Hydroxyapatite (HAp) has been used as a biomaterial for hard tissues, because of its excellent biocompatibility and osteoconduction. However, the non-absorbable HAp remains as a foreign body in a living body and may trigger inflammation. The aim of this study was to develop biomimetic ceramics from bovine bone and to estimate the absorbable property in vivo histomorphometrically.
Spongy and cortical bones in bovine femur were used as starting materials and calcined at 500～800℃ to obtain b-HAp. The spongy b-HAp was partially dissolved in HNO3 solution, and the cortical b-HAp was completely dissolved in the other HNO3 solution. After the two solutions were mixed, HAp (r-HAp) crystals were precipitated on the macropores and micropores of spongy b-HAp at pH 10.5 and 25℃. The modified spongy b-HAp was filtrated and dried to fabricate the functionally graded HAp (fg-HAp) ceramics. The fg-HAp ceramics were characterized by the pore sizes of 100～600μm, porosities of 70～80%, and small amounts of metal ions. SEM photographs of the fg-HAp showed spherical moss-like grains of about 1.0μm in size, which consisted of about 10-nm r-HAp microcrystals. Micro-XRD analyses indicated that the crystallinity of fg-HAp single phase was better from the surface layer to bulk region in the ceramics.
The fg-HAp (3×3×3mm) ceramics were implanted into the subcutaneous tissue in 4-weeks old Wistar rats. At 1, 2, 3, 4 and 8 weeks after the implantation, the ceramics were explanted and stained with hematoxylin and eosin and evaluated histopathologically.
The ceramics were covered by a thin connective tissue. At 4 weeks, body fluid had well invaded and diffused into the micropores and microcracks of the ceramics and fibroblasts populated in the macropore spaces. The fluid that had invaded into the HAp was stained with albumin antibody. At 8 weeks, the HAp was degraded from not only the surface layer of the ceramics but also the bulk region, and many giant cells appeared on the surface and inside of the ceramics. Morphometric analysis showed the HAp volume diminished from 40% at 4 weeks to 32% at 8 weeks.
These results indicated that the newly developed biomimetic fg-HAp bioceramic had superior bioabsorption and biocompatibility characteristics.
After multiple tooth loss, the alveolar process of the posterior maxilla is often affected by resorption. Maxillary sinus floor elevation has opened up a new way of increasing alveolar bone height in the posterior edentulous maxilla for implant placement. However, morphological variations and abnormal conditions of the maxillary sinus are sometimes observed. This study investigated the morphology of the maxillary sinus and these abnormal conditions using CT images.
Materials and methods: Seventy cases of Denta ScanCT images of the maxilla, which were taken before implant placement, were observed.
Results: Abnormal conditions of the maxillary sinus were found in 30 sinuses; absence or severe deformity of the maxillary sinus caused by radical sinusectomy or tumor resection in 11 sinuses, swelling of the sinus mucosa in 7, osteoma or osteosis on the sinus wall in 5, and sinusitis in 4. Sinus septa were found in 43 of 125 sinuses (57 septa in 30 patients). In 57.6% of the cases, the minimum alveolar bone height between the alveolar crest and maxillary sinus floor was less than 5 mm.
Conclusion: Most of the maxillary posterior regions did not provide sufficient bone height for implant placement without maxillary sinus floor elevation, and sinus septa existed in approximately 30% of the sinus floor. It is very important to obtain detailed knowledge of maxillary sinus anatomy to avoid complications during the sinus augmentation procedure.
Purpose: We evaluated occlusal contacts in the inter-cuspal position (ICP) of prostheses with stress absorbing elements on osseointegrated implants (the prostheses) and natural teeth. Using this information, we investigated how to best create occlusal contacts on the prostheses with opposing teeth.
Materials and methods: We selected five subjects who showed excellent clinical observation for two years or more after placement of the prostheses on IMZ implants in unilateral free-end cases and obtained informed consent to the purpose of this research. The registration of occlusal contacts using silicone impression materials were made during clenching in ICP at two levels (10% and 30%MVC) under maximum EMG amplitude (100%MVC). To read the silicone occlusal records quantitatively, we used the add-picture method which visualizes occlusal contacts by digital image processing. We observed variations in the number and size of occlusal contacts between two occlusal forces. A statistical analysis was performed using the Wilcoxon test in comparison between two levels.
Results: The number and area of occlusal contacts increased with occlusal force both on the natural teeth and on the prostheses. However, the location of the contacts remained the same in both the healthy dentulous subjects and those with the prostheses. For each teeth, with the increase in occlusal force, the number of occlusal contacts in natural teeth increased significantly (p＜0.05) and so the area of occlusal contacts in natural teeth and the prostheses increased significantly (p＜0.05). There was no significant difference between the natural teeth and the prostheses in the increase of the area of occlusal contacts with the increase in occlusal force.
Discussion: The prostheses and the remaining teeth in ICP cooperated with each other, since the stress absorbing elements worked effectively.
These results were probably due to displacement of opposing teeth, strain on their supporting tissue and displacement of the stress absorbing elements.
Conclusion: We concluded that a harmonious intercuspal position with natural teeth can be established by imparting appropriate occlusal contacts to the prostheses.
Recent reports have described the use of titanium mesh and autogenous bone particles for alveolar ridge augmentation. However, it has been unclear how much bone volume, height, or width would be obtained by this technique. This paper studied the predictability of the alveolar bone ridge augmentation with autogenous particulate bone graft and titanium mesh by investigating postoperative complications and quantitative measurements of augmented bone.
The subjects were 13 patients, 6 males and 7 females. The range of patients'age was 18 to 56 years old, and the average age was 37.5 years old. Alveolar ridge augmentation was performed by using autogeneous bone graft and titanium mesh. The primary lesion was dental disease in nine and trauma in four. The operation mainly aimed at increasing bone height in four patients and bone width in nine.
Donor sites were the iliac bone or the jaw bone.
First, the kinds and incidence of postoperative complications were surveyed. The augmented bone was then quantitatively evaluated with the reconstructed CT images. Parameters were as follows:augmented bone ratio (ABR); the percentage of bone in the space created by titanium mesh, increased bone height (IBH); the difference of the bone height before and after the operation of the patients aiming at increasing bone height, the ratio of the increased bone height (%IBH); the percentage of increased bone height against the vertical gap between the mesh and the alveolar crest in the patients, increased bone width (IBW); the difference of the bone width before and after the operation on patients aiming at increasing bone width, and the ratio of the increased bone width (%IBW);the percentage of increased bone width against the horizontal gap between the mesh and the cortical bone in the patients.
The following results were obtained
1. The mesh was exposed in one patient (7.7%) 8 months after the bone graft.
2. The ABR was 39.7～100%, average 90.4%.
3. The IBH was 2.5～11.8 mm, average 6.4 mm and the%IBH was 70～100%, average 91.5%.
4. The IBW was 1.0～11.2 mm, average 4.9 mm and the%IBW was 22～100%, average 87.4%.
5. Even the patients who underwent CT examination 20 months after the bone graft showed high quantitative data: ABRs were from 89.1% to 97.2%, average 93.6%.
6. The low values in an image -ABR of 39.7% and %IBW of 22%- might result from the deficit of bone particles at the operation.
These results indicated the predictability of alveolar bone ridge augmentation with autogenous particulate bone graft and titanium mesh. It is accomplished by adequate surgical procedures avoiding wound dehiscence and tight packing of bone particles into the space created by the titanium mesh.