Xbow System Lectures

The Four Tool Boxes for Class II Treatment

Informed consent is the legal responsibility of the orthodontist to explain the pros and cons of all possible treatment options, and to help the patient and their family determine which option is best for them.

One type of Class II bite problem is when there is a horizontal gap between the upper and lower front teeth, also known as excess overjet. 53% of the population has a Class II bite with an overjet greater than 3mm. 15% of the population has a moderate to severe Class II bite problem with 5mm or more of overjet.

The cause of excess overjet is usually a small or receding lower jaw and chin, but there can also be a protrusion of the upper front teeth.

The Four Tool Boxes Analogy

In Dr. Higgins’ office there are four different options for the treatment of a Class II bite problem.

1. The Surgery Tool Box
   Braces to straighten the teeth and place the front teeth and lips in an ideal position, followed by surgery to lengthen the lower jaw, is often the best option to correct the bite and balance the appearance of the nose, lips, and chin.
2. The Traditional Treatment Tool Box
   Braces and the extraction of two upper teeth are used to retract or “pull back” the upper front teeth to correct the bite and camouflage the small or receding lower jaw and chin. We call this Class II compensation. This is a good choice if the upper front teeth are crowded or protruding. The down side of this treatment is it can result in loss of upper lip fullness.
3. The Crossbow Tool Box
   The Crossbow Class II Corrector shares the correction between the upper and lower teeth. It moves upper teeth back and lower teeth forward. This minimizes the retraction of the upper front teeth and upper lip. This is another type of Class II compensation. It is meant to be used in a growing patient, and works best if the patient is in their growth spurt. The down side is that it still moves the upper lip back, just not as much as traditional extraction treatment. It also moves the lower lip forward, which can be a plus or a minus. Even if surgery is the best option, most patients still choose the Crossbow Tool Box, to avoid surgery and extractions. Sometimes the Crossbow is not a good option, especially if the patient is finished growing, or if the lower front teeth are crowded or protruded, or if the lower lip is protruded.
4. The Class II Elastic Tool Box
   Braces or Aligners combined with Class II elastics is probably the most common treatment in use today. It is popular because it is the least expensive. It requires the least effort by the orthodontist, but the most effort by the patient. Simply put, if the patient does not wear the elastics, they end up with straight teeth but with a remaining bite problem, or excess overjet. If the patient wears the elastics well, the result may be similar to the Crossbow, with two exceptions. One, Class II elastics have a tendency to pull the upper front teeth down, making a gummy smile worse. Two, when used with aligners Class II elastics may push the lower front teeth out of the bone, exposing the roots. The other problem with aligners is they require much more patient cooperation than braces, and there are many tooth movements that aligners don’t do well or not at all. This is why the best orthodontists that use aligners use them in conjunction with braces. Braces are still used to do the “heavy lifting”.The general rule is it is best to choose a treatment plan that decreases elastic wear and patient cooperation because poor cooperation can increase the length of treatment. Long treatment time increases the risk of root resorption (root shortening) and decalcification (white spot lesions or cavities).Dr. Higgins has developed systems that decrease the time in braces to 12 to 18 months, even for extraction treatment. This includes indirect (precision) bonding of brackets (braces). He also uses a low force technique with a smaller bracket slot and smaller wires compared to the majority of orthodontists. This is more comfortable for the patients and may result in less root resorption.

   The Crossbow appliance is part of Dr. Higgins’ “foundation building” philosophy of treatment. It is based on the principle of waiting until all teeth have erupted, including second molars, before placing full braces. “Building the foundation” includes establishing a normal upper jaw width with an expander (RME), correcting a Class II bite with a Crossbow appliance, and opening space for upper canine teeth with partial braces (RME X 6).

   Dr. Higgins is a clinical assistant professor at the University of British Columbia. More information can be found on the Crossbow website at www.crossboworthodontic.com.

