Comparative study of extracellular recording methods for analysis of afferent sensory information: Empirical modeling, data analysis and interpretation

BACKGROUND

Physiological studies of sensorial systems often require the acquisition and processing of data extracted from their multiple components to evaluate how the neural information changes in relation to the environment changes. In this work, a comparative study about methodological aspects of two electrophysiological approaches is described.

NEW METHOD

Extracellular recordings from deep vibrissal nerves were obtained by using a customized microelectrode Utah array during passive mechanical stimulation of rat´s whiskers. These recordings were compared with those obtained with bipolar electrodes. We also propose here a simplified empirical model of the electrophysiological activity obtained from a bundle of myelinated nerve fibers.

RESULTS

The peripheral activity of the vibrissal system was characterized through the temporal and spectral features obtained with both recording methods. The empirical model not only allows the correlation between anatomical structures and functional features, but also allows to predict changes in the CAPs morphology when the arrangement and the geometry of the electrodes changes.

COMPARISON WITH EXISTING METHOD(S)

This study compares two extracellular recording methods based on analysis techniques, empirical modeling and data processing of vibrissal sensory information.

CONCLUSIONS

This comparative study reveals a close relationship between the electrophysiological techniques and the processing methods necessary to extract sensory information. This relationship is the result of maximizing the extraction of information from recordings of sensory activity.

Effectiveness of Dental Bleaching With 37.5% and 6% Hydrogen Peroxide and Its Effect on Quality of Life

Objective:

This study investigated whether it is possible to achieve equally satisfactory results between 37.5% hydrogen peroxide (HP) gel and 6% HP gel. We also assessed the psychosocial impact and self-perception of esthetics generated by extracoronal tooth whitening.

Methods and Materials:

A prospective, double-blind, randomized clinical trial was carried out. A total of 33 patients were selected from the clinic of the Faculty of Dentistry at the University of Chile. The patients included men and women over 18 years old without prior tooth whitening treatments, tooth decay, or restorations of the maxillary anterior teeth. The patients had tooth colors of A3 or less according to the Vita Classical scale, which was determined with a Vita Easy Shade spectrophotometer. The study was carried out with a “split-mouth” design. One side of each mouth was randomly treated with 37.5% HP, and the other side was bleached with 6% HP. Each group received 3 to 12 minutes of treatment with the respective gel applications. Two sessions of bleaching were carried out each week. A spectrophotometer was used to measure the total variation of color (ΔE), and a subjective evaluation was made with Vita Classical scale (ΔSGU) between the baseline (session 1) and different measurement times. We compared ΔE and ΔSGU for both agents using the Mann-Whitney test (α=0.05).

Results:

In both groups, there was variation among the initial color and the color in the different measurement times. In the month after the treatment was completed, ΔE was 9.06 in the 37.5% HP group and 5.69 in the 6% HP group. The difference between the two groups was statistically significant starting in the second session (p=0.000).

Conclusion:

There was a significant difference between the effectiveness of the bleaching gel concentrations of 37.5% and 6% HP according to spectrophotometer measurements and subjective evaluations. There was also a positive effect on psychosocial impact and esthetic self-perception among patients.

Modification of Crystal Violet – Sulfite Ion Equilibrium Induced by Sds Micelles

The presence of sodium dodecylsulfate micelles was found to displace the equilibrium between crystal violet and sulfite ion in the direction of the former and lead to complete recovery of the dye. The underlying mechanism for this anomalous behaviour was elucidated and the rate of the reversal process determined.

