Ortho level 3 unit B module 1 2 Flashcards
1
Q
What is the prognosis of children having crowded primary incisors?
A
As a general rule, children who present with crowded primary incisors will have major crowding problems in the permanent dentition
2
Q
What is the early mesial shift?
A
Prior to the eruption of the first permanent molars there is an average of about 2 mm of spacing in the maxillary incisor segment and about 1 mm of spacing in the mandibular incisor segment. As the first permanent molars erupt, they drift forward, closing some of the interdental spacing found in the primary dentition. This is called the early mesial shift.
3
Q
How much crowding develops in the mandibular arch?
A
As the larger permanent incisors erupt and replace the primary incisors, additional crowding occurs. In the maxillary arch, males tend to have no incisor crowding, while most females develop minor incisor crowding (<1 mm) when the permanent incisors erupt. In the mandibular arch both males and females appear to develop 2 mm of incisor crowding with the eruption of the lateral incisors. In all four cases, once the primary canines exfoliate this initial incisor crowding resolves.
4
Q
What causes the dental crowding?
A
Dental crowding is a function of two things: (1) the size of the teeth, and (2) the size of the dental arch supporting the teeth.
5
Q
What assumptions are made during space analysis?
A
There is a reasonably good correlation between the size of the erupted mandibular incisors and the permanent canines and premolars
Prediction tables are valid for your patient’s sex and ethnicity
All succedaneous teeth are present and developing normally
Arch dimensions do not change appreciably during growth molar position is stable.
6
Q
What kind of space analysis is used by the UNC space analysis?
A
The Tanaka-Johnston space analysis procedure.
7
Q
How is space analysis done using the Tanaka Johnston space analysis method?
A
The first step in the Tanaka and Johnston space analysis is the measurement of the erupted lower incisors using a Boley gauge or dividers (image 1). The mixed dentition analysis (MDA) assumes that there is a correlation between the width of the lower incisors and unerupted canines and premolars in both arches.
The width of the unerupted permanent canine and premolars in each buccal segment is determined by the following simple calculation:
Mandible: half the sum of the widths of the mandibular incisors + 10.5 mm
Maxilla: half the sum of the widths of the mandibular incisors + 11.0 mm
8
Q
What is the key assumption of the Tanaka Johnston space analysis method?
A
There is a good correlation between the size of the mandibular incisors and the unerupted canines and premolars. If there is an obvious discrepancy between the size of the mandibular centrals and laterals, as sometimes occurs, that would produce an over-estimate of the size of the unerupted teeth.
9
Q
How is the space available calculated?
A
The space available in the dental arch is determined by measuring the arch segments between the mesial surfaces of both first permanent molars (image 1). One must estimate an ideal dental arch where the teeth are arranged in a stable position in the alveolar bone. Using a Boley gauge or dividers, the arch segments are as follows:
- Mesial of first permanent molar to mesial of primary canine
- Mesial of primary canine to the mesial of the permanent central
- Mesial of permanent central to mesial of primary canine
- Mesial of primary canine to mesial of first permanent molar.
10
Q
How is the space required to accommodate permanent teeth calculated?
A
The space required to accommodate the permanent teeth is determined in each arch by adding together:
- The sum of the incisor widths (image 2)
- The predicted widths of the unerupted left canine and premolars
- The predicted widths of the unerupted right canine and premolars
11
Q
How is the space discrepancy calculated?
A
Discrepancy = Total Space Available – Total Space Required
12
Q
What is the endpoint of space analysis?
A
The endpoint of the analysis is a number for each arch that may be either positive (spacing) or negative (crowding). As you learned previously, these numbers have very limited significance when viewed alone. The practitioner must now refocus on other relationships to interpret the results for each individual patient.
13
Q
What considerations should be made when analysis available space for analysis?
A
Lip posture
Lip competence
Incisor position
Skeletal jaw relationship
Future molar shift (leeway space)
Occlusal relationship of the 1st permanent molars
The results of the profile analysis are crucial in assessing crowding and incisor position. Protrusive lips, significant lip incompetence (>4 mm) and proclined incisors indicate dental crowding even if the teeth are aligned on the dental arches. These patients usually require extraction of permanent teeth to position the lips in acceptable positions, reduce lip incompetence, and upright the incisors in the alveolar bone.
14
Q
How is generalized crowding classified?
A
When classifying generalized crowding (where the discrepancy numbers would be negative) the following clinical descriptions can be used:
0-2 mm/arch: mild crowding
2-4 mm/arch: moderate crowding
>4 mm/arch: severe crowding
>10 mm/arch: very severe crowding
15
Q
How is type of intervention chosen based on crowding?
A
The type of intervention depends on:
Amount of crowding (mild, moderate, or severe)
Location of crowding (localized or generalized)
16
Q
What questions should be considered when interpreting crowding?
A
Was there initially sufficient space, and loss of a primary tooth resulted in localized crowding?
Will a primary tooth have to be extracted, and will intervention to prevent space loss be required?
In mild cases of crowding, can the leeway space be used to align the teeth?
17
Q
When are space maintenance, space regaining, and serial extraction indicated?
A
In situations of mild crowding.
If there is severe crowding serial extraction is indicated.
18
Q
When is space maintenance used?
