Full-Cusp Class II Malocclusion with 12 mm Overjet:
Non-Extraction Treatment with Bone Screws and
Passive Self-Ligating Appliance
Debby Y. W. Sung,
Training Resident, Beethoven Orthodontic Center (Left)
Lily Y. Chen,
Training Resident, Beethoven Orthodontic Center (Center left)
Chris H. Chang,
Founder, Beethoven Orthodontic Center
Publisher, Journal of Digital Orthodontics (Center right)
W. Eugene Roberts,
Editor-in-Chief, Journal of Digital Orthodontics (Right)
Abstract
History: A 12-year-old female presented with flared maxillary central incisors.
Diagnosis: The skeletal Class I relationship (SNA, 85°; SNB, 80°; ANB, 5°) was associated with a full-cusp Class II molar relationship on
the right side and an end-on Class II molar relationship on the left side. Dental analysis revealed flared maxillary central incisors (U1-
to-NA, 10 mm; U1-to-SN, 128.5°) with an excessive overjet of 12 mm. The facial profile was convex with protrusive lips (1.5 mm/4.5 mm
to the E-line). The Discrepancy Index was 20.
Treatment: A fully fixed passive self-ligating (PSL) appliance was bonded on all present permanent teeth (UR6-UL6 and LL6-LR6).
Skeletal anchorage was provided by bilateral infrazygomatic crest (IZC) miniscrews. Class II elastics were implemented to reduce
the overjet and overbite.
Results: After 22 months of active treatment, satisfactory facial profile and dental alignment were achieved. The Cast-Radiograph
Evaluation score was 18, and the Pink and White esthetic score was 0.
Conclusions: A full-cusp Class II malocclusion with 12 mm overjet, flared U1s, 100% overbite, and periodontal impingement was
treated without extraction. Bilateral IZC anchorage facilitated the retraction of the entire maxillary dentition. The 12 mm overjet was
corrected to a pleasing result with stability noted at the 5-year follow-up. (J Digital Orthod 2023;72:4-18)
Key words:
Excessive overjet, full-cusp Class II malocclusion, periodontal impingement, Class II elastics, infrazygomatic crest miniscrews, passive
self-ligating appliance, interproximal reduction
Introduction
The dental nomenclature used in this report is a modified Palmer notation with four oral quadrants: upper right (UR), upper left (UL), lower right (LR), and
lower left (LL). From the midline, permanent teeth are numbered 1-8.
Traditionally, an overjet greater than 10 mm required orthognathic surgery for optimal correction.1,2 To correct full-cusp Class II malocclusions with lip and incisor protrusion, bicuspid extraction is the usual option in non-surgical treatment planning.3 In this case report, however, a full-cusp Class II
malocclusion with a 12 mm overjet was treated to a pleasing result with neither surgical intervention nor extraction. The primary objective for this case
report is to present a conservative option for treating this challenging malocclusion.
History and Etiology
A 12-year-old female sought orthodontic consultation for bimaxillary protrusion. Extraoral examination showed protrusive lips with a trapped lower lip. Intraoral examination revealed an excessive overjet of 12 mm associated with flared U1s and 100% overbite complicated by periodontal impingement (Figs. 1-5). No contributing dental trauma, oral habits, nor significant signs or symptoms of temporomandibular dysfunction were noted.
◼︎Fig. 1: Pre-treatment facial and intraoral photographs
◼︎Fig. 2:
Pre-treatment panoramic radiograph. Unerupted upper second
molars were noted.
◼︎Fig. 3: Pre-treatment cephalometric radiograph
◼︎Fig. 4:
Inferior (a) and left lateral (b) intraoral views show a 12 mm
overjet, periodontal impingement, and flared maxillary
anterior teeth.
Diagnosis
Skeletal:
• Intermaxillary relationship: Skeletal Class I relationship (SNA, 85°; SNB, 80°; ANB, 5°)
• Mandibular plane angle: Within normal limits (WNL) (SN-MP, 36.5°; FMA, 29.5°)
• Vertical Dimension of Occlusion (VDO): WNL (Na-ANS-Gn, 54.5%)
Facial:
• Convexity: Convex profile (G-Sn-Pg’, 14.5°)
• Symmetry: WNL
• Lip Protrusion: Protruded upper and lower lips were 1.5 mm/4.5 mm to the E-line.
Dental:
• Classification (molar relationships)
Right side: Full-cusp Class II;
Left side: End-on Class II
• Overjet: 12 mm
• Overbite: 5 mm 100% overbite with periodontal impingement
The American Board of Orthodontics (ABO) Discrepancy Index (DI) was 20, as documented in the supplementary Worksheet 1.4
◼︎Fig. 5: Pre-treatment dental models (casts).
Treatment Objectives
The treatment objectives were to correct:
(1) 12 mm overjet,
(2) impinging overbite,
(3) protrusive maxillary dentition,
(4) flared maxillary anteriors,
(5) protruded upper and lower lips, plus
(6) Class II molar and canine relationships.
