An Introduction to Orthodontics, 2nd Edition

3. Management of the developing dentition


Many dental practitioners find it difficult to judge when to intervene in a developing malocclusion and when to let nature take its course. This is because experience is only gained over years of careful observation, and decisions to intercede are often made in response to pressure exerted by the parents to do something. It is hoped that this chapter will help impart some of the former, so that the reader is better able to resist the latter.


It is important to realize that normal in this context means average, rather than ideal. An appreciation of what constitutes the range of normal development is essential. One area in which this is particularly pertinent is eruption times (Table 3.1).

3.1.1. Calcification and eruption times

Knowledge of the calcification times of the permanent dentition is invaluable if one wishes to impress patients and colleagues. It is also helpful for assessing dental as opposed to chronological age, for determining whether a developing tooth not present on radiographic examination can be considered absent, and for estimating the timing of any possible causes of localized hypocalcification or hypoplasia (chronological hypoplasia).

3.1.2. The transition from primary to mixed dentition

The eruption of a baby's first tooth is heralded by the proud parents as a major landmark in their child's development. This milestone is described in many baby-care books as occurring at 6 months of age, which can lead to unnecessary concern as it is normal for the mandibular incisors to erupt at any time in the first year. Dental textbooks often dismiss teething, ascribing the symptoms that occur at this time to the diminution of maternal antibodies. Any parent will be able to correct this fallacy!

Eruption of the primary dentition (Fig. 3.1) is usually completed around 3 years of age. The deciduous incisors erupt upright and spaced a lack of spacing strongly suggests that the permanent successors will be crowded. Overbite reduces throughout the primary dentition until the incisors are edge to edge, which can contribute to marked attrition.

The mixed dentition phase is usually heralded by the eruption of either the first permanent molars or the lower central incisors. The lower labial segment teeth erupt before their counterparts in the upper arch and develop lingual to their predecessors. It is usual for there to be some crowding of the permanent lower incisors as they emerge into the mouth, which reduces with intercanine growth. As a result the lower incisors often erupt slightly lingually placed and/or rotated (Fig. 3.2), but will usually align spontaneously if space becomes available. If the arch is inherently crowded, this space shortage will not resolve with intercanine growth.

Fig. 3.1. Primary dentition.

Table 3.1 Average calcification and eruption times


Calcification commences (weeks in utero)

Eruption (months)

Primary dentition

Central incisors



Lateral incisors






First molars



Second molars



Root calcification complete 11˝ years after eruption


Calcification commences (months)

Eruption (years)

Permanent dentition

Mand. central incisors



Mand. lateral incisors



Mand. canines



Mand. first premolars



Mand. second premolars



Mand. first molars

Around birth


Mand. second molars



Mand. third molars



Max. central incisors



Max. lateral incisors



Max. canines



Max. first premolars



Max. second premolars



Max. first molars

Around birth


Max. second molars



Max. third molars



Root calcification complete 23 years after eruption

The upper permanent incisors also develop lingual to their predecessors. Additional space is gained to accommodate their greater width because they erupt onto a wider arc and are more proclined than the primary incisors. If the arch is intrinsically crowded, the lateral incisors will not be able to move labially following eruption of the central incisors and therefore may erupt palatal to the arch. Pressure from the developing lateral incisor often gives rise to spacing between the central incisors which resolves as the laterals erupt. They in turn are tilted distally by the canines lying on the distal aspect of their root. This latter stage of development used to be described as the ugly duckling stage of development (Fig. 3.3), although it is probably diplomatic to describe it as normal dental development to concerned parents. As the canines erupt, the lateral incisors usually upright themselves and the spaces close. The upper canines develop palatally, but migrate labially to come to lie slightly labial and distal to the root apex of the lateral incisors. In normal development they can be palpated buccally from as young as 8 years of age.

Fig. 3.2. Crowding of the labial segment reducing with growth in intercanine width: (a), (b), (c) age 8 years; (d), (e), (f) age 9 years.







