The Orthodontics Professors
the latest in contemporary & evidence-based orthodontics
By TATE H. JACKSON and TUNG T. NGUYEN
The use of skeletal anchorage for true orthopedic effect in growing Class III patients has now been well documented. Might the same strategy, using skeletal plates in both the maxilla and mandible, be effective to modify mandibular growth in Class II patients? A recent publication provides some initial evidence that it might.
28 growing children (age 11.83 +/- 0.83 years) with an ANB of 5 or greater, an OJ of 5mm or greater, and a ½ cusp Class II buccal relationship or greater were all treated with a standardized protocol by a single orthodontist.
Each patient first went through alignment with fixed appliances for an average of 7 months before miniplates were placed in the anterior maxilla (2 just distal to the lateral incisors) and posterior mandible (2 just distal to the first molar).
A cephalometric radiograph was taken after alignment and just before orthopedic traction began. Patients were instructed to wear intermaxillary elastics to the bone plates full-time beginning 20 days after plate fixation. The plates were ultimately loaded with ~450g on each side, and orthopedic traction was carried out for an average of 9 months. Another cephalometric radiograph was taken once each patient had a Class I molar and canine relationship and 1-3mm of OJ.
Cephalometric superimposition of the pre-orthopedic and post-orthopedic radiographs were compared to non-treated Class II controls from another recent study matched based on age, race, observational period, gender, and skeletal maturity.
Compared to controls, patients with Class II bone plates showed a significant:
WHAT THE PROFESSORS THINK
This study represents a nice initial approach to a topic for which randomized controlled data might be very difficult to obtain. The use of cephalometric radiographs following alignment and then immediately after orthopedic traction was a clever way to help account for potentially confounding tooth movement as a part of Class II correction.
Using a well-matched control group of untreated Class II patients from a cohort who were apparently followed recently strengthens the data – despite the fact that 2D cephalometric analysis has limitations.
It is key to note that the orthopedic effects reported (most importantly, mandibular elongation/forward-positioning) are not only larger than those described in meta-analyses with the use of more traditional appliances such as a Herbst or Twin-Block, but also that the 95%CI range is small (3.15-4.51).
Of further clinical importance are the rotational mandibular changes and the overall combination of ANB and OJ reduction, with an accompanying increase in OB and uprighting of the incisors. Together, these changes suggest an absence of the dentoalveolar side-effects seen with functional appliances.
What’s the bottom line for clinicians?
Bone anchors, not surprisingly, show great promise for true orthopedic correction of Class II skeletal relationships, through a combination of elongation/forward-positioning of the mandible, as well as maxillary restraint.
The use of skeletal plates for growth modification in Class II patients should be considered when:
Article Reviewed: Al-Dumanini et. al. A novel approach for treatment of skeletal Class II malocclusion: Miniplates-based skeletal anchorage. Am J Orthod Dentofac Orthop 153:239-47. 2018
BY WILLIAM R. PROFFIT, DDS, PHD
This study at the University of Melbourne, Australia, provides new data for the prevalence of enamel damage from debonding brackets, and relates such damage to the type of bracket, the type of adhesive, and the surface preparation of the enamel for bonding. Four groups of brackets and bonding techniques were examined. All brackets were GAC Innovation – either the metal “R” version or the ceramic “C” version. All brackets were bonded and removed in the setting of 5 private orthodontic practices. 437 total brackets from anterior teeth were analyzed.
The four in-vivo bracket and bonding protocol combinations were:
Debonding was accomplished for metal brackets with a debonding instrument (444-761 bracket lifter from Unitek) and for ceramic brackets with a debonding plier. Only maxillary canine to canine brackets were collected. The back of each bracket was visualized with scanning electron microscopy at 60 x magnification. An elemental map was made using dispersive x-ray spectrometry to detect calcium, phosphorus, aluminum, and silicon. Calcium and Phosphorus together indicated the presence of enamel that had sheared from the tooth. Areas of bonding material and enamel were mapped, the amount of bonding material was categorized, and bracket fracture was tabulated.
