Iatrogenic Challenges by Dr. Adith Venugopal and Dr. Can-Florian Keles

 

By failing to plan, are we planning to fail?

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by Dr. Adith Venugopal and Dr. Can-Florian Keles

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Orthodontic treatment aims to correct dental and skeletal issues while enhancing facial aesthetics. Through clinical examination, radiological analysis and expertise, practitioners diagnose and plan treatment. Satisfaction is achieved when treatment objectives are successfully executed, though it can entail challenges despite appearing straightforward.

Treatment procedures involve a large number of relevant variables determined by patient characteristics, such as the dynamics of facial development and growth; the biomechanical interactions between appliances, dentition and bone physiology; the dynamics of the dentist/patient/family interaction; the large variety of treatment approaches; and the continuity of follow-up during the retention phase.^1,2

Difficulties in treatment may arise from various factors such as improper selection of dental procedures, incorrect treatment indications, adoption of risky strategies, inadequate execution of treatment, misjudgment of treatment duration, failure to adjust the treatment plan as needed, incomplete resolution of malocclusion, insufficient follow-up during retention and poor communication with the patient. These failures can significantly affect the effectiveness, quality and stability of correction, highlighting the intricate nature of orthodontics and the potential for adverse outcomes resulting from neglecting key variables.^3–6

In this case report, I will first outline a transfer case involving a young man treated during the initial stages of my orthodontic career, where I proceeded without sufficient awareness or consideration of the existing periodontal conditions. This approach ultimately resulted in a satisfactory aesthetic outcome, but with heightened risk of future periodontal complications.

Then, I’ll discuss a subsequent case treated after accumulating substantial experience, wherein I analyzed every aspect to ensure a comprehensive understanding of the diagnosis. With sound knowledge of the patient’s periodontal status, a carefully planned treatment strategy was devised that aimed to achieve both pleasing aesthetics and functional outcomes.


Case 1
A 17-year-old male presented to our office with his mother. He had undergone orthodontic treatment for the past 4½ years and had recently had his braces debonded because of lack of confidence in the treating dentist.

On clinical and radiological examination, he presented with excessively proclined incisors, mildly proclined lower incisors, an anterior open bite, Class III molar and canine relationships, four missing first premolars because of previous extractions, a temporary anchorage device (TAD) on the right maxillary posterior region, and an excessively steep mandibular plane, all on a Class III skeletal base (Figs. 1 and 2).

The patient had brought his pretreatment records from 4½ years ago for evaluation. Initial pretreatment extraoral records revealed a convex and hyperdivergent profile with incompetent lips. Pretreatment intraoral records revealed severe crowding on the maxillary arch and moderate crowding on the lower arch, buccally and highly positioned maxillary ectopic canines, Class III molar relationship on the right and left sides. Clinical and radiographic evaluation of the initial pretreatment records revealed a very steep mandibular plane (Fig. 3).

In this skeletal Class III hyperdivergent pattern case, presenting with four premolars already extracted to camouflage the sagittal discrepancy, a significant loss of anchorage in the mandible resulted in an excessive buccal flaring of the maxillary anterior teeth in an attempt to allow adequate dental contacts. Two treatment options were suggested to the patient to normalize the occlusion:

 

• The first consisted of a combination between an orthodontic and orthognathic surgery treatment approach.
• The second proposed only orthodontics, assisted by TADs in the mandible. After the extraction of the lower third molars, the mandibular teeth were to be distalized using two buccal-shelf TADs. Then in the maxillary arch, the anterior teeth were to be palatally tipped to achieve satisfactory overjet and overbite.

Because the patient had been undergoing orthodontic treatment for 4½ years before even visiting our practice, he and his mother expressed frustration with the treatment’s long duration and unsatisfactory outcome. Preferring to avoid the financial strain of orthognathic surgery, they sought a satisfactory solution through conservative means and opted for the second option. An informed consent form was approved and signed to this effect. This case was treated using 0.022-by-0.028-inch slot preadjusted edgewise appliances with an MBT prescription.


