Chinese Journal of Dental Research, 02/2010

In the past decade, research on the potential applications of stem cells in dentistry has made great progress. There are at least five different types of multipotent mesenchymal stromal cells (MSCs) originating from exfoliated primary teeth, including dental pulp, apica papilla, periodontal ligament, and dental follicle. It has been reported that dental tissue-derived MSCs are able to generate dentine-pulp-like complexes as well as differentiate into periodontal and craniofacial progenitor cells. Similar to these dental tissue-derived MSCs, bone marrowderived MSCs are also capable of developing into ameloblasts, odontoblasts and periodontal ligament progenitor cells, as well as regenerating cementum, alveolar bone, craniofacial bone and articular condyles. Besides adult stem cells, embryonic stem cells are an alternative cell source for dental tissue regeneration, but the current data are preliminary and are based predominantly on in vitro data. In addition to these commonly reported stem cells, other progenitor cells with MSC properties are also found in salivary glands, tongue muscle, taste buds and oral mucosa, and these may play a role in recovering the function of the residing tissues. Other than these regenerative applications, many reports have demonstrated the utility of these stem cells in cytotoxicity testing, biocompatibility testing and developmental research. The present article summarises the above findings regarding the regenerative and other potential applications of both MSCs and embryonic stem cells. Keywords: dental application, embryonic stem cells, mesenchymal stromal cells, regeneration

Infantile haemangioma is the most common tumour of infancy, yet the pathogensis of this lesion remains unknown and the predictable life cycle is poorly understood. Though much new information on infantile haemangioma has emerged over the past decade, researchers continue to debate the fundamental features; including cells of origin, nonrandom distribution, and mechanisms regulating the sometimes explosive growth and slow involution. The development of biomarkers has shed light on the pathogenesis and management of infantile haemangioma. Several useful biomarkers and their suggestions as to the aetiology of infantile haemangioma are reviewed. In addition, the application in clinical diagnosis and choice of treatment methods of infantile haemangioma is summarised. Keywords: angiogenesis, CD133, GLUT-1, immune response, infantile haemangioma, vasculogenesis

Objective: To examine the possible association of CCR2-V64I and MCP-1-2518A/G polymorphisms with generalised aggressive periodontitis (GAgP) in the Chinese population. Methods: One hundred and twenty-four GAgP patients and 94 healthy subjects were included in the study. A peripheral blood sample was obtained from each subject and genomic DNA was isolated. Gene polymorphisms of CCR2-V64I and MCP-1-2518A/G were analysed by standard polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Results: A possible combined effect of CCR2-V64I and MCP-1-2518A/G was observed in the female GAgP patients, as the odds ratio for VV genotype (CCR2) and G+ genotype ( MCP-1) was 0.2 (P = 0.023). Individuals carrying VV genotype and G+ genotype were at reduced risk for GAgP. A possible combined effect of genotype and smoking was observed in the male GAgP patients, as the odds ratio for VV genotype (CCR2) and smoking, or G+ genotype (MCP-1) and smoking were 7.4 (P = 0.022) and 4.9 (P = 0.030), respectively. Conclusion: The combined association of CCR2-V64I and MCP-1-2518A/G polymorphisms may play an important role in determining GAgP susceptibility in Chinese females. A possible combined effect of genotype and smoking on GAgP susceptibility was suggested in males. Keywords: aggressive periodontitis, CCR2, MCP-1, polymorphism

Objective: To identify dominant pathogens in the periapical lesions associated with persistent apical periodontitis. Methods: Thirty-three root-filled teeth with persistent apical periodontitis referred for surgical treatment were selected. Microbial samples were collected from the periapical lesions during apical surgery. Microbial identification was performed with species-specific primers prepared according to the sequence analysis data using a 16S rRNA technique. Results: Among the 33 cases, in 5 cases none of the target species were detected, 6 cases showed the presence of only one species, and 22 cases showed more than two species. Porphyromonas endodontalis (45% of sample) was the most commonly detected dominant microbial species in the study sample, followed by Actinomyces viscosus (42%), Candida albicans (36%) and Porphyromonas gingivalis (27%). Fusobacterium, Actinomyces israelii and Enterococcus faecalis were also detected in 27%, 21% and 15% of the sample, respectively. The most frequently isolated species, P. endodontalis, was in most cases detected together with Actinomyces (14 cases) and P. gingivalis (6 cases). None of the lesions analysed in the present study contained Prevotella intermedia. There was no correlation in relation to the presence of sinus tracts and the bacterial species. Conclusion: A mixed population of pathogens was found in the endodontic lesions associated with persistent apical periodontitis. P. endodontalis, A. viscosus, C. albicans and P. gingivalis were the dominant species identified. Keywords: bacteria, microbiology, persistent apical periodontitis, 16S rRNA

