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Severe bimaxillary dento-alveolar protrusion with dental anterior open bite treated with absolute anchorage – a case report Dental Update 2024 5:2, 707-709.
Abstract
This article describes the orthodontic treatment of an 18-year-old boy with severe bimaxillary dento-alveolar protrusion and an anterior open bite. Orthodontic mini-implants were placed in the alveolar bone in all the four quadrants to provide anchorage for en masse retraction. The patient had an anterior tongue thrust with an anterior open bite. Successful dental retraction was achieved, along with closure of the anterior open bite. Facial aesthetics were improved for the patient, fullness of the upper and lower lips was reduced, and the interdental relationship was corrected.
Clinical Relevance: To describe the use of mini-implants to provide anchorage in a case of severe bimaxillary dento-alveolar protrusion.
Article
Bimaxillary dento-alveolar protrusion is one of the most prevalent malocclusions in the Asian population.1 Traditionally, orthodontic treatment often involves the extraction of four first premolars2 and the use of headgear for anchorage conservation, which requires maximum patient co-operation.3 Anchorage loss often leads to incomplete treatment results and further produces an extension of orthodontic treatment period.4 Adult patients in particular often desire that their treatment be completed in as short a period as possible and reject the prescribed use of headgear because of aesthetic and social concerns The recent introduction of temporary anchorage devices (TADs)5 such as titanium screws and mini-plates, provides clinicians with an alternative anchorage system instead of the conventional extra-oral appliances that depend on patients' co-operation. The TAD system has been shown to provide effective anchorage6,7,8,9,10 to obtain en masse retraction of anterior teeth without loss of anchorage. In extremely severe cases, however, orthodontists still face the limitations of purely orthodontic treatment and opt for orthognathic surgery. This article demonstrates the treatment of an adult patient with severe bimaxillary protrusion and dental anterior open bite, treated with mini-implants as the temporary skeletal anchorage aid, producing dramatic improvement.
Case report
A boy, aged 18 years 4 months, presented at the Department of Orthodontics with the chief complaint of protruding anterior teeth. His medical history was unremarkable, and temporomandibular joint function was normal. He showed good general health with no history of trauma or serious illness.
The pre-treatment facial photographs (Figure 1) showed a convex facial pattern, marked protrusive lips, hypermentalis muscle activity, and an acute nasolabial angle with lack of lip support. On smiling, he had a reverse smile line with inadequate upper incisor show and short upper lip length.
The pre-treatment intra-oral photographs (Figure 2) showed bilateral Class I molar and canine relationships, anterior tongue thrust and presence of an anterior open bite of 5 mm. The aetiology was partly skeletal and partly due to a history of prolonged thumb-sucking. Functional assessment revealed that mouth opening and excursions were within normal functional limits.
A pre-treatment panoramic radiograph revealed the mesially tipped right mandibular third molar (Figure 3) and cephalometric analysis (Table 1) showed a mild skeletal Class II relationship (ANB angle, 5°) with a slightly increased mandibular plane angle (FMA, 28°). Both upper and lower incisors displayed severe bimaxillary protrusion with a small inter-incisal angle (95°).
Figure 3. Pre-treatment radiographs.
Measurement
Normal
Pre-treatment
Post-treatment
SNA(°)
82 ± 2
88
87
SNB (°)
80 ± 2
83
83
ANB (°)
2
5
4
FMA (°)
25
28
27.5
SN-GoGn (°)
32
34
33
FMIA (°)
65
35
64
IMPA (°)
90
115
90
Inter-incisal angle (°)
132
95
133
Jarabak's ratio (PFH/AFA) (%)
62-65
60.8
62.1
UI-NA (°)
22
38
18
UI-NA (mm)
4
13
4
LI-NB (°)
25
45
25
LI-NB (mm)
4
14
5
E line- U (mm)
-4
+5
-1
E line- L (mm)
-2
+9
0
Diagnosis
The patient was diagnosed as skeletal Class II and dental Class I with severe bimaxillary dento-alveolar protrusion and a dental anterior open bite.
Treatment objectives
The main objective in treating this malocclusion was to retract the incisors to reduce the severe upper and lower-lip protrusion using the absolute anchorage needed for the maintenance of the Class I molar relationships, hence achieving maximum retraction of incisors, which in turn would aid in the closure of the anterior open bite.
Treatment options
The patient's chief concern was severely protruding incisors, and the goal was complete retraction of the anterior teeth to improve the facial aesthetics. A treatment plan involving extraction of all four first premolars, followed by conventional edgewise mechanotherapy and the use of high pull headgear for maximum anchorage, was discussed. The patient was also informed that total treatment time would be about 2 years. He was, however, not enthusiastic about wearing headgear and demanded a shorter treatment time. Thus, the second alternative, involving en masse retraction with mini-implants, was presented using conventional mini-implants as indirect anchorage to reinforce the banded posterior anchor teeth during anterior retraction.
The second treatment plan was preferred. This plan would allow maximum retraction of the anterior teeth without affecting the molar occlusal relationship, minimize adverse periodontal effects, and reduce the treatment time.
Treatment plan
Extraction of all first four bicuspids;
Placement of four self-drilling mini-implants as indirect anchorage;
Placement of fixed tongue crib to prevent anterior tongue thrust;
Use of sliding mechanics for en masse retraction of incisors;
Finishing and detailing;
Retention using fixed bonded lingual retainers from premolar to premolar in both the arches, followed by Begg's wraparound retainers.
