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Abstract: Ectopic lower third molar is an uncommon condition, and its etiology remains unclear. The main approach used for its surgical removal is the intraoral one, but there are cases in which this may not be the best option. When the lower third molar is located below the lower alveolar canal or when it is close to the lower edge of the jaw, the most recommended approach is the extraoral one. The critical issues related to the extraoral approach are the possibility of damaging anatomical structures such as marginal mandibular branch of the facial nerve (craniofacial nerve VII), facial artery and vein, and submental artery. This complication can occur during incision and dissection of the superficial layers or during osteotomy with rotating instruments.This paper reports a case of extraction of ectopic lower third molar using a minimally invasive extraoral approach combined with piezoelectric surgery in order to prevent intraoperative injury of anatomical structures., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by Mutaz B. Habal, MD.)

To harvest bone for autologous grafting is a daily problem encountered by craniofacial and oral surgeons. Stem cells derived from human dental pulp are able to differentiate in osteoblasts and are a potential source of autologous bone produced in vitro. The authors describe their preliminary results in this new field with its potential application in craniomaxillofacial surgery. Dental pulp was gently extracted from 34 human permanent teeth (all third molars) of patients 19 to 37 years of age. After they were digested, the cells were selected using a cytometer for c-kit, STRO-1, CD34, CD45, and then for CD44 and RUNX-2. This study, made on a considerable number of cases, provided evidence that dental pulp is extremely rich in stem cells, which were c-kit+/CD34+/STRO-1+/CD45-, capable of differentiation toward several stromal-derived differentiated cells and mainly osteoblasts. These findings, supported by the large number of cases, are of great interest for tissue regeneration, tissue-based clinical therapies, and transplantation.

Central giant cell granuloma (CGCG) of the jaws is a central osteolytic lesion characterized histologically by multinucleated giant cells in a background of ovoid to spindle-shaped mesenchymal cells. Whether CGCG is a reactive lesion or a truly benign neoplasm remains undetermined, and the mechanism determining the onset of the disease remains unknown. To have more information regarding the genetic events involved in CGCG, the authors decided to perform an expression profile. Samples were derived from two surgically resected CGCG of the mandible. RNA extracted from a pool of three normal bone tissues was used as control. By using DNA microarrays containing 19,200 genes, the authors identified several genes whose expression was significantly up- or down-regulated. The differentially expressed genes cover a broad range of functional activities: cell cycle regulation; signal transduction; and vesicular transport. It was also possible to detect some genes whose function is unknown. The authors believe the data reported to be the first genetic portrait of CGCG of the jaws. Several markers have been identified that can potentially help in identifying some biological behavior (ie, quiescent versus aggressive lesions), as well as genes whose products could be potentially disease-specific targets for therapy. However, the authors think that more cases are needed, especially those comparing quiescent and aggressive lesions, before the exact profile of CGCG is known.

Distraction osteogenesis (DO) is a mechanotransduction process capable of generating viable osseous tissue by the gradual separation of osteotomized bone edges. Several variables are implicated in DO: magnitude of mechanical strain, distraction rate, and type of distracted bone. The combination of these factors acts on different types of cells inducing apoptosis, cell proliferation, and differentiation. The elucidation of the molecular mechanisms has important clinical implications because it may facilitate the use of recombinant proteins or gene therapy to accelerate bone regeneration. Previous reports have analyzed several molecules such as extracellular matrix proteins, cytokines, bone morphogenetic proteins, hormones, and angiogenic factors. Moreover, a single protein can have multifunctional roles. With such a huge number of mechanical, histologic, cellular, and molecular variables, there is the need to have a cell culture model that enables the selection of the effect of a specific strength to a single cell type at different time points and with or without cytokines. The analysis of the genetic profiling of a cell line cultured on an equibiaxial stretch device has such characteristic. Because there is a recruitment and commitment of preosteoblastic cells during bone lengthening and no previous report has focus on them, the authors used a preosteoblast MC3T3-E1 cell line to detect the early molecular effects of distraction on mesenchymal cells. By using DNA microarrays containing 15,000 clones, the authors identified several genes the expression of which was significantly up- or down-regulated. The differentially expressed genes cover a broad range of biological processes: cell growth, metabolism, morphogenesis, cell communication, response to stress, and cell death. The data reported are the first genetic portrait of stretched preosteoblasts. They can be relevant in the better understanding of the molecular mechanism of DO and as a model for comparing the effect of distraction on different cell lines and primary cultures, rate and strength of distraction, and with or without cytokines.

Granular cell tumor (GCT), or granular cell myoblastoma, is a relatively uncommon lesion of the soft tissues. It can occur in any organ, and the tongue is more often affected. GCT has unknown etiology, uncertain histogenesis, and a not always benign nature. Benign myoblastomas are the great majority, but rare malignant lesions have been reported. To have more information regarding the genetic events involved in GCT, the authors decided to perform an expression profile. A sample was derived from a surgically resected GCT of the tongue. RNA extracted from normal tongue (mucosa plus muscle) was used as control. By using DNA microarrays containing 19,200 genes, the authors identified several genes for which expression was significantly up- or down-regulated. The differentially expressed genes cover a broad range of functional activities: (1) signal transduction, (2) cell cycle regulation, and (3) cytoskeleton organization. It was also possible to detect some genes whose function is unknown. The data reported are, to the authors' knowledge, the first genetic portrait of GCT. Mutations in some of the described genes are related to neural alterations and mental diseases, and this fact supports the idea of a neural origin of myoblastoma. Several markers have been identified that will help in identifying the biological behavior (when malignant lesions will be described), as well as the gene whose products could be potentially disease-specific targets for therapy.

Nonsyndromic cleft of the lip and/or palate (CLP or orofacial cleft) derives from an embryopathy with consequent failure of the nasal process and/or palatal shelves fusion. This severe birth defect is one of the most common malformations among live births. Nonsyndromic CLP is composed of two separate entities: cleft lip and palate (CL+/-P) and cleft palate only (CPO). Both have a genetic background, and environmental factors probably disclose these malformations. In CL+/-P, several loci have been identified, and, in one case, a specific gene has also been found. In CPO, one gene has been identified, but many more are probably involved. Because of the complexity of the genetics of nonsyndromic CLP as a result of the difference between CL+/-P and CPO, heterogeneity of each group caused by the number of involved genes, type of inheritance, and interaction with environmental factors, we discuss the more sound results obtained with different approaches: epidemiological studies, animal models, human genetic studies, and in vitro studies.