Very early orthodontic treatment: when, why and how?

ABSTRACT Introduction: Several orthodontic problems should already be treated at an early age to prevent the necessity of future complex and expensive procedures. Scientific evidence suggests that posterior crossbites, mild to moderate Class III, as well as certain Class II malocclusions, open bites and arch length discrepancies can benefit from simple, but efficient interceptive therapy. Objective: To summarize the existing evidence-based literature on early orthodontic treatment, and to illustrate its application and effectiveness by showcasing multiple clinical examples. Conclusion: Early short-term interceptive orthodontic treatment with simple appliances, in the deciduous or early mixed dentition phase, can efficiently correct certain malocclusions and help to either reduce the complexity or even avoid the necessity of complex and expensive procedures during puberty. For certain patients with significant arch length discrepancy the concept of serial extractions should be part of the orthodontic armamentarium.


INTRODUCTION
The American Association of Orthodontists recommends that children should get their first check-up with an orthodontic specialist at the first recognition of a developing orthodontic problem, but no later than 7 years of age. Research has shown that certain malocclusions can benefit from early intervention and can help to either reduce the duration or even avoid the necessity of a more substantial and more expensive treatment at a later stage -not to mention the positive effect on the child's quality of life by resolving psychosocial problems related to the malocclusion, as pointed out by Artese 1

in 2019.
In the case of uni-or bilateral posterior crossbites and Class III malocclusion, enough evidence-based literature is available to proof that a relatively short phase of interceptive treatment with simple appliances can normalize anomalous growth, and that the result of this treatment approach will remain stable over time. On the other hand, the existing literature on the benefits of early intervention for Class II, open bite and significant arch length discrepancy is controversial, which means that the clinician often must rely on her or his previous orthodontic education and acquired clinical experience.
The possible advantages of the early intervention are the emotional satisfaction of the child, the growth potential available at this stage of development, greater collaboration with treatment, the possibility of a more simplified second phase, and the possible reduction of extractions in the corrective phase of treatment.
Thus, the aim of the present article is to summarize the current state of the art on early, or very early, orthodontic treatment, to present the evidence-based literature on the topic and, for situations where research is controversial, to provide the readers with simple short-term treatment approaches that proved to be efficient in the vast experience of the authors.

POSTERIOR CROSSBITE
Posterior crossbites in the deciduous dentition are frequent findings, with a reported prevalence of 8-22%. 2,3 The origin of these crossbites is a constriction of the maxilla, with an associated maxillary arch length discrepancy, which can lead to functional mandibular shifts caused by tooth interferences.
Roughly 80% of all unilateral posterior crossbites in the mixed dentition are due to these functional shifts and, although spontaneous correction has been reported, it is more likely that the crossbite will be transferred to the permanent dentition and will cause asymmetrical muscle activity and mandibular growth, with an increased risk for future temporomandibular joint dysfunction. [4][5][6][7][8][9][10][11][12][13][14][15] For preventing these negative looming sequelae, early orthodontic intervention is advisable as soon as the patient and the parents accept treatment, for normalizing the occlusion, with subsequent normal occlusal development by preventing the first permanent molars to erupt in crossbite, and to avoid future longer and more complex orthodontic treatments. [16][17][18][19][20][21] The appliance of choice is a tooth-borne Rapid Palatal Expander (RPE) anchored on the second deciduous molars, which is usually activated once a day for four to six weeks, depending on the severity of the transverse discrepancy, and left in place for 9 to 12 months (Figs 1-4). In the absence of additional sagittal or vertical issues, no retention device is necessary. Although Masucci et al. 22 reported about 30-40% relapse after palatal expansion in the pure deciduous dentition, other research groups described excellent overall long-term stability of very early crossbite correction. [22][23][24][25][26] The authors of the present paper have only very rarely (less than 2%) experienced transverse relapse in their patients, who had to be either retreated by a second RPE or by insertion of a transpalatal bar.

CLASS III MALOCCLUSION
Since Class III malocclusion tends to worsen during adolescent growth, early interception is recommended, preferably during the deciduous dentition phase, to gain maximum skeletal effect from orthodontic treatment.
For accurate diagnosis and realistic Class III treatment planning, it is very important to evaluate not only molar and incisor dental relationships, but also to assess any functional Centric Occlusion-Centric Relation (CO-CR) shift on mandibular closure, a cephalometric analysis to determine the amount of underlying sagittal and vertical jaw relationships, and to screen for any very unfavorable genetic predisposition in the family history. 27,28 Especially in cases of hereditary Class III malocclusion, a cephalometric radiograph is mandatory to assess the Wits appraisal, an important diagnostic criterion for successful prognosis of interceptive Class III treatment, and for evalua-  As the facemask (FM) is mostly worn during night-time only, additional intermaxillary elastics from posterior hooks soldered to the RPE to bonded cleats on the mandibular deciduous canines can help to apply Class III traction almost full-time.
It was reported that early treatment with a facemask appliance has a positive impact on both dental and skeletal parameters, and reduces the need for orthognathic surgery in the future when treatment is performed before the age of 10 years in mild  to moderate Class III with a retrusive maxilla and no hyperdivergent facial growth pattern. [34][35][36][37][38][39][40][41][42][43] Baccetti et al 44,45 demonstrated that, especially in the pure deciduous dentition at age 5 years, treatment produces more beneficial skeletal effects such as significantly smaller increments in mandibular total length (Co-Pg) compared to more maxillary dentoalveolar protrusion when treatment is performed in the mixed dentition (around 8 years of age).
There is no evidence that adding RPE to a protraction facemask protocol, with the aim to loosen the circummaxillary sutures and to increase forward movement of the maxilla, will enhance maxillary protraction and should therefore only be undertaken in patients with existing transverse maxillary constriction. 46 To avoid extraoral traction, the use of Class III elastics to a mentoplate has been proposed by Nienkemper et al. 54,56,57 and by Sar et al. 55 , and has shown promising results in the short term especially in hyperdivergent patients.

