Journal of Contemporary Orthodontics

Official Publication of Indian Orthodontic Society


Kadam, Aphale, and Nagmode: Revolutionizing orthodontics: Effective management of Class III skeletal malocclusion using innovative buccal shelf bone screws


Introduction

In the Asian ethnic groups, the prevalence of Class III malocclusions is the greatest compared to other sagittal malocclusions. These patients along with the skeletal discrepancy show dentoalveolar, functional and also vertical, and transverse deviations which complicate the treatment planning.1 The main reason why these patients seek orthodontic treatment is compromised facial aesthetics and functions. Skeletal Class III malocclusions are the most difficult malocclusions to treat particularly because of the unfavorable growth pattern of the mandible and associated with the dental compensations.1 Many of these cases require orthopedic correction during the growing phase in children and for the non-growing patients orthognathic surgery is required for the best treatment outcome. The ideal treatment in adult patients is orthognathic surgery, which many patients refuse due to the invasive nature of the procedure.2, 3, 4

Expanding the conventional envelope of discrepancy, in some skeletal malocclusions, orthodontic camouflage may be considered to achieve appropriate occlusion, which would improve aesthetics and optimum function.5 The objective of the orthodontic camouflage involves the uprighting of the maxillary & mandibular anteriors on their respective jaw bases, sometimes needing selective extractions. Another alternative method for orthodontic camouflage in skeletal Cl III is by en-masse distalization of mandibular dentition.5

Before the advent of skeletal anchorage, distalization of the lower arch was difficult to achieve, time consuming and involved complicated appliances which were many times not accepted by the patient. Conventionally, individual molar distalization was done, followed by retraction of remaining teeth into gained space. However, with the advent of TAD’s and increasing use of extra alveolar TAD’s, it is now possible to distalize the lower arch en masse, without the use of complicate appliances or difficult biomechanics. This method is gaining rapid popularity as it is easy to perform, shortens the treatment time and is relatively more patient friendly.

Case Report

A 19 year old adult patient reported with a chief complaint of forwardly placed lower front teeth. He presented with a hypodivergent skeletal Cl III pattern with a prognathic mandible which was complicated by a negative overjet of 2 mm and asymmetric molar relation of full cusp angles Cl III molar relation on the right side and a half cusp Cl III molar relation on the left side. The general extra oral and intra oral features are summarised in Table 1 and Table 2.

Figure 1
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Figure 2
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Figure 3
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Figure 4
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Figure 5
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Figure 6
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Figure 7
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Figure 8
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Figure 9
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The pre-treatment images (Figure 1, Figure 2, Figure 3, Figure 4).

Treatment Objectives

The treatment objectives of the case are summarised in the table 3.

Treatment plan

Keeping the mentioned treatment objectives in view, a treatment plan of orthodontic camouflage was devised. An asymmetric en masse distalization was planned to end in a Cl I molar relation bilaterally. The anchorage was gained using extra alveolar TAD’s placed in the buccal shelf area of the lower jaw bilaterally. An asymmetric molar relation dictated an asymmetric setback of the lower dentition. A posterior acrylic bite plate was used to facilitate no anterior tooth contact while en masse distalization in both the lower quadrants.

Alignment and levelling were done in the upper arch. Here a couple force was used with the help of a transpalatal arch to achieve the denotation of the second molar and to correct its overhanging palatal cusp. The upper and lower midlines were matched to the facial midline facilitated by asymmetric lower arch distalization (the third molars to be extracted and available space distal to the 2nd molars). The case finished with Class I molar and canine relationship bilaterally, dental midlines matching the facial midline, ideal overjet, ideal overbite, and correction of protrusive soft-tissue profile.

Treatment progress

The treatment sequence and biomechanics are summarized in Table 4. The bite plate is utilized for relieving the anterior crossbite, Figure 5 A.

Figure 5 B illustrates the mandibular arch distalization with the buccal shelf implants.

The mechanics for the correction of the rotations of the maxillary second molars are illustrated in Figure 6.

The post-completion of the treatment is seen in Figure 7, Figure 8, Figure 9.

Table 1

Chief complaint

Forwardly placed lower front teeth.

Examination

Extra-oral

Hypodivergent face pattern

Obtuse nasolabial angle

Anterior divergent face

Positive lip step

Everted lower lip

Shallow mento-labial sulcus

Intra-oral

Angle’s Class III molar relationship

Canine relation Class III on the right aspect and Class I on the left aspect

Reverse overjet of 2mm

Crowding in the upper arch

Maxillary dental midline shift towards right

Disto-buccal rotation with 17 and 27

Ellis Class I fracture with maxillary central incisors

Radiographic findings

Orthopantomogram

Impacted mandibular third molars

Table 2

Parameter

Readings

SNA

86˚

87˚

ANB

-1

WIT’S APPRAISAL

-5mm

GoGN-SN plane

19˚

FMA

17˚

Y-axis

59˚

U1-NA line (angle)

34˚

U1-NA line (linear)

5mm

L1-NB line (angle)

22˚

L1-NB line (linear)

4mm

L1-A-Pog line

4mm

IMPA

94˚

S line to upper lip

-1mm

S line to lower lip

5mm

Cephalometric Summary:

•Skeletal Class III jaw base with horizontal growth pattern.

