4-Active and Retentive Components Of

Active and Retentive Components of

Removable Appliances

Today we will talk about clinical management using removable appliances.

*Components of removable appliances:

-active component

-retentive component

-anchorage component

-connecting base plate

Now the active component, it could be any spring or screw that provides force to move the tooth.

* Examples of the most commonly used active components are:

-Buccal canine retractor

-Palatal finger spring

-Double cantilever

-Expansion screw

-Robert’s retractor

Let’s start with

1-Buccal canine retractor:

-From the name you can tell that it’s used to retract the buccaly erupted canine.

-the gauge of the wire is 0.7 mm

-the direction of movement: the canine will be buccally erupted so the direction will be palatal,if the canine was mesially tipped then the direction will be distal, if it was high the direction will be to pull it down occlusally (occlusally means to the level of the occlusal plane )

-components: active arm which touches the canine then a coil then the retentive arm.

-the gauge of the wire of the canine retractor is 0.7 mm, but with tubing it’s 0.5mm.

2-Double Cantilever:

-it’s used to procline the retroclined incisors, and some people call it a Z spring which is used only for one tooth. You can fit the double cantilever on only one tooth, and you can fit it on both centrals as well.

-the gauge of the wire is 0.5 mm.

-direction of movement is labially of course, “proclination of the central incisors” with rotation if there was another source of force. For example if I have a proclined incisor and I put the double cantilever, It will touch the distal side first and will try to move it labially and if u put another force touching the mesial side you can produce some rotation, but mainly its used to retrocline the proclined incisors.

-components: active arm which touches the tooth, then the coils, there are two coils that’s why it’s called double, and a retentive arm which goes into

the acryl, then the guard, we put the guard to protect the appliance itself from the bite of the lower incisors.

3-Robert’s retractor:

-it’s used to retrocline the proclined incisors.

-in addition to proclined incisors, several indications should be present to be able to use this appliance, which are:

1-space should be available (because to move any tooth back there should be space)

2-overjet should be increased (because if there wasn’t an increased overjet the upper incisors will hit the lower incisors when they are retroclined)

3-overbite should be reduced (if there was a deep overbite which means that the lower incisors are over erupting and touching the palate, again you won’t be able to retroclined the proclined incisors)

4-also the canines should be in class 1

-the gauge of the wire is 0.5 mm with tubing (inner diameter=0.5 mm)

-direction of movement: retroclination of incisors

-components: labial bow which touches the labial surface of the upper incisors, two coils for adjustment and to increase the length of the wire, and retentive arms which go palataly into the acryl.

*Note:

Tubing: it’s a wire entering a tube, we use it in the wires that pass labially or buccaly, to protect the wire from occlusal forces and soft tissue forces (the

lips, cheeks, food, crushing) because when the wire is within a tube its gauge is 0.5 mm which means its flexible, if we don’t have a tube we can use 0.7 mm wire which is stiffer and can withstand these forces.

4-Expansion Screw:

It’s used to expand the maxillary arch, so if you have a cross bite you can use removable appliance with midline expansion screw to expand the two halves of the maxilla.

Some of you may ask does the expansion happen to the bone or only to the teeth. Usually if a removable appliance is used, the expansion happens to the teeth only and it also depends on the patient’s age, if it’s a young patient you can achieve some skeletal expansion because you are aiming on splitting the mid palatal suture, where as if the patient is an adult for sure you won’t be able to do any skeletal expansion and most of your expansion will be dental (teeth tipping buccally).

*the second component is the Retentive Component:

The most commonly used retentive components are

1-Adam’s clasp

2-C-clasp

3-Southend clasp

4-Ball clasp

5-Labial bow

Let’s start with

1-Adam’s clasp

-gauge of the wire 0.7 mm (every retentive component its gauge is 0.7mm in order for it to be strong)

-function of the clasp: retention and anchorage (we mentioned in the previous lecture that there are other components that can act as anchorage components like the retentive component (Adam’s) and the base plate)

-components: arrow head in the undercut, bridge, cross over, retentive arm which extends in the acryl.

2-C-clasp

-From its name it looks like a C letter, it’s the same one that you take in the prostho.

-gauge of the wire is 0.7mm

-position on tooth: under the height of contour (under the undercut buccally).

-Most commonly I use it on the primary teeth “the primary canine”.

3-Southend clasp

-It’s two Cs attached to each other, so it’s like two C-clasps.

-components: 2 C-clasps connected together, crossover, retentive arms.

-usually it’s used on the two central incisors.

4-Ball Clasp

-it’s a wire with a ball at the end of it, and this ball enters the embrasure between two teeth.

-gauge of the wire is 0.7mm.

-Components: ball, crossover, retentive arms.

5-labial bow

-gauge of the wire is 0.7 mm.

-Components: bow, U-loops, crossover, retentive arms.

*Mesial and Distal movements:

If I have a tooth and I want to move it mesially or distally I use

1- The palatal finger spring.

-palatal finger spring moves the tooth in the line of the arch.

-if it’s used for incisors and canines, the gauge will be 0.5 mm S.S (stainless steel) wire.

-it it’s used for molars, the gauge will be 0.6mm S.S wire.

-adjustments: correct the point of contact (sometimes you might need to bend the point of contact in order to make sure that the tooth will move in the line of the arch), also in the adjustments you have to do activation, so you can activate from the loop itself or do a bend just above the loop.

-Activate 2-4 mm in the free arm spring

How to do activation? When you open the wire, what happens is that it will be in a different level than it was before it got activated, so when you enter the spring you’ll try to enter it mesially or distally then it will try to get back to its original position, so by doing that, it will create some sort of force on the tooth and that’s how the movement of the tooth happens. Also if you don’t want to open the loop, you can do a bend and change the whole direction of the wire.

2-Buccal canine retractor

-moves the tooth palatally as well as distally

-made of 0.7 mm S.S wire

-adjustments: close the coil by 1-2 mm every time the patient comes back for a review.

*Labial movements:

Double Cantilever:

-The gauge is 0.5 mm S.S wire when it’s used on incisors, and 0.6 mm when it’s used on premolars and molars but it’s rarely used on molars and premolars so for them instead of double cantilever we go for something called T-spring.

-wire guard to enhance the stability (protect the double cantilever from the lower incisors)

-adjustments: 1-2 mm of activation, you have two coils, if you open the 1st coil you’ll move the 1st active arm, and if you open the 2nd coil you’ll move the 2nd arm (connecting arm), so the active arm will be parallel again. So you

need to make sure of the direction of your movement. For example if you have upper incisors retroclined in a certain way, you have to open the two coils to make sure that the active arm is parallel to the incisal edge. And the amount of activation depends on the level of the incisal edge because when I want to open the coils there has to be a limit for opening them, not to over-activate and not to under-activate, so I open the coils until the active arm is parallel to the incisal edge, then when you want to insert the appliance you push it palately which will create force on the tooth and this force is the amount of activation.

*Buccal movements:

For premolars and molars you can use a T-spring.

-the gauge for premolars is 0.5 mm and for molars it’s 0.6 mm

-adjustments: pull the free end of the spring away from the baseplate.

*Labial and buccal movements

Now if we need to expand we have mentioned the double cantilever for anteriorly and for posteriorly it’s possible to use the double cantilever but it’s preferable to use the T-spring. But this is if you are aiming to move just a single tooth, but if you’re aiming to move more than one tooth you can use something called coffin spring.

-Coffin spring is used for expansion, so its use is similar to the use of midline expansion screw.

-gauge is 1.25 S.S wire, extra retention is needed because if the appliance isn’t retentive it will keep falling in the patient’s mouth.

-adjustment: 2-3 mm expansion, you’ll make the adjustment from the U-loop, around 2-3 mm every time.

*Palatal movements

1-Robert’s Retractor.

- used for incisors.

-gauge is 0.5mm S.S wire supported by 0.5 mm internal diameter tubing for stability.( In the picture, the thick line is the tube)

-Adjustments: 3-4 mm of activation by closing the coil until the labial bow comes to the level of the incisal edge, and again when you insert it for activation you push it.

2-also for palatal movements for an upper canine or premolar, (if the canine wasn’t mesially tipped and it’s not occlusally high, you can’t use buccal canine retractor), if the tooth is within the line of the arch and its inclination is normal and you just need pure palatal movement you can use something called Self Supporting Palatal Spring.

-its gauge is 0.7 mm S.S wire.

-self supporting means that it surrounds the whole tooth, unlike the buccal canine retractor which touches the tooth on the mesial or distal contact point only, where as the self supporting palatal spring contacts the whole labial surface so the tooth won’t move mesially or distally, only palataly.

*Screws

-Arch expansion or contraction.

Like the Mid palatal expansion screw which is used for expansion and to treat the cross bite, it has a key that’s used to open this screw, you enter the key in a hole and you turn it with the direction of the arrow to give expansion.

*Someone asks: when do we use the screw and when do we use the coffin spring?

Dr. Answers: we can use both in the same situation, they do the same job but I prefer to use the expansion screw because it’s more acceptable to the patient than the coffin spring.

- Produce A-P or transverse expansion, depending on how you put the screw.

We said that most commonly we use the expansion screw for lateral expansion for a maxillary cross bite, but also if we turn the screw by 90 degrees it will give expansion anterio-posteriorly, so you can use it as well to give anterior expansion, so if the upper incisors are retroclined you can use the anterior expansion screw to procline them, because proclination is expansion.

-Adjustment: you need to open the screw using the key, one quarter of a turn per week, which means 0.25mm/week, and this is equivalent to 1 mm/month. (Sometimes you might need to open it two quarters per week)

Usually we aim to achieve 1 mm of tooth movement per month in a healthy situation.

*Bite Planes

Do you remember when we talked about the deep bite? We said that we put anterior bite plane to disclude posterior teeth so they will supra erupt and that itself will reduce the deep bite.

*Note:

Disclusion: A separation of the teeth when the jaw is slightly opened; especially, a separation

of posterior teeth when the lower jaw moves forward, as a natural result of the alignment of the anterior teeth

Now we have Anterior bite planes and Posterior bite planes.

1-Anterior bite plane

-It means that you are aiming to over erupt the posterior teeth to reduce the over bite. There are many types of anterior bite planes, but the most common one is the flat anterior bite plane. From its name you can tell that it’s flat, there is another type which is beveled, but this is not required from you.

So anyways it has to be flat, touching all the lower incisors to spread the force and to avoid trauma because if it was touching one tooth the force will cause mobility to that tooth. It also has to be rough; we don’t want it to be smooth in order not to keep the teeth sliding over it.

-It’s a simple form of functional appliance; a functional appliance is any appliance that does stretching to the muscles and so the muscles indirectly influence bone growth because the flat anterior bite plane will raise the bite and that will stretch the muscles so the muscles will try to bring the teeth together but the flat anterior bite plane will prevent them. So it’s possible that the force will indirectly move to the incisors and that will cause intrusion in the incisors.

-Allows overbite reduction by:

*Passive eruption of posterior teeth (when you disclude the teeth posteriorly to allow passive/natural over eruption)

*Relative intrusion of incisors, meaning that the teeth will appear to be intruded as a result of over eruption of posterior teeth, and if there wasn’t true intrusion of the incisors then at least prevent their further eruption. Now generally with time there will be eruption of teeth and this eruption brings the bone with it so it’s growth of the bone, now if you prevent the lower incisors from erupting, after a while the adjacent teeth will erupt and the incisors won’t (as if they were ankylosed so it will appear as infra occlusion), so this is relative, meaning that there is no true intrusion but because they were prevented from eruption, it appeared as intrusion.

*True intrusion of incisors (what we mentioned earlier about simple form of functional appliance, stretching the muscles, muscles will try to bring teeth together, however the lower incisors will be opposed by the bite plane and the force will be moved indirectly to the incisors and cause intrusion).

Now we mentioned that we use bite planes to:

*Reduce the overbite

*There’s another use for them which is to clear possible occlusal interferences with tooth movement. For example if you have an upper 5 in a cross bite and it bites lingually to the lower 5, can we move the lower 5 buccally without opening the bite? Of course not, so we have to open the bite. If you want to open the bite and disclude the posterior teeth then you have to use the anterior bite plane, but if you have the incisors in a class 3 classification and you want to procline the upper incisors you also have to open the bite but in this case you need to use the posterior bite plane.

We talked about the anterior biteplanes; it’s like a base plate, thick anteriorly so that the lower incisors will touch the bite plane and that will cause disclusion posteriorly. The disclusion posteriorly should be around 2-3 mm, more than that will cause discomfort to the patient.

Again it should be flat, allows eruption of posterior teeth, all anterior teeth should occlude with it to prevent trauma, should be high enough to produce 2-3 mm of molar separation.

2-Posterior bite plane

You are aiming for either to over erupt the anterior teeth to deepen a reduced over bite but this is rare in clinical situations, or to intrude the posterior teeth.

In posterior biteplanes the acryl covers the occlusal surfaces of molars and premolars and this will disclude the occlusion anteriorly.

Sometimes it’s used for temporary propping of the occlusion to allow teeth to move over the bite in a correction of anterior crossbite, which is what we mentioned earlier, if the upper incisors are lingual to the lower incisors and you want to procline the upper which means you need to open the bite first by using posterior bite planes.

The thickness is just enough to disengage the anterior teeth which means until the upper incisors are free to move.

*Maxillary Expansion

-There are 3 ways to do maxillary expansion:

1-The one we mentioned earlier, upper removable appliance with expansion screw or coffin spring.

2-Quad Helix.

3-Rapid Maxillary Expansion: bonded or banded

*Also I have 2 types of expansion:

-slow expansion

The one we talked about which achieves 0.25mm/ week 1mm/month

-rapid expansion (which is the 3rd type)

Within a week you can achieve 2.5 mm expansion.

Let’s start with the first one:

1-URA (upper removable appliance)

-Slow expansion

-Adjustment: 1-2 quarters of a turn/week 0.25-0.5mm/week >1mm/month

2-Quad Helix

-Slow expansion

-Fixed type (not removable, because the patient might not be cooperative enough to wear the removable appliance so there should be a fixed type)

- There are 4 helixes that’s why it’s called quad helix and it’s soldered to the bands to do expansion, if you open those two coils (I think he was referring to the anterior ones) you will achieve posterior expansion, and if you open the other two coils (I think he was referring to the posterior ones) you will achieve more anterior expansion, if you want to expand the whole segment you need to open all of the coils to achieve parallel expansion.

-Provide anterior and posterior expansion

-Wire gauge: 1-1.25 mm

3-Rapid maxillary expansion

-It gives rapid expansion, examples: Hyrax appliance, Hass appliance.

-it can be bonded or banded, banded means it has bands like in the picture there are bands on the 6s and the 4s soldered to the wires and in the middle the expansion screw, it’s a strong screw so that when you open it, it will give 2.5 mm expansion/week. The bonded however, we do cementation by glass ionomer cement to the occlusal, buccal and palatal surfaces of posterior teeth, so they’re not bands, it’s acrylic like the posterior bite block except that it’s cemented on teeth.

-2 turns per day.

-0.5 mm expansion per day, so around 3.5 mm per week. It’s usually from 2.5-3.5 mm per week.

-Usually expansion period 1-2 weeks, since it’s rapid and you achieve such amount of expansion, you can’t keep expanding for two months, otherwise the patient’s head will be split into two halves :D so 1-2 weeks maximum.

-Heavy expansion screw to withstand pressure.

-Open the mid palatal suture. The aim from this is to achieve skeletal expansion, remember when we talked about dental expansion and skeletal

expansion? So the skeletal expansion is achieved by splitting the mid palatal suture, if you put heavy force in young patients you can split this suture and achieve expansion, then you need to wait for bone-fill in the area of the splitting and during that period you just keep the appliance as a retainer.

-So provide dental and skeletal expansion.

In the pictures you can notice the banded hyrax appliance, notice the bands on the 6s and 4s with wires soldered with the Jack screw or the rapid expansion screw. However the bonded, it’s acryl, you take an impression and do acryl and just cement it on the teeth.

*note: the script includes everything in the slides, you can only refer to them for the pictures

Sorry for any mistakes…

Done by:

Ruby Daoud

4-Active and Retentive Components Of

Documents

Transcript of 4-Active and Retentive Components Of