10.1
Very Early Treatment of Dentofacial Asymmetries: Why, When, and How?
Ute E.M. Schneider‐Moser and Lorenz Moser
Introduction
Unilateral posterior crossbites (UPC) in the deciduous dentition are frequent findings, affecting between 8 and 22% of the children (Figure 10.1.1) (da Silva Filho et al. 2007; Shalish et al. 2013).
Studies have shown that the status of the primary occlusion affects the development of the permanent occlusion and that a UPC in the deciduous dentition will most likely be transferred to the mixed and permanent dentition (Kutin and Hawes 1969; Clifford 1971). Moreover, children with UPC have reduced bite force and asymmetrical muscle function leading to abnormal chewing or clenching which can negatively affect normal development of the orofacial system (Sever et al. 2011; Primožič et al. 2013).
Although research has shown that a spontaneous correction of a unilateral posterior crossbite can occur (Thilander et al. 1984; Kurol and Berglund 1992), the chances of its transfer from the primary to permanent dentition are by far higher, which can have long‐term effects on the growth and development of the teeth, jaws, and the temporomandibular joint, leading ultimately to TMD and craniofacial asymmetry (Mohlin and Thilander 1984; Mongini and Schmid 1987; Riolo et al. 1987; O’Byrn et al. 1995; Piley et al. 1997; Egermark et al. 2001; Thilander et al. 2002; Kilic et al. 2008).
Early treatment is advised to normalize the occlusion and to create conditions for normal occlusal development, especially preventing the first molars to erupt in crossbite (Harrison and Ashby 2001; Lippold et al. 2013; Evangelista et al. 2020). Furthermore, postponement of treatment has been claimed to result in prolonged treatment of greater complexity (Lindner 1989; Bell and Kiebach 2014).
It seems, therefore, advisable not to delay orthodontic treatment to an older patient age, but to start treatment as soon as the crossbite is detected and the patient and the parents accept treatment (Viazis 1995; Bell and Kiebach 2014).
Figure 10.1.1 Unilateral posterior crossbite on the right with concomitant lower midline deviation.
Etiology
Fortunately, more than 80% of the early crossbites are only due to a transverse deficiency of the maxilla or of the upper dental arch, possibly associated with a low tongue posture, which causes a mandibular shift due to tooth interferences, and is not the result of underlying structural asymmetric mandibular growth (Shalish et al. 2013; Bell and Kiebach 2014). A thorough screening for associated factors, i.e. sucking habits, irregular tongue posture and function, impaired nasal breathing caused by enlarged tonsils and adenoids, or allergies involved in the etiology of the crossbite, besides heredity, is important for long‐term stability of successful early orthodontic crossbite correction (Melsen et al. 1987; Oulis et al. 1994; Góis et al. 2008; Ovsenik 2009; Melink et al. 2010).
Diagnostic Evaluation
Clinical Examination
The most important part of the diagnostic process is the clinical examination. In presence of a UPC, children present a chin deviation to the affected side in maximum intercuspation. At a very young age, the asymmetry is limited to the lower facial third (Figure 10.1.2), without any repercussions on the midface or the maxillary arch in terms of a canted anterior occlusal plane (Primožič et al. 2013). Assessing maxillary constriction as the main causative factor can be performed by asking the children to close only until the first teeth contact (Figure 10.1.3). Spontaneous centering of the lower midlines during opening is a favorable sign for a mere functional asymmetry, while persistence of the mandibular midline deviation and tilting of the lower occlusal plane frequently indicate the development of a skeletal asymmetry (Figures 10.1.4 and 10.1.5).
Associated sagittal (Class II or III) and vertical (open or deep bite) dental and skeletal discrepancies should be clinically assessed and documented with standardized extraoral and intraoral photographs. It is advisable to add an intraoral frontal photograph upon opening to record any change in the lower midline. Alginate impressions or an intraoral scan are necessary for a thorough model analysis and for fabrication of the orthodontic appliance for crossbite correction.
In very young patients who present a UPC, it is very important to evaluate not only the maxillary transverse discrepancy and the resulting amount of upper dental crowding, but also the form of the lower dental arch. Thilander and Lennartsson (2002) have described that the combination of a narrow maxillary arch and a broad lower arch on the crossbite side, is a negative predictor for long‐term stability of early crossbite correction by maxillary expansion, and hence an important diagnostic finding.
What About Radiographs?
