Microhardness of demineralized enamel following home bleaching and laser-assisted in office bleaching

Pinching dynamics, extensional rheology, and stringiness of saliva substitutes

Saliva substitutes are human-made formulations extensively used in medicine, food, and pharmaceutical research to emulate human saliva's biochemical, tribological, and rheological properties. Even though extensional flows involving saliva are commonly encountered in situations such as swallowing, coughing, sneezing, licking, drooling, gleeking, and blowing spit bubbles, rheological evaluations of saliva and its substitutes in most studies rely on measured values of shear viscosity. Natural saliva possesses stringiness or spinnbarkeit, governed by extensional rheology response, which cannot be evaluated or anticipated from the knowledge of shear rheology response. In this contribution, we comprehensively examine the rheology of twelve commercially available saliva substitutes using torsional rheometry for rate-dependent shear viscosity and dripping-onto-substrate (DoS) protocols for extensional rheology characterization. Even though most formulations are marketed as having suitable rheology, only three displayed measurable viscoelasticity and strain-hardening. Still, these too, failed to emulate the viscosity reduction with the shear rate observed for saliva or match perceived stringiness. Finally, we explore the challenges in creating saliva-like formulations for dysphagia patients and opportunities for using DoS rheometry for diagnostics and designing biomimetic fluids.

Effectiveness of Diode (810 nm) Laser in Periodontal Parameters and Reduction of Subgingival Bacterial Load in Periodontitis Patients

AIM

This split-mouth randomized trial (RCT) aimed to assess the effect of diode laser on the clinical parameters in patients with periodontitis, compare the results with scaling and root planing (SRP) alone, and assess the implications of diode laser (DL) on plaque bacteria.

MATERIALS AND METHODS

Seventeen periodontitis patients were randomly assigned into two equal groups based on the therapy delivered. Group I (control site) received just SRP at baseline, while group II (test site) received both SRP and DL irradiation. For both groups, the clinical periodontal parameters probing pocket depth (PPD), and clinical attachment level (CAL) were measured at baseline, 30 days, and 90 days. Microbiological amount was also measured at baseline, 30, and 90 days after periodontal treatment. The amounts of Aggregatibacter actinomycetemcomitans (A.a), Prevotella intermedia (Pr. intermedia), and Porphyromonas gingivalis (P. gingivalis) were determined using real-time PCR probing with specific bacterial primers.

RESULTS

In both groups, PPD and CAL showed statistically significant reductions at different time intervals (p < 0.05). No significant difference were observed in CAL values after 1 and 3 months in both test and control groups (p > 0.05). The mean values of the concentration of A.a, Pr. intermedia and P. gingivalis were lower in the case group as compared to the control group and the difference was statistically significant after 1 month (*p = 0.001).

CLINICAL SIGNIFICANCE

According to this study, non-invasive laser treatment has the potential to improve clinical outcomes by lowering the quantity of A.a, Pr. intermedia and P. gingivalis.

CONCLUSION

In both groups, a considerable decrease in the periodontal pathogens A.a, Pr. intermedia and P. gingivalis were discovered; however, the intergroup comparison was insignificant in relation to PD and CAL. The adjunctive treatment with diode laser showed better efficacy in ensuring a better periodontal treatment than SRP alone. How to cite this article: Abdullah LA, Hashim N, Rehman MM, et al. Effectiveness of Diode (810 nm) Laser in Periodontal Parameters and Reduction of Subgingival Bacterial Load in Periodontitis Patients. J Contemp Dent Pract 2023;24(12):1008-1015.

