Mandibular Incisor Extraction and Interproximal Reduction Facilitates Clear Aligner Treatment to Correct UR2 Crossbite with Moderate Crowding

Drs. Huang YH, Chang CH & Roberts WE.

Abstract

Introduction: A 25 yr 6 mo male presented with a chief complaint of poor dental esthetics.

Diagnosis: Facial assessment revealed reduced facial convexity (6 ̊) with a protrusive maxilla (SNA 84 ̊) and mandible (82 ̊). All other facial and skeletal measurements were within normal limits (WNL). The Class I malocclusion had an anterior crossbite (UR2), upper dental midline deviated 3 mm to the right, and 6 mm of crowding in the lower anterior dentition. The Discrepancy Index (DI) was 13.

Etiology: The severe anterior crowding indicated limited development of arch width probably due to inadequate functional loading during the juvenile years. The UR2 crossbite is consistent with ectopic eruption.

Treatment: Clincheck® software and clear aligners (Align Technology Inc., San Jose, CA) were used for treatment planning and correction of the moderate crowding and UR2 crossbite. The lower left central incisor (LL1) was extracted. The virtual set-up of the final alignment documented the need for extensive interproximal reduction (IPR) and maxillary arch expansion. Vertical rectangular attachments were bonded on lower incisors adjacent to the extraction site to close space and align roots. Simultaneous aligner- mediated tooth movement, IPR, and interproximal elastics were used to achieve a pleasing interproximal alignment. During active treatment, the aligners went off-track on UR2, so additional IPR was performed and auxiliaries were added for additional retention. After treatment with the 1st set of aligners was complete, the dental alignment was inadequate so the dentition was scanned and resubmitted to prepare a new set of finishing aligners to achieve expansion of the upper arch, torque correction, angulation control, and detailing.

Results: All the teeth were moved the minimum distance to achieve an optimal result according to the virtual treatment plan, designed in the Clincheck® software. This moderate malocclusion with a DI of 13, was treated in 24 months to an excellent outcome: Cast-Radiography Evaluation (CRE) score of 6, and Pink & White dental esthetic score of 4. Both arches were well-aligned in a Class I relationship with the lower midline centered on the middle incisor (LR1). Small black triangles in the lower anterior region required restoration rather than IPR and space closure.

Conclusion: Class I crowded malocclusion with anterior crossbite can be effectively treated with aligners, extraction of a lower incisor, and IPR. This method avoids braces, multiple extractions and miniscrews, but it did require extensive IPR. However, the outcome featured a comprised dental midline with lower anterior black triangles. (J Digital Orthod 2019;55:4-22)

Key words: Invisalign, clear aligner treatment, severe crowding, anterior crossbite, occlusal canting, mandibular incisor extraction, end-on Class III
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Probable Airway Etiology for Skeletal Class III Openbite Malocclusion with Posterior Crossbite: Camouflage Treatment with Extractions

Drs. Peydro Herrero D, Chang CH, Roberts WE.

Abstract

History: A 27-year-old female presented for evaluation with a chief complaint (CC) of crooked front teeth with gummy smile.

Diagnosis: Class II malocclusion was associated with dental crowding, overjet, anterior open bite, and a gummy smile in maxillary buccal regions. Periodontal evaluation revealed anterior recession and moderate bone loss in the anterior segments of both arches. There were problems with chewing and maximum interdigitation was uncomfortable due to a functional retrusion of the mandible on closing. The Discrepancy Index (DI) was 16.

Etiology: Inadequate arch width, open bite and functional retrusion of the mandible was apparently due to childhood development problems. Inadequate functional loading of the dentition (soft diet) and a nocturnal airway problem resulted in aberrant soft tissue posturing of the lips and tongue.

Treatment:Stabilize the periodontal deterioration with scaling, oral prophylaxis and hygiene instruction. Utilize a series for clear aligners to expand both arches to correct crowding, and extrude incisors in anterior segments to correct the open bite. Correct the Class II discrepancy by allowing more anterior posturing of the mandible to resolve the functional retrusion. Improve the posterior gummy smile with maxillary arch expansion, and increased axial inclination of the posterior segments.

Outcomes:Crowding was corrected in both arches with expansion, and there was a slight increase in lip protrusion. Openbite was corrected with extrusion and retraction of the incisors. Bone loss in the anterior segments was stabilized. The maxillary molars were retracted to resolve the Class II discrepancy. The Cast-Radiograph Evaluation (CRE) score was 15.

Conclusion:Class II crowded malocclusion with anterior open bite (DI 16) was corrected to a pleasing dentofacial result (CRE 15) by eliminating a functional retrusion of the mandible. The posturing of the mandible should be evaluated periodically to determine if a centric occlusion (CO) to centric relation (CR) discrepancy occurs after treatment. (J Digital Orthod 2019;55:26-39)

Key words: Invisalign®, clear aligner treatment, anterior open bite, gummy smile, severe crowding, non-extraction treatment, functional retrusion of the mandible
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Severe Unilateral Scissors-bite with a Constricted Mandibular Arch: Bite Turbos and Extra-alveolar Bone Screws in the Infra-zygomatic Crests and Mandibular Buccal Shelf

Drs. Lee A, Chang CH, Roberts WE.