The combined width of the deciduous canine, first molar, and second molar is greater than that of their permanent successors, particularly in the lower arch. This difference in widths is called the leeway space (Fig. 3.4) and in general is of the order of 11.5 mm in the maxilla and 22.5 mm in the mandible (in Caucasians). This means that if the deciduous buccal segment teeth are retained until their normal exfoliation time, there will be sufficient space for the permanent canine and premolars.

The deciduous second molars usually erupt with their distal surfaces flush anteroposteriorly. The transition to the stepped Class I molar relationship occurs during the mixed dentition as a result of differential mandibular growth and/or the leeway space.

Fig. 3.3. ‘Ugly duckling’ stage.

Fig. 3.4. Leeway space.

3.1.3. Development of the dental arches

Intercanine width is measured across the cusps of the deciduous/permanent canines, and during the primary dentition an increase of around 12 mm is seen. In the mixed dentition an increase of about 3 mm occurs, but this growth is largely completed around a developmental stage of 9 years with some minimal increase up to age 13. After this time a gradual decrease is the norm.

Arch width is measured across the arch between the lingual cusps of the second deciduous molars or second premolars. Between the ages of 3 and 18 years an increase of 23 mm occurs; however, for clinical purposes arch width is largely established in the mixed dentition.

Arch circumference is determined by measuring around the buccal cusps and incisal edges of the teeth to the distal aspect of the second deciduous molars or second premolars. On average, there is little change with age in the maxilla; however, in the mandible arch circumference decreases by about 4 mm because of the leeway space. In individuals with crowded mouths a greater reduction may be seen.

In summary, on the whole there is little change in the size of the arch anteriorly after the establishment of the primary dentition, except for an increase in intercanine width which results in a modification of arch shape. Growth posteriorly provides space for the permanent molars, and considerable appositional vertical growth occurs to maintain the relationship of the arches during vertical facial growth.


3.2.1. Screening

Early detection of any abnormalities in tooth development and eruption is essential to give the opportunity for interceptive action to be taken. This requires careful observation of the developing dentition for evidence of any problems, for example deviations from the normal sequence of eruption. If an abnormality is suspected then further investigation including radiographs is indicated. Around 9 to 10 years of age it is important to palpate the buccal sulcus for the permanent maxillary canines in order to detect any abnormalities in the eruption path of this tooth.

3.2.2. Natal teeth

A tooth, which is present at birth, or erupts soon after, is described as a natal tooth. These most commonly arise anteriorly in the mandible and are typically a lower primary incisor, which has erupted prematurely (Fig. 3.5). Because root formation is not complete at this stage, natal teeth can be quite mobile, but they usually become firmer relatively quickly. If the tooth (or teeth) interferes with breast feeding or is so mobile that there is a danger of inhalation, removal is indicated and this can usually be accomplished with topical anaesthesia. If the tooth is symptomless, it can be left in situ.

Fig. 3.5. Natal tooth present at birth.

3.2.3. Eruption cyst

An eruption cyst is caused by an accumulation of fluid or blood in the follicular space overlying the crown of an erupting tooth (Fig. 3.6). They usually rupture spontaneously, but very occasionally marsupialization may be necessary.

Fig. 3.6. Eruption cyst.

3.2.4. Failure of/delayed eruption

There is a wide individual variation in eruption times, which is illustrated by the patients in Fig. 3.7. Where there is a generalized tardiness in tooth eruption in an otherwise fit child, a period of observation is indicated. However, the following may be indicators of some abnormality and therefore warrant further investigation (Fig. 3.8):

·     A disruption in the normal sequence of eruption.

·     An asymmetry in eruption pattern between contralateral teeth. If a tooth on one side of the arch has erupted and 6 months later there is still no sign of its equivalent on the other side, radiographic examination is indicated.

Fig. 3.7. (a) Normal variation in eruption times: (a) patient aged 12.5 years with deciduous canines and molars still present; (b), (c) patient aged nine years with all permanent teeth to the second molars erupted.