Regardless of the selected mechanical approach for early
Class III correction, after this early interceptive phase of treatment, a follow-up lateral cephalogram should be taken 2-4 years after maxillary protraction, to calculate the Growth Treatment Response Vector, as suggested by Ngan et al. 58,59 , to determine the individual mandibular growth rate and direction, and to decide whether the malocclusion can be treated by means of orthodontic camouflage or will require future orthognathic surgical correction.

CLASS II MALOCCLUSION
Although the evidence about the benefit of early treatment for Class II malocclusions is striking, there seems to be a big gap between existing scientific knowledge and its daily clinical application. While numerous well-performed studies have revealed that a two-phase approach is not more effective than a late single approach during the pubertal growth spurt, and can neither significantly reduce the complexity of the second phase -including the necessity of extraction treatments, the percentage of orthognathic surgery or treatment duration of phase II-, it is still advocated by many clinicians. [60][61][62][63][64] Franchi et al. 65,66 clearly evidenced that an early approach of Class II correction is simply 'overtreatment', because functional appliance therapy results only in extra mandibular growth if the pubertal stage is incorporated into the treatment plan, which does not occur during the primary and early mixed dentition periods.
The only justification of early intervention of Class II treatment is a mild increased risk of maxillary incisor trauma and psychosocial problems due to bullying. 67,68 However, if Class II malocclusion is associated with either a transverse (lingual or buccal crossbite) or a vertical discrepancy (open bite or deep bite with palatal impingement), early Class II treatment can be advocated. This early approach should be carried out with simple but efficient mechanics, in order not to burn the patient's compliance and the parent's economic resources for a potential second phase of treatment during the pubertal growth spurt, which is the 'gold standard' for Class II treatment.        Concomitant myofunctional therapy with or without additional tongue repositioning devices, such as spurs or cribs, is advisable to close the anterior open bite (Fig 18). [74][75][76][77] It must be acknowledged that stability of open bite treatment is unpredictable irrespective of the treatment modality. [78][79][80] Hopefully, skeletal anchorage devices will help to increase the amount of orthodontic posterior vertical control and achieve more predictable and more stable results of open bite closure in the future. 81,82

ARCH LENGTH DISCREPANCY
Substantial hereditary tooth size-arch length discrepancy is a frequent finding already in early childhood, and the crucial question for the orthodontists is whether the appropriate treatment plan is to change the form of the basal bone or the arch form by either expansion, distalization or proclination or to perform a serial extraction treatment approach instead.
In the presence of a lingual crossbite due to maxillary constriction, the first treatment approach will always be maxillary expansion, and the decision to extract or not to extract will be postponed until after the expansion. If no crossbite is present, the decision whether to expand or to extract will depend on the   » Impaction of the mandibular second molars. 83,84 Once the decision is made that serial extractions are the best treatment option, the extraction of all deciduous canines is prescribed, which will lead to a self-correction of the anterior crowding by tooth migration towards the extraction sites, reduction of bimaxillary protrusion, closure of an existing dental open bite and perhaps even to spontaneous correction of an anterior crossbite ('driftodontics') (Figs 22, 23). [85][86][87] The patient is only seen every six months for monitoring of tooth eruption. Should the mandibular canines tend to erupt prior to the mandibular first premolars, extraction of the mandibular first deciduous molars is advisable to speed up the eruption of the first premolars. Once the maxillary and mandibular premolars have erupted, they will be immediately extracted and monitoring of further tooth eruption is continued until all permanent teeth, including the second molars, have erupted. The beauty of serial extraction treatment is that the natural eruption pathway can be utilized in order to reduce the active treatment time and to keep treatment as comfortable as possible (Fig 24). 88 Critics of serial extraction treatment often state that early extraction of deciduous canines is a 'one-way street' and conditions these patients to pursue the pathway of later premolar extractions. This is not the case, as the final decision whether to extract premolars or to perform any kind of orthodontic arch development is only postponed until eruption of the first premolars and can be critically re-evaluated by the treating orthodontist. Only once the mandibular second molars have fully erupted, active orthodontic treatment is initiated, which on average takes around 12 to 15 months, depending on the mechanics applied.
One of the great advantages of serial extraction treatment is its reduced duration, compared to a two-phase non-extraction or to a late premolar extraction treatment, and may yield more stable long-term results. [89][90][91][92][93] The persisting claims that extraction treatments in general may