Does fluoride exposure affect thyroid function? A systematic review and dose-response meta-analysis.

INTRODUCTION: Fluoride exposure may have various adverse health effects, including affecting thyroid function and disease risk, but the pattern of such relation is still uncertain. METHODS: We systematically searched human studies assessing the relation between fluoride exposure and thyroid function and disease. We compared the highest versus the lowest fluoride category across these studies, and we performed a one-stage dose-response meta-analysis for aggregated data to explore the shape of the association. RESULTS: Most retrieved studies (27 of which with a cross-sectional design) were conducted in Asia and in children, assessing fluoride exposure through its concentrations in drinking water, urine, serum, or dietary intake. Twenty-four studies reported data on thyroid function by measuring thyroid-related hormones in blood (mainly thyroid-stimulating-hormone - TSH), 9 reported data on thyroid disease, and 4 on thyroid volume. By comparing the highest versus the lowest fluoride categories, overall mean TSH difference was 1.05 µIU/mL. Dose-response curve showed no change in TSH concentrations in the lowest water fluoride exposure range, while the hormone levels started to linearly increase around 2.5 mg/L, also dependending on the risk of bias of the included studies. The association between biomarkers of fluoride exposure and TSH was also positive, with little evidence of a threshold. Evidence for an association between fluoride exposure and blood concentrations of thyroid hormones was less evident, though there was an indication of inverse association with triiodothyronine. For thyroid disease, the few available studies suggested a positive association with goiter and with hypothyroidism in both children and adults. CONCLUSIONS: Overall, exposure to high-fluoride drinking water appears to non-linearly affect thyroid function and increase TSH release in children, starting above a threshold of exposure, and to increase the risk of some thyroid diseases.

Push-out bond strength and SEM fractographical analysis of hollow fibre posts used with self-adhesive resin cement: a pilot study.

Detachment is the major cause of failure of endodontic fibre posts. Hollow posts have been recently introduced to overcome such issue. The primary aim of this pilot study was to compare the push-out bond strength of hollow posts and traditional solid posts. Eight round-shaped single-canal premolars extracted for periodontal reason were selected as sample and equally randomized into two groups: (i) traditional solid fibre posts-TECH21xop and ii) hollow fibre posts-TECHOLE. A dual-curing self-adhesive cement (new TECHCEM) was used for posts placement. Six horizontal sections-two from each portion of the root (coronal, middle and apical)-were obtained from each sample root, yielding a total of 24 sections for each group. Push-out test was performed on the sections and bond strength values were compared between groups and within each group. Scanning electron microscope (SEM) fractographical analysis was conducted on each section. Additional SEM and EDX analyses were performed on new samples of both posts, to assess fibres density and distribution, and the chemical composition of the fibres and the matrix. Hollow posts showed a significantly higher push-out bond strength (6.36 ± 1.22 MPa) than solid posts (3.64 ± 1.62 MPa). Among the three root portions of the same group, there was no significant difference in bond strength. In both groups, the most frequent type of fracture was a mixed adhesive failure with the cement covering 0 to 50% of the post perimeter. Hollow post fibres appear more similar in size and have a more homogeneous distribution, compared to solid posts. The two post types also have different chemical compositions.

Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis.

Many uncertainties still surround the possible harmful effect of fluoride exposure on cognitive neurodevelopment in children. The aim of this systematic review and meta-analysis was to characterize this relation through a dose-response approach, by comparing the intelligence quotient (IQ) scores in the highest versus the lowest fluoride exposure category with a random-effects model, within a one-stage dose-response meta-analysis based on a cubic spline random-effects model. Out of 1996 potentially relevant literature records, 33 studies were eligible for this review, 30 of which were also suitable for meta-analysis. The summary mean difference of IQ score, comparing highest versus lowest fluoride categories and considering all types of exposure, was -4.68 (95% confidence interval-CI -6.45; -2.92), with a value of -5.60 (95% CI -7.76; -3.44) for drinking water fluoride and -3.84 (95% CI -7.93; 0.24) for urinary fluoride. Dose-response analysis showed a substantially linear IQ decrease for increasing water fluoride above 1 mg/L, with -3.05 (95% CI -4.06; -2.04) IQ points per 1 mg/L up to 2 mg/L, becoming steeper above such level. A weaker and substantially linear decrease of -2.15 (95% CI -4.48; 0.18) IQ points with increasing urinary fluoride emerged above 0.28 mg/L (approximately reflecting a water fluoride content of 0.7 mg/L). The inverse association between fluoride exposure and IQ was particularly strong in the studies at high risk of bias, while no adverse effect emerged in the only study judged at low risk of bias. Overall, most studies suggested an adverse effect of fluoride exposure on children's IQ, starting at low levels of exposure. However, a major role of residual confounding could not be ruled out, thus indicating the need of additional prospective studies at low risk of bias to conclusively assess the relation between fluoride exposure and cognitive neurodevelopment.

