The orthodontic patient: treatment planning

7 The orthodontic patient

treatment planning

One of the most difficult, but important aspects of orthodontic management is treatment planning. With the advent of modern fixed appliance systems it is deceptively easy to straighten teeth. The skill of the orthodontist lies in placing the dentition in the optimal position and achieving the correct aesthetic and occlusal result for each patient. This process starts with clinical examination, record collection and diagnosis. The next stage is treatment planning, which should ideally be carried out in a formal manner and away from the patient, using the clinical data and collected records. It is a two-stage process, initially defining the treatment aims and then deciding how these are to be achieved. In this chapter, treatment aims and the general principles of treatment planning are discussed. The specifics of treatment for different types of malocclusion are covered in Chapters 10 and 11.

Timing of treatment

Many traits of a malocclusion can manifest in the early mixed dentition and there is often a temptation to begin treatment at this stage. In particular, both ‘arch development’ (or expansion) to relieve crowding and growth modification to correct a skeletal discrepancy have been proposed by some to benefit from an early approach.

Advocates of these early treatment strategies suggest that they maximize growth potential, compliance and orthopedic change in the young patient, reduce the risk of trauma when maxillary incisors are prominent, simplify any further treatment that may be required in the permanent dentition, reduce the need for extractions and ultimately establish a more stable result. They can also have a psychological benefit, promoting self-esteem by correcting potentially socially debilitating malocclusions early.

However, there are disadvantages associated with starting treatment too soon. The overall duration will be extended, because almost inevitably a second phase of treatment will be required in the permanent dentition and this can lead to problems with compliance over the longer term. The original arch form and growth patterns will tend to reimpose themselves following the first phase of early treatment and a prolonged retention period may be required to maintain any correction during the transition from mixed to permanent dentition. Finally, there is a growing body of evidence to suggest that the treatment result for growth modification will be the same whether carried out in the early mixed or permanent dentition, the only difference being the increased duration if started early (Harrison et al, 2007). In the case of arch development in the early mixed dentition, the long-term results are poor, particularly with regard to the stability of tooth alignment (Little et al, 1990).

The most appropriate time to start treatment aimed at growth modification is usually the late mixed dentition, essentially just before loss of the second deciduous molars. This results in the shortest treatment time, whilst still utilizing growth potential and is least demanding upon compliance. The majority of routine orthodontic treatment with fixed appliances is carried out in the early permanent dentition and this is generally the best time to address problems of crowding. However, there are exceptions and some malocclusions will benefit from earlier treatment:

• Class III cases associated with maxillary hypoplasia can benefit from interceptive treatment to move the maxilla forward with protraction headgear. This appears to be more effective if carried out in the early mixed dentition (see Figs 10.45 and 10.46) (Kim et al, 1999).

• Treatment to correct a class II skeletal base relationship is most effective during the adolescent growth spurt. In females, this will generally occur earlier than in males and is poorly correlated with dental age. Therefore, this type of treatment should often be started earlier in females than males.

• Certain malocclusions, especially an increased overjet, can be a source of teasing and bullying, which can be very distressing. In these circumstances, early treatment may be indicated.

• An increased overjet increases the risk of dentoalveolar trauma, especially before the age of ten. Early treatment to reduce the overjet is indicated in those individuals where little protection is provided by the lips, due to gross lip incompetence and marked maxillary protrusion.

• Early treatment of a posterior crossbite associated with a displacement can prevent perpetuation into the permanent dentition (Harrison & Ashby, 2001). An anterior crossbite can result in mucogingival problems associated with the lower incisors (see Fig. 10.42). Both these forms of malocclusion are amendable to simple removable appliance treatment in the early mixed dentition.

Aims of treatment

The principle aims of orthodontic treatment relate to aesthetics and function:

• Positioning the dentition within the skeletal and soft tissue environment for optimal facial and dental aesthetics; and

• Achieving a stable and ideal static, and functional occlusion.

The extent to which these aims need to be considered will vary between patients and depend upon the diagnosis. The treatment required to achieve them may range from simple occlusal change to complex multidisciplinary intervention.

