The effect of fractional CO2 laser irradiation on remineralization of enamel white spot lesions

White spot lesions in fixed orthodontic treatment: Etiology, pathophysiology, diagnosis, treatment, and future research perspectives

White spot lesions (WSLs) refer to localized areas of hypo-mineralization limited to the enamel of the teeth surface, which is noticeable clinically to the naked eye on drying of the teeth. During fixed orthodontic treatment, it is very hard for the patient to maintain excellent oral hygiene as the brackets, bands, wires, elastics, and other appliances and attachments worn intra-orally provide a platform for food retention, plaque formation, and then colonization by acidogenic bacteria like Streptococcus mutans and Lactobacillus. This review aims to elaborate and focus on etiology, pathophysiology, diagnosis, treatment aspect, and future scope for research about the WSLs occurring due to fixed orthodontic treatment.

Photoinactivation Effects of Curcumin, Nano-curcumin, and Erythrosine on Planktonic and Biofilm Cultures of Streptococcus mutans

Introduction: This in vitro study was conducted to assess the phototoxic effects of curcumin, nano-curcumin, and erythrosine on the viability of Streptococcus mutans (S. mutans) in suspension and biofilm forms. Methods: Various concentrations of curcumin (1.5 g/L, 3 g/L), nano-curcumin (3 g/L), and erythrosine (100 μM/L, 250 μM/L) were examined for their impact on planktonic and biofilm cultures of S. mutans, either individually or in conjunction with light irradiation (photodynamic therapy or PDT). A blue light-emitting diode (LED) with a central wavelength of 450 nm served as the light source. The results were compared to 0.12% chlorhexidine digluconate (CHX) as the positive control, and a solution containing neither a photosensitizer (PS) nor a light source as the negative control group. The dependent variable was the number of viable microorganisms per experiment (CFU/mL). Results: Antimicrobial PDT caused a significant reduction in the viability of S. mutans in both planktonic and biofilm forms, compared to the negative control group (P<0.05). The highest cell killing was observed in PDT groups with curcumin 3 g/L or erythrosine 250 μmol/L, although the difference with PDT groups using curcumin 1.5 g/L or erythrosine 100 μmol/L was not significant (P>0.05). Antimicrobial treatments were more effective against planktonic S. mutans than the biofilm form. Conclusion: PDT with either curcumin 1.5 g/L or erythrosine 100 μmol/L may be suggested as an alternative to CHX to inactivate the bacteria in dental plaque or deep cavities. Nano-curcumin, at the selected concentration, exhibited lower efficacy in killing S. mutans compared to Curcumin or erythrosine.

CO2 laser irradiation combined with fluoridated dentifrice improved its protective effect on caries lesion progression regardless of the acidulated phosphate fluoride gel application: An in situ study

OBJECTIVE

This in situ study aimed to investigate the efficacy of CO2 laser at a 10.6-µm wavelength combined with 1.23% acidulated phosphate fluoride (APF) and fluoridated dentifrice with 1100 µg F/g (FD) to control enamel caries progression.

MATERIALS AND METHODS

Sixteen volunteers wore palatal appliances containing eight demineralized enamel specimens for four 14-day phases under sucrose exposure. These specimens were submitted to CO2 laser irradiation and APF alone or combined with FD. Treatment groups were non-fluoridated dentifrice-NFD, NFD + CO2 laser, NFD + APF, NFD + CO2 laser + APF, FD, FD + CO2 laser, FD + APF, and FD + CO2 laser + APF. Mineral loss, calcium fluoride (CaF2), fluorapatite (FAp), and fluoride in the biofilm were analyzed by analysis of variance followed by the Student-Newman-Keuls test, p < 0.05.

RESULTS

The highest mineral loss inhibition was noted when FD and CO2 laser irradiation were combined, which did not significantly differ from the FD + CO2 laser + APF group. The CaF2, FAp, and F in the biofilm were more pronounced when the FD and APF were combined. The CO2 laser irradiation promoted a slightly higher concentration of CaF2 in the enamel and F in the biofilm.

CONCLUSION

Although APF promotes the high formation of CaF2 and FAp, the combined use of FD with CO2 laser overcomes the APF effect in inhibiting the progression of artificial caries-like lesions in situ.

CLINICAL SIGNIFICANCE

Under the in situ design of this study, remineralization of white spot lesions was achieved through CO2 laser irradiation and daily use of fluoridated dentifrice. Future clinical trials are encouraged to substantiate this finding.

Effect of sodium fluoride plus tricalcium phosphate with and without CO2 laser on remineralization of white spot lesions

Objectives

The aim of this in vitro study was to evaluate the effect of NaF plus TCP with and without CO₂ laser irradiation on management of demineralized enamel using microhardness test and digital microscopy.

Methods

Eighty intact extracted human premolar teeth were randomly divided into 4 groups (20/each). Each group was subjected to a demineralizing solution to create white spot lesion. Group 1 was treated with 3M Vanish™. Group 2 was irradiated with CO₂ laser. Group 3 was subjected to CO₂ laser followed by 3M Vanish™. Group 4 was treated by 3M Vanish™ then CO₂ laser. The teeth were immersed in artificial saliva. Surface microhardness was measured for each tooth before demineralization at base line (M1 as a control), after demineralization (M2) and after management (M3). Comparison of microhardness values between groups was performed using one way ANOVA test with significant level (0.05) followed by multiple comparisons post-hoc Tukey test between groups. Enamel surface was photographed by digital microscope.

Results

All intervention methods used in the current study significantly increased microhardness values of demineralized enamel (P < 0.001). Little improvement of enamel appearance was observed in all groups meanwhile using CO₂ laser on demineralized enamel directly led to signs of white and black dots affecting the appearance of enamel surface.

Significance

The most effective intervention regarding microhardness was group 2 followed by group 3, group 4 and group 1. Coating the enamel surface with 3M Vanish™ before CO₂ laser irradiation acted as a protective layer from the undesirable effects of laser on the teeth with increasing enamel microhardness values more than using Vanish alone. So the promising intervention method regarding both microhardness and appearance was group 4.

