Bio-active titanium has been developed as a biomaterial with osseointegration function to bond firmly to natural bone. This material has high potential as an immediately placed dental implant.
In this study, we investigated in vitro whether the surface condition of bio-active titanium could accelerate the bone-binding ability, osseointegration or osteoconductivity. Pure titanium with four kinds of surface roughness were used as specimens,　processed in the chemical and heat treatments, and soaked in simulated body fluid for the planned time-periods.　The surfaces of samples were observed by using scanning electron microscopy, X-ray diffraction etc.to assess the state of hydroxyapatite formation.
The SEM showed a richer and finer layer of hydroxyapatite-like compounds covering the rough surface as compared with the smooth surface group.
These findings suggest that the nucleation and crystallization of hydroxyapatite might be promoted on the rough surface. Further research and control of the surface of bio-active implants are necessary for further improvement of the osseointegration for dental implant.

View full abstract

Our previous study revealed the in vitro effects of surface roughness on the osteoconductivity of bioactive titanium. To access the in vivo effects, an animal experiment was performed using rabbits.
Bio-active pure titanium samples with two kinds of surface roughness were implanted into the femur of rabbits for 2 weeks. The tissues surrounding the titanium specimens were observed and evaluated by scanning electron microscopy (SEM), histological methods and mechanical extraction test.
Titanium samples with a rough surface tended to show marked postoperative bone formation surrounding the implants. These results suggest that osteoconductivity can be accelerated by increasing the surface roughness condition of bioactive titanium for dental implants.

View full abstract

In this study, bio-resorbable synthetic bone graft material and platelet-rich plasma (PRP) was applied to extraction sockets in dogs. To examine the relationship between the bone formation and vascular changes, a micro-vascular resin cast model was examined under a scanning electron microscope (SEM). The mandibular premolars of beagle dogs on both sides were extracted and eight sockets were created on mandibular bones. Platelet-rich plasma was made for experimental animals. Synthetic bone (TCP, Japan Medical Material) was grafted on one side for the experimental group and on the other side the synthetic bone was only grafted on the tooth sockets for the control group. Vascular resin injection was performed 14, 30 and 90 days after surgery.
The microvascular resin cast is a method for observing the vasculature and clear, three-dimensional images can be observed through complete infusion of an injected synthetic resin up to the capillaries. SEM images were captured and loaded onto the image programs (Image J, NIH). The bone formation ratio and vascular regeneration ratio was measured.
In the control group at 14 days after operation, newly formed blood vessels were found in the sockets. The blood vessels extended from the bone marrow space vessels were regenerated in the socket. In the experimental group, the socket was filled with the newly formed bone. The regenerated blood vessels were surrounded by new bone. The inside of the socket at 30 days after operation was filled with newly formed bone in both groups. In the control group, thin new bone formation was seen along the blood vessels. In the experimental group, bone trabecula and blood vessels were arranged in the bone marrow space. At 90 days after surgery, in the control group, new bone had filled the inside of sockets. However, we could not definitely identify any new trabeculae. In the experimental group at 90 days after surgery, the resemblance of the pattern of the trabeculae and its vascular network to bone marrow space had become even stronger.
These results suggest that PRP promotes the regeneration of the blood vessels and bone.

View full abstract

Purpose:The load applied to an implant is directly transmitted to the jaw and is considered to be one of the causes of remodeling of internal trabecular bones. However, the longitudinal changes during loading and the rearrangement of the trabecular bone structure are mostly unknown.The aim of this study was to clarify the changes in internal jaw bone structure longitudinally during natural tooth eruption as well as tooth extraction and post-implantation periods in a dog model by micro computed tomography (micro-CT).
Materials and Methods:Maxillae of 16 male beagle dogs were used in this study. First, 4 dogs with all maxillary molar teeth erupted were euthanized as a control group. Next, 6 teeth consisting of the bilateral maxillary fourth premolars, and first and second molars were extracted from each of the 12 dogs. Then, 4 dogs of the tooth-extracted group were euthanized 3 months after extraction of the teeth. At this time, three implants were inserted in the left side of the maxilla of the remaining 8 dogs, and the superstructures were placed after 3 months. Four of these 8 dogs with implants were euthanized at 3 months and the other 4 at 1 year after placement of the superstructure. Then, the maxillary bone was removed from each dog as a specimen and sequential micro-CT images were taken. After reconstruction of three-dimensional images, morphological and metrical observation of the jaw trabecular bone structure was performed.
Results:A decrease of the trabecular bone in the tooth-extracted group was morphologically and morphometrically observed, whereas the implanted group showed thick, rich trabecular bone. Although a longitudinal decrease in the bone tissue volume was recognized both in the tooth-extracted and the implanted groups, the amount was smaller in the implanted group than in the tooth-extracted group.
Conclusions:The results suggested that the application of load by implants in the case of tooth loss inhibits resorption of the alveolar bone and prevents thinning of the jaw.

