The limited effectiveness of over-the-counter whitening strips on posterior teeth, such as molars, stems primarily from their design and application method. These strips are typically manufactured to conform to the shape of anterior teeth the incisors and canines that are visible when smiling. As a result, they often fail to make adequate contact with the broader, flatter surfaces of molars, leading to uneven distribution of the whitening agent.
Effective tooth whitening depends on consistent and prolonged contact between the whitening agent and the tooth enamel. When molars are not adequately covered by the whitening strip, the active ingredients, such as hydrogen peroxide or carbamide peroxide, cannot penetrate the enamel effectively to break down the stain molecules. This uneven application results in minimal or no noticeable color change on these teeth. Furthermore, the saliva present in the mouth can dilute the whitening agent in areas where the strip is not properly adhered, further diminishing its effectiveness.
