Biology of tooth replacement in amniotes

Tooth replacement is a common trait to most vertebrates, including mammals. Mammals, however, have lost the capacity for continuous tooth renewal seen in most other vertebrates, and typically have only 1–2 generations of teeth. Here, we review the mechanisms of tooth replacement in reptiles and mammals, and discuss in detail the current and historical theories on control of timing and pattern of tooth replacement and development.     

Ultrastructural Characterization of Mesenchymal and Epithelial Cells Co-Cultured from Human Dental Root Apical Explants

Previous studies have shown the role of cell-cell and cell-matrix interactions in the differentiation of the specific secretory cells of the tooth. In order to elucidate the mechanisms implicated in root dentin formation, we developed a co-culture system of human pulpal mesenchymal and epithelial root sheath cells. Root tips of premolars were cultured in Eagle's basal Medium supplemented with fetal calf serum, ascorbic acid, antibiotics and, for some of them, with sodium β-glycerophosphate. After 60 days of culture, cells were prepared for light and electron microscopy. Three main cell types were observed: (1) polygonal mesenchymal cells showing a functional polarity and producing a dense network of tactoid collagenous fibers. The latter had a specific circular organization that delimited small lacunae around the cells and mineralized in the presence of β-glycerophosphate; (2) spindle-shaped mesenchymal cells mainly localized inside epithelial-mesenchymal knots and synthesizing an abundant collagenous matrix; and (3) epithelial cells lying on the plastic culture dish, on the dense collagenous matrix, or on spindle-shaped cells. Epithelial cells deposited a structured basement membrane when they were lying on the plastic culture dish or on spindle-shaped cells. On the contrary, no basement membrane was found when epithelial cells were overlying the dense collagenous network. Immunoelectron microscopic analysis of type IV collagen and laminin indicated that these two specific basement membrane components were produced by all cell types. These results show that the co-culture system should be valuable for (1) studying the in vitro formation of human dental root hard tissues, (2) characterizing cell-cell and cell-matrix interactions implicated in dental basement membrane production, and (3) isolating populations of cells implicated in dental root formation.     

Long‐term tooth loss in periodontally compromised but treated patients according to the type of prosthodontic treatment. A retrospective study

If prosthodontic treatment is considered after periodontal therapy, the questions arise i) does prosthodontic treatment affect the treatment outcome of the dentition in general and ii) which type of prosthesis is related to best treatment outcome of abutment teeth? Our goal was to compare long‐term tooth loss after comprehensive periodontal therapy in patients with or without prosthodontic treatment. Ninety patients' charts with a total of 1937 teeth who had received comprehensive periodontal treatment 5–17 years ago by the same periodontist were retrospectively evaluated. Sixty‐five patients received fixed dental prostheses (FDP; n = 29) and/or removable partial dentures anchored with clips (RPDC; n = 25) or double crowns (RPDD; n = 25). Twenty‐five patients were also periodontally compromised but treated without prosthodontic treatment and served as a control group. A total of 317 teeth and 70 abutment teeth were lost during 9·7 ± 4·1 years of observation. Thereof, 273 teeth and 48 abutment teeth were lost due to periodontal reasons. Mean tooth loss amounted to 1·2 ± 1·5 (controls) and 4·4 ± 3·4 (partial dentures). Abutment tooth loss was 0·4 ± 1·1 (FDP), 1·0 ± 1·2 (RPDC) and 1·3 ± 1·0 (RPDD). Poisson regressions identified prosthodontic treatment, age, socio‐economic status, diabetes mellitus, mean initial bone loss and aggressive periodontitis as factors significantly contributing to tooth loss. Age, diabetes and non‐compliance contributed to abutment tooth loss. Not considering biomechanical factors, patients with prosthodontic reconstructions under long‐term supportive periodontal therapy were at higher risk for further tooth loss than patients without prostheses. Not only the type of partial denture but also the patient‐related risk factors were associated with abutment tooth loss.     

Orthodontic traction of a transmigrated mandibular canine using mini-implant: a case report and review

The patient in this case is an 11-year-old girl, whose mandibular left canine was transmigrated. The traction to the arch was assisted by using a temporary skeletal anchorage device. After 5 months of poor response to traction, the biomechanics were re-adjusted, obtaining effective traction in to the arch in 12 months. After this period, the treatment was completed with fixed orthodontic appliances.     

