Evaluation of an experimental rat model for comparative studies of bleaching agents

Cintra, Luciano Tavares Angelo; Benetti, Francine; Ferreira, Luciana Lousada; Rahal, Vanessa; Ervolino, Edilson; Jacinto, Rogério de Castilho; Gomes Filho, João Eduardo; Briso, André Luiz Fraga

doi:10.1590/1678-775720150393ar

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ORIGINAL ARTICLES • J. Appl. Oral Sci. 24 (1) • Jan-Feb 2016 • https://doi.org/10.1590/1678-775720150393ar linkcopy

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10.1590/1678-7757-2025er003

Evaluation of an experimental rat model for comparative studies of bleaching agents

Authorship SCIMAGO INSTITUTIONS RANKINGS

Dental materials, in general, are tested in different animal models prior to their clinical use in humans, except for bleaching agents.

Objectives To evaluate an experimental rat model for comparative studies of bleaching agents by investigating the influence of different concentrations and application times of H₂O₂ gel in the pulp tissue during in-office bleaching of rats’ vital teeth.

Material and methods The right and left maxillary molars of 50 Wistar rats were bleached with 20% and 35% H₂O₂ gels, respectively, for 5, 10, 15, 30, or 45 min (n=10 rats/group). Ten animals (control) were untreated. The rats were killed after 2 or 30 days, and the maxillae were examined by light microscopy. Inflammation was evaluated by histomorphometric analysis with inflammatory cell counting in the coronal and radicular thirds of the pulp. The counting of fibroblasts was also performed. Scores were attributed to the odontoblastic layer and to vascular changes. The tertiary dentin area and the pulp chamber central area were histomorphometrically measured. Data were compared by the analysis of variance and the Kruskal-Wallis test (p<0.05).

Results After 2 days, the amount of inflammatory cells increased in the occlusal third of the coronal pulp until the time of 15 min for both concentrations of bleaching gels. In 30 and 45 min groups of each concentration, the number of inflammatory cells decreased along with the appearance of necrotic areas. After 30 days, a reduction in the pulp chamber central area and an enlargement of tertiary dentin area were observed without the detection of inflammation areas.

Conclusion The rat model of extra coronal bleaching showed to be adequate for bleaching protocols studies, as it was possible to observe alterations in the pulp tissues and in the tooth structure caused by different concentrations and periods of application of bleaching agents.

Bleaching agents; Animal models; Hydrogen peroxide

Group		Coronal			Radicular
		Occlusal	Middle	Cervical	Cervical	Middle	Apical
Control		0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
20% H₂O₂ gel	5 min	3.6 ±0.5^b	2.2 ±0.4^ab	1.0 ±0.4^ab	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	10 min	5.6 ±1.1^bc	4.6 ±1.1^bcd	2.2 ±0.5^abc	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	15 min	7.6 ±1.5^c	6.0 ±1.4^ce	3.4 ±0.9^bd	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	30 min	5.2 ±0.8^bc	8.2±1.3^e	5.2 ±1.1^d	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	45 min	3.2 ±0.8^b	13.0 ±2.9^fg	9.0 ±2.3^e	5.6 ±0.9^b	0.0 ±0.0^a	0.0 ±0.0^a
35% H₂O₂ gel	5 min	4.0 ±0.7^b	4 ±1.0^bc	2.2 ±0.5^abc	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	10 min	10.6±2.3^d	7.4 ±1.1^de	4.4 ±1.1^cd	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	15 min	14.6±3.6^e	11.8±2.3^f	5.2 ±1.3^d	0.0 ±0.0^a	0.0 ±0.0^a	0.0 ±0.0^a
	30 min	6.0±1.4^bc	15.6±1.3^g	9.8 ±2.6^e	5.8 ±0.8^b	0.0 ±0.0^a	0.0 ±0.0^a
	45 min	0.0 ±0.0^a	12.0±2.9^f	11.0±2.6^e	7.6±1.5^c	0.0 ±0.0^a	0.0 ±0.0^a

