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Stationary anchorage
STATIONARY ANCHORAGE RICHARD LOWY, D.D.S., NEWARK, N. J. I was limited to a ten-minute discussion of the edgewise arch mechaSI NCE nism, it was most difficult to decide what part of the appliance could be adequately discussed in the time allotted me. After deciding upon my subject I realized that it would appear elementary to some of the men present. However, in reviewing the literature I found that the subject had not been discussed before this Society. Therefore I borrowed freely from several of the outstanding Angle adherents and shall attempt to present anchorage as applied to the new Angle appliance. Allen C. Brodie made the following comment in the January, 1931, Angle Orthodontist: "This brings us to a consideration of what has always been the orthodontist's nightmare-anchorage, for it is in anchorage that the factor of safety lies to the greatest extent. Anchorage has probably been the greatest obstacle in the path of orthodontic progress. It has held us down to the point where we have dared to think of little else, and it has dictated all theories of treatment. We have had to unravel our cases tooth by tooth watching our anchorage with bated breath for fear that it would give way and bring our house of cards down around our ears. Some of the most necessary tooth movements in a great many cases were, and are being, winked at or completely overlooked owing to this fear." To Newton we are indebted for the law: To every action there is an equal and contrary reaction. We make use of this law of force in the mechanical movement of malposed teeth, especially in the movement of teeth from points of dental resistance. Here we see that force extended to move one or more teeth has an equal force exerted in the opposite direction upon whatever is used for the base action. Since action and reaction are equal, the amount of movement is proportional to the respective resistances. McCoy in the 1922 edition of his textbook Applied Orthodontics states: "In discussing the subject of 'Anchorage' different writers have submitted classifications which show a divergence of opinion." Therefore, since we are to discuss anchorage relating to the edgewise appliance, I quote the following definition from Dr. Robert H. W. Strang's Textbook of Orthodontia: tl"By Anchorage in Orthodontia, we refer to those units in the dental arch that, by virtue of their inherent stability, combined with their peculiar and favorable relationship to the mechanism by which teeth are moved, are capable of being used as the base from which the power, inherent in the appliance, can take its origin." Read before the New York Society of Orthodontists, New York, N. Y., Nov. 24, 1936.
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R1chard Lowy
Dr. Cecil C. Steiner, in a paper presented in 1933 before the Edward H. Angle Societ y, said: " Let us r emember that an orthodontic problem is like a game of chess. In chess a certa in number of men on one side are pitted aga inst a lik e number on t he other. Th e problem being to outwit your opponent befor e he outwits you. In orthodontia a given amount of resistan t t issue, t he oppone nt, is availabl e against which to pi t a certain amount of tooth movement, one's own' men, ' the prob lem being to transform or translat e t he resistan ce into t he desired toot h movement wit h greatest efficiency and t he least amoun t of wast e, or before r esistan ce gives way. Simple ancho rage makes use merely of r esistan ce of th e superficial str ucture , while stationa ry anchorage uses it to t he root ends, thus employing a solid wall of bone. " Logically it would appear that the most desirabl e type of appliance would be one in which stationary anchorage could be used and force controlled in t he greatest possible dir ecti on or combinations of directions. With the use of th e tie bracket mechanism th e arch wire is the fa ctor of force while the bra ckets and bands ar e the fixati on points between the teet h and ene rg izing factor . Th is accounts for the fac t t hat the slots of t he bracket are so constructed as to hold exactly th e arc h wire . By t his mean s t he fixation is sufficiently ri gid, and control of th e exerted stationary anchorage and bodily movements of t he teeth can be accomplished. Thus by banding all t he t eeth and secur ing br acket engagement of t he arc h wir e th e teeth can be moved into t heir cor rect positi on. Furth erm ore each tooth is contributing its share of anchora ge and the st rain is no longer on the molar t ooth. Let us now discuss chiefly t he use of additi onal force, the elastic band. The promiscuous usc of in term axillary elastics has done considerable harm when there has been a lack of operator's kn owledge and proper understanding of the use and application of stationary an chorage. Dr. Strang defines stationary anchorage as charac ter ized by mechani cal adj ustment of fixtures upon the tooth or t eeth chosen as anchor units as to necessitate such teeth bein g displaced bodily if t hey fail to withstand th e force brought to bear upon th em. It must be borne in mind that in extreme cases of maxillary protrusion th e axial inclination of th e incisor teeth must be corrected first. Why ~ Becau se th ey afford stationary anc horage and with the use of elastics will undoubtedly per mit an undesirable tipping of the mandibular incisor s. Ther efore the firs t step to be taken is that of break ing up maxillary stationary anchorage by chang ing t he axial inclinat ion of t he incisors, and t he closing up of the spa ces in th e maxillary ar ch. A round 0.018 or 0.020 sta inless steel arch wire should be used at first. By shortening t he wire with loops the spaces are closed, and crowns of t he protruding incisors may be tipped back wit hout appreciabl e movement at t he apex , and wit hout much displac ement of the molar teeth. The use of a light wir e in the mandibular arc h in or der to obtain the necessary bracket engagement, th e gr adua l stepping up of the wire from 0.018 to 0.020, 0.022 x 0.028 will materi ally assist in cha ngi ng t he exaggerated curve
Stationary Anchorage
10J3
of Sp ee. The elevation of th e molars and pr emolars and th e depression of the in cisors are of utm ost importance. Slight dist al bends in t he mandibular 0.022 »: 0.028 arch wire can be used to insure aga inst un desirable displacement of t he incisors. Th e combination of th e maxillary tip hack bend s and the interm axillary elastics will cause t he proper distal movement of the maxillary tee th to eliminate th e so-called tooth y appear ance obtained when improper treatment is instituted. Th e progr ess of successful movement of teeth depends largely upon t he operator 's appreciation of th e dynamics in volved in whatsoever appliance he may use. I fully r ealize that I ha ve merely scrat ched the surface in discussin g anchor age, and I hop e that this paper will merely act as a stimulant for additional thought along th ese lines.
