Ortho level 3 unit B module 1 2 Flashcards
What is the prognosis of children having crowded primary incisors?
As a general rule, children who present with crowded primary incisors will have major crowding problems in the permanent dentition
What is the early mesial shift?
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.
How much crowding develops in the mandibular arch?
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.
What causes the dental crowding?
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.
What assumptions are made during space analysis?
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.
What kind of space analysis is used by the UNC space analysis?
The Tanaka-Johnston space analysis procedure.
How is space analysis done using the Tanaka Johnston space analysis method?
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
What is the key assumption of the Tanaka Johnston space analysis method?
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.
How is the space available calculated?
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.
How is the space required to accommodate permanent teeth calculated?
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
How is the space discrepancy calculated?
Discrepancy = Total Space Available – Total Space Required
What is the endpoint of space analysis?
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.
What considerations should be made when analysis available space for analysis?
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.
How is generalized crowding classified?
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
How is type of intervention chosen based on crowding?
The type of intervention depends on:
Amount of crowding (mild, moderate, or severe)
Location of crowding (localized or generalized)
What questions should be considered when interpreting crowding?
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?
When are space maintenance, space regaining, and serial extraction indicated?
In situations of mild crowding.
If there is severe crowding serial extraction is indicated.
When is space maintenance used?
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.
Why is space maintenance used?
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.
What are the types of space maintainers?
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)
How should treatment with space maintainers be approached?
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.
Why are fixed space maintainers used more often than removable?
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.
Which space maintainers are often used for loss of a single tooth?
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.
Which space maintainers are often used for loss of multiple teeth?
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.
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
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.
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.
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.
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.
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.
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.
What is required after space regaining?
Space maintenance, otherwise it will be quickly lost again.
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.
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.
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.
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.
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.
What are the effective mandibular arch space regaining appliances?
Active lingual arch
Lip bumper
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.
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.
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.
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.
How much leeway space is present in the maxillary and mandibular arch?
Maxillary arch = 0.9 mm/quadrant
Mandibular arch = 1.8 mm/quadrant
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.
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.
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.
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).
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.
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.
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).