Facial aims

There is a greater awareness amongst orthodontists of the importance associated with facial and soft tissue aesthetics in treatment planning (Box 7.1). Obtaining a class I incisor and canine relationship is usually a fundamental aim of treatment, but this must not be achieved at the expense of the soft tissue profile. Reconciling the facial and occlusal aims of treatment can be difficult and will depend in part on the underlying skeletal relationship:

• In the absence of any significant discrepancy in the skeletal pattern, treatment planning will be concerned primarily with obtaining the correct occlusal relationship (Fig. 7.1).

• If there is a mild to moderate skeletal discrepancy, appliances aimed at growth modification can be used in an attempt to improve the skeletal relationship. These appliances tend to rely on good patient compliance combined with favourable facial growth, results can be variable and they are much more effective at correcting class II discrepancies than class III. Alternatively, orthodontic camouflage may be appropriate, accepting the skeletal pattern and planning the necessary occlusal changes to correct the malocclusion (Fig. 7.2) (Box 7.2).

• If the skeletal discrepancy is severe and the patient is growing, growth modification should certainly be considered, but success will be less predictable. However, orthodontic camouflage in these cases can be more problematic, particularly in terms of achieving good facial aesthetics. Surgical repositioning of the jaws is a definitive method of changing a more severe skeletal pattern, but this is only carried out once facial growth is complete. Attempts have been made to define the relative limits of orthodontic and surgical tooth movement for the correction of malocclusion, but these can only ever represent a guide (Fig. 7.3).

Box 7.1 Planning treatment around the face

Orthodontic treatment planning should begin with the position of the dentition, particularly the upper incisors, within the face. This represents something of a shift in emphasis from planning based around the lower incisor position and treating to isolated static occlusal goals.

In the infancy of orthodontics it was assumed that if all the teeth were aligned and the occlusal goals achieved, each individual would have ideal facial aesthetics. However, it soon become apparent that this was not the case, resulting in extreme protrusion of the dentition in some cases and extensive relapse in others. With the advent of cephalometric analysis, it was argued that facial growth was genetically determined and that orthodontic treatment could have little influence on the facial skeleton. Treatment became based around arbitrary hard tissue cephalometric standards, especially in relation to lower incisor position, even though these bear little relation to the soft tissues and facial profile (Park & Burstone, 1986). Since then, conventional thinking has shifted again, with the soft tissues defining the limits of orthodontic treatment in each individual (Ackerman & Proffit, 1997). The main reasons for this are a resurgence of interest in functional appliance therapy, advances in orthognathic surgical techniques, a greater understanding of orthodontic relapse and the acceptance of long-term retention strategies. There is also an appreciation of how the face ages and therefore how treatment carried out in the teenage years will impact on facial appearance many years into the future.

Figure 7.1 Occlusal correction of a crowded class I case using fixed appliances following the extraction of four first premolar teeth.

Figure 7.2 Correction of class II division 1 malocclusion.

A case with a moderate class II skeletal base relationship treated initially with a functional appliance to correct the anteroposterior discrepancy. This was followed by the extraction of four premolars to alleviate crowding and fixed appliances to detail the occlusion (upper four panels). A case with a milder skeletal discrepancy treated with orthodontic camouflage involving premolar extraction and fixed appliances (lower two panels).

Box 7.2 Camouflage treatment

In a young patient with a class II skeletal discrepancy, utilizing growth with a functional appliance can facilitate treatment, which is not possible in an older patient or adult, where growth potential either is poor or has disappeared. In these cases there are two treatment options: surgically repositioning the jaws or moving the teeth to mask the skeletal discrepancy. The latter is known as camouflage treatment and can be very successful in mild to moderately severe skeletal class II cases. One of the main limiting factors in this type of treatment is the soft tissue profile, as treatment will involve retraction of the upper incisors and with them, the upper lip. If the upper lip is protrusive, some retraction will be beneficial to the profile. However, if the lip profile is retrusive and the nasolabial angle obtuse, any further retraction will increase prominence of the nose and worsen aesthetics. Similarly, over-retraction of the lower incisors to camouflage a class III skeletal discrepancy can result in unacceptable prominence of the chin. Therefore, when planning camouflage treatment, although it may be possible to achieve a good occlusal result, it should not be done at the expense of facial aesthetics. Generally the more severe the skeletal discrepancy, the harder it is to achieve camouflage with tooth movement alone.

