Masticatory function after unilateral distal extension removable partial denture treatment: intra-individual comparison with opposite dentulous side

Due to large individual differences of masticatory function, an inter-individual comparison between denture patients and complete dentate people would be insufficient. This cross-sectional study aimed to evaluate patients' masticatory performance (determined by Mixing Ability Index, MAI) and bite force (determined by maximum bite force, MBF) after removable partial denture (RPD) treatment by comparing those of the RPD replaced side with those of their own opposite dentulous side, and to evaluate influence of bite force on masticatory performance in different dentitions. Subjects included patients with unilateral distal extension RPDs (n=28). Apart from the RPD replaced area on one-side, all subjects had intact dentitions. Both masticatory parameters were evaluated separately on each chewing side. MAls and MBFs obtained from the RPD replaced side (0.65 +/- 0.50 and 220 +/- 155 N, mean +/- SD) were significantly lower than those from the dentulous side (1.06 +/- 0.64 and 450 +/- 268 N; Wilcoxon signed-ranks, P < 0.001). MBF significantly influenced MAI in both RPD replaced (Univariate linear regression; R2 = 0.17, P < -0.001) and dentulous sides (R2 = 0.51, P < 0.001). After RPD treatment, masticatory performance and bite force of RPD replaced side were lower than those of their own dentulous side. The influence of the bite force on masticatory performance in RPD replaced side was less significant than that in the dentulous side.     

Comparison of United States and Korean dental hygiene students using the Hiroshima university-dental behavioural inventory(HU-DBI)

OBJECTIVE: To compare cross-national differences of dental health behaviour among dental hygiene students. DESIGN: Cross-cultural differences. Setting: United States (USA) and Korea. SUBJECTS AND METHODS: One hundred and twenty-six dental hygiene students in USA and 246 in Korea were surveyed using the Hiroshima University-Dental Behavioural Inventory (HU-DBI) (in English and Korean versions respectively). RESULTS: There were considerable differences in oral health behaviour between USA and Korean dental hygiene students. Of great significance were findings that while only a small proportion of the USA students (1%) reported gum bleeding when they brushed their teeth, 37% of the Korean students did so (P<0.001). Furthermore, only 19% of the Korean students had been told by their dentist that they were performing a high level of plaque control, contrasted with 76% of the USA students. Logistic regression model showed that it was possible to distinguish USA students from Korean peers with a probability of more than 90% by using the HU-DBI. CONCLUSIONS: There were considerable differences in dental health attitudes/behaviour among dental hygiene students in the two countries. The variation in the favourable attitudes/behaviour toward oral health appeared to reflect the students' clinical training experience in Korea.     

Ultrastructural and histochemical study of β-tricalcium phosphate resorbing cells in periodontium of dogs

beta-TCP was implanted in surgically prepared alveolar bone defects on the mesial side of the upper canine. The dogs that we used were sacrificed after 5 weeks, fixed by perfusion, and the beta-TCP resorbing cells were examined ultrastructurally and histochemically, with the following results: (1) beta-TCP was resorbed by macrophages and multinucleated giant cells. (2) Mitochondria, vacuoles and Golgi apparatus were abundant in beta-TCP-resorbing multinucleated giant cells that possessed neither ruffled borders nor clear zones. (3) The addition of tartric acid inhibited acid phosphatase activity in the cytoplasm of the multinucleated giant cells and macrophages.     

A study on kinetic frictional properties in Begg/KB orthodontic appliances at posterior sites

In Begg and KB techniques, the kinetic frictional force generated between their characteristic orthodontic appliances at posterior sites and the orthodontic wire affects the efficiency of tooth movement. We compared the kinetic frictional force between the recent orthodontic appliances for posterior sites: the by-pass loop-KB buccal tube system (loop-KB tube system) and the conventional by-pass clamp-round buccal tube system (clamp-round tube system), and elucidated the frictional properties of the loop-KB tube system. We used 016"/018" round wires (016/018 round) and 022" × 016" ribbon wire (022 ribbon) with anchorage bend/curve applied. The results obtained were as follows:

T2-weighted MRI for the assessment of joint effusion: comparative study of conventional spin-echo and fast spin-echo sequences

OBJECTIVE: This study aimed to evaluate the usefulness of suitable conventional spin-echo (CSE) and fast spin-echo (FSE) T2-weighted imaging parameters for the assessment of joint effusion in a phantom study and in a comparative study of CSE and FSE using clinical cases. STUDY DESIGN: In the phantom study, the signal ratios of water and oil signal fields were determined and studied comparatively. The shape and size of signals were evaluated separately. In the study of joint effusion images, 318 joints were evaluated. CSE T2-weighted imaging and FSE T2-weighted imaging were carried out, and a comparative assessment was performed. RESULTS: In both CSE and FSE imaging, the ratios of mean MRI signal values showed divergence as TR/TE values increased. The evaluation of joint effusion with FSE TR/TE 8000/120 msec was significantly better than that in all other groups (P <.01). CONCLUSION: The use of FSE requires investigation of TR/TE values. When a 0.5 T static field strength MRI apparatus is employed, TR/TE 8000/120 msec is recommended.     

