Biomaterial is indispensable for tissue engineering, and needs to biodegrade with bone formation. The aim of this study was to investigate the characteristics of biodegradation and the dose-response of bone induction morphohistologically in recombinant human BMP-2/HAp systems, based on different surface structures. Calcined bovine spongy bone apatite at 500-800℃ was designated as b-HAp. The fg-HAp was designed by the partial dissolution-precipitation method. The fg-HAp ceramics had a large specific surface area (200 m2 /g), microcrystals about 10 nm in length, and Mg2+ or Na+ ions.
The fg-HAp block (3×3×3 mm) and the b-HAp (3×3×3 mm) containing 5.0, 1.0, 0.5, 0.3, 0.1, 0.05, or 0.0μg of BMP-2 were implanted into the back subcutis of 4-week-old Wistar rats. At 3 weeks after implantation, the implanted blocks were explanted, and the degradation of the ceramics and the induction of hard tissues were evaluated morphohistologically.
Ectopic bone induction occurred in the fg-HAp/BMP2 (5.0, 1.0, 0.5, 0.3 μg) system at 3 weeks, while in the bHAp/BMP-2 (5.0 μg), only bone induction was found. Interestingly, the biodegradation of the fg-HAp and bone induction occurred simultaneously in the fg-HAp/BMP-2 system.The excellent bone induction and biodegradation in the fg-HAp/BMP-2 system might result from the increase of BMP-2 affinity/binding sites and artificial nano-micro pores. The results also suggest that the retention amount of BMP-2 must be enough to induce ectopic bone formation, compared to the b-HAp/BMP-2 system.
It is important to measure implant stability when evaluating the state of osseointegration and the prognosis of implant treatment. Resonance frequency analysis (RFA) has made it possible to measure the implant stability quotient (ISQ) value at any time during the course of implant treatment.
In this study, implants of differing Youngʼs modulus were placed, and the obtained ISQ value was evaluated.
The following results were obtained.
1. The ISQ value also became large with Young's modulus. However, the ISQ value and Youngʼs modulus closely matched an involution regression curve instead of a straight line with the rise of Youngʼs modulus.
Therefore, the bone-implant-smartpeg (OsstellTM mentor) system had two modes of behavior. One was a rigid body behavior and the other was a bending behavior.
Rigid body behavior was found for low stiffness (＜5,000 MPa), whereas bending behavior was found for high stiffness (＞5,000 MPa).
This result showed that resonance frequencies in the case of rigid body behavior were more sensitive to changes in bone stiffness than resonance frequencies in the case of bending behavior.
2. In the model of the same Youngʼs modulus, an increase in implant diameter resulted in higher ISQ value.
3. OsstellTM mentor is suited for following up the stability of an implant, but not to comparing the stability of implants in absolute terms.
We often encounter bone defects in patients who underwent surgery for diseases in the oral and maxillofacial region. Large bone defects need to be restored. These defects can usually be reconstructed well with fresh bone autografts. A second surgery has to be performed to extract donor bone. For patients, an operation to retrieve fresh bone autografts is quite stressful. In recent years, calcium phosphate-based materials have been used for bone regeneration. Many clinical studies have reported the use of hydroxyapatite (HAP) for bone reconstruction. Two forms of HAP, namely blocks and granules, are available. However, the handling and molding characteristics, as well as the form-maintaining property of granular HAP, are not satisfactory.
Hiruma added a viscoelastic binding agent to HAP to improve its characteristics. HApG was prepared by adding gelatin to granular HAP. The addition of gelatin improved the handling and molding characteristics, in addition to the form-maintaining property. A dried specimen of this material was produced in this study. When this dried specimen was soaked in body fluid in vivo,the viscosity of the binding agent was reduced. As a result, granular HAP might gradually become scattered. Therefore, we assumed that better healing of the bone defects would occur as a result of increased new bone volume, when granular HAP is gradually scattered.
In this study, we used a dried specimen of HApG which was prepared by adding gelatin to granular HAP, and soft X-ray and histological analyses were conducted.
The results were as follows:
1. The density of the dried specimen increased in the order of HAp200G1 and HAp100G1, when we mixed them with purified water at a powder and liquid ratio of 1.5.
2. When analyzed with soft X-rays, both HAp100G1 and HAp200G1 appeared radiodense.
3. We measured the bone mineral density using soft X-ray photography. The bone mineral density of both HAp100G1 and HAp200G1 increased with time.
4. HAp100G1 and HAp200G1 showed similar histological findings. New bone formation occurred inwards from the defect border;bone appeared to grow towards the defect center as time passed.
A dried specimen of HApG demonstrated improved handling and molding characteristics as well as form-maintaining property, and the osteoconduction was good.
Objective: Acceleration of bone and titanium integration is a critical concern in dental implantation. Low-intensity pulsed ultrasound (LIPUS) has been widely used for accelerating healing of bone fracture in orthopedic practice. Some studies demonstrated that LIPUS accelerated bone formation around a titanium implant in vivo animal model. We hypothesized that LIPUS would enhance osteoblastic differentiation. To test the hypothesis, we examined the effects of exposure to LIPUS on the behaviors of osteoblastic cells derived from rat bone marrow cells.
