Titanium and its alloys are frequently used for dental and orthopedic implants. However, the function of osteoblasts around the titanium implants remains unexplored. In this in vitro study, we investigated the proliferation and mitogenic-activated protein kinase (MAPK;p42/p44, p38, JNK) activity of osteoblastic MC3T3-EI cells on titanium plates. Although there were no significant differences in the levels of cell attachment between titanium and plastic plates (used as a control), cell proliferation on titanium plates was delayed compared with the control. The titanium level in the cells on titanium plates was higher compared with the control. Morphological changes in cells on titanium plates were similar to those of control cells. Proliferation on titanium plates was induced by the addition of insulin-like growth factor 1 (IGF-1), but the induction activity was decreased at a low concentration of IGF-1. The phosphorylation activity of p42/p44 in cells on titanium plates was similar to the control, whereas phosphorylated p42/p44 protein levels on titanium plates were delayed compared with the control. On the other hand, the phosphorylation of p38 and JNK in cells on titanium plates was similar to the control. These results suggest that the delay in osteoblast proliferation on titanium plates might be caused by alterations in the pathway upstream of p42/p44.
Calcium phosphates are the most popular biomaterials for implantation into bone. However, it is still unclear how calcium phosphates affect the activities of osteoblasts. In this study, we investigated the effects of calcium phosphates that have different solubilities on osteoblastic proliferation and differentiation using osteoblastic cell-line MC3T3-E1. In addition, we investigated how the cell situation influenced osteoblastic response to calcium phosphates.
Particles (diameter 53-106 μm) of tetracalcium phosphate (TTCP), α-tricalcium phosphate (α-TCP), β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) were used for this experiment. All kinds of calcium phosphate particles inhibited osteoblastic proliferation. Though the calcium and phosphorus content in the medium was influenced by calcium phosphate particles, culture medium incubated with calcium phosphates (experimental medium) did not influence osteoblastic proliferation.
The effects of calcium phosphate particles on osteoblastic differentiation were investigated by alkaline phosphatase (ALP) activity and reverse transcription polymerase chain reaction (RT-PCR) using dispersed cells or confluent cells. When the calcium phosphate particles were added to confluent cells, ALP activity was not changed, and there was no change of mRNA levels of osteoblast-related genes. However, when the calcium phosphate particles were added to dispersed cells, ALP activity was enhanced by TTCP and α-TCP. The mRNA level of osteopontin (OPN) was enhanced especially by TTCP and α-TCP. The mRNA level of type I collagen (COL) was enhanced especially by α-TCP, and β-TCP. On the other hand, mRNA levels of osteocalcin (OCN), bone sialoprotein (BSP) were not affected by calcium phosphate particles.
These results indicate that the inhibitory effects of calcium phosphate particles on osteoblastic proliferation are not due to the changes of calcium and phosphate ions in the medium but are due to the surface property of the materials. The effects of the calcium phosphate particles on osteoblastic differentiation may be changed by the cell situations such as confluent cells or dispersed cells.
To compare a resonance frequency analyzer and tooth mobility measurement device for the evaluation of dental implant stability, we experimentally installed various implants in vertebral bones of cows and connected abutments. We measured the Implant Stability Quotient (ISQ) calculated from the resonance frequency with Osstell®; and the periotest value with Periotest®.
The results are summarized as follows:
1. With higher abutment, the periotest value decreased, but ISQ was not affected by abutment connection or the height of abutment.
2. With longer installed implant, both the periotest value and the ISQ increased.
3. With larger diameter of installed implants, the ISQ increased, but the periotest value was not affected by implant diameter.
4. Both the ISQ and the periotest value were affected by the direction of the transducer connection or direction of striking.
5. As the marginal bone level decreased, both the ISQ and the periotest value decreased.
6. Both the ISQ and the periotest value were correlated with the implant placement torque, but the ISQ was more correlated than the periotest value.
This research suggests that resonance frequency analysis with Osstell is useful for the evaluation of dental implant stability.
In contrast to mandibular cases, treatment plans for implant placement in the maxillary posterior region are often restricted by the presence of the maxillary sinus. We examined the surgical techniques and treatment results of dental implants placed in the maxillary posterior region using socket lift procedures performed during a 6.5-year period from the establishment of our clinic on October lst, 1997 to March 31st, 2004.
