Introduction
The evolution of fixed orthodontic appliance systems and their components is closely linked to the development of the science of metals, technology, milling instruments and recent advances in computer-aided design, 3D printing and manufacturing technology.
Most modern appliances are manufactured through computer-aided design (CAD) and computer-aided manufacturing (CAM). Research studies on facial growth, a better understanding of occlusion, histological and molecular studies on the biology of tooth movement, analysis of treatment outcomes, clinicians’ experience and patients’ perceptions over the years have influenced the design of modern orthodontic appliance systems.
The discovery of special metals and their unique features, such as shape memory alloys and consistent delivery of forces for longer duration, have been integrated into active components of the orthodontic appliance, such as holding clips, self-ligation brackets and springs. The contemporary orthodontic appliance is precise, relatively small, gentler to biological tissues and more predictable in final tooth positions.
Evolution of fixed orthodontic appliance: Antiquity to the ‘orthodontia’
Historically, our ancestors placed a high value on the health and aesthetics of the dental apparatus. In both prose and poetry of classical Greece and Rome, there are numerous references to teeth showing appreciation, not only for their usefulness but also as a contributing factor to the beauty of women and of enunciation in oratory.
Hippocratic writings (400 BC) have references to the correction of irregularities of the teeth as ‘among those individuals whose heads are long in shape, some have thick necks, strong members and bones; others have strongly arched palates, their teeth disposed irregularly, crowding one on the other and they are molested by a headache and otorrhoea’ .
In a Roman tomb in Egypt, Breccia found some teeth bound with a gold wire.
Pierre Fauchard, a French dentist and the author of Le Chirurgien Dentiste , is credited with the original thoughts on fixed plates ‘bandeau’ to align teeth. , He suggested using ligature wires and gold or silver mechanical devices. Dr. Fauchard was the originator of Edward Hartley Angle’s E arch and the modern banding of the teeth. Extending what Fauchard had written, Etienne Bourdet another famous dentist in Paris also mentioned in his book on the practice of dentistry in AD 1757. His appliance generally consisted of perforated metal bands, either labial or lingual, as anchorage for the ligatures applied to the teeth to be moved. ,
Foundation of orthodontics
Pre-angle era (19th century)
The scientific foundation of orthodontics was laid with significant contributions by clinicians and researchers during the second half of the 18th century. To name a few:
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Chapin A. Harris (1806–1860) used gold caps on molars to open the bite and knobs soldered to a band for tooth rotations.
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Amos Westcott (1840s) placed chin cups on his class III patients and used a telescopic bar in the maxilla to correct a cross-bite (1859). ,
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D. William Dwinelle introduced jackscrew in 1849.
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A modification of the screw called the crib was introduced by J.M.A. Schange in 1841. ,
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C.R. Coffin introduced a new design for an expansion appliance in 1871 that still bears his name. He embedded spring-action piano wire, bent into a ‘W’ shape into a vulcanite plate, separated the plate in the middle and activated the spring so that its halves pressed the alveolar process to the outside. Emerson C. Angell was probably the first person to advocate the opening of the median suture to provide space in the maxillary arch (1860).
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John Nutting Farrar made significant contributions based on research findings (1876–1886). He suggested an intermittent use of orthodontic forces that must not exceed certain fixed limits. He preferred metallic apparatus operated by screws and nuts, which according to him, produced good results, without pain or nervous exhaustion compared to the use of elastics. He suggested precise activation of the appliance to move the tooth at the rate of 1/240 of an inch two times a day, the faster rate being pathological. His significant contributions compiled in ‘Treatise on Irregularities of the Teeth and their Correction’ (1888) made him known as the father of American Orthodontics.
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Dr. Norman W. Kingsley’s dental activities early in his career (1865) became directed to orthodontia, and his first writing on the subject description of the ‘jumping bite’ was the forerunner of functional appliances. His book A Treatise on Oral Deformities (1880) is considered the first textbook with a scientific treatment of irregularities of teeth. He also described appliances for cleft palate and introduced the headgear to apply extraoral force and provide occipital anchorage. ,
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The use of intermaxillary elastics with rubber bands to correct protrusion was advocated by Henry A. Baker (1893). This type of anchorage is popularly called Baker’s anchorage.