Foundation Rules

1. Treat the biggest problem first.
2. Sequence treatment based on the eruption.
3. Begin with primary maxillary expansion if there is a posterior crossbite or if the maxillary lateral incisors are impacted. These teeth erupt at 8 to 9 years old on average.
4. Time first phase treatment when the first bicuspids are erupting at 10 to 12 years old to make room for the erupting maxillary canines at 11 to 12 years. This will reduce the incidence of impacted maxillary canines.
5. Don't place full edgewise appliances until the second molars have erupted or you will prolong your second phase treatment and increase decalcification and root resorption.
6. Save cooperation with Class II elastics in deep overbite cases until you are in full-size stainless steel arch wires and the overjet is reduced enough to place a bite turbo.
7. Try to postpone IPR (interproximal reduction) of the incisors until all spaces are closed, the buccal occlusion is Class I, and the overbite and overjet are corrected. The goal is to create long, flat interproximal contacts without black triangles keeping in mind not to create a tooth mass discrepancy. This is impossible to do with early IPR.
8. Always go back to the foundation base during treatment to make sure the patient can breathe through the nose, keep the tongue on the anterior palate, swallow without a tongue thrust, and keep the lips together at rest, if possible.
9. Initial, posterior Crossbite, & Anterior Crowding

RME X 6: Combining Maxillary Expansion & Anterior Alignment to Establish the Maxillary Foundation

The Xbow System is based on treating to an ideal maxillary arch form and width. Combining anterior alignment with Rapid Maxillary Expansion is more effective than archwire expansion by itself.

RME X 6/Xbow Cases Treated by Dr. Higgins

This next patient is an example of upper anterior crowding where the molars are Class I but the bicuspids are a half cusp Class II and the upper canines are blocked out and a full cusp Class II. This required an RME X 6 appliance to align the anteriors before the placement of the Triple "L" Arch and springs.

Class III Malocclusion

The RME X 6 is used with Class III malocclusions when maxillary expansion and/or upper incisor proclination is indicated. A reverse pull headgear (protraction face mask) can be added by attaching elastics to the first bicuspid hooks or the long ends of the archwire distal to the bicuspid tubes.

Class II Compensation Compared to Class III Compensation

In Dr. Casko's untreated ideal occlusion study where the ANB angle was -3 degrees, the lower incisor was compensated back to 83 degrees while the upper incisor was compensated out to 120 degrees. In order to prevent Class III surgery orthodontists will procline upper incisors out to 120 degrees without a second thought, which is 18 degrees past the norm. The same orthodontists may criticize a lower incisor proclined to 106 degrees in a Class II patient, which is only 10 degrees past the norm.

Same patient as above, flipped lower to upper. Why should a Class II be treated differently than a Class III?

Proclining Upper Incisors to Avoid Cl III Surgery

Maxillary expansion only to open space for the upper lateral incisors, mandible rotated down and back, correcting the anterior crossbite.

Combination Active Anteriors and Passive Posteriors (CAAPP) Orthodontic Skating: Sliding with Control

.018 inch bracket slot, .018X.025 inch archwire, Carriere passive self-ligating bracket sliding on archwire with Innovation active self-ligating brackets acting as end stops.

.018 inch bracket slot, .016X.022 inch archwire, Lotus Plus passive self-ligating bracket sliding on archwire with Lotus Plus interactive self-ligating brackets acting as end stops.

In a group of 145 consecutively debonded patients from the author's practice, the average treatment time from bonding to debonding was 16 months. 78% of the patients had an average treatment time of 13.4 months.

The part of treatment that the orthodontist has control over (other than the treatment plan) is Alignment and Space Closure (ASC). The patient has control over elastic wear to coordinate the arches and finish the occlusion. In a group of 42 consecutively treated patients where 34 were non-extraction and 8 were extraction cases, ASC took an average of 9 months to complete for the non-extraction group and 11 months for the extraction group.

The following is a bicuspid extraction case showing rapid alignment with CAAPP.

Four arch sizes=three pairs (Small, Medium, Large)
To purchase these wires in most sizes contact Mark James at G and H Orthodontics.

