Chinese Journal of Dental Research, 01/2013

Wounds in the oral cavity heal faster and with less scarring than wounds in other parts of the body. One of the factors implicated in this phenomenon is the presence of saliva, which promotes the healing of oral wounds in several ways. Saliva creates a humid environment, which improves the survival and functioning of inflammatory cells that are crucial for wound healing. Furthermore, saliva contains a variety of proteins that play a role in the various stages of the intraoral wound healing. Tissue factor, present in salivary exosomes, accelerates the clotting of blood dramatically. The subsequent proliferation of epithelial cells is promoted by growth factors in saliva, especially epidermal growth factor. The importance of secretory leucocyte protease inhibitor is demonstrated by the observation that in the absence of this salivary protein, oral wound healing is considerably delayed. Members of the salivary histatin family promote wound closure in vitro by enhancing cell spreading and cell migration. Cell proliferation is not enhanced by histatin. Cyclization of histatin increased its biological activity approximately 1,000-fold compared to linear histatin. These studies suggest that histatins could potentially be used for the development of new wound healing medications. Keywords: growth factor, histatin, peptides, saliva, wound healing

Primary saliva is formed by salivary epithelial endpieces through two pathways, the transcellular and the paracellular pathways. While the mechanisms of ion transport through the transcellular pathway have been well studied, our understanding of fluid and electrolyte transport through the paracellular pathway remains rudimentary. Increasing evidence indicates that the tight junction (TJ) proteins form and regulate the paracellular pathway, although other intercellular junctions are probably involved. The structure of the TJ is complex and has not been well characterised. A functioning TJ is formed by multiple proteins, including membrane, cytoplasmic scaffolding, and signalling proteins. Paracellular fluid and electrolyte flow is mediated by high-capacity, charge- and size-restrictive small pores with a radius of 4 to 6 Å, whereas macromolecules pass through low-capacity, nonrestrictive large pores. Although the characteristics of these pores need to be further delineated, it is clear that they are under the regulation of the autonomic nervous system, endocrine, paracrine and autocrine systems, and various pathological factors. To date, the majority of the evidence for paracellular fluid and ion transport is accumulated from the studies using various epithelia other than salivary glands. Further investigations to explore the structure, function, and regulation of the paracellular pathway in salivary epithelia are needed to better understand the mechanism of saliva secretion. Keywords: tight junction, paracellular fluid and ion transport, saliva secretion

Objective: To investigate the apical sealing ability of glass ionomer and resin-based root canal obturation systems in comparison to a conventional vertical compaction of warm guttapercha. Methods: Forty-five extracted human teeth were randomly assigned into 3 groups of 15 each: a resin-based (EndoRez), a glass ionomer-based (Activ GP), and a conventional gutta-percha plus pulp sealer obturation system (GP/EWT). Apical and root canal space sealing abilities were assessed on five cross-sections 1.0 mm apart starting from the apex. Cross-section images were analysed using a focus-variation 3D scanning microscope and unsealed space was calculated as the percentage of total root canal space occupied by voids and debris. Results: EndoRez had significantly higher rate of apical leakage and deeper dye penetration as compared to GP/EWT and Activ GP. EndoRez group had also more voids and debris (22.5%) in the root canal spaces as compared to GP/EWT (10.5%) and Activ GP (10.8%). Apical leakages occurred not only along the root canal walls, but also along the gutta-percha cones with EndoRez as a result of significant polymerisation shrinkage of the resin sealer. Conclusion: Resin-based EndoRez did not form an adequate apical seal of filled root canals. Glass ionomer-based Activ GP was comparable to a vertical compaction of warm guttapercha plus EWT sealer in sealing root canal spaces. Keywords: root canal therapy, gutta-percha, glass ionomer, methacrylate resin, dye leakage