Anthropogenic nutrient inputs in the NW Iberian Peninsula estuaries determined by nitrogen and carbon isotopic signatures of Zostera noltei seagrass meadows

Coastal watersheds of the NW Iberian Peninsula have undergone increases in population densities and urbanization over the past decades. However, the effect of altered nutrient inputs to estuarine Zostera noltei ecosystems associated to these anthropogenic pressures remains largely unknown. Eleven Zostera noltei meadows located in the NW Iberian Peninsula were studied to assess the relationship between the anthropogenic pressure over coastal watersheds and the nitrogen and carbon isotopic signatures of Z. noltei meadows. Anthropogenic pressure on the watersheds was estimated from human population data and land cover classes. Carbon and nitrogen stable isotopic analyses were performed on Z. noltei leaves and in the sediments surrounding the rhizospheres. Our results indicate that the N and C isotopic signatures of Z. noltei meadows from the NW Iberian Peninsula reflect the impact of anthropogenic pressures. Nevertheless, these relationships are complex due to several processes acting simultaneously altering the expected isotopic responses.

Epidemiological changes of acute/recent human immunodeficiency virus type 1 infection in Barcelona, Spain (1997-2015): a prospective cohort study

OBJECTIVE

To describe the epidemiology of acute/recent human immunodeficiency virus (HIV) infection over two decades in Barcelona (Spain).

METHODS

Prospective, single-centre cohort including all patients with an acute/recent HIV infection (<180 days) since 1997. Patients were stratified into four periods. Phylogenetic analysis was performed to determine clusters of transmission.

RESULTS

A total of 346 consecutive acute/recently infected patients were included. The annual proportion of recent infections among total new HIV diagnoses increased over time from 1% (29 out of 1964) to 8% (112 out of 1474) (p <0.001). Proportion of men who have sex with men (MSM) in the cohort increased from 62% (18 out of 29) to 89% (100 out of 112) (p <0.001). The proportion of migrants showed a non-significant increasing trend (24% (7 of 29) to 40% (45 of 112)) likewise the non-B subtype (0% to 22% (22 of 112)). The mean time from infection to diagnosis was 53.6 days (interquartile range (IQR) 50-57), comparable among all periods. Mean time from infection to treatment decreased over the years from 575 (IQR 467-683) to 471 (IQR 394-549) days (p <0.001) without significant differences between migrants and non-migrants (133 (IQR 71-411) versus 208 (IQR 90-523) days p 0.089). Almost 50% (152 of 311) of recently infected individuals were included in a cluster of transmission, and 92% (137 of 149) of them were MSM.

CONCLUSION

The MSM population has progressively grown within acutely/recently infected patients in Barcelona, and is frequently involved in transmission clusters. Although the time between diagnosis and treatment has been reduced, the time between infection and diagnosis still needs to be shortened.

Color Regression and Maintenance Effect of Intracoronal Whitening on the Quality of Life: RCT-A One-year Follow-up Study

OBJECTIVE:

This randomized clinical study evaluated two parameters: 1) the clinical color rebound of whitening patients' tooth discoloration using the walking bleaching technique and 2) the impact on psychological and aesthetic self-perception at the one-year follow-up of patients who underwent bleaching of nonvital teeth.

METHODS AND MATERIALS:

Fifty study participants with nonvital tooth discoloration were recruited. Teeth were assigned randomly into one of two groups: 1) 35% hydrogen peroxide (n=25) and 2) 37% carbamide peroxide (n=25). Intracoronal bleaching was carried out over the course of four sessions using the walking bleach technique. Tooth color was evaluated after each session in order to measure the total color variation (ΔE). The guide was arranged from highest (B1) to lowest values (C4) for evaluating color, and color changes using Vita Classical Shade (ΔSGUs) units were calculated. Subjective and objective assessments were compared with the counterpart of the tooth. Aesthetic perception and psychosocial factors were evaluated before and after treatment by the Oral Health Impact Profile (OHIP) and Psychological Impact of Dental Impact Questionnaire (PIDAQ) surveys.

RESULTS:

Color changes (ΔE) were 15.48 ± 5.17 and 14.02 ± 4.85 for carbamide and hydrogen peroxide groups, respectively. There were no significant differences ( p>0.05) between these two groups at the one-year follow-up. There was a decrease in the PIDAQ scores after treatment compared to baseline values ( p<0.05). The majority of OHIP values regressed to baseline values.

