Potential Crown Discoloration Induced by the Combination of Various Intracanal Medicaments and Scaffolds Applied in Regenerative Endodontic Therapy.

BACKGROUND: Regenerative endodontics involves the use of various root canal medicaments and scaffolds, which may cause crown discoloration. AIM: This study aimed to investigate the combined crown discoloration of scaffolds [platelet-rich fibrin (PRF) and blood clot] applied after administration of different medicaments [modified triple antibiotic paste including doxycycline (mTAPd), modified double antibiotic paste (mDAP), calcium hydroxide (CH), and propolis]. METHODS: In total, 100 human mandibular premolar teeth were selected and prepared. The teeth were apically resected to simulate immature teeth. The positive and negative control groups (n = 10) consisted solely of blood-only and serum-only samples. The remaining 80 teeth were used for the experimental groups with four different medicaments. Three weeks later, either blood or PRF was applied as a scaffold after removing the medicaments (n = 10). Color changes were assessed before medication placement and at the end of the first, second, and third weeks, as well as on days 0, 1, 30, 60, and 90 after scaffold application. Analysis was carried out using repeated measures of variance, Friedman, one-way ANOVA, Kruskal-Wallis, the dependent paired t-test, and Wilcoxon test. RESULTS: Statistical significance was determined at P = 0.05. All groups including blood and the group including propolis and PRF combination, resulted in a significant increase in discoloration (P < 0.05) and discoloration exceeding clinically acceptable thresholds. CONCLUSIONS: CH and the modified versions of TAP (mTAPd) and DAP (mDAP) demonstrated an acceptable level of discoloration when used with a combination of PRF at day 90.

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.

Crown discoloration promoted by materials used in regenerative endodontic procedures and effect of dental bleaching: spectrophotometric analysis.

OBJECTIVES: To assess tooth crown's color after intracanal treatment with triple antibiotic paste (TAP) or calcium hydroxide (CH); cervical sealing with glass ionomer cement (GIC) or mineral trioxide aggregate (MTA); and bleaching with carbamide peroxide. MATERIAL AND METHODS: After pulp removal and color spectrophotometer measurement, 50 bovine incisors were divided into 4 experimental groups and one control (untreated). Experiments were performed in phases (Ph). Ph1: TAP (ciprofloxacin, metronidazole, minocycline), TAPM (ciprofloxacin, metronidazole, amoxicillin), DAP (ciprofloxacin, metronidazole), or CH treatment groups. After 1 and 3 days (d); 1, 2, 3 weeks (w); and 1, 2, 3 and 4 months (m), color was measured and medications were removed. Ph2: GIC or MTA cervical sealing, each using half of the specimens from each group. Color was assessed after 1d, 3d; 1w, 2w, 3w; 1m and 2m. Ph3: Two bleaching sessions, each followed by color measurement. Data were analyzed with ANOVA and post-hoc Holm-Sidak method. RESULTS: Ph1: Specimens of TAP group presented higher color alteration (ΔE) mean than those of TAPM group. No significant difference was found among TAP or TAPM and CH, DAP or Control groups. Ph2: cervical sealing materials showed no influence on color alteration. Ph3: Different ΔE means (from different groups), prior to bleaching, became equivalent after one bleaching session. CONCLUSIONS: TAP induces higher color alteration than TAPM; color alteration increases over time; cervical sealing material has no influence on color alteration; and, dental bleaching was able to recover, at least partially, the tooth crown's color.

Crown discoloration promoted by materials used in regenerative endodontic procedures and effect of dental bleaching: spectrophotometric analysis

