MANAGING THE ARCH CIRCUMFERENCE

1. MANAGING THE ARCH CIRCUMFERENCE Diagnosis and Treatment Planning

2. 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.

3. 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.

4. 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.

8. The Problem of Pathologic Loss of Arch Circumference

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

11. Primary Causes of Loss of Arch Circumference • Extraction of posterior primary teeth due to pulpal pathology. • Interproximal caries

12. Premature Loss of Primary Tooth (Extraction)

16. Proximal Caries

18. Additional Causes of Loss of Arch Circumference • Ankylosis of primary tooth • Ectopic eruption of the first permanent molar

19. 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.

21. 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.

23. Ectopic Eruption of Lateral Incisor

24. TREATMENT ALTERNATIVES In Managing the Arch Circumference

25. 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.

26. TREATMENT DECISIONS For Space Management in the Primary Dentition

27. 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.

28. 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

29. Band and Loop Space Maintainer

30. 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.

35. Intra-Alveolar(Distal Shoe)

36. 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.

43. Removable Acrylic Space Maintainer

45. 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.

46. 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.

47. 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.