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Eugene Talbot, in 1891, made the earliest attempt to apply an accurate analysis of the cast that reflected measurements of the jaws with registering callipers and the T-square with a graduated sliding indicator.
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While Bonwill said, ‘in vying with nature in matching the teeth, there must be more than mere mechanics, more than being capable of filling a tooth or treating an abscess-we must be dental artists’; he developed what is known as the Bonwill’s equilateral triangle (1891). He advocated a speciality of orthodontia many years before Angle. He further stated , ‘Really, in every city, someone should make use of this special practice, and the profession should encourage such practice by sending cases for inspection and consultation’.
Angle era (20th century)
Angle made an immense contribution to orthodontia. He gave this profession a complete system of diagnosis and treatment appliances, as well as his philosophy on malocclusion and appreciation of beauty and life. He believed in simplification and standardisation of appliances. ‘In art, in everything, the one supreme principle is simplicity’ , he often said. With the founding of the first school of orthodontia in 1900, modern orthodontics began with his teachings only.
E arch
Inspired by the Bandeau of Pierre Fauchard, Angle’s first invention of appliances was the E arch. It consisted of clamp bands, an attached expansion arch and ligatures to tie the teeth. This system had poor control of tooth movement. Thus, the next appliance was modified by adding a tube on the band and pins on the primary rigid wire.
The pin and tube appliances were thus founded. The fabrication of the appliance demanded a very high degree of skill in precisely obtaining the parallelism between the pin and the tube on the arch wire, which required to be redone on each appointment. The appliance offered a poor rotational control ( Fig. 44.1 ).
Pin and tube appliance by Edward H. Angle.
Source: Wahl N. Orthodontics in 3 millennia. Chapter 5: the American Board of Orthodontics, Albert Ketcham, and early 20th-century appliances. Am J Orthod Dentofacial Orthop 2005 Oct; 128(4): 535–40.
Ribbon arch bracket
The next step was cutting half the tube length to house a flat wire. The tube partially cut to accommodate wire was the first ever bracket made with a vertical slot called ribbon-arch appliance. The gold ribbon arch of 0.022 in. × 0.036 in. dimensions was secured firmly with pins. This appliance offered an effective rotational control but was weak in control of mesiodistal tooth movement. As a result, the premolar teeth could not be bodily moved ( Fig. 44.2 ).
Ribbon arch appliance by Edward H. Angle.
Source: Angle EH. Some new forms of orthodontic mechanisms and the reasons for their introduction. Dent Cosmos 1916;58:969–94 .
Edgewise bracket
It was in the year 1928 when Angle introduced the latest and the best in orthodontics, the marvellous piece of a precious metal (gold alloy) 0.050 in. dimensions that has a slot-like cut running in it in the mesial to distal directions, and one which could house a piece of 0.022 in. × 0.028 in. wire inserted in its slot at the edge (reverse of ribbon mode) to deliver a three-dimensional (3D) control on the teeth. These brackets were required to be soldered on gold bands. The modern bracket designs are derivatives, or extensions of this fundamental design of the bracket introduced more than 90 years ago by Angle ( Fig. 44.3 ).
First edgewise appliance by Edward H. Angle.
(A and A1) Shows a band of 0.125 in. wide, long, and 0.004 in. thick, with a bracket brazed to the centre of its labial surface. The outer ends of the bracket are bevelled from the slot to the edges of the band. (B and B1) It shows another band of the same dimensions as in A but bearing a somewhat different type of horizontally slotted bracket. The portions of the bracket above and below the slot, instead of being bevelled, form overhanging flanges or wings. (C and D) Show the two types of bracket bands, seated within the brackets which are segments of two types of elastic arch material of which the arches are to be made. (E, F) Show diminutive staples of precious metal to be attached by solder to bands, arches and so on. (G) The ligatures are of two dimensions, 0.010 and 0.015 in., and are made of a particular quality of brass to afford the maximum toughness and softness.
Source: Based on the concept of Angle EH. The latest and best in orthodontic mechanism. Dent Cosmos 1928;70(12):1143–58 .
Although the edgewise bracket was considered a great system, expected to provide 3D control on tooth movement, the small mesiodistal width offered poor rotational control, especially on teeth with large mesiodistal dimensions. The problem was partly solved by soldering a gold eyelet to be placed mesial and distal to the bracket. The ligature wire tied from the eyelet to the arch wire affected rotational correction. ,
During Angle’s era, the treatment philosophy hovered around the non-extraction approach. In subsequent years, information on the growth of the face, research findings from histological studies about tooth movement with variable levels of force and advances in the development of material alternatives to gold significantly influenced the thinking on appliance design and treatment philosophy.
