The Xbow® Orthodontic Treatment System


This page is divided into the following:

1. Xbow® (Crossbow®) Blended Two Phase Treatment

2. The Class II Compensation Compromise

3. Airway and Obstructive Sleep Apnea

All images are the property of Dr. Duncan W. Higgins

and cannot be copied or reproduced without the consent of Dr. Higgins.

The Xbow System is focused on the best outcome in the shortest time possible.

The Higgins Xbow® (Crossbow®) Class II Corrector, the CAAPP low force system of braces,

and Dr. Higgins' Indirect Bonding technique all add up to less time in braces,

usually 12 to 18 months.


Xbow (Crossbow) Blended Two Phase Treatment


The Xbow system focuses on hitting phase one targets so there is less to do in phase two.

The critcal components of Xbow phase one are:

1. Beginning after the maxillary first bicuspids erupt to make space for the erupting canines.

2. The RME is essential as practically all Class II's require maxillary expansion.

3. The Triple "L" Arch allows the use of Class II springs with the RME to correct overjet and open space for maxillary canines in phase one.

4. The Class II spring side effects such as posterior openbite settle between phases instead of the need for elastics to

counter the side effects late in single phase treatment.

The Xbow phase including compensatory maxillary expansion takes approximately one year. The second phase in full braces also takes

approximately one year.

The end result is that the lower incisors are proclined 4.6 degrees on average which is similar to untreated, naturally compensated Class I occlusions

with Class II skeletal patterns.

Xbow opens space for upper anterior alignment by bicuspid and molar distalization and transeptal fiber tension, and reduces overjet by passive retraction,

without a continuous archwire to the upper incisors.

The goal is to maintain or enhance upper lip fullness.

Xbow has been studied at the University of Alberta which has resulted in seven published articles in peer reviewed orthodontic journals.


Drs. Miller, Tieu, and Flores-Mir's article titled "Incisor inclination changes produced

by two compliance-free Class II correction protocols for the treatment of mild to

moderate Class II malocclusions" is in the online version of the Angle Orthodontist.

It is based on Dr. Bob Miller's clinical study.

He compared 36 Class II patients treated in one phase with Forsus to the archwire

in a full edgewise appliance to 38 similar Class II patients treated in two phases

with Xbow followed by a full edgewise appliance. The Forsus to the archwire group

was finished in an average of 30.2 months (between records). The Xbow group was finished

in an average of 24.2 months (between records), which included a 4 to 6 month rest period

to allow for relapse. The two phase Xbow patients were completed 6 months faster on

average than the one phase Forsus to the archwire patients (time between records). 

The Forsus to the archwire group had full braces for an average of 26.75 months. The

Xbow group had full braces for an average of 16.68 months, or 10 fewer months.

There was no significant difference in the lower incisor to mandibular plane angle

between the two groups. The Xbow patients ended up with lower incisors at an average

of 100 degrees to mandibular plane which is considered a reasonable compromise for

non-extraction Class II compensation.

Editor's note: Longer treatment time with Forsus to the archwire is due to dealing

with the spring side effects late in treatment such as posterior openbite and

buccal flaring of the upper molars. The greater the correction the greater the

side effects and the longer it takes to deal with them.

There is no buccal flaring of the upper molars with Xbow.

Much of the posterior openbite and proclination of the lower incisors rebound

before full braces are placed.

Unilateral openbite and occlusal cant after unilateral Class II spring on the archwire.

This side effect requires good elastic compliance to resolve.

Initial unilateral Class II

Left spring only

Over-correction after 5 months, incisors edge to edge, note side effect of posterior openbite but no anterior occlusal canting

After 1 month settling

After 2 months settling

After 5 months settling

Over-correction and rebound is important when using Class II springs because the movement is rapid and the teeth are mobile and relapse quickly.

Lower incisor proclination is an unstable movement. It makes sense to perform over-correction and allow rebound of lower incisor proclination

in phase one instead of late in phase two.

If the plan includes an RME and lower lingual arch anyway, why not add Class II springs instead of waiting for the permanent dentition,

a full edgewise appliance, and rectangular wires?

Crossbow is something to do while your Class II patient is growing and you are waiting for second molars.


Xbow with springs for 4 months, day of spring removal and beginning of compensatory maxillary expansion.

