Effects of Time-Elapsed Bleaching on the Surface and Mechanical Properties of Dentin Substrate Using Hydrogen Peroxide-Free Nanohydroxyapatite Gel.

Introduction: There is a critical need to address concerns surrounding the potential impact of bleaching gels specifically on the tooth substrate. Therefore, this laboratory investigation aimed to assess the impact of a hydrogen peroxide (HP)-free bleaching (HiSmileTM) in comparison to an HP-based bleaching (Opalescence RegularTM) on the surface and mechanical characteristics of tooth substrate. Methods: Sixty sound human premolar teeth were sectioned to produce dentin fragments and divided into two primary groups based on the bleaching agent used. Each group was subdivided into three subgroups (n = 10) per distinct bleaching regimens: (T1) fragments underwent a 7-day immersion in distilled water at 37°C without any bleaching treatment, (T2) fragments underwent a 7-day immersion in distilled water at 37°C, with the application of bleaching gel occurring on the seventh day for 10 minutes, and (T3) fragments underwent a bleaching regimen for seven consecutive days, each session lasting for 10 minutes. The initial and final evaluations of surface roughness, nano-hardness, and elastic modulus were performed. Following the bleaching regimens of T3, a composite stub was fabricated on the dentin fragments for the shear bond strength (SBS) test. Statistical testing was accomplished using the analysis of variance (P < 0.05). Results: HP-based bleaching gel showed significant differences between measurement intervals in surface roughness, elastic modulus, and SBS parameters (P < 0.05). In contrast, HP-free bleaching gel showed insignificant differences within the group (P > 0.05). The SBS between dentin-composite was significantly affected with the use of HP-based bleaching gel, while HP-free bleaching gel showed insignificant difference between measurement intervals. The qualitative validation of the treatment's impact was further demonstrated using the scanning electron microscopy. Conclusion: The findings suggest that the bonding stability of composite restorations to dentin may be compromised after bleaching with an HP-based gel, whereas immediate bonding procedures can be safely conducted following the application of an HP-free bleaching gel.

The effect of final irrigation with different solutions on smear layer removal and dentin erosion: A scanning electron microscope study.

AIM: This study aimed to compare the effectiveness of initial irrigation with sodium hypochlorite (NaOCl) and final irrigation with QMix, 40% citric acid, and 17% ethylenediaminetetraacetic acid (EDTA) on smear layer removal and dentin erosion. METHODOLOGY: Forty extracted human mandibular premolar teeth were randomly divided into four groups (n = 10) according to the type of final irrigants used: 17% EDTA, QMix, citric acid, and control (normal saline). Canals were mechanically prepared using ProTaper Next instruments to an apical size of X3. Subsequently, the roots were sectioned in a buccolingual direction. Scanning electron microscopy (SEM) was used to assess the presence of the smear layer and the amount of dentin erosion in the coronal, middle, and apical thirds of the root canals. RESULTS: In regards to smear layer removal, there was a significant difference between the control group and the other tested groups. Moreover, it was significantly higher in the coronal and middle thirds than in the apical third. However, there were no significant differences between the groups of EDTA, QMix, and citric acid. Concerning dentin erosion, citric acid produced significantly more dentin erosion than the other tested groups. CONCLUSION: Final irrigation with solutions had a higher ability to remove the smear layer in the coronal and middle thirds compared to the apical third. Of all the solutions tested, 40% citric acid had the most pronounced impact on dentin erosion, followed by 17% EDTA and QMix.

Effects of Soft Tissue Closure on Medication-Related Osteonecrosis of the Jaw in a Rabbit Model with Tooth Extraction: A Pilot Study.

