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The Advanced Molar Distalization Appliance
30
The Advanced Molar Distalization Appliance Moschos A. Papadopoulos
INTRODUCTION A number of systems have been developed to use miniscrew implants (MIs) as temporary anchorage devices to support orthodontic movements. Chapter 29 describes one such system, the miniscrew implant-supported distalization system (MISDS). While this system has many advantages, one disadvantage is the laboratory work needed for the fabrication of the appliance, and the consequent increased cost of treatment and delay in initiating treatment. This chapter describes a novel MI-supported device, the Advanced Molar Distalization Appliance (AMDA), that has all the advantages of the MISDS but eliminates the need for laboratory work. The AMDA can be used for the efficient, invisible, non-compliant bilateral or unilateral distalization of maxillary molars (Fig. 30.1), as well as in conjunction with full fixed appliances for the subsequent retraction of the anterior teeth.1
THE ADVANCED MOLAR DISTALIZATION APPLIANCE The AMDA (available soon by Dentaurum, Ispringen, Germany) is a prefabricated device anchored to the palate by MIs (Fig. 30.1A),2 and comprising:
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a tubing system with encased compressed nickel-titanium (Ni-Ti) open coil springs to provide the necessary distalization force; in the conventional form this is used on both sides of the dental arch but can be activated unilaterally if needed conventional orthodontic bands on maxillary first molars equipped with lingual sheaths a horseshoe-type palatal archwire a palatal anchorage unit.
The design of the appliance unit and the use of palatal MIs to provide temporary and stationary anchorage for all phases of treatment avoids the unwanted problems of conventional non-compliance devices (see Chapter 2) such as molar rotation or distal crown tipping and forward movement and proclination of the anterior teeth. In contrast to conventional noncompliance devices, spaces are created between all the posterior teeth rather than just between the maxillary first molars and second premolars. This is because the premolars and canines are able to drift distally under the pull of the transeptal fibers, which also shortens overall treatment time.
THE TUBING SYSTEM The tubing system (Fig. 30.1) runs on a horseshoe-type archwire and consists of two tubes sliding one into the other: an outer tube (approximate
length, 10–12 mm; outer diameter, 3 mm) and an inner tube (approximate length, 8–10 mm; outer diameter, 2.3 mm). Compressed Ni-Ti open coil springs encased in each tubing system deliver a distalization force of approximately 300–350 g when fully activated. Two stop screws are incorporated in the tubing system, one at the mesial end of the inner tube and another at the distal end of the outer tube. Activation or deactivation of the force system takes place by screwing or unscrewing these stop screws. In addition, an SS extension wire (diameter, 0.9 mm; approximate total height, 10 mm) is attached to the external surface of the outer tube. It has an S-shape to allow height adjustment. The wire has a transpalatal type of ending (similar to a conventional transpalatal arch [TPA]) to facilitate insertion of the appliance into the lingual sheaths of conventional orthodontic bands cemented on the maxillary first molars. The single tubing system version used for unilateral maxillary molar distalization (Fig. 30.1C) has an almost straight palatal archwire with one anterior loop for the insertion of a single MI, with an additional SS wire extension (diameter, 0.9 mm) soldered approximately 2 mm distal to the anterior loop and bonded to the occlusal surface of the first premolar for dental anchorage to avoid any rotational movements of the system during unilateral distalization. Alternatively, for unilateral molar distalization a conventional AMDA relying only on skeletal anchorage can be used. In this case from the two bilateral tubing systems of AMDA only one is activated (Fig. 30.1B).
THE HORSESHOE-TYPE ARCHWIRE The horseshoe-type SS archwire (diameter, 0.9 mm) is positioned on the palate at a distance of 1–2 mm from the mucosa and runs inside the inner tube of the tubing system (Fig. 30.1). The archwire is positioned approximately 10 mm apically to the occlusal surfaces of the maxillary molars, thus passing through or very close to their centers of resistance in order to facilitate an almost pure bodily molar distalization. Its position parallel to the occlusal plane forces the maxillary molars to slide on it and guides them distally without, or with minimal, rotation. Two symmetrical closed loops (or in a later version two movable metallic rings) are attached to the archwire to indicate the insertion sites for the MIs, as well as to secure the appliance onto the MIs.
THE ANCHORAGE UNIT Two self-drilling and self-tapping MIs (suggested diameter 2 mm and length 8–10 mm) are used to anchor the AMDA and to resist the reciprocal forces during molar distalization and anterior teeth retraction. The MIs should have collars of varying lengths to allow a suitable size to be chosen for the individual’s width of palatal mucosa. The MIs are placed in the
Fig. 30.1 The Advanced Molar Distalization Appliance (AMDA). (A) The horseshoe-type palatal archwire with the tubing systems for bilateral use. (B) The conventional AMDA for unilateral use relying only on skeletal anchorage with bilateral tubing systems of which only one is activated. (C) A single tubing system for unilateral use using both dental and skeletal anchorage. (A from Papadopoulos, 2010,1 with permission of Bentham Science.) A
160
B
C
The Advanced Molar Distalization Appliance
paramedian region of the palate 3–6 mm from the midpalatal suture and 3–6 mm posterior to the incisive foramen. The insertion of the two MIs at a distance of 3–6 mm posterior to the incisive foramen provides a safety clearance of approximately 7–10 mm between the MIs and the dental roots of the anterior teeth (depending on the root inclination of these teeth). This avoids contact of the MIs and these teeth during molar distalization, and, more importantly, during anterior teeth retraction.
CLINICAL PROCEDURE
PHASE ONE: MOLAR DISTALIZATION The AMDA and MIs can be inserted in a single appointment by the orthodontist. Normal full infection control measures similar to those for extractions should be used, including sterilization of the MI kit. Conventional orthodontic molar bands with lingual sheaths are cemented on the maxillary first molars. The AMDA is prefabricated and so some individual adjustments are only necessary, which can be carried out either directly in the patient’s mouth or indirectly on the initial maxillary cast. The palatal archwire extensions are inserted in the lingual sheaths of the molar bands. Once the parallel positioning of the appliance and its width and height have been checked, the mesial stop screws are moved distally to fully compress the coil spring encased in the tubing system and the distal stop screws are screwed in place to stabilize the tubing systems on the archwire. The final length of the palatal archwire is determined by marking its distal ends with a pencil, leaving approximately 8–10 mm extending out of the distal screw. With the appliance removed from the patient’s mouth, the distal ends are cut off at the mark and a bend or loop is formed on each distal end to act as mechanical stop to prevent any distalization of the molars beyond this point and to avoid any tissue irritation. Alternatively or in addition, a small amount of light-cured resin can be added to the ends to ensure that the molars cannot slip out of the wire. The appliance is then inserted into the patient’s mouth, ensuring that it is parallel to the occlusal plane and the two symmetrical loops are 3–6 mm posterior of the incisive foramen. The wire extensions welded on the tubing systems are inserted into the lingual sheaths of the molar bands and secured in position with SS ligature wires. MIs with appropriate collar length are inserted through the loops using the normal procedure. The head of the MI should be wider than the diameter of the loops to provide the appropriate stability to the system. However, in some cases, fixing of the AMDA with the MIs through SS ligature wires (diameter, 0.012 inch) might be necessary, particularly when MIs with smaller head dimensions are used. In some cases, SS ligature wires of a smaller diameter (0.012 inch instead of 0.040 inch) might be needed if the chosen MIs have smaller heads. A small portion of light-cure resin can be added to cover the top of each implant head plus the endings of the ligature wires and the loops of the palatal archwire to avoid plaque accumulation. The AMDA can be loaded immediately with light orthodontic forces by unscrewing the distal screws to allow free distal sliding of the posterior part of the tubing system and thus distal movement of the maxillary molars. The mesial stop screws of the tubing systems (which are already moved and fixed distally) are not altered and so the compressed coil springs can begin to exercise their distalizing force. Distal movement of the maxillary molars can be enhanced through disocclusion of the posterior teeth using lower acrylic splints with posterior bite blocks or cemented build-ups. Lateral cephalometric radiography can be used to check the installation immediately after placement, at the end of phase one and at a completion of treatment.
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Patients are given clear instructions on how to maintain oral hygiene. They are monitored every 4 weeks for hygiene, for the stability of the MIs, and for further adjustments and reactivation of the appliance. Reactivation occurs by unscrewing the mesial stop screw, moving the anterior part of the tubing system more distally, thus squeezing the encased coil springs, and then rescrewing the stop screws in the new position. Any tendency for rotation of the maxillary molars can be countered by bending the wire extensions of the transpalatal archwire extensions welded to the tubing systems. A treatment period of 4–8 months is usually needed for distalization of the first maxillary molars into a Class I molar relationship.
