Class III Malocclusion with an Atrophic Edentulous Ridge Treated with Autotransplantation, Lower First Molar Extraction and Space Closure

Drs. Derek Teng-Kai Yang, Po-Jan Kuo, Nancy Nie-Shiuh Chang, John Jin-Jong Lin, W. Eugene Roberts

Abstract

Diagnosis: A 19-year-10-month-old female with chief complaints of crowding and missing teeth presented for a second opinion. Clinical examination revealed a straight profile, 3° G-Sn-Pg’ facial convexity, and high mandibular plane angle (SN-MP 35°). The occlusion was Class III, crowded anterior segments, missing left maxillary first and second premolars, and an edentulous atrophic ridge. All third molars were present and the lower right first molar (LR6) was compromised with poor tooth structure and failed endodontics. The ABO Discrepancy Index (DI) was 20.

Etiology: Class III dentofacial malocclusion was due to genetics and environmental factors. The absence of both upper left premolars had resulted in the mesial migration of her upper left molars and a residual atrophic edentulous ridge.

Treatment: The emphasis was on a conservative treatment plan that preserved healthy teeth. The right upper second premolar (UR5) was endodontically treated and autotransplanted into the edentulous atrophic site (UL4). Both mandibular first molars were extracted and the adjacent second and third molars were protracted to close space and substitute for the first molars.

Outcome: The autotransplanted premolar healed successfully, crowding was corrected, and the dentition was well aligned with Class I canine and Class II molar relationships. The ABO Cast Radiograph Evaluation (CRE) was 16. (J Digital Orthod 2019;56:4-20)

Key words: Autotransplantation, Class III malocclusion, wisdom teeth replacement
Download Article

The Long and Winding Road: How to Regain the Severe Torque Loss in the InsigniaTM System

Dds. Laurel Shern, Kristine Chang, Jennifer Chang, Drs. Chris H. Chang, W. Eugene Roberts

Abstract

Introduction: Choosing the correct archwire sequence is essential for achieving optimal outcomes in a timely manner. A digital custom appliance is designed for ideal alignment with the finishing archwire. Translating teeth is problematic when a horizontal force is applied to the arch. Archwires with inadequate stiffness can result in severe loss of incisor torque when anterior segments are retracted. Iatrogenic axial inclination problems increase treatment time and may result in elevated root resorption.

Diagnosis: An 18-year old female presented with a chief complaint (CC) of protrusive lips. Clinical evaluation revealed skeletal protrusion (SNA 88 ̊, SNB 82 ̊, ANB 6 ̊), steep mandibular plane angle (FMA 30 ̊), bimaxillary lip protrusion (4mm/6mm to the E-line), and a Discrepancy Index (DI) of 26.

Treatment: All four first premolars were extracted, and an InsigniaTM system appliance with passive self-ligating brackets was prescribed. Extraction spaces were closed in all four quadrants using titanium molybdenum alloy (TMA) archwires. Bilateral reaction force of ~400cN was anchored with infrazygomatic crest (IZC) bone screws (BSs). The archwire torsional stiffness in the anterior segment was inadequate for the applied load, resulting in decreased axial inclination of maxillary incisors when the anterior segment was retracted. Correction mechanics were: 1. lingual root torque in the anterior segment, 2. anterior nasal spine (ANS) bone screw, and 3. anterior root torquing auxiliary spring.

Outcome: 16mo of space closure resulted in severe distal tipping (31 ̊) of upper incisors. An additional 12mo of active treatment was required to correct the upper incisal inclination to an optimal 104 ̊. After 28 months of active treatment, a Cast Radiograph Evaluation (CRE) score of 10 was achieved.