Anti-phagocytic role of surface fibrous structure of an invasive Porphyromonas gingivalis strain

Recent studies have shown that invasive and non-invasive strains of Porphyromonas gingivalis can both be isolated from patients with periodontitis. We examined the interaction between an invasive 16-1 P. gingivalis strain and phagocytes obtained from human peripheral blood and guinea pig peritoneal cavity. Phagocytes from human peripheral blood, mainly polymorphonuclear leukocytes (PMNs) isolated by centrifugation in Ficoll Hypaque, and macrophages collected from the peritoneal cavity of guinea pigs, were exposed to P. gingivalis cells. After this exposure, greater numbers of the non-invasive P. gingivalis ATCC 33277 were observed in human PMNs and guinea pig macrophages compared with the invasive P. gingivalis 16-1. Electron microscopic observations showed that invasive 16-1 within phagosomes in human PMNs and guinea pig macrophages retained their surface fibrous structures as well as their outer membranes. Electron microscopic examination showed that destruction and damage to the cell membranes and inner structures were clear in human PMNs and guinea pig macrophages after exposure to invasive 16-1 for 6 and 24 hours; this was a clear difference from exposure to the non-invasive ATCC 33277. Release of lactate dehydrogenase (LDH) activities into the culture supernatant of PMNs after exposure to the invasive 16-1 for 4 and 6 hours was significantly greater than that after exposure to the non-invasive ATCC 33277 (p<0.05). On the other hand, the LDH activity after exposure for 21 hours to the invasive 16-1 was significantly lower than that of untreated cells and cells after exposure to the non-invasive ATCC 33277 strain (p<0.05). The PMN viabilities after exposure to cells of the invasive 16-1 for 3, 4, and 6 hours as evaluated by trypan blue staining were similar to those after exposure to cells of the non-invasive ATCC 33277, but that after exposure to the invasive 16-1 strain for 21 hours was significantly lower than that after exposure to cells of the non-invasive ATCC 33277 strain.     

Effect of overglazed and polished surface finishes on the compressive fracture strength of machinable ceramic materials

Controversy prevails over the effect of overglazing on the fracture strength of ceramic materials. Therefore, the effects of different surface finishes on the compressive fracture strength of machinable ceramic materials were investigated in this study. Plates prepared from four commercial brands of ceramic materials were either surface-polished or overglazed (n=10 per ceramic material for each surface finish), and bonded to flat surfaces of human dentin using a resin cement. Loads at failure were determined and statistically analyzed using two-way ANOVA and Bonferroni test. Although no statistical differences in load value were detected between polished and overglazed groups (p>0.05), the fracture load of Vita Mark II was significantly lower than those of ProCAD and IPS Empress CAD, whereas that of IPS e.max CAD was significantly higher than the latter two ceramic materials (p<0.05). It was concluded that overglazed and polished surfaces produced similar compressive fracture strengths irrespective of the machinable ceramic material tested, and that fracture strength was material-dependent.     

Cyclic AMP-dependent protein kinase-independent angiotensin II-induced inhibition of calcium current in hamster submandibular ganglion neurons

In a previous study, we demonstrated that angiotensin II (AngII) inhibited voltage-dependent calcium channels (VDCCs) currents (ICa) in hamster submandibular ganglion (SMG) neurons. In sinoatrial node cells, it has been reported that AngII inhibits ICa by suppressing cyclic AMP production. In this study, to investigate the possible involvement of a cyclic AMP-cyclic AMP dependent protein kinase (PKA) pathway in the AngII-induced inhibition of ICa, effects of AngII were examined in SMG neurons after treatment with an activator and inhibitor of PKA. Neither pretreatment of neurons with membrane permeable cyclic AMP nor intracellular dialysis of PKA blocker attenuated the AngII-induced inhibition of ICa. These results indicate that AngII inhibited ICa via a cyclic AMP-PKA-independent mechanism in SMG neurons.     

Bond strength between luting materials and a fiber-reinforced resin composite for indirect restorations

The purpose of the present study was to evaluate the bond strength between a fiber-reinforced composite (FRC) and six luting agents (Panavia F 2.0, Linkmax MC, Chemiace II, Multibond, Super-Bond C&B, and Fuji I). A prosthodontic resin composite material (RC-control) and a luting agent containing no functional monomer (MT) were used as controls. Shear bond strengths between alumina-blasted FRC and the luting agents were determined after 20,000 thermocycles. The FRC showed superior bond strength when compared with the RC-control. Highest bond strengths were achieved when FRC was bonded with Panavia F 2.0, Linkmax MC, Multibond, Super-Bond C&B, and MT, whereas Chemiace II trailed in the list of resin-based luting agents evaluated. Insufficient bonding was obtained with Fuji I. Results of the present study revealed that when fabricating restorations, the clinician should select an appropriate combination of resin composite material and luting agent so as to ensure the longevity of restorations.