A
A number of factors must be evaluated prior to the initiation of space maintenance:
Space analysis should confirm that there is adequate space available.
When was the primary molar extracted? Space loss almost always starts immediately after the loss of a primary molar. If the tooth was lost more than 3 months previously, space loss probably has occurred, and then space regaining will be required rather than space maintenance.
When will the underlying permanent tooth erupt? If the permanent tooth will require more than 6 months to erupt, space maintenance will be required. Eruption charts give average values for the general population; one must remember that individual variation exists. Dental age as determined by assessing the general eruption schedule and root development is more informative than chronological age. A permanent tooth normally erupts when 2/3 to 3/4 of root development is complete, and in general, a permanent tooth takes about 1 month to erupt through 1 mm of overlying bone. Extraction of primary teeth can also either accelerate or slow the eruption of underlying permanent teeth depending on root development.
Is there a permanent successor tooth present ? If not, long-term maintenance of the space for eventual prosthetic replacement may or may not be the best plan. This must be weighed against the possibility of closing the space orthodontically or forgoing space maintenance and allowing the permanent teeth to drift into the extraction site to close the space.
19
Q
Why is space maintenance used?
A
In a patient with adequate space for the permanent teeth, space maintenance is the intervention used to prevent loss of space after extraction of a primary first or second molar. Once a primary molar is extracted, mesial drift and distal tipping of adjacent teeth will occur, reducing the space available for eruption of the underlying permanent premolars.
20
Q
What are the types of space maintainers?
A
Fixed (cannot easily be removed by the patient or adjusted in the mouth)
Removable (can be removed by the practitioner for minor adjustments or can be removed by the patient to allow easier access for oral hygiene)
21
Q
How should treatment with space maintainers be approached?
A
With any type of appliance, adequate follow-up is crucial. Space maintainers are not an “insert it and forget it” type of treatment. All patients must be on a regular recall schedule and have adequate oral hygiene to ensure success.
Patients with space maintainers are instructed to avoid hard, sticky, and chewy foods to decrease the chance of damage and loosening of appliances. Fixed appliances reduce the chance of failure, but some children do not follow these suggestions very well and damage even the best-designed fixed space maintainers.
22
Q
Why are fixed space maintainers used more often than removable?
A
The adaptation of orthodontic bands on primary teeth, especially first primary molars, can be difficult. This reduces the effectiveness of fixed banded appliances on these teeth. But this is even more of a problem with removable appliances, since primary teeth do not have a pronounced height of contour that can be used to engage retentive elements such as wire clasps.
In general, fixed space maintainers are more effective in children than removable space maintainers.
23
Q
Which space maintainers are often used for loss of a single tooth?
A
Band and loop space maintainers are most commonly used after the extraction of a single primary first molar in the primary or mixed dentition. Bilateral band and loop space maintainers are indicated if both first primary molars are lost in an arch prior to the eruption of the permanent incisors. A variation of this appliance is the crown and loop space maintainer.
24
Q
Which space maintainers are often used for loss of multiple teeth?
A
If multiple primary teeth are lost and both the permanent incisors and first permanent molars have erupted, a lingual arch contacting the incisors (mandible) or a lingual arch with a palatal button that does not contact the incisors (Nance appliance, maxilla) can be used to prevent posterior space loss. Both appliances require the use of cemented orthodontic bands to attach the appliance to the 1st permanent molars. Variations of both appliances can be made to be removable by the use of special lingual attachments on the molars. The appliances can also include adjustment loops that can be activated to procline the incisors and tip the molars distally.
25
When is a lower lingual arch contraindicated?
Lower lingual arches are contraindicated prior to the eruption of the permanent mandibular incisors. Remember, the permanent lower incisors tend to erupt lingual to the primary incisors. A lingual arch that is contoured to the lingual surfaces of the primary teeth can impede the eruption of the permanent teeth
26
When is a distal shoe space maintainer used? What should be done to avoid needing it in the first place?
A distal shoe space maintainer is used in the primary dentition or early permanent dentition after the extraction of a 2nd primary molar before the 1st permanent molar has erupted. The goal is to prevent the first molar from drifting mesially as it erupts, which is likely to occur. If at all possible, the 2nd primary molar should be maintained through endodontic intervention (i.e., pulpectomy) even if the prognosis is guarded, because the intact tooth is a much better space maintainer than a distal shoe appliance.
27
How is a distal shoe space maintainer designed?
Radiographs are used to construct the appliance, which uses a blade to engage the mesial surface of the 1st permanent molar to guide its eruption. As the erupting permanent molar engages the blade, it is guided into the correct position in the arch. Distal shoe space maintainers can fail to guide the eruption of the first permanent molar. In this radiograph the molar has drifted forward underneath the blade of the space maintainer and become positioned underneath the wire loop. The space maintainer must be removed and the tooth allowed to erupt into the mouth. Space regaining may then be used to reposition the tooth distally into a normal position.
28
When are removable acrylic partial dentures indicated as space maintainers?
The major indication for use of removable acrylic partial denture space maintainers is when multiple primary molars have been lost (image 1). In these cases, long spans of wire make band and loop space maintainers impractical, and unerupted or partially erupted permanent incisors make the use of a lingual arch problematic. Clasps are used to retain the appliances, and acrylic can be placed into the extraction sites to prevent tooth movement.