Objective: To investigate the relation between handling characteristics and application time of four composite materials with subjectively different viscosities. Methods: Eight experienced faculty members placed one Class II and one Class IV restoration in a random sequence into pre-prepared plastic teeth mounted on a typodont model, each using 4 types of composites (Herculite Précis (M1), Kerr; Tertic N-Ceram (M2), Ivoclar Vivadent; Filtek Z350 (M3), 3M-ESPE; Charisma Opal (M4), HareausKulzer), resulting in a total of 64 restorations. The application process was filmed with a high definition video camera. Two evaluators watched the recordings in a random sequence as well, timed the composite application and wrote down their observations, which were dichotimised into positive and negative ones. Application times were analysed with a two-way Kruskal Wallis test (time x dentist) and the observation data were analysed with a chi-square test (P 0.05). Results: Materials did not differ in their application time (P > 0.05). The mean application time was 12 ¼ minutes for the Class II and 9 ¾ minutes for Class IV restorations. However, there were statistically significant differences between the dentists in terms of application time. The observation data showed no significant difference between Class II and Class IV restorations but there were significant material differences (P 0.05). M2 yielded 6% negative observations, while the other materials were between 35% and 38%. Conclusion: There was no association between the handling characteristics of the tested composite resins and the speed of application. However, one of the tested materials (M2) showed significantly less problems in the application process. Keywords: Composite direct application, handling, observation study, in vitro, viscosity

Objective: To evaluate the genotypic diversity and some virulence traits of Streptococcus sobrinus (S. sobrinus) isolated from caries-free children and children suffering severe early childhood caries (SECC). Methods: S. sobrinus isolated from stimulated whole saliva samples of 91 caries-free children and 87 SECC children were subcultured, identified by polymerase chain reaction and genotyped by arbitrarily primed polymerase chain reaction. Polysaccharide synthesis ability, acidogenicity, aciduricity and the adherence ability of these S. sobrinus isolates were measured. Results: The frequency of S. sobrinus detection was 18.39% (16/87) in SECC children, which was significantly higher than that (3.30%, 3/91) in caries-free children. One to three different genotypes of S. sobrinus were detected in each SECC child. Only one genotype was colonised in each caries-free child. In SECC children, the production of water-insoluble glucan (WIG) was positively correlated with the ability of S. sobrinus adhering to a glass surface. Conclusion: The presence of S. sobrinus could be a risk factor for high caries activity in severe early childhood caries. The multi-genotypes could be related to different caries suceptibility. Water-insoluble glucan plays an important role in the adherence and accumulation of S. sobrinus on tooth surfaces. Keywords: Streptococcus sobrinus, genotypic diversity, virulence trait, cariogenic ability, severe early childhood caries

Ghost cell differentiation within an ameloblastic fibroma is extremely rare. The ghost cells found in an ameloblastic fibroma in previously reported cases were all associated with a typical calcifying odontogenic cyst. Here, we report a case of an ameloblastic fibroma with focal ghost cells and calcifications in some neoplastic epithelial islands, but without other histologic manifestations consistent with a calcifying odontogenic cyst. The patient was a 13-year-old Chinese boy who presented with a bony-hard swelling in the posterior mandibular region over a 6-month period. Radiographs showed a well-defined multilocular radiolucency associated with an unerupted tooth. The lesion was mostly cystic-solid and comprised of odontogenic epithelial strands, islands and myxoid ectomesenchymal component microscopically. Small groups of ghost cells and calcification were noted in the epithelial islands. Keywords: ghost cell, ameloblastic fibroma

The mandibular first molars mostly have two mesial canals. In this report, two cases of mandibular first molars with three mesial canals are presented. The middle mesial canal was detected under endodontic microscope and further confirmed by cone-beam computed tomography and angled radiography, respectively. The purpose of this paper was to highlight the possibility of an aberrant root canal in a mandibular first molar and to help reduce the failure rates of the dental pulp treatment of the mandibular first molar. Keywords: mandibular first molar, middle mesial canal, root canal morphology

In the present case of a 35-year old patient, platelet-rich fibrin, which is an autologous platelet concentrate, was used to fill the osseous defect following surgery. The case was assessed both clinically and radiographically for a period of 9 months. Keywords: bone regeneration, periapical surgery, platelet-rich fibrin