|Year : 2013 | Volume
| Issue : 2 | Page : 90-96
Segmented and sectional orthodontic technique: Review and case report
Faculty of Medicine and Dentistry, Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, Canada
|Date of Web Publication||5-Jul-2013|
Faculty of Medicine and Dentistry, Katz Group Centre for Pharmacy and Health Research, University of Alberta, Edmonton, 7-020D Alberta T6G 2E1
Friction in orthodontics has been blamed for many orthodontic-related problems in the literature. Much research as well as research and development by numerous companies have attempted to minimize friction in orthodontics. The aim of the present study was to critically review friction in orthodontics and present frictionless mechanics as well as differentiate between segmented arch mechanics (frictionless technique) as compared to sectional arch mechanics. Comparison of the two techniques will be presented and cases treated by either technique are presented and critically reviewed regarding treatment outcome and anchorage preservation/loss.
Keywords: Case report, friction in orthodontics, sectional arch mechanics, segmented arch mechanics
|How to cite this article:|
El-Bialy T. Segmented and sectional orthodontic technique: Review and case report. J Health Spec 2013;1:90-6
| Introduction|| |
Friction is defined as the resistance to motion when one object moves tangentially against another.  Friction in orthodontics has received much attention in the literature, particularly, in closing spaces either due to generalized spacing between teeth or closing extraction spaces. Slow tooth movement during closing spaces (also known as resistance to slide [RS]) has been studied extensively. Kusy and Whitley  reported that the RS in archwire-guided tooth movement is because of three components, which are classical friction (FR), binding (BI) and notching (NO). FR depends on many factors including type of ligation , materials of the brackets and wires that is mainly attributed to the roughness at the microscopic level of each wire or bracket material, ,,, slot size  and dry versus wet state of the bracket/wire complex.  Moreover, there are other factors that also can affect the FR part of the RS, which also include masticatory forces;  periodontal ligament width and compressibility;  torque at wire-bracket interface  as well as temperature. 
Kusy pointed out that FR is just part of the whole equation of RS, and, in reality, BI and NO play more major roles in RS than FR does.  This was also confirmed by another study.  Binding is inversely related to wire stiffness. It is clear from the current literature that RS is an unavoidable concern in archwire-guided tooth movement, especially in closing spaces.
Segmented arch mechanics (SAM) was proposed to have a better controlled tooth movement than with archwire-guided tooth movement and is multifactorial, as reflected by the literature. Segmented arch technique was first proposed by Burstone in 1962,  which was followed by few publications that aimed at optimizing and refinement of the technique. ,,,,, SAM suggests dividing the dental arch into three major segments (especially in extraction cases). These three segments were one anterior (incisors and canines [in cases of first premolar extraction, which is the common pattern of tooth extraction in orthodontics]) and two posterior (teeth posterior to the extraction site). SAM proposed two methods in closing extraction spaces, the first was to retract the canine teeth first into the extraction spaces and then retract the incisors or align the crowded incisors in cases where extraction was performed to alleviate crowded incisors/front teeth. This technique aimed at minimizing posterior teeth movement forward, also known as maximum anchorage. The second method in closing extraction space utilizing SAM was by en masse retraction or space closure. In en masse retraction, all anterior teeth including the canines are retracted as a one unit into the first premolar extraction. Usually, this technique compromises anchorage, and the posterior teeth usually move forward unless the posterior teeth are reinforced using headgear or temporary anchorage devices (TADs).  It was postulated and reported that, if the first method was utilized precisely, canine teeth can move into the extraction spaces with minimum or no forward movement of the posterior teeth, without even using headgear or TADs. The concept is based on modulating the moment-to-force ratio (M/F) to provide tip back of the posterior teeth crowns in an attempt to prevent them from moving forward, while allowing the canine to move distally with controlled tipping. It is known that bodily movement requires higher M/F while controlled tipping require less M/F. With this differential moment, differential anchorage can be achieved and maximum anchorage can be produced during canine or anterior teeth retraction. However, due to the perceived complexity of the technique, especially activating only anterior and posterior parts of the retraction T loops, SAM did not receive global acceptance by new generations of practicing orthodontists or even senior orthodontists that usually prefer wire-guided space closure over the SAM.
Attempts have been made to use sectional archwires to retract canines into the first premolar extraction, thinking that this sectional archwire technique was similar in principle to SAM.  Although the technique describes an easy method for canine retraction, however it was not mentioned in that report anything about anchorage loss using this technique.
