23.1 Incisor Extraction
Extraction of incisors is indicated in:
- Dental Class III with lower crowding and microdontia of upper lateral incisors
- Dental Class I with significant mandibular incisors crowding
- Acceptable soft tissue profile
- Minimal growth potential
- Minimal to moderate overjet and overbite
Prescription for Extraction Cases
Question 10: select the teeth you are going to extract, among these three options:
- First: extraction of a lower incisor
- Second: extraction of 4s with maximum anchorage (up to 2 mm posterior mesialization)
- Third: extraction of 4s with minimum anchorage or extractions of 5s (more than 2 mm posterior mesialization)
Factors to Choose the Incisor to be Extracted 1
- Periodontically compromised mandibular incisor
- Most severely displaced mandibular incisor
- Mesiodistal width of the incisor
- Adjacent root inclination: adjacent root inclinations that diverge away from the extraction site will make it difficult to achieve adequate root parallelism at the end of the treatment. In contrast, when the roots of the adjacent teeth are convergent to the extraction site, there will be a highly predictable crown movement with a final parallelism between the roots
- Lateral incisors are usually preferred
Software Consideration on Incisor Extraction Cases
- Vertical attachments should be placed on the three remaining incisors to control tipping during the closure of the extraction site. The software normally only places the vertical attachment in the two incisors adjacent to the extraction site, not in all three
- Ask for a virtual gable bend of 10 degrees across the extraction site
- Pontic can be requested for covering the space of the extraction site, a small pontic should be considered to allow the aligner material to fully cover the adjacent teeth to the extraction site for a better control of the movements of those teeth
- If the adjacent teeth to the extraction site are divergent, aesthetic buttons and Powerchain by labial should be used to help the aligner to provide lingual tipping to the roots and achieve a final position that has adequate root parallelism
- To help achieve perfect root parallelism, Powerarms might be needed in order to get closer to the centre of resistance of the teeth
23.1.1 Class III with Lower Incisor Extraction
A 48‐year‐old man with a normodivergent skeletal Class III pattern presented with severe lower crowding, centred upper midline, microdontia of 12 and 22, and a missing 26. They had multiple gum recessions but appropriate lip seal posture and exposure of lower incisors when smiling.
- Expansion, opening space for missing 26 through sequential distalization of 28 and 27.
- In the mandible, 31 extraction, so final occlusion, in terms of buccal relationship would be similar to the pretreatment condition.
- Microdontia in 12 and 22 prevented much IPR in the upper arch, in order to be able to finish with an appropriate overjet after the lower extraction.
Requirement for the Technician
- Expansion 16 to 25, sequential distalization 28 and 27
- proclination of upper incisors
- Expansion 36 to 46, 31 extraction of 31; vertical attachments in three remaining lower incisors
- Precision cut for class III elastic. Button cutouts in upper 16 and 27 and precision cut in lower 33 and 43
- Apply a gable bend movement of the root of the incisors during the space closure and a small pontic for the 31
- The patient wore 32 aligners, replaced at 10‐day intervals
- First set of aligners closed the space of the 31 completely, but a set of additional aligners was requested to close black triangles and to increase the final overjet
- The whole treatment lasted 18 months and ended with an excellent parallelism between the roots
- An implant was placed for missing 26
23.1.2 Class I with Lower Crowding and Periodontal Problem Lower Incisor Extraction
A 47‐year‐old woman with a normodivergent skeletal Class I pattern presented with severe lower crowding and a periodontal problem
- Before starting the orthodontic treatment, the patient needed root scaling and planning and periodontal surgery.
- In the maxilla, the periodontal tissue was thin and does not allow much expansion to create space for 12 by proclining and IPR.
- In the lower arch, the treatment plan included 42 extraction in order to create positive overjet.
- Extraction of 42 was chosen because the roots of 43 and 41 were inclined towards the extraction site and only a crown tipping would be necessary to the space closure.
Requirements for the Technician
- Proclination and IPR to make room for 12.
- Anteroposterior limit for proclination 1 mm.
- IPR in early stages to avoid round tripping of incisors.