Step 1: Gaining a positive overjet by distalizing the lower arch
Initially, after extractions of the mandibular third molars, brackets were placed only on the lower arch to level and align the lower dentition. Leveling was performed on a 0.016-inch nickel titanium (NiTi) wire, followed by 0.017-by-0.025-inch NiTi and 0.019-by-0.025-inch NiTi archwires, respectively.

Once the arch was completely leveled, two TADs (1.8 by 12 mm) were placed extraradicularly on the buccal shelves in the mandible to distalize the entire lower arch. Two crimpable hooks—one between the lower premolar and canines and the other between the canines and lateral incisors—were crimped on a 0.019-by-0.025-inch stainless steel archwire.

Initially, elastic chains were activated from the head of the buccal-shelf miniscrews to the distal hook with a force measured at 250 g on each side. After the application of four months of active distalization forces, a positive overjet was achieved with a combination of lower incisor tipping and mandibular distalization. The elastic chains were now engaged from the miniscrew head to the mesial hook on the archwire for further activation (Fig. 4).


Step 2: Palatal tipping of the upper incisors
Brackets were then placed on the upper arch. The four maxillary incisor brackets were inverted to generate more palatal crown torque when a rectangular wire was inserted. Initially, a 0.014-inch NiTi archwire was placed to level the dentition. An intermaxillary 5/16-inch, 2-ounce elastic was placed from the upper canine bracket to the lower TAD head to begin tipping the upper incisors. A Kobayashi hook was fabricated on the head of the extraradicular TAD to prevent elastic slippage on placement. The upper leveling archwires further transitioned from a 0.016-by-0.025-inch thermal NiTi to a 0.017-by-0.025-inch NiTi. The thickness of the intermaxillary elastics were also increased with the increase in wire dimensions.

Lower distalization was continued along with upper palatal tipping for the next seven months until a satisfactory upper incisor inclination, along with Class I molar and canine relationships, had been achieved (Fig. 5).


Step 3: Finishing and retention
A 0.016-inch NiTi wire was reinserted into the upper and lower arches and 1/8-inch, 4½-ounce settling elastics were used for minor occlusal detailing to develop a better interdigitation. The case was retained with an upper fixed lingual retainer in conjunction with upper and lower Essix clear retainers (Figs. 6–8).


One of the main reasons for the pretreatment anterior open bite and the severely proclined incisors after the first orthodontic treatment was the premature and early engagement of the buccal and highly placed canines after extraction of all bicuspids. High ectopic canines have the tendency to pull the anchorage unit away from the occlusal plane and usually cause an open bite.⁷

It is important to avoid early archwire engagement of high labial canines so unwanted vertical movement of lateral incisors and premolars does not occur. A piggyback archwire with a heavier base archwire or cantilever mechanics may be best to bring such ectopic canines into occlusion.^8,9

Studies have shown that the extent of distalization on the lower dentition after the extraction of the third molars is approximately 2–3 mm before the second molars begin to distally tip. The most common reason for such less bodily movement is the premature contact of the distolingual root of the second molar with the mylohyoid ridge. In cases where there is good clearance between the mylohyoid ridge and the roots of the second molars, more distalization is possible.^10,11


Root exposure of the lower anterior teeth
Looking at the before and after cephalograms, it is evident that the lower incisors have much less bone coverage on the labial aspect after treatment. A CBCT (Fig. 9) confirms very thin plate of bone ahead of the lower incisors after the second round of orthodontic treatment. A study by Wu et al.¹² showed a 16.1% and 20.7% prevalence of fenestration and dehiscence, respectively, in skeletal Class III subjects at the tooth level. They also stated that male patients who had a history of orthodontic treatment were more likely to exhibit alveolar dehiscence.


Moreover, Class III patients have been known to present a thinner mandibular symphysis, compared with Class I and Class II patients. Movements in the sagittal direction or labiolingual movements must be done very carefully, because the presence of dehiscence and fenestrations are positively correlated to thin alveolar bone.^10,13,14


Case 2
A 17-year-old female patient reported with a skeletal Class III malocclusion, which was attributed to an orthognathic maxilla and prognathic mandible with upright incisors. She also presented with high clinical FMA, increased lower anterior facial height, anterior crossbite and an anterior open bite. The dental condition included rotated lower molars, an ectopically placed #23 and a palatally displaced #15. Extraction spaces were seen on the lower #36 and #46 region. The lower second molars drifted mesially into the extraction space and caused steepening of the occlusal plane by prematurely contacting the maxillary first molars. Radiographic findings correlated with the clinical condition (Figs. 10 and 11).