Figure 7.3 The envelope of discrepancy showing the tooth movements theoretically possible for correcting a malocclusion.

With the ideal position shown at the origin of the x and y axes, the movement possible with orthodontics alone (inner black envelope), growth modification (middle red envelope) and surgery (outer red envelope) are shown.

Redrawn from Proffit WR, White RP Jr and Sarver DM (2003). Contemporary Treatment of Facial Deformity (St Louis: Mosby).

Occlusal aims

The occlusal aims of treatment are defined in terms of dental aesthetics and both static and functional occlusion (Table 7.1) and are generally listed in the order in which they will be corrected. Whilst these will vary between cases, in practical terms occlusal correction will usually require some or all of the following:

• Creating space to relieve crowding;

• Levelling and aligning the dental arches;

• Correcting the buccal segment relationship; and

• Correcting the incisor relationship.

Table 7.1 Occlusal aims of orthodontic treatment

• Andrews six keys;

• Canine guidance or group function;

• No non-working side interferences;

• Anterior guidance; and

• RCP and ICP coincident.

A further consideration related to the occlusion is health of the temporomandibular joints, but this is a contentious area. Despite evidence showing orthodontic treatment having little impact on temporomandibular dysfunction (Luther, 2007a, b), much conjecture exists regarding the ideal position for the condyle at the end of treatment and the need to treat to an ideal functional occlusion. However, orthodontics is one area in dentistry where treatment can result in significant occlusal change. Therefore it would seem sensible practice to aim for an ideal static and functional occlusion wherever possible.

Planning to achieve the facial aims of treatment

Treatment planning should begin with some consideration regarding the upper incisor position and whether this needs to be changed (Table 7.2). Achieving an ideal position for these teeth will be more difficult in the presence of a skeletal discrepancy and in some cases may not be possible with orthodontic treatment alone.

Table 7.2 Positioning the upper incisors within the face

• Vertically around 3–4 mm of the upper central incisors should be shown at rest;

• The labial face should be parallel to the true vertical and adequately support the upper lip;

• Curvature of the incisal edges should be parallel with the lower lip on smiling; and

• The dental centreline should be coincident with the facial midline.

Anteroposterior position of the upper incisors

The upper incisors can be positioned too far forward within the face as a result of maxillary skeletal excess or simple dentoalveolar disproportion. The skeletal and soft tissue morphology will influence the resulting incisor relationship:

• The overjet can be increased, resulting in a class II division 1 relationship. The upper incisors are normally inclined or proclined. If they are proclined this is often due to the position of the lower lip or a digit sucking habit.

• The upper incisors can be retroclined, resulting in a class II division 2 relationship with an increased overbite, which is usually due to a high lower lip position (see Fig. 1.8).

In a growing child with skeletal maxillary excess, restraint of maxillary growth can be achieved with extraoral force, although the use of a functional appliance can also provide some maxillary restraint, particularly when used in combination with headgear. Any associated mandibular retrognathia is indicative of the need for a functional appliance.

Alternatively, the position of the maxilla can be accepted and orthodontic camouflage carried out to retract the upper incisors into a class I occlusion, by either tipping or bodily movement, depending upon their position. In many cases, space will be required to facilitate this movement and this can be achieved by retraction of the buccal segments using headgear or by extractions.

Conversely, the upper incisors can be positioned too far back within the face, resulting in a class III relationship. This can again be associated with dentoalveolar disproportion but is more commonly due to skeletal maxillary deficiency. A patient in the mixed dentition with marked maxillary deficiency may be a candidate for attempted growth modification to improve the maxillary position. This will require extraoral force to the maxilla provided by a facemask and reverse headgear. A rapid improvement in the incisor relationship can be achieved using this type of treatment; however, it requires excellent cooperation and the subsequent pattern of facial growth will significantly influence long-term stability of any change achieved (see Figs 10.45 and 10.46).

A class III incisor relationship can also be associated with mandibular excess, either alone or in combination with maxillary deficiency. These cases are even less amenable to growth modification and likely to worsen with age. Definitive treatment will almost always require surgical intervention, which should be delayed until facial growth is complete.

