The circadian clock in enamel development.

Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes. The circadian clock mechanisms in brain and peripheral tissues can oscillate independently or be synchronized/disrupted by external stimuli. Dental enamel is a type of mineralized tissue that forms the exterior surface of the tooth crown. Incremental Retzius lines are readily observable microstructures of mature tooth enamel that indicate the regulation of amelogenesis by circadian rhythms. Teeth enamel is formed by enamel-forming cells known as ameloblasts, which are regulated and orchestrated by the circadian clock during amelogenesis. This review will first examine the key roles of the circadian clock in regulating ameloblasts and amelogenesis. Several physiological processes are involved, including gene expression, cell morphology, metabolic changes, matrix deposition, ion transportation, and mineralization. Next, the potential detrimental effects of circadian rhythm disruption on enamel formation are discussed. Circadian rhythm disruption can directly lead to Enamel Hypoplasia, which might also be a potential causative mechanism of amelogenesis imperfecta. Finally, future research trajectory in this field is extrapolated. It is hoped that this review will inspire more intensive research efforts and provide relevant cues in formulating novel therapeutic strategies for preventing tooth enamel developmental abnormalities.

Comparing the remineralization potential of undemineralized dentin powder versus chicken eggshell powder on artificially induced initial enamel carious lesions: an in-vitro investigation.

BACKGROUND: White spot lesions are a widespread undesirable effect, especially prevalent during fixed orthodontic treatments. The study compared the in vitro enamel remineralization potential of undemineralized dentin matrix (UDD) versus chicken eggshell powder (CESP) for artificially induced enamel lesions. METHODS: 100 caries-free and sound maxillary premolars were randomly divided into four groups each contain 25 teeth: Group I (Baseline): No treatment was done to the enamel surface. Group II (Negative control ): The enamel surface of the teeth underwent demineralization using demineralizing solution to create artificial carious lesions then kept in artificial saliva. Group III (CESP treated): After demineralizing the tooth surface, the teeth have been suspended in the CESP remineralizing solution. Group IV (UDD treated): After enamel demineralization, the teeth were suspended in UDD remineralizing solution. The remineralization potential was assessed by Vickers microhardness testing, scanning electron microscopic examination (SEM), and energy dispersive X-ray (EDX). RESULTS: The current study demonstrated an increase in the mean microhardness of CESP and UDD-treated groups; however, It was nearer to the baseline level in the UDD group. SEM imaging revealed greater enamel remineralization in the UDD group compared to the remaining groups. The UDD group disclosed complete coverage for the prismatic enamel compared to the CESP group, which revealed a partially remineralized enamel surface. Interestingly, the Ca/P ratio increased significantly in the CESP group compared to the negative control group. In contrast, a higher significant increase in the mean Ca/P ratios was recorded in the UDD group compared to the test groups. CONCLUSION: biomimetic UDD and CESP powder should be utilized to treat enamel early carious lesions. However, UDD demonstrated the most significant remineralization potential.

Onset and progression of dental erosion in a mouse model.

OBJECTIVE: Purpose of this research was to examine the onset, progression and wear rates of dental erosion in an established mouse model. MATERIAL AND METHODS: Dental erosion in mice was experimentally induced, and the acidic effects of cola drink on their teeth after 2, 4 and 6-weeks were closely analysed by scanning electron microscopy. The tooth height and enamel or dentin loss were established.  Results: The dental erosion on the molars showed clear progression from 2 to 6 weeks. By the 2-week mark, a significant portion of enamel was already eroded, revealing the dentin on the lingual cusps. When adjusted for attritional wear, molars exposed to cola for 2 weeks showed a 35% drop in lingual tooth height compared to controls (533 µm vs. 818 µm). At 4 and 6 weeks, the cola-exposed group continued to display decreased lingual tooth heights by 40% (476 µm vs. 799 µm) and 43% (440 µm vs. 767 µm), respectively. CONCLUSION: This study revealed significant acidic effects of cola drink on mouse molars as early as 2 weeks. These findings highlight the challenge of monitoring dental erosion clinically and underscore the importance of early preventive and intervention measures.