This is why we segment the archwire distal to the upper canine before connecting the spring. Note the tipping of the buccal segment occlusal plane

and the eruption of the first bicuspid. Xbow prevents the eruption of the upper anteriors and loss of torque.

The intrusion of the upper first molar will relapse but extrusive or eruptive movements will not.

Bite opening in phase two with eruption mechanics (bite turbo and Class II elastics) while

the patient is growing and mandibular growth can compensate for the downward and backward

rotation of the mandible. This is not the best time to be using intrusive mechanics with Class II

springs to the archwire which results in side effects such as posterior openbite, canting, and

buccal flaring of the upper molars. The correction of these side effects prolongs treatment

time in full edgewise appliances.



The Xbow system uses eruption based treatment sequencing which begins when the first bicuspids

erupt in order to make space for the erupting maxillary canines. Full edgewise appliances are not

placed until the second molars erupt.

The Class II Compensation Treatment Pyramid is built on normalizing the maxillary width and idealizing the anterior archform.

This is done for 4 reasons:

1. Increasing arch length to decrease the need for bicuspid extractions.

2. Smile esthetics of an ovoid arch form compared to a tapered arch form.

3. Normalizing tongue posture to an anterior palatal position. This can only occur with nasal breathing.

4. Removing anterior interferences and unlocking a Class II occlusion to allow the lower dentition to mesialize

with normal mandibular growth. It also allows lower labial and buccal uprighting in a deep overbite.

Space for the upper incisors and canines is opened by four methods.

1. Primary maxillary expansion to make space for the upper lateral incisors which usually erupt at 8 to 9 years of age.

2. Proclining upper incisors if they are retroclined with the RME X 6.

This can begin as early as 10 to 11 years of age after the upper first bicuspids erupt but is most effective when done

while the upper canines are erupting, around 11 to 12 years old.

3. Distalizing the upper bicuspids and molars with Xbow, usually at around 11 to 12 years old.

4. Ovoid archwire expansion with a full edgewise appliance. Full braces are not placed until the second molars have erupted,

usually 12 to 13 years of age.

This final treatment stage usually takes place on average between 13 and 14 years old.

The correction of a deep overbite with full braces, an anterior bite-turbo, and Class II elastics is best accomplished

during a period of growth so that compensatory mandibular growth occurs to compensate for the

downward and backward rotation of the mandible.


Initial, posterior crossbite and anterior crowding

4 years after maxillary expansion

Xbow with springs removed after 3 months, followed by compensatory maxillary expansion, no braces used, photos taken 2 years after Xbow removal

________________Initial ______________________4 years after maxillary expansion_____________2 years after Xbow, no braces used_____

Archform expansion maintaining molar width



Problem: Over-retracting the upper incisors and upper lip.

Solution:  Share the correction between the upper and lower to decrease upper lip retraction with Xbow.


1. RMEX4 followed by Xbow, springs for 3 months. 2. Full braces for 1 year

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____________________________________Progress after 7.5 months Xbow and maxillary expansion

Profile change possible with short lower facial height


Impinging overbite

1. Upper 2X6 and posterior bite openers, 2. 6 months Xbow followed by compensatory maxillary expansion,

now hold expansion and test Cl II correction for 5 months

Day of bite opener switch from posterior to anterior (bite-turbo) 5 months into full braces

______________posterior bite openers______________________________bite openers removed_______________

We begin most cases with posterior bite openers. They remove occlusal interferences to prevent debonds as well as

allowing lower alignment with the lightest forces


_____________________bite turbo placed_____________________Class II elastics to erupt lower molars and correct overjet from bite opening


This is where patient cooperation is needed. Class II springs cannot open the bite. Over-correct to incisal edge to edge


9 months progress with full braces

12 months braces

3 years post deband


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



Progress after Xbow, maxillary expansion, and upper canine alignment

Initial__________________________________Progress after 2X4 followed by 4 months Xbow followed by maxillary expansion

Progress after canine alignment______________Progress after 6 months full braces


Initial_________________________________Progress after 6 months full braces

10 months full braces

2 years post deband




Airway Enhancement

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

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.



After 8 months Xbow, no expansion needed, after photos taken 1 month after springs removed, cephs below

Positive airway change

12 months braces


Obstructive Sleep Apnea

Airway before and after maxillary and mandibular advancement surgery by Dr. Bill McDonald.

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


Superimposition of before and after surgery ceph tracing for above patient

Initial for above patient

After 14 months including two jaw advancement 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.