Table 3.2 Causes of delayed eruption

Generalized causes
Hereditary gingival fibromatosis
Down syndrome
Cleidocranial dysostosis
Cleft lip and palate
Localized causes
Congenital absence
Delayed exfoliation of primary predecessor
Supernumerary tooth (see below)
Abnormal position of crypt
Primary failure of eruption

Fig. 3.8. Disruption of normal eruption sequence as 21/2 erupted, but /1 unerupted.


3.3.1. Premature loss of deciduous teeth

Balancing extraction is the removal of the contralateral tooth. Compensating extraction is the removal of the equivalent opposing tooth.

The major effect of early loss of a primary tooth, whether due to caries, premature exfoliation, or planned extraction, is localization of pre-existing crowding. In an uncrowded mouth this will not occur. However, where some crowding exists and a primary tooth is extracted, the adjacent teeth will drift or tilt around into the space provided. The extent to which this occurs depends upon the degree of crowding, the patient's age, and the site. Obviously, as the degree of crowding increases so does the pressure for the remaining teeth to move into the extraction space. The younger the child is when the primary tooth is extracted, the greater is the potential for drifting to ensue. The effect of the site of tooth loss is best considered by tooth type, but it is important to bear in mind the increased potential for mesial drift in the maxilla.

·     Deciduous incisor: premature loss of a deciduous incisor has little impact, mainly because they are shed relatively early in the mixed dentition.

·     Deciduous canine: unilateral loss of a primary canine in a crowded mouth will lead to a centreline shift (Fig. 3.9). As this is a difficult problem to treat, often requiring fixed appliances, prevention is preferable and therefore premature loss of a deciduous canine should be balanced in any patient with even the mildest crowding.

·     Deciduous first molar: unilateral loss of this tooth may result in a centre-line shift. In most cases an automatic balancing extraction is not necessary, but the centreline should be kept under observation and, if indicated, a tooth on the opposite side of the arch removed.

·     Deciduous second molar: if a second primary molar is extracted the first permanent molar will drift forwards (Fig. 3.10). This is particularly marked if loss occurs before the eruption of the permanent tooth and for this reason it is better, if at all possible, to try to preserve the second deciduous molar at least until the first permanent molar has appeared. In most cases balancing or compensating extractions of other sound second primary molars is not necessary. However, where extraction of a carious upper deciduous molar alone would change the molar relationship from a half-unit Class II to a full Class II, it may be advisable to consider balancing with the extraction of the lower second deciduous molar.

Fig. 3.9. Centre-line shift to patient's left owing to early unbalanced loss of lower left deciduous canine.

Fig. 3.10. Loss of a lower second deciduous molar leading to forward drift of first permanent molar.

It should be emphasized that the above are suggestions, not rules, and at all times a degree of common sense and forward planning should be applied. For example, if extraction of a carious first primary molar is required and the contralateral tooth is also doubtful, then it might be preferable in the long term to extract both. Also, in children with an absent permanent tooth (or teeth) early extraction of the primary buccal segment teeth may be advantageous to encourage forward movement of the first permanent molars if space closure (rather then space opening) is planned.

The effect of early extraction of a primary tooth on the eruption of its successor is variable and will not necessarily result in a hastening of eruption.

3.3.2. Retained deciduous teeth

A difference of more than 6 months between the shedding of contralateral teeth should be regarded with suspicion. Provided that the permanent successor is present, retained primary teeth should be extracted, particularly if they are causing deflection of the permanent tooth (Fig. 3.11).

Fig. 3.11. Retained primary tooth contributing to deflection of the permanent successor.

3.3.3. Infra-occluded (submerged) primary molars

Infra-occlusion is now the preferred term for describing the process where a tooth fails to achieve or maintain its occlusal relationship with adjacent or opposing teeth. Most infra-occluded deciduous teeth erupt into occlusion, but subsequently become submerged because bony growth and development of the adjacent teeth continues (Fig. 3.12). Estimates vary, but this anomaly would appear to occur in around 19 per cent of children.