Microhardness and surface roughness of resin infiltrated bleached enamel surface using atomic force microscopy: An in vitro study

to evaluate the microhardness (VHN) and surface roughness (Ra) of human enamel surface treated with resin infiltration followed by in office bleaching and to study the effect of artificial saliva (AS) storage time on the VHN and Ra of resin infiltrated enamel. Materials and methods: Eighty enamel specimens were prepared from extracted human premolar teeth. Specimens were divided into two main groups (I and II) then, they were demineralized to create white spot lesions (WSLs). Group I was divided into A and B sub groups. Group A was treated with in office bleaching material while for group B, resin infiltration (Icon) was applied after 24 h storage in AS followed by bleaching. Group II was divided into (C and D). Group C was treated like group B. Specimens in group D were stored in AS for 14 d after treatment with Icon and before application of bleaching. Atomic force microscopy (AFM) Ra analysis and VHN calculation were done. Independent T Test was used to compare between groups at P < 0.05. Results: Group B demonstrated a significant increase in VHN compared with group A. Storage time in AS showed no significant difference on VHN or Ra between groups. Conclusion: Application of resin infiltration before bleaching significantly increased VHN and slightly improved Ra of WSLs compared with bleaching alone. Application of bleaching material after 24 h or 14 days of the application of resin infiltration did not have a significant effect or surface hardness or roughness of WSLs.

Evaluation of the laser wavelength role on tooth bleaching in terms of color change, roughness, and microhardness with pulpal rapid temperature monitoring: an in vitro study

This in-vitro study evaluates the efficacy of the teeth bleaching approach using different laser wavelengths (405 nm blue diode, 940 nm infrared diode, and Er,Cr:YSGG 2780 nm lasers) in comparison to the conventional method using light-emitting diode (LED) sources (420-480) nm. Eighty caries-free sound human premolars were randomly divided into four groups (N=20). Each group received a different bleaching procedure. Then each group was further subdivided into two subgroups (N=10) stained with different solutions. The pulp chamber temperature rise was recorded using an optical fiber sensor with a novel design and fabrication. The color was analyzed using a digital spectrophotometer. Five samples of each subgroup were tested for surface roughness, while the others were tested for Vickers microhardness. The bleaching process with a short wavelength 405 nm blue diode laser showed the best results for the shade, with a minimum pulpal temperature increase indicating no possible necrosis and hence maintaining tooth vitality. Additionally, a remarkable reduction in bleaching time was achieved compared to the conventional approach. This process also yielded the highest color change (Δ E) and increased microhardness, with no noticeable change to the tooth roughness. The 405 nm blue diode laser applied for bleaching showed the best bleaching activity against tested stains and negligible pulpal temperature rise with a noticeable reduction in the bleaching time. The proposed novel method to measure temperature change could be used to develop a promising smart sensor for quick, effective, repeatable, and in-situ monitoring of human body temperature.

Synthesis, Characterization, and Investigation of Novel Ionic Liquid-Based Tooth Bleaching Gels: A Step towards Safer and Cost-Effective Cosmetic Dentistry

The objective of this study was to synthesize a novel choline hydroxide ionic liquid-based tooth bleaching gel. Ionic liquid-based gels were synthesized and characterized using FTIR along with pH testing. Tooth sample preparation was carried out in line with ISO 28399:2020. The effects of synthesized gels on tooth samples were tested. Tooth samples were stained and grouped into three experimental groups: EAI (22% choline hydroxide gel), EAII (44% choline hydroxide gel), and EB (choline citrate gel) and two control groups: CA (commercial at-home 16% carbamide peroxide gel) and CB (deionized water). The tooth color analysis, which included shade matching with the Vitapan shade guide (n = 2), and digital colorimetric analysis (n = 2) were evaluated. The surface characteristics and hardness were analyzed with 3D optical profilometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and Microhardness testing (n = 3), respectively. The tooth color analysis (Vitapan shade guide) revealed that all the tooth samples treated with synthesized choline citrate gel (EB) showed an A1 shade as compared to the other four groups, giving a range of shades. An analysis of the ΔE values from digital colorimetry; EAI, EAII, CA, and CB showed ΔE values in a range that was clinically perceptible at a glance. However, EB showed the highest value of ΔE. The mean microhardness values for the five groups showed that the effects of three experimental gels i.e., 44% choline hydroxide, 22% choline hydroxide, and choline citrate, on the microhardness of the tooth samples were similar to that of the positive control, which comprised commercial at-home 16% carbamide peroxide gel. SEM with EDX of three tested subgroups was closely related in surface profile, elemental composition, and Ca/P ratio. The roughness average values from optical profilometry of four tested subgroups lie within approximately a similar range, showing a statistically insignificant difference (p > 0.05) between the tested subgroups. The synthesized novel experimental tooth bleaching gels displayed similar tooth bleaching actions without any deleterious effects on the surface characteristics and microhardness of the treated tooth samples when compared with the commercial at-home tooth bleaching gel.

