GAP Magazine Clear Idea Volume 5

18 www.acasociety.com | info@acasociety.com Discussion A study published in 2020 12 which compared the Invisalign appliance of 2009 with that of 2019, where the incorporation of the new SmartTrack ® material and G5 ® bite opening protocols could be assessed found that incisor intrusion was challenging& failed to show improvement since 2009, even with G5 ® enhancements. This is supported by other studies and the conclusions are perhaps best summarized in this quote from Brenner: “Even with the advent of newer auxiliaries, such as attachments and bite ramps, it is unclear how to predictably correct deep bites using Invisalign ® .” 6 It is interesting that a postgraduate thesis 7 looking specifically at G5 ® innovations under the supervision of Dr Willy Dayan, using his cases, concluded that “while G5 ® is effective in bite opening at both skeletal & dentoalveolar levels, it is not as effective as full fixed appliances.” They further concluded that “Aligners in general are not recommended as first treatment choice for hypodivergent patients,” and warned that as most studies on deep bites the cases were treated by experienced clinicians and still showed poor results. Therefore, use of aligners in deep bites without sufficient clinical experience is not encouraged. Aligner strategies to assist bite opening: While the clinician must acknowledge the inherent weakness for bite opening that aligner treatment has, there are 2 strategies promoted to attempt to reduce the deficiencies. 1. Overcorrect the bite opening in the digital treatment plan. It appears from the current literature that a figure of 60% overcorrection is indicated, although this may still fail due to biological, compliance and appliance factors. (Fig 3) 2. Use of bite ramps. There is some weak evidence 7 that bite ramps may aid to a limited degree. Bite ramps must be placed in positions that effectively engage the teeth in the opposing arch without interfering with retraction of incisor teeth, as may occur if the lower teeth get lingual to the bite ramps. A potentially useful strategy is to augment existing upper arch bite ramps, which are necessarily limited in dimension, by placing a lower arch “bite ramp” – an attachment on the lower anterior teeth into which no composite resin is placed. I term this BRICA (bite ramp interfering canine attachment) or BRIIA (bite ramp interfering incisal attachment). Alternatives to aligner bite opening: 1. Use of temporary anchorage devices or bone plates to improve intrusion. 2. Posterior dental overlays where opening of the vertical dimension can be tolerated by the musculature and temporomandibular joints. 3. Ameloplasty (reduction of the incisal edges) 4. Orthognathic surgery 5. Acceptance of a compromised out- come, as against an ideal one Summary “The severe deep bite cases in this study were not able to be corrected with Invisalign restricting the benefits to mild to moderate cases only.” 9 This perhaps is the best takeaway message summary. Aligners have a proven weakness for bite opening. Therefore, doctors must: a. Take care to select appropriate cases for treatment. b. Employ enhanced strategies to improve ability of aligners to open the bite – bite ramps, BRICA, suitable time & low force. Due to the need for low force, 1 week aligner change needs to be questioned in such cases. These requirements become more acute for deep or potential deep bite cases (eg extraction/space closure/overjet retraction) than for simple cases. References: 1. Ng et al. True incisor intrusion attained during orthodontic treatment: A systematic review and meta-analysis Am J Orthod Dentofacial Orthop 2005;128: 212-9 2. Nanda R. Correction of deep overbite in adults. Dent Clin North Am 1997;41:67-87. 3. Proffit W et al Contemporary Orthodontics 6th Edition Mosby Published Date: 6th August 2018 4. Blundell et at. Predictability of overbite with the Invisalign® appliance Accepted for publication September 2021 AJODO 5. Catherine Fontaine-Sylvestre: Predictability of deep overbite correction using Invisalign®: Thesis Faculty of Graduate Studies of The University of Manitoba 2019 6. Brenner R. Cephalometric Analysis of Deep Bite Correction in Patients Treated with Invisalign. ProQuest: Saint Louis University; 2019:54. 7. Henick D. Effects of Invisalign (G5) with virtual bite ramps for skeletal deep overbite malocclusion correction in adults. Proquest: State University of New York; Unpublished results:62. 8. Krieger et al. Invisalign® treatment in the anterior region: Were the predicted tooth movements achieved? J Orofac Orthop 2012;73:365-376. 9. Tai C. How Accurate is Invisalign? Are predicted tooth positions achieved? USA: University of Minnesota, 2017. Master of Science. 10. Khosravi et al. Management of overbite with the Invisalign appliance. Am J Orthod Dentofacial Orthop 2017;151:691-699 e692. 11. Glassick A et al. Evaluating the Efficacy of Lower Incisor Intrusion with Clear Aligners. J Clin Orthod. 2017 Apr;51(4):233-239. 12. Haouili et al. Has Invisalign improved? A prospective follow-up study on the efficacy of tooth movement with Invisalign Am J Orthod Dentofacial Orthop DOI:https://doi. org/10.1016/j.ajodo.2019.12.015 Figure 3. Initial overbite (A), intended final treatment outcome position (B) – note overcorrection of overbite and clinically achieved outcome (C). Note failure to achieve any meaningful bite opening, regardless of employment of overcorrection. Figure 4: A bite ramp (blue) on an upper canine or incisor tooth is augmented if a lower “bite ramp” or unfilled attachment (red) is placed to oppose it.