Materials and Methods: A LIPUS exposure system that could generate a 2 msec burst of 3.0 MHz sine waves repeated at 100 Hz was constructed for the cell culture study model. Bone marrow cells, obtained from the femurs of 8-week male SD rats, were suspended in α-MEM supplemented with 15% fetal bovine serum, 10-8M dexamethasone, 10 mM Na-β-glycerophosphate and 50 μg/ml L-ascorbic acid 2-phosphate. The suspension was poured into 12-multiwell cell culture plates and cultured at 37℃ in an atmosphere supplemented with 5% CO2 . The treatment group was exposed to LIPUS underneath culture plates with a coupling gel for 15 min/day from day 3 after primary seeding (LIPUS group). The intensity of LIPUS was 40 mW/cm2. The control group without ultrasound treatment was cultivated in the same manner. Cell proliferation was observed by using the WST-8 assay. Collagen synthesis was measured by using a colorimetric method of sirius red dye. von Kossa staining was performed to analyze the calcification nodule formation, and the orthocresolphthalein complexone method was performed to detect the calcium deposition in each cell culture tissue. Total RNA was extracted from each group and realtime quantitative polymerase chain reaction analysis after reverse transcriptase reaction was performed to quantify the osteoblastic gene expressions.
Results: Cell proliferation in the LIPUS group was more suppressed than that in the control group on day 7 (p＜0.01). Collagen synthesis in the LIPUS group was further developed than that in the control group on day 14 and 21 (p＜0.01). The total area of bone nodule in the LIPUS group was wider than that in the control group on days 14 and 21 (p＜0.01) and calcium concentration in the culture of the LIPUS group was thicker than in the control group on days 7, 14 and 21 (p＜0.01). Osteocalcin and osteopontin gene expressions were more upregulated in the LIPUS group than in the control group on days 7 and 14 (p＜0.01).
Conclusion: LIPUS suppressed the proliferation of osteoblastic cells, but enhanced osteoblastic differentiation and calcification in the in vitro cell culture model.
Factors that influence decisions regarding the placement of implants include anatomical factors, such as bone mass and the mandibular canal, and prosthetic factors, such as function and esthetics.
One of the anatomical factors is the presence of adjacent teeth, which mainly restrict the mesiodistal location of implant placement. The presence of mesial adjacent canine teeth or premolars in particular, influences decisions regarding the position of implant placement for implant therapy in the mandibular molar region. According to the measurements made in this study, the roots of 85.9% of the lower canines and premolars as a whole were located in the distal direction, and it was especially noteworthy that the roots of 94.8% of the canine teeth were located in the distal direction. In addition, even the average measured distance of the canines and premolars as a whole was 1.47 mm,which was large when compared with the mesiodistal width of the teeth.
Thus, implant therapy must be performed without damaging adjacent teeth, aware of the fact that in almost all cases the roots of the lower canine and premolar teeth are located in the distal direction.
Computed tomography (CT) is a useful diagnostic imaging modality of dental implants for evaluating the location of the mandibular canal, maxillary sinus and quality of jaw bone in recent clinical situations. However, there is little awareness of the usefulness of highspeed volume scanning for dental implants using 64-row multi-detector computed tomography (MDCT).
The purpose of this study was to evaluate the usefulness of high-speed volume scanning for dental implants using 64-row multi-detector computed tomography (MDCT) in comparison with single slice CT regarding with motion artifacts.
The subjects consisted of 136 patients (64 men, 72 women, mean age 55.2 years, range 34-65 years) on MDCT mandibular images and 120 patients (53 men, 67 women, mean age 52.2 years, range 29-69 years) on single slice CT mandibular images.
These CT images were compared with reconstructed MDCT images and reconstructed single slice CT images.
Reconstructed MDCT mandibular images contained no images in motion artifacts. Reconstructed single slice CT mandibular images demonstrated motion artifacts in 20% of all 120 patients.
Reconstructed MDCT images were superior to single slice CT images on imaging diagnosis for the evaluation of motion artifacts (p＞0.0001). Reconstructed mandibular images with 64-section MDCT provide useful diagnostic images for dental implants.
It is suggested that 64-row MDCT is beneficial for reducing motion artifacts on dental implants.
We report four cases whose implant fixtures were uncertainly placed and inserted into the maxillary sinus.The patients consisted of 2 males and 2 females whose ages ranged from 46 to 56 years. All cases were referred to us from private dental clinics. There were three cases of accidental insertion in the maxillary sinus on the left side and one case on the right side, but all of them had no symptoms at the first visit. All implant fixtures were surgically removed without any episodes, although one case was complicated with chronic maxillary sinusitis.
It is considered that it is necessary to minimize invasion and time to remove the implant fixture in the maxillary sinus, and especially important to inspire the patient with confidence.
It is difficult to apply a denture to a severely resorbed maxilla. In such cases, reconstruction of the severely resorbed maxilla could be a useful procedure for preprosthetic surgery.
Recently, occlusal rehabilitation by implant-supported prostheses has been performed. In severe cases, endosseous implants have been inserted after such reconstructions as sinus lift augmentation, onlay graft, GBR, and distraction osteogenesis.
We performed reconstruction of a severely resorbed maxilla in combination with Le Fort I osteotomy, interpositional iliac bone grafting, and the placement of endosseous implants.
After wearing the implant-supported overdenture the patientʼs occulusion improved considerably and to the patientʼs satisfaction.