The treatment objectives were aimed at leveling and aligning the upper and lower arches and closing the residual spaces to attain a positive overjet and overbite and to improve the overall facial aesthetics of the patient.

The proposed treatment plan was to extract two premolars in the upper arch (#15, #24), to retract the lower anterior segment using moderate to minimum anchorage, and to correct the open bite with intrusion of the upper molars while protracting the lower molars to close all residual spaces (Fig. 12). The alternate treatment option, which the patient ruled out, would have been a surgical approach with a mandibular setback combined with orthodontic treatment.


Full-arch fixed appliances were bonded and extractions of #15 and #24 were done at the same appointment to align the maxillary canine and start alleviating the crowding using space created by the extractions. After leveling and alignment, a 0.019-by-0.025- inch stainless steel (SS) archwire was left in place until they were passively engaged in all bracket slots; at that point infrazygomatic crest (ICZ) implants were placed to intrude the upper molars.

Class III elastics were used from the IZC implants to the lower canines initially, to retract/tip them into the extraction space while the upper molars were being intruded. Another advantage of this strategy was the avoidance of the counterclockwise rotation of the mandible that would otherwise result from the intrusion of the maxillary molars. The counterclockwise rotation of the mandible would be detrimental to the profile of this patient since it would enhance the chin prominence even more (Fig. 13).


Protraction of the lower molars was performed with a 0.019-by-0.025-inch SS archwire with a tip-back bend placed distal to the second premolar. For space closure, a power chain extended from the second molar in the third quadrant to the second molar in the fourth quadrant. The anchorage was further reinforced with Class II elastics (Fig. 14). This strategy helped us to achieve bodily movements of the second molars.


The wire on the lower anterior segments was torqued (lingual root torque) to correct the inclination of the lower incisors after molar protraction. The midlines were corrected by using Class III elastics on the right side and Class II elastics on the left side. The occlusion was settled using 3/16-inch, 2½-ounce settling elastics (Fig. 15).


Active treatment lasted 26 months. The case was finished in a Class II molar relation with a Class I canine relation and coincident dental midlines. The soft-tissue profile improved greatly, with adequate lip competency and balanced vertical proportions (Figs. 16 and 17). The superimposition revealed intrusion of the upper molars and protraction of lower molars with good improvement of the open bite and occlusal planes (Fig. 18).



Orthodontists are still striving to develop biomechanical systems that can overcome the undesired side effects of extrusion of anchorage teeth, mandibular rotation and the increase in lower anterior face height when treating skeletal Class III malocclusions.¹³ A successful camouflage treatment should camouflage both the skeletal and softtissue discrepancies, achieve a good and acceptable facial aesthetic result and establish a stable occlusion.

Significant changes were seen in the anterior-posterior dental position, skeletal sagittal and vertical position, and upper molar vertical position and position of lower lips.

Class III malocclusion can benefit from the use of Class III elastics running from TADs placed in the posterior maxilla to the anterior mandibular dentition, typically to the canines. Maxillary TADs can prevent undesirable proclination of incisors and extrusion of maxillary posterior teeth, which is a common side effect of the conventional Class III elastic usage. Specifically, these mechanics are adequate for Class III patients having a high mandibular plane angle and/or a long face tendency.


Conclusion
Strategic use of TADs, coupled with a thorough grasp of the biomechanical principles at play, has the potential to broaden treatment horizons for severe Class III malocclusions. Paramount to this approach is a meticulous initial case analysis to ascertain treatment limitations, effectively communicating these boundaries to the patient to obtain informed consent and proactively anticipating potential side effects. By doing so, the correction strategy can be streamlined and reversible measures readily implemented as necessary.

 

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References
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13. Yagci A, Veli I, Uysal T, Ucar FI, Ozer T, Enhos S. Dehiscence and fenestration in skeletal Class I, II, and III malocclusions assessed with cone-beam computed tomography. Angle Orthod. 2012 Jan; 82(1):67–74.
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