PHASE TWO: ANTERIOR TEETH RETRACTION The AMDA is easily converted to a passive skeletally anchored horseshoetype palatal arch providing indirect anchorage for the posterior teeth during a second phase of treatment to retract the anterior teeth and level and align the dental arches using a full fixed appliance. For this purpose, the distal stop screws are tightened to prevent any further molar distal movement and the mesial stop screws are moved distally and screwed in this position again, totally squeezing the coil springs encased in the tubing systems. This retains the first maxillary molars in their new positions and allows them to become the anchors to support the subsequent retraction of the anterior teeth. In some cases, such as when the first maxillary molars are already rotated prior to the initiation of orthodontic treatment and the second molars are already erupted, rotation of first maxillary molars cannot be totally avoided during the active distalization phase through bend adjustments of the transpalatal archwire extensions of the tubing systems. In these cases the AMDA and the MIs are removed after retraction of the anterior teeth and, since there is no more need to support molar anchorage, a TPA is used until completion of treatment to correct this rotation.
REMOVAL OF THE APPLIANCE The MIs are removed by unscrewing the head of the MI. Local anesthesia may be needed if there is any tissue covering the MI. The AMDA is removed by cutting the SS ligature wires that secure the transpalatal wire extensions to the lingual sheaths of the molar bands. The AMDA can then be removed from the sheaths in the normal way. Debonding of the conventional fixed orthodontic appliances (bands and brackets) and cleaning procedures are performed as usual.
CLINICAL APPLICATIONS The AMDA can be used efficiently for the comprehensive treatment of Class II malocclusion. The following two case studies illustrate its use for bilateral and unilateral maxillary molar distalization.
CASE 1: BILATERAL MAXILLARY MOLAR DISTALIZATION A 12-year-old girl was referred with a chief complaint of protrusion of the upper anterior teeth. She had a symmetric face and a convex facial profile with protruded lips, a retruded mandible and increased overjet (6 mm) and overbite (5 mm). She had permanent dentition, with the second permanent molars erupted, no caries and good oral hygiene. Both maxillary first molars, particularly the left one, were mesially rotated. Occlusal analysis revealed a Class II, division 1 malocclusion, with bilateral Class II molar relationships: three-quarters cusp on the right and full cusp on the left. She
162 SECTION VII: MINISCREW IMPLANTS FOR THE TREATMENT OF CLASS II MALOCCLUSION
Treatment
Table 30.1 Cephalometric analysis during treatment Normal values
T0
T1
T2
T3
SNA (o)
82.1
84.5
85.8
87.9
84.2
SNB (o)
80.2
80.3
78.9
79.7
79.7
Facial angle (o)
85.6
94.7
94.5
91.5
93.4
ANB(o)
1.9
Variables Sagittal relationships
Individual ANB(o)
4.2
6.9
8.2
4.5
5.1
6.1
6.9
5.3
NA-APog (o)
0.4
10.2
14.2
16.9
8.6
H angle (o)
11.3
17.4
10.9
21.7
20.2
SN-SGn (o)
65.3
64.1
66.2
65.4
65.1
SN-NL (o)
6.8
4.8
5.7
5.5
4.1
SN-ML (o)
29.8
32.2
34.8
34.7
33.9
Ar-Go-Me (o)
124.4
135.8
132.3
137
136.2
SGo : NMe × 100 (%)
68.2
64.5
62.9
63.5
63.7
1s-NL (o)
112
122.4
115.6
106.9
110.8
1i-ML (o)
92.7
94.5
92.2
95.1
98.7
1s-SN (o)
104
117.6
109.9
101.3
106.7
Lower incisor to A-Pg (mm)
1.2
4.1
2.6
3.8
5.3
Interincisal angle (o)
132.3
117.6
123.1
128.9
120.7
112
93.2
105.3
99.8
99.7
Vertical relationships
Dental relationships
Soft tissue relationships Nasolabial angle (o)
T0, initiation of treatment; T1, after maxillary molar distalization; T2, after completion of anterior teeth retraction; T3, immediately after completion of total orthodontic treatment.
had spaces in her upper anterior teeth, which were also proclined, and there was a mild crowding in the lower anterior teeth. Maxillary midline was coincident with the facial midline, while the mandibular one deviated 2 mm to the left. Functional analysis revealed no disturbances of mandibular movements and normal temporomandibular joint function. The initial panoramic radiograph showed that the third molars were present, no teeth were missing and alveolar bone and root formation were within normal limits. Cephalometric analysis of the lateral cephalometric radiographs using ViewBox version 3.1 (dHal, Athens, Greece) showed skeletal Class II relationships associated with a prognathic maxilla and an orthognathic mandible (Table 30.1). Analysis of vertical skeletal relationships showed a slight tendency towards a vertical growth pattern with a corresponding clockwise rotation of the mandible and an upward inclination of the palatal plane. Analysis of dental relationships revealed protrusive incisors, as well as proclination of the upper and lower incisors in relation to the anterior cranial base and the mandibular plane, respectively. Finally, soft tissue analysis showed a decreased nasolabial angle. The patient did not want to wear any extraoral appliances and together with her parents requested orthodontic treatment without any extractions. The treatment objectives were to distalize the first maxillary molars bilaterally and then to correct overjet and overbite by retracting and intruding the maxillary anterior teeth, to improve the interincisal angle relationship, correct the midline deviation and achieve a stable, functional occlusion as well as improve lip competence and facial balance.
Two MIs were placed in the paramedian region of the palate and the AMDA fitted; it was activated and correct placement confirmed radiographically as described above (Fig. 30.2A,B). Since both first and second molars had to be moved simultaneously, and in order to enhance distal movement of these teeth, a removable acrylic splint with posterior bite blocks was also inserted to disocclude the posterior teeth. The patient was instructed to wear this splint 24 hours a day including meals and to remove it only for cleaning. After 4 months, the splint with bite blocks was removed as the maxillary molar cusps no longer interfered with the mandibular molar cusps. After 7 months, both first and second maxillary molars were distalized bilaterally and the first maxillary molars had a Class I molar relationship (Fig. 30.2C,D). The maxillary premolars and canines had also drifted to an almost Class I relationship. Further radiographic evaluation confirmed that the MIs were stable and would not interfere with retraction of the anterior teeth. The second phase was commenced by bonding a preadjusted edgewise appliance with Roth’s prescription and 0.018 inch slot (Silkon esthetic brackets; American Orthodontics, Sheboygan, WI, USA), and a Ni-Ti archwire (0.012 inch) was inserted for initial alignment of the teeth (Fig. 30.2E). The AMDA was converted to a horseshoe-type TPA as described above (Fig. 30.2F). After another month, Ni-Ti wires (0.016 inch) were used for teeth alignment in both arches. Two months later, Ni-Ti archwires (0.016 × 0.016 inch) were placed and elastic chains were also inserted on the maxillary arch in order to start the en masse retraction of the maxillary anterior teeth. One month later, SS archwires (0.016 × 0.016 inch) were inserted to further align both dental arches and for the continuation of the en masse retraction of the maxillary anterior teeth. After a further month (i.e. 12 months after initiation of treatment), the retraction of the anterior teeth was completed (Fig. 30.2G,H). At that time, a slight increase in mesial rotation of the maxillary first molars was observed despite adjustment of the transpalatal-type wire extensions of the AMDA during treatment. Therefore, it was decided to remove the AMDA and the MIs and insert a TPA to correct the rotations. After 3 months, the molar rotation had been corrected and SS archwires (0.016 × 0.016 inch) with reverse curves of Spee and asymmetric elastics were inserted to fully align the dental arches, correct the midline deviation and further correct the deep bite (Fig. 30.2I,J). Four months later, new SS archwires were used for final alignment of the teeth and detailing the occlusion. The fixed appliances were removed 5 months later (i.e. after 24 months of total treatment time), following establishment of a nice posterior intercuspation and a well-functioning and stable occlusion (Fig. 30.2K,L). After debonding, a lingual fixed retainer was bonded to the mandibular anterior teeth extending from canine to canine. Maxillary retention was accomplished by means of a removable acrylic retainer. The patient was instructed to wear the retainer 24 hours a day for 2 months and then at night only.