Does the application of whitening dentifrices during at-home bleaching affect the bond strength of resin composite to dentin?

AIM

This study aimed to evaluate the effect of using whitening dentifrices during at-home bleaching on the shear bond strength (SBS) of resin composite to dentin, and investigate whether the increased polymerization time would improve SBS.

METHODS

Ninety-six bovine incisors were divided into 4 groups of 24, according to the whitening treatment applied as follows: group 1, at-home bleaching + brushing with a regular dentifrice; group 2, at-home bleaching + brushing with a whitening dentifrice containing ozone; group 3, at-home bleaching + brushing with a commercial whitening dentifrice; and group 4 (control), no whitening/brushing treatment. Each group was divided into two subgroups (n = 12) to assess the effect of curing time (20 versus 80 s) on SBS. A self-etch adhesive was bonded to dentin, and after 2-day water storage, SBS was determined.

RESULTS

SBS was significantly affected by the whitening treatment (P = 0.03), but increasing the curing time had no significant effect on SBS (P = 0.137). Bond strength in group 1 was comparable to the control group (P > 0.05). The specimens in group 3 displayed significantly lower SBS than either group 4 or group 1 (P > 0.05). No significant difference was observed between the SBS of group 2 compared to any other group (P > 0.05). There was no significant association between the treatment group and failure type (P > 0.05).

CONCLUSION

The bonding interface was not negatively influenced by the at-home bleaching procedure. However, using a commercial whitening dentifrice during at-home bleaching produced a significant detrimental effect on SBS. Extending the curing time would have no beneficial effect on adhesion to a whitened dental substrate.

The effect of minimally invasive treatments on enamel microhardness and resistance to further demineralization

Objectives: The present study aimed to compare microhardness of inactive proximal lesions treated by resin infiltration, Er:YAG laser + resin infiltration and Bioactive glass, and investigate the resistance of treated lesions to further demineralization challenge. Methods: In this in-vitro study, 30 human molars with inactive proximal lesions were selected and randomly divided into three groups of 10. In group 1 (resin infiltration), the lesions were treated by a resin infiltrant (Icon). In group 2, the surface was conditioned by an Er:YAG laser prior to resin infiltration. The specimens in group 3 were remineralized by bioactive glass. The treated specimens were kept in artificial saliva for 1 week and then immersed in a demineralization solution for 8 weeks. Surface microhardness was measured at baseline (T0), after remineralization (T1) and after exposure to the demineralization solution (T2), and the difference in microhardness between time points (ΔVHN) was calculated. Results: Microhardness after demineralization (T2) was significantly lower than those of other intervals (P0.05). The statistical analysis revealed no significant difference either in ΔVHNT1-T0 or in ΔVHNT2-T1 among the study groups (P>0.05) Conclusion: Pretreatment by the Er:YAG laser prior to resin infiltration was more effective that other treatments in enhancing microhardness and protecting the tooth against acidic challenge. However, the difference between groups did not reach a statistical significance, implying the need for further studies to achieve more conclusive results.