Effect of adhesive strategy on resin cement bonding to dentin.

OBJECTIVE: The cement bonding strategy and the polymerization mode can influence the prognosis of indirect restorations. The microtensile bond strength (µTBS) and dentin endogenous enzymatic activity of a dual-cure resin cement (PV5) used in combination with two dentin surface conditioners (accelerator-enhancer primer, TP or universal adhesive, UA) were evaluated. MATERIALS AND METHODS: PV5 was used to lute composite overlays after dentin treatment with TP or UA. The resin cement was self-cured, SC (1 h at 37 °C) or dual-cured, DC (20 s light-cure followed by 15 min self-cure at 37°C). The µTBS test, fractographic analysis, and the in situ zymography evaluations were performed after 24 h (T0 ) or 1 yr (T12 ) of artificial storage. Data were statistically analyzed (α = 0.05). RESULTS: TP/DC obtained the highest adhesive strengths (45 ± 9 and 36.6 ± 8), while UA/SC (17 ± 8 and 11 ± 4) the lowest, both at T0 and T12 , respectively. DC resulted in superior bonding values than the SC, independent of the dentin surface treatment (p < 0.05). The type of adhesive, curing mode and aging influenced the gelatinolytic activity (p < 0.05). CONCLUSIONS: The dual-cure resin cement used in combination with its accelerator-enhancer primer showed superior bonding performances with respect to universal adhesive. Dual-curing the resin cement was determinant to enhance bonding capability over time, independent of the adhesive strategy. CLINICAL RELEVANCE: Clinicians must be aware to faithfully follow manufacturer's recommendation regarding the adhesive strategy suggested with the resin cement used.

Fluoride Exposure and ADHD: A Systematic Review of Epidemiological Studies.

Background and objectives: Attention deficit hyperactivity disorder (ADHD) is a childhood-onset neurodevelopmental disorder characterized by two dimensions: inattentiveness and hyperactivity/impulsivity. ADHD may be the result of complex interactions between genetic, biological and environmental factors possibly including fluoride exposure. Materials and methods: A literature search was performed on 31 March 2023 in the following databases: PubMed, Embase and Web of Science. We defined the following inclusion criteria according to the PECOS statement: a healthy child and adolescent population (P), fluoride exposure of any type (E), comparison with low or null exposure (C), ADHD spectrum disorder (O), and ecological, cross-sectional, case-control and cohort studies (S). Results: We found eight eligible records corresponding to seven different studies investigating the effect of fluoride exposure on children and adolescents. One study had a cohort design and one a case-control one, while five were cross-sectional. Only three studies applied validated questionnaires for the purpose of ADHD diagnosis. As regards exposure assessment, levels of fluoride in urine and tap water were, respectively used in three and two studies, while two used both. Three studies reported a positive association with ADHD risk, all assessing exposure through fluoride levels. By using urinary fluoride, conversely, a positive correlation with inattention, internalizing symptoms, cognitive and psychosomatic problems was found in three studies, but no relation was found in the other one. Conclusions: The present review suggests that early exposure to fluoride may have neurotoxic effects on neurodevelopment affecting behavioral, cognitive and psychosomatic symptoms related to ADHD diagnosis. However, due to the heterogeneity of the studies included, current evidence does not allow to conclusively confirm that fluoride exposure is specifically linked to ADHD development.

Influence of the activation mode on long-term bond strength and endogenous enzymatic activity of dual-cure resin cements.