Resorption of the primary teeth is not a continuous process. In fact, resorption is interchanged with periods of repair, although in most cases the former prevails. If a temporary predominance of repair occurs this can result in ankylosis and infra-occlusion of the affected primary molar.

Fig. 3.12. Ankylosed primary molars.

The results of recent epidemiological studies have suggested a genetic tendency to this phenomenon and also an association with other dental anomalies including ectopic eruption of first permanent molars, palatal displacement of maxillary canines, and congenital absence of premolar teeth. Therefore, it is advisable to be vigilant in patients exhibiting any of these features.

Where a permanent successor exists the phenomenon is usually temporary, and studies have shown no difference in the age at exfoliation of a submerged primary molar compared with an unaffected contralateral tooth. Therefore extraction of a submerged primary tooth is only necessary under the following conditions:

·     There is a danger of the tooth disappearing below gingival level (Fig. 3.13).

·     Root formation of the permanent tooth is nearing completion (as eruptive force reduces markedly after this event).

·     The permanent successor is missing, as in this situation the submergence may be progressive.

Fig. 3.13. Marked submergence of deciduous molar (with second premolar affected).

3.3.4. Impacted first permanent molars

Impaction of a first permanent molar tooth against the second deciduous molar occurs in approximately 26 per cent of children and is indicative of crowding. It most commonly occurs in the upper arch (Fig. 3.14). Spontaneous disimpaction may occur, but this is rare after 8 years of age. Mild cases can sometimes be managed by tightening a brass separating wire around the contact point between the two teeth over a period of about 2 months. This can have the effect of pushing the permanent molar distally, thus letting it jump free. In more severe cases the impaction can be kept under observation, although extraction of the deciduous tooth may be indicated if it becomes abscessed or the permanent tooth becomes carious and restoration precluded by poor access. The resultant space loss can be dealt with in the permanent dentition.

3.3.5. Dilaceration

Dilaceration is a distortion or bend in the root of a tooth.


There appear to be two distinct aetiologies:

·     Developmental this anomaly usually affects an isolated central incisor and occurs in females more often than males. The crown of the affected tooth is turned upward and labially and no disturbance of enamel and dentine is seen (Fig. 3.15).

·     Trauma intrusion of a deciduous incisor leads to displacement of the underlying developing permanent tooth germ. Characteristically, this causes the developing permanent tooth crown to be deflected palatally, and the enamel and dentine forming at the time of the injury are disturbed, giving rise to hypoplasia. The sexes are equally affected and more than one tooth may be involved depending upon the extent of the trauma.

Fig. 3.14. Impacted bilateral upper first permanent molars.

Fig. 3.15. A dilacerated central incisor.


Dilaceration usually causes failure of eruption. Where the dilaceration is severe there is often no alternative but to remove the affected tooth. In milder cases it may be possible to expose the crown surgically and apply traction to align the tooth, provided that the root apex will be sited within cancellous bone at the completion of crown alignment.

3.3.6. Supernumerary teeth

A supernumerary tooth is one that is additional to the normal series. This anomaly occurs in the permanent dentition in approximately 2 per cent of the population and in the primary dentition in less than 1 per cent, though a super-numerary in the deciduous dentition is often followed by a supernumerary in the permanent dentition. The aetiology is not completely understood, but suggestions include an offshoot of the dental lamina of the permanent dentition or a tertiary dentition. This anomaly occurs more commonly in males than females. Supernumerary teeth are also commonly found in the region of the cleft in individuals with a cleft of the alveolus.

Supernumerary teeth can be described according to their morphology or position in the arch.

Fig. 3.16. A supplemental lower lateral incisor.


·     Supplemental: this type resembles a tooth and occurs at the end of a tooth series, for example an additional lateral incisor, second premolar, or fourth molar (Fig. 3.16).

