Microbiome of Deep Dentinal Caries from Reversible Pulpitis to Irreversible Pulpitis

Introduction

This study examined the identity of the microbiome of deep dentinal caries and its correlation with the inflammation status of caries-induced pulpitis.

Preparation and properties of nano-sized calcium fluoride for dental applications.

OBJECTIVES: The aim of the present study was to prepare nano-sized calcium fluoride (CaF(2)) that could be used as a labile F reservoir for more effective F regimens and as an agent for use in the reduction of dentin permeability. METHODS: Nano-sized CaF(2) powders were prepared using a spray-drying system with a two-liquid nozzle. The properties of the nano-CaF(2) were studied and the effectiveness of a fluoride (F) rinse with nano-CaF(2) as the F source was evaluated. The thermodynamic solubility product of the nano-CaF(2) solution was determined by equilibrating the nanosample in solutions presaturated with respect to macro-CaF(2). Reactivity of the nano-CaF(2) was assessed by its reaction with dicalcium phosphate dehydrate (DCPD). F deposition by 13.2 mmol/L F rinse with the nano-CaF(2) as the F source was determined using a previously published in vitro model. RESULTS: X-ray diffraction (XRD) analysis showed pattern of low crystalline CaF(2). BET measurements showed that the nano-CaF(2) had a surface area of 46.3m(2)/g, corresponding to a particle size of 41nm. Transmission electron microscopy (TEM) examinations indicated that the nano-CaF(2) contained clusters comprising particles of (10-15) nm in size. The nano-CaF(2) displayed much higher solubility and reactivity than its macro-counterpart. The CaF(2) ion activity product (IAP) of the solution in equilibrium with the nano-CaF(2) was (1.52+/-0.05)x10(-10), which was nearly four times greater than the K(sp) (3.9 x 10(-11)) for CaF(2). The reaction of DCPD with nano-CaF(2) resulted in more F-containing apatitic materials compared to the reaction with macro-CaF(2). The F deposition by the nano-CaF(2) rinse was (2.2+/-0.3)mug/cm(2) (n=5), which was significantly (p<0.001) greater than that ((0.31+/-0.06)mug/cm(2)) produced by the NaF solution. SIGNIFICANCE: The nano-CaF(2) can be used as an effective anticaries agent in increasing the labile F concentration in oral fluid and thus enhance the tooth remineralization. It can also be very useful in the treatment for the reduction of dentin permeability.     

Plasma-arc generated light inhibits proliferation and induces apoptosis of human gingival fibroblasts in a dose-dependent manner.

OBJECTIVE: This study examined the effects of blue light exposure on the proliferation and cytotoxicity of human gingival fibroblasts (HGF). Cellular mechanism by which blue light causes cytotoxic effects was also investigated. METHODS: HGF were exposed to the plasma-arc generated blue light with various energy densities ranging from 2 to 48J/cm(2). After light exposure of the cells, they were processed for analyzing tritium incorporation, succinate dehydrogenase (SDH) activity, trypan blue exclusion, and DNA fragmentation. In addition, possible mechanism of the light-mediated cytotoxicity was investigated through flow cytometric and Western blot analyses. RESULTS: Blue light exposure significantly inhibited proliferation and SDH activity of HGF in a dose-dependent manner; exposure more than 12J/cm(2) had a toxic effect on the cells. The blue light-induced cytotoxicity of the cells resulted from apoptosis, as proven by the migration of many cells to the sub-G(1) phase of cell cycle and the appearance of DNA ladders. Additional experiments revealed that blue light induces apoptosis of HGF through mitochondrial stress and poly (ADP ribose) polymerase cleavage. SIGNIFICANCE: This study suggests that plasma-arc generated blue light exerts some harm to cells, particularly damaging effect to DNA, and thus a long curing time more than recommended can cause biological damage on the oral tissue.     

Evaluation of stress patterns generated by reduction forceps within a photoelastic mandibular model.

INTRODUCTION: Little attention has been paid to the mechanical effects of fracture reduction forceps. AIM: This study aims to evaluate the stress patterns within the fractured mandible generated by reduction forceps. MATERIAL AND METHODS: Thirty-six mandibular models were fabricated using a photoelastic resin. Each of the three sets of mandibular models was osteotomized according to one of three different fracture types. After reducing the cut segments, reduction forceps were placed into different engagement holes to compress the segments. Photoelastic stress analysis was used to visualize the stress patterns within the fractured mandibular models as generated by the reduction forceps. RESULTS: In the case of symphyseal or parasymphyseal fractures, an optimum distribution of stresses over the fracture site was achieved when placing the reduction forceps more than 12mm away from either side of the fracture line, between the midway level of the mandibular height (bisecting the mandible) and 5mm below this level. In the case of body fractures, optimum stress distribution was achieved when the reduction forceps were placed more than 16mm from the fracture line at the midway level. CONCLUSION: Correct use of the reduction forceps helps to provide a precise three-dimensional reduction for mandibular fractures.     