Do the methods for cleaning the base of brackets used in indirect bonding interfere with adhesion to tooth enamel?

OBJECTIVE: The objective of this study was to evaluate the shear bond strength of metal brackets bonded with indirect bonding, under different surface treatment protocols. MATERIAL AND METHODS: 40 bovine teeth were randomly divided into four groups (n = 10), according to the type of surface treatment: G1 = 70% alcohol, G2 = air/water spray, G3 = 100-µm aluminum oxide blasting, G4 = direct boning. After drying, the standard Edgewise central incisor brackets were bonded with light-cured resin. The brackets were moved from the plaster models by means of a transfer tray made with condensation silicone, and bonded to the surface of the enamel with self-curing adhesive. The samples were submitted to shear tests by a universal test machine. Data were analyzed with SPSS 20.0 by the one-way ANOVA test and the Tukey post-test. RESULTS: No statistically significant difference (p=0.174) was observed between the mean forces measured between the group for shear strength values of the groups during the test: G1 (5.33 MPa), G2 (3.52 MPa) and G3 (4.58 MPa). CONCLUSION: The bracket surface treatment protocols presented similarities in shear bond strength test. However, alcohol 70% and oxide blasting presented higher absolute values of resistance than the water group.

[The effect of erbium laser pretreatment on bond strength between dentin and enamel and microleakage at the edge of CAD/CAM glass ionomer cement restorations for repairing tooth defects].

PURPOSE: To investigate the effects of erbium laser pretreatment on the bond strength of dentin and enamel,as well as microleakage at the edge of tooth defects repaired with computer-aided design (CAD) and computer-assisted manufacturing (CAM) glass-ceramic restorations for repairing dental defects. METHODS: A total of 62 fresh, nondecayed, nondiscoloration and noncracked wisdom teeth were collected from the Oral Surgery Clinic between January 2020 and January 2023. According to different pretreatment methods, they were randomly divided into two groups, erbium laser group and phosphoric acid group, with 31 teeth in each group. Each group was further divided into two subsets for bond strength testing (16 teeth) and microleakage testing (15 teeth).The shear bond strength between enamel and dentin of both groups was compared, as well as the degree and distribution of microleakage.Statistical analysis was performed with SPSS 17.0 software package. RESULTS: The shear bond strength between enamel and dentin of the erbium laser group was significantly higher than that of the phosphoric acid group (P＜0.05); the degree and distribution of microleakage at the lateral walls and gumline of the erbium laser group were significantly lower than those of the phosphoric acid group (P＜0.05). The scores of microleakage at the lateral walls of the erbium laser group mainly concentrated in grade 1 and 2, whereas those of the phosphoric acid group mainly concentrated in grade 2. There was significant difference in the distribution of lateral wall microleakage scores between the two groups (P＜0.05). The scores of microleakage at the gumline of the erbium laser group mainly concentrated in grade 1 and 2, whereas those of the phosphoric acid group mainly concentrated in grade 2 and 3. There was significant difference in the distribution of gumline microleakage scores between the two groups (P＜0.05). CONCLUSIONS: Erbium laser pretreatment can improve bonding strength between glass ionomer cement and dentin and enamel, reduce microleakage at the edge of CAD/CAM glass ionomer cement restorations, and enhance marginal fit.

A label-free quantification method for assessing sex from modern and ancient bovine tooth enamel.

Identification of the sex of modern, fossil and archaeological animal remains offers many insights into their demography, mortality profiles and domestication pathways. However, due to many-factors, sex determination of osteological remains is often problematic. To overcome this, we have developed an innovative protocol to determine an animal's sex from tooth enamel, by applying label-free quantification (LFQ) of two unique AmelY peptides 'LRYPYP' (AmelY;[M+2] 2 + 404.7212 m/z) and 'LRYPYPSY' (AmelY;[M+2] 2 + 529.7689 m/z) that are only present in the enamel of males. We applied this method to eight modern cattle (Bos taurus) of known sex, and correctly assigned them to sex. We then applied the same protocol to twelve archaeological Bos teeth from the Neolithic site of Beisamoun, Israel (8-th-7-th millennium BC) and determined the sex of the archaeological samples. Since teeth are usually better preserved than bones, this innovative protocol has potential to facilitate sex determination in ancient and modern bovine remains that currently cannot be sexed.

