Effects of Bleaching Associated with Er:YAG and Nd:YAG Laser on Enamel Structure and Bacterial Biofilm Formation

Objective. To compare the effects of bleaching associated with Er:YAG and Nd:YAG laser on enamel structure and mixed biofilm formation on teeth surfaces. Materials and Methods. Sixty-eight enamel samples were randomly divided into four groups ( n = 17 ), control, Opalescence Boost only, Opalescence Boost plus Er: YAG laser, and Opalescence Boost plus Nd:YAG laser. The structure was observed using SEM after bleaching. Subsequently, the treated enamel samples were also cultured in suspensions of Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Fusobacterium nucleatum (Fn) for 24 and 48 h. Biofilm formation was quantified by crystal violet staining, and the structure was visualized by confocal laser scanning microscopy. The data were analyzed using the Kruskal-Wallis method. Results. The enamel structure significantly changed after bleaching. There was no obvious difference in the biofilm formation after 24 h; however, after 48 hours, the amount of biofilm increased significantly. Remarkably, the amount was significantly higher on enamel bleached only, however, there was no significant difference between samples bleached with Er:YAG or Nd:YAG laser compared to the control. Conclusions. Bleaching only appeared to markedly promote biofilm formation after 48 h, and the biofilms on samples bleached with Er:YAG or Nd:YAG laser did not change significantly, showing that bleaching with Er:YAG or Nd:YAG laser can be safely applied in clinical practice.

Variation in mechanical and structural properties of enamel in primate molars

Mechanical properties of enamel are known to vary across molar crowns in some primates, but the association of this variation with phylogeny, structural properties and tribological behaviour is not well understood. In this study, 20 molars from a range of primate taxa (n=15) were studied using nanoindentation, micro-CT scanning, and SEM imaging. After micro-CT scanning, teeth were sectioned in the lingual-buccal plane through the mesial cusps. Five positions (buccal lateral, buccal cuspal, occlusal middle, lingual cuspal, lingual lateral) were studied in three locations (inner, middle, outer enamel regions). The results show middle enamel had the highest hardness and elastic modulus values in all positions. 'Non-functional' molar sides (lingual in lower molars and buccal in upper molars) had higher hardness values than their 'functional' counterparts. Increase in prism size was associated with a decrease in hardness in some tooth positions, and mineral density showed a significant relationship with elastic modulus values. Variation in enamel structure variation (e.g., enamel Schmelzmuster, Hunter-Schreger band thickness), may also be crucial in explaining variation in mechanical properties, with decussation zones associated with higher mechanical properties values. Primate enamel is not a homogeneous material, with variation in mechanical and structural properties across the crown likely associated with functional differences and variation in force distribution. Overall structural and mechanical patterns were similar in the primate species studied despite substantial differences in diet, suggesting these properties are potentially evolutionary conserved.

Assessing the Mechanical Properties of 3D Printed Bio-Inspired Structures and Integrating Them Into a Product

The Honeycomb structure is one of the most common natural structures used in sandwich panel cores. The Enamel structure’s mechanical properties were compared to the Honeycomb structure’s mechanical properties to investigate if the Enamel structure can improve the compressive strength, stiffness and energy absorption capabilities of sandwich panel cores and potentially replace the common Honeycomb structure. Also, the optimal cellular configurations for the Honeycomb and Enamel structures were explored. Indeed, it was found the Enamel structure can potentially replace the Honeycomb structure and a wall thickness of 1.2 mm and a wall length/cell radius of 8.14 mm will maximize the natural structures mechanical properties. Furthermore, it was found that both the natural structures have good compressive strength. Therefore, the natural structures with their optimal cellular configurations were integrated into a novel automobile floor mat to ensure the mat possesses good compressive strength to resist failure or permanent deformation. Moreover, the novel automobile floor mat has a design feature that offers an efficient debris capturing and removal system that adds value to the automobile floor mat.

Enamel Surface Damage following Debonding of Ceramic Brackets: A Hospital-Based Study

