Two-phase treatment of skeletal Class II malocclusion with the combination of the Twin-block appliance and high-pull headgear Yan Lv, a Bin Yan, b and Lin Wang c Nanjing, China The patient was a boy with a Class II skeletal and dental relationship, a large overjet, an impinging overbite, and a steep mandibular plane angle. Treatment started with the Twin-block appliance combined with high-pull head- gear to promote growth of the mandible, restrain the maxilla in the anteroposterior and vertical planes, and improve his profile. This was followed by extraction of the maxillary second premolars and the mandibular first premolars. Then fixed appliances were used to align and level the dentition. Pretreatment and posttreatment records are shown, and the treatment results are stable 2 years after debonding. (Am J Orthod Dentofacial Orthop 2012;142:246-55) F unctional appliances have been used for many years in the treatment of Class II malocclusions. Alteration of maxillary growth, improvement in mandibular growth and position, and change in dental and muscular relationships are the expected effects of these appliances. 1 The Twin-block appliance, originally developed by Clark, 2 is a widely used functional appliance for the management of Class II malocclusion. It combines splints with extraoral force and functional orthopedic forces. The appliance can be worn most of the time, with the advantage of allowing nearly a full range of mandibular movement, easy acclimation, and reason- able speech. Its popularity also comes from its high pa- tient acceptability and its ability to produce rapid results. High-pull headgear is used in Class II patients with increased lower facial height. Teuscher 3 suggested that forward and downward growth of the maxilla could be altered, and that the mandible could also change its growth direction to a more forward and upward position with condylar adaptation using the high-pull headgear. Functional appliance therapy is followed by com- prehensive fixed-appliance therapy with or without extractions. Extraction of 4 premolars is indicated primarily for dental crowding, cephalometric discrep- ancy, or a combination in growing Class II patients. 4,5 This case report demonstrates the use of the Twin- block appliance and high-pull headgear in a skeletal Class II Division 1 patient with a retrognathic mandible, protruding maxillary anterior teeth, excessive overjet, and complete overbite. By means of extraction of the maxillary second premolars and the mandibular first premolars, a well-aligned and leveled dentition and an acceptable profile were achieved. DIAGNOSIS AND ETIOLOGY The patient, a Chinese boy aged 12 years 2 months, was in fair health and motivated for treatment with the chief complaint of protruded maxillary anterior teeth and a receding chin for 6 years. He had been biting his lip since eruption of the deciduous dentition. He was introverted and had poor self-esteem, despite his normal medical history. His father had a similar profile of pro- truded maxillary anterior teeth. The facial photographs indicated a convex facial appearance, protruded lips, and moderate exposure of the maxillary incisors (Fig 1). He had a normal range of mandibular motion and no joint noise or pain. The midline of the mandible was shifted 2 mm to the right. Other intraoral findings included gingivitis of the incisors, a short lingual frenum, and swollen tonsils. He had a Class II Division 1 malocclusion (bilateral full Class II molars and canines) with a 15-mm overjet and From the Institute of Stomatology, Department of Orthodontics, Nanjing Med- ical University, Nanjing, China. a Postgraduate student, orthodontics. b Associate chief physician, orthodontics. c Professor and chief physician, orthodontics. Yan Lv and Bin Yan contributed equally to this work as joint first authors. Reprint requests to: Lin Wang, Institute of Stomatology, Nanjing Medical University, Nanjing 210029, China; e-mail, [email protected]. Submitted, October 2010; revised and accepted, December 2010. 0889-5406/$36.00 Copyright Ó 2012 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2010.12.024 246 CASE REPORT
Transcript
CASE REPORT
Two-phase treatment of skeletal Class IImalocclusion with the combination of theTwin-block appliance and high-pull headgear
The patient was a boy with a Class II skeletal and dental relationship, a large overjet, an impinging overbite, anda steep mandibular plane angle. Treatment started with the Twin-block appliance combined with high-pull head-gear to promote growth of the mandible, restrain the maxilla in the anteroposterior and vertical planes, andimprove his profile. This was followed by extraction of the maxillary second premolars and the mandibular firstpremolars. Then fixed appliances were used to align and level the dentition. Pretreatment and posttreatmentrecords are shown, and the treatment results are stable 2 years after debonding. (Am J Orthod DentofacialOrthop 2012;142:246-55)
Functional appliances have been used for manyyears in the treatment of Class II malocclusions.Alteration of maxillary growth, improvement in
mandibular growth and position, and change in dentaland muscular relationships are the expected effects ofthese appliances.1
The Twin-block appliance, originally developed byClark,2 is a widely used functional appliance for themanagement of Class II malocclusion. It combinessplints with extraoral force and functional orthopedicforces. The appliance can be worn most of the time,with the advantage of allowing nearly a full range ofmandibular movement, easy acclimation, and reason-able speech. Its popularity also comes from its high pa-tient acceptability and its ability to produce rapid results.