In short, sectional arch technique utilized arch-guided space closure as the sectional wire was used to guided canine movement, while orthodontic tooth movement is achieved by active components (elastics). It is hypothesized that utilizing sectional arch mechanics does not eliminate FR and BI, which contributes to RS and lose of anchorage.
The cases that are presented below show one case treated solely by SAM, and the other case that was treated by sectional arch mechanics.
| Case Reports|| |
History and aetiology
Patient was 15 years and 5 months old African-American male who was referred to the orthodontic clinic with a chief complaint of crowded upper teeth. Medical history showed no medical concerns.
Clinical and cephalometeric analyses [Table 1], [Figure 1] revealed the following
|Figure 1: Clinical photographs showing convex profile of the patient, with labially erupted upper canines (class II left side and end-to-end right side) with severe crowding and missing lower first molars. Molars are class I and average overbite and overjet|
Click here to view
Specific objectives of treatment
- Skeletal: Class II skeletal tendency due to a slightly retrognathic mandible relative to his profile. The growth evaluation is CVS6.
- Dental: Bilateral super class I molar and class II canine relationships. Upper 10 mm crowding and lower 1 mm spacing. Overjet 5 mm, overbite 4 mm. Proclined and protruded upper incisors and protruded (relative to NB) and retroclined (relative to MP) lower incisors. Intermolar width (recorded from central fossa for the first molars) 48 mm for the upper and lower intermolar width 42 mm. Intercanine width 29 mm between cusp tips. Missing lower first premolars.
- Facial: Lip competent at repose, average nasolabial angle, everted and protrusive lower lip relative to the E-plane, and interlabial gap at rest is 0 mm and slight convex facial profile.
Maxilla is relatively well-positioned and the objective was to maintain its position. Mandible is slightly retrognathic, however, growth direction is favourable. The objective was to monitor mandibular growth and improve mandibular apical base anteroposteriorly (AP) whenever possible. Objectives for maxillary dentition were to maintain AP molar relationship and improve canine relationship. Relieve crowding with maximum anchorage initially. Improve upper incisor protrusion. Objective for vertical dimension was to maintain molar position allowing no vertical change. In addition, the objective for maxillary dentition width was to maintain intermolar width. Objectives for mandibular dentition were to maintain AP molar and improve lower incisor protrusion and inclinations as well as maintain lower incisor and molar vertical positions. Also, maintain lower intermolar and intercanine widths.
Objectives for facial aesthetics were to maintain facial profile and improve upper lip protrusion.
- Extract upper first premolar teeth.
- Bands on the molars and bond remaining teeth using 0.022" × 0.028" slot MPT and transpalatal arch.
- Insert 0.017" × 0.022" TMA T loops with an overlay 0.014 cupper Niti to achieve initial incisor levelling [Figure 2]. Once upper canines are retracted fully into the extraction spaces.
|Figure 2: 0.017" × 0.022" TMA T-loops used for canine retraction, while initial incisor alignment was achieved using an overlay 0.014" Cupper Niti archwire|
Click here to view
- Proceed with arch wires: 0.018" × 0.025" NiTi then SS.
- Use coordinated 0.019" × 0.025 SS wires to finish, detail and coordinate arch forms.
- Take progress X-rays and add bends as needed.
- Retention: Upper Hawley and lower bonded 3-3 retainers.
- Refer for extraction of third molars. Appliance proceed as planned.
[Figure 3] shows clinical photos of the patient after treatment. Maxilla position was maintained in three dimensions [Figure 4], [Table 2].
|Figure 3: Clinical photos and cephalometeric x-ray of the SAM case after treatment|
Click here to view
|Figure 4: Superimposition of the cephalomteric tracings of before and after treatment of case 1|
Click here to view
Final evaluation of treatment
- Mandible: The mandible showed growth at the condyle in the regional superim position and slight increase in its AP projection as seen in the overall superimposition. Maxillary incisors maintained their AP position and inclination, some anchorage loss in the posterior, molar advanced about 2 mm, which improved the initial super class I relationship. Molars and incisor maintained vertical positions. Intermolar width was reduced 3 mm and intercanine width was decreased 3 mm.
- Mandibular dentition: The lower incisors' inclination was improved with slight protrusion relative to NB. Molars maintained their AP position. Molars and incisor maintained their vertical positions. Intermolar width was reduced 3 mm, but intercanine width maintained.
- Facial aesthetics: Improved facial profile convexity and improved lower lip position relative to aesthetic plane.