OBJECTIVES: The study investigated the effect of soft tissue closure after tooth extraction on the prevention of medication-related osteonecrosis of the jaw in a rabbit model. MATERIALS AND METHODS: Twenty female New Zealand white rabbits were randomly assigned into the experimental group administrated with zoledronic acid (ZA) and control groups treated with saline. Bilateral lower premolar extraction was performed 4 weeks after ZA/saline administration. Immediately after extraction, the wound on the right mandible was closed by suture while the other side was left open. Animals were sacrificed 4 weeks and 8 weeks after tooth extraction. Fluorochrome labeling solutions were injected subcutaneously to evaluate the bone growth rates. The mandibles were harvested and subjected for microcomputed tomography, confocal microscope, and histomorphological examinations. RESULTS: All extraction sites healed well without any signs of infection. Trabecular thickness (Tb.Th) was significantly higher in the ZA-treated group than in the control group at both week 4 and week 8, while no significant difference was detected in the rest of the assessed parameters. The bone growth rate in mandibles showed gradual reduction in the ZA-treated group. Histological analysis showed that at week 8, the animals in the ZA-treated group had significantly higher incidence of osteonecrosis than that in the control group, while no significance was revealed between the sutured and nonsutured side. CONCLUSIONS: ZA treatment significantly reduces bone growth rates but does not reveal a significant effect on bone mineral density and bone microarchitecture. Soft tissue closure of the extraction socket does not reduce the incidence of ONJ in the ZA-treated rabbit model.

Compromised dental cells viability following teeth-whitening exposure.

This study aimed to assess the viability of dental cells following time-dependent carbamide peroxide teeth-whitening treatments using an in-vitro dentin perfusion assay model. 30 teeth were exposed to 5% or 16% CP gel (4 h daily) for 2-weeks. The enamel organic content was measured with thermogravimetry. The time-dependent viability of human dental pulp stem cells (HDPSCs) and gingival fibroblast cells (HGFCs) following either indirect exposure to 3 commercially available concentrations of CP gel using an in-vitro dentin perfusion assay or direct exposure to 5% H2O2 were investigated by evaluating change in cell morphology and by hemocytometry. The 5% and 16% CP produced a significantly lower (p < 0.001) enamel protein content (by weight) when compared to the control. The organic content in enamel varied accordingly to the CP treatment: for the 16% and 5% CP treatment groups, a variation of 4.0% and 5.4%, respectively, was observed with no significant difference. The cell viability of HDPSCs decreased exponentially over time for all groups. Within the limitation of this in-vitro study, we conclude that even low concentrations of H2O2 and CP result in a deleterious change in enamel protein content and compromise the viability of HGFCs and HDPSCs. These effects should be observed in-vivo.

Zirconia implant abutments supporting single all-ceramic crowns in anterior and premolar regions: A six-year retrospective study.

BACKGROUND: Clinical studies regarding zirconia implant abutments reported good survival rates in the short-term observation period. The purpose of this study was to assess the six-year clinical performance of zirconia abutments supporting all-ceramic crowns in anterior and premolar regions. METHODS: The patients received zirconia implant abutments to support all-ceramic crowns in Chang-Gung Medical Center during the period August 2010 to August 2011 were enrolled. In the following six years of observation period after the implant-crown had finished, the clinical parameters of all of the included patients were registered on a special form. The records regarding the following variables: age, gender, implant location, the condition of edentulous site before implant placement, esthetic performance at baseline, presence or absence of technical complications, and biological outcomes were registered and scrutinized for evaluation. RESULTS: Out of the 32 zirconia implant abutments and 32 all-ceramic crowns that were followed for six years. Neither abutments nor crowns were lost, yielding 100% survival rates for both zirconia abutments and crowns. The esthetic outcomes were excellent except that a score of 2 was given to two restorations. With regard to technical complications, there was one instance of abutment screw loosening, two cases of veneering ceramic chipping, one restoration with occlusal roughness, and three instances of crowns loosening. Overall, the success rates were 96.8% and 81.2% for abutments and crowns respectively. In biological performance, only 1 implant was classified in group II (satisfactory survival) in the Misch classification, while all the others were classified in group I (excellent). CONCLUSIONS: Zirconia abutments supporting all-ceramic crowns demonstrated high survival rate, good biological and esthetic results. While some technical complications were frequently observed, the complication-free rates were 96.8% for abutments and 81.2% for crowns in the medium-term observation period.

Effects of Fluoride and Calcium Phosphate Materials on Remineralization of Mild and Severe White Spot Lesions.