Group		Coronal			Radicular
		Occlusal	Middle	Cervical	Cervical	Middle	Apical
Control		65.2 ±8.7^a	67.0 ±7.8^ab	44.0 ±4.6^abc	38.0 ±3.7^a	33.8 ±2.9^a	37.2 ±3.3^a
20% H₂O₂ gel	5 min	51.8 ±6.6^ab	72.2 ±11.9^a	52.8 ±8.5^bc	39.4 ±4.2^a	35.8 ±3.0^a	37.0 ±2.3^a
	10 min	45.2 ±9.2^bc	54.0 ±4.2^bc	55.6 ±11.2^c	36.8 ±2.9^a	37.6 ±3.1^a	35.0 ±3.2^a
	15 min	36.2 ±3.6^c	46.4 ±2.4^cd	43.2 ±8.4^ac	41.2 ±0.8^a	38.2 ±3.6^a	35.2 ±3.3^a
	30 min	5.8 ±1.6^de	32.4±7.5^de	34.6 ±5.5^ad	39.6 ±1.9^a	36.2 ±3.8^a	37.2 ±2.2^a
	45 min	0.0 ±0.0^d	26.0 ±1.6^efg	29.0 ±8.2^def	36.0 ±4.5^a	37.6 ±4.2^a	38.2 ±2.6^a
35% H₂O₂ gel	5 min	15.2 ±2.8^e	64.8 ±11.3^ab	40.8 ±8.0^abe	35.2 ±2.9^a	34.8 ±3.9^a	39.0 ±2.3^a
	10 min	13.2±3.0^de	54.6±12.4^abc	35.2 ±3.6^ae	38.6 ±1.5^a	36.2 ±4.3^a	37.6 ±3.6^a
	15 min	10.8±2.9^de	41.6±9.7^cdf	34.2 ±3.0^ae	37.6 ±2.5^a	38.8 ±1.6^a	37.6 ±4.3^a
	30 min	5.8±0.8^de	23.2±5.0^eg	30.4 ±4.0^aef	36.0 ±4.2^a	37.8 ±2.2^a	39.6 ±4.5^a
	45 min	0.0 ±0.0^d	10.2±2.7^g	19.6±1.8^f	38.0±2.7^a	36.8 ±2.6^a	40.2 ±4.2^a

Group		Coronal			Radicular
		Occlusal	Middle	Cervical	Cervical	Middle	Apical
Control		1^a	1^a	1^a	1^a	1^a	1^a
20% H₂O₂ gel	5 min	1^a	1^a	1^a	1^a	1^a	1^a
	10 min	2^ab	1^a	1^a	1^a	1^a	1^a
	15 min	2^ab	1^a	1^a	1^a	1^a	1^a
	30 min	3^ab	1^a	1^a	1^a	1^a	1^a
	45 min	3^b	2^ab	1^a	1^a	1^a	1^a
35% H₂O₂ gel	5 min	2^ab	1^ab	1^a	1^a	1^a	1^a
	10 min	3^ab	2^ab	1^a	1^a	1^a	1^a
	15 min	3^ab	2^ab	1^a	1^a	1^a	1^a
	30 min	3^b	3^ab	1^a	1^a	1^a	1^a
	45 min	3^b	3^b	2^a	1^a	1^a	1^a

Group		Coronal			Radicular
		Occlusal	Middle	Cervical	Cervical	Middle	Apical
Control		1^a	1^a	1^a	1^a	1^a	1^a
20% H₂O₂ gel	5 min	1^a	1^a	1^a	1^a	1^a	1^a
	10 min	2^ab	2^ab	1^a	1^a	1^a	1^a
	15 min	2^ab	2^ab	1^a	1^a	1^a	1^a
	30 min	2^ab	2^ab	1^a	1^a	1^a	1^a
	45 min	3^b	2^ab	1^a	1^a	1^a	1^a
35% H₂O₂ gel	5 min	2^ab	2^ab	2^a	1^a	1^a	1^a
	10 min	2^ab	2^ab	2^a	1^a	1^a	1^a
	15 min	2^ab	2^ab	2^a	1^a	1^a	1^a
	30 min	3^ab	2^ab	2^a	1^a	1^a	1^a
	45 min	3^b	3^b	2^a	1^a	1^a	1^a

Group		Mean (105)*	SD (105)	% reduction
Control		18.46^a	2.38	0.00
20% H₂O₂ gel	5 min	17.57^a	2.30	4.82
	10 min	17.18^a	1.85	6.93
	15 min	15.65^ab	1.78	15.22
	30 min	13.47^bc	1.43	27.03
	45 min	11.23^cd	1.17	39.16
35% H²O₂ gel	5 min	14.61^ab	0.46	20.85
	10 min	13.41^bc	0.72	27.36
	15 min	12.56^bcd	0.71	32.33
	30 min	10.01^de	0.62	45.77
	45 min	6.98^e	0.51	62.18

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[TFN1] *Different letters in the columns indicate significant difference between the groups (Kolmogorov-Smirnov normality test and the Two-way ANOVA and Tukey test - p<0.05).