Activation of endodontic irrigants using a 9.3 µm CO2 and diode lasers: A laboratory proof of concept model.

PURPOSE: To investigate the differences between irrigant propagation and temperature changes using laser-activated irrigation (LAI) at different settings in an artificial root canal model. METHODS: Using an artificial resin root canal model, irrigant activation was achieved in 19 experimental groups with eight samples each. A 9,300 nm CO2 laser, two diode lasers with different settings (wavelengths 455, 808, 970, and 980 nm) were compared to 2,940 nm Er:YAG laser and traditional needle irrigation. Er:YAG and CO2 laser were activated in the pulpal chamber only, while diode lasers and needles were inserted into the main root canal. Lasers were activated for 5x 20 seconds resulting in 100 seconds of activation or rinsing for each sample. After each activation of 20 seconds, a photo was taken of the side canals and the propagation of the dye was measured with a digital measuring tool after calibration. Further, the temperature of the irrigant was reported after activation of 20 seconds and repeated 5 times. Data were checked for normality and statistically compared. RESULTS: All lasers increased the irrigant propagation compared to conventional irrigation. Significant differences were found between groups regarding propagation and temperature (P< 0.0027). Er:YAG and CO2 laser had similar effects on irrigant propagation in middle and apical located side-canals with specific power parameters and were superior to diode lasers and syringe irrigation. The irrigant's temperature increased significantly with the diode and CO2 lasers. CLINICAL SIGNIFICANCE: Diode lasers and CO2 lasers have not been established for irrigant activation. 9,300 nm CO2 lasers absorb well in water and were shown to introduce vapor bubble formation and streaming in water. Diode lasers are highly accepted in periodontics. The laser light is not absorbed in water but interacts with bacteria as well as soft tissues and contributes therefore to infection control. With a modified laser tip it was however possible to introduce cavitation and streaming in irrigants.

Efficacy of one-time application of low-level laser therapy in the management of complications after third molar surgery: A retrospective practice-based study.

PURPOSE: To evaluate in a retrospective practice-based clinical study, the effects of additional laser therapy on side effects following the removal of all four impacted third molars. The secondary objective was, based on those results, to rationalize a protocol for low-level laser therapy (LLLT) in terms of irradiation settings. METHODS: 96 subjects requiring simultaneous surgical removal of the four third molars were treated from 2017 to 2019. For each subject, one side was randomly assigned to laser treatment, the other receiving the placebo. LLLT was performed by applying an infrared diode laser of 810 nm. In the LLLT irradiated side of the mouth, three groups were randomly assigned to a specific protocol of irradiation. Controllable settings include power, energy density and also scanning technique. The main outcome was pain, registered on a visual analog scale (VAS) performed by the patients. RESULTS: There was a statistically significant difference for one of the tested protocols. Self-reported annoyance and pain scores were lower for the side submitted to a 30-second laser radiation at a power of 0.3 W with the slow scanning technique (P< 0.05). CLINICAL SIGNIFICANCE: The present treatment approach, using a one-time low-level laser therapy intra-oral application, showed a beneficial effect of LLLT reducing pain after third molar surgery, which should be confirmed through further study.

Effect of light-curing time and direction on microhardness of a light-cured resin composite to cement CAD-CAM restorations.

PURPOSE: To evaluate the effect of light-curing exposure time and location on polymerization of a restorative bulk-fill resin composite to lute endocrowns. METHODS: A light-cured restorative bulk-fill resin composite (Filtek One Bulk Fill) was submitted to direct light-curing by a high-power LED light-curing unit for 20 seconds as the positive control group (n= 10). Five more groups (n= 10) were light-cured in a natural tooth mold from two sites (labial and lingual) through a nanohybrid resin composite CAD-CAM restoration (Lava Ultimate A2 LT), for different irradiation times: 90 seconds per site, 40 seconds per site, 30 seconds per site, 20 seconds per site and 10 seconds per site. Vickers microhardness measurements were made at two different depths and test/control ratios were calculated. Ratios of 0.8 were considered as an adequate level of curing. A quantile regression was run to identify the minimally sufficient time of light-curing, and a two-way ANOVA was used to compare the results to previous findings and evaluate the effect of curing location. RESULTS: Analysis showed that 40 seconds x 2 is the minimal irradiation time that presents a test/control ratio above 0.8. Quantile regressions showed that the required irradiation time to reach a test/control ratio of 0.8 at a confidence level of 95% is 41.5 seconds and 39.2 seconds at 200 µm and 500 µm depths in the luting agent, respectively. There was no statistically significant difference between microhardness of the two depths except for the irradiation time of 10 seconds. The two-site to three-site light curing comparison showed no statistically significant difference except for the 90-second time. CLINICAL SIGNIFICANCE: Systematic light-curing through the labial, lingual and occlusal surfaces of thick indirect restorations is not always required for sufficient polymerization and can even waste valuable clinical time especially in the case of multiple restorations luted with resin composites.