Treatment Plan
To correct the full-cusp Class II molar relationship with an excessive overjet, adequate space was necessary to retract the entire maxillary dentition.
Three treatment options were proposed:
(1) Try non-extraction treatment for 12 months with bilateral infrazygomatic crest (IZC) bone screws inserted to retract the maxillary dentition.5
(2) Extract U4s with bilateral IZC bone screws inserted to retract the maxillary dentition.
(3) Extract U4s and L4s, and close spaces.
After a thorough explanation of the advantages and disadvantages of the different treatment plans, the patient chose treatment plan (1), fully aware that bicuspid extraction was indicated if progress was not adequate after the initial 12 months of treatment.
Treatment Progress
0.022” slot Damon Q® passive self-ligating (PSL) brackets (Ormco, Brea, CA) were bonded on all teeth except for the unerupted U7s and L7s. 0.014” CuNiTi archwires were inserted in both arches; low torque was selected for both the maxillary and mandibular anteriors (Fig. 6). Class II elastics (Quail, 3/16”, 2 oz) were then applied to reduce the excessive overjet in the early stage of treatment:6 they were bilaterally attached from U4 drop-in hooks to L6 buccal hooks (Fig. 7) and were discontinued 1 month after application. The maxillary archwire was changed month (3M) of treatment.
After 4 months (4M) of initial alignment, 2×12-mm OrthoBoneScrews® (iNewton Dental, Inc., Hsinchu City, Taiwan) were placed bilaterally in the infrazygomatic crests (IZCs) (Fig. 8). These bone screws anchored a continuous retracting force to retract the maxillary dentition. The maxillary and
mandibular archwire sequences were: 0.014×0.025” CuNiTi, 0.017×0.025” TMA, and 0.016×0.025” SS. Interproximal reduction (IPR) was performed in the
6th month (6M) on both maxillary and mandibular
◼︎Table 1: Cephalometric summary
◼︎Fig. 6:
Torque selection: Low torque for both (a) maxillary anteriors and
(b) mandibular anteriors.
◼︎Fig. 7:
Class II elastics were attached bilaterally from U4 drop-in hooks to
L6 buccal hooks to facilitate reduction of the excessive overjet
(0M~1M).
◼︎Fig. 8:
IZC screws (arrow) were inserted bilaterally in the 4th month to
retract the maxillary dentition (4M~14M).
incisors (Fig. 9) in order to (1) gain space to relieve crowding, (2) reshape the tooth forms, and (3) eliminate black triangles after alignment.7-12
After 12 months (12M) of treatment, both canine and molar relationships were significantly improved (Fig. 10). The overjet was reduced from 12 to 0 mm. The brackets on the L4s and L5s were rebonded to more gingival positions, and the mandibular archwire was thus changed back to 0.014×0.025” CuNiTi.
Bilateral IZC bone screws were removed in the 14th month (14M) of treatment. L7s were erupted and bonded. A composite resin restoration was
performed on UR1 to fix the incisal edge defect. In the 20th month of treatment, the maxillary archwire was sectioned distal to the canines, and drop-in hooks were inserted from U3s to U5s (Fig. 11). Continuous intermaxillary elastics (Ostrich, 3/4”, 2 oz, full-time) were prescribed to settle the occlusion.
Archwire adjustments were performed on both maxillary and mandibular archwires for detailing and finishing. After 22 months of active mechanics, all
appliances were removed (Figs. 12-15).
Retention
Lingual fixed retainers were bonded on the lower incisors, and Essix overlay retainers (Densply Sirona, Charlotte, NC, USA) were delivered on both arches.
Treatment Results
A Class I occlusion with an ideal overbite and overjet was achieved. The ABO Cast-Radiograph Evaluation (CRE) was 18 points (Worksheet 2).13 The
Pink and White esthetic score was 0 (Worksheet 3).14 Compared to the protrusive lips before orthodontic treatment, the facial profile was nearly
ideal to the E-line (Fig. 15). From the superimposed cephalometric tracings (Fig. 16), three points were noted. (1) The maxillary incisors were retracted 7 mm, which decreased the U1-SN angle by 21.5° (Table 1). (2) U6s were retracted. Such a huge amount of maxillary retraction could be attributed to the continuous retracting force provided by the IZC screws and the arch expansion effect of the Damon system application. (3) The mandibular incisors were slightly flared by an increase of 3.5° in the L1-MP angle with mandibular molar extrusion, attributable to the effects of Class II mechanics and
non-extraction after relieving the crowding.
Follow-up
The whole treatment progress, along with follow-up
records, documents the stability of the final occlusion
(Figs. 17-20).
◼︎Fig. 9:
Interproximal reduction (IPR) was performed: (a) before IPR; (b)
after IPR.
◼︎Fig. 10:
Class I canine and molar relationships were almost achieved by
the 12th month (12M). The overjet was reduced to 0 mm.
◼︎Fig. 11:
Finishing and detailing: maxillary archwire was sectioned distal
to the canines with archwire adjustment. Continuous
intermaxillary elastics (Ostrich, 3/4”, 2 oz, full-time) were
prescribed to settle the occlusion (20M).