WHAT THE PROFESSOR THINKS
This is a particularly interesting study because it analyzes data from patients treated across several orthodontics clinics, rather than just from laboratory testing. Despite some limitations, clinical orthodontists can use the following points to help inform their practice:
Article Reviewed: Cochrane NJ, Lo TWG, Adams GG, Schneider PM. Quantitative analysis of enamel on debonded orthodontic brackets. Am J Orthod Dentofac Orthop 152:312-319, 2017.
Lessons Learned from 75 BAMP Cases – Part III of Our Series on Management of Class III Malocclusion using Bone Anchors
BY TUNG T. NGUYEN, DMD, MS
In two previous posts (BAMP Part I and BAMP Part II), we have:
The purpose of this post is to share practical information learned from our clinical care of patients. Failures are rarely discussed at meeting or in publications, yet we often learn more from our failures than from our successes. It is these failures that keep us humble and allows us to grow as clinicians.
The following article will highlight some of the potential complications encountered in the BAMP treatment and summarize our current philosophy on the use of BAMP.
Expect some failures
When we started using the BAMP protocol in 2005, our 6-month plate failure rate was 30-35%. The maxillary plates tended to fail more than the mandibular plates, primarily due to bone thickness and quality. With surgical refinements such as the use of pilot holes in the maxilla, the use of the Y-shape plates, localized CBCT to assess infrazygomatic crest bone thickness, and in some cases delaying treatment for a year or more, our plate failure rate has decreased to 10-15%.
Our first instinct upon encountering a loose plate is to send the patient back to the surgeon and have it replaced. While experience has shown that replaced plates tend to be more stable due to callus formation at the surgical site, re-operating carries an additional financial cost, as well as psychological anxiety to the patients and doubt from the parents that the procedure might not work. If the plate is loose at 4 weeks post-op, test it by taking a ligature director or scaler and pushing on the plate in a distal direction. Our experience has shown that plates with up to 2mm of mobility have a chance of healing. Load these plates with ¾” 2oz elastics. The light forces will help promote boney remodeling and healing around the surgical site. If the patient cannot tolerate the light elastics, bond a button to the closest tooth and secure the anchor to the button with a ligature tie and recall in 6-8 weeks. This ligature helps to limit the mobility of the loose plate and allows the site to heal. Typically, the mobility of the plate will decrease, and you can start traction force with a ¼” 2oz elastic and progress to stronger elastics at 6-week intervals. Bone plates tend to fail more under the following conditions:
we often have the mindset that if 250g of force is good for orthopedic traction, then 500g is better. After all, reverse pull face masks are often loaded with 500-800g of force. The reality is that heavy forces are often detrimental with BAMP cases. The plates are designed to flex a little to adapt to shape changes that occur with growth of the zygoma and maxilla – and therefore the plates can only resist 400-500 of force. We have seen plate breakage when they are loaded with 500g or more. Orthopedic traction is not correlated most closely to the magnitude of the force, but rather to continuous force application. Based on our experience, we can obtain effective orthopedic maxillary protraction with only 250g of force connecting two bone plates (i.e. 250g of force per side).
Retain until cessation of growth
When we started the BAMP protocol in 2005, we would remove the plates after 1 year of treatment or when adequate positive overjet was obtained. The rational for removal at this time was that bone would occasionally grow over the head of the screws making removal difficult. However, we neglected an important concept. Class III mandibular prognathic patients tend to have mandibular growth into late adolescence.1 Our current treatment protocol is to overcorrect to 3-4mm overjet. Patients are instructed to wear 250g elastics (2 x ¼” 4oz on each side) elastics at night and are recalled at 6-month intervals. If the overjet is decreasing, patients are instructed to wear elastics full time. In the rare instances that overjet increases, patients are instructed to only wear elastics every other night or decrease the force level to 125g (¼” 4oz). The plates are then removed at 18 year of age in conjunction with 3rd molar extractions to minimize the amount of surgery.
Applications of BAMP
Craniofacial cleft patients often have a Class III skeletal malocclusion. Recent studies have shown that BAMP is effective for protracting the maxilla and restraining mandibular growth in these patients.2-3 While effective maxillary protraction decreases after the age of the 14, our long-term study shows BAMP is still effective at restraining mandibular growth into late adolescence. One of our recent applications is using BAMP in older patients (>14 years of age) to reduce the severity of the surgical movement or reduce the need for 2-jaw surgery.