Comparative Evaluation of Influence of Nd:YAG Laser (1064 nm) and 980 nm Diode Laser on Enamel around Orthodontic Brackets: An In Vitro Study

(1) Background: The prevention of demineralizing lesions at the enamel structure level continues to represent a challenge in daily dental practice. When bacteria influence the pH level, this will decrease below the threshold for remineralization and the dissociation of hydroxyapatite will occur with a high percentage of phosphate and calcium loss. These elements continue to be studied by many authors in order to obtain a working protocol that will lead to their stabilization at the level of the enamel structure, thus preventing the demineralization process. The aim of this study is to evaluate and compare the influence of two types of laser wavelengths on the surface morphology and mineral components of the enamel through an examination with scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX). (2) Methods: Thirty permanent human incisors extracted for periodontal reasons from patients aged 25−40 years old were selected for this study. Metallic brackets (SS Standard 022 Slot, OC Orthodontics, McMinnville, OR, 97128, USA) were bonded onto each tooth. The buccal surface was randomly assigned three sections: Section A—negative control (no treatment), section B—treated with 980 nm Gallium−Aluminum−Arsenide diode laser (a 300 µm optic fiber was used with 0.8 W output power, energy density of 5.33 J/mm2, in continuous mode, for 30 s, oriented perpendicularly to the enamel surface in contact mode) (KaVo GENTLEray 980 Diode Laser, Kaltenbach & Voigt GmbH, Biberach, Germany), and section C—treated with Nd:YAG laser (a 300 µm fiber was carried out at a 1 mm distance from the enamel surface with 0.75 W power, 75 mJ pulse energy, pulse repetition rate of 10 Hz, 5 J/mm2 fluency, average exposure time of 30 s, and water cooling assisted) (LIGHTWALKER AT S, M021-5AF/1 S, Fotona d.o.o, Ljubljana, Slovenia). The elements evaluated in this study were calcium (Ca), phosphate (P), oxygen (O), and carbon (C). A one-way analysis of variance, paired t-tests, and independent t-tests were carried out to evaluate the results using the SPSS 19 IBM Statistical package software for Microsoft. (3) Results: The evaluation of the data indicated that both wavelengths produced an increase in Ca wt% (for diode laser the mean of Ca wt% before irradiation was 21.06, while that after treatment reached 28.24; and for Nd:YAG laser, the mean of Ca wt% before irradiation was 21.31, while that after treatment reached 33.88); as well, the 980 nm diode laser decreased P wt% (from 17.20 before irradiation to 16.92 after irradiation) and the Nd:YAG laser increased P wt% (from 17.46 before irradiation to 18.28 after irradiation). These results showed a statistically significant difference at the p < 0.05 level. (4) Conclusions: It can be concluded that the best improvement of enamel chemical composition was obtained with Nd:YAG irradiation.

Comparison of the Effectiveness of CO2 and Diode Lasers for Gingival Melanin Depigmentation: A Randomized Clinical Trial

Introduction: Gingival hyperpigmentation is an esthetic concern for some individuals. This study compared the effectiveness of CO2 and diode lasers for gingival depigmentation. Methods: This randomized, split-mouth, clinical trial consisted of 12 patients with the chief complaint of hyperpigmented gingival areas. The upper right and left anterior segments and the mandibular anterior segment were randomly allocated to one of the treatment groups. The segments in group 1 underwent gingival depigmentation with a diode laser (810 nm) at 6 W and pulsed mode, whereas group 2 was ablated with a diode laser at 3 W and continuous mode. The removal of gingival pigments in group 3 was contemplated with a CO2 laser (10600 nm, 3 W, continuous mode). The operation chair time, bleeding during the procedure and post-operative pain were recorded. The gingival color and esthetic appearance were measured before the operation and at 1 week and 6 months later. Results: There was no significant difference in the bleeding scores, pain level, and color alteration values between the groups (P>0.05). The operation chair time was significantly shorter when the diode laser was applied at pulsed mode (P<0.05). The segments treated with the diode laser (pulsed or continuous mode) showed a higher esthetic appearance at the 6-month follow-up compared to those ablated with the CO2 laser (P<0.05). Conclusions: Higher esthetic appearance is expected when using the diode laser for gingival depigmentation compared to the CO2 laser. The application of the diode laser at pulsed mode could be recommended for gingival depigmentation, as it produced pleasing esthetic outcomes at reduced chair time.

Rehardening of Eroded Enamel with CPP-ACFP Paste and CO2 Laser Treatment

BACKGROUND

Diet and lifestyle can destroy tooth structure due to the dissolution of enamel by acidic beverages. The present study evaluated the effect of CO2 laser irradiation and CPP-ACFP (casein phosphopeptide and amorphous calcium phosphate with fluoride) paste on the remineralization of enamel eroded by carbonated soft drinks.

METHODS

In the present in vitro study, 46 human sound premolar teeth were sectioned mesiodistally to achieve 84 samples. Fourteen samples were assigned to the positive control group (G1), and the remaining samples were immersed in 500 mL of cola drink for 2 minutes, followed by rinsing with distilled water for 10 seconds. This procedure was carried out three times to create erosive lesions. Then, the 60 eroded samples were randomly assigned to five groups of G2 to G6 in terms of the treatment as follows: negative control (G2), CO2 laser irradiation (G3), CPP-ACFP paste (G4), CO2 laser irradiation followed by CPP-ACFP paste application (G5), and CPP-ACFP paste application followed by CO2 laser irradiation (G6). The mean surface microhardness of the enamel surface was evaluated and determined at three points for each sample. Data were analyzed with one-way ANOVA and Tukey HSD tests (α = 0.05).

RESULTS

The highest and the lowest hardness values were recorded in the G1 (314 ± 12 kg/mm2) and G2 (213.7 ± 12 kg/mm2) groups, respectively. ANOVA revealed significant differences between the study groups (P < 0.001). Two-by-two comparisons showed significant differences between the G2 group and the other groups, indicating the efficacy of all the treatment modalities in tooth remineralization and rehardening procedures (P < 0.05). Only in group G6, the enamel microhardness was not significantly different from the G1 positive control group (P > 0.05).

CONCLUSION

Considering the parameters used in the present study, CO2 laser irradiation or CPP-ACFP paste application alone increased eroded enamel's surface hardness; however, their sequential application was more effective in rehardening the eroded enamel's surface to near-normal levels.