- Virtual extraction of 42 in aligner 2 and vertical attachment placed in the adjacent teeth of the extraction site, as well as a pontic for the missing lower incisor.
- A gable bend movement of the root is also required during the closure of the space.
- At the end of the treatment, additional overcorrection of the tipping of the roots in the extraction site.
- Patient wore 24 aligners, replaced at 10‐day intervals
- The first set of aligners closed completely the space of the 42
- A set of additional aligners were requested to close black triangles and for settle the occlusion
- The patient was required to use night wear triangular elastic on the posterior zone
- The whole treatment lasted 17 months and resulted in excellent parallelism between the roots on the extraction site
Tips for Incisor Extraction Treatment
- Check before extracting the incisor, for a favourable root position of adjacent incisors toward the extraction site
- Vertical attachments in the other three incisors for tip control during the space closure. Optimized root control attachment might be used in the canines
- Ask the technician to do a simultaneous intrusion + tipping movement of lower incisors to help parallelism of the roots
- ‘Speed of root movement must be half of the maximum permitted’ gable bend movement starting by movement of the root. Ask for 10 degrees of virtual gable bends when closing extraction sites
23.2 Extraction of Premolars
Management of the anchorage and understanding of the biomechanics of extraction space closure are of paramount concern in extraction treatments.
Ideal cases for extracting premolars include:
- Dento‐alveolar protrusion. Proclined incisors where some loss of torque might be acceptable
- Mesially tipped canines with favourable root inclinations adjacent to the extraction sites
- Severe crowding, where excessive IPR would be necessary to solve align the teeth
There are four types of anchorage:
- Absolute anchorage
- Maximum anchorage
- Medium or moderate anchorage
- Minimum anchorage: extraction of second premolars (5s
23.2.1 Absolute Anchorage
This is only achieved when using TADs or implants in the posterior zone. It is possible to create an absolute anchorage situation by ligating the posterior segment to a fixed anchor in basal bone: in this way the posterior segment can be made immovable as an implant, and the entire extraction space can be therefore closed by retraction of the anterior segment.
23.2.2 Maximum Anchorage
This protocol only applies to first premolar extraction treatments where the posterior loss in anchorage must be 2 mm or less to finish in a cusp‐to‐fossae relationship. G6 is automatically applied by the software program in quadrants where the criteria for maximum anchorage are met.
Extractions of First Premolars: Maximum Anchorage (Less Than 2 mm of Posterior Mesialization)
- SmartForce optimized retraction attachments: in canines for retraction and works at the same time as the activation of Smartstage on the aligner
- SmartForce optimized anchorage attachments: 5s/6s and 7s to increase posterior anchorage and works with the Smartstage activations on the aligners
- Smartstage activations on the upper incisors: to prevent bowing effect (extrusion and lingual tipping of upper incisors during closure of extractions) these are in the aligners and not visible in the Clincheck
We cannot place or eliminate any of the activations on the tooth or all the multidental activations will disappear together.
G6 Align Protocol
In the G6 protocol, the canine is first retracted one‐third of the space into the extraction site, while at the same time the posterior segment is mesialized up to a maximum of 2 mm.
- When the canine has distalized one‐third of its total movement, there is a simultaneous retraction of both the canine and the incisors until the extraction site is closed
- The extraction site will not be closed until the end of the treatment
- In order to achieve a maximum anchorage, elastics should be used from the beginning
This protocol was designed by Align Technology to maximize posterior anchorage while maintaining root parallelism during retraction and space closure. It also maintains the incisor torque and prevents the overbite from deepening during incisor retraction.
Medium or Moderate Anchorage
- This is also part solved with G6 protocol, as long as anchorage loss between 2‐5mm
- Mechanics: retraction of anterior teeth and mesialization of posterior teeth to close extraction space
- Staging: reciprocal space closure followed by simultaneous staging
- Closure of the extraction space begins by moving the canines distally at the same time as the second premolar and first molar move mesially until one‐third of the extraction space is closed
- The remaining space will be closed simultaneously from both anterior and posterior
How to Prescribe it