OBJECTIVE: To investigate the long-term microtensile bond strength (µTBS), interfacial nanoleakage expression (NL), and adhesive stability of dual-cure resin cements with/out light activation to dentin. MATERIALS AND METHODS: Composite overlays (N = 20) were luted to deep dentin surfaces with RelyX Ultimate (RXU, 3M) or Variolink EstheticDC (VAR, Ivoclar-Vivadent). A universal adhesive was used for bonding procedures (iBond universal, Heraeus Kulzer). The resin cements were either self-cured (SC; 1 h at 37 °C) or dual-cured (DC; 20s light-cure followed by 15 min self-cure at 37 °C). Specimens were submitted to µTBS immediately (T0) or after 1 year of laboratory storage (T12). The fracture pattern was evaluated using scanning electron microscopy (SEM). Data were statistically analyzed with two-way ANOVA/Tukey test. Further, the NL was quantified and analyzed (chi-square test) and in situ zymography was performed to evaluate the endogenous enzymatic activity within the hybrid layer (HL) at T0 and T12 (Mann-Whitney test). The significance level for all statistical tests was set at p = 0.05. RESULTS: DC resulted in higher bond strength and decreased fluorescence at the adhesive interface, irrespective of the material and the storage period (p < 0.05). Significantly lower bonding performances (p < 0.05) and higher endogenous enzymatic activity (p < 0.05) were observed within the HL at T12 compared to T0 in all tested groups. CONCLUSIONS: Light-curing the dual-cure resin cements, more than the cement materials, accounted for good bonding performances and higher HL stability over time when used with a universal adhesive. Clinical significance The curing condition influences the bonding performances of dual-cure resin cements to dentin when used with a universal adhesive.

Endogenous Enzymatic Activity in Dentin Treated with a Chitosan Primer.

The aim of this study was to evaluate the effect of different concentrations of chitosan polymer on dentinal enzymatic activity by means of gelatin and in situ zymography. Human dentin was frozen and ground in a miller. Dentin powder aliquots were demineralized with phosphoric acid and treated with three different concentrations of lyophilized chitosan polymer (1, 0.5 and 0.1 wt%) dissolved in distilled water. Dentin proteins were extracted from each experimental group and electrophoresed under non-reducing conditions in 10% SDS-PAGE containing fluorescein-labeled gelatin. After 48 h in the incubation buffer at 37 °C, proteolytic activity was registered under long-wave UV light scanner and quantified by using Image J software. Furthermore, additional teeth (n = 4) were prepared for the in situ zymographic analysis in unrestored as well as restored dentin pretreated with the same chitosan primers. The registered enzymatic activity was directly proportional to the chitosan concentration and higher in the restored dentin groups (p < 0.05), except for the 0.1% chitosan primer. Chitosan 0.1% only showed faint expression of enzymatic activity compared to 1% and 0.5% concentrations. Chitosan 0.1% dissolved in water can produce significant reduction in MMPs activity and could possibly contribute to bond strength preservation over time.

The perceived impact of the COVID-19 pandemic on dental undergraduate students in the Italian region of Emilia-Romagna.

INTRODUCTION: The outbreak and diffusion of the novel SARS-CoV2 coronavirus have caused an emergency status in the dental education system. MATERIALS AND METHODS: An anonymous survey composed of 34 questions was delivered to students of the Master Degree Programme in Dentistry and Dental Prosthodontics of the Universities of Emilia-Romagna, the fifth Italian region most affected by the pandemic. The psychological impact of COVID-19 was assessed by means of the Generalised Anxiety Disorder-7 scale (GAD-7). Numerically recoded data were analysed using the Analysis of Variance (ANOVA), whilst to investigate the association between quantitative variables, the Pearson correlation coefficient (R) was computed. RESULTS: The questionnaire was completed by 399 students (75%) out of 532. Most students experienced difficulties in working at the thesis during the COVID-19 emergency. For over half of them, online teaching could only partially replace traditional face-to-face lessons. The negative impact on the study career was judged as particularly high by sixth-year students. Clinical training activities were considered as exposing to the risk of contracting COVID-19 infection by the majority of the students. The level of concern of contracting COVID-19 infections during future university activities was positively correlated to risk perception related to clinical training. CONCLUSION: The results of this survey could be used to train students to a correct risk assessment. Students reported experiencing concern whilst thinking of COVID-19 and 6.5% of them showed symptoms related to high levels of anxiety. These data may guide Universities in trying to reduce students' anxiety by means of correct communication strategies.

Clinical and histological reaction of periodontal tissues to subgingival resin composite restorations.

