|Year : 2013 | Volume
| Issue : 1 | Page : 56-60
Early class III management in deciduous dentition using reverse twin block
SS Sargod1, N Shetty2, A Shabbir1
1 Department of Pedodontics, Yenepoya Dental College, Derlakatte, Mangalore, Karnataka, India
2 Department of Orthodontics, Yenepoya Dental College, Derlakatte, Mangalore, Karnataka, India
|Date of Web Publication||27-May-2013|
S S Sargod
Department of Pedodontics, Yenepoya Dental College, Derlakatte, Mangalore
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Class III malocclusion poses a challenging dilemma for the clinician because these children have of growth patterns that differ from that of children with class I malocclusion. The mandible grows more rapidly than the maxilla, exacerbating the class III malocclusion as the child go through adolescence. Ever since Clark described a version of the twin block, it has steadily gained popularity in the management of early class III malocclusion in children. However, not many cases are reported in the literature on its use in deciduous dentition. This article tries to provide an insight into the reverse twin block appliance and reports two cases of early class III malocclusion treated using reverse twin block.
Keywords: Class III malocclusion, deciduous dentition, reverse twin block
|How to cite this article:|
Sargod S S, Shetty N, Shabbir A. Early class III management in deciduous dentition using reverse twin block. J Indian Soc Pedod Prev Dent 2013;31:56-60
|How to cite this URL:|
Sargod S S, Shetty N, Shabbir A. Early class III management in deciduous dentition using reverse twin block. J Indian Soc Pedod Prev Dent [serial online] 2013 [cited 2020 Sep 19];31:56-60. Available from: http://www.jisppd.com/text.asp?2013/31/1/56/112418
| Introduction|| |
Class III malocclusions may be limited to dentoalveolar discrepancies but are more frequently skeletal in nature.  The characteristic features of a class III malocclusion are present at an early age, usually between 3 and 5 years of age. [2-4] The skeletal and dental features in class III malocclusion are established early in childhood and do not self-correct during child development. 
The maxilla is reported to grow less anteriorly in class III subjects than in class I normal controls. In addition, the vertical growth pattern of the craniofacial structures of class III subjects differ when compared to that of class I subjects. 
A developing class III malocclusion presents with maxillary skeletal retrusion, mandibular skeletal protrusion, or a combination of the two. In addition to these sagittal problems there may be posterior and anterior crossbites also present. Other factors determining a class III malocclusion are vertical in nature and may have their origin in either deficient vertical skeletal growth (brachycephalic) or excessive vertical growth (dolicocephalic). If left untreated, the class III malocclusion or severe anterior crossbite may worsen, with the majority of these patients ultimately requiring orthognathic surgery as adults.
The timing of treatment of class III malocclusion is critical for optimum outcomes. Delaying appropriate treatment beyond the mixed dentition stage (10 years of age) will limit the effectiveness of orthopedic correction. required to treat most of the class III malocclusions. More importantly, treating a class III malocclusion in the late deciduous and early mixed dentition stages has been shown to be more beneficial to the child because there is improved maxillary orthopedic correction combined with controlled mandibular growth than when treatment is undertaken in the later childhood growth stages.  Treatment strategies directed at the cause of the class III malocclusion may consist of corrective orthodontics, dentofacial orthopedics, and orthognathic surgery, or a combination of these, depending on the type of class III malocclusion and the age of the patient.
Orthopedic correction of class III malocclusion has been described utilizing a Petit- or Delaire-style face mask or reverse headgear for maxillary deficiency. A chin-cup type headgear may also be used for the treatment of mandibular prognathism. The most commonly used is the functional regulator III (FR III) described by Frankel.
The twin block appliance is widely used for the treatment of class II malocclusions. However, Clark has described a version of the twin block that may be used for class III malocclusions, known as the class III twin block appliance or the reverse twin block.
Reverse twin block: Appliance design 
Functional correction of class III malocclusion is achieved in the twin block technique by reversing the angulation of the inclined planes and harnessing occlusal forces as the functional mechanism to correct arch relationships by maxillary advancement, while using the lower arch as the means of anchorage. The position of the bite blocks is reversed compared to twin blocks for class II treatment. The occlusal blocks are placed over the upper deciduous molars and the lower first molars.