Background and Objective. The primary responsibility of an orthodontist is to preserve the dental enamel structure during debonding ceramic brackets. The enamel injury caused at the time of bracket removal causes inconvenience to the patient and disturbs the treating orthodontist. This paper aims for an effective evidence-based debonding protocol to keep the enamel surface intact. Methods. The current study includes 80 extracted premolars of human from the patient visiting for orthodontic treatment of Coorg Institute of Dental Sciences, Karnataka, India. The brackets were debonded using four different methods. The enamel surface damage after the procedure was assessed with the Enamel Surface Index (ESI); similarly, the Adhesive Remnant Index (ARI) score was used to determine the adhesive residual deposit. Scanning electron microscopy (SEM) was used to visualize better microporosities and micromechanical retention of adhesive remnants on the enamel surface. The normality of the data was tested using the Kolmogorov–Smirnov test. Depending upon the normality test result, the one-way ANOVA test or Kruskal–Wallis test was used to test the mean ESI and mean ARI differences among different debonding methods along with the appropriate post hoc tests. The necessary ethical clearance was obtained from the Ethics Committee of the institute. Results. The ultrasonic scaler (US) technique led to more significant enamel surface damage, with 13 (65%) samples in the ESI scores III and IV against the satisfactory surface in 2 (10%) samples with the ligature cutter (LC) technique (ESI-I) reflecting LC as a better technique. The ESI scores (III and IV) for debonding plier (DP) and thermal method (TM) reflected a higher value in 12 (60%) and 10 (50%) samples and caused more damage to the enamel surface as compared to the LC technique. The ARI score was highest (ARI-1 = 40%) with the LC technique, followed by the US (ARI-1 = 20%), TM (ARI-1 = 15%), and DP (ARI-1 = 5%) methods. We have observed a significant association ( p value <0.05) of the ARI score among four different debonding ways in terms of each tooth’s residual adhesive after the bracket removal. Conclusion. The result establishes the LC technique as a more acceptable one as it causes minimal harm to the debonded surface. The adhesive left on the debonded area is also minimum as compared to the other three methods tested. Therefore, it can be suggested as an ideal method.

The Effect of Er:YAG Laser on a Shear Bond Strength Value of Orthodontic Brackets to Enamel—A Preliminary Study

We sought to evaluate the effects of Er:YAG laser (LightTouch, LightInstruments, Israel) conditioning on enamel roughness and shear bond strength of orthodontic brackets on enamel. Eighteen human molars (n = 9) and premolars (n = 9), were divided into 3 groups depending on the enamel conditioning method; Er:YAG laser (G1, n = 6), conventional etching with 37% orthophosphoric acid (G2, n = 6), Er:YAG laser combined with conventional etching (G3, n = 6). Er:YAG laser parameters were as follows: energy: 100 mJ, frequency: 10 Hz, exposure time: 10 s, applicator diameter: 600 μm, fluence: 35.37 J/cm2, distance: 1 mm away from a tooth, cooling: 80%. An MTS 858 MiniBionix® machine was used to determine the shear bond strength (MTS System, Eden Prairie, MN, USA). The enamel structure was assessed using X-ray microtomography (SkyScan 1172, Bruker, Kontich, Belgium). The highest values of shear bond strength were obtained in the G3 group (9.23 ± 2.38 MPa) and the lowest values in the G2 group (6.44 ± 2.11 MPa) (p < 0.05). A significant change in the enamel surface was noted after applying laser, reaching up to 9% of enamel thickness, which was not observed in the etched samples. Moreover, the Er:YAG laser-irradiated enamel surface was characterized by the greatest roughness. The combined use of an Er:YAG laser with a conventional etching improves the adhesion of composite materials to the tooth.

In Vivo Effects of Two In-Office Vital Tooth Bleaching Systems on Enamel Permeability

Tooth bleaching is a common treatment for the amelioration of the aesthetic of discoloured teeth. In this context, there are two common approaches that employ concentrated solutions (30–40 wt.%) of either hydrogen peroxide or carbamide peroxide as bleaching agents. However, there is an ongoing debate on the possible adverse effects of these different treatments on tooth health, such as variation of the enamel structure, surface morphology, and chemistry, which also affect tooth sensitivity. In the present work, a study on the effect of the two bleaching agents, a 35 wt.% solution of hydrogen peroxide and a 30 wt.% solution of carbamide peroxide, on the permeability and surface morphology of enamel is reported. The investigation was carried out on replicas of incisors obtained after different treatment times and for several patients, employing scanning electron microscopy to study the morphological features of the treated teeth. The significance of the analytical study was corroborated by a statistical analysis of the results. The collected data suggest that hydrogen peroxide treatment increases the enamel permeability, and this could be related with tooth sensitivity, whereas the carbamide peroxide solution increases the formation of precipitates on the tooth enamel.

Examining the effect of exposure time on the erosive potential of sour candy

This study aimed to evaluate the erosive potential of sour candy at a different time of exposure within a laboratory-based setting. Fifty human anterior tooth samples were randomly assigned into three groups, namely: sour candy, regular candy A, and deionized water (n=15). Each tooth sample was exposed to a solution containing the sample groups at different time intervals. Vickers hardness tester was used to measure the surface hardness pre- and postexposure. The mean surface hardness value measured was compared using a paired sample test (α =.05). Raman spectroscopy was used to study the change in the enamel structure in all sample groups. A significant difference in the surface hardness value was measured pre and post-exposure in all the sample groups (P<0.01). The samples exposed to sour candy had the highest tooth surface loss. In terms of the time of exposure, it was found that prolonged exposure had a significant effect on the surface hardness (P<0.01). The Raman intensity change confirmed that samples exposed to sour candy, after 2 hrs of exposure, had the highest loss of structural integrity. The study conclude that sour candies are very erosive and its impact enhances with time.

