A tooth is a complex biological organ and consists of multiple tissues including the enamel, dentin, cementum and pulp. Tooth loss is the most common organ failure. Can a tooth be regenerated? Can adult stem cells be orchestrated to regenerate tooth structures such as the enamel, dentin, cementum and dental pulp, or even an entire tooth? If not, what are the therapeutically viable sources of stem cells for tooth regeneration? Do stem cells necessarily need to be taken out of the body, and manipulated ex vivo before they are transplanted for tooth regeneration? How can regenerated teeth be economically competitive with dental implants? Would it be possible to make regenerated teeth affordable by a large segment of the population worldwide? This review article explores existing and visionary approaches that address some of the above‐mentioned questions. Tooth regeneration represents a revolution in stomatology as a shift in the paradigm from repair to regeneration: repair is by metal or artificial materials whereas regeneration is by biological restoration. Tooth regeneration is an extension of the concepts in the broad field of regenerative medicine to restore a tissue defect to its original form and function by biological substitutes.
When adipose‐derived stem cells (ASCs) are retrieved from the stromal vascular portion of adipose tissue, a large amount of mature adipocytes are often discarded. However, by modified ceiling culture technique based on their buoyancy, mature adipocytes can be easily isolated from the adipose cell suspension and dedifferentiated into lipid‐free fibroblast‐like cells, named dedifferentiated fat (DFAT) cells. DFAT cells re‐establish active proliferation ability and undertake multipotent capacities. Compared with ASCs and other adult stem cells, DFAT cells showed unique advantages in their abundance, isolation and homogeneity. In this concise review, the establishment and culture methods of DFAT cells are introduced and the current profiles of their cellular nature are summarized. Under proper induction culture in vitro or environment in vivo, DFAT cells could demonstrate adipogenic, osteogenic, chondrogenic and myogenic potentials. In angiogenic conditions, DFAT cells could exhibit perivascular characteristics and elicit neovascularization. Our preliminary findings also suggested the pericyte phenotype underlying such cell lineage, which supported a novel interpretation about the common origin of mesenchymal stem cells and tissue‐specific stem cells within blood vessel walls. Current research on DFAT cells indicated that this alternative source of adult multipotent cells has great potential in tissue engineering and regenerative medicine.
MicroRNAs (miRNAs) have been demonstrated to play an important role in regulation of the immuno‐inflammatory response; however, the function of miRNAs in periodontal inflammation has not been investigated. The objective of this study was to explore the properties of miRNAs in periodontal inflammation by comparing miRNA profiles of inflamed and healthy gingival tissues. Gingival tissues were obtained from 10 periodontitis patients and 10 healthy subjects. After RNA extraction, miRNA profiles were analyzed by microarray, and expression levels of selected miRNAs were confirmed by real‐time quantitative reverse transcription polymerase chain reaction (RT‐PCR). Analyses using two computational methods, Targetscan and MicroRNA.org, were combined to identify common targets of these miRNAs. Finally, the individual miRNA expression levels of three toll‐like receptor (TLR)‐related miRNAs from inflamed and healthy gingival tissues were evaluated by RT‐PCR. Ninety‐one miRNAs were found to be upregulated and thirty‐four downregulated over two‐fold in inflamed gingival tissue compared with those in healthy gingival tissue. Twelve selected inflammatory‐related miRNAs, hsa‐miR‐126*, hsa‐miR‐20a, hsa‐miR‐142‐3p, hsa‐miR‐19a, hsa‐let‐7f, hsa‐miR‐203, hsa‐miR‐17, hsa‐miR‐223, hsa‐miR‐146b, hsa‐miR‐146a, hsa‐miR‐155, and hsa‐miR‐205 showed comparable expression levels by microarray and real‐time quantitative RT‐PCR analyses. In addition, the putative inflammation targets of these miRNAs were predicted, and three that were tested (hsa‐miRNA‐146a, hsa‐miRNA‐146b, and hsa‐miRNA‐155), showed significant differences between inflamed and healthy gingiva. This remarkable difference in miRNA profiles between periodontal diseased and healthy gingiva implicates a probable close relationship between miRNAs and periodontal inflammation. The data also suggest that the regulation of TLRs in periodontal inflammation may involve miRNA pathways.
