of the patients.
4. A long interval after bone grafting was associated with greater difficulty in implant surgery.
These results reconfirmed the safety and certainty of the technique. An adequate time interval from bone grafting to implant placement is essential for easy placement of the implant.
Magnetic attachments are regarded as the third generation retainer, and they are used extensively for the implant prosthesis. However, damage of the denture and recovery of it should be taken into consideration for long-term usage.
We have treated 20 cases with magnetic bar attachments in six years. Although there are very few cases of trouble, we report the causes, recovery, and consideration points.
The main trouble is ill fitness of dentures. In direct rebase after tissue conditioning and pressure impression was done for recovery. It was suggested that rebase could be done securely and easily because the relations of the bars and dentures were stable.
The maxillary posterior region is often a problem area for the placement of implants. The advanced resorption of the alveolar bone is combined with an increase in pneumatization of the maxillary sinus because of the increased air pressure in the pneumatized sinus cavities. The sinus floor elevation method with a crestal approach is a modified approach of the sinus lift method and is less invasive than the usual sinus lift method.
A 42-year-old male desired prosthetic treatment supported by implant because of an edentulous right posterior maxilla, mobility of bridge of the left mandibular molar region, severe marginal periodontitis including lower left premolar, lower left second molar and upper left second molar, and a loss of lower right first molar. Because of bone loss at the edentulous right posterior maxilla, there was inadequate bone for implant anchorage. The patient was a candidate for the sinus lift method including sinus floor elevation method.
The procedures used for this patient included the following. The lower left second molar with advanced periodontal involvement was extracted. The lower left second premolar and the upper left second molar were replanted and transplanted to the lower left molar region, respectively. The lower right second molar was mesially moved surgico-orthodontically to the lower right first molar region. The sinus floor elevation method was performed to place the implant for anchorage at the upper right posterior region. An 11-month period was allowed for graft consolidation and integration. At that time, an endosseous implant was placed. Adequate bone was obtained and then placement of a 10 mm length of implant was carried out. Following a 10-month period of healing, the implant was uncovered and found to be clinically and radio graphically well integrated. An abutment was then placed and subsequently loaded with a fixed prosthesis.
The six-year four-month follow-up of this case revealed a good outcome after the sinus floor elevation method.