CONCLUSION:

The technique of walking bleaching was highly effective and showed minimal color rebound in nonvital teeth and had a positive effect on patients' psychological impact at the one-year follow-up.

Does the Use of a "Walking Bleaching" Technique Increase Bone Resorption Markers?

OBJECTIVE

This randomized clinical trial evaluated the effect of 35% hydrogen peroxide in comparison with 37% carbamide peroxide in a nonvital bleaching technique of "walking bleaching" (four sessions of treatment) on periodontal markers: nuclear factor kappa B-ligand (RANK-L-process of root resorption marker) and interleukin 1β (IL-1β-inflammatory response marker).

METHODS AND MATERIALS

Fifty volunteers presenting with discoloration of nonvital teeth and endodontic treatment in good condition participated. Fifty teeth were randomly divided into two study groups according to bleaching gel: HP = 35% hydrogen peroxide (n=25) and 37% carbamide peroxide (n=25). Nonvital bleaching was performed with a walking bleaching technique consisting of four sessions of bleach application. Gingival crevicular fluid samples were taken in order to quantify the RANK-L and IL-1β levels by enzyme-linked immunosorbent assay. Samples were obtained from six periodontal sites for each bleached tooth: three vestibular and three palatine (mesial, middle, and distal) at seven time periods: baseline, after each of the four sessions of nonvital bleaching, at one week, and at one month after nonvital bleaching. Tooth color variations were analyzed in each session by VITA Bleachedguide 3D-MASTER (ΔSGU).

RESULTS

Significant increments in the RANK-L and IL-1β levels were detected in each evaluated time compared with baseline ( p<0.05); however, no differences were detected between hydrogen peroxide and carbamide peroxide on increments of the biomarkers studied. The change of color was effective for both nonvital bleaching therapies ( p<0.05).

CONCLUSIONS

Nonvital bleaching induced a significant increment in the RANK-L and IL-1β levels in periodontal tissues around bleached, nonvital teeth.

Prevalence of Second-Hand Smoke Exposure After Introduction of the Italian Smoking Ban: The Florence and Belluno Survey

Aims and Background

A law banning smoking in enclosed public places was implemented in Italy on January 10, 2005. The aim of this paper is to present a cross-sectional survey on two representative samples of non-smokers of two Italian towns (Florence and Belluno), conducted one year after the introduction of the ban, in order to assess prevalence of second-hand smoke exposure, to record the attitudes towards the ban, and the perception about its compliance in a representative sample of non-smokers.

Methods

Computer-assisted telephone interviews were carried out in March 2006, from a random sample of households from telephone registries. Respondents were 402 non-smokers from Belluno and 1,073 from Florence.

Results

About 12% of Florentines and 7% of Belluno respondents were exposed at home; 39% and 19%, respectively, at work; 10% and 5% in hospitality venues; 20% and 10% in cars. The smoke-free law was almost universally supported (about 98%) even if a smaller proportion of people (about 90%) had the perception that the ban was observed.

Conclusions

Second-hand smoke exposure at home and in hospitality premises has dropped to ≤10%, whereas exposure at work remained higher. These results suggest the need for more controls in workplaces other than hospitality venues.

Metacarpophalangeal portal safety. An anatomical study

AIM

To quantify the risk of dorsal innervation injury when performing direct metacarpophalangeal joint portals of the second to fifth fingers.

MATERIAL AND METHOD

An anatomical study of 11 upper limbs of fresh corpses was carried out. After placing them in a traction tower, the metacarpophalangeal portals were developed on both sides of the extensor tendon. The dorsal sensory branches were dissected and the distances between the portal and the nearest nerve were measured by a digital caliper. The portals of all the fingers were compared globally to assess the safest finger and two to two radial and ulnar portals were compared in each of the fingers to assess the safest portal within each finger.

