Abstract

Objectives

We evaluated the effects of low-level laser therapy (LLLT) using an infrared laser (IRL) and a red laser (RL) on the pulp of molar teeth in rats after dental bleaching to assess inflammation, collagen fiber maturation, and tertiary dentin formation.

Materials and methods

Eighty Wistar rats (Rattus norvegicus, albinus) were randomly divided into eight groups with 10 hemimaxillae in each of the following: control; bleached (Ble, 35% hydrogen peroxide [H₂O₂]); Ble-1IRL and Ble-1RL (one IRL [808 nm, 30 s, 3 J] or RL [660 nm, 15 s, 1.5 J] application immediately after H₂O₂); Ble-3IRL and Ble-3RL (three [immediately, 24 h, and 48 h] IRL or RL applications after H₂O₂); and 3IRL and 3RL (three IRL or RL applications without bleaching). The rats were euthanized after 2 and 30 days for histological evaluation of inflammation (hematoxylin-eosin) and maturation of collagen fibers (picrosirius red). Additionally, the dentin deposition in the specimens obtained at 30 days was quantified via microtomography of the pulp chamber volume. Statistical analyses were performed (P < 0.05).

Results

Initially, severe damages to the pulp were observed in the Ble and Ble-1RL groups. Ble-1IRL and Ble-3RL groups showed lower inflammation. The bleached groups had a greater amount of mature collagen fibers than the control group. The Ble-3IRL group had a greater number of immature fibers than the Ble group. At 30 days, there was an absence of inflammation and equal proportion of mature and immature collagen fibers. All bleached groups showed a reduction in the volume of the pulp chamber.

Conclusion

Three consecutive applications of RL and one IRL application can minimize damage to the pulp of bleached teeth, whereas three IRL applications can minimize pulp fibrosis. However, LLLT did not prevent deposition of tertiary dentin.

Clinical relevance

This study describes LLLT protocols capable of minimizing inflammation and maturation of collagen fibers in pulp tissue after dental bleaching. However, the protocols proved insufficient for reducing the formation of tertiary dentin in bleached teeth.

中文翻译：

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低水平激光治疗对漂白牙髓中炎症，胶原纤维成熟和叔牙本质沉积的影响

摘要

目标

我们评估了在漂白后使用红外激光（IRL）和红色激光（RL）的低水平激光疗法（LLLT）对大鼠磨牙牙髓的影响，以评估炎症，胶原纤维成熟和叔牙本质的形成。

材料和方法

将80只Wistar大鼠（Rattus norvegicus，albinus）随机分为8组，每组10个半上颌。漂白（无水，35％过氧化氢[H ₂ O ₂ ]）；Ble-1IRL和Ble-1RL（在H ₂ O ₂之后立即施用一个IRL [808 nm，30 s，3 J]或RL [660 nm，15 s，1.5 J] ）；Ble-3IRL和Ble-3RL（在H ₂ O ₂之后进行三次[立即，24小时和48小时] IRL或RL应用）; 和3IRL和3RL（三种IRL或RL应用而无需漂白）。2天和30天后对大鼠实施安乐死，以进行组织学评估炎症（苏木精-伊红）和胶原纤维成熟（picrosirius红）。另外，通过牙髓腔容积的显微照相术定量了在30天获得的样品中的牙本质沉积。进行统计分析（P  <0.05）。

结果

最初，在Ble和Ble-1RL组中观察到对果肉的严重损害。Ble-1IRL和Ble-3RL组显示出较低的炎症。漂白组比对照组具有更多的成熟胶原纤维。与Ble组相比，Ble-3IRL组的未成熟纤维数量更多。在30天时，没有炎症，并且成熟和未成熟的胶原纤维比例相同。所有漂白组均显示纸浆室的体积减少。

结论

连续3次使用RL和1次IRL可以最大程度地减少对漂白牙齿的牙髓的损害，而3次IRL可以最大程度地减少牙髓的纤维化。但是，LLLT不能阻止叔牙本质的沉积。

临床相关性

这项研究描述了LLLT协议，该协议能够最大程度地减少牙漂白后牙髓组织中胶原纤维的炎症和成熟。然而，该协议证明不足以减少漂白牙齿中叔牙本质的形成。