Ortho. Labs 5e4j5c

Lab. 1

General Principles

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Types of orthodontic appliances:1. 2. 3. 4.

Removable appliances. Fixed appliances. Myofunctional appliances. Combination between removable and fixed appliance.

Removable orthodontic appliances:They have 4 main components: Active components :( ACTIVATION) which produces force for tooth movement, as springs. screws, active plates 2. Retentive components :( ADJUSTMENT) responsible for holding the appliance inside the mouth without dislodgment, as clasps. 3. Acrylic base plate: as a major connector connecting the various components. 4. Anchorage: which is an imaginary component resisting unwanted tooth movement 1.

Materials in Removable orthodontic appliances:Pliers: universal pliers and spring forming pliers are only two essential ,they possess the following characteristics ;A-Short blades for rigidity B-large comfortable handles C-taper of blades accurately ground as blades become parallel when grasping 1 mm wire D-sharp edges to beaks E-No roughing or grooving of grasping surfaces F-not rusted otherwise it will change the physical properties of stainless steel wires and it should manufacture from super hard stainless steel alloys. 1.

The types of pliers used in the orthodontic laboratory are: a) Angle pliers (spring forming pliers): with one cone-shaped beak and one pyramidal beak b) Adams pliers (universal pliers): with two pyramidal beaks. 2-cutter;- these are of 2 types heavy cutter used for wires up to 2mm in diameter and light cutter used for wire gauges 0.4 mm and smaller. In the lab usually we use a heavy cutter and it's highly recommended to use a cutter with cutting edges free from carbide since the carbide can influence the physical characteristics of st. st. wires. 3.

Stainless steel wires

4. Acrylic

Stainless steel wire:-

Is used to make the active and retentive components as it will not corrode in the patient's mouth, because of the oral environment. It consists mainly of iron with 18% chromium, 8% nickel and small amounts of carbon incorporated in the alloy. That's why it is called 18-8 stainless steel wire. The chromium will coat the wire with a colorless layer of chromium oxide

which will prevent the iron from rusting, it can be classified according to its hardness to: 1 Extra-hard' used in orthodontics cutters edges 2. Medium Hard: used in removable appliances for active and retentive components because it’s a malleable and can be formed into springs and clasps. Can be bent sharply and straightened if incorrect but fatigue if overworked and breaks. This type of wire can be annealed (softened) if it subjected to a high temperature 3. Soft used for legation in fixed appliances, hooks and for surgery. The wire has a gauge of 0.3-1.5mm. In removable appliances we use 0.5-0.7mm hard stainless steel wire. Stainless steel wires are cheap strong excellent tolerance by tissues. 0.3--0.4mm for apron spring. 0.5 mm for z and recurved z spring, guarded finger spring, sleeved buccal canine retractor, sleeved Robert retractor,T spring 0.6 mm finger spring and for C-clasp for deciduous canines 0.7 mm Adams clasp, c-clasp, fitted labial arch, uned Robert retractor, uned buccal canine retractor, Hawley arch,Mills bow

Advantages of stainless steel:-

Dose not harms the mouth, allergies unknown. Is not tarnished by oral tissues. 3- Can be supplied hard or soft 4- can be annealed 5- can be welded using spot welder 6- can be soldered 7- once adjusted, maintain its displacement 8 -economical 12-

Physical properties of stainless steel wire:

Fatigue: is that mean cracks if bent for four times at the same position as a right bent quickly, Deflection: It is the distance of change of the free end of the wire from the original position to the new position due to a given amount of force. The deflection equal to the potential energy which is stored inside the spring due to the amount of force of activation. 3. Flexibility: It is the ability of the free end of the spring or wire to return to its original position due to a given amount of force which is not exceeding its modulus of elasticity. Flexibility is very important for the active component (springs) of the removable appliance like z-spring or finger spring. 4. Rigidity: It is the ability of the free end of the spring or wire to withstand a change in position due to a given amount of force that is not exceeding the modulus of elasticity of the alloy. Rigid body dose not change its shape or size under the action of forces .Rigidity is very important for the retentive component (clasps) of the removable appliance like Adams -clasp or fitted labial arch. 1. 2.

