Early Mixed Dentition Period

Transcription

1 REVIEW ARTIC CLE AODMR The Effects of a Prefabricated Functional Appliance in Early Mixed Dentition Period Toshio Iwata 1, Takashi Usui 2, Nobukazu Shirakawa 2, Toshitsugu Kawata 3 1 Doctor of Philosophy (Dentistry, Orthodontics), Lecture, Division of Orthodontics, Department of Oral function & Restoration, Graduate School of Dentistry, Kanagawa Dental University; 2 Graduate student, Department of Oral function & Restoration, Graduate School of Dentistry, Kanagawa Dental University; 3 Doctor of Philosophy (Dentistry, Orthodontics), Professor, Chairman, Division of Orthodontics, Department of Oral function & Restoration, Graduate School of Dentistry, Kanagawa Dental University Address for Correspondence: Dr. Toshio Iwata, Doctor of Philosophy (Dentistry, Orthodontics), Lecture, Division of Orthodontics, Department of Oral function & Restoration, Graduate School of Dentistry, Kanagawa Dental University. ABSTRACT: Objective: We present 2 cases in which a prefabricated functional appliance (trainer system TM ) was used, and evaluate its mechanismm of action, indications for treatment, and cases requiring attention. Cases: The patients were a 7-year 8-month-old girl and a 9-year 0-month-old boy. Both patients showed skeletal maxillary protrusion with excessive overjet and crowding in the mandibular anterior tooth area. Clinical examination and results: Both patients showed improvements of overjet, overbite, molar relationship, cephalographic ANB, and maxillary anterior tooth axis. However, patient 2, a high- Furthermore, angle case, presented deterioration of ANB due to mandibular clockwise rotation. marked labial tipping movement of the mandibular anterior tooth axis was noted. Conclusion: Regarding the trainer system, greater effects can be achieved through understanding the disadvantages of the appliance and its application based on appropriate diagnosis of treatment cases. Keywords: Early mixed dentition, Eruption guidance, Orthodontic treatment, Prefabricated functional appliance. INTRODUCTION Regarding mouthpiece-type functional orthodontic appliances, 4 types are currently commercially available in Japan. Among them, pedodontists frequently apply a prefabricated functional appliance (PFA) for the treatment of patients with malocclusion in the deciduous and mixed dentition periods. The effects of the PFA are considered to be not only functional improvement, 1 but also lateral expansion of the maxillo-mandibular dentition, improvement of crowding of the anterior teeth, and facilitation of growth of the mandibular bone.2,3 The above authors have also applied the PFA to the treatment of patients in the deciduous and mixed dentition periods, and confirmed its appropriate effects. A characteristic of the appliance is that, due to fabrication with silicone or polyurethane for medical use, it is very soft and its intra-oral insertion is easy to perform. Therefore, it is applicable for younger children with resistance to orthodontic appliances, and is frequently selected as an introduction to orthodontic treatment. However, orthodontists need to perform appropriate preoperativee diagnosis when selecting any type of orthodontic appliance. Furthermore, it is necessary to have a sufficient understanding of the advantages and disadvantages of the appliance for use. At present, although there have been reports on the effects of the PFA, 4,5,6,7 there have been few reports regarding cases requiring attention and contraindications. Therefore, in this report, we present 2 cases in which the PFA was used, and evaluate its mechanism of action, indications for treatment, and cases requiring attention. 28