Efficiency of 3D-printed composite resin restorations compared with subtractive materials: Evaluation of fatigue behavior, cost, and time of production.

STATEMENT OF PROBLEM: Three-dimensionally (3D)-printed composite resins have been marketed as materials for definitive restorations. However, limited information is available regarding the stability of the adhesive interface and the efficiency of 3D-printed composite resins. PURPOSE: The purpose of this in vitro study was to evaluate the integrity of the marginal adhesive interface before and after thermal and mechanical fatigue of an initial formulation of a 3D-printed composite resin and to evaluate the efficiency of this manufacturing method. MATERIAL AND METHODS: Freshly extracted molars were prepared for onlays and adhesively restored with either 3D-printed composite resin (VarseoSmile Crown Plus) (Group 3D), milled composite resin (Tetric CAD) (Group MCOMP), milled PMMA (Telio CAD) (Group PMMA), and milled lithium disilicate (IPS e.max CAD) (Group EM). Marginal analysis was performed under a scanning electron microscope before and after fatigue by thermomechanical cyclic loading, and initial and terminal percentages of continuous margin (%CM) were compared. The time required for the production of each type of restoration was recorded, and the production costs were also compared. RESULTS: Before aging, 3D, MCOMP, and EM presented comparable values of %CM (69.8%, 75.9%, and 63.1%, respectively) that were statistically significantly higher (P<.05) than those of PMMA (45.1%). After aging, 3D and EM had comparable results (44.7% and 43.7%, respectively), which were lower than those of the MCOMP group (68.5%) but higher than those of the PMMA group (20.5%). Regarding time efficiency, 3D printing took less time than MCOMP or PMMA if more than 8 restorations were fabricated. For the production costs, 3D printing was 5.5, 8.7, and 10.2 times less expensive than PMMA, MCOMP, and EM, respectively. The initial equipment cost was also lower for the additive manufacturing method. However, 3D printing did not always considerably reduce waste. CONCLUSIONS: In terms of marginal adaptation, the evaluated initial formulation of a 3D-printed composite resin behaved similarly to other well-established definitive restoration materials and better than milled PMMA, both before and after fatigue. Three-dimensionally printed resins present advantages in terms of equipment and consumable costs, even for a single restoration, but also for production time when more than 8 restorations were fabricated.

Fracture strength of non-invasively reinforced MOD cavities on endodontically treated teeth.

The purpose of this in-vitro study was to evaluate the fracture resistance and failure mode of non-invasively reinforced endodontically treated mandibular molars. Sixty freshly extracted defect-free mandibular molars were divided into four experimental groups with extensive MOD cavities on endodontically treated teeth with different restoration types and one control group with intact teeth (n = 12). The groups were as follows: "Normal": direct resin composite; "Ring": glass fiber-reinforced strip (Dentapreg) wrapped around buccal and lingual walls followed by direct resin composite; "Inlay": indirect CAD/CAM resin composite inlay; "Onlay": indirect CAD/CAM resin composite onlay; "Intact": Intact teeth (Control). Tetric EvoCeram and Adhese Universal (Ivoclar Vivadent) were used for direct restorations and Tetric CAD (Ivoclar Vivadent) adhesively luted with Adhese Universal and Variolink Esthetic LC (Ivoclar Vivadent) were used for indirect restorations. All teeth were submitted to thermo-mechanical cyclic loading. All samples were then submitted to a compressive load until fracture. Fracture load was noted and teeth were analyzed to classify the failure mode as either catastrophic (C) or non-catastrophic (NC). No statistically significant difference was found between fracture strength of the five groups when all specimens were considered (p = 0.1461). Intact group showed the lowest percentage of catastrophic failures (41.67%). Ring group presents less catastrophic failures (75%) than Normal group (83.34%), and failures of indirect restorations-Inlay and Onlay-were almost all catastrophic (91.67% and 100%, respectively).

