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Treatment of Class II open bite malocclusion supported by skeletal anchorage
44
Treatment of Class II open bite malocclusion supported by skeletal anchorage Kazuo Tanne, Junji Ohtani, Hiroko Sunagawa, Masato Kaku and Tadashi Fujita
INTRODUCTION Class II open bite morphologically is characterized by large molar height and subsequent mandibular displacement backward and downward. The large mandibular plane angle in Class II open bite is regarded as the most difficult malocclusion for orthodontic treatment because of the associated nasopharyngeal respiratory disorders that may have induced it. Nasopharyngeal disorders may lead to Class II open bite by the following sequence.2,3 ■
Nasopharyngeal airway obstruction Habitual mouth opening and breathing Reduction in masticatory muscle activity, masseter muscle in particular, with abnormal swallowing and tongue thrusting Prominent vertical growth of posterior dentoalveolar structures with large molar height Backward and downward displacement of the mandible Onset of Class II open bite with small and/or distally located mandible.
■ ■
■
■ ■
Based on this, it could be reasonably assumed that open bite can be corrected efficiently by molar intrusion and the resultant forward and upward rotation of the mandible (in other words, mandibular autorotation). An edgewise technique with extraction of teeth does enable correction of open bite through alignment of teeth, movement of the molar teeth into the extraction site and extrusion of the anterior teeth. However, this anterior teeth extrusion can lead to substantial root resorption. The multiloop edgewise archwire (MEAW) technique1 was developed for distalizing and intruding molars for the treatment of open bite (Fig. 44.1) and for treatment of mandibular prognathism and maxillary protrusion. However, the MEAW technique and the vertical elastics create repetitive intrusion and extrusion forces on the anterior teeth experience, and a certain amount of anterior teeth extrusion is almost always produced, which could lead to relapse of open bite and root resorption of the anterior teeth. Consequently, approaches using miniscrew implants (MIs) and miniplates may be an opportune way to obtain the desired results without unwanted side effects.
TREATMENT OF CLASS II OPEN BITE WITH MINISCREW IMPLANT-SUPPORTED TREATMENT It has been shown that molar intrusion is superior to incisor extrusion for open bite treatment in terms of lower incidences of relapse and root resorption.4 The treatment biomechanics when using MI anchorage may be similar to that when using the MEAW technique; however, the efficiency of molar intrusion is substantially higher with MI anchorage than with the MEAW technique. Successful use of MIs and miniplates as anchorage is dependent upon the clinician’s knowledge of the many factors that may affect their primary stability, both host factors (e.g. age, comorbidities, oral hygiene, bone quality) and technical factors (e.g. length, diameter of the MI, insertion technique, torque). Section II discusses in detail the factors for successful use of MIs and miniplates as temporary anchorage devices for orthodontic treatment. The twisting torque used during MI insertion has been shown to be one key determinant for successful implantation. The optimal twisting torque for MI insertion in humans is 5–15 Ncm for the maxilla and 6–17 Ncm for the mandible and clinicians are recommended to maintain MI insertion torques within these optimal ranges. Our group has recently developed an electrical driver (approved by the Japanese Ministry of Health) that facilitates control of rotation direction, speed and twisting torque (Fig. 44.2). This electrical hand driver is rechargeable, very light and easy to use.
CASE EXAMPLES The cases described below illustrate treatment approaches based on MIs (Cases 1 and 2) and a miniplate (Case 3).
CASE 1: AN ADULT WITH OPEN BITE A 23-year-old woman presented with open bite with a Class II molar relationship and large overjet and overbite (7.2 mm and −3.6 mm, respectively; Fig. 44.3A,B). Tooth–jaw discrepancy was prominent, and
O
O A
B
C
E
O O
E
E E
D
Fig. 44.1 (A-D) Biomechanics of the MEAW technique for the correction of open bite.
235
236 SECTION VIII: TREATMENT OF CLASS II MALOCCLUSION WITH DIFFERENT TEMPORARY ANCHORAGE DEVICES
so the maxillary first premolars and mandibular second premolars were extracted. After initial leveling with fixed appliances, four MIs were placed interradicularly in the maxilla, two on the buccal side and two on the palatal side (Fig. 44.3C,D). Elastics were used for the intrusion of the maxillary first and second molars and second premolars. The mandibular molars were fixed with a lingual arch because the curve of Spee was straight, indicating that molars were not extruded. After 8 months of treatment, the overbite was corrected from −3.6 to 2.0 mm. At the end of active treatment after 29 months, overjet and overbite were improved from 7.2 to 2.5 mm and from −3.6 to 2.5 mm, respectively, and a well-functioning occlusion was established (Fig. 44.3E,F). On the superimposition of the cephalometric tracings before and after treatment, maxillary molar intrusion and subsequent counterclockwise rotation of the mandible were observed (Fig. 44.3G). These changes constitute the principal mechanism for an upward and forward displacement
Rotation direction
Rotation speed
Maximum twisting torque Fig. 44.2 The electronic torque controllable hand driver.