◼︎Fig. 12: Posttreatment facial and intraoral photographs
◼︎Fig. 13: Posttreatment panoramic (left) and cephalometric radiographs (right)
◼︎Fig. 14 Posttreatment dental models (casts)
Before
◼︎Fig. 15:
Pre- and posttreatment photographs showing changes in the lip
position and correction of the excessive overjet
◼︎Fig. 16:
Superimpositions of the cephalometric tracings before (black) and after treatment (pink) document (1) retraction and decreased inclination
of U1s, (2) retraction of the maxillary first molars, and (3) slight flaring of L1s and extrusion of mandibular first molars. See text for details.
◼︎Fig. 17: Treatment progress – overjet
The overjet was corrected from an excessive 12 mm to 0 mm, and the result was still stable 5 years after treatment.
◼︎Fig. 18: Treatment progress – frontal view with archwire specifications
Discussion
This young patient with an excessive 12 mm overjet, full-cusp Class II malocclusion, and lip protrusion was delighted that neither orthognathic surgery1,2
nor extraction of four bicuspids3 was performed during her treatment. Nevertheless, bilateral Class I canine and molar relationships, reduced overjet (0
mm), and an acceptable facial profile to the E-line were achieved (Figs. 12-16). The upper lip was retruded 4 mm, to -2.5 mm to the E-line (Table 1).
The finish was 1.5 mm more retrusive than ideal (-1.0 mm to the E-line) but it was harmonious with the facial profile. Three notable aspects of the treatment are discussed below:
1. Treatment planning: Try non-extraction
In treatment planning, three options were given. After a thorough explanation and discussion with the patient, option (1) was chosen: try non-extraction
treatment for 12 months with bilateral IZC bone screws inserted to retract the maxillary dentition. Although extraction of U4s could solve the excessive overjet with full-cusp Class II malocclusion more predictably,3 as in treatment options (2) and (3), the patient was still given the chance to try non-extraction treatment with a deadline for evaluation. If after 12 months of treatment with IZC bone screws the overjet was still not solved, extraction would be considered.
◼︎Fig. 19: Treatment progress – right buccal view.
U7s were unerupted, allowing space to retract the maxillary de
◼︎Fig. 20: Treatment progress – maxillary occlusal view. Note arch form development was stable at the 5-year follow-up.
In this case, the result after 12 months of treatment was more than satisfactory (Fig. 10). Therefore, extractions were ruled out. Nevertheless, it is
important to give a thorough explanation of the possibility/probability of extraction before commencing the treatment.
2. Temporary Skeletal Anchorage Devices: IZC bone screws
Since both U7s were unerupted (Fig. 1), there was adequate space to retract the whole maxillary dentition. However, in patients with a protrusive
profile, if retraction was attempted with only Class II elastics, it would lead to an excessively convex facial profile and posterior rotation in the mandible, which increases the lower facial height, and.19 Temporary skeletal anchorage devices (TSADs), however, can provide skeletal anchorage and vertical control while retracting the maxillary dentition without the adverse effect of Class II elastics, making it possible to perform a non-extraction treatment. IZC bone screws were inserted in the 4th month and were removed in the 14th month, when a reduced overjet (0 mm) and bilateral Class I canine and molar relationships were achieved. In retrospect, a better correction could have been achieved without Class II elastics.
It should be noted that the insertion site of IZC bone screws was above the U6 buccal root (Fig. 8) instead of the area between U6 and U7 as commonly used in adults.5 The bone width and quality for screw retention in this site was much better than between U6 and U7, since the U7s were unerupted.
3. Arch form Development: PSL brackets
To correct such a large overjet, adequate space was required to retract the maxillary anteriors. Since the U4s were not extracted, the space was gained from: (1) retracting the entire maxillary dentition into the space of the unerupted U7s, accomplished with power chains anchored by IZC screws, (2) IPR of maxillary anteriors, and (3) arch form expansion (development). In this present case, the maxillary arch form was tapered (Fig. 1); therefore, arch form expansion yielded substantial space for anterior retraction. With the aid of Damon Q® PSL brackets, arch expansion was achieved with a light continuous force instead of a traditional heavy short force generated by a rapid palatal expander (RPE).20,21 Expansion performed with PSL brackets results in less
discomfort and complications, it is not age-limited,21 and it results in more physiologically determined tooth positions than RPE.20-23 It is important to note that the expanded arch form was still stable at the 5-year follow-up with the retention of lingual fixed retainers on the lower arch and Essix overlay retainers on both arches (Fig. 20).
Conclusions
This case report demonstrates the treatment of a fullcusp Class II malocclusion complicated by an excessive 12 mm overjet, flared U1s, and 100%
overbite with periodontal impingement. Nonextraction treatment was made possible by using TSADs as anchorage to retract the entire maxillary
dentition and by expanding the arch with PSL brackets. The result was stable at the 5-year follow-up.
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