How much can I safely reduce an overgrowth by?

Equine teeth erupt at a rate of approximately 2–3 mm/year [1], which is similar to the rate of attrition on the occlusal aspect of the tooth, provided that the horse is fed grass or a predominantly fibrous diet. Because horse’s teeth are worn away by the grinding action of a herbivorous diet, the odontoblasts lining the pulp horns respond by secreting subocclusal secondary dentine (SO2D) to protect the pulp horns from being exposed [2].
Equine teeth are predisposed to the development of enamel overgrowths, due to anelodontia, and the differential wear rates of their mineralised dental components. The aetiology of focal dental overgrowths (FDOs) include maxillary prognathism, developmental and acquired dental disorders such as dental displacements, supernumerary cheek teeth, diastemata and tooth loss [3]. Concentrates making up a large proportion of the daily calorific intake has been shown to exacerbate FDOs [4,5]. In clinical surveys of equids FDOs were found to occur commonly [6–8].
Overgrinding of teeth with motorised dental instruments (MDIs) resulting in pulpar thermal necrosis of the pulp horn or even causing pulpar exposure leading to death of the tooth has been noted as a potential problem [9–11]. Current information on the critical temperature threshold (5.5o C) above which irreversible damage to the pulp horns of equine cheek teeth (CT) can occur is based on a primate study by Zach and Cohen [12]. […]