2 Simulation using typodonts (Figure 1) Before applying the PFA to the treatment of patients, we performed simulation usingtypodonts. We arranged artificial teeth in a malocclusal condition in a typodont articulator for orthodontic training as in the figure. We constricted the maxillo-mandibular dentition in the form of a V, and lingually inclined the maxillo-mandibular bilateral lateral incisors to induce crowding in the maxillo-mandibular anterior tooth areas. The results are shown in the figure. The maxillo-mandibular dentition was expanded in the antero-lateral direction, and the crowding in the maxillo-mandibular anterior tooth areas improved. Because the typodont has no lips, cheek, or tongue, these results should only be used as a reference; however, typical effects of the PFA were confirmed. In particular, the effects on the antero-lateral expansion of the mandibular dentition were marked, and the mandibular anterior teeth showed a marked tipping movement in the labial direction. On the other hand, although the maxillary dentition was also expanded in the lateral direction, tipping movement of the maxillary anterior teeth in the labial direction was slight, in comparison with that of the mandibular dentition. Figure 1: Stimulation with the typodont articulator CASE REPORTS 1. Case 1 1) Diagnosis and etiology At the initial examination, a girl, aged 7 years 8 months, had a chief complaint of anterior crowding. Her face was symmetric from the frontal view and her smile line was good, but her profile was convex because of upper lip protrusion and mandibular retrognathism. Lip 29 incompetence was observed and the perioral muscles were strained on lip closure (Figure 2). Figure 2: Facial Photograph (Case 1) Intraoral findings included a 7.0-mm overjet and a 1.0-mm overbite. The molar relationship was Angle Class II. The maxillary and mandibular dental arches were narrow, and marked crowding was observed in the anterior regions. The arch length discrepancies were 6.7 mm in the maxilla and 1.1 mm in the mandible (Figure 3). Figure 3: Intraoral Photograph (Case 1) The panoramic radiograph did not show tooth germs of the bilateral maxillary and mandibular third molars (Figure 4). The lateral cephalometric radiograph showed an SNA angle of 77.0, an SNB angle of 71.0, and an ANB angle of 6.0, producing a skeletal Class II relationship due to mandibular retrognathism. In addition, the gonial angle was 122.0, the ramus inclination was 88.0, and the Frankfort-mandibular plane angle (FMA) was 29.0, showing a standard angle. Dentally, the maxillary central incisor to the SN plane (SN) was 110.0, the incisor mandibular plane angle (IMPA) was 100.0, the Frankfort mandibular-incisor angle (FMIA) was 51.0, and the interincisal angle was Labial inclination of the mandibular central incisors was observed

3 Iwata et al: The effects of a prefabricated functional appliance (Table 1). The patient was diagnosed with maxillary protrusion and dental crowding. the maxillary incisor to the SN plane (SN) was 97.9, IMPA was 100.8, FMIA was 49.1, and the interincisal angle was The angle of tooth axis inclination was normal for the maxillary central incisors, but the mandibular central incisors had a labial inclination. Figure 4: Panoramic Radiograph at initial visit (Case 1) Figure 5: Superimposition (Case 1) 2) Treatment objectives 1. In the mandible, maximize anterior growth with the PFA. 2. In the mandible, maintain or reduce the anterior vertical dimension. 3. In the maxillary and mandibular dentition, maintain the intermolar and intercanine widths, expand the canine width with the PFA, and slightly decrease the molar width during extraction space closure with an edgewise appliance. 5. Improve the facial esthetics by reducing lip protrusion and mentalis strain. 6. As for the patient, treatment effects will be re-examined at a Hellman dental age of IIIC. 3) Treatment results Lip incompetence was improved and perioral muscle tension disappeared (Figure 2). The overjet was reduced to 3.0 mm and the overbite to 1.0 mm. The molar relationship was Class I (Figure 3). The lateral cephalometric radiograph showed improvement in SNA to 79.1, SNB to 73.9, and ANB to 5.2. Growth of the mandible was forward. In addition, the gonial angle was 122.8, the ramus inclination was 87.3, FMA was 30.1, and mandibular counterclockwise rotation was not observed (Figure 5). Dentally, Case 2 1) Diagnosis and etiology At the initial examination, a boy, aged 9 years 0 months, had a chief complaint of maxillary incisor protrusion. His face was symmetric in the frontal view and his smile line was good, but the profile was convex because of upper lip protrusion and mandibular retrognathism. Lip incompetence was observed and the perioral muscles were strained on lip closure (Figure 6). Figure 6: Facial Photograph (Case 2) Intraoral findings included a 10.0-mm overjet and a 5.0-mm overbite. The molar relationship was Angle Class II. The maxillary and mandibular dental arches were narrow, and marked crowding was observed in the anterior regions of the mandible. The arch length discrepancy was 2.2 mm in the mandible (Figure 7).

