Orthodontic Appliances and Treatment Philosophy

1. 1 Orthodontic Orthodontic A Appliance and and Treatment Treatment P Philosophy Prepared by: Prepared by: Dr. Mohammed Alruby Dr. Mohammed Alruby ppliances s hilosophy Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

2. 2 Development of appliance Development of controlled root movement Pin and Tube appliance Ribbon arch appliance Edgewise appliance Baker anchorage Labio-lingual appliance Open tube attachment The universal appliance Johnston – Twin wire attachment appliance Extraction in conjunction with orthodontic therapy Light wire technique – Begg appliance Rickets bio- progressive technique Straight wire appliance – Andrews appliance Tweed philosophy Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

3. 3 The development of appliance The 1st description of tooth movement, dated a few years BC, most of early appliance were of the removable type The early fixed appliance can be traced back to a French Man P. Fauchared who, made a buccal metal arch to which the teeth were ligated by fibrous ligation. This appliance was described in 1726 and it enable alignment of the teeth by means of expansion of dental arches = Schange invented a band in 1841 that were fitted to the teeth by means of clamps which were adjustable to accommodate the different sized teeth, bands were made from precious metal, copper and brass = in 1871 Megill first used dental cement == The extra-oral force was first described by Kisngsley in 1866, and inter-maxillary traction (Baker anchorage) was used late in the nineteenth century. By that time, the need for greater control over the tooth development led to the development of the attachment which were soldered to the lingual aspect of the bands enabling the misplaced tooth to be ligated to the buccal arch wire ==The early attachment was a single spur which act to prevent slippage of ligature wire from upon the tooth and allows some rotational control = brass ligature was used and progressively tightened as the tooth moves. At this stage of development, there was no attempts to correct the malocclusion by placing the teeth in a stable soft tissue environment = Angle stated that: {if the teeth were moved into their correct occlusal relationship, stability would be assured}. Angle’s early appliance had a buccal tubes soldered to the molar bands and a buccal expansion arch wire which was activated by screws to which the malposed teeth were tied, tooth movement took place by tipping Development of controlled root movement Farrar, Kingsley, Angle, Case and others soon found most of the treated cases by tipping movement underwent relapse. They soon realized that, for any effective tooth movement, some means must be advised to control the individual teeth, this led to the development of attachment that were soldered on modified crown or bands – the early attachment were in the form of spurs, spurs were soon modified to form hooks and hooks become the early form of modern bracket The Pin and Tubes appliance Angle was well aware of the value of bodily movement of the teeth so, one of the most effective early appliance was developed by Angle in 1912 is the Pin and tube appliance which was the 1st appliance capable of root movement. This appliance consists of: 1-Bands to which vertical tubes were soldered, the tubes are parallel to the long axis of the teeth 2-The arch wire to which vertical Pins were soldered to fit the vertical tubes on the bands of individual teeth Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

