Chinese Journal of Dental Research, 01/2007

Cardiovascular disease (CVD) describes diseases of the heart and blood vessels, consisting mainly of coronary heart disease and stroke, which are among the main causes of premature death in humans. It is currently believed that long-lasting infections and low-grade chronic systemic inflammation play an important role in the pathogenesis of atherosclerosis and CVD. Periodontal diseases are induced by bacteria and bacterial products of plaque biofilm and characterised by inflammatory destruction of tooth-supporting connective tissues and alveolar bone. A number of case-control, cross-sectional and longitudinal studies indicate an association between periodontal disease and CVD after adjustment of common confounders, and a potential effect of periodontal infections on an increased risk of atherosclerosis, ischaemic heart disease and stroke, although a causal association of periodontal infection with atherosclerotic CVD remains to be elucidated. The emerging evidence suggests that periodontal disease, as one of the most common and unique infections in humans, may significantly contribute to systemic inflammation. Observations include the relationship between periodontitis and an elevated number of peripheral blood leukocytes, as well as increased levels of C-reactive protein (CRP) and IL-6, which may partly explain the association of periodontal disease with CVD, as documented in a number of studies. Although some initial studies have shown promising effects of periodontal treatment on the reduction of serum levels of CRP and IL-6, and improvement of the endothelial function in periodontitis patients, the potential mechanisms and exact effects of controlling periodontal infections on the reduction of systemic inflammation remain to be determined. Future studies are highly warranted to clarify these points and elaborate the relevant clinical implications. Keywords: atherogenesis, cardiovascular disease, C-reactive protein, inflammation, periodontal disease/infections

Objective: To study the differentiation of bone marrow mesenchymal stem cells (BM-MSCs). When co-cuttured with tooth germ cells (TGCs). Methods: The BM-MSCs were isolated from tibiae and fibula of Sprague-Dawley (SD) rats aseptically and cultured. The fist molar tooth buds were isolated from E17 SD foetus and processed to obtain TGCs. The BM-MSCs were co-cultured with TGCs indirectly. The differentiation potentiality of BM-MSCs and the tooth-forming potentiality of TGCs were assessed. Results: The BM-MSCs started to express odontogenic markers, dentin sialoprotein (DSP) and dentin matrix protein 1 (DMP1) after 7 days co-culture with TGCs. Implants of co-cultured pellets formed osteoid dentin under renal capsules, while control groups self-differentiated into osseous tissue. Conclusion: BM-MSCs could be differentiated by co-cultured with TGCs into dental tissues, although the molecular mechanism requires further study. Keywords: co-culture, differentiation, mesenchymal stem cell, tooth germ

Objective: To validate two-dimensional (2D) digital intraoral and three-dimensional (3D) cone beam CT (CBCT) images in assessment of periodontal bone craters and furcation involvements. Methods: Forty-one periodontal bone defects of human skulls were evaluated using intraoral digital radiography and CBCT. Digital radiographs were made with a size #2 CCD sensor and a 60 kV DC X-ray unit, with a 0.28 mAs exposure setting. For CBCT, jaw bone images were obtained at 120 kV and 23.87 mAs. Periodontal bone craters and furcation involvements on both imaging modalities were assessed and compared with the gold standard, the direct skull observation. Results: Detection of both craters and furcation involvements was improved significantly by using 3D CBCT images (p = 0.374 and p = 1.000 respectively) than by 2D intraoral CCD images (p = 0.001 and p = 0.006 respectively), when compared with the gold standard. 2D images had a failure rate of 31% and 42% for detection of craters and furcation involvements. In contrast there was 100% detection with 3D CBCT. For crater assessment, 2D images overestimated in 62% of sites and underestimated in 13% of sites. CBCT showed 88% accurate classifications, and 12% overestimations. For furcation involvements, only 25% were correctly classified from the 2D digital images. CBCT images allowed correct classification 100% of the time. Distinctions between the vestibular and oral bony defects were only marked on CBCT images. Conclusion: CBCT demonstrated more potential in the morphological description of periodontal bone craters and furcation involvements than 2D intraoral images. The latter mostly overestimated the defects or showed insufficient information of the bone defects. These findings may be useful for further studies on periodontal diagnosis using CBCT. Keywords: cone beam CT, crater, furcation involvement, intraoral radiography, jaw bone, periodontium

Objective: To construct a cDNA library of human tongue squamous cell carcinoma cell line (Tca8113) for further study of protein-protein interaction in oral squamous cell carcinoma cells for exploring the mechanisms of carcinogenesis. Methods: Total RNA was extracted and reverse-transcribed into cDNA, followed by long distance PCR. The product was co-transformed into the competent AH109 with Sma I-linearised pGADT7-Rec. After growing on SD/-Leu plates, these transformants were harvested and the quality of the constructed library was analysed. Results: The transformation efficiency was 1 × 106 transformants/3 µg pGADT7-Rec. The library size was 4 × 107 cfu/ml. The inserts were from 500 bp to 3 kb. With the antibody of HAtag of pGADT7-Rec, the corresponding fusion proteins expressing in AH109 were detected. Conclusion: A two-hybrid cDNA library from Tca8113 has been constructed. Analysis of the quality of this two-hybrid cDNA library indicated that this library would be useful for identifying protein-protein interactions in oral squamous cell carcinoma. Keywords: cDNA library, squamous cell carcinoma cell line, yeast two-hybrid