29
What is the most important advantage of using a removable space maintainer?
The appliances allow ready access for oral hygiene in patients with a high caries rate. Compliance with wearing the appliance can then become an issue. If the appliance is not worn all the time, space loss will occur.
30
When is space regaining used?
If space maintenance is not instituted after extraction of a primary tooth, space loss will occur during the next few months. Repositioning the teeth to regain space, not just space maintenance, is required to stabilize the situation.
31
How much space can be regained with simple space regaining appliances?
Up to 3 mm of space can be reestablished in a localized area with relatively simple appliances. Localized space loss greater than 3 mm constitutes a severe problem and is more difficult to manage.
32
What is required after space regaining?
Space maintenance, otherwise it will be quickly lost again.
33
How do space regainers work?
There are two coil springs on the wire loop, which is free to slide through the tubes attached to the orthodontic band. The springs are compressed when the appliances is cemented and apply a force to push the teeth apart.
34
How do removable space regaining appliances apply force?
Removable appliances generally are designed to apply forces to a single point on a tooth surface resulting in tipping of the tooth and de-rotation if desired. As a majority of space loss manifests itself as tipping and rotation, these types of forces can be used with removable appliances to reposition teeth to their normal position.
35
How should an expansion screw be activated?
If an expansion screw is used to regain space, the screw should be activated slowly (1/4 turn 2-3 times per week). When the screw is activated too quickly, the teeth will not move at the same rate as the screw is activated and the appliance may not seat correctly.
36
How can headgear be used for maxillary space regaining?
Extraoral forces can be applied to maxillary molars through the use of headgear. Unilateral space loss in the maxillary arch can be treated using an asymmetric headgear in which the outer bow of the headgear on the side with space loss is longer than the unaffected side. A cervical pull neck strap is used along with the asymmetric outer bow to distalize the first permanent molar and upright the molar at the same time if mesial tipping is present, and the inner bow can be used for de-rotation.
37
What issues make mandibular space regaining more difficult than maxillary?
n the mandibular arch, removable space regaining appliances are less efficient due to frequent problems with irritation of the lingual tissues, breakage, and lack of retention
They are recommended infrequently because poor compliance becomes a major problem.
38
What are the effective mandibular arch space regaining appliances?
Active lingual arch
Lip bumper
39
What is the best choice of tool for space regaining in the mandibular arch?
A passive lingual arch is the best choice for space maintenance in the mandibular arch when multiple posterior teeth have been lost and the first molars have erupted. Lingual arches can also be designed to actively apply a distal force to the molars and procline the incisors, thus regaining space bilaterally in the mandibular arch.
Adjustable loops of wire, fabricated into the posterior sections of the lingual arch, can be opened to expand the length of the lingual arch
Since lingual arches are usually constructed of heavy round steel wire that fits into lingual sheaths on the molar bands, large single activations generate excessive large forces. The loops must be opened only a little at the time, and this is done by the dentist after removing the lingual arch. It fits tightly enough that the patient cannot remove it.
40
How does the lip bumper work?
A lip bumper is attached to the lower first molars. It can be soldered or welded to the molar bands, or can be made to fit into tubes on the orthodontic bands (so the patient can remove it for meals and tooth brushing--which of course introduces compliance issues). The anterior portion of this heavy wire is coated with acrylic and is positioned off the labial surface of the teeth so it actively stretches the lower lip away from the teeth. The lip in turn puts force on the wire and the wire transfers the force to the molar teeth.
41
How do the lower lingual arch and the lip bumper cause the incisors to procline?
Both the active lower lingual arch and the lip bumper regain space by tipping the mandibular molars distally while proclining the incisors. With a lip bumper, even though the device does not touch the incisors, tongue forces procline the incisors when it eliminates lip pressure against them.
42
What is the approach taken with patients that have generalized crowding of 4mm or less?
In patients with generalized rather than localized crowding predicted to be less than 4 mm, space management uses leeway space to align the teeth. The mixed dentition space analysis shows the amount of crowding that could be alleviated if mesial shifting of the permanent molars were prevented.
43
How much leeway space is present in the maxillary and mandibular arch?
Maxillary arch = 0.9 mm/quadrant
Mandibular arch = 1.8 mm/quadrant
44
What is done in patients where a class 1 molar relationship is not established following use of a lingual arch?
The mandibular leeway space allows the lower first permanent molars to shift mesially into a Class I molar relationship. If a lower lingual arch is placed to utilize the leeway space to align the permanent mandibular teeth, a Class I molar relationship may not result. In cases where a lower lingual arch is used for space management, headgear or other appliances may be required to distalize the maxillary molars to establish a Class I molar relationship.
45
What is a common sign of severe crowding in the early mixed dentition?
A common sign of severe crowding in the early mixed dentition is early unilateral loss of a mandibular primary canine, which results in a shift of the dental midline.
46
What causes early loss of primary canines?
Initially there is inadequate space for the eruption of the permanent mandibular lateral incisor. As the incisor erupts it causes extensive resportion of the mesial surface of the primary mandibular canine, which causes increased mobility and early loss of the tooth. After the canine is lost unilaterally, the incisors are free to shift toward the side where the canine was lost.