OBJECTIVES: To compare the clinical and histological response of supracrestal periodontal tissues to subgingival composite restorations versus natural root surfaces MATERIAL AND METHODS: In 29 subjects with a single tooth requiring subgingival restorations, a deep margin elevation (DME) procedure with composite resin was applied. Full-mouth plaque score (FMPS), full-mouth bleeding score (FMBS), and focal probing depth (PD) were measured at baseline, before DME, and after 3 months. The distance between the coronal marked (CM) point to the apical margin of the composite reconstruction (AMR), at baseline, and to the tip of the periodontal probe inserted to reach the bottom of the sulcus (APP), 3 months later, was measured. An all-around secondary flap, harvested to ensure the subsequent single-crown prosthetic rehabilitation was histologically processed. The histological inflammation degree was evaluated in areas of gingival tissues adjacent to the composite (group B) and adjacent to the natural surface of each single tooth (group A). RESULTS: Significant FMPS, FMBS, and PD decreases were observed (p < 0.05). CM-AMR and CM-APP were significantly different (p < 0.05), suggesting an attachment gain after 3-months. The inflammation level of gingival tissue was similar in groups A and B (p > 0.05). CONCLUSIONS: For the first time, this topic was clinically and histologically studied in humans. Subgingival restorations resulted compatible with gingival health, with levels similar to that of untreated root surfaces. CLINICAL RELEVANCE: Deep margin elevation procedure produces favorable clinical and histological outcomes allowing a routine utilization in reconstructive dentistry.

Antimicrobial effectiveness of etidronate powder (Dual Rinse® HEDP) and two EDTA preparations against Enterococcus faecalis: a preliminary laboratory study.

This study aimed to evaluate the antimicrobial and antibiofilm activity of two chelating agents: ethylenediaminetetraacetic acid (EDTA) combined or not with detergents, and etidronic acid combined with sterile saline. The bacterial inhibitory and bactericidal concentrations (MIC and MBC, respectively) were determined on Enterococcus faecalis ATCC 4083 strain. Antimicrobial tests were performed on a biofilm model after treatment with the chelating agents at different times (1, 3, and 5 min) using a biofilm eradication concentration (MBEC) and confocal laser scanning microscope (CLSM) assays. Quantification of cell biomass and percentage of live and dead cells in the biomass was assessed for each group. The normality of the distributions for each variable was assessed using the D'Agostino and Pearson's omnibus normality test. The comparison of bacterial viability among groups and between any two groups was performed using the non-parametric Kruskal-Wallis one-way analysis of variance and the Dunn's test, respectively. No significant between-group difference was observed regarding biomass reduction. On the other hand, EDTA combined with detergents displayed a substantial increase of the dead bacteria ranging between 35 and 43%; whereas, the number of cells killed in the control group and in the other treated groups always ranged between 1 and 6%, at all experimental times. The addition of detergents to EDTA can improve its anti-biofilm activity by reducing EPS production and enhancing the killing of sessile bacterial cells. Clinical relevance EDTA presents a relevant antimicrobial activity when combined with surface-active agents.

Isolation through rubber dam to prevent COVID-19 exposure during flapless trans-crestal sinus lift procedures.

In 2020, a highly infective new pathogen (Sars-CoV-2) spread from China to the whole globe, and became responsible of an acute respiratory syndrome, often asymptomatic but potentially lethal, named COVID-19. Airborne and direct contact contamination are the major infection pathways of Sars-CoV-2 and it has been shown that virus spread can also happen in absence of clinical symptoms. SARS-CoV-2 transmission during dental procedures can happen through inhalation of droplets from infected patients or direct contact with mucous membranes, oral fluids, and contaminated instruments. Both sinus lift and implant surgeries often involve bleeding and exposure to oral fluids, and a rubber dam could be used to reduce direct contact and the amount of potentially infected aerosol. The aim of this short case presentation is to illustrate how the use of a rubber dam could be extremely useful in preventing COVID-19 exposure during flapless trans-crestal sinus lift procedures.

Correction to: The fate of root canals obturated with Thermafil: 10-year data for patients treated in a master's program.

The author names in the original version of this article were inadvertently interchange. Correct presentation of author names is reflected here.

Impact of a modified motion on the fatigue life of NiTi reciprocating instruments: a Weibull analysis.

