Determination of the Effect of Conventional Elastomeric Ligature of Different Ligation techniques versus Nonconventional type on Canine Position using Frictional Mechanics ( Typodont Study )

Aims: To evaluate the effect of different ligature types and ligation techniques on the rate of space closure, tipping and rotation of canine after sliding. Materials and Methods: The total number of the samples were 50 sample classified under five groups according to the method and type of ligation; the first group: preformed stainless steel ligature wire (SL), the second group: preformed stainless steel kobayashi ligature wire (KL), the third group: elastomeric ligature in figure – O (EO), the fourth group: elastomeric ligature in figure – 8 (E8) and the fifth group: non-conventional Slide Leone elastomeric ligature (NE). A typodont used in this study with preadjusted Roth stainless steel brackets 0.022×0.030 inch and a stainless steel orthodontic arch wire 0.017×0.025 inch. A bite plane extension bar (BPB) and canine extension bar (CB) are constructed for the measurement of canine tipping and rotation. A 180 gm. of force applied by short continuous elastomeric power chain to retract the right canine. After immersion of the typodont in water bathe with 50-55 0 C for 5 minutes, the rate of space closure were measured in millimeter using vernier (from the distal wings of canine bracket and the mesial wings of the second premolar), the tipping and rotation were measured by taking a photograph to the typodont using digital camera, with transvers projection (for tipping) and occlusal projection (for rotation) from right side (directly toward the right canine), then the angle between (BPB) and (CB) measured directly on the photograph using Protractor. Results: A statistical analysis (descriptive statistics, ANOVA and Duncan Multiple Analysis Range Test) used in this study, for the rate of space closure the results showed that there is a significant difference between the five groups at p ≤ 0.001, the NE group had the highest amount of tooth movement while KL group had the lowest level, for the tipping; the NE group had the highest level of tipping while SL, KL and E8 groups had the lowest level with a non-significant difference between them, for the rotation; the results showed that NE group had the highest level of rotation, while www.rafidaindentj.net Determination of the Effect of Conventional Elastomeric Ligature of Different Ligation techniques versus Nonconventional type on Canine Position using Frictional Mechanics (Typodont Study) ISSN: 1812–1217 Al – Rafidain Dent J

ABSTRACT Aims: To evaluate the effect of different ligature types and ligation techniques on the rate of space closure, tipping and rotation of canine after sliding. Materials and Methods: The total number of the samples were 50 sample classified under five groups according to the method and type of ligation; the first group: preformed stainless steel ligature wire (SL), the second group: preformed stainless steel kobayashi ligature wire (KL), the third group: elastomeric ligature in figure -O (EO), the fourth group: elastomeric ligature in figure -8 (E8) and the fifth group: non-conventional Slide Leone elastomeric ligature (NE). A typodont used in this study with preadjusted Roth stainless steel brackets 0.022×0.030 inch and a stainless steel orthodontic arch wire 0.017×0.025 inch. A bite plane extension bar (BPB) and canine extension bar (CB) are constructed for the measurement of canine tipping and rotation. A 180 gm. of force applied by short continuous elastomeric power chain to retract the right canine. After immersion of the typodont in water bathe with 50-55 0 C for 5 minutes, the rate of space closure were measured in millimeter using vernier (from the distal wings of canine bracket and the mesial wings of the second premolar), the tipping and rotation were measured by taking a photograph to the typodont using digital camera, with transvers projection (for tipping) and occlusal projection (for rotation) from right side (directly toward the right canine), then the angle between (BPB) and (CB) measured directly on the photograph using Protractor. Results: A statistical analysis (descriptive statistics, ANOVA and Duncan Multiple Analysis Range Test) used in this study, for the rate of space closure the results showed that there is a significant difference between the five groups at p ≤ 0.001, the NE group had the highest amount of tooth movement while KL group had the lowest level, for the tipping; the NE group had the highest level of tipping while SL, KL and E8 groups had the lowest level with a non-significant difference between them, for the rotation; the results showed that NE group had the highest level of rotation, while

