Biomateriales

Keywords: Antibacterial activity, carbamide peroxide, dental bleaching, oral microorganisms, randomized clinical trial, Streptococcus mutans

How to cite this article:

Franz-Montan M, Ramacciato JC, Rodrigues JA, Marchi GM, Rosalen PL, Groppo FC. The effect of combined bleaching techniques on oral microbiota. Indian J Dent Res 2009;20:304-7

How to cite this URL:

Franz-Montan M, Ramacciato JC, Rodrigues JA, Marchi GM, Rosalen PL, Groppo FC. The effect of combined bleaching techniques on oral microbiota. Indian J Dent Res [serial online] 2009 [cited 2011 Jan 5];20:304-7. Available from: http://www.ijdr.in/text.asp?2009/20/3/304/57367

Dental bleaching, performed at home or in an office, is a simple and conservative procedure for aesthetic restoration of vital and nonvital discoloured or stained teeth. [1],[2]

First described in 1989 by Haywood and Heymann, [3] the at- home dental bleaching, proven safe and effective, [4] has been associated with the in-office dental bleaching to achieve tooth whitening in a shorter period of time, especially in the cases of more severe stains. [5]

Although previous studies have shown some antimicrobial effect of bleaching systems containing carbamide peroxide on oral microorganisms, [6],[7],[8] there are still controversies concerning the in vivo antimicrobial activity of the bleaching agents.

The present study was conducted to evaluate the effect of the association of two different dental bleaching techniques, on oral microorganisms, from human saliva.

Materials and Methods

The Ethical Committee of Piracicaba Dental School, State University of Campinas, approved this research. All volunteers signed a written informed consent.

This double blind study evaluated 32 healthy volunteers between the age range of 18 to 31 years. They were in good health, had no history of allergy to the dental bleaching agents used, and had all teeth (no fixed or removable dentures). The ones wearing orthodontic appliances, pregnant, nursing, smokers, having dentin sensitivity, ingesting medicines that would decrease salivary flow, or taking antimicrobial agents/mouthrinses at least three months prior to the study were also excluded.

Dental bleaching

The volunteers were randomly distributed into four different groups (n = 8) and received the combination of the in-office (IO) and the at-home (AH) dental bleaching, according to each group [Table 1]. The IO dental bleaching comprised a 37% carbamide peroxide gel (CP-37 - Whiteness Super- FGM, Joinville, Brazil), and the AH dental bleaching was 10% carbamide peroxide gel (CP-10 - Whiteness Perfect- FGM, Joinville, Brazil). A placebo gel (PG - Carbopol 934P gel, FGM, Joinville, Brazil) was also used in combination with the IO or the AH treatment.

Two weeks before the treatment began, the volunteers received toothbrushes (Oral B 40, Gillete do Brasil Ltd., Manaus, Brazil), and dentifrices without fluoride (52.5% of calcium carbonate, 25% of glycerin, 18% of natrosol, 2% of sodium lauril sulphate, and distilled water - Proderma Drugstore, Piracicaba, Brazil). They were instructed to use both, toothbrush and dentifrice, during all the experiment.

Impressions were taken of the upper and lower arches in order to manufacture trays with reservoirs for the AH dental bleaching. [8] The trays were trimmed and polished up to the cervical margin of the teeth.

The IO dental bleaching was performed under rubber dam isolation in three different sections lasting one hour, considering seven days interval. The treatment was then applied on the surface of all teeth (CP 37% or PG, according to each group) during one hour. After this time, the gel was carefully removed with air/water spray.

The AH dental bleaching treatment was kept for three weeks and the volunteers were instructed to use the trays all night long for at least six hours. Depending on the group, the treatment was either CP 10% or PG.

Saliva samples collection and microbiological methods

Saliva samples were collected after stimulation (paraffin wax chewing), as previously described by Dasanayake et al., [9] during five weeks according to the following periods of time: Right before the treatment starts (baseline); right after the IO application (zero hour), and 12 hours after the treatment (12 hours). During the fourth and the fifth weeks, when the treatments stopped, just the baseline collections were performed. The subjects deposited the saliva samples in sterilized eppendorfs tubes by using sterilized straws in order to avoid skin contamination. [10]

Immediately after the saliva collection, the samples were submitted to dispersion of cell aggregates in an ultrasonic cell disrupter (VibraCell 400 W, Sonics and Materials Inc. - at 5% amplitude, 9.9 seconds cycle, 6 pulses), followed by 10-fold dilutions in 0.9% NaCl solution (1:10, 1:100, 1:1000, 1:10000).

Aliquots of each dilution (5 μL) were spread on three different culture media in Petri dish More Detailses (5 ΄ 2 cm 2 ), in duplicates. The media were blood agar (Difco Co - agar base + 5% sheep blood), MSA (Difco Co - Mitis Salivarius Agar, supplemented with 1% potassium tellurite and 15% sucrose), and MSB (Difco Co - Mitis Salivarius Bacitracin agar, supplemented with 200 IU of bacitracin/mL, 1% potassium tellurite, and 15% sucrose), in order to isolate the total microorganisms, streptococci, and mutans streptococci, respectively.[11] The plates were placed in an incubator (Jovan IG 150) with 10% of CO 2 at 37 o C, for 48 hours. Blood agar dishes were also incubated in an aerobic incubator at 37 o C, for 24 hours.

The results were compared by the Friedman test and Wilcoxon sign-ranked test for pair-wise comparison as the post hoc test (Bioestat 4.0, Mamirauα Institute, Belιm, PA, Brazil). The significance level was set at 5%.

Results

The numbers of all microorganisms were not affected (P > 0.05) during the period of time by any of the bleaching agents. There were also no significant differences (P > 0.05) among the groups concerning any of the isolated microorganisms.

[Table 2],[Table 3],[Table 4] shows the bacterial growth (ufc/μL) on blood agar, MSA, and MSB, respectively.

Discussion

Hydrogen peroxide was first used in 1913 to improve healing after gingival surgery as well as to inhibit plaque or periodontal microorganisms. [12] Hydrogen peroxide, with more than 100 years of use, is the active bleaching agent in carbamide peroxide. [13],[14] It is a potent

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