RESULTS

The overall comparison of all portals and fingers showed that the third finger is the safest in any of its portals, while the ulnar side of the second and radial of the fourth are the portals with the highest risk of nerve injury (P=8.96·10^-5). Comparing two to two of the radial and ulnar portals in each of the fingers showed that the ulnar portal is safer than the radial on the fourth finger (P=.042), while the radial is safer than the ulnar on the fifth finger (P=.003).

CONCLUSIONS

The third finger was the safest to perform metacarpophalangeal portals, while the ulnar side of the second finger and radial side of the fourth had the highest risk of nerve injury.

Effectiveness and Impact of the Walking Bleach Technique on Esthetic Self-perception and Psychosocial Factors: A Randomized Double-blind Clinical Trial

OBJECTIVE

This trial evaluates the impact of psychosocial and esthetic self-perceptions of patients undergoing nonvital tooth bleaching using the walking bleach technique. We also assessed the clinical effectiveness of bleaching tooth discoloration.

METHODS

Fifty volunteers with nonvital tooth discoloration were enrolled. Teeth were randomized into two groups: 35% hydrogen peroxide (n=25) and 37% carbamide peroxide (n=25). Intracoronal bleaching was performed over four sessions using the walking bleach technique. Tooth color was evaluated at each session to measure total color variation. The shade guide was arranged from highest (B1) to lowest (C4) values to assess the color and calculate the color change in the number of shade guide units. Subjective and objective assessments were compared with the tooth counterpart. Esthetic self-perception and psychosocial factors were assessed before and after treatment.

RESULTS

Color change was 15.48<5.17 for hydrogen peroxide and 14.02<4.85 for carbamide peroxide. There was no significant difference at any time point (p>0.05) except at sessions 3 and 4 (p<0.05). Overall, whitened teeth values were similar to those of counterpart teeth (p>0.05). There was a decrease in Oral Health Impact Profile and Psychosocial Impact of Dental Esthetics questionnaire scores after treatment compared with baseline (p<0.05).

CONCLUSION

The walking bleach technique was highly effective on nonvital teeth and had a positive effect on self-esthetic perception and psychological impact for the patients.

Factors associated with implementation of the 5A's smoking cessation model

Background

Several health organizations have adopted the 5A’s brief intervention model (Ask, Advise, Assess, Assist, Arrange), based on evidence-based guidelines for smoking cessation. We examine individual, cognitive, behavioral, and organizational factors associated with the 5A’s performance among clinical healthcare workers in Catalonia. We also investigate how these factors interact and potentially predict the implementation of each component of the 5A’s.

Methods

A cross-sectional survey was conducted among clinical health workers enrolled in an online smoking cessation training course (n = 580). The survey included questions about individual characteristics as well as cognitive, behavioral, and organizational factors previously identified in research. We assessed self-reported performance of the 5A’s, assessed on a scale from 0 to 10, and used Multivariate regression to examine factors associated with its performance.

Results

The performance means (standard deviation) were moderate for the first 3A’s [Ask: 6.4 (3.1); Advise: 7.1 (2.7); Assess: 6.3 (2.8)] and low for the last 2A’s [Assist: 4.4 (2.9); Arrange: 3.2 (3.3)]. We observed a high correlation between Assist and Arrange (r = 0.704, p < 0.001). Having positive experiences and feeling competent were positively associated with performing the 5A’s model and having organizational support with Assist and Arrange. Personal tobacco use among healthcare workers was negatively associated with Advice and Arrange.

Conclusions

Our study found that clinical healthcare workers do not perform the 5A’s completely. The main barriers identified suggest the need of training and making available practical guidelines in healthcare services. Organizational support is essential for moving towards the implementation of Assist and Arrange.

Electronic supplementary material

The online version of this article (10.1186/s12971-017-0146-7) contains supplementary material, which is available to authorized users.