Fixed orthodontic treatments often lead to enamel demineralization and cause white spot lesions (WSLs). The aim of this study was to evaluate the mineralization degree of 2 types of WSLs based on ICDAS index and compare the remineralizing efficacy of 3 oral hygiene practices after 1 month and 3 months. 80 mild demineralized and 80 severe demineralized enamel specimens were randomized into three treatments: fluoride toothpaste (FT), fluoride varnish plus fluoride toothpaste (FV+FT), and CPP-ACP plus fluoride toothpaste (CPP-ACP+FT). Microhardness tester, DIAGNODent Pen 2190, and scanning electron microscope were used to evaluate the changes of mineralization degree. Both qualitative and quantitative indicators suggested that the mild and severe white spot lesions were different in the degree of mineralization. Severe WSLs demineralized much more seriously than mild lesions even after 3 months of treatment. Despite the variation in severity, both lesions had the same variation trend after each measure was applied: FT had weak therapeutic effect, FV + FT and CPP-ACP + FT were effective for remineralization. Their remineralizing efficacy was similar after 1 month, and combined use of CPP-ACP plus F toothpaste was more effective after 3 months. In order to fight WSLs, early diagnosis was of great importance, and examination of the tooth surface after air-dry for 5 seconds was recommended. Also, when WSLs were found, added remineralizing treatments were required.

Qualitative analysis of smear layer treated with different etidronate concentrations: A scanning electron microscopy study.

The aim of this study was to examine the smear layer removal capacity of various etidronate treatments. Seventy-eight roots were instrumented up to apical size X4 and randomly divided into five treatment groups and a positive control group (n = 13). Groups were as follows: irrigation with 5 ml of sterile saline (control) for 3 min, 5 ml of 17% ethylenediaminetetraacetic acid (EDTA) for 3 min, 5 ml of 9% A1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 3 min, 5 ml of 18% HEBP for 3 min, irrigation with 5 ml of 1% sodium hypochlorite (NaOCl) + 9% HEBP for 3 min, and 5 ml of 2% NaOCl + 18% HEBP for 3 min. The roots were examined using a scanning electron microscope. The smear layer scores in the 2% NaOCl + 18% HEBP group were lower than those in the other treatment groups and the control group (p < .05). There were no significant differences among the treatment groups in the smear layer scores of the coronal and middle thirds. However, the smear layer scores in the 2% NaOCl + 18% HEBP treatment group were lower those in the 9% HEBP and 18% HEBP treatment groups in the apical third (p < .05). In the clinical setting, the recommended concentration of HEBP is 18%, and it should be used with an oxidizing agent to ensure optimum smear layer removal.

New generation bulk-fill resin composites: Effects on mechanical strength and fracture reliability.

PURPOSE: To investigate the mechanical performance and fracture reliability of new generation, bulk-fill resin composites of different viscosities. METHODS: Forty sound maxillary premolars were prepared into Class I cavities comprised of 5 mm width × 5 mm length × 5 mm thickness. The teeth were randomly allocated into four groups (n = 10) according to the restorative material: Negative control - without restoration; Positive control - conventional resin composite (Opallis; FGM) was applied using increments of up to 2.0 mm-thick; Bulk-Regular - bulk-fill resin composite of regular viscosity (Opus Bulk Fill; FGM) was applied using a single increment of 5 mm-thick; and Bulk-Flow - a low-viscosity bulk-fill resin composite (Opus Bulk Fill Flow; FGM) was applied as the first increment with ∼3.5 mm-thick, followed by two final increments of Opallis (∼1.5 mm-thick). The teeth were stored at 37 °C, for 24 h, and submitted to a mechanical testing machine (DL500; EMIC) under a compressive loading. Work of fracture (Wf) was also obtained. All data were analyzed using ANOVA and Tukey (α = 5%). Reliability of restorations and probability of failure were analyzed by Weibull analysis. RESULTS: The non-restored teeth showed the weakest behavior of the study. All the restored groups demonstrated similar mechanical properties to each other (p ≥ 0.242). The positive and negative controls failed exclusively within the cohesiveness of enamel/dentin, whereas the bulk-fill-based restorations showed a mixture of cohesive and mixed failures. The restored groups showed an overall similar reliability, although the Bulk-Regular group demonstrated greater characteristic strength than the positive control. CONCLUSION: The novel bulk-fill resin composites of low and regular viscosities show promising application in the restoration of Class I cavities in premolars, demonstrating similar mechanical performance and reliability as compared with restorations prepared using conventional resin composites. From the bulk-fill materials, the version with regular viscosity presented the greatest compliant behavior of the study.

Dentine tubule disinfection by different irrigation protocols.

