An in vitro study on the secondary caries-prevention properties of three restorative materials.

STATEMENT OF PROBLEM: Secondary caries is considered to be the most important and common reason for the replacement of all types of restorations. PURPOSE: The purpose of the study was to evaluate in vitro both the anticaries efficacy and marginal integrity of amalgam, glass ionomer cement, and composite resin restorations in a cariogenic condition. MATERIAL AND METHODS: Class II cavities were prepared on 60 extracted teeth, which were assigned to 3 groups and restored either with amalgam, glass ionomer, or composite resin. After thermal cycling and sterilization, the teeth were set in an artificial carious environment for 10 days. The bacteria from the margin of the restorations were then collected, and microleakage was evaluated by means of dyeing. According to the locations, the demineralization of tooth tissue around the restoration was divided into 3 parts: artificial outer lesion, artificial enamel wall lesion, and artificial dentin wall lesion. The depths of the artificial outer lesion and the areas of the artificial enamel and dentin wall lesions were investigated with a confocal laser scanning microscope after all the specimens had been stained with 0.1 mM Rhodamine B. Statistical analyses consisted of 1-way ANOVA and Kruskal-Wallis tests (α=.05). RESULTS: No significant difference was noted in terms of the number of bacteria around the restorations for the 3 materials; the microleakage of amalgam was the least among the 3 types of restorations; the outer enamel lesion depth around the glass ionomer cement was the lowest, and the wall lesion area around the amalgam was the smallest. CONCLUSIONS: No definite inhibitory effect of fluoride releasing restorative materials (glass ionomer) was apparent on Lactobacillus acidophilus in this study. The amalgam restorations showed the best marginal integrity and the smallest artificial wall lesion among the 3 types of restorations.

A clinicopathological study on verrucous hyperplasia and verrucous carcinoma of the oral mucosa.

BACKGROUND: Oral verrucous hyperplasia (VH) and verrucous carcinoma (VC) are two clinicopathologically distinctive oral verrucous lesions. The objective of this study was to investigate the clinicopathological features of the two verrucous lesions and estimate their relationship from China. METHODS: Retrospective review of two series of patients with histologically confirmed VH (n = 121) and VC (n = 56) between 1996 and 2009 in our hospital were conducted. RESULTS: The average age of VH was 58.5 years (ratio male:female = 1.37) with the tongue being the predominant site. The average age of VC was 64.3 years (ratio male:female = 1.15) with the lower lip being the predominant site. Multivariate analysis revealed that the elderly patient with verrucous lesion (≥60 years) was associated with 3.06-fold (P = 0.007) increased carcinoma risk compared with the non-elderly patient. The lesion located on lower lip was associated with 13.54-fold (P < 0.001) increased carcinoma risk compared with other sites. CONCLUSION: Clinicopathological features of VH and VC in China were elucidated. Elderly patient with oral verrucous lesion located on the lower lip correlates with higher risk of carcinoma.

A retrospective clinicopathological study on oral lichen planus and malignant transformation: analysis of 518 cases.

OBJECTIVE: To investigate the epidemiological and clinical characteristics of a relatively large cohort of patients with oral lichen planus (OLP) from eastern China. STUDY DESIGN: A total of 518 patients with histologically confirmed OLP in a long-term follow-up period (6 months-21.5 years) were retrospectively reviewed in our clinic. RESULTS: Of the 518 patients, 353 females and 165 males were identified. The average age at diagnosis was 46.3 years (range 9-81 years) with the buccal mucosa being the most common site (87.8%). At initial presentation, white lichen and red lichen was seen in 52.3% and 47.7% patients, respectively. Of these, 5 (0.96%) patients previously diagnosed clinically and histopathologically as OLP developed oral cancer. All of them were the females with no a history of smoking or alcohol use. CONCLUSIONS: Clinical features of eastern Chinese OLP patients were elucidated. Notably, approximately 1% of OLP developed into cancer, which provides further evidence of potentially malignant nature of OLP.

[Effect of different root canal file tapers on fracture strength of root canal wall].

PURPOSE: To compare the effects of different nickel-titanium rotary tapers on fracture strength of root canal and the application value of finite element analysis in root canal therapy. METHODS: Twenty four mandibular premolars were selected and all crowns were removed. All samples were randomly divided into 4 groups: A, B, C and D. Group A and C were instrumented with Z-K3 nickel titanium file as 0.04 taper for root canal preparation. Group B and D were instrumented with Z-K3 nickel titanium file as 0.06 taper. Group C and D were sliced into 2 mm thick slices 3 times after root canal preparation. Two teeth were selected from group A and group B and scanned with micro-CT. The model was imported into different softwares to optimize. The assembly model was built and imported into ANSYS for finite element analysis. Universal testing machine and force bar were used to apply 100 N force to samples until fracture occurring at any place of tooth sample. The fracture load was recorded and comparative analysis was conducted. RESULTS: The results of finite element analysis showed that the maximum stress of 0.04, 0.06 taper models was 138.88 MPa and 78.812 MPa, respectively. The average fracture load of group A, B was 490.12 N and 501.83 N, respectively. In group C and D, the maximum average fracture load was 93.61 N and 141.53 N, respectively. From the neck to the middle and then to the tip, the average fracture load of root canal decreased in turn. CONCLUSIONS: For normal form mandibular premolars, the fracture strength of the root instrumented with 0.06 taper nickel titanium rotary file was significantly higher than that instrumented with 0.04 taper. Three dimensional finite element analysis could guide dentists to choose a suitable taper file in root canal treatment to reduce the incidence of root fracture.

[Expression and subcellular localization of XIAP and XAF1 in human normal oral keratinocytes and Tca8113 cells].

OBJECTIVE: To clarify expression and subcellular localization of XIAP and XAF1 protein in human normal oral keratinocytes (hNOK) and Tca8113 cells human tongue carcinoma cell line. METHODS: The hNOKs and Tca8113 cells were cultured in vitro. Expression and subcellular localization of XIAP and XAF1 protein were examined by combination of indirect immunofluorescence and confocal laser scanning microscopy. RESULTS: XIAP expression was weak in the hNOKs and fluorescence staining localized chiefly in the cytoplasm and perinuclear areas. In the Tca8113 cells, high level of XIAP protein could be detected in both the cytoplasm and the nucleus. In the hNOKs, XAF1 distributed mostly in the nucleus. Homogeneous nuclear and cytoplasmic distribution of XAF1 could be visualized in the Tca8113 cells. CONCLUSIONS: In cancerization of oral mucosa, XIAP protein could play an important antiapoptotic role by overexpression, while XAF1 protein does not appear to antagonize effectively the role of XIAP.