Chinese Journal of Dental Research, 02/2012

Oral squamous cell carcinoma (OSCC) is the most common cancer type in head and neck with approximately 500,000 new cases diagnosed each year worldwide. Advances have been made from cancer risk assessment to treatment. However, the clinical impact of these advances has been modest so far. With an increased understanding of genetic and epigenetic features in oral tumorigenesis, novel biomarkers have emerged and been tested for their potential use in assessing oral cancer risk and OSCC classification. New therapeutic strategies targeting molecules critical for OSCC maintenance and progression have shown promise. This article provides a general picture of the current status in the field of OSCC clinical and translational research for the oral health community. Keywords: oral squamous cell carcinoma, risk assessment, treatment

Objective: To assess whether N-methyl-D-aspartate (NMDA) receptor (NR) or oestrogen receptor (OR) expression plays a role in the differences that temporalis muscle afferent fibres are less sensitive to peripheral receptor activation than masseter muscle afferent fibres and do not exhibit sex-related differences in NMDA-evoked discharge. Methods: Immunohistochemical techniques were used to examine the expression of NR1, 2A, and 2B subunits of the NMDA receptor in male and female rats and the co-expression of NR2B subunits with ORs in female rats by trigeminal ganglion neurons that innervate the temporalis muscle. In vivo electrophysiological recording methods were employed to assess the response of afferent fibres to injection of NMDA into the temporalis muscle in female rats. Results: Approximately 20% of temporalis ganglion neurons expressed NR1, NR2A and NR2B subunits, respectively, and there was no sex-related difference in the expression of these subunits. In female rats, both ORα and ORß receptors were identified in the trigeminal ganglion by Western blot. ORs were found on the majority (~80%) of temporalis ganglion neurons that expressed NR2B subunits. A significant positive correlation between blood oestrogen concentration and NMDA-evoked afferent discharge was identified. Conclusion: The absence of sex-related differences in NMDA receptor expression may account for the lack of sex-related differences in NMDA-evoked temporalis afferent discharge. The association of elevated oestrogen concentration with increased afferent response to NMDA and the co-expression of NRs and ORs in temporalis ganglion neurons suggest that sensory input from the temporalis muscle may be modulated by oestrogenic tone. Keywords: nociception, estrogen, NMDA, temporomandibular disorders, sex differences

Objective: To explore the relationship between the genotypes and phenotypes of these hypophosphatasia patients caused by gene mutations of tissue-nonspecific alkaline phosphatase (TNSALP). Methods: Based on the genotypes of these patients, site-directed mutations of TNSALP cDNA at c.1162T>C or c.1120G>A or c.668G>A or c.535G>A were performed in the expression plasmids, respectively. The plasmids were transfected into U2OS cells and the alkaline phosphatase activity of the cells were measured. Transfected U2OS cells were induced to mineral formation, and mineralisation assay were performed by Alizarin Red staining. Results: The cells transfected with mutated TNSALP (c.1162T>C, c.1120G>A, c.668G>A, and c.535G>A) showed 39.7%, 57.6%, 2.9%, and 10.9% of alkaline phosphatase activity and 48.5%, 74.4%, 10.4%, and 16.7% mineralisation ability compared to those cells transfected with the wild-type TNSALP. Conclusion: Our results suggested that the new mutation c.1162T>C would moderately decrease the function of TNSALP while the mutations c.1120G>A and c.668G>A would mildly and severely decrease the function of TNSALP, respectively. Keywords: tissue-nonspecific alkaline phosphatase, mineralisation, mutation, hypophosphatasia

Objective: To evaluate the effects of recasting on the biocompatibility of a commercially available Ni-Cr alloy. Methods: The alloy tested was cast and subsequently recast four more times. For each cast condition, 24 disk shaped specimens were fabricated (5 mm in diameter, 0.5 mm in thickness). All the recasting was performed without adding new alloy. After the first cast and following each recast, the surface composition and microstructure of the alloy were determined using an X-ray fluorescence spectrometer and optical microscope, respectively. The in vitro cytotoxicity and in vivo mucous irritation potential of the cast and recast Ni-Cr alloy were investigated. The results were statistically analysed at the significance level of 0.05. Results: Recasting neither yielded to cytotoxicity or to changes in the surface composition of the Ni-Cr alloy tested. However, an increase in impurities and porosity of the surface structure was observed with recasting. Also, the segregation of the impurities to grain boundaries was evident after multiple castings. After the fourth recast, the alloys showed significantly greater mucosal irritation than the control. Conclusion: After fourth recast, the alloy of this type may contribute to mucosal inflammation. Furthermore, there is a need for diverse methods addressing different biological endpoints for the evaluation of dental alloys. Keywords: recasting, cytotoxicity, membrane irritation, X-ray fluorescence spectrometry, Ni-Cr alloy