The purpose of this study was to test the antimicrobial activity and the smear layer removal of different irrigation protocols-sodium hypochlorite (NaOCl), NaOCl followed by ethylenediaminetetraacetic acid (EDTA), and NaOCl combined with etidronic acid (HEBP)-against infected dentine tubules during root canal preparation. Single rooted premolars contaminated with Enterococcus faecalis were chemomechanically prepared. Depending on the irrigation protocols, the roots were divided into the following groups: (1) distilled water during and after instrumentation; (2) 2.5% NaOCl during and after instrumentation; (3) 2.5% NaOCl/9% HEBP during and after instrumentation; and (4) 2.5% NaOCl during instrumentation followed by 17% EDTA after instrumentation. The percentage of dead cells and the biovolume in infected dentine tubules were measured using confocal laser scanning microscopy and the live/dead technique. Smear layer removal on root canal wall surfaces was observed by means of scanning electron microscopy. Results were compared through parametric tests (p < .05). The groups NaOCl, NaOCl/HEBP, and NaOCl+EDTA exerted the highest antimicrobial activity (p > .05), followed by the group irrigated with water. All the irrigation protocols-including water-significantly reduced the bacteria biovolume. No dentine tubules free of smear layer were found in the positive control or the 2.5% NaOCl group. With NaOCl/HEBP and NaOCl+EDTA, respectively, 90.41% ± 7.33 and 76.54% ± 15.30 of dentine tubules were free of smear layer (p = .01). NaOCl/HEBP and NaOCl+EDTA exerted an important antimicrobial activity against bacteria inside dentine tubules, lowering the bacteria biovolume and eliminating a high amount of the smear layer, particularly in the NaOCl/HEBP group.

Effect of EDTA, sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis.

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)2 ], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH - 5.25% Ca(OCl)2 ; CHE - 5.25% Ca(OCl)2 + 17% EDTA; SH - 5.25% NaOCl; SHE - 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal-Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)2 and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.

The evaluation of the transport medium for extracted premolars prior to cryopreservation: an in vitro study.

Autotransplantation is a versatile technique for the replacement of a missing tooth and cryopreservation can expand its scope. The aim of this in vitro study is to compare the antimicrobial effect of different transport protocols on procured teeth prior to cryopreservation. Streptococcus oralis biofilms were grown on ten sterile premolars, incubated for 48 h and subjected to the following transport procedures: an untreated (contaminated) control group, a group rinsed with phosphate buffered saline (PBS), a group transported in PBS, a group transported in Dulbecco's Modified Eagle's medium (DMEM) supplemented with fetal calf serum (FCS), and a group transported in DMEM supplemented with FCS and antibiotics (AB). The effect of cryopreservation as such, as well as the combination with a transport medium (DMEM + FCS + AB) on the contamination was also tested. The surviving bacteria were harvested, and determined by plate counting. There was no significant reduction in contamination after rinsing the tooth, after transport in PBS or after transport in DMEM with FCS. Significant reductions were observed for transport in DMEM with AB when compared to the control group (p = 0.003). Cryopreservation as such reduced the biofilm significantly (p < 0.001). No cumulative effect could be found when transport in DMEM + FCS + AB was followed by cryopreservation. Within the limitations of this laboratory set-up, DMEM + FCS + AB was the most effective transport medium in S. oralis biofilm elimination. It could not be concluded that rinsing of the tooth gives an additional reduction. Cryopreservation as such decontaminated the teeth more effectively than any tested transport procedure.

A Novel Protein Testing Model to Assay the Efficacy of Multiple Irrigation Activation Techniques for Removal of Ex Vivo Biomolecular Film.

OBJECTIVE: This study aimed to compare the debris removal efficacies of irrigation activation techniques using ex vivo biomolecular film. MATERIALS AND METHODS: Root canals of 50 human mandibular premolars were prepared, and freshly prepared collagen solutions were applied into the root canals using a peristaltic pump. Specimens were randomly divided into the five groups and irrigated with 3 mL of 5.25% sodium hypochlorite (NaOCl): G1 (needle irrigation and control group): a 27-gauge notched-tip irrigation needle (Endo-Eze; Ultradent, South Jordan, UT); G2, Vibringe sonic irrigation system (VSS) (Vibringe B.V. Corp., Amsterdam, Netherlands); G3, EndoActivator sonic irrigation system (EA) (Dentsply Tulsa Dental Specialties, Tulsa, OK); G4, passive ultrasonic irrigation (PUI) (EMS, Nyon, Sweden); and G5, photon-induced photoacoustic streaming (PIPS) (Fotona, Ljubljana, Slovenia). Postirrigation solution was collected in beakers containing 3% sodium thiosulfate by which NaOCl solution was neutralized. Residual protein levels in NaOCl solution were evaluated by the Bradford method. Data were analyzed using ANOVA with Duncan post hoc tests (α = 0.05). RESULTS: PIPS (laser-activated irrigation) method removed more artificial collagen than other experimental groups (EA, PUI, VSS) or the control group (p ≤ 0.05). There were no statistical differences among the EA, PUI, and VSS groups. The PIPS, PUI, and EA groups were superior compared with the conventional irrigation (p ≤ 0.05); however, there were no significant differences between VSS and the conventional irrigation groups. CONCLUSIONS: Although all the methods and techniques examined in this study were suitable in extruding the ex vivo biomolecular film, the PIPS method was found significantly more effective than all the other tested groups (p ≤ 0.05).