In very young children who exhibit only a functional crossbite without any special redundant findings, taking radiographs on a regular basis is unnecessary and should be avoided, as these records will not affect the primary treatment plan. Even in the presence of a non‐centering mandibular midline upon opening, which might reveal an underlying skeletal asymmetrical component, taking radiographs is not mandatory at this stage, as the first orthodontic treatment approach will not differ from treatment of functional crossbites. However, should the first phase of treatment not lead to a complete correction of the crossbite or should crossbite correction relapse during the later stage of growth, a thorough three‐dimensional radiographic evaluation with cone beam computer tomography (CBCT) becomes necessary.
Figure 10.1.2 (a) and (b) In very young children, a UPC causes only an asymmetry of the lower facial third.
Figure 10.1.3 (a)–(c) In 80% of children in the pure deciduous or early mixed dentition, a mandibular midline shift toward the crossbite side from centric relation to centric occlusion is the main symptom.
Figure 10.1.4 (a) and (b) If the midline deviation upon opening disappears, the crossbite is only functional in nature, while its persistence reveals an underlying skeletal asymmetry.
Figure 10.1.5 (a) and (b) In these patients, a cant of the lower anterior occlusal plane is a common finding, which is a second important criterion for a possible structural mandibular asymmetry.
In very young patients with a history of congenital, developmental, or traumatic disturbances, additional sagittal or vertical discrepancies, or in the presence of congenitally missing deciduous teeth, taking additional pre‐treatment radiographs can help the clinician to better estimate the complexity of the malocclusion and to inform the parents more reliably about the overall treatment needs.
Very Early Treatment for Unilateral Posterior Crossbite with Class I, II, III Malocclusion
Unilateral Posterior Crossbite and Class I Malocclusion
If the UPC is only caused by interferences of one or two single teeth. In this instance either grinding of these teeth or application of a simple criss‐cross elastic can eliminate the problem in a very short time (6–12 weeks) (Figure 10.1.6).
As maxillary constriction is very often the main cause for a functional mandibular shift, early rapid palatal expansion in the deciduous dentition of around 4 or 5 years is the first treatment approach.
In the absence of any additional sagittal discrepancies, the gold‐standard orthodontic appliance for UPC correction is the rapid palatal expander. With an activation of 1 turn per day, most maxillary transverse deficiencies can be resolved within 4–6 weeks. The maxilla should be over‐expanded until the palatal cups of the maxillary posterior teeth touch the buccal cusps of the lower posteriors, as some amount of relapse must be expected after removal of the appliance. After a stabilization period of 6–12 months, the appliance is removed and no further treatment is necessary, if the crossbite has been fully corrected and if no asymmetrical skeletal component is present (Figures 10.1.7–10.1.10).
Figure 10.1.6 (a)–(c) Single tooth crossbite correction with 6 weeks of criss‐cross elastic wear.
Sometimes, the mandible does not center spontaneously after rapid palatal expansion. In this case, a buccal crossbite on the former well‐occluding side, and insufficient correction of the former crossbite side will result. Crossbite elastics, either on one or on both sides, are very efficient accessories to reposition the mandible and to guide the attached muscles, which supports mandibular midline correction.
Figure 10.1.7 (a)–(e) Lower facial asymmetry due to a UPC on the left with functional mandibular shift.
Figure 10.1.8 (a) and (b) One daily activation of the rapid maxillary expander’s screw (0.25 mm/day) for 5 weeks has led to complete crossbite correction and spontaneous centering of the mandible and the lower midline.
Figure 10.1.9 (a)–(d) After 6 months of stabilization, the RPE was removed. The crossbite was fully corrected and the mandible has centered spontaneously. No retention device was applied.
The 5‐year‐old little girl presented a unilateral crossbite on the right side due to a mandibular shift. Her mother was worried because of her asymmetric chewing pattern (Figure 10.1.11). After 6 weeks of maxillary expansion, incomplete crossbite correction on the right side and a buccal crossbite on the left were present (Figure 10.1.12).
Application of a criss‐cross “box” elastic from the left upper and lower canines and first deciduous molars for 5 weeks has led to full correction of the transverse problem (Figure 10.1.13).
Four years later, at 9 years of age, the result of very early crossbite correction in the deciduous dentition has remained stable. Very likely, the patient will not require any further orthodontic treatment (Figure 10.1.14).
Figure 10.1.10 (a)–(d) Ten years later, very early crossbite correction has remained stable without any further treatment need.
Figure 10.1.11 (a)–(e) The right UPC causes a chin deviation to the right side.
Figure 10.1.12 (a)–(c) Despite rapid maxillary expansion, the mandible did not center spontaneously.
Figure 10.1.13 (a)–(c) A “box” criss‐cross elastic helps to guide the mandible and the musculature for centering the midlines.
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