Abstract

A 33-year-old woman had a chief complaint of difficulty chewing, caused by a constricted mandibular arch and a unilateral full buccal crossbite (scissors-bite or Brodie bite). She requested minimally invasive treat- ment but agreed to anchorage with extra- alveolar temporary anchorage devices as needed. Her facial form was convex with protrusive but competent lips. Skeletally, the maxilla was protrusive (SNA, 86°) with an ANB angle of 5°. Amounts of crowding were 5 mm in the mandibular arch and 3 mm in the maxillary arch. The mandibular midline was deviated to the left about 2 mm, which was consistent with a medially and inferiorly displaced mandibular right condyle. Ectopic eruption of the maxillary right permanent first molar to the buccal side of the mandibular first molar cusps resulted in a 2-mm functional shift of the mandible to the left, which subsequently developed into a full buccal crossbite on the right side. Treatment was a conservative nonextraction approach with passive self-ligating brackets. Glass ionomer bite turbos were bonded on the occlusal surfaces of the maxillary left molars at 1 month into treatment. An extra- alveolar temporary anchorage device, a 2x12-mm OrthoBoneScrew (Newton A, HsinChu City, Taiwan), was inserted in the right mandibular buccal shelf. Elastomeric chains, anchored by the OrthoBoneScrew, extended to lingual buttons bonded on the lingually inclined mandibular right molars. Cross elastics were added as secondary uprighting mechanics. The maxillary right bite turbos were reduced at 4 months and removed 1 month later. At 11 months, bite turbos were bonded on the lingual surfaces of the maxillary central incisors, and an OrthoBoneScrew was inserted in each infrazygomatic crest. The Class II relationship was resolved with bimaxillary retraction of the maxillary arch with infrazygomatic crest anchorage and inter maxillary elastics. Interproximal reduction was performed to correct the black interdental spaces and the anterior flaring of the incisors. The scissors-bite and lingually inclined mandibular right posterior segment were sufficiently corrected after 3 months of treatment to establish adequate intermaxillary occlusion in the right posterior segments to intrude the maxillary right molars. The anterior bite turbos opened space for extrusion of the posterior teeth to level the mandibular arch, and the infrazygomatic crest bone screws anchored the retraction of the maxillary arch. In 27 months, this difficult malocclusion, with a Discrepancy Index score of 25, was treated to a Cast-Radiograph Evaluation score of 22 and a pink and white esthetic score of 3. (Reprinted with permission from Am J Ortho Dentofacial Ortho 2018;154;554-69). (J Digital Orthod 2019;55:44-62)

Key words: Scissors-bite, Brodie bite, buccal crossbite, lingually inclined lower molars, ectopic eruption, maxillary protrusion, lip protrusion, cross elastics, occlusal bite turbo, extra-alveolar anchorage, mandibular buccal shelf, mandibular rotation, infra-zygomatic crest, inter- proximal reduction, bone screws, TADs
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SmartArch^® Multi-Force, Super-Elastic Archwires: A New Paradigm in Orthodontics

Drs. Roberts WE, Roberts JA, Tracey S, Sarver DM.

Abstract

SmartArch® (S-A) archwires are laser-conditioned CuNiTi wires with a differential force profile that is based on the optimal compressive stress in the periodontal ligament (PDL) to achieve rapid tooth movement with minimal necrosis. Compared to alignment with a progression of two CuNiTi archwires (0.016 and 0.018-in), a single 0.016-in S-A is significantly (p<0.02) more efficient in correcting interproximal discrepancies, decreasing deepbite, and leveling the Curve of Spee. Failure to bond and align lower second molars results in marginal ridge discrepancies of up to 3mm that substantially delay treatment. Beta testing of initial alignment with a 3mo each sequence of 0.016-in and 0.017x0.025-in S-A archwires in a 0.018-in slot Ti Orthos® brackets revealed that simultaneous leveling and aligning of deepbite malocclusions was achieved in ~6mo. Three of the 10 moderate malocclusions treated were finished to <26 points on a cast alignment evaluation (CAE). These optimal results broadened the focus of clinical investigation to address an important limitation of indeterminate mechanics in orthodontics: excessive treatment time due to the repetitive PDL necrosis, associated with frequent reactivations. The new paradigm in orthodontics is an emphasis on precise bracket positioning to enable simultaneous 3D alignment of both arches with the 2-Step S-A sequence. Intermaxillary mechanics (Class II/III) should be avoided until the arches are aligned, and finishing TMA or SS archwires are in place. Then utilize determinate mechanics by applying elastics to archwire lugs mesial to the canines for the correction of midlines and buccal interdigitation. Detailing bends (only if required) should be the last stage in mechanics before debonding. 2-Step S-A 3D alignment, in the context of precise bracket positioning and determinate major mechanics, is expected to decrease chair-time, improve outcomes, and decrease treatment time at least 50%. (J Digital Orthod 2019;55:66-79)

Key words: Indeterminate and determinate mechanics, CuNiTi, accelerated treatment, decreased treatment deration, multiforce, superelastic, multiple memory technology, ideal physiologic load, martensite-austenite transition, interbracket distance
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The Beethoven Team Received the CDABO Case Report of the Year Award — The First Chinese Speaking Team to be Presented with this Award

Chang CH.

This year's AAO meeting in particular was personally a highlight, as together with my mentor, Dr. Roberts and Dr. Angle Lee (who unfortunately was unable to attend). We were the recipients of the CDABO's Case Report of the Year Award……

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In Memoriam: Dr. Burstone’s Lecture in Croatia in 2005

Slavica AS.

I met Dr. Burstone in April 2005. He was lecturing mechanics at the first ortho course I organized in my newly founded company……

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