A QUANTITATIVE ROENTGENO-DENSITOMETRIC STUDY OF THE CHANGES IN TEETH DUE TO ATTRITION

¹ Departments of Pathology, Biochemistry and Pharmacology, and Medicine (Radiology), University of Rochester, School of Medicine and Dentistry, Rochester, New York

In summary, it is noted that in these 4 teeth showing a prominent cone of transparent secondary dentine and a tiny attrition cone: (1) the average interpolated values for the attrition cone are 4, 5, and 6 percent greater than normal coronal dentine; (2) the secondary dentine differs from the normal by -2, -1, -4, and +4 percent; and (3) the root dentine is less radiopaque than the crown by 0, 5, 2, and 4 percent.

For the purpose of this discussion the teeth showing attrition have been grouped into three classes on the basis of similarities in roentgenographic appearance and absorption measurements, supplemented by their appearance when observed grossly using transmitted light. When these groups are compared with a normal young tooth, the interesting conjecture is made that these classes represent stages in the change which takes place in dentine exposed by attrition. Thus we think that slight attrition of the dentine might produce a prominent attrition cone and a laying down of a small amount of secondary dentine in the tip of the pulp chamber; that advancing attrition and [see table in the pdf file] continued exposure of the tubules is accompanied by an increased amount of secondary dentine in the pulp chamber, giving rise to the "hour glass" effect; that advancing attrition removes more and more of that part of the tooth which includes the attrition cone leaving only the prominent cone of transparent secondary dentine. Further credence is given to the aptness of this classification by considering the summary of average interpolated values given in Table XVII.

It is at least a coincidence that the 4 teeth showing a prominent attrition cone have the greatest percent increase in radiopacity in the attrition cone, while the 5 teeth with the hour glass and the 4 teeth with the prominent secondary dentine cone have only moderate increases in radiopacity of the attrition cone. The coincidence is increased by noting 1) that the group of teeth with prominent attrition cones have secondary dentine about as radiopaque as the normal, 2) that the hour glass type show markedly less radiopacity in the secondary dentine, while 3) those teeth having prominent secondary dentine cones show small differences from normal dentine. Furthermore, it is seen that in the normal young tooth # 39, the root dentine is unquestionably less radiopaque than the crown; this is also the case for the hour glass type and those showing a prominent secondary dentine cone whereas, in teeth showing slight attrition and prominent attrition cones, the root dentine does not differ appreciably from the crown.

Attrition cones are more radiopaque than the normal coronal dentine in the same tooth, attributable only to an increase in the calcific material in the changed area. Because the attrition cone penetrates too deeply into the dentine to be ascribed to an effect of the packing forces of mastication the changed appearance may be caused by a chemical action of the saliva, a physiological action in the dentine or both. However, the increased radiopacity cannot be explained as an effect of soft tissue change or necrosis and it is highly probable that the calcific deposition has occurred in the lumen of the tubules or the tubule processes into the matrix of the dentine. The exact histological location of the additional calcific material cannot be found by the densitometric method since by it we measure only gross changes involving a comparatively large area.

All of the teeth showing prominent attrition cones are from the same individual. All of the teeth showing the hour glass effect are from the same individual. Of the 4 teeth showing prominent secondary dentine cones, 2 are from one individual, 2 from another. It is impossible to rule out the possibility that the differences in roentgenray absorption found between these groups may have been closely dependent on the state of health of the individuals concerned.

However, the grouping of the abraded teeth in the discussion is shown to be an apt division since the teeth with prominent attrition cones all have markedly increased radiopacity of the attrition cones, the teeth with the hour glass effect all have secondary dentine with marked less roentgen-ray opacity than normal crown dentine, while the teeth with the prominent secondary dentine cone show little or no difference between radiopacity of the secondary dentine and that of normal coronal dentine. These findings do not answer the question of what happens to dentine exposed by attrition. They will serve their purpose if they direct attention to the possibilities offered by this method of study.