- Retention: Upper Hawley removable retainer (full-time wear for 2 years then night time only to maintain arch form and the closed extraction spaces) and lower bonded 3-3 lingual permanent retainers (to prevent future re-crowding of the lower incisors) were delivered.
Crowding was relieved and facial profile was improved. Patient and parents were very happy with results. Patient was referred for oral surgery for wisdom teeth extraction before debonding as per patient's and parents' desire. Initial cuspid retraction was accomplished over 3 months using upper 017" × 025" TMA T-Loop retraction springs, as shown in [Figure 2].
Patient was a 17-year-old female who presented to the orthodontic clinic with a chief complaint of crowded upper and lower anterior teeth. Clinical photography and cephalometeric /panoramic radiographs [Figure 5] and [Figure 6] as well as cephalometeric analysis [Table 3] revealed slightly convex, however, acceptable profile. Patient had orthographic maxilla and mandible as well as upper and lower dentition position and inclination were acceptable.
|Figure 6: Case 2, sectional arch case cephalometeric and panoramic x-rays before treatment|
Click here to view
Maintain maxillary and mandibular apical bases, improve maxillary and mandibular crowding via upper and lower first premolar extractions and improve dental aesthetics.
The patient was fitted with transpalatal arch and lower lingual arch as in SAM. However, retraction of upper and lower canines was performed using sectional wire (0.016" × 0.022" Stainless Steel) guided retraction using class I latex elastics (1/8" 2 oz) [Figure 7].
|Figure 7: Sectional arch case during upper canine retraction utilizing 0.016" × 0.022" stainless steel sectional wire|
Click here to view
Upper and lower canine retracted over 1 year [Figure 7] as compared to 3 months in the SAM (case 1). After canine retraction, full archwire was built to 0.018" × 0.025" Nitinol, 0.018" × 0.025" SS, then 0.019" × 0.025" TMA that was used as a finishing wire.
Upper and lower dental crowding was alleviated and facial aesthetics was improved [Figure 8]. Cephalometric superimposition revealed loss of anchorage in the upper and lower arches as seen by forward movement of the upper and lower first molars in the cephalometric superimposition. Upper incisors were slightly retraced, while lower incisors' position was maintained [Figure 9] and [Table 4].
|Figure 9: Case 2, sectional arch case cephalomteric tracing superimposition|
Click here to view
| Discussion|| |
The current literature suggests that wire-guided tooth movement cannot overcome the multifactorial friction and resistance to sliding. Without additional anchorage reinforcement, like headgear or TADs, maximum anchorage cannot be achieved with wire-guided space closure. This concept is applied to sectional arch mechanics, where archwire-guided canine retraction is performed. This may explain the loss of anchorage in case II and the longer time spent during canine retraction compared to case 1 when canine retraction was finished in 3 months. On the other hand, SAM can provide maximum anchorage without the need to use headgear or TADs. The use of cupper Niti wire in the segmented arch case during canine retraction did not affect the total outcome, and, in fact, it might have contributed to the shorter treatment time compared to the sectional arch mechanics case.
Both cases have average face type in terms of mandibular plane inclination to cranial base; however, case I had an initial class II tendency compared to case 2. No major skeletal or dental initial cephalometeric analysis was initially found between the two cases. The other main difference was that case I was a male and case 2 was a female and they were close in their ages at the beginning of treatment. Utilization of transpalatal arch did not improve anchorage in the sectional arch case; this is in agreement with a recent report.  It can be argued that transpalatal arch and lower lingual arch can prevent molar rotations; however, the present case reports, especially the sectional arch case, did not show that transpalatal arch can provide maximum anchorage. On the other hand, a previous report showed that friction does not affect anchorage loss.  Although this could be theoretically presented, utilization of recent data about friction and its role in resistance to sliding compared to frictionless mechanics warrants further in-depth investigation. Although sectional arch mechanics was proposed,  further evaluation of the sectional arch mechanics with prospective randomized clinical trials is needed.
| Conclusion|| |
The presented literature review suggests that archwire-guided space closure does not eliminate friction, and the present case reports using arch-guided sectional arch canine retraction show of minimum anchorage or (loss of anchorage) regardless of the use of transpalatal and lingual arches. On the other hand, SAM, as shown in the present case report, provided maximum anchorage without the use of headgear or TADs. The results of the case should be interpreted with care, as case reports may be considered only as an eye opener. However, in order to use the results of case reports as evidence-based knowledge, prospective randomized clinical trials are required.
