The image on the right shows that the upper molars are further forward than the lower molars. The incisors also may be slightly mismatched but they usually wear reasonably level, unlike those of a horse with a parrot mouth. It is estimated that overbite occurs in about 35 percent of all horses. In some horses the condition is hardly noticeable but in others it is very pronounced. In horses with overbite the molar teeth, which are growing and/or erupting, are not worn down in areas where they do not meet opposing teeth. Points will then develop on the first upper molars, actually called 2nd premolars, which can make contact with the lower jaw. Similarly, the last lower molars, actually called 3rd molars, develop points which may touch the upper jaw. The horse can suffer considerable pain when trying to chew with teeth which are in contact with the gum and bone structure of the opposing jaw.