1011
1012
R1chard Lowy
Dr. Cecil C. Steiner, in a paper presented in 1933 before the Edward H. Angle Societ y, said: " Let us r emember that an orthodontic problem is like a game of chess. In chess a certa in number of men on one side are pitted aga inst a lik e number on t he other. Th e problem being to outwit your opponent befor e he outwits you. In orthodontia a given amount of resistan t t issue, t he oppone nt, is availabl e against which to pi t a certain amount of tooth movement, one's own' men, ' the prob lem being to transform or translat e t he resistan ce into t he desired toot h movement wit h greatest efficiency and t he least amoun t of wast e, or before r esistan ce gives way. Simple ancho rage makes use merely of r esistan ce of th e superficial str ucture , while stationa ry anchorage uses it to t he root ends, thus employing a solid wall of bone. " Logically it would appear that the most desirabl e type of appliance would be one in which stationary anchorage could be used and force controlled in t he greatest possible dir ecti on or combinations of directions. With the use of th e tie bracket mechanism th e arch wire is the fa ctor of force while the bra ckets and bands ar e the fixati on points between the teet h and ene rg izing factor . Th is accounts for the fac t t hat the slots of t he bracket are so constructed as to hold exactly th e arc h wire . By t his mean s t he fixation is sufficiently ri gid, and control of th e exerted stationary anchorage and bodily movements of t he teeth can be accomplished. Thus by banding all t he t eeth and secur ing br acket engagement of t he arc h wir e th e teeth can be moved into t heir cor rect positi on. Furth erm ore each tooth is contributing its share of anchora ge and the st rain is no longer on the molar t ooth. Let us now discuss chiefly t he use of additi onal force, the elastic band. The promiscuous usc of in term axillary elastics has done considerable harm when there has been a lack of operator's kn owledge and proper understanding of the use and application of stationary an chorage. Dr. Strang defines stationary anchorage as charac ter ized by mechani cal adj ustment of fixtures upon the tooth or t eeth chosen as anchor units as to necessitate such teeth bein g displaced bodily if t hey fail to withstand th e force brought to bear upon th em. It must be borne in mind that in extreme cases of maxillary protrusion th e axial inclination of th e incisor teeth must be corrected first. Why ~ Becau se th ey afford stationary anc horage and with the use of elastics will undoubtedly per mit an undesirable tipping of the mandibular incisor s. Ther efore the firs t step to be taken is that of break ing up maxillary stationary anchorage by chang ing t he axial inclinat ion of t he incisors, and t he closing up of the spa ces in th e maxillary ar ch. A round 0.018 or 0.020 sta inless steel arch wire should be used at first. By shortening t he wire with loops the spaces are closed, and crowns of t he protruding incisors may be tipped back wit hout appreciabl e movement at t he apex , and wit hout much displac ement of the molar teeth. The use of a light wir e in the mandibular arc h in or der to obtain the necessary bracket engagement, th e gr adua l stepping up of the wire from 0.018 to 0.020, 0.022 x 0.028 will materi ally assist in cha ngi ng t he exaggerated curve
Stationary Anchorage
10J3
of Sp ee. The elevation of th e molars and pr emolars and th e depression of the in cisors are of utm ost importance. Slight dist al bends in t he mandibular 0.022 »: 0.028 arch wire can be used to insure aga inst un desirable displacement of t he incisors. Th e combination of th e maxillary tip hack bend s and the interm axillary elastics will cause t he proper distal movement of the maxillary tee th to eliminate th e so-called tooth y appear ance obtained when improper treatment is instituted. Th e progr ess of successful movement of teeth depends largely upon t he operator 's appreciation of th e dynamics in volved in whatsoever appliance he may use. I fully r ealize that I ha ve merely scrat ched the surface in discussin g anchor age, and I hop e that this paper will merely act as a stimulant for additional thought along th ese lines.