4 The panoramic radiograph did not show tooth germs of the bilateral mandibular third molars (Figure 8). The lateral cephalometric radiograph showed an SNA angle of 85.0, an SNB angle of 76.0, and an ANB angle of 9.0, producing a skeletal Class II relationship due to maxillary protrusion and mandibular retrognathism. In addition, the gonial angle was 126.0, the ramus inclination was 88.0, and the FMA was 35.0, showing a high mandibular angle. Dentally, the maxillary central incisor to SN was 120.0, IMPA was 89.0, FMIA was 56.0, and the interincisal angle was Labial inclination of the maxillary central incisors was observed (Table 2). The patient was diagnosed with a high mandibular angle, maxillary protrusion, and dental crowding. Figure 7: Intraoral Photograph (Case 2) Figure 8: Panoramic Radiograph at Initial Visit (Case 2) 2. In the mandible, maintain or reduce the anterior vertical dimension. 3. In the maxillary and mandibular dentition, maintain the inter-molar and the inter-canine widths, expand the canine width with the PFA for kids, and slightly decrease the molar width during extraction space closure with an edgewise appliance. 5. Improve the facial esthetics by reducing lip protrusion and mentalis strain. 6. As for the patient, treatment effects will be re-examined at a Hellman dental age of IIIC. 3) Treatment results Lip incompetence was improved and perioral muscle tension disappeared (Figure 6). The overjet was reduced to 3.0 mm and the overbite to 1.0 mm. The molar relationship was Class I (Figure 7). The lateral cephalometric radiograph showed improvement in SNA to 82.6, SNB to 74.9, and ANB to 7.7. Growth of the maxilla was translated downward, and that of the mandible was downward and only somewhat forward. In addition, the gonial angle was 123.5, the ramus inclination was 89.21, FMA was 37.6, and mandibular clockwise rotation was observed (Figure 9). Dentally, the maxillary incisor to SN was 108.2, IMPA was 99.6, FMIA was 42.8, and the interincisal angle was The angle of tooth axis inclination was normal for the maxillary central incisors, but the mandibular central incisors had labial inclination. Figure 9: Superimposition (Case 2) 2) Treatment objectives 1. In the mandible, maximize anterior growth with the PFA for kids. 31 DISCUSSION 1. Structure and selection of the PFA 1) Structure of the PFA Various kinds of the PFA are currently commercially available, and it is