Abstract Regenerative endodontic procedure (REP) has been proposed as a new approach to treat immature permanent teeth. However, materials used in REP for root canal disinfection or cervical sealing may induce tooth discoloration. Objectives To assess tooth crown’s color after intracanal treatment with triple antibiotic paste (TAP) or calcium hydroxide (CH); cervical sealing with glass ionomer cement (GIC) or mineral trioxide aggregate (MTA); and bleaching with carbamide peroxide. Material and Methods After pulp removal and color spectrophotometer measurement, 50 bovine incisors were divided into 4 experimental groups and one control (untreated). Experiments were performed in phases (Ph). Ph1: TAP (ciprofloxacin, metronidazole, minocycline), TAPM (ciprofloxacin, metronidazole, amoxicillin), DAP (ciprofloxacin, metronidazole), or CH treatment groups. After 1 and 3 days (d); 1, 2, 3 weeks (w); and 1, 2, 3 and 4 months (m), color was measured and medications were removed. Ph2: GIC or MTA cervical sealing, each using half of the specimens from each group. Color was assessed after 1d, 3d; 1w, 2w, 3w; 1m and 2m. Ph3: Two bleaching sessions, each followed by color measurement. Data were analyzed with ANOVA and post-hoc Holm-Sidak method. Results Ph1: Specimens of TAP group presented higher color alteration (ΔE) mean than those of TAPM group. No significant difference was found among TAP or TAPM and CH, DAP or Control groups. Ph2: cervical sealing materials showed no influence on color alteration. Ph3: Different ΔE means (from different groups), prior to bleaching, became equivalent after one bleaching session. Conclusions TAP induces higher color alteration than TAPM; color alteration increases over time; cervical sealing material has no influence on color alteration; and, dental bleaching was able to recover, at least partially, the tooth crown’s color.

Pit and fissure sealants or fluoride varnishes?

Despite the general advances in dental care, dental caries is still a global health problem affecting many children. Occlusal surfaces of first permanent molars are the most susceptible sites in the developing permanent dentition. Dentists should use sealants or fluoride varnish - as well as other means - to limit the onset of tooth decay. Application of sealants is a recommended procedure to prevent or control caries. Sealing occlusal surfaces of newly erupted permanent molars in children and teenagers delays caries onset up to 48 months compared with unsealed teeth. However longer follow-ups shows a reduction of the preventive effect [Tikhonova et al., 2015]. A review of 2013 pointed out how sealants are effective in high risk children, however information about the benefits of sealing in other conditions is still scant [Ahovuo-Saloranta et al., 2013]. Fluoride varnishes are frequently used to prevent early childhood caries and reduce caries increment in very young children [Weintraub et al., 2006] and in the most vulnerable populations, where the prevalence of caries is higher and specialist visits are occasional [Chu et al., 2010]. Many studies have reported the effectiveness of different types and forms of fluoride agents in preventing dental caries among children and adolescents [Divaris et al., 2013]. A review clarifies that professional application of a 5% sodium fluoride varnish leads to remineralisation of early enamel caries in children. Solutions of 38% silver diamine fluoride are effective in arresting active dentine caries [Gao et al., 2016]. The last systematic review [Ahovuo-Saloranta et al., 2016], comparing pit and fissure sealants with fluoride varnishes explains that the pooled estimate slightly favours resin sealants over fluoride varnishes at two years. At four and nine years, the only comparative study (with high drop-out rates) found more caries on fluoride-varnished occlusal surfaces than on resin-sealed surfaces. There is evidence suggesting the superiority of resin-based fissure sealants over fluoride varnishes for prevention of occlusal caries in permanent molars, however it is not relevant. Eventually, Ahovuo-Saloranta et al. state that current data do not allow to draw definitive conclusions on whether to apply sealants or fluoride varnishes on occlusal surfaces of permanent molars [2016]. We will publish your opinion and experiences related to this topic in the next EJPD issue: join the discussion and write a letter to the editor!

Is pit and fissure sealing of buccal surfaces useful in reducing incidence of caries of first permanent molars?

