Du. TiioMbOX on Caries, en' Decay of the Teeth. 131 



The Joint Committee were intrusted with discretionary power as to 

 details. The following communication was read : — 



On Caries, or Decay of the Teeth. — By F. Hay Thomson, M.D. 



The teeth, which are composod of onamel, bone or dentine, and a sub- 

 stance which has received various names, suoh as corticle, crusta petrosa, 

 and cement, possess the following composition. The enamel contains 

 phosphate of lime, 88*5 ; carbonate of lime, 8* ; phosphate of magnesia, 

 V 5', membrane, alkali, and water, 2\ The dentine contains phosphate 

 of limo, 64*3; carbonato of lime, 53 ; phosphate of magnesia, 1* ; soda 

 with chloride of sodium, 1*1: while the cortical part, or crusta petrosa, 

 consists of organic matter, 42-18; phosphate of lime, 53*84; carbonate 

 of limo, 3*98. Those analyses show that the enamel is almost destitute 

 of organic matter. The dentine scarcely diners from true bone, and 

 as such, is highly organized. The crusta petrosa contains more organic 

 matter than the dentine. Hence, we see, that writers on the subject 

 of diseases of the bones have every reason to suppose that disease 

 of the teeth may be similar in its origin to caries in other bones, since 

 it happens that in some kinds of caries the result is much the same in 

 external appearance, although analysis shows that a deficiency of earthy 

 matter in diseased teeth is not always a symptom of caries of other bones. 



According to Mr. Fox, the cause of the decay of teeth appears to be an 

 inflammation in the bone of the crown of the tooth, which, on account 

 of its peculiar structure, terminates in mortification. The membrane 

 which is contained within the cavity of the tooth is very vascular, 

 and possesses a high degree of nervous sensibility ; and inflammation of 

 this membrane is liable to be occasioned by any excitement which produces 

 irregular action ; and as the bone of the tooth is very dense, and possesses 

 little living power, death of some part of it may speedily follow. 



Mr. Bell considers the proximate cause of caries to be an inflamma- 

 tion of the external surface of the bone immediately under the enamel. 

 He thinks that, when from cold or any other cause a tooth becomes 

 inflamed, the part which suffers most severely is unable, from its possessing 

 comparatively but a small degree of vital power, to recover from the 

 effects of inflammation, and mortification of that part is the consequence. 



Mr. Hunter appears to have come nearer the true cause of caries than 

 any other writer, as, although ho states that oaries is a disease arising 

 originally in the tooth itself, ho evidently had a strong idea that the 

 different articles containing powerful menstrua, exercised an influence in 

 the production of caries. Ho remarks, "if it had always been in the 

 inside of the cavity, it might have been supposed to be owing to a 

 deficiency of nourishment ; but as decay begins most commonly externally, 

 in a part where in a sound state the teeth receive little or no nourish- 

 ment, wo cannot refer it to that cause." He was of opinion, however, 

 that caries is a diseaso arising originally in the tooth itself. 