Effect of Chlorhexidine Varnish and Fluoride Varnish on White Spot Lesions in Orthodontic Patients- a Systematic Review

Aim:

The aim of this study is to critically review the studies that studied the effect of Chlorhexidine varnish and fluoride varnish on White Spot Lesion (WSL) in patients undergoing orthodontic treatment.

Materials and Methods:

The electronic database PubMed, The Cochrane Library, Medline, Embase, Google Scholar, Web of Knowledge along with a complimentary manual search of all orthodontic journals till the first week of December 2019 was searched. English language study performed on humans, randomized or nonrandomized clinical trials, comparing the effect of fluoride and chlorhexidine varnish on WSL was included in the review. Quality assessment of included studies was performed.

Clinical Significance:

The need for an adjunct oral hygiene aid to reduce the incidence and prevalence of white spot lesions in orthodontic patients is necessary. The use of these varnishes will aid in the same and thus make the adverse effects of fixed orthodontic treatment negligible.

Review of Literature:

Enamel demineralization is a significant risk associated with orthodontic treatment when oral hygiene is poor. Prevention of demineralization during orthodontic treatment is one of the greatest challenges faced by clinicians despite modern advances in caries prevention. The development of White Spot Lesions (WSLs) is attributed to prolonged plaque accumulation around the brackets.

Results:

The search identified a total of 3 studies that were included in this review. One study had Low risk of bias and the remaining 2 studies had moderate overall risk. Results showed that there was a reduction in the incidence of white spot lesions in orthodontic patients after application of chlorhexidine and Fluoride varnish.

Conclusion:

Low level evidence is available to conclude that the use of chlorhexidine varnishes and fluoride varnishes reduces the prevalence of white spot lesions in patients undergoing fixed orthodontic treatment. Due to its limitations, the results of this systematic review should be handled with caution and further well-planned Randomized Clinical Trial (RCT) are needed to provide a discrete conclusion.

Moist exposed burn therapy in recovery of patients with immature, red hypertrophic scars successfully treated with a pulsed dye laser in combination with a fractional CO2 laser

BACKGROUND

The efficacy of pulsed dye laser combined (PDL) and UltraPulse fractional CO₂ in treatment of hypertrophic scars is well documented. The present study investigates the efficacy of moist exposed burn ointment (MEBO)/moist exposed burn therapy (MEBT) in postlaser wound management.

METHODS

Sixty-one patients with immature, red hypertrophic scars were enrolled in this clinical trial. Patients were randomly divided into two groups: (a) the MEBO treatment group (n = 30) and (b) the control group (n = 31) treated with chlortetracycline hydrochloride ointment. Demographic data such as age, gender, and cause of scars were recorded. A visual analogue score (VAS) was collected to measure pain at 1, 6, 24, 72 hours, and 7 days post-treatment. The Vancouver Scar Scale (VSS) was used to determine the response of the scars before and 3 months after the treatment. The wound healing time and pigmentation scores were also recorded.

RESULTS

No significant differences were found in age, gender, and etiology of the scars in the two groups. The VAS scores in MEBO group were significantly lower than the control group within the first 3 days after treatment. The wound healing time of the MEBO group was significantly shorter than the control group. For both groups, VSS scores were significantly decreased and the scar markedly improved. However, the VSS scores were significantly lower in the MEBO group compared with the control group 3 months after treatment and pigmentation formation was dramatically lower in MEBO group compared with the control.

CONCLUSION

MEBT/MEBO treatment reduced the post-treatment pain, shortened the wound healing duration, promoted the overall scar condition, and reduced the incidence of pigmentation.

Effect of CO2 laser (10.6 μm) and Remin Pro on microhardness of enamel white spot lesions

This study investigated the combined effect of CO₂ laser irradiation and Remin Pro paste on microhardness of enamel white spot lesions (WSLs). Seventy-eight intact premolars were randomly assigned into six groups and then stored in a demineralizing solution to create WSLs. Afterwards, the teeth in group 6 (negative control) remained untreated, while groups 1 and 4 were exposed to CO₂ laser irradiation (20 Hz, 1 W, 30 s) and Remin Pro paste, respectively. In groups 2 and 3, the teeth were exposed to laser either before (group 2) or after (group 3) Remin Pro application. The teeth in groups 1 to 5 were then immersed in artificial saliva for 90 days while subjected to fluoride mouthwash and weekly brushing. Finally, the teeth were sectioned, and Vickers microhardness was measured at the enamel surface and at 50, 100, and 150 μm from the surface. One sample of each group was also examined with scanning electron microscope (SEM). Data were analyzed by two-way analysis of variance (ANOVA) and Tukey's test. The significance was set at 0.05. Laser irradiation followed by Remin Pro application (group 2) caused a significant increase in total WSLs' microhardness compared with laser alone (group 1) and control groups (P < 0.05). Microhardness at depths of 100 and 150 μm was also significantly greater in group 2 compared with those of group 3 and control groups (P < 0.05). Combined application of CO₂ laser with Remin Pro paste, when laser is irradiated before the paste, is suggested for re-hardening of WSLs in deep layers of enamel.

The Impact of CO2 Laser Treatment and Acidulated Phosphate Fluoride on Enamel Demineralization and Biofilm Formation

Introduction: This study evaluated the impact of CO₂ laser treatment and acidulated phosphate fluoride (APF) on enamel demineralization and biofilm formation, using in vitro and in situ designs. Methods: Demineralized enamel slabs were distributed among 8 groups: placebo, placebo + continuous CO₂ laser, placebo + repeated CO₂ laser, placebo + ultrapulsed CO₂ laser, 1.23% APF, APF + continuous CO₂ laser, APF + repeated CO₂ laser and APF + ultrapulsed CO₂ laser. In the in vitro study, 15 enamel slabs from each group were subjected to a pH-cycling regimen for 14 days. In the cross over in situ design, 11 volunteers wore palatal appliances with demineralized enamel slabs for 2 periods of 14 days each. Drops of sucrose solution were dripped onto enamel slabs 8×/day. Biofilms formed on slabs were collected and the colony-forming units (CFU) of Streptococcus mutans and Lactobacillus were determined. Results: For both in vitro and in situ studies, there was no significant difference between treatments (P>0.05). However, all treatments increased microhardness of demineralized enamel (P<0.05). After a further in situ cariogenic challenge, with the exception of the placebo, all treatments maintained microhardness values (P<0.05). Microbiological analysis showed no difference in Streptococcus mutans (P>0.05) or Lactobacillus (P>0.05) counts between groups. Conclusion: The results suggest that APF gel combined with the CO₂ laser, regardless of the pulse emission mode used, was effective in controlling enamel demineralization, but none of the tested treatments was able to prevent bacterial colonization.