The Class II Compensation Compromise: Preserving the Upper Lip

As an orthodontic student in 1979 we were taught that our tool for a Class II malocclusion was orthodontic retraction and every problem was a protrusion.

Our toolbox had headgear and upper bicuspid extraction in it. In an emergency we could pull the red handle and use Class II elastics, but only if the lower incisors were retroclined or if we also extracted lower bicuspids. We looked at the models and the hard tissue ceph measurements.

For years I have been looking at the face as the most important determinant of which treatment I should recommend. For Class II patients this often means I will recommend jaw surgery as the best treatment. If the patient declines surgery I tell them treatment will involve dental compensation for their underlying jaw problem and that a compromise will involve a certain amount of upper incisor and upper lip retraction.

To minimize the retraction, Xbow shares the correction with the lower arch. This means lower incisor proclination and pemanent retention.

Xbow proclines lower incisors 3 degrees on average after a short period of over-proclination and rebound uprighting. In an unpublished study at the U of Alberta on 172 consecutively treated Xbow patients, the average lower incisor started at 99 degrees and ended up at 102.

The literature is very clear. Lower incisor proclination does not cause gingival recession in healthy periodontium.

The literature is also very clear that all inter-arch Class II appliances procline the lower incisors a similar amount, even functional appliances. The non-edgewise Herbst appliance is capable of temporary over-proclination of the lower incisors similar to Xbow. This same over-correction is why the results are stable, and why phase two is shorter.

Xbow two phase non-extraction treatment to preserve the upper lip

The Xbow system for Class II compensation is based on building the maxillary foundation for ideal treatment as if we were proceeding with jaw surgery. After maxillary expansion and upper anterior alignment, instead of proceeding with full braces and jaw surgery, we use the Xbow appliance to share the correction between both arches to minimize retracting the upper incisors and upper lip, compared to headgear or upper extractions.

This case shows the importance of non-extraction treatment and not over-retracting the upper lip in a Class II patient with a convex profile.

Profile change after 7 months Xbow, after photo taken 2 months after spring removal

Initial to Progress after 7.5 months Xbow and maxillary expansion. Profile change possible with short lower facial height.

This case is an example of non-extraction treatment in a Class II crowded deep overbite malocclusion with a convex profile.

Surgical correction to preserve the upper lip. Initial to 15 months total treatment time including lower bicuspid extraction site space closure and lower jaw surgery by Dr. Bill McDonald.

After lower bicuspid extraction site space closure and lower jaw surgery by Dr. Bill McDonald. The upper second molars are unopposed and can be removed if they ever cause a problem which is very rare.

There are only two upper molars in occlusion and the molar relationship is Class III. In these cases we look for a Class I bicuspid relationship. When a patient chooses surgery we concentrate on ideal facial esthetics.

The upper incisors are slightly proclined which prevents the upper lip from hanging straight down. This creates complementary curves between the nose and upper lip, and the lower lip and chin. Upper lip projection should be slightly ahead of the lower lip. Lower lip projection should line up with chin. The nose blends in beautifully with the face.

Below are pretreatment cephs with Class I skeletal patterns with good lip fullness, but different soft tissue convexity angles and midface development.

The goal should be to maintain the upper incisor position. If this is not possible it is better to end up with a slight protrusion and long-term retention instead of a retrusion based on the wishful thinking of better stability. We cannot predict how much more nasal growth will occur, only that it will.

More Compromises

This is a common conversation I have with orthodontists that criticize Crossbow. It starts by an orthodontist saying he uses headgear to prevent lower incisor proclination. I ask what if the patient doesn't wear the headgear? The orthodontist will reply that they will add Class II elastics. I add that will procline lower incisors. They reply that they use a full size wire and -6 degree lower incisor brackets to prevent the lower arch from coming forward. (Myth) I ask what if the patient doesn't wear the elastics. They reply that is when they place Forsus Springs. I add that will push the lower arch forward. They reply not if they use a full size wire and -6 degree lower incisor brackets. (Myth)

I ask what if they see side effects like posterior openbite, upper molar flaring, or occlusal plane canting. They reply they add vertical elastics. I thought they wouldn't wear elastics. They reply the result will be a compromise:)

Lower incisor proclination is not ideal, but neither is orthodontic compensation when the ideal treatment is jaw surgery. Sometimes we get lucky and the patient and parents agree to ideal treatment. Sometimes we compromise.

