Serial extraction


Serial extraction is the planned extraction of certain deciduous teeth and specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favorable position.

History

In 1929, Kjellgren of Sweden used the term "serial extraction" for the first time. In the 1940s the technique was popularised in the United States by Hayes Nance as “planned and progressive extraction”. Nance is known as the Father of serial extraction in the United States. In 1970 Hotz in Switzerland called it active "supervision of teeth by extraction".

Procedure

There is no fixed technique to be followed while carrying out serial extractions. Careful diagnosis and continuous re-evaluation during the course of treatment is mandatory to achieve required results.
However based on the usual eruption sequence of teeth, deciduous canines are extracted at the age of 8–9 years to create space for proper alignment of incisors, followed by extraction of deciduous first molars a year later so that the eruption of first premolars is accelerated and lastly extraction of the erupting first premolars to give space for the alignment of permanent canines. In some cases a modified technique is followed in which the first premolars are enucleated at the time of extraction of the deciduous first molar. This modification is frequently necessary in the mandibular arch where the canines often erupt before the first premolars.

Selection of suitable extraction procedure

Extracting the primary canines only – it produces rapid self-improvement in incisor crowding and alignment intercepting the development of lingual crossbite of the lateral incisors.
Extracting the first primary molars only – this approach produces the earlier eruption of first premolars but reduces the rapidity and amount of incisor alignment. This is the result of retention of primary canines.
Extracting both primary canines and first molars – this is a compromise between rapid improvement in incisor alignment and the desired early eruption of first premolars. In some cases this sequence results in simultaneous eruption of canines and first premolar, which may cause an increased distal translation of the permanent canines and possible impaction of first premolars.
Enucleation of first premolar buds – it is advocated when first premolar eruption is behind that of canines and second premolars. This allows maximal distal translation of the erupting canines.it is rarely indicated in the maxillary arch.

Indications

Intraoral diagnostic assessment

The diagnosis is based on a thorough case history, clinical examination of the patient, photographs, plaster study models, cephalometric radiographs, panoramic and periapical radiographs.

Growth and development analysis

Periodic growth assessment records should be made in all patients where growth is still going on i.e. made until 14 to 16 year old in girls and 18 to 19 year old in boys.

Functional analysis

Checking various functional movements like swallowing, respiration, speech, opening and closing and excursive movements of the mandible and careful palpation of both temporomandibular jointsis important.

Morphologic assessment

It includes assessment of tooth mass, arch form, arch length, skeletal pattern, skeletal growth potential, orofacial musculature, facial aesthetics, oral habits and hereditary assessment of parents and siblings.
The most favorable morphologic factors for serial extraction include class 1 malocclusion, a favorable morphogenetic pattern – one that does not change, a flush terminal plane or a mesial step relationship of the primary second molars, minimum overjet and minimum overbite.

Space analysis

Assessment of the tooth size – arch length relationship in the mixed dentition determines the presence or absence of any future or existing discrepancy, whether it is crowding or spacing. It involves the prediction of tooth size of the unerupted permanent canines and premolars.
A caliper or a fine line divider is used to measure the combined width of teeth in each segment using study models. The circumferential measurement is made on the plaster cast from mesial aspect of first molar on one side to the mesial aspect of the first molar on the opposite side, and this measurement is recorded. Combined width of the permanent teeth is taken from intraoral radiographs and compared with the available arch length.

Factors to be considered in space analysis