This page is divided into the following sections:

1. Patents and Licensed Labs

2. Testimonial from Dr. Herb Hughes

3. Xbow® Research

4. Clinical Use of the Xbow®

5. "L" Pin and Pushrod Adjustment


All images are the property of Dr. Duncan W. Higgins and cannot be copied or reproduced

without the consent of Dr. Higgins.

Xbow Movie

Dolphin Aquarium TM Crossbow Movie

IACT TM Crossbow Movie

Xbow® shown with ForsusTM Fatigue Resistant Device with 22 mm pushrods and Gurin Locks (rotated 180 degrees)

from 3M Unitek and Spring Caps from Comfort Solutions Inc.


March, 2019: I am using the large size Rocky Mountain Lock in some cases. It is easier to install and doesn't seem to slip between appointments like the Gurin Lock sometimes does. The Gurin Lock still has the advantage of controlling the pushrod position relative to the gingiva.



Xbow 2017: We have switched from headgear tubes to .036 X .072 sheaths. The "L" pins are made from .036 ball clasps with annealed ends. My favorite pushrod is still a 25mm with a bayonet bend.


Mesial or "Shorty" Hook-Up with .036 X .072 sheath and 22 mm pushrod with bayonet bend.

There is less "flipping" of the spring with mesial hook-ups with the sheath compared to the

headgear tube. This is the main reason we switched to the sheath.


RME X 6:"Maxillary Transverse/Anterio-Posterior Expansion Appliance (Max TAP)"

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.


Xbow (Crossbow) Class II Corrector. Distalizing the upper bicuspids and molars opens space for the canines and corrects

overjet by sharing the correction between the upper and lower.

This maintains the upper incisor position and upper lip fullness as much as possible.

The upper incisors are retracted passively by transeptal fibre tension to decrease root resorption.


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

US Patent No. 6,168,430 B1

Canadian Patent No. 2,392,021


Licensed Orthodontic Labs

Cottonwood Labs

6526 South State St. Suite #301 Murray, Utah 84107

Phone (801)904-2006


Extreme Dental Lab Inc.

87 Thornmount, Unit 27, Toronto, Ontario, M1B 5S5. 

Phone (416)286-0111 or 1-888-237-5950.



Great Lakes Orthodontics, LTD.


Integral Dental Lab  

#1402-805 West Broadway, Vancouver, British Columbia, V5Z 1K1. 

Phone (604)872-6656.


Preferred Ortho Dental Laboratory   

 #207, 14065 Victoria Trail, Edmonton, Alberta, T5Y 2B6. 

Phone (780)490-6585.


QC Orthodontics Lab, Inc.

109 Spence Mill Road, Fuqua-Varina, North Carolina 27526

Phone (800)537-1018 or (919)577-2250


Testimonial from Dr. Herb Hughes


“Our Orthodontic Study Club flew Dr. Higgins across North America to address our membership

and to learn about his appliance and treatment philosophy.

My patients and I couldn’t be more pleased with the results from Dr. Higgins’ Crossbow appliance!

It has shortened their length of treatment time as well as deliver a superior final result.

Dr. Higgins is a pioneer in the orthodontic field and very well respected amongst his orthodontic peers.

Thanks for caring enough to share your ideas with our orthodontic community!”

Dr. Herb Hughes

President –Northern Virginia Orthodontic Study Club


Xbow Research

Dr. Carlos Flores-Mir, Associate Professor and Division Head of Orthodontics and Orthodontic Graduate Program Director at the University of Alberta

has analyzed the cephs of 172 consecutively treated two phase Xbow cases from Dr. Higgins' office. The following is the summary of the statistical analysis.

Unpublished data, UAlberta 2015

  • 172 consecutive cases analyzed
  • L1MGo change from T1 (99.1) to T2 (102.2). Mean difference 3.1 degrees is significant (p<0.001).
  • L1MGo change from T2 (102.2) to T3 (103.7) Mean difference 1.5 degrees is significant (p=0.01).
  • L1MGo change from T1 (99.1) to T3 (103.7). Mean difference 4.6 degrees is significant (p<0.001).
  • Mean age at T1 12.3, at T2 13.5, at T3 15.2.
  • Only OB at T1 seems to have some predictive value for L1MGo changes.
  • For every extra mm of OB (greater than the ideal overbite of 2mm) there is an increase in lower incisor inclination of 1.3 degrees.