The Debate Over Lower Incisor Proclination and Gingival Recession

Read More

Crossbow’s Competition: Dealing With Side Effects

Read More

1981-1984: I was an associate with my mentor, Dr. Michael Wainwright. He taught me indirect bonding, two-phase treatment, and combined orthodontic/orthognathic surgical treatment.

1984: I opened my office in North Delta. I began using functional appliances. I took a ceph at the final records.

I was proclining lower incisors with the functional appliances, but I was not seeing gingival recession. This became a subject that would interest me for my entire career.

Dr. Casko published his findings that questioned Tweed's 95-degree IMPA in untreated Class II skeletal patterns with Class I occlusions. More myth debunking.

Dr. Casko believed that incisor inclination was linked to the skeletal pattern and showed that it was normal for the lower incisor to have an IMPA higher than 95 degrees in an untreated skeletal Class II with a Class I occlusion.

He argued that this should be the goal for Class II compensation.

Example from my practice:

Naturally occurring Class II skeletal with Class I dental and a retroclined upper incisor and proclined lower incisor

Dr. Creekmore agreed with Dr. Casko.

1990: My study club invited Dr. William Clark to speak to us about twin blocks. I began using them.

1991: Dr. DeVincenzo publishes his research which is the first of many to question the ability of functional appliances to increase mandibular length in the long term. Dr. Lysle Johnston coined the term "mortgaging mandibular growth".

More myth debunking.

1995: I began using the four crown Herbst appliance which got me interested in non-compliance appliances.

My main concern was with over-correction I was seeing noticeable lower incisor proclination that I had not noticed with removable functional appliances. I tried placing -5 to -10 degree lower incisor brackets but instead of proclining the lower incisors I noticed that the bodily mesialization of the incisors resulted in a "washboard effect". I preferred tipping the lower incisors temporarily and then allowing them to upright before phase two.

The important thing was I did not see the gingival recession that I had been taught would happen.

Dr. Alan Lowe developed the Klearway appliance for snoring and sleep apnea. Long term wear has resulted in severe proclination of lower incisors without significant recession.

1997: Dr. Pancherz published his summary of the effects of the Herbst appliance. There was no long term increase in mandibular length. He did not recommend it in non-growing patients, possibly due to the risk of condylar resorption, which he had shown. (Dr. Woodside also showed condylar resorption with the Herbst appliance. When I lectured at the University of Toronto, Dr. Woodside commented that the Crossbow Appliance was probably kinder to the condyle than the Herbst appliance because the springs were stress breakers and allowed the condyle to function in the fossa.)

The takeaway message was that mixed dentition treatment was not recommended because "a stable cuspal interdigitation after therapy is difficult to achieve and relapses are prone to occur." Pancherz had proven what Dr. Herbst called "the bite catching effect".

Thanks to Dr. Herb Hughes for the above slide showing over-correction with Xbow and the bite catching effect of the steep cuspal inclines of the first bicuspids.

1998: Dr. Jay Bowman published an article in the JCO using Jasper Jumpers attached to a lower lip bumper instead of a bypass. I was convinced that most Class II's required maxillary expansion. I was also using lower lingual arches to preserve the "e" space. I added a lip bumper and Ormco's Bite Fixer springs. This led to the Xbow appliance.

Dr. Pancherz publishes his findings on the Herbst appliance and gingival recession.

2000: Dr. Gianelly gives us a target to shoot for.

