Bone regeneration after alveolar dehiscence due to orthodontic tooth movement – A case report
While performing non-extraction orthodontic therapy, there is an inevitable tendency to procline the lower incisors. While not ideal, it is usually regarded as an acceptable compromise when camouflaging skeletal base discrepancies. To minimize proclination, buccal root torque can be added to the archwire. This case report shows the sequelae of excessive lower incisor torque using a customized appliance and the long-term results after correction. An anterior negative 20-degree pre-torqued 19×25 NiTi wire was placed in the lower arch and the patient did not return for 3 months. This resulted in the apices of the anterior lower incisors being placed outside the alveolar housing. To correct this, the wire was then flipped and reinserted to obtain positive torque. After 4 months, the roots were back within the alveolar bone according to cephalometry. Four years after treatment, a cone-beam computed tomography (CBCT) scan indicated that there was normal and adequate bone covering of the lower incisor roots with no sign of any adverse effects.
Animal studies[2-5] have previously reported that the occurrence of bone reapposition after teeth was initially expanded through the cortical plate and then returned toward their normal positions in the arch. Wainwright, Karring et al., Engelking and Zachrisson, and Thilander et al. all concluded that dehiscence or fenestrations can be produced in the buccal alveolar plate by moving teeth in a facial direction and that the bone will reform when the teeth are moved back toward their original positions. Only Engelking and Zachrisson showed gingival recession after dehiscence or fenestration formation, which was also not recovered after moving the teeth back to their original positions.
A case report by Pazera et al. showed a deformed lower fixed retainer causing approximately 35 degrees of buccal root torque of the lower right canine. A CBCT showed the apex of the tooth outside of the cortical bone; however, the tooth was vital and had only mild recession. The patient was then retreated orthodontically and a new CBCT was taken before debonding. They found minor bone regeneration around the apical and buccal surfaces.
A 15-year-old male patient presented for orthodontic treatment for the correction of crowding. Extraoral examination showed a convex profile with lip incompetence, increased lower facial height, and a flat smile arc. Intraoral examination exhibited a Class I molar and canine relationship, 2 mm overjet, and 1 mm overbite. Both upper and lower arches were asymmetrical with a collapse in the buccal segments of the 2nd and 3rd quadrants resulting in scissor bites of the upper left 2nd premolar and 2nd molar. Crowding of 2 mm in the upper arch and 6.5 mm in the lower arch was found. A Bolton discrepancy with excess tooth material in the lower arch was present (1.7 mm anterior and 7 mm total) [Figure 1].
A panoramic radiograph showed that all teeth were present with potentially impacted 3rd molar. Cephalometric examination indicated a skeletal Class II relationship with a mild dolichofacial pattern and proclined and protruded upper and lower incisors [Figure 2 and Table 1].
|Value||Norm||Std. dev.||Dev. norm|
|Craniofacial relation-Cranial structure|
|Cranial length (mm)||62.1||60.3||2.5||0.7|
|Posterior facial height (Go-CF) (mm)||69.7||61.0||3.3||2.6|
|Cranial deflection (°)||31.1||29.6||3.0||0.5|
|Porion location (mm)||–44.0||–37.0||2.2||–3.2|
|Ramus position (°)||77.7||77.5||3.0||0.1|
|Craniofacial relation-Mx position|
|Maxillary depth (FH-NA) (°)||93.2||93.4||3.0||–0.1|
|Maxillary height (N-CF-A) (°)||61.5||58.3||3.0||0.9|
|SN-Palatal plane (°)||7.0||7.3||3.5||–0.1|
|Craniofacial relation-Md position|
|Facial angle (FH-NPo) (°)||89.0||91.0||3.0||–0.6|
|Facial axis-rickets (NaBa-PtGn) (°)||83.1||89.2||3.5||–1.7|
|FMA (MP-FH) (°)||31.6||23.5||4.5||1.8|
|Total face height (NaBa-PmXi) (°)||64.4||60.0||3.0||1.5|
|Facial taper (°)||59.4||68.5||3.5||–2.6|
|Convexity (A-Npo) (mm)||4.7||3.2||2.0||0.8|
|Corpus length (Go-Gn) (mm)||85.2||75.8||4.4||2.1|
|Mandibular arc (°)||34.7||33.7||4.0||0.3|
|Lower face height (ANS-Xi-Pm) (°)||50.8||44.5||4.0||1.6|
|Dental relationships-Mx dentition|
|U-Incisor protrusion (U1-APo) (mm)||12.4||6.7||2.3||2.5|
|U incisor inclination (U1-APo) (°)||36.1||30||4||1.5|
|U6-PT vertical (mm)||21.6||19||3||0.9|
|Dental relationships-Md dentition|
|L1-Protrusion (L1-Apo) (mm)||9.5||3.6||2.3||2.5|
|L1 to A-Po (°)||33.6||27.7||4.0||1.5|
|Md incisor extrusion (mm)||–0.1||2.4||2.0||–1.2|
|Hinge axis angle (°)||99.2||90.0||4.0||2.3|
|Dental relationships-Mx/Md dentition|
|Interincisal angle (U1-L1) (°)||110.3||124.0||6.0||–2.3|
|Molar relation (mm)||–2.8||–1.6||1.0||–1.2|
|Occ plane to FH (°)||7.9||8.5||5.0||–0.1|
|Lower lip to E-Plane (mm)||6.4||–2.0||2.0||4.2|
|Class I molar relationship|
|Skeletal Class II (A-Po)|
|Skeletal Class II (ANB)|
|High mandibular plane angle|
|Facial pattern: mild vertical|
Treatment goals involved resolving upper and lower crowding, correcting the teeth in scissor bite, maintaining Class I occlusion, and improving smile esthetics.