·     Conical: the conical or peg-shaped supernumerary most often occurs between the upper central incisors (Fig. 3.17). It is said to be more commonly associated with displacement of the adjacent teeth, but can also cause failure of eruption or have no effect at all.

·     Tuberculate: this type is described as being barrel-shaped, but usually any supernumerary which does not fall into the conical or supplemental categories is included. Classically, this type is associated with failure of eruption (Fig. 3.18).

·     Odontome: This variant is rare. Both compound and complex forms have been described.

Fig. 3.17. Two conical supernumeraries lying between 1/1 with /A retained.


Supernumerary teeth can occur within the arch, but when they develop between the central incisors they are often described as a mesiodens. A supernumerary tooth distal to the arch is called a distomolar, and one adjacent to the molars is known as a paramolar.

Effects of supernumerary teeth and their management

Failure of eruption

The presence of a supernumerary tooth is the most common reason for the non-appearance of a maxillary central incisor. However, failure of eruption of any tooth in either arch can be caused by a supernumerary.

Management of this problem involves removing the supernumerary tooth and ensuring that there is sufficient space to accommodate the unerupted tooth in the arch. If the tooth does not erupt spontaneously within 1 year, then a second operation to expose it and apply orthodontic traction may be required. Management of a patient with this problem is illustrated in Fig. 3.19.

Fig. 3.18. A tuberculate supernumerary lying occlusal to 2/.


The presence of a supernumerary tooth can be associated with displacement or rotation of an erupted permanent tooth (Fig. 3.20). Management involves firstly removal of the supernumerary, usually followed by fixed appliances to align the affected tooth or teeth. It is said that this type of displacement has a high tendency to relapse following treatment, but this may be a reflection of the fact that the malposition is usually in the form of a rotation or an apical displacement which are particularly liable to relapse.

Fig. 3.19. (a) Management of a patient with failure of eruption of the upper central incisors owing to the presence of two supernumerary teeth: (a) patient on presentation aged 10 years; (b) radiograph showing unerupted central incisors and associated conical supernumerary teeth; (c) following removal of the supernumerary teeth a URA was fitted to open space for the central incisors, until 1/ erupted 10 months later; (d) 7 months later /1 erupted and a second URA with a buccal spring was used to align /1; (e) occlusion 3 years after initial presentation.






Fig. 3.20. Displacement of 1/1 caused by two erupted conical supernumerary teeth.

Fig. 3.21. Crowding due to the presence of two supplemental upper lateral incisors.


This is caused by the supplemental type and is treated by removing the most poorly formed or more displaced tooth (Fig. 3.21).

No effect

Occasionally a supernumerary tooth (usually of the conical type) is detected as a chance finding on a radiograph of the upper incisor region (Fig. 3.22). Provided that the extra tooth will not interfere with any planned movement of the upper incisors, it can be left in situ under radiographic observation. In practice these teeth usually remain symptomless and do not give rise to any problems.

Fig. 3.22. Chance finding of a supernumerary on routine radiographic examination.



3.3.7. Habits

The effect of a habit will depend upon the frequency and intensity of indulgence. This problem is discussed in greater detail in Chapter 9, Section 9.1.4.

3.3.8. First permanent molars of poor long-term prognosis

Treatment planning for a child with poor-quality first permanent molars is always difficult because several competing factors have to be considered before a decision can be reached for a particular individual. First permanent molars are never the first tooth of choice for extraction as their position within the arch means that little space is provided anteriorly for relief of crowding or correction of the incisor relationship unless appliances are used. Removal of maxillary first molars often compromises anchorage in the upper arch, and a good spontaneous result in the lower arch following extraction of the first molars is rare. However, patients for whom enforced extraction of the first molars is required are often the least able to support complicated treatment. Finally, it has to be remembered that, unless the caries rate is reduced, the premolars may be similarly affected a few years later. Nevertheless, if a two-surface restoration is present or required in the first permanent molar of a child, the prognosis for that tooth and the remaining


first molars should be considered as the planned extraction of first permanent molars of poor quality may be preferable to their enforced extraction later on (Fig. 3.23).