3D-Image analysis of the impact of toothpaste abrasivity on the progression of simulated non-carious cervical lesions.

OBJECTIVES: To investigate the effect of toothpaste abrasive level on the progression of non-carious cervical lesions (NCCLs) using 3D-image subtraction. METHODS: Upper first premolars were allocated into seven groups (n = 16) of toothpaste/abrasive slurries: A-Zeodent113/5%, B-Zeodent124/10%, C-Zeodent103/15%, D-Sensodyne Pronamel, E-Crest Cavity-Protection, F-Crest Pro-Health-Whitening, and G-Deionized water (DIW). Teeth were mounted on acrylic blocks, and their root surfaces covered with acrylic resin, except for 2-mm near the cemento-enamel junction that was exposed to toothbrushing. Specimens were brushed with the slurries for 5000-, 15,000-, 35,000- and 65,000-strokes. Impressions were taken at baseline and after each brushing time, and then scanned by a 3D optical profilometer. Dentine volume loss was calculated by image subtraction software and subjected to mixed-model ANOVA and multiple comparison tests (α = 0.05). RESULTS: No significant differences among slurries were observed at 5000 and 15,000. At 35,000, F showed higher loss than all other groups except C, which did not differ from the others. At 65,000, F (4.19 ±â€¯3.29 mm3) showed the highest loss, followed by C (2.33 ±â€¯1.47 mm3), which differed from all the other groups except B (1.85 ±â€¯0.91 mm3). Groups B, A (1.35 ±â€¯0.65 mm3), D (1.17 ±â€¯0.48 mm3), E (1.40 ±â€¯0.68 mm3) and G (1.12 ±â€¯0.73 mm3) did not differ from each other. Groups F and C showed significant increase of volume loss starting at 35,000, while B, A, D and E only at 65,000; no increase loss was observed for G. CONCLUSIONS: 3D-image subtraction was able to quantify and differentiate tooth loss, but only at advanced stages. The progression of NCCLs was more evident and faster for highly abrasive slurries. CLINICAL SIGNIFICANCE: Upon root dentin exposure, brushing with lower abrasive dentifrices is advisable to reduce the risk for NCCLs development.

Tooth bleaching with low-temperature plasma lowers surface roughness and Streptococcus mutans adhesion.

AIM: To evaluate the structural-morphological changes in enamel surface roughness and Streptococcus mutans adhesion after tooth bleaching using plasma in combination with a low concentration of 15% carbamide peroxide (CP). METHODOLOGY: Sixty pairs of premolars were randomly assigned to the treatment groups (n = 30; buccal surface, groups 1A/2A) or controls (n = 30; palatal surface, Groups 1B/2B). Group 1A received a low concentration of 15% CP and low-temperature plasma. Premolars in group 1B were placed in phosphate-buffered saline and served as controls. The buccal surface of Groups 2A was subjected to 15% CP alone, whilst the palatal surface was subsequently immersed in PBS (group 2B). After bleaching, all teeth were soaked for 1 h in artificial saliva at 37 °C. Subsequently, teeth were placed in brain-heart infusion with S. mutans at 37 °C for 24 h. The assessment of the structural-morphological changes was carried out using a biofilm assay, scanning electron microscopy and atomic force microscopy. Statistical analysis of the data was performed with the SPSS (SPSS Inc., Version 18.0, Chicago, IL, USA). The Student's t-test was used to determine whether there was a significant difference in the structural-morphological effects with and without plasma. RESULTS: Significantly less S. mutans adhesion was observed in group 1A compared with the other groups (P < 0.05). Moreover, the surface roughness was significantly greater in group 2A compared with the other groups (P < 0.05). CONCLUSIONS: The application of plasma did not result in any structural-morphological and topographic changes in the enamel. The combined bleaching method using plasma and a low concentration of 15% CP was less destructive, particularly with respect to tooth surface changes.