Mechanical properties of stainless steel wire: 1. 2. 3.

The force generated by the wire is: directly proportional to the diameter of the wire (r4) directly proportional to the deflection (d) inversely proportional to the length of the wire (L3)

Force & D*R4| L3 So the wire becomes more flexible if it is long and thin (small radius).if the length of wire is doubled, there is eight times the displacement, if the width of the wire is doubled; there is 16 times the pressure on a tooth. For normal orthodontic pressure, the wire should be as thin as possible and as long as possible .but if too thin, there is danger of damage to the wire and soft tissues .this can be reduced by 1- Guarding the spring or sleeving the part adjacent to acrylic. 2- The length can best be increased in the limited space available by winding the wire into loops. 3- The best design for spring is when its stability ratio will equal to 1. The stability ratio is the

product for dividing the flexibility on rigidity .In other word the spring should be rigid enough to withstand the occlusal forces and maintain the force of activation and flexible enough to perform the required tooth movement

Types of tooth movement done by removable appliances:1. Tipping movement: the unequal movement of the crown and the root along a center of rotation

Labio-Iingual (bucco-palatal) direction mesiodistal direction. 2-Rotation of less than 90* (couple force system) 3-Bodily tooth movement which is the movement of the crown and the root in the same amount and direction 4-Intrusion and extrusion the movement of the tooth along the long axis of the tooth a) b)

Orthodontic force:-

The force applied by removable appliances is light and intermittent. Since the best pressure to move a tooth is 25-30g/ 1cm2 of enface root surface area, so the springs are designed to give that amount of pressure.

Types of wire bends:-

1. Soft curve: formed by holding one end of the wire firmly on one hand by pliers and forming a

curve with the thumb and finger of the other hand. please note the curve is made by the fingerand thumb while the pliers is used just for grasping the wire and this true for wire gauge up to 1 mm but above that gauge the condition is vice versa, additionally a very small diameter circle(less than 3 cm in diameter for o.5 mm st.st.wire) is difficult to be made by the thumb and finger 2. Right angle bends: formed by pressing the wire firmly at right angle to the pliers. 3. Acute bend: formed by holding the wire along the peaks of the pliers and bending firmly back with the forefinger.

Art principles of wire bending:

Sitting position should be comfortable with the elbows within the level of the working table and stand above it. This will gives a good s for the hands while working with wire bending. 2. Cutting the wire should be under the bench as this will prevent trauma to your self or your colleagues. 3. Make the wire straight before starting and avoid the sharp ends at this stage 4. Do non-traumatic ends by forming a very small coils (1 mm in diameter) at each ends 5. Pliers are mostly used for gripping and not for bending for any arc. Squeeze the pliers lower arm ends by your hand to get the maximum force for pliers grasping of the wire(force * arm length) 6. Always use the universal pliers (Adams pliers) for wire grasping this will give an area of with the wire while using the coil forming pliers (Angle pliers) will give a point of with the wire which will form a stress accumulation point that leads to fracture of the wire during use. 7. Wire gripping should be firm with no movement for its part gripped between plier's blades and usually the wire is perpendicular to the blades slot. 8. Its preferable to clean the left hand (or the hand grasp the pliers) from any oil or moisture by a piece of cotton dipped by alcohol. 9. Mark the site of the bend(by a marker pencil) and make a trial bend before the final one so you can check the accuracy of the mark site 10. Avoid notching and sharp angles ~ fracture 11. Avoid repetition —> fracture 12. Don't go back 1.