47
How can early loss of primary canines be prevented?
it is best to extract the contralateral primary canine and place a lingual arch. This prevents the incisors from moving lingually and allows self-correction of the midline shift, which can occur if the incisors have not drifted too far laterally. A partial fixed appliance may be used to actively create space and correct the midline shift. A lower lingual arch can be used to maintain the leeway space in the mandibular arch while a fixed orthodontic appliance (first molar bands, bonded brackets on incisors--often called a 2x4 appliance) is used to align the mandibular incisors and correct the midline shift. The 2x4 appliance along with the LLA can be activated to create arch length by advancing the incisors and distally tipping the lower molars (image 2).
48
What should be done if there is early unilateral loss of a primary canine?
In the maxillary arch, early unilateral loss of a primary canine also is an indication for extraction of the contralateral one, but placement of a lingual arch to hold space usually is unnecessary.
49
What should be done to patiens with >4mm of crowding?
Patients with >4 mm of crowding/arch will require more extensive treatment and may best be referred to an orthodontist.
The critical treatment decision in these patients is whether to expand the dental arches to create space to align the teeth or to extract permanent teeth in each quadrant (usually, first premolars) to make room for the others.
50
What contraindicates the use of arch widening techniques for >4mm crowding?
Expansion of the dental arches to create space must not cause excessive incisor protrusion, compromise alveolar bone support or periodontal attachment, or exceed the tolerance of the soft tissues (i.e., produce lip incompetence and protrusion).
51
What is serial extraction?
Serial extraction can be defined as the orderly removal of selected primary and permanent teeth in a predetermined sequence to alleviate crowding.
52
What are the main advantages of serial extraction?
The main advantages of serial extraction is that it potentially makes future orthodontic treatment less complicated and decreases periodontal problems due to eruption of teeth outside the dental arch. Perhaps it also improves long-term stability.
53
What is the ideal patient for serial extractions?
The ideal patient for serial extraction should have:
1. Early mixed dentition with a large amount of predicted crowding, 8-10 mm of discrepancy per arch. If the amount of crowding is less than 10 mm, serial extraction alone is not recommended because more residual spacing and more uncontrolled tipping of the teeth will occur.
2. No skeletal disproportions.
3. Class I molar relationship.
4. Normal overbite. Serial extractions will deepen the bite.
5. No congenitally missing permanent teeth.
54
What is the objective of serial extractions?
The sequence followed during serial extractions is designed to allow the first premolars to erupt ahead of the canines so that the first premolars can be extracted early to allow eruption of the canines and second premolars. If severe crowding exists, the result is that in each quadrant, the canine and second premolar share the space vacated by the first premolar.
55
What are the steps of the serial extraction sequence?
Step 1 of serial extraction sequence
Primary canines are extracted first to allow the permanent incisors to align (image 1). A lower lingual arch may be placed to prevent the lower incisors from retroclining and deepening the bite prior to the eruption of the permanent canines.
Step 2 of serial extraction sequence
The first primary molars are extracted when the roots of the lower first premolars are about 2/3 formed and the crown is about to penetrate into the gingiva (image 2). This will accelerate the eruption of the first premolars so they erupt before the canines.
Step 3 of serial extraction sequence
The first premolars are then extracted soon after they erupt. This allows the canine and second premolars to erupt into this space.
56
What kind of outcome results from serial extractions?
Serial extraction is not a panacea for the treatment of severe crowding. In the vast majority of patients, future comprehensive orthodontic treatment is required to treat the tipping, residual spacing, and increased overbite that usually occurs after serial extraction.
However, the advantage of serial extraction is that the comprehensive treatment usually is shorter and less complicated than if serial extractions had not been done.
In cases with very severe crowding, the amount of residual tipping and drifting may be minimal after serial extractions, as shown in this panoramic radiograph of a patient who had serial extractions but no orthodontic treatment (image 1). Even in this favorable situation, a period of fixed appliance treatment would improve both alignment and root positions.
57
What is a crossbite?
A crossbite is the condition in which the anterior or posterior teeth occlude against the opposing teeth in an abnormal anteroposterior or transverse relationship, respectively. An anterior crossbite occurs when the maxillary incisors occlude lingual to the mandibular incisors. A posterior crossbite occurs when the maxillary posterior teeth occlude lingual to the mandibular posterior teeth. In either case a single tooth or multiple teeth may be in a crossbite relationship.
58
How should a crossbite be assessed?
When assessing a crossbite, it is important to assess the patient’s occlusion in maximum intercuspation (MI) and centric relation (CR). A unilateral posterior crossbite is often due to a lateral shift from the point of initial contact (CR) (image 1), while an anterior crossbite can be due to a forward shift. A mandibular shift between CR and MI frequently makes the crossbite appear more severe.
59
How can dental and skeletal crossbites be distinguished?
Dental crossbites arise due to displacement of teeth within the dental arch. Single or multiple teeth may be involved. These problems usually arise as the eruption path of a tooth or teeth is deflected because of crowding within the dental arch.