4. 4 This appliance was very difficult to use, requiring a high degree of technical skills to fabricate the arch wire, however in the hands of few men it was very successful appliance that showed greater control over the tooth movement The Ribbon arch appliance = The Ribbon arch appliance was described by Angle in 1916. This appliance consists of modified hooks or machined brackets soldered to the bands of individual teeth to which a flat rectangular arch wire was fitted with its wide dimension toward the labial surface of the teeth (lies vertically) = This is being the first use of rectangular arch wire which provide a greater control over the tooth movement and produce an accurate repositioning of the roots = The philosophy of treatment was changed a little with the development of more efficient attachment but expansion was still the major therapeutic goal in most cases The Edgewise mechanism About 10 years later to 1926 Angle described the Edgewise mechanism to provide a better control over the individual teeth This attachment consists of: 1-Bands soldered and fitted to most of the teeth 2-Brackets: machined brackets with their longer dimension horizontally soldered to the bands 3-Rectangular arch wire made to fit the bracket with its narrow dimension toward the labial surface of the teeth and its wide dimension lies horizontally, hence the term Edgewise was applied The arch wire was tied in place by ligature wire and eyelets were soldered on to the bands to aids in correction of rotations Treatment was still based on non-extraction philosophy or expansion Baker Anchorage Many authors noticed that a large percentage of patients had a relatively straight tooth, at the same time the upper and lower teeth were not properly related to each other with the presence of large over jet or reversed over jet (Class II and Class III) In such cases the expansion of the arch would not produce a desired correction so Baker anchorage was developed which utilized correction of class II and class III by using inter-maxillary rubber bands Labio-lingual appliance = in the middle of 1920, the lingual appliance was developed by Mershon. This appliance consisted of a relatively rigid mandibular and maxillary lingual arch attached to the molar bands, these arches carried a spring that produce tooth movement by tipping, similar to the action of modern removable appliance = The mandibular arch was used also to produce a tooth movement in the maxillary arch by means of inter-maxillary elastics using the principle of baker anchorage, but proclination of lower incisors was frequently occurs (during use of class II elastics) = As with philosophy of expansion, there was a little concern over the movement of lower incisors into an abnormal position with this type of therapy. The primary consideration was to achieve normal occlusion regardless the environmental and functional forces Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

5. 5 = The subsequent experience had shown that Mershon lingual arch is better used as a space maintainer or for part time inter-maxillary elastic traction = Combination of labial and lingual arches were refined by Oliver, he introduced the fixed guide plane to be used in conjunction with inter-maxillary elastics, the fixed guide plane is constructed on the maxillary lingual arch and has the following functions: 1-Guide the mandible to close in proper position and eliminate functional retrusion 2-Activate the growth at condyles like activators 3-Reduce the excessive overbite in class II 4-Inhibit the abnormal tongue thrust habit Open tube attachment Also in the middle of 1920, the open tube attachment was developed by John Mcloy This appliance consisted of round arch wire which fit within a horizontal tubes soldered on the labial surface of the bands cemented on the teeth The arch wire contains a soldered spur which produce root movement This technique is also based on no-extraction philosophy of arch expansion regardless the functional forces so that neither this technique nor Edgewise mechanism was capable of producing satisfactory results to overcome relapse The Universal Appliance Universal appliance which is a combination of Edgewise and Ribbon arch attachment was developed by Spancer Atkinson to provide a greater fine control over the individual teeth, the appliance consists of: 1-The attachments: machined double slot brackets which have lower Edgewise slot and upper Ribbon arch slot 2-The arch wire: round and rectangular arch wire may be used, three combinations are possible: a-Two round arch fit the lower slot and tied with ligature b-Rectangular Edgewise arch fit the lower slot c-Rectangular Edgewise arch fit the lower slot and Ribbon arch fit the upper slot This technique is also based on – non-extraction philosophy. Johnston – Twin wire attachment appliance The force generated by the early Edgewise mechanism was very high so that, Twin wire appliance was introduced by Josef Johnson in 1930 which designed to produce lighter forces The original appliance was consisting of: 1-Two round light buccal arches used in combination to produce alignment and rotation correction of upper incisors 2-The maxillary arch wires were filled into the upper four incisors bracket and molars tubes 3-Class II traction can be used on the lower lingual arch An advantage of this appliance is the ability to correct the incisor displacement with minimum of bands The twin arches are constructed of two 0.25mm diameter hard stst wires inserted into ends tubes of 0,90mm outside diameter. The ach is rigid in buccal segment and flexible in the labial segment Special brackets were advised in the original technique but it can also use with Edgewise brackets Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