10. imagine the direction and size 11. Always follow the anatomy and make space for acrylic (tag should away 0.5 mm from the palate) 12. All wire bending is parallel to the gum or palate or vestibule or the line of occlusion in a straight or curved line according to the anatomy. 13. circles:a) its recommended to be done by thumb and fingers in such away that the plane of the index finger and the thumb holding the wire is perpendicular on the slot of the pliers this right angle of bending as it become more acute the circle will become smaller Smaller circles easily can be converted to larger but a larger circles is difficult until become smaller by pliers c) Coils are done by pliers (coil forming pliers). The ideal pliers should have a peak of 1squre mm in area and a 22 mm beak height that can perform coils from 1mm diameter till 5mm. d) Circles and coils should be smooth in texture with no overworked points b)

General principles for spring design;1-wire dimension as the length of wire increases the force will be reduced and the flexibility will be increased

and vice versa for the diameter of wire. 2-force of activation which is within the optimal threshold for the force that is needed for tooth movement which is limited to that of capillary blood pressure ( 20-26 grammas per sq. cm. ) for each square cm. of tooth root embedded into the alveolar bone. 3-Directin of tooth movement ;-ideal spring design should submit a perpendicular force on the long axis of the tooth at a nearest point from the center of resistance of that tooth moving the tooth either toward or within the line of occlusion. 4-Ease of insertion and patient comfort. For cross bite the use of Z spring for anterior teeth will facilitate the treatment while it is difficult for post. th. Therefore its preferable to use T spring for post. Tooth in cross bite. The ends of spring should be smooth & don’t dig into the pt cheeks. Palatal spring is superior for buccal springs for pt. comfort. buccal springs & bows will produce ulceration & trauma for mucosa & cheecks if they are extended too deeply in the vestibule. Therefore they end 2mm away from the highest point of oral vestibule & 0.5 – 2mm away from the mucosa.

Lab. 2______________________Z-Spring___________________________ " \■

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From its name, it is similar to the letter z in shape. It is an active component of removable orthodontic appliance (palatally situated). It is used to push one anterior tooth from the lingual (palatal) position into a labial direction (linguo- labially or palato-Iabially).

Components:1. Three equal arms, the first of them {active arm) has a nontraumatic end in a shape of a small coil (1mm in diameter) directed away from the gingiva. This arm is directed to the mesial side unless the tooth is rotated so it is directed to the site of rotation. 2. Two coils (2-3mm in internal diameter) to increase the flexibility of the wire and decrease its force. The direction of the first coil is upwards while the second coil is directed downwards to keep the spring in one plane. 3. Retentive arm (tag): It is that part that is embedded in the acrylic base plate for retention of the spring into the acrylic. It is zigzag in shape and parallel to the palate midline.

Properties: 1.

2. 3.

4.

5.

6.

Constructed from 0.5mm hard stainless steel wire for incisors and 0.6mm for canines. Its width is equal to the mesio-distal width of the tooth from the areas. The active arm sits on the cingulum and the level of the Coils with the arms should be perpendicular on the palatal aspect of the tooth to prevent slippage of the wire. The spring is covered by a thin layer of acrylic from theacrylic base-plate to prevent food stagnation in the area during eating, trauma to the wires, and slippage of the spring in incisal direction. The three arms (active arm, connecting arm, distal arm) should be very well squeezed with no spacing between the small coil of active arm and the 2nd coil or between the end of distal arm and 1st coil. The level of the three arms is perpendicular on the level of the retentive tag as the instanding tooth is mostly vertical or retoclined.This right angle situated at the junction of the distal end of the distal arm and the beginning of the tag.

Uses:The main use is the correction of an anterior crossbite of one tooth (proclination of an instanding incisor). 2. Correction of rotation of one incisor less than 90* together with a Hawley arch (couple force system). 1.

Activation:1- Instanding tooth:By opening the coils so that the distance between the active arm and the distal arm increases by 2mm in a symmetrical way. This gives a small force (25-30 g \ sq cm of root) for tooth movement for a long duration (2-3 weeks interval). The active arm is pulled by the Angle pliers upwards and forwards so that the spring is activated exactly perpendicular on the palatal aspect of the tooth in such away that the spring does not interfere with the path of insertion or produce discomfort for the patient.