INTRODUCTION
Orthodontic tooth movement during space closure is achieved through two types of mechanics: segmental or sectional mechanics (non frictional system) and sliding mechanics (frictional system) that involve either moving the brackets along an arch wire or sliding arch wire through brackets and tubes. (1) One of main differences between two mechanics is the friction, since sectional mechanics do not involve friction; while friction plays a significant role in sliding space closure. (2) Friction is the resistance to motion when an object moves tangentially against another. (3,4) During orthodontic space closure with sliding mechanics, frictional force is generated at the bracket arch wire interface and has a tendency to inhibit the desired tooth movement. (5) During orthodontic treatment with fixed appliances, frictional forces should be kept to a minimum so that lower levels of force can be applied to obtain an optimal biological response for effective tooth movement. (6,7) Many studies have evaluated the factors that influence frictional resistance: bracket and wire materials, surface conditions of arch wires and bracket slot, wire section, torque at the wire-bracket interface, type and force of ligation, use of self-ligating brackets, interbracket distance, saliva, and influence of oral functions. (8)(9)(10)(11) The method of arch wire ligation would appear to be an important determinant in the generation of friction, (12) Ligature elastic either placed around the bracket in a figure-O pattern or in a figure-8 pattern, this ligation method will increase the frictional force about 80%. (13) New low-friction ligatures have been introduced, similar to elastic ligatures, but with an anterior part that is more rigid and similar to the mechanical device of self-ligating brackets. (14) The ''nonconventional'' elastomeric ligature (low-friction ligatures) is used on conventional brackets to produce low levels of frictional resistance in treatment mechanics with the preadjusted appliance.
Once the unconventional ligature is applied on the bracket, the interaction between the ligature and the slot forms a ''tube-like'' structure, which allows the arch wire to slide freely and to produce its effects more readily on the dentoalveolar component. (15) The aims of the study were to evaluate the effect of different ligature types and ligation techniques on the rate of space closure, tipping and rotation of canine after sliding.

MATERIALS AND METHODS
The typodont used in this study prepared according to manufacturer's instructions (Ormco), the preadjusted Roth stainless steel brackets 0.022×0.030 inch (Dentaurum, Germany) were fixed on the metallic typodont teeth by using epoxy steel adhesive, (16) the vertical accuracy of brackets were checked by using the bracket positioning gauge, (17) the preadjusted Roth stainless steel molar bands were also fixed to the metallic typodont first molar tooth by using Zinc phosphate orthodontic cement. A class II typodont wax form was used, so alignment of the teeth was done by using arch wires started from 0.014 inch NiTi and gradually upgraded till we reach 0.017×0.025 inch Stainless steel arch wire, (18,19) The first right premolar was removed from the typodont to allow a space for canine sliding. Acrylic bite plane was constructed by taking a primary alginate impression for the aligned teeth then pouring by plaster materials after that a special tray was made and a final impression taken with alginate to construct a master cast, then wax materials was applied in a way that cover the occlusal, incisal, palatal, labial and lingual surface of the teeth (except the canine and the first premolar extraction space), then the wax replaced by hot cure acrylic resin. (20) A special two bars were constructed, a bite plane extension bar (BPB) and canine extension bar (CB) (Figure 1), the BPB is a L-shape bar made from 0.016×0.016 inch stainless steel rectangular wire, the short arm is inserted in the simulated rugae area in the palatal midline of the acrylic bite plane, this bar emerges upward for 10 mm then it bends and extends facially 20 mm to make right angle with CB, (20) the CB were also constructed from 0.016×0.016 inch stainless steel rectangular wire in a form of L-shape, the short arm is welded to the distal aspect of the right canine (the tooth to be slides), this arm extended upward incisally 10 mm then it bends at right angle and extended anteriorly 20 mm and 5 mm over the tip of canine cusp and under the BPB by about 5 mm. such two bars are used as a guide to determine the position of canine after sliding regarding the degree of tipping and rotation, this method is a modification of Huffman and Way procedure. (21) A special wooden table was constructed with two metallic bases, one to fix the digital camera (vertically for rotational measurements and horizontally for tipping measurements), and the other to fix the typodont in a way to allow a standard method for taking a photograph before and after each sliding.
The samples of this study divided into five groups ( (Figure 3), Lancer, USA. for the (SL) and (KL), the wire twisted 8 turns by using Mathieu needle holder (Dentaurum, Germany) and then cut the access leaving small part of it tucked behind the arch wire, (22) this procedure was repeated after each reading.
The retraction of canine was done by using a short continuous elastomeric power chain attached distally to the hook of the first molar band and mesially to the canine hook, the force that applied is about 180 gm according to manufactures instruction (Ormco), measured by using a tension gauge. The typodont was immersed in a water bath (HAAKE -England) with 50-55 0 C for 5 minutes then removed and immersed directly in a tap water (5 0 -10 0 C). (23) Canine position measurements before sliding: Before starting sliding of right canine into first premolar site (for the all readings), the following was checked; first: all the teeth situated in well aligned position. Second: the distance between the distal wings of canine bracket and the mesial wings of the second premolar were measured in millimeter by using digital vernier before each sliding (available space). Third: the angle between BPB and CB should be 90 0 from both horizontal and vertical direction; this angle is considered as CB original angle.

