The most common problem presented to the orthodontist is correction of skeletal Class II malocclusions. In the past, most Class II malocclusions have been corrected with surgical procedures, headgear and/or elastic therapy.

In most cases, the improper bite is caused by a lower jaw that is too far back in relationship to the rest of the face. A good indicator of this type of malocclusion would be a case where the upper lip is balanced with the rest of the face by sliding the lower jaw forward, thus creating a more pleasing profile.

When the patient is still growing, it is possible to accelerate the growth of the lower jaw to catch up with the upper part of the face by using the MARA. The MARA is a functional appliance because it postures the patient's lower jaw in a forward direction. Over a period of months this forward posture of the lower jaw usually promotes growth in the same direction.

MARA’s, because they are permanently attached to the teeth for the duration of treatment, address the lack of success that removable functional appliances have experienced in the past due to patient non-compliance. When the patient tries to bite in Class II, the fixed lower arms interfere with closing, and they can only close in Class I. The patient must bite forward in front of the upper (elbow) and is guided by the appliance to habitually hold the jaw in a Class I relationship. Opening and closing movements occur easily and patients adjust to the appliance in about a week.

It is a difficult appliance to use in the early mixed dentition because there is insufficient room in the cheek area. It is suggested not to attach this appliance to deciduous teeth because the lever arms may resorb deciduous roots. Late mixed dentition all the way through advanced adulthood is appropriate. Adults are apparently capable of remodeling of the fossa and reshaping of the condyle, but this predictability is not yet certain in the literature.

It is reported that the appliance produces remodeling similar to what the Herbst sometimes shows except it has less vertical effect on the teeth: lower teeth move forward a little, upper teeth move backward a little, mandible (condyle) grows forward a little, maxilla growth is slightly restrained, glenoid fossa may remodel forward, and the temporal bone may rotate forward.

Changes the MARA produces:

1. The upper jaw is in good position and you want to advance the lower jaw.

2. It is desirable to inhibit maxillary anterior growth and to produce an increase in mandibular length.

3. Patient presents with an obtuse nasiolabial angle and the use of headgear or Class II elastics would increase the angle, thus creating a less attractive face.

4. Adult cases, when lower jaw surgery is not an option, needing a good compromise Class II correction. While the result is mostly dental, some mesial migration of the fossa may occur.

Having utilized removable functional appliances therapy in the 70’s and 80’s,

Dr. Jim Eckhart, Manhattan Beach, CA, knew they worked, but began searching for a way to avoid lost and broken appliances, which were expensive for parents and ineffective for his practice. By the late 80’s Dr. Eckhart was using the Herbst, and had many successful treatments, but patient complaints were common because of lip/cheek irritation.

In 1991, he was attracted to an appliance created by Dr. Douglas Toll, of Germany, which he called the MARA (Mandibular Anterior Repositioning Appliance.) It consisted of cams on the molars, which guided the patient to bite into Class I. The appliance was low in bulk and easily tolerated by the patient. Dr. Eckhart and Dr. Toll began experimenting with ways to improve the appliance’s reliability and to provide greater flexibility in adjustment. By 1995 with the help of Ormco and AOA laboratory, a new design was provided for clinical trials. Clinical trials were successful and feedback from Dr. Eckhart’s table clinics at the 1996, 1997 and 1998 AAO meetings were positive, as well as from Dr. Toll’s 1997 and 1998 AAO lectures.

1. The patient's profile immediately looks better after the appliance has been inserted.
2. Class II malocclusions are treated more efficiently making treatment much easier on the orthodontist, staff, patients and parents.
3. The MARA gives an immediate distal movement to the upper first molars and a simultaneous mesial to buccal rotation. (Note: at the appropriate time these movements will need to be stopped.)
4. Stainless steel crowns are easier to fit, stronger, less expensive and have more retention than bands.
5. There are no removable parts, thus cooperation is an issue; treatment time is predictable.
6. Breakage is minimal and hygiene is not a problem
7. Orthodontic appliances can be worn in conjunction with the appliance.

There is basically one MARA design. However, the appliance can be modified to accommodate upper and lower expansion, a transpalatal arch, lower lingual arch, orthodontic appliances, intrusion mechanics, distalization of upper molars, and can be used unilaterally, and with asymmetric cases.

As the orthodontist becomes comfortable in his or her command of the appliance, the simplicity of design becomes more appreciated because there is little to master. Efficiency, profitability, and consistently predictable results are what the MARA affords today’s orthodontic practices.

Normally, a MARA consists of:

1. Four crowns on the first molars.

2. The lower arms soldered to the crowns.

3. Archwire tubes for the upper and lower arches soldered to the crowns.

4. Upper elbow tubes soldered to the crowns.

5. Upper elbows shimmed to provide the desired advancement.

6. Lower lingual arch soldered to lower crowns (recommended but optional.) A lingual arch is useful because the upper elbows will have a tendency to cause the lower molars to rotate and tip mesial lingual, thus crowding out the second bicuspids.

NOTE: If a lingual arch is not incorporated into the appliance design, it is recommended that lower incisor brackets with negative 5-10 degree torque along with an archwire with step bends mesial to the lower molars be placed to stabilize the lower molars.

7. Other rotation and tip modalities include direct bonding to adjacent teeth, or lip bumpers.

Variable specifications would include: Occlusal, horizontal or vertical removal holes in the crowns, lower lingual arch, expander(s) or transpalatal arches. Band designs are available.

Note: Band designs may be prone to breakage.