Enhanced tooth bleaching with a hydrogen peroxide/titanium dioxide gel.

BACKGROUND: This study aimed to explore the effects of the titanium dioxide (TiO2) concentration and particle size in hydrogen peroxide (HP) on tooth bleaching effectiveness and enamel surface properties. METHODS: TiO2 at different concentrations and particle sizes was incorporated into 40% HP gel to form an HP/TiO2 gel. The specimens were randomly divided into 8 groups: C1P20: HP + 1% TiO2 (20 nm); C3P20: HP + 3% TiO2 (20 nm); C5P20: HP + 5% TiO2 (20 nm); C1P100: HP + 1% TiO2 (100 nm); C3P100: HP + 3% TiO2 (100 nm); C5P100: HP + 5% TiO2 (100 nm); C0: HP with LED; and C0-woL: HP without LED. Bleaching was conducted over 2 sessions, each lasting 40 min with a 7-day interval. The color differences (ΔE00), whiteness index for dentistry (WID), surface microhardness, roughness, microstructure, and composition were assessed. RESULTS: The concentration and particle size of TiO2 significantly affected ΔE00 and ΔWID values, with the C1P100 group showing the greatest ΔE00 values and C1P100, C3P100, and C5P100 groups showing the greatest ΔWID values (p < 0.05). No significant changes were observed in surface microhardness, roughness, microstructure or composition (p > 0.05). CONCLUSIONS: Incorporating 1% TiO2 with a particle size of 100 nm into HP constitutes an effective bleaching strategy to achieve desirable outcomes.

New Generation of Orthodontic Elastomeric Ligature to Prevent Enamel Demineralization In Vivo.

This study aimed to synthesize a novel elastomeric ligature with dimethylaminohexadecyl methacrylate (DMAHDM) grafted, providing a new strategy for improving the issue of enamel demineralization during fixed orthodontics. DMAHDM was incorporated into elastomeric ligatures at different mass fractions using ultraviolet photochemical grafting. The antibacterial properties were evaluated and the optimal DMAHDM amount was determined based on cytotoxicity assays. Moreover, tests were conducted to evaluate the in vivo changes in the mechanical properties of the elastomeric ligatures. To assess the actual in vivo effectiveness in preventing enamel demineralization, a rat demineralization model was established, with analyses focusing on changes in surface microstructure, elemental composition, and nanomechanical properties. Elastomeric ligatures with 2% DMAHDM showed excellent biocompatibility and the best antibacterial properties, reducing lactic acid production by 65.3% and biofilm bacteria by 50.0% within 24 h, without significant mechanical property differences from the control group (p > 0.05). Most importantly, they effectively prevented enamel demineralization in vivo, enhancing elastic modulus by 73.2% and hardness by 204.8%. Elastomeric ligatures incorporating DMAHDM have shown great potential for application in preventing enamel demineralization, providing a new strategy to solve this issue during fixed orthodontics.

Spot-etch technique and other adhesive strategies for provisional veneers.