2- Instanding tooth with rotation:-

For a rotated tooth the activation is done by opening of the 1 st coil only in such away the angle between the long axis's of active arm and distal arm is equal to the angle between the mesiodistal axis of the rotated tooth and the line of dental arch .This will give a differential activation and allow for the rotated part of the tooth to wove 1stly then will followed by the other parts in a gradual way. After the correction of rotation the spring can be activated as given in No.1

Anterior anchorage:The activation force Is applied on a 60° inclined palatal surface. This force is divided into two components - vertical and horizontal. The vertical component will dislodge the appliance incisally making the spring inactive. Therefore, it is important to put addition retentive clasps on the anterior teeth, e.g.: (Adam's clasp on the adjacent incisor, Adam's clasp on 4|4 or C-clasp on clc.

Design of removable appliance:-

1. Z-spring 2. Adams clasps on 6!6 and 4\4. 3. Hawley arch (in case of rotated incisors). 4. Acrylic base plate 5. Posterior bite plane in case of anterior crossbite.

Alternatives:-

1. 2.

T-springs when space is very limited as in the premolars. Screw.

Modification:-

In the modified z-spring the non-traumatic end extended to the proximal aspect of the tooth as a c-shape, ending on the labial surface of the incisor or canine to give a slight mesio-distai(or disto-mesial) movement in addition to the palato-labial movement. This modification always needed when the instanding tooth is partially hidden to its adjacent .The activation of the M.Z.S. wil be done in a normal way with a slight tilting of the whole spring to the correct direction at the junction of the distal arm and the tag.

Lab, 3_________________Recurved Spring ______________________ The basic form is a combination of 2 Z-springs ed at the anterior region to form one active arm. Its properties are similar to z-spring.

Components:1. One large active arm 2. Two small connecting arms 3. Two small distal arms 4. Four equal coils each of them 2-3mm in interna! Diameter 5. 2 retentive arms

Properties:-

1. Constructed from 0.5mm hard stainless steel wire. 2. Its width is equal to the collected mesio-distal widths of the teeth to be moved from the cingulum area. 3. The level of the coils with the arms should be perpendicular on the palatal aspect of the teeth at the cingulum. 4. The spring is covered by a thin layer of acrylic. 5. The outer coils are directed upwards and the inner coils are directed downwards (opposite direction to keep the spring in one plane). 6. The inner coils are separated by 0.5-1 mm.

Uses:Correction of crossbite of more than one incisor. 2. Correction of mild rotations and irregularities of more than one incisor together with a Hawley arch (couple force system). 1.

Activation and design: Similar to a Z-spring by opening the four coils.

Anterior anchorage: Similar to a Z-spring.

Design of removable appliance:

Recurved spring Adams clasps on 6\6 and 4\4. Hawley arch (in case of rotated incisors). 4. Acrylic base plate 5. Posterior bite plate in case of anterior crossbite. 1. 2. 3.

Alternatives:-

Screw.

Lab. 4 and 5_____________

Finger spring_________________________

It is an active component of removable orthodontic appliance (palatally situated).

Uses:It is used for mesio-dislal movement of any tooth (incisors, canines, premolars and even molars) which is located within the line of the arch. However, it is mostly used for distal movement of canines.

Types:1- Simple finger spring (self-ed finger spring) 2- Guarded finger spring (ed finger spring)

Components: 1. Coil: Internal diameter of it is 3-4mm. consist from one complete coil plus half Direction— it should be directed opposite to the direction of teeth movement so that when activated the coil is opened, Location the coil is located by drawing a line perpendicular on the line of occlusion from the midpoint of the mesio-distal width of the tooth to be moved, and about 2mm away from the palate midline. *the coil is wound in a way that the active arm becomes upwards and the tag becomes downwards. 2. Active arm: It begins from the coil and continues to the labial or buccal aspect of the tooth. it should end with a non-traumatic coil and can have a C-shape well adapted to the labial surface of the tooth for better engagement of the tooth and to keep the tooth movement within the the line of dental arch, the coil and/the active arm are protected by the acrylic base plate. For canine the active arm has a crank located 1|3 away from the coil, while for other teeth it has a small curve near to the coil. 3. Tag: ln the simple finger soring: the tag forms a zigzag shape, 5-6 mm long, parallel and 2mm away from the palate midline and elevated about 1mm form the palate for embedding in the acrylic. * In the guarded finger spring: the tag (guard) begins, about 2mm away from the coil, with a small U shape (2mm wide and 2mm long) and then extends below the active arm parallel to the line of the dental arch and 2mm away from the teeth, and ends with a small L-shape at the middle of the tooth adjacent to the extraction site. The guard prevents palatal displacement of the active arm and trauma to the mucosa. The U-loop and the Lshaped are elevated about 1 mm from the palate to be embedded in the acrylic.

