Odontogenic tumors are uncommon lesions in the Chilean population and malignant odontogenic tumors are very rare. The relative frequency of various types of odontogenic tumors, as well as the age and gender distribution are similar to those reported in the North American series and different from those found in recently published Asian and African series.

Our observations show an increased expression of MT1-MMP and TIMP-2 in periodontitis-affected gingival tissues. The altered balance between these two molecular mediators of collagen remodeling suggests their involvement in human periodontal disease.

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Background Cyclooxygenase‐2 protein is a critically important mediator in inflammation that influences proliferation, apoptosis, angiogenesis and metastasis. Previous works showed a relationship between cyclooxygenase‐2 and tumourigenesis in humans and animal models. In epithelial odontogenic tumours and cysts, increased cell proliferation and survival have been linked to its pathogenesis and tumour development. The aim of the present study was to analyse the immunohistochemical expression of cyclooxygenase‐2 in solid ameloblastoma and odontogenic keratocyst and its association with proteins related to cell proliferation and apoptosis. Methods This study was conducted on 40 cases from the Pathological Anatomy Service, University of Chile. The cases were diagnosed as solid ameloblastoma (n = 21) and odontogenic keratocyst (n = 19) according to WHO 2017. Slides prepared from paraffin‐embedded sections were immunohistochemically stained for cyclooxygenase‐2, cyclin D1, Ki‐67, p63 and Bcl‐2. Statistical evaluation was performed by the Shapiro–Wilk test, ANOVA Mann–Whitney test and Spearman's correlation coefficient (p < 0.05). Results There were significant differences in the immunoexpression of cyclin D1, Ki‐67 and Bcl‐2 between solid ameloblastoma and odontogenic keratocyst. Likewise, there was a significant difference in the immunoexpression of p63 between follicular and plexiform histological types/subtypes of solid ameloblastoma. Lastly, there were statistical associations between cyclooxygenase‐2 and Ki‐67 for solid ameloblastoma and between cyclooxygenase‐2 and p63 for odontogenic keratocyst. Conclusion A high level of cyclooxygenase‐2 is related to increased cell survival and proliferative activity in solid ameloblastoma and odontogenic keratocyst. This event might contribute to tumoural progression and local invasiveness in these lesions.

SUMMARY: Activation of macrophages in periapical granulomas occurs through the presence of cytokines, endotoxin and other genetic and epigenetic factors, allowing the initiation of inflammation and bone resorption. The present study aims to analyze the presence of CD133 protein (marker of stem cells) and the AR (androgen receptor) protein in biopsies of human odontogenic periapical granuloma. Biopsies from 14 adult male patients with diagnosis of periapical granuloma included in paraffin blocks were processed histologically to obtain 5-µm thick sections. Protein presence was detected and analyzed by immunohistochemistry of CD133 and AR. The quantification considered the number of positive cells in 0.17 mm2 random areas under the microscope using a 1000X objective. Both CD133 and AR proteins are expressed abundantly in cells in pathological periapical granulomas tissue. The number of cells expressing CD133 and AR shows a wide variation coefficient, so its variation is a particular feature for each individual. We concluded that in human odontogenic periapical granuloma there are abundant stem cells and cells expressing AR that may be important for the pathogenic inflammatory process.

The removal of necrotic and vital pulp substrates and microorganisms and their toxins from the root canal system (RCS) has been found to be the basis for a successful endodontic treatment. In this study, our aim was to evaluate the effect of passive ultrasonic irrigation (PUI) on the elimination of the organic remnant tissue from infected, narrow and curved mandibular root canals during their instrumentation. For this purpose, mesiobuccal canals from mandibular first molars were instrumented with the RaCe rotary system, using PUI activation or conventional irrigation (CI) and two apical diameters (#25 and #35). The root canal cleanness of the samples was evaluated by microscopy and using a modified Langeland’s ordinal scale. Parametric and non-parametric statistical analyses and principal coordinates analysis (PCoA) of the samples were performed. When PUI was used, there was a significant reduction of the organic remnant in the apical enlargement of 25 at 2 mm from the apex (p < 0.001). After pooling the groups, regardless of the depth of the observation (2 and 4 mm from the apex), the pair #35 + PUI vs. #25 + CI showed statistically significant differences (p < 0.001). The effect of PUI explained 65% of the overall variance when compared with the CI samples. The use of PUI reduced the organic material of narrow infected and curved root canals with an apical enlargement of #25 and #35. When PUI is not used, a biomechanical instrumentation up to a diameter ≥#35 is recommended.

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