Table 3

Parameter

Normalvalues

Pre-treatment

Inference

Maxilla to Cranium

SNA

820

820

Orthognathic maxilla

N-Point A

0+/-2mm

-4mm

Backwardly placed maxilla

N-A(∏ HP)

0.0+/-3.7mm

2mm

Average

Mandible to Cranium

800

870

Prognathic mandible

N-Pog

0 to -4 mm

-5mm

Backwardly positioned chin

N-B(∏ HP)

-5.3+/-6.7mm

5mm

Average

N-Pg(∏ HP)

-4.3+/-8.5mm

6mm

Average

Go-Gn to SN

320

19o

Horizontal growth pattern

Maxillary Teeth to Cranium

NA to U1(Angle)

220

280

Proclined maxillary incisors

NA to U1(Linear)

4mm

4mm

Normally positioned incisors

U1 to NF(┴ NF)

30.5+/-2.1mm

21mm

Decreased

U6 to NF(┴ NF)

26.2+/-2mm

16mm

Decreased

U1 to SN

102+/-20

1230

Proclined maxillary incisors

U1 to ANS-PNS

70+/-50

60o

Proclined maxillary incisors

Mandibular teeth to cranium

NB to L1

250

220

Upright lowner incisors

NB to L1(mm)

4mm

4mm

Normally positioned incisors

L1 to A-Pog

1-2 mm

4mm

Protrusive incisors

IMPA

900

94o

Proclined lower incisors

L1 to MP(┴ MP)

45+/-2.1mm

32mm

Decreased

L6 to MP(┴ MP)

35.8+/-2.9mm

27mm

Decreased

Maxilla to Mandible

Interincisal angle

1300

111o

Proclination of incisors

ANB

20

-5o

Skeletal class III jaw base relationship

WITS appraisal

+1mm

-4mm

Skeletal class III jaw base relationship

Vertical Relation

Y-axis

660

59o

Anterior positioning of mandible w.r.t cranial base

Facial axis angle

00

4o

Horizontal growth pattern

J angle

850

92o

Anticlockwise rotation of the maxilla

LAFH

45+/-2

50mm

Average

Basal plane angle

250

22o

Horizontal growth pattern

Facial height ratio

62-65%

68%

Horizontal growth pattern

FMA

250

23o

Horizontal growth pattern

Gonial angle

128+/-70

116 o

Horizontal growth pattern

Soft tissue

'S' line to upper lip

0mm

-1mm

Lies behind the s line

'S' line to lower lip

0mm

3mm

Lies ahead of the s line

Nasolabial angle

900-1000

88o

Acute

Table 4

Treatment Objectives

Dimension

Skeletal

Dental

Soft tissue

Anteroposterior

-

To achieve ideal overjet

To achieve ideal lip

To achieve Angle’s Class III molar relationship

position

To achieve Class I canine relationship

Transverse

To achieve ideal alignment in the upper and lower arches

-

To correct the dental midline discrepancy.

Vertical

Open up the mandibular plane and increase the lower anterior facial height as a resultant to distalization of upper arch (wedge effect)

Establish ideal overbite

-

Other

-

Resin based restoration with 11 and 21.

Disimpaction with the mandibular third molars

Table 5

Treatment sequence and biomechanical plan

Maxilla

Mandible

Bonding with maxillary arch (MBT 0.022”slot) along with cemented posterior biteplate.

Bonding with mandibular arch (MBT 0.022”slot)

Leveling and alignment with 0.014, 0.016, 0.016×0.022 Niti wires. Followed by 0.017 x 0.025” SS and 0.019 x 0.025” SS.

Leveling and alignment with 0.014, 0.016, 0.016×0.022 Niti wires. Followed by 0.017 x 0.025” SS and 0.019 x 0.025” SS.

Buccal shelf orthodontic bone screws of 12 mm length placed in the right lower buccal shelf region and immediate loading done with e-chain delivering a force of about 300 G for asymmetrical retraction of the right buccal segment to correct the dental midline and develop adequate overjet. Bilateral placement of forces was to avoid the cant of occlusal plane.

Full arch distalization was continued on the right side till Class I molar and canine relation was attained. The archwire was periodically checked for transverse co-ordination of arches.

The bite plate was removed adequate overjet observed.

