Normative transitional dimensional changes and anticipatory guidance
Stage 1—Eruption guidance in the mandibular incisor segment (6–9 years of age)
Disking of primary canines
- 1.Local anesthesia (block, infiltration, or topical anesthetic compound) may be required as the canine must be sliced subgingivally to completely free the contact area. Disking just the crown is not adequate as the contact area is subgingival. Placement of a wedge is sometimes necessary to protect the lateral incisor and access the contact area. Thirdly, dentin exposure is usually necessary to reduce the primary canine width adequately—another indicator for local anesthesia or nitrous oxide support. Coordinating with restorative work requiring anesthesia in the area may be beneficial in treatment planning.
- 2.A tapered fissured bur (#699 or #169) to allow effective tooth reduction and access without injury to adjacent permanent teeth is recommended. Re-approximating diamond disks or strips at this stage of development is not recommended due to risk of soft tissue injury. Emphasis on the mesiolingual corner of the primary canine rather than the straight mesial surface is facilitated with tapered fissure burs.
- 3.Timing is critical to allow ease of access and optimal tooth positioning response. Given the normative intercanine width increases during lateral incisor eruption, disking should be delayed until “wedging” effects of erupting incisors and arch width increases are realized. Disking is best around 7 ½ to 8 ½ years of age in proximity to the completion of lateral incisor eruption. The primary canine roots should be relatively intact without ectopic resorption changes from the erupting lateral incisors or due to the eruption timing of the lower permanent canines.
Extraction/ectopic loss of primary canines
- Sjogren A.
- Arnrup K.
- Lennartsson B.
- Huggare J.
- Sjogren A.
- Arnrup K.
- Lennartsson B.
- Huggare J.
Stage 2—Guidance in mandibular canine/first premolar segment (age 10–11 years)
Stage 3—Guidance in mandibular second premolar/molar segment (age 11–12 years)
Summary of “age-appropriate” and “staged” guidance of eruption concepts
- (1)Preservation of inherent arch dimensions through a comprehensive preventive, restorative, and space maintenance oversight program to optimize the integrity of the primary and the mixed dentitions throughout the transitional periods.
- (2)After incisor eruption is complete, the average lower alignment shows crowding of 1.5 ± 1.0 mm. No subsequent “growth” changes will increase lower anterior canine-to-canine arch dimensions. The preferred approach during active incisor transition is to allow any “wedging” effect of eruption to influence arch dimensions. After lateral incisor eruption is complete at 8 years of age, what you see is what you get! NOW is the time for Stage 1 decision as to no intervention necessary, accept as is, disking of the primary canines, extraction of primary canines, or Phase 1 arch development.
- (3)Selected disking of primary canines to enhance incisor positions when crowding is in the range of 2–4 mm and the lower incisors are lingually malpositioned to the arch form is the first choice of intervention, especially in deepbite/brachyfacial occlusion patterns. If intercanine space can be “fine-tuned” with disking, tongue pressures will tend to position the lingually displaced incisors forward into an enhanced arch form alignment. Intercanine space of 1–2 mm per side for incisor alignment can be achieved by disking the mesiolingual corner of the primary canines to provide “sluiceway” for incisor alignment once the lateral incisors are erupted (usually around 7 ½ to 8 ½ years of age).
- (4)Decompensation of severe lower incisor malpositioning, midline asymmetry associated with ectopic eruption patterns, and lower incisor crowding at a level where removal of lower primary canines is required to allow proper incisor alignment integrity (greater than 3–4 mm of liability). Clinicians must understand and relate to the parent that the necessity of early primary canine extraction indicates a significant tooth size–arch size problems. It is frequently step one of a serial extraction program, particularly in vertically sensitive dolichofacial patterns. The negative effects with lingual collapse of incisors, arch length loss, deepening of bite, and increased overjet all are significant detriments in brachyfacial cases.Such levels of tooth size–arch size discrepancy may indicate the need for an early Phase 1 intervention using Edgewise 2 × 4 mechanics to position incisors and molars toward favorable Class I relationships, with incisor integrity, midline coincidence, and normal overbite and overjet. Crowding and incisor positioning discrepancies requiring canine extraction or extensive arch expansion to relieve incisor crowding and offset negative effects of space loss are candidates for early 2 × 4 intervention, and it generally implies a long-range non-extraction protocol as compared to a situation where the extraction of the primary canines is the first step in a serial extraction plan. The amount of crowding discrepancy and facial type are critical factors in the decision-making process as to long-term extraction vs. non-extraction plan. Brachyfacial deepbite patients lead to a prioritized arch development with arch expansion to enhance facial balance. Dolichofacial openbite patients tend to be directed toward a serial extraction protocol that is much more likely to offset vertical facial imbalance.
- (5)Consideration of selective disking of the mesial surface of the second primary molars to enhance more distal eruptive positioning of the permanent canines and first premolars.
- (6)Timely use of passive lingual holding arches, lip bumpers, and/or late-staged Edgewise setups along with selected extraction of second primary molars to provide space for relief of typical lower crowding amounts (2–4 mm). The space control allows canines and premolars to erupt in more distal positions than under normal transitional patterns. This “driftodontics” of the buccal segments will in turn result in more intercanine distance for relief of incisor malpositioning in about two-thirds to three-fourths of patients. In keeping with the idea of supervising space changes in the late transitional dentition, patients should be evaluated before the transition of the buccal teeth in each arch. A good clinical guide for timing is upon the clinical emergence of the lower canines and first premolars around 10–11 years of age. These teeth erupt about 1 year ahead of the final buccal segment transition, leaving adequate time to assess dimensional needs and plan treatment interventions for the relief of crowding.
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