Skeletal crossbites tend to involve multiple teeth and are caused by the underlying position of the basal bone. Posterior skeletal crossbites are most commonly caused by a narrow maxilla but could also be due to an abnormally wide mandible. Significant posterior skeletal crossbites may be identified by significant incompatibility of the maxillary and mandibular arch forms. One arch may be V-shaped while the other is U-shaped, or one may be narrower than the other.
60
Why is it important to determine the type of crossbite (skeletal or dental)?
The determination of whether the crossbite is skeletal or dental determines the degree of difficulty in treating it. If an anterior or posterior crossbite is dental in nature and involves a few teeth, treatment can usually be accomplished with simple appliances. On the other hand, skeletal crossbites are very difficult to treat and many times require orthognathic surgery to reposition the jaws to allow correct positioning of the teeth.
61
What is the most common aetiological factor for nonskeletal anterior crossbites?
The most common etiological factor of nonskeletal anterior crossbites is lack of space for the permanent incisors. Since the permanent tooth buds for the maxillary incisors develop palatally to the primary incisors, a shortage of space may force the permanent teeth to remain palatally.
62
What is a pseudo-class III malocclusion?
Patients with a significant anterior shift of the mandible from CR to MI due to interferences caused by a dental anterior crossbite may appear to have a significant mandibular prognathism. It is very important to evaluate the patient’s occlusion and facial profile in CR and MI. An anterior dental crossbite with a significant anterior shift is called a pseudo-Class III malocclusion.
63
What does occlusion often look like in patients with a pseudo-class III malocclusion? How does the shift appear when they move from CR to MI?
These patients usually can be manipulated into an edge-to-edge incisor relationship in centric occlusion. When they shift forward into MI, the profile appears prognathic.
64
What is the rationale behind correcting anterior crossbites in children?
Allow normal jaw function by eliminating significant CR–MI functional interferences.
Establish normal interincisal contact. Lingually positioned incisors may interfere with lateral jaw excursions and cause significant abnormal incisal wear patterns that can compromise incisor esthetics.
Prevent periodontal involvement of the lower incisors. Significant dental compensations may also develop in response to the altered incisor positions. An anterior crossbite may force the mandibular incisors to be positioned more facially in the lower arch. If positioned too far facially the periodontal support of the lower incisors may be compromised due to loss of attached gingiva and gingival recession.
Allow correction of localized space loss.
65
How can space be created to allow alignment of the incisors?
Space may be created to allow alignment of the incisors and correction of the crossbite by:
Proclining the maxillary incisors
Extracting adjacent primary teeth
Reducing the mesial-distal width of the adjacent primary teeth
66
How can anterior crossbites be repaired?
Relatively simple removable acrylic appliances can be used to tip the maxillary teeth into the correct labial position. Adams clasps can be used for retention, while springs (20 mil stainless steel) can be designed to tip teeth labially.
67
What are the most common problems that arise with using simple removable acrylic appliances?
Such appliances must be worn 24 hours/day to be efficient and effective. The finger spring can be activated 1.5–2 mm per month and will produce approximately 1 mm of tooth movement in that time. The most common problem with these types of removable appliances is lack of patient compliance. Poor appliance design and lack of adequate retention will greatly reduce compliance. Improper activation may also lead to inadequate untimely results.
Forces applied by finger springs dislodge the appliance causing reduced retention. It is important to have adequate retention. Resin may be added to the lingual surfaces of the maxillary incisors to allow the finger spring to seat properly against the incisor rather than slide upward toward the incisal edge
68
What are the types of fixed orthodontic appliances that can be used to correct an anterior crossbite?
Cemented maxillary lingual arch with soldered finger or whip springs.
A 2 x 4 appliance
69
How can relapse of crossbite be prevented?
A passive removable appliance can be used for 2 months post treatment to prevent relapse.
70
How can skeletal anterior crossbites be treated?
True skeletal anterior crossbites are difficult to treat.
One must carefully evaluate the patient’s facial profile using facial form analysis. Interventions are skeletal in nature and may use growth modification techniques to improve the skeletal relationship.
Reverse pull headgear may be used in patients with maxillary deficiency in the early mixed dentition, while chin cup therapy has been used to help control mandibular growth in patients with mandibular excess
A new and potentially more effective approach in the late mixed dentition after eruption of lower permanent canines is the use of Class III elastics to miniplates bonded to the maxilla and mandible
71
Why are chin cup appliances not so successful for treating mandibular excess?
Chin cup appliances have limited success as they require an extended period of compliance and must be worn during the majority of the adolescent growth spurt to be effective.
72
When can class III elastics to miniplates bonded to the maxilla and mandible be used?
Bone screws to hold the miniplates are not stable until the alveolar bone has reached the stage of maturity seen at about age 11, when eruption of the canines would be expected, so that is the earliest time it can be used.
73
What should a dentist do when there are suspected skeletal anterior crossbites?
Patients with suspected skeletal anterior crossbites should be referred early in the mixed dentition for evaluation and possible treatment by an orthodontist.
74
How should skeletal and dental posterior crossbites be approached?
Tip the teeth buccally in dental crossbites
Expand the maxillary width in skeletal crossbites.
75
Which crossbites do class III skeletal malocclusions usually present?
Usually a posterior as well as an anterior crossbite.
The upper and lower jaw may be of normal transverse width but due to the abnormal anteroposterior relationship, the lower arch appears relatively wider than the upper arch, and the patient presents with a posterior crossbite as well as an anterior crossbite.
