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Skeletal Class III surgical orthodontic case of mandibular first molars mesially moved using an anchor plate for closing space from the congenital absence of mandibular second premolars
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Received: ,
Accepted: ,
How to cite this article: Shimada E, Takizawa A, Yamauchi K, Igarashi K. Skeletal class III surgical orthodontic case of mandibular first molars mesially moved using an anchor plate for closing space from the congenital absence of mandibular second premolars. APOS Trends Orthod. doi: 10.25259/APOS_117_2025
Abstract
The mandibular second premolar is a favored site for congenital absence of permanent teeth. If the second deciduous molar, which remains, were extracted, the space of about 10.0 mm would exist between the mandibular premolar and first molar. In cases where the labio-lingual position and tip of the mandibular incisors are appropriate or where the lateral profile is good, the second deciduous molar should be extracted, and the space of nearly 10.0 mm should be closed by mesial movement of the first molar. In addition, although absolute anchorage is necessary for such dynamic tooth movement, miniscrews implanted in young patients are less stable than those implanted in adults. In the case described herein, the first molars were moved using anchor plates approximately 10.0 mm mesial to the congenitally absent second premolar to close the space. Simultaneously, proper improvement of the tooth axis of the lingually inclined mandibular incisors was performed. The anchor plate was stable as an absolute anchorage even in young patients. It was possible to move the teeth reliably to the target position.
Keywords
Anchor plate
Congenital absence
Mandibular molar
Mesial movement
Orthognathic surgery
INTRODUCTION
Congenital absence of teeth is a common congenital anomaly in permanent dentition,[1,2] the most common being the mandibular second premolars (2PMs).[2] When congenital absence of teeth occurs in a dentition with little or no crowding, prosthetic options can be considered for sites with missing permanent teeth. In young patients, the space left by the congenital absence can be closed by orthodontic treatment: Shifting the teeth. Patients should be allowed to occlude with only their teeth to the greatest extent possible, without prosthetics. However, in cases with congenital absence of mandibular 2PMs and remaining second deciduous molars (2DM) with a good lateral profile, it would be necessary to maintain the mandibular anterior teeth position and close the extraction space by mesial movement of the molars after extraction of the deciduous teeth. Moving mandibular molars nearly 10.0 mm by bodily mesial movement is not easy.
This report describes the case of a skeletal Class III patient with congenitally absent bilateral mandibular 2PMs who was treated with anchor plates[3,4] to close the space by mesially moving the mandibular bilateral first molars (1MS), with subsequent surgical orthodontic treatment, achieving good results.
CASE REPORT
The patient, an 11.1-year-old girl, presented to the hospital with the chief complaint of an anterior crossbite. She showed no facial asymmetry. The soft tissue profile was concave type. She was skeletal Class III with a large and anteriorly positioned mandible. Intraorally, she had anterior teeth with crossbite, bilateral Angle Class III moral relations, labially tipped maxillary anterior teeth, and lingually tipped mandibular anterior teeth with dental compensation. Bilateral mandibular 2PMs were congenitally absent; bilateral mandibular 2DMs remained [Table 1 and Figure 1].