Effects of 10,600 nm Carbon Dioxide Laser on Remineralizing Caries: A Literature Review

Objective: To study the effects of carbon dioxide (CO₂) lasers (λ = 10,600 nm) on remineralizing dental caries. Methods: This study involved performing a systematic search of English articles archived in the PubMed, Scopus, and Web of Science databases. The keywords used to identify the relevant articles were ((CO₂ laser) OR (carbon dioxide laser)) AND ((dental caries) OR (tooth remineralization)). Publications before 2019 were selected. The titles and abstracts of the initially identified articles were screened. Duplicate records, reviews, and irrelevant studies were removed. Full texts were retrieved for publications that studied the effects of CO₂ lasers on remineralizing dental caries. Results: The search identified 543 potentially relevant publications. A total of 285 duplicate records were removed. Sixteen articles were included in this review. Four studies reported that CO₂ lasers inhibited bacterial growth. The growth of cariogenic bacteria, mainly Streptococcus mutans, on an irradiated tooth surface was slower compared with nonirradiated ones. Four studies investigated the reduction of the demineralization of enamel with cariogenic challenge. They found that CO₂ lasers reduced the carbonate content of mineralized tissues and increased the microhardness of enamel. Nine studies used CO₂ lasers associated with topical fluorides in remineralizing dental caries. The results of the synergistic effect of laser irradiation and fluoride application with regard to the inhibition of caries progression varied among these studies, whereas laser irradiation could enhance fluoride uptake to demineralized mineral tissues. Conclusions: CO₂ laser irradiation increased acid resistance and facilitated the fluoride uptake of caries-like lesions. In addition, it reduced the growth of cariogenic bacteria.

Efficacy of erbium-doped yttrium aluminum garnet laser with casein phosphopeptide amorphous calcium phosphate with and without fluoride for remineralization of white spot lesions around orthodontic brackets

Objective

This study aimed to assess the efficacy of erbium-doped yttrium aluminum garnet (Er:YAG) laser, pastes containing casein phosphopeptide amorphous calcium phosphate (CPP-ACP) with and without fluoride and their combination for prevention of white spot lesions in the enamel.

Materials and Methods

This in vitro experimental study was conducted on 90 extracted sound premolars. The teeth were then randomly divided into six groups of 15: (1) Control, (2) laser, (3) CPP-ACP with fluoride (GC MI Paste, Recaldent™ 900 ppm as NaF), (4) CPP-ACP without fluoride (GC Tooth Mousse Recaldent™), (5) laser + CPP-ACP with fluoride, and (6) laser + CPP-ACP without fluoride. In each group, enamel surface was exposed to the remineralizing agent. The teeth were then subjected to pH cycling for 14 days. The teeth were then sectioned, polished, and underwent cross-sectional microhardness testing at 20-160 μ depth quantitatively. Using the Simpson's rule, the amount of mineral loss was calculated in each group. Statistical Analysis Used: ANOVA was used for the comparisons, and Tukey's test was applied for pairwise comparisons.

Results

The highest mean volume percentage of microhardness at 20-60 μ depth belonged to the group laser + CPP-ACP with fluoride and the lowest belonged to the control group (P = 0.001). The differences were not significant at 80-120 μ depth (P > 0.05). These finding are confirmed according to △Z (mineral loss).

Conclusion

Based on these results, Er: YAG laser was able to decrease demineralization and was a potential alternative to preventive dentistry and was more effective when combined with CPP-ACP products.

Effect of CO2 Laser on the Prevention of White Spot Lesions During Fixed Orthodontic Treatment: A Randomized Clinical Trial

Objective

This study aimed to assess the effect of carbon dioxide (CO2) laser on prevention of white spot lesions (WSLs) associated with fixed orthodontic treatment.

Methods

In this parallel controlled trial, 554 maxillary anterior teeth in 95 patients with age range of 12-30 years were included. The samples were randomly divided in two groups: 1) CO2 laser (n=278) and 2) control (n=276) groups. Following bracket attachment, the teeth in the laser group were exposed to CO2 laser (0.4 mw, 10.6 μm, 5 Hz) for 20 s, and the control group received placebo light. Incidence, severity, and extent of the lesions were assessed in four surface regions (gingival, incisal, mesial, and distal) at baseline and 6 months post-irradiation. The inter-group comparison was performed by the Mann-Whitney U test and McNemar analysis.

Results

A significant difference regarding WSLs incidence in all teeth was observed between the two study groups (p<0.001). The two study groups illustrated a significant difference in lesion extent and incidence in incisal, mesial, and distal regions (p<0.05). The WSLs were significantly different in terms of severity in the incisal and mesial sites (p<0.05).

Conclusion

The CO2 laser irradiation seemed to effectively prevent incidence of WSLs. In addition, its effectiveness varied depending on the surface region.

Laser-assisted prevention of enamel caries: a 10-year review of the literature

Since the invention of lasers in dentistry, investigations in caries prevention by the use of laser radiation have been proposed. There are several mechanisms stated for this purpose such as photothermal and/or photochemical interaction processes with the enamel. Alone or in conjugation with topical fluoride application, this treatment modality may improve enamel acid resistance in high-caries-risk populations. Data collection was done by searching the keywords caries, prevention, and laser in PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar. Lasing protocols of the collected literature and their effectiveness as well as examination methods used to verify treatment outcomes have been evaluated. One hundred eighteen publications were found for the last 10 years. The wavelengths investigated for caries prevention are mainly located in the near and the mid-infrared spectral range. In the evaluated period of time, investigations using CO₂; Er:YAG; Er,Cr:YSGG; Er:YLF; fundamental, second, and third harmonic generations of Nd:YAG; diodes; and argon ion lasers were found in the databases. Accounting for 39% of the literature, CO₂ laser was the most examined system for this purpose. Reviewing the literature in this narrative review showed that all laser systems presented a positive effect in varying degrees. Laser irradiation could be an alternative or synergistic to topical fluoridation for enamel caries prevention with longer lasting effect. Further research should be focused on selecting proper laser settings to avoid damage to enamel and developing effective evidence-based clinical protocols.