Clinical and cephalometric research findings of Charles H. Tweed’s and studies on attritional occlusion by P.R. Begg considerably changed orthodontic thinking towards an extraction approach in many cases of malocclusion. Clinicians and technologists continued their work on improving appliance design to conserve anchorage, use lighter forces and possibly minimise wire-bending.
Begg’s appliance
P. Raymond Begg assisted Angle in teaching the new edgewise mechanism in the USA. However, upon returning to Australia and practising in Adelaide, Begg experienced difficulties with the edgewise system, attempting to close extraction spaces and reduce deep overbites. He, therefore, developed a light wire bracket in 1933. This new bracket was primarily a ribbon arch bracket turned upside down. The first bracket system used single, round, stainless steel wire of 0.016 in. diameter or less. Begg also developed a highly resilient, stainless steel ‘Australian’ wire in the 1940s, replacing the precious metal and advocated differential light force technique in 1956 ( Fig. 44.4 ).
Begg bracket and round tubes used by P.R. Begg.
(A) Begg’s light wire bracket is a modification of the original ribbon-arch bracket. The open end of the cut slot is swapped upside down. (B) The round tube. (C) One point safety brass pin is used to hold the round wires in the slot, which allows tipping during stage 1 and stage 2 of Begg’s treatment stages. (D) A hook-shaped lock pin is for use during stage III. (E) Up-righting spring made by 0.014-in. Australian wire. (F) Rotating spring right. (G) Rotating spring left.
Lewis’s modification of the edgewise bracket
The edgewise bracket, too, was continuously modified with clinical experience on its limitations. Paul D. Lewis soldered curved rotation arms or ‘wings’ to a single bracket that contact the inside of the arch wire ( Fig. 44.5 ).
Lewis brackets.
(A) Lewis’s bracket. (B) Alexander’s bracket. Alexander modified the Lewis’s bracket with a power arm and a hole in each rotation wing. The bracket slot is 0.018 in. or 0.022 in.
Swain’s Siamese bracket: To achieve better rotational control, Brainerd F. Swain (1949) attached two edgewise brackets to a single base at the width of a single bracket, and thus, a twin or Siamese bracket was born ( Fig. 44.6 ).
Standard edgewise weldable brackets.
(A) Single, (B) small/junior Siamese, (C) medium Siamese, (D) large or wide Siamese and (E) extra large/extra wide Siamese.
The original edgewise brackets were milled in gold and soldered on gold bands. With the discovery of stainless steel, which provided an excellent combination of strength and resistance to corrosion, the need for costly gold brackets was eliminated.
Building treatment into appliance
Several attempts were made in the first half of the 20th century at ‘building treatment into the appliance’, a phrase coined by Joseph R. Jarabak.
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Glendon Terwilliger was among the first to attempt soldering brackets onto bands into tip and torque positions.
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Holdaway suggested that the brackets in the mandibular buccal segments could be angulated by an amount proportional to the severity of the malocclusion ( Fig. 44.7 ).
Figure 44.7 Holdaway’s method of placing the brackets at angulation.
(A) Shows mesiogingival angulations of premolar and molars attachment to upright and distally tip the mesially inclined buccal teeth. (B) After uprighting of the buccal segment, the extent to which brackets are angulated will vary according to the severity of the problem and type of malocclusion. Holdaway suggested 2–3 degrees to maintain the teeth in upright position in bimaxillary protrusions and 10–12 degrees in Class II cases. A lower 0.018-inch round wire is tied in on which a sliding yoke with an incorporated intermaxillary hook distal to the lateral incisor is placed for transmitting force mesial to the bicuspid bracket.
Source: Drawings based on the concept given by Holdaway RA. Bracket angulation as applied to the edgewise appliance. Angle Orthod 1952;22(4):227–36 .
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However, Ivan F. Lee (1959) advocated building torque into the bracket.
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The first commercially viable torque brackets for anterior teeth were marketed by the orthodontic company Unitek (2724 S. Peck Road, Monrovia, CA 91016, USA).