6. 6 If there is considerable rotation or teeth displacement, partial engagement of the arch is indicated at the start of treatment. Also it is possible to engage wire to the twin arch into the brackets of severely displaced tooth to reduce the force applied In cases of over rotation, it may be necessary to use spurs or wings soldered to the bands or to use a rotating spring, which forced under the wire and tied to the bracket with ligature wire. The Twin arch wire can be also used for over jet correction using inter-maxillary elastics on the lower lingual arch or intra-maxillary elastics hooked into hooks at the medial aspect of the end tube The twin arch usually suffers from permanent deformation rapidly and often replacement before satisfactory alignment is achieved Another disadvantage of Twin arch wire is the less control of anchorage in extraction cases, 4 incisors against two molars Extraction in conjunction with orthodontic therapy = as we mentioned before that, Angle’s philosophy of non-extraction or expansion therapy was not capable to produce satisfactory results and followed by relapse in the majority of cases, So that, an alternative philosophy utilizing the extraction of the teeth for correction of crowding and dental arch mal-relationship was developed to overcome the problem of over expansion and its undesirable sequelae Tweed was the 1st to use Edgewise technique in conjunction with extraction and his treatment method forms the basis of many todays Edgewise techniques Tweed said that, (when the cannot brought into normal alignment and proper occlusion without procumbancy of incisors, then extraction is indicated to reduce the dental arch) = of course this philosophy met a great antagonism from Angle’s followers in their defense, it must be said that, (extraction have produced orthognathic malocclusion, deep bite, collapsed lower anterior segment, pockets, spacing and tissue damaged when done by faulty decision. Light wire technique The use of light forces in fixed appliances techniques of which Johnson Twin wire appliance is an early example has continued, in this way, the light wire appliance was developed by Begg in 1926. The Begg bracket are modifications of the early Angle’s Ribbon arch brackets Begg technique is based on the idea of differential force control, since some types of tooth movements evoke more tissue resistance than another and some movements occurs faster than others, so Begg was selectively chosen the movements required and relating the reciprocal action properly The Begg system is an extraction based philosophy which utilized intra-oral anchorage and use of an auxiliary spring for certain tooth movements Differential light force: The new light wire differential forces philosophy has been introduced by many authors such as: Holmes, Kissling, Begg, Steiner, and others to overcome: Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

7. 7 = the limitation of Twin wire appliance = the frictional component in classic Edgewise appliance = the production of orthognathic malocclusion in labio-lingual appliances. The new trend in the Edgewise technique is to use a lighter round arch wires in the initial tooth movement keeping the thicker rectangular wires for the later stage of treatment to overcome the lack of torque control in the light wire technique Begg Technique The Begg technique was developed by Dr P R Begg in 1926 and is widely used. Dr Begg was the 1st who introduced the idea of differential force control, since some teeth evoke more tissue resistance than others and some movements occurs faster than others, Begg selectively chosen the movements required for each tooth and magnitude of force required to achieve this movement and relating the reciprocal reactions properly Disadvantages of this technique: 1-Low mechanical efficiency which make the control of mesio – distal axial inclination is more difficult during the 3rd phase of treatment 2-Root torqueing is difficult to obtain by this technique 3-Difficulty in coordination the maxillary and mandibular arch form, an elastomeric positioner is usually employed to obtain the desired root movement 4-Difficulties in obtaining bilateral symmetry 5-Difficulties in stabilizing the teeth in the final artistic position 6-The vertical loops may cause injuries of labial and gingival tissues 7-Difficulties in cleaning the appliance and in maintaining good oral hygiene Principles of Begg technique: Begg technique is based on 3 fundamental concepts: 1-Employment of light, continuous physical forces (differential force concepts): Vertical loops occasionally with helical are made in the light wire to permit the following: a-Full engagement of the arch within the brackets without applying an excessive force b-The wire become more resilience thus the force becomes lighter with longer duration c-This allows a reciprocal anchorage in the anterior region and minimize the load over the anchor unit, thus the stability of molars can be maintained during treatment and no needs for extra-oral anchorage, this make suit extraction case. d-Rapid controlled tooth movement without causing discomfort of the patient, loosening of the teeth or damaged of periodontium The use of small vertical brackets increases the inter-bracket distance which make the appliance more resilient 2-The Begg technique utilize two tooth movements: a-The first is allowing the teeth to tip freely, this can be achieved by insertion of light round wire so that it is fit into the bracket loosely b-The 2nd movement is uprighting of the teeth by using auxiliary springs, thus the Begg technique involve 1st, tipping of crowns then followed by tipping of the root 3-The third concept: There is continuous mesial and vertical physiologic migration of the teeth throughout the life Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