Frequent use of emergency departments and chronic conditions in ageing societies: a retrospective analysis based in Italy.

BACKGROUND: Most western countries are facing relevant demographic changes, and the percentage of older people is destined to rise in the next decades. This fact is likely to affect the sustainability of healthcare systems significantly, mainly due to the connected issue of chronicity. METHODS: In this paper, using an extensive and comprehensive administrative dataset, we analyse the phenomenon of frequent use of emergency departments (ED) in the oldest region in Europe (i.e. Liguria) over 4 years (2013-2016). Two alternative approaches are used to define categories of ED users based on the intensity and frequency of accesses and splitting patients into different age groups. RESULTS: Results allow identifying clinical and socio-demographic risk-factors connected to different levels of ED utilisation and highlight the influential role played by chronic conditions (particularly mental disorders, respiratory diseases) and by multiple chronic conditions. CONCLUSIONS: The study aims at representing an informative tool to support policy-makers in setting proper policies addressed, on the one side, towards the potentially preventable frequent users and, on the other, towards those accessing due to complex medical conditions. The results can help in building a warning system to help general practitioners in the identification of potential frequent users and to develop preventive policies.

Influence of mechanical and chemical degradation on surface gloss of direct and CAD-CAM resin composite materials.

PURPOSE: To compare the gloss retention of four resin based materials, two direct resin composites (Tetric EvoCeram and Filtek Supreme) and two indirect resin composite CAD-CAM blocks (Tetric CAD and Lava Ultimate). METHODS: 36 samples of 1 mm thickness were readied of each test material and manually polished with polishing discs (Sof-Lex) up to the finest grit size. Three gloss measurements per sample were taken (one every 120 degrees of sample rotation) by means of a glossmeter (Novo-Curve) for a total of 60 values obtained per tested material. Samples of each material were then randomly divided into three equal groups and aged with 75% alcohol (Group 1), amine fluoride gel (Elmex gelée) (Group 2) or mechanical brushing (Group 3). Another set of gloss measurements was performed on all samples after 1 hour of aging. Gloss values were statistically evaluated by means of repeated measures ANOVA and Fisher's LSD post-hoc tests. RESULTS: Gloss retention values ranged from 59.0 (Tetric EvoCeram) to 70.9 (Lava Ultimate) for alcohol, from 59.3 (Filtek Supreme) to 67.5 (Lava Ultimate) for Elmex gelèe and from 33.3 (Tetric EvoCeram) to 53.4 (Lava Ultimate) for mechanical brushing. Statistical analysis revealed: (1) significant difference between intial and final gloss values for all materials and groups; (2) significant difference between final gloss values of all the materials in the alcohol group; (3) significant difference between final gloss values of Lava Ultimate and all the other materials in the Elmex gelèe group; (4) significant difference between final gloss values of Lava Ultimate and Tetric CAD with the other tested materials in the brushing group. CLINICAL SIGNIFICANCE: Direct resin composites in general are widely used, and CAD-CAM resin composite materials are becoming progressively more accessible. Making the choice between direct and indirect techniques is still a challenge, and understanding the advantages of CAD-CAM resin composites in the form of higher gloss retention, which translates into higher durability of esthetics, may be one the parameters facilitating the decision.

Staining susceptibility of resin composite materials.