If using a band design, provide the laboratory a thick blank band:

TMD symptoms have not been reported from the design or advancements of the MARA and do not seem to be an issue. As with the Herbst, the MARA is frequently used to relieve TMD symptoms, and is useful to recapture anteriorly displaced discs and to unload the joints. Dr. Toll, from Germany, recommends and routinely uses MRI’s for a detailed position diagnosis and subsequent treatment modifications to obtain optimal disc repositioning.

Diagnostic records requirements are as diversified and unique as the clinicians’ diagnoses.

Listed below is a compilation of recommended and optional records.

If sending your appliance to AOA laboratory, you will not have to separate the patient for space mesial and distal to the first molars before taking impressions for work models. The lab will disc the teeth during fabrication of the appliance. Separators should be placed between the patient’s teeth one week before they return for insertion of the MARA.

Maxillary and mandibular alginate impressions are required for the working models. Impressions must be free of distortions, bubbles and voids. Perforated or metal impression trays are recommended when taking impressions directly on the patient. It is important to keep in mind that the laboratory technician can only make an appliance to fit the models it receives and it all starts with impressions.

Wax or silicone bite registrations are not necessary when fabricating a MARA. Work models may be marked indicating the prescribed incisor and molar relationships in the advanced position. The amount of advancement to request depends on the severity of the Class II. If the case is 4-5mm Class II, advance it to end-to-end incisors. If the case is 8-9mm Class II, advance it only half way because to advance it the entire distance at once might strain the TMJ excessively and would probably lead to appliance breakage. It would also lead to the patient being able to bite behind the elbow in the retruded position; possibly getting the appliance locked up. The remainder can be advanced gradually over 6 months. The advancement marks should have the midlines centered over each other.

Pearl: While not necessary, a silicone or wax bite sent along with marked work models is sometimes of help to the laboratory technician when ascertaining the vertical leg height of the elbows.

MARA’s only require separation of maxillary and mandibular first permanent molars. Separators are placed one or up to two weeks before the appliance is inserted.

Note: If the laboratory is going to indirect fit your crowns, you do not need to separate the teeth before taking impressions for the work models. The lab will disc the model when fitting the crowns. Schedule the patient to return one week before appliance delivery to place, or replace lost separators if they were put in at the time you took impressions, so there will be space on delivery day.

1. The patient may present with a very small vestibule and not have enough room in the back cheek area to accommodate the MARA’s lower arm and upper elbow placed on the crowned permanent first molars. In this case wait until the patient is older. Don’t treat patients too young. Late mixed dentition all the way through advanced adulthood is appropriate.

2. The first molars must be well erupted. No operculum should cover the distal of the lower first permanent molar. It is not recommended to place the MARA on primary teeth because the long lever arms may resorb deciduous roots.

3. Make sure the maxilla is wide enough. Check that the upper and lower arches are coordinated when the mandible is placed in the advanced position. If not, expansion of the upper and/or lower arches may be indicated before the MARA is inserted.

4. The upper incisors should be uncrowded, properly torqued, and intruded if necessary, so they can serve as references for where to move the lower incisors.

5. Don’t advance severe Class II patients too far initially. The patient will find it difficult to function in the advanced position and the appliance may lock up.

The goal is to advance the incisors to end-to-end incisal relationship overcorrecting because some relapse is expected. A medium 4-5mm Class II can be advanced the entire 4-5mm initially. A severe 8-9mm Class II should be advanced half way (4-5mm) at first. Hold the patient at the half way advancement for about 6 months. Final advancement should be to the end-to-end incisal relationship and held for an additional 6 months.

*ALERT: Mark guidelines on work models to reflect only the partial advancement in a case where a two-phase advancement will be necessary.

Impressions are poured in hard orthodontic stone. The models must be free of any voids or distortions. The work models are hand articulated into the advanced position, usually a Class I, edge-to-edge. Mark advancement guidelines on the models in pencil extending from upper to lower arch. Also mark midlines. The laboratory will use these lines to mount the models to the clinician’s prescription.

If the patient's models are in a buccal cusp to buccal cusp relationship, or in a lingual cross bite when articulated into the advanced position, this is an indication that the maxillary arch is too narrow. The patient will need to have the upper arch expanded before placing the appliance, or an expander can be incorporated into the appliance during fabrication. If the patient's maxillary arch is too narrow, the upper elbows on the MARA will be unable to hang buccally to the mandibular crowns without excessive buccal flaring, which causes difficult engagement of the lower arms and cheek irritation. The laboratory should recognize the problem during the fabrication process and call to discuss options.

Currently there are three types of crowns on the market suitable for MARA fabrication: Ormco Crowns, 3M Stainless Steel Crowns and 3M Ni-Chro Crowns. All of these crowns have characteristics unique to the way they fit on a tooth. 3M crowns are shaped with a long, narrow base, giving it a rigid, tight "snap fit" feel. These crowns usually require more trimming. Ormco crowns when fit properly have a looser "snug fit" feel, but do not slip off the tooth. Ormco crowns are routinely re-crimped or contoured immediately prior to cementing on the tooth, ensuring a tight fit at the gingival margin.

Commercial laboratories have a tendency to favor certain crowns. If a crown has a different feel ask the laboratory what type of crown they used. If that crown is different from what you are accustomed, request the laboratory to provide the type of crown your office prefers. (AOA laboratory routinely uses Ormco crowns when fabricating appliances requiring crowns, but will provide 3M crowns upon request.