Contemporary approaches for the orthopaedic correction of class III malocclusion

Introduction

The most widely used and traditional class III growth modification appliance is the protraction facemask, with and without rapid maxillary expansion. Several studies have shown that the effect of a protraction facemask on the maxilla and mandible leads to an improvement in the ANB angle of 2–5 degrees in the short term. ^, These changes were shown to reduce the need for orthognathic surgery by 25%–30%. However, although there was a reduction in the need for orthognathic surgery in patients using facemasks, the initial skeletal changes are only partially maintained after phase 1 therapy since the class III growth pattern resumes in the long term. ^,

Several alternative methods to protraction facemask have been introduced over the years to improve treatment outcomes and minimise the side effects. These approaches include modifications of expansion protocols and the use of skeletally anchored appliances such as bone-anchored maxillary protraction and hybrid tooth-bone-borne expanders. Fixed correctors were also utilised to overcome compliance issues.

Almost all studies investigating the effects of facemasks incorporate rapid maxillary expansion (RME) into protraction treatment. Most class III patients display a small maxilla in three planes of space and need transverse expansion. RME was shown to displace the maxilla downward and forward, thereby helping to correct the class III relationship. The rigid framework was also suggested to protect the anterior segment of the maxilla from the constrictive forces applied by the facemask. Furthermore, RME is a commonly used method to gain space in patients with mild-moderate crowding, which would be preferable in class III patients with maxillary deficiency. Another reason for using RME is the belief that expansion improves the sutural response to maxillary protraction by disarticulating the circum-maxillary sutures and reducing treatment time. ^, Although some studies have shown improved efficiency of facemask treatment when combined with RME, other studies failed to show any significant benefits.

The amount of expansion is usually determined/limited by the transverse relationship of posterior teeth. When the maxilla is widened using RME, it was shown that the skeletal response is 20%–50% of screw expansion. Alternating rapid maxillary expansion and contraction (ALT-RAMEC) was introduced by Liou and Tsai to increase the disarticulation of the circum-maxillary suture. In this method, the maxilla is expanded and constricted in a weekly schedule of alternating fashion for 7–9 weeks. Liou and Tsai showed that a combination of Alt-RAMEC and a protraction spring provided twice as much maxillary protraction as RME in cleft lip and palate patients. Evidence that followed was inconclusive about the role of Alt-RAMEC, with some showing improved outcomes, while others showing no significant difference with RME. Later studies on the use of Alt-RAMEC with mini-screw supported expanders have demonstrated improved maxillary protraction outcomes compared to previous reports. The findings of these studies suggested that Alt-RAMEC can be effective in older children and reduce treatment duration. Adding mini-screws may help reduce anchorage loss that can arise from the jiggling forces from Alt-RAMEC and help increase anchorage in children who are shedding deciduous teeth and have immature permanent premolar and molar roots.

Skeletal anchorage

Using skeletal anchorage to correct class III malocclusion aims to maximise orthopaedic changes by preventing, or at least reducing the unwanted dental effects and vertical changes of traditional protraction facemask. The most common side effects of conventional RME-facemask combination include anchorage loss in the maxillary dentition, proclination of incisors, mesialisation of posterior maxillary teeth causing increased crowding in the canine area, retroclination of lower incisors and extrusion of maxillary posterior teeth, resulting in posterior rotation of mandible and increase in facial height. ^,

The conventional facemask is indicated for pre-pubertal, treatment compliant patients with horizontal or neutral growth patterns and sufficient posterior teeth for anchorage. However, not all class III patients fit these criteria. To enable adequate maxillary protraction and to reduce side effects, skeletally anchored appliances may need to be considered. Table 70.1 summarises considerations for a personalised approach to decide the need for skeletal anchorage.

TABLE 70.1

Factors to consider for a personalised approach to decide the need for skeletal anchorage

Patient characteristics	Facemask only	Add skeletal anchorage
Age	Pre-pubertal or before 10 years Most favourable time for maxillary protraction with facemask	Past pre-pubertal, older than 10 years At this stage, maxillary sutures become more inter-digitated, difficult for tooth-anchored appliances to generate skeletal changes without significant anchorage loss
Anchorage of maxillary dentition	Enough anchor teeth —no special anchorage requirement	Insufficient anchor teeth If not enough anchorage from teeth, the present teeth may mesialize, increase crowding and space loss, increase dental side-effects, may reduce skeletal improvement
		Special anchorage requirements Previous space loss—early loss of Es needing space regain or Missing permanent teeth that require skeletal anchorage for space closure
Compliance	Good compliance	Non-compliant with facemask and children with many after school activities
	Success depends on good compliance with wear times, 14–16 h/day	May need skeletal anchorage to maximise outcomes and to enable class III elastics
Severity of class III and vertical configuration	Mild class III and horizontal or neutral growth pattern	Severe class III and vertical growth pattern The correction needs are significant and would benefit from skeletal anchorage. Patients with vertical growth patterns tend to relapse more and have increased vertical changes with conventional facemask treatment.