Effects of At-home Bleaching in Smokers: 30-month Follow-up

Objective:

This clinical study evaluated the color longevity after 30 months of at-home bleaching with 10% carbamide peroxide (CP) in smokers and nonsmokers.

Methods:

Sixty patients, 30 smokers and 30 nonsmokers, were subjected to bleaching with 10% CP (Whiteness Perfect–FGM) for three hours daily for three weeks. The color was measured at baseline and at one month and 30 months after the completion of dental bleaching using the shade guide Vita classical organized by value (ΔSGU) and the shade guide Vita Bleachedguide 3D-MASTER. At the 30-month recall, the color was assessed before and after dental prophylaxis. Data from color evaluation were analyzed by two-way repeated-measures analysis of variance and Tukey test for the contrast of means (α=0.05).

Results:

Twenty-one smokers and 22 nonsmokers attended the 30 month recall. For both shade guides, only the main factor of assessment time was statistically significant (p&lt;0.001). Effective whitening was observed in both groups at the baseline, which was stable at one month. However, color rebound was observed after 30 months for both groups of participants when color was measured before and after dental prophylaxis.

Conclusion:

Thirty months after at-home bleaching with 10% CP gel, dental darkening was detected in both groups, which cannot be solely attributed to stains caused by extrinsic staining from daily food, drinks, and smoke (in smokers).

12 Years of Repair of Amalgam and Composite Resins: A Clinical Study

OBJECTIVE

The objective of this study was to clinically evaluate repaired posterior amalgam and composite restorations over a 12 year period, investigate the influence of repair in the survival of restorations, and compare their behavior with respect to controls.

METHODS

Thirty-four patients, 18 to 80 years of age with 167 restorations, 67 composite resin (RC), and 100 amalgam (AM) restorations, participated. Restorations with localized, marginal, anatomical deficiencies and/or secondary caries, and "clinically judged" suitable for repair or replacement according to US Public Health Service (USPHS) criteria, were randomly assigned to four groups: repair (n=35, 20 AM, 15 RC), replacement (n=43, 21 AM, 22 RC), positive control (n=71, 49 AM, 22 RC), or negative control (n=18, 10 AM, 8 RC). The quality of the restorations was blind scored according to the modified USPHS criteria. Two examiners scored them at initial status (κ=0.74) and after one to five, 10, and 12 years (κ=0.88). Wilcoxon and Mann-Whitney tests provided for comparisons within the same group and between years, respectively.

RESULTS

After 12 years, all groups behaved similarly in marginal adaptation, marginal stain, teeth sensitivity, anatomic form, and luster ( p≥0.05). Better behavior in roughness was observed in replaced RC ( p=0.049).

CONCLUSIONS

Given that most clinical parameters investigated were similar between all groups during the follow-up, the repair of RC and AM restorations is a good clinical option because it is minimally invasive and can consistently increase the longevity of restorations.

Effect of Refurbishing Amalgam and Resin Composite Restorations After 12 Years: Controlled Clinical Trial

OBJECTIVES

The aim of this study was to clinically evaluate posterior amalgam and resin composite restorations refurbished over a period of 12 years by investigating the influence of refurbishing on the survival of restorations and comparing their behaviors with respect to controls.

METHODS AND MATERIALS

Thirty-four patients were enrolled, ages 18 to 80 years, with 174 restorations, 48 restorations of resin composite (RC), and 126 restorations of amalgam (AM). Restorations with localized defects in anatomy, roughness, luster, or marginal staining that were clinically judged as suitable for refurbishing according to US Public Health Service (USPHS) Ryge criteria were assigned to group A-refurbishing (n=85; 67 AM, 18 RC)-or group B-control (n=89; 59 AM, 30 RC); the quality of the restorations was evaluated blindly according to the modified USPHS criteria. Two observers conducted evaluations at the initial state (k=0.74) and after one to five, 10, and 12 years (k=0.88). Wilcoxon, Friedman, and Mantel-Cox tests were performed to compare the groups, respectively.