Effectiveness of an 810-nm Diode Laser in Addition to Non-surgical Periodontal Therapy in Patients With Chronic Periodontitis: A Randomized Single-Blind Clinical Trial

Introduction: This study evaluated the effectiveness of an 810-nm diode laser as an adjunct to scaling and root planning (SRP) in improving periodontal parameters in patients with chronic periodontitis. Methods: This randomized clinical trial consisted of 36 patients (16 females and 20 males) with chronic periodontitis and pocket depths of 4-6 mm. The quadrants were randomly divided into two sides; one side of each patient was selected as the laser group (SRP + laser) and the other side served as the control group (SRP alone). An 810-nm diode laser was applied in the laser side to remove the outer gingival epithelium (1.5 W, CW) as well as the inner epithelium of the periodontal pockets (1 W, CW). The clinical parameters including bleeding on probing (BOP), probing depth (PD), plaque index (PI), and clinical attachment level (CAL) were measured at baseline and 6 and 18 weeks after therapy. Results: In both groups, there was a significant improvement in BOP, PD, PI and CAL over the course of the experiment (P < 0.001). Significantly lower BOP was found in the SRP + laser group than the SRP alone group after 6 and 18 weeks of intervention (P < 0.05). The difference in other parameters was not significant between the two groups, neither at 6 nor at 18 weeks after the treatment (P > 0.05). Conclusion: Within the limitations of this study, the association of the diode laser with standard non-surgical periodontal therapy (SRP) provided minimal additional benefits for patients with moderate chronic periodontitis.

Evaluation of dental enamel microproperties after bleaching with 35% hydrogen peroxide and different light sources: An in vitro study

Background

To evaluate the tooth enamel surface morphology after the action of 35% hydrogen peroxide with and without LED activation.

Material and Methods

70 bovine incisors with an enamel surface of 4x4x3 mm were used, prepared for reading superficial microhardness and roughness. Specimens were randomly distributed and divided into 7 experimental groups (n = 10); G1 = artificial saliva; G2 = 35% HP - 2 sessions (3x15´); G3 = Phosphoric Acid + 35% HP - 3 sessions (3x15´); G4 = 35% HP - 2 sessions (3x15´) + blue LED; G5 = 35% HP - 2 sessions (3x15´) + green LED; G6 = 35% HP - 2 sessions (3x20´) + violet LED; G7 = Violet LED - 2 sessions (3x20´). The results were analyzed by the Anova, Wilcoxon, Dunnett and Tukey tests (α = 0.05).

Results

The G4 group showed a greater change in microhardness. Regarding roughness, the biggest mean difference between groups occurred in G2, G5 and G7. Optical microscopy showed a smooth enamel surface in groups G2, G5 and G7.

Conclusions

Changes in the enamel surface were observed in relation to microhardness, but without significant changes in roughness, where the LED (green and violet) resulted in a smooth surface. Key words:Tooth whitening, superficial morphology, light, photoradiatio.

Effects of Different Bleaching Agents on the Surface Topography and the Microhardness of Artificial Carious Lesions

Objectives The aim of this study was to evaluate the effects of in-office and at-home bleaching agent applications on the surface topography and microhardness of artificially demineralized enamel.

Materials and Methods A total of 224 enamel specimens were prepared using bovine sound central incisors. 4 mm × 4 mm enamel windows were exposed on the buccal surfaces covering the remaining surface with nail varnish. Samples were immersed in a demineralizing solution for 16 hours to produce artificial caries lesions, then divided into four groups according to the bleaching agent’s type and concentration. Group I; in-office bleaching 35% hydrogen peroxide (HP) (Whiteness HP Maxx; FGM, Brazil), Group II and Group III at-home bleaching 16 and 22% carbamide peroxide CP, respectively (Whiteness Perfect). Group IV; control (not bleached). The microhardness Vickers hardness number (VHN) was measured at the baseline, after demineralization, and after bleaching consequently. The micro-surface changes of the enamel surface after demineralization and bleaching were evaluated by scanning electron microscope (SEM).

Statistical Analysis Data were evaluated by the one-way analysis of variance (ANOVA) test followed by Post Hoc Tukey’s and Fisher’s least significant difference. Tow- sided p -values were considered statistically significant at p ≤ 0.05.