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At the 1960 American Association of Orthodontists (AAO) meeting, Dr. Jarabak, with James A. Fizzell, demonstrated the first bracket featuring combined torque and angulation.
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Around these years, Robert Murray Ricketts believed lighter forces within biological limits were more efficient for tooth movement than those generated by the traditional edgewise appliance. He evolved a philosophy called ‘Bioprogressive Therapy’ . He promoted the use of 0.018 in. slot Siamese brackets. He devised preformed bands, angulated and torqued brackets and tubes in 1959 ( Fig. 44.8 ). These developments set the stage for producing standardised, pre-adjusted orthodontic appliances. He also advocated treating ‘segments’ of dental arches and the use of ‘utility arch’ therapy in 1960s. ,
Figure 44.8 Ricketts’ bracket system.
He used single and Siamese brackets with three torque values suggested initially by Dr. Jarabak.
The era of the pre-adjusted appliance and modern orthodontics
Andrews’ straight-wire appliance
Twelve years later (1972), Lawrence F. Andrews announced an appliance whose brackets were designed for each tooth so that, on being aligned on an arch wire, the teeth would assume ideal positions. Based on his studies published on ‘Six keys to normal occlusion’, he called his design a ‘Straight Wire Appliance’ (SWA) ( Fig. 44.9 ).
Distinct features of pre-adjusted appliance vis-à-vis standard edgewise appliance.
(A) Left top and middle pictures: Standard edgewise appliance necessitates the creation of ‘first order’ bends in the arch wire. To maintain natural arch form and compensate for the variable labiolingual thickness of the crowns of the central incisor, lateral incisor and canine. A molar offset is required to maintain molar rotation. (B) Right top and middle: Pre-adjusted appliances use arch wires without bends. The variable thickness of bracket bases, buccal tubes and built-in contoured base of the tube eliminates the need for first-order bends. (C) Each tooth in the arch has its unique distal tip. Second-order bends are given in the arch wire to maintain the distal tip and prevent mesial anchor loss of the buccal segment. (D) The tip of the tooth is built into the bracket by milling the slot at an angle specific to each tooth. (E) Each tooth in the arch has its unique labiolingual inclination called torque. Torque bends (third order bends) are given in the arch wire to maintain the correct labiolingual inclination of the teeth. Each tooth requires its value of torque. In general, anterior teeth have a +ve crown torque (palatal root torque), while teeth in the buccal segment need a −ve crown torque (buccal root torque). (F) The required torque in the bracket is built into the base of each tooth, thereby eliminating the need for torque in the wire in most instances.
Building on the innovations of Lee and Jarabak, Andrews milled each bracket with appropriate amount of torque and angulated the bracket concerning its base. It was the first bracket to combine ‘torque’, ‘angulation’ and ‘in and out’, offset. These developments were the real beginning of the pre-adjusted appliance era ( Table 44.1 ). The bracket system and biomechanics developed by L.F. Andrews were available as SWA. A detailed description of SWA is given in Chapter 53 .
TABLE 44.1
Andrews’ prescription for straight-wire appliance
| MAXILLARY | MANDIBULAR | |||
|---|---|---|---|---|
| Tooth | Tip (degree) | Torque (degree) | Tip (degree) | Torque (degree) |
| Central incisor | +5 | +7 | +2 | −1 |
| Lateral incisor | +9 | +3 | +2 | −1 |
| Canine | +11 | −7 | +5 | −11 |
| First premolar | +2 | −7 | +2 | −17 |
| Second premolar | +2 | −7 | +2 | −22 |
| Andrews’ prescription for straight-wire appliance: buccal tubes | ||||
| MAXILLARY | MANDIBULAR | |||
| Tooth | Tip (degree) | Torque (degree) | Tip (degree) | Torque (degree) |
| First molar | +5 | −9 | +2 | −30 |
| Second molar | +5 | −9 | +2 | −35 |
Roth’s modification
Subsequently, Ronald Roth modified the SWA. , The purpose of Roth’s set-up was to provide slightly over corrected tooth positions before appliance removal that would allow the teeth, in most instances, to settle in ‘non-orthodontic normal’ norms proposed by Andrews. Roth followed a principle that natural teeth should be positioned from a gnathological standpoint; in other words, occlusion should incorporate the ‘six keys to normal occlusion’ with the mandible in gnathological-centric relation, that is, seated in the condylar reference position.
