orthodontic bracket prescription 1

THE DIFFERENCE BETWEEN BRACKT PRESCRIPTION OF MBT ,ROTH AND ANDREWS IS PRESENTED

1. Orthodontic bracket prescription Prof Dr Maher Fouda Mansoura Egypt 1

2. Tooth movement normally occurs in three dimensions. The dimensions were originally incorporated in the edgewise mechanotherapy by specific adjustments to the arch wires, since the first generation of brackets was known as standard edgewise brackets with no prescription. Typical finshing archwire incorporating individual tooth bends for an edgewise appliance . Edgewise slot .

3. The arch wire adjustments are called first-, second-, and third-order bends. First-order bends are the so-called in-out bends, which are represented by the distance of the bracket slot to the tooth surface and is a horizontal adjustment. This accommodates for the differences in the buccal tooth anatomy . First-order bends (in-out) in edgewise, left, compared with straight- wire, right.

4. Second-order bends refer to the vertical adjustments, up and down or tip bends, to provide correct axial inclination and tooth-root alignment in a mesiodistal dimension. The mesial to distal tip of the bracket slot in respect to the long axis of the tooth represents this adjustment of the bracket prescription. Second-order bends (tip) in edgewise, left, compared with straight- wire, right .

5. Third-order or torque adjustments refer to the bucco -palatal or bucco -lingual position of the roots in respect to the crowns of the teeth. Third-order bends (torque) in edgewise, left, compared with straight-wire, right .

6. All three orders are built into the bracket by the manufacturer and thus represent the prescription of contemporary brackets and in turn meet the requirements of the straight-wire or preadjusted appliance Siamese edgewise brackets showing twin design and contoured base

7. In the edgewise bracket system, to achieve an ideal alignment of teeth all the bends —first order (in and out), second order ( mesiodistal ) and third order ( torquing ) have to be built into the archwire by the clinician . n

8. First order bends and arch form. (A) Maxillary, (B) Mandibular

9. Third-order bends (torque) in edgewise, left, compared with straight-wire, right

10. After studying a large sample of untreated ideal occlusions, Lawrence Andrews published his six keys of occlusion ( Andrews, 1972 ) and introduced an edgewise bracket system that has revolutionized fixed appliance orthodontics ( Andrews, 1979 ).

11. The preadjusted edgewise or straight-wire appliance that Andrews described is the most popular fixed appliance system in use today . Prescription in Andrews technique .

12. Unlike standard edgewise brackets, which are identical for each tooth and require bends within the archwire to generate individuality of tooth position, each tooth in the preadjusted edgewise system has a customized bracket. Fully Programmed SWA Genuine Straight-Wire Appliance brackets are fully programmed so that each tooth’s bracket slot lines up horizontally with all others to eliminate the need for time-consuming wire bends.

13. The pre-adjusted edgewise brackets were programmed to impart specific prescriptions of tip (second order), torque (third order), in-out and rotational (first order) control on each tooth and reduced the need for wire bending to control tooth position.

14. T he name STRAIGHT WIRE suggests , in the pre-adjusted edgewise appliance (PEA) all these are built into the brackets or the appliance Siamese edgewise brackets showing twin design and contoured base

15. Bracket prescriptions Pre-adjusted edgewise fixed appliances have first-order (in-out), second-order (tip) and third-order (torque) adjustments built into the individual brackets.

16. This built-in prescription was based around Andrews ’ measurements from the untreated sample of ideal occlusions he studied and included a number of features : ● Pre-angulated slots for correct mesiodistal tooth angulation or tip; ● Bracket bases inclined for correct inclination or torque; and ● Variable distance from base of slot to base of bracket for correct in/out position .

17. In this preadjusted system, the work in accurately positioning the teeth is done by the bracket prescription, significantly reducing the amount of wire bending required .

18. A further advantage is that it also allows groups of teeth to be moved and spaces closed by sliding them in unison along a rigid archwire ; because once tooth alignment has been achieved, the archwire sits passively in each bracket slot .

19. The original Andrews bracket prescription is still available, although there have been adaptations made as the appliance system has been developed clinically .

20. Lawrence Andrews described the original bracket prescriptions for his preadjusted appliance based upon data he obtained measuring tooth positions from untreated ideal occlusions ( Andrews, 1972 ).

21. As experience was obtained with this appliance during clinical use, Andrews went on to describe several different bracket series for extraction and non-extraction cases, in addition to series for use with different amounts of crowding .