High-pull headgear is used in Class II patients withincreased lower facial height. Teuscher3 suggested thatforward and downward growth of the maxilla could bealtered, and that the mandible could also change itsgrowth direction to a more forward and upward positionwith condylar adaptation using the high-pull headgear.
the Institute of Stomatology, Department of Orthodontics, Nanjing Med-niversity, Nanjing, China.raduate student, orthodontics.ciate chief physician, orthodontics.ssor and chief physician, orthodontics.v and Bin Yan contributed equally to this work as joint first authors.t requests to: Lin Wang, Institute of Stomatology, Nanjing Medicalrsity, Nanjing 210029, China; e-mail, [email protected], October 2010; revised and accepted, December 2010.5406/$36.00ight � 2012 by the American Association of Orthodontists..1016/j.ajodo.2010.12.024
Functional appliance therapy is followed by com-prehensive fixed-appliance therapy with or withoutextractions. Extraction of 4 premolars is indicatedprimarily for dental crowding, cephalometric discrep-ancy, or a combination in growing Class II patients.4,5
This case report demonstrates the use of the Twin-block appliance and high-pull headgear in a skeletalClass II Division 1 patient with a retrognathic mandible,protruding maxillary anterior teeth, excessive overjet,and complete overbite. By means of extraction of themaxillary second premolars and the mandibular firstpremolars, a well-aligned and leveled dentition and anacceptable profile were achieved.
DIAGNOSIS AND ETIOLOGY
The patient, a Chinese boy aged 12 years 2 months,was in fair health and motivated for treatment withthe chief complaint of protruded maxillary anteriorteeth and a receding chin for 6 years. He had been bitinghis lip since eruption of the deciduous dentition. He wasintroverted and had poor self-esteem, despite his normalmedical history. His father had a similar profile of pro-truded maxillary anterior teeth.
The facial photographs indicated a convex facialappearance, protruded lips, and moderate exposure ofthe maxillary incisors (Fig 1). He had a normal rangeof mandibular motion and no joint noise or pain. Themidline of the mandible was shifted 2 mm to the right.Other intraoral findings included gingivitis of theincisors, a short lingual frenum, and swollen tonsils.He had a Class II Division 1 malocclusion (bilateral fullClass II molars and canines) with a 15-mm overjet and
Fig 1. Pretreatment facial and intraoral photographs.
Lv, Yan, and Wang 247
an impinging overbite. Mild maxillary and moderatemandibular crowding as well as mesial inclination ofmandibular posterior teeth were observed. The curveof Spee was severe (6 mm), and the Bolton analysiswas 78% anteriorly and 88.4% totally. The cephalomet-ric analysis confirmed a skeletal Class II jaw relationshipwith a retrognathic mandible and a steep mandibularplane angle. Additionally, the maxillary and mandibularincisors were labially inclined. The panoramic radio-graph showed tooth buds of 4 third molars andsymmetric bilateral joints. A hand-wrist radiographshowed that he was at the stage of a growth spurt(Figs 2 and 3).
The etiology of this patient's malocclusion was prob-ably a combination of his lip-biting habit and geneticfactors.
TREATMENT OBJECTIVES
The treatment objectives were to correct the skeletalClass II malocclusion (retrognathic mandible), improvehis overjet and overbite, solve the dental crowding,
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and improve his facial appearance. Cessation of thelip-biting habit was considered essential. Much atten-tion would be given to controlling the vertical growthof his molars because of the steep mandibular planeangle.