PURPOSE: To evaluate the color stability of three resin-based materials continuously exposed to various staining agents. METHODS: 144 disc-shaped specimens were made of each of the three tested composites (Essentia, Brillant, Inspiro). Half of them were 1 mm thick, the other half 1.2 mm thick. The thicker group was then polished up to 4,000 grit and reduced to 1 mm thickness, also. All specimens, after 24-hour dry storage in an incubator, received an initial color measurement by means of a calibrated reflectance spectrophotometer (SpectroShade). Specimens were then divided into six groups (n=6) and immersed in five staining solutions or artificial saliva (control). All specimens were kept in an incubator at 37°C for 28 days. Staining solutions (red wine, curry mixed in water, curry mixed in oil, tea and coffee) were changed every 7th day to avoid bacteria or yeast contamination. After 28 days of storage, spectrophotometric measurements were repeated and L*a*b* scores once more recorded to determine the color (ΔE00) changes. RESULTS: All tested materials showed significant color changes after 28 days staining immersion. ΔE00 of polished samples varied from 1.1 (Essentia/distilled water measured over a white background as well as Essentia, Inspiro/distilled water measured over a black background) to 32.5 (Inspiro/wine measured over a white background). CLINICAL SIGNIFICANCE: Staining of restorative materials seems to be dependent on the composition of the product itself. Unpolished samples were more prone to staining than the polished ones.

What should we expect from Switzerland's compulsory dental insurance reform?

BACKGROUND: A vast and heated debate is arising in Switzerland as a result of some recent citizens' initiatives aimed at introducing compulsory dental health care insurance. The Grand Conseils of the Vaud, Geneva, and Neuchâtel cantons recently approved three public initiatives and their citizens are expected to vote on the proposal in 2018. The process of collecting signatures has begun in several other cantons and the discussion has now moved to a national level. DISCUSSION: At present, there is no scientific research that can help policy-makers and citizens to understand the main economic implications of such reform. We attempt to fill this gap by analysing three critical issues: the level and determinants of unmet needs for dental care in Switzerland; the protection of vulnerable individuals; and the economic sustainability of reform. RESULTS AND SHORT CONCLUSIONS: The results show that income is not a unique determinant of barriers to access to dental care but rather, cultural and socio-demographic factors impact the perceived level of unmet dental care needs. The reform might only partially, if at all, improve the equity of the current system. In addition, the results show that the 1% wage-based contribution that the reform promoters suggest should finance the insurance is inadequate to provide full and free dental care to Swiss residents, but is merely sufficient to guarantee basic preventive care, whereas this could be provided by dental hygienists for less.

Protection Against Discolouration by Two Over-the Counter Desensitising Products.

PURPOSE: To determine in vitro the protection potential against discolouration of two OTC (over-the-counter) desensitising products on enamel and dentin in comparison to a standard toothpaste and water by means of a spectrophotometer. MATERIALS AND METHODS: A total of 96 samples of bovine enamel-dentin complex and 48 of bovine dentin were alternatively immersed in red wine, tea, coffee or water after having been treated by a sodium monofluorophosphate- and calcium phosphate-based product (Curodont Protect), an amine fluoride-based toothpaste (Elmex Red), a stannous chloride-based toothpaste (Elmex Protection Erosion) or distilled water (negative control). Initial (T0) and final colour (T1, after 4 weeks of immersion in staining solutions) of each specimen were assessed by a spectrophotometer. Statistical analysis was done by means of repeated measures ANOVA followed by Fisher's LSD post-hoc test. Differences between T0 and T1 were considered stastistically significant at p ≤ 0.05. RESULTS: When enamel samples were measured over a black background, ΔE00 values (T0-T1) varied from 2.2 (SD 0.7) for amine fluoride-based product/water to 53.9 (SD 7.6) for amine fluoride-based-product/red wine. When dentin samples were measured over a black background, ΔE00 values (T0-T1) varied from 5.4 (SD 0.9) stannous chloride based product/water to 61.6 (SD 3.7) amine fluoride-based product/red wine. CONCLUSION: Specifically, the application of the sodium monofluorophosphate was able to statistically significantly (p ≤ 0.05) reduce discolouration induced by the staining solutions tested only on the enamel-dentin complex, while distilled water and the stannous fluoride-based product were able to statistically significantly (p ≤ 0.05) reduce discolouration induced by the staining solutions tested in pure dentin samples.

Is it still worthwhile to perform quarterly cd4+ t lymphocyte cell counts on hiv-1 infected stable patients?

