. The science and practice of dental surgery. differentcases between three and five inches. Hismethod Ls as follows (see Fig. 245)— Measure the \^idth of a central incisor, lateralincisor, and canine. Let the combined width V)eA B. From B as centre describe a circle withthis as radius. From any point A mark twopoints on the circle J, H, so that the chordsA J, A H equal the radius A B. Produce A Bto cut the circle at C. Join C J and C a tangent to the cucle at A, to cut C Jand C H produced in E and D, and form theequilateral triangle C D E. On A C producedmark A I equal to D E, and from
. The science and practice of dental surgery. differentcases between three and five inches. Hismethod Ls as follows (see Fig. 245)— Measure the \^idth of a central incisor, lateralincisor, and canine. Let the combined width V)eA B. From B as centre describe a circle withthis as radius. From any point A mark twopoints on the circle J, H, so that the chordsA J, A H equal the radius A B. Produce A Bto cut the circle at C. Join C J and C a tangent to the cucle at A, to cut C Jand C H produced in E and D, and form theequilateral triangle C D E. On A C producedmark A I equal to D E, and from I as centreand with AI as radius describe a this circle inscribe the equilateraltriangle A F G. Join F J, and G H, on A Jand A H measure off widths equal to thewidths of the central, lateral and canine, andfrom J F, H G measure off J K, and HL, 146 equal to the combined widths of the premolarsand molars. Then the curve K J A H L repre-sents the arch, and F, G, the condyles. Thecircular arc J A H is, of course, sUghtly longer. FiQ. 245. than the total width of incisors and canines,because the chords A J, A H equal that width,but the slight difference is not of much practicalimportance. Hawley gives no explanation of his reasonfor taking one side of the triangle C D E as theradius of the large circle A F G. As a matterof fact it may be shown mathematically thatA F or AG, a side of the BonwiLl equilateraltriangle, is four times A B, the radius of thesmall circle, and Hawleys diagram may beproduced in a much simpler way as follows (seeFig. 246)— Describe a circle from centre B, with radiusA B equal to the combined widths of central,lateral, and canine. Draw B J at an angle of60° with B A, to cut the circle at J, and on theother side of B A draw^B H in a similar B A, and draw tangents to the circleat J, H at angles of 20° to B A, meeting B Aproduced at a point 0. Extend O J, 0 H toF, G, until A F, A G equal F G. From J, Hmeasure J K, H L, equal to t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectdentistry, bookyear19