Objective: To investigate bone formation after enucleation of mandibular odontogenic keratocysts (keratocystic odontogenic tumours) by computed densitometry of preoperative and post-operative panoramic radiographs. Methods: Fifty-eight patients with mandibular keratocysts were treated by surgical enucleation and primarily closed without grafting. The largest diameters of the cysts were 3.5 cm to 7.1 cm. Post-operative clinical and radiographic examinations were performed at 1, 3, 6 and 12 months. Bone density of the residual cavity was measured on the preoperative and postoperative panoramic radiographs with Digora® through a greyscale of 254 tonalities. Student t test was used for comparison of bone density values of different time periods. Results: Progressive bone formation in the residual cavity was observed after enucleation of mandibular odontogenic keratocysts. The mean increase of bone density was 6.85% at post-operative 1 month, 22.61% at 3 months, 49.45% at 6 months and 71.77% at 12 months in comparison with that of the preoperative radiograph. Although increase in bone density was not significantly different between the post-operative first 3 months and second 3 months, this increase was significantly higher in the first 6 months than that in the later 6 months (P 0.05). No significant correlation was found between increase of bone density and patient gender or the maximal diameter of the cysts. Conclusion: Bone regeneration could progressively occur in the defect area without grafting materials after enucleation of mandibular odontogenic keratocysts, with significant increase of bone density at 6 months post-operatively. Keywords: bone healing, computerised analysis, enucleation, odontogenic keratocyst, panoramic radiographs

Objective: To investigate the correlation between the expression of nerve growth factor (NGF) and tissue injury in irradiated rat submandibular gland. Methods: The salivary gland regions of the rats were irradiated with a single dose of 15 Gy X-ray. The histopathological changes in the submandibular gland were observed, while the expression of NGF was determined by immunohistochemistry and real-time PCR. Results: The weight of the body and submandibular gland decreased in the irradiated rats 30 days after irradiation, compared with the control group. There were also significant histopathological changes in the submandibular gland of the irradiated rats compared with the non-irradiated rats. The acinar cells and ducts were degenerated obviously. Fibrosis appeared around the ducts. The mRNA and protein expression of NGF in the submandibular gland decreased in the irradiated rats compared with the control group. Protein expression of NGF was even observed in the striated duct in the irradiated rats. Conclusion: NGF may play an important role in protection of the submandibular glands of rats from radiation. Keywords: ionising radiation, nerve growth factor, submandibular gland

Objective: To evaluate the value of the ultrasonographic features for differentiation between benign and malignant tumours of salivary glands. Methods: Eighty-four cases of salivary gland tumours were analysed. Sixty-five cases were benign and 19 were malignant. All cases were confirmed by histopathological examination. The ultrasonographic features analysed included the shape of the tumour, the boundary echo, the internal echo and the posterior echo. Each feature was graded into three ranks. For statistical analysis, they were ranked respectively 1, 2 and 3. Another 28 cases of salivary gland tumours were analysed to verify the diagnostic accuracy of the ultrasonography. All data were analysed using SPSS 16.0 for windows. The Mann-Whitney U test, the receiver operating characteristic (ROC) curve and Fisher's discriminant test were performed. Results: The differences between benign and malignant tumours were statistically significant in the shape of the tumour (P = 0.001), the boundary echo (P = 0.001) and the posterior echo (P = 0.000). However, the difference in the internal echo was not statistically significant (P > 0.05). The diagnostic accuracy, sensitivity and specificity were 82.1%, 63.2% and 87.7%, respectively, while the predicting diagnostic accuracy was 85.7%. Conclusion: The present study indicates that the shape of the tumour, the boundary echo and the posterior echo could be effective ultrasonographic criteria for differential diagnosis of benign tumours from malignant tumours in the salivary glands. Keywords: diagnosis, salivary gland, tumour, ultrasonography