8. 8 Begg used this fact in movement of the teeth in favorable direction assisted by growth Combination of Edgewise and light wire techniques Other combination has been developed which combine certain aspect of the Edgewise and Begg methods Attempts have been made to unite the precision and greater torque control of Edgewise mechanism with the light continuous forces and rapid tooth movement of Begg technique in a single technique Tweed introduced the use of light wires in the initial stage of edgewise treatment, while the rectangular heavy arch is placed later in treatment and during finishing the case. The light wire appliance described by Jabark, the bracket used is basically of Edgewise type, however large part of treatment is carried out by using light round wires incorporating carefully designed vertical loops and horizontal helical In the combination technique described by Fogel and Mcgill, a Siamese Edgewise brackets with vertical slots are used, in the initial stage of treatment, the light wire placed in the vertical slot of the bracket which permit single point of contact and less friction like Begg brackets, while in the later stage of treatment the rectangular wire is inserted into the Edgewise slot for finishing the case Fogell and Mcgill described 3 stages of treatment: a-Gentle tipping of the teeth; using single round wire b-Uprighting and general alignment of the teeth: using Multistrand round light wire (orthoflex) c-Detailed axial positioning of the teeth: using Edgewise rectangular arch wire Rickets Bioprogressive technique This technique described by Ricketts does not demand bonding of all teeth in the arch at the beginning of treatment Banding is carried out progressively throughout treatment and removable appliance may be used in the early stage (as expansion screw and correction of cross bite) The technique is a combination of light wire and Edgewise mechanisms Arch wire flexibility is increased by incorporation of loops and helical performed arch wire can be used for easily fabrications Pretorqued brackets are used with this technique, this achieved torque without the needs for bending the wire Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

9. 9 Straight wire appliance Andrew’s technique Most of orthodontic techniques can achieved a successful esthetic results in the majority of cases, but would you capable to obtain the same successful results in two similar cases Andrews provided us with the solution, through his straight wire appliance which was developed to achieved the same beautiful results in all case. Time after time in a more predictable and efficient manner Andrews philosophy is based upon the possibility of transferring the 6 keys of ideal occlusion which are normally present in the nature untreated case into treated cases To achieve this objective, Andrews used a careful designed brackets with pre-angulated base which are capable to producing torque in the three planes, so that, there is no needs to placing any torqueing bends in the wire, hence the name straight wire technique In this manner, the orthodontist goes ahead to treat only the malocclusion and not consuming his time in treating his appliance With the use of this appliance, the teeth can move automatically into ideal occlusion Bracket design and six keys of occlusion: 1-Key 1: molar relationship: -The distal surface of the distal marginal ridge of upper 6 contacts and occlude with the mesial surface of mesial marginal ridge of lower 7 -The mesio-buccal cusp of upper 6 occlude within the buccal groove of lower 6 -The mesio-lingual cusp of upper 6 occludes within the central fossa of lower 6 The straight wire appliance has been carefully designed to move the molars into normal relationship that will achieve a solid points of contact 2-Key 2: crown angulation: the mesio-distal tip: In normally occluded teeth, the gingival portion of the long axis of each crown is distal to the occlusal portion of that axis The degree of mesio-distal tip varies according to each tooth Each straight wire bracket has a predictable degree of mesio-distal tip which suit each individual tooth, so that, each tooth will achieve the proper mesio-distal angle 3-Key 3: crown inclination: labio-lingual torque: It is the angle between a line perpendicular to the occlusal plane and a line tangent to the middle of the labial or buccal clinical crown a-The anterior crown: in maxillary incisors, the occlusal portion of the crown is labial to the gingival portion. In all other anterior crowns, the occlusal portion of the crown is lingual to the gingival portion b-Upper posterior crowns: the buccal the degree of lingual inclination is more pronounced in the molars than cuspids and bicuspids c-Lower posterior crowns: the occlusal portion of crowns is buccal to the gingival portion. The degree of inclination is progressively increase from cuspids to molars The inter-incisal angle was found in Andrews non treated best norm 174 degree Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

