Class II Division 1 Malocclusion with 5 mm of Crowding Treated Non-Extraction with IZC Miniscrews Anchorage
Shih YH, Lin JJ, Roberts WE.
A Class II Division 1 malocclusion in a 26 yr old male was associated with a convex profile (ANB 5.5), lip incompetence, 7 mm of overjet, and 5-7 mm of crowding in each arch. This complex malocclusion in an adult male was treated non-extraction, by retracting both arches, and intruding the incisors with anterior bite turbos, placed on the lingual surfaces of upper central incisors. Following 25 months of active treatment, this difficult malocclusion (DI 21) was treated to an excellent dental (CRE 17) and facial result. (Int J Orthod Implantol 2016;41:4-17)
Key words: Class II Division 1, IZC bone screws, miniscrews, bite turbo, adult male
Conservative Treatment of Severe Malocclusion in a 15y5m Nongrowing Female: Growth-like Skeletal Adaptation 3 Years Later
Chen HH, Chang CH, Roberts WE.
Introduction: A 15y5m post-menarche female presented with a severe skeletal Class II, crowded malocclusion: ANB 7º, FMA 37º, discrepancy index (DI) 41, and buccal crossbite of the upper right first premolar ( #5). Conservative treatment with no extractions or orthognathic surgery was requested.
Methods: After a careful discussion of potential risks in a potentially nongrowing patient, the family opted for fixed appliance treatment with passive self-ligating brackets, bite turbos, intermaxillary elastics, and extra-alveolar bone screws anchorage to differentially retract both arches.
Results: With only 20 months of active treatment, an acceptable result was achieved: good facial form, lip competence, and cast-radiograph evaluation (CRE) of 28 points. The only concern was a 1-2° increase in the mandibular plane, which was attributed to the posterior bite turbos, used to correct the posterior buccal crossbite. The patient was fitted with lower 3-3 fixed and upper clear overlay retainers. Follow-up records 3 years later revealed an improvement in dental alignment (CRE decreased from 28 to 20). There was also a downward and forward, growth-like response of the mandible, which appears to be a favorable skeletal adaptation to optimized stomatognathic function.
Conclusions: Conservative correction of severe skeletal malocclusion resulted in a favorable dentofacial adaptation that is consistent with the ability of the face to adapt to environmental factors over a lifetime. (Int J Orthod Implantol 2016;41:22-38)
Key words: Self-ligating appliance, bite turbo, bone screws, conservative treatment, long-term follow-up, skeletal adaptation
Class II, Excessive Overjet and Deep Bite with a Congenitally Missing Lower Incisor
Su YY, Chang CH, Roberts WE.
A 9-year-11-month female was placed on recall until her buccal segments erupted. At 13-years of age she returned with a severe dentofacial malocclusion: (1) convex facial profile, (2) protrusive and everted upper lip, (3) Class II buccal segments, 5 mm on the right and 2 mm on the left (4) overjet 11 mm, (5) overbite 9 mm, and (6) a congenital missing lower left lateral incisor. The Discrepancy Index (DI) for this complex malocclusion was 22. Treatment involved extraction of both upper first premolars as well as the lower left central incisor. The overjet was corrected by retraction with miniscrews placed in the infrazygomatic crest (IZC). The lower canines were moved into the lateral incisor positions (canine substitution). The treatment outcomes were excellent, as evidenced by the Cast Radiograph Evaluation (CRE) of 24 and a Pink and White dental esthetics score of 3. (Int J Orthod Implantol 2016;41:42-55)
Key words: Maxillary lip protrusion, severe overjet, deep bite, congenital missing lower incisor, mandibular canine substitution
Forty Consecutive Ramus Bone Screws Used to Correct Horizontally Impacted Mandibular Molars
Lin SY, Chang CH, Roberts WE.
Failure of temporary anchorage devices (TADs) is a serious limitation when treating complex problems like horizontal impactions of mandibular molars, because there are few other viable options. From a biomechanics perspective, the anterior ramus of the mandible is an ideal location for a TAD. However, this area appears to be a high risk site because it is covered with thick, mobile soft tissue.
Objective: Assess the failure rate and efficacy of ramus bone screws used as anchorage to upright horizontal impactions of mandibular molars within four months.