A
B
E
F
of the mandible, directly leading to the correction of the Class II open bite. In addition, both maxillary and mandibular incisors experienced a prominent lingual tipping movement, which contributed to the correction of lip protrusion.
CASE 2: A 19-YEAR-OLD WOMAN WITH OPEN BITE AND IMPAIRED MASTICATORY FUNCTION A 19.5-year-old woman with open bite tendency complained that she had impaired masticatory function from the reduced occlusal contacts. Four premolars had been extracted previously. Her facial profile was convex, with mentalis muscle overactivity. She had Class II molar relationships with 5.5 mm overjet and 0.5 mm overbite (Fig. 44.4A). Functional examination showed that the patient had pain on the temporomandibular joints (TMJ) during chewing and mouth opening. She had skeletal Class II relationships of the jaws (ANB angle, 9.8°) with severe mandibular deficiency (ANB angle, 66.7°) and a steep mandibular plane angle (37.1°) (Table 44.1). On TMJ radiographs taken by the Schüller method, the condyles occupied a relatively posterior position on the glenoid fossa (Fig. 44.4E), implying an anterior displacement of the articular disk. Her diagnosis was as a skeletal Class II open bite with TMJ problems. The initial treatment plan, involving surgery, was refused by the patient. Treatment commenced with bonding of fixed appliances in both arches; a self-drilling titanium alloy MI (diameter, 1.6 mm; length, 6 mm; DualTop Auto Screw) was inserted into the midpalatal region at the level of the maxillary first molars in order to intrude the maxillary posterior teeth (Fig. 44.4B,C). A transpalatal arch was also placed in order to maintain the transversal dimension of the maxillary molars. The molars were intruded using elastic chains attached between the MI and the lingual sheaths of the first molar bands. Class II elastics were never used during treatment to avoid extrusion of mandibular posterior teeth. After 1 year of treatment, intrusion of the maxillary molars was completed. Overjet was changed from 5.5 to 2.0 mm and overbite from 0.5 to 2.5 mm; the teeth were well aligned in a good intercuspal position and the TMJ pain had disappeared. After a 3-year retention period, the occlusion was stable with no symptoms of TMJ problems (Fig. 44.4D). Radiography revealed that
C
D
G Fig. 44.3 Orthodontic treatment of Case 1. (A,B) Pre-treatment intraoral photographs. (C,D) Intrusion of the maxillary molars using MIs. (E,F) Post-treatment intraoral photographs. (G) Superimposition of the cephalometric tracings on the anterior cranial base (SN) before (black line) and after (red line) treatment.
Treatment of Class II open bite malocclusion supported by skeletal anchorage
A
B
C
E
237
D
F
H
G
I
Fig. 44.4 Orthodontic treatment of Case 2. (A) Pretreatment intraoral photograph. (E) Pretreatment TMJ radiograph of the right and left condyle. (B,C) Progress intraoral photographs during intrusion of maxillary molars using an MI. (D) Post-treatment intraoral photographs. (F) Post-treatment TMJ radiograph of the right and left condyle. (G-I) Superimpositions of the cephalometric tracings on the anterior cranial base (G), on the maxilla (H), and on the mandible (I) before (black line) and after (red line) treatment.