OBJECTIVES: To evaluate the impact of a modified motion on the fatigue life of four brands of nickel-titanium (NiTi) reciprocating instruments. MATERIALS AND METHODS: Cyclic fatigue (CF) resistance of 160 instruments was evaluated in an artificial stainless-steel canal (90° angle, 5-mm radius of curvature). WaveOne and WaveOne Gold (Denstply Maillefer, Baillagues, Switzerland) and Reciproc and Reciproc Blue (VDW, Munich, Germany) were tested with two different motions: (1) X-Smart Plus (Denstply Maillefer) endodontic motor and (2) a 4:1 contra-angle with an experimental motion (EVO) with different rotation angles and based on a sinusoidal acceleration. Motions with X-Smart Plus and EVO were recorded and analyzed at a reduced speed with VLC Media Player software for a more accurate analysis. Mean half-life, beta, and eta Weibull parameters were determined and compared. RESULTS: Reciproc Blue resulted the most resistant instruments either with EVO or X-Smart. WaveOne Gold lasted significantly longer than WaveOne with EVO (probability of 91%) while no significant differences were found with X-Smart. Considering NCF, Reciproc, WaveOne Gold, and Reciproc Blue lasted significantly longer with EVO (probabilities of 66%, 80%, and 89% respectively). WaveOne Gold showed the highest beta parameter. CONCLUSIONS: The experimental motion was found to have a positive impact on fatigue lifetime of reciprocating instruments. CLINICAL RELEVANCE: Current findings provide insight for future improvements in the clinical use of reciprocating files. Experimental motions may be considered when searching for additional strategies in order to increase the safer use of NiTi files during endodontic procedures.

The fate of root canals obturated with Thermafil: 10-year data for patients treated in a master's program.

OBJECTIVES: Retrospective description of the 10-year success rate of endodontic treatments with Thermafil (TF). MATERIALS AND METHODS: Patients treated by postgraduate students in an Endodontics Master's Program (2006-2008) were enrolled. All treated root canals were filled with TF and AH Plus. Teeth satisfying the inclusion criteria (206 teeth in 89 patients) were reexamined clinically and radiographically to estimate a 10-year survival and periapical health. Demographic and medical data were registered; collected information included pre-, intra-, and postoperative variables. Teeth were classified as "healthy" (PAI ≤ 2 in absence of signs/symptoms), "endodontically diseased" (presenting at least one of the following: PAI ≥ 3, signs/symptoms, retreated in the course of the follow-up, or extracted for endodontic reasons), or "non-endodontically diseased" (extracted for non-restorable fractures or periodontal disease). For teeth lost during the 10-year follow-up, details and reason of extraction were analyzed. Two PAI-calibrated examiners assessed outcomes blinded to preoperative status. Bivariate and multilevel analyses were performed (α level set at 0.05). RESULTS: At 10 years, 179 (87%) teeth survived and 27 were extracted: 20 for non-endodontic reasons (excluded from success analysis) and 7 for endodontic reasons (considered "endodontically diseased"). Multilevel analysis revealed that the probability of extraction was increased by the presence of preoperative pain (odds ratio = 6.720; 95% confidence interval, 1.483-30.448) and by maxillary location (odds ratio = 2.950; 95% confidence interval, 1.043-8.347). Concerning periapical status, 159/186 teeth (85%) were assessed as "healthy." Multilevel analysis confirmed that maxillary location (odds ratio = 3.908; 95% confidence interval, 1.370-11.146), presence of flare up (odds ratio = 9.914; 95% confidence interval, 2.388-41.163), and fracture occurrence (odds ratio = 35.412; 95% confidence interval, 3.366-372.555) decreased the odds of healing, respectively. CONCLUSIONS: After 10 years, teeth filled with Thermafil in a specialist master's program presented a survival and a periapical health comparable to cohorts where root canals were filled with other obturation techniques. CLINICAL RELEVANCE: Carrier-based techniques provide time savings for clinicians while satisfying clinical quality criteria for the root filling and consequently the clinical outcome.

Evaluation of the usage-induced degradation of Genius and Reciproc nickel-titanium reciprocating instruments.

