In general, the two major diseases causing the loss of teeth are caries and pyorrhea; in particular, cases of gingival recession due to periodontal disease are not susceptible to interdental plaque control by a common toothbrush, resulting in the need for extensive use of an oral cleaning device such as an interdental brush. A typical cleaning device, an interdental brush, is a twisted brush with nylon bristles arranged concentrically around a twisted metal filament, but these types have been plagued with numerous problems which limit their widespread adoption for oral care: when the tip of the brush hits the gum during an interdental insertion, it often injures the gum; it causes discomfort when the metal tip touches the tooth; and repeated use during cleaning causes high breakage of the twisted metal filament due to metal fatigue. When cleaning is performed between three-dimensionally concave, complicated teeth, such as in a root branching site, the metal which constitutes the interdental brush stem not only resists insertion, causing problems, but also suffers from the risk of leaving uncleaned sections, if the cleaning brush is pre-curved to accommodate its insertion. The use of a shape memory nickel titanium alloy is conceivable for avoiding this problem, but, if a shaping method similar to that used for a twisted brush is involved, the de-twisting of the metal filament will end up causing nylon bristles to fall out. Therefore, resin materials have been studied as materials to constitute the stem; but, since the interdental brush requires the brush section to penetrate through a 0.8 mm diameter space for cleaning interdentally, it has been difficult to injection mold so as to insert nylon bristles into a resin material of this diameter. Other methods include electrostatically implanting nylon piles in the radial direction into a shape memory metal filament rod or a resin filament rod, but it is necessary for the diameter of the stem for penetration of the brush section into a 0.8 mm diameter space to be about 0.4 mm or less. It has been difficult to uniformly implant nylon bristles about 2 mm to about 4 mm in total length into a filament rod of this diameter and, in addition, to find an adhesive with no biological hazard so as to prevent the loss of bristles. Applications for such small twisted brushes also include cosmetic tools such as cosmetic mascara brushes and the like, where basically the stem material has been a metal material.
In addition, this type of twisted shape brush is also used for polishing or cleaning various pipe-shaped items, but use in a complex curved section gave no choice but to connect a supple material to the handle, if the handle is made of metal, because the depth of penetration was limited.
Patent Reference 1: Japanese Patent Application 10-181595 and Japanese Patent Application 4-152991