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.

Influence of Ultrapulsed CO2 Laser, before Application of Different Types of Fluoride, on the Increase of Microhardness of Enamel In Vitro

Objective

To evaluate the influence of ultrapulsed CO₂ laser in combination with commercial fluoride products in order to verify the increase of microhardness of artificial enamel caries lesions.

Materials and Methods

Bovine enamel specimens were prepared, and artificial enamel caries lesions were created. Teeth were randomly divided into 5 groups (n=10): treated with laser (L), laser + neutral fluoride gel 2% (LNF), laser + acidulated phosphate fluoride gel 1.23% (LAFG), laser + acidulated fluoride mousse 1.23% (LAFM), and laser + fluoride varnish 5% (LFV). Microhardness was evaluated at baseline, after caries induction, after CO₂ laser irradiation + fluoride treatment in the 1st week, and after fluoride treatment at 3rd and 5th week.

Results

There was a decrease in microhardness in all groups after artificial enamel caries lesion formation; no increase in microhardness was found in the first and third weeks in all groups (p > 0.05). In the fifth week, an increase in microhardness occurred in all groups (p < 0.05).

Conclusion

Although CO2 laser irradiation in combination with different commercial fluoride products was capable of increasing microhardness on enamel caries lesions in bovine tooth enamel it is necessary to confirm these results by testing the isolated effect of fluoride on enamel surface microhardness. Also, although microhardness was higher in the fluoride varnish group than in the other groups in the fifth week it is not possible to discard the best effect of fluoride varnish treatment on absence of artifacts that may occur with the other fluoride treatments.

Clinical Relevance

In order to prove that CO2 laser may contribute to an increase in microhardness when applied to enamel lesions in combination with different commercial fluoride products it is necessary to conduct additional studies. Also, higher microhardness of fluoride varnish group should be carefully considered.

The effect of diode laser irradiation associated with photoabsorbing agents containing remineralizing materials on microhardness, morphology and chemical structure of early enamel caries

Background

This study investigated the effects of laser irradiation associated with photo-absorbing agents containing sodium fluoride (NaF), MI paste Plus or Remin Pro® on microhardness and surface structure of white spot lesions (WSLs).

Material and Methods

Fifty-six premolars were divided into two halves, then immersed in a demineraling solution to induce WSLs. The samples were divided into 8 groups by treatment (n=12) : (1) control, (2) diode laser (810 nm, 500 mW, 90 s), (3) NaF, (4) MI Paste plus, (5) Remin Pro®, (6) NaF + Laser, (7) MI Paste Plus + Laser, (8) Remin Pro® + Laser. Microhardness was measured before and after remineralization treatments. Two samples from each group were selected for SEM analysis.

Results

Microhardness increased significantly after all treatments with the exception of control, Laser and Remin Pro® groups (p >0.05). ANOVA revealed no significant difference in initial microhardness (P=0.21), whereas a significant difference was noted after treatment (P=0.009). The application of sodium fluoride with or without laser irradiation produced the highest microhardness among the groups (p<0.05). SEM analysis revealed some cracks on lased enamel and non-homogenous coatings of minerals after the use of remineralizing products.

Conclusions

The use of NaF either alone or combined with laser irradiation was the most effecttive strategy for increasing microhardness of WSLs. The application of diode laser through photoabsorbing agents containing sodium fluoride or MI Paste Plus did not produce any additional effects in enhancing remineralization of WSLs, whereas the combined application of diode laser with Remin Pro® was effective.

Key words:CPP-ACP, Enamel caries, fluoride, Hydroxyapatite, Low level laser, Microhardness, Remineralization, casein phosphopeptide amorphous calcium phosphate.

Effect of CPP-ACP paste with and without CO2 laser irradiation on demineralized enamel microhardness and bracket shear bond strength

Introduction:

Many patients seeking orthodontic treatment already have incipient enamel lesions and should be placed under preventive treatments. The aim of this in vitro study was to evaluate the effect of CPP-ACP paste and CO₂ laser irradiation on demineralized enamel microhardness and shear bond strength of orthodontic brackets.

Methods:

Eighty caries-free human premolars were subjected to a demineralization challenge using Streptococcus mutans. After demineralization, the samples were randomly divided into five equal experimental groups: Group 1 (control), the brackets were bonded without any surface treatment; Group 2, the enamel surfaces were treated with CPP-ACP paste for 4 minutes before bonding; Group 3, the teeth were irradiated with CO₂ laser beams at a wavelength of 10.6 µm for 20 seconds. The samples in Groups 4 and 5 were treated with CO₂ laser either before or through CPP-ACP application. SEM photomicrographs of a tooth from each group were taken to observe the enamel surface. The brackets were bonded to the buccal enamel using a conventional method. Shear bond strength of brackets and ARI scores were measured. Vickers microhardness was measured on the non-bonded enamel surface. Data were analyzed with ANOVA and Tukey test at the p< 0.05 level.

Results:

The mean shear bond strength and microhardness of the laser group were higher than those in the control group and this difference was statistically significant (p< 0.05). All groups showed a higher percentage of ARI score 4.

Conclusion:

CO₂ laser at a wavelength of 10.6 µm significantly increased demineralized enamel microhardness and enhanced bonding to demineralized enamel.

The effects of fractional CO2 laser, Nano-hydroxyapatite and MI paste on mechanical properties of bovine enamel after bleaching

Background

This study investigated the effect of post bleaching treatments to the change of enamel elastic modulus and microhardness after dental bleaching in- vitro.

Material and Methods

Fifty bovine incisor slab were randomly assigned into five groups (n=10). The samples were bleached for three times; 20 minutes each time, by 40% hydrogen peroxide. Next it was applied fractional CO2 laser for two minutes, Nano- hydroxy apatite (N-HA) and MI-paste for 7 days and 2 minutes per day. The sound enamel and bleached teeth without post treatment remained as control groups. The elastic modulus and microhardness were measured at three times; 24 hours, 1 and 2 months. Data were statistically analyzed by two-way analysis of variance with 95% confidence level.