Editors comments: It is interesting that the T1 LIMGo was 99.1 degrees. It shows that this patient population already had some dental compensation

commonly seen in untreated Class II's. The results show that once the teeth were allowed to settle for approximately six months after spring removal

the lower incisors had proclined 3.1 degrees. At the end of phase two the lower incisors had proclined an additional 1.5 degrees for a total of 4.6 degrees.

This result is similar to other two phase treatment studies.


Published Xbow Articles

"Short-term skeletal and dental effects of the Xbow appliance as measured on lateral cephalograms"

is in the December, 2009 American Journal of Orthodontics and Dentofacial Orthopedics.

"Lower incisor inclination changes during Xbow treatment according to vertical facial type"

is in the November, 2010 Angle Orthodontist.

"Prediction of lower incisor proclination during Xbow treatment based on initial cephalometric variables"

is in the October, 2011 Angle Orthodontist.

Drs. Flores-Mir, McGrath, Heo, and Major's "Efficiency of Molar Distalization with the Xbow Appliance Related to Second Molar Eruption Stage

is in the November, 2012 European Journal of Orthodontics.

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 May, 2013 Angle Orthodontist

Upper Airway Changes after Xbow appliance Therapy Evaluated with CBCT

is in the July, 2014 Angle Orthodontist

External Apical Root Resorption generated by Forsus simultaneously with brackets vs. Xbow followed by brackets to correct Class II malocclusions.

is in the September, 2015 Journal of the World Federation of Orthodontists

Dental and skeletal changes in mild to moderate Class II malocclusions treated by either a Twin-block or Xbow appliance followed by full fixed orthodontic treatment

is in the November, 2015 Angle Orthodontist


Dr. Bob Miller also compared 8 two phase Herbst cases with

7 two phase Xbow cases and 7 single phase Forsus cases.

                                        Herbst (two phase)        Xbow (two phase)          Forsus on arch wire (single phase)                      


Avg # of Visits                             29                                  19                                            26

Avg Chair Time (min/visit)            32                                  26                                            32

Avg Time in Office (min) ______868________________556_____________________818



Clinical Use of the Xbow Appliance

The stages of treatment are:

1. Maxillary expansion if a posterior crossbite exists or if there is maxillary constriction.

2. Maxillary incisor alignment, if necessay.

3. Distalization and over-correction of the maxillary bicuspids and molars to open space for maxillary canines,

4. Compensatory maxillary expansion, if necessary,

5. Expansion retention and replacement of springs on one or both sides, if necessary, and

6. Phase 2 Alignment, overbite correction, space closure, and arch coordination using a full edgewise appliance.

The Xbow  is made up of a maxillary expansion appliance, the Triple "L" ArchTM, the 3M Unitek Forsus Fatigue Resistant Device with "L" pins,

22 mm Direct Push Rods, and  Gurin locks (3M Unitek large size Order #560-400).  Don't forget to order a Gurin lock wrench. 

Ask for the  Dentaurum "Variety" two leg expansion screw.  There is less chance of palatal impingement with distal tipping and intrusion

of the first molars than with a four leg screw design.  If the patient has a posterior crossbite or a narrow maxilla, expand the maxilla first. 

It makes it easier in a patient with a narrow maxilla to attach the Forsus device if you expand the maxilla first. 

If more than 12 mm of expansion is necessary use a SuperScrew. 

Band the upper 6’s and  the upper 4’s.  Control of the upper first bicuspids is important if the goal is overcorrection

and the bite-catching effect of the first bicuspids.

Fit the bands and take an alginate impression.  Place the bands in the impression and secure with sticky wax.

Pour the impression and check the band position before sending the case to the lab.

Dr. Bob Miller places compound material over the bands before taking the alginate impression.

This method ensures that the band placement in the impression is correct. 

Another method is to place separators for a week, remove the separators, take impressions, and replace the separators.

