Correction of Angle’s Class II Division 1 Malocclusion with Anterior Deep Bite using Frictionless Loop Mechanics

INTRODUCTION

In orthodontics, the primary concerns of patients surround esthetic outcomes, although treatment plans are designed with structural balance and functional efficiency in mind. The overbite increases since the uprighting of the incisors frequently lengthens the crown vertically. Orthodontic treatment for this problem is accompanied by a challenging biomechanical problem. Dental protrusion with a deep overbite is widespread amongst different ethnic groups worldwide. ^[1]

Malocclusions are considered in the vertical, transverse, and sagittal planes. Both sagittally and vertically, the maxillary anteriors overlap the mandibular anteriors. This vertical overlap is referred to as overbite, and the sagittal overlap is known as overjet. This is a typical observation in human teeth. Deep bite is the term used to describe patients who have an unjustified vertical overlap of the lower anteriors by the upper anteriors. This deep overbite is an orthodontic issue that can lead to difficulties with the temporomandibular joint, periodontal health, chewing habits, and excessive tooth wear, which can cause early tooth loss.^[2,3]

Correcting deep bites, the most prevalent and challenging malocclusion, is the objective of orthodontic treatment.Thus, for the optimum care of deep bites, a comprehensive diagnosis, systematic treatment strategy, and efficient appliance design are required.^[4]

This article represents a case study of an angle’s class II division I malocclusion with a deep bite that was successfully treated by extractions of the upper first and lower second premolars. The upper arch was retracted using frictionless mechanics, Kalra Simultaneous Intrusion and Retraction (K-SIR) LOOP, while the lower arch was subjected to friction mechanics.

CASE REPORT

A 15-year-old female arrived with a complaint of her front teeth being positioned forward. A convex profile, anterior divergence, an acute nasolabial angle, incompetent lips, and a deep mentolabial sulcus were found during the extraoral examination. An intraoral examination showed a proclined and crowded upper and lower anterior, a deep bite, and an enhanced overjet. The canine relationships were endon and the molar relationships were class II [Figure 1]. A skeletal class II pattern was found in the cephalometric examination, and model analysis showed a Bolton’s disparity of 7 mm in the maxillary arch and 5 mm in the mandibular arch.

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Figure 1:

(a) Pretreatment extraoral photograph – front view, (b) Pretreatment extraoral photograph – front smile view, (c) Pretreatmentextraoral photograph –profile view, (d) Pretreatment extraoral photograph –oblique view, (e) Pretreatment intraoral photograph – right view, (f) Pretreatment intraoral photograph – front view, (g) Pretreatment intraoral photograph –left view, (h) Pretreatment intraoral photograph – maxillary arch, (i) Pretreatment intraoral photograph – mandibular arch.

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Treatment plan

Therapeutic removal of the maxillary first premolars and mandibular second premolars was carried out, followed by the application of a fixed appliance therapy employing a Preadjusted Edgewise Appliance with a 0.022 × 0.028 McLaughlin, Bennett, and Trevisi (MBT)prescription. A K-SIR arch [Figure 2] was utilized to facilitate simultaneous intrusion and retraction of the upper anterior teeth. The K-SIR Loop, arch was selected because it enables both intrusion and retraction to occur concurrently, requires less anchorage management, is easy to fabricate, is more economical compared to Temporary Anchorage Devices (TADs), and demands minimal cooperation from the patient.

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Figure 2:

K-SIR arch for simultaneous intrusion and retraction in upper arch.

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Treatment progress

After the extraction of the premolars, the transpalatal arch and Nance palatal arch were implemented in the upper arch. Once the teeth were adequately aligned and levelled with a 0.016” Nickel-Titanium wire, a 0.017 × 0.025” NiTi wire, and then a 0.019 × 0.025” SS wire were placed. Then a K-SIR arch (continuous 0.019”x 0.025” Titanium-Molybdenum Alloy (TMA) was introduced in the upper arch to enable the simultaneous intrusion and retraction of the upper anterior teeth, while in the lower arch, en masse retraction and lower molar mesialization was continued with a type I active tie back. (Group A anchorage in the upper arch and Group B anchorage in the lower arch). The K-SIR arch wire exerts about 125 g of intrusive force on the anterior segment and a similar amount of extrusive force distributed between the two buccal segments, generally 2^nd premolars and 1^st molars, which is countered by the forces of occlusion and mastication. Activation schedule is 6 to 8 weeks. Aftercorrection of the deep bite and retraction of anteriors, the K-SIR arch was removed. Settling elastics were given for the proper establishment of occlusion [Figure 3].

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Figure 3:

K-SIR arch for simultaneous intrusion and retraction in upper arch.