76
Why do posterior crossbites in children often appear unilateral in appearance?
Closer examination usually reveals that this results from a true bilateral constriction of the maxillary arch with a transverse shift of the mandible from CR to MI.
This can rarely also occur due to intra-arch or jaw asymmetry.
77
Which common habit leads to a posterior crossbite?
Thumb sucking.
78
When should a posterior crossbite be treated?
Crossbites caused by a mandibular shift should be treated as soon as they are discovered, even in the primary dentition if patient cooperation allows.
79
Why should posterior crossbites be treated?
Undesirable soft tissue growth modification
Dental compensation
Abnormal wear of the primary and permanent teeth
Reduced maxillary arch space required to align the teeth
80
When should posterior crossbite be treated?
Correction in the primary dentition is recommended if a mandibular shift is present and the child will cooperate with treatment. However if the permanent first molars are expected to erupt within 6 months, it is recommended that expansion be delayed until these teeth erupt and can be included in the treatment.
81
How can skeletal posterior crossbites be fixed?
Posterior crossbites can be treated with a number of appliances, both removable and fixed:
Removable split plate appliances
W-arch appliance
Quad helix appliance
Rapid maxillary expander (RME)
82
How do removable split plate appliances work?
These removable appliances use a split acrylic palate incorporating a wire spring or jackscrew for force generation to expand the maxillary arch.
83
What is the limitation of using split plate appliances?
The forces generated by the appliance to expand the maxillary arch also tend to dislodge the appliance, which may further reduce compliance. Unless the expansion screw is turned very slowly, the appliance will not seat properly because the teeth have not had enough time to move between activations. As a result, these appliances are not as effective and successful as fixed appliances.
84
When are quad helix and W-arch appliances used?
The preferred appliances for correction of maxillary constriction in preadolescent patients are the quad helix and W-arch appliances. These lingual arch appliances are preferred in this age group, as the midpalatal suture is most likely open and heavy force is unnecessary to achieve dental and skeletal expansion.
85
What are the quad helix and W-arch appliances made of?
Both appliances are constructed using 36 mil steel wire soldered to orthodontic bands cemented to the maxillary first permanent molars. The wire is positioned about 1 mm above the soft tissue to prevent impingement.
86
How mdo the quad helix and W-arch appliances generate their force and how much force do they generate?
Both appliances generate approximately 2-4 pounds of force, which creates about 2 mm of slow expansion per month. The appliances are activated about 3-4 mm prior to cementation, which is roughly about 1/2 the facial lingual width of the permanent molar. It is recommended that both appliances should be removed and recemented to be accurately reactivated.
87
How long does treatment take with the quad helix and W-arch appliances?
Using these appliances, a posterior crossbite usually requires 2-3 months of active treatment followed by 3 months of retention utilizing the passive cemented appliance. The quad helix appliance, by virtue of the additional wire and helices, has increased range and springiness. The anterior helices may also act as a reminder to aid in stopping a thumb habit
88
What is maxillary expansion with high forces over a short period of time called?
It is known as rapid palatal (or maxillary) expansion (RPE or RME)
89
How is rapid maxillary expansion achieved?
Banded or bonded expansion screws are used to achieve this type of expansion in adolescent patients, whose mid-palatal suture has become so interdigitated that heavy force is needed to open it. The jackscrew is activated at a rate of 0.5 to 1.0 mm per day. Since the force generated between activations does not completely dissipate, cumulative forces of 10-20 lbs may be present during treatment. 10 mm or more of expansion can be seen in a period of 2-3 weeks.
90
What are the limitations of using rapid palatal expansion techniques?
As the suture expands, a maxillary midline diastema usually occurs as the bony expansion carries the teeth apart.
Whether they are attached to bands or are bonded, fixed palatal expansion appliances make adequate oral hygiene difficult and may interfere temporarily with normal speech.
91
Which is better for maxillary expansion in the long term?
Slower and rapid expansion produce similar long-term results. (in the short term not enough time for tooth movement to occur relative to supporting bone but stretched palatal mucosa creates allows relapse during stabilization and healing.
92
Which age groups should not use rapid maxillary expansion? What should be used instead?
Rapid palatal expansion is not recommended in young children. The midsagittal suture can be opened with moderate forces as generated by a W-arch or quad helix. If rapid palatal expansion is used in this age group, the risk of distorting the more pliable facial structures of the midface is markedly increased.
In preadolescent children (8-11 years old), a W-arch or quad helix appliance is recommended because the midsagittal suture still is patent enough that the lower forces generated by these appliances can deliver both dental and skeletal expansion.
93
Which age groups should use rapid maxillary expansions?
In late adolescence the suture is more organized and may require more force to achieve skeletal expansion. In these cases an RPE-type appliance may be require to achieve skeletal expansion.
94
How should maillary skeletal expansion be done in adults?
In adults, surgery is usually required to accomplish maxillary skeletal expansion, as the suture is highly organized and fused.
95
What are the vertical effects of correcting a posterior crossbite?
One must be aware that any forces applied to posterior teeth to correct a posterior crossbite have a vertical as well as a transverse vector that tends to open the bite anteriorly. This vertical vector tends to extrude the posterior teeth as well as tipping the lingual cusps downward. Both of these will result in a bite-opening effect.