| Variables | Mean±standard deviation (Japanese adolescent) | Pre-1st phase treatment | Mean±standard deviation (Japanese adult) | Pre-2nd phase treatment | Post-2nd phase treatment | Retention 2-year |
|---|---|---|---|---|---|---|
| SNA (°) | 79.7±3.0 | 84.9 | 82.2±2.8 | 83.5 | 83.8 | 83.8 |
| SNB (°) | 76.3±3.1 | 90.4 | 80.4±2.9 | 89.9 | 82.4 | 82.8 |
| ANB (°) | 3.3±1.4 | −5.5 | 1.8±1.7 | −6.4 | 1.4 | 1.0 |
| Wits appraisal (mm) | - | −12.6 | - | −13.1 | −2.9 | −4.3 |
| Mand.Pl. to SN (°) | 36.9±4.8 | 26.3 | 33.7±5.2 | 24.3 | 31.7 | 31.5 |
| U1 to SN (°) | 105.5±7.1 | 117.2 | 107.4±6.9 | 127.8 | 113.3 | 115.3 |
| L1 to Mand. Pl. (°) | 99.1±5.2 | 78.2 | 91.8±5.3 | 88.8 | 83.6 | 89.6 |
| Interincisal angle (°) | 118.5±10.0 | 138.3 | 127.1±8.7 | 119.0 | 131.3 | 123.5 |
| Gn-Cd (mm) | 108.3±4.5 | 123.8 | 121.9±5.1 | 129.8 | 117.4 | 117.8 |
| Pog’-Go (mm) | 72.3±2.9 | 80.6 | 79.2±4.3 | 83.8 | 78.7 | 79.2 |
| Cd-Go (mm) | 52.1±3.5 | 62.1 | 62.9±3.9 | 67.1 | 55.3 | 55.4 |
SNA: Sella, nasion, point A, SNB: Sella, nasion, point B, ANB: Point A, nasion, Point B, SN: Sella, nasion
- 11.1-year-old patient (pre-1st phase treatment): (a) Facial photographs, (b) Intraoral photographs, (c) Panoramic radiograph. Orange triangles indicate retained mandibular second deciduous molars, (d) Cephalometric radiograph, (e) Cephalometric tracing
Treatment objectives
Achieving a good profile
Obtaining proper anterior tooth axis, overjet, and overbite
Angle Class I molar relation.
Treatment alternatives
The following three treatment plans can be applied.
Maxillary bilateral first premolar (1PMs) extraction, followed by maxillary anterior teeth axis improvement. Subsequent performance of mandibular bilateral 2DMs extraction and mandibular bilateral molars protraction + orthognathic surgery (OGS).
Maxillary bilateral 1PMs extraction. Mandibular bilateral 2DMs extraction and implant placement + OGS.
Extraction of mandibular bilateral 2DMs, along with mandibular anterior teeth lingual tipping to improve proper overjet by orthodontic treatment alone. Mandibular bilateral third molars erupted and occluded.
The treatment plan outlined in (3) can avoid OGS, but it requires severely tipped maxillary and mandibular anterior teeth, in addition to greater dental compensations. It also does not engender adequate improvement of the profile. The treatment plan explained as (2) avoids 10.0 mm mesial movement of the mandibular bilateral molars and shortens the treatment period, but it requires the placement of two dental implants in a young patient. After explaining to the patient that (1) was the best plan to improve the profile sufficiently, to keep the anterior teeth roots in the alveolar bone with the appropriate teeth axis, and to allow the patient to bite using only her own teeth, the patient and her parent agreed to the treatment plan of (1).
Treatment progress
As the first phase treatment, mandibular bilateral 2DMs were extracted at age 11.5 years. An anchor plate (Ortho Anchor; Dentsply Sirona Inc., Japan), which had been cut from T type to L type, was placed in the mandibular body to obtain sufficient anchorage [Figure 2a]. Then, 0.018-inch slot multi-bracket appliances (Dentsply Sirona Inc., Japan) were placed on the mandibular teeth. Leveling began. After leveling of the mandibular dentition and improving the anterior teeth axis, mesial movement of the mandibular bilateral 1MS was performed by an anchor plate [Figure 2b]. At 14.9 years, mesial movement of the mandibular bilateral molars was completed [Figure 2c]. Growth was observed. At 15.4 years, the patient began second-phase treatment [Figure 3]. Maxillary bilateral 1PMs were extracted, as were maxillary and mandibular bilateral third molars. At 17.5 years, a LeFort I osteotomy was performed on the maxilla; a sagittal split ramus osteotomy was performed on the mandible.