Vertical position of the upper incisors

Any significant vertical excess in the upper incisor position, particularly when associated with a gummy smile, can be difficult to correct with orthodontic intrusion and ideally will require either growth modification or surgery for correction. As the face ages there is a tendency to show less upper incisor and it is important that these teeth are not overintruded during treatment; otherwise, the smile can become prematurely aged. In a growing child, a full-coverage maxillary intrusion splint in combination with high-pull headgear can be used to restrict vertical maxillary growth and reduce upper incisor show. However, treatment of this type is difficult, requiring excellent compliance and favourable growth to be successful. In an adult, excess incisor show in the vertical plane will require surgical impaction of the maxilla for definitive correction.

Lower incisor position

The planned upper incisor position will also need to be decided in relation to the lower incisors to achieve a class I relationship—a fundamental aim of treatment in most cases. Longitudinal studies have demonstrated that any labial movement of the lower incisors with an orthodontic appliance is inherently prone to relapse in the long-term (Mills, 1966, 1968). Therefore, as a general rule it is advisable to avoid proclining these teeth to any significant extent during treatment, although some exceptions to this do exist (Table 7.3).

Table 7.3 Clinical situations where lower incisor proclination may be acceptable

• Mild lower incisor crowding;

• Class II division 2 cases with retroclined lower incisors;

• Lower incisors retroclined by an active lower lip; and

• Decompensation prior to orthognathic surgery.

Class I malocclusion

If the incisor relationship is initially class I, the anteroposterior position will not require correction during treatment and labiolingual movement of the lower incisors to any great extent can be easily avoided. An exception to this is a class I incisor relationship with significant bimaxillary proclination. If a goal of treatment is the correction of this position, some retraction of the lower incisors will be required and this will usually mean extractions to provide the necessary space.

Class II malocclusion

The lower incisors can be set back within the face in association with mandibular retrognathia, which will also give rise to a class II relationship. In common with class II cases associated with maxillary excess, more severe mandibular deficiency and habitual positioning of the lower lip behind the upper incisors tends to result in an increased overjet and class II division 1 incisor relationship; whilst class II division 2 cases are more commonly seen with milder skeletal discrepancies, reduced vertical proportions and a high lower lip line.

A class II incisor relationship will require some change in the position of these teeth to obtain the goal of a class I occlusion. How this is achieved will depend upon the underlying skeletal and soft tissue relationships and it should be remembered that wide variation is seen in the extent and combinations of skeletal patterns that occur.

For class II cases associated with a normal or only mild skeletal discrepancy and an acceptable profile, the existing lower incisor position will generally be accepted and a class I incisor relationship achieved by changing the upper incisor position. The necessary tooth movement is often relatively minor and rarely has any negative consequences for the facial profile.

In moderate class II malocclusions, it may be possible to achieve a class I incisor relationship with orthodontic tooth movement alone. Camouflage treatment of this kind will usually involve mid-arch premolar extractions, maxillary incisor retraction and maintenance of lower incisor position (although some class II division 2 cases can be very demanding to treat in this manner without some lower incisor proclination). More severe class II cases, particularly those associated with mandibular retrognathia, may require significant upper incisor retraction to achieve camouflage, which can worsen a retrusive soft tissue profile as the lips move back with the teeth. There is not a simple relationship between incisor retraction and lip movement, and how far the lips can be acceptably retracted depends upon many factors, including their thickness and competence, the original incisor position and the underlying skeletal anatomy (Handelman, 1996; Ramos et al, 2005). However, care must be taken not to over-retract incisors, particularly in the more severe cases that already have a retrusive soft tissue profile.

In a growing child with a moderate or severe class II skeletal pattern associated with mandibular deficiency, treatment with a functional appliance aimed at modifying growth should always be considered in an attempt to improve the incisor relationship. In successful cases this will improve the lower incisor position through advantageous jaw growth and dentoalveolar change prior to a second phase of treatment aimed at achieving th/>

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Tags: Handbook of Orthodontics

Jan 1, 2015 | Posted by mrzezo in Orthodontics | Comments Off

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