View full abstract

Purpose:The appropriateness of implant placement combined with repositioning of the inferior alveolar nerve was examined based on long-term observation and assessment of neurosensory recovery in 8 patients (7 females and 1 male).
Materials and methods:The patientsʼaverage age at surgery was 53.0±13.3 years old, with a total of 9 surgeries. The number of implants placed was 15, all endosseous implants. There was one case of complete and 2 cases of partial nerve severance during surgery. The average observation period from surgery to final follow-up was 166±55.8 months, ranging from 70 to 218 months. Analysis of sensory disturbance was based on the results of four different sensory tests, and on the recorded chart descriptions of patientsʼ complaints reinterpreted according to the modified HIGHET classification separated into S0,S1/2,S3 and S4 phases.
Results:At the initial examination the day after surgery, neurosensory disturbance was observed in 8 of 9 cases in phase S0 (numbness). At the final check-up, 7 cases were in phase S4 (normal sensation) with the other 2 cases in phase S3 (paresthesia absence of pain and hyperalgesia). One of the S3 cases died of unrelated causes 76 months after surgery, and one suffered cerebral infarction and dementia at 70 months postoperatively, making the test results unreliable. All 7 cases reached recovery via S0, S1/2 (pain and hyperalgesia) and S3. The average period for each phase was 2.5±3.4 months for S0;30.0±33.9 months for S1/2;and 45.0±43.4 months for S3. An average of 92±41.2 months was necessary before returning to normal sensation (S4). The survival rate of the 15 placed implants was 100%.
Discussion and conclusion:It was concluded that the implant placement combined with repositioning of the inferior alveolar nerve presented here is appropriate in mandibular molar cases where alveolar bone is in a state of advanced resorption. However, prior to surgery, the doctor must obtain informed consent, with the patient recognizing that they will probably experience some disturbance in sensation, and it could take several years before returning to normality.

View full abstract

In recent years, the demand for safer and more secure implant treatment has been increasing. This paper reports a case in which dental implants were successfully placed in the treatment of an edentulous mandible. The procedures were completed safely in accordance with the preoperative plan by using simulation software and a surgical guide plate.
The patient was a 47-year-old female who came to our clinic complaining about pain in her lower right molars. All the remaining teeth in her mandible had to be extracted because of severe periodontitis, requiring an immediate denture placement.
Hematological and biochemical tests were carried out preoperatively together with a CT scan. Based on the CT scan data, safe and ideal implant locations were identified, in the process of which dental implant simulation software was useful. A surgical guide plate was fabricated, accordingly. Under the guidance of the results thus obtained, eight implants were placed in the mandible.
Since it was an immediate implantation after a major tooth extraction, sufficient bone density had not yet been achieved in the tissues surrounding the surgical sites. However, all the implants were correctly oriented and placed as planned using the guide plate. After a suitable non-loading time, full-arch fixed provisional restorations were introduced in the maxilla and mandible to examine the dental articulation. When a proper occlusion was confirmed, a final superstructure was placed. No detrimental change has since occurred in the tissues surrounding the implants, or in the periodontia of the unaffected teeth at the time of follow-up observation three and half years later.
In order to provide patients with safe and secure treatment, correct diagnosis based on thorough preoperative examination is extremely important. It is important to consider the type of surgical guide plate and its clinical use very thoroughly.

View full abstract