User:Globalorthodontist/Lawrence Andrews

Lawrence Andres was known as the father of Straight-Wire Appliance (SWA).

Straight-Wire Appliance
Andrews first came out with Straight-Wire appliance in 1972. His work on the SWA was based on 120 adult cases that were not orthodontically treated. He developed what became later known as the first generation of the Straight-Wire Brackets. These first generation brackets, had tip and torque built into them.

Tip
Andrew added extra tip in each of the bracket compared to what he found in his research in all of his Class 1 cases. He mentioned that when a torque is added on clinical crowns, it leads to loss of tip and therefore to avoid that loss of tip, this was added in these straightwire brackets.

Torque

Initial Problems
Andrews initially recommended various brackets for each clinical case types such as extraction, crowding etc. This initial recommendation of his lead to an inventory problem which meant that orthodontists all over the world had to carry an inventory of different brackets for different cases. Another set of problems arose with using high forces. Orthodontists applied heavy forces with cases with premolar extractions, with eventually lead to a side-effect known as the 'roller coaster' effect. In a first premolar extraction case where high forces are used, roller coaster effect would lead to canine and first premolar teeth to tip towards each other. This would lead to a lateral open bite and an uneven occlusal plane.

Roth's Influence
Roth was one of the early adapters of Andrew's SWA. His also faced same challenges as Andrews and other clinicians. Therefore, he came up with recommendation that one type of brackets should be used for all types of cases, whether extraction or non-extraction. His recommendation came to be known as the second generation of preadjusted brackets. Roths' treatment approach focused on the correct condylar position.

His work was different from Andrews in that he recommended wider or broader arches so as to not damage the tips of the upper incisors and also to have a more protrusive jaw function.

Between 1975-1993
Mclaughlin and Bennett were also one of the early adopters of Andrew's Straightwire appliance. They worked on treatment mechanics based for more than 15 years mainly using the SWA brackets. Their work was published in series of papers in early 1990s and then as a book in 1993. They were advocates of very using light continuous forces as they believed that light forces produced more efficient orthodontic tooth movement. As contrast to Roth, they recommended an ovoid arch form for all patients. Along with ovoid arch, they also recommended placing brackets on the center of the clinical crown, along with closing spaces on 0.19 x 0.25 inch stainless steel wires.

Between 1993-1997
Having been able to work on their philosophy for 18 years, they thought to devise the 3rd generation of Straight-Wire Appliance. They worked with Hugo Trevisi to devise a new system of brackets. They changed the previous bracket designs from rectangular to rhomboidal shape which reduced the bulk of these brackets. They decided to visit the original Andrews tip and torque values and decided that 3rd generation bracket's tip will be based on the original Andrew's research. These three orthodontists, added three different options for canine torque to deal with different patient arch forms and other clinical variables. Therefore, the upper canine brackets were available with +7, 0. -7 prescription torque. They published their second book in 1997, where they changed their earlier stance from positioning brackets in the middle of the clinical crown to the a new way of placing it vertically.

Tip
In terms of bracket tips, they recommended having 0 degree tip on upper premolar and molar brackets. This is to help cases with anchorage bilaterally as less anchorage will be needed from this 8 degree of tip reduction in the upper arch. In the lower arch, the premolar tips were kept at 2 degrees to keep the cuspid tips in Class 1 position. They mentioned that with a 19x25 the tip of each bracket is fully expressed.

Torque
Having Torque control means that upper incisors roots should be moved palatally and lower incisor roots labially. This is primarily helpful in 3 types of cases 1) Class II cases, where Class II elastics can cause torque to be "lost" on upper incisors and where lower incisors tend to procline during leveling and in response to Class 2 elastics 2) Class I cases, where correct incisor torque helps to achieve good anterior tooth fit 3) Class III cases, where correct torque can help to compensate for mild Class III dental bases.

Between 1997-2001
Their primary message was the individualization of all patients. Therefore multiple different types of wires were recommended: Ovoid, Tapered or Square. These arch forms are primarily different at the inter-canine and inter-premolar width. In addition, they recommended to use the 0.19 x 0.25 SS wire for complete arch leveling, overbite control, correct A/P discrepancies and torque and to close spaces whenever necessary.