Objective: To develop an in vitro shade-measuring model to evaluate the reliability and accuracy of the Crystaleye spectrophotometric system, a newly developed spectrophotometer. Methods: Four shade guides, VITA Classical, VITA 3D-Master, Chromascop and Vintage Halo NCC, were measured with the Crystaleye spectrophotometer in a standardised model, ten times for 107 shade tabs. The shade-matching results and the CIE L*a*b* values of the cervical, body and incisal regions for each measurement were automatically analysed using the supporting software. Reliability and accuracy were calculated for each shade tab both in percentage and in colour difference (ΔE). Difference was analysed by one-way ANOVA in the cervical, body and incisal regions. Results: Range of reliability was 88.81% to 98.97% and 0.13 to 0.24 ΔE units, and that of accuracy was 44.05% to 91.25% and 1.03 to 1.89 ΔE units. Significant differences in reliability and accuracy were found between the body region and the cervical and incisal regions. Comparisons made among regions and shade guides revealed that evaluation in ΔE was prone to disclose the differences. Conclusion: Measurements with the Crystaleye spectrophotometer had similar, high reliability in different shade guides and regions, indicating predictable repeated measurements. Accuracy in the body region was high and less variable compared with the cervical and incisal regions. Keywords: colour analysis, colour measurement, shade guide, shade selection, spectrophotometric system

Objective: To investigate the effects of different background colours (black, white or pink), direction and intensity of ambient light, measuring position, and the adjacent teeth, on the in vitro colour measurement of maxillary anterior teeth, using the Minolta CR-321 colorimeter. Methods: Ten extracted human maxillary central incisors were selected. A fibre-optic light MI-150 was used as the ambient illuminant. Teeth were irradiated from a 3- or 12-o'clock direction. L*a*b* values of seven sites on the labial surfaces were obtained by means of the Minolta CR-321 colorimeter, using three background colours, with or without the adjacent teeth. The recorded data were analysed with two-tailed Student t tests and analysis of variance (α = 0.05). Results: The ambient light did not affect the colour measurement of anterior teeth, regardless of the presence or absence of the adjacent teeth. There were no statistically significant differences in L*a*b* values at the same position under different background colours, except ΔE12 (colour difference between site 1 and site 2) between black and white backgrounds. ΔE12 (under black background), ΔE13 and ΔE15 were greater than 1.5, while the others were lower than 1.5. Conclusion: The background, ambient light and the presence of adjacent teeth did not affect the colour measurement of anterior teeth using the Minolta CR-321 colorimeter in vitro. The inherent disadvantages of using the naked eye during clinical visual shade assessment may be overcome by the colorimeter. Keywords: background colour, colorimeter, colour measurement, in vitro, tooth colour

Objective: To investigate the cytotoxic and apoptotic effects of saponins from Plumeria acuminata Ait on oral squamous carcinoma cells (OSCC). Methods: OSCC cells seeded at 2 × 104 cells/well in a 96-well plate were treated with saponins from P. acuminata Ait and cisplatin in various concentrations for 24 h. Trypan blue dye exclusion assay and ethidium bromide/acridine orange were used to evaluate their cytotoxic and apoptotic effects on the cells, respectively. Results: The results showed that both saponins and cisplatin had cytotoxic and apoptotic effects on OSCC cells. Conclusion: Saponins from P. acuminata Ait may be potential anti-cancer agents for OSCC. Keywords: apoptosis, OSCC, Plumeria acuminata Ait, saponins

Calcifying epithelial odontogenic tumour (CEOT) is a rare and benign odontogenic neoplasm that affects the jaws. Here we present a maxillary case of CEOT showing features of malignant transformation, and a review of the literature. Keywords: calcifying epithelial odontogenic tumour, malignant transformation, review