Table 44.1 Case 2: cephalometric measurements Measurements
Pre-retreatment
Post-treatment
SNA (°)
76.5
76.5
SNB (°)
66.7
67.8
ANB (°)
9.8
8.6
FMA (°)
37.1
35.1
FMIA (°)
41.2
44.3
IMPA (°)
101.6
100.6
U1-FH (°)
111.8
106.3
Z-angle (°)
56.0
62.7
Overjet (mm)
5.5
2.0
Overbite (mm)
0.5
2.5
IMPA, incisor mandibular plane angle; FMA, Frankfort-mandibular plane angle; FMIA, Frankfort-mandibular incisor angle.
after treatment both condyles were shifted significantly to an anterior position, occupying a more central position in the glenoid fossa (Fig. 44.4F). The facial profile was slightly changed, with a more relaxed mentalis muscle. Superimposition of the lateral cephalometric tracings before and after treatment revealed that the maxillary molars were intruded by 2 mm, the
mandible rotated in a counterclockwise direction (Fig. 44.4G–I), while the maxillary incisors experienced a lingual root torque. The ANB angle changed from 9.8 to 8.6°, the mandibular plane angle from 37.1 to 35.1° and the Z-angle from 56.0 to 62.7°, indicating an improvement of the lateral soft tissue profile (Table 44.1).
CASE 3: AN ADULT WITH SEVERE OPEN BITE AND DIFFICULTY IN LIP CLOSURE A 32-year-old woman with severe open bite complained of difficulty in lip closure, which was caused by the severe maxillary protrusion and the open bite. Although orthognathic surgery was proposed, she requested a conservative non-surgical treatment plan. She had a convex lateral soft tissue profile with mentalis muscle overactivity caused by habitual mouth opening and breathing. She had bilateral Class II molar relationships and a severe open bite, with an overjet and overbite of 5.0 mm and −4.0 mm, respectively (Fig. 44.5A,B). Cephalometric analysis revealed skeletal Class II relationships of the jaws (ANB angle, 11.0°) and a skeletal open bite with a large mandibular plane angle (39.3°). The treatment plan included molar intrusion and retraction of the anterior teeth after the extraction of maxillary second premolars with use of a miniplate placed on the zygomatic bone to provide skeletal anchorage (Fig. 44.5C).
238 SECTION VIII: TREATMENT OF CLASS II MALOCCLUSION WITH DIFFERENT TEMPORARY ANCHORAGE DEVICES
A
B
C
D
E
K
F
G
J
L H
I
Fig. 44.5 Orthodontic treatment of Case 3. (A,B) Pre-treatment intraoral photographs. (C) Intraoral photograph depicting the positioning of the zygomatic miniplate. (D,E) Progress intraoral photographs during intrusion of the molars with miniplates. (F,G) Post-treatment intraoral photographs. (H,I) Post-retention intraoral photographs. (J-L) Superimpositions of the cephalometric tracings on the anterior cranial base (J), on the maxilla (K), and on the mandible (L) before (black line) and after treatment (red line).
After insertion of fixed appliances and leveling of both dental arches, intrusion of the first and second molars was initiated using elastic chains connected to the miniplate. Seven months later, the open bite was corrected (Fig. 44.5D,E). After 2 years of treatment, an acceptable occlusion was achieved and retention was initiated with lingual bonded retainers on both dental arches and removable retainers for night wear (Fig. 44.5F,G). The occlusion was stable even after 2 years in retention (Fig. 44.5H,I). The overall facial balance was improved. Superimposition of the cephalometric tracings before and after treatment showed that the maxillary molars were intruded by 4.0 mm and a counterclockwise rotation of the mandible had occurred (Fig. 44.5J–L). The ANB angle changed from 11.0 to 5.2° and the mandibular plane angle from 39.3 to 37.0°.
CONCLUSIONS The treatment outcomes described here indicate that MIs are more reliable and efficient for the treatment of open bite than the MEAW approach, in terms of quick molar intrusion and distalization with less dependence on patient cooperation. Skeletal anchorage with miniplates on the zygomatic
bone (Case 3) provided more extensive and efficient tooth movements than MIs in terms of molar intrusion, molar distalization and retraction of anterior teeth, all of which are essential for the treatment of Class II open bite. These findings suggest that some patients with skeletal open bite, which would ideally have been treated by surgical correction, may be treated solely orthodontically. However, more extensive studies are required to examine the nature of relapse of molar intrusion and the long-term stability of the results.
REFERENCES 1. Kim YH. Anterior open bite and its treatment with MEAW. Angle Orthod 1987;57: 290–321. 2. Tanne K. Association between nasopharyngeal disease and orthodontic treatment. Part 1: the onset of malocclusion resulted from nasorespiratory disturbances. J Orthod Pract 2000;16:11–20. 3. Shikata N, Ueda HM, Kato M, et al. Association between nasal respiratory obstruction and vertical mandibular position. J Oral Rehabil 2004;31:957–62. 4. Chang YI, Moon SC. Cephalometric evaluation of the anterior open bite treatment. Am J Orthod Dentofacial Orthop 1999;115:29–37.
