Histomorphometric assessment of bone necrosis produced by two cryosurgery protocols using liquid nitrogen: an experimental study on rat femurs

OBJECTIVE: The aim of this study was to evaluate the effects of liquid nitrogen cryosurgery on the femoral diaphysis of rats. MATERIAL AND METHODS: The femoral diaphyses of 42 Wistar rats were exposed to three local and sequential applications of liquid nitrogen for 1 or 2 min, intercalated with periods of 5 min of passive thawing. The animals were sacrificed after 1, 2, 4 and 12 weeks and the specimens obtained were processed and analyzed histomorphometrically. RESULTS: The depth and extent of peak bone necrosis were 124.509 µm and 2087.094 µm for the 1-min protocol, respectively, and 436.424 µm and 12046.426 µm for the 2-min protocol. Peak necrosis was observed in the second experimental week with both cryotherapy protocols. CONCLUSIONS: The present results indicate that the 2-min protocol produced more marked bone necrosis than the 1-min protocol. Although our results cannot be entirely extrapolated to clinical practice, they contribute to the understanding of the behavior of bone tissue submitted to different cycles of liquid nitrogen freezing and may serve as a basis for new studies

Establishing the natural history and growth rate of ameloblastoma with implications for management: systematic review and meta-analysis

Background: Ameloblastoma is the second most common odontogenic tumor, known to be slow-growing, persistent, and locally aggressive. Recent data suggests that ameloblastoma is best treated with wide resection and adequate margins. Following primary excision, bony reconstruction is often necessary for a functional and aesthetically satisfactory outcome, making early diagnosis paramount. Despite earlier diagnosis potentially limiting the extent of resection and reconstruction, an understanding of the growth rate and natural history of ameloblastoma has been notably lacking from the literature.\ud \ud Method: A systematic review of the literature was conducted by reviewing relevant articles from PubMed and Web of Science databases. Each article's level of evidence was formally appraised according to the Centre of Evidence Based Medicine (CEBM), with data from each utilized in a meta-analysis of growth rates for ameloblastoma.\ud \ud Results: Literature regarding the natural history of ameloblastoma is limited since the tumor is immediately acted upon at its initial detection, unless the patient voluntarily refuses a surgical intervention. From the limited data, it is derived that the highest estimated growth rate is associated with solid, multicystic type and the lowest rate with peripheral ameloblastomas. After meta-analysis, the calculated mean specific grow rate is 87.84% per year.\ud \ud Conclusion: The growth rate of ameloblastoma has been demonstrated, offering prognostic and management information, particularly in cases where a delay in management is envisaged