MANAGING THE ARCH CIRCUMFERENCE

Diagnosis and Treatment Planning

Arch Circumference

The distance from the distal of the second primary molar (or mesial surface of the first permanent molar) on one side of the arch to that same surface on the opposite side of the arch.

Arch Circumference

It is the space which during the primary dentition is occupied by the 10 primary teeth, and the space that will be available for the eruption of the 10 succendaneous teeth.

Physiologic Forces

A tooth is maintained in its correct relationship by the action of several forces. An alteration in these forces can alter the relationship among the teeth.

The Problem of Pathologic Loss of Arch Circumference

Physiologic Forces

Of primary concern is the mesial migration of the first permanent molar; any mesial movement, by definition, reduces arch circumference.

Primary Causes of Loss of Arch Circumference

Extraction of posterior primary teeth due to pulpal pathology.

Interproximal caries

Premature Loss of Primary Tooth (Extraction)

Proximal Caries

Additional Causes of Loss of Arch Circumference

Ankylosis of primary tooth

Ectopic eruption of the first permanent molar

Anklyosis

Ankylosis

An aberration in the eruption of teeth in which the continuity of the periodontal ligament becomes compromised, with fusion of the cementum and bone at one or more locations. Results in the tooth being “submerged” relative to the occlusal plane. Adjacent teeth may tip into space, resulting in loss of arch circumference.

Ectopic Eruption

Ectopic Eruption Eruption of first

permanent molar into the root of the second primary molar. Prevalence 2-3% Generally self-correcting, but can cause loss of second primary molar if not corrected, with first permanent molar positioning itself anteriorly, with resultant loss of arch circumference.

Ectopic Eruption of Lateral Incisor

TREATMENT ALTERNATIVES

In Managing the Arch Circumference

Four Alternatives MAINTAIN SPACE

By means of appliance therapy provide for the maintenance of the arch circumference present at the time of examination.

REGAIN SPACE By means of active appliance therapy attempt to

regain arch circumference (space) which was at one time available but has now been lost for whatever reason

CREATE SPACE By a more sophisticated application of knowledge of

the developing occlusion and/or by application of biomechanically active appliance therapy increase the amount of space available for the teeth as they erupt and possibly increase overall arch circumference.

ELIMINATE SPACE Through extraction of permanent teeth with the

subsequent closure of excess space, resolve sever discrepancies between tooth size and arch circumference.

TREATMENT DECISIONS

For Space Management in the Primary Dentition

Treatment PlanningPrimary Dentition

Decision making regarding space management is not as challenging in the primary dentition as it becomes later in the mixed dentition.

This is due to a meager data base. At this stage of development it is difficult to

ascertain the existence of a tooth size/arch circumference discrepancy, and generally dento-skeletal malocclusions are not identifiable at this time.

Because of these diagnostic constraints, maintenance or preservation of the available space is accomplished should a primary tooth be lost prematurely.

Treatment PlanningPrimary Dentition

Three appliances are used to maintain the available arch circumference in the primary dentition: Band and loop Intra- alveolar or distal shoe Removable acrylic appliance

Band and Loop Space Maintainer

Band and Loop

The band and loop is used to maintain space subsequent to the loss of the first primary molar.

The band is attached to the second primary molar and the loop extends to the distal of the primary canine.

This effectively reserves the space that is available for the eruption of the first premolar.

Intra-Alveolar(Distal Shoe)

Intra-Alveolar(Distal Shoe)

The intra-alveolar or distal shoe space maintainer is indicated following premature loss of the second primary molar and prior to the eruption of the first permanent molar.

The abutment tooth is the first primary molar with a wire extending distally to the mesial aspect of the unerupted molar and extending gingivally to contact the mesial surface of the permanent molar.

The gingival extension provides a surface along which the first permanent molar can erupt.

Subsequent to the eruption of the molar at age 6, an alternative appliance (lingual arch) must be placed.

Employment of a distal shoe dictates the employment of 2 appliances to maintain space until the eruption of the second premolar, at age 10-12.

Removable Acrylic Space Maintainer

Removable Acrylic Appliance A removable acrylic appliance is required

should multiple posterior teeth be lost in one quadrant.

Extraction of both the first and second primary molars in one arch would prevent the utilization of either a band and loop or a distal shoe.

Removable Acrylic Appliance Unless absolutely dictated by the

circumstances, removable acrylic appliances should not be utilized for three reasons: their success is too dependent on the

child’s cooperation and compliance. their ability to maintain the space for which

they were designed is sometimes questionable,

children tend to break and/or lose them.