2001: Granted a US patent and registered trademarks for the Xbow

2002: I lectured on the Xbow appliance with Dr. Pancherz at the GLAO/MASO meeting. We discussed lower incisor proclination and agreed that temporary over-proclination followed by uprighting did not cause a gingival recession and in fact over-correction followed by the bite catching effect and cuspal interdigitation was necessary for long term stability.

2009: First Xbow research paper published in the AJODO after working with Dr. Carlos Flores-Mir at the U of Alberta.

We showed the lower incisor proclined a similar amount to the Herbst appliance. A total of seven papers on Xbow would be published as a result of Dr. Flores-Mir's effort.

2013: Drs. Bob Miller and Carlos Flores-Mir publish the definitive research paper on the efficiency of two phase Xbow treatment compared to one phase Forsus to the arch wire treatment.

2015: The data from 172 consecutively treated Xbow patients was studied at the U of Alberta. An interesting finding was that the average initial lower incisor inclination was 99 degrees. This agrees with Dr. Casko's belief that Class II skeletal cases are naturally compensated.

2016: I was asked to speak at the AAO Scientific Session. My conclusion was that the results are similar for all inter-arch Class II appliances. The differences are probably not clinically significant. We should be focusing on preserving the upper lip and treatment efficiency, including decreasing the treatment time in full edgewise appliances.

2017: Dr. Gianelly's 76% non-extraction target looks right on.

The eye-opener:

2019:

These are some heavy hitters in our profession. Dr. Buschang's research has shown there is little evidence to prove that lower incisor proclination causes gingival recession. Dr. Behrents told us in 1981 that some recession was normal and that severe recession could be prevented as long as there was an attached gingiva present or a graft placed before ortho.

Dr. Lindauer asked me to speak on Crossbow at the AAO in 2016.

Part 3: Ancient History

Dr. Angle's Class II "bite-jumping" appliance, photo courtesy of Dr. Lysle Johnston. This would have resulted in lower incisor proclination. If this caused gingival recession Dr. Angle would have reported it.

Dr. Angle's students, Begg and Tweed, stopped doing what they had been taught and followed the teachings of Calvin Case. Dr. Tweed was able to control the torque of the upper incisors as he retracted them to reduce the overjet in Class II's. He was also able to level the Curve of Spee with full-size rectangular archwires and Class II elastics to erupt the lower posterior teeth. When you just looked at the model's Tweed was able to make a Class II case look like an ideal Class I skeletal-dental, complete with upright incisors. In 1930 Dr. Broadbent invented the cephalometer, which allowed Tweed to measure the inclination of the incisors and compare his results to untreated Class I dental-skeletal patients. This led to the Tweed Triangle and the goal of treating an upright lower incisor. Tweed was known for saying, "Put your plaster on the table," but it was the cephalometric measurements that gave scientific support to the upright lower incisor.

It wasn't until 1956 that Tweeds results were studied closely by Drs. Stoner and Lindquist at Indiana University. Their study "Consecutive Cases Treated by Dr. Charles Tweed" was published in the Angle Orthodontist.

It looked at the claim that Tweed mechanics resulted in improved facial esthetics.

The main finding was that overjet reduction was almost all by upper incisor retraction.

I met Dr. Lindquist while I attended Indiana University. He was the first orthodontist that I heard warn of over-extracting. He said that serial extracting was a "self-fulfilling prophecy" in that extracting primary canines increased the odds that first bicuspids would need to be extracted. He advised to only extract lower primary canines if the lateral incisors were impacted or blocked out.

Upper Airway Changes after Xbow appliance Therapy Evaluated with CBCT Angle Orthodontist, Vol 84, No 4, 2014

Conclusions

1. Treatment with the Xbow appliance in Class II patients resulted in favorable dental and skeletal changes in the direction of a Class II correction.
2. In cephalometric and three-dimensional evaluation of the upper airway, increase in the oropharyngeal airway dimensions and volume was observed.

There were no changes in the nasopharyngeal region and adenoid tissues.