Therefore, the idealised tooth positions should achieve centric relation closure, mutually protected occlusion and elimination of excursive interferences.
Roth’s prescription has extended prescription values to finish an ‘end of appliance therapy’ goal in which all tooth positions are slightly overcorrected and from which the teeth will most likely settle into non-orthodontic normal positions ( Table 44.2 ).
TABLE 44.2
Roth’s prescription of the pre-adjusted appliance system
| MAXILLARY | MANDIBULAR | |||||
|---|---|---|---|---|---|---|
| Tooth | Tip (degree) | Torque (degree) | Rotation (degree) | Tip (degree) | Torque (degree) | Rotation (degree) |
| Central incisor | +5 | +12 | 0 | 2 | −1 | 0 |
| Lateral incisor | +9 | +8 | 0 | 2 | −1 | 0 |
| Canine | +13 | −2 | 4-degree mesial | 7 | −11 | 2-degree mesial |
| First premolar | 0 | −7 | 2-degree distal | 1 | −17 | 4-degree distal |
| Second premolar | 0 | −7 | 2-degree distal | 1 | −22 | 4-degree distal |
| Roth’s prescription of pre-adjusted system: buccal tubes | ||||||
| MAXILLARY | MANDIBULAR | |||||
| Tooth | Tip (degree) | Torque (degree) | Rotation | Tip (degree) | Torque (degree) | Rotation |
| First molar | 0 | −14 | 14-degree distal | −1 | −30 | 4-degree distal |
| Second molar | 0 | −14 | 14-degree distal | −1 | −30 | 4-degree distal |
Tip edge appliance
Another interesting, intelligent modification of the bracket was chopping off part of the edgewise bracket slot onto either end but the opposite surfaces of the slot that permitted initial controlled tipping (Begg’s type tooth movement) and final edgewise torque and tip control with straight wires. These brackets were called the ‘Tip Edge’ system, introduced by Peter C. Kesling ( Fig. 44.10 ).
Tip edge bracket.
(A) Edgewise bracket with conventional arch wire slot. (B) Diagonally opposed corners (x and y) of the slot are removed to permit mesiodistal tipping in a predetermined direction. (C) Tip edge bracket slot can control the desired tip angle through horizontal surfaces and torque from a rectangular wire between central ridges or pivots. (D) Features of tip edge brackets for the maxillary right canine. Internal components of the ‘propellor’ slot include: a- crown tipping control surface; b- root uprighting control surfaces; c- vertical and torque control ridges or pivots; and d- rotational control surfaces.
Source: Based on the concept given by Kesling PC. Expanding the horizons of the edgewise arch wire slot. Am J Orthod Dentofacial Orthop 1988;94(1):26–37. PubMed PMID: 3164580. doi:10.1016/0889-5406(88)90448-9.
McLaughlin, Bennett and Trevisi (MBT) system
In the early 1990s, Drs. Richard McLaughlin, John Bennett and Hugo Trevisi collaborated with 3M Unitek Orthodontic manufacturer to develop the MBT Versatile + appliance system. McLaughlin and Bennett formulated their prescription for pre-adjusted appliance by adding a ‘theoretical bracket placement chart’ based on the distance from the incisal or occlusal edge to the centre of the clinical crown ( Table 44.3 ).
TABLE 44.3
McLaughlin, Bennett, Trevisi (MBT) prescription of pre-adjusted appliance
| MAXILLARY | MANDIBULAR | |||
|---|---|---|---|---|
| Tooth | Tip (degree) | Torque (degree) | Tip (degree) | Torque (degree) |
| Central incisor | +4 | +17 | 0 | −6 |
| Lateral incisor | +8 | +10 | 0 | −6 |
| Canine | +8 | −7, 0, +7 | +3 | −6, 0, +6 |
| First premolar | 0 | −7 | +2 | −12 |
| Second premolar | 0 | −7 | +2 | −17 |
| McLaughlin, Bennett, Trevisi (MBT) prescription of pre-adjusted appliance: buccal tubes | ||||
| MAXILLARY | MANDIBULAR | |||
| Tooth | Tip (degree) | Torque (degree) | Tip (degree) | Torque (degree) |
| First molar | 0 | −14 | 0 | −20 |
| Second molar | 0 | −14 | 0 | −10 |
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