| References|| |
|1.||Loftus BP, Artun J, Nicholls JI, Alonzo TA, Stoner JA. Evaluation of friction during sliding tooth movement in various bracket-arch wire combinations. Am J Orthod Dentofacial Orthop 1999;116:336-45. |
|2.||Kusy RP, Whitley JQ. Friction between different wire-bracket configurations and materials. Semin Orthod 1997;3:166-77. |
|3.||Schumacher HA, Bourauel C, Drescher D. The effect of the ligature on the friction between bracket and arch. Fortschr Kieferorthop 1990;51:106-16. |
|4.||Yamaguchi K, Nanda RS, Morimoto N, Oda Y. A study of force application, amount of retarding force, and bracket width in sliding mechanics. Am J Orthod Dentofacial Orthop 1996;109:50-6. |
|5.||Kusy RP, Whitley JQ, Prewitt MJ. Comparison of the frictional coefficients for selected archwire-bracket slot combinations in the dry and wet states. Angle Orthod 1991;61:293-302. |
|6.||Reicheneder CA, Baumert U, Gedrange T, Proff P, Faltermeier A, Muessig D. Frictional properties of aesthetic brackets. Eur J Orthod 2007;29:359-65. |
|7.||Shivapuja PK, Berger J. A comparative study of conventional ligation and self-ligation bracket systems. Am J Orthod Dentofacial Orthop 1994;106:472-80. |
|8.||Articolo LC, Kusy RP. Influence of angulation on the resistance to sliding in fixed appliances. Am J Orthod Dentofacial Orthop 1999;115:39-51. |
|9.||Kusy RP, Whitley JQ. Assessment of second-order clearances between orthodontic archwires and bracket slots via the critical contact angle for binding. Angle Orthod 1999;69:71-80. |
|10.||Griffiths HS, Sherriff M, Ireland AJ. Resistance to sliding with 3 types of elastomeric modules. Am J Orthod Dentofacial Orthop 2005;127:670-5. |
|11.||Thorstenson GA, Kusy RP. Resistance to sliding of self-ligating brackets versus conventional stainless steel twin brackets with second-order angulation in the dry and wet (saliva) states. Am J Orthod Dentofacial Orthop 2001;120:361-70. |
|12.||Reicheneder CA, Baumert U, Gedrange T, Proff P, Faltermeier A, Muessig D. Frictional properties of aesthetic brackets. Eur J Orthod 2007;29:359-65. |
|13.||Thorstenson GA, Kusy RP. Effects of ligation type and method on the resistance to sliding of novel orthodontic brackets with second-order angulation in the dry and wet states. Angle Orthod 2003;73:418-30. |
|14.||Yeh CL, Kusnoto B, Viana G, Evans CA, Drummond JL. In vitro evaluation of frictional resistance between brackets with passive-ligation designs. Am J Orthod Dentofacial Orthop 2007;131:704.e11-22. |
|15.||Burstone CJ. The rationale of the segmented arch. Am J Orthod 1962;48:805-21. |
|16.||Burstone CJ. The mechanics of the segmented arch techniques. Angle Orthod 1966;36:99-120. |
|17.||Marcotte MR. Biomechanics in Orthodontics. Toronto: Mosby; 1990. |
|18.||Braun S, Marcotte MR. Rationale of the segmented approach to orthodontic treatment. Am J Orthod Dentofacial Orthop 1995;108:1-8. |
|19.||Burstone CJ. The segmented arch approach to space closure. Am J Orthod 1982;82:361-78. |
|20.||Kuhlberg AJ, Burstone CJ. T-loop position and anchorage control. Am J Orthod Dentofacial Orthop 1997;112:12-8. |
|21.||Shroff B, Yoon WM, Lindauer SJ, Burstone CJ. Simultaneous intrusion and retraction using a three-piece base arch. Angle Orthod 1997;67:455-61. |
|22.||Sharma M, Sharma V, Khanna B. Mini-screw implant or transpalatal arch-mediated anchorage reinforcement during canine retraction: a randomized clinical trial. J Orthod 2012 Jun;39(2):102-10. |
|23.||Orton HS, McDonald F. A simple sectional canine retraction technique using the properties of nickel titanium rectangular wire. Eur J Orthod 1985;7(2):120-126. |
|24.||Southard TE, Marshall SD, Grosland NM. Friction does not increase anchorage loading. Am J Orthod Dentofacial Orthop 2007;131:412-4. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
[Table 1], [Table 2], [Table 3], [Table 4]