Conclusions: The upper incisal moment to force ratio (M:F) was inadequate for optimal upper incisor retraction. The problem was preventable with: 1. less reaction force (~200cN/side), 2. 20 ̊ increase in anterior lingual root torque (torsion) on the archwire to increase the moment, and/or 3. a stiffer stainless steel (SS) archwire. The M:F should be carefully evaluated prior to initiating space closure, and incisor axial inclinations should be carefully monitored with progress cephalometrics during space closure. Iatrogenic axial inclination problems (dumping) can usually be corrected with extended treatment time, but prevention is far more efficient and cost effective. (J Digital Orthod 2019;56:26-42)

Key words: InsigniaTM system, customized passive self-ligating brackets, digital set-up, moment to force ratio, archwire sequence, IZC screw, temporary anchorage devices (TADs), bimaxillary protrusion, extraction of premolars
Download Article

Class III Malocclusion, Anterior Crossbite and Missing Mandibular First Molars: Bite Turbos and Space Closure to Protract Lower Second Molars

Drs. Ashley Huang, Angle Lee, Chris H. Chang, W. Eugene Roberts

Abstract

Diagnosis: A 32-year-old female presented with a long face (55%), maxillary retrusion (SNA 79.5o), mandibular protrusion (SNB 82.5o), retruded lips (-4.0/-3.5mm), relative lower lip protrusion, missing lower first molars (LR6, LL6), atrophic edentulous spaces, Class III buccal segments, and anterior crossbite. The Discrepancy Index (DI) was 25.

Etiology: Early loss of L6s was probably due to molar-incisal hypomineralization (MIH). Anterior crossbite is a common functional compensation after lower second deciduous molars are lost at about age 12yr.

Treatment: A passive self-ligating (PSL) appliance, posterior bite turbos, early light short Class III elastics were used to correct the anterior crossbite. The L6 extraction sites were closed with primarily Class II elastics. Active treatment time was 20 months.

Results: Closure of the atrophic L6 sites was achieved by retracting the anterior segment and protracting lower molars. No significant root resorption nor periodontal problems were noted. The patient was pleased with treatment: excellent occlusal function, improved dentofacial esthetics, and an attractive smile arc. Clinical outcomes were a cast-radiograph evaluation (CRE) of 21 and a Pink & White (P&W) dental esthetic score of 3.

Conclusions: Severe skeletal malocclusion was corrected in 20 months with a full-fixed PSL appliance, posterior bite turbos, intermaxillary elastics, and space closure mechanics. (J Digital Orthod 2019;56:48-63)

Key words: Missing first molar, mesially tipped molar, atrophic edentulous ridge, anterior crossbite, passive self-ligating brackets, Class III elastics
Download Article

Conservative Camouflage Treatment of Pre-Treated Asymmetrical Skeletal Class III alocclusion

Drs. Joy Hui-Wen Cheng, Sheau Ling Lin, Chris H. Chang, W. Eugene Roberts

Abstract

History: A 22-year-10-month-old female sought retreatment for an orthodontic correction for skeletal Class III malocclusion. Two years of conservative orthodontic treatment at the age of 11 resolved the malocclusion, but the Class III malocclusion recurred in adolescence. Orthognathic surgery was not an acceptable option.

Diagnosis: Facial examination revealed an acute nasolabial angle, concave profile, protruded lower lip (LL to E-line: 2mm), and facial asymmetry that was associated with a 3mm shift of the dental midline to the right. Cephalometric analysis showed a skeletal Class III relationship (ANB -2.5°) with Class III incisal compensation. Occlusal concerns were Class III buccal segments bilaterally, asymmetric arch form particularly in the mandible, anterior crossbite of the upper right lateral incisor (UR2), and an end-on relationship of the adjacent UR3. The ABO Discrepancy Index (DI) was 30 points.

Treatment: Four third molars were extracted prior to installing a full-fixed passive self-ligating appliance. Bone screws (BSs) were inserted in the Mandibular Buccal Shelves (MBSs) bilaterally to retract the mandibular arch. Class lll elastics corrected the intermaxillary relationships, and the dental midline deviation was corrected with asymmetric application of elastics as needed.

Outcome: Following 28 months of active treatment with MBS bone screws, the skeletal Class lll malocclusion was successfully aligned. The facial profile was improved by retracting the lower dentition, opening the vertical dimension of occlusion (VDO), and rotating the mandibular plane in a clockwise direction. The final result had a Cast-Radiograph Evaluation (CRE) of 26 and a Pink and White dental esthetic score of 6. (J Digital Orthod 2019;56:68-82)

Key words: Self-ligating fixed appliance, miniscrews, buccal shelves, pretreated asymmetric skeletal Class lll malocclusion, dental midline discrepancy
Download Article