AIM: The aim of the study was to establish whether caries prevalence on the buccal surfaces of first lower permanent molars (FLPMs) can be compared to those on the occlusal surfaces in order to justify the utility of extending pit and fissure sealing also to the extra-occlusal surfaces. MATERIALS AND METHODS: Design: an observational study was carried out in the children population (n=779) aged ≤14 years (mean age 7.68, SD 3.53) that presented at the Paediatric Dentistry Department of the University of Perugia. In the study were included 460 patients, and absolute frequency (number) of FLMP occlusal and buccal caries, together with their ratio and their difference in percentage, were recorded and analysed. Moreover, FLMP buccal caries variation related to age, sex and parent's nationality were calculated. RESULTS: Among the 460 children included (243 males) aged 5-14 years, 103 erupted FLPMs were analysed. Of their decayed surfaces (n=115), the occlusal surfaces were 62 (53.9%) and the buccal surfaces 53 (46.1%); the absolute frequency ratio was 1.17 and the percentage difference was 7.8%. The female gender was significantly related to buccal caries of FLPMs [OR = 2.66 (95% CI; 1.27-5.59; p=0.0096)] as was the age ranging between 10-14 years [OR = 2.73 (95% CI; 1.36-5.50; p =0.004)]. The parents nationality was not significantly related to buccal caries [Odds Ratio =1.47 (95% CI; 0.70-3.06; p = 09040)]. CONCLUSIONS: The similar caries susceptibility of buccal and occlusal surfaces of FLPMs stimulates further comparative studies about the usefulness of extending pit and fissure sealing to the buccal surfaces in addition to the occlusal prophylactic intervention, particularly with regard to the female sex and during the early eruption stages of these teeth.

An application of microscopic investigation on extracted premolar with dyschromia, related to the components of endodontic sealer.

The aim of this study was an assessment of the overall optical characteristics changes in volume of the dentin, after the diffusion of the chemical components included in the sealer throughout the endodontic space, in order to demonstrate the discoloration effect of the endodontic sealer on tooth crown of a recently extracted maxillary premolar. Thin sections were studied using the polarized transmitted light microscopy and under a stereomicroscope, operating in transmitted light and reflected light. There were performed serial images of magnitude 40×. Each image was covered by a grid aimed for microscopic sections volumetric measurements. Therefore, all the serial images were merged and resulted a global image of the entire section surface. Thus, we have analyzed a total of three sections of the same tooth. Based on these sets of images, there were made estimations of the areas affected by colorations, determinations that can be extrapolated to total tooth areas, in terms of volumetric color change of dentin. The proportion of low coloristic infiltrated dentin was very close to the deeply impregnated dentin and the overall impregnated dentin covered half of the total dentin analyzed area.

Comprehensive analyses of how tubule occlusion and advanced glycation end-products diminish strength of aged dentin.

In clinical dentistry, since fracture is a major cause of tooth loss, better understanding of mechanical properties of teeth structures is important. Dentin, the major hard tissue of teeth, has similar composition to bone. In this study, we investigated the mechanical properties of human dentin not only in terms of mineral density but also using structural and quality parameters as recently accepted in evaluating bone strength. Aged crown and root dentin (age ≥ 40) exhibited significantly lower flexural strength and toughness than young dentin (age < 40). Aged dentin, in which the dentinal tubules were occluded with calcified material, recorded the highest mineral density; but showed significantly lower flexural strength than young dentin. Dentin with strong alignment of the c-axis in hydroxyapatite exhibited high fracture strength, possibly because the aligned apatite along the collagen fibrils may reinforce the intertubular dentin. Aged dentin, showing a high advanced glycation end-products (AGEs) level in its collagen, recorded low flexural strength. We first comprehensively identified significant factors, which affected the inferior mechanical properties of aged dentin. The low mechanical strength of aged dentin is caused by the high mineral density resulting from occlusion of dentinal tubules and accumulation of AGEs in dentin collagen.

Effects of bleaching on laser Doppler blood-flow signals recorded from human teeth in vitro.

OBJECTIVE: To determine if bleaching a tooth affects significantly laser Doppler recordings of pulpal blood flow that are made through the treated enamel and dentine. DESIGN: Recordings of blood flow (flux) were made with a laser-Doppler flow meter from the crowns of 14, recently extracted, human premolars while diluted blood was pumped at three different rates through a cannula that was inserted into the pulp cavity with its tip in the coronal pulp chamber. The recordings of flux were made before and after bleaching the crown with 38% hydrogen peroxide for 30min. The colour changes produced by bleaching were also measured with a digital spectrophotometer in 15 teeth. The effects of bleaching on both blood flow recordings and tooth colour were studied in 11 of the teeth. RESULTS: Both before and after bleaching, there was a linear relationship between blood perfusion rate and flux. After bleaching, the flux readings increased by an average of 46%, and were significantly increased in every tooth (P<0.001, Wilcoxon Signed Rank Test). There was no significant correlation between the changes in flux and the changes in tooth colour. CONCLUSION: A laser Doppler flow meter cannot be used to determine the effect of bleaching on pulpal blood flow in intact teeth.