AIM: The objective of the present study was to evaluate the influence of different adhesive strategies regarding shear bond strength (SBS) of provisional resin--based materials bonded to the enamel surface as well as on the enamel surface roughness. MATERIALS AND METHODS: Bovine incisors were randomly divided into six groups (n = 10) according to the adhesive strategy used: BRControl (bis-acrylic resin); Spot-etch+BR (spot-etch + bis-acrylic resin); Spot--etchSB2+BR (spot-etch + adhesive + bis-acrylic resin); Spot-etchZ350Flow+BR (spot-etch + flowable composite resin + bis-acrylic resin); SBU+BR (universal adhesive + bis-acrylic resin); Spot-etchSBMP+Z350 (spot-etch + adhesive + composite resin). The enamel surface roughness was determined by a surface profil-ometer. An SBS test was performed in a universal testing machine, and failure modes were classified under magnification. The SBS data were analyzed by one-way analysis of variance (ANOVA). A paired t test was used for enamel surface roughness intragroup comparisons, and the Friedman one-way repeated meas-ures analysis of variance by ranks was used for differences in enamel surface roughness between groups, with the Tukey post hoc test (a = 0.05). RESULTS: BRControl had the lowest SBS values (MPa), with a significant difference (P ≤ 0.001) from the other groups. Spot-etch+BR had the highest SBS values but with no significant differences from the other groups in which the spot-etch technique was also used. Adhesive failure mode was predominant for all groups. BRControl had the lowest surface roughness difference, significantly different (P = 0.001) from all the other groups. CONCLUSIONS: Spot-etch and other adhesive strategies could be applied to increase the SBS values of provisional restorations to enamel compared with no surface pretreatment. However, the adhesive strategy may change the enamel surface roughness, revealing the importance of cleaning the tooth surface.

Evaluating the Effects of Cigarette Smoking and Heated Tobacco Products on Hard Dental Tissues: A Comparative Histological and Colorimetric Analysis.

OBJECTIVES: This study aimed to evaluate and compare the impact of cigarette smoking (CS) and heated tobacco (HT) on the alteration of color and ultrastructural characteristics of human enamel and cementum. BACKGROUND: According to tobacco companies, a less harmful substitute for CS is HT products. Nevertheless, comprehensive research on the effects of HT on tooth structures has been lacking. This study aimed to evaluate and compare the impact of CS and HT on the alteration of color and ultrastructural characteristics of human enamel and cementum. MATERIALS AND METHODS: Thirty intact and noncarious human maxillary premolars extracted for orthodontic treatment purposes, previously disinfected, were used in the study. The specimens were randomly separated into six groups (n = 10), as follows: Group 1: enamel without smoking exposure; Group 2: enamel exposed to CS; Group 3: enamel exposed to HT; Group 4: cementum without smoking exposure; Group 5: cementum exposed to CS; and Group 6: cementum exposed to HT. The measurement of color change was conducted using a spectrophotometer. The surface alterations and mineral composition of enamel and cementum were evaluated using scanning electron microscopy and energy-dispersive X-ray spectroscopy. ANOVA test followed by Tukey's post hoc test was used to determine significant differences between groups. RESULTS: Results showed that CS had a more pronounced effect on enamel and cementum color changes than HT. The impact of CS and HT on color changes was more evident in cementum than in enamel. Surface morphology of enamel and cementum showed alterations in histology following exposure to both smoking types. Moreover, the mineral content experienced a significant reduction after using CS and HT. The reduction in calcium content after CS and HT exposure was similar. However, HT led to a significant decrease in the phosphorus content of enamel when compared with CS. At the same time, CS exposure in cementum resulted in a more significant reduction in Ca/P ratio than HT. CONCLUSIONS: Although HT may appear to present a lower danger to hard dental tissues than CS, it is not entirely harmless. CS results in more color changes on the enamel and cementum of teeth. Both smoking methods affected the mineral content of teeth, with CS having a significant effect on the roots, while HT significantly affected the crowns' mineral composition.

Remineralizing effect of NSF on artificial enamel caries.