Results A significant reduction was noticed in the enamel microhardness after demineralization p < 0.05. However, there is no statistically significant difference between the mean VHN of the demineralized and bleached enamel ( p > 0.001). SEM images showed significant changes on the surface of the demineralized enamel after bleaching (pattern type III).

Conclusions The low and high concentrations of HP and CP bleaching agents increased the demineralization severity of artificial caries lesions without significantly altering their microhardness values.

Effect of diode laser-assisted bleaching on the bond strength of different adhesive systems to enamel: Interfacial SEM analysis

The aim of this study was to investigate the effectiveness of diode laser-assisted bleaching on the shear bond strength (SBS) of different adhesive systems to enamel and examine the adhesive enamel interface under scanning electron microscope (SEM). 180 incisor teeth were randomly divided into three bleaching groups: (1) Unbleached control group, (2) Opalescence Boost (OB) 40%, and (3) Diode laser-assisted LaserWhite20 (LW20) 45%. After bleaching, each group was divided into two subgroups according to waiting time: immediately or 7 days' delay. The six groups were then divided into three subgroups based on the adhesive procedure: Single Bond 2 (SB2), Clearfil SE Bond (CSB), and Clearfil Universal Bond (CUB). After adhesive procedures, composite resin cylinders were bonded to the enamel surfaces. All specimens were subjected to a SBS test after 24 hr of storage in water. Data were analysed using three-way variance analysis (p < .05). Specimens were examined under a stereomicroscope and SEM. There was a significant difference between the groups bonded immediately and 7 days after bleaching (p < .05). SB2 after 7 days showed the highest SBS values (19.24 ± 2.18), whereas CUB showed the lowest values in both bleaching treatments and control groups (10.84 ± 1.66). SEM analysis of the unbleached specimens revealed long tags and uniform hybrid layer compared OB and LW20 bleaching groups. LW20 and OB bleaching adversely affected SBS to enamel when bonded immediately. Diode laser-assisted bleaching might be an alternative option due to the short working time but delaying bonding for 7 days after bleaching may not be enough for ideal adhesion. RESEARCH HIGHLIGHTS: Bleaching agents containing high concentration hydrogen peroxide reduces the enamel bond strength of adhesive systems. Postponing composite restorations for 7 days after bleaching may not be sufficient to achieve ideal adhesion. Diode laser-assisted bleaching may be preferred as an alternative bleaching method today due to its ability to shorten the operation time and cause minimal morphological changes on the enamel surface.

Esthetic Management of Incisors with Diffuse and Demarcated Opacities: 24 Month Follow-up Case Report

CLINICAL RELEVANCE

A minimally invasive esthetic treatment can provide longevity and color stability.

SUMMARY

This clinical case report describes a minimally invasive approach to mask diffuse and demarcated opacities in permanent anterior teeth in an eight-year-old child who was upset with the appearance of her incisors. Clinical examination showed diffuse opacities in teeth 7, 8, 9, and 10, diagnosed as dental fluorosis associated with yellow demarcated opacity in tooth 9 related to molar-incisor hypomineralization. The treatment was based on conservative dentistry using the low-viscosity resin infiltration technique and resin composite restoration in an attempt to mask the lesions. The follow-up time was 24 months.

The effect of laser-activated bleaching with 445 nm and 915 nm diode lasers on enamel micro-hardness; an in vitro study

BACKGROUND

The appearance of the teeth is of great importance to patients, particularly tooth color. In recent years, tooth whitening has been one of the most popular ways to restore tooth color. Bleaching gels can be affected by heat, light or laser, which can improve its effects. This study intends to examine the effects of two different wavelengths of diode laser (445 & 915 nm) after the bleaching process, on the enamel micro-hardness.

METHODS

A total of 65 caries-free humans third molars were randomly divided into five groups (N = 13): first group: bleaching gel activated with 915 nm diode laser (1.5 W), second: bleaching gel activated with 915-nm (2.5 W), third: bleaching gel activated with 445-nm (1 W), fourth: bleaching gel activated with 445-nm (1.5 W), fifth (control group): bleaching gel without laser activation. Micro-hardness test (Vickers test) was performed before and after the treatment. The data were submitted to repeated measurement ANOVA and Tukey's HSD post hoc test (α = 0.05).