Canine position measurements after sliding:
The distance between the distal wings of canine bracket and the mesial wings of the second premolar were again measured by using digital vernier after each sliding (remaining space), then the rate of space closure was measured in millimeter (by subtraction of the remaining space from the available space).
The canine's tipping degree after movement was measured by taking a photograph to the typodont using digital cam-era, with transvers projection from right side (directly toward the right canine) where the angle between BPB and CB is exposed and then can be measured directly on the photograph using Protractor, this angle is considered as CB inclination angle, then the canine's tipping was measured by subtraction of the CB inclination angle from the CB original angle.
The canine's rotation degree after movement was measured by taking a photograph to the typodont using digital camera, with vertical projection from occlusal side (directly toward the right canine) where the angle between BPB and CB is exposed and then can be measured directly on the photograph using Protractor, this angle is considered as CB rotational angle, then the canine's rotation was measured by subtraction of the CB rotational angle from the CB original angle.

RESULTS
The descriptive statistics (mean, standard deviations, standard error, minimum and maximum values) for the rate of space closure, tipping and rotation of the five groups of ligation are listed in the Table  (1

Rate of space closure:
The ANOVA test for the rate of space closure showed that there is a significant difference between the five groups at p ≤ 0.001 as shown in the Table (2).The Duncan Multiple Analysis Range Test showed that NE group had the highest amount of tooth movement while KL group had the lowest level, while the remaining groups distributed on statistical levels between the highest and lowest groups with a significant differences at p ≤ 0.001 as shown in the Table (3).

Effect of Ligation Techniques on Canine Position
Al -Rafidain Dent J Vol. 13, No2, 2013 Tipping: The ANOVA test for the tipping showed that there is a significant difference between the five groups at p ≤ 0.001 as shown in the

Rotation:
The ANOVA test for the rotation showed that there is a significant difference between the five groups at p ≤ 0.001 as shown in the

DISCUSSION
Regarding the amount of tooth movement after canine sliding, the result of this study showed that the NE group had the highest amount of tooth movement and this is due to low frictional resistance associated with the using of non-conventional elastomeric ligature, this is agree with Baccetti and Franchi (23) who stated that when the non-conventional elastomeric ligature is applied on the bracket, the interaction between the ligature and the slot form a tube-like structure which allows the arch wire to slide freely and achieve a large amount of tooth movement. While the lowest amount of tooth movement that occurs with KL group may be attributed to the highly frictional force that is generated between the bracket and arch wire due to a large diameter and stiff kobayashi ligature wire (gauge 0.012 inch). Regarding the degree rotation after canine sliding the results showed that NE group had the highest degree of rotation and this is may be due to the design of non-conventional elastomeric ligature that makes it fit on bracket slot without any pressure on arch wire (tube like structure) that allowing the bracket to rotate, (23,15) while KL group shown a lowest degree of rotation after canine sliding and this is because that the large diameter (gauge 0.012 inch) kobayashi ligature wire that press the arch wire tightly against the bracket provide enough force to produce the adequate anti-rotation moment. Regarding the degree tipping after canine sliding, this study showed that all the groups had a different degrees of tipping, and this is agree with Ehsania et al., (24) who mentioned that the tipping is a constant phenomenon during sliding and it always occurs when orthodontic force is applied to the tooth. The highest degree of tipping that associated with NE group may be attributed to high rotational degree that makes part of the arch wire completely out of the slot at the distoocclusal and distogingival wings, while the SL, KL and E8 groups had the lowest degree of tipping with a non-significant difference between them, and this is may be due to proper orientation and position of canine during sliding resulting from the pressure of ligation, and also the same bracket width, arch wire cross section and the same point of force application.

CONCLUSIONS
It was concluded that the higher rate of space closure, the higher rotational degree and the higher tipping degree were associated with non-conventional elastomeric ligature (NE group), while kobayashi ligature (KL) group was shown the lowest rate of space closure and the lowest rotational degree. While the lowest degree of tipping was associated with the SL, KL and E8 groups.