Fig. 3.23. All four first permanent molars were extracted in this patient because of the poor long-term prognosis for 6 and /6.

Factors to consider when assessing first permanent molars of poor long-term prognosis

It is impossible to produce hard and fast rules regarding the extraction of first permanent molars, and therefore the following should only be considered a starting point:

·     Check for the presence of all permanent teeth. If any are absent, extraction of the first permanent molar in that quadrant should be avoided.

·     If the dentition is uncrowded, extraction of first permanent molars should be avoided as space closure will be difficult.

·     Remember that in the maxilla there is a greater tendency for mesial drift and so the timing of the extraction of upper first permanent molars is less critical.

·     In the lower arch a good spontaneous result is more likely if:

a. the lower second permanent molar has developed as far as its bifurcation;

b. the angle between the long axis of the crypt of the lower second permanent molar and the first permanent molar is between 15° and 30°;

c.  the crypt of the second molar overlaps the root of the first molar (a space between the two reduces the likelihood of good space closure).

·     Extraction of the first molars will relieve buccal segment crowding, but will have little effect on a crowded labial segment.

·     If space is needed anteriorally for the relief of labial segment crowding or for retraction of incisors (i.e. the upper arch in Class II cases or the lower arch in Class III cases), then it may be prudent to delay extraction of the first molar, if possible, until the second permanent molar has erupted in that arch. The space can then be utilized for correction of the labial segment.

·     Serious consideration should be given to extracting the opposing upper first permanent molar, should extraction of a lower molar be necessary. If the upper molar is not extracted it will over-erupt and prevent forward drift of the lower second molar (Fig. 3.24).

·     A compensating extraction in the lower arch (when extraction of an upper first permanent molar is necessary) should be avoided where possible as a good spontaneous result in the mandibular arch is less likely.

·     Impaction of the third permanent molars is less likely, but not impossible, following extraction of the first molar.

Fig. 3.24. Over-eruption of 6/ preventing forward movement of the lower right second permanent molar.

3.3.9. Median diastema


Median diastema occurs in 98 per cent of 6-year-olds, 49 per cent of 11-year-olds, and 7 per cent of 1218-year-olds.


Factors, which have been considered to lead to a median diastema include the following:

·     physiological (normal dental development)

·     small teeth in large jaws (a spaced dentition)

·     missing teeth

·     midline supernumerary tooth/teeth

·     proclination of the upper labial segment

·     prominent fraenum.

Fig. 3.25. Patient with missing 2/2 and a median diastema with a low fraenal attachment.

A median diastema is normally present between the maxillary permanent central incisors when they first erupt. As the lateral incisors and then the canines emerge the diastema usually closes. Therefore a midline diastema is a normal feature of the developing dentition; however, if it persists after eruption of the canines, it is unlikely that it will close spontaneously.

In the deciduous dentition the upper midline fraenum runs between the central incisors and attaches into the incisive papilla area. However, as the central incisors move together with eruption of the lateral incisors, it tends to migrate round onto the labial aspect. In a spaced upper arch, or where the upper lateral incisors are missing (Fig. 3.25), this recession of the fraenal attachment is less likely to occur and in such cases it is obviously not appropriate to attribute the persistence of a diastema to the fraenum itself. However, in a small proportion of cases the upper midline fraenum can contribute to the persistence of a diastema. Factors, which may indicate that this is the case include the following:

·     When the fraenum is placed under tension there is blanching of the incisive papilla.

·     Radiographically, a notch can be seen at the crest of the interdental bone between the upper central incisors (Fig. 3.26).

·     The anterior teeth may be crowded.

Fig. 3.26. Notch in interdental bone between 1/1 associated with a fraenal insertion running between 1/1 into the incisive papilla.


It is advisable to take a periapical radiograph to exclude the presence of a midline supernumerary tooth prior to planning treatment for a midline diastema.

