Early Transverse Treatment

Summarized and edited by : 
Dr. Amjad Alotaibi , Dr. Hani Alhebshi

Expansion of the maxillary arch to improve transverse interarch relationships during the primary or mixed dentition stage is considered early transverse treatment as part of a two-phase treatment protocol. 

Three possible reasons for early transverse treatment:

1. Correct posterior crossbite (The most common)
2. Improve arch length deficiency 
3. Facilitate correction of skeletal class II malocclusions 

Posterior crossbite:

Types

Based on the position of the maxillary teeth:

• Posterior lingual crossbite (most common)
• Posterior buccal crossbite 

(N.B; Canine involvement is often seen and considered part of a posterior crossbite even though canines are not, by definition, posterior teeth) 

Based on the involved side of the arch :

• Unilateral
• Bilateral 

Incidence

In the primary and mixed dentition: Estimates range from 7% to 23% with a greater prevalence of unilateral crossbite coupled with a lateral shift of the mandible. 

Etiologies

A range of possible causes includes genetics, environmental factors, and habits that result in transverse maxillary skeletal deficiency, asymmetric growth of the maxilla or mandible, discrepant widths of basilar maxilla and mandible, and so on. 

Management

Spontaneous correction

Yes, it could occur. However, several controlled studies have reported wide variation in rates of spontaneous correction in the primary and early mixed dentition, ranging from 8% to 45%. 

Interceptive orthodontic for posterior crossbites with a functional shift 

The rationale: Evidence suggests that a lateral shift of the mandible into unilateral crossbite occlusion may promote adaptive remodeling of the temporomandibular joint and asymmetric mandibular growth. As a result, it should be corrected early and the best time is during the early mixed dentition period because of;

• There is still adequate time for growth modification in the early mixed dentition. 
• Favorable improvement of a mandibular asymmetry associated with a mandibular shift is seen in patients treated in the early mixed dentition 

 

The principles of diagnosis of the transverse problems 

Diagnosis in the transverse dimension includes a systematic evaluation of the face and dentition in the frontal view, the sagittal jaw relationships, and the transverse dental relationships on study casts. 

Frontal facial examination (chairside) 

• To assess facial symmetry 
• To notice the presence/absence of lateral deviation of the chin

If there is a unilateral crossbite with the chin asymmetry, the underlying causes would be;

1. A functional mandibular shift (CR=/ CO)
2. A true unilateral skeletal asymmetry (CR=CO); Posteroanterior or submental radiographs are helpful in assessing the presence and magnitude of maxillary or mandibular asymmetry 

 If there is a unilateral crossbite in the absence of skeletal asymmetry and lateral shift is most commonly the result of aberration of transverse tooth positions. 

 

Sagittal Relationships examination (on study casts) 

Transverse interarch relationships change as sagittal interarch relationships change. Clearly, planning for treatment to correct improper sagittal interarch relationships will dictate if, and how, transverse interarch relationships should be adjusted in the overall plan. 

Transverse discrepancies can be relative or absolute.

Relative transverse discrepancies;

If a crossbite disappears and the occlusion is proper when the casts are articulated into a Class I canine relationship. 

Absolute transverse discrepancies; 

 If a crossbite still exists when the casts are articulated into a Class I canine relationship. 

 

Transverse Dental Relationships examination (on study casts) 

In the presence of an absolute transverse discrepancy, study casts are used to determine;

• The origin of crossbite (Dental/Skeletal)
• The magnitude of crossbite 

               

The examination’s sequence  :

• Measure transverse axial inclination of the permanent first molars; 

It is estimated by viewing the casts or can be measured using the American Board of Orthodontics (ABO) measuring gauge. This value compared with normal values of molar buccolingual inclination, which are at the age of 7 years; 

• Max first molar 10 +/- 4 of buccal crown inclination 
• Mand first molar 10+/- 5 of lingual crown inclination
• With later growth, molars are changing their inclination and being more perpendicular to the transverse occlusal plane. 

 

• Visualize removing transverse dental compensations (uprighting the molars) on the casts;

If the posterior transverse interarch relationship improves > the discrepancy is probably of dental origin

If the posterior transverse interarch relationship worsens > the discrepancy is probably of skeletal origin 

• Compare a patient’s maxillary and mandibular intermolar width to published “norms” to determine the magnitude of a posterior transverse discrepancy, but only after the molars have been uprighted on casts or at least visualized to be.  

 

Are posteroanterior (PA) cephalograms necessary in diagnosing transverse jaw relationships? 

A cephalograms are useful in quantifying skeletal asymmetries, but they have only very limited value in evaluating transverse discrepancies without asymmetries. 

 

The treatment of the transverse problems :

 When should early treatment for crossbite begin? 

Other than attempting to correct functional shifts in the primary dentition by selective occlusal adjustment, it is recommended that treatment be postponed until the early mixed dentition. 

How should crossbites be treated? 

The treatment decision is made on a case-by-case basis and includes consideration of the following factors:

• presence or absence of a lateral mandibular shift,
• degree of skeletal discrepancy,
• and the degree of posterior tooth compensations in each arch. 

 

• In general, there are fundamentally two treatment options to correct bilateral posterior crossbites in the early mixed dentition;

1. For skeletal crossbites, increasing the basilar maxillary width by lateral expansion of the midpalatal suture is the most common treatment approach 
2. For dental crossbites, medial or lateral dental tipping and/or translation can reposition individual teeth into a more correct transverse occlusion 

 

• Oral appliances;

It is further recommended that fixed appliances are used to make the correction in the early mixed dentition to avoid problems of patient cooperation. In particular, A Hyrax jackscrew appliance is the most common technique. Nevertheless, If the patient is young enough (maxillary skeletal resistance low enough), then a removable expansion plate may be attempted.

 

• Which jaw should be treated to correct a skeletal transverse discrepancy? 

If a child presents with a constricted maxilla, then the obvious choice is to treat the maxilla. However, even if a transverse discrepancy results from an excessively broad mandibular arch, a reasonable choice may still be to leave the mandibular arch alone and to expand the maxilla. 

 

• For dental crossbites; 

Posterior crossbites correctable by tooth movement alone, buccal or lingual tipping can be accomplished with many appliances as well as crossbite elastics. In the maxilla, teeth tipped buccally and in the mandible teeth tipped lingually. 

 How should true unilateral (maxillary lingual) crossbites be treated in children? 

A rapid maxillary expander (RME) with reverse crossbite elastics on the noncrossbite side, in conjunction with a lower lingual holding arch, is recommended. 

The importance of reverse crossbite elastics is to counteract the force of RPE on the non-crossbite side and prevent reverse crossbit from happening. In addition to this, the lower lingual holding arch is inserted to prevent the mandibular teeth from tipping buccally.  

 

In the absence of a posterior crossbite, should rapid maxillary expansion be used to correct a Class II relationship? 

Since functional appliances, which actively posture the mandible forward, do not enhance mandibular growth (long term), it is doubtful that rapid maxillary expansion enhances mandibular growth.

 

Should dental arches be expanded in the absence of a crossbite to gain arch perimeter and avoid extractions? 

Maxillary expansion increases arch perimeter. However, the mandibular arch limits the amount of maxillary expansion that can be achieved. Expansion of the arches beyond the point where the mandibular molar crowns are upright is inherently unstable and not recommended. 

 

 Reference :

Steven D. Marshall et al .. Early Transverse Treatment .. Seminars in orthodiontics 11:130-139 / 2005.