Interdisciplinary Approach of Amelogenesis Imperfecta: 10 Years of Clinical Follow-Up

Amelogenesis imperfecta (AI) is an inherited disease that expresses a disorder in the development of enamel structure. In its mildest form, it promotes tooth color change; and in more severe cases, it presents a loss of enamel structure initiated during the eruption phase. Different AI manifestations can coexist in the same patient or in the same tooth, both in the primary and permanent dentures. In addition, several subtypes are described, characterized according to the variety of phenotype and genotype. Successful treatment requires early diagnosis and therapeutic solutions involving different dental specialties. Although some professionals prefer to postpone permanent rehabilitation until the development of complete permanent dentures, the aesthetic and functional impact of this disease in childhood and adolescence requires that restorative treatment be started as soon as possible. The proposed therapies demonstrate numerous challenges such as extreme dentinal sensitivity, difficulties installing and maintaining the orthodontic appliance and the need for restorative and prosthetic intervention in malformed teeth. This work aims to demonstrate the interaction between Orthodontics, Restorative Dentistry and Prosthesis in the treatment of a patient with AI, reporting the success of treatment involving aesthetics, function and well-being and the long-term benefit of this interdisciplinary approach for patients with this disease. Keywords: Orthodontics. Amelogenesis Imperfecta. Mouth Rehabilitation. ResumoA amelogênese imperfeita (AI) é uma doença hereditária que expressa uma desordem no desenvolvimento da estrutura do esmalte. Na sua forma mais branda, promove alteração na cor dos dentes; e em casos mais severos, apresenta perda de estrutura do esmalte iniciada durante a fase de irrupção. Diferentes manifestações da AI podem coexistir no mesmo paciente ou no mesmo dente, tanto na dentadura decídua quanto na permanente. Além disso, são descritos diversos subtipos, caracterizados de acordo com a variedade do fenótipo e genótipo. O sucesso do tratamento requer diagnóstico precoce e soluções terapêuticas que envolvam diversas especialidades odontológicas. Embora alguns profissionais prefiram adiar a reabilitação definitiva até o desenvolvimento da dentadura permanente completa, o impacto estético e funcional desta doença na infância e adolescência exige que o tratamento restaurador seja iniciado o mais cedo possível. As terapias propostas demonstram inúmeros desafios como a sensibilidade dentinária extrema, as dificuldades para instalação e manutenção do aparelho ortodôntico e a necessidade de intervenção restauradora e protética em dentes com má formação. O presente trabalho tem como finalidade demonstrar a interação entre a Ortodontia, a Dentística Restauradora e a Prótese no tratamento de um paciente com AI, relatando o sucesso do tratamento envolvendo estética, função, bem estar e o benefício em longo prazo desta abordagem interdisciplinar para os portadores desta doença. Palavras-chave: Ortodontia. Amelogênese Imperfeita. Reabilitação Bucal.

ATR-FTIR, EDS and SEM evaluations of enamel structure after treatment with hydrogen peroxide bleaching agents loaded with nano-hydroxyapatite particles

Background Tooth whitening is one of the most requested dental treatments, but it still presents some side effects. Indeed, the bleaching agent can generate patients’ discomfort and dental hard tissue damages, not achieving an efficient and long-lasting treatment with optimum whitening effect. To overcome these limitations, the bleaching agents containing nano-hydroxyapatite can represent a reliable solution to avoid these detrimental effects. Methods In this study, human third molars were treated with commercial bleaching agents, containing nano-hydroxyapatite (nHA) and 6% (at-home treatment), 12% and 18% (in-office treatments) of hydrogen peroxide (HP), named respectively G1, G2 and G3. The results were evaluated descriptively and analytically using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS), comparing the treated groups with a commercial gel containing 10% carbamide peroxide (CONV) and with a non-treated control group (CTRL). Results ATR-FTIR analysis revealed a similar composition in carbonates and phosphates for CTRL, G1 and G2 groups, which showed no significant differences in their spectral profiles; an increased amount of organic matter was found in G3, while CONV displayed an intermediate behavior. SEM analysis did not highlight significant changes in the enamel microstructure of G1 and CONV when compared to CTRL; the pattern observed in G2 presented a slight increase of enamel irregularities, while G3 displayed a partial removal of the aprismatic layer and microporosities. No evident effects due to nHA were observed in the structure of the hydroxyapatite component of G1, G2 and CONV, if compared to CTRL, while G3 showed a slight loss of crystallinity. In all groups, EDS identified slight changes in the concentration of chemical elements O and Ca, while the Ca/P ratio was similar when compared to CTRL. Conclusion The obtained results suggest that the application of the tested commercial bleaching agents, with a concentration of HP up to 12%, does not alter the morphological and chemical composition of the enamel surface and maintains its crystallinity.