INTRODUCTION: Nanotechnology offers new approaches and endless opportunities for remineralizing tooth decay without being toxic or causing allergies. This study aimed to determine the effect of nanosilver fluoride (NSF) on the remineralization potential of enamel caries-like lesions compared to 5% sodium fluoride varnish in permanent teeth. METHODS: Fifteen teeth (molars and premolars) were gathered, cleaned, and polished using a scaler. After sectioning the teeth mesiodistally and removing the roots, the thirty specimens were subjected to a demineralized solution to induce early enamel lesions and then assigned randomly into two equal groups. The test materials were applied, and then all the specimens were subjected to a pH cycling model for 30 days. DIAGNOdent and surface roughness were investigated, and an evaluation of the enamel Ca and P weight% for Ca/P ratio calculation was done using SEM-EDX to analyze the specimens at the end of the study. The data were analyzed using an independent t-test. RESULTS: The mean values for the DIAGNOdent measurements for NSF and NaF at baseline and after demineralization were not significantly different (p > 0.05). After treatment, NaF varnish showed a significantly higher mean DIAGNOdent measurement (11.8 ± 5.80) than NSF (4.7 ± 1.6). The mean surface roughness of the NaF group (1.64 ± 0.39) was much higher than NSF's mean surface roughness (1.07 ± 0.21). Specimens treated with NSF had statistically significant smoother surfaces (p < 0.001). The NSF group had a higher mean Ca/P ratio (2.9 ± 0.35) than NaF (2.2 ± 0.11). This difference was statistically significant (p = 0.012). CONCLUSION: The study reveals that nano silver fluoride is a more effective treatment than sodium fluoride varnish in enhancing teeth's clinical characteristics, particularly in terms of mineral content and surface roughness, suggesting it could be an improved strategy to prevent dental caries and maintain enamel integrity.

Clinical SWIR and CP-OCT imaging of interproximal lesions.

BACKGROUND: Enamel is highly transparent at short wavelength infrared imaging (SWIR) wavelengths allowing the detection of dental decay without the need for ionizing radiation. The purpose of this study was to use SWIR imaging methods including cross polarization optical coherence tomography (CP-OCT), occlusal transillumination (SWIR-OT), proximal transillumination (SWIR-PT), and occlusal reflectance (SWIR-R) to image interproximal lesions in vivo and compare the sensitivity with radiography. METHODS: Participants (n = 30) aged 18-80 each with a radiopositive interproximal lesion scheduled for restoration were enrolled in the study. Studies have shown that the opposing proximal surfaces across the contact will likely also have lesions. SWIR images were acquired of the adjoining teeth at each contact with an interproximal lesion scheduled for restoration. Lesion presence and depth were assessed on each side of the contact for radiography and each SWIR imaging method. Lesions on radiographs and in CP-OCT images were identified by a single examiner while lesions in SWIR images were identified by a contrast threshold via semi-automatic image segmentation. RESULTS: All SWIR imaging methods had significantly higher sensitivity (P < 0.05) than radiographs for the detection of interproximal lesions on the teeth opposite those restored. CP-OCT and SWIR-R imaging methods had significantly higher sensitivity than the other methods. SWIR imaging methods showed significantly higher lesion contrast than radiography. CONCLUSIONS: SWIR imaging methods can be used to detect interproximal lesions on posterior teeth with higher diagnostic performance than radiographs. CP-OCT appears well suited as a potential gold standard for the detection of interproximal lesions and assessment of their severity in vivo.

Infrared spectral library of tooth enamel from African ungulates for accurate electron spin resonance dating.

Electron spin resonance coupled with uranium-series dating (ESR/U-series) of carbonate hydroxyapatite in tooth enamel is the main technique used to obtain age determinations from Pleistocene fossils beyond the range of radiocarbon dating. This chronological information allows to better understand diachronic change in the palaeontological record, especially with regard to the evolution of the genus Homo. Given the relative paucity of human teeth at palaeontological and archaeological localities, ESR/U-series is widely applied to the teeth of ungulate species. However, the accuracy of ESR/U-series ages is greatly affected by the incorporation of uranium in the enamel during burial in sediments. It has been shown that uranium content is positively correlated with an increased degree of atomic order in carbonate hydroxyapatite crystals, the latter determined using infrared spectroscopy. Here we present a reference infrared spectral library of tooth enamel from African ungulates, based on the grinding curve method, which serves as baseline to track the diagenetic history of carbonate hydroxyapatite in different species and thus select the best-preserved specimens for dating.