Objective: To investigate the neutralising effects of subsequent arginine bicarbonate rinse on sucrose-induced decrease in plaque pH with interdental plaque pH telemetry. Methods: Six participants wearing partial lower prostheses incorporating a miniature glass pH electrode were included. After 5 or 6 days of plaque accumulation on the tip of the electrode, the subjects rinsed with a 15 ml 10% sucrose solution, followed no subsequent rinsing or rinsing with 15 ml of water, or 85 mmol/L NaHCO3, or 0.5%, 1% or 2% arginine bicarbonate for 2 min. The plaque pH was continuously recorded for 120 min. Results: Without a subsequent rinse, the plaque pH decreased at 10 min to 4.38 and stayed below the critical 5.7 for 83 min after sucrose rinse. Subsequent water rinse showed little effects on the sucrose-induced decrease in plaque pH and NaHCO3 induced only an instantaneous pH rise, whereas subsequent arginine bicarbonate rinses all immediately and effectively neutralised the sucrose-induced decrease in plaque pH. Conclusion: These results strongly suggested that regular use of an arginine bicarbonate rinse after carbohydrate consumption could help prevent caries. Keywords: plaque pH, caries prevention, sucrose, Stephan curve, arginine

Objective: To examine changes of four proinflammatory proteins in whole saliva in the early stage of plaque-induced experimental gingivitis. Methods: Eleven young male volunteers were recruited following the cessation of all oral hygiene measures for a period of 21 days. The levels of Interleukin-6 (IL-6), Interleukin-1ß (IL-1ß), calprotectin in saliva were determined with enzyme linked immunosorbent assay. The activity of elastase in saliva was examined. Results: IL-1ß, IL-6 and calprotectin in saliva increased gradually as plaque accumulated and peaked on the 14th and 21st day respectively. Moreover, the three proinflammatory proteins showed good correlations with clinical parameters, with IL-1ß correlating with clinical parameters more closely in particular. The activity of elastase in saliva elevated rapidly and peaked on the second day (P 0.01). However, after the seventh day, elastase activity declined slowly continuously. The change of IL-6 and IL-1ß in saliva showed a similar tendency throughout the experiment, the correlation coefficient was r = 0.687 (P 0.01), but there was no obvious correlation between calprotectin and elastase, even though both mainly come from neutrophils. Conclusion: Our study demonstrated that IL-6, IL-1ß and calprotectin concentrations in saliva could reflect the degree of gingival inflammation. The longitudinal change of elastase activity in saliva during the experimental gingivitis period was quite different from that of other pro-inflammatory proteins; reasons for the decrease of elastase activity in the late gingivitis period need further study. Keywords: saliva, interleukin-6, interleukin-1ß, calprotectin, elastase, experimental gingivitis

Objective: To evaluate the Chinese public preferences for asymmetrically altered incisor angulations, with the goal of linking preferences to gender. Methods: Five variations of 5 separate digital smiling photographs were used in this survey. The alterations included discrepancy between the dental and facial midlines, inclination of dental midline and two central incisors, inclination of left central incisor (mesially or distally) and occlusal cant. The raters used a 100-point visual analogue scale to evaluate each image on a web page. Results: Overall 1,022 raters joined the evaluation and they were reliable (intraclass correlation coefficient = 0.76-0.80). Raters identified range of approval for several smile characteristics. A 2 mm dental to facial midlines discrepancy was the maximum acceptable deviation for females and 3 mm was the maximum for males. Females could accept a 4-degree occlusal cant and males could accept a 6-degree cant. These two characteristics were related to gender. The dental midline and relevant two central incisors with a 5-degree slope or less were generally acceptable. The approval of a left central incisor inclination was 5 degrees mesially and 10 degrees distally. These three characteristics were unrelated to gender. Conclusion: The approval for five smile characteristics could be identified reliably. The ranges of acceptability were large and slight changes in the angulations of incisors did not influence the smile attractiveness. Keywords: public preferences, dental aesthetics, incisor angulations, internet evaluation, visual analogue scale

