CATEGORY AUSTRALASIAN DENTIST61 CLINICAL esthetic, and functional results. Anterior segment may negatively alter the facial profile. X Biological and anatomical limits of the tissues – Moving teeth too far forward (labially) can exceed what the gum and bone can tolerate. – If the roots are pushed too far forward, the bone may resorb or form defects (fenestration or dehiscence) in the cortical plate, which can later cause gum recession. X Instability of tooth position – Teeth moved beyond their natural bony base are harder to keep stable. – Long-term retention becomes difficult if teeth are pushed too far forward or outward because soft tissue forces (lips, cheeks, tongue) push them back toward equilibrium. – Intermolar and especially intercanine widths should stay close to their original size for better long-term stability, though slight incisor advancement and molar expansion may be tolerated. X Impact on facial esthetics – Expanding the arch too much, especially by moving front teeth forward, can worsen a patient’s facial profile—making an already convex face look more protrusive. – Conversely, retracting teeth too much can flatten a face that is already flat or concave, which may look unattractive. – This follows the “principle of opposites”: if a profile is convex, think about making it less convex; if concave, think about making it less concave. Evidence Summary Systematic reviews (e.g., Janson et al. 2023, Zhou et al. 2024): X No clear superiority of extraction or non-extraction in terms of long-term stability of crowding correction. X Patient selection (initial crowding, skeletal pattern, facial esthetics, softtissue balance) is the key factor. X Profile changes are significant: extraction tends to retract lips, nonextraction tends to procline incisors and increase lip fullness. X Comparison / Key Factors Influencing Stability Many studies show that both extraction & nonextraction cases have relapse, but the degree depends on amount of crowding originally, how well alignment is finished, how much arch expansion was used, etc. A big predictor of relapse is how much expansion was done during treatment. If you expand a lot, there’s more tendency for relapse of width. Also initial arch form, retention protocol (type & duration), quality of finishing, and patient growth/aging. The ideal is balancing these. Stability is better when tooth movements remain within anatomical limits, and profile and soft tissue considerations are part of treatment plan. Also, good retention is essential. Findings in Extraction Cases Extraction cases allow space closure, which can reduce crowding more thoroughly at end of treatment. But relapse also occurs. In extraction cases, arch width expansion is usually less (or sometimes arch width decreases) because space is made by removing teeth rather than expanding/bulging the arch. Relapse still happens. Extraction allows for retraction of anterior teeth, which can reduce protrusion and improve profile in some cases; but can also flatten or worsen lip support if overdone. Profile relapse/changes post-treatment also occur. Findings in NonExtraction Cases Some relapse is inevitable. Incisor irregularity (especially in the lower arch) tends to increase over time postretention. In non-extraction cases, arch widths are often increased (via expansion or proclination). Some relapse (narrowing) of intermolar or intercanine widths after treatment/ post-retention is common. Non-extraction sometimes involves proclination/ protrusion of incisors and increase in facial convexity; patient-specific risk depending on lip support, facial type. Aspect Relapse of crowding / incisor irregularity Changes in arch width (intercanine, intermolar, interpremolar widths) Effect of extraction on facial/softtissue profile etc that may affect perceptual stability Key difference in extraction vs non-extraction treatment Fig 1: From pretreatment (left) and post-treatment (right) profile views of adult female extraction patient, it is impossible to determine whether treatment involved extractions. Key References for Further Reading Janson G, et al. Extraction vs Nonextraction Treatment: Systematic Review of Posttreatment Stability. Angle Orthod. 2023;93(3):261–271. Little RM, et al. Postretention Dental Arch Changes in Class I Malocclusion with Four Premolar Extractions. Am J Orthod. 1981;80(4):349-365. Zhou Y, et al. Arch Width Changes and Long-Term Stability in Extraction vs Nonextraction Orthodontic Treatment: Systematic Review and Meta-Analysis. Am J Orthod Dentofacial Orthop. 2024. Proffit WR, Fields HW. Contemporary Orthodontics. (Chapter on Extraction Controversy – classic discussion). geoff@orthoed.com.au Tel +613 91080475 2-STEP DIAMOND POLISHING SYSTEM Deluxe Deluxe double diamond combination for the aesthetic and high shine polish on all composite restorations Excellent choice for aesthetic dentistry No additional paste for high shine polishing ShapeGuard – One Shape for All Surfaces ing
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