Vincenzo D’Antò

Effect of Nickel Chloride on Cell Proliferation

Objective: Metal alloys used in dentistry and in other biomedical fields may release nickel ions in the oral environment. The release of nickel might influence the normal biological and physiological processes, including tissue wound healing, cell growth and proliferation. The aim of this study was to evaluate in vitro the effects of nickel ions on cell cycle, viability and proliferation. Materials and Methods: Human osteosarcoma cells (U2OS) and human keratinocytes (HaCat) were exposed to different nickel chloride (NiCl2) concentrations (0 - 5mM) for various periods exposure. The viability of cultured cells was estimated by flow cytometry using Annexin V-FITC and Propidium Iodide (PI). Cell proliferation was evaluated by using carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) and flow cytometry. Finally, the effects of NiCl2 on cell cycle were assessed and quantified by flow cytometry. Statistical analysis was performed by means of ANOVA followed by Tukey’s test. Results: NiCl2 induced a dose and time dependent decrease in cell viability. After 24h, 1mM NiCl2 caused a similar and significant reduction of viability in U2OS and HaCat cells, while higher NiCl2 concentrations and longer exposure times showed a reduced cytotoxic effect in HaCat as compared to U2OS cells. Exposure to NiCl2 caused a dose- and time-dependent inhibition of cell proliferation in both cell lines tested, with a prominent effect on U2OS cells. Furthermore, both cell lines exposed to NiCl2 exhibited significant changes in cell cycle distribution after 24h exposure 2mM NiCl2, as compared to untreated cells (p<0.05). Conclusion: Our results indicate that release of nickel ions may affect cell proliferation. The inhibition of cell growth by NiCl2 is mediated by both cell cycle arrest and by induction of cell death.

In vitro cellular detoxification of triethylene glycol dimethacrylate by adduct formation with N-acetylcysteine

OBJECTIVE Various protective effects of N-acetylcysteine (NAC) against triethylene glycol dimethacrylate (TEGDMA)-induced cell damage have been demonstrated, but so far there is no evidence on NAC direct monomer detoxification mechanism. Here, we hypothesized that NAC might reduce TEGDMA cytotoxicity due to direct NAC adduct formation. METHODS We measured the cytotoxic effects of TEGDMA in presence and in absence of NAC by MTT test. Then we analyzed the presence of TEGDMA-NAC adduct formation in extracellular and intracellular compartments by capillary electrophoresis-UV detection (CE-UV) and capillary electrophoresis-mass spectrometry (CE-MS) analytical techniques. Moreover, we quantified the effective intracellular and extracellular TEGDMA concentrations through HPLC in the presence and absence of 10 mmol/L NAC. RESULTS TEGDMA reduced 3T3 cell vitality in a dose- and time-dependent manner, while NAC decreased monomer cytotoxicity and extracellular monomer concentrations by a direct reaction with TEGDMA. The adducts between the two molecules were detected both in the presence and absence of cell. Moreover a signal ascribed to the methacrylic acid was present in the CE-UV electropherogram of cellular lysates obtained after incubation with TEGDMA. SIGNIFICANCE Our results suggest that in vitro detoxification capability of NAC against TEGDMA-induced cell damage might occur also through the formation of NAC-TEGDMA adduct.

Effect of pH on in vitro biocompatibility of orthodontic miniscrew implants

BackgroundAlthough the clinical use of miniscrews has been investigated on a large scale, little is known about their biocompatibility. Since low pH can affect corrosion resistance, the aim of this study was to evaluate the cytotoxic effect of orthodontic miniscrews in different pH conditions.MethodsFour orthodontic miniscrews of stainless steel and grade IV and grade V titanium were immersed in a pH 7 and pH 4 saline solution for 1, 7, 14, 21, 28, and 84 days. Human osteogenic sarcoma cells (U2OS), permanent human keratinocytes (HaCat), and primary human gingival fibroblasts (HGF) were exposed to eluates, and the mitochondrial dehydrogenase activity was measured after 24 h to assess the cytoxicity. The results were analyzed using the Mann-Whitney U test (P < 0.05).ResultsWhen exposed to pH 7-conditioned eluates, the cell lines showed an even greater viability than untreated cells. On the contrary, the results revealed a statistically significant decrease in U2OS, HaCat, and HGF viability after exposure to eluates obtained at pH 4. Among the cell lines tested, HGF showed the most significant decrease of mitochondrial activity. Interestingly, grade V titanium miniscrews caused highest toxic effects when immersed at pH 4.ConclusionsThe results suggested that at pH 7, all the miniscrews are biocompatible while the eluates obtained at pH 4 showed significant cytotoxicity response. Moreover, different cell lines can produce different responses to miniscrew eluates.

Nonsynonimous mutation of catechol-O-methyl-transferase (COMT) gene in a patient with temporomandibular disorder.

