Abstract
Objective. The effect of cyclic forces on bone remodeling and morphology is extensively documented in the orthopedic literature, yet its systematic application in orthodontics remains limited. This study describes a protocol combining the light, constant forces of conventional orthodontics with cyclic forces of muscular origin, and evaluates their effects on sutural adaptation, maxillary transversality, and craniofacial proportions. These cyclic forces originate from functional activities such as mastication, deglutition, and respiration. A second objective is to define an objective reference parameter for the design of palatal transversality that is consistent with, and physiologically proportionate to, the overall craniofacial proportions and correct function.
Materials and Methods. In a preliminary phase, 320 subjects aged 8 to 60 years were selected, all presenting a Class I occlusion and no prior orthodontic treatment. In each subject, the cutaneous bizygomatic distance (Zy’-Zy”) was measured and related to the distance between the palatal cusps of the first upper premolars (14-24), a landmark approximating the incisive-canine suture. A constant ratio close to φ³ was identified, from which a predictive formula for physiological palatal transversality and an anthropometric scale for direct clinical measurement were derived. The therapeutic protocol (Nuvola OPSystem) combines aligners equipped with neurological pins for lingual recall with an interposed viscoelastic device (Freedom), through which the patient performs daily clenching exercises (30 minutes) at a frequency within the “bioactive window” (0.5–5 Hz). Changes were quantified by CBCT (Carestream CS 9600, 16×17 cm FOV) at the beginning and end of treatment, measuring the angles between the frontozygomatic suture, the zygomaticomaxillary suture, and the crista galli, following a previously published and validated protocol, approved by the Institutional Review Board. Three consecutive clinical cases are presented (duration 18–36 months).
Patient compliance: The material of the Freedom viscoelastic device is specifically designed to record, by means of small grooves, the daily clenching performed by the patient during treatment; this allows the clinician to monitor correct execution of the prescribed functional exercises.
Results. In all three cases, an adaptive external rotation of the maxillary bones was observed, with an increase in transversality at the zygomaticomaxillary suture: +1.9 mm with a symmetric 2° rotation (Case 1); +2.7 mm with a 1° angular increase per side (Case 2); palatal transversality increasing from 26.7 to 30.7 mm (Case 3). In Case 3, characterized by open bite and hyperdivergence, the gonial angle decreased from 140° to 134° and the SN-GoGn angle from 45° to 40°, with closure of the open bite and restoration of respiratory and swallowing function. Final transversality values were consistent with those predicted by the formula.
Conclusions. The combination of functional cyclic muscular forces with constant orthodontic forces produced measurable and repeatable angular and transverse changes in adults, beyond the growth phase. Cyclic forces are confirmed as an adequate stimulus for activating sutural adaptation and bone remodeling mediated by mechanotransduction. The bizygomatic-to-palatal-transversality ratio offers a clinical reference for therapeutic design. Because these forces are generated by the patient, their intensity is individually determined; this is, on the one hand, an advantage, as it avoids dangerous excess, but on the other hand may represent a limitation if patient compliance is not monitored.