later, and if that point is reached the margin must be carried to where the structure can be trusted.

The next tooth worked on was a lower third molar of very perfect form, which is interesting chiefly as showing the extent of defect around apparently very good occlusal grooves, and the direction of rods on a very flat occlusal surface. Fig. 18 shows the occlusal surface and Fig. 19 the same after cutting. Numbering from the mesial, sections I and 2 were lost, but 3, 4 and 5 were mounted. Fig. 20 is from No. 3.

The upper first molar was selected as the next tooth, cutting so as to show the structure of the disto-lingual cusp and the enamel

around the disto-lingual groove. Fig. 21 shows a typical first molar with fairly well closed developmental lines. Fig. 22 shows the direction of the cuts. From this tooth sections 1 and 2, numbering from the lingual, were lost; sections 3, 4 and 5 were mounted, but section 5 was of little value. Fig. 23 shows the cut through the crown in the position of section 3. There is shown the disintegration of the enamel in the region of the mesial pit, and the arrangement of the rods over the disto-lingual cusp, which is a position of weakness, especially when caries of the disto-lingual groove is complicated by caries on the distal surface. In many such cases the only way a strong wall can be made is by removing the cusp and cutting from the point of the dentin cusp in the horizontal plane.

Another upper molar of less typical form was cut in the same

way. One of the sections showed the complicated condition of a rough occlusal surface, and especially the rod-direction over the distal marginal ridge. Notice the inclination distally from the buccolinguo-axial plane as the ridge, which is very flat, is approached. This is seen in the higher power of the ridge (Fig. 24), which also shows the twisting of the rods over the dentin tip.

The central incisor was the last tooth to be worked on, and here the only regions to which attention is called are the mesial and distal marginal ridges. Often proximal cavities extend far to the lingual, and we are tempted to leave a margin on the summit of the ridge. This is a point of weakness, to be compared to the tip of a cusp or the marginal ridges in bicuspids and molars.

An incisor was cut in a similar way (Fig. 25), from which sec

tions 1, 2 and 3, numbering from the incisal, were mounted. No. 4 was broken. Fig. 26 is from the first section and shows the enamel worn off the marginal ridges near the occlusal edge. It is noticeable

that wherever enamel is removed by abrasion the wall is left, fulfilling the requirements given for strong enamel walls. Next the dentin are short rods whose ends abut on the abraded surface, growing longer to the enamel surface. This is better shown in Fig. 27,

a higher power of the corner, and in worn incisor tips. When decay occurs on these worn surfaces some of the short rods are broken out and decay begins at the dento-enamel junction. Fig. 28, from the second piece, cuts well through the marginal ridges in the middle of the crown, almost if not quite in the direction of the rods, and shows the enamel over the distal ridge broken away, but the mesial

ridge perfect. Suppose a mesial cavity whose margin is approaching this region, if it reaches the point (a) it must be cut well over onto the lingual, or the enamel will be broken out by the force of occlusion from the lingual, if it is not fractured in packing gold against it in making the filling. Fig. 29 shows the structure in the limited area more perfectly.

MAXILLARY FRACTURES.

SPECIAL ESSAY BY ROBT. T. OLIVER, REPRESENTATIVE OF ARMY DENTAL EXAMINING BOARD.

The subject of maxillary fractures is one fraught with considerable interest, both to the general practitioner of medicine and surgery, and to the specialist of oral or dental surgery. To many of the former these cases are highly undesirable on account of the extreme difficulty of management, coupled with the uncertainty of accomplishing perfect results. To the oral surgeon, who perhaps is better able to cope with the peculiar characteristics of these cases, on account of his intimate knowledge of and familiarity with the parts involved, and his accustomed dexterity with the instruments, appliances and materials necessary in intra-oral operations, the average of perfect results is much greater.

The primary requisites for this class of fractures are essentially the same as for any of the "Osseous solutions of continuity" of long bones, namely, Reduction, Fixation and Immobilization.

In passing, it may be of interest to know that while these factors in the treatment of maxillary fractures were undoubtedly known and recognized long before the days of Esculapius and his associates, it was not until centuries afterward that the famous Ambroise Pare, successively known as the "Barber Dentist," "Army Surgeon," "Surgeon to the King and Surgeon General of the French Armies," in 1569 promulgated theories and developed practical methods for the accomplishment of these points which are sufficient proof that his ideas were advanced far beyond his era. His method of wiring the fragments in position, and then wiring the upper and lower teeth together, so as to tightly close the jaws with teeth in original occlusion, for the prevention of deformity and the reestablishment of the plane of articulation, is worthy of emulation at this late date.