We report a case of temporomandibular disorder patient with disc displacement without reduction, myofascial pain, limited opening and a novel, never described, nonsynonimous mutation of catechol-O-methyl-transferase (COMT) gene. COMT is one of the enzymes that metabolizes catecholamines, thereby acting as a key modulator of dopaminergic and adrenergic/noradrenergic neurotransmissions, which play a key role in pain modulation. This novel mutation, p.R58S, changed a codon (58 from arginine to serine) in the COMT protein. The introduction of a serine residue in a highly organised secondary structure, in critical regions of the protein, results in a structural alteration. Therefore, we speculate an influence of the mutation on the high pain sensitivity of the patient.

Reproducibility of the assessment of the Fränkel manoeuvre for the evaluation of sagittal skeletal discrepancies in Class II individuals

OBJECTIVES The Fränkel manoeuvre is a procedure by which the mandible of Class II individuals is postured forward in dental Class I relationship. The evaluation of the resulting facial profile provides information concerning the components determining the sagittal discrepancy. Data concerning the reproducibility of its assessment are not available. This study aimed to evaluate the intra-observer and inter-observer reproducibility of the assessment of the manoeuvre and to assess whether the amount of clinical experience affects its reproducibility. METHODS Two lateral photographs, one in centric occlusion, and the other with the mandible postured forward (Fränkel manoeuvre) of 100 Angle Class II individuals aged between 9 and 13 years were evaluated by six orthodontists (T0). Each examiner was asked whether the facial profile worsen or not with the manoeuvre after being trained by an expert orthodontist. The test was repeated after 2 weeks interval (T1). Intra-observer and inter-observer agreement were evaluated by computing the Cohens K. RESULTS The agreement (K values) between observations (T0 versus T1) for each examiner ranged from 0.49 to 0.72. The overall agreement was 0.65 [95% confidence interval (CI) = 0.54-0.75]. The agreement in the group with less clinical experience was 0.61 (95% CI = 0.46-0.76), while it was 0.68 (95% CI = 0.53-0.83) in the more experienced group. The amount of clinical experience did not affect intra-observer agreement (P = 0.50). The overall agreement between the examiners and the trainer was 0.74 (95% CI = 0.65-0.83) and 0.73 (95% CI = 0.64-0.83) at T0 and T1 respectively. CONCLUSION The assessment of the Fränkel manoeuvre is reproducible and it is not influenced by the amount of clinical experience.

Erratum to: Evaluation of masticatory muscle activity in patients with unilateral posterior crossbite before and after rapid maxillary expansion

Objectives The relationship between unilateral posterior crossbite (UPCB) and the possible asymmetric activation of the jaw muscles in children is still under debate. This study aimed at evaluating the jaw muscle activity of children with UPCB before and after rapid maxillary expansion (RME) by means of surface electromyography and a standardized sampling protocol. Subjects and methods Twenty-nine children with UPCB (UPCB-group, mean age 9.6 ± 1.6 years) and 40 UPCB-free controls (Control-group, 10.5 ± 1.1) were recruited. The activity of the left and right anterior temporalis (AT) and superficial masseter muscles (MM) was recorded during maximum voluntary clenching and a chewing task (T0). In the UPCB-group, data were collected, also, after the correction of the UPCB with RME (T1) and 6 months later (T2), without any further treatment. Electromyographic indices comparing the activity of paired muscle were computed via software to estimate the extent of asymmetric AT and MM activity. Paired and unpaired t-test or Wilcoxon-signed rank and Mann-Whitney U test, ANOVA or Friedman test and chi-squared test were used in the statistical analysis. Results Both groups presented with asymmetric activity of the muscles, which did not differ between groups (T0, all P > 0.05). The treatment determined a decrease in muscular activity (T1, P = 0.040), and a more asymmetric pattern of muscle activation during chewing (T1, P = 0.040), which returned similar to baseline values at T2 (all P > 0.05). Conclusions UPCB does not contribute to an asymmetric activation of AT and MM during functional tasks. The treatment of UPCB by RME did not determine a more symmetric activity of the assessed muscles.

Pain Experience and Behavior Management in Pediatric Dentistry: A Comparison between Traditional Local Anesthesia and the Wand Computerized Delivery System

Aim. To evaluate the pain experience and behavior during dental injection, using the Wand computerized delivery system versus conventional local anesthesia in children and adolescents. Methods. An observational crossover split mouth study was performed on 67 patients (aged 7 to 15 years), requiring local anesthesia for dental treatments in both sides of the dental arch. Patients received both types of injections in two separate appointments, one with the use of a Computer Delivery System (the Wand STA system) and one with the traditional syringe. The following data were recorded: pain rating; changes in heart rate; level of collaboration; patient satisfaction. The data were analyzed using ANOVA for quantitative outcomes and nonparametric analysis (Kruskal–Wallis) for qualitative parameters. Results. The use of the Wand system determined significantly lower pain ratings and lower increase of heart rate than the traditional syringe. During injection, the number of patients showing a relaxed behavior was higher with the Wand than with the traditional local anesthesia. The patient level of satisfaction was higher with the Wand compared to the conventional local anesthesia. Conclusions. The Wand system may provide a less painful injection when compared to the conventional local anesthesia and it seemed to be better tolerated with respect to a traditional syringe.