A micro-computed tomographic analysis of the apical anatomy of permanent three-rooted mandibular first molars / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the anatomic features of the root apexes of permanent three-rooted mandibular first molars.</p><p><b>METHODS</b>A total of 122 permanent mandibular first molars of Han Chinese patients were collected. Twenty three-rooted and 25 two-rooted molars were scanned by micro-CT and then reconstructed three-dimensionally. The apical anatomy of the tooth models were analyzed in software Mimics 10.01. The long and short diameters of the apical constriction (AC), the distances between AC, apical foramen (AF) and apex were measured. One-way ANOVA and LSD-t tests were used to compare the groups in relation to AC diameter and the distances between the AC, AF and apex.</p><p><b>RESULTS</b>The AF of the mesiobuccal (MB) canals most frequently presented at the distal side of the apex (10 cases in three-rooted and 6 cases in two-rooted group), and of the mesiolingual (ML) canals, most often at the lingual side (8 cases in each group). The AF of the distobuccal (DB) roots were frequently located at the distolingual (DL) side (10 cases), and those of the DL roots and distal canals of two-rooted molars were most often at the buccal (7 cases) and distal (11 cases) sides, respectively. The percentage of the "classical" singular AC was 53% (80/151). The average long(D) and short(d) diameters of the AC of the DB canals were (0.32 ± 0.09) mm and (0.25 ± 0.05) mm, respectively, significantly larger than the DL canals [D = (0.27 ± 0.08) mm, d = (0.22 ± 0.06) mm, P < 0.05] and the ML canals [D = (0.24 ± 0.06) mm, d = (0.19 ± 0.06) mm, P < 0.01). In three-rooted group, the mean distances between AC and AF, AF and apex, and AC and apex were (0.67 ± 0.32), (0.49 ± 0.28) and (1.01 ± 0.34) mm, respectively.</p><p><b>CONCLUSIONS</b>The AF of three-rooted mandibular molars frequently deviate from the root apex, and the AC of the DB canal is wider than those of the other canals. The mean distances between AC, AF and the apex suggest that root canal therapy should terminate at 1 to 1.5 mm short of the radiographic apex.</p>

The use of dental papillae cells and millipore filter for bioengineered dentin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe the ability of SD rat dental papillae cells forming dentin-like structure induced by millipore filter combined with transforming growth factor-β(1) (TGF-β(1)).</p><p><b>METHODS</b>The first passage SD rat dental papillae cells were enzymatically dissociated and centrifuged to obtain a cell mass. The cell mass was seeded on the millipore filter combined with TGF-β(1). The complex was incubated for 6 d in vitro or transplanted under the renal capsule for 2 weeks. Then the differentiation of dental papillae cells on the filter and the formation of mineral tissue on the implant were analyzed.</p><p><b>RESULTS</b>A layer of polarized columnar cells were observed along the surface of the millipore filter, with cell processes extending into the porous media. Dentin sialoprotein (DSP) and dentin matrix protein-1 (DMP-1) were positive in these cells. After 2 weeks, tubular dentin matrix was deposited on the surface of the aligned cells. Scanning electron microscopy showed that the thickness of newly formed tubular dentin was consistent. DSP and DMP-1 were expressed in columnar cells, tubular matrix and the dental papillae cells adjacent to the filter.</p><p><b>CONCLUSIONS</b>The millipore filter combined with TGF-β(1) could effectively recruit progenitors onto its surface and induce odontoblast differentiation, secrete matrix in a homogenous manner, leading to dentinogenesis.</p>

Influence of luxS of Streptococcus mutans on biofilm of dental plaque / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To construct luxS mutant aften luxS gene of Streptococcus mutans (S. mutans) was knocked out, and examine their ability of biofilm formation.</p><p><b>METHODS</b>A recombinant plasmid containing the flanking fragment of luxS of S. mutans was transformed into S. mutans UA159, and selected by brain heart infusion (BHI) agar medium with kanamicin. The luxS mutant further confirmed via polymerase chain reaction (PCR) and the autoinducer-2 (AI-2) bioluminescence assay of Vibrio harveyi (V. harveyi), and ability of luxS mutant and S. mutans UA159 biofilm formation was examined in different phases, in BHI medium with 1% sucrose and 1% glycose by scanning electron microscopy (SEM).</p><p><b>RESULTS</b>LuxS-deficient S. mutans strains were successfully constructed. Compared with S. mutans UA159, the luxS mutant maintained in BHI medium containing 1% sucrose displayed an apparent defect in biofilm formation, while they showed no significant deviation in BHI medium containing 1% glycose.</p><p><b>CONCLUSION</b>luxS gene in S.mutans can play a role in dental plaque biofilm formation, and the luxS gene is possible to regulate sucrose-dependent biofilm formation.</p>

Establishment and application of an in vitro model for apatite crystal mineralization / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To establish an in vitro model for the apatite crystal mineralization. To evaluate the influences of bovine serum albumin (BSA) and fluoride to the mineralization of apatite crystal.</p><p><b>METHODS</b>The model was constructed using cation selective membrane (CMV) and dialysis membrane. Double distilled water (DDW), BSA, 5, 20, 100 mg x L(-1) fluoride were added into the reaction space of the model. Reaction was carried out at 37 degrees C for 3 days under gentle stirring. The crystals were identified by scanning electron microscope (SEM) and X-ray diffraction (XRD).</p><p><b>RESULTS</b>The model was established successfully. When DDW and BSA were added respectively, the main component of the deposit was octacalcium phosphate (OCP), but the shape and size of the crystals differs from each other. When fluoride with different concentration were added, the main component of the crystal turned to rod-like and prism-like fluoroapatite (FAP) crystal. The size and crystallinity of the FAP increased with the increase of the fluoride concentration.</p><p><b>CONCLUSION</b>It is an effective way to evaluate the influence factors of the apatite crystal mineralization by using the in vitro model.</p>