Treatment of Class II malocclusion with tooth movement through the maxillary sinus

This case report describes the successful extraction treatment of a Class II malocclusion with excessive maxillary sinus pneumatization. A 20-year-old man sought treatment with the major complaint of protrusive mouth and anterior teeth. He was diagnosed with a skeletal Class II relationship and protrusion of the maxilla. The clinical examination showed a severe Class II molar relationship with excessive overjet and deep overbite. Panoramic radiograph showed obvious maxillary sinus pneumatization bilaterally. Three premolars and one deciduous molar were extracted, and spaces were used to correct molar relationship and retract maxillary incisors. Light forces and low speed movement were applied to overcome the challenge of moving teeth through the maxillary sinus wall. Balanced facial esthetic and stable occlusion were obtained posttreatment with a notable bone formation of the maxillary sinus wall. This result highlights the possibility of tooth movement through cortical floor with bone remodeling and no obvious complications.


  • This case report described the successful extraction treatment of a skeletal Class II patient with excessive maxillary sinus pneumatization.

  • Teeth movements through maxillary sinus floor were achieved with significant bone modeling and no obvious complications.

  • Retraction of the anterior teeth and bodily movement of posterior teeth were accomplished with balanced facial esthetic and stable occlusion obtained posttreatment.

The maxillary sinus is one of the largest paranasal sinuses located in the body of the maxilla. It is pyramidal in shape and exhibits anatomical variability in adults. Pneumatization is the most common variation occurring during the growth period, when the sinus floor extends downwards following teeth eruption, resulting in extension of the antral surface and increase of sinus volume. Thus, a close relationship of sinus floor and roots could be observed. In some cases, the floor completely extends into the interproximal space of the maxillary posterior roots.

The maxillary sinus floor is structured with compact cortical bone, formed by the alveolar process and part of the hard palate. Due to the difference in bone turnover and surface active frequency between the cortical bone and the trabecular bone, tooth movement in cortical bone is considered one of the anatomical limitations in orthodontics for adults.

Tooth movement through the floor of maxillary sinus has been reported as a challenge. A proper force system is required for bodily movement of the target teeth through the maxillary sinus. Some studies reported that, segmented archwire mechanics with a T-loop fabricated from beta-titanium archwire can bodily move teeth through the maxillary sinus. Oh et al demonstrated that, a low speed movement is necessary in bodily movement of the teeth through the cortical wall of the maxillary sinus for adults. Additionally, histological and animal studies reported that the risk of complications such as root resorption, alveolar bone loss, pulp devitalization, and sinus membrane perforation is high when moving teeth through the maxillary sinus.

This case report presents the extraction treatment of a skeletal Class II malocclusion with excessive maxillary sinus pneumatization. It demonstrates that light forces and low speed movement can move teeth through maxillary sinus wall with bone modeling and no obvious complications.

Diagnosis and etiology

A young man aged 20 years came to the orthodontics department with flaring teeth and protrusive mouth being his chief complaints. No temporomandibular disorder signs were detected in clinical and radiographic examinations. His past medical history was noncontributory.

Facial photographs showed a convex profile and an acute nasolabial angle ( Fig 1 ). He presented a Class II molar relationship with deep overbite and overjet of 7 mm. Mild crowding was noted in both arches, and both arches were narrow in the middle. A retained deciduous molar was in the left mandibular arch ( Fig 2 ).

Fig 1
Pretreatment facial and intraoral photographs.

Fig 2
Pretreatment casts.

The pretreatment panoramic radiograph showed that, the floor of the maxillary sinus extended into the middle level of the posterior roots. No permanent tooth germ was evident under the deciduous molar. All third molars were present but the mandibular third molars were mesially impacted. Clinical examination and the pretreatment panoramic radiograph showed the right maxillary incisor was discolored, with the root canal enlarged ( Fig 3 ).

Fig 3
Pretreatment lateral cephalogram and tracing and panoramic radiograph.

The pretreatment lateral cephalometric assessment indicated a Class II skeletal relationship with maxillary protrusion (SNA, 86.6°), a low mandibular plane (MP-FH, 22.2°), and severely proclined maxillary and mandibular incisors (U1/SN, 121.4°; L1/MP, 100.6°) with lip protrusion in relation to E-line (upper lip to E-Plane, 1.2 mm). ( Fig 3 & Table ).

