The Orthodontics Professors
the latest in contemporary & evidence-based orthodontics
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:
BY TATE H. JACKSON AND CHING CHANG KO
Orthodontic information is everywhere: from traditional publications to open-access web-based outlets to Facebook and Instagram.
Increasingly, we are confronted with a question:
A recent publication in the European Journal of Orthodontics offers an interesting perspective and approach.
Livas and Delli used a Web screening tool, Altmetric, to conduct an analysis of the visibility of articles published in eleven Orthodontics Journals in the popular press (e.g. New York Times), social media such as Facebook, and on-line citation managers like Mendely. The authors monitored visibility two time points, January and April of 2017 and reported the top 200 articles referenced, as well as an AAS (Altmetric Attention Score – range 1-199) for each article. The full list of the top 200 articles is here.
AAS serves as a measure of digital attention. In other words, how visible was the journal article in our web-based world - in the popular press and social media? A score of 1 indicates low visibility, while 199 indicates very high visibility.
Just three journals contributed 86% of the papers referenced digitally. The most popular articles were classified as “original research” and fell into the categories of “evaluation of treatment outcomes”, “growth”, “side-effects”, and “quality of life”. There was no association of visibility, as judged by AAS, with publication date or authorship.
What was the singular most “popular” article? It was a work from 2016 on pain control using a micropulse vibration device, published in the Angle Orthodontist; it received an AAS score of 196 (out of a possible 199).
The authors reported no association between AAS and citations in Scopus, one measure of peer-review scholarly citations, a traditional measure of the impact of research publications.
WHAT THE PROFESSORS THINK
The authors address an important and very timely topic. The traditional definition of impact factor is a measure of how often an paper is cited by other articles published in peer-reviewed journals. The concept of altmetrics moves outside of the academic sphere and into “real world exposure.”
The idea of almetrics has been around for nearly a decade now, but the recent surge in both the use and validation of social media outlets has re-focused the importance of both “alternative” sources of information and alternative ways to measure the impact of an idea or new knowledge.
Although there are several altmetric web applications, the use of Altmetric in this study appears to be reasonable. Gleaning results from multiple time points was appropriate. The association of AAS with Scopus data was also suitable as a means to compare Altmertic results with a more traditional measure of impact.
Only articles that have a doi (digitial object identifier) can be analyzed by Altmetric, and only a subset of Orthodontic journals were considered, so this investigation has limitations. Its real value is not so much in which articles were captured, but in demonstrating the methodology.
So what do these results really mean for Orthodontists?
Knowing what the popular press tells our patients about Orthodontics matters. That fact is not really new information. What is interesting is that there are simple and free ways to track topics and their exposure to the public. For example, one can download a browser plugin for free and then use it to instantly see if an article you have read has made it into the public domain.
You can investigate or try some of those tools here:
For the practicing Orthodontist confronted by new controversies and technologies, it is simply both practical and good practice to have a grasp not just on the best evidence, but also on what is being presented to our patients by way of both traditional and social media.
It is also informative that the most valued articles, as judged by traditional academic metrics, are not necessarily the most widely-read. That fact too may not really be new information. It is information that may continue to find relevance, however, as social media expands and new ways to spread knowledge develop more rapidly .
Article Reviewed: Livas C. & Delli, K. Looking Beyond Traditional Metrics in Orthodontics: An Altmetric Study on the Most Discussed Articles on the Web. Eur J Orthod. 2017.
BY TUNG T. NGUYEN, DMD, MS & HUGO DE CLERK MS, PHD
In 2008, an innovative approach to the treatment of Class III skeletal malocclusions in growing patients was introduced by Hugo De Clerk. Bone Anchored Maxillary Protraction (BAMP) uses intra-oral skeletal plates and intermaxillary elastics (IME) to produce true orthopedic changes by protracting the maxilla and redirecting growth of the mandible, without dentoalveolar side-effect.(1)
The purpose of this clinical multi-part series is to summarize 8 years of clinical research on BAMP and give clinicians the tools to apply this protocol to their daily practice.