Treatment of Class II open bite malocclusion supported by skeletal anchorage Kazuo Tanne, Junji Ohtani, Hiroko Sunagawa, Masato Kaku and Tadashi Fujita
INTRODUCTION Class II open bite morphologically is characterized by large molar height and subsequent mandibular displacement backward and downward. The large mandibular plane angle in Class II open bite is regarded as the most difficult malocclusion for orthodontic treatment because of the associated nasopharyngeal respiratory disorders that may have induced it. Nasopharyngeal disorders may lead to Class II open bite by the following sequence.2,3 ■
Nasopharyngeal airway obstruction Habitual mouth opening and breathing Reduction in masticatory muscle activity, masseter muscle in particular, with abnormal swallowing and tongue thrusting Prominent vertical growth of posterior dentoalveolar structures with large molar height Backward and downward displacement of the mandible Onset of Class II open bite with small and/or distally located mandible.
■ ■
■
■ ■
Based on this, it could be reasonably assumed that open bite can be corrected efficiently by molar intrusion and the resultant forward and upward rotation of the mandible (in other words, mandibular autorotation). An edgewise technique with extraction of teeth does enable correction of open bite through alignment of teeth, movement of the molar teeth into the extraction site and extrusion of the anterior teeth. However, this anterior teeth extrusion can lead to substantial root resorption. The multiloop edgewise archwire (MEAW) technique1 was developed for distalizing and intruding molars for the treatment of open bite (Fig. 44.1) and for treatment of mandibular prognathism and maxillary protrusion. However, the MEAW technique and the vertical elastics create repetitive intrusion and extrusion forces on the anterior teeth experience, and a certain amount of anterior teeth extrusion is almost always produced, which could lead to relapse of open bite and root resorption of the anterior teeth. Consequently, approaches using miniscrew implants (MIs) and miniplates may be an opportune way to obtain the desired results without unwanted side effects.
TREATMENT OF CLASS II OPEN BITE WITH MINISCREW IMPLANT-SUPPORTED TREATMENT It has been shown that molar intrusion is superior to incisor extrusion for open bite treatment in terms of lower incidences of relapse and root resorption.4 The treatment biomechanics when using MI anchorage may be similar to that when using the MEAW technique; however, the efficiency of molar intrusion is substantially higher with MI anchorage than with the MEAW technique. Successful use of MIs and miniplates as anchorage is dependent upon the clinician’s knowledge of the many factors that may affect their primary stability, both host factors (e.g. age, comorbidities, oral hygiene, bone quality) and technical factors (e.g. length, diameter of the MI, insertion technique, torque). Section II discusses in detail the factors for successful use of MIs and miniplates as temporary anchorage devices for orthodontic treatment. The twisting torque used during MI insertion has been shown to be one key determinant for successful implantation. The optimal twisting torque for MI insertion in humans is 5–15 Ncm for the maxilla and 6–17 Ncm for the mandible and clinicians are recommended to maintain MI insertion torques within these optimal ranges. Our group has recently developed an electrical driver (approved by the Japanese Ministry of Health) that facilitates control of rotation direction, speed and twisting torque (Fig. 44.2). This electrical hand driver is rechargeable, very light and easy to use.
CASE EXAMPLES The cases described below illustrate treatment approaches based on MIs (Cases 1 and 2) and a miniplate (Case 3).
CASE 1: AN ADULT WITH OPEN BITE A 23-year-old woman presented with open bite with a Class II molar relationship and large overjet and overbite (7.2 mm and −3.6 mm, respectively; Fig. 44.3A,B). Tooth–jaw discrepancy was prominent, and
O
O A
B
C
E
O O
E
E E
D
Fig. 44.1 (A-D) Biomechanics of the MEAW technique for the correction of open bite.
235
236 SECTION VIII: TREATMENT OF CLASS II MALOCCLUSION WITH DIFFERENT TEMPORARY ANCHORAGE DEVICES
so the maxillary first premolars and mandibular second premolars were extracted. After initial leveling with fixed appliances, four MIs were placed interradicularly in the maxilla, two on the buccal side and two on the palatal side (Fig. 44.3C,D). Elastics were used for the intrusion of the maxillary first and second molars and second premolars. The mandibular molars were fixed with a lingual arch because the curve of Spee was straight, indicating that molars were not extruded. After 8 months of treatment, the overbite was corrected from −3.6 to 2.0 mm. At the end of active treatment after 29 months, overjet and overbite were improved from 7.2 to 2.5 mm and from −3.6 to 2.5 mm, respectively, and a well-functioning occlusion was established (Fig. 44.3E,F). On the superimposition of the cephalometric tracings before and after treatment, maxillary molar intrusion and subsequent counterclockwise rotation of the mandible were observed (Fig. 44.3G). These changes constitute the principal mechanism for an upward and forward displacement
Rotation direction
Rotation speed
Maximum twisting torque Fig. 44.2 The electronic torque controllable hand driver.