5 recommended to select the type based on the age of the patient. Although various kinds of the PFA differ in size, they have almost the same structure. They are maxillo-mandibularly integrated mouthpieces, and regarding maxillo- mandibular antero-posterior occlusion, Some kinds of the PFA is produced at an edge-to-edge bite, which is a construction bite taken at the time of use of functional orthodontic appliances. The level of raising of the vertical bite is approximately 3.5 mm in the most distal area, 4 mm in the molar area, 3 mm in the canine area, and 2 mm in the anterior tooth area (Figure 10). Figure 10: Mouthpiece-type Prefabricated Functional Appliance (PFA) Furthermore, to facilitate training to take an appropriate tongue position, a tongue tag is established at the spot regarded as an appropriate position of the tongue apex. Furthermore, because an appropriate inclination is established in the tongue guard to prevent tongue thrust, the antero-lateral expansion of the dentition can be conducted by occlusal force. Other than this, a lip protector is added in the most PFA, so the activity of the lower lip and mentalis muscle can be suppressed. 2) Selection of the PFA Regarding the application of the other PFA, because an overjet of 1 mm is added to the PFA, and although the level of bite raising is approximately 3 mm in the most distal area, which is lower than some of the PFA, it is approximately 4.5 mm in the thickest area of the molar area and 4 mm in the canine and anterior tooth areas, which are higher than some of the PFA (Figure 9); thus, it is considered appropriate to select the other PFA 32 for cases of Angle Class II div. 1 with more marked overjet and overbite. On the other hand, it is considered that some of the PFA should be applied to Angle Class I cases with constricted dentition and slight crowding of the anterior teeth, or slight Angle Class II cases. Regarding the selection of the PFA, it is initially most important that patients can wear it without discomfort for a long time. To achieve this, it is important to understand each patient s dentition and the condition of the intra-oral soft tissue, and to select a PFA of an appropriate size. The each of the PFA has a particular size, whereas regarding the series of the PFA, although the some types PFA with differing hardness have the same size. To select the PFA of an appropriate size among these types, it is essential to take an impression of study models, and it is important to possess size-samples for testing. However, patients who wear the PFA frequently complain of pain, so adjustment is necessary. Furthermore, to perform lateral expansion effectively, it is desirable to select an appropriate size in each case. Therefore, as a reference of the effects of expansion, we measure the width between the maxillo-mandibular lingual base margin, which is called the tongue guard, and the deepest point of the occlusal plane, and use it as an aid for selecting an appropriate PFA. SUMMARY It is considered that the main effects of the PFA are 1) lateral expansion of the maxillomandibular dentition and 2) labial tipping movement of the mandibular anterior teeth. Adjustment of the tooth axis is performed in that, by tipping movement, the labially inclined maxillary anterior tooth axis is lingually inclined, and the lingually inclined tooth axis is labially inclined. Furthermore, we consider that, although the effects as a functional orthodontic appliance on the facilitation of mandibular bone growth are noted, they are not marked. In particular, because the effects on the lateral expansion of

6 the maxillo-mandibular dentition and labial tipping movement of the mandibular anterior teeth appear at an early stage, the mandibular bone shows clockwise rotation, and the growth direction becomes open in high-angle cases, and because, owing to the labial tipping movement of the mandibular anterior teeth, they come into contact with the maxillary anterior teeth, the mandible is not readily induced in the anterior direction. Regarding the PFA, we consider that greater effects can be achieved through an understanding of these disadvantages under an appropriate diagnosis of applicable cases. How to cite this article: Iwata T, Usui T, Shirakawa N, Kawata T. The Effects of a Prefabricated Functional Appliance in Early Mixed Dentition Period. Arch of Dent and Med Res 2016;2(5): REFERENCES 1.Quadrelli C, Gheorgiu M, Marchetti C, Ghiglione V. Approcciomio funzionale precocenelle II Classischeletriche. Mondo Orthod 2002;2: Serdar U, Tancan U, Zafer S. The Effects of Early Preorthodontic Trainer Treatment on Class II, Division 1 Patients. Angle Orthod 2004;74: Masuko M, Kanao A, Kanao Y. Inflection of applied TRAINER SYSTEM of the functional appliance in the mandibular retro-position. Jap J Clin Dent Children 2009;14(4): Tripathi NB, Patil SN. Treatment of class II division 1 malocclusion with myofunctional trainer system in early mixed dentition period. J Contemp Dent Pract 2011;12(6): Ramirez-Yañez G, Faria P. Early treatment of a Class II, division 2 malocclusion with the Trainer for Kids (T4K): a case report. J Clin Pediatr Dent 2008;32(4): Pallavi P, Pai SM. Effect of Preorthodontic Trainer in Mixed Dentition. Case Reports in Dentistry 2013; Article ID :6 page. 7.Ramirez-Yañez G, Sidlauskas A, Junior E, Fluter J. Dimensional changes in dental arches after treatment with a prefabricated functional appliance. J Clin Pediatr Dent 2007;31(4):