Objective: Low-intensity pulsed ultrasound (LIPU) treatments have been used for intractable fractures in the orthopedics field. In this study, we examined the influence of LIPU for osseointegration in bone defects between titanium implants and bone tissue after primary operation for two-stage dental implants and then evaluated whether the LIPU is effective in reducing the period between the first and second operations.
Materials and methods: Both sides of the mandibular premolars of beagle dogs were extracted prior to the primary dental implant operation. After three months, titanium implants were placed in both sides. One week after implantation, the irradiation was started for the left sides. The right sides (controls) were not LIPU. Two kinds of irradiation pattern (1.0 MHz or 3.0 MHz) were administered 15 minutes per day for seven days. The dogs were sacrificed the day after the final irradiation was performed. The specimens were fixed with 10% neutral buffered formalin and embedded with MMA resin. The quantity of newly formed bone was analyzed by a color image system with 30μm thin sections after histochemical staining.
Results: No inflammation was observed for control and experimental sites. According to the color image analysis, with the 3.0 MHz irradiation newly formed bone occupied 34.7% of the new bone measurement area and 17.3% with the 1.0 MHz irradiation, while only 11.2% of the new bone measurement area was occupied for the control sides, indicating that the irradiation with 3.0 MHz LIPU was almost three times as effective as non LIPU for osseointegration.
Conclusion: These results suggested that 3.0 MHz LIPU treatment was useful to reduce the period between primary and secondary operation of dental implants.
Evaluation of jawbone quality is very important for successful implant treatment; however, a method to evaluate bone quality of the jaw has not been established. Furthermore, at present, bone classifications are relatively rough and subjective methods for pre-operative assessment. This study compared the buccal and the lingual cortical bone mineral densities (BMD), and correlation trabecular BNID and cortical BMD by quantitative computed tomography (QCT).
The subjects were 56 patients with mandibular distal extension defect (20 males, 17 pre-menopausal and 19 post-menopausal women;age range 30 to 79 years). The buccal and lingual cortical BMD and the trabecular BMD were measured by QCT. The difference and the correlation among the three groups were estimated.
The results were as follows.
1. The buccal cortical BMD was significantly higher than the lingual cortical BMD in the male and pre-menopausal group. However, no significant difference was seen between the buccal and the lingual cortical BMD in the post-menopausal group.
2. The buccal cortical BMD correlated well with the trabecular BMD in the male group.
3. The buccal and the lingual cortical BMD did not
correlate with the trabecular BMD in the pre-menopausal group.
4. The buccal cortical BMD correlated significantly with the trabecular BMD in the post-menopausal group.
In conclusion, it is important to consider these tendencies of mandibular BMD in dental implant treatment.
It has been reported that titanium materials suffer from fatigue fracture, so the working strain must be removed. However, when titanium is heated at elevated temperatures, the material will deteriorate due to absorbed gases such as atmospheric oxygen. Characteristic material changes of titanium were investigated when titanium was heated to 400, 600 and 800℃ for 40, 60 and 80 minutes, respectively. After these heat treatments, bend strength, strain amount, yield strength, hardness, color changes, diffusion of oxygen and nitrogen, and micro structural changes were investigated and compared. The main results were as follows.
1. The bend strength, yield strength and hardness decrease with increasing temperature. The influence of heating time was not recognized.
2. The strain amount was not influenced by temperature or heating time.
3. The weight gain due to air oxidation tended to increase with increasing temperature and heating time.
4. Inward diffusion of oxygen and nitrogen was observed during heating,
5. There were no changes in grain size before and of ter heating at 400℃ and 600℃. On the other hand, grain growth was observed when titanium was heated to 800℃.
6. Some of the working strain was removed with 600℃ heating which was not accompanied with grain growth.
This study analyzed the clinical prognosis of HA-coating implants in the mandibular posterior region in patients with varying experience of periodontal bone loss in the natural dentition before implant placement. By assessing the degree of radiographic marginal bone loss in the remaining natural dentition at the time of the implant therapy, an age-related bone loss score (ArB-score) was calculated to describe the patient's experience of periodontal destruction. The two end quartiles of the description of the patients with regard to the ArB-score were defined as High ArB-score group and Low ArB-score group, respectively.
For the prognosis observation after implant placement, a parameter of implant was bone resorption of implant body circumference and drop-out of implant. As a result, a total of 223 HA-coating implants were inserted in the 68 patients. In the Low ArB-score group, 6 implants failed from the time of bridge installation to 5-11 years as compared to 15 in the High ArB-score group. Hence, the 5-11 success rate was 94.9% in the Low ArB-score and 85.7% in the High ArB-score group. The High ArB-score group had a significantly higher incidence of implant failure than the Low ArB-score group.
These results showed that the patients who were characterized as Low ArB-score had a good prognosis even if HA-implant was selected. However, in the case of HA-implant placement in a patient characterized as High ArB-score, the possibility of resorption of implant body circumference bone and drop-out of implant during the maintenance period was high.
To clarify the effects of two different surface roughnesses of Brånemark implants (Nobel Biocare, Gotebörg, Sweden), a relatively smooth machined surface and a rougher surface created by anodic oxidation, on the failure of osseointegration establishment (early failure), we statistically carried out a clinical examination on those implants, 432 fixtures with smooth surface and 118 fixtures with rough surface.
The results are summarized as follows:
1. Fifteen smooth fixtures (3.5%) and one rough fixture (0.8%) failed to establish osseointegration before the fitting of superstructures. However, there was no significant difference in early failure between them.
2. In the maxilla, the early failure of the rough fixture was significantly lower than that of the smooth fixture.
3. In the case of low initial stability of a fixture at the installation, the early failure of the rough fixture was significantly lower than that of the smooth fixture.
4. Although the length of a fixture, bone quality and bone quantity affected the early failure of the smooth fixture, they did not affect the early failure of the rough fixture.
5. Sex, age, site of placement, diameter of a fixture, the healing period between fixture installation and abutment connection and smoking habit did not affect the osseointegration establishment of those fixtures.
The immediate or early loading method can shorten the duration of treatment with relevant satisfaction for patients. A 66-year-old female patient with completely edentulous mandible received four implants placed in the interforaminal area using CT images as the reference. Two weeks later, the implants were connected with a Dolder bar and loaded with an overdenture. Each implant was evaluated at the time of prosthetic loading and at every 2 months after initial prosthetic loading. At each follow-up visit, a panoramic radiograph was taken and the mobility of each implant was examined using the Periotest.
Ahigher Periotest value than usual in one of the combination implants was obtained at 4 months after initial prosthetic loading and periimplant inflammation was suspected. However, periimplant bone loss was not observed in the radiograph. Six months after initial prosthetic loading, the Periotest value reduced to baseline and periimplant bone loss in the radiograph became clearly visible. This delay may be due to the latent stage of the inflammatory periimplant bone loss in the radiograph.