Effects of water flow on ablation rate and morphological changes in human enamel and dentin after Er:YAG laser irradiation

Purpose: To investigate the laboratory effect of Er:YAG laser on ablation rate and morphological changes in human enamel and dentin with varying water flow. Methods: 23 human third molars were sectioned in mesio-distal and buccal-lingual directions. The slabs were flattened and weighted on an analytical laboratory balance (control). A 4-mm(2) area was demarcated and the samples were randomly assigned into three groups according to water flow employed during the laser irradiation (1.0, 1.5, and 2.0 mL/minute). An Er:YAG laser was used to ablate enamel (80.22-J/cm(2), 300 mJ/4Hz) and dentin (96.26-J/cm(2), 250 mJ/4Hz). After irradiation, the samples were immersed in distilled water for 1 hour and then weighted again. The final mass was obtained and laser-irradiated substrate mass loss was calculated by the difference between the initial and final mass. Afterwards, specimens were prepared for SEM. Results: Data were submitted to ANOVA and Tukey's test (P< 0.05). It was observed that the 2.0 mL/minute resulted in a higher mass loss, 1.0 mL/minute showed a lower mass loss, and 1.5 mL/minute demonstrated intermediate results (P< 0.05). The increase of water flow promoted less melting areas and cracks. Furthermore, dentin was more ablated than enamel. It may be concluded that the water flow of Er:YAG laser and the substrates affected the ablation rate. Among the tested parameters, 2.0 mL/minute improved the ability of ablation in enamel and dentin, with less morphologic surface alteration. (Am J Dent 20 12;25:332-336).

Iron supplementation reduces the erosive potential of a cola drink on enamel and dentin in situ

Iron has been suggested to reduce the erosive potential of cola drinks in vitro. Objective: The aim of this study was to evaluate in situ the effect of ferrous sulfate supplementation on the inhibition of the erosion caused by a cola drink. Material and Methods: Ten adult volunteers participated in a crossover protocol conducted in two phases of 5 days, separated by a washout period of 7 days. In each phase, they wore palatal devices containing two human enamel and two human dentin blocks. The volunteers immersed the devices for 5 min in 150 mL of cola drink (Coca-Cola (TM), pH 2.6), containing ferrous sulfate (10 mmol/L) or not (control), 4 times per day. The effect of ferrous sulfate on the inhibition of erosion was evaluated by profilometry (wear). Data were analyzed by paired t tests (p<0.05). Results: The mean wear (+/- se) was significantly reduced in the presence of ferrous sulfate, both for enamel (control: 5.8 +/- 1.0 mu m; ferrous sulfate: 2.8 +/- 0.6 mu m) and dentin (control: 4.8 +/- 0.8 mu m; ferrous sulfate: 1.7 +/- 0.7 mu m). Conclusions: The supplementation of cola drinks with ferrous sulfate can be a good alternative for the reduction of their erosive potential. Additional studies should be done to test if lower ferrous sulfate concentrations can also have a protective effect as well as the combination of ferrous sulfate with other ions.

Impact of experimental Nano-HAP pastes on bovine enamel and dentin submitted to a pH cycling model

This in vitro study evaluated the preventive potential of experimental pastes containing 10% and 20% hydroxyapatite nanoparticles (Nano-HAP), with or without fluoride, on dental demineralization. Bovine enamel (n=15) and root dentin (n=15) specimens were divided into 9 groups according to their surface hardness: control (without treatment), 20 Nanop paste (20% HAP), 20 Nanop paste plus (20% HAP + 0.2% NaF), 10 Nanop paste (10% HAP), 10 Nanop paste plus (10% HAP + 0.2% NaF), placebo paste (without fluoride and HAP), fluoride paste (0.2% NaF), MI paste (CPP-ACP, casein phosphopeptide-amorphous calcium phosphate), and MI paste plus (CPP-ACP + 0.2% NaF). Both MI pastes were included as commercial control products containing calcium phosphate. The specimens were treated with the pastes twice a day (1 min), before and after demineralization. The specimens were subjected to a pH-cycling model (demineralization–6-8 h/ remineralization-16-18 h a day) for 7 days. The dental subsurface demineralization was analyzed using cross-sectional hardness (kgf/mm 2 , depth 10-220 µm). Data were tested using repeated-measures two-way ANOVA and Bonferroni's test (p<0.05). The only treatment able to reduce the loss of enamel and dentin subsurface hardness was fluoride paste (0.2% NaF), which differed significantly from the control at 30- and 50-µm depth (p<0.0001). The other treatments were not different from each other or compared with the control. The experimental Nanop pastes, regardless of the addition of fluoride, were unable to reduce dental demineralization in vitro.