RESULTS

Enamel micro-hardness did not change significantly in groups 3 and 4 but decreased in groups 1 and 2. Group 2 showed the most reduction in micro-hardness. There were no significant changes in the control group.

CONCLUSION

According to the results of this study, 445 nm Diode laser did not reduce enamel micro-hardness, making it suitable for bleaching treatments. However, more studies are required to consider other factors, such as color changes and pulp temperature.

Non-invasive analysis of bleaching effect of hydrogen peroxide on enamel by reflectance confocal microscopy (RCM): study of series of cases

The aim of this study is to evaluate in vivo the effects of in-office tooth whitening hydrogen peroxide (HP) agent on enamel-microstructured surface by a reflectance confocal microscopy (RCM). Ten healthy volunteers assisted at the Dental School presenting teeth with vital pulp were selected. The 35% HP whiteness product was applied in two visits on discolored teeth, 1-week interval between, via 20-min applications. A commercially available hand-held RCM (Vivascope3000^®, Lucid, Rochester, NY, USA) was used to image in vivo the dental surface of the selected tooth of each volunteer. Twenty upper central incisors' vestibular surfaces were imaged, before bleaching (T0), immediately after (T1) and 1 week later (T2). The peculiar structure of the enamel was seen at T0. After bleaching, white reflective circular bodies were found all over the teeth surfaces, which disappear 1 week later (T2). When the HP gel^® was imaged, the same white circular areas were observed. Going deeper, the regular enamel architecture was preserved. Textural analysis of the images in T0 and T2 was performed: GLCM parameters were extracted. Mann-Whitney U test was performed to evaluate statistical differences between two groups of data (p > 0.05). Finally, 35 prisms were randomly selected from T0 and T2 image and diameters were measured; a paired t test was performed (p = 0.381). The RCM is a promisor tool for investigating the features of enamel in vivo, immediately after bleaching procedures, as well as longitudinally.

Evaluation of biochemical changes in dental tissues after different office bleaching methods

The color of the teeth is an important topic for many people and can be influenced by intrinsic and extrinsic stains. There is an increasing demand for whitening of the teeth year by year. The most popular way of whitening is "bleaching," which is the result of the breakdown of pigments located in the enamel and/or the dentin, caused by reactive oxygen species (ROS) released from bleaching agents. These bleaching agents could increase matrix metalloproteinase (MMP)-mediated collagen degradation in dentin. The aim of this study was to compare biochemical changes and oxidative stress levels of the human premolar dentin-pulp complex after three different bleaching methods containing hydrogen peroxide (H₂O₂) bleaching agents. Individuals, whose first four premolars were extracted for orthodontic purposes, included into the study. Group 1-Laser: bleaching gel containing 46% H₂O₂ (LaserWhite20 whitening gel, Biolase Technology Inc., San Clemente, CA, USA) and a diode laser activation (Ezlase 940 nm system). Group 2: 35% H₂O₂ containing whitening gel (Whiteness HP Maxx, FGM) and halogen light source activation (Optilux 501, Kerr, Orange, CA, USA). Group 3: 35% H₂O₂ containing whitening gel (Whiteness HP Maxx, FGM). Group 4-Control: No whitening treatment. According to the test results, there were no significant differences among groups in the values of cathepsin B and MMP proteolytic activities ( p > 0.05). The total ROS values released from the dentin tissue were higher than those obtained from the pulp tissue ( p < 0.05). There were significant differences among the bleaching groups in the ROS values released from the dentin tissue.

Effect of different bleaching protocols on whitening efficiency and enamel superficial microhardness

Background

Tooth bleaching is a popular aesthetic treatment to modify the color of teeth. Despite the extensive literature concerning the subject, there is still no consensus regarding the application mode of the different bleaching agents and their effect on enamel. Therefore, this study evaluated the influence of different bleaching protocols on whitening efficiency and enamel superficial hardness.