Contemporary class III growth modification with skeletal anchorage utilises mini-plates or mini-screws in combination with class III elastics or facemask. The principle of using absolute anchorage for maxillary protraction was described by Kokich et al., when applying protraction forces from a facemask to ankylosed upper deciduous teeth. Other investigators applied protraction forces through intra-oral implants. Kircelli et al. in 2006 were the first to combine expansion using ‘intraosseous titanium screw’ anchorage and maxillary protraction, using zygomatic miniplates and facemask in a case with hypodontia and severe maxillary hypoplasia. Using skeletal anchorage helped achieve significant maxillary expansion and protraction without the dental side effects in the hypodontia patient. Other studies followed with variations in the location of mini plates, either placed in the lateral nasal wall or the infra zygomatic crest. However, the technique only became more widespread with the introduction of miniplates designed explicitly for this purpose, known as the Bollard miniplates ( Fig. 70.1 ).

Bone-anchored maxillary protraction (BAMP)

BAMP for the treatment of midface deficiency was introduced by De Clerk et al. in 2009 as an alternative to traditional protraction facemask treatment.

The BAMP technique

The technique typically involves the placement of four mini plates: two mini plates in the infra zygomatic buttress of the maxilla (right and left) and two mini plates in the anterior mandible between the lateral incisors and canines. Mucoperiosteal flaps are raised, and the plates are secured with screws, leaving the hooks visible intra-orally adjacent to the upper molars and between the canines and lateral incisors in the lower. The hooks should emerge through the attached gingivae. Due to the challenges of access, the surgical procedure of placing bone plates is typically undertaken under general anaesthetic and antibiotic cover. Placing of the upper plates, in particular, is a technique-sensitive procedure.

The bone plates are usually left to stabilise for 3–6 weeks and then loaded with intra-oral class III elastics with an initial force of 100 g per side, increasing to 200 g after 2–3 months. A bite plane may be required to dis-occlude the teeth if there is a deep overbite. Treatment duration is typically 12–18 months. When the plates need to be removed, a general anaesthetic is often necessary due to the difficulty of accessing the upper plates.

While the treatment is not particularly uncomfortable, complications include infection at the site of plates (11.1%) and plate failure (8.3%) . The miniplate survival rate has been reported 93.6%. A total of 25.7% of the patients suffered failure of one of the miniplates. While infection can usually be treated with antibiotics, failure of the plate is a more complicated issue to resolve, as this usually requires another operation to remove the old plate and place a new one.

Timing of treatment

BAMP treatment is recommended when there is still some residual growth remaining to allow for some growth modification. While facemask therapy is recommended on patients under the age of 10, BAMP is more frequently used when the child is older (>10), when the bone is relatively more mature, making the failure of the plates less likely. This also means that the patient is nearer the end of growth when they complete BAMP treatment, compared with traditional facemask therapy. As the patient is older when they complete BAMP treatment than when they finish facemask treatment, there is less opportunity for relapse of the class III correction as a result of ongoing mandibular growth.

How effective is BAMP?

BAMP is a relatively new clinical modality and therefore, long-term prospective controlled clinical trials are not available. Initial studies showed favourable and promising changes in the skeletal and soft tissues of the maxilla. ^, Cevidanes et al. reported that there was 2–3 mm more maxillary advancement in BAMP patients compared to facemask. However, studies that followed later had different levels of success. Nguyen et al. showed that although there was a significant advancement of the zygomatic arch in most patients, the mid-face change was quite variable, with 32% of patients showing about 4–5 mm, while 20% showed almost no change. BAMP also was shown to have positive effects on the mandible, with the chin position unchanged due to posterior displacement of the ramus and posterior remodelling of the glenoid fossa. A previous study demonstrated a similar effect on the mandible when using face mask. Additionally, one of the suggested benefits of BAMP is its ability to provide excellent control over vertical changes. This is because the force applied to the mandible is directed towards the anterior portion, which facilitates the closure of the gonial angle.

