Defined as correctly timed, planned removal of certain deciduous and permanent teeth in mixed dentition cases with dentoalveolar disproportion

- Introduced by KJELLGREN
- Father of SE = nance 1940
- RATIONALE
- Arch length deficiency as compared to the tooth material using Model analysis method
- Physiological tooth material = eg wilkinson extraction of 1st permanent molar
- FACTORS THAT PLAY ROLE IN CORRECTION OF CROWDING IN ANTERIOR SEGMENT
- Leeway space of nace
- Max = 1.8 mm
- Mand = 3.4 mm
- Tongue pressure
- Interdental spacing
- Incisal liability = amount of space available and required by permanent tooth
- Max = 7 mm
- Mand = 5mm
- Leeway space of nace
- INDICATIONS 2m
- Tooth material and arch length discrepancy of 10mm
- Class I malocclusion
- Absence of Spacing
- Midline shift
- Premature loss of primary canine
- CONTRAINDICATIONS 2m
- Class II and Class III malocclusion
- Anodontia
- Oligodontia
- Deep bite
- ADVANTAGES = Prevents fixed appliances and malocclusions in the pt
- DISADV =
- Long follow up = pt compliance
- Operator = highly trained
- Delay of permanent tooth
- DWELLS PROCEDURE
- Extraction of three teeth
- Primary canine = at age of 8-9 years
- Primary 1st molar = at age of 9-10 years
- 1st premolar
- Always bilateral extraction in the same arch
- If done unilateral = midline shift happens
- In the 1 st Step, the deciduous canines are extracted to create a space for alignment of the incisors. This step is carried out at 8-9 years of age.
- After 1 years, the deciduous 1st molars are extracted so that the eruption of 1st premolars is accelerated.
- This is followed by the extraction of the erupting 1 st premolar to permit the permanent canines to erupt in their place.
- Extraction of three teeth

- TWEED METHOD = D4C

- NANCE METHOD = D4C

- BOTH methods involve the extraction of the deciduous 1 st molars around 8 years of age. This is followed by the extraction of the 1 st premolar & the deciduous canines.
- MOYERS METHOD = based on intercanine width = BCD4
- Maxillary arch
- Boys = 10 years
- Girls = 9 years
- Mandibular arch
- Boys = 18 years
- Girls = 12 years
- Maxillary arch