Material and Methods

Bovine enamel fragments were embedded in acrylic resin and wet-sanded to obtain a flat buccal surface. The specimens were then randomly divided into 6 groups (n=10), based on the bleaching material [HP Maxx 35% (35% hydrogen peroxide), HP Blue 35% (35% hydrogen peroxide + Ca) and Whiteness Perfect 10% (10% carbamide peroxide)] and application mode (3 applications of 15 min, 1 application of 45 min, 1 application of 1h30 or 1 application of 3h30). The color and superficial hardness were assessed before and after bleaching. The color was assessed by means of a digital spectrophotometer, using CIELab parameters. Vickers hardness was determined using a load of 200g for 10s. Data were statistically analyzed by one-way ANOVA with repeated measures and Tukey’s test (α = 0.05).

Results

Concerning the color alteration, the groups were similar to each other, except for at-home bleaching protocols, which were statistically different from each other. Similarly, there was a reduction in hardness values comparing the initial and final periods, with lowest final hardness for the at-home bleaching protocol group applied for 3h30.

Conclusions

It can be concluded that the bleaching protocols influenced the final color and enamel surface hardness, evidencing that lower gel concentrations applied for longer periods promoted greater variation in color and lower final hardness.

Key words:Tooth bleaching, roughness, microhardness, in-office, at-home bleaching.

In Vitro Effect of Bleaching With 810 nm and 980 nm Diode Laser on Microhardness of Self-cure and Light-Cure Glass Ionomer Cements

Introduction: This study sought to assess the effect of bleaching combined with irradiation of 810 nm and 980 nm diode laser on microhardness of 2 commonly used self-cure and light-cure glass ionomer cements (GICs) in comparison with conventional bleaching (without laser). Methods: In this in vitro, experimental study, 60 samples were fabricated of A2 shade of Fuji IX and Fuji II LC GICs (n=30) and each group was divided into 3 subgroups (n=10). The first subgroups were subjected to bleaching with Opalescence Xtra Boost plus 980 nm diode laser irradiation. The second subgroups were subjected to bleaching with Opalescence Boost plus 810 nm diode laser irradiation and the third subgroups were subjected to bleaching with Opalescence Xtra Boost without laser. Microhardness was measured at baseline and after the intervention using Vickers hardness tester. The data were analyzed using two-way analysis of variance (ANOVA) (P<0.05). Results: Microhardness decreased in all subgroups after the intervention (P<0.001) irrespective of the type of GIC (P=0.201) or surface treatment (P=0.570). The baseline microhardness of the three subgroups within each group of GIC was not significantly different (P=0.456), but the baseline microhardness of conventional GIC was significantly higher than that of resin modified GIC (P=0.004). Conclusion: Bleaching with/without laser irradiation decreases the microhardness of GICs. The baseline microhardness of conventional GIC is higher than that of resin modified GIC.

The effects of three remineralizing agents on regression of white spot lesions in children: A two-week, single-blind, randomized clinical trial

BACKGROUND

This study investigated the effect of three remineralizing agents on improving white spot lesions (WSLs).

MATERIAL AND METHODS

This clinical trial included children who had at least one WSL on anterior teeth of upper or lower jaws. The participants were randomly assigned to 4 groups by treatment: 1) a cream containing casein phosphopeptide-amorphous calcium phosphate and fluoride (MI Paste Plus); 2) a cream containing hydroxyapatite and fluoride (Remin Pro); 3) a 2% sodium fluoride gel; and 4) usual home care (control). The treatment was performed for 3 times over 10 days using special trays for retaining remineralizing agents. The area and mineral content of WSLs were measured at baseline (T1) and 1 day after finishing treatment (T2). Blinding was applied for outcome assessment.