In a multi-centre randomised controlled trial (RCT) conducted by Mandall et al., the effects of BAMP were compared to those of untreated controls, with patients followed up for 3 years. On average, the results showed small but noticeable improvements in the skeletal pattern among the patients treated with BAMP.

Fig. 70.2 shows pre-treatment, post BAMP treatment and after completion of second phase of therapy. This case is an example of the average response to BAMP. However, the skeletal differences were more subtle over the next 3 years thus orthognathic surgery was avoided.

A study found that fewer patients who underwent BAMP treatment required orthognathic surgery (48%) as compared to the untreated control group, where 75% of patients would benefit from orthognathic surgery. Further research is required to determine the relative benefits and predictability of this intervention compared to the risks and burden of treatment for the patient.

Variations of BAMP—the mentoplate and the modified mentoplate

The mandibular component of the original BAMP, as described by DeClerck is placed between the laterals and canines, necessitating the lower permanent canines to be erupted in order to commence treatment. To address the problem, Wilmes et al. have introduced a variation called the ‘mentoplate’. A single plate is fixated to the inferior border of the mandible, avoiding injury to tooth germs.

A hybrid, tooth-and-bone-borne hyrax expander (HHE) has been used in the maxilla. The potential advantage of a maxillary appliance supported by miniscrew implants versus BAMP is that the HHE can be placed in children even younger than 10 years-of-age allowing class III correction to start earlier. The potential disadvantage of a hybrid appliance is that there may be relatively more unwanted dentoalveolar effects due to the appliance having dental components as well.

There are only a few studies that investigated the effects of mentoplate. Willmann et al. compared the effects of mentoplate to facemasks in a group of pre-adolescent children (mean age 9.43 vs 8.74, respectively). The amount of maxillary protraction was similar at this young age for both groups, although there was improved vertical control for the mentoplate patients. Due to the relative invasiveness of the procedure, they concluded that this treatment modality is suited for patients who are non-compliant with facemask treatment and for whom treatment needs to start at an earlier age.

Another recent study by Tarraf et al. that used a modified mentoplate and hybrid-expander (MM-HE) design showed significantly improved outcomes in comparison to the RME-facemask. ( Fig. 70.3 ). The mandibular plates were conventional trauma plates, L-plate (Stryker Universal Orthognathic; Stryker, Kalamazoo, MI, USA), placed apical to the central and lateral incisors, which require a smaller incision compared to the mentoplate. After an initial 8-week healing period, during which the maxillary expansion was completed, elastics were started with 100 g/side. After 6 weeks, the elastic force was increased to 170 g, then at 4 months, to 230 g until the end of treatment. The mean age of patients was slightly older than in Willmann et al.’s study, 10.24 versus 10.56 years for the modified mentoplate and facemask groups, respectively. While the effects on the mandible were similar for both groups, there was three times more improvement in the maxillary position in the MM-HE group. This large difference in this study may be related to the facemask group not having miniscrew-assisted expansion and forces acting on the maxilla more consistently in the modified mento-plate group.

The hybrid expanders and its modifications

The use of hybrid, tooth-bone borne expanders in growing children was introduced in 2008 to share the expansion load with the anchorage teeth and to reduce unwanted side effects. ^, The use of mini-screws also allows the delivery of protraction forces to be transferred closer to the centre of resistance of the maxilla in class III growth modification.

Clinical application of hybrid expanders

Two palatal mini-screws (BENEfit PSM Medical Solutions, Gunningen, Germany) are placed in the anterior palate at the T-Zone, where the best cortical bone can be found. This is in the paramedian area in the anterior palate behind the third rugae. If the patient has had a cone beam computerised tomography (CBCT) image, the length of the mini-screw can be selected based on the height of the palate in the respective region to achieve bi-cortical anchorage for increased stability. If no CBCT is available, the greatest effective bone height at the first premolar level has been measured as 8.38±3.75 mm (3 mm paramedian) and 8.42±3.70 mm (6 mm paramedian).

Construction of the hybrid expander

Analogue construction

In conventional analogue construction, impression caps or copings are placed over the mini-implants prior to taking impressions to accurately transfer the position of the mini-screw through the impression to the laboratory. Once the impression is taken, laboratory analogues are placed, and the plaster working model is produced for appliance manufacturing. The laboratory can then prepare the appliance using the implant neck surrounding ring abutments that fit over the mini-screw heads and molar bands.