In the developing dentition a diastema of less than 3 mm rarely warrants intervention; in particular, extraction of the deciduous canines should be avoided as this will tend to make the diastema worse. However, if the diastema is greater than 3 mm and the lateral incisors are present, it may be necessary to consider appliance treatment to approximate the central incisors to provide space for the laterals and canines to erupt. However, care should be taken to ensure that the roots of the teeth being moved are not pressed against any unerupted crowns as this can lead to root resorption. If the crowns of the teeth are tilted distally, an upper removable appliance (URA) can be used to approximate the teeth, but fixed appliances are required for bodily movement. Closure of a diastema has a notable tendency to relapse, therefore long-term retention is required. This is most readily accomplished by placement of a bonded retainer.


Serial extraction was first advocated in 1948 by Kjellgren, a Swedish orthodontist, as a solution to a shortage of orthodontists. Kjellgren hoped that his scheme would facilitate the treatment of patients with straightforward crowding by their own dentists, thus minimizing demands upon the orthodontic service. He suggested the employment of a planned sequence of extractions designed to allow crowded incisor segments to align spontaneously during the mixed dentition by shifting labial segment crowding to the buccal segments where it could be dealt with by premolar extractions.

3.4.1. Classical technique

·     Extraction of the deciduous canines, as the lateral incisors were are erupting. This step was designed to allow the incisors to align.

·     Extraction of the first deciduous molars when their roots were approximately half resorbed. The purpose of this was is to hasten the eruption of the first premolars.

·     Extraction of the first premolars on eruption.

3.4.2. Pitfalls and disadvantages

·     This approach involves putting the child through several sequences of extractions.

·     As intercanine growth continues up to around 13 years of age, it is difficult to assess accurately how crowded a child's teeth will actually be at the stage when serial extraction is usually embarked upon.

·     Extraction of the deciduous canines and first molars will allow forward drift of the buccal segment teeth and an effective increase in anterior crowding. This may be unhelpful in a child with severe crowding.

·     Extraction of lower deciduous canines may result in the lower incisors tilting lingually, causing an increase in overbite. Therefore serial extraction should be avoided in Class II division 2 cases.

·     Appliance therapy may still be required.

3.4.3. Conclusion

The technique of serial extraction can produce a nice result in carefully selected cases, namely Class I with moderate crowding and all permanent teeth present in a good position, but often this type of case also responds well to extraction of the first premolars upon eruption. Omitting the deciduous extractions removes some of the potential pitfalls and diminishes the guesswork involved, and, most importantly, reduces the number of extractions required.

3.4.4. Indications for the extraction of deciduous canines

Nevertheless there are a number of occasions where the timely extraction of the deciduous canines may avoid more complicated treatment later:

·     In a crowded upper arch the erupting lateral incisors may be forced palatally. In a Class I malocclusion this will result in a crossbite and in addition the apex of an affected tooth will be palatally positioned, making later correction more difficult. Extraction of the deciduous canines whilst the lateral incisors are erupting often results in their being able to escape spontaneously into a better position.

·     In a crowded lower labial segment one incisor may be pushed through the labial plate of bone, resulting in a compromised labial periodontal attachment. Relief of crowding by extraction of the lower deciduous canines usually results in the lower incisor moving back into the arch and improves periodontal support (Fig. 3.27).

·     Extraction of the lower deciduous canines in a Class III malocclusion can be advantageous (Fig. 3.28).

·     To provide space for appliance therapy in the upper arch, for example correction of an instanding lateral incisor, or to facilitate eruption of a incisor prevented from erupting by a supernumerary tooth.

·     To improve the position of a displaced permanent canine (see Chapter 14).

Fig. 3.27. (a) In this patient all four deciduous canines were extracted to relieve the labial segment crowding; (b) note how the periodontal condition of the lower right central incisor has improved six months later(b)



Fig. 3.28. (a) Class III prior to extraction of the lower deciduous canines; (b) same patient 13 months later.




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