Send the models (or impressions) to the lab. The lab will fit bands on the models.

You can use VPS impression material if you want the lab to pour the model . 

Don't try to take an impression of the bands on the teeth with VPS. 

It's difficult enough trying to get those impressions out of the mouth WITHOUT bands.

Alternate method for the Extreme Xbow by Extreme Dental Lab in Toronto which has a license to make Xbows in Canada and the US.

Take alginate impressions or digital impressions with an scanner and send to Extreme.

Place separators on the upper and lower first molars only after the impressions are taken. (Don't ask me how this works but it does).

Extreme will fit bands on the first molars and place occlusal rests on the upper and lower first bicuspids

(and upper second molars if they are erupted) Micro-etching the occlusal rests and bonding them to the teeth is critical with this technique,

especially to the upper first bicuspids when bands are not used.

"Extreme Xbow" on printed models from an iTero digital scan by Dr. Bob Miller

Use occlusal headgear tubes on the upper 6’s to attach the Forsus device springs. 

Once space is gained from the expansion, use upper 2X4 or 2X6 mechanics, if necessary. After alignment, segment the archwire

distal to the lateral incisor or canine.

This allows over-correction of the Class II buccal segments and opening space for the upper canines without over-retraction of the upper incisors.

If the upper incisors are well aligned and the maxilla doesn't need expanding initially, cement the maxillary expander and the Triple "L" Arch

at the same time and place the springs immediately or one week later.  If you need to expand the maxilla first,

wait to cement the Triple "L" Arch until you are ready to attach the springs. 

Microetch the bands and occlusal rests just before cementation.  We use the UnitekTM Multi-Cure Glass Ionomer Band Cement from 3M Unitek.

This powder-liquid cement has a long working time and on demand light cure.  We rarely have a loose band.

Bond the occlusal rests with  Transbond™ Supreme LV Low Viscosity Light Cure Adhesive.

If the upper second molars have erupted bond an occlusal rest to prevent the first molars from intruding too much.  

Occlusal rests for the maxillary second molars can be placed even if they are just erupting and still mostly covered with soft tissue. 

The rest can be placed at the level of the soft tissue so that when the second molar erupts further the rest will contact the occlusal surface. 

It is not necessary to bond the rest in this case.

If the labial bow is too close to the gingiva of the lower incisors use a three prong plier posteriorly to raise it.

If the buccal section of the labial bow is too close to the teeth and the pushrod is hung up then use a three prong plier from the occlusal

on the spot with the least clearance to bow out the wire.

To open the pushrod loop enough to place it on the labial bow simply push a bird beak far enough into the loop and squeeze the tips together

through the opening.  To remove the rod from the labial bow take the end with your fingers and flip it anteriorly so that the labial bow passes

through the loop opening.

See the patient every six weeks and overcorrect the maxillary first bicuspid to a half  cusp Class III.

This ensures that the bicuspid and molar root apices end up Class I after tipping has relapsed.

Initial, first bicuspid relationship is a half cusp Class II

Half cusp overcorrection of first bicuspids after 4 months Xbow

"Bite-catching" by first bicuspids after rebound (7 months post Forsus)


The use of the Forsus device causes rapid over-correction, usually in four to five months. 

Fully compress the springs by distalizing the Gurin locks with the Gurin lock wrench. 

A fully compressed spring will stay active longer as the patient opens. 

A fully compressed Forsus device has 200 grams of force and looses 20 grams for every 1 mm of deactivation. 

If you run out of length on the labial bow to reactivate the spring then you can either replace the pushrod with a longer one or use a "shorty" hook-up.

A "shorty" hook-up uses an "L" pin inserted from the mesial of the headgear tube with a 22mm pushrod.

Once overcorrection has been achieved remove the springs and Gurin locks and start maxillary expansion, if necessary.

Test the stability of the Class II correction for a couple of months and replace the springs on one or both sides, if necessary. 

The goal is a socked-in Class I first bicuspid. If the lower e's have not exfoliated cut the labial bow and occlusal rests off with a high speed.

We overcorrect maxillary expansion depending on the amount of constriction. 

