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Year : 2017  |  Volume : 6  |  Issue : 1  |  Page : 64-68

Class II malocclusion treatment using combined twin block and fixed orthodontic appliances: A case report

Department of Orthodontics, Institute of Dental Sciences, SOA University, Bhubaneswar, Odisha, India

Date of Web Publication20-Mar-2017

Correspondence Address:
Sumita Mishra
Department of Orthodontics, Institute of Dental Sciences, SOA University, Bhubaneswar - 751 030, Odisha
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2277-8632.202575

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Dentofacial orthopedic treatment can significantly alter and improve facial appearance in addition to correcting irregularity of the teeth. Functional appliance therapy can be used successfully in Class II malocclusion, e.g., in a growing patient. Twin blocks are simple bite blocks that interlock at a 70° angle and correct the maxillomandibular relationship through functional mandibular displacement. The twin block appliance was developed by Clark in 1980s. They modify the occlusal inclined plane, guiding the mandible forward into correct occlusion. The use of these appliances is greatly dependent on patient's compliance and they simplify the fixed appliance phase. In this case, a 13-year-old adolescent was treated with twin block appliance followed by fixed appliance to detail the occlusion. The design and treatment effects are demonstrated in this case report.

Keywords: Class II malocclusion, case report, twin block appliance

How to cite this article:
Mishra S. Class II malocclusion treatment using combined twin block and fixed orthodontic appliances: A case report. J NTR Univ Health Sci 2017;6:64-8

How to cite this URL:
Mishra S. Class II malocclusion treatment using combined twin block and fixed orthodontic appliances: A case report. J NTR Univ Health Sci [serial online] 2017 [cited 2022 Aug 13];6:64-8. Available from: https://www.jdrntruhs.org/text.asp?2017/6/1/64/202575

  Introduction Top

Functional appliances may be defined as orthodontic appliances that use the forces generated by the muscles to achieve dental and skeletal changes.[1],[2] These appliances have been used in clinical orthodontics for a long time and are extensively featured in the literature.[3],[4] Their effect is produced from the forces generated by the stretching of the muscles.[5] It is a commonly used functional appliance partly due to its acceptability by patients.

The patients can function normally in twin blocks and can eat and speak without restriction of the normal movements of the tongue, lips, and mandible. Here, a case report of a 13-year-old male patient is presented who was treated by a twin block functional appliance in combination with a fixed appliance to manage his class II malocclusion.

  Case Report Top

The patient had a moderate class II skeletal pattern with slight increase in the lower anterior face height. There was no facial asymmetry and the lips were incompetent with the lower lip trapped at rest behind the upper central incisors, as shown in [Figure 1].
Figure 1: A 13-year-old male patient with proclined anterior region with missing 31 and 41, rotated 45, end on canine, and end on molar relationship on patient right side and Class II relationship on the left side of the patient

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In the intraoral assessment, oral hygiene was good. All teeth from the permanent second molars had erupted in both the upper and lower arches. The maxillary arch was spaced with a midline diastema. Furthermore, lower central incisors were missing. The incisor relationship was class II division 1; the overjet was 12 mm, whereas the overbite was increased and complete to the palate. The buccal segment relationship was Class II on the right side and ended on molar on the left side. The profile showed mandibular retrognathism.

The main objectives for phase I of the treatment were as follows:

  • To reduce the overbite and overjet
  • To achieve class I molar relationship and gain anchorage.

In phase II of the treatment, the aims were:

  • To level and align the arches
  • To close the upper labial segment space
  • To achieve class I canine and incisor relationship
  • Long term retention with upper Hawley retainer and lower prosthetic replacement.

Treatment rationale

Phase I of the treatment involved the use of functional appliance to reduce the overjet, achieve class I molar relationships, and gain anchorage at the start of the treatment to simplify the fixed appliance stage and improve the patient's profile by causing a small skeletal change, as in [Figure 2]. The design of the upper component of the twin block involved an acrylic base plate, which covers the palate and occlusal surfaces of the first molars and second premolars.
Figure 2: After phase I therapy

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There was an inclined plane at the end of the mesial end of the acrylic block. A labial bow was used for anterior retention of the appliance. A midline screw was also included. The lower component consisted of a lingual acrylic base plate covering the edge of the lower incisors.

This phase was followed with upper and lower fixed appliances (0.022′ slot brackets) to close spaces, detailing, and finishing of the case.

Treatment progress

The aims of the functional treatment phase were achieved successfully due to good patient compliance. This phase of treatment was completed in over 12 months. The upper incisors were retroclined by 3° whereas the lower incisors proclined by 2°. This resulted in reduction of the overjet. The patient was instructed to activate the midline screw twice a week which was reviewed every 4 weeks. The second phase of the treatment with fixed appliances aimed to close the remaining spaces and finish the case which lasted 12 months.

The overall treatment time was 24 months, i.e., 12 months of functional appliance wear and 12 months of fixed appliance treatment. The molar relationship was overcorrected to a super Class I on the left side and Class I on the right side.

  Treatment Results Top

The treatment objectives were achieved. Levelling and alignment was achieved, as evident in [Figure 3]. The profile of the patient has improved after the treatment [Figure 4].
Figure 3: Levelling and alignment

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Figure 4: Post treatment

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The incisor, canine and molar relationships were Class I at the end of treatment. The overbite and overjet were reduced to the average values. The overall superimposition of the lateral cephalometric radiographs is shown in [Table 1],[Table 2],[Table 3].

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Click here to view

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  Discussion Top

Twin block functional appliance has several well established advantages including the fact that it is well tolerated by patients and it can be used in the mixed and permanent dentition.[6] There are potential disadvantages such as the proclination of the lower incisors and development of posterior open bites. In this case, the treatment objectives were achieved largely due to good compliance by the patient.

The patient's chief complaint was the increased proclination. Thus, by reducing the overjet with the functional appliance, the patient's confidence improved; the risk of sustaining trauma to the upper incisor was also minimized. The posterior open bite was managed by the part time wear of the functional appliance during the transient phase between functional and fixed appliance and also by coordinating the stainless steel arch wires during the fixed appliance phase.

The selection of functional appliances is dependent upon several factors which can be categorized into patient factors, such as age and compliance, and clinical factors, such as preference/familiarity and laboratory facilities.

During treatment, the Sella Nasion angle (SNA) value was reduced by 2° whereas the SNB value increased by 3°. As a consequence, the (Maxillo mandibular skeletal angular sagital discrepancy) ANB value decreased by 2° toward class I skeletal pattern. The upper incisor inclination reduced to 104°. The lower incisors were proclined by 2° post-functional treatment and was later maintained after the orthodontic treatment. The lower incisors to the APo line remained relatively unchanged. This resulted in an improvement in the patient's profile, which is largely attributed to the favorable growth and partly to the functional appliance.

The superimposition of the lateral cephalometric radiographs taken during pre-treatment and pre-debond demonstrated that the patient grew in a favorable direction towards a Class I skeletal pattern. The radiographs were registered on stable structures in the anterior cranial base (Decoster line). The maxilla demonstrated vertical growth. The upper incisors were extruded and the molars moved mesially. The mandible demonstrated down and forward growth with a slight anterior growth rotation. It has been proved in the literature that functional appliances do not produce long-term skeletal changes and most of their effects are dentoalveloar.[7] In a prospective controlled trial with twin blocks and controls to investigate the skeletal and dental effects showed that the ANB angle reduced by 2°, which was almost entirely due to mandibular length increase which was 2.4 mm compared to the controls as measured from Ar-Pog.[8] There was no evidence of a restriction in maxillary growth. However, it can be seen in this case that functional appliance can facilitate the fixed appliance phase dramatically to achieve good results.

In terms of soft tissue changes, a study aimed to identify and quantify soft tissue changes during treatment with twin block and Dynamax appliance using the techniques of three-dimensional optical surface laser scanning, cephalometric, and clinical measurements.

It was found that there is a soft tissue difference after the treatment, which is likely to be clinically relevant. In this particular case, the profile had improved. The patient was satisfied with the outcome and the appliances were removed. The patient was provided with upper Hawley retainer and lower Maryland bridge for the missing lower incisors. There are claims in the literature that Essix retainers are more effective in maintaining the labial segments as well as cost-effective, and that patients prefer them over Hawley retainers.[9] Arrangement has been made to review the patient regularly during the retention phase of treatment. It was explained to the patient that long term wear of the retainers is required to ensure stability.[10]

  Conclusion Top

The effect of twin block functional appliances is mostly dentoalveloar with small skeletal component. There are a number of situations where functional appliances can be successfully used to correct Class II malocclusion. It is important that functional appliances are used in a growing patient to achieve the maximum benefit. They simplify the following phase of fixed appliance by gaining anchorage and achieving Class I molar relationship. In this case, the patient was treated with twin block appliance followed by fixed appliance phase.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Clark WJ. The Twin Block technique. A functional orthopaedic appliance system. Am J Orthod Dentofac Orthop 1988;93:1-18.  Back to cited text no. 1
Graber TM, Rakosi T, Petrovic A. Dentofacial orthopedics with functional appliances. 2nd ed. St Louis: Mosby; 1997.  Back to cited text no. 2
O Brien. The effectiveness of treatment of class II malocclusion with the Twin Block appliance: A randomised, controlled trial. Am J Orthod Dentofac Orthop 2003;124:128-37.  Back to cited text no. 3
O Brien. The effectiveness of treatment of class II malocclusion with the Twin Block appliance: A randomised, controlled trial. Part 2: Psychological effects. Am J Orthod Dentofac Orthop 2003;124:488-95.  Back to cited text no. 4
Mills JR. The effect of functional appliances on the skeletal pattern. Br J Orthod 1991;18:267-75.  Back to cited text no. 5
Harradine N, Gale D. The effects of torquing spurs in Clark Twin Block appliances. Clin Ortho Res 2000;3:202-10.  Back to cited text no. 6
Lee RT, Kyi CS, Mack GJ. A controlled clinical trial of the effects of the Twin Block and Dynamax appliances on the hard and soft tissues. Eur J Ortho 2007;29:272-82.  Back to cited text no. 7
Lund DI, Sandler PJ. The effect of Twin Blocks: A prospective controlled study. Am J Orthod Dentofac Orthop 1998;13:104-10.  Back to cited text no. 8
Hichens L, Rowland H, Williams A, Hollinghurst E, Ewings P, Clark S, et al. Cost-effectiveness and patient satisfaction: Hawley and vacuum-formed retainers. Eur J Orthod 2007;29:372-8.  Back to cited text no. 9
Little RM. Stability and relapse of mandibular anterior alignment: University of Washington studies. Semin Orthod 1999;5:191-204.  Back to cited text no. 10


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3]


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