The purpose of this study was to establish an acid-etching procedure for altering the Ca/P ratio of the nanostructured surface of hydroxyapatite (HAP) by using surface chemical and morphological analyses (XPS, XRD, SEM, surface roughness, and wettability) and to evaluate the in vitro response of osteoblast-like cells (MC3T3-E1 cells) to the modified surfaces. This study utilized HAP and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid solution for 10 minutes at 25°C, followed by rinsing 3 times with ultrapure water. The 30% phosphoric acid etching process that provided a Ca/P ratio of 1.50, without destruction of the grain boundary of HAP, was selected as a surface-modification procedure. Additionally, HAP treated by the 30% phosphoric acid etching process was stored under dry conditions at 25°C for 12 hours, and the Ca/P ratio approximated to 1.00 accidentally. The initial adhesion, proliferation, and differentiation (alkaline phosphatase (ALP) activity and relative mRNA level for ALP) of MC3T3-E1 cells on the modified surfaces were significantly promoted (P < 0.05 and 0.01). These findings show that the 30% phosphoric acid etching process for the nanostructured HAP surface can alter the Ca/P ratio effectively and may accelerate the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells.

The purpose of this study was to evaluate preoperative CT-derived bone densities in Hounsfield units (HU) at implant sites that acquired primary stability, and to compare these values to the optimal bone densities proposed in the literature. Fifty-one patients, 18 males (37 implant sites) and 33 females (67 implant sites) between 2003 and 2010 were assessed. CT data for different jaw sections, regions, and operating procedures were compared using the Kruskal-Wallis test and Scheffe's test for multiple comparisons (P < 0.05). The mean bone density in the maxilla was significantly lower than that in the mandible (P < 0.05); the mean bone densities in the 4 jaw regions decreased in the following order: anterior mandible > anterior maxilla > posterior mandible > posterior maxilla. The bone densities assessed by HU fell into the range of optimal bone densities associated with acquired primary implant stability proposed in the literature.

This study aimed to analyse occlusal force, area and pressure for individual maxillary and mandibular teeth by assessing their occlusal-supporting abilities. Ninety-nine subjects (49 men and 50 women; average age, 24·7 ± 3·4 years; range, 20-37 years) performed maximal voluntary clenching twice for 3 s in both the intercuspal position and the intercuspal position with sliding movement from edge-to-edge occlusion, with a pressure-sensitive sheet placed between the maxillary and mandibular dental arch. Occlusal force, area and pressure of individual teeth were calculated by colour development in the pressure-sensitive sheet with special analytical equipment and software. Occlusal contact condition of individual teeth was confirmed using the intra-occlusal record. All data were analysed using unpaired Student's t-test, Kruskal-Wallis test and Scheffe's test for multiple comparisons with a significance level of P < 0·05. The occlusal pressure in the intercuspal position with sliding movement from edge-to-edge occlusion was adopted as the representative occlusal-supporting ability for each individual tooth, although there were, in part, statistically significant differences in the effects of laterality, performance and gender. Overall, the occlusal pressure increased gradually from the central incisor, peaked at the canine or first premolar and decreased sharply-and significantly (P < 0·01)-towards the second molar. We conclude that the occlusal pressure of individual teeth can be used as an indicator of occlusal-supporting ability. This is therefore proposed as a possible suitable parameter for epidemiologic research, specifically for verifying the relationship between occlusal-supporting ability and status of residual periodontal ligament support.

The purpose of this study was to investigate a new biochemical surface modification technique for titanium implants using phospho-amino acid. Pure titanium disks were pretreated with 10 N HC1 and ultrapure water at room temperature for 30 minutes respectively.Then these disks were modified with either L-threonine (Thr) or O-phospho-L-threonine (P-Thr) at 37°C for 12 hours. X-ray photoelectron spectroscopy (XPS) chemically analyzed the modified surfaces. It was revealed that the N Is peak which originated from Thr was not detected in the wide-scan spectrum of Thr-modified surface, whereas three peaks of N Is, P 2s, and P 2p which originated from P-Thr were detected in the wide-scan spectrum of P-Thr-modified surface. Moreover, the P 2p peak of P-Thr which reacted with the surface significantly shifted to a lower binding energy (p < 0.05) . Based on the results of this study, it was concluded that P-Thr chemically bonded to the titanium surface treated with HC1.

The aim of this study was to investigate the dynamic viscoelastic properties of seven commercially available vinyl polysiloxane denture soft lining materials. Five rectangular specimens (2 x 10 x 30 mm) were prepared from each material. The complex modulus E* (MPa) and loss tangent (tan delta) of each specimen were determined with a non-resonance forced vibration method using an automatic dynamic viscoelastometer at 1 Hz after 1 day of dry storage, and after 1, 30, 60, 90 and 180 days of wet storage at 37 degrees C. All data were analysed using one-way anova and Bonferroni/Dunn's test for multiple comparisons with a significance level of P< 0.01. All materials varied widely in terms of viscoelasticities and showed both an increase in E* and a decrease in tan delta at 1 Hz after the 1-day wet storage. After 60 days of wet storage, both E* and tan delta did not change significantly. The stiffer materials (>30% filler content) with high E* values (>2.00 MPa) showed elastic behaviour with tan delta values of around 0.03. The softer materials (6% filler content) with high tan delta values (initial value > 0.10) showed viscous behaviour and were easily affected by water absorption after the 1-day wet storage. It can be concluded that for the proper selection of vinyl polysiloxane denture soft lining materials, it is very important to evaluate the viscoelastic properties after 60 days of wet storage.