Impact of different fluoride concentrations and pH of dentifrices on tooth erosion/abrasion in vitro

Background: This in vitro study analysed the effect of different fluoride concentrations in acidic or neutral liquid dentifrices in protecting enamel and dentine from erosive and abrasive wear. Methods: Bovine enamel and dentine specimens (n = 132) were randomly allocated to 11 groups (each n = 12): experimental liquid dentifrices with 550 ppm F, 1100 ppm F, 5000 ppm F or 0 ppm F/placebo (each at pH 4.5 and pH 7.0); and commercial dentifrices with 550 ppm F (Colgate Baby, pH 7.0), 1100 ppm F (Crest, pH 7.0) and 5000 ppm F (Duraphat, pH 7.0). The specimens were subjected to erosion for 90 seconds, 4 times/day, over 7 days. Immediately after the first and last erosion, the specimens were brushed for 15 seconds using one of the dentifrices. Tooth wear was measured profilometrically (lm) and analysed by ANOVA (p < 0.05). Results: All fluoridated liquid dentifrices significantly reduced enamel wear compared to the placebo and commercial dentifrices. Only liquid dentifrices with 1100 and 5000 ppm F significantly reduced dentine wear compared to placebo dentifrice. The pH had no effect, but the consistency had a significant impact on the effect of dentifrices. Conclusions: Liquid dentifrices with high F concentration appear to be a good option to prevent tooth wear

Shear bond strength between different materials bonded with two resin cements

Background: The aim of this study was to compare the shear bond strength between Ni-Cr alloy specimens bonded to air-abraded Ni-Cr, bur-abraded Ni-Cr, etched ceramic and etched enamel substrates using the resin cements RelyX ARC or Enforce. Materials and methods: Ni-Cr specimens were made and sandblasted with Al2O3 airborne-particles. Disc-shaped patterns were made for each of the four experimental substrates: Ni-Cr treated with Al2O3 airborne-particles, Ni-Cr treated with diamond bur abrasion, etched enamel and etched ceramic. Results: Significant differences in shear bond strength were found between the different materials and luting agents evaluated. The Ni-Cr alloy cylinders bonded to Ni-Cr surfaces sandblasted with 50 lm Al2O3 particles and bonded with Enforce achieved the highest bond strength when compared with other substrates (28.9 MPa, p < 0.05). Bur-abraded metal discs had lowest values, regardless the cement used (2.9 and 6.9 MPa for RelyX and Enforce, respectively). Etched enamel and etched ceramic had similar shear bond strengths within cement groups and performed better when RelyX was used. Conclusions: Bonding Ni-Cr to Ni-Cr and ceramic may result in similar and higher bond strength when compared to Ni-Cr/enamel bonding. For metal/metal bonding, higher shear bond strength was achieved with resin cement Enforce, and for metal/ceramic and metal/enamel bonding, RelyX had higher results.

Systemically alendronate was incorporated into dental tissues but did not cause morphological or mechanical changes in rats teeth

This study evaluated the effect of the systemic use of sodium alendronate in rats in vivo. Forty-five Wistar rats aged 36 to 42 days and weighing 200 to 230 g were randomly assigned to a control group (n = 20), which received distilled water, and an experimental group (n = 25), which received 2 weekly doses of 1 mg/kg of chemically pure sodium alendronate. The animals were killed after 60 days of treatment. The tibias were removed for analysis of bone mineral density by dual-energy X-ray absorptiometry (DXA). Then, the maxillary incisors were extracted for analysis of the mineralized dental tissues using fluorescence spectroscopy (FS), scanning electron microscopy (SEM), bright field microscopy (BFM), and cross-sectional microhardness (CSMH) testing. DXA and CSMH data were subjected to statistical analysis by Kruskal-Wallis test (5% significance level). The experimental group presented higher bone mineral density than the control group by DXA. FS analysis revealed presence of alendronate in the mineralized dental tissues of the specimens of the experimental group. Significant morphological differences were not found by SEM and BFM. Enamel and dentin (100 and 300 mu m from the dentinoenamel junction) CSMH data did not show significant difference between the control and experimental groups. Based on the obtained results, we conclude that while alendronate increased the bone mineral density and was incorporated into the mineralized dental tissues it did not cause significant alterations in the morphology and microhardness of rat incisor enamel and dentin. Microsc. Res. Tech. 75:12651271, 2012. (C) 2012 Wiley Periodicals, Inc.