Treatment options included extraction and non-extraction treatment; however, a non-extraction plan was agreed on, using a customized appliance (Insignia) with low torque compensations in the customized brackets (labial root torque) and lower interproximal stripping and intermaxillary elastics [Figure 3].
Treatment proceeded first with a 14 CuNiTi archwire in the upper and lower arches (5 months), followed by 14×25 CuNiTi (5 months, with Class II elastics used on the left), 18×25 CuNiTi (1.5 months – Class II elastics on left), 19×25 TMA (3 months – bilateral Class II elastics), and 19×25 NiTi with 20 degrees buccal root torque to upright incisors. The patient did not attend his appointment until 3 months later.
On his return, a cephalometric radiograph was taken which showed that the apex of one of the lower incisors was completely out of the alveolar bone [Figure 4]. Clinically, it appeared that the lower right lateral incisor was the tooth affected, although there were minimal signs of gingival recession and all teeth were vital [Figure 5]. The 19×25 NiTi with 20 degrees torque was then flipped to express positive torque (lingual root torque) for 4 months.
Finishing was performed using 19×25 TMA and treatment completed in 21 months with fixed retainers placed from 3 to 3 in the upper and lower arches [Figure 6]. There appeared to be no visible adverse effects on the periodontium. A cephalometric radiograph taken at debonding showed the roots of the lower incisors within the alveolar housing [Figure 7].
A panoramic radiograph taken at debonding showed acceptable root angulations, no evidence of root resorption, and stable bone levels. The radiograph did reveal impaction of the lower left 3rd molar [Figure 8]. Cephalometric superimposition [Figure 9] showed reduced upper and lower incisor proclination, resulting in an increased interincisal angle.
The patient returned after 4 years post-treatment with a stable occlusion despite debonding and loss of the lower fixed retainer [Figure 10]. Clinical assessment showed that the periodontium around the lower incisors was healthy, and a CBCT (Kavo OP 3D, 5 cm×5 cm, 85 µ) was taken to further asses the status of the lower incisors. The CBCT showed good bone coverage of the roots with no apparent adverse effects from the orthodontic treatment [Figure 11].
The patient in this report had severe dehiscence of the lower incisors, but surprisingly no apparent periodontal pathology. Merely placing the roots back into the alveolar bone resulted in a favorable long-term result. The question arises that if there were periodontal issues, would the same treatment be effective? According to Engelking and Zachrisson, it would not. Therefore, if periodontal pathology was present, it would likely be better to also perform a bone and connective tissue graft. According to Mandelaris et al., a pre-treatment CBCT could improve prediction of alveolar bone changes caused by orthodontic tooth movement and can influence periodontal decision-making if lower incisor protrusion is initially predicted, especially in hyperdivergent patients.[8,9] In such a case, periodontally accelerated osteogenic orthodontics could be performed initially to increase the scope of treatment.[10,11]
Orthodontists should be aware of possible complications of excessively torquing lower incisors to prevent proclination. Although permanent damage could occur, it is imperative to note that a good long-term prognosis is possible using orthodontics alone, especially if there is no gingival pathology.
Declaration of patient consentThe authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorshipNil.
Conflicts of interestThere are no conflicts of interest.
- Angle Orthod. 1996;66:95-109.The anterior alveolus: Its importance in limiting orthodontic treatment and its influence on the occurrence of iatrogenic sequelae.
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