Effect of hydrogen peroxide versus charcoal-based whitening mouthwashes on color, surface roughness, and color stability of enamel.

BACKGROUND: Patients tend to favor the whitening mouthwashes as they are easily applied and affordable. This study aimed to evaluate the effect of hydrogen peroxide versus charcoal-based whitening mouthwashes on color, surface roughness, and color stability of enamel. In the current study, the whitening mouthwashes used have the ability to stop future stains due to their white seal technology. METHODS: A total of 21 permanent central incisor teeth extracted for periodontal reasons were used in the present study. Teeth roots were sectioned and crowns were mounted in self-cured acrylic resin blocks. The specimens were randomly divided into three groups (n = 7) according to the tested whitening mouthwash: Control group ? DW" (Distilled water), ?OW" group: Peroxide-based mouthwash (Colgate Optic White) and ?CP" group: Charcoal-based mouthwash (Colgate® Plax Charcoal). Regarding ?OW" and ?CP" groups, the specimens were immersed in 20 ml of the tested mouthwash in each corresponding group for 1 min twice daily (morning and evening) for a total of 12 uninterrupted weeks. Color change was assessed using VITA Easyshade spectrophotometer and surface roughness (Ra) was measured using a white light interferometer. The specimens were stained using black tea solution and color was measured after 24 h of immersion for assessment of color stability. RESULTS: Color change results revealed that both whitening mouthwashes were able to restore color comparable to the control group with no significant difference between them. Regarding surface roughness, the control group showed the highest mean Ra value, followed by ?OW" group while ?CP" group showed the lowest mean Ra value. While color stability after staining, the control group showed a significantly higher value than the ?CP" and ?OW" groups. CONCLUSION: Hydrogen peroxide and charcoal-based whitening mouthwashes improve the color of enamel with no adverse effect on the surface roughness. Both whitening mouthwashes were beneficial to maintain the color after staining and prevent future enamel stains.

Influence of coffee characteristics on tooth discoloration.

PURPOSE: To evaluate the impact of coffee attributes on tooth discoloration, emphasizing the importance of potential factors such as serving temperature, bean variety, and chlorogenic acid (CGA) content. METHODS: Coffee preparation involved the extraction of espresso from four types of roasted beans (Vietnam Robusta, Uganda Robusta, Ethiopia Yirgacheffe Arabica, and Colombia Supremo Arabica), followed by chlorogenic content analysis using high-performance liquid chromatography. Bovine tooth enamel specimens were carefully prepared and stained with coffee (hot and iced), with a color assessment conducted at different time intervals (3, 9, 24, 48, and 72 hours). The Vickers hardness tester was employed to ensure specimen quality, while spectrophotometry aided in color analysis using the CIEDE2000 formula. RESULTS: The results revealed varying effects of serving temperature, bean type, and CGA content on tooth discoloration. It was demonstrated that perceptible color differences occur after a 3-hour immersion in coffee, with hot coffee showing higher staining potential compared to iced variations. Furthermore, chlorogenic acid content and bean type significantly affected tooth discoloration, with higher chlorogenic acid levels associated with increased staining. Notably, Robusta coffee showed less discoloration compared to Arabica, potentially due to differences in pH levels. CLINICAL SIGNIFICANCE: The findings provide valuable insights for both dental practitioners and coffee consumers, assisting in making informed decisions regarding coffee intake and oral hygiene.

Effects of graphene oxide and graphene quantum dots on enhancing CPP-ACP anti-caries ability of enamel lesion in a biofilm-challenged environment.