Treatment Results The treatment results were within the initial treatment goals and both the patient and her parents were very pleased with her final facial and dental appearance (Fig. 30.2K,L) and because treatment did not involve extraoral appliances, intermaxillary elastics or extractions. Treatment took 24 months and achieved a bilateral Class I molar and canine relationship with optimal alignment of both maxillary and mandibular teeth, a well-intercuspated and
The Advanced Molar Distalization Appliance
A
B
C
D
E
F
G
H
I
J
K
L
N
M
163
O
P
Fig. 30.2 Case 1: unilateral maxillary molar distalization. (A,B) Pretreatment views immediately after insertion of the Advanced Molar Distalization Appliance (AMDA). (C,D) Molar distalization completed. Note the initial drifting of the premolars and canines. (E,F) Insertion of conventional full fixed orthodontic appliances and conversion of the AMDA to a skeletally anchored horseshoe-type transpalatal arch. (G,H) Retraction of the maxillary anterior teeth. (I,J) Correction of molar rotation. (K,L) At end of treatment following removal of the fixed appliances. (M,N) Superimposition of the cephalometric tracings to show changes from before treatment start (black line) to end of active molar distalization (blue line) on the anterior cranial base (M) and the maxillary plane (N). (O,P) Superimposition of the cephalometric tracings on the maxillary plane to show changes from after active molar distalization (black line) to retraction of the maxillary anterior teeth (red line) (O) and from after retraction of the maxillary anterior teeth (blue line) to completion of treatment and removal of all appliances (black line) (P). (A–G from Papadopoulos, 2010,1 with permission of Bentham Science.)
stable occlusion and ideal overjet and overbite. The mild crowding, the midline deviation and the medial diastema were also corrected (Fig. 30.2K,L). Root parallelism was confirmed radiographically.
Cephalometric Analysis after Distalization After distalization, the first maxillary molars were moved almost bodily without distal tipping, while the anterior teeth did not procline at all; instead they were slightly retruded. Further, during the subsequent
retraction of the anterior teeth, the maxillary molars, which served as anchors during this phase, remained almost totally stable, while the anterior teeth retruded substantially. Skeletal Class II relationships were maintained as were the sagittal skeletal positions of the maxilla and mandible (Table 30.1). There was a slight increase in vertical growth pattern. The maxillary incisors were notably retracted, while the mandibular incisors had a slight lingual inclination. The interincisal angle was also significantly increased. There was an increase in nasolabial angle.
164 SECTION VII: MINISCREW IMPLANTS FOR THE TREATMENT OF CLASS II MALOCCLUSION
Superimposition of the cephalometric tracings on the anterior cranial base from before treatment start and after active molar distalization (and subsequent passive drifting of the anterior teeth; Fig. 30.2M) showed a slight downward positioning of the mandible due to movement of maxillary molars into a more distal position, forcing the bite to open. The corresponding superimposition on the maxillary plane (Fig. 30.2N) showed a pure bodily distal movement of the first maxillary molars with a slight extrusion but without distal tipping, as well as slight retrusion and extrusion of the anterior teeth.
Table 30.2 Cephalometric analysis during treatment Normal values
T0
T1
T2
SNA (o)
82.1
84.3
83.2
83
SNB (o)
80.2
80.6
79.7
81.8
Facial angle (o)
85.6
96
95.4
99.2
ANB(o)
1.9
3.7
3.5
1.2
4.8
4.4
4.1
NA-APog (o)
0.4
5.5
4.1
−0.5
H angle (o)
11.3
17.9
17.4
15.9
SN-SGn (o)
65.3
65.2
65.7
64.2
SN-NL (o)
6.8
9.4
6.7
4.8
SN-ML (o)
29.8
31.1
31.4
30.1
Ar-Go-Me (o)
124.4
116.6
122.8
123.5
SGo : NMe X 100 (%)
68.2
65.4
66.7
67.8
1s-NL (o)
112
110.3
111.6
116
1i-ML (o)
92.7
96
96.7
102.5
1s-SN (o)
104
100.9
104.8
111.3
Cephalometric Analysis at End of Treatment
Lower incisor to A-Pg (mm)
1.2
0.3
0.4
1.8
A comparison of the final result with that before treatment start showed maintenance of the skeletal Class II relationships as well as of the sagittal skeletal positions of the maxilla and mandible (Table 30.1). There was a slight increase in vertical growth pattern, the maxillary incisors were significantly retracted, the mandibular incisors slightly proclined and the interincisal angle was slightly increased. Finally, there was an increase in nasolabial angle. Superimposition of the cephalometric tracings on the maxillary plane after anterior teeth retraction and after completion of treatment revealed that the position of the first molars remained unchanged, while the anterior teeth were further intruded and slightly retruded (Fig. 30.2P).
Interincisal angle (o)
132.3
132
127.2
116.1
112
101.6
100.5
101.8
Cephalometric Analysis after Anterior Teeth Retraction A comparison of the situation after the anterior teeth retraction phase with that at the end of molar distalization showed maintenance of the skeletal Class II relationships, while both the maxilla and mandible were moved slightly anteriorly (Table 30.1). Vertical growth pattern remained almost stable. The maxillary incisors were further retracted, while the mandibular incisors had a slight labial inclination. The interincisal angle was also significantly increased. Soft tissue analysis showed a decrease in the nasolabial angle. Trace comparisons confirmed that the first molars remained stable in position while the anterior teeth were retracted and slightly extruded (Fig. 30.2O).
CASE 2: UNILATERAL MAXILLARY MOLAR DISTALIZATION A 14-year-old boy was referred with a complaint of a crossbite by the upper right lateral incisor. He had a symmetric face and a slightly convex facial profile. He had a complete permanent dentition with the second permanent molars already erupted in both arches, good oral hygiene and no caries. Occlusal analysis revealed a one-half cusp Class II molar relationship on the right and a Class I on the left side. There was a crossbite between the right upper and lower lateral incisors, a normal overjet of 6 mm, an overbite of 3 mm and a slight maxillary midline deviation of 1 mm to the left. In addition, there was 3 mm crowding on the maxillary anterior teeth and a mild crowding on the mandibular anterior teeth. Functional analysis revealed no disturbances of the mandibular movements and normal temporomandibular joint function. The initial panoramic radiograph showed that the third molars were present, and no teeth were missing. Cephalometric analysis of the pretreatment lateral cephalometric radiograph showed skeletal Class I relationships associated with a slight prognathic maxilla and an orthognathic mandible (Table 30.2). There was a slight tendency towards a vertical growth pattern with a corresponding clockwise rotation of the mandible and a downward inclination of the palatal plane. There was also a slight retroclination of the upper incisors in relation to the anterior cranial base and proclination of the lower incisors in relation to the mandibular plane,
Variables Sagittal relationships
Individual ANB(o)
Vertical relationships
Dental relationships
Soft tissue relationships Nasolabial angle (o)
T0, initiation of treatment; T1, after maxillary molar distalization; T2, immediately after completion of total orthodontic treatment.
while the interincisal angle was normal. Finally, there was a decreased nasolabial angle. The patient and his parents wanted a treatment plan that did not involve extraoral appliances or extractions. The treatment objectives were to distalize the right first maxillary molar into a Class I relationship, to maintain the Class I relationship of the left first molars and then to correct the crossbite between the right upper and lower lateral incisors, the anterior crowding in both arches and the midline deviation, plus to achieve a stable, functional occlusion by establishing a well-intercuspated bilateral Class I molar and canine relationship.
Treatment Treatment was started with the placement of the single-tube configuration of AMDA (Fig. 30.1C) on the right side of the palate. Skeletal anchorage was provided by a single MI inserted through the anterior loop of the AMDA, while additional dental anchorage was provided by bonding the extension wire on the occlusal surface of the right maxillary first premolar (Fig. 30.3A,B). The AMDA was activated and correct placement confirmed radiographically, as described above. Light-cured resin was applied to the top of the implant head to avoid plaque accumulation. A removable acrylic splint with posterior bite blocks was also inserted to disocclude the posterior teeth in order to enhance simultaneous distal movement of the first and second molars and to facilitate correction of the crossbite of the right maxillary lateral incisor (Fig. 30.3C). The patient was instructed to wear this splint 24 hours a day including meals, and to remove it only for cleaning. After 3 months, the extension wire bonded on the occlusal surface of the right maxillary first premolar was cut in order to facilitate distal drifting of the right first premolar and canine (Fig. 30.3D). During the following
The Advanced Molar Distalization Appliance
A
B
C
D
E
F
G
H
I
J
K
L
+
M
N
+
+ +
O
165
+
Q
P Fig. 30.3 Case 2: unilateral maxillary molar distalization. (A,B) Immediately after insertion of the unilateral Advanced Molar Distalization Appliance (AMDA). (C,D) After extension wire bonded on the occlusal surface of the first premolar. (E,F) After unilateral molar distalization has been completed. Note the initial drifting of the premolars and canines and the labial movement of the lateral incisor. (G,H) Insertion of conventional full fixed orthodontic appliance on the maxillary arch and conversion of the unilateral AMDA to a passive skeletal anchored device. (I,J) Insertion of conventional full fixed orthodontic appliance on the mandibular arch. (K,L) Following removal of the fixed appliances. (M,N) One year after the removal of the fixed appliances. (O,P) Superimposition of the cephalometric tracings to show changes from before treatment start (black line) to end of active molar distalization (blue line) on the anterior cranial base (O) and the maxillary plane (P). (Q) Superimposition of the cephalometric tracings on the maxillary plane before treatment (black line), after molar distalization (blue line) and after completion of treatment (red line).
