We evaluated the healing process of experimental periodontal tissue defects in rats after the application of enamel matrix derivative (EMD). Palatal dehiscence defects were surgically created on the bilateral maxillary first molars in forty rats. EMD was applied to cover both sides of the denuded dentin surfaces in the experimental group, and none was applied in the control group. Rats were sacrificed at 1, 2, 3 and 4 weeks after surgery, and biopsies of the tooth, gingiva and bone were examined for the appearance and kinetics of tartrate-resistant acid phosphatase (TRAP)-positive cells by histopathology and enzyme histochemistry. There were more TRAP-positive cells on the new bone surfaces and the denuded dentin surfaces in the experimental group than in the control group. This suggests that TRAP-positive cells have the potential to promote new attachment formation and new bone formation.
We fabricated implants covered with a thin film of hydroxyapatite (HAp) using the pulse laser-deposition technique (PLD). They had good mechanical properties, crystal structure, and homogeneity in composition, all of which are needed for good clinical results. We performed animal experiments to evaluate the osteoconductivity and did quantitative analysis on 50 nm ultra thin film. We found that bone conduction by the HAp film was adequate in the early stages, even though it was thin, suggesting that this technique might improve clinical results. We confirmed that the PLD technique produces an HAp film with improved mechanical properties, such as increased tensile strength and decreased film thickness.
We used functional magnetic resonance imaging (fMRI) to examine the relationship of the activation region of the cerebral cortex during mastication with the language dominant hemisphere. Twelve healthy volunteers were selected for this study. Measurements were performed on a conventional whole body 1.5 T clinical scanner using a single shot, multislice echo-planar imaging sequence. The subjects were ask to masticate on the right side, and then the left side. As well, they were instructed to perform capping tasks. Computer analysis of the fMRI was done using the SPM 99 software. The results showed that the language dominant hemisphere might influence the activation region of the sensorimotor cortex during mastication. This study was supported in part by a Grant-in-aid for Scientific Research (B) (No.14370650) from the Japan Society for the Promotion of Science.
We evaluated the retentive force and energy of partial denture retainers using a tensile testing machine. We tested the RPI clasp, clasps with no guide plane (NP clasps), clasps with guide planes (GP clasps), the Magmax-C 600, the Magdome C, the cone crown telescope (Konus), the Bona 604, the Bona 604 A and the Rothermann. We measured the displacement before (DBP) and after (DAP) the peak retentive force, and calculated the retentive energy before (EBP) and after (EAP) the peak. The NP clasp had a larger retentive force, DBP and EBP than did the other clasps. This suggests that preparation of a guide plane reduces the load on the abutment tooth. Magnetic attachments had characteristics effective in preserving abutment teeth because of a shorter DBP and lower retentive energy. The Konus crown also had similar retentive properties, but a shorter DAP.
We investigated the influence of the shape of the temporary anchorage device (TAD) on stress distribution in the surrounding jaw bone. We used the three-dimensional finite element method to examine four different types of TAD screws (straight, slender, short and conical). The results demonstrated that the different TAD shapes produced significant variations in stress distribution in the bone. The slender type had distinctly higher stress per unit area in the bone than did the other types, and the conical type had lower stress per unit area. Moreover, the diameter of the TAD seemed a more important factor for anchorage stability than was the total length.
Water cooling is necessary when cutting with the Er : YAG laser. Perfluorocarbon (PFC) has also been used to increase the cutting efficiency (CE) of human bone. I investigated the influence of PFC on bovine dentin. Three types of PFC, whose boiling points were 56, 80 and 102℃, were used for cooling when cutting polished dentin. The CE, thickness of the denatured layer and bond strength of the composite resin were investigated. I also studied the effect of increased irradiation and etching by phosphoric acid. The use of PFC with boiling points of 56 and 80℃ increased CE. The lower the boiling point, the thicker the denatured layer. Although the use of PFC lowered the bond strength, additional irradiation with water cooling and etching increased it.
We undertook three-dimensional analysis of the human face and examined the effect of oral myofunctional therapy (MFT) on the health of the face. Examinees were divided into the physical exercise group, which performed daily MFT, and a control group. The faces of subjects in the physical exercise group displayed significant changes compared with the controls from 0-6 months (p<0.05). Somatic fat content and volume decreased significantly from 0-6 months in the physical exercise group (p<0.05), even though somatic weight remained unchanged. Based on these results, we concluded that continuous MFT can result in changes to the face and body fat.
We investigated the use of two types of digital image analysis to objectively evaluate gingival condition. Digital images were taken of gingiva using two special CCD camera systems. The subjects were requested not to brush for 7 days. Analysis of the gingival images showed that changes in the surface form and color could be objectively expressed. We found that this apparatus could be useful for the objective evaluation of gingivitis because changes could be expressed quantitatively.
We attempted to establish a method of animal passage for keeping the exopolysaccharide (EPS) production of Prevotella nigrescens strain 22 at high levels, and examined the protein expression patterns before and after animal passage by 2-D electrophoresis. The EPS production of strain 22 increased and the mesh-like structures around the cells became denser after animal passage. N-terminal sequence analysis of protein revealed that the expression of a few heat shock protein homologs were up-regulated in response to the stress of animal passage, suggesting the relation between a regulatory pathway of EPS production in Prevotella nigrescens with a heat shock response.
We investigated the effect of photocatalytic reactions of titanium dioxide finepowder on rat tongue carcinoma cells induced by 4-nitroquinoline 1-oxide. Three types of titanium dioxide finepowder, anatase type ST-41, rutile type TP-3 and mixed type P-25, were added separately to culture fluid and were cultured for 48 hours. Each mixture was then exposed to 254 nm ultraviolet light. The cell survival rate was decreased in the cells cultured with any type of titanium dioxide finepowder, and the decrease was marked in the cells cultured with ST-41. Furthermore, the cell survival rate was decreased in correlation with irradiation time and concentration in the ST-41 group. We found an apoptosis ladder pattern which suggests that the apoptosis was concerned with the mechanism of cultured cell kill. These findings indicate that the photocatalytic reactions of ST-41 titanium dioxide finepowder may develop a new modality for cancer treatment.
I examined the β-lactamase gene of Prevotella intermedia (P. intermedia) in order to better understand the β-lactam-resistance mechanism. The polymerase chain reaction (PCR) performed on β-lactam-resistant P. intermedia gave a product the same size as one previously reported, as well as another product not previously observed. The PCR products of the CfxA 2 and CfxA 3 β-lactamase gene primers were amplified into products that had high homogeneity with the CfxA 2 and CfxA 3 β-lactamase genes. These results suggest that β-lactam-resistant β-lactamase producers have genes that resemble the CfxA 2 and CfxA 3 genes, and that these genes are seen throughout the strain. However, Escherichia. coli transformed by the PCR product did not show resistance to β-lactams. This may be the result of inactivation by mutation of a sequence, or the existence of a specific phenotype.