A
B
E
F
of the mandible, directly leading to the correction of the Class II open bite. In addition, both maxillary and mandibular incisors experienced a prominent lingual tipping movement, which contributed to the correction of lip protrusion.
CASE 2: A 19-YEAR-OLD WOMAN WITH OPEN BITE AND IMPAIRED MASTICATORY FUNCTION A 19.5-year-old woman with open bite tendency complained that she had impaired masticatory function from the reduced occlusal contacts. Four premolars had been extracted previously. Her facial profile was convex, with mentalis muscle overactivity. She had Class II molar relationships with 5.5 mm overjet and 0.5 mm overbite (Fig. 44.4A). Functional examination showed that the patient had pain on the temporomandibular joints (TMJ) during chewing and mouth opening. She had skeletal Class II relationships of the jaws (ANB angle, 9.8°) with severe mandibular deficiency (ANB angle, 66.7°) and a steep mandibular plane angle (37.1°) (Table 44.1). On TMJ radiographs taken by the Schüller method, the condyles occupied a relatively posterior position on the glenoid fossa (Fig. 44.4E), implying an anterior displacement of the articular disk. Her diagnosis was as a skeletal Class II open bite with TMJ problems. The initial treatment plan, involving surgery, was refused by the patient. Treatment commenced with bonding of fixed appliances in both arches; a self-drilling titanium alloy MI (diameter, 1.6 mm; length, 6 mm; DualTop Auto Screw) was inserted into the midpalatal region at the level of the maxillary first molars in order to intrude the maxillary posterior teeth (Fig. 44.4B,C). A transpalatal arch was also placed in order to maintain the transversal dimension of the maxillary molars. The molars were intruded using elastic chains attached between the MI and the lingual sheaths of the first molar bands. Class II elastics were never used during treatment to avoid extrusion of mandibular posterior teeth. After 1 year of treatment, intrusion of the maxillary molars was completed. Overjet was changed from 5.5 to 2.0 mm and overbite from 0.5 to 2.5 mm; the teeth were well aligned in a good intercuspal position and the TMJ pain had disappeared. After a 3-year retention period, the occlusion was stable with no symptoms of TMJ problems (Fig. 44.4D). Radiography revealed that
C
D
G Fig. 44.3 Orthodontic treatment of Case 1. (A,B) Pre-treatment intraoral photographs. (C,D) Intrusion of the maxillary molars using MIs. (E,F) Post-treatment intraoral photographs. (G) Superimposition of the cephalometric tracings on the anterior cranial base (SN) before (black line) and after (red line) treatment.
Treatment of Class II open bite malocclusion supported by skeletal anchorage
A
B
C
E
237
D
F
H
G
I
Fig. 44.4 Orthodontic treatment of Case 2. (A) Pretreatment intraoral photograph. (E) Pretreatment TMJ radiograph of the right and left condyle. (B,C) Progress intraoral photographs during intrusion of maxillary molars using an MI. (D) Post-treatment intraoral photographs. (F) Post-treatment TMJ radiograph of the right and left condyle. (G-I) Superimpositions of the cephalometric tracings on the anterior cranial base (G), on the maxilla (H), and on the mandible (I) before (black line) and after (red line) treatment.
Table 44.1 Case 2: cephalometric measurements Measurements
Pre-retreatment
Post-treatment
SNA (°)
76.5
76.5
SNB (°)
66.7
67.8
ANB (°)
9.8
8.6
FMA (°)
37.1
35.1
FMIA (°)
41.2
44.3
IMPA (°)
101.6
100.6
U1-FH (°)
111.8
106.3
Z-angle (°)
56.0
62.7
Overjet (mm)
5.5
2.0
Overbite (mm)
0.5
2.5
IMPA, incisor mandibular plane angle; FMA, Frankfort-mandibular plane angle; FMIA, Frankfort-mandibular incisor angle.
after treatment both condyles were shifted significantly to an anterior position, occupying a more central position in the glenoid fossa (Fig. 44.4F). The facial profile was slightly changed, with a more relaxed mentalis muscle. Superimposition of the lateral cephalometric tracings before and after treatment revealed that the maxillary molars were intruded by 2 mm, the
mandible rotated in a counterclockwise direction (Fig. 44.4G–I), while the maxillary incisors experienced a lingual root torque. The ANB angle changed from 9.8 to 8.6°, the mandibular plane angle from 37.1 to 35.1° and the Z-angle from 56.0 to 62.7°, indicating an improvement of the lateral soft tissue profile (Table 44.1).