10. 10 Straight wire bracket has been designed with a specific torque which made at the bracket base help each tooth to achieve proper bucco-lingual inclination relative to the arch. All inclination is based on the crown long axis, not the tooth long axis The torque made in the base of the bracket has a great advantage than the torque made in the bracket slot which is: The center of slot and center of the base lies on the same plane which is very important in bracket positioning at the proper height, while when the torque is placed in bracket slot like pre-torqued edgewise bracket used by Ricketts in bioprogressive technique, the center of slot not coincident with the center of bracket which may be misleading during the bracket placement 4-Key 4: rotation: The teeth should be free from undesirable rotation Rotated molars and bicuspids will occupy space molars and bicuspids will occupy space more than the normal while incisors if rotated will occupy a space less than normal Straight wire appliance is carefully designed to rapidly correct the rotation 5-Key 5: tight contact: In the absence of tooth size discrepancies, the contact point should be tight. With correct bracket placement at the center of clinical crown’s long axis at the beginning of treatment, the straight wire appliance can be achieved a tight contact without crowding 6-Key 6: the curve of spee: It is an imaginary curve passing through condyles and measured from the most prominent cusp of the lower 2nd molar to the incisal tip of most prominent lower incisors The flat curve is most respective to normal occlusion, the curve of spee should not deeper than 1.5mm Advantages of straight wire mechanism: 1-Can adapt well to varieties of technique and mechanisms as the operator can use the straight wire appliance without the need to learn a new procedure 2-Reliable results and reduced chair time 3-The bracket is carefully contoured to fit each tooth in a specific single point so that enable the operator to place brackets more easily 4-The pre-torqued and pre-angulated bracket base eliminate the needs for placing torque bends in wire which is time consuming and may complicate treatment if done improperly 5-The appliance is more esthetically pleasant 6-The teeth are automatically guided into ideal occlusion 7-Precise control in finishing the case and more stable results 8-Precise control of molar and premolar torque 9-Bilateral symmetry of bucco-lingual and mesio-distal inclination which is difficult to be obtained by wire bending 10-The appliance is simple, easily cleaned and more hygienic 11-Less discomfort in practiced by the patient 12-Place the teeth in functional excellent positions so that: more stable results are obtained, decreased occlusal wear less periodontal problems Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

11. 11 less TMJ pain dysfunction or problems Disadvantages of straight wire mechanisms: 1-The wider bracket ------ the smaller inter-bracket distance, so that, the force is more heavy 2-Difficulties in obtaining rapid correction of crowding because the angular relation of the bracket to the malposed teeth 3-Difficulties in obtaining rapid correction of overbite 4-Addition anchorage is necessary 5-Extra-oral force often required Appliance selection A company straight wire appliance Developed by Lawrence Andrews to move the teeth into positions oriented to the six keys of occlusion as he found in his untreated best sample Straight wire bracket: = Are precisely contoured in both horizontal and vertical direction and designed to seat at the midpoint of vertical long axis of each crown in a specific single point, so that, the bracket can seat themselves in the proper position making bracket placement simpler, faster and more easy = Most other bracket bases are not contoured to fit a specific area on the crown, so that, the bracket placement may be difficulties and create a source of error. And if you attempt to contour the bracket by a plier the bracket will be distorted = The bracket base is torqued so that, the center of the slot on the same plane with the center of the base, this allows bracket placement at proper height = the torque incorporated into the base is predicted for each tooth, so that, the 3rd order bends are not necessary thus the teeth will move automatically into ideal occlusion which balanced well with muscle function, thus more efficient and stable results are obtained = Other pre-torqued brackets have a slot which is not coordinated with the base, thus when the bracket bases are lined-up horizontally, their slot will lie at different heights making the 2nd order bends are necessary which would complicate treatment, increase the variables and increase chair time = The in and out measurement of each tooth is incorporated to the bracket base so that, the 1st order bends the wire are not necessary = Mesio-distal crown angulation is incorporated into the bracket base in a predictable manner so that, artistic and Gable bends are not necessary incorporated into the wire = Straight wire appliance provides a varieties of bracket such as twins, single wing bracket (comfort) and active (self-ligating bracket) so that can adapt to any technique Roth set up appliance: Roth modified the Andrews appliance for the purpose of moving the teeth into over corrected position prior to the removal of the appliance and thus when the appliance removed, the slight relapse movement will allow the teeth to occupy the ideal occlusal position found in non-treated best sample studied by Andrews Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