Out of 44 cases involving 85 implants, socket lift procedures were performed in 31 cases and for 50 implants (58.8%). When performing a socket lift procedure, we first measured the vertical residual bone height (RBH) between the alveolar crest and the maxillary sinus floor. Postoperatively, we measured the elevated height (E-H). The RBH values were between 4 and 8 mm, with an average of 6.1 mm. The E-H values were between 2 and 7 mm, with an average of 5 mm. RBH values were divided into the categories RBH-1 (less than 4 mm), RBH-2 (5-7 mm) and RBH-3 (greater than 8 mm), while E-H values were divided into categories E-H1 (1-3 mm), E-H2 (4-6 mm) and E-H3 (greater than 7 mm). The results of this classification were as follows: RBH-1,10 implants; RBH-2,30 implants; RBH-3, 10 implants; E-H1, 13 implants; E-H2, 30 implants; E-H3, 7 implants. After sinus floor elevation by the socket lift procedure, 50 implants were installed in the maxillary posterior regions of the 31 cases. The superstructures were placed on the 30 implants, two of which were lost after occlusal loading. Of the other 20 implants, 18 were embedded in the maxilla, and 2 were lost before the second-stage surgery. Therefore, the five-year accumulated survival rate of the implants placed using the socket lift procedure was 89.5%.
From these results, the socket lift procedure can be considered a useful surgical technique for patients with a severely resorbed maxilla.
The atrophied edentulous mandible had been the first indication for implant-supported prostheses early in the development of the Brånemark Implant System. Today, there are a large number of cases treated with dental implant restorations worldwide. We believe that a relatively small number of cases with edentulous mandibles are treated with implant-supported overdentures in Japan. Recently, Prof. G.E. Carlsson of Göteborg University, Sweden, proposed that 10 countries including Japan investigate, using international surveys, the use of mandibular implant-supported overdentures in 2001. Therefore, we sent questionnaires to 17 dental hospitals or private dental clinics in the Kyushu area to survey the use in 2001 and 2002.
The aim of this study was to estimate the use of mandibular implant-supported overdentures in the Kyushu area in 2001 and 2002.
In 2002, 1,123 cases were treated with dental implant restorations in 16 clinics and dental hospitals in the Kyushu area, and 102 cases of totally edentulous mandible (9.0%) were included in this series. Overdentures were indicated in 39 of these cases, and the other 63 cases were restored by means of implant bridges. By comparison, in 2001, 1,269 cases were treated with dental implant restorations in 17 clinics and dental hospitals, and 68 cases of totally edentulous mandible (5.4%) were included in this series. Overdentures were indicated to 26 of these cases, and the other 42 cases were restored by an implant bridge. This result suggests that demand for implant prostheses from patients with a totally edentulous mandible has been recently increasing in the Kyushu area.
Microvascular surgery has become the preferred method for mandibular reconstruction. Dental rehabilitation through the use of prostheses and dental implants are important parts of the reconstructive process to optimize function. This report presents a case of dental implant placed in vascularized scapular bone graft for mandibular reconstruction to restore masticatory function. The patient was a 38-year-old man with ameloblastoma of the mandible. Immediately after mandibular resection, the defect of the mandible was reconstructed with a vascularized scapular bone graft. Three years after the operation, four implants were placed in the reconstructed mandible. The patient's mastication was improved after wearing a prosthesis supported by these four implants. The patient's postoperative course has been good with no evidence of recurrence as of 4 years after the operation.
Implant installation training was introduced as a trial during the postgraduate residency program aiming to make residents recognize the importance of acquiring profound knowledge and training based on scientific evidence concerning implant treatments.
Forty residents participated in the training program using phantom models and answered questionnaires with visual analog scale (VAS) both before and after the program.
After a small group discussion about the implant installation and a lecture on the basic implant surgical procedure, residents installed three screw-type implants (3.75×13 mm) into the designated area of the phantom model. Variances of installed angle of implants among residents were also measured three dimensionally.
As a result, most residents understood the aim of the training program by recognizing the need for further knowledge and training. They also showed interest in applying implants in their own individual field of dental practice in future. Regarding implant installation angle, there was a tendency to incline in the mesial and lingual direction along with large variation.