Case Report |
Corresponding author: Harpreet Singh ( drhpreetesic@gmail.com ) Corresponding author: Raj Kumar Maurya ( bracedbyraj@gmail.com ) © 2024 Harpreet Singh, Pinaki Roy, Raj Kumar Maurya, Poonam Sharma, Pranav Kapoor, Tanmay Mittal.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Singh H, Roy P, Maurya RK, Sharma P, Kapoor P, Mittal T (2024) Nonsurgical class III correction in adolescence using modified fixed reverse twin-block therapy and fixed appliances – a case series. Folia Medica 66(4): 555-567. https://doi.org/10.3897/folmed.66.e119060
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Skeletal class III malocclusion is a therapeutic challenge in orthodontic practice. Reverse functional appliances such as reverse twin block (RTB) are used to correct class III skeletal and occlusal disharmonies associated with functional anterior shift in growing patients. However, treatment options become limited with increasing age, especially when patients desire nonsurgical and nonextraction camouflage treatment. This report illustrates the successful nonsurgical treatment of class III malocclusion during adolescence and adulthood, exacerbated by a functional anterior shift that resulted in overclosure of the mandible. A modified fixed RTB was utilized to posture the mandible backwards, thereby inducing active clockwise rotation of the mandible. After treatment, patients demonstrated significantly improved maxillomandibular relationships, well-maintained stable occlusion, and facial esthetics. Satisfactory occlusal, esthetic, and functional outcomes achieved in the present cases underline the fact that dentoalveolar changes induced by fixed RTB can be utilized even past a patient’s peak pubertal growth period to obtain changes that aid in correcting a class III malocclusion. A synergistic combination of modified fixed RTB therapy accompanied by comprehensive fixed mechanotherapy is a viable treatment alternative for the correction of aptly selected mild to moderate skeletal class III malocclusions associated with functional anterior shift, anterior crossbites, and mandibular overclosure.
class III malocclusion, fixed reverse twin-block, fixed mechanotherapy, functional, late adolescence
In spite of lower prevalence rates as compared to class I and class II malocclusions[
In adolescent and adult patients, although camouflage of the skeletal class III condition (through dentoalveolar compensations) by employing temporary skeletal anchorage devices (TSADs) for mandibular total arch distalization, extractions, or class III elastics can improve overall occlusion, the profile may worsen due to increasingly visible chin projection, thereby negatively impacting smile aesthetics.[
This article chronicles the treatment of two patients with skeletal class III malocclusion during late adolescence and early adulthood. The patients were treated using a renovated and modified fixed RTB appliance as a functional treatment modality in conjunction with comprehensive fixed mechanotherapy. The stability of clinically acceptable aesthetic and functional outcomes is also discussed.
The modified fixed RTB consists of a banded maxillary and mandibular component cemented to the permanent maxillary and mandibular molars, respectively, using glass ionomer type-I luting cement. The maxillary component consists of bite blocks anchored on a modified palatal arch soldered onto the molar bands. The mandibular component comprises a modified lingual arch onto which the lower occlusal planes are anchored. The entire wire framework is fabricated with 0.040-inch stainless steel wire. In accordance with the recommendations of Clark[
A 17-year-old girl presented with complaints of prominent lower front teeth and compromised mastication and phonation. Her familial, medical, and dental histories were non-contributory. Extraoral examination revealed an apparently bilaterally symmetrical face, concave facial profile with midface deficiency, relatively strong chin projection, retrusive upper lip, prominent lower lip, and a shallow mentolabial sulcus (Fig.
Pretreatment extraoral and intraoral photographs showing class III malocclusion with anterior crossbites and the ability to achieve an edge-to-edge incisor relationship during posterior mandibular positioning.
Intraorally, she displayed Angle’s class III subdivision left malocclusion, with three incisors in the anterior crossbite. A reverse overjet of 4 mm and a reverse overbite of 8 mm were also found. The upper arch form was square with mild anterior crowding, whereas moderate crowding was observed in the ovoid-shaped lower arch (Fig.
A panoramic radiograph did not reveal any bony or periodontal abnormalities (Fig.
Variable | Pretreatment | Posttreatment |
Sagittal | ||
SNA (°) | 87 | 87 |
SNB (°) | 89 | 87 |
SND (°) | 86 | 83 |
ANB (°) | −2 | 0 |
Wits (mm) | −13 | −6 |
Vertical | ||
SN-MP (°) | 30 | 32 |
FMA (°) | 25 | 31 |
Dental | ||
U1 to SN (°) | 100 | 115 |
U1 to NF (mm) | 30 | 29 |
U1 to NA (°/mm) | 15/4 | 32/9 |
IMPA (°) | 78 | 84 |
U6 to NF (mm) | 24 | 29 |
U6 to PtV (mm) | 27.5 | 29 |
L1 to MP (mm) (perpendicular to MP) | 46 | 48 |
L1 to NB (°/mm) | 19/6 | 23/7 |
L1 to A-Pog (mm) | 6.5 | 7.5 |
L6 to MP (mm) | 33 | 37 |
L6 to PtV (mm) | 31 | 28 |
Interincisal angle (°) | 149 | 126 |
Soft tissue | ||
Nasolabial angle | 90 | 98 |
H line-nose (mm) | 8 | 4 |
Upper lip protrusion – esthetic plane (mm) | −5 | −3 |
Lower lip protrusion – esthetic plane (mm) | 0 | 0 |
Based on the clinical and cephalometric examinations, the patient was diagnosed as having a class III malocclusion with moderate anteroposterior jaw disharmony, anterior crossbite with mandibular overclosure.
The treatment goals were to (1) improve the skeletal jaw relationship, (2) correct the anterior crossbite, (3) achieve esthetically favorable and functionally effective overjet and overbite, (4) establish canine guided functional occlusion with anterior guidance, and (5) improve frontal and profile esthetics.
A traditional camouflage treatment approach involving mandibular premolar extractions and class III elastics was considered a tentative treatment plan. However, in view of the inadvertent effects of camouflage treatment involving the extraction of mandibular premolars and the use of class III elastics on the inclination of the occlusal plane, the interincisal relationship, the TMJ, and soft tissue profile esthetics [
Another possible treatment option of miniscrew-assisted enmasse distalization of the mandibular arch was contemplated and discussed, but the patient and her parents intensely rejected or did not agree with the use of TSADs. Since the patient’s mandible could be postured backwards to achieve an edge-to-edge incisal relationship in the retruded contact position (RCP) with no pain or discomfort in the TMJ, a conservative, noninvasive, two-stage treatment approach commensurate with the patient’s wish/desire was adopted. A functional approach involving the use of modified fixed RTB was contemplated as a stage 1 procedure, followed by fixed orthodontic mechanotherapy during phase 2 to achieve well-intercuspated buccal occlusion. However, because of the possibility of worsening of the intermaxillary sagittal relationship during late mandibular growth, the patient was also informed about the possibility of requiring orthognathic surgery in the future.
Following acceptance of the functional treatment protocol by the patient and her family, a modified fixed RTB appliance was delivered. The appliance was constructed at the position of maximum possible retrusion of the mandible with an interincisal clearance of 2 mm and a posterior vertical clearance of 5 mm (Fig.
Stage photographs: (a-c) Incisor alignment in progress in conjunction with modified fixed RTB; (d-f) Improvement in the overjet and appearance of a bilateral posterior open bite after the RTB appliance had been removed; (g-i) Alignment and leveling of upper and lower arches in progress and sectional box loop being used for uprighting of upper left canine.
Following treatment, overjet and overbite improved, and well-interdigitated class I occlusion was achieved (Fig.
Posttreatment extraoral and intraoral photographs depicting improved facial esthetics, corrected anterior crossbite with well-intercuspated class I occlusion.
Posttreatment radiographs: (a) Panoramic radiograph; (b) Lateral cephalogram; (c) Overall superimposition on Basion-nasion plane registered at CC (center of the cranium) point.
A 20-year-old male with euryprosopic facial features presented with anterior crossbites, a concave profile, and anterior mandibular displacement with a prominent chin. His past medical, dental, and familial histories were unremarkable. Intraoral examination showed a class I molar relationship on the right side and a 1/2 cusp class III molar relationship on the left side. Overjet was −3.5 mm, and overbite was 6 mm. Mild crowding was observed in the upper arch. A Bolton discrepancy was observed in the anterior segment of the upper arch. The mandibular dental midline was 3 mm to the left of the facial midline. The patient demonstrated mandibular overclosure and an anterior functional shift, making the class III problem appear worse than it was (Fig.
Cephalometrically, a class III anteroposterior skeletal discrepancy (ANB, −3°; Wits appraisal, −8 mm) was noted with a protrusive mandible (SNB, 87°) and hypodivergent pattern of growth (SN-MP, 17°) (Figs
Pretreatment extraoral and intraoral photographs indicating reverse overjet, mandibular overclosure, and functional shift of the mandible
Pretreatment radiographs: (a) Panoramic radiograph; (b) Lateral cephalogram showing hypodivergent class III pattern.
The treatment objectives were to: (I) correct the skeletal class III relationship by rotating the vertical segment clockwise to improve the ANB angle; (II) achieve coordination of upper and lower dental arches; (III) establish normal overjet, overbite, and functional occlusion; and (IV) improve facial appearance and profile by increasing the vertical dimension of the occlusion.
To accomplish these objectives, a two-phase treatment plan involving modified fixed reverse twin block therapy during phase 1 accompanied by comprehensive fixed mechanotherapy during phase 2 was formulated.
Phase 1 of treatment commenced with the placement of a modified fixed RTB appliance (Figs
Treatment progress photographs showing: (a-c) Placement of a fixed RTB appliance; (d-f) Improvement in the sagittal relationship and presence of a posterior open bite following completion of functional phase.
(a-c) Space gaining in upper anterior segment in conjunction with leveling and alignment of both arches; (d-f) Progression of alignment, leveling and settling of the posterior open bite; (g-i) improvement of torque in anterior segment and detailed buccal occlusion during final stages.
Post-debonding, Hawley-type retainers were delivered in the maxillary and mandibular arches. The maxillary right central and lateral incisors were reshaped/restored with composite resin to increase their mesiodistal size to improve anterior fit and optimize smile esthetics.
After 17 months of treatment, an adequate overjet, overbite, and well-interdigitated canine-guided class I buccal occlusion was established with a corrected midline (Fig.
Variable | Pretreatment | Posttreatment |
Sagittal | ||
SNA (°) | 84 | 84 |
SNB (°) | 87 | 84 |
SND (°) | 83 | 81 |
ANB (°) | −3 | 0 |
Wits (mm) | −8 | −3 |
Vertical | ||
SN-MP (°) | 17 | 20 |
FMA (°) | 15 | 16 |
Dental | ||
U1 to SN (°) | 103 | 120 |
U1 to NF (mm) | 31 | 30 |
U1 to NA (°/mm) | 18/4 | 37/10 |
IMPA (°) | 97 | 102 |
U6 to NF (mm) | 23 | 25 |
U6 to PtV (mm) | 20 | 24.5 |
L1 to MP (perpendicular to MP) | 43 | 44 |
L1 to NB (°/mm) | 20/6 | 26/6 |
L1 to A-Pog (mm) | 6 | 6 |
L6 to MP (mm) | 37 | 37 |
L6 to PtV (mm) | 26 | 26.5 |
Interincisal angle (°) | 144 | 117 |
Soft tissue | ||
Nasolabial angle | 90 | 101 |
H line-nose (mm) | 7 | 4 |
Upper lip protrusion-esthetic plane (mm) | −6 | −2 |
Lower lip protrusion– esthetic plane (mm) | +2 | +1 |
Posttreatment extraoral and intraoral photographs showing improved facial appearance and restored occlusal symmetry with well-interdigitated class I buccal occlusion.
Posttreatment radiographs: (a) Panoramic radiograph; (b) Lateral cephalogram; (c) Cephalometric superimpositions.
The present case series chronicles the individualized orthodontic management of two patients who presented with a class III malocclusion, anterior crossbites, and evident functional shifts with an acceptable facial profile in centric relation. The etiology of the class III malocclusion in the reported patients appeared to be a combination of skeletal, dental, and functional factors. The patients were successfully treated nonsurgically over two phases of treatment that included the use of modified fixed RTB and fixed appliances. The main mechanisms included the active clockwise rotation of the mandible, the labial inclination of the maxillary incisors, and the mild labial inclination of the mandibular incisors.
It has been observed that many class III patients presenting either late for treatment in adolescence or adulthood usually reject or are not willing to accept surgical orthodontic therapy, and persist in their pursuit of conservative orthodontic treatment, which often presents a therapeutic challenge.[
Regarding the functional therapeutic choices for skeletal class III correction, favorable treatment outcomes with the use of removable RTB appliances in mixed dentition and early permanent dentition have been well-documented.[
It is worth noting that the mechanics of a functional treatment for the correction of a class III malocclusion using a novel modified fixed RTB appliance was applied to our patients. In contrast to the modification proposed by Liu et al.[
Clark[
Establishment of the individualized treatment plan envisaging the concept of goal-oriented therapy should be based on efficacy, ease of application by the clinician, and acceptance by the patient. Based on the Wits appraisal of −13 mm (i.e., greater than 12 mm) in Case 1, the severity of class III was labeled as ‘red’ category, and in Case 2 as ‘yellow’ category in accordance with the Wits appraisal of −8 mm.[
For our modified fixed RTB, promising results have been obtained with the use of the appliance at the late permanent dentition stages, when patients have growth potentials of 5% to 65% according to vertebral evaluations. Unlike removable functional appliances, treatment protocols using modified fixed RTB do not rely on the patient’s compliance, and by virtue of the unlocking of posterior interdigitation, brackets can be used concurrently with the RTB appliance. Other advantages include ease of adaptation to normal functions of speech and mastication, ease of fabrication with minimal armamentarium (no specialized inventory required), cost-effectiveness, and minimalistic design allowing for correction of interarch relationships.
With correction of the skeletal problems during late adolescence by tooth movement alone, the major concern is the impending possibility of adaptive difficulties due to a change in condylar position within the fossa, thus resulting in discomfort or pain in some patients. However, with the accomplishment of nonsurgical treatment by the use of fixed RTB therapy accompanied by simple fixed orthodontic treatment, satisfactory occlusion was established while respecting the anatomic limits of the alveolar housing. No signs or symptoms of temporomandibular dysfunction were noted during treatment or in the follow-up period, and the entire treatment process was well tolerated by all patients.
Class III malocclusions not amenable to functional correction and patients exhibiting allergy/delayed hypersensitivity to methyl methacrylate resins are contraindications to the use of modified fixed RTB therapy.
From both functional and esthetic standpoints, orthodontic treatment involving the use of modified fixed RTB and fixed appliances was satisfactory based on the final outcome. However, high-quality, long-term studies are warranted to support the benefits of a combination of modified fixed RTB therapy and fixed mechanotherapy to improve skeletal and dental relationships in patients with class III malocclusion.
In aptly selected cases, a synergistic combination of modified fixed RTB therapy accompanied by comprehensive fixed mechanotherapy can be a viable treatment alternative for the correction of mild to moderate skeletal class III malocclusion associated with functional anterior shift and mandibular overclosure. Based on the principle of patient-centered outcome and in accordance with clinical practice guidelines, this minimally invasive treatment protocol brought about significant improvement in esthetics and occlusion with long-term stability, addressed the patients’ chief concerns, and improved their self-esteem.
None.
Written informed consent was obtained from patients for their information and images to be published in this article.
There is no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.