Identification of a Tooth-Like Foreign Body in Swine Sausage

A tooth-like foreign body (FB) was found inside a sausage bread. Analysis aimed to investigate whether the FB was a tooth and its origin. The FB was measured, weighed, photographed, and radiographed. Macroscopic findings were suggestive of an anterior tooth. Histological slides of undecalcified cross-sections of the FB and samples of human and swine teeth were prepared. Histological features of the FB (in light microscopy, 125X magnification) were discrepant from human tissues. Compared histological analysis displayed majority of features consistent with a hypsodont swine tooth, probably a canine. Cellularized cementum in crown region, adjacent to the enamel, and shape of the cementocytes were the main criteria excluding the possibility of human origin of the FB. Scanning electronic microscopy and energy-dispersive spectroscopy were not performed because of fewer features to be analyzed and FB size. It was concluded that the FB may have been incorporated during meat grinding of the sausage.

Comparison Between Micro- and Macrosurgical Techniques for the Treatment of Localized Gingival Recessions Using Coronally Positioned Flaps and Enamel Matrix Derivative

Background: The aim of this study is to compare the macro- and microsurgery techniques for root coverage using a coronally positioned flap (CPF) associated with enamel matrix derivative (EMD). Methods: Thirty patients were selected for the treatment of localized gingival recessions (GRs) using CPF associated to EMD. Fifteen patients were randomly assigned to the test group (TG), and 15 patients were randomly assigned to the control group (CG). The microsurgical approach was performed in the TG, and the conventional macrosurgical technique was performed in the CG. The clinical parameters evaluated before surgery and after 6 months were GR, probing depth, relative clinical attachment level, width of keratinized tissue (WKT), and thickness of keratinized tissue (TKT). The discomfort evaluation was performed 1 week postoperative. Results: There were no statistically significant differences between groups for all parameters at baseline. At 6 months, there was no statistically significant difference between the techniques in achieving root coverage. The percentage of root coverage was 92% and 83% for TG and CG, respectively. After 6 months, there was a statistically significant increase of WKT and TKT in TG only. Both procedures were well tolerated by all patients. Conclusions: The macro- and microsurgery techniques provided a statistically significant reduction in GR height. After 6 months, there was no statistically significant difference between the techniques regarding root coverage, and the microsurgical technique demonstrated a statistically significant increase in WKT and TKT. J Periodontol 2010;81:1572-1579.

Argon and Nd:YAG Lasers for Caries Prevention in Enamel

Objective: The aim of this study was to investigate the effect of Nd:YAG and argon laser irradiations on enamel demineralization after two different models to induce artificial caries. Background data: It is believed that the use of the high-intensity laser on the dental structure can lead to a more acid-resistant surface. Materials and methods: Twenty-one extracted human third molars were sectioned into tooth quarters. The quarters were distributed in three groups: Group I (control), untreated; Group II, Nd:YAG laser (60 mJ, 15 pps, 47.77 J/cm(2), 30 sec); and Group III, argon laser (250mW, 12 J/cm(2), 48 sec). Tooth quarters from each group were subjected to two different demineralization models: cycle 1, a 14 day demineralization (pH 4.5; 6 h) and remineralization (pH 7.0; 18 h) solutions, 37 degrees C and cycle 2, 48 h in demineralization solution (pH 4.5). Samples were prepared in slices (60-100 mu m thick) to be evaluated under polarized light microscopy. Demineralization areas were measured (mm(2)) (n = 11). Data were analyzed by ANOVA and Tukey's test (p < 0.05). Results: Means followed by different letters are significantly different: 0.25 A (control, cycle 48 h); 0.18 AB (control, cycle 14 days); 0.17 AB (Nd:YAG, cycle 14 days); 0.14 BC (argon, cycle 48 h); 0.09 BC (Nd:YAG, cycle 48 h), and 0.06 C (argon, cycle 14 days). Conclusions: The argon laser was more effective for caries preventive treatment than Nd: YAG laser, showing a smaller demineralization area in enamel.