22. The extraction series brackets included adjustments for tip and rotation to counter the effects of space closure ( Andrews, 1976 ), but overall these different series significantly complicated stock management for the orthodontist. Andrews’s prescription for maxillary arch For mandinbular arch

23. In particular , it was found that some of the torque prescriptions in the original Andrews appliance were not being fully expressed, most notably in the upper incisors due to the ‘ slop ’ or free space that inevitably exists between the wire and bracket slot. Andrews’s prescription for maxillary arch For mandinbular arch

24. Therefore, many later prescriptions have increased torque values in the upper labial segment to compensate for this.

25. Andrews soon recognised that his prescriptions were not universal and soon developed an array of prescriptions based on extraction usage and malocclusion type . Soon, however, the inventory became complicated and was rationed down to a single prescription. Since then, a range of prescriptions have been developed with various increments of torque and angulation values (Roth 1987 ). Andrews/Roth/MBT tip values ;

26. Roth prescription and MBT have become particularly popular in the USA and UK, respectively. Both incorporate more torque in the upper anterior region, likely related to the inefficiency of the fixed system in respect of torque delivery . Andrews/Roth/MBT tip values

27. The amount of ‘torque’ in the incisor brackets controls their inclination and therefore contributes to the delivery of decompensation during pre-surgical orthodontics.

28. In contrast, Ronald Roth recommended a single series based on the Andrews extraction prescription.

29. Roth also incorporated more mesial crown tip in the maxillary canines in order to promote mesial crown positioning and canine guidance; this led to a commensurate increase in anchorage requirements in Class II cases, however. Andrews/Roth/MBT tip values ;

30. Ronald Roth This prescription had extra torque in the upper labial segment because the edgewise slot does not express the full torque value of the bracket, particularly as the upper labial segment is retracted during space closure.

31. Roth also placed a greater emphasis on functional occlusion and gave the canines greater tip to facilitate cuspal guidance . Prescription in Andrews technique

32. There was also greater torque in the maxillary molar region to prevent dropping of the palatal cusps and eliminate non-working side interferences ( Roth, 1976). Andrews’s prescription for maxillary arch For mandinbular arch

33. More recently, Richard McLaughlin, John Bennett and Hugo Trevisi have developed the MBT prescription, which has increased torque in the upper labial segment and lingual crown torque in the lower labial segment.

34. This was designed to minimize proclination of the lower incisors during treatment.

35. The MBT prescription also has reduced tip, most notably in the upper arch, to reduce anchorage requirements . Andrews/Roth/MBT tip values

36. MBT also incorporates more labial root torque (6°) in the lower incisor attachments relative to Andrews or Roth (1°) designed to resist the use of Class II traction in Class II cases and potentially facilitate retraction of lower anteriors in Class III cases. Andrews/Roth/MBT tip values

37. One of the most common currently used prescriptions, MBT ™ , has negative torque in the lower incisor brackets and increased torque in the upper incisor brackets, which is aimed primarily at conserving anchorage in the orthodontic camouflage treatment of class II malocclusions.

38. Relative to Andrews’ original research, the MBT System reduces lingual crown torque in the lower posterior area for three reasons: • In cases of cuspid and bicuspid gingival recession, the teeth may benefit from having the roots moved closer to the center of the alveolar process.

39. Relative to Andrews’ original research, the MBT System reduces lingual crown torque in the lower posterior area for three reasons: • In cases that show narrowing of the maxillary arch with lower posterior segments that are inclined lingually , buccal uprighting for the posterior area is a favorable step for both arches .

40. Relative to Andrews’ original research, the MBT System reduces lingual crown torque in the lower posterior area for three reasons: • Lower 2nd molars tend to torque lingually over the course of treatment, especially when there is a high degree of buccal root torque in the buccal tube. Therefore, reduced torque values can more consistently assist the effort to keep the posterior segment centered and uprighted .

41. Biological and anatomical variation, as well as mechanical deficiencies associated with the appliance, mean that one overall prescription does not fit all cases .

42. Different appliance prescriptions have different torque values for the upper and lower incisors and so may be more or less suitable as aids to decompensation Dental compensation in skeletal Class II malocclusion Direction of incisor decompensation in Class II malocclusion: the lingual inclination of the lower incisors is increased and in some cases (Class II.1 malocclusion), the upper incisors retroclined Dental compensation seen in skeletal Class III malocclusion Direction of incisor decompensation in Class III malocclusion: the labial inclination of the lower incisors is increased and the upper incisors reduced

43. MBT prescription is advantageous in the pre-surgical preparation of class II cases, where retraction of lower incisors and the maintenance of a large overjet are required. The MBT ™  prescription .