Treatment progress
The maxillary and mandibular first premolars were extracted. Four self-drilling mini-implants (8 mm long, 1.3 mm in diameter) were placed in the interseptal bone between the second premolars and the first molars. The patient received 0.022″ slot pre-adjusted Roth brackets on all the teeth, with upper triple tubes and lower double tubes welded to the first molar bands.
The patient was given an anterior tongue crib and trained in tongue exercises to prevent anterior tongue thrust. The initial archwires were 0.016″ nickel titanium, followed by 0.016″ x 0.022″ stainless steel to complete the levelling of both the arches. The presence of a fixed anterior tongue crib prevented the tongue from protruding between the anterior teeth and aided in closing the anterior open bite. After one month it was noticed that the implant on the lower right side was loose. Hence, it was removed and placed between first and second molar (Figure 4). At this stage all the implants were fixed to the first molar bands with 0.019″ x 0.025″ sandblasted stainless steel wire attached to implants using composite adhesive material.
Figure 4. Panoramic radiograph showing mini-implants used for indirect anchorage.
After three months of levelling, improvement in tongue posture and reduction in anterior open bite was achieved. It was decided to remove the tongue crib and start with anterior retraction 0.019″ × 0.025″ stainless steel wires were placed in both the arches and en masse retraction was started with sliding mechanics using elastic chains between the first molars and canines, applying 100–200 g of force (Figure 5). The E-chains were replaced every four weeks and any projecting distal ends of the wires were cut.
Figure 5.
(a–c) En masse retraction of the anterior teeth with the elastic chains.
From the start of comprehensive orthodontic treatment, the patient was instructed to maintain ideal oral hygiene and, especially, not to allow food impaction or inflammation near the implants. He was also told to rinse with chlorhexidine mouthwash twice daily.
The inter-incisal angle decreased gradually after 2 months of en masse retraction, and the extraction spaces closed whilst maintaining the posterior occlusal relationship. The patient's facial profile experienced a significant change. All the four mini-implants were stable and firm. They were removed simply by unscrewing them. The total active treatment time was 13 months. Root paralleling was confirmed on the panoramic radiograph, and the appliances were removed. After fixed appliance treatment, a tooth positioner was used for a month to detail the occlusion. Retention was provided by maxillary and mandibular fixed lingual bonded retainers, bonded from premolar to premolar.
Treatment results
The change in the patient's facial profile was the most dramatic part of his treatment. With the extraction of four first premolars and application of mini-implants as absolute anchorage, significant retraction of his upper and lower lips was achieved (upper lip protrusion was reduced by 6 mm and lower lip by 9 mm). As a result, mentalis muscle strain was reduced and chin contour was improved (Figure 6). Intra-orally, Class I canine and molar relationships with a good interdigitation of the teeth and ideal anterior overbite and overjet were achieved (Figure 7).
The post-treatment panoramic radiograph (Figure 8) demonstrated adequate root paralleling in both arches. Cephalometric superimposition (Figure 9) and analysis (Table 1) showed a small reduction in FMA angle (27.5°) as well as significant retraction of incisors in both the arches. As a result of compensation for the Class II skeletal relationship, the inclination of the upper incisors was overcorrected. The lips were competent in repose (upper lip to E-plane, –1 mm; lower lip to E-plane, 0 mm). The inter-incisal angle was improved to within normal range (133°). The ANB angle decreased during treatment by 1° as point A moved posteriorly during treatment. The maxillary molars showed slight intrusion, whereas mandibular molars experienced a little extrusion, perhaps due to the use of Class II elastics. Maxillary incisors were extruded by 3 mm and lower incisors by 2 mm to allow the closure of anterior open bite. This resulted in improvement of the smile arc and upper incisor show during smiling.
Figure 8. Post-treatment radiographs.Figure 9. Pre-treatment (black) and post-treatment (red) cephalometric tracings, superimposed on: (a) sella-nasion plane at sella; (b) palatal plane at ANS; (c) mandibular plane at menton.
Discussion
Bimaxillary dento-alveolar protrusion2 is a malocclusion characterized by dento-alveolar flaring of both the maxillary and mandibular anterior teeth, with resultant protrusion of the lips and convexity of the face. For these patients, it is accepted that extraction of the four first premolars is the most viable and effective extraction alternative to reduce their facial convexity,2 and maximum anchorage is believed to be the most critical part of the treatment plan. Effectiveness, efficiency and potential patient co-operation are important considerations in achieving maximum retraction of incisors in the treatment of severe dento-alveolar protrusion. Headgear is an uncomplicated and highly effective appliance to enhance the anchorage potential of posterior teeth while retracting the incisors, but considerable patient co-operation is required.3
However, in the case presented, the patient strongly rejected this option and asked for a treatment alternative which would involve no extra-oral appliance. Therefore, it was decided to do en masse retraction with the help of indirect anchorage provided by the mini-implants.10 Mini-implants were placed in buccal alveolar bone of the maxilla and mandible and covered by composite to provide easier oral hygiene maintenance. Mini-implants were necessary in this case to retract the maxillary anterior teeth to ensure absolute anchorage of maxillary molars whilst improving severe upper and lower-lip protrusion and maintaining Class I relationships. The extraction spaces were closed with power chains using sliding mechanics with improvement in the smile arc.11 The superimposition of pre- and post-treatment cephalometric radiographs showed no mesial movement of the maxillary molars. The patient was highly satisfied with the treatment outcome.
Conclusion
This case report demonstrates the use of mini-implants in treating severe dento-alveolar protrusion with maintenance of absolute anchorage throughout the treatment maximizing the treatment results.