Improvement of Total Etching Dentin Bonding with Subpressure.

This study aimed to investigate the effects of subpressure on the bond properties of total-etching adhesive to dentin. Thirty-six caries-free premolars were sectioned parallel to the occlusal plane and randomly divided into four groups (n = 9): a control group (C, no treatment) and three subpressure groups, which were treated under 0.8, 0.6 or 0.4 bar after applying adhesives, named S8, S6 and S4, respectively. Afterward, resin was bonded to the dentin surface, and 27 beams (1.0 mm × 1.0 mm) of each group were sectioned. One was selected to observe the bonding interface from each group by SEM. Each group was divided into two subgroups (n = 13): 24 hours of water storage (I) and 10,000 thermocycling (A). The microtensile bond strength (µTBS), failure modes and nanoleakage expression were evaluated. SEM results showed that the subpressure groups had longer and denser resin tags. The µTBS of the subpressure groups was higher than that of the control group (p < 0.05). The subpressure groups were dominated by mixed failure, whereas main interfacial failure appeared in group C. The subpressure groups showed less silver deposition than the control group (p < 0.05). The subpressure technique may remarkably improve bonding strength and decrease nanoleakage on total-etching bonding.

Omega-3 and Omega-6 Fatty Acids Act as Inhibitors of the Matrix Metalloproteinase-2 and Matrix Metalloproteinase-9 Activity.

Polyunsaturated fatty acids have been reported to play a protective role in a wide range of diseases characterized by an increased metalloproteinases (MMPs) activity. The recent finding that omega-3 and omega-6 fatty acids exert an anti-inflammatory effect in periodontal diseases has stimulated the present study, designed to determine whether such properties derive from a direct inhibitory action of these compounds on the activity of MMPs. To this issue, we investigated the effect exerted by omega-3 and omega-6 fatty acids on the activity of MMP-2 and MMP-9, two enzymes that actively participate to the destruction of the organic matrix of dentin following demineralization operated by bacteria acids. Data obtained (both in vitro and on ex-vivo teeth) reveal that omega-3 and omega-6 fatty acids inhibit the proteolytic activity of MMP-2 and MMP-9, two enzymes present in dentin. This observation is of interest since it assigns to these compounds a key role as MMPs inhibitors, and stimulates further study to better define their therapeutic potentialities in carious decay.

Efficacy of 10 percent Carbamide Peroxide as an Intracoronal Bleaching Agent in Nonvital Discolored Primary Teeth: An In Vitro Study.

PURPOSE: The purpose of this study was to evaluate, in vitro, the efficacy of 10 percent carbamide peroxide used as an intracoronal bleaching agent in blood-stained primary teeth. METHODS: Thirty extracted primary canines were stained using rabbit blood and randomly divided into two groups of 15 teeth each. Stained teeth in the test group were bleached intracoronally using 10 percent carbamide peroxide for 21 days. The bleaching agent was replaced at days seven and 14. The control group was not subjected to bleaching, and a cotton pellet damped with distilled water was placed in the pulp chamber. Shade alteration from the prestaining value was evaluated using a VITA Easyshade spectrophotometer at days zero, seven, 14, and 21. RESULTS: All specimens in the test group returned to the initial baseline shade, with no significant differences from the prestaining values (P=0.097). Teeth in the control group did not undergo any shade alteration after staining, with no significant differences noted from the prestaining values (P<0.001). CONCLUSIONS: Intracoronal bleaching using 10 percent carbamide peroxide is an effective approach for whitening discolored extracted primary teeth.

Spectrophotometric analysis of crown discoloration induced by two different sealers: An In vitro study.