Treatment PlanningPrimary Dentition

In cases where there is bilateral loss of a single tooth it is preferable to fabricate and place two unilateral appliances than to place one bilateral one.

For example, a lingual arch placed on the second primary molars would interfere with the eruption of the permanent incisors.

Additionally, there is some growth in arch width with the eruption of the permanent incisors, and no appliance should be placed that would restrict this.

Fixed Anterior Esthetic Appliance

TREATMENT DECISION MAKING

For Managing Space Problems in the Mixed Dentition

Treatment PlanningMixed Dentition

Treatment decision making during the mixed dentition is more complex.

Primary dentition - basically a decision to maintain space

Mixed dentition - decision is to maintain, regain, create, or eliminate space.

BASIC PREREQUISITES FOR MANAGING ARCH CIRCUMFERENCE IN THE MIXED DENTITION

Profile is orthognathic Relationship between the maxillary and

mandibular dentitions is normal as evidenced by molar relationship, canine relationship, overbite, and overjet

This does not mean that the various management procedures to be discussed are not, or should not be utilized, only that absent the above prerequisites, there is likely an underlying malocclusion that simple management of the arch circumference in one plane of space one not resolve. Referral to a specialist competent to treat the case comprehensively is indicated.

Maintaining Arch Circumference(Mixed Dentition)

Appliances Utilized:

Mandibular Arch - Lingual Arch Maxillary Arch - Palatal Arch

Lingual Arch

Lingual Arch

Nance (Palatal) Arch

Nance (Palatal) Arch

Maintaining Arch Circumference(Mixed Dentition)

The utilization of these “full arch” appliances emphasizes the concept of maintaining the integrity of the arch circumference rather than individual tooth spaces.

Single tooth appliances, such as a band and loop, are generally not appropriate in the mixed dentition due to the eruption sequence of teeth.

For example, a band and loop extending from the first permanent molar to the first primary molar would lose its anterior abutment, the first primary molar, prior to the eruption of the succedaneous tooth, the second premolar. The mesial component of force with the erupting second molar could force the first permanent molar forward reducing arch circumference and compromising the space for the second premolar.

Regaining Arch CircumferenceMixed Dentition Regaining arch circumference is not

particularly complex and the prognosis is good.

The objective is simply to regain arch circumference that has been lost; for example, by distalizing first permanent molar(s) that have migrated mesially subsequent to the premature loss of posterior primary teeth.

Regaining Arch CircumferenceMixed Dentition

Appliances used:

Amount to be gained Mandible Maxilla

0-2 mm helical spring helical spring

loop lingual arch headgear

split saddle jackscrew

2-4 mm sling shot split saddle

split saddle headgear

lip bumper jackscrew

Loop Lingual Arch

Loop Lingual Arch

Head Gear

Jackscrew Appliance

Jackscrew Appliance

Helical Spring Appliance

Helical Spring Appliance

Slingshot Appliance

Split Saddle Appliance

Creating Arch CircumferenceMixed Dentition

Typical appliance therapy might consist of using a headgear in the maxillary arch to distalize the first permanent molars, and a loop lingual arch in the mandibular to advance the incisors.

If the discrepancy is small, 1-2 mm, it may be possible to provide additional space in the anterior region to permit favorable alignment of the permanent incisors by selective stripping of the primary canines and/or sequential extraction without employing active appliance therapy. The option for ‘creating space’ in this manner is due to the existence of the leeway space; essentially borrowing space from the posterior for the anterior. Another way of saying it is using the leeway space to overcome incisor liability.

Leeway Space

Nota Bene

Remember that the majority of the leeway space is ‘housed’ in the primary second molar/second premolar differential.

Creating Arch CircumferenceMixed DentitionTypical space creation protocol: Removal of primary canines to allow for the alignment of

the permanent incisors. One of the incisors may have been lost due to ectopic eruption of the lateral inciosr. Should this have occurred, extraction of the contra-lateral canine should be accomplished to preserve the midlines.

Placement of a lingual arch. Failure to place a lingual arch will result in the incisors positioning themselves lingually. This will close the canine space and shorten the arch circumference.

Removal of first primary molar and stripping of mesial surface of second primary molar. This is accomplished when it appears the canine cannot erupt normally; thus allowing the canine to erupt distally.

Removal of second primary molar when the first premolar is erupting to allow room for its eruption.

Removal of the lingual arch after eruption of the second premolar.

Lingual Arch