OBJECTIVE: To investigate the anticaries effects of graphene oxide (GO) and graphene quantum dots (GQDs) combined with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on enamel in a biofilm-challenged environment. MATERIAL AND METHODS: GO and GQDs were synthesised using citric acid. The antibiofilm and biofilm inhibition effects for Streptococcus mutans were evaluated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and colony-forming units (CFU). Remineralisation ability was determined by assessing mineral loss, calcium-to-phosphorus ratio, and surface morphology. To create a biofilm-challenged environment, enamel blocks were immersed in S. mutans to create the lesion and then subjected to artificial saliva/biofilm cycling for 7 days. Anticaries effects of GO, GQDs, GQDs@CPP-ACP, GO@CPP-ACP, and CPP-ACP were determined by broth pH and mineral changes after 7-day pH cycling. Biocompatibility was tested using a Cell Counting Kit-8 (CCK8) assay for human gingival fibroblasts (HGF-1). RESULTS: GQDs and GO presented significant antibiofilm and biofilm inhibition effects compared to the CPP-ACP and control groups (P < 0.05). The enamel covered by GQDs and GO showed better crystal structure formation and less mineral loss (P < 0.05) than that covered by CPP-ACP alone. After 7 days in the biofilm-challenged environment, the GO@CPP-ACP group showed less lesion depth than the CPP-ACP and control groups (P < 0.05). GO and GQDs showed good biocompatibility compared to the control group by CCK8 (P > 0.05) within 3 days. CONCLUSION: GO and GQDs could improve the anti-caries effects of CPP-ACP, and CPP-ACP agents with GO or GQDs could be a potential option for enamel lesion management. CLINICAL SIGNIFICANCE: GO and GQDs have demonstrated the potential to significantly enhance the anticaries effects of CPP-ACP. Incorporating these nanomaterials into CPP-ACP formulations could provide innovative and effective options for the management of enamel lesions, offering improved preventive and therapeutic strategies in dental care.

Influence of Different Application Modes of a Universal Adhesive System on the Bond Strength of Bulk-Fill Composite Resin to Enamel and Dentin in Primary Teeth.

OBJECTIVES: The objective of this study was to assess how the application mode of a universal adhesive system affects the microshear bond strength (µSBS) of bulk-fill and conventional composite resins to enamel and dentin in primary teeth. METHODS: A total of 80 caries-free primary second molars were randomly assigned to eight experimental groups (n = 10) based on the bonding substrate (enamel or dentin), the application mode of the universal adhesive system (etch and rinse [E&R], or self-etch [SE]), and the type of composite resin used (bulk-fill or conventional). After bonding the composite resin to enamel or dentin, the µSBS of the bonded composite resins was measured. RESULTS: The mean µSBS value of bulk-fill composite resin was significantly higher than that of conventional composite resin for both enamel and dentin substrates, regardless of the application mode (p < 0.001). An interaction effect between the bonding substrate and the application mode of the adhesive system was observed, indicating a significant relationship (p < 0.001). The highest µSBS values for primary teeth enamel were achieved using the E&R mode with bulk-fill composite resin, while for dentin specimens, the SE mode with bulk-fill composite resin yielded the highest µSBS values. The µSBS of the E&R group was significantly higher than that of the SE group for enamel specimens (p < 0.001), whereas the µSBS of the SE group was significantly higher than that of the E&R group for dentin specimens (p < 0.001). CONCLUSION: Bulk-fill composite resin demonstrated higher µSBS in comparison to conventional composite resin. The universal adhesive system exhibited superior performance in the SE mode compared to the E&R mode on primary dentin. Pre-etching the enamel before the application of the universal adhesive enhanced the µSBS to primary teeth enamel, highlighting the importance of selectively acid etching the enamel of primary teeth.

EFFECT OF LASER IRRADIATION ASSOCIATED WITH FLUORIDE IN DECREASING EROSIVE TOOTH WEAR: A SYSTEMATIC REVIEW WITH A NETWORK META-ANALYSIS  .