RESULTS

Eighty patients were assigned to MI Paste Plus, Remin Pro, NaF or control groups. The application of all remineralizing agents caused a significant decrease in area and a significant increase in mineral content of WSLs (p<0.05), whereas the control patients did not experience any significant alteration (p>0.05). At T2, the area of WSLs was significantly lower in three experimental groups compared to the control group (p=0.023), but between-group difference in mineral content of WSLs failed to achieve statistical significance (p=0.08).

CONCLUSIONS

The in-office application of either MI Paste Plus or Remin Pro was as effective as 2% NaF for reducing area and increasing mineral content of WSLs. MI Paste Plus and Remin Pro could be recommended as suitable alternatives to NaF for managing WSLs. Key words:White spot lesion, caries, casein phosphopeptide-amorphous calcium phosphate, hydroxyapatite, sodium fluoride, CPP-ACP, MPlus, Remin Pro, NaF.

Effectiveness of sodium bicarbonate combined with hydrogen peroxide and CPP-ACPF in whitening and microhardness of enamel

Background

This study investigated the effects of sodium bicarbonate (NaHCO3) combined with 1.5% hydrogen peroxide (H2O2) and casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACPF) on color and microhardness of enamel.

Material and Methods

Seventy-five bovine incisors were immersed in a tea solution for 7.5 days. The specimens were randomly divided into five groups according to the whitening agent applied: 1) 94% NaHCO3, 2) a blend of 94% NaHCO3 and CPP-ACPF, 3) a blend of 94% NaHCO3 and 1.5% H2O2, 4) a blend of 94% NaHCO3, 1.5% H2O2 and CPP-ACPF, 5) control. The whitening procedure was performed for 10 times over 10 days. At each day, the buccal surfaces were covered with whitening agents for 5 minutes and then brushed for 30 seconds. After the 10 days, the teeth were again immersed in a tea solution for 10 minutes. Color assessment was performed at baseline (T1), after the first staining process (T2), after the whitening procedure (T3), and after the second staining process (T4). Finally, the specimens were subjected to microhardness test.

Results

There was a statistically significant difference in the color change between T2 and T3 stages among the study groups (p<0.05), with the greatest improvement observed in group 4. Microhardness was significantly greater in groups 2 and 4, as compared to the other groups (p<0.05).

Conclusions

The combination of 94% NaHCO3, 1.5% H2O2 and CPP-ACPF was effective in improving color and microhardness of teeth with extrinsic stains and could be recommended in the clinical situation.

The efficacy of laser-assisted in-office bleaching and home bleaching on sound and demineralized enamel

AIMS

This study investigated the effectiveness of laser-assisted in-office bleaching and home-bleaching in sound and demineralized enamel.

MATERIALS AND METHODS

The sample consisted of 120 freshly-extracted bovine incisors. Half of the specimens were stored in a demineralizing solution to induce white spot lesions. Following exposure to a tea solution for 7.5 days, the specimens were randomly assigned to 4 groups of 30 according to the type of enamel and the bleaching procedure employed. Groups 1 and 2 consisted of demineralized teeth subjected to in-office bleaching and home bleaching, whereas in groups 3 and 4, sound teeth were subjected to in-office and home bleaching, respectively. A diode laser (810 nm, 2 W, continuous wave, four times for 15 seconds each) was employed for assisting the in-office process. The color of the specimens was measured before (T1) and after (T2) staining and during (T3) and after (T4) the bleaching procedures using a spectrophotometer. The color change (ΔE) between different treatments stages was compared among the groups.

RESULTS

There were significant differences in the color change between T2 and T3 (ΔE T2-T3) and T2 and T4 (ΔE T2-T4) stages among the study groups (p<0.05). Pairwise comparison by Duncan test revealed that both ΔET2-T3 and ΔET2-T4 were significantly greater in demineralized teeth submitted to laser-assisted in-office bleaching (group 1) as compared to the other groups (P< 0.05).

CONCLUSION

Laser-assisted in-office bleaching could provide faster and greater whitening effect than home bleaching on stained demineralized enamel, but both procedures produced comparable results on sound teeth.