Care of the mouth and teeth; a primer of oral hygiene . d glance at them they are arranged in a regular manner, that is,speaking of the permanent set, they form in eachjaw a rounded curve or ellipse, that of the upperjaw being a little rounder than the lower, so thatthe upper teeth slightly overlap the lower teethand are so arranged that all of the upper orbiting surfaces come into contact with those ofthe opposite jaw, thus perfectly allowing for thethorough mastication of the food to assist in diges-tion. Every tooth in each jaw meets two teeth inthe opposite jaw, with the ex
Care of the mouth and teeth; a primer of oral hygiene . d glance at them they are arranged in a regular manner, that is,speaking of the permanent set, they form in eachjaw a rounded curve or ellipse, that of the upperjaw being a little rounder than the lower, so thatthe upper teeth slightly overlap the lower teethand are so arranged that all of the upper orbiting surfaces come into contact with those ofthe opposite jaw, thus perfectly allowing for thethorough mastication of the food to assist in diges-tion. Every tooth in each jaw meets two teeth inthe opposite jaw, with the exception of the upperthird molars and lower central incisors. This isplainly shown in the illustration (Fig. 5). Besides the function of the teeth in mastica-tion they serve us in speech, and by their rela-tionship with the lips, tongue, cheek and palatemake possible the formation of various sounds, orvocalization. Knowing, then, these elementary facts concern-ing the healthy oral cavity, we will look at itfrom another standpoint, that is, we will next. Fig. 5. CARE OF THE MOUTH AND TEETH 27 glance over some results of its unhealthful con-dition and by observing the effects of neglectingthe mouth and teeth, help emphasize upon ourminds the absolute necessity of oral hygiene. CHAPTER IV RESULTS OF NEGLECTING THE CLEANLINESS OFTHE ORAL CAVITY We often hear people speak of decayed teeth,but hardly ever stop to think of their evil conse-quences. Let us see what happens when a toothbecomes decayed and how it is brought about. If a person were to eat a meal containing somesugary or starchy substance, the latter would beacted upon by the saliva, which would convert itinto glucose, as we previously remarked, and inall probability if the oral cavity were not thor-oughly cleansed after eating, some remnants ofthis glucose would remain between the teeth orbe held by means of a gluey substance in some pitor crevice of the tooth. Now in our mouths arealways present hordes of microscopic bodi
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