RESULTS

After 12 years, both groups experienced a similar decline, except for an evidently better performance in marginal adaptation in RC control (p=0.043) and in anatomy in AM refurbished (p=0.032).

CONCLUSIONS

After 12 years, no difference was found in the clinical condition and longevity of the refurbished restorations compared to the control group.

Comparison of Effectiveness and Sensitivity Using Two In-Office Bleaching Protocols for a 6% Hydrogen Peroxide Gel in a Randomized Clinical Trial

Objective:

The aim of this blinded and randomized clinical trial was to compare two application protocols (one 36-minute application vs three 12-minute applications). We then assessed the effectiveness of the bleaching and any increase in sensitivity that was induced by bleaching via a split-mouth design.

Methods and Materials:

Thirty patients were treated. One group had a half arch of teeth treated with a traditional application protocol (group A: 3 × 12 minutes for two sessions). The other received an abbreviated protocol (group B: 1 × 36 minutes over two sessions). Two sessions were appointed with a two-day interval between them. The tooth color was registered at each session, as well as one week and one month after completing the treatment via a spectrophotometer. This measured L*, a*, and b*. This was also evaluated subjectively using the VITA classical A1-D4 guide and VITA Bleachedguide 3D-MASTER. Tooth sensitivity was registered according to the visual analogue scale (VAS) scale. Tooth color variation and sensitivity were compared between groups.

Results:

Both treatments changed tooth color vs baseline. The ΔE* = 5.71 ± 2.62 in group A, and ΔE* = 4.93 ± 2.09 in group B one month after completing the bleaching (p=0.20). No statistical differences were seen via subjective evaluations. There were no differences in tooth sensitivity between the groups. The absolute risk of sensitivity reported for both groups was 6.25% (p=0.298). The intensity by VAS was mild (p=1.00).

Conclusions:

We used hydrogen peroxide (6%) that was light activated with a hybrid LED/laser and two different protocols (one 36-minute application vs three 12-minute applications each for two sessions). These approaches were equally effective. There were no differences in absolute risk of sensitivity; both groups reported mild sensitivity.

Spanish experience on the design of radon surveys based on the use of geogenic information

One of the requirements of the recently approved EU-BSS (European Basic Safety Standards Directive, EURATOM, 2013) is the design and implementation of national radon action plans in the member states (Annex XVIII). Such plans require radon surveys. The analysis of indoor radon data is supported by the existing knowledge about geogenic radiation. With this aim, we used the terrestrial gamma dose rate data from the MARNA project. In addition, we considered other criterion regarding the surface of Spain, population, permeability of rocks, uranium and radium contain in soils because currently no data are available related to soil radon gas concentration and permeability in Spain. Given that, a Spanish radon map was produced which will be part of the European Indoor Radon Map and a component of the European Atlas of Natural Radiation. The map indicates geographical areas with high probability of finding high indoor radon concentrations. This information will support legislation regarding prevention of radon entry both in dwellings and workplaces. In addition, the map will serve as a tool for the development of strategies at all levels: individual dwellings, local, regional and national administration.

Design and properties of 3D scaffolds for bone tissue engineering

In this study, the Voronoi tessellation method has been used to design novel bone like three dimension (3D) porous scaffolds. The Voronoi method has been processed with computer design software to obtain 3D virtual isotropic porous interconnected models, exactly matching the main histomorphometric indices of trabecular bone (trabecular thickness, trabecular separation, trabecular number, bone volume to total volume ratio, bone surface to bone volume ratio, etc.). These bone like models have been further computed for mechanical (elastic modulus) and fluid mass transport (permeability) properties. The results show that the final properties of the scaffolds can be controlled during their microstructure and histomorphometric initial design stage. It is also shown that final properties can be tuned during the design stage to exactly match those of trabecular natural bone. Moreover, identical total porosity models can be designed with quite different specific bone surface area and thus, this specific microstructural feature can be used to favour cell adhesion, migration and, ultimately, new bone apposition (i.e. osteoconduction). Once the virtual models are fully characterized and optimized, these can be easily 3D printed by additive manufacturing and/or stereolitography technologies.