BACKGROUND: In the last 20 years routine T CD4+ lymphocyte (CD4+) cell count has proved to be a key factor to determine the stage of HIV infection and start or discontinue of prophylaxis for opportunistic infections. However, several studies recently showed that in stable patients on cART a quarterly CD4+ cell count monitoring results in limited (or null) clinical relevance. The research is intended to investigate whether performing quarterly CD4+ cell counts in stable HIV-1 patients is still recommendable and to provide a forecast of the cost saving that could be achieved by reducing CD4+ monitoring in such a category of patients. METHODS: The study is based on data referring to all HIV-infected patients > 18 years of age being treated at two large infectious diseases units located in the metropolitan area of Genoa, Italy. The probability of CD4+ cell counts dropping below a threshold value set at 350 cells/mm3 is assessed using confidence intervals and Kaplan-Meier survival estimates, whereas multivariate Cox analysis and logistic regression are implemented in order to identify factors associated with CD4+ cell count falls below 350 cells/mm3. RESULTS: Statistical analysis reveals that among stable patients the probability of maintaining CD4+ >350 cell/mm3 is more than 98%. Econometric models indicate that HCV co-infection and HIV-RNA values >50 copies/mL in previous examinations are associated with CD4+ falls below 350 cells/mm3. Moreover, results suggest that the cost saving that could be obtained by reducing CD4+ examinations ranges from 33 to 67%. CONCLUSIONS: Empirical findings shows that patients defined as stable at enrollment are highly unlikely to experience a CD4+ value <350 cell/mm3 in the space/arc of a year. The research supports a recommendation for annual CD4+ monitoring in stable HIV-1 patients.

The influence of stratification on color and appearance of resin composites.

The aim of this in vitro study was to determine the influence of the order of composite layers' stratification on resin composites color and appearance when restoring an anterior composite tooth on the 3D color coordinates L*a*b* by use of a spectrophotometer. A total of 192 discs samples made of two different commercial available composite materials (Miris 2 and HRI) of enamel (E) and dentin (D) shade, each with a 1 mm thickness, were divided into 6 configurations. The superposition of 4 samples for a total of 16 specimens per group determined the investigated configurations. All groups showed significant (p < 0.05) differences between them except groups E1DDE and EDDE1 which represent the same order of stratification, measured from the buccal side and from the palatal side. Perceptible differences were detected between all groups except for E1DDE, EDDE1 and EDDD, independent of the background (white or black). The realization of the palatal layer with dentin composite shade did not change the final outcome within the limit of a total 4 mm thickness in comparison to the palatal layer with enamel composite shade.

Silorane, ormocer, methacrylate and compomer long-term staining susceptibility using ΔE and ΔE 00 colour-difference formulas.

The aim of this study was to evaluate the staining susceptibility of a silorane (Filtek Silorane), an ormocer (Ceram X Duo), a methacrylate (Tetric EvoCeram) and a compomer (Dyract) exposed on the long term to various staining agents by using ΔE and ΔE 00 colour-difference formulas. Thirty-six disc-shaped specimens were made of each of the four chemically different materials, randomly divided in six groups (n = 6) and immersed in five staining solutions (red wine, juice, coke, tea and coffee) or stored dry (control) in an incubator at 37 °C for 99 days. Spectrophotometric measurements by means of a spectrophotometer (Spectroshade Handy Dental, MHT) were repeated over a white (L* = 92.6, a* = -1.2, b* = 2.9) and black (L* = 1.6, a* = 1.2, b* = -1.0) background made of plasticized paper, in order to determine the colour changes according to ΔE, ΔE 00 and translucency formulas. Statistical analysis was performed by means of factorial Anova, Fisher's LSD test (post hoc) and a Spearman rank correlation between ΔE and ΔE 00. When analysed over a white background, mean ΔE 00 values were highly significantly different and varied from 0.8 (Ceram X Duo/air) to 20.9 (Ceram X Duo/red wine). When analysed over a black background, mean ΔE 00 values were highly significantly different and varied from 1.0 (Ceram X Duo and Tetric/air) to 25.2 (Ceram X Duo/red wine). Differences in translucency varied from 0.3 (Ceram X Duo/air) to 21.1 (Ceram X Duo/juice). The correlation between ΔE and ΔE 00 over a white background was 0.9928, while over a black background, it was 0.9886.

