Odontoma. 



419 



strous tooth-formations, which arise from faults in the embry- 

 onic development of dental suijstanccs and present themselves 

 either as excrescences on the teeth, of bone-like hardness and 

 composed of cement and dentine, or as abnormities in which an 

 entire tooth has been changed into a shapeless, nodular form 

 with enlargement; or in which in combination with an accom- 

 panving proliferation of the soft connective tissues a compound 

 dental tumor has been produced. These neoplasms arc always 

 congenital, either becoming apparent at the time of the eruption of 

 the tooth or the teeth fail to erupt and a tumor slowly develops 

 in the alveolar portion of the jaw beneath the gum, bulging the 

 latter and expanding the bone as it enlarges within the alveolus. 

 The composition and form of these odon- 

 toblastomata var}' considerabl\- with the 

 part taken by the different tissues con- 

 cerned in embryonic tooth formation, the 

 dentine and its covering of enamel, the den- 

 tal sac and the peripheral alveolar bone. 

 The simple odontoma durum, now and 

 then seen on single teeth in the cow and 

 horse, occurs as a mass about the size of 

 a nut, rounded, hard as bone, and usually 

 surrounding the crown or niore rarely the 

 root of the tooth. In other instances, as 

 observed by \Xe6\ and ^^lagitot. the whole 

 tooth lying within the alveolar process is 

 changed into a mass of bony hardness as 

 large as an orange or possibly weigh- 

 ing as much as a kilogram. The name 



odontoma mi.vfum is applied to a growth composed partly of 

 fibrous tissue, bloodvessels, odontoblasts and agglomerated tooth 

 papilL-e, with the hard parts in rudimentary unshaped masses of 

 dentine and enamel over the surface or mixed in the interior. 

 Sutton has met with a mixed growth of this type weighing seven 

 hundred grams in a horse. Similar tumors, sometimes only 

 enclosing in their structure a single hard rudiment of a tooth, or 

 sometimes containing a number, possibly several dozen, mis- 

 shapen or fairly well formed teeth, occur as cysts or bunches 

 of cysts, completely included by fibrogelatinous dental sacs and 

 alveolar bone capsules (odontocystoma capsulars cystoma dcnti- 

 fcrum alveolare). In other instances the proliferation of the 

 bony capsule is especially marked, surrounding the dental sac- 



Fig. 128. 



Odontoma of incisor tooth 

 of cow (natural size). 