Our Treatment Philosophy for Class III patients
When Class III malocclusion is detected early, Reverse Pull Headgear (RPHG) has been shown to be effective at reducing the need for orthognathic surgery.4 After 10 years of age, the effects of RPHG are primarily dentoalveolar with a higher relapse rate.5 From age 11-14, BAMP has been shown to be effective at protracting the maxilla and restraining mandibular growth.6-7 After 15 years of age, orthognathic surgery is the treatment of choice, especially if the severity of the malocclusion is large. BAMP can be used to reduce the serverity of the malocclusion and reduce the amount of surgical movement. To Summarize:
BY TATE H. JACKSON & LORNE KOROLUK
Data on the long-term stability of orthodontic treatment is often very difficult to obtain, but a group from Germany has managed to recall 20 Class II, Division 2 adolescent patients – all of whom completed treatment with the Herbst appliance more than 15 years earlier. The patients were selected based on pre-treatment characteristics and treatment protocol, not on treatment outcome.
In this retrospective study, the average age of the patients at the start of treatment was 14.4 years. All patients were nearly full cusp Class II at the molar, had at least two retroclined maxillary incisors (Div.2), and had a deep bite (average OB 5.3mm).
14 of the 20 patients were decompensated (incisors were proclined to allow advancement of the mandible) for an average of 8.6 months before Herbst delivery.
All patients were then treated non-extraction with a Herbst appliance + bonded brackets. The Herbst was advanced to an edge to edge incisor relationship and remained in place for 7.7 +/- 1.7 months. After removal, full fixed appliance therapy continued for a total of 24.9 +/- 6.9 months of overall treatment. Multiple bracket types were used.
At recall, the average patient age was 33.9 +/- 2.7 years. 11 of the 20 patients had no retainers at recall; of the other 9 patients: 8 had a bonded mandibular canine to canine retainer and 1 had a bonded maxillary retainer only.
Results were compared to a historic Class I growth study cohort who had no treatment.
At the end of treatment and at long-term recall, all Class II, Div. 2 patients had a Class I molar relationship with 2mm OJ. The bite deepened from the end of treatment to recall by 1mm.
Compared to the untreated control group, the Class II, Div. 2 patients had less OJ and a lower PAR score at long-term recall, but were otherwise statistically no different.
WHAT THE PROFESSORS THINK
This study falls victim to the same issues as any retrospective study in terms of heterogeneity of the patient pool and treatment, as well as the use of a historic growth study Class I control group – rather than a randomized design.
Importantly, no cephalograms were available at recall, and examiners were not blinded as to whether the casts they examined were from the end of treatment or long-term recall.
Nonetheless, for the practicing orthodontist who is concerned about the stability of the occlusal correction obtained with a Herbst, this study provides one more piece of evidence, based on a relatively-standardized treatment protocol.
The patient population is of particular interest in terms of stability because all of these patients had:
Additionally, more than half of the patients had no retainers at recall. So, the results in terms of stability might better reflect “real life” conditions where patients lose retainers over time.
Based on these data, the anterior-posterior correction to Class I was maintained long-term to an acceptable level, as was the overbite and overjet correction.
What’s the bottom line for a clinical orthodontist?
In growing patients with a Class II, Division 2 malocclusion for whom correction to dental Class I is a major priority, Herbst plus fixed appliance treatment can be quite stable into adulthood, even without long-term retention.
This study does not suggest that retention is not needed - nor does it dive into the details of incisor alignment and relapse.
But for those of us who fear a higher risk of anterior-posterior relapse with Herbst treatment because of incisor proclination or posturing of the mandible, this study suggests that might not always be the case in the long-term, at least when it comes to Angle Classification and OJ.
Article Reviewed: Bock NC, et al. Outcome quality and long-term (≥15 years) stability after Class II:2 Herbst-multibracket appliance treatment in comparison to untreated Class I controls. Eur J Orthod. Online early December 2017.