TREATMENT ALTERNATIVES
Our plan was 2-phase treatment. To reduce theskeletal discrepancy anteroposteriorly by growth modifi-cation, a functional appliance (Twin-block with high-pull headgear) was planned for the phase 1 treatmentin preadolescence. Even though the patient did nothave a posterior crossbite, it was necessary to achievecompensatory lateral expansion of the maxillary archwith a maxillary expander. We aimed to inhibit thegrowth of the maxilla, promote that of the mandible,and control the eruption of his molars, thus to correctthe skeletal Class II relationship and improve his profile.Meanwhile, cessation of the lip-biting habit, functionaltraining of lip muscles, and psychological counselingwere important parts in the phase 1 treatment.
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Fig 3. Pretreatment radiographs and tracing.
Fig 2. Pretreatment dental casts.
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Fig 4. Facial and intraoral photographs after phase 1 treatment.
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The need for extraction was to be determined accord-ing to the profile, the molar relationship, and other re-sults after phase 1 treatment. A straight-wire appliancewas then applied to align and level the dentition andto achieve a neutroclusion and a better profile.
TREATMENT PROGRESS
The Twin-block appliance was used with the maxil-lary expander activated once a week after an adaptationperiod of 2 weeks. Meanwhile, the high-pull headgearwas worn for 9 months to restrict downward andforward growth of the maxilla. The patient wasinstructed to wear the Twin-block appliance 24 hoursa day, especially during eating, and to wear the headgearat least 14 hours per day. During the phase 1 treatment,the Twin-block appliance was adjusted twice to guidethe mandible forward. The patient was initially seen10 days after the first visit, then monthly so that theblocks and the headgear could be adjusted for retentionand stability as needed.
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Based on the crowding and slightly convex profileafter phase 1 treatment, we decided to extract themaxillary second premolars and the mandibular firstpremolars. Leveling and alignment progressed withnickel-titanium wires for 5 months. A lingual arch wasapplied to enhance anchorage during the early stageof phase 2 treatment.
An 0.018 3 0.025-in rectangular stainless steelarchwire in the maxillary arch was used with T-loopsto close space, and a 0.019 3 0.025-in rectangularstainless steel archwire with elastic chains was used inthe mandibular arch. Meanwhile, intermaxillary trac-tion was used to adjust the occlusion. After severaladjustments of the occlusion, the fixed applianceswere removed. The patient was given a pair of Hawleyretainers with an inclined maxillary biteplane.
TREATMENT RESULTS
When the phase 1 treatment ended, the patient'smandible was positioned forward, and the profile was
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Fig 5. Radiographs and tracing after phase 1 treatment.
250 Lv, Yan, and Wang
greatly improved (Fig 4). A skeletal anteroposteriorreduction was significant with 3.8� change in the ANBangle (the SNA angle had decreased from 81.2� to79.6�). The height of the maxillary first molar changedfrom 12.3 to 9 mm (Figs 5 and 6; Table). The intraoralexamination showed an expanded maxillary arch,improvement of the deep overbite and large overjet,labially inclined maxillary anterior teeth, and a mesial re-lationship of the first permanent molars.
After active treatment, a normal occlusion withoptimal overbite and overjet was achieved. The patientwas satisfied with his facial profile, which had changedfrom convex to straight. Lip protrusion was alsoimproved. Neutroclusion of the canines and the molars,good alignment and leveling of the maxillary andmandibular teeth, and correction of the dental midlinewere achieved (Fig 7). The posttreatment panoramicradiograph confirmed no apparent root resorption withthe restored maxillary and mandibular left first molars.It was still necessary to extract the mesially inclinedman-dibular third molars. The posttreatment cephalometric
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radiograph showed an acceptable anteroposteriorrelationship with a slightly increased mandibularplane angle of 0.3�. The cephalometric superimpositiondepicted an increased mandibular length, a forwardposition of the mandible, and a good interincisal angle(Figs 8 and 9; Table).
After retention with Hawley retainers for 2 years, astable occlusion and a coordinated facial profile wereobserved (Fig 10).
DISCUSSION
Because the patient had a skeletal Class II patternwith a retrognathic mandible at the preadolescent stage,indicated by the hand-wrist radiograph, it was necessaryto use a functional appliance and extraoral forces tocorrect the skeletal anteroposterior and vertical discrep-ancies.