Digital construction

For digital construction and 3D printing, intra-oral scans are taken following mini-screw insertion, either using a scan body (analogue to the impression caps) on the mini-screws, scan powder, prosthodontic occlusion spray or by simply placing some orthodontic wax into the mini-screw internal hole. Graf et al. described the 3Shape Appliance Designer software (3Shape, Copenhagen, Denmark) to design the framework digitally ( Fig. 70.4.i ). The design gets printed by a laser-melting machine (Concept Laser, Lichtenfels, Germany) with Remanium star metal alloy (Dentaurum, Ispringen, Germany). The expansion mechanism is then laser-welded to the bedding prepared in the framework. Fig. 70.4.ii shows the appliance cemented in mouth.

The computer-aided design/computer-aided manufacturing (CAD-CAM) hybrid expander’s fitting surface is treated with sandblasting using CoJet Sand (3M Unitek Corp, Monrovia, CA, USA) for 10–15 s to improve bonding, followed by the application of a 3M ESPE SIL silane coupling agent (3M Unitek Corp, Monrovia, CA, USA). The finished appliance can then be cemented to the teeth using dual cured resin cement, while other users have also reported the use of glass ionomer cement (GIC) and resin modified GIC (personal communication) for the CAD-CAM design; and glass ionomer cement for the conventional design and fixation screws placed (BENEfit PSM Medical Solutions, Gunningen, Germany).

CAD/CAM—metal-printed appliances

With the use of 3D printed appliances, the elimination of separators and impressions improves workflow and patient comfort. In addition, these metal-printed appliances are more rigid due to the alloy material used in 3D printing. This rigid appliance may create hurdles in delivery if the scanning and printing steps are not executed correctly, as making adjustments to the metal framework is almost impossible. However, this increased rigidity, in combination with miniscrew implants, may result in greater skeletal outcomes with reduced dental side effects. Laboratory studies had reported that the increased rigidity of expanders improves force transmission and reduces deformation. ^, A study investigating the effects of a printed hybrid expander and facemask combination showed much more significant maxillary changes in comparison to traditional RME-facemask (3.12 degrees greater increase in SNA). Other research comparing analogue hybrid expanders with RME in class III correction failed to show a significant difference in maxillary protraction between the two interventions. ^, So whether the rigidity of metal-printed expanders has a role in the improved outcomes warrants further investigation with RCTs.

Hybrid Hyrax expanders and facemask

Maxillary protraction using hybrid expanders has been shown to be possible with the use of traditional facemasks, class III elastics or inter-maxillary springs.

In a retrospective study, Nienkemper et al., showed that Hybrid Hyrax expander and facemask produced 2 degrees increase in SNA without significant incisor proclination or vertical changes in a group of children with a mean age of 9.5 years and concluded that unwanted maxillary dental movements can be avoided with Hybrid Hyrax expander. When the effects of the Hybrid Hyrax expander facemask were compared to the RME-facemask, there were no significant differences between the two modalities; however, similar to Nienkemper et al. (2013), there were no significant dental or vertical side effects with Hybrid Hyrax expander. In another retrospective study, Maino et al. showed a 2.5-degree increase in SNA in slightly older children (mean age 11 years 4 months) in only 4 months of facemask use. In addition to Hybrid Hyrax expander, this study also utilised Alt-RAMEC, so it can be hypothesised that this may have helped accelerate the class III correction. These patients were followed up in the long term, and after 7 years and 10 months, all of the positive outcomes were still maintained, with only 0.7 mm relapse in SNA. Only one of the patients out of the 27 needed orthognathic surgery.

The results of these retrospective studies suggest skeletal anchorage produces similar outcomes for children in the pre-pubertal stages and younger than 10 years of age. However, for older or young children who require anchorage support due to insufficient teeth, skeletal anchorage is still necessary to maximise orthopaedic outcomes. Case study depicted in Fig. 70.5 shows a patient who had insufficient anchorage from maxillary posterior teeth due to resorption of deciduous teeth roots and was treated with a hybrid expander facemask combination.

Patient compliance

Compliance in orthodontics is one of the challenges clinicians face daily. The facemask is required to be worn for approximately 14–16 h a day. The length of treatment from different studies ranges from 4 months with the use of skeletal anchorage and Alt-RAMEC to 16 months+ with a conventional RME facemask. ^, For children to wear a cumbersome orthopaedic appliance for extended periods may not be realistic, which may explain the poorer outcomes in some patients. Studies revealed that even if the patients are instructed to wear the facemask for at least 14–16 h/day, patients wore it for an average of 8–11.5 h/day. ^,

Clinicians have devised different strategies to help overcome compliance issues by trying different approaches, including class III elastics and compliance-free springs. This next section will explore growth modification approaches using these techniques.