The aim of this study was to analyze the specific influence of root canal anatomy on the accessibility of working length during root canal therapy. Four hundred seventy‐six root canal therapy cases (amounting to a total of 1 005 root canals) were examined. The anatomy risk factors assessed in each case included: tooth type (tooth location), root canal curvature, and root canal calcification, as well as endodontic retreatment. The investigation examined the correlation between each of these anatomic factors and the working length, with statistical analysis consisting of Chi‐square tests and multiple logistic regression analysis. In an independent factor analysis, tooth type (tooth location), root canal curvature, canal calcification, and endodontic retreatment were determined to be the primary risk factors. In a multiple‐factor regression model, root curvature and canal calcification were found to most significantly influence root canal working length accessibility (P<0.05). Root canal anatomy increases the difficulty of root canal preparation. Appropriate consideration of tooth anatomy will assist in accurate determination of preparation difficulty before instrumentation. This study alerts clinical therapists to anatomical factors influencing the working length accessibility, and allows for a direct estimate of success rate given in situ measurements of tooth factors during the root canal treatment procedure.
This article provides an overview of metastases to jaws (MJ), mainly concerning the differences between American and Chinese patients, and exploring the relationship between the primary tumors' prevalence (PTP) and constituent ratio of MJ. Information concerning of 399 MJ cases in 215 papers, including one new case in our hospital, was subjected to statistic analysis. The main clinical features of MJ, such as constituent ratio of PTP and that of MJ, metastatic sites, treatments, and prognosis were summarized. Breast, lung, kidney, prostate and thyroid (in descending order) were the leading primary sites of MJ. Furthermore, the constituent ratio of MJ was found to be correlated with that of PTP in all subjects including American and Chinese subjects in our study. As to metastatic sites in the mandible, a specific “M” shaped pattern appeared regardless of the tumor type or constituent ratios of MJ were in all subjects. Almost all subjects received traditionally palliative treatments, and the prognosis was quite poor. The PTP had a significant impact on the constituent ratio of MJ. However, it was the properties of the microenvironment rather than characteristics or constituent ratios of tumor cells, that decided the metastatic sites in various tumor subjects.
The distinction of some particular forms of periapical area, involving diseases from regular periapical disease, is a matter of considerable importance when choosing a correct treatment. The aim of this study is to describe the differential diagnosis of periapical diseases from six rare cases in clinical practice. The six rare cases are examples of situations where it is difficult to make a differential diagnosis in clinical practice. By retrospective surveys on the clinical examination, radiographs and pathological results, six patients referred to endodontic treatment in our department were analyzed for the accuracy of diagnosis and therapy. The pathoses of the six cases included two atypical radical cysts, periapical cemental dysplasia, cemento‐ossifying fibroma, thymus cancer metastasis in the periapical site and tuberculosis. This report indicates that endodontists should be cognizant of a few particular circumstances when clinically treating periapical diseases.
Orthognathic surgery is frequently accompanied by intermaxillary fixation. Intermaxillary fixation impedes the maintenance of effective oral hygiene and prolonged fixation can result in periodontal disease. A potential shorter term effect is the generation of oral malodour. It is unclear, however, as to how the production of malodorous compounds in the oral cavity is altered post‐surgery. Oral air concentration of sulphur containing compounds, short chain organic acids, ammonia, isoprene and acetone were measured using selected ion flow tube‐mass spectrometry in a patient who had undergone orthognathic surgery with subsequent intermaxillary fixation. Total sulphide levels rose approximately 5‐fold during fixation with metal ties, with smaller increases recorded for the other compounds measured with the exception of isoprene which remained close to baseline levels. Organic acid levels declined markedly once elastic ties had replaced metal ties, with a lesser reduction being observed in sulphide levels, with both declining further after the commencement of a chlorhexidine‐containing mouthwash. These data suggest that bacterial generation of a variety of malodorous compounds increases markedly following intermaxillary fixation. This single case also suggests that the use of elastic ties and effective oral hygiene techniques, including the use of chlorhexidine mouthwash, may help ameliorate such post‐surgical effects.