166 SECTION VII: MINISCREW IMPLANTS FOR THE TREATMENT OF CLASS II MALOCCLUSION
appointments, spontaneous drifting of the right premolars and canines could be seen plus spontaneous opening of the space between the right maxillary canine and central incisor, proclination of the right lateral incisor and spontaneous correction of the crossbite. Seven months after start of treatment, the tip of the right maxillary lateral incisor was positioned slightly more labially to the tip of the right mandibular lateral incisor and the crossbite had vanished. The cusps of his posterior maxillary teeth no longer interfered with those of the mandibular teeth. The lower splint with the posterior bite blocks was removed. After a further month, both right first and second maxillary molars were distalized while the first maxillary molars presented a Class I molar relationship on both sides (Fig. 30.3E,F). The maxillary premolars and canines had also drifted distally, the space for the right lateral incisor was enlarged and the spontaneous labial movement and proclination of the lateral incisor was further improved. Further radiographic evaluation confirmed that the MIs were stable and would not interfere with retraction of the anterior teeth. Eight months after start of treatment the molar relationship was Class I; distal drifting of the right premolars and canines had occurred and the anterior crossbite was slightly corrected. A fully bonded preadjusted edgewise appliance with Roth’s prescription and 0.018 inch slot (Mini Master Series metallic and Silkon esthetic brackets, American Orthodontics) and a Ni-Ti archwire (0.012 inch) was inserted for initial alignment of the teeth (Fig. 30.3G,H). The AMDA was converted to a passive skeletal anchorage device as described above. One month later, a Ni-Ti archwire (0.016 inch) was inserted on the maxillary dental arch, and after another month (i.e. 10 months after initiation of treatment) the AMDA and MIs were removed and a Ni-Ti archwire (0.016 × 0.016 inch) was inserted for further alignment of the maxillary dental arch. Eleven months after treatment start, the lower dental arch was bonded, a Ni-Ti archwire (0.012 inch) was inserted for initial alignment in the lower arch, and a SS archwire (0.016 × 0.016 inch) was inserted in the upper arch (Fig. 30.3I,J). At that point, the slight mesial rotation of the right maxillary first molar had been corrected. Two months later, a Ni-Ti archwire (0.016 × 0.016 inch), and after another month a SS archwire (0.016 × 0.016 inch) were used for further alignment of the lower dental arch. Fifteen months after initiation of treatment, SS archwires (0.016 × 0.016 inch) with reverse curves of Spee were inserted to fully align both dental arches and detail the occlusion. The fixed appliances were removed 5.5 months later (i.e. 20.5 months from treatment start). The anterior crossbite had been corrected and a good posterior intercuspation and a well-functioning and stable occlusion had been established (Fig. 30.3K,L). After debonding of the fixed appliances, a lingual fixed retainer was bonded to the mandibular anterior teeth extending from canine to canine. Maxillary retention was accomplished with a removable acrylic retainer. The patient was instructed to wear the retainer 24 hours a day for 2 months and then only at night. The patient followed these recommendations and 18 months after debonding his occlusal relationships as well as his facial appearance remained stable with no evident relapse (Fig. 30.3M,N).
were unaffected on the contralateral side. The crossbite between the upper and lower right lateral incisors, the midline deviation and the anterior crowding were also corrected, while an optimal alignment of both maxillary and mandibular teeth, and a well-intercuspated and stable occlusion were obtained. Ideal overjet and overbite were also achieved (Fig. 30.3K,L). There was a great improvement in the patient’s smile and facial esthetics. Root parallelism was confirmed radiographically.
Treatment Results
■
The treatment results were within the initial treatment goals and both the patient and his parents were very satisfied with his final facial and intraoral (Fig. 30.3K,L) appearance, particularly because this had been achieved without extraoral appliances or extractions. Treatment took 20.5 months to achieve a Class I molar and canine relationship on the right side of the maxillary dental arch, while relationships
Cephalometric Analysis after Distalization After distalization, the right first maxillary molar had moved almost bodily without distal tipping, while the anterior teeth did not procline at all; instead they were very slightly retruded. During the subsequent phase of distal movement of the right maxillary canines and premolars, the maxillary molars, which served as anchors, and the anterior teeth remained almost totally stable. Skeletal Class I relationships and the sagittal skeletal positions of the maxilla and mandible were maintained (Table 30.2). There was a slight decrease of the vertical growth pattern, moving close to average values. The inclination of maxillary incisors was slightly increased towards labial, while the inclination of the mandibular incisors remained almost unaffected. The interincisal angle was slightly decreased. There was a slight decrease in nasolabial angle. Superimposition of the cephalometric tracings on the anterior cranial base from before treatment start and after active molar distalization (Fig. 30.3O) showed a slight downward positioning of the mandible resulting from the movement of maxillary molars to a more distal position, forcing the bite to open. The corresponding superimposition on the maxillary plane (Fig. 30.3P) revealed a pure bodily distal movement of the right first maxillary molar without distal tipping, as well as a slight retrusion and extrusion of the anterior teeth.
Cephalometric Analysis at End of Treatment A comparison of the final result with that before treatment start showed strengthening of the skeletal Class I relationships, maintenance of the sagittal skeletal position of the maxilla and a slightly more forward position of the mandible (Table 30.2). There was a further decrease of the vertical growth pattern towards average. The inclination of maxillary and mandibular incisors was slightly increased towards labial, while the interincisal angle was decreased. The nasolabial angle was maintained. Superimposition of the cephalometric tracings on the maxillary plane after molar distalization and after completion of treatment showed that the position of the first molars and the anterior teeth remained unaffected (Fig. 30.3Q).
CONCLUSIONS The construction and application of the AMDA is based on careful consideration of the issues related to the use of non-compliance distalization appliances with orthodontic implants. Features include:
■
■
■ ■
use of self-drilling and self-tapping MIs to make insertion easier for the patient and a process that can be carried out by the orthodontist MI dimensions of 2 mm diameter and 8–10 mm length to give ideal stability MIs with varying collar length to allow a choice of length to suit the patient’s mucosal thickness two MIs to provide effective skeletal anchorage the paramedial region of the palate (3–6 mm from the midpalatal suture and 3–6 mm posterior to the incisive foramen) as the safest site for MI insertion
The Advanced Molar Distalization Appliance
■
■
a palatal force system with the line of force application passing as close as possible to the center of resistance of the maxillary molars the open Ni-Ti coil springs encased in the tubing system to reduce issues of plaque accumulation and irritation of the tongue.
The AMDA can be used for either bilateral or unilateral maxillary molar distalization without the need of extractions, as illustrated in the two cases. The cephalometric evaluations described above confirm that the AMDA achieves the desired tooth movements without the side effects of other distalization systems, such as anchorage loss and molar tipping. The two cases illustrate its effectiveness in bilateral treatment as well as for unilateral distalization without side effects on the contralateral side. A unique advantage of the AMDA is that it can be easily converted chair-side to a skeletal anchored horseshoe-type transpalatal arch to support subsequent treatment with a conventional full fixed orthodontic appliances. The advantages of the AMDA can be summarized as:
■
■ ■ ■ ■ ■ ■ ■
■
can be used for the complete non-compliance correction of Class II malocclusion, initially to distalize the maxillary molars and later to retract the anterior teeth prefabricated design eliminates complicated laboratory procedures insertion is easily carried out in one appointment by the orthodontist activation is initiated immediately after its insertion appliance is invisible during distalization of maxillary molars no side effects of distal molar tipping no anchorage loss of anterior teeth during active distalization distal drifting of posterior teeth and the incisors during molar distalization, which reduces the total treatment time conversion of the AMDA to a horseshoe-type palatal arch is simply performed intraorally
■
■ ■
■
167
no anchorage loss of the molars is anticipated during anterior teeth retraction can be used bilaterally or unilaterally closed tubing system protects from excessive distalization if the patient misses an appointment the AMDA can be used for a broad spectrum of orthodontic problems requiring maximum anchorage on the maxillary dental arch.
There are also some disadvantages: ■ ■ ■ ■
it may cause discomfort, especially during swallowing and speech there can be difficulties in maintaining optimal oral hygiene irritation of the tongue or palatal soft tissues can occur bodily movement of the maxillary molars may cause a mandibular downward rotation and thus worsen Class II jaw relationships; therefore, this system should be used with caution in patients with a vertical growth pattern or open bites.
The AMDA can be used for the efficient, invisible, non-compliant bilateral or unilateral distalization of maxillary molars, as well as in conjunction with full fixed appliances for the subsequent retraction of the anterior teeth (i.e. for the comprehensive treatment of Class II malocclusion).
REFERENCES 1. Papadopoulos MA. The “Advanced Molar Distalization Appliance”: a novel approach to correct Class II malocclusion. Recent Pat Biomed Eng 2010;3:6–15. 2. Papadopoulos MA. German patent 10 2006 033 774; US patent 7,785,102.
