Introduction

Carbamide peroxide, also known as urea-hydrogen peroxide, is a water-soluble, white crystalline solid compound consisting of hydrogen peroxide and urea. As it is a source of hydrogen peroxide, it can be found in disinfecting and dental bleaching products. Some adverse effects of carbamide peroxide as a dental bleaching agent include dentin sensitivity and/or gingival irritation led by unstable and reactive H+ free radicals and low pH from prolonged use. It may also alter enamel surface morphology via enamel mineral loss and surface roughening .

Uses

Carbamide peroxide is a medication used to loosen ear wax, whiten teeth, and clean oral wounds.

Indicated as a dental bleaching agent.

Indicated as an oral wound healing agent in oral mucosal injuries.

Indicated as an aid in the removal of hardened ear wax.

Associated Conditions

Excess ear wax

Pharmacodynamics

Carbamide peroxide releases hydrogen peroxide and free radicals upon contact with water or outer surfaces of ear and tooth. Hydrogen peroxide exerts cerumenolytic, enamel-bleaching and antiseptic actions. In vitro, the chemical stability of ceramics against bleaching agents was observed after treatment with 15% carbamide peroxide for 56 h, 16% carbamide peroxide for 126 h, 10% or 15% carbamide peroxide and 38% hydrogen peroxide for 30 minutes or 45 minutes, respectively . According to in vitro studies, high (37%) or low (10 or 16%) concentrated carbamide peroxide agents were similarly effective as oral bleaching agents . Treatment with carbamide peroxide may lead to demineralization which involves decreased mineral content of enamel calcium, phosphate, and fluoride, and alteration of the chemical, structural, and mechanical properties . Carbamide peroxide may affect the organic components of the enamel and lead to increased susceptibility to erosion, fracture stability or decreased abrasion resistance of the treated area .

Mechanism of Action

Carbamide peroxide release hydrogen peroxide upon contact with teeth, which is a strong oxidizing and bleaching agent. It also release free radicals such as H+ or H3O+ . Hydrogen peroxide also acts as an antiseptic, especially in sites with relative anaerobiosis. Following otic administration, carbamide peroxide complex releases hydrogen peroxide that breaks up the hardened wax. The hydrogen peroxide component, which further breaks down into water, is also a cerumenolytic that hydrates the desquamated sheets of corneocytes, which are the major constituent of cerumen plugs . The glycerol and urea facilitates softening of the cerumen, either with or without syringing . Both hydrogen peroxide and urea mildly induce keratolysis with disintegration of the ear wax to help reduce the keratin-load in the ear debris and allow other active components to reach the skin under the debris .

Absorption

Upon treatment into the external auditory canal or the dental cavity, exposure to carbamide peroxide is limited to the intimate contact with the treated area without any systemic absorption.