CSF-1对体外培养人牙囊细胞OPG表达的影响

目的研究集落刺激因子(CSF-1)对体外培养的人牙囊细胞骨保护素(OPG)表达的影响。方法原代培养人牙囊细胞,传代至第3代,制备细胞爬片,进行OPG免疫组化染色;3~6代人牙囊细胞长至80%时,用胰酶消化,离心,重悬,制成单细胞悬液,接种到细胞培养皿,细胞长满至80%时,培养基中加入25ng/ml的CSF-1,孵育0.5、1、3、6h,分别收集上清液,ELISA法检测OPG蛋白分泌量的变化,提取总RNA进行RT-PCR,检测OPG mRNA的表达变化。结果正常人牙囊细胞OPG蛋白表达阳性;25ng/ml的CSF-1可降低人牙囊细胞OPG的表达,共同孵育1h,OPG表达降至最低(P<0.05)。结论牙囊细胞表达OPG,同时在牙齿萌出的特定时期,CSF-1通过下调人牙囊细胞OPG,减弱对破骨细胞形成的抑制作用,促进破骨细胞分化成熟,调节牙齿萌出。     

Measuring the residual stress in dental composites using a ring slitting method.

OBJECTIVES: The objective of this experiment was to employ the ring slitting method for the measurement of the residual stress (RS) produced in dental composite materials after polymerization. This study was designed to determine the effect of slitting and measuring time on the residual stress. METHODS: Rings were made in a split brass mold from three composites (Z100/3MESPE; Herculite/Kerr; Heliomolar/Ivoclar) and cured in a Triad II (Dentsply). Two points were scribed, and the rings were slit at either 1 h (Early-group) or 24 h (Delayed-group) after curing the composite. The change in the distance between the scribed points was measured using an image analyzer system at both 1 and 24 h after slitting. From the measured change, circumferential RS was calculated and statistically analyzed with ANOVA/Tukey's (P<0.05). The degree of conversion of each composite at 1 and 24 h was measured with FTIR and analyzed using Student's t-test (P<0.05). RESULTS: In general, the residual stress (range=0.42-2.84 MPa) was highest for Z100 and lowest for Heliomolar, but this depended upon the test conditions. The early cut (1 h slitting), 24 h measurement groups showed the highest residual stress values. SIGNIFICANCE: This study, describes a ring slitting method to measure residual stress generated in dental composites during and after curing. The stress of composite can be affected by the cutting and measurement time.     

Group distal movement of teeth using microscrew implant anchorage

The purpose of this study was to quantify the treatment effects of distalization of the maxillary and mandibular molars using microscrew implants. The success rate and clinical considerations in the use of the microscrew implants were also evaluated. Thirteen patients who had undergone distalization of the posterior teeth using forces applied against microscrew implants were selected. Among them, 11 patients had mandibular microscrew implants and four patients had maxillary implants, including two patients who had both maxillary and mandibular ones at the same time. The maxillary first premolar and first molars showed significant distal movement, with no significant distal movement of the anterior teeth. The mandibular first premolar and first and second molars showed significant distal movement, but no significant movement of the mandibular incisor was observed. The microscrew implant success rate was 90% over a mean application period of 12.3 +/- 5.7 months. The results might support the use of the microscrew implants as an anchorage for group distal movement of the teeth.     

Study of the location of mandibular mental foremen in modern and neolithic adult]

37 cases of mandible of Neolithic adult that both sexes without missing teeth,alveolar bone were studied.The result showed that the location of the mental foramen below the apex of the lower second premolar was the most common(67.97%) in the modern adult,and the location of the mental foramen below between the apex of the lower second premolar and the first molar was the most common (64.86%) in the neolithic adult.     

Surface alteration of human tooth enamel subjected to acidic and neutral 30% hydrogen peroxide

Objectives

To investigate the effects of acidic and neutral 30% hydrogen peroxide (HP) on human tooth enamel in terms of chemical structure, mechanical property, surface morphology and tooth colour.

Methods

Twenty-seven human dental blocks were obtained from premolars and randomly divided into three groups (n = 9): Group acidic HP (30% HP, pH ≈ 3.6), Group neutral HP (30% HP, pH ≈ 7.0) and Group DW (distilled water, pH ≈ 6.8). Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, atomic force microscopy (AFM) investigation, microhardness test and colour measurements were carried out before and after treatments. ATR-FTIR and Raman spectroscopy were analysed and then the carbonate:mineral ratio (C:M), Raman absolute intensity (RAI), Raman relative intensity (RRI), and laser-induced fluorescence intensity (FI) were obtained for evaluation.

Results

The C:M, percentage microhardness and percentage RRI of group acidic HP decreased more significantly than those of group neutral HP (P = 0.02, P = 0.001, P < 0.001, respectively) and group DW (P = 0.01, P = 0.008, P < 0.001, respectively). Whilst group neutral HP and group DW had no statistical difference in above terms (P = 0.818, P = 0.528, P = 0.158, respectively). Significant morphological alterations were observed in group acidic HP. Group acidic HP and neutral HP had no significant difference in percentage FI (P = 0.652) and ΔE (P = 0.906).

Conclusions

This study suggested that neutral 30% HP had the same efficiency in tooth bleaching and it caused less deleterious effects on enamel than acidic 30% HP.