Cephalometric measurements
Measurement Norm Pretreatment Posttreatment
Mean SD
SNA (°) 84.0 3.0 86.6 84.4
SNB (°) 80.0 3.0 81.5 80.8
ANB (°) 4.0 2.0 5.1 3.6
Wits appraisal (mm) −1.0 1.0 7.5 4.6
FMA (MP-FH) (°) 29.0 4.0 22.2 21.3
U1/NA (mm) 4.0 2.0 6.5 3.3
Interincisal angle (U1/L1) (°) 121.0 9.0 108.0 119.9
U1/SN (°) 105.2 6.4 121.4 116.1
IMPA (L1-MP) (°) 97.0 6.0 100.6 95.3
Upper lip to E-Plane (mm) −2.0 2.0 1.2 −0.0
Lower lip to E-plane (mm) −3.0 3.0 1.2 −0.2
Nasolabial angle (Col-Sn-UL) 102.0 8.0 105.3 111.8

Treatment objectives

The treatment objectives for the patient were to (1) improve facial profile and eliminate lip protrusion, (2) correct crowding and level both arches, (3) achieve normal overjet and overbite, and (4) obtain Class I molar and canine relationships.

Treatment alternatives

Three treatment alternatives were considered for the patient. Orthognathic surgery was suggested to the patient for correction of the anteroposterior skeletal discrepancy. A protrusive maxillary dentoalveolar segment can be retruded surgically and extraction of the mandibular second premolar and the deciduous molar would be applied to align and level the lower arch. A harmonious skeletal relationship could be established through this option, but the patient was strongly reluctant to undergo orthognathic surgery.

The second option was to reduce maxillary protrusion and correct the molar relationship with extraction of 2 maxillary first premolars, the mandibular second premolar, and the retained deciduous molar, as well as all third molars. The protrusive profile could be significantly improved through a large amount of anterior teeth retraction. However, considering the pneumatized maxillary sinus in this case, long-distance root movement through cortical bone was inevitable during the space closing stage. Closure of spaces could be incomplete and easily relapse, and a long treatment duration and a high risk of root resorption were likely.

The third option was a maxillary dentition distalization approach, which corrected crowding and leveled the arches through expanding arch and interproximal reduction of anterior teeth. To reduce the overjet and the maxillary protrusion, the third molars were to be extracted and headgear or temporary skeletal anchorage devices would be used to distalize the maxillary dentition. However, a considerable distalization of the maxillary dentition would be required to achieve normal overjet where stability of treatment result is questioned, and long-distance tooth movement through the maxillary sinus wall could not be avoided. From this option, great improvement of protrusive profile would not be achieved, and treatment time would not be markedly reduced, so the patient declined this option.

Treatment progress

The patient was referred to the endodontics department for root canal treatment of the maxillary right central incisor before the orthodontic treatment. Periodontal examination was performed to ensure the health of the periodontal tissue and regular periodontal checkups each 3 months were committed by the patient throughout the orthodontic treatment.

After extraction of 3 premolars and the deciduous molar, fixed 0.022 × 0.028-in straight wire appliance were bonded on all teeth except for the second and third molars. The second molars were obviously in a lower site than the first molars, so early alignment of the second molars would extrude and loosen the teeth, which brings pain when the patient bites, especially for patients who have low-angle mandibular plane and powerful bites. Considering the cortical anchorage of the maxillary sinus wall could provide enough anchorage for retraction, the second molars were not bonded initially. Initial alignment and leveling was achieved in both arches by placing nickel-titanium archwires in sequence (0.014 in, 0.016 in, 0.016 × 0.022 in, and 0.017 × 0.025 in). With stiffer archwires progressively placed, both arches were worked up to 0.019 × 0.025 in stainless-steel archwires for space closure. Early light and short Class II elastics (3/16 in, 2 oz) on nickel-titanium archwires and long Class II elastics (1/4 in, 3.5 oz) on stainless-steel archwires were applied to mesialize the mandibular first molars and reduce the overjet.

Sliding mechanics was used to close the spaces in both arches. A reciprocal movement of anterior and posterior teeth was achieved with elastic chains and nickel-titanium closed-coil springs pulling from molar tubes to hooks. Accentuated reverse curve and light force were maintained throughout space closing to control the inclination of anterior teeth and bodily movement of posterior teeth.

After 1.5 years of treatment, progress photographs showed an obvious profile improvement, which came from the retraction of maxillary incisors. Intraorally, spaces were closing in all quarters ( Fig 4 ). Cone beam computed tomography (CBCT) images showed the bottom of the sinus floor was extending into the mesial direction of the maxillary first molar. The dense cortical bone provided almost anchorage and strongly against the forward shift of the posterior teeth. Thus, spaces in maxillary arch took longer to close ( Fig 5 ).

Jan 7, 2020 | Posted by in Orthodontics | Comments Off on Treatment of Class II malocclusion with tooth movement through the maxillary sinus
Premium Wordpress Themes by UFO Themes