Reverse twin blocks are designed to encourage maxillary development by the action of reverse occlusal inclined planes cut at a 70° angle to drive the upper teeth forwards by the forces of occlusion and at the same time to restrict forward mandibular development [Figure 1]. In cases with maxillary contraction and distal relationship of the mandible, the maxillary appliance should include provision for three-way expansion to increase the size of the maxilla in both the sagittal and the transverse dimensions.
An alternative design uses a three-way expansion screw to combine transverse and sagittal expansion. This is also effective in expanding a contracted maxilla and in correcting lingual occlusion if used in combination with reverse inclined planes.
| Case Reports|| |
A child of 5 years and 8 months reported to our private dental clinic with the chief complaint of multiple decayed posterior teeth. On examination, most of the molars were decayed, with pulpal involvement. We also noted that the anteriors were in crossbite from canine to canine [Figure 2]a and b.
|Figure 2: (a) Preoperative casts - front view. (b) Preoperative casts - lateral view.|
Click here to view
Maxillary growth seemed to be restricted due to the postural shift of the mandible in a class III position, which may have been due to the grossly decayed lower posteriors. The possible outcome of the jaw relationships was explained to the parent. After completing all the pulp therapy and restorative procedures, the treatment was aimed at eliminating the anterior interlock. Since there was no maxillary growth restriction, we decided to treat the patient with the reverse twin block appliance. We expected that this would promote maxillary growth and position the mandible backwards.
A usual wax bite registration in a maximum retrusive position of the mandible was made, leaving sufficient clearance between the posterior teeth for occlusal bite blocks,. Following this, upper and lower bite blocks were fabricated using cold-cure acrylic resin, with clasps on the maxillary and mandibular molars. The bite blocks were made to cover the upper primary first molar and the lower second molar, with a reverse direction of the inclined planes. A lower outer passive labial bow and upper anterior eyelet clasps were incorporated for the purpose of retention [Figure 3]a and b.
|Figure 3: (a) Fabrication of reverse twin block appliance – front view. (b) Fabrication of reverse twin block appliance – lateral view.|
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The patient was instructed to wear the appliance continuously for as long as possible, including during meal times initially [Figure 4].
The patient developed an almost edge-to-edge bite with mild crossbite in relation to 52 and 62, which was relieved by trimming 72 and 82. The appliance was activated every 2 weeks by addition of acrylic resin on the inclines of the bite blocks. At the end of 4 months, a significant improvement in the profile and positive anterior relation was noted [Figure 5].
A 5-year - old child was brought to our private dental clinic with the chief complaint of inwardly placed upper front teeth. On examination, the patient had anterior crossbite from canine to canine [Figure 6]. There was no family history of class III malocclusion. The maxillary growth seemed to be restricted due to the postural shift of the mandible in a class III position. A lateral cephalogram revealed that the point A was in the range of normal values, whereas the point B was slightly greater than the normal values. Based on the above findings, a diagnosis of pseudo-class III malocclusion was made.
the possible outcome of the jaw relationships was explained to the parent, and a reverse twin block appliance was constructed as described earlier. The patient was instructed to wear the appliance continuously for as long as possible. Improvement in the profile on wearing the appliance was noted and appreciated by the parent immediately. The appliance was activated every 2-3 weeks by addition of acrylic resin on the inclines of the bite blocks.
The patient developed a habitual closure of the mandible in a backward position, and correction of the anterior crossbite was observed within 6 weeks of starting to wear the appliance [Figure 7]. The patient was asked to continue with this appliance for another 6 weeks for retention purpose. At the end of 4-5 months, a significant improvement in the patient's profile was appreciable.
| Discussion|| |
A class III malocclusion is not a single diagnostic entity but rather a spectrum of clinical manifestations, with varying clinical and cephalometric features that predict differing biologic potential. Most importantly, identification of a specific class III malocclusion in the young child allows both early treatment of the malocclusion and correction of the underlying etiology. 
Early treatment is often indicated to counter the unfavorable developmental pattern. There are not many reports in the literature about the use of reverse twin block in the deciduous dentition. However, its use in the mixed dentition stage is well documented in the literature. After taking into account the compliance of the child, intervention as early as in deciduous dentition is advisable for better results in children. With good motivation and periodic reinforcement, most patients cooperate with the treatment since opening and closing of the mouth is not restricted.