Synchrotron X-ray diffraction characterization of healthy and fluorotic human dental enamel

With the introduction of fluoride as the main anticaries agent used in preventive dentistry, and perhaps an increase in fluoride in our food chain, dental fluorosis has become an increasing world-wide problem. Visible signs of fluorosis begin to become obvious on the enamel surface as opacities, implying some porosity in the tissue. The mechanisms that conduct the formation of fluorotic enamel are unknown, but should involve modifications in the basic physical-chemistry reactions of demineralization and remineralisation of the enamel of the teeth, which is the same reaction of formation of the enamel's hydroxyapatite (HAp) in the maturation phase. The increase of the amount of fluoride inside of the apatite will result in gradual increase of the lattice parameters. The aim of this work is to characterize the healthy and fluorotic enamel in human tooth using Synchrotron X-ray diffraction. All the scattering profile measurements were carried out at the X-ray diffraction beamline (XRD1) at the Brazilian Synchrotron Light Laboratory-LNLS, Campinas, Brazil. X-ray diffraction experiments were performed both in powder samples and polished surfaces. The powder samples were analyzed to obtain the characterization of a typical healthy enamel pattern. The polished surfaces were analyzed in specific areas that have been identified as fluorotic ones. X-ray diffraction data were obtained for all samples and these data were compared with the control samples and also with the literature data. (c) 2012 Elsevier Ltd. All rights reserved.

A bayesian network meta-analysis on comparisons of enamel matrix derivatives, guided tissue regeneration and their combination therapies

Aims: Guided tissue regeneration (GTR) and enamel matrix derivatives (EMD) are two popular regenerative treatments for periodontal infrabony lesions. Both have been used in conjunction with other regenerative materials. We conducted a Bayesian network meta-analysis of randomized controlled trials on treatment effects of GTR, EMD and their combination therapies. Material and Methods: A systematic literature search was conducted using the Medline, EMBASE, LILACS and CENTRAL databases up to and including June 2011. Treatment outcomes were changes in probing pocket depth (PPD), clinical attachment level (CAL) and infrabony defect depth. Different types of bone grafts were treated as one group and so were barrier membranes. Results: A total of 53 studies were included in this review, and we found small differences between regenerative therapies which were non-significant statistically and clinically. GTR and GTR-related combination therapies achieved greater PPD reduction than EMD and EMD-related combination therapies. Combination therapies achieved slightly greater CAL gain than the use of EMD or GTR alone. GTR with BG achieved greatest defect fill. Conclusion: Combination therapies performed better than single therapies, but the additional benefits were small. Bayesian network meta-analysis is a promising technique to compare multiple treatments. Further analysis of methodological characteristics will be required prior to clinical recommendations.

In situ effect of sodium fluoride or titanium tetrafluoride varnish and solution on carious demineralization of enamel

This study evaluated the effect of titanium tetrafluoride (TiF4) formulations on enamel carious demineralization in situ. Thirteen subjects took part in this cross-over, split-mouth, double-blind study performed in three phases of 14 d each. In each subject, two sound and two predemineralized specimens of bovine enamel were worn intra-orally and plaque accumulation was allowed. One sound and one predemineralized specimen in each subject was treated once with sodium fluoride (NaF) varnish or solution (Treatment A); TiF4 varnish or solution (Treatment B); or placebo varnish or no treatment (Treatment C). The initially sound enamel specimens were exposed to severe cariogenic challenge (20% sucrose, eight times daily for 5 min each time), whereas the predemineralized specimens were not. Eleven subjects were able to finish all experimental phases. The enamel alterations were quantified by surface hardness and transversal microradiography. Demineralization of previously sound enamel was reduced by all test formulations except for the NaF solution, while both TiF4 formulations were as effective as NaF varnish. For the predemineralized specimens, enamel surface hardness was increased only by TiF4 formulations, while subsurface mineral remineralization could not be seen in any group. Within the experimental protocol, TiF4 was able to decrease enamel demineralization to a similar degree as NaF varnish under severe cariogenic challenges, while only TiF4 formulations remineralized the enamel surface.