Intra-oral class III elastics and hybrid expanders

Class III elastics for maxillary protraction can be attached to the lower lingual arch supported with mini-screw anchorage or directly applied onto mini-screws.

A tandem traction bow appliance was one of the first attempts to use class III elastics for growth modification. ^, Tortop et al. investigated the effects of a modified version, using a removable expander in the maxilla and showed that it improved SNA similarly to a facemask. However, the changes were smaller for ANB and overjet. This may have been due to the age group of patients and the use of a removable maxillary expander.

Al-Mozany et al. investigated the effects of class III elastics attached to a bonded mini-screw assisted expander in the maxilla (two palatal temporary anchorage devices (TADs) of 2 × 9 mm BENEfit system (PSM Medical Solutions, Tuttlingen, Germany) and a lower lingual arch that was anchored to lower mini-screws (6 × 1.5 mm, Aarhus miniscrew implants, American Orthodontics, WI, USA) in a group of patients with a mean age of 12.05 years. The patients had 9 weeks of Alt-RAMEC, with four turns a day, and protraction with 400 g of intermaxillary elastics for a mean period of only 8.5 weeks. Only one mini-screw in the mandible was lost. There were significant improvements in SNA (1.87 degrees), SNB (−2.03 degrees) and ANB (3.95 degrees). The above findings are clinically significant, given the age of the patients and a short protraction duration. Since there was skeletal anchorage in the maxilla and mandible, applying a force similar to that used with a facemask (400 g) was possible. A 4-year follow-up study showed that the correction was maintained in all 15 patients except 1, showing stability rates higher than that reported for RME facemask.

A recent randomised clinical trial investigated the effects of HH and mini-screw anchored class III elastics. They randomised patients into intervention or control groups and showed a clinically significant improvement in maxillary protraction with the use of elastics compared to controls. Expansion followed the Alt-RAMEC protocol, and in the mandible, two mini-screws were placed mesial to lower canines and were connected with a unique bar with elastic hooks. The duration of the intervention was much longer than Al-Mozany et al.’s study, which may be due to the lower force levels used in this study (17–18 weeks vs 11–12 months and 400 g vs 100–200 g, respectively).

Another study using class III elastics directly on mini-screws placed distal to the lower canine teeth and to a hybrid expander in the maxilla compared the effects to the regular RME group. The main aim was to identify whether using mini-screw anchorage in the maxilla made a significant difference in maxillary protraction. The dental changes were more pronounced in the RME group patients; however, although both groups showed significant forward movement of the maxilla, neither was better in terms of maxillary protraction. SNA change was 1.37±1.37 and 0.82±1.26 for HH and RME groups, respectively, much lower than previous studies. These effects may be due to differences in expansion protocols (RME vs Alt-RAMEC) and light force levels of 150–250 g.

Mini-screws in the mandible have high failure rates, 16.5% as opposed to 11.0% in the maxilla. Although the failure rate was much lower in Al-Mozany et al. study, Miranda et al. reported 15.78% and 17.85% failure in hybrid hyrax and conventional hyrax expanders. In addition to the issue of failure potential, placement of lower mini-screws also require mandibular canine teeth to be erupted. To overcome this issue for patients who are non-compliant to facemask, a study compared class III traction between a lower lingual arch and HH, to conventional RME-facemask, in order to investigate if comparable results can be achieved without skeletal anchorage in the mandible. Similar age group patients to Al-Mozany study were recruited for this study (12.74 years ± 0.81 months). Alt-RAMEC was applied for 8–9 weeks. Since there was no skeletal anchorage in the mandible for the lower lingual arch, a lighter protraction force range was used (150–200 g). The changes were similar for both groups for SNA, SNB and ANB, which were also comparable to other facemask studies. This is a significant finding because this is achieved with low force levels and no facemask, on pubertal patients. Case study depicted in Fig. 70.6 shows a patient treated with the modality and approach described above. When compared outcomes described by Al-Mozany et al., the effects were less pronounced, and correction took longer, approximately 1 year versus 8.97 weeks. Nevertheless, although these patients were also older than Miranda et al.’s study, and similar force levels are used, the results are slightly better with significant changes in the followings: SNA: 1.79 ± 0.24, SNB: −0.87 ± 0.17 and ANB: 2.75 ± 0.24. ^,

Tags: Kharbanda's Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities, Oyku Dalci, Simon J Littlewood; Nour Eldin Tarraf

May 10, 2026 | Posted by drzezo in Orthodontics | 0 comments

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Contemporary approaches for the orthopaedic correction of class III malocclusion

Introduction

Skeletal anchorage