Influence of background on natural tooth colour coordinates: an in vivo evaluation.

The aim of this study was to evaluate the influence of different backgrounds on spectrophotometric colour values of natural teeth. Twenty volunteers (10 males and 10 females) with a mean age of 25 years and 9 months (±3 years and 2 months) were each subjected to 4 spectrophotometric measurements of their upper right central incisor. Each sample was measured with alternatively black, 50% grey, white or no background (positive control). ΔE medians ranged from 0.9 to 5.9. All artificial backgrounds presented significant differences (p < 0.05) when compared to values obtained without any background. No significant differences were observed between black and 50% grey background (p > 0.05). If an artificial background needs to be used, as for example when performing in vitro studies, preference should be given to a black background as it approaches best the clinical situation (i.e. no background). Even if no statistically significant differences were found when compared with the grey background, the black background should be preferred due to its lower ΔE medians, standard deviation as well as lower minimum and maximum values.

An in-vitro study on effects of laser activation on dye penetration in human root dentin.

Objective: To evaluate the penetration of a dye in root dentin after activation with different laser wavelengths. Materials: Palatal roots of 38 human molars were enlarged and disinfected. Irrigation activation was performed with an Er:YAG laser: @50 mJ, 15 Hz (Er:YAG); a 9.3 µm CO2 laser: @40% power (CO2); diode lasers 455 nm/970 nm: @0.8 W, 15 Hz (D455, D970) and 808/980 nm: @1 W (D808, D980) and compared to positive control: etching with 35% H3PO4 (POS); negative control: water (NEG) and conventional needle irrigation: NaOCl and ethylenediaminetetraacetic acid (EDTA) (CONV). Methylene blue solution was introduced in the canal and laser-activated or left untouched for 100 s before the roots were dried and cut into horizontal slices. Dye penetration was automatically calculated by color recognition of two samples per root third (n = 8 per group in each coronal, middle and apical root thirds). The presence and absence of a smear layer was checked in two additional samples of the negative and positive control under scanning electron microscopy (SEM). Results: Full-depth infiltration was not achieved in any group. Dye penetration in CONV was significantly less than in Er:YAG, CO2, POS, D455, D970, D808 and similar to NEG and D980 when results of different root thirds were pooled. Conclusion: Laser activation using certain parameters enhanced dye penetration compared to conventional needle irrigation with NaOCl and EDTA (CONV).

Comparison of Class II Bulk-Fill, Self-Adhesive Composites, Alkasite, and High-Viscosity Glass Ionomer Restorations in Terms of Marginal and Internal Adaptation.

(1) Background: Restoring decayed teeth in young patients can be challenging. This calls for a simplification of the protocols through new biomaterials. Therefore, the aim of this study was to compare the marginal adaptation delivered by restorative materials applied on class II cavities by using a simplified protocol, before and after fatigue test, followed by the assessment of the internal adaptation. (2) Methods: Forty-eight human teeth were divided into six groups (n = 8). Dentinal fluid simulation was performed before restoring the class II cavities: Gr 1-adhesive (Clearfil Universal Bond Quick) and nanohybrid flowable composite (Clearfil Majesty ES Super Low Flow), Gr 2-adhesive (Clearfil Universal Bond Quick) and nanohybrid composite (Clearfil Majesty ES standard), Gr 3-bulk fill self-adhesive composite (Surefil One), Gr 4-bioactive powder-liquid filling material (Cention Forte), Gr 5-universal adhesive (Adhese Universal) and nanohybrid composite resin (Tetric Powerfill); and control group (CT)-high-viscosity glass ionomer (Equia Forte). Marginal adaptation was observed with scanning electron microscopy (SEM) and compared before and after a fatigue test consisting of repeated thermal and mechanical cycles. The specimens were then cut mesio-distally, and internal adaptation was undertaken using SEM again. Repeated measures and one way ANOVA followed by a Fisher's LSD test and Fisher's LSD post hoc test were used in order to compare the statistically significant differences among groups. (3) Results: As for the marginal adaptation after loading, Cention Forte (58%) and Equia Forte HT (53%) were statistically equivalent and presented the highest results, followed by Clearfil Majesty ES Standard (32%) and Tetric Powerfill (27%), with Surefil One (8%) and Clearfil Majesty ES Flow Super Low (7%) showing the worst results. In terms of internal adaptation, Cention Forte (85%) and Clearfil Majesty ES Standard (74%) had the highest percentages of continuous margins. Tetric powerfill (56%) and Equia Forte HT (44%) showed statistically significantly lower results, followed by Clearfil Majesty ES Flow Super Low (33%) and eventually Surefil One (17%). (4) Conclusions: This in vitro study showed promising results for the marginal and internal adaptation of alkasite dual cured Cention Forte in the restoration of class II cavities. This material could be considered an interesting restorative alternative for the restoration of deciduous teeth.