Results

Different methods of enamel treatment caused a significant increase in elastic modulus compared to bleached group (P<0.05). Modulus was significantly increased in 1 and 2 months (P<0/001: bleach, P= 0/015: laser, P= 0/008: NHA, P=0/010: MI paste) but there were no significantly difference between 1 and 2 months (P>0.05). There was any significance difference for hardness among treated and control groups, but hardness increased significantly by increasing storage time (P<0.05).

Conclusions

The use of the protective tested agents can be useful in clinical practice to reduce negative changes of enamel surface after whitening procedures.

Key words:Bleaching enamel, CO2 laser, MI pastes, Nano-hydroxy apatite, Microhardness, Elastic modulus.

Effect of CO2 Laser and Fluoride Varnish Application on Microhardness of Enamel Surface Around Orthodontic Brackets

Introduction: Orthodontic treatment has many advantages such as esthetic improvement and self-esteem enhancement; yet it has some disadvantages such as increasing the risk of formation of white spot lesions, because it makes oral hygiene more difficult. It is rational to implement procedures to prevent these lesions. The present study was aimed to assess the effect of CO₂ laser and fluoride varnish on the surface of the enamel surface microhardness around the orthodontic braces. Methods: Eighty extracted premolar teeth were selected, scaled, polished with nonfluoridated pumic and metal brackets were bonded to them. Then, they were randomly allocated to 5 groups: control (neither fluoride nor laser is used on enamel surfaces), fluoride (4 minutes fluoride varnish treatment of the enamel surfaces), CO₂ laser (10.6 µm CO₂ laser irradiation of the teeth), laserfluoride (fluoride application after laser irradiation) and fluoride-laser (fluoride was applied and then teeth were irradiated with laser). After surface treatment around brackets on enamel, the samples were stored in 0.1% thymol for less than 5 days and then they were exposed to a 10-day microbiological caries model. Microhardness values of enamel were evaluated with Vickers test. One sample of each group (5 teeth from 80 samples) was prepared for SEM (scanning electron microscopy) and the data from 75 remaining teeth were analyzed with analysis of variance (ANOVA) and chi-square tests (α =0.05). Results: Microhardness mean values from high to low were as follow: fluoride-laser, laser-fluoride, laser, fluoride and control. Microhardness in fluoride-laser group was significantly higher compared with that of the control group. Distribution adhesive remnant index (ARI) scores were significantly different between groups and most of bond failures occurred at the enamel-adhesive interface in groups 2 to 5 and at the adhesive-bracket interface in the control group. Conclusion: Combination of fluoride varnish and CO2 laser irradiation can reduce enamel demineralization around orthodontic brackets.

Management of post-orthodontic white spot lesions: an updated systematic review

Background/objectives

The management of post-orthodontic white spot lesions is based on remineralization strategies or a minimal-invasive camouflage of the lesions.

Aim

The aim of this systematic review was to identify and assess the quality of evidence for the various clinical technologies.

Search methods

Four databases were searched for relevant literature published in English between 2011 and 31 October 2015 according to a pre-determined PICO. Only controlled clinical studies were considered. Abstract lists and the selected full-text papers were independently examined by two reviewers and any differences were solved in consensus. The Cochrane handbook and the AMSTAR tool were used for grading the risk of bias. The quality of evidence was rated according to GRADE.

Results

Out of 280 identified publications, seven studies on remineralization, micro-abrasion and resin infiltration met the inclusion criteria. Two of them were assessed with low risk of bias. No pooling of results was possible due to study heterogeneity. The quality of evidence for all technologies was graded as very low.

Limitations

Only papers published in English with more than 20 adolescents or young adults were considered. Furthermore, a follow-up period of at least 8 weeks was required. The publication bias could not be assessed due to the paucity of included trials.

Conclusions/clinical implications

There is a lack of reliable scientific evidence to support re-mineralizing or camouflaging strategies to manage post-orthodontic white spot lesions. Further well-performed controlled clinical trials with long-term follow-up are needed to establish best clinical practice.

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.

Effect of Nd:YAG and CO2 Laser Irradiation on Prevention of Enamel Demineralization in Orthodontics: In Vitro Study

OBJECTIVE

The aim of this study was to investigate Nd:YAG and CO₂ laser effects in the prevention of demineralization in deeper layers of enamel via successive acid challenge cycles.

BACKGROUND DATA

Lasers are promising in the prevention of enamel demineralization around the orthodontic brackets; however, there are very few studies that evaluate if the effects of treatment could be extended after successive acid challenge cycles due to permanent enamel structural alterations.

MATERIALS AND METHODS

Human enamel samples were divided into five groups (n = 12): G1-application of 1.23% acidulated fluoride phosphate gel (AFP, control); G2-Nd:YAG laser irradiation (0.6 W, 84.9 J/cm², 10 Hz, 110 μs, contact mode); G3-Nd:YAG laser irradiation associated with AFP; G4-CO₂ laser irradiation (0.5 W, 28.6 J/cm², 50 Hz, 5 μs, and 10 mm focal distance); and G5-CO₂ laser irradiation associated with AFP. The samples were submitted to successive acid challenge cycles. Quantitative light-induced fluorescence and scanning electron microscopy were used to assess enamel demineralization. The data were statistically compared (α = 5%).

RESULTS

G1: 50.87 ± 4.57; G2: 47.72 ± 2.87; G3: 50.96 ± 4.01; G4: 28.21 ± 2.19; and G5: 30.13 ± 6.38. The CO₂ laser groups had significantly lower mineral losses than those observed in all other groups after successive acid challenge cycles.

CONCLUSIONS

Only the CO₂ laser (10.6 μm) irradiation prevents enamel demineralization around the orthodontic brackets even after exposure to successive acid challenges. The CO₂ laser at 10.6 μm showed a deeper effect in enamel regarding caries prevention.

Comparison of enamel remineralization potential after application of titanium tetra fluoride and carbon dioxide laser

BACKGROUND AND AIMS

The aim was comparison of enamel remineralization after application of APF, TiF₄ and CO₂ laser alone or in combination.