The maxillary second molars were bonded, and de-rotations was done with round 0.014” Niti wire and elastics from modified TPA.

Post distalization and space closure - consolidation of arch was done, and the same 0.019×0.025 SS wire was kept for extended period to aid in ideal root parallelism

The consolidation of the arch was done with the continuous ligature wire, and 0.012 Niti wire was placed for the settling process.

Postdistalization and space closure - consolidation of arch was done, and the same 0.019×0.025 SS wire was kept for extended period of two months.

For retention fixed lingual bonded retainers along with Hawley’s retainers.

Pericision was done for the corrected rotations of the maxillary second molars.

Ellis Class I fractures of the central incisors were restored with resin based esthetic cements.

For retention fixed lingual bonded retainers along with Hawley’s retainers.

Table 6

Parameter

Normal values

Current

Inference

Maxilla to Cranium

SNA

820

820

Orthognathic maxilla

N-Point A

0+/-2mm

-4mm

Backwardly placed maxilla

N-A(∏ HP)

0.0+/-3.7mm

1mm

Average

Mandible to Cranium

800

860

Prognathic mandible

N-Pog

0 to -4 mm

-4mm

Backwardly positioned chin

N-B(∏ HP)

-5.3+/-6.7mm

4mm

Average

N-Pg(∏ HP)

-4.3+/-8.5mm

6mm

Average

Go-Gn to SN

320

200

Horizontal growth pattern

Maxillary Teeth to Cranium

NA to U1(Angle)

220

300

Proclined maxillary incisors

NA to U1(Linear)

4mm

4mm

Normally positioned incisors

U1 to NF(┴ NF)

30.5+/-2.1mm

21mm

Decreased

U6 to NF(┴ NF)

26.2+/-2mm

17mm

Decreased

U1 to SN

102+/-20

1250

Proclined maxillary incisors

U1 to ANS-PNS

70+/-50

580

Proclined maxillary incisors

Mandibular Teeth to Cranium

NB to L1

250

200

Upright lowner incisors

NB to L1(mm)

4mm

3mm

Normally positioned incisors

L1 to A-Pog

1-2 mm

3mm

Forwardly positioned incisors

IMPA

900

910

Normally positioned lower incisors

L1 to MP(┴ MP)

45+/-2.1mm

32mm

Decreased

L6 to MP(┴ MP)

35.8+/-2.9mm

27mm

Decreased

Maxilla to Mandible

Interincisal angle

1300

1150

Proclination of incisors

ANB

20

-40

Skeletal class III jaw base relationship

WITS appraisal

+1mm

-3mm

Skeletal class III jaw base relationship

Vertical Relation

Y-axis

660

600

Anterior positioning of mandible w.r.t cranial base

Facial axis angle

00

+30

Deficient vertical development of the face

J angle

850

920

Anticlockwise rotation of the maxilla

LAFH

45+/-2

52 mm

Average

Basal plane angle

250

240

Horizontal growth pattern

Facial height ratio

62-65%

67%

Horizontal growth pattern

FMA

250

240

Horizontal growth pattern

Gonial angle

128+/-70

1170

Horizontal growth pattern

Soft Tissue

'S' line to upper lip

0mm

-1mm

Lies behind the s line

'S' line to lower lip

0mm

0mm

Lies over the s line

Nasolabial angle

900-1000

880

Acute

Results

The case was finished with Angle’s Class I molar relationship along with Class I canine relation. The incisor relationship with normal overjet and overbite of 2 mm was achieved. The upper and lower dental midlines matched at the end of the treatment. All displacements and crossbites were corrected by the end of the treatment. No occlusal wear facets were noted with mutually protected occlusion and canine-guided excursive movements established. A consonant smile arc was achieved, and smile esthetics was significantly improved along with the facial profile.

Cephalometric changes – The Cephalometric changes along with the pre-treatment cephalometric values (Table 5) and post-treatment cephalometric values (Table 6) are mentioned in the.

Discussion

In the treatment of orthodontic camouflage in skeletal Cl III malocclusions, counter clockwise rotation of the jaws is undesirable. 6, 7, 8 This can be facilitated planning biomechanics where the vectors of force is as parallel to the lower occlusal plane as possible. Here in this case report, the correction is achieved by minimal clockwise rotation of the mandibular plane with the fixed appliance along with the buccal shelf bone screw in a Class III adult patient. The severity of the skeletal discrepancy, degree of the incisor compensations, facial growth pattern, periodontal status, anterior facial proportions, and aesthetic appearance of the patient are the important factors to be considered during planning the biomechanics of a skeletal Cl III case where orthodontic camouflage is desired. 9, 10, 11, 12, 13

There have been various studies that determine which cases of skeletal Class III malocclusion can be treated by orthodontic camouflage by enlarging the envelope of discrepancy. 14, 15, 16, 17, 18, 19 In general it is hypothesized that surgery is ideally indicated when the ANB angle is more than -5 degrees, and the Wits appraisal shows mandibular prognathism more than 5mm. In the present case report, the ANB angle was – 5 degrees, IMPA was 94 degrees, and the Wits appraisal was -5mm. This made the present case a borderline case and as the patient did not agree to a surgical treatment plan, orthodontic camouflage was planned by asymmetric en masse distalization of the lower arch.