An in vitro study on the influence of laser-activated irrigation on infiltration and leakage of a dual curing-resin cement as an endodontic sealer.

Objectives: The study aims to investigate the effects of laser-activated irrigation on infiltration and microleakage of a dual-curing resin cement applied as a root canal sealer. Methods: Thirty-eight extracted upper molars were attributed to four experimental groups. Roots were mechanically enlarged and disinfected (NaOCl). Control samples (n = 11) were irrigated with conventional needles and three different lasers were used to activate the irrigant in the other groups (n = 9): 2.94 µm Er:YAG laser, 9,300 µm CO2 laser and 808 nm diode laser with a modified black coated laser tip. Final irrigation was performed in each group with ethylenediaminetetraacetic acid (EDTA), sodium hypochlorite (NaOCl) and sodium chloride (NaCl) activated with lasers and in the control without activation.Dentin tubules were then labeled with a red fluorophore (Rhodamine B) and the root canals were sealed with a dual-curing resin cement (Paracore). The cement fixed the dye on the sealed and infiltrated dentin parts. To remove the Rhodamine not fixed by the cement, roots were then sectioned horizontally and immersed in hydrogen peroxide (H2O2). The empty dentin tubules spaces were then labeled with a green fluorophore (Fluorescein) allowing the visualization of infiltration and microleakage by confocal microscopy. Results: Percentages of infiltration were significantly higher in the middle root third of the control and Er:YAG laser-activated samples compared to CO2 or diode laser groups. Microleakage was present in all experimental groups but significantly less after CO2 laser activation. Conclusion: Laser-activated irrigation impacted resin cement infiltration and microleakage dependent on the applied wavelength. Er:YAG laser activation led to higher values of infiltration and microleakage compared to CO2 and diode lasers.

In Vitro Evaluation of Tooth-Whitening Potential of Peroxide-Free OTC Dental Bleaching Agents.

Purpose: To evaluate and compare the tooth-whitening potential of five over-the-counter (OTC), peroxide-free dental bleaching methods as well as an experimental tooth-whitening solution containing 0.1% hydrogen peroxide complexed with doping agents with a gold standard (positive control) containing 16% carbamide peroxide. Material and Methods: Eighty permanent bovine incisor teeth were randomly allocated to eight different groups. Two teeth from each group were immerged into five staining solutions represented by coffee, tea, red wine, and curry mixed in warm oil or distilled water (control group) and stored at 37 °C for 28 days in an incubator. The teeth were then reallocated to the eight groups, resulting in ten samples per group, and each group was matched with a bleaching product. The bleaching procedures were executed following the manufacturer's recommendations. The color of each sample was assessed over a white and black background using a quantitative numerical measurement approach with a calibrated spectrophotometer. Spectrophotometric measurements were performed after exposing the teeth to the bleaching agent for 60 min (T2), 100 min (T3), and 200 min (T4), and ΔE00 was calculated. Results: When analyzed over a white background, the mean ΔE00 values ranged from 2.14 (placebo) to 6.32 (Opalescence PF). When analyzed over a black background, the mean ΔE00 values ranged from 2.31 (placebo) to 5.78 (Opalescence PF). Statistically significant ΔE00 color changes over time for the eight groups and five staining solutions at T1 and T4 were assessed for both backgrounds using repeated ANOVA followed by Fisher's LSD post hoc test (p-value < 0.01). Conclusions: All tested over-the-counter whitening kits except one exhibited positive color variation. However, the individual performance differed vastly from one brand to the other, and the overall performance was less effective compared to the conventional carbamide-peroxide-based positive control.