MATERIALS AND METHODS

Enamel blocks were prepared from human third molars. The initial surface hardness was determined by Vicker's hardness tester. The samples underwent a demineralization regimen for 7 days to produce artificial initial caries. The hardness of enamel blocks with white spot lesions was measured, and the samples which had the mean hardness change of 65-90%, were selected, and randomly divided into 5 groups (N=15): G1: control; G2: APF 1.23%; G3: TiF₄ 4%; G4: TiF₄ 4% followed by CO₂ laser (10.6 µm wavelength, 1 W peak power, 10 ms pulse duration, 500 ms repeat time, 0.2 mm beam spot size, 2 cm distance); G5: CO₂ laser (same parameters) followed by TiF₄ 4%. Surface hardness recovery was measured after the treatments. Three samples in each group were observed under scanning electron microscope at ×1,000 magnification. Data were analyzed by repeated measure ANOVA and Bonferrouni tests. Significance level was set at 0.05.

RESULTS

G2, G3, G4 indicated significant differences with control and G5 (p<0.05). Surface hardness in G5 was not significantly different from control (p=0.7) in enamel hardness test. There was not a significant difference between G2 & G3, G2 & G4, and G3 & G4 (p=1). The SEM results indicated globules of calcium fluoride on the surface in G2, and a smooth glaze-like surface layer in G3 and G4. In G5, some micro-cracks without any glaze-like layer were observed.

CONCLUSIONS

APF, TiF₄ and TiF₄ before CO₂ laser irradiation significantly increased the micro-hardness of initially demineralized enamel surfaces. CO₂ laser irradiation before TiF₄ application could not remineralize the white-spot lesions.

Bonding brackets on white spot lesions pretreated by means of two methods

OBJECTIVE

The aim of this study was to evaluate the shear bond strength (SBS) of brackets bonded to demineralized enamel pretreated with low viscosity Icon Infiltrant resin (DMG) and glass ionomer cement (Clinpro XT Varnish, 3M Unitek) with and without aging.

METHODS

A total of 75 bovine enamel specimens were allocated into five groups (n = 15). Group 1 was the control group in which the enamel surface was not demineralized. In the other four groups, the surfaces were submitted to cariogenic challenge and white spot lesions were treated. Groups 2 and 3 were treated with Icon Infiltrant resin; Groups 4 and 5, with Clinpro XT Varnish. After treatment, Groups 3 and 5 were artificially aged. Brackets were bonded with Transbond XT adhesive system and SBS was evaluated by means of a universal testing machine. Statistical analysis was performed by one-way analysis of variance followed by Tukey post-hoc test.

RESULTS

All groups tested presented shear bond strengths similar to or higher than the control group. Specimens of Group 4 had significantly higher shear bond strength values (p < 0.05) than the others.

CONCLUSION

Pretreatment of white spot lesions, with or without aging, did not decrease the SBS of brackets.

Structural and Morphological Changes in Human Dentin after Ablative and Subablative Er:YAG Laser Irradiation

INTRODUCTION

This study investigated the influence of Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser on microhardness, chemical composition and subsurface morphology of dentin cavity walls.

METHODS

Forty sound human premolars were selected and randomly assigned into four groups. Class V cavities were prepared either with an Er:YAG laser (groups 1 and 2; 15 Hz, 250 mJ for enamel, 10 Hz, 200 mJ for dentin) or with a high speed handpiece (groups 3 and 4). The specimens in groups 1 and 3 served as the control, whereas those in groups 2 and 4 were exposed to subablative laser irradiation following cavity preparation (10 Hz, 50 mJ). After bisecting the specimens, one half was subjected to microhardness assessment and the other half was evaluated by SEM-EDS analysis.

RESULTS

Microhardness was significantly greater in the specimens prepared by both ablative and subablative laser irradiation (group 2) than that of the bur-prepared cavities (groups 3 and 4) (P < 0.05). The quantity of calcium ion was significantly greater in cavities prepared by the Er:YAG laser (groups 1 and 2) compared to that of the bur cavities (groups 3 and 4) (P < 0.05). Subablative irradiation improved microhardness and weight percentage of calcium ion in both laser and bur cavities, but the difference was not significant compared to that of the relevant control group (P > 0.05).

CONCLUSION

Cavity preparation with an Er:YAG laser could be considered as an alternative to the conventional method of drilling, as it enhances the mechanical and compositional properties of lased dentin, especially when combined by subablative irradiation.

The Influence of Post Bleaching Treatments in Stain Absorption and Microhardness

Objectives:

This study investigated the effects of post bleaching treatments to prevent restaining and the change of enamel surface microhardness after dental bleaching in vitro.

Methods:

Sixty intact human incisor teeth were stained in tea solution and randomly assigned into four groups (n=15). Then samples were bleached for two weeks (8 hours daily) by 15% carbamide peroxide. Tooth color was determined both with a spectrophotometer and visually before bleaching (T1) and immediately after bleaching (T2). Next, it was applied in group 1 fluoride (Naf 2%) gel for 2 minutes, and in group 2 a fractional CO₂ laser (10 mJ, 200 Hz, 10 s), and in group 3, nanohydroxyapatite gel for 2 minutes. The bleached teeth in group 4 remained untreated (control group). Then teeth placed in tea solution again. Color examinations were repeated after various post bleaching treatments (T3) and restaining with tea (T4) and color change values recorded. The microhardness was measured at the enamel surface of samples. Data was analyzed using ANOVA, Tukey HSD test and Dunnett T3 (α = 0.05).

Results:

Directly after bleaching (ΔE _T3-T2), the treatment with nanohydroxyapatite showed significantly the least color lapse in colorimetric evaluation. In experimental groups, the color change between T3 and T4 stages (ΔE _T4-T3) was significantly lower than control group (P < 0.05). Different methods of enamel treatment caused a significant increase in surface microhardness compared to control group (P < 0.05).

Significance:

Application of fluoride, fractional CO₂ laser and nanohydroxyapatite as post bleaching treatments are suggested for prevention of stain absorption and increasing the hardening of bleached enamel.

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.