The Advanced Molar Distalization Appliance Moschos A. Papadopoulos
INTRODUCTION A number of systems have been developed to use miniscrew implants (MIs) as temporary anchorage devices to support orthodontic movements. Chapter 29 describes one such system, the miniscrew implant-supported distalization system (MISDS). While this system has many advantages, one disadvantage is the laboratory work needed for the fabrication of the appliance, and the consequent increased cost of treatment and delay in initiating treatment. This chapter describes a novel MI-supported device, the Advanced Molar Distalization Appliance (AMDA), that has all the advantages of the MISDS but eliminates the need for laboratory work. The AMDA can be used for the efficient, invisible, non-compliant bilateral or unilateral distalization of maxillary molars (Fig. 30.1), as well as in conjunction with full fixed appliances for the subsequent retraction of the anterior teeth.1
THE ADVANCED MOLAR DISTALIZATION APPLIANCE The AMDA (available soon by Dentaurum, Ispringen, Germany) is a prefabricated device anchored to the palate by MIs (Fig. 30.1A),2 and comprising:
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■
■ ■
a tubing system with encased compressed nickel-titanium (Ni-Ti) open coil springs to provide the necessary distalization force; in the conventional form this is used on both sides of the dental arch but can be activated unilaterally if needed conventional orthodontic bands on maxillary first molars equipped with lingual sheaths a horseshoe-type palatal archwire a palatal anchorage unit.
The design of the appliance unit and the use of palatal MIs to provide temporary and stationary anchorage for all phases of treatment avoids the unwanted problems of conventional non-compliance devices (see Chapter 2) such as molar rotation or distal crown tipping and forward movement and proclination of the anterior teeth. In contrast to conventional noncompliance devices, spaces are created between all the posterior teeth rather than just between the maxillary first molars and second premolars. This is because the premolars and canines are able to drift distally under the pull of the transeptal fibers, which also shortens overall treatment time.
THE TUBING SYSTEM The tubing system (Fig. 30.1) runs on a horseshoe-type archwire and consists of two tubes sliding one into the other: an outer tube (approximate
length, 10–12 mm; outer diameter, 3 mm) and an inner tube (approximate length, 8–10 mm; outer diameter, 2.3 mm). Compressed Ni-Ti open coil springs encased in each tubing system deliver a distalization force of approximately 300–350 g when fully activated. Two stop screws are incorporated in the tubing system, one at the mesial end of the inner tube and another at the distal end of the outer tube. Activation or deactivation of the force system takes place by screwing or unscrewing these stop screws. In addition, an SS extension wire (diameter, 0.9 mm; approximate total height, 10 mm) is attached to the external surface of the outer tube. It has an S-shape to allow height adjustment. The wire has a transpalatal type of ending (similar to a conventional transpalatal arch [TPA]) to facilitate insertion of the appliance into the lingual sheaths of conventional orthodontic bands cemented on the maxillary first molars. The single tubing system version used for unilateral maxillary molar distalization (Fig. 30.1C) has an almost straight palatal archwire with one anterior loop for the insertion of a single MI, with an additional SS wire extension (diameter, 0.9 mm) soldered approximately 2 mm distal to the anterior loop and bonded to the occlusal surface of the first premolar for dental anchorage to avoid any rotational movements of the system during unilateral distalization. Alternatively, for unilateral molar distalization a conventional AMDA relying only on skeletal anchorage can be used. In this case from the two bilateral tubing systems of AMDA only one is activated (Fig. 30.1B).
THE HORSESHOE-TYPE ARCHWIRE The horseshoe-type SS archwire (diameter, 0.9 mm) is positioned on the palate at a distance of 1–2 mm from the mucosa and runs inside the inner tube of the tubing system (Fig. 30.1). The archwire is positioned approximately 10 mm apically to the occlusal surfaces of the maxillary molars, thus passing through or very close to their centers of resistance in order to facilitate an almost pure bodily molar distalization. Its position parallel to the occlusal plane forces the maxillary molars to slide on it and guides them distally without, or with minimal, rotation. Two symmetrical closed loops (or in a later version two movable metallic rings) are attached to the archwire to indicate the insertion sites for the MIs, as well as to secure the appliance onto the MIs.
THE ANCHORAGE UNIT Two self-drilling and self-tapping MIs (suggested diameter 2 mm and length 8–10 mm) are used to anchor the AMDA and to resist the reciprocal forces during molar distalization and anterior teeth retraction. The MIs should have collars of varying lengths to allow a suitable size to be chosen for the individual’s width of palatal mucosa. The MIs are placed in the
Fig. 30.1 The Advanced Molar Distalization Appliance (AMDA). (A) The horseshoe-type palatal archwire with the tubing systems for bilateral use. (B) The conventional AMDA for unilateral use relying only on skeletal anchorage with bilateral tubing systems of which only one is activated. (C) A single tubing system for unilateral use using both dental and skeletal anchorage. (A from Papadopoulos, 2010,1 with permission of Bentham Science.) A
160
B
C
The Advanced Molar Distalization Appliance
paramedian region of the palate 3–6 mm from the midpalatal suture and 3–6 mm posterior to the incisive foramen. The insertion of the two MIs at a distance of 3–6 mm posterior to the incisive foramen provides a safety clearance of approximately 7–10 mm between the MIs and the dental roots of the anterior teeth (depending on the root inclination of these teeth). This avoids contact of the MIs and these teeth during molar distalization, and, more importantly, during anterior teeth retraction.
CLINICAL PROCEDURE
PHASE ONE: MOLAR DISTALIZATION The AMDA and MIs can be inserted in a single appointment by the orthodontist. Normal full infection control measures similar to those for extractions should be used, including sterilization of the MI kit. Conventional orthodontic molar bands with lingual sheaths are cemented on the maxillary first molars. The AMDA is prefabricated and so some individual adjustments are only necessary, which can be carried out either directly in the patient’s mouth or indirectly on the initial maxillary cast. The palatal archwire extensions are inserted in the lingual sheaths of the molar bands. Once the parallel positioning of the appliance and its width and height have been checked, the mesial stop screws are moved distally to fully compress the coil spring encased in the tubing system and the distal stop screws are screwed in place to stabilize the tubing systems on the archwire. The final length of the palatal archwire is determined by marking its distal ends with a pencil, leaving approximately 8–10 mm extending out of the distal screw. With the appliance removed from the patient’s mouth, the distal ends are cut off at the mark and a bend or loop is formed on each distal end to act as mechanical stop to prevent any distalization of the molars beyond this point and to avoid any tissue irritation. Alternatively or in addition, a small amount of light-cured resin can be added to the ends to ensure that the molars cannot slip out of the wire. The appliance is then inserted into the patient’s mouth, ensuring that it is parallel to the occlusal plane and the two symmetrical loops are 3–6 mm posterior of the incisive foramen. The wire extensions welded on the tubing systems are inserted into the lingual sheaths of the molar bands and secured in position with SS ligature wires. MIs with appropriate collar length are inserted through the loops using the normal procedure. The head of the MI should be wider than the diameter of the loops to provide the appropriate stability to the system. However, in some cases, fixing of the AMDA with the MIs through SS ligature wires (diameter, 0.012 inch) might be necessary, particularly when MIs with smaller head dimensions are used. In some cases, SS ligature wires of a smaller diameter (0.012 inch instead of 0.040 inch) might be needed if the chosen MIs have smaller heads. A small portion of light-cure resin can be added to cover the top of each implant head plus the endings of the ligature wires and the loops of the palatal archwire to avoid plaque accumulation. The AMDA can be loaded immediately with light orthodontic forces by unscrewing the distal screws to allow free distal sliding of the posterior part of the tubing system and thus distal movement of the maxillary molars. The mesial stop screws of the tubing systems (which are already moved and fixed distally) are not altered and so the compressed coil springs can begin to exercise their distalizing force. Distal movement of the maxillary molars can be enhanced through disocclusion of the posterior teeth using lower acrylic splints with posterior bite blocks or cemented build-ups. Lateral cephalometric radiography can be used to check the installation immediately after placement, at the end of phase one and at a completion of treatment.
161
Patients are given clear instructions on how to maintain oral hygiene. They are monitored every 4 weeks for hygiene, for the stability of the MIs, and for further adjustments and reactivation of the appliance. Reactivation occurs by unscrewing the mesial stop screw, moving the anterior part of the tubing system more distally, thus squeezing the encased coil springs, and then rescrewing the stop screws in the new position. Any tendency for rotation of the maxillary molars can be countered by bending the wire extensions of the transpalatal archwire extensions welded to the tubing systems. A treatment period of 4–8 months is usually needed for distalization of the first maxillary molars into a Class I molar relationship.