Management of Class III Malocclusion using Bone Anchors: True Orthopedics Part II – Clinical Technique
BY TUNG T. NGUYEN, DMD, MS
The following article outlines our protocol for early treatment of Class III malocclusion using Bone Anchored Maxillary Protraction (BAMP). In a future post, we will include more clinical tips and tricks, as well as information on how to handle unusual complications.
Age of the Patient
The typical age for BAMP treatment for a patient who has a Class III skeletal relationship with a component of maxillary retorgnathia is 11-14 years. Broadly stated, the younger the patient, the better the chance for orthopedic protraction of the maxilla and midface. The success of BAMP treatment is primarily dependent on 2 factors:
Surgical Management – Placement of the Plates
We recommend the Bollard plate with the Y-Design (center plate in the image below). The Standard (screw holes in-line) design can also be used with success.
The maxillary bone plates are inserted in the infrazygomatic crest, with the plate arm emerging through attached tissue near the maxillary molars. The mandibular bone plates are inserted between the mandibular lateral incisors and canines – again with the intraoral attachment emerging from attached tissue. For the placement of both the maxillary and mandibular plates, a small flap is raised with a design that maintains good blood flow to the tissue. We refer all plate placement to qualified oral and maxillofacial surgeons familiar with the technique and treatment goals.
Ideally 1.5-2.0 mm of cortical plate thickness is needed to ensure both short-term and long-term stability of the plates. For these reasons, we often delay BAMP treatment until the age of 11. In the mandible, extraction of primary canines (M & R) will expedite the eruption of the permanent canine to help provide the inter-radicular space needed for the plates and screws.
If the permanent mandibular canines have not yet erupted, the mandibular plates can still be placed, however. In these special circumstances, we use the maxillary plates with 3 screw holes (in-line, not the Y-Design) and utilize the bottom 2 screws with the most apical hole placed just beneath the lateral incisor root. The plates are placed with a distal angulation – so that the hooks on the plates still emerge into keratinized gingiva in the region just buccal and apical to where the permanent canine crown will erupt.
The screws can either be inserted with the surgeon making small pilot holes or using self-drilling screws. We recommend the use of a pilot hole, as it decreases the mechanical stress on the bone and facilitates faster healing.
The plates are loaded 3-4 weeks after surgery, if they are stable. We test stability clinically at each plate before loading.
Initial traction is 100g per side for 6 weeks. The patient is instructed to wear the elastics 24/7 and to change the elastics at every meal. Make sure that the patient does not experience sharp or dull nagging pain when wearing the elastics. If the patient experiences sharp pain upon elastic loading, instruct them to discontinue elastic wear immediately. Sharp pain usually indicates plate instability. Stopping traction is most often the best way to allow the plates to re-stabilize.
After 6 weeks of initial loading, the traction force can be increased to 150g per side for an additional 6 weeks. The final loading force is 250g per side about 6 weeks later.
Often, patients who have a Class III skeletal relationship with a deepbite and anterior crossbite require some sort of bite-opening appliance to allow the crossbite to be most efficiently corrected. To accomplish this goal, we place temporary bite turbos on the mandibular first molars, but a retainer with a posterior bite plate is also effective.
Most often, we start BAMP treatment with a full fixed appliance in the lower arch to decompensate the mandibular incisors. Our experience suggests that young patients are more motivated to wear elastics until the anterior crossbite is corrected. By simultaneously decompensating (proclining) the lower incisors with a fixed appliance, we know the true amount of orthopedic correction needed in order to obtain positive overjet with an aligned mandibular arch.
Once positive overjet is obtained, we place full maxillary appliances and continue elastics to overcorrect to ~4mm overjet or ½ cusp Class II. Elastics can then be decreased to only night time wear for retention of the orthopedic improvement until mandibular growth is completed. After debond, the patient is seen every 6 months for growth observation. If the overjet decreases, we increase elastic wear to full time in order to help account for continued Class III mandibular growth. In the rare instances in which the overjet increases, the patient can cut elastic wear to every other night. The plates and screws can often be maintained successfully for several years and then removed in conjunction with 3rd molar extractions, if indicated.
In summary, the clinical protocol is as follows: