Ortho level 3 unit A module 1 2 3 Flashcards

Question

What are the steps of treatment planning?

Answer 1

1) to separate out the patient’s pathologic problems, which will require other types of treatment, from the developmental problems that are treated with orthodontics Then the developmental problems are placed in priority order, and the treatment plan is developed by evaluating the possible treatment procedures relative to the patient’s prioritized problem list

Answer 2

Consider the possible solutions to each problem, starting with the most important one Examine the “practical considerations” of interactions among the possible solutions, cost-benefit, necessary compromises, and other factors Meet with the patient/parent to review alternative treatment possibilities, seek their input, and obtain informed consent

Answer 3

The fluid in the PDL space

Answer 4

When you bite down, the fluid is incompressible, and the first thing that happens is that the alveolar bone bends. The tooth (or teeth) moves relative to the jaw, but not relative to the alveolar bone. After one second or so, the fluid begins to be squeezed out, and at that point the cellular elements begin to feel pressure. If you bite down on what you thought was a peanut and it doesn’t break apart, you probably maintain the force and bite a little harder. If it still doesn’t shatter, you begin to feel pain because the cellular elements are being loaded more as the fluid continues to be squeezed out—and you stop biting.

Answer 5

We know now that bone bending is necessary to maintain normal calcification and remodeling.

Answer 6

Bone bending produces an interesting electrical effect, the generation of a piezo-electric current. Force against a crystalline structure (many nonbiologic crystals, but also bone and collagen) mechanically distorts the crystals. This produces a rapid current flow as electrons move to a different location within the crystal lattice, which quickly declines as they reach their new position. When the force that produced bending is removed, the electrons move back to their original position, and a reverse current flow is observed. As you walk down the street, there is a rhythmic current flow with each step. When you chew, the same rhythmic current flow occurs in your alveolar bone and throughout your jaws.

Answer 7

No, piezo-electric currents are important for maintenance of calcification of bones that are loaded during function, which very much includes alveolar bone, but are irrelevant for orthodontic tooth movement

Answer 8

Tooth is displaced and alveolar bone bends. The bone springs back creating pressure in the PDL and fluid is expressed from the pressure side. Tension is created on the opposite side. The side with pressure gets less blood supply and cells are distorted, side with tension gets more blood supply and distorted PDL cells leading to chemical messengers that change the position of the tooth.

Answer 9

The blood vessels in that area are totally cut off leading to necrosis of the tissue in that area. (sterile necrosis) after 3 - 5 seconds cytokines and prostaglandins are released..

Answer 10

cAMP is released at 4 hours increasing cell differentiation.

Answer 11

2 answers to this question: 1) Adjacent PDL areas that are not necrotic 2) Bone marrow spaces outside the lamina dura. If necrotic area is small adjacect areas are the major source. If not bone marrow undergoes undermining resorption.

Answer 12

Undermining resorption has that name because when there are large necrotic areas in the PDL, it is necessary for osteoclasts to resorb the lamina dura from its underside. The necrotic area sends a chemical signal to stimulate the formation of osteoclasts, but it takes a few days for this to penetrate through the lamina dura into the bone marrow. So instead of 2 days for remodeling to begin, it’s 3-5 days before an osteoclastic attack on the underside of the lamina dura begins.

Answer 13

7 - 14 days

Answer 14

Moving entire tooth = ~100 grams Rotation within the socket = ~50 grams Extrusion/Retrusion = ~50 grams Torque in which root apex is moved further than the crown of the tooth = ~75 grams

Answer 15

Extremely difficult and requires an exceptionally light force ~10 grams applied down the long axis of the tooth smaller teeth would require less and larger or multirooted teeth would require more. (PDL should be compressed only at the apex of the root)

Answer 16

Light continuous force is the best way to move teeth, because it is more biologically acceptable and achieves maximum movement. Heavy continuous force can cause destruction of the lamina dura due to repeated occlusion of blood vessels and no opportunity for repair..

Answer 17

Appointments are made for adjustments. Heavy forces are only acceptable if they decline all the way to zero before the next reactivation appointment.

Answer 18

Ideally every 4 to 6 weeks. If it is too frequent there might be heavy continuous force leading to significant tissue damage.

Answer 19

There should be no immediate pain. Pain would indicate heave pressure. Several hours later patient should feel a mild aching sensation and teeth should be sensitive to pressure so that biting something hard hurts. Pain usually lasts 2 - 4 days then disappears until the next activation of the appliance.

Answer 20

Mild pulpitis usually results.

Answer 21

In the absence of necrotic (hyalinized) PDL areas, uncalcified cementum on the root surface protects against osteoclastic attack, but cementum adjacent to a necrotic area is “marked” or stained by adjacent necrotic tissue in the PDL, and clast cells attack this area when the PDL is repaired. Cementum (and dentin if the attack penetrates all the way through the cementum) is removed, and then new cementum is formed to fill in the defect in the tooth root.

Answer 22

Islands of root structure that are separated from the root surface can form and they can be resorbed and lost. This can often involve the apex. As a result each year of orthodontic treatment would lead to ~1mm of root length lost.

Answer 23

3 types: Mild to moderate generalized Severe generalized Severe localized

Answer 24

Very rare, the average dentist is likely to encounter only one or two such cases in a career. Not necessarily caused by orthodontic treatment

Answer 25

The maxillary incisors are most commonly affected.

Answer 26

It is good practice to take an OPG 6 - 9 months after orthodontic treatment.

Answer 27

1) You can’t modify growth that isn’t happening. That means treatment at a period of rapid growth usually is the best plan, and for practical purposes, it means that the adolescent growth spurt is the preferred time for most growth modification treatment 2) When growth modification is desired, tooth movement almost always is undesirable. Correction of a malocclusion is not a primary goal of growth modification treatment, correction of an improper jaw relationship is. 3) The hours of the day are not created equal relative to growth. In fact, almost all skeletal growth (and tooth eruption) occurs in a critical time period between early evening and midnight. Whatever the growth modification device is, it’s important for it to be worn during these hours—but wearing it all the time may be neither necessary nor desirable.

Answer 28

Excessive maxillary growth contributes to both Class II and long face problems.

Answer 29

Since formation of new bone as the sutures above and behind the maxilla are pulled apart by soft tissue growth is a major mechanism of growth, a force to restrain growth at the sutures ought to be effective. A force of 250 grams per side minimum is required. The force duration should be at least 12 hours per day.

Answer 30

The mid-palatal suture is an open straight-line structure in infants and young children. It shows some convolutions in childhood (early mixed dentition)and by late childhood / early adolescence the suture is so interdigitated that opening it requires micro-fractures of the bone spicules along the suture line. After the adolescent growth spurt opening the suture is possible only with surgical assistance.

Answer 31

No, for many reasons. The only successful treatment is surgery. However if done early enough could potentially be effective

Answer 32

the use of Class III elastics from miniplates at the base of the zygomatic arch to miniplates mesial to the mandibular canines

Answer 33

Facemask: Before sutures become so locked up and interdigitated. (6 - 8 years old) TAD = 10.5 or 11 yo

Answer 34

Very variable in efficacy and long-term outcomes are yet to be understood completely.

Answer 35

1. The gingival and periodontal tissues require time for reorganization after the orthodontic appliances are removed; 2. The teeth may be in an inherently unstable position, so that soft tissue pressures constantly produce a relapse tendency 3. Changes produced by growth may alter the treatment result.

Answer 36

Disruption of the collagen fiber bundles in the PDL and widening of the PDL space are necessary to allow tooth movement to occur. Even if active tooth movement stops, reorganization of the PDL does not occur as long as each tooth is tightly splinted to the one next to it by a heavy archwire. After the braces are removed, reorganization of the PDL takes 3-4 months, and only at that point does the slight mobility that is normal after treatment disappear. During this time the teeth will be unstable against occlusal and soft tissue pressures that can be resisted later. For this reason, every patient needs retainers for at least a few months

Answer 37

Gingival fibers are stretched when a tooth is moved a considerable distance or is rotated significantly. These fibers remodel quite slowly, and are still capable of rotating a tooth back towards its original position even a year after treatment. This becomes a reason for more prolonged retention after correction of severe crowding. For a tooth or teeth that had correction of severe rotations, like the maxillary incisors shown in these images, it is wise to sever the gingival fiber network around them (which must be done carefully to maintain the interdental papillae) before the braces are removed. Without this it can be almost impossible to maintain the rotation correction.

Answer 38

It is based on how far the tooth has been moved not how their position after treatment compares to population average. As a general rule (to which there are exceptions), the lower arch can be considered a foundation on which the upper arch rests, so how far the lower teeth were moved is important.

Answer 39

Patients who received growth modification treatment for a skeletal problem. Growth pattern is constant. Patients without a skeletal problem whose incisors were aligned with some expansion or who had space closure in the maxillary incisor area. A little late mandibular growth in the late teens that occurs after maxillary growth has essentially ceased is to be expected. This has the potential to create lower incisor crowding, even in an individual who never had orthodontic treatment.

Answer 40

4 measures: Proportional limit reached when the wire begins to deviate from normal elastic behaviour. Yield strength when measureable deviation is observed (when elastic limit of material is reached and begins to bend) Ultimate tensile strength is the point where the material begins to fail Failure point is where it breaks.

Answer 41

Enough strength that the spring didn’t get bent out of shape. That would mean that the distance along the y axis to the yield point should be as large as possible. Note that a spring still works beyond the yield point, but it doesn’t totally spring back to its original position if it’s loaded beyond its yield point. The best possible springiness. That would mean that the slope of the line should be tilted to the right (i.e., more horizontal), so that the amount of force delivered by the spring would be as constant as possible. The best possible range. That would mean that the distance along the x axis at the point of permanent deformation should be as large as possible. Reslience (area under the curve of stress strain until the proportional limit) Reasonable formability (Distance between elastic limit and the point at which the wire breaks)

Answer 42

The size of a wire obviously would affect its basic properties. The bigger it gets, the stronger but the less springy it will be, and the less range it will have. This means that for orthodontic purposes there are a range of useful wire sizes. You don’t have to memorize those wire sizes—you can always look them up—but you do need to understand that concept. Steel is stronger than gold or titanium, so all other things being equal, smaller steel wires would be used for orthodontic purposes.

Answer 43

Cantilever beams attached only at one end (eg finger spring from removable appliance) Supported beams attached at both ends (Section of arch wire between brackets on adjacent teeth)

Answer 44

Doubling the size of wire used to make a finger spring: increases its strength 8 times: x * 2x3 = 8x strength decreases its springiness 16 times: x * 2x-4 = 1/16x springiness decreases its range by half: x * 2x = 1/2x range

Answer 45

For a cantilever beam (finger spring), doubling its length: Cuts its strength in half: x * 2x = ½ strength Increases its springiness 8 times: x * 2x3 = 8x springiness Increases its range 4 times: x * 2x2 = 4x range

Answer 46

Superelastic materials. These materials have different force/deflection curves from elastic materials.

Answer 47

It would deliver the correct force without change over a wide range. The amount of force they deliver can be changed by releasing a wire from a bracket on a tooth, and then tying or clipping it back into the bracket. (Clinically, that’s rarely important because the plateau is nearly flat anyway, but it’s an amazing property.)

Answer 48

Because superelastic materials undergo a phase transition with changes in temperature or internal stress. For a material with a transition temperature close to mouth temperature, stressing it by tying it to irregular teeth literally turns it into a different material than the one you picked up off the counter near the dental chair.

Answer 49

nickel-titanium-alloy (nitinol)

Answer 50

Almost zero formability. The manufacturer shapes it while forming it by controlling it's temperature. But practitioner can't really do the same.

Answer 51

Mc: A pure moment (MC) that would rotate the object but not displace it. Mf: A force (grams for our purposes, newtons in scientific reports) that is delivered at a distance from the center of resistance. Its magnitude is force x distance (gm-mm). If Mc/Mf ratio is = 0, tooth tips around the center of resistance. if 0 < Mc/Mf < 1, Mc=Mf, tooth moves bodily If Mc/Mf > 1 torque is created so that the root apex moves more than the crown

Answer 52

Because it takes 2 points of contact against the crown to create a couple, and a finger spring from a removable appliance gives you only a single point of contact. This produces a force and its moment that causes the tooth to tip around its centre of resistance.

Answer 53

A wide bracket creates a couple in the mesiodistal direction A square wire in a rectangular bracket slot produces a couple in the facio-lingual direction

Answer 54

The wider the bracket the lower the force because the moment arm across the bracket is longer

Answer 55

The wire must be undersized relative to the bracket to prevent friction and the effect of wire contacting both corners of the bracket. if you want to slide a tooth along an archwire, a wider bracket is better, but friction is not an important factor when an undersized wire is used.

Answer 56

Friction Contact of wire with the corners of the bracket. A smaller wire is often used to counteract friction. This however, will not counteract the contact of the wire with the bracket

Answer 57

Functional appliances for growth modification (for jaws not teeth) Active plates with finger springs or screws for minor tooth movement Clear aligners for certain types of malocclusion in adults.

Answer 58

Adding springs to a functional appliance to move teeth is possible, but may be counter-productive. If you’re trying to produce forward growth of the mandible, reducing overjet by tipping upper incisors back and lower incisors forward decreases the amount of overjet reduction from growth that might be achieved.

Answer 59

It accelerates it for a while but the rate slows down to allow the jaw to reach the size it would have been later in life without treatment. The reaction of the soft tissues to holding the mandible forward is a backward force against the maxilla that tends to restrict its forward growth (in other words, a headgear effect).

Answer 60

Clear aligners are “suckdown appliances” produced by vacuum-forming clear thermoplastic sheets over a dental cast.

Answer 61

There is no way to account for growth changes in the dental occlusion with a series of aligners, so Invisalign is just for adults or older adolescents, but the fact that a clear aligner is almost invisible when it’s in the mouth appeals to some adults.

Answer 62

Almost all types of tooth movement can be produced with clear aligners, so long as you’re willing to bond attachments to some teeth to improve the grip of the aligners. The attachments can be clear plastic, so they too are almost invisible.

Answer 63

Accurate impressions of the teeth are sent to the Invisalign laboratory, and CT scans are used to develop a digital model With input from the doctor, the company’s software is used to reposition the teeth in the digital model in a series of steps, with a new digital model for each step The digital models for each step are used to create a series of stereolithographic casts a suckdown aligner is made to fit each of the casts

Answer 64

Rectangular arch wires in a bracket with a rectangular slot (this has gone 5 major changes and changes are continuing to occur)

Answer 65

The bonding is too strong and can require removal of enamel to remove the brackets.

Answer 66

Major indication is a need for greater strength, particularly when a heavy force will be encountered. To support a lingual arch More generally, bands often are used on first molars and sometimes on second molars in a complete fixed appliance

Answer 67

Bonded brackets replaced bands Different brackets used for the same wire instead of bending wires to get the right forces on the teeth. (wires are still bent but much less dramatically) Self ligating brackets Custom prescription brackets instead of prescribed straight wires (using 3d scan) Lingual appliances

Answer 68

Active clip (In an active-clip bracket, the springiness of the clip would add to the springiness of the wire, reducing the force against a tooth during initial alignment.) Active-passive clip (active initially but then no longer forces the wire into the bracket after position of tooth is correct) Passive (rigid) clip (has a rigid cap and depends entirely on the springiness of the wire at all stages of treatment)

Answer 69

Custom brackets for each tooth and arch wires that are formed only to the desired arch form are one way to reduce wire bending to a minimum if not totally eliminate it. An alternative approach, now commercially available, is to use “plain vanilla” brackets with no prescription (or any prescription, so long as it is known), and then fabricate the necessary rectangular arch wires with a computer robot.

Answer 70

Bonding a thin bracket to the variable lingual surfaces of the teeth Inserting a rectangular wire into a rectangular slot without great difficulty (disturbing the tonsils in doing so is not good!) Forming the arch wire, which requires major bends to compensate for tooth thickness and careful use of tilt and torque Computer fabrication has provided solutions to all of these major issues

Answer 71

The resistance of a tooth to unwanted movement

Answer 72

The lightest force (and resulting pressure in the PDL) that will produce tooth movement at a near-maximum rate.