PHASE TWO: ANTERIOR TEETH RETRACTION The AMDA is easily converted to a passive skeletally anchored horseshoetype palatal arch providing indirect anchorage for the posterior teeth during a second phase of treatment to retract the anterior teeth and level and align the dental arches using a full fixed appliance. For this purpose, the distal stop screws are tightened to prevent any further molar distal movement and the mesial stop screws are moved distally and screwed in this position again, totally squeezing the coil springs encased in the tubing systems. This retains the first maxillary molars in their new positions and allows them to become the anchors to support the subsequent retraction of the anterior teeth. In some cases, such as when the first maxillary molars are already rotated prior to the initiation of orthodontic treatment and the second molars are already erupted, rotation of first maxillary molars cannot be totally avoided during the active distalization phase through bend adjustments of the transpalatal archwire extensions of the tubing systems. In these cases the AMDA and the MIs are removed after retraction of the anterior teeth and, since there is no more need to support molar anchorage, a TPA is used until completion of treatment to correct this rotation.
REMOVAL OF THE APPLIANCE The MIs are removed by unscrewing the head of the MI. Local anesthesia may be needed if there is any tissue covering the MI. The AMDA is removed by cutting the SS ligature wires that secure the transpalatal wire extensions to the lingual sheaths of the molar bands. The AMDA can then be removed from the sheaths in the normal way. Debonding of the conventional fixed orthodontic appliances (bands and brackets) and cleaning procedures are performed as usual.
CLINICAL APPLICATIONS The AMDA can be used efficiently for the comprehensive treatment of Class II malocclusion. The following two case studies illustrate its use for bilateral and unilateral maxillary molar distalization.
CASE 1: BILATERAL MAXILLARY MOLAR DISTALIZATION A 12-year-old girl was referred with a chief complaint of protrusion of the upper anterior teeth. She had a symmetric face and a convex facial profile with protruded lips, a retruded mandible and increased overjet (6 mm) and overbite (5 mm). She had permanent dentition, with the second permanent molars erupted, no caries and good oral hygiene. Both maxillary first molars, particularly the left one, were mesially rotated. Occlusal analysis revealed a Class II, division 1 malocclusion, with bilateral Class II molar relationships: three-quarters cusp on the right and full cusp on the left. She
162 SECTION VII: MINISCREW IMPLANTS FOR THE TREATMENT OF CLASS II MALOCCLUSION
Treatment
Table 30.1 Cephalometric analysis during treatment Normal values
T0
T1
T2
T3
SNA (o)
82.1
84.5
85.8
87.9
84.2
SNB (o)
80.2
80.3
78.9
79.7
79.7
Facial angle (o)
85.6
94.7
94.5
91.5
93.4
ANB(o)
1.9
Variables Sagittal relationships
Individual ANB(o)
4.2
6.9
8.2
4.5
5.1
6.1
6.9
5.3
NA-APog (o)
0.4
10.2
14.2
16.9
8.6
H angle (o)
11.3
17.4
10.9
21.7
20.2
SN-SGn (o)
65.3
64.1
66.2
65.4
65.1
SN-NL (o)
6.8
4.8
5.7
5.5
4.1
SN-ML (o)
29.8
32.2
34.8
34.7
33.9
Ar-Go-Me (o)
124.4
135.8
132.3
137
136.2
SGo : NMe × 100 (%)
68.2
64.5
62.9
63.5
63.7
1s-NL (o)
112
122.4
115.6
106.9
110.8
1i-ML (o)
92.7
94.5
92.2
95.1
98.7
1s-SN (o)
104
117.6
109.9
101.3
106.7
Lower incisor to A-Pg (mm)
1.2
4.1
2.6
3.8
5.3
Interincisal angle (o)
132.3
117.6
123.1
128.9
120.7
112
93.2
105.3
99.8
99.7
Vertical relationships
Dental relationships
Soft tissue relationships Nasolabial angle (o)
T0, initiation of treatment; T1, after maxillary molar distalization; T2, after completion of anterior teeth retraction; T3, immediately after completion of total orthodontic treatment.
had spaces in her upper anterior teeth, which were also proclined, and there was a mild crowding in the lower anterior teeth. Maxillary midline was coincident with the facial midline, while the mandibular one deviated 2 mm to the left. Functional analysis revealed no disturbances of mandibular movements and normal temporomandibular joint function. The initial panoramic radiograph showed that the third molars were present, no teeth were missing and alveolar bone and root formation were within normal limits. Cephalometric analysis of the lateral cephalometric radiographs using ViewBox version 3.1 (dHal, Athens, Greece) showed skeletal Class II relationships associated with a prognathic maxilla and an orthognathic mandible (Table 30.1). Analysis of vertical skeletal relationships showed a slight tendency towards a vertical growth pattern with a corresponding clockwise rotation of the mandible and an upward inclination of the palatal plane. Analysis of dental relationships revealed protrusive incisors, as well as proclination of the upper and lower incisors in relation to the anterior cranial base and the mandibular plane, respectively. Finally, soft tissue analysis showed a decreased nasolabial angle. The patient did not want to wear any extraoral appliances and together with her parents requested orthodontic treatment without any extractions. The treatment objectives were to distalize the first maxillary molars bilaterally and then to correct overjet and overbite by retracting and intruding the maxillary anterior teeth, to improve the interincisal angle relationship, correct the midline deviation and achieve a stable, functional occlusion as well as improve lip competence and facial balance.
Two MIs were placed in the paramedian region of the palate and the AMDA fitted; it was activated and correct placement confirmed radiographically as described above (Fig. 30.2A,B). Since both first and second molars had to be moved simultaneously, and in order to enhance distal movement of these teeth, a removable acrylic splint with posterior bite blocks was also inserted to disocclude the posterior teeth. The patient was instructed to wear this splint 24 hours a day including meals and to remove it only for cleaning. After 4 months, the splint with bite blocks was removed as the maxillary molar cusps no longer interfered with the mandibular molar cusps. After 7 months, both first and second maxillary molars were distalized bilaterally and the first maxillary molars had a Class I molar relationship (Fig. 30.2C,D). The maxillary premolars and canines had also drifted to an almost Class I relationship. Further radiographic evaluation confirmed that the MIs were stable and would not interfere with retraction of the anterior teeth. The second phase was commenced by bonding a preadjusted edgewise appliance with Roth’s prescription and 0.018 inch slot (Silkon esthetic brackets; American Orthodontics, Sheboygan, WI, USA), and a Ni-Ti archwire (0.012 inch) was inserted for initial alignment of the teeth (Fig. 30.2E). The AMDA was converted to a horseshoe-type TPA as described above (Fig. 30.2F). After another month, Ni-Ti wires (0.016 inch) were used for teeth alignment in both arches. Two months later, Ni-Ti archwires (0.016 × 0.016 inch) were placed and elastic chains were also inserted on the maxillary arch in order to start the en masse retraction of the maxillary anterior teeth. One month later, SS archwires (0.016 × 0.016 inch) were inserted to further align both dental arches and for the continuation of the en masse retraction of the maxillary anterior teeth. After a further month (i.e. 12 months after initiation of treatment), the retraction of the anterior teeth was completed (Fig. 30.2G,H). At that time, a slight increase in mesial rotation of the maxillary first molars was observed despite adjustment of the transpalatal-type wire extensions of the AMDA during treatment. Therefore, it was decided to remove the AMDA and the MIs and insert a TPA to correct the rotations. After 3 months, the molar rotation had been corrected and SS archwires (0.016 × 0.016 inch) with reverse curves of Spee and asymmetric elastics were inserted to fully align the dental arches, correct the midline deviation and further correct the deep bite (Fig. 30.2I,J). Four months later, new SS archwires were used for final alignment of the teeth and detailing the occlusion. The fixed appliances were removed 5 months later (i.e. after 24 months of total treatment time), following establishment of a nice posterior intercuspation and a well-functioning and stable occlusion (Fig. 30.2K,L). After debonding, a lingual fixed retainer was bonded to the mandibular anterior teeth extending from canine to canine. Maxillary retention was accomplished by means of a removable acrylic retainer. The patient was instructed to wear the retainer 24 hours a day for 2 months and then at night only.