If there is a complete bilateral crossbite we overcorrect the upper molars into a buccal crossbite. 

If the crossbite is unilateral we overcorrect the non-crossbite side into a buccal crossbite. 

If there is a crossbite tendency as a result of Class II correction we overcorrect the molars until the lingual cusp tip of the upper molar

contacts the buccal cusp tip of the lower molar on one side.  We leave the RME in place to retain the expansion for an additional five months. 

This gives us the opportunity to check for Class II relapse two months after completing expansion and replacing the Forsus device on one or both sides.



"L" Pin and Pushrod Adjustment (Thanks to my orthodontic assistant, Sandra Ipsen)

Xbow Comfort: Orthodontists are contacting Comfort Solutions after their patients experience sores. 

I recommend that you start with anterior and posterior spring caps and have Spring Sleeves and Spi-Wrap on hand.

Spi-Wrap is spiral cut tubing that works well for sores from the lower labial bow as well as transpalatal arches. 

distal hookup________________________________________________________

mesial hookup

"Spring Sleeve" combined with anterior and posterior caps to form a "Comfort Capsule".

Spring Sleeves are used when the spring is irritating or catching the cheek.

We are using "L" pins instead of EZ2 modules.

We find it is easier to adjust "L" pins to position the spring ideally.

Insert "L" pin with attached spring into headgear tube and let spring and "L" pin fall straight down.

Support spring against maxillary teeth with finger and bend "L" pin straight back at 90 degrees to the ball and"axle".

Rotate spring so that "axle" points slightly gingivally and end of pin is gingival and against bracket.

Begin with a straight 22 mm pushrod. We routinely rotate the Gurin Lock 180 degrees after completely tightening it

and then rotate it a few degrees clockwise to positon the anterior spring (with cap) about 1 or 2 mm off the gingiva.

If the spring or anterior cap still impinges on the gingiva, or if the posterior spring hits the lower labial bow or solder,

bend the "L" pin gingivally (see below).

1. straight "L" pin, mesial hookup with spring touching gingiva___2. bending pin gingivally with a fine bird beak plier

3. buccal movement of spring with bent pin and Gurin lock rotated 180 degrees (22 mm pushrod)

"L" pin bent up and Gurin lock spun 180 plus degrees to move spring buccally


"L" Pin Adjustment

Adjust the "L" pin so that the spring is parallel to the lower labial bow.This example shows a mesial hookup.

This has to be right or the pushrod will not function properly.



If the spring is still too close to the gingiva, bend an offset (bayonet bend)

as far anteriorly as possible on a 22 mm pushrod. (see below)



Use a heavy plier such as an Adam's. The first bend is 45 degrees towards the buccal.




The second bend is made with the beak of the plier inserted into the loop of the pushrod.

This second bend determines how far buccal the spring is. The more obtuse the angle between the rod and loop is,

the more buccal the spring will be. In other words, opening the angle between the rod and loop moves the spring buccally.

If the bend is too obtuse the loop will bind on the labial bow and will not slide which reduces the amount of opening before

the rod disengages from the spring.


22 mm pushrod with bayonet bend.

If the pushrod connects too far posteriorly on the labial bow it may be necessary to use a 25 or 29 mm pushrod OR

a mesial hookup (see below).

Mesial pin entry, 22 mm pushrods with offset bend, mini tube on bicuspid band


If a 25 or 29 mm pushrod is used a bayonet bend reduces lip impingement by the pushrod.

Straight 25 mm rod ____25 mm rod with bayonet bend

25 mm rod with bayonet bend

Video clip of Dr. Bob Miller bending a bayonet bend in a 25 mm pushrod.

29 mm pushrods with bayonet bend, missing lower second bicuspids

29 mm pushrods with bayonet bend, missing lower second bicuspids



EZ2 Clip Instructions

There is a greater chance for interference between the thicker clip and the lower molar solder joint.

This may cause the upper molar bracket weld to fail or the band to tear.

In this case it is better to expand the maxilla before you place the springs or remove the anti rotation arm. (See photo below.)

EZ2 with anti-rotation arm removed, 22 mm pushrod, and Gurin lock rotated 180 degrees.


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