Marginal Adaptation of In Vitro Class II Restorations Made Out of Bulk or Conventional Composite Using Single- or Multi-Layered Techniques.

Objective: Testing the influence of various restorative materials (conventional or bulkfill composites) and filling techniques (single- or multi-layered techniques) on the in vitro marginal adaptation of large class II direct composites with supra and sub-gingival margins subjected to thermomechanical loading (TML). Methods: A total of 40 prepared teeth were attributed randomly to five experimental groups. In Group 1, restorations were made of multi-layered high-viscosity conventional composite (Tetric EvoCeram); in Groups 2 and 3, restorations were made of a high viscosity bulkfill composite (Tetric EvoCeram Bulk Fill) applied in one (Group 2) or three layers (Group 3); in Groups 4 and 5, restorations were made of a flowable bulkfill composite (SDR flow) applied in one (Group 4) or two layers (Group 5), covered with a layer of high-viscosity conventional composite (Ceram-X Universal). A single adhesive (OptiBond FL) was used in all groups. All specimens were submitted to a staged TML comprising three phases (2 × 500,000 and 1,000,000 cycles) at 50 N with 3350 thermal cycles (5 to 55 °C) every 500,000 cycles. The tooth-restoration interfaces on proximal surfaces were evaluated quantitatively by scanning electron microscopy, before and after each TML phase, hence at three timepoints (T0, T1, T2 and T3). The following segments were considered for evaluation: proximal, vertical enamel margins (assessed individually on both restoration sides), cervical enamel (restoration side above CEJ) and cervical dentin margin (restoration side below the CEJ). Results: TML induced a significant reduction in continuous adaptation at both enamel and dentin margins in all groups, with percentages of continuous margins ranging from 75.2 to 91.8% at T0, and decreasing to values ranging from 21.3 to 73.9% at T3. Both composite systems and layering protocols had a significant influence on marginal adaptation of the restorations, with statistical associations depending on the restoration group and the timepoint considered. Defective margins in enamel were all of a cohesive nature with micro-fractures, while in dentin, interfacial gaps were the main defect observed. Conclusions/Clinical significance: The present results highlighted significant degradation of marginal adaption after long-term in vitro fatigue test using materials even with high-viscosity conventional resin composites, applied with a proper layering approach in medium-large sub-gingival cavities. While no significant differences were observed at the dentin cervical margins, there was a tendency for better adaptation at the enamel margin when using a higher modulus material with a multi-layered technique.

Evaluating the use of self-conditioning adhesive combined with dual curing resin cement as an endodontic sealer: An in vitro study.

Objectives: To compare infiltration, sealing and microleakage in root dentin with a self-conditioning adhesive system combined with dual curing resin (resin-based cement) to a conventional epoxy-resin-based sealer using confocal microscopy imaging. Methods: 26 roots were enlarged and disinfected. Dentin tubules of 24 teeth were labelled with a red fluorophore (Rhodamine B) (two samples served as controls). Root canal samples were sealed in group AH (n = 11) with a conventional sealer (AH Plus Root Canal Sealer, Dentsply DeTrey) and in group RC (n = 11) with a resin-based cement (Parabond combined with Paracore, Coltène). Roots were then sectioned horizontally and immersed in H2O2 to remove the Rhodamine B not fixed by the sealers. The empty dentin spaces were labeled with a green fluorophore (Fluorescein) enabling the evaluation of infiltration as well as microleakage by confocal microscopy. Two additional samples were fractured in vertical direction for observation under SEM. Results: Group RC presented significantly more infiltration in the middle third than in the middle and apical thirds of group AH. Microleakage was significantly higher in group AH than in group RC. SEM images revealed more dentin plugs and a homogenous resin layer in group RC in contrast to group AH. Conclusion: The resin-based cement revealed promising outcomes compared to a traditional epoxy resin based sealer.

Infiltration and microleakage in infiltrated and sealed root dentin samples are higher in middle than apical root thirds. Root dentin infiltration and sealing with a self-conditioning adhesive system and a dual-curing resin cement revealed less microleakage than with an epoxy-resin-based sealer.