STATEMENT OF SIGNIFICANCE

The significance of this article goes far beyond the specific objectives on which it is focussed. In fact, it shows, in a guided way, the entire novel process that can be followed to design graded porous implants, whatever its external shape and geometry, but internally tuned to the exact histomorphometric indices needed to match natural human tissues microstructures and, consequently, their mechanical and fluid properties, among others. The significance is even more relevant nowadays thanks to the available new computing and design software that is easily linked to the 3D printing new technologies. It is this transversality, at the frontier of different disciplines, the main characteristic that gives this article a high scientific impact and interest to a broaden audience.

Note: Effects of Oak Wood on the Aromatic Composition of Vitis vinifera L. var. treixadura Wines

Treixadura wines from the 1998 vintage were obtained from traditional vinification in a winery. After alcoholic fermentation, the wine was subjected to ageing in oak barrels for three months. One part of the wine is placed in barrels of American oak and the other part in French oak (Allier oak). Wine stored simultaneously in a stainless steel tank was used as a control. Chemical composition and volatile compounds of wines were analysed. There were no appreciable differences in alcohol and tartaric acid among the wines stored under different conditions, but differences were observed in pH, total and volatile acidity, reducing sugars, malic and lactic acids. Ageing in oak barrels resulted in an increase in volatile acidity and Folin—Ciocalteu index, and a decrease of free and total sulphur dioxide. Various monoterpenes, norisoprenoids, hexenols, sulphurs, volatile phenols, acetals and lactones increase their content notably when aged in barrels of both American and French oak. On the other hand, some acetates, ethyl esters and fatty acids were present in higher concentrations in the wine stored in stainless steel tank. Sensory results indicated that the wine aged in French (Allier) oak was better scored than when aged in American oak, as it provided subtle and delicate nuances of wood, which did not mask the fruity aroma of the Treixadura wine but contributed to its aromatic complexity.

Longevity, Esthetic Perception, and Psychosocial Impact of Teeth Bleaching by Low (6%) Hydrogen Peroxide Concentration for In-office Treatment: A Randomized Clinical Trial

OBJECTIVE

The aim was to evaluate the color longevity after nine months of in-office bleaching with gel (6% hydrogen peroxide), to compare this to a control concentration of 35% in a split-mouth study model, and to assess the dental confidence and psychosocial impact on patients.

METHODS AND MATERIALS

Twenty-seven patients were assessed at the nine-month recall. The bleaching procedure with 6% or 35% hydrogen peroxide gel was performed randomly in the upper hemi-arch of each patient. The color was measured at baseline and at one week, one month, and nine months after the procedure, using the Vita Easyshade spectrophotometer, the Vita classical shade guide organized by value, and Vita Bleach Guide 3DMaster. Moreover, two surveys, OHIP-Esthetics and PIDAQ, were used to assess the esthetic self-perception and psychosocial impact of the bleaching procedure. During the nine-month recall, the color was assessed before and after dental prophylaxis.

RESULTS

Twenty-seven patients participated in the nine-month recall. There was a significant difference in ΔE between the two groups at all times assessed (p<0.011). The ΔL, Δa, and Δb showed a difference between the two groups at all times assessed (p<0.038), except for ΔL from the baseline vs nine-month after prophylaxis value (p>0.20). There was no significant difference in ΔSGU at all times (p>0.05). There was a significant difference in OHIP-Esthetics and PIDAQ sums compared with baseline scores (p<0.03).

CONCLUSION

The two compounds remained effective at nine months, with a slight rebound of color, and maintained their objective color difference but not the subjective color difference. Patients were satisfied with the bleaching procedure, and this had a positive impact on esthetic perception and a positive psychosocial impact at the nine-month recall.