The investigation of non-invasive techniques for treating early approximal carious lesions: an in vivo study.

OBJECTIVES: The aim of this study was to examine non-cavitated approximal caries using non-invasive treatment methods. MATERIALS AND METHODS: Molar and premolar teeth with approximal caries were used in this in vivo study. Approximal caries lesions were evaluated with visual and radiographic inspection and with the DIAGNOdent device. Five groups were formed to study non-invasive treatment, and each had at least 25 early approximal carious lesions. Patients in the control group were not treated. After the separation, either ozone application, acidulated phosphate fluoride gel, CPP-ACP-containing material (Tooth Mousse), or an antibacterial bonding agent (Clearfil Protect Bond) was used. For 18 months after the non-invasive treatment, radiological controls were used to observe the progress of the initial and approximal caries in the 1st, 3rd, 6th and 12th months of follow-up. A Mann-Whitney U-test was used to perform the statistical analysis; in-group comparisons were made with the Wilcoxon signed-rank test, and a quantitative assessment was performed using a chi-squared test. RESULTS: At the end of 18 months, the caries lesions in the control group were observed to progress (P < 0.01). The lesions that were scored as 1a during a visual inspection recovered by using non-invasive treatments. CONCLUSION: Approximal caries lesions that were detected at the early stages remained stationary when using antibacterial agents and materials that promoted remineralisation. CLINICAL RELEVANCE: Antibacterial agents and remineralisation materials can be used in treatment of early approximal caries lesions.

Low-temperature atmospheric pressure plasma enhanced tooth whitening: the next-generation technology.

OBJECTIVES: To evaluate the safety and effectiveness of the plasma pencil (PP) device in conjunction with H2 O2 gel. The purpose of this study was to determine whether LTAPP delivered using the PP would enhance the tooth-whitening process while causing no thermal threat. METHODS: The study consisted of thirty extracted human teeth that were randomized into two groups: Group I received LTAPP plus 36% H2 O2 gel at 10, 15 and 20 min and Group II received 36% H2 O2 gel only at the same time intervals. Tooth surface temperature was measured periodically throughout the experiment using a non-contact thermometer. Digital photographs were taken pre- and post-treatment and transferred to Adobe Photoshop for comparison, using the CIELAB Color Value System. Only L* (lightness) values were evaluated in this study. Data were analysed using descriptive statistics and t-test at the 0.05 level. RESULTS: The results revealed a statistically significant difference in mean CIE L* values after exposure to LTAPP plus 36% H2 O2 gel, compared with 36% H2 O2 only, in the 10- and 20-min groups (P = 0.0003 and 0.0103, respectively). The temperature in both treatment groups remained under 80°F throughout the study, which is below the thermal threat for vital tooth bleaching. CONCLUSION: Utilizing PP device in conjunction with 36% H2 O2 safely accelerates and enhances the tooth-whitening process.

Evaluation of the colour change in enamel and dentine promoted by the interaction between 2% chlorhexidine and auxiliary chemical solutions.

To evaluate the colour change in enamel and dentine, promoted by interaction of 2% chlorhexidine gluconate (CHX) with 5.25% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA). Fragments containing enamel and dentine were obtained from the crowns of extracted bovine incisors. Before and after immersion of the samples in the substances, they were evaluated with reference to the colour of the enamel and dentine. The values obtained in numerical scores were subjected to statistical analysis using Wilcoxon test. A colour change in the enamel and dentine in groups treated with CHX gel + NaOCl and CHX gel + NaOCl + EDTA, and a change in colour only in the dentine in groups treated with CHX solution + NaOCl and CHX solution + NaOCl + EDTA. When used prior to NaOCl, CHX has the ability to induce a colour change in dental structures.