CONTEXT: Endodontic materials have been assessed with regards to their potential for dental staining. AIMS: To evaluate the coronal discoloration effect of Apexit Plus and Resino Seal in mandibular premolars using spectrophotometer. SETTINGS AND DESIGN: The study design was original research. MATERIALS AND METHODS: Forty human single-rooted mandibular first premolar teeth were selected for the study. They were divided into four groups of ten specimens each. Group 1 - Apexit Plus sealer, Group 2 - Resino Seal sealer, Group 3 - positive control (Blood), and Group 4 - negative control (distilled water). Teeth were resected 3 mm below at cementoenamel junction. In all samples, access cavities were prepared, instrumented, and irrigated. Sealers were mixed and placed into the pulp chamber through cervical access and control groups were filled with blood and distilled water. Coronal orifices were sealed using self-cure glass ionomer cement. Samples were analyzed using spectrophotometer to determine the discoloration in each group at 10, 17, and 24 days interval. STATISTICAL ANALYSIS USED: Statistical analysis used Wilcoxon signed-rank test. RESULTS: All sealers used in the present study caused a progressive coronal discoloration over a time period of 17-24 days. There was statistically significant difference between resino seal sealer and apexit plus sealer , with resino seal showing greater coronal discoloration. CONCLUSION: Resino seal sealer has greater potential to cause discoloration of crown as compared to apexit plus sealer over a period of time.

Prevention of secondary caries using silver diamine fluoride treatment and casein phosphopeptide-amorphous calcium phosphate modified glass-ionomer cement.

OBJECTIVE: To study the effect of silver diamine fluoride (SDF) treatment and incorporating casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into a glass-ionomer cement (GIC) to prevent secondary caries. METHOD: A cervical cavity was prepared on 32 premolars for the following restoration groups: group 1, conventional GIC restoration; group 2, SDF (38%) treatment and conventional GIC restoration; group 3, CPP-ACP (3%) modified GIC; and group 4, SDF treatment and CPP-ACP modified GIC. The restored teeth were thermal-cycled before undergoing a multi-species cariogenic biofilm challenge. The restored teeth were examined by micro-computed tomography (micro-CT), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and Fourier transform infrared (FTIR) spectroscopy. Data were analyzed by two-way ANOVA. RESULTS: Micro-CT determined outer lesion depths for groups 1-4 were: 123±6µm, 87±7µm, 79±3µm and 68±5µm respectively. An interaction effect on the outer lesion depth was found between the restorative materials and SDF treatment (p<0.001). Both SDF treatment and modification with CPP-ACP had a significant effect on outer lesion depth (p<0.001). SEM/EDX showed an increase of calcium and phosphorus at the root dentine adjacent to the restoration in groups 3 and 4 (CPP-ACP modified GIC). FTIR revealed that SDF treatment and CPP-ACP modified GIC had a significant effect on amide I-to-hydrogen phosphate ratio on the material-root interface (p=0.001). CONCLUSION: SDF treatment and incorporation of CPP-ACP into GIC restorative material can prevent secondary root caries development. CLINICAL SIGNIFICANCE: The results provide useful information to dentists in formulating clinical management protocols and material when treating root caries.

Effect of application time of maleic acid on smear layer removal and mechanical properties of root canal dentin.

OBJECTIVES: To evaluate the effect of maleic acid (MA) on the cleaning efficacy and mechanical properties of root canal dentine with respect to different time exposure. MATERIALS AND METHODS: One hundred and eighty single-canal premolars were instrumented with rotary-files and then randomly assigned to test groups receiving 7% MA for 30 s, 45 s, 1 min, or 3 min or to control groups treated with 0.9% saline or 17% ethylenediaminetetraacetic acid for 45 s. The micro-hardness, nano-hardness and elastic modules were measured before and after treatment, while the amount of smear and erosion in the coronal, middle and apical thirds in root canal were evaluated by scanning electron microscopy, finally, the fracture strength was assessed by vertical root fracture testing. RESULTS: The efficacy of smear layer removal increased with increasing MA application time. The largest effect was observed at 45 s, even in the apical third, whereas the treatment for 1 min resulted in irreversible erosion of the dentine surface. The micro-hardness and nano-indentation testing confirmed that the micro- and nano-scale mechanical properties were significantly decreased after MA application for 1 min. Furthermore, the specimens treated with MA for 3 min presented the lowest fracture resistance among all groups. In contrast, the 45 s treatment appeared to increase the fracture resistance of the tooth. CONCLUSIONS: The cleaning efficacy and mechanical properties of root canal dentine varied with MA exposure time. The application of MA for 45 s was found to be the most promising for clinical use.