The aim of this study was to characterize the main features and the usage-induced degradation of the Genius file after four severely curved root canal instrumentations and to compare their properties to the Reciproc files. Brand new and ex vivo used files were analysed by scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), X-ray diffraction (XRD), optical metallography, and nano-indentation to disclose their morphological, chemical, mechanical, thermal, and phase composition features. Nano-indentation data were statistically analysed using the Student's t test for normal distribution or the Kolmogorov-Smirnov test for not-normal distributions. SEM analysis showed the presence of micro-cracks near the tip on both files after ex vivo usage test. EDS analysis confirmed that both files are manufactured from an almost equiatomic NiTi alloy. DSC analysis revealed that the transition temperature of the Genius is below 20 °C, while that of the Reciproc is above 20 °C. XRD analysis of Genius files identified cubic B2 austenite with minor peaks of residual monoclinic B19 martensite, while the contemporaneous presence of martensite, austenite and hexagonal R-phase was observed in the Reciproc files. Significant differences in nanohardness and modulus of elasticity (P < .05) were observed in both Genius and Reciproc files before and after use. The collected results showed that both instruments can be safely used as single-use files.

Dual Rinse® HEDP increases the surface tension of NaOCl but may increase its dentin disinfection efficacy.

The aim of this study was to evaluate the surface tension and the antimicrobial activity in infected dentin of a NaOCl solution combined with an etidronate powder (Dual Rinse® HEDP), compared to pure NaOCl and the classic NaOCl + EDTA irrigating sequence, respectively. The surface tension of three irrigants was measured by Wilhelmy technique. To evaluate the antimicrobial activity of the solutions, 26 human teeth were contaminated for 5 days with E. faecalis. After bacterial contamination, ten samples were irrigated with NaOCl followed by EDTA, another ten with NaOCl/Dual Rinse® HEDP, and four were used as positive controls. Two specimens not contaminated were used as negative controls. After live/dead BacLight staining, samples were examined by CLSM for analyzing % of residual live and dead cells. Comparison of bacterial viability between and within groups was performed using the Mann-Whitney test for independent samples and the Wilcoxon signed-rank test, respectively. The mean surface tension of EDTA was significantly lower than that of the other irrigants tested (p < 0.001). Conversely, the surface tension of NaOCl/Dual Rinse® HEDP solution was significantly higher than that of all the other solutions (p < 0.001). Residual bacterial viability in the NaOCl/Dual Rinse® HEDP (1.71%) was significantly lower (p = 0.019) than in the NaOCl + EDTA group (3.77%). All of the experimental groups showed significantly lower proportion of viable bacterial cells than the positive control group (p < 0.01). Clinical relevance adding etidronate to NaOCl increases its antimicrobial effect in dentinal tubules even though increases its surface tension.

From Osteoclast Differentiation to Osteonecrosis of the Jaw: Molecular and Clinical Insights.

Bone physiology relies on the delicate balance between resorption and formation of its tissue. Bone resorption depends on a process called osteoclastogenesis in which bone-resorbing cells, i.e., osteoclasts, are produced by the differentiation of more undifferentiated progenitors and precursors. This process is governed by two main factors, monocyte colony-stimulating factor (M-CSF) and receptor activator of NFκB ligand (RANKL). While the former exerts a proliferating effect on progenitors/precursors, the latter triggers a differentiation effect on more mature cells of the same lineage. Bone homeostasis requires a perfect space-time coordination of the involved signals. When osteoclastogenesis is poorly balanced with the differentiation of the bone forming counterparts, i.e., osteoblasts, physiological bone remodelling can turn into a pathological state, causing the systematic disruption of bone tissue which results in osteopenia or osteolysis. Examples of these conditions are represented by osteoporosis, Paget's disease, bone metastasis, and multiple myeloma. Therefore, drugs targeting osteoclastogenesis, such as bisphosphonates and an anti-RANKL monoclonal antibody, have been developed and are currently used in the treatment of such diseases. Despite their demonstrated therapeutic efficacy, these agents are unfortunately not devoid of side effects. In this regard, a condition called osteonecrosis of the jaw (ONJ) has been recently correlated with anti-resorptive therapy. In this review we will address the involvement of osteoclasts and osteoclast-related factors in the pathogenesis of ONJ. It is to be hoped that a better understanding of the biological mechanisms underlying bone remodelling will help in the design a medical therapeutic approach for ONJ as an alternative to surgical procedures.

Gingival tissue reaction to direct adhesive restoration: A preliminary study.