Answer 73

that could occur only if the pressure in the PDL of the anchor teeth was less than the pressure in the PDL of the tooth you’re trying to move, and if you were on the vertical leg of the tooth movement/pressur graph

Answer 74

No because this causes the anchor tooth to move further and anchorage control becomes impossible.

Answer 75

Reciprocal anchorage which occurs when movement of one tooth (eg maxillary central incisor) was pitted against one exactly like it (the other central incisor)

Answer 76

Anchorage where one side of the force exerts more pressure than the other.

Answer 77

A strategy to increase the anchorage value is to take advantage of the different loading of the PDL for bodily movement vs. tipping. Since a force is distributed over twice as much PDL area for bodily movement as for tipping, you would move a tooth twice as much as its anchor if the anchor could only move bodily while the movement tooth was allowed to tip. Arranging the force and moments on the anchor unit so those teeth can only move bodily is called "stationary anchorage".

Answer 78

Teeth normally are in medullary bone, which remodels relatively quickly adjacent to a stressed PDL. Cortical bone can and does remodel, but it does so much more slowly. Cortical bone can be used as a more resistant anchor.

Answer 79

More force will be needed to retract the anterior teeth and this leads to the posterior teeth moving more anteriorly.

Answer 80

Use less anterior teeth at a time so that the forces move the anterior teeth without mosiving the posterior teeth then add the anterior tooth that has moved back to the anchorage of the posterior teeth. The alternative is to move segments of wire with the teeth attached, so that there is no sliding of brackets along a wire (image 2). This can be accomplished with loops that form the retraction spring. Then the typical incisor retraction could be achieved in one step, pitting the entire anterior segment against the posterior anchorage. The price of resistance to sliding then becomes clearer: the difficulty of controlling anchorage as teeth slide along an archwire increases treatment time to achieve the desired result.

Answer 81

A determinate force system means that you can measure, and therefore determine, the force and moments felt by all teeth. An indeterminate force system means that it is impossible to know exactly what forces and moments are produced.

Answer 82

The answer is that a one-couple system is determinate, while two-couple systems are indeterminate.

Answer 83

Simply a system in which a couple is present at only one place, and a force or forces without a couple are felt elsewhere. Two-couple systems have forces and couples present in at least two places.

Answer 84

Removable appliances rarely become two-couple systems—they have enough trouble producing one moment, much less two. So although they are not very efficient, you can at least know what forces and moments are being delivered.

Answer 85

A two-couple system is guaranteed if you place a continuous rectangular wire in more than one rectangular bracket. The rectangular wire creates a couple within the bracket in the torque plane of space if there is any twist when it is inserted

Answer 86

This requires two things: a long span of wire that bypasses some teeth (so that it will deliver the necessary light force), and the absence of a couple where it attaches to the incisor teeth.

Answer 87

No it is very difficult to make a one-couple system with a fixed appliance even if you bypass brackets.

Answer 88

If it is in a good position then it can act as perfect anchorage in the same way an implant can. If it is in a bad position then it can prevent correct movement of other teeth leading to movement of other teeth in the wrong direction.

Answer 89

The answer to that also is yes. Temporary anchorage devices (TADs) now are coming into widespread use in orthodontics, especially in adults but also in adolescents. The lower age limit for TADs is about age 11. In children younger than that, the bone is not mature enough to maintain a bone anchor.

Answer 90

Positioning individual teeth when no other satisfactory anchorage is available Intrusion of posterior teeth to close an anterior open bite Retraction and intrusion of protruding maxillary incisors Distal movement of molars (and the entire maxillary or mandibular arch if needed)

Answer 91

Using bone screws in the palate to stabilize a lingual arch that holds the posterior anchor teeth in position Using bone screws in the alveolar process posteriorly Using mini-plates placed at the base of the zygomatic arch, with an arm projecting into the vestibule

Answer 92

In attached gingiva (not alveolar mucosa)

Answer 93

To correct an anterior open bite as they are usually caused by posterior overeruption.