The patient was previously treated for sleep apnea with an intraoral mandibular repositioning appliance which gave temporary relief until the malocclusion which resulted from tooth movement became too great. She stopped the intraoral appliance and used a CPAP machine until the time of her surgery. She has not needed CPAP since her jaw surgery.

Airway before and after maxillary and mandibular advancement surgery by Dr. Bill McDonald. The combined orthodontic/orthognathic surgery was done to treat a malocclusion, but the patient coincidentally had severe sleep apnea and was being treated with CPAP. The patient stopped using CPAP immediately after the surgery.

Dr. Reginald H.B. Goodday, associate professor and head, division of oral and maxillofacial surgery, Dalhousie University was on an expert panel with Dr. Higgins on the treatment of Class II malocclusion at the 2014 Canadian Association of Orthodontists Scientific Session. Dr. Goodday spoke on the orthodontist's and surgeon's role in the treatment of Obstructive Sleep Apnea.

He said "In patients with identifiable anatomic abnormalities of the maxilla and mandible resulting in a narrow pharyngeal airway, orthognathic surgery appears to be an excellent treatment option." In a recent communication the author asked Dr. Goodday to review the following section for accuracy. He added: "My intention was to provide information that would encourage this specialty to think long term when recommending treatment options to young patients. I also feel that patients should be informed of an underlying jaw deformity and why it should be considered  when deciding  on treatment options." His advice to orthodontists included the following:

1. Severe Class II skeletal patients with retognathic mandibles may develop OSA.
2. These patients are best treated with combined orthodontic/orthognathic surgery with mandibular advancement and possibly maxillary advancement as well.
3. In these cases orthodontic decompensation gives the best esthetic and airway result. Decompensation involves non-extraction in the maxilla and two bicuspid extraction in the mandible.
4. In young patients with Class II skeletal patterns that choose a non-surgical treatment plan, thought should be given to consevative treatment that will allow combined orthodontic/orthognathic surgical treatment to be done in the futrure.

Non-surgical treatment planning should keep in mind the following points:

• Pure upper incisor retraction in a severe mandibular retrognathic patient may result in an unesthetic increase in the naso-labial angle.
• This may lead to posterior positioning of the tongue.
• It also makes it difficult for the future surgeon to achieve an esthetic result as well as normalizing the airway. The maxilla may need to be advanced more than if the upper arch was previously treated non-extraction.
• Four bicuspid extraction to retract the incisors and close an anterior openbite may encroach on tongue space.

If the lower incisors are proclined and the profile is convex with a retrognathic mandible, the best treatment may be the extraction of lower first bicuspids, the retraction and uprighting of the lower incisors, and mandibular advancement surgery, with possible maxillary surgery with posterior impaction if a skeletal openbite exists.

• In severe cases where surgery is the only option and the patient declines but still wants some improvement, alignment only and leaving the malocclusion may be the best alternative, instead of over-retracting the upper incisors.
• Take a family history of snoring and sleep apnea.
• Consider early maxillary expansion and a non-extraction approach in borderline extraction patients instead of serial extractions.
• Refer for possible adenoid and tonsil removal in airway obstructed patients. If the maxilla is constricted a combination of maxillary expansion and adenoid and tonsil removal has been shown to give the greatest improvement.

I use the following types of retainers:

Full Coverage Essix Retainers

Essix retainers a re very good at maintaining the entire arch and keeping spaces closed. Upper and lower essix retainers resist wear due to plastic against plastic. Whenever there are natural teeth against essix plastic the retainer will need replacement in as short a time as one year, depending on the grinding habits of the patient. This is why upper and lower essix retainers act as a grinding or bruxing guard and help to cushion the TM joint.

After the braces are removed impressions are taken and two upper and two lower Essix retainers are made in our lab and delivered to the patient on the same day. An appointment is made for one month later. At that appointment final photos are taken and the retainers are checked. The patient is given the models that the retainers were made on so that if a retainer is lost a new one can be made immediately.

