Comparison of Apical Root Resorption encountered during Maxillary Incisor retraction using Stainless Steel Boot Loop and TMA Boot Loop – A Case Series

External apical root resorption (EARR) is probably the most common iatrogenic sequel of orthodontic treatment. The present case series focuses on the incisor retraction using frictionless mechanics. Boot loop made up of .019x.025 Stainless steel or TMA archwire were used for maxillary incisor retraction. Retraction with stainless steel boot loop showed greater root resorption as compared to TMA boot loop.


INTRODUCTION
External apical root resorption (EARR) is probably the most common iatrogenic sequel of orthodontic treatment.
Orthodontically induced root resorption has been studied repeatedly in the orthodontic literature, however the etiological factors bear no single consensus and is attributed to be multifactorial. 1Inflammatory root resorption is a side effect related to the biological tissue response that enables the teeth to be moved during orthodontic treatment.It was first reported in 1914.Histologically root resorption is found in up to 100% of orthodontically treated teeth but is less obvious in panoramic and intraoral radiographs.Although the severity of orthodontically induced inflammatory root resorption (OIIRR) is mostly clinically insignificant, the literature shows that 1-5% of orthodontically treated teeth have severe OIIRR, which is defined as resorption exceeding 4 mm or a third of the original root length.3] This has a great clinical significance, especially when it is coincident with alveolar bone loss or combined with orthodontic retreatment.Apical root loss of 3 mm is equivalent to 1 mm of crestal bone loss, which means that periodontal bone loss will reach a critical stage more rapidly if it is accompanied by OIIRR. 4 The prospective current study included patients having Class II div 1 malocclusion or Class I bimaxillary protrusion cases in the age range of 14-17 years requiring first premolar extraction followed by maximum retraction of incisor teeth.Those cases requiring en-mass retraction of all the anteriors were not included in the study.
The primary purpose of this study was to assess any predisposition of apical root resorption experienced in association with orthodontic treatment mechanics undertaken for space closure using closing loops made of different wire material (Figure 1).A null hypothesis was proposed that there is no difference in the amount of root resorption with both the loops or there is equal amount of resorption.

Case Presentation
All the cases were first levelled and aligned and canines

DISCUSSION
2][3][4] Apical root resorption is a frequent undesirable side effect during orthodontic treatment.Its multifactorial etiology includes individual predisposition, amount of force applied, characteristics associated to orthodontic treatment, and root morphology.However, root loss resulting from orthodontic treatment does not mostly decrease the longevity or functional capacity of the involved teeth.
Frictional mechanics require more force to bring about tooth movement compared to frictionless mechanics.This force is twice than that is desirable because half is required to overcome friction and the rest is needed to move the tooth. 4Extent of root resorption depends upon the amount of force application.Distribution of resorbed lacunae is directly related to the amount of stress on the root surface and the rate of lacunae development is more rapid with increasingly applied forces resulting in more root resorption. 5Schwarz found that applied force exceeding the optimal level of 20-26 gm/cm 2 causes periodontal ischemia, which can lead to root resorption. 6 The study revealed that the amount of root resorption observed qualitatively on orthopantomogram 9 was higher in stainless steel boot loop cases (Table 1) as compared to TMA boot loop (Table 2).[12][13] OJN Application of the retraction force during space closure with frictionless mechanics generates a moment on tooth crown that causes an initial crown tipping and later root uprighting.
The amount and constancy of force depends on the method of retraction and the material of archwire

CONCLUSION
The qualitative assessment of external apical root resorption reveals clinically considerable amount of root resorption in stainless steel boot loop group which can be attributed to higher force delivery by stainless steel loop which accounts to the inherent property of the materials used for retraction.
Gupta G, Singh RK, Relhan A, Singh G, Goyal A : Comparison of Apical Root Resorption encountered during Maxillary Incisor retraction using Stainless Steel Boot Loop and TMA Boot Loop -A Case Series were retracted till class I canine relation achieved.All the four incisors were consolidated and before putting boot loop .019x.025 stainless steel was left atleast for one month and then boot loop was placed to start incisor retraction.In all cases, space closure was done using frictionless mechanics, either with .019x.025TMA boot loop or .019x.025 stainless steel boot loop.Average period of retraction in both the groups was around six months.The stainless steel boot loop and TMA boot loop were activated according to their desired force delivery protocols.The selected cases were subjected to undergo qualitative assessment based on orthopantomogram taken before the placement of boot loop and after the completion of retraction.The pre-retraction and post-retraction orthopantomogram revealed clinically significant external apical root resorption in the group in which retraction was carried out using stainless steel boot loop (

Table 2 ,
Figure 2-5).G, Singh RK, Relhan A, Singh G, Goyal A : Comparison of Apical Root Resorption encountered during Maxillary Incisor retraction using Stainless Steel Boot Loop and TMA Boot Loop -A Case Series , Figure 6-9) in comparison to TMA boot loop (

Table 1 : Root resorption in patients with stainless steel boot loop
Accentuated resorption (loss of almost one third of root length)2Grade 2 Moderate resorption (small area of root loss with the apex exhibiting an almost straight contour)