For the purpose of establishing a method to preserve frozen extracted teeth for the transplantation of long-term cryopreserved teeth, we investigated in vitro the cell adhesion, proliferation, morphology and bioactivity of human periodontal membrane-derived fibroblasts that had been frozen in D-MEM at freezing rates (℃/min) of -0.5, -5, -10 and -15 using DMSO, glycerol and trehalose as antifreezing agents. In addition, X-ray and histological findings in beagle dogs were comparatively examined to know the condition of autotransplantation of long-term cryopreserved teeth.
In the cell adhesion and proliferation tests, freezing in D-MEM＋ 10% glycerol and D-MEM＋10% DMSO showed the best cell activity, followed by D-MEM＋ 10% trehalose and D-MEM in this order. The freezing rate of -0.5℃/min was most appropriate among the four freezing rates tested. In morphological observation, the fibroblasts cryopreserved in D-MEM＋10% glycerol and D-MEM＋10% DMSO showed good growth of cell processes with cell morphology nearly identical to fresh cells.
In X-ray observation of the long-term cryopreserved teeth autografted in beagle dogs, immediately replanted teeth and the teeth cryopreserved in D-MEM＋10% glycerol showed no dental root absorption, and radiolucent images suggesting probably the alveolar hard line and periodontal membrane cavity were observed. The teeth cryopreserved in D-MEM, however, showed obscure images of both the alveolar hard line and periodontal membrane cavity, and an image suggesting bony fusion was observed. In histological observation, immediately replanted teeth and the teeth cryopreserved in D-MEM＋10% glycerol were histologically similar, and showed neither dental root absorption nor fusion in comparison with healthy teeth. Fibrous connective tissue was also observed between the alveolar bone and the cementum. Teeth cryopreserved in D-MEM showed proliferated bony tissues on almost all dental root surfaces and fused to the alveolar bone without intervening fibrous connective tissue.
These results suggest that the gentle freezing of teeth at a freezing rate of -0.5℃/min using glycerol as an antifreezing agent is a very effective method of cryopreservation and useful enough for clinical application.
Globular titanium with a diameter of 212～250 μm was prepared using the rotating electrode method. It was then sintered under vacuum conditions to produce solid titanium material, to make the implant.
We investigated the titanium implant material by evaluating the bond strength of the titanium particles to the titanium implant, the void area between titanium particles, the polarization resistance of titanium particles to the globular titanium implant, and alternating-current (AC) impedance properties. The following findings were obtained.
1. A shear force of about 5N was shown between the globular titanium implant and the titanium particles, although measurement was difficult.
2. The void area between globular titanium particles with a diameter of 212～250 μm ranged from 1.84×10-3 mm2 to 2.56×10-3mm2.
3. The Ecorr range of the titanium and globular titanium implant in 0.9% NaCl and artificial saliva aolution was -201～ -347 mV, and Icorr was 0.04×10-5～1.3×10-5mA/cm2. For titanium particles, Ecorr was -346 mV, and Icorr was 1.04×10-5mA/cm2.
4. The alternating current impedance measurement demonstrated increased corrosion resistance of the titanium material and globular titanium implant, which formed a passive oxide film in 0.9% NaCl and artificial saliva.
The efficacy of absorbable collagenous sponge for bone regeneration was evaluated in critical size mandibular bone defects in the absence of periosteum, focusing on the healing process between the cortical cut-ends. Eighteen white Japanese rabbits were operated on to create a uni-cortical bone defect (12×9×3.5 mm) without periosteum in the right mandible. The defects were filled with collagenous sponges or left empty (unfilled). At 2, 4 and 8 weeks after the operation, the mandibles were removed and coronal sections were stained with hematoxylin-eosin for histological observation and morphometric analysis.
In the collagenous sponge group, mesenchymal cells proliferated in the highly porous matrix at 2 weeks, and a trabecular bone bridge was found between the cortical cut-ends at 4 weeks. The collagen-filled defects achieved complete bony bridge formation by 8 weeks,whereas the unfilled defects were interposed by soft tissues. Histomorphometric analysis of the area between cortical cut-ends at 4 weeks demonstrated that the bone tissue occupied 93.9% of the volume in the collagenous sponge group compared to 9.3% in the unfilled group.The volume of the collagenous sponge was 11.5% and 0%, at 2 and 4 weeks, respectively.
