Inverse Forsus Fred and bimaxillary splints

Summary

The purpose of the study is to present a new application of the Forsus Fred, combined with bimaxillary acrylic splints for the correction of Class II malocclusions, providing an additional orthodontic alternative in the correction of this type of malocclusion.

Its main biomechanical functions are: A bidirectional effect towards mesial, distal, and intrusive, and its inversion with splints allows for a distal effect in the mandible and mesial in the maxilla, thus restricting or redirecting mandibular growth and stimulating maxillary growth. The splints adapt easily and their insertion in the mouth is simple, their recommended usage is 8:14 hours, it does not prevent speaking, and they should only be removed during meals. The activations of the device should be performed at intervals of 1 to 2 months and 2-4 mm, depending on the patient's growth stage.

Conclusions: Like any orthopedic device, the results of its application are of a dentoalveolar type within the first 8:12 weeks, and after a longer period, 16-20 weeks, bone changes occur.

Clinical advantages were observed in relation to traditional appliances used, as their size is reduced and easy to handle, the activation of the appliance is simple and quick, requiring only wire from the lathe; the results are immediate, reducing the anxiety of parents when observing improvement in their children, with the results subsequently consolidating in the orthodontic phase.

Keyword: Forsus Fred inverse with bimaxillary acrylic splints.

Introduction:

Epidemiological studies of class II malocclusion report that it is less frequent in the global population compared to other malocclusions, depending on the origin and race of the observed population; between 3.2 to 5% in Japan, 2 to 3% in China, and in the American continent, the incidence decreases to 1.96.

It has been demonstrated that this type of malocclusion responds adequately to treatments focused on the correction and orientation of the growth pattern when it is in full activity, and the potential for dentoalveolar adaptation is evident in certain cases where the mandibular bone base is more developed than the maxillary bone base.

The differential diagnosis is important. Before considering the therapeutic possibilities of class II malocclusion, corrective treatment can be of a conservative type (orthopedic, orthodontic) and it is important to distinguish between a localized malocclusion with a good therapeutic prognosis, and those class III cases that affect the entire maxillomandibular complex, limiting their corrective possibilities with uncertain or unfavorable prognosis, affecting the final outcome.

The correction of the inverted or intermaxillary incisal overjet is conditioned by the position of the incisors and the sagittal and vertical relationship of the maxillary bases. The initial relationship is corrected in dental Class III and pseudoprognathism, through the labial movement of the upper incisors and the lingual movement of the lower ones; however, in skeletal class III, the incisors cannot move sufficiently to compensate for the distant position of the supporting bony bases.

The corrective stability depends on the degree of overbite achieved by the incisors; the relapse will be expressed by the tendency of the upper incisors to palatinate and that of the lower incisors to labialize. Without sufficient overbite, it is difficult to maintain a balanced occlusion.

The correction of the occlusion is related to the position of the maxilla and the mandible; it is necessary to apply orthopedic measures to promote the advancement of the maxilla if the upper incisors are in retrusion or at the level of the lower apical base, in addition to redirecting mandibular growth to stop the forward movement of the lower incisors.

Orthopedic Appliances:

Orthopedic appliances are universally applicable, where the control of the development of the maxilla and the mandible constitutes the therapeutic foundation. Within the classification of orthopedic appliances, there are fixed intermaxillary devices such as the Forsus Fred.

Forsus Fred:

Fixed intermaxillary appliance for class II correction, with a telescopic component, covered by a stainless steel spring that compresses and generates approximately 8 ounces of bidirectional force, resistant to compression fatigue and mouth opening. Although this appliance is indicated for class II, in this work it was used combined with removable acrylic bimaxillary splints for the correction of class III malocclusions in patients in the growth phase.

Manufacturing procedure:

Two impressions are taken for study models, two rigid acetate splints are made and covered with self-curing acrylic; the connecting pin is inserted into the acrylic, at the level of the canines in the maxilla, and in the mandible a segment of wire is placed that allows the omega of the pusher to be secured at the height of the lower first molar; in this way, the Forsus Fred must be connected by inserting the pusher into the piston, which will be taken to the mouth, fitting it into the upper and lower dentition (Fig. 1).

Use: A minimum use of 8-14 hours is recommended and it should be removed during meals.

Advantages: It does not interfere during speech, is comfortable, not bulky, and easy for the patient to insert into the mouth.

Methodology

The sample consisted of 10 patients, of both sexes, randomly selected and meeting the established inclusion criteria, aged 8-12 years, who underwent basic diagnostic studies, Ricketts cephalometric tracing, taking from this 1 angular measurement ANB, and 2 linear measurements Wits and Over-jet, to record the position of the bone and dental structures at the beginning and end of the study.

Impressions were taken that were poured in stone plaster, bimaxillary splints were made with acetate and acrylic, the components of the Forsus Fred inverse were placed; control appointments were made every 2 months for patients under 10 years old, and every month for patients aged 10 to 12 years, activated with brass wire 3, 5, 7, and 9 turns on the pushing rod; at the end of 16-20 weeks, control radiographs and photographs were taken to compare the results. (Fig. 1, 2, 3, 4, and 5).

Results

When analyzing the 2 linear measurements and the angular one, significant changes are observed. Dental changes are rapid, which motivates and reduces parents' anxiety about the appearance they see in their children, providing them with peace of mind, achieving a positive overjet and correcting the crossbite.

The paired T statistical test was applied for comparisons before and after treatment, measuring variables on the ratio scale and obtaining the following results (table 1).

Discussion:

The results obtained are significant, providing an additional biomechanical function of the Forsus Fred in reverse and bimaxillary acrylic splints; the principles of functional appliances are applied as mentioned by Baccetti, who describes the importance of the usage time factor and patient cooperation to improve outcomes.

The study also revealed favorable changes in those patients with pseudoprognathism, as reported by Ferro A., to redirect mandibular growth and through dentoalveolar changes, providing an adequate occlusion for the patient.

An important aspect regarding the appliances used is the acceptance by the patient, being a non-bulky device that is easy to insert in the mouth, motivating the patient and the parents, as the changes occur in a shorter time.

References:

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