The horse has a full complement of between 36 (in females) and 40 (in males) teeth. The four extra teeth in males are the canines (some mares have canines....often much smaller, rudamentory teeth) and it is estimated that approximately 20% of horses, regardless of sex, breed, colour etc,etc, will develop wolf teeth. The majority of the horses teeth are involved in the processing of food. The canines are used as fighting teeth in males and wolf teeth are the remnants of evolutionary process (they are "vestigal" pre-molars) and are not required or involved in the mastication processes of today''s modern horse.
The teeth are arranged in rows known as "arcades" each containing six teeth. There are two main groups of teeth which perform seperate functions, e.g. the inscisors or "front" teeth and the pre-molars & molars commonly termed "cheek teeth". The inscisors are there to help with gathering and nipping off the vegitation, whilst the "cheek teeth" are utilised to a much greater extent and perform the hard work involved in the mastication process of the food. Consequently, it is fair to say that the greatest majority of dental problems directly attributed to irregularity of wear are found to exist in the pre-molars and molars in comparison to the inscisors.
Equine teeth begin developing in the mouth at the foetal stage and when the foal is born it has very few or no teeth in view or in wear. There are often (if not at birth ...then within a few days of birth) three cheek teeth visabily present and in wear in each side of the jaw and the skull, which are pre-molars....12 in total. Then the inscisors will erupt into view (in groups of four....two upper & two lowers) at periods of 6-8 days...6-8 weeks and 6-8 months. All the teeth at this stage (pre-molars & incisors) will be deciduous, (or milk teeth or "baby" teeth ) eg they will be replaced by more permanent or "adult" teeth.
At around one year of age, the first molars (one each side upper and lower....4 in total) will erupt and within 6 months come into contact and wear with each other. Then at the age of two years, the same happens to the second molars and at three years of age the final molars erupt and within six months come into wear.
In between these developments, at the age of approximately two & half years, the first decidous incisors will be replaced by permanent teeth and at the same time, the first pre-molars will be replaced by permanent teeth. The newly erupted permanent inscisors and pre-molars will take six months to come into contact and wear with each other.
The next major development period is at three years of age when the second of three decidous premolars are replaced by the permanent teeth and these will, again, take six months to come into wear with each other.
Next stage is at three and half years age when the third and final decidous pre-molars are replaced by permanent teeth and at the same time the next set of decidous incisors are replaced by permanent teeth...both groups taking six months to come into contact and wear with each other.
So, by the age of four years the horse will have "a full set" of permanent "cheek teeth" or "grinders" and an almost full set of "nippers"....with the last set of decidous incisors being replaced by permanent teeth at four and half years which will be in wear at five years of age. At five years we have a "full mouthed" horse.
Other development stages include at between 6-18 months the eruption of "wolf teeth" and between 4-6 years (in male horses) the eruption of "canine teeth".