Floss threaders for braces or interdental brushes are also an option. The main purpose of the interdental gingiva is to prevent food impaction during routine mastication. Additional aids include interdental brushes, water picks, and mouthwashes. There is a facial side interdental papilla and a lingual side interdental papilla. This may be done with dental floss or interdental brushes. In inflammations the interdental papilla loses its concavity. The importance of using interdental brushes along standard or electric toothbrush should be stressed on. Most Rukai dialects have four vowels and retroflex and interdental consonants. Special appliances or tools may be used to supplement toothbrushing and interdental cleaning. It seems to grow from below the free gingival margin/interdental papilla. The practitioner can also prescribe specialised plaque removal techniques (tooth brushing, interdental cleaning). The size of interdental brushes is standardized in ISO 16409. The gums are divided anatomically into marginal, attached and interdental areas. VoQS letters may also be used, as in for a "buccal interdental trill" (a raspberry). The central point between the interdental papillae is called the col.