Dr. Chris H. Chang
During the Last year, with a non-existent international traveling schedule, I have had time to consider 3 questions that I have often been asked when abroad:
1. How can such a small country like Taiwan be at the summit of the world’s semi-conductor industry?
2. How did Taiwan manage to produce international orthodontic speakers?
3. What does the typical Taiwanese lifestyle look like?
The answer to these three questions has always been that I don’t know. Do we need to know the answer to every question? If I don’t know the answer to these questions, then what do I know?…
Pseudo-Class III Malocclusion in an Adolescent Treated with Mandibular Bone Screws and Bite Opening to Enhance Late Maxillary Growth
Alex Lin, Chris H. Chang, W. Eugene Roberts
History: A 12-year-old female presented with a chief complaint (CC) of anterior crossbite.
Diagnosis: Skeletal Class III (SNA 77.5 ̊, SNB 82 ̊, ANB -4.5 ̊) relationship in centric occlusion (CO) was associated with midface deficiency, crossbite of the entire dentition except the molars, and lingually inclined lower incisors (L1 to MP 75.5 ̊). The Discrepancy Index (DI) was 28.
Treatment: Bone screws were placed in the mandibular buccal shelves to retract the mandibular arch. To enhance adolescent maxillary growth, the bite was opened at the start of treatment with posterior bite turbos, and Class III elastics were applied. Left posterior crossbite was corrected with cross elastics. Lower arch retraction was limited by soft tissue impingement in the retromolar area.
Outcomes: After 25 months of active treatment, a near ideal profile and occlusal alignment was achieved. The Cast-Radiograph Evaluation (CRE) was 19. Pink and White esthetic score was zero. There were two discrepancies from ideal: crossbite of the upper left second molar, and excessive lingual inclination of lower incisors (66.5 ̊).
Conclusions: This case report demonstrated the use of OBSs to resolve skeletal Class III malocclusion in a growing adolescent. Class III elastics in addition to bite opening for removal of incisal constraint resulted in enhanced anterior growth expression of the maxilla. A single phase of treatment in the early permanent dentition efficiently resolved a difficult skeletal Class III malocclusion. (J Digital Orthod 2021;61:4-22)
Key words: Pseudo-Class III, anterior crossbite, late maxillary growth, passive self-ligating brackets, mandibular buccal shelf, bone screws
Premolar Substitution for a Missing Maxillary Canine
Yu Hsin Huang, Chris H. Chang, W. Eugene Roberts
History: A 19-year-old female presented with a chief complaint (CC) of missing maxillary left canine and crowding.
Diagnosis: A skeletal Class I (SNA 78 ̊, SNB 76 ̊, ANB 2 ̊) relationship was associated with a mandibular plane angle (SN-MP 31 ̊) that was within normal limits (WNL). This Class I malocclusion had an overjet of 2mm at the upper right canine (UR3), a missing upper left canine (UL3), and horizontal fractures (root and crown) of upper left lateral incisor (UL2). The Discrepancy Index (DI) was 9 for this unusual malocclusion.
Treatment: Translate the upper left first premolar (UL4) anteriorly to substitute for the missing UL3. The Damon Q® passive self ligating (PSL) system was used to align both arches. At the end of treatment, a diode laser was used for a midline frenectomy and selective gingivectomy in the maxillary anterior region to achieve better esthetics.
Outcomes: After 23 months of active treatment, the space for the missing UL3 was successfully substituted by the UL4. The Cast- Radiograph Evaluation (CRE) was 14, and the IBOI Pink & White esthetic score was 5.
Discussion: The most important advantage for tooth substitution in the maxillary anterior esthetic zone is permanence and biological compatibility. To achieve optimal esthetics, careful detailing is required during orthodontic treatment in addition to follow- up soft tissue and dental modifications. Compatible crown torque for all teeth in the segment is coupled with new techniques and materials in esthetic dentistry. The primary objective is to restore natural tooth shapes and sizes. In addition, it is important to provide symmetric gingival contours for all dental units, as well as to secure optimal occlusion with cuspid guidance or group function.
Conclusions: Interdisciplinary cooperation among orthodontists and other dental specialists is critical for achieving high quality treatment outcomes for premolar substitution to simulate a cuspid. (J Digital Orthod 2021;61:28-44)
Key words: Missing left maxillary canine, premolar substitution, canine guidance, group function, frenectomy, laser gingivectomy
Severe Class IlI Open Bite Malocclusion: Conservative Correction
with Lower First Molar Extraction
Joy Cheng, Chris H. Chang, W. Eugene Roberts
History: A 29-year-old male presented with a severe Class III openbite malocclusion. His chief complaint was poor masticatory function.
Diagnosis & Etiology: An increased vertical dimension of occlusion (58%) was associated with flat mandible plane (26 ̊), openbite (4mm), and negative overjet (-9mm), but there was no functional shift from centric relation (CR), to maximal intercuspation (centric occlusion, CO). The dental midline was 2mm to the right of the facial midline. The probable etiology for this severe skeletal malocclusion was a genetic tendency for prognathism (ANB -9 ̊) that was associated with airway obstruction in the juvenile years. Applying Lin’s three-ring diagnosis in CR, facial profile was concave (G-Sn-Pg’ -14 ̊), molar relationship was Class III (>10 mm), and there was no functional shift. The patient was not an ideal candidate for conservative orthodontic correction, but he declined orthognathic surgery and preferred to avoid temporary anchorage devices (TADs). The lower left first molar (LL6) was compromised so he agreed to extracting both lower first molars (L6s) to maintain symmetry, and close space with primarily Class III elastics. The Discrepancy Index (DI) was 100.
Treatment: Bilateral L6s were removed to produce posterior space for retraction of the lower anterior segment to correct the anterior crossbite. A passive self-ligating (PSL) appliance was bonded on the dentition with high torque brackets on lower incisors and low torque brackets on upper incisors. Axial inclination for the lower anterior was controlled with progressive pre-torqued NiTi and stainless archwires with 15 ̊ of lingual root torque to compensate for lingual tipping, which is a side effect of Class III elastics.
Outcome: Following 26 months of active treatment, this difficult malocclusion, with a DI=100, was treated to a Cast-Radiograph Evaluation (CRE) score of 29 points and a Pink and White esthetic score of 4 points.
Conclusions: Conservative orthodontic treatment for severe skeletal Class III malocclusion is challenging and may not achieve an ideal outcome. The patient must be informed of potential risk, provide informed consent, and be very cooperative during treatment. Both the clinician and the patient were pleased with the outcome. (J Digital Orthod 2021;61:50-66)
Key words: Skeletal Class III pattern, Class III molar relationship, Class III intermaxillary elastics, first molar extraction
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
Angle Lee, Chris H. Chang, W. Eugene Roberts
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 treatment, 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 5mm in the mandibular arch and 3mm in the maxillary arch. The mandibular midline was deviated to the left about 2mm, 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 2mm 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® (iNewton, Inc., 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 2021;61:72-90)
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