The staining effect of different mouthwashes containing nanoparticles on dental enamel

Background

This study aimed to evaluate the effects of several mouthwashes containing nanoparticles on discoloration of dental enamel, and compare the results with that of 0.2% chlorhexidine (CHX).

Material and Methods

Sixty intact premolars were randomly assigned to six groups. A spectrophotometer was used to measure the color of the teeth (T1) according to the CIELAB system. The specimens in groups 1 to 4 were then immersed in colloidal solutions containing nanoTiO2 (Group 1), nanoZnO (Group 2), nanoAg (Group 3) and nanoCuO (Group 4). In groups 5 and 6, a 0.2% CHX mouthwash and distilled water were used as positive and negative controls, respectively. After 24 hours of immersion, color determination was repeated (T2). The third color assessment was accomplished after brushing (T3). The L, a, and b values were recorded and the color change (?E) between different stages was calculated.

Results

ANOVA revealed significant between-group differences in the color change between T1 and T2 stages, as well as between T1 and T3 time points (p<0.05), whereas the color change between T2 and T3 was not significantly different among the study groups (p=0.09). ?ET1-T3 was significantly lower in the specimens immersed in distilled water or CHX as compared to the nanoparticle-containing mouthwashes (p<0.05). The highest ?E value pertained to the specimens immersed in nanoZnO-containing solution. The TiO2 nanoparticles caused the lowest staining among the tested nanoparticles.

Conclusions

The mouthwashes containing nanoparticles produced comparable or even greater enamel discoloration compared to CHX. Brushing had little effect on removal of induced stains.

Key words:Nanoparticle, mouthrinse, mouthwash, staining, enamel, discoloration, chlorhexidine.

Nickel Ion Release from Three Types of Nickel-titanium-based Orthodontic Archwires in the As-received State and After Oral Simulation

Background and aims. This study aimed to investigate release of nickel ion from three types of nickel-titanium-based wires in the as-received state and after immersion in a simulated oral environment.

Materials and methods. Forty specimens from each of the single-strand NiTi (Rematitan "Lite"), multi-strand NiTi (SPEED Supercable) and Copper NiTi (Damon Copper NiTi) were selected. Twenty specimens from each type were used in the as-received state and the others were kept in deflected state at 37ºC for 2 months followed by autoclave sterilization. The as-received and recycled wire specimens were immersed in glass bottles containing 1.8 mL of artificial saliva for 28 days and the amount of nickel ion released into the electrolyte was determined using atomic absorption spectrophotometry.

Results. The single-strand NiTi released the highest quantity of nickel ion in the as-received state and the multi-strand NiTi showed the highest ion release after oral simulation. The quantity of nickelion released from Damon Copper NiTi was the lowest in both conditions. Oral simulation followed by sterilization did not have a significant influence on nickel ion release from multi-strand NiTi and Damon Copper NiTi wires, but single-strand NiTi released statistically lower quantities of nickel ion after oral simulation.

Conclusion. The multi-strand nature of Supercable did not enhance the potential of corrosion after immersion in the simulated oral environment. In vitro use of nickel-titanium-based archwires followed by sterilization did not significantly increase the amount of nickel ion released from these wires.

Comparative evaluation of the effect of Er:YAG laser and low level laser irradiation combined with CPP-ACPF cream on treatment of enamel caries

Objectives: This study investigated the effectiveness of low power red and infrared lasers and that of Er:YAG laser, in association with CPP-ACPF cream, on remineralization of white spot lesions. Study Design: Fifty intact premolars were immersed in a demineralization solution for 10 weeks to induce caries like lesions and then were divided into five groups. In group 1, the teeth were covered with a CPP-ACPF cream for 3 minutes and then irradiated with a low power red laser (660 nm, 200 mW) for 1 minute through the cream. In group 2, the treatment was the same as that in group 1, but an infrared laser (810 nm, 200 mW) was employed. The specimens in group 3 were irradiated with an Er:YAG laser (100 mJ, 10 Hz) combined with CPP-ACPF. In group 4, the CPP-ACPF cream was applied for 4 minutes and group 5 was submitted to neither laser nor CPP-ACPF. The micro Vickers hardness was compared at 20, 60 and 100 µ from the enamel surface among the groups. Results: The highest microhardness was observed in the low power red and Er:YAG laser groups and the lowest one belonged to the CPP-ACPF alone and control groups. However, no significant difference was found in microhardness of the experimental groups at any of the evaluation depths (p>0.05). Conclusions: With the laser parameters used in this study, neither the combined application of Er:YAG laser with CPP-ACPF nor the combination of low power lasers with CPP-ACPF provided a significant increase in remineralization of enamel caries.

Key words:Low level laser, Er:YAG, laser, enamel caries, CPP-ACP, microhardness, white spot lesion.

Microleakage and shear bond strength of orthodontc brackets bonded to hypomineralized enamel following different surface preparations

Objectives: This study investigated the effects of several conditioning methods on shear bond strength (SBS) and microleakage of orthodontic brackets bonded to demineralized enamel. Study Design: One hundred premolars were selected and immersed in a cariogenic solution for 12 weeks. The teeth were randomly assigned into 5 groups. In groups 1 and 2, the teeth underwent acid etching for 30 and 120 seconds, respectively. In group 3, a combination of laser and acid etching was employed. A self-etch primer (SEP) was applied in group 4 and in group 5, the teeth were exposed to acidulated phosphate fluoride (APF) for 4 minutes before etching. After bracket bonding, the teeth were immersed in methylen blue for 12 hours and then were mounted in acrylic resin. SBS was determined with an Instron Universal Testing Machine and the amount of microleakage under the brackets was assessed under a stereomicroscope. Results: The lowest SBS was related to the SEP group and the highest one was observed in the specimens prepared by APF+acid etching. There was a significant difference in SBS (p=0.009), but not in microleakage (p=0.971) of the study groups. The SBS of the specimens treated with SEP was significantly Lower than the other groups, which were not significantly different from each other. The SEP group displayed a higher frequency of bond failure at the enamel-adhesive interface. Conclusions: Enamel preparation with SEP provided the lowest SBS among the groups. All groups showed some degree of microleakage. There was no significant correlation between SBS and microleakage.

Key words:Bond strength, microleakage, bonding, self-etch primer, Er:YAG laser.