- (a) Anchor plate (Ortho Anchor). (b) Panoramic radiograph at 13.7 years of age. Anchor plates were used to move the mandibular bilateral first molars mesially; (c) Panoramic radiograph at 14.9 years of age. Completed mesial movement of the mandibular bilateral first and second molars. Blue triangles indicate anchor plates.
- 15.4-year-old patient (pre-2nd phase treatment): (a) Facial photographs, (b) Intraoral photographs, (c) Panoramic radiograph, (d) Cephalometric radiograph, and (e) Cephalometric tracing.
Treatment results
The treatment duration was 3.3 years for the first phase treatment and 2.3 years for the second phase treatment. Although mesial movement of the mandibular bilateral 1MS took some time, no observable root resorption or mesial tipping of the molars occurred. The lingually upright mandibular anterior teeth were unaffected by the mesial movement of the mandibular bilateral 1MS. Torque control was achieved with multi-bracket appliances, which improved them to the proper tooth axis [Table 1]. After surgical orthodontic treatment, the profile was Neutro, skeletal Class I, the molar relation was Angle Class I, and the anterior teeth occlusion was improved to proper overjet and overbite [Figure 4]. Even 2.9 years after orthodontic treatment, the skeletal structure and occlusion remained stable with no marked change [Figures 5 and 6].
- 17.5-year-old patient (post-2nd phase treatment): (a) Facial photographs, (b) Intraoral photographs, (c) Panoramic radiograph, (d) Cephalometric radiograph, and (e) Cephalometric tracing.
- 20.6-year-old patient (2.9-year post-treatment): (a) Facial photographs, (b) Intraoral photographs, (c) Panoramic radiograph, (d) Cephalometric radiograph, and (e) Cephalometric tracing.
- Superimpositions: Pre-1st phase treatment cephalometric tracing (black line), pre-2nd phase treatment cephalometric tracing (red line), post-2nd phase treatment cephalometric tracing (blue line), and 2.9-year post-treatment cephalometric tracing (green line).
DISCUSSION
In this case, the anchor plates were used to move the mandibular bilateral 1MS bodily into the spaces for the extraction of the mandibular bilateral 2DMs. Miniscrews used in young patients, as in this case, present a higher risk of failure than when the miniscrews are placed in adults.[5]
In addition , likely, many cases with severe crowding or in the mixed dentition period would have difficulty with the implantation point. The anchor plates used for this patient were stronger than miniscrews because two or three screws are used to fix the anchor plate to the jawbone. Reportedly, it has a lower failure rate.[6] Furthermore, a low risk of damage to the tooth roots exists because it is fixed to the infrazygomatic crest or to the mandibular body. In contrast, the placement or removal of anchor plates requires elevating mucoperiosteal flaps and exposing the bone surface. The plate is then secured with two to three screws per plate, followed by suturing of the incised mucoperiosteal tissue. As a result, the procedure is more complex and invasive than the insertion of miniscrews,[7] and post-operative facial swelling and pain occur more frequently. Moreover, even with miniscrews, substantial mesial movement of the molars can be achieved by modifying the biomechanics[8] or performing corticotomy.[9] However, miniscrew placement in the mandibular premolar area can be challenging when conditions such as cortical bone thickness and interradicular space are insufficient.[10] If patients are able to tolerate the invasiveness associated with anchor plate placement, anchor plates may be preferable for younger individuals, given their superior stability as anchorage devices and the reduced risk of permanent tooth root damage during screw insertion.
Using anchor plates, stronger anchorage was obtained even in this young patient. Mesial bodily movement of mandibular molars was performed without causing lingual tipping of the mandibular anterior teeth. The patient was very satisfied with the results because all the patient’s own teeth were used for occlusion, with no prosthetic treatment.
CONCLUSION
The anchor plate is very effective for moving the mandibular 1M to mesial bodily movement. It is useful stably even in young patients.
Ethical approval:
Institutional review board approval is not required.
Declaration of patient consent:
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients 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.
Conflicts of interest:
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript, and no images were manipulated using AI.
Financial support and sponsorship: Nil.
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