There were some problems during early treatment,including psychosocial, behavioral, and financial factors,risks of tissue damage, treatment complexity, duration,and stability.6-10 However, early treatment can bring
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Fig 6. Superimposed pretreatment and postphase 1 treatment cephalometric tracings. The overallsuperimposition was registered on SN at sella. The maxillary superimposition was registered on thepalatal plane at ANS. The mandibular superimposition was registered on the lingual aspect of thesymphysis. Black line, Pretreatment; green line, postphase 1 treatment.
Table. Cephalometric analysis from lateral radio-graphs
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many benefits.11,12 In this patient, early intervention byfunctional appliances resulted in using his growthpotential, improved compliance and self-esteem, andstable results, as described in several studies.11-14
With regard to functional intervention, somearticles confirmed that more correction was accom-plished through dentoalveolar changes than by skeletalchanges.15,16 In this patient, the restrained maxilla andthe advanced mandible confirmed the skeletal changes.Meanwhile, the dentoalveolar changes includedmovement and inclination of the molars and incisors(Fig 6).
Several studies show that a Twin-block, an acti-vator, or a Herbst appliance can induce significantfavorable modifications in growing subjects with ClassII malocclusions.1,17-19 Compared with the Herbst andactivator appliances, the Twin-block appliance has2 obvious advantages.17 One advantage is greatermandibular growth because of the duration and timingwhen the appliance is worn. Another advantage wasthe apparent elongation of the mandibular ramusin our patient; this could be attributed to a greatervertical activation of the appliance (bite-blocks must beat least 5 to 7 mm thick vertically). In our patient, the
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Fig 7. Facial and intraoral photographs after phase 2 treatment.
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forward movement of the mandibular molars by theTwin-block appliance was significantly obvious (Fig 6).
Although the Twin-block appliance could providerelative distalization of the maxillary molars, high-pullheadgear was used because of the steep mandibularplane angle.1,20 The headgear also helped to restrainmaxillary growth, distally tip the maxillary teeth, andrestrain the eruption of the posterior maxillary teeth(Fig 6).21 Superimpositions showed that the maxillaryfirst molars moved distally without extrusion afterphase 1 treatment, followed by moving mesially witheruption after the phase 2 treatment (Figs 6 and 9).The eruption, which could have been due to thepatient's growth, was acceptable. This kind of erup-tion had little influence on the mandibular angleand the vertical facial height, since the firstmolars moved mesially when the spaces were beingclosed.
Furthermore, most researchers agree that the Twin-block produces retroclination of the maxillary incisorsand proclination of the mandibular incisors.15,22-24 Themaxillary incisors of this patient approached the goal
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of retroclination by 15.9� (U1-NA), whereas the mandib-ular incisors were proclined from 33� to 37.6� (L1-NB).Because of the subsequent fixed appliance treatment,the excess proclination of the mandibular incisors wasimproved from 37.6� to 36.1�.
Because of the overcorrection of the mesial molarrelationship after phase 1 treatment, 1 approach wasproposed tomove themandibular secondmolarsmesiallyinto neutroclusionwith implants after removing the thirdmolars. However, the crowded mandible, deep curve ofSpee, proclined mandibular incisors, and slightly convexprofile led to the decision to extract. Therefore, thealternative plan of removing the maxillary second pre-molars and mandibular first premolars was used to reachneutroclusion, resolve crowding, align the mandibularincisors, and improve the profile. Another importantreason for extracting the maxillary second premolarswas the steep mandibular plane angle, because movingposterior teeth mesially would be more favorablefor treatment stability. In this patient, there were noapparent differences between the T-loops and elasticchains when the extraction spaces were closed.
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Fig 8. Radiographs and tracing after phase 2 treatment.
Fig 9. Superimposed postphase 1 treatment and postphase 2 treatment cephalometric tracings. Theoverall superimposition was registered on SN at sella. Themaxillary superimposition was registered onthe palatal plane at ANS. The mandibular superimposition was registered on the lingual aspect of thesymphysis. Green line, Postphase 1 treatment; red line, postphase 2 treatment.
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Fig 10. Facial and intraoral photographs after 2 years of retention.
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