CASE 3: AN ADULT WITH SEVERE OPEN BITE AND DIFFICULTY IN LIP CLOSURE A 32-year-old woman with severe open bite complained of difficulty in lip closure, which was caused by the severe maxillary protrusion and the open bite. Although orthognathic surgery was proposed, she requested a conservative non-surgical treatment plan. She had a convex lateral soft tissue profile with mentalis muscle overactivity caused by habitual mouth opening and breathing. She had bilateral Class II molar relationships and a severe open bite, with an overjet and overbite of 5.0 mm and −4.0 mm, respectively (Fig. 44.5A,B). Cephalometric analysis revealed skeletal Class II relationships of the jaws (ANB angle, 11.0°) and a skeletal open bite with a large mandibular plane angle (39.3°). The treatment plan included molar intrusion and retraction of the anterior teeth after the extraction of maxillary second premolars with use of a miniplate placed on the zygomatic bone to provide skeletal anchorage (Fig. 44.5C).
238 SECTION VIII: TREATMENT OF CLASS II MALOCCLUSION WITH DIFFERENT TEMPORARY ANCHORAGE DEVICES
A
B
C
D
E
K
F
G
J
L H
I
Fig. 44.5 Orthodontic treatment of Case 3. (A,B) Pre-treatment intraoral photographs. (C) Intraoral photograph depicting the positioning of the zygomatic miniplate. (D,E) Progress intraoral photographs during intrusion of the molars with miniplates. (F,G) Post-treatment intraoral photographs. (H,I) Post-retention intraoral photographs. (J-L) Superimpositions of the cephalometric tracings on the anterior cranial base (J), on the maxilla (K), and on the mandible (L) before (black line) and after treatment (red line).
After insertion of fixed appliances and leveling of both dental arches, intrusion of the first and second molars was initiated using elastic chains connected to the miniplate. Seven months later, the open bite was corrected (Fig. 44.5D,E). After 2 years of treatment, an acceptable occlusion was achieved and retention was initiated with lingual bonded retainers on both dental arches and removable retainers for night wear (Fig. 44.5F,G). The occlusion was stable even after 2 years in retention (Fig. 44.5H,I). The overall facial balance was improved. Superimposition of the cephalometric tracings before and after treatment showed that the maxillary molars were intruded by 4.0 mm and a counterclockwise rotation of the mandible had occurred (Fig. 44.5J–L). The ANB angle changed from 11.0 to 5.2° and the mandibular plane angle from 39.3 to 37.0°.
CONCLUSIONS The treatment outcomes described here indicate that MIs are more reliable and efficient for the treatment of open bite than the MEAW approach, in terms of quick molar intrusion and distalization with less dependence on patient cooperation. Skeletal anchorage with miniplates on the zygomatic
bone (Case 3) provided more extensive and efficient tooth movements than MIs in terms of molar intrusion, molar distalization and retraction of anterior teeth, all of which are essential for the treatment of Class II open bite. These findings suggest that some patients with skeletal open bite, which would ideally have been treated by surgical correction, may be treated solely orthodontically. However, more extensive studies are required to examine the nature of relapse of molar intrusion and the long-term stability of the results.
REFERENCES 1. Kim YH. Anterior open bite and its treatment with MEAW. Angle Orthod 1987;57: 290–321. 2. Tanne K. Association between nasopharyngeal disease and orthodontic treatment. Part 1: the onset of malocclusion resulted from nasorespiratory disturbances. J Orthod Pract 2000;16:11–20. 3. Shikata N, Ueda HM, Kato M, et al. Association between nasal respiratory obstruction and vertical mandibular position. J Oral Rehabil 2004;31:957–62. 4. Chang YI, Moon SC. Cephalometric evaluation of the anterior open bite treatment. Am J Orthod Dentofacial Orthop 1999;115:29–37.