Materials and Methods: The sample (n = 37) was thirty-seven consecutive patients (20 males, 17 females, mean age 18±6 yr) with horizontal impactions distal to the functioning lower arch. Three patients had bilateral horizontal impactions, for a total of 40 consecutive ramus bone screws. The crowns of the impactions were uncovered and bone was removed down to the cementoenamel junction, if needed. All screws were placed perpendicular to the ascending ramus, about 5 mm superior to the occlusal plane of the mandible. For oral hygiene access, the head of the screw was at least 5 mm above the soft tissue. The load applied to upright the molars ranged from 2-4 oz (57 g-113 g, 56 cN-112 cN).
Results: Ramus screw anchorage was very effective for uprighting horizontal impactions. Two of the 40 screws failed (2/40 = 5%) due to soft tissue hypertrophy that covered the head of the screw, but none were loose relative to supporting bone. Both failing screws were repositioned with additional soft tissue clearance, and then they were then successful for the purpose intended.
Conclusion: Ramus screws were highly successful (38/40 = 95%) as anchorage units to upright horizontal impactions in the posterior mandible. When the two failed screws were repositioned, they were successful as planned, so the overall success rate for ramus screw anchorage was 100%. (Int J Orthod Implantol 2016;41:60-72)
Key words: Horizontally impacted second molars, molar up-righting, ramus screws, TAD failure rate, soft tissue hypertrophy, TAD repositioning
3D Cortical Bone Anatomy of the Mandibular Buccal Shelf: a CBCT study to define sites for extra-alveolar bone screws to treat
Class III malocclusion
Huang C, Chang CH, Roberts WE.
Objective: Assess the feasibility of a proposed bone screw site in the mandibular buccal shelf (MBS) region, relative to the orientation of the skeletal platform and quantity of the available cortical bone, for either perpendicular or angled bone screws.
Materials and Methods: CBCT images were obtained retrospectively for 12 Asian patients treated with bilateral MBS bone screws (n=24) for Class III skeletal malocclusion. None of the subjects had periodontal or buccal-lingual alignment problems. Cortical bone thickness adjacent to the first and second molars was measured on the mesial, midpoint and distal surfaces. Seven progressive sites were measured in frontal cuts of the CBCT image from the mesial of the first molar to the distal of the second molar. The angle was measured between a line that was the best fit of the MBS surface and the axial inclination of the adjacent molar. Cortical bone thickness was measured perpendicular and at a 30° angle along the surface of the MBS at 3, 5 and 7 mm apical to the alveolar crest of the molars.
Results:There was a statistically significant increase (t-test P<.0001) for cortical bone thickness for a 30° angled insertion, compared to a perpendicular measurement. The increase in cortical bone thickness for an angled insertion ranged from 0.56-1.24 mm. The median for cortical bone thickness at the 30° inclination ranged from 2.92-4.10 mm for all sites.
Discussion: Boxplots of the data indicated that the optimal location for a MBS bone screw is 5-7 mm below the alveolar bone crest, at approximately the plane between the mandibular first and second molars. At the recommended insertion angle of 30° cortical bone thickness lateral to the interproximal area between the molars ranged from 3.54-4.05 mm. This is a sufficient site for routinely achieving primary stability with MBS bone screws.
Conclusion: The MBS lateral to the first and second molars is an appropriate site for extra-alveolar (E-A) temporary anchorage devices (TADs) that are inserted at ~30° The most ideal skeletal location for the bone screw is about 5-7 mm below the alveolar crest. (Int J Orthod Implantol 2016;41:74-82)
Key words: Mandibular buccal shelf, miniscrews, CBCT, Skeletal anchorage, Cortical bone engagement, Extra-Alveolar orthodontic anchorage
Tips in solving clinical errors : Management of wire dislodegment
Lee SA, Chang CH, Roberts WE.
Wire dislodgment is a common issue found in routine appointments. Two of the primary causes include closing of extraction spaces and sliding of the main archwire. Doctors should perform a careful examination before cutting flush with the end of a tube. If wire dislodgment is caused by sliding, cutting the wire renders it short to engage all brackets. Therefore, a checklist is proposed to help clinicians rule out unintended sliding before cutting. (Int J Orthod Implantol 2016;41:86-87)
- Check if an explorer can enter the molar tube.
- Check if the molar is rotated.
- Check if bilateral extraction spaces are not closed symmetrically.
- Check if one or more resin stops are lost.