Activation:-

The simple type is activated by opening the coils using an Angle pliers so that the tip of the active arm is deflected 2mm or one third the mesio-distal dimension of the tooth to give a small force for tooth movement (25-30g) for a 2-3 weeks duration. In the guarded type, activation is done so that the tip of the active arm is deflected half the mesio-distal dimension of the tooth to give a small force for long duration (3-4 weeks).

Force: The force resultant of the spring at the point with the tooth should be parallel to the line of dental arch (line of occlusion) to move the tooth within the line of occlusion; otherwise the tooth will move

and rotate disto-buccaily. This would necessities placing the coil too far anteriorly (especially when retracting canines), therefore the active arm is bent or a crank is added to apply the active force parallel to the line of occlusion and at the same time this will allow to put the coil more backward which will gives a good length for the active arm and increasing its flexibility.

Design:-

1- 2 finger springs on 3]3 2- 2 Adam's clasps en 616 3- Fitted labial arch on Hi 4-Acrylic base plate >

Differences between simple and guarded: _____________________________________Simple___________Guarded

Component Constructed from hard SS wire Activation by opening the coil Appointment weeks

has a tag 0.6mm V3 of tooth width every 2 weeks

Advantages of guarded finger spring:-

has a guard 0.5mm Y2 of tooth width every 4

1- The active arm of the guarded spring is more flexible in horizontal direction because it is

made of 0.5mm hard SS wire — less number of visits 2- Stabile in vertical direction because it is located between the acrylic and the guard which prevents trauma to the palatal mucosa.

Design of removable appliance containing finger spring:-

The ideal use for the finger spring is for distal movement of the canines during the 1st stage of cl 11 div 1 correction which includes 1-Double Adams clasp on 5&6 on both sides(assuming the extraction of 4 on both sides for space creation). 2-guarded finger spring on3 on both sides 3-acrylic base plate as a major connector' 4-anterior bite plate ( in presence of deep bite) 5-modified fitted labial arch on 1&2 on both sides to increase the anchorage and retention of the appliances

Lab. Sa7

Adam's Clasp______________________

It is very extremely important clasp nearly as all removable appliances have Adam's clasps in its construction, it is the major retentive component of the appliance in the patient's mouth (and therefore aids in anchorage and allows the active components to work properly).

Components:-

1. Bridge: Its height should be equal to 1/2 of the anatomical crown or at the end of the buccal developmental groove. Its width is equal to the distance between the mesio-buccal and disto-buccal cusp tips. The bridge should form 45° with the long-axis of the tooth because: a) The U-loop will be engaged into available undercut areas. The best undercut area is located below the r cusp tips. b) It will be non-traumatic as above 45° is traumatic to the cheek and below 45° it will interfere with opposing teeth. 2. U-loops: a) Situated at the available undercut area. b) Its height equals half the height of the bridge. c) !t forms 45° with the bridge plane. 3. Occlusal part: It contains 3 angles: a) Angle A: it determines the angle of the bridge b) Angle B: located at the occlusal area between 2 adjacent teeth on the buccal side c) Angie C: located at the between 2 adjacent teeth in the lingua! or palatal side.. 4. Retentive arms: Located at the lingua! (Palatal) side, ending 2mm away from the palate midline.

Properties:-

It is a universal clasp, constructed with one pliers only (Adam's pliers). It is small neat and utilizes minimal space in the buccal vestibule. 3. Its bridge is used as a grasp for insertion and removal of the appliance. 4. The bridge can receive a lot of modifications and attachments. 5. It is constructed from 0.7mm hard stainless steel wire. 6. It can be used on a semi erupted tooth or tilted tooth. 7. It is strong but resilient enough to give firm grip for every retention purposes 8. it can be used on any tooth except lower permanent and deciduous incisors. However, when the centrals are very proclined, then the U of Adam's clasp will be difficult in insertion of the appliance so we use a fitted labial arch. 1. 2.