INTRODUCTION: It is debated whether composite resin marginal/submarginal direct restoration can be usefully performed without inflammatory consequences. This histological study is the first human analysis aimed to compare, in the same tooth, the gingival tissue close to composite resin restorations with gingival tissue close to hard tissue. METHODS: Eight healthy patients with almost a residual strategic tooth needing endodontic therapy, and post-and-core restoration, then indirect prosthetic restoration, were selected. Direct margin relocation with composite resin was necessary to perform endodontic treatment. The crown lengthening with a secondary flap harvested was necessary to perform prosthetic rehabilitation. Three months after marginal relocation, the secondary flap was harvested, embedded in PMMA, 4-µm sectioned, and stained to analyze the inflammation degree. RESULTS: All patients completed post-and-core reconstruction and the planned prosthetic therapy, maintaining the stringent hygienic protocol plan. The inflammation level comparison, slightly lower in gingiva close to the teeth (3.62 ± 0.38) than in gingiva close to the composite (3.75 ± 0.26), results in a p-value of 0.11 after Wilcoxon test. CONCLUSIONS: Results highlight a minimal, statistically not significant difference in the inflammation degree after margin relocation, conceivably due to patients, teeth and cases selection, together with adopted stringent methodological and supportive measures.

Plaque accumulation on titanium disks with different surface treatments: an in vivo investigation.

Implants with rough surfaces are today widely used. It has been speculated that rough surfaces (Ra > 0.2 µm) provide a better "substrate" for retention and accumulation of plaque in terms of area, thickness and colony-forming unit that can eventually lead to peri mucositis and/or peri-implantitis. The aim of this investigation was to evaluate in vivo the plaque accumulation after 48 h on three implant surfaces with different treatments. For this investigation, we used 21 sterilized titanium disks, with a diameter of 8mm and a thickness of 3 mm, provided by the manufacturer: 7 with machined surface, as smooth control, 7 with HA grit sandblasted RBM surface and 7 with Ca++ incorporated in titanium Xpeed surface. One disk for each surface treatment was characterized at time 0 by SEM and AFM to study, respectively, the surface morphology and roughness. The other 18 disks were mounted randomly on three upper acrylic bites in a buccal lateral position, worn for 48 h by three volunteer students for plaque accumulation. After 48 h each disk was removed and analyzed qualitatively and quantitatively by an independent operator, not involved into the study, in order to avoid bias. Data collected were statistically analyzed by one-way ANOVA. The qualitative analysis showed no differences in terms of total plaque accumulation between the surfaces. Data from quantitative analysis using Anova Test showed no significance between all groups. In this in vivo investigation all the surfaces studied promoted plaque formation. The degree of surface roughness seems not to be a critical factor for plaque accumulation.

Sodium hypochlorite penetration into dentinal tubules after manual dynamic agitation and ultrasonic activation: a histochemical evaluation.

The aim of this study was to compare the effects of Manual Dynamic Agitation and Passive Ultrasonic Irrigation on sodium hypochlorite (NaOCl) penetration into dentinal tubules using its bleaching ability. Thirty-four single-rooted teeth with round-shaped root canals were distributed in two homogeneous groups and one control group, characterized by different NaOCl activation systems: Manual Dynamic Agitation and Passive Ultrasonic Irrigation. After instrumentation, all root canals were stained with 10% copper sulphate solution followed by 1% rubeanic acid alcohol solution under vacuum. Final irrigation was performed with 5 mL of 5.25% NaOCl solution for 1 min and activated with Manual Dynamic Agitation or Passive Ultrasonic Irrigation for another 1 min depending on the treatment group. The teeth were transversely sectioned at the middle portion of the apical, middle, and coronal thirds and observed under light microscope. NaOCl solution penetration was evaluated by measuring the percentage of bleached circumference of the root canal relative to the stained circumference, bleached areas, mean, and maximum penetration depth. No differences in the evaluated parameters were observed between groups (p > 0.05). Within groups, an increase of values was recorded from apical to coronal direction as for percentage of staining, percentage of bleaching and bleached area. NaOCl penetration into dentinal tubules did not significantly vary among the three levels. No significant differences in penetration of sodium hypochlorite into dentinal tubules when activated by means of Manual Dynamic Agitation or Passive Ultrasonic Irrigation were observed in the apical, middle, and coronal thirds of teeth with single straight round root canals.