FTIR and SEM analysis of CO2 laser irradiated human enamel

Objectives: Considering the enamel chemical structure, especially carbonate band, which has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO2 laser by means of FTIR spectroscopy and SEM analysis. Design: The enamel surfaces were analysed on a spectrometer for acquisition of the absorption spectrum relative to the chemical composition of the control sample. The irradiation was conducted with a 10.6-mu m CO2 laser (0.55 W, 660 W/cm(2)). The carbonate absorption band at 1600-1291 cm(-1) as well as the water absorption band at 3793-2652 cm(-1) was measured in each sample after the irradiation. The water band was measured again 24-h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was normalized by the phosphate band (1190-702 cm(-1)). Results: There was a statistically significant decrease (p < 0.05) in the water content after irradiation (control: 0.184 +/- 0.04; irradiated: 0.078 +/- 0.026), which increased again after rehydration (0.145 +/- 0.038). The carbonate/phosphate ratio was measured initially (0.112 +/- 0.029) and its reduction after irradiation indicated the carbonate loss (0.088 +/- 0.014) (p < 0.05). Conclusion: The 10.6-mu m CO2 laser irradiation diminishes the carbonate and water contents in the enamel after irradiation. (C) 2012 Elsevier Ltd. All rights reserved.

Influence of ultrasound or halogen light on microleakage and hardness of enamel adjacent to glass ionomer cement

Background. The use of external sources of energy may accelerate the setting rate of glass ionomer cements (GICs) allowing better initial mechanical properties. Aim. To investigate the influence of ultrasound and halogen light on the microleakage and hardness of enamel adjacent to GIC restorations, after artificial caries challenge. Design. Cavities were prepared in 60 primary canines, restored with GIC, and randomly distributed into three groups: control group (CG), light group (LG) - irradiation with a halogen lightcuring unit for 60 s, and ultrasonic group (UG) application of ultrasonic scaler device for 15 s. All specimens were then submitted to a cariogenic challenge in a pH cycling model. Half of sample in each group were immersed in methylene blue for 4 h and sectioned for dye penetration analysis. The remaining specimens were submitted to Knoop cross-sectional microhardness assessments, and mineral changes were calculated for adjacent enamel. Results. Data were compared using Kruskal-Wallis test and two- way ANOVA with 5% significance. Higher dye penetration was observed for the UG (P < 0.01). No significant mineral changes were observed between groups (P = 0.844). Conclusion. The use of halogen light- curing unit does not seem to interfere with the properties of GICs, whereas the use of ultrasound can affect its marginal sealing.

The erosion and abrasion-inhibiting effect of TiF4 and NaF varnishes and solutions on enamel in vitro

Objective. Previous in vitro study has shown that TiF(4) varnish might reduce enamel erosion. No data regarding the effect of this experimental varnish on enamel erosion plus abrasion, however, are available so far. Thus, this in vitro study aimed to analyse the effect of TiF4 compared with NaF varnishes and solutions, to protect against enamel erosion with or without abrasion. Methods. Enamel specimens were pre-treated with experimental-TiF4 (2.45% F), experimentalNaF (2.45% F), NaF-Duraphat (2.26% F), and placebo varnishes; NaF (2.26% F) and TiF4 (2.45% F) solutions. Controls remained untreated. The erosive challenge was performed using a soft drink (pH 2.6) 4 u 90 s / day (ERO) and the toothbrushing abrasion (ERO+ ABR) 2 u 10 s / day, for 5 days. Between the challenges, the specimens were exposed to artificial saliva. Enamel loss was measured profilometrically (lm). Results. Kruskal-Wallis / Dunn tests showed that all fluoridated varnishes (TiF4-ERO: 0.53 +/- 0.20, ERO+ ABR: 0.65 +/- 0.19/ NaF-ERO: 0.94 +/- 0.18, ERO+ ABR: 1.74 +/- 0.37 / Duraphat-ERO: 1.00 +/- 0.37, ERO+ ABR: 1.72 +/- 0.58) were able to significantly reduce enamel loss when compared with placebo varnish (ERO: 3.45 +/- 0.41 / ERO+ ABR: 3.20 +/- 0.66) (P < 0.0001). Placebo varnish, control (ERO: 2.68 +/- 0.53 / ERO+ ABR: 3.01 +/- 0.34), and fluoridated (NaF-ERO: 2.84 +/- 0.09 / ERO+ ABR: 2.40 +/- 0.21 / TiF4-ERO: 3.55 +/- 0.59 / ERO+ ABR: 4.10 +/- 0.38) solutions did not significantly differ from each other. Conclusion. Based on the results, it can be concluded that the TiF4 varnish seems to be a promising treatment to reduce enamel loss under mild erosive and abrasive conditions in vitro.