Steps of construction:-(written by Prof. Dr. Basher Kinaan) 1. Take 10cm of stainless steel wire and make it straight. 2. Make a 90° angle near the centre. 3. Make another 90° angle to determine the width of the bridge. 4.

Make a U loop on the mesio-buccal corner to determine the height of the bridge.

5.

Bend the U-!oop 45° to engage the mesio-buccal corner of the tooth.

6. Repeat the steps 4 and 5 on the disto-buccal corner. 7.

Make a sharp bend 1|2 of the bridge height towards the mesial marginal ridge of the firstmolar at its occlusal surface to determine the bridge angulations.

8.

the wire at the marginal ridge between 6 and 5.

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9. Make the mesial tag and finish it vertical to the palatal surface 0.5mm for space of acrylic. 10. Repeat steps 7, 8 and 9 on the distal arm. 11.

Bend the distal arm mesially to minimize acrylic size in the horse-shoe design.

Notes:

If a tooth is not fully erupted, we need to trim the cast mesially and distaliy at the points, Undercut in the tooth to allow for engagement of the clasp in them.

Modifications:-

It can be-done as double Adams clasp on 5 and 6. It can be done with one U-loop and the other U-loop omitted, especially on tilted molars. We can do it on a molar and solder to it half an Adam's clasp done on an adjacent tootending with 3 Uicops. 4. Its bridge can contain a small hook or U-shape used to receive elastics. 1. 2. 3.

5. 6.

It is bridge can contain small coils on both sides to receive a face bow for extra oral traction It is bridge can receive tube by soldering to be used for E .O .T.

Attachments: The bridge of the Adams ciasp can be soldered to: 1. a hook which can receive inter- or intra-maxillary traction elastics or whip spring. 2. buccal canine retractor or Hawley arch. 3. a small coils or tube which can receive sliding Hawley arch or the inner bow of the fac bow.

Adjustment:

The Adam's clasp is checked every visit for loosening and adjusted as necessary so the U-!oops fully engaged the undercut by decreasing the angles A and B.

Alternatives: 1. 2.

Arrow-head clasp Boll-end clasp

Additional retention: 1. Fitted labial arch 2. C-clasp

B.

BUCCAL CANINE RETRACTOR (BCR) Uses: Distal movement of a mesially inclined canine which is located within the line of occlusion (for simple BCR) while modified BCR is used to move the mesially inclined and buccally malposed canine distally and palatally Sometimes the BCR is used to retract the premolars especially in the lower arch.

Components:1 - Simple BCR: - Has a -Main coil.located just distal to the long axis of canine and 2 mm below the higest couture of the oral sulcus(for upper arch). b - Mesial arm ends with a smail non traumatic coil (acts as site of force Application). c - Distal arm. d - Occlusal part (extends over the area between 1st and 2nd Premolars. e - Tag (retentive arm). 2 - Modified BCR: -

Has the same components of simple BCR but instead of a small non traumatic coil, the mesial arm ends with a small u - loop(act as site of force application). and c - shape

Properties:1 - Gauge of the wire is 0.7 mm hard S.S. (this is for the self ed type). 2 -The main coil of 3 -4 mm in diameter, should be located just distal to the long axis of the canine and 2 mm away from the deepest part of the buccal vestibule, also should be 0.5 - 1 mm away from the buccal mucosa.

