In this month’s Dental Student Guide, Hannah Hook discusses the extraction of first permanent molars in children, including complications, timings and guidelines.
First permanent molars (FPMs) with poor long-term prognosis may require elective extraction at an appropriate time to enable the spaces to be closed orthodontically.
Radiographs should be taken to enable evaluation of the developing dentition. This allows assessment of the presence and positioning of the teeth.
If a general anaesthetic is deemed necessary for the extractions, any primary teeth of poor long-term prognosis should be considered as candidates for balancing/compensating extractions. The aim of these extractions is to preserve the symmetry of the arch and the occlusal relationship.
The following is based on the guidance from the Royal College of Surgeons of England (2014).
Compensating extractions
- This is the extraction of the same tooth from the opposing quadrant in the opposing arch
- Usually recommended for upper FPMs when a lower FPM is planned for extraction
- For example, LR6 is planned for extraction, so a compensating extraction would be the removal of the UR6.
Balancing extractions
- This is the extraction of the same tooth from the opposite side of the same arch
- Balancing extractions are not recommended to preserve a dental centreline
- For example, extraction of the LR6 is planned, so a compensating extraction would be the removal of the LL6.
Considerations
When considering whether FPMs require extraction, the long-term prognosis and overall condition of the remaining FPMs should be assessed.
The presence of the developing dentition should be analysed both clinically and radiographically. Any underlying malocclusions should also be noted.
Treatment planning goals
- Extraction of FPMs should be followed by eruption of second permanent molars (SPMs) to replace them.
Complications
- Particularly in the lower arch, timing of removal of FPMs can influence the eruptive position of SPMs
- Extraction decisions may have to be made before third permanent molar development can be confirmed.
Timings for extractions of first permanent molars
Upper arch
- Where the SPM is unerupted, a good occlusal position can be achieved following removal of the FPM.
Lower arch
- The outcome is much more variable in the lower arch
- The best age for extraction of FPMs is between eight-10 years before the eruption of the SPMs when there is radiographic evidence of bifurcation of the crowns of the SPMs
- Extraction before eight years of age can lead to drifting, tipping, and rotation of the second premolars
- Early extraction can also result in retroclination of the labial segments and in turn an increased overbite
- However, delayed extraction of SPMs can lead to mesial tipping, rotation, spacing and poor occlusal contacts of the SPM.
Guidelines for elective extraction
Class I cases:
Minimal crowding
- FPMs should not be balanced unilaterally with healthy FPMs in either lower or upper arches
- Where a lower FPM is planned for extraction, a compensating extraction of the opposing upper FPM should be considered is poor long-term prognosis
- Should an upper FPM require extraction, a compensation extraction should not be carried out for a healthy lower FPM.
Moderate crowding
- Extraction of FPMs should be carried out at an optimal time to enable good positioning of SPMs and reduce the amount of crowding
- If there is bilateral crowding of buccal segment present, consideration should be given to balancing extractions of contralateral FPMs
- Premolar crowding may be relieved by compensating extractions of the upper FPMs may be considered
- FPM extraction results in minimal spontaneous relief of labial crowding.
Class II cases:
Planning is more difficult for class II than for class I due to the need for space to correct the incisor relationship in the upper arch.
Minimal crowding
- Correction of the buccal segment may be achieved with the use of a functional or removable appliance and head gear should the FPMs require immediate extraction
- If further space is required for the incisors, the loss of two upper premolars may be considered if there is radiographic evidence of the development of third molars
- If the FPMs are able to be temporised or restored, the extraction of them can be delayed until the eruption of the SPMs has occurred
- In patients where all FPMs are sound, extraction of these teeth should be delayed until there is radiographic evidence of third permanent molars.
Crowding
- In patients with crowding there are greater requirements for space
- Where possible any FPMs should be temporised or restored to prolong their life
- Where there is radiographic evidence of third molars, lower FPMs can be extracted at the optimum time, therefore allowing SPM eruption and premolars can be extracted at a later stage
- Extraction of FPMs after the eruption of SPMs is another option, however crowding would need to be corrected with fixed appliances
- Lower FPMs do not usually require balancing or compensating extractions.
Class III cases
- Generally, balancing, and compensating extractions are not recommended.
Key points
- Compensating extractions are the same tooth in the opposing quadrant of the opposing arch (UR6/LR6)
- Balancing extractions are the same tooth on the opposite side of the same arch (UR6/UL6)
- Factors to consider when extraction of a FPM is planned includes the patient’s age, developing dentition, presence/absence of teeth, occlusion and degree of crowding.
References
Cobourne M, Williams A, Harrison M (2014) A guideline for the Extraction of First Permanent Molars in Children: An update of the 2009 Guidelines written by MT Cobourne, A Williams and R McMullen. RCS Eng
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