The patient also showed some functional forward shift of the mandible, which can be observed in many cases of Cl III with an anterior cross bite due to occlusal interferences. Orthodontic camouflage in many Class III cases addresses the sagittal problems, but seldom on the improvement of vertical deficiency. 20, 21, 22, 23, 24 The extrusion of the maxillary anteriors was planned to improve the incisor visibility and smile arc as reported in a few can reports published. 24 The clockwise rotation of the occlusal plane was advantageous in improving smile arc as proposed by Eric Liou et al. 9 Posterior bite plate was used on the upper posteriors to open the bite while the reverse overjet was corrected. After achieving a positive overjet, the posterior bite plate was discontinued. Two buccal shelf bone screws (2x12mm) were placed in the third and fourth quadrants. A parallel force vector was used. Asymmetric mandibular dentition distalization was desired which was more on the right side to correct a full cusp Cl III molar relation to a Cl I molar relation. On the left side the amount of distalization was limited to correct a half cusp Cl III to a Cl I molar relation. The distalization force was stopped after achieving Cl I molar relation bilaterally. The goal of achieving a functional mutually protected occlusion with cuspid rise was achieved.

Critical appraisal

Although the results from an orthodontic point of view look satisfactory, as a new modality of treatment, a long-term follow-up will determine the success achieved. All the aesthetic and functional goals were achieved and a stable posterior occlusion with symmetric cusp to fossa relation was established bilaterally. The case selection, the biomechanics, and the appreciation of the anatomic limitations would remain as some of the important perspectives for achieving the final objective.

Conclusion

The primary objective of any new clinical protocol is to enhance treatment quality by incorporating precision, expanding treatment horizons, and to make the treatment more acceptable to the patient.

By employing extra radicular bone screws in distalization techniques, with careful biomechanical consideration, we can effectively address emerging challenges and surpass limitations, ultimately striving for the pinnacle of the ever eluding clinical excellence.

Patient Consent Declaration

The author affirms that all appropriate patient consent forms have been obtained. The patients have willingly given their consent for the usage of their images and other clinical information in the journal. The patients are aware that their names and initials will not be disclosed, and utmost efforts will be taken to protect their identity. However, complete anonymity cannot be guaranteed.

Source of Funding

None.

Conflict of Interest

None.

References

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JW Eric YC Liou Orthodontic clockwise rotation of maxillomandibular complex for improving facial profile in late teenagers with Class III malocclusion: A preliminary reportAPOS Trends Orthod20188139

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HS Baik HK Han DJ Kim W Proffit Cephalometric characteristics of Korean Class III surgical patients and their relationship to plans for surgical treatmentInt Adult Orthod Orthognath Surg200015211947

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WJS Kerr Class III malocclusions: Surgery or OrthodonticsBr J Orthod1992191215

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NR Burns DR Musich C Martin T Razmus E Gunel P Ngan Class III camouflage treatment: What are the limits?Am J Orthod Dentofac2010137919

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V Tekalepd Orthodonticcamouflageinskeletal class III malocclusion: A contemporary reviewJ Orofac Res20144298102

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EY Kwon JY Lee J Choi Effect of slow forced eruption on the vertical levels of the interproximal bone and papilla and the width of the alveolar ridgeKorean J Orthod201646637985

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C Chang S S Liu W E Roberts Primary failure rate for 1680 extra-alveolar mandibular buccal shelf mini-screws placed in movable mucosa or attached gingivaAngle Orthod201585905915

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CH Chang JS Lin WE Roberts Failure rates for stainless steel versus titanium alloy infrazygomatic crest bone screws: A single-center, randomized double-blind clinical trialAngle Orthod2018891406

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SN Papageorgiou IP Zogakis MA Papadopoulos Failure rates and associated risk factors of orthodontic miniscrew implants: A meta-analysisAm J Orthod Dentofac Orthop201214257795

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J Lin E Roberts CBCT imaging to diagnose and correct the failure of maxillary arch retraction with IZC screw anchorage. Int IOrthop Impl201435417

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SJ Kim TH Choi HS Baik YC Park KJ Lee Mandibular posterior anatomic limit for molar distalizationAm J Orthod Dentofac Orthop201414621907



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Received : 11-03-2024

Accepted : 05-06-2024


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https://doi.org/10.18231/j.jco.2024.057


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