Objective: To compare the skeletal changes between female hyperdivergent adolescents and adults with Class II Division 1 malocclusion after orthodontic treatment. Methods: Thirty adolescent girls and 30 adult women both with hyperdivergent Class II Division 1 malocclusions were selected. The 2 groups were matched by both treatment period and treatment method. Cephalometric radiographs taken before and after treatment were traced and measured. Data were statistically examined. Results: After treatment, SNA decreased significantly in both groups. SNB remained unchanged in the adolescent group, while it decreased in the adult group. ANB decreased significantly only in the adolescent group and remained unchanged in the adult group. Obvious growth was found in the adolescent group. Ar-Gn, Ar-Go, N-Me and S-Go increased significantly in adolescents. In the adult group, N-Me and ANS'-Me increased after treatment, but with less magnitude than those in the adolescent group. All the angular measures (MP-SN, PP-SN, Ar- Go-Gn and N-S-Ba) remained quite stable in both the adolescent and adult groups. Conclusion: Although obvious vertical growth was found in the female hyperdivergent adolescent Class II Division 1 group, no clockwise rotation of the mandible and no mandibular catch-up growth were found. Vertical growth of the mandible was helpful in maintaining the MP-SN angle with conventional orthodontic mechanism in the adolescent group. Keywords: Class II Division 1 malocclusion, hyperdivergent, cephalometric analysis, skeletal changes, vertical growth

Objective: To observe the effects of ionic dissolution products on nano-sized 58S bioactive glass (nano-58S) on proliferation and specific osteogenic genes expression in MG-63 cells. Methods: Ionic dissolution products were prepared by incubating nano-58S or sol-gel bioactive glass 58S (58S) particulates in Dulbecco's modified Eagle's medium (DMEM) at 1% w/v for 24 hr and filtrated through 0.22 µm filters to remove the particulates. MG-63 cells were cultured in the nano-58S extraction, 58S extraction, and DMEM, respectively, for different time periods to assay the proliferation, mRNA expression of alkaline phosphatase (ALP), Cbfa1, Collagen type I (Col-I) and osteocalcin (OCN), as well as ALP staining, activity and matrix mineralisation. Results: In the nano-58S group, cell proliferation and mRNA expression of ALP, Cbfa1 and OCN were significantly enhanced in a time-dependent manner compared with the control group. mRNA expression of Cbfa1 on day 4 and OCN on day 7 was significantly higher than that in the 58S group. Moreover, there was significantly more ALP protein expression and mineralisation in the nano-58S group than in the 58S group. Conclusion: The nano-58S enhanced proliferation, osteogenic markers expression in MG-63 cells and induced stronger mineralization than 58S. Keywords: human osteoblast-like cells, nano-sized bioactive glass, gene expression, bone, osteogenesis

Osteoblastoma is a very rare primary bone tumour in the maxillofacial region. We report 2 cases of osteoblastoma in the maxilla and mandible, respectively. Histologically, the tumour is composed of small, irregular bony trabeculae and osteoids that are separated by a vascular stroma, and it should be considered in the differential diagnosis of an osteoblastic lesion. Total surgical resection is recommended. The absence of recurrence is largely due to adequate initial treatment. Keywords: osteoblastoma, bone tumors, mandible, maxilla, orthopaedic oncology

Cyclic neutropenia is a rare haematologic disorder. This case report presents a 6-year-old girl who was referred in order to treat gingival recession, and was finally diagnosed as having cyclic neutropenia based on an oral examination, complete blood counts and a sternal puncture bone marrow test. The patient received systematic granulocyte colony-stimulating factor therapy, full-mouth scaling and root planing and was followed up for 4 years. Due to irregular periodontal maintenance and poor oral hygiene, severe gingival inflammation and deep pockets persisted in the permanent dentition of the patient. Keywords: cyclic neutropenia, periodontitis, oral hygiene, periodontal initial therapy