96
How will patients with short lower face height and shallow mandibular plane angle and patients with steep mandibular plane and increased lower face height be affected by posterior crossbite correction?
In patients with short lower face height and a shallow mandibular plane angle, this may have a positive effect. However, in patients with a steep mandibular plane and increased lower face height, such vertical changes will make the situation worse.
97
How do dental and skeletal vertical problems differ in their difficulty to treat?
Vertical problems that are dental in nature may be easy to correct, while skeletal vertical problems may be very difficult to treat and may require surgical correction.
98
What kinds of problems cause anterior open bites in children with thumb sucking habits?
Labial tipping of the maxillary incisors
Lingual tipping of the mandibular incisors
Reduced eruption of the incisors and overeruption of the posterior teeth
Reduced maxillary intercanine and intermolar width.
99
What aspects of thumb sucking lead to the type of effects seen as a result?
In the primary and mixed dentition, simple anterior open bites in children with good facial proportions are most commonly associated with prolonged thumb-sucking habits. The effects are related to the duration and intensity of the habit.
100
How do patients with prolonged thumb sucking present?
Patients with a prolonged thumb habit usually present with increased overjet, reduced overbite (open bite), and a posterior crossbite.
101
Can the dento-alveolar changes caused by thumb sucking be resolved spontaneously?
The majority of children discontinue thumb-sucking habits before they reach school age. If the habit is stopped before the eruption of the permanent incisors, most of the dento-alveolar changes associated with the habit resolve spontaneously.
102
How can further thumb sucking after eruption of permanent incisors be prevented?
Some children continue their habit after the incisors erupt. A sequence of inventions that may be used to help children discontinue thumb-sucking habits include:
Reminder therapy where a bandage is placed on the finger that is sucked.
Reward therapy, where a series of small daily rewards and a larger major reward are given to the child when the habit is not practiced over a period of time.
An elastic bandage wrapped around the elbow to prevent flexion of the elbow so that the finger cannot be sucked.
Appliance therapy, where a reminder appliance is cemented on the teeth.
103
What patient compliance measures should be placed to prevent patient from further thumb sucking with the preventative measures in place?
For any of these methods to be effective, a child must wish to stop the habit. The intervention must not be perceived as punishment by the child. Appliance therapy requires a compliant patient who wishes to stop the habit, because noncompliant patients can easily distort or remove the appliances if they wish.
104
How does appliance therapy work in preventing thumb sucking?
Appliance therapy uses a cemented maxillary lingual arch that has a crib constructed of soldered wire (usually 0.038”) on the anterior portion of the appliance. The anterior crib functions as a reminder and interferes with thumb position during sucking
105
What are the major vertical problems in teenagers?
In adolescents the major vertical problems are anterior open bite and anterior deep bite. At this age any vertical discrepancy tends to be more related to skeletal proportions rather than simple displacement of the teeth.
106
What are the skeletal indicators of an anterior open bite?
Skeletal indicators of an anterior open bite include:
Increased anterior open bite
Steep mandibular plane
Excessive vertical growth of the maxilla
Downward rotation of the mandible
Excessive eruption of the posterior teeth
107
What are the causes of anterior deep bite?
Anterior deep bite (excessive overbite) may result from excessive eruption of the mandibular incisors or from upward and forward rotation of the mandible that leads to a short face. The first of these would be described as a dental deep bite; the second would be termed a skeletal deep bite.
108
What is the objective of correcting a dental deep bite?
An important concept: the objective of correcting a dental deep bite is to level the lower dental arch, which can be accomplished in a growing patient by impeding eruption of the lower incisors and allowing eruption of the posterior teeth. In a Class II patient it would be important to prevent an increase in anterior face height as this was done, because that would magnify any underlying mandibular deficiency. The mandible would rotate backward as well as downward.
109
What are the features of a patient with a skeletal deep bite?
A child with a skeletal deep bite presents with a short face appearance. These children usually have:
Anterior deep bite
Some mandibular deficiency
A Class II division 2 malocclusion
Reduced lower face height
Everted and prominent lips
Low mandibular plane angle
Long mandibular ramus (long posterior face height)
Decreased eruption of the maxillary and mandibular posterior teeth
Anteriorly directed growth pattern with upward and forward rotation of the mandible
Many of these children can be described as skeletal Class II with the mandible rotated upward and forward toward a Class I jaw relationship. One objective of treatment is to increase the eruption of the posterior teeth and have the mandible rotate downward to increase the lower face height. However as the mandible rotates downward the chin also rotates downward and backward, which may make the chin less prominent and make the Class II problem more severe.
110
How is a skeletal deep bite treated?
Cervical headgear: Results in more eruption of maxillary posterior teeth than mandibular teeth. Headgear does not control eruption of the incisors, which is important in correcting the deep bite.
Deep bite functional appliance: Eruption of the maxillary posterior teeth and the incisors in both arches is blocked, while eruption of the mandibular posterior teeth is allowed. The effect is to level an excessive curve of Spee in the lower arch as face height is increased.
111
What are the features of a skeletal open bite?