It is important that the patient always has two sets of retainers so that if one is lost there is always a backup. The models are made of resin-reinforced stone that resists breakage and allows multiple retainers to be made.

Patients are asked to wear the retainers full time for one week and then every night after that for two years. At that time the patient is given the option of wearing the retainers less but at least two nights per week, or continuing with every night.

Bonded Lingual Retainers

Full coverage Essix retainers are made for all patients to be worn at night, even if they have bonded lingual retainers. This is to retain posterior teeth and closed extraction sites. If a bond fails on a fixed lingual retainer (and they do) the Essix retainer is worn full time to maintain tooth positions until a new lingual retainer is bonded indirectly.

Lingual Retainers Indirect Bonded Before Debond

Lingual Retainer on Model & In Transfer Tray and Lingual Retainer Bonded to Canines Only, Always Combined with a Removable Essix

The Following Articles Reinforce Why I Like Essix Retainers

1. Casko J, Shepherd W.  Dental and Skeletal Variation Within the Range of Normal.  Angle Orthod 1984; 54: 5-17.
2. Sameshima GT, Sinclair PM. Predicting and preventing root resorption: part II. Treatment factors. Am J Orthod Dentofacial Orthop 2001;119:511-5.
3. Sondhi, Anoop:  Efficient and Effective Indirect Bonding.  Am J Orthod Dentofacial Orthop 1999;115:352-9.
4. Kalange J: Ideal appliance placement with APC brackets and indirect bonding. J Clin Orthod 33:516-526, 1999
5. Brin I. Tulloch C. Koroluk L. Philips C. External apical root resorption in Class II malocclusion: A retrospective review of 1- versus 2-phase treatment. Am J Orthod Dentofacial Orthop 2003; 124:151-6.
6. Higgins D. Indirect Bonding with Light-Cured Adhesive and a Hybrid Transfer Tray. Semin Orthod 2007;13:64-68.
7. Miles P, Weyant R,  Rustveld L. A clinical trial of Damon 2 vs conventional twin brackets during initial alignment.  Angle Orthod 2006; 76: 480-485.
8. Harris D, Jones A, Darendeliler A.  Volumetric analysis of root resorption craters after application of controlled intrusive light and heavy orthodontic forces: A microcomputed tomography scan study.  Am J Orthod Dentofacial Orthop 2006; 130: 639-647.
9. Badawi H, Toogood R, Carey J, Heo G, Major P.  Torque expression of self-ligating brackets.  Am J Orthod Dentofacial Orthop 2008;133:721-8.
10. O'Brien, K et al. Effectiveness of treatment for Class II malocclusion with the Herbst or Twin-block appliances: A randomized, controlled trial. Am J Orthod Dentofacial Orthop 2003;124:128-37.
11. Ruf S, Hansen K, Pancherz H. Does orthodontic proclination of lower incisors in children and adolescents cause gingival recession? Am J Orthod Dentofacial Orthop 1998;114.
12. Barbagallo L, Jones A, Petocz P, Darendeliler A. Physical properties of root cementum: Part 10. Comparison of the effects of invisible removable thermoplastic appliances with light and heavy orthodontic forces on premolar cementum. A microcomputed-tomography study. Am J Orthod Dentofacial Orthop 2008;133:218-27
13. Carlos Flores-Mir, Abenaa Ayeh, Ashim Goswani, Shouresh Charkhandeh. Skeletal and Dental Changes in Class II division 1 Malocclusions Treated with Splint-Type Herbst Appliances.The Angle Orthodontist The Angle Orthodontist Volume 77, Issue 2 (March 2007) pp. 376-381
14. Carlos Flores-Mir, Michael P. Major, Paul W. Major. Soft Tissue Changes with Fixed Functional Appliances in Class II division 1. The Angle Orthodontist Volume 76, Issue 4 (July 2006) pp. 712-720