Our present results indicate that the collagenous matrix provides a space for the proliferation and differentiation of mesenchymal cells and contributes to the mandibular contour formation by bony bridging. The collagenous sponge may be effective in promoting regeneration of bone defects in the absence of periosteum by acting as a scaffold and eventually being absorbed and replaced by new bone.
Diabetes mellitus (DM), one of the world's widespread chronic diseases, is not regarded today as an absolute contraindication for implant surgery. However, little data is available concerning the clinical outcomes involving the use of implant treatment for patients with DM. This study investigated the clinical course of patients who had undergone implant therapy in our institution to clarify the key points of the maneuver.
Seven patients with Type II diabetes mellitus (mean age:65.6 years, range:52-76 years) participated in this retrospective study, and in whom a total of 24 Branemark or HA-coating implants had been placed. The follow-up period after implant placement ranged from 12 to 96 months (average 4 years and 8 months).
The survival rate was assessed using the Kaplan-Meier test and compared statistically with our data of controls. Probing depth (PD) was also evaluated during the follow-up period.
The results obtained were as follows:
1. There were no severe postoperative complications.
2. Only one implant, placed in a patient with uncontrolled DM, failed to osseointegrate at the second surgery.
3. The survival rate was 86.7% at 60 months. A statistical difference (p＜0.05) existed between the controls: the corresponding survival rate was 94.7%.
4. No statistical difference existed when the uncontrolled patient's data were omitted:the survival rate increased to 89.7%.
5. Average PD decreased gradually during the follow-up period. Two implants that failed during the follow-up period did not have large PD just before the failure.
These results suggested that diabetic control is essential for osseointegration of the placed implants. Periodical close examination is very important during the follow-up period.
Dermabrasion using a diamond bur at the cutaneous layer reconstructed by revascularized osteocutaneous flap in cases of oral cancer was used for peri-implant soft tissue management. One patient with carcinoma of the lower gingiva (case 1) who underwent tumor resection and reconstruction with free fibular flap and the other with carcinoma of the lower gingiva (case 2) who underwent tumor resection and reconstruction involving free latissimus dorsi-scapular osteomusculocutaneous flap are reported. Branemark dental implants were placed in these two cases. In case 1, free palatal mucosa graft was performed around the abutments of the implants after widening narrowed alveolar mucosa. Free skin graft after dermabrasion from the lumbar region was carried out in order to widen the narrowed floor of the mouth and the donor site was closed primarily. Two years after setting of the superstructure, reepithelization was observed in the peri-implant soft tissue and grafted floor of the mouth and the clinical course was uneventful. In case 2, dermabrasion and defatting were performed for thinning and immobilization of the flap. However, proliferation of the peri-implant tissue was observed 6 weeks after setting of the superstructure. The proliferating dermis around the dental implants was excised and free palatal mucosa graft was performed around the abutments.
In conclusion, when a lot of implants need to be placed in the case of reconstruction with free osteocutaneous flap limited size of donor site is a problem for the mucosal graft. In such a case, free palatal mucosal graft might be performed only around the abutment and free skin graft after dermabrasion is considered to be useful for plasty of the floor of the mouth and oral vestibule.
An endosseus implant placement at the anterior site of the maxilla using bone augmentation was performed for the recovery of severe bone resorption following distraction osteogenesis. However, initial treatment by distraction could not obtain an adequate bone volume. Therefore, we needed additional bone augmentation at the buccal site after distraction. As donor bone, mandibular bone was harvested from cortical bone at the buccal site of the posterior molar region. This method was designed as a modified ramus harvesting technique. The results of this procedure showed that a larger volume of bone compared to other oral regions could be harvested. Six months later, adequate bone volume was confirmed and two fixtures were inserted at the grafted area. This combined method is considered to be useful for the placement of dental implants in case of atrophic alveolus.