Treatment Results The treatment results were within the initial treatment goals and both the patient and her parents were very pleased with her final facial and dental appearance (Fig. 30.2K,L) and because treatment did not involve extraoral appliances, intermaxillary elastics or extractions. Treatment took 24 months and achieved a bilateral Class I molar and canine relationship with optimal alignment of both maxillary and mandibular teeth, a well-intercuspated and
The Advanced Molar Distalization Appliance
A
B
C
D
E
F
G
H
I
J
K
L
N
M
163
O
P
Fig. 30.2 Case 1: unilateral maxillary molar distalization. (A,B) Pretreatment views immediately after insertion of the Advanced Molar Distalization Appliance (AMDA). (C,D) Molar distalization completed. Note the initial drifting of the premolars and canines. (E,F) Insertion of conventional full fixed orthodontic appliances and conversion of the AMDA to a skeletally anchored horseshoe-type transpalatal arch. (G,H) Retraction of the maxillary anterior teeth. (I,J) Correction of molar rotation. (K,L) At end of treatment following removal of the fixed appliances. (M,N) Superimposition of the cephalometric tracings to show changes from before treatment start (black line) to end of active molar distalization (blue line) on the anterior cranial base (M) and the maxillary plane (N). (O,P) Superimposition of the cephalometric tracings on the maxillary plane to show changes from after active molar distalization (black line) to retraction of the maxillary anterior teeth (red line) (O) and from after retraction of the maxillary anterior teeth (blue line) to completion of treatment and removal of all appliances (black line) (P). (A–G from Papadopoulos, 2010,1 with permission of Bentham Science.)
stable occlusion and ideal overjet and overbite. The mild crowding, the midline deviation and the medial diastema were also corrected (Fig. 30.2K,L). Root parallelism was confirmed radiographically.
Cephalometric Analysis after Distalization After distalization, the first maxillary molars were moved almost bodily without distal tipping, while the anterior teeth did not procline at all; instead they were slightly retruded. Further, during the subsequent
retraction of the anterior teeth, the maxillary molars, which served as anchors during this phase, remained almost totally stable, while the anterior teeth retruded substantially. Skeletal Class II relationships were maintained as were the sagittal skeletal positions of the maxilla and mandible (Table 30.1). There was a slight increase in vertical growth pattern. The maxillary incisors were notably retracted, while the mandibular incisors had a slight lingual inclination. The interincisal angle was also significantly increased. There was an increase in nasolabial angle.
164 SECTION VII: MINISCREW IMPLANTS FOR THE TREATMENT OF CLASS II MALOCCLUSION
Superimposition of the cephalometric tracings on the anterior cranial base from before treatment start and after active molar distalization (and subsequent passive drifting of the anterior teeth; Fig. 30.2M) showed a slight downward positioning of the mandible due to movement of maxillary molars into a more distal position, forcing the bite to open. The corresponding superimposition on the maxillary plane (Fig. 30.2N) showed a pure bodily distal movement of the first maxillary molars with a slight extrusion but without distal tipping, as well as slight retrusion and extrusion of the anterior teeth.
Table 30.2 Cephalometric analysis during treatment Normal values
T0
T1
T2
SNA (o)
82.1
84.3
83.2
83
SNB (o)
80.2
80.6
79.7
81.8
Facial angle (o)
85.6
96
95.4
99.2
ANB(o)
1.9
3.7
3.5
1.2
4.8
4.4
4.1
NA-APog (o)
0.4
5.5
4.1
−0.5
H angle (o)
11.3
17.9
17.4
15.9
SN-SGn (o)
65.3
65.2
65.7
64.2
SN-NL (o)
6.8
9.4
6.7
4.8
SN-ML (o)
29.8
31.1
31.4
30.1
Ar-Go-Me (o)
124.4
116.6
122.8
123.5
SGo : NMe X 100 (%)
68.2
65.4
66.7
67.8
1s-NL (o)
112
110.3
111.6
116
1i-ML (o)
92.7
96
96.7
102.5
1s-SN (o)
104
100.9
104.8
111.3
Cephalometric Analysis at End of Treatment
Lower incisor to A-Pg (mm)
1.2
0.3
0.4
1.8
A comparison of the final result with that before treatment start showed maintenance of the skeletal Class II relationships as well as of the sagittal skeletal positions of the maxilla and mandible (Table 30.1). There was a slight increase in vertical growth pattern, the maxillary incisors were significantly retracted, the mandibular incisors slightly proclined and the interincisal angle was slightly increased. Finally, there was an increase in nasolabial angle. Superimposition of the cephalometric tracings on the maxillary plane after anterior teeth retraction and after completion of treatment revealed that the position of the first molars remained unchanged, while the anterior teeth were further intruded and slightly retruded (Fig. 30.2P).
Interincisal angle (o)
132.3
132
127.2
116.1
112
101.6
100.5
101.8
Cephalometric Analysis after Anterior Teeth Retraction A comparison of the situation after the anterior teeth retraction phase with that at the end of molar distalization showed maintenance of the skeletal Class II relationships, while both the maxilla and mandible were moved slightly anteriorly (Table 30.1). Vertical growth pattern remained almost stable. The maxillary incisors were further retracted, while the mandibular incisors had a slight labial inclination. The interincisal angle was also significantly increased. Soft tissue analysis showed a decrease in the nasolabial angle. Trace comparisons confirmed that the first molars remained stable in position while the anterior teeth were retracted and slightly extruded (Fig. 30.2O).
CASE 2: UNILATERAL MAXILLARY MOLAR DISTALIZATION A 14-year-old boy was referred with a complaint of a crossbite by the upper right lateral incisor. He had a symmetric face and a slightly convex facial profile. He had a complete permanent dentition with the second permanent molars already erupted in both arches, good oral hygiene and no caries. Occlusal analysis revealed a one-half cusp Class II molar relationship on the right and a Class I on the left side. There was a crossbite between the right upper and lower lateral incisors, a normal overjet of 6 mm, an overbite of 3 mm and a slight maxillary midline deviation of 1 mm to the left. In addition, there was 3 mm crowding on the maxillary anterior teeth and a mild crowding on the mandibular anterior teeth. Functional analysis revealed no disturbances of the mandibular movements and normal temporomandibular joint function. The initial panoramic radiograph showed that the third molars were present, and no teeth were missing. Cephalometric analysis of the pretreatment lateral cephalometric radiograph showed skeletal Class I relationships associated with a slight prognathic maxilla and an orthognathic mandible (Table 30.2). There was a slight tendency towards a vertical growth pattern with a corresponding clockwise rotation of the mandible and a downward inclination of the palatal plane. There was also a slight retroclination of the upper incisors in relation to the anterior cranial base and proclination of the lower incisors in relation to the mandibular plane,
Variables Sagittal relationships
Individual ANB(o)
Vertical relationships
Dental relationships
Soft tissue relationships Nasolabial angle (o)
T0, initiation of treatment; T1, after maxillary molar distalization; T2, immediately after completion of total orthodontic treatment.
while the interincisal angle was normal. Finally, there was a decreased nasolabial angle. The patient and his parents wanted a treatment plan that did not involve extraoral appliances or extractions. The treatment objectives were to distalize the right first maxillary molar into a Class I relationship, to maintain the Class I relationship of the left first molars and then to correct the crossbite between the right upper and lower lateral incisors, the anterior crowding in both arches and the midline deviation, plus to achieve a stable, functional occlusion by establishing a well-intercuspated bilateral Class I molar and canine relationship.
Treatment Treatment was started with the placement of the single-tube configuration of AMDA (Fig. 30.1C) on the right side of the palate. Skeletal anchorage was provided by a single MI inserted through the anterior loop of the AMDA, while additional dental anchorage was provided by bonding the extension wire on the occlusal surface of the right maxillary first premolar (Fig. 30.3A,B). The AMDA was activated and correct placement confirmed radiographically, as described above. Light-cured resin was applied to the top of the implant head to avoid plaque accumulation. A removable acrylic splint with posterior bite blocks was also inserted to disocclude the posterior teeth in order to enhance simultaneous distal movement of the first and second molars and to facilitate correction of the crossbite of the right maxillary lateral incisor (Fig. 30.3C). The patient was instructed to wear this splint 24 hours a day including meals, and to remove it only for cleaning. After 3 months, the extension wire bonded on the occlusal surface of the right maxillary first premolar was cut in order to facilitate distal drifting of the right first premolar and canine (Fig. 30.3D). During the following
The Advanced Molar Distalization Appliance
A
B
C
D
E
F
G
H
I
J
K
L
+
M
N
+
+ +
O
165
+
Q
P Fig. 30.3 Case 2: unilateral maxillary molar distalization. (A,B) Immediately after insertion of the unilateral Advanced Molar Distalization Appliance (AMDA). (C,D) After extension wire bonded on the occlusal surface of the first premolar. (E,F) After unilateral molar distalization has been completed. Note the initial drifting of the premolars and canines and the labial movement of the lateral incisor. (G,H) Insertion of conventional full fixed orthodontic appliance on the maxillary arch and conversion of the unilateral AMDA to a passive skeletal anchored device. (I,J) Insertion of conventional full fixed orthodontic appliance on the mandibular arch. (K,L) Following removal of the fixed appliances. (M,N) One year after the removal of the fixed appliances. (O,P) Superimposition of the cephalometric tracings to show changes from before treatment start (black line) to end of active molar distalization (blue line) on the anterior cranial base (O) and the maxillary plane (P). (Q) Superimposition of the cephalometric tracings on the maxillary plane before treatment (black line), after molar distalization (blue line) and after completion of treatment (red line).