OBJECTIVE: The present systematic review with a network meta-analysis (NMA) aimed to evaluate the effect of high-power lasers, associated or not with fluoride compounds, to control and prevent Erosive Tooth Wear (ETW). METHODS: The review was registered in the PROSPERO (CRD42021242547) and followed the PICO question: P (population): enamel and dentin substrate; I (Intervention): high-power laser irradiation, associated or not with fluoride compounds; C (Control): no-treatment; and O (Outcomes): prevention/control of ETW. The electronic databases PubMed, Scopus, and EMBASE were searched. Two independent reviewers evaluated in vitro and in situ studies. The risk of bias was assessed using the RoBDEMAT tool. The estimated treatment effect derived from direct and indirect comparisons were analyzed and the difference between these effects was calculated based on the data of enamel and dentin surface loss (in µm). RESULTS: A total of 179 studies were retrieved and after the exclusion of duplicates, 103 studies had their titles and abstracts evaluated. Thirty-nine studies had their full text analyzed for data extraction (Cohen Kappa = 0.88). For sound enamel, the laser irradiation (L), fluoride application (F) and, the association of treatments (L + F) promoted higher protection than No-Treatment (NT). For eroded enamel, L + F and F did not differ, but both treatments reduced surface loss compared to NT and L. For sound and eroded dentin, treatments with laser increased surface loss. CONCLUSIONS: Although a high-power laser has some potential to prevent erosive tooth wear, this effect is not better than that of standard fluoride. The use of laser in the management of dentin erosive wear can be harmful.

Comparison of various methods of restoring adhesion to recently bleached enamel.

AIM: This study compared the effectiveness of several techniques in restoring compromised bonding to recently bleached enamel. METHODS: Seventy-five healthy bovine incisors were divided into five groups (n = 15). Fifteen teeth (Group 1) remained intact, whereas 60 (Groups 2 to 5) underwent at-home bleaching with 16% carbamide peroxide. The bonding procedures were as follows: Group 1: Bonding of resin composite to unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: Application of a 10% sodium ascorbate solution for 10 min before bonding; Group 4: Enamel removal to the depth of 0.5 mm; and Group 5: Increased curing time of the bonding agent to 80 instead of 20 s. After 24 h, the specimens were subjected to micro-shear testing, and the failure mode was determined. RESULTS: ANOVA revealed a significant difference in bond strength among the groups (P < 0.001). The mean bond strength was significantly lower in group 2 than in other groups (P < 0.05), which showed comparable bond strength to each other (P > 0.05). Adhesive failure was the most predominant failure type in all groups. The mixed failure occurred with a frequency of 26.7% in groups 3 and 5. The Fisher's exact test revealed a significant difference in failure modes among the groups (P = 0.047). CONCLUSIONS: The three experimental procedures used in this study, including the application of 10% sodium ascorbate before bonding, enamel removal to the depth of 0.5 mm, and increasing the curing time of the bonding agent to 80 s, were effective in restoring the compromised bonding to recently bleached enamel.

Influence of using different toothpaste during bleaching with violet LED light (405 nm) on the colour and roughness of dental enamel: an in vitro study.

This in vitro study aimed to investigate potential changes in the color and roughness of dental enamel resulting from the use of different toothpaste formulations during bleaching with violet LED light (405 nm). Sixty specimens of bovine incisors, each measuring 6 × 6 × 3 mm, were segregated into six distinct experimental groups based on their respective treatments (n = 10): C + VL: Brushing with Colgate® Total 12 + bleaching with violet LED; LB + VL: Brushing with Colgate® Luminous White Brilliant + bleaching with violet LED; LI + VL: Brushing with Colgate® Luminous White Instant + violet LED bleaching; C: Brushing with Colgate® Total 12; LB: Brushing with Colgate® Luminous White Brilliant; LI: Brushing with Colgate® Luminous White Instant. The examined variables included alterations in color (∆L*, ∆a*, ∆b*, ∆Eab, and ∆E00), surface roughness (Ra), and scanning electron microscopy observations. No statistically significant distinctions emerged in total color variations (∆E00 and ∆E) among the groups under scrutiny. Notably, the groups that employed Colgate® Luminous White Instant displayed elevated roughness values, irrespective of their association with violet LED, as corroborated by scanning electron microscopy examinations. It can be concluded that whitening toothpastes associated to violet LED do not influence the color change of dental enamel in fifteen days of treatment. Toothpastes with a higher number of abrasive particles showed greater changes in enamel roughness, regardless of the use of violet LED.