Using bearing area parameters to quantify early erosive tooth surface changes in enamel: a pilot study.

OBJECTIVES: Most in vitro studies investigate the erosive process using relatively simple roughness parameters such as roughness average (Ra). In isolation, Ra may misrepresent the surface features. Further, few studies report baseline surface characteristics after sample preparation. This study aimed to test the hypothesis that measuring the bearing area parameters in addition to Ra may be useful when qualifying the surface of enamel at baseline and after an erosive challenge. The null hypothesis for this study was that the bearing area parameters provide no more useful information than Ra alone, when qualifying the surface of enamel at baseline and after an erosive challenge. METHODS: Enamel slabs (n=20) were prepared from human (n=2) and bovine (n=4) incisor teeth and polished with 0.05µm paste. Roughness average (Ra) and bearing parameters (MR1, MR2, Rpk, Rk, Rvk) were used to record baseline characteristics. Specimens were subjected to erosion with 1% citric acid solution for 1min. Profilometric characteristics were recorded post-erosion, along with the maximum height changes within the profile. T-tests were carried out in order to compare baseline surface characteristics between tissue types. Post-erosion, analysis of variance (ANOVA) was used to test the effects of tissue type (bovine or human). RESULTS: There was no significant difference in Ra between human and bovine incisor enamel at baseline (human 0.11µm, bovine 0.12µm P>0.05), and no significant difference was observed post-erosion (human 0.23µm, bovine 0.20µm P>0.05). There were significant differences in bearing parameters at baseline and post-erosion that were not identified by the Ra measurement alone. CONCLUSIONS: The results suggest that if Ra alone is measured, important differences in surface characteristics may be missed. The null hypothesis is rejected, and the recommendation is made that bearing parameters are included within profile measurements in order to further triangulate the results of surface analysis studies. CLINICAL RELEVANCE: In isolation, Ra may misrepresent the surface features of a profile. These results have shown that the bearing parameters are an important and informative set of measurements. The recommendation is made that bearing parameters are included within profile measurements at baseline and post-erosion, in order to further triangulate the results of surface analysis studies.

Comparison of the bleaching efficacy of three different agents used for intracoronal bleaching of discolored primary teeth: an in vitro study.

UNLABELLED: Everyone wants whiter teeth to make them feel younger and to provide beautiful smiles with the accompanying increase in self-esteem. Bleaching is an established, simple, cost-effective and conservative method for improving the color of the discolored teeth. AIM: The aim of this in vitro study was to compare the bleaching efficacy of 10% carbamide peroxide, 10% hydrogen peroxide and 2g sodium perborate as bleaching agents on the artificially discolored human primary maxillary central incisors. MATERIALS AND METHODS: Forty extracted human primary central incisors with intact crowns were selected for the study. Pulpectomy was performed and each tooth was artificially stained with 2 ml of fresh human blood and centrifuged. --The teeth were randomly divided into four experimental groups of 10 teeth each and the baseline color evaluation was performed. 0.04 ml of the bleaching agent is syringed into the access cavity of the tooth and, in the control group, 0.04 ml of distilled water was syringed into the access cavity and it was sealed with IRM and placed at 37°C in an incubator throughout the experiment. The color of the bleached teeth was determined at 0, 7 and 14 days. The data obtained were analyzed using ANOVA and Turkey's test. RESULTS: There was statistical significance (P = 0.00) among the carbamide peroxide, sodium perborate, hydrogen peroxide and control groups after 7 and 14 days and a significance of P = 0.013 among the carbamide peroxide, sodium perborate and hydrogen peroxide after two bleaching sessions (day 14) was seen. CONCLUSIONS: The bleaching efficacy of 10% hydrogen peroxide gel was more effective than 10% carbamide peroxide and sodium perborate in bleaching the artificially discolored primary teeth.

Spectrophotometric analysis of crown discoloration induced by MTA- and ZnOE-based sealers.

