1. Space supervision and guidance of eruption in management of lower transitional crowding: A non-extraction approach 
Ronald A. Bell, DDS, MEd, Andrew Sonis, DMD 
Seminars in Orthodontics 
Volume 20, Issue 1, Pages (March 2014)
DOI: /j.sodo
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2. Figure 1
Dimensional changes show an average increase in lower intercanine width of 2–3mm (range of 0–5mm) during incisor transition, with no other increases in the lower intercanine width noted after the lower lateral incisors have fully erupted by 8 years of age. The normative finding is a resulting average lower incisor crowding of 1.5mm, with a SD of ±1mm. Thus, lower crowding in the range of 1–4 mm should be expected in the majority of mixed dentition children at 8–9 years of age.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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3. Figure 2
Lower arch length decreases significantly on exfoliation of the lower second primary molar as the permanent first molars shifts forward toward the available “E-space.” The decrease of 2–3mm in each lower quadrant translates to an arch perimeter decrease of 4–6mm during this late “mesial shift” transition period.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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4. Figure 3
An increase in lower arch perimeter during the 2-year incisor eruption period (Inc—age 6–8 years) is related to increase in intercanine width associated with incisor transition and counter-balanced arch length adjustments. A stable period of arch dimensions follows during the mid-mixed dentition (8–11 years) until a dramatic decrease in arch length of 2–3mm per side is associated with turnover of the buccal dentition, specifically second primary molar exfoliation. The resultant decrease in arch perimeter associated with the late mesial shift period (LMS—11–12 years of age) is on the order of 4–5mm.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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5. Figure 4
Disking the mesiolingual angle of lower primary canines provides additional space for an improved alignment of the permanent incisors without overly encroaching on leeway space. Two examples of primary canine mesiolingual disking and the favorable response in terms of incisor alignment are shown. Top images shows one-time disking using #169 tapered fissure bur and response at 1-year follow-up. Bottom images represents two sequential disking procedures—first at initial presentation and second at the child's 6-month recall visit.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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6. Figure 5
Unilateral ectopic loss of a lower primary canine typically results in an asymmetric space loss as the incisors shift toward the side of loss and move lingually (A and B). Bilateral ectopic loss of lower primary canines (C and D) allows maintenance of arch symmetry, but results in significant lingual retroclination and supraeruption of the lower incisors, increased overjet, deepened overbite, and reduction in overall lower arch dimensions.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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7. Figure 6
Extraction of lower primary canines. (A) Lingually positioned lateral incisors, dental shift to right, retained left primary lateral. Decision made to extract the primary canines. (B) A year later—symmetry of incisor alignment achieved at expense of arch length and perimeter through lingual and distal movement of the incisors.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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8. Figure 7
Loss of primary canines—what about a lingual holding arch? Usually not that simple as incisors tend to align along LHA wire shaped to the most lingual position, i.e., loss of arch length as incisors drift distal and lingual along lingual wire into the canine space.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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9. Figure 8
Phase 1 2 × 4 arch development—pre-treatment (upper left): arch changes associated with bilateral ectopic loss of lower primary canines and narrowed maxillary arch form. Upper 2 × 4 arch development supported by E-spyder expander to emphasize fan-like anterior expansion of maxillary arch (upper right). Tieback of NiTi archwires restrained upper incisors and resulted in some retraction. Lower 2 × 4 arch development using AW lock stopped sequential archwires (0.016 NiTi, NiTi, and SS) to advance lower incisors, correct midline discrepancy, and increase arch perimeter to accommodate leeway space adjustments (at 4 months). Active appliances removed at 7-month treatment time (lower left). Retention with upper transpalatal bar and lower lingual holding arch at 18 months post-treatment maintained achieved arch width and arch length changes. Note facial profile changes influenced by correcting initial excessive overjet and lip interpositioning.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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10. Figure 9
Removal of primary first molars concurrent with disking the mesial surfaces of second primary molars enhances distal eruptive positioning of the permanent canine and first premolar as illustrated above on upper left. The case on the lower right had primary canines disked at 8 years and 4 months of age. After exfoliation of primary canines and first primary molars, lower second primary molars were disked at 10 years and 8 months as the canines and first premolars erupted. This continued the guidance concept of unraveling anterior crowding toward available leeway/E-space.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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11. Figure 10
Control of late lower arch length decrease using lingual holding arches and selected extraction of second primary molars allows alignment of crowded lower incisors on the order of 3–4mm as the buccal dentition (canines and premolars) erupt more distally into the leeway space maintained by the LHA.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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12. Figure 11
Case example—Removable lip bumper. Lip bumper placed as lower second primary molars exfoliated at age 11 years and 6 months. Bumper placement low in vestibule provided holding force on molars while allowing lip to contour over the bumper to lessen incisor labial movement. After 8 months of bumper wear (age 12 years and 2 months), a significant relief of anterior crowding resulted. Edgewise appliances aligned the dentition into the established arch form.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
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13. Figure 12
Case example—Soldered lip bumper placed before second primary molars exfoliated. Bumper positioned at cervical margins provided holding force on molars, reduced lip contact on incisors to enhance labial movement. At 6 months (12 years and 5 months), lower crowding reduced through distal movement of canines and premolars toward E-space, with some arch expansion. Edgewise appliances aligned dentition with retraction of buccal segments and establishment of a broader arch form.
Seminars in Orthodontics  , 16-35DOI: ( /j.sodo )
Copyright © 2014 Elsevier Inc. Terms and Conditions