Objective: To assess the effects of superficial parotidectomy on the treatment of chronic obstructive parotitis. Materials and Methods: Between 1995 and 2005, 17 patients (median age, 43 years; range 23 to 63) with chronic obstructive parotitis received parotidectomy after failure of conservative treatments. They had continued symptoms for 3 to 10 years. Patients were diagnosed by sialography prior to surgery and were subjected to superficial parotidectomy. The anterior part of the main ducts was preserved in four cases, and the entire main ducts were removed in the remaining 13 cases. Results: A total of 16 patients had complete resolution of their symptoms following surgery. One case displayed persistent facial swelling for 4 months, resulting from an infection of the residual ducts; the symptoms disappeared after the removal of the ducts. Temporary facial paralysis occurred after surgery in seven cases, with complete recovery of all cases 6 to 12 months later. Conclusions: Parotidectomy is an effective surgical approach for the patients with chronic obstructive parotitis who fail to respond positively to conservative treatment and with symptoms recurring frequently. Superficial parotidectomy is the surgical technique of choice. It is essential to remove the entire main duct to prevent the recurrence of facial swelling. Keywords: chronic parotitis, facial nerve, operation, parotid, parotidectomy

Objective: To prepare and characterise monoclonal antibodies (mAbs) against highly abundant proteins in human parotid saliva for the depletion of these highly abundant proteins in the future proteomic studies of saliva. Methods: Proteins in human parotid saliva were concentrated by using ultrafiltration and analysed by SDS-PAGE. The protein band between 50-65 kDa was cut, ground and used to immunise BALB/c mice. The mAbs against highly abundant proteins in human parotid saliva were prepared through hybridoma technology and characterised by ELISA and Wetstern blot. Results: Eleven hybridoma cell lines secreting mAbs against highly abundant proteins in human parotid saliva were established, and Western blot assay showed that these antibodies were specific for the highly abundant proteins in human parotid saliva. mAbs against salivary amylase, the most abundant protein in human parotid saliva, were characterised by ELISA and Western blot. Conclusions: mAbs against human highly abundant proteins in parotid saliva were successfully prepared and characterised. The present study provides an approach for using these mAbs for the depletion of highly abundant proteins in human parotid saliva in order to better enrich and visualise lower abundant proteins for the studies of disease-related biomarkers in human saliva proteome. Keywords: highly abundant proteins, monoclonal antibody, parotid saliva, proteome

Objective: To compare the initial penetration depth of nickel-titanium (NiTi) and stainless steel (SS) spreader during lateral compaction of .04 and .02 tapered master gutta-percha cones and the quality of the canal seal. Methods: Forty extracted mandibular premolars with a single curved canal were prepared using standardised rotary instrumentation technique. NiTi and SS spreaders were used to obturate the canals containing a .04 or .02 master cone while the penetration depths were measured. Horizontal sections were cut 2 and 4 mm from the apex and photographed under a stereomicroscope. The area of the canal and gutta-percha in cross-section was measured using an image analysis program. Results: NiTi spreaders penetrated to a significantly greater depth than SS spreaders (p 0.01). At the 2-mm level, there was significantly more gutta-percha using the .02 tapered gutta-percha cone in the NiTi spreader group than in the SS spreader group (p 0.05), but no significant difference occurred using .04 tapered gutta-percha (p > 0.05). At the 4-mm level, there was no significant difference in obturation density either between the NiTi spreader and the SS spreader or between the .02 and .04 tapered gutta-percha (p > 0.05). Conclusion: NiTi spreaders penetrated to a significantly greater depth than SS spreaders and the area occupied by gutta-percha was significant greater when filling curved canals with .02 tapered gutta-percha. Keywords: lateral condensation, master cone, nickel-titanium, spreader

Objective: To study the relationship between human papilloma virus (HPV) infection and abnormal expression of p53 protein in oral squamous cell carcinoma (OSCC). Materials and Methods: A total of 50 biopsy specimens from patients with OSCC were studied. Molecular biological and immunohistochemical methods were used to detect HPV infection in OSCC and abnormal expression of p53 protein. Results: Of the 50 specimens, 14 showed HPV DNA. HPV type 16 was dominant, and one case was infected with HPV type 16 and 18. There were 9 cases of HPV infection in 24 samples with p53 overexpression, and 5 cases in 15 samples without p53 overexpression. Conclusions: HPV type 16 and 18 seem to be risk factors in oral carcinoma development. However, results are greatly varied, from 5% to 95%. The cause may be due to sensitivity of detection methods and the number of samples. Regarding p53 expression, the present study shows that the HPV infection and p53 expression in oral cancer are not closely related. Keywords: human papilloma virus (HPV), oral cancer, p53

Objective: To analyse comparatively flow rate, pH, buffer capacity and biochemistry of the mixed saliva in miniature pigs (minipigs), Sprague-Dawley (SD) rats and humans. Materials and Methods: Twelve minipigs, 10 rats, and 16 human subjects were selected for tests of stimulated mixed saliva flow rate, pH, buffer capacity, and biochemistry. Results: Mixed saliva flow rate of minipigs was 1.401 ± 0.387 ml/min, similar to those of humans (1.183 ± 0.869 ml/min, p > 0.05). The pH and buffer capacity were higher in the minipigs' mixed saliva than in the humans'mixed saliva. There were some differences in the mixed saliva biochemistry indices among minipigs, rats, and humans. Conclusions:The minipig is considered a good animal candidate for saliva research. The characteristics of mixed saliva of minipigs and rats can be used in the selection of animal models for dental research. Keywords: biochemistry, buffer capacity, miniature pig, pH, rat, saliva flow rate