The use of fixed retainers at the end of a course of orthodontic treatment has become standard practice. The main complication that can occur with fixed retainers is the detachment of the wire from one or more teeth. A less common complication is unwanted tooth movement. This article presents a patient with extreme tooth movement associated with a mandibular fixed retainer. Ten years after orthodontic treatment, a 26-year-old male sought treatment for post-orthodontic movement of the mandibular anterior 6 teeth. Despite the fixed retainer still being attached to all teeth, the apex of the right canine was completed avulsed labially. Severe labial recession was also present on the left lateral incisor. The canine was extracted, and the fixed retainer was removed. Significant root resorption identified on a panoramic radiograph contraindicated any further extensive orthodontic intervention. This case highlights that clinicians and patients should be aware of this rare but serious complication.
Highlights
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The provision of fixed retainers is now becoming standard practice.
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Complications with fixed retainers can occur.
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Unwanted tooth movement is a rare but potentially serious complication.
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A case of canine avulsion is presented with a mandibular fixed retainer still attached.
The use of a fixed retainer for the mandibular anterior 6 teeth is a standard form of retention after orthodontic treatment. In the United Kingdom, 59% of orthodontists in a private practice setting were using a fixed mandibular retainer, either alone or in combination with a removable retainer in 2009.
Two variations of fixed retainers are common: those bonded to the lingual surfaces of the canines only and those bonded to all 6 anterior teeth.
A fixed retainer bonded to the mandibular anterior 6 teeth with a flexible spiral wire is common in clinical orthodontic practice. , Similar to flexible spiral wires, a dead soft wire of various dimensions can also be bonded to each anterior tooth. Fixed retainers bonded to all mandibular anterior teeth have been shown to maintain good alignment of the anterior teeth after active orthodontic treatment.
The main problem associated with a fixed retainer is detachment of the wire from one or more teeth. In one study, almost a third of participants (32.2%) experienced retainer failure, with detachment being highest in the first 2 years after placement of the fixed retainer.
Unwanted tooth movements can also occur; however, a clear distinction must be made between mild relapse sometimes seen even with the presence of a fixed retainer and tooth movement produced by the fixed retainer itself. This latter post-treatment change cannot be considered as relapse of orthodontic treatment because the tooth movement is not towards the pre-treatment tooth position.
Katsaros et al, was the first to describe unwanted tooth movements in the labiolingual inclination or position of mandibular anterior teeth. Subsequently, more severe unwanted tooth movements in the presence of a fixed mandibular retainer have been reported.
This article presents a patient with a severe complication of a mandibular fixed retainer in which a canine was completely avulsed.
Case report
A 26-year-old male, who in his early teens had been previously treated orthodontically with 4 premolar extractions and retained with a mandibular fixed retainer, came in for a consultation because of tooth movement of the mandibular anterior teeth. His medical history revealed that he suffered from hay fever and was allergic to penicillin. The orthodontic treatment had been undertaken in another part of the United Kingdom, where the patient had grown up.
He had been provided with a fixed mandibular retainer bonded to the anterior 6 teeth and maxillary and mandibular vacuum-formed removable retainers 10 years ago. The removable retainers were prescribed for the first year, and then the patient recalled he was asked to stop wearing them when the supervised retention period ended 9 years ago.
After several years, the patient began to notice the mandibular right canine beginning to turn toward his lip. At 2 separate dental appointments, the patient had raised this concern with 2 different dentists. On both occasions, the fixed retainer was checked and found intact; the patient had been reassured that small tooth movements could occur even with a fixed retainer. The patient reported no significant pain during any of this time.
Nine years after the fixed retainer had been in place, the patient started to notice significant movement of the mandibular right canine, and he observed that it was happening at a rapid rate. The global 2019 coronavirus pandemic prevented him from readily accessing dental care, and so he delayed seeking advice. In the months that followed, the patient witnessed the tooth turn completely on its side . Again, during the most recent tooth movements, the patient reported no significant pain.
When the patient presented clinically, the maxillary arch was well aligned ( Fig 1 ); however, the mandibular right canine root had torqued 70° labially, and the apex was completely exposed, revealing a shortened root apex ( Fig 2 ). The mandibular left lateral incisor root was exposed labially, almost revealing the apex, and the mandibular left canine appeared with lingual root torque ( Fig 3 ). A lateral open bite was present in the right canine region ( Figs 4 and 5 ).
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