3 - The mesial arm extends in a slightly curved shape from the main coil till reach the mesial aspect of the crown of the canine which ends with either a small non traumatic coil or a small u - loop (both of them should be located in the interdental area and as near as possible to the cervical part of the crown, in addition to that they should be parallel to the long axis of the tooth so that the applied force will be perpendicular to the long axis of the moved tooth). 4 - The distal arm extends in a curved shape from the main coil till reach the area between the 1st and 2nd premolars (the purpose of the curved shape is to apply a horizontal force that leads to distal movement of the tooth and avoids extrusion movement). 5

- The tag extends in a straight shape and well adapted on

the palatal embrasure area between 4&5 and continue to be parallel to the palate till ends with a small L-shape_towards the palate (to provide enough room for the acrylic beneath the tag also to prevent rotation of the wire inside the acrylic). 6

- Both type of the BCR could be;a - self ed (0.7 mm) or called non - sleeved type. b - ed (0.5 mm ) called sleeved Type, in which the main wire inserted inside a Stainless steel tube with internal diameter 0.7 or 0.8 (from the beginning of distal arm till the end of the tag), the purpose of the sleeved type is to combine between the increased flexibility of the main wire (specially the active coil) and the increased rigidity of the sleeved distal arm and the tag, so we can increases the interval between visits and decrease possibility of deformation of the spring and trauma to soft tissue .

7- The c- shape in modified BCR usually located in the middle of the crown and parallel to the line of occlusion and should be well adapted (to prevent trauma to the soft tissue and food stagnation). 8 - The spring should touch the dental cast in 3 points only (site of force application, occlusal part and the end of the tag).

Activation: For the self ed type we close the active coil so that the mesial arm reaches 1/3 of the mesio-distal width of the crown every 2-3 weeks while in sleeved type reaches 1|2 of the mesio-distal width of the crown every 3-4 weeks, also in modified BCR we should activate mesial arm (with the u - loop and c shape) palatally to gain paiatal movement in addition to distal movement).

Disadvantages : 1-

Liable to deformation (espically the self ed) because, the spring is

suspended buccally, therefore there is high possibility of trauma to the surrounding soft tissue. 2- Difficult to construct and adjust. 3 - Uncomfortable to the patient (as it suspend buccaify).

Modifications: 1-Sleeved type. 2- Can be soldered to the bridge of Adam's clasp.

Note : -

When the canine lies within the line of occlusion, we prefer to use finger spring over BCR because:1-

The finger spring is protected by the acrylic, so it is more stable; less traumatic and more

comfortable to patient. 2-

Easier to construct and adjust.

Fitted labial Arch "FLA" It means fitted to the labial aspect of teeth "usually the incisors". It is mainly used on the upper incisors and rarely on the lower incisors because it is constructed from 0.7mm HSS wire, so it is considered to be rigid for the lower incisors due to their small size.

Function:1- To increase the retention. 2- To increase the anchorage.

Components:1- Small U-loop 2mm in width and height. It must be away from the interdental papilla by at least 0.5mm to prevent trauma to it. It should engage the undercut area between 2 adjacent teeth, i.e. the embrasure area between 2 central incisors. 2- Two horizontal arms at the junction between the incisal and middle thirds of incisor. 3- Two small vertical arms extending from the horizontal arms. They must between the 2 adjacent incisors to prevent the interface with opposing teeth. 4- Two retentive arms extending from the vertical arms. They must be well adapted to the palatal interproximal area between the central and lateral ''to prevent the interference with the opposing incisors", then extend to the rugae area and end by 0.5mm vertical bends for better retention inside the acrylic.

Adjustment:-

By slight squeezing of the U-loop with slight bending towards the undercut "embrasure" area.

Modifications:• •

More than one U-loop can be located between two incisors or between incisor and canine. Small coils can be added to FLA to receive J-hooks of EOT or other attachments.

Note:on severely proclined incisors , the FLA is preferred over the Adam's clasp because of the severe undercut which makes the Adam's clasp difficult to be inserted.

Hawley Arch "H.A." An important and very common labial bow, designed by Dr.Hawley in the 1920s to be used on the anterior teeth as a retentive and/or an active component.

Components:1- Smooth curve bow (arc). Starts from the mesial third of one canine to the mesial third of the canine on the other side. Its height is at the junction between the incisal and middle thirds of incisors It must form just a light with the labial aspect of the anterior teeth, or only with the most prominent teeth if they where misaligned. 2- Two U-loops. The width of the U-loop is from the junction between the mesial and middle thirds of the canine to the distal proximal surface of the canine. The height of the U-loop must extend 2mm apical to the gingival margin of the canine. The U-loop should be 1-2mm away from the gingival tissue to be non traumatic. 3- Occlusal parts. The free end of the U-loop should cross over the area between the canine and 1st premolar to form the occlusal part which must be very well adapted to prevent the interference with the opposing teeth. 4- Two retentive tags. They follow the curve of palate and end by 0.5mm vertical bend on the palate, about 2mm away from the midpalatal suture.

