To start off, it is important to understand that the main difference between medium and soft bristles is simply their thickness, or diameter. You can easily test the bristles by running them over your finger pads- if the bristles do not easily fall and cause discomfort with light pressure, then they are most likely medium bristles.
While it is generally recommended to use a soft toothbrush for long-term tooth cleaning, it is also recommended to occasionally switch to a medium toothbrush, about once every six months, to ensure a more thorough cleaning. The use of soft toothbrushes in the market is mainly due to concerns surrounding tooth damage and gingival sulcus cleaning. Prolonged use of hard-bristled toothbrushes may increase the efficiency of tooth cleaning but also geometrically increase the wear on tooth enamel. Additionally, hard bristles cannot effectively clean the gingival sulcus where tartar tends to accumulate, thus leading to the formation of dental plaque and calculus.
Still, the use of bristles is necessary for thorough cleaning of inner and outer tooth surfaces as well as occlusal surface areas. For individuals with thicker tooth enamel, a hard-bristled toothbrush may be appropriate, but it is vital for those of Asian populations, whose teeth tend to be smaller, with thinner enamel and poorer health, to use soft bristles. Whether it be a manual or electric toothbrush, the use of soft bristles is highly recommended to maintain optimal oral health.