CATEGORY 56 AUSTRALASIAN DENTIST LINICAL suture reaches the point that opening it may no longer be possible. For patients of this type, tooth-supported expansion should not be attempted. Instead, micro-implant assisted palatal expansion (MARPE) should be used with one activation of the screw (0.25 mm) per day, rather than using heavy force against the teeth. This approach along with surgically assisted palatal expansion (SARPE) and segmental osteotomy of the maxilla are the possibilities for the more mature patients in whom tooth-supported expanders will not work. Guideline The general guideline is that after any type of maxillary expansion, the fixed expansion device should remain in place until the new bone formed in the midline suture has had time to calcify and at least partially mature, and that a tooth-supported retainer is needed for another 6 to 12 months after that. With RPE, a tooth-supported expansion appliance should remain in place for 3 to 4 months, and then can be replaced with a removable retainer or other retention device. After slow expansion, the expansion device is not replaced with a toothsupported retainer for another 12 weeks after expansion is completed. With implant-supported expansion, the guideline is about the same as with toothsupported expansion. u Dr Geoff Hall, Specialist orthodontist Founder and Director of OrthoED, Smilefast, CAPS and Clear Aligner Excellence Tel: 03 9108 0475 geoff@orthoed.com.au For a list of references email: gapmagazines@gmail.com Rapid expansion Slow expansion Nature of expansion Skeletal and Dental Dentoalveolar changes Final expansion 50% Skeletal – 50% Dental Only Dental Force level 10–20 pounds 2–4 pounds Activation 0.5–1mm/day 1mm/month Effect on mid-palatal suture Opening of mid-palatal suture Rare Occurance of midline diastema Yes No Duration of treatment 2–3 weeks 2–3 months Indication Skeletal crossbite cases in Class II and Class III Minor space discrepancy cases Retention 9 months 3 months
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