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Treatment results

After 15 months of treatment, the Angle’s class I relationships of both the canines and molars were successfully established, and all gaps were closed. All treatment goals were met, resulting in a proper occlusion. Comparison of pretreatment and post-treatment cephalometric variables was done [Table 1].

Table 1: Comparison of pretreatment and posttreatment cephalometric variables

Variables	Norms	Pre treatment	Post treatment
SNA in degree	82°	79	78
SNB in degree	80°	73	75
ANB in degree	2 ± 2°	6	3
N perpendicular to pt A in mm	1.1 mm	-3	1
N-Pog in degree	82.8° (82 - 95)	83	83
GoGn-SN in degree	32°	28	28
Y- AXIS in degree	53-66°	60	60
Facial axis in degree	90 ± 3°	89	89
Gonial angle in degree	128 ± 7°	122	122
Jaraback index in %	62 – 65 %	70	63
Interincisal angle in degree	135°	107	130
Upper incisor to NA in degree, mm	22°, 4 mm	42, 7	24, 4
Lower incisor to NB in degree, mm	25°, 4 mm	30, 9	26, 4
Upper incisor to SN in degree	102°	118	101
Lower incisor to A- Pog in mm	2.7 mm	3	2.5
IMPA in degree	90°	100	100
Nasolabial angle in degree	102°	95	104

SNA: Sella-Nasion-A point angle, SNB: Sella-Nasion-B point angle, ANB: A point-Nasion-B point angle, N-Pog: Facial angle, GoGn-Sn: Mandibular plane angle, NA: Nasion to point A, NB: Nasion to point B, SN: Sella to point N, A-Pog: Point A to Pogonion, IMPA: Incisor mandibular plane angle

The alignment of the upper and lower arches was satisfactory, with the midlines of both arches being aligned perfectly.The patient's facial profile showed considerable enhancement following the completion of treatment [Figure 4].

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Figure 4:

(a) Pretreatment extraoral photograph – front view, (b) Pretreatment extraoral photograph – oblique view, (c) Pretreatment extraoral photograph – front smile view, (d) Pretreatment extraoral photograph – profile smile view, (e) Pretreatment intraoral photograph – right view, (f) Pretreatment intraoral photograph – front view, (g) Pretreatment intraoral photograph – left view, (h) Pretreatment intraoral photograph – maxillary arch, (i) Pretreatment intraoral photograph – mandibular arch.

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Retention plan

The retention plan includes the use of Essixretainers for both the upper and lower arches, with guidelines for continuous wear for the first 6 months, transitioning to nighttime wear for the subsequent 6 months [Figure 5].

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Figure 5:

Retention protocol

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DISCUSSION

Burstone and Nanda have demonstrated molar anchoring control; nevertheless, using a non-frictional loop (K-SIR loop) mechanics achievesen masse retraction of the anterior teeth that compares well to conventional edgewise sliding mechanics.

The K-SIR or Kalra Simultaneous Intrusion and Retraction archwire when introduced, was considered to be a modification of the segmented loop mechanics by Burstone and Nanda. K-Sir arch consists of .019”x.025” TMA archwire with closed 7mm x 2 mm U-loops at the extraction sites.^[5]

Archwire reactivation needs to be done every 6-8 weeks until complete closure of the extraction site has occurred. The adjustable archwire is capable of closing extraction spaces under both minimal and moderate anchorage conditions, accommodating various levels of overbites. The 0.019" × 0.025" TMA is robust enough to withstand deformation and sufficiently rigid to provide the necessary moments.^[3] The space closure can occur within 8 weeks due to the combination of the archwire's design and the properties of TMA, which together create relatively lower forces, a reduced activation range, and a slower load deflection rate. Agnani S, Bajaj K presented the correction of Angle’s Class II division 1 Malocclusion with deep bite with KSIR arch and achieved simultaneous movements and a successful outcome.^[6] Similar studies by Chouksey M, Taori K, Gurav T, et al. have shown that K-SIR loops are effective in the intrusion retraction and alignment of teeth in Class II malocclusion patients. They help reduce the treatment time and help patients have maximum anchorage conservation.^[7]

The K-SIR archwire reduces the timing of orthodontic treatment when compared to conventional edgewise mechanics, as it allows for the simultaneous intrusion of the six anterior teeth and retraction of the canines and incisors. Furthermore, when canine retraction is done separately, the unattractive area behind the incisors will not become visible because the six anterior teeth are being retracted at the same time.^[8]

CONCLUSION

The K-SIR loop offers various advantages, including reduced friction between the bracket and archwire during the space closure, retraction, and concurrent tooth intrusion in cases of deep biting. This arch is primarily utilized for retracting anterior teeth in individuals with significant overjet and deep bites who require optimal molar anchorage alongside the intrusion of front teeth following the extraction of premolars.