Restor Dent Endod.  2016 Feb;41(1):44-54. 10.5395/rde.2016.41.1.44.

Antioxidant therapy enhances pulpal healing in bleached teeth

• Lima AF
• Marques MR
• Soares DG
• Hebling J
• Marchi GM
• de Souza Costa CA

• KMID: 2316963
• DOI: http://doi.org/10.5395/rde.2016.41.1.44

Abstract

OBJECTIVES
The purpose of this study was to evaluate the histopathological effects of an antioxidant therapy on the pulp tissue of rat teeth exposed to a bleaching gel with 35% hydrogen peroxide.
MATERIALS AND METHODS
Forty rats were subjected to oral ingestion by gavage of distilled water (DW) or ascorbic acid (AA) 90 min before the bleaching therapy. For the bleaching treatment, the agent was applied twice for 5 min each to buccal surfaces of the first right mandibular molars. Then, the animals were sacrificed at 6 hr, 24 hr, 3 day, or 7 day post-bleaching, and the teeth were processed for microscopic evaluation of the pulp tissue.
RESULTS
At 6 hr, the pulp tissue showed moderate inflammatory reactions in all teeth of both groups. In the DW and AA groups, 100% and 80% of teeth exhibited pulp tissue with significant necrosis and intense tissue disorganization, respectively. At 24 hr, the AA-treated group demonstrated a greater regenerative capability than the DW group, with less intense inflammatory reaction and new odontoblast layer formation in 60% of the teeth. For up to the 7 day period, the areas of pulpal necrosis were replaced by viable connective tissue, and the dentin was underlined by differentiated odontoblast-like cells in most teeth of both groups.
CONCLUSIONS
A slight reduction in initial pulpal damage during post-bleaching was promoted by AA therapy. However, the pulp tissue of AA-treated animals featured faster regenerative potential over time.

Keyword

Ascorbic acid; Dental pulp; Hydrogen peroxide; Tooth bleaching

MeSH Terms

Animals
Ascorbic Acid
Connective Tissue
Dental Pulp
Dentin
Eating
Hydrogen Peroxide
Molar
Necrosis
Odontoblasts
Rats
Tooth Bleaching
Tooth*
Water
Ascorbic Acid
Hydrogen Peroxide
Water

Figure

• 

  Figure 1 (a) DW-6 hr. Pulp horn presenting partial necrosis (N). The root pulp presents normal histological characteristics (arrows). H&E, ×32; (b) DW-6 hr. High magnification of (a). Observe that adjacent to the necrotic area (N), there is an intense inflammatory infiltrate of macrophages and neutrophils, and an overflow of blood plasma (arrow). H&E, ×250; (c) AA-6 hr. Presence of a large necrotic area (N) in the pulp horn of a DW-treated rat, and adjacent to this area one can observe viable pulp (P) tissue with inflammatory cell response. H&E, ×125; (d) AA-6 hr. Panoramic view of the pulp horn. Note smaller areas of necrosis (N) when compared with the pulp tissue of DW-treated rats in which the molars were bleached in (a). H&E, ×32; (e) AA-6 hr. High magnification of (d), in which one can observe that a broad area of the pulp (P) adjacent to the necrosis (N) is viable. H&E, ×64; (f) AA-6 hr. Viable coronal pulp (P) tissue, albeit with an inflammatory reaction, can be observed adjacent to the necrotic (N) area. H&E, ×125.

• 

  Figure 2 (a) DW-24 hr. Residual necrotic tissue (N) surrounded by macrophages as well as a large area of fibro-angioblastic proliferation can be observed along with numerous dilated and congested blood vessels (arrows). H&E, ×250; (b) AA-24 hr. Intense fibro-angioblastic proliferation in the pulp horn as well as some differentiated odontoblast-like cells underlying the predentin (arrows) can be seen. Only a slight mononuclear inflammatory cell infiltrate in the pulp (P) is observed. Masson's trichrome, ×250; (c) AA-3 day. Panoramic view of the pulp horn in which new sound connective tissue is replacing the previously necrotic areas of the pulp. H&E, ×32; (d) DW-3 day. Detail of Figure 2(c), where a residual necrotic area (N) surrounded by a few macrophages is observed. Note that new viable connective pulp tissue with numerous small blood vessels covers almost the entire pulp horn. A continuous layer of odontoblasts is underlying the predentin (arrows). H&E, ×125.

• 

  Figure 3 (a) AA-7 day. Panoramic view of the coronal pulp horn with viable pulp tissue. H&E, ×32; (b) AA-7 day. A thin layer of collagen-rich dentin matrix (predentin, arrows) is underlying the mineralized dentin. No residual necrotic area can be seen. H&E, ×125; (c) AA-7 day. Upper region of the pulp horn, where the predentin is underlined by a layer of new differentiated odontoblast-like cells (arrows). Note that the pulp tissue regeneration process is basically complete. H&E, ×250; (d) Control group. Coronal (P) and radicular (RP) pulp tissue exhibits normal histologic characteristics. Masson's trichrome, ×32; (e) Control group. Detail of (d). The odontoblast layer underlying the dentin substrate (arrows) and the subjacent pulp (P) tissue present equilibrium between the cells and extracellular matrix. Masson's trichrome, ×125.

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