15. Carlos Flores-Mir, Paul W. Major. Cephalometric Facial Soft Tissue Changes with the Twin Block Appliance in Class II division 1 Malocclusion Patients. The Angle Orthodontist Volume 76, Issue 5 (September 2006) pp. 876-881
16. Sayeh Ehsani, Marie-Alice Mandich, Tarek H. El-Bialy, Carlos Flores-Mir. Frictional Resistance in Self-Ligating Orthodontic Brackets and Conventionally Ligated Brackets. The Angle Orthodontist Volume 79, Issue 3 (May 2009) pp. 592-601
17. Amy Archambault, Ryan Lacoursiere, Hisham Badawi, Paul W. Major, Jason Carey, Carlos Flores-Mir. Torque Expression in Stainless Steel Orthodontic Brackets. The Angle Orthodontist Volume 80, Issue 1 (January 2010) pp. 201-210
18. Anchalee Paetyangkul, Tamer Türk, Selma Elekdağ-Türk, Allan S. Jones, Peter Petocz, M. Ali Darendeliler. Physical properties of root cementum: Part 14. The amount of root resorption after force application for 12 weeks on maxillary and mandibular premolars: A microcomputed-tomography study. American Journal of Orthodontics & Dentofacial Orthopedics October 2009 (Vol. 136, Issue 4, Pages 492.e1-492.e9)
19. Short-term skeletal and dental effects of the Xbow appliance as measured on lateral cephalograms. Carlos Flores-Mir, Gregory Barnett, Duncan W. Higgins, Giseon Heo, Paul W. Major. Am J Orthod Dentofacial Orthop 2009; 136: 822-32
20. Three-dimensional orthodontic force measurements. Hisham M. Badawi, Roger W. Toogood, Jason P. R. Carey, Giseon Heo, Paul W. Major. Am J Orthod Dentofacial Orthop 2009;136:518-28
21. Lower incisor inclination changes during Xbow treatment according to vertical facial type. Carlos Flores-Mir, Arden Young, Amira Greiss, Matthew Woynorowski, James Peng. Angle Orthod 2010;80:1075–1080.
22. Self-ligating vs conventional brackets in the treatment of mandibular crowding: A prospective clinical trial of treatment duration and dental effects. Nikolaos Pandis, Argy Polychronopoulou, Theodore Eliades. Am J Orthod Dentofacial Orthop 2007;132:208-15.
23. Orthodontic therapy and gingival recession: a systematic review. Joss-Vassalli I, Grebenstein C, Topouzelis N, Sculean A, Katsaros C: Orthod Craniofac Res 2010;13:127–141.
24. Interarch Maxillary Molar Distalization Appliances for Class II Correction. Berkman M, Haerian A, McNamara J. J Clin Orthod 2008;42:35-42.
25. Effectiveness of orthodontic treatment with functional appliances on mandibular growth in the short term. Elvira Marsico, Elda Gatto, Maryalba Burrascano, Giovanni Matarese, and Giancarlo Cordasco. Am J Orthod Dentofacial Orthop 2011;139:24-36.
26. Treatment effects of the edgewise Herbst appliance: A cephalometric and tomographic investigation. Ryan VanLaecken, Chris A. Martin, Terry Dischinger, Thomas Razmus, Peter Ngane. Am J Orthod Dentofacial Orthop 2006;130:582-93.
27. Prediction of lower incisor proclination during Xbow treatment based on initial cephalometric variables. Tehnia Aziz; Usama Nassar; Carlos Flores-Mir

Angle Orthodontist Online, October 2011.

The Xbow® Class II Corrector is protected by the following patents:

US Patent No. 6,168,430 B1
Canadian Patent No. 2,392,021
Australian Patent No. 774128
Taiwan Patent No. 143,056

Herbst is a trademark of Dentaurum, Inc.
APC, Filtek, Forsus, SmartClip, Transbond, and Unitek are trademarks of 3M Company.
Crossbow, Xbow, Triple "L" Arch and "Straight to the Target When Straight is the Target" are registered trademarks of Dr. Duncan W. Higgins.
Aquarium is a trademark of Dolphin Imaging and Management Solutions.