44. However , in class III cases MBT PRESCRIPTION will tend to be disadvantageous, limiting lower incisor proclination and maintaining upper incisor proclination

45. A variety of modifications in bracket prescription and occasionally some wire bending are often required during the normal clinical use of a preadjusted appliance .

46. These may be needed to overcome errors in bracket positioning, significant variations in tooth structure or position, and the presence of marked skeletal discrepancies ( Creekmore & Kunik, 1993 ; Thickett et al, 2007 ).

47. The degree of buccal root torque in the upper buccal segment has also been increased, progressive uprighting torque added to the lower molars and increased torque options provided for the maxillary canines (McLaughlin and Bennett 2015 ). Prescription in Andrews technique . Prescription in Roth technique . Prescription in MBT technique.

48. In class III cases the amount of lower incisor proclination that will be achieved as a result of crowding should be assessed. As a general rule, each millimetre of lower arch crowding will produce approximately 0.5mm of labial movement of the incisal edges, in the midline. Equally, in a class II case, where retraction of the lower incisors is required, each millimetre of space will allow 0.5mm of lingual movement

49. Individual adaptations. Whilst some clinicians may opt for customised prescriptions to ensure that the brackets are working in sympathy with their treatment goals in all cases, it is possible to make certain adaptations that can help to overcome some of these problems. In this class III case with an absence of lower incisor crowding, the lower MBT™ incisor brackets have been inverted to convert 6° of lingual crown torque to 6° of labial crown torque to encourage incisor proclination

50. Individual adaptations. For example, the torque values of the lower incisor brackets can be changed from − 6° to + 6° by inverting them, which will help to procline the lower incisors in a class III case with minimal crowding . In addition, incisor inclinations can be adjusted by introducing third order bends into stainless steel rectangular archwires In this class III case with an absence of lower incisor crowding, the lower MBT™ incisor brackets have been inverted to convert 6° of lingual crown torque to 6° of labial crown torque to encourage incisor proclination

51. Does the prescription matter ? Moesi et al and Mittal et al demonstrated that there was no difference in subjective aesthetic judgement or anterior tooth angulation between MBT and Roth bracket prescriptions, and small changes in the prescription do not make clinically detectable results ( Kattner & Schneider, 1993; Mittal et al., 2015; Moesi et al., 2013). Angulation prescription (in degrees) with popular pre-adjusted edgewise prescriptions. Positive values indicate mesial crown tip Inclination/torque prescription (in degrees) with popular pre-adjusted edgewise prescriptions. Positive values indicate palatal root torque

52. Does the prescription matter ? The concept of torsional (slot) play must be addressed. The engagement angle between the bracket and wire is variable, so small changes in brackets may not fully express as the working wire only engages the bracket at few points and full prescription expression may never occur ( Archambault et al., 2010). the concept of torsional play

53. Does the prescription matter? Prescription expression is dependent on the working archwire and the variation in engagement . The amount of play between the bracket and archwire depends on the size of the archwire

54. Does the prescription matter? Increasing the thickness of archwires in different bracket slots decreases torsional play; a change in archwire is a similar difference to the prescription difference in degrees between Roth and MBT .

55. Does the prescription matter? Increasing the thickness of archwires in different bracket slots decreases torsional play . change in wire size versus slop; from (Johnson, 2013)

56. Does the prescription matter? A change in archwire is a similar difference to the prescription difference in degrees between Roth and MBT .

57. Does the prescription matter? Using a wire sequence that gradually expresses the prescription and finishing cases in the thickest wire possible is therefore essential.

58. Does the prescription matter? Errors in prescription can also stem from improper machining . In an attempt to express more of the desired values, high torque prescriptions have been advocated .

59. Clinicians must understand prescriptions to achieve ideal tooth position. Even with preadjusted appliances, achieving all six keys of occlusion is still difficult (Davies, Gray, Sandler, & O'Brien, 2001; Kattner & Schneider, 1993). Does the prescription matter? Angulation prescription (in degrees) with popular pre-adjusted edgewise prescriptions. Positive values indicate mesial crown tip Inclination/torque prescription (in degrees) with popular pre-adjusted edgewise prescriptions. Positive values indicate palatal root torque

60. There is a need for a bracket inventory to include a variety of prescriptions and the knowledge to apply them in different scenarios for individual patient needs. . Does the prescription matter?

61. Whilst the pre-adjusted appliance is economical and efficient, and has no doubt revolutionised orthodontic treatment, it relies heavily on accuracy of bracket placement, and no single prescription totally eliminates wire bending. Does the prescription matter?

62. The outcome of orthodontic treatment, however, does not rely on the prescription alone. Does the prescription matter?