Children with skeletal open bite present with a long anterior face height, which usually (though not always) is accompanied by anterior open bite. These children usually have:
Normal upper face
Overeruption of the maxillary and mandibular posterior teeth
Steep mandibular plane
Reduced posterior face height and increased anterior face height
Downward and backward rotation of the mandible
Downward-directed growth
Downward tipping of the posterior maxilla
112
What is the goal of treatment of a skeletal open bite?
The goal of treatment is to prevent further downward growth of the posterior maxilla and prevent further eruption of the posterior teeth in both arches, so the mandible can rotate upward and forward to decrease the lower face height. To be effective, this growth modification must be used during active growth, which would mean that a protracted treatment time from the late mixed dentition to the completion of growth in postadolescence.
113
What kind of treatment is done for severe skeletal open bites?
Surgical repositioning of the maxilla and chin is likely to be needed.
114
What are the approaches used for limiting further vertical growth and skeletal open bite?
High Pull Headgear to Maxillary Molars
High Pull Headgear to a Maxillary Splint
Functional Appliance with Bite Blocks
High Pull Headgear to Functional Appliance with Bite Blocks
115
How does the high pull headgear to maxillary molars work?
A high pull headgear to bands on the maxillary first molars provides a force to maintain the vertical position of the posterior maxilla and prevent eruption of these teeth.
116
How much force should a high pull headgear place on maxillary molars to slow down their eruption? How long should they be worn?
The headgear should deliver a force of 12 ounces per side and be worn 14 hours per day. The force vector will be determined by the relationship of the line of force between the outer bow of the headgear and the head cap
117
How does a high pull headgear to maxillary splint work?
A vertical force can be applied to all the maxillary teeth, which provides better control of excessive maxillary vertical growth and controls the eruption of all the maxillary teeth. A long-face child who displays an excessive amount of maxillary gingiva below the upper lip line would be a good candidate for this type of treatment.
118
What are the limitations of high pull headgear to maxillary splint?
the appliance does not control the eruption of the mandibular posterior teeth. (If the mandibular molars erupt, the bite opens further as the mandible rotates downward and backward, increasing the vertical face height.)
As with all interventions that rely on growth modification, long-term treatment during the entire active phase of growth will be required to successfully maximize the treatment result.
119
Where in the mouth does the headgear pull on in high pull headgear with occlusal splint?
The force vector when using a high pull headgear and a maxillary splint is different from a high pull headgear attached to the maxillary molars only. In the combination appliance the entire maxilla is deemed to be a single unit with a single center of resistance.
This center of resistance is deemed to be located between the apices of the maxillary premolars. The line of force should be directed through this point in an upward and backward direction. This would mean that a high pull headgear with a short outer bow bent upward would be required.
120
How does the functional appliance with bite block work?
a functional appliance that includes posterior bite blocks so that the mandible is rotated beyond the freeway space, which (at least theoretically) generates force from the stretched muscles to inhibit eruption of the posterior teeth and prevent vertical descent of the maxilla. The appliance can also be designed to reposition the mandible anteriorly depending on the degree of mandibular deficiency present.
With this appliance, the anterior teeth are allowed to erupt while the posterior teeth are restricted.
121
What is the limitation of using a functional appliance with bite block?
Appliances of this type do lead to closure of anterior open bites, but the change is primarily from eruption of the incisors, not from upward-forward rotation of the mandible--so there is only a small if any effect on the growth pattern.
122
What is the ultimate approach to controlling the pattern of growth in patients with skeletal open bite?
A combination of high pull headgear to restrict vertical growth and a functional appliance with posterior bite blocks to control eruption of the teeth
The high pull headgear applies a vertical force to the whole maxilla as headgear to a splint does, and the functional appliance with bite blocks) controls eruption of the mandibular and maxillary posterior teeth while allowing eruption of the incisors.
none of the types of treatment that have been advocated for patients with skeletal open bite of any severity really are effective in controlling the excessive vertical growth.
123
What are the limitations of using a high pull headgear to functional appliance with bite blocks?
Recent studies have shown that there is remarkably little effect on the long face growth pattern from even this combination of headgear and functional appliance.
124
What does the evidence say about using functional appliances for controlling skeletal open bite?
None of the types of treatment that have been advocated for patients with skeletal open bite of any severity really are effective in controlling the excessive vertical growth. So instead Current treatment methods involve intruding maxillary posterior teeth.
125
As the dentist responsible for patients with deep bite or open bite problems, what should you expect?
thumbsucking is the major cause of most open bites in children, and treatment to extinguish this habit--in a child who wants to stop--is indicated in those whose thumbsucking extends into the elementary school years.
open bite that persists probably has a skeletal component. Treatment of these patients is complex and difficult, and for those with a severe long face / open bite problem, the prognosis is poor.
deep bite is strongly related to overjet, so most Class II children with normal face height will also have a dental deep bite that will need to be corrected during orthodontic treatment.
in contrast to skeletal open bite, functional appliance treatment to correct short face/ deep bite problems is reasonably effective, and damage to the tissues palatal to the maxillary incisors and/or the gingiva in the lower incisors from an impinging overbite is an indication for treatment during the mixed dentition.
management of patients with a combination of a-p and vertical problems is complex enough to indicate referral to an orthodontist in most instances.