166 SECTION VII: MINISCREW IMPLANTS FOR THE TREATMENT OF CLASS II MALOCCLUSION
appointments, spontaneous drifting of the right premolars and canines could be seen plus spontaneous opening of the space between the right maxillary canine and central incisor, proclination of the right lateral incisor and spontaneous correction of the crossbite. Seven months after start of treatment, the tip of the right maxillary lateral incisor was positioned slightly more labially to the tip of the right mandibular lateral incisor and the crossbite had vanished. The cusps of his posterior maxillary teeth no longer interfered with those of the mandibular teeth. The lower splint with the posterior bite blocks was removed. After a further month, both right first and second maxillary molars were distalized while the first maxillary molars presented a Class I molar relationship on both sides (Fig. 30.3E,F). The maxillary premolars and canines had also drifted distally, the space for the right lateral incisor was enlarged and the spontaneous labial movement and proclination of the lateral incisor was further improved. Further radiographic evaluation confirmed that the MIs were stable and would not interfere with retraction of the anterior teeth. Eight months after start of treatment the molar relationship was Class I; distal drifting of the right premolars and canines had occurred and the anterior crossbite was slightly corrected. A fully bonded preadjusted edgewise appliance with Roth’s prescription and 0.018 inch slot (Mini Master Series metallic and Silkon esthetic brackets, American Orthodontics) and a Ni-Ti archwire (0.012 inch) was inserted for initial alignment of the teeth (Fig. 30.3G,H). The AMDA was converted to a passive skeletal anchorage device as described above. One month later, a Ni-Ti archwire (0.016 inch) was inserted on the maxillary dental arch, and after another month (i.e. 10 months after initiation of treatment) the AMDA and MIs were removed and a Ni-Ti archwire (0.016 × 0.016 inch) was inserted for further alignment of the maxillary dental arch. Eleven months after treatment start, the lower dental arch was bonded, a Ni-Ti archwire (0.012 inch) was inserted for initial alignment in the lower arch, and a SS archwire (0.016 × 0.016 inch) was inserted in the upper arch (Fig. 30.3I,J). At that point, the slight mesial rotation of the right maxillary first molar had been corrected. Two months later, a Ni-Ti archwire (0.016 × 0.016 inch), and after another month a SS archwire (0.016 × 0.016 inch) were used for further alignment of the lower dental arch. Fifteen months after initiation of treatment, SS archwires (0.016 × 0.016 inch) with reverse curves of Spee were inserted to fully align both dental arches and detail the occlusion. The fixed appliances were removed 5.5 months later (i.e. 20.5 months from treatment start). The anterior crossbite had been corrected and a good posterior intercuspation and a well-functioning and stable occlusion had been established (Fig. 30.3K,L). After debonding of the fixed appliances, a lingual fixed retainer was bonded to the mandibular anterior teeth extending from canine to canine. Maxillary retention was accomplished with a removable acrylic retainer. The patient was instructed to wear the retainer 24 hours a day for 2 months and then only at night. The patient followed these recommendations and 18 months after debonding his occlusal relationships as well as his facial appearance remained stable with no evident relapse (Fig. 30.3M,N).
were unaffected on the contralateral side. The crossbite between the upper and lower right lateral incisors, the midline deviation and the anterior crowding were also corrected, while an optimal alignment of both maxillary and mandibular teeth, and a well-intercuspated and stable occlusion were obtained. Ideal overjet and overbite were also achieved (Fig. 30.3K,L). There was a great improvement in the patient’s smile and facial esthetics. Root parallelism was confirmed radiographically.
Treatment Results
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The treatment results were within the initial treatment goals and both the patient and his parents were very satisfied with his final facial and intraoral (Fig. 30.3K,L) appearance, particularly because this had been achieved without extraoral appliances or extractions. Treatment took 20.5 months to achieve a Class I molar and canine relationship on the right side of the maxillary dental arch, while relationships
Cephalometric Analysis after Distalization After distalization, the right first maxillary molar had moved almost bodily without distal tipping, while the anterior teeth did not procline at all; instead they were very slightly retruded. During the subsequent phase of distal movement of the right maxillary canines and premolars, the maxillary molars, which served as anchors, and the anterior teeth remained almost totally stable. Skeletal Class I relationships and the sagittal skeletal positions of the maxilla and mandible were maintained (Table 30.2). There was a slight decrease of the vertical growth pattern, moving close to average values. The inclination of maxillary incisors was slightly increased towards labial, while the inclination of the mandibular incisors remained almost unaffected. The interincisal angle was slightly decreased. There was a slight decrease in nasolabial angle. Superimposition of the cephalometric tracings on the anterior cranial base from before treatment start and after active molar distalization (Fig. 30.3O) showed a slight downward positioning of the mandible resulting from the movement of maxillary molars to a more distal position, forcing the bite to open. The corresponding superimposition on the maxillary plane (Fig. 30.3P) revealed a pure bodily distal movement of the right first maxillary molar without distal tipping, as well as a slight retrusion and extrusion of the anterior teeth.
Cephalometric Analysis at End of Treatment A comparison of the final result with that before treatment start showed strengthening of the skeletal Class I relationships, maintenance of the sagittal skeletal position of the maxilla and a slightly more forward position of the mandible (Table 30.2). There was a further decrease of the vertical growth pattern towards average. The inclination of maxillary and mandibular incisors was slightly increased towards labial, while the interincisal angle was decreased. The nasolabial angle was maintained. Superimposition of the cephalometric tracings on the maxillary plane after molar distalization and after completion of treatment showed that the position of the first molars and the anterior teeth remained unaffected (Fig. 30.3Q).
CONCLUSIONS The construction and application of the AMDA is based on careful consideration of the issues related to the use of non-compliance distalization appliances with orthodontic implants. Features include:
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■
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use of self-drilling and self-tapping MIs to make insertion easier for the patient and a process that can be carried out by the orthodontist MI dimensions of 2 mm diameter and 8–10 mm length to give ideal stability MIs with varying collar length to allow a choice of length to suit the patient’s mucosal thickness two MIs to provide effective skeletal anchorage the paramedial region of the palate (3–6 mm from the midpalatal suture and 3–6 mm posterior to the incisive foramen) as the safest site for MI insertion
The Advanced Molar Distalization Appliance
■
■
a palatal force system with the line of force application passing as close as possible to the center of resistance of the maxillary molars the open Ni-Ti coil springs encased in the tubing system to reduce issues of plaque accumulation and irritation of the tongue.
The AMDA can be used for either bilateral or unilateral maxillary molar distalization without the need of extractions, as illustrated in the two cases. The cephalometric evaluations described above confirm that the AMDA achieves the desired tooth movements without the side effects of other distalization systems, such as anchorage loss and molar tipping. The two cases illustrate its effectiveness in bilateral treatment as well as for unilateral distalization without side effects on the contralateral side. A unique advantage of the AMDA is that it can be easily converted chair-side to a skeletal anchored horseshoe-type transpalatal arch to support subsequent treatment with a conventional full fixed orthodontic appliances. The advantages of the AMDA can be summarized as:
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can be used for the complete non-compliance correction of Class II malocclusion, initially to distalize the maxillary molars and later to retract the anterior teeth prefabricated design eliminates complicated laboratory procedures insertion is easily carried out in one appointment by the orthodontist activation is initiated immediately after its insertion appliance is invisible during distalization of maxillary molars no side effects of distal molar tipping no anchorage loss of anterior teeth during active distalization distal drifting of posterior teeth and the incisors during molar distalization, which reduces the total treatment time conversion of the AMDA to a horseshoe-type palatal arch is simply performed intraorally
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167
no anchorage loss of the molars is anticipated during anterior teeth retraction can be used bilaterally or unilaterally closed tubing system protects from excessive distalization if the patient misses an appointment the AMDA can be used for a broad spectrum of orthodontic problems requiring maximum anchorage on the maxillary dental arch.
There are also some disadvantages: ■ ■ ■ ■
it may cause discomfort, especially during swallowing and speech there can be difficulties in maintaining optimal oral hygiene irritation of the tongue or palatal soft tissues can occur bodily movement of the maxillary molars may cause a mandibular downward rotation and thus worsen Class II jaw relationships; therefore, this system should be used with caution in patients with a vertical growth pattern or open bites.
The AMDA can be used for the efficient, invisible, non-compliant bilateral or unilateral distalization of maxillary molars, as well as in conjunction with full fixed appliances for the subsequent retraction of the anterior teeth (i.e. for the comprehensive treatment of Class II malocclusion).
REFERENCES 1. Papadopoulos MA. The “Advanced Molar Distalization Appliance”: a novel approach to correct Class II malocclusion. Recent Pat Biomed Eng 2010;3:6–15. 2. Papadopoulos MA. German patent 10 2006 033 774; US patent 7,785,102.