12. 12 Roth philosophy is based on two assumptions: 1-With the appliance in place, it is being impossible to position the teeth into occlusion shown in non-orthodontic normal because of the bracket interference 2-After the appliance removal: the teeth is most cases may shift slightly from their corrected position For these reasons Roth modified the Andrews appliance to permit the teeth to occupies a slightly over corrected position in the 3 planes of space, so that, when the appliance is removed, the over correction will compensate for the slight relapse movement and thus the teeth will moves to the ideal occlusion shown in non-orthodontic norm Size of bracket used with Roth set up: 0.018, and 0.022 slot can be used but 0.022 is preferable for the following: 1- any size of wire up to 0.022 can be used so it will allow wire size selection, while 0.018 slot is very restrictive in wire size selection 2-permit the use of many techniques 3-heavy rectangular wire can be used for finishing the case 4-permit the use of stabilizing arch in orthognathic surgery 5-more torque control in the buccal segment Types of bracket used with Roth set up: = single wing bracket with anti-rotational arms as, Steiner wings or long anti-rotational arms are used. The use of single wing bracket will increase inter-bracket distance which is more advantageous in the term of force delivered to the teeth, but this point is not important in straight wire technique since this technique utilize highly flexible nickel titanium wires = Roth has incorporated into his appliance a number of hooks for various types of elastics configuration, also he used a double and triple tubes for the use of auxiliary wires and extra-oral face bow = Roth set up has its own specific requirements for bracket placement which varies slightly from the position advocated by Andrews = the major difference between Roth and Andrews philosophies lies in the manner of tooth movement (Andrews moves the teeth bodily – translation without any tipping movement but Roth allows slight tipping of the teeth) = according to Roth opinion: 1-No appliance being effective in translating the teeth 2-Some tipping movement is necessary during the treatment course for seek of efficiency and rapidity. After that a rectangular wire can be used to gradually move the teeth to their desired final position Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

13. 13 Tweed method Tweed philosophy This method is based on Tweed contention that the majority of malocclusion are characterized by a deficiency between the size of the teeth and basal bone which manifest itself in an abnormally forward relationship of the teeth to the bodies of respective jaws Tweed observed that, for achievement of harmony in occlusal and facial pattern, the mandibular incisors should be suited in a correct position over the basal bone of the mandible, therefore, orthodontic treatment should be directed first to correct procumbancy of incisors, then followed by elimination of other dental abnormalities When this procumbancy cannot be corrected due to excessive tooth materials and basal arch deficiency, then extraction is indicated The stable anchorage: It is of fundamental importance in prevention of forward mandibular teeth movement during the use of inter-maxillary elastics and during retraction of mandibular incisors According to Tweed, the preparation of anchorage is the 1st and important step in treatment of malocclusion Tweed 1st prepare the anchorage in the mandibular arch, then moves the mandibular teeth to correct axial inclination, after treatment in the mandibular arch is completed, the mandibular arch then can be used successfully as an anchorage for the movement of maxillary teeth Anchorage preparation: Tipping of the teeth distally in the mandibular buccal segment using class III inter-maxillary elastics, at the same time extra-oral forces with headgear is used on the maxillary arch to anchor that arch against class III elastics The last mandibular molars should not tie to the arch wire to prevent their roots from moving mesially while tipping their crown distally Thus the axial inclination of mandibular teeth is prepared from canine to 2nd molars to create toe- hold, to overcome the tendency for mesial shifting when class II elastics are used. Also 2nd order bends can be incorporated into the wire (tip back) Principle of Tweed philosophy: 1-Normal occlusion is best maintained when the axial of mandibular incisors to FHP (FMIA) is approximately 65 degree 2-The occlusal balance and facial harmony is achieved when mandibular incisors are placed in correct position over the basal bone 3-The normal relationship of mandibular incisors to their basal bone is most reliable guide in diagnosis and treatment planning of class I and class II bimaxillary protrusion Objectives of treatment: 1-Facial balance and harmony 2-Stability of post treatment results 3-Healthy oral tissues Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