UNLABELLED: Crown discoloration can be induced by root canal sealer remnants following root canal treatment. OBJECTIVE: The aim of this study was to evaluate chromatic alterations in human tooth crowns induced by a Mineral Trioxide Aggregate-based sealer (MTA Fillapex®) and a commonly used ZnOE-based sealer (Roth-811). The tested null hypothesis was that the application of the materials did not induce clinically perceptible crown discoloration (Ho: CIE color difference ΔE<3.7). MATERIAL AND METHODS: Forty five fully developed, intact, mandibular third molars were sectioned 1 mm below the cemento-enamel junction. The pulp chambers were chemomechanically debrided via the cervical access. The specimens were randomly assigned into three groups Group 1: MTA Fillapex, Group 2: Roth 811, Group 3: Negative control (unfilled) and immersed in individually marked vials containing distilled water up to the cervix (37±1°C). The spectral reflectance lines were recorded by utilizing a UV-VIS spectrophotometer equipped with integration sphere in the visual spectrum at baseline, 1 week, 1 and 3 months after material placement. Data were transformed into values of the CIE L*a*b* color system and the corresponding ΔE values were calculated. Statistical analysis was performed using two-way mixed ANOVA models, at p=0.05 level of significance. RESULTS: A statistically significant increase in a* and b* chromatic parameters of the MTA Fillapex Group was measured. However, ΔE values did not exceed the human eye perceptibility threshold (set at ΔE<3.7) during the experimental period (ΔEt3=2.88). In Roth-811 Group, a statistically significant decrease in L* and a statistically significant increase in a* and b* chromatic parameters was measured, during all observation periods. Resultant ΔE values exceeded the human eye perceptibility threshold after 1 week (ΔEt1=5.65). CONCLUSIONS: Application of MTA Fillapex in tooth crowns resulted in minimal color alterations, while Roth 811 induced severe discoloration, in vitro. It could be suggested that, in terms of aesthetics, the use of MTA Fillapex appears to be favorable.

The whitening effect of chlorine dioxide--an in vitro study.

OBJECTIVES: The aim of this study was to investigate the whitening properties and rate of bleaching action of chlorine dioxide and compare them with those of hydrogen peroxide of similar concentration. METHODS: Sixty bovine central incisor crowns were ground and polished until flat surfaces were obtained. The crowns were subjected to extensive staining cycles of artificial saliva, chlorehexidine and tea before being randomly assigned to three groups: chlorine dioxide (ClO2), hydrogen peroxide (H2O2) and deionised water (H2O). The crowns in each group were subjected to seven 2 min exposure cycles in addition to an extra 30 min cycle. CIE LAB spectrophotometric measurements were taken at baseline, after each 2 min, and each extended 30 min bleaching cycle. RESULTS: L* for ClO2 specimens was significantly higher only after the first 2 min cycle (p<0.001) while for H2O2 specimens, L* significantly increased after the first two cycles (p<0.001) and continued to increase, at a slower rate, until the end of the treatment cycles. ΔE was significantly greater within H2O2 than within ClO2 specimens (p<0.001). CONCLUSION: Chlorine dioxide whitens teeth at a faster rate than hydrogen peroxide. Specimens treated with chlorine dioxide were significantly lighter than those treated with hydrogen peroxide at the end of the first 2 min application cycle, however, extended exposures did not enhance color.

Hydrogen peroxide penetration into the pulp chamber and dental permeability after bleaching.

This study sought to quantify the concentration of hydrogen peroxide (HP) in the pulp chamber and evaluate changes on dental permeability after bleaching with 3 HP concentrations (10%, 35%, and 50%). This study was divided into 2 experiments and the bleaching treatments consisted of 3 applications of HP for 30 minutes during a single session. The first experiment tested HP penetration into the pulp chamber of 4 experimental groups (n = 10) of bovine crowns, which were divided by HP concentration: an unbleached control group (0% HP), 10% HP, 35% HP, and 50% HP. Acetate buffer solution was placed into the pulp chamber and after each application of HP. This solution was collected to determine spectrophotometrically the concentration of HP that reached the pulp chamber. The second experiment evaluated dental permeability. Bovine crowns were divided into 3 groups (n = 10). The crowns were connected to a permeability device and the initial permeability was measured at 10 psi. Three different concentrations of HP gels (10%, 35% and 50%) were applied to the buccal enamel surfaces and the dental permeability was measured after the first, second, and third applications of HP. The data were analyzed by 2-way ANOVA and Tukey test (P ≤ 0.05). All concentrations of HP reached the pulp chamber, although no significant differences were noted between the 3 concentrations tested (P > 0.05). However, the increase of dental permeability in the group that received 50% HP was significantly higher than the 10% HP group (P < 0.05). The results indicate that the HP bleaching treatments increased dental permeability.