Uses of the H.A. A-as a retentive component:1- To increase the retention and anchorage in the anterior segment. 2- To construct retainers which consist of: - H.A. on the anterior teeth, Adam's clasp on the 1st molars, and acrylic base plate. These retainers are used to maintain the teeth in their position following orthodontic treatment.

B- as an active component:Correction of incisors rotation {which is less than 90o} in combination with Zspring or recurved Z-spring {i.e. couple force system}. 2- Retraction of proclined incisors. 3- To close very mild spacing between the incisors by sight retraction. 4- To reduced increased overjet which is not more than 6mm 1-

Adjustment:When used as a retentive component, we slightly squeeze the U-loop so that the labial arc s the teeth lightly.

Activation:• •

For derotation : by slight squeezing of the U-loops with actication of the Zspring or rec. Z-spring to achieve couple force. For retraction : by slight squeezing of the U-loops { so that the labial bow about 1mm behind the labial aspect of incisors } with 1mm trimming of acrylic behind the incisors to allow foe their retraction.

Modification:1- Soldered H.A. : Instead of forming occlusal part and retentive tags, a horizontal arm extends from the U-loops to the bridge of Adam's clasp to be soldered there. 2- Reverse H.A. : here the U-loops are made closed. It is used to correct slight buccal malposotion of the canine. Activation is by widening of closed U-loop. It can also be soldered to the bridge of Adam's clasp.

Roberts retractor "R.R." It is an active component, designed by Dr. Roberts in 1956. it consists of 2 buccal canine retractors ed anteriorly at the central midline, used for O.J. reduction.

Components:1- Smooth curve labial bow:- extends from the distall aspect of the lateral incisor to the distal aspect of the lateral on the other side. It is situated at the junction between the incisal and middle thirds of incisors. 2- Two mesial limbs:- straight arms extend from the labial bow to the coils. 3- Two coils:-about 3mm internal diameter,it is 2 mm away from the highest contour of the vestibule and 0.5 mm away from the gingival tissue , and it is located 1mm mesial to the long axis of the canine. 4- Two distal limbs: - slightly curved arms start from the coils and extend to over the distal proximal area of the canine to form the retentive tags. 5- Two retentive tags: - the same as in the Hawley Arch.

Wire Gauge:the sleeved Robert retractor constructed from 0.5mm HSS wire with sleeving of the distal limbs and retentive tags by 0.7mm internal diameter HSS tube . It is recommended to use 0.7mm sleeve and o.5 mm wire to prevent fracture of the wire at its entrance to the tube because if we use 0.5 mm wire and tube, the wire entrance will be very firm and will act as point for force accumulation that leads to the fracture of the spring at this point. This design will apply suitable biologic force on the incisors; also good is gained from the sleeve. However, it has certain problems:1- It requires HSS tube {i.e. not economic}. 2- Difficult in construction. 3- May fracture at the point between the coil and sleeve.

Therefore, the R.R. can be constructed from 0.7mm HSS wire without the need for a sleeve. In this condition the force will be heavier than the sleeved one, so it needs lighter activation.

Use of the R.R.:For retraction of the incisors when the O.J. is more than 6mm. it is usually used in the second stage of treatment of class II division I malocclusion {the 1st stage UR4|UL4 include UR3|UL3 exo. and distalization} & correction of deep bite. The 2nd stage include retraction of incisors I, e reduction of increased overjet.

Activation:It is done every 3-4 weeks for sleeved type by closing the coils so that the mesial limbs move 2-3 mm backwards on each side, in addition to 2 mm trimming of acrylic behind the incisors. For the R.R. which is made of 0.7 mm, the amount of activation is half that for the sleeved type and it is done every 2-3 weeks.