14. 14 4-Efficient functions Facial types: Using the lateral cephalogram, Tweed classified the facial skeleton into the following types: 1-Type A: The maxilla and mandible on serial examination shows a forward and downward growth, the ANB angle remains unchanged The prognosis is good and treatment during mixed dentition is not indicated of ANB does not exceeds 4.5 degree Subdivision: The ANB is greater than 4.5 degree, the headgear is used on maxillary arch after extrcation of the 1st premolars, greater amount of tooth movement is required 2-Type B: The maxilla and mandible on serial examination grows forward and downward but maxilla growing forward more rapidly than mandible The growth is undesirable, since the B point will not advance in relation to A point during treatment When ANB is 4.5 degree or less, the prognosis is good Headgear should be wear immediately after removal of 1st premolars to restrict or redirect maxillary growth Subdivision: The ANB angle is larg and increase during observation period Prognosis may be poor, treatment may be long and difficult Extraction is required as a rule 3-Type C: The maxilla and mandible grows downward and forward but the mandible grows forward more than the maxilla, the ANB angle decreased Treatment is not indicated until eruption of canines Subdivision: The mandible grows more than maxilla but slightly downward Tweed diagnostic triangle: Tweed introduced his triangle as a basis for diagnosis –treatment planning and prognosis It consists of: Frankfort horizontal plane Mandibular plane Lower incisors axis And contain 3 angles: 1-Frankfort mandibular plan angle FMA ------- 25 degree 2-Mandibular incisor plane angle ------- 90 degree 3-Frankfort mandibular incisors angle FMIA --- 65 degree === retraction of incisors ----- increase FMA === protraction of incisors ---- decrease FMIA The use of class II elastics will displace the mandibular incisors forward about 5 degree during treatment Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby

15. 15 Tweed advised never to exceed an IMP angle than 92 degree regardless the FMA angle when treating in mixed dentition FMA formula: According to Tweed, the FMA angle average is 16 degree with a mean value 25 degree If FMA between 16 and 25, less extraction is required than when exceeds 30 degree When FMA is 30 degree, the mandibular incisors must be tipped to 35 degree to maintain FMIA 65 degree The ANB angle is reduced by the following methods: 1-Distal movement of A point 2-Mesial movement of B point 3-Combination Tweed provides the following instruction: 1-The aim is to obtain FMIA of 70 to 75 when FMA is 20 degree 2-FMIA 65 when FMA is 30 3-When FMA below 20, the aim should not to exceed with IMP than 92 degree, the FMIA should be upward of 70 degree Tweed showed that, in well balanced face, the IMP angle should be 90-+5 degree He conceived a theory that, - for every degree that FMA in excess than 25 degree, -- the IMP would to be decreased by 1 degree to preserve FMIA at normal value, as: When FMA is 26 -------- the IMP should be 89 When FMA is 27 --------- the IMP should be 88 When FMA is 28 --------- the IMP should be 87 In this manner the FMIA is maintained at 65 degree Orthodontic appliance Orthodontic appliances s and philosophy and philosophy Dr. Mohammed Dr. Mohammed Alruby Alruby