Class III malocclusions are among the most difficult to treat, with a large percentage of these patients requiring orthognathic surgery after mandibular growth is complete (after 16-18 years of age). Ideally, the option of a successful treatment approach that avoids surgery is needed. Such a treatment would:
Conventional treatment for young Class III patients often involves extra-oral devices designed to either increase maxillary length or restrain mandibular growth. Both approaches have had limited success due to undesirable dentoalveolar movements, limited skeletal changes, poor compliance, or relapse of dental movements.
Even with appliance modifications to minimize tooth movement and maximize orthopedic correction, some dentoalveolar side-effects are inevitable because these appliances are attached to the teeth. In addition, compliance is critical for success with these treatment modalities. Unfortunately, compliance proves to be difficult, as these cumbersome and socially stigmatizing extra-oral devices require 12-18 hrs of wear per day. Even with good compliance, it is difficult to maintain the correction: 25% to 33% of these patients experience post-treatment relapse within a year.(2)
With Bone Anchored Maxillary Protraction, patient compliance was improved due to the discreet nature of intra-oral elastics compared to the cumbersome extra-oral headgear. In addition, our studies showed BAMP was significantly more effective than the current gold standard for early treatment of Class III and can be implemented at a later age.(3)
In this, Part I of our BAMP Series, we will discuss the background and some of the existing evidence for the efficacy of this treatment modality. In later parts, we will discuss the clinical technique, tips, and strategies for managing complications.
One of our initial studies involved the 3D analysis of treatment outcomes for BAMP. Twenty-five consecutive Class III patients were enrolled in the study.(4) Using 3D registration of initial and final Cone Beam Computed Tomography (CBCT) for patients treated using the BAMP protocol, we evaluated orthopedic changes in the maxilla, mandible, and glenoid fossa.
Using the BAMP protocol, we saw an average anterior displacement in the maxilla by approximately 3.7mm with a range from 1.5mm to as high as 8.5mm. One explanation for the high variations in treatment response between patients might be due to the diversity of the original malocclusions. Some of the Class III patients presented with a severe -5mm overjet while others manifested a mild edge to edge incisor relationship. Other reasons for the high variation in treatment response include compliance with elastics, age, skeletal malocclusion, and maturation of the cranial sutures at the start of treatment.
We also saw forward The displacement of zygoma and midface by approximately 3.7mm, a phenomenon that rarely occurs with other treatment modalities. To explain this phenomenon, we examined the circummaxillary sutures and saw that the BAMP protocol resulted distraction of many of these circummaxillary sutures. It may be plausible that a constant force from the elastics, when applied before sutural maturation can effectively produce distraction of these sutures resulting in the forward displace of the entire midface. Recent animal studies have shown that continuous force application is more effective at expanding the sutures when compared to intermittent forces.(5)
The changes in the anterior mandibular region were more variable in both magnitude and direction. Many subjects exhibited a distal displacement of the chin, while some continued to grow in a normal forward direction.(6) While the anterior position of the chin stay relatively the same throughout the course of treatment (-0.5mm), this was significant when compared against matched untreated Class III subjects, who showed an mean forward growth of 2.2mm during the same time interval.(1)
It is also interesting to note that the BAMP protocol did not restrain growth of the mandible - but instead, it altered the direction of mandibular growth by closing the gonial angle and distalizing the posterior ramus and condyles.(6) The glenoid fossa remodeled to adapt to the new position of the condyle. While these findings are promising; long term studies are needed to evaluate the stability of this compensatory mechanism as well as the health of the temporomandibular joint complex.
In summary, BAMP is a promising protocol for true orthopedic treatment, one that has the potential to reduce the need for orthognathic surgery in growing Class III patients.
In Part II of our BAMP series, we will address the BAMP clinical technique in detail.