In treatment with reverse twin block, the occlusal force exerted on the mandible is directed downwards and backwards by the reverse inclined planes. No damaging force is exerted on the condyles because the bite is hinged open with the condyles down and forward in the fossae, and the inclined planes are directed downwards and backwards on the mandibular teeth. The force vector in the mandible passes from the lower molar towards the gonial angle. This is the area of the mandible best able to absorb occlusal forces. 
The degree of skeletal discrepancy is an important factor in case selection. There should be minimal maxillary skeletal deficiency and the mandibular plane angle should not be very steep. In some cases class III occlusion may respond to treatment in the deciduous and mixed dentition, but relapse may occur during the pubertal growth spurt and the position may need to be reviewed.
Clinically, the important question is whether or not the patient can occlude squarely edge to edge on the upper and lower incisors. The ease with which the patient can achieve this position is an indication of the prognosis for correction. The most favorable cases for correction present a postural class III, where the incisors can meet comfortably edge to edge but the patient is forced to move the mandible forward in order to occlude on the posterior teeth. If an edge-to-edge occlusion is achieved only with difficulty, the prognosis for orthodontic correction is poor. 
Once the appliance is delivered, the maxilla starts to advance anteriorly within 4 weeks. This will be evident with the patient's edge-to-edge bite anteriorly. Addition of acrylic to the inclined planes may be necessary to increase the forces over the maxilla and mandible to establish a positive overjet. Kidner et al., in their evaluation of the reverse twin block appliance on 14 subjects of <12 years of age, found that the changes were mainly dentoalveolar, with the skeletal changes limited to slight downward and backward rotation of the mandible. The average treatment time in their patients was only 6.6 months. 
Twin blocks are designed to be worn 24 hours per day to take full advantage of all functional forces applied to the dentition, including the forces of mastication. The appliance is well tolerated and changes are observed within 6 weeks of starting to wear the appliance. The first principle of appliance design is simplicity. The patient's appearance is noticeably improved when the twin blocks are fitted.
Reverse twin blocks are designed to be comfortable, esthetic, and efficient. By addressing these requirements, reverse twin blocks satisfy both the patient and the operator as it one of the most patient friendly of all the functional appliances. 
| Conclusions|| |
It is important to remove the anterior interlock as early as possible so as to allow for normal unrestricted growth of the maxilla and also to guide the mandible to a normal retrusive position. Reverse twin block or class III twin blocks can be used successfully for early treatment of class III malocclusions in deciduous dentition. The appliance is easy to fabricate and is well tolerated by children; also, faster correction can be achieved with these appliances than with other appliances. However, a prospective study with long-term evaluation is required to fully evaluate the efficacy of this appliance.
| References|| |
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|2.||Dietrich UC. Morphological variability of skeletal class III relationships as revealed by cephalometric analysis. Rep Congr Eur Orthod Soc 1970;131-43. |
|3.||Jacobson AJ, Evans WG, Preston CB, Sadowsky PL. Mandibular prognathism. Am J Orthod 1974;66:140-71. |
|4.||Guyer EC, Ellis EE 3rd, McNamara JA Jr, Behrents RG. Components of Class III malocclusion in juveniles and adolescents. Angle Orthod 1986;56:7-30. |
|5.||Graber TM. Current orthodontic concepts and techniques. Philadelphia: WB Saunders; 1969. |
|6.||Reyes BC, Baccetti T, McNamara JA Jr. An estimate of craniofacial growth in class III malocclusion. Angle Orthod 2006;76:577-84. |
|7.||Franchi L, Baccetti T, McNamara JA. Postpubertal assessment of treatment timing for maxillary expansion and protraction therapy followed by fixed appliances. Am J Orthod Dentofacial Orthop 2004;126:555-68. |
|8.||Clark WJ. Treatment of class III malocclusion, Twin block functional therapy. 1 st ed. Mosby- Wolfe publication, 2004,USA . |
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|10.||Kidner G, DiBiase A, DiBiase D. Class III twin blocks: A case series. J Orthod 2003;30:197-201. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]