Regulation of SFRP-1 Expression in the Rat Dental Follicle

Tooth eruption requires osteoclastogenesis and subsequent bone resorption. Secreted frizzled-related protein-1 (SFRP-1) negatively regulates osteoclastogenesis. Our previous studies indicated that SFRP-1 is expressed in the rat dental follicle (DF), with reduced expression at days 3 and 9 close to the times for the major and minor bursts of osteoclastogenesis, respectively; but it remains unclear as to what molecules contribute to its reduced expression at these critical times. Thus, it was the aim of this study to determine which molecules regulate the expression of SFRP-1 in the DF. To that end, the DF cells were treated with cytokines that are maximally expressed at days 3 or 9, and SFRP-1 expression was determined. Our study indicated that colony-stimulating factor-1 (CSF-1), a molecule maximally expressed in the DF at day 3, down-regulated SFRP-1 expression. As to endothelial monocyte-activating polypeptide II (EMAP-II), a highly expressed molecule in the DF at day 3, it had no effect on the expression of SFRP-1. However, when EMAP-II was knocked down by siRNA, the expression of SFRP-1 was elevated, and this elevated SFRP-1 expression could be reduced by adding recombinant EMAP-II protein. This suggests that EMAP-II maintained a lower level of SFRP-1 in the DF. TNF-α is a molecule maximally expressed at day 9, and this study indicated that it also down-regulated the expression of SFRP-1 in the DF cells. In conclusion, CSF-1 and EMAP-II may contribute to the reduced SFRP-1 expression seen on day 3, while TNF-α may contribute to the reduced SFRP-1 expression at day 9.     

Efficacy of adjuvant ozone therapy in reducing postsurgical complications following impacted mandibular third-molar surgery: A systematic review and meta-analysis

BackgroundResults from several randomized controlled trials have shown a beneficial effect of ozone in reducing postsurgical complications after impacted mandibular third-molar surgery, but the literature is lacking a systematic review and meta-analysis.MethodsThe authors conducted this systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines after exclusion and inclusion criteria were applied and the following outcome parameters were evaluated: pain, swelling, trismus, quality of life, number of analgesics consumed, and adverse events. RevMan Cochrane Collaboration software, Version 5.3, was used to perform meta-analysis and the Grading of Recommendation Assessment, Development and Evaluation approach was used to rate the certainty of evidence.ResultsPatients who underwent adjuvant ozone application reported lower pain scores than patients in the control group at 24 hours after surgery (95% CI, –3.94 to –1.56) and at 7 days (95% CI, –1.67 to –0.78). Pooled analysis of all 4 included trials revealed a standardized mean difference (SMD) in swelling of –0.44 at 24 hours, 0.63 at 72 hours, and –0.87 at 7 days after surgery in the experimental group. Higher mean estimates in mouth opening were experienced by patients who received ozone at 24 hours (SMD, 2.74; 95% CI, –1.93 to 7.41; 4 studies, 133 patients), 72 hours (SMD, 2.77; 95% CI, –0.63 to 6.17; 4 studies, 133 patients), and 7 days after surgery (SMD, 1.42 SMD; 95% CI, –1.34 to 4.18; 4 studies, 133 patients).Practical ImplicationsEvidence suggests that adjuvant ozone application can offer some benefit for reducing pain, improving quality of life, and decreasing mean intake of analgesics after impacted mandibular third-molar surgery, but it is not effective in reducing facial swelling and trismus, which paves the way for future research.     

形状记忆合金弓齿钉治疗腕舟状骨腰部骨折

正2013年10月~2015年3月,我科采用腕掌侧切开复位形状记忆合金弓齿钉治疗17例腕舟状骨腰部骨折患者,疗效满意,报道如下。1材料与方法1.1病例资料本组17例,男15例,女2例,年龄16~42岁。左侧1例,右侧16例,均为闭合骨折。新鲜骨折16例,陈旧性骨折1例,合并桡骨茎突骨折1例。1.2治疗方法臂丛麻醉下手术。取