Spectrophotometric analysis of crown discoloration induced by MTA- and ZnOE-based sealers

Crown discoloration can be induced by root canal sealer remnants following root canal treatment. Objective: The aim of this study was to evaluate chromatic alterations in human tooth crowns induced by a Mineral Trioxide Aggregate-based sealer (MTA Fillapex®) and a commonly used ZnOE-based sealer (Roth-811). The tested null hypothesis was that the application of the materials did not induce clinically perceptible crown discoloration (Ho: CIE color difference ΔE<3.7). Material and Methods: Forty five fully developed, intact, mandibular third molars were sectioned 1 mm below the cemento-enamel junction. The pulp chambers were chemomechanically debrided via the cervical access. The specimens were randomly assigned into three groups Group 1: MTA Fillapex, Group 2: Roth 811, Group 3: Negative control (unfilled) and immersed in individually marked vials containing distilled water up to the cervix (37±1°C). The spectral reflectance lines were recorded by utilizing a UV-VIS spectrophotometer equipped with integration sphere in the visual spectrum at baseline, 1 week, 1 and 3 months after material placement. Data were transformed into values of the CIE L*a*b* color system and the corresponding ΔE values were calculated. Statistical analysis was performed using two-way mixed ANOVA models, at p=0.05 level of significance. Results: A statistically significant increase in a* and b* chromatic parameters of the MTA Fillapex Group was measured. However, ΔE values did not exceed the human eye perceptibility threshold (set at ΔE<3.7) during the experimental period (ΔEt3=2.88). In Roth-811 Group, a statistically significant decrease in L* and a statistically significant increase in a* and b* chromatic parameters was measured, during all observation periods. Resultant ΔE values exceeded the human eye perceptibility threshold after 1 week (ΔEt1=5.65). Conclusions: Application of MTA Fillapex in tooth crowns resulted in minimal color alterations, while Roth 811 induced severe discoloration, in vitro. It could be suggested that, in terms of aesthetics, the use of MTA Fillapex appears to be favorable.

Coronal tooth discoloration and white mineral trioxide aggregate.

INTRODUCTION: This study assessed and characterized discoloration when white MTA (wMTA) was placed in the coronal aspect of the root canal ex vivo and the influence of red blood cells on this discoloration. METHODS: Canals were prepared from the apical aspect and restored with either wMTA + saline (n = 18), wMTA + blood (n = 18), or controls (n = 4 + 4) (blood or saline alone). Color was assessed according to the CIE L*a*b* color space using standardized digital photographs at 3 time points: baseline, day 1, and day 35. Statistical analysis was performed by using 1-way analysis of variance and a 2-sample t test with P < .05. RESULTS: All teeth discolored when restored with wMTA, which was most prominent in the cervical third of the crown. The presence of blood within the canal adjacent to the setting wMTA exacerbated the discoloration (P = .03). CONCLUSIONS: wMTA induces the gray discoloration of the tooth crown, and the effect is compounded in the presence of blood.

[The study on the influence of bovine enamel hardness measurement methods on the result evaluation].

The variation in hardness of enamel is a frequently used method to evaluate the influence of whiting materials on the enamel. The purpose of this study is to improve the veracity on the evaluation tests caused by the tooth itself with point selection method. Three kinds of testing point selection methods on enamel were carried out, i. e. random selection, grid measurement and symmetrical measurement, respectively. The selected points were used to measure the micro hardness by Vickers. The influence of the variation of tooth structure itself on the hardness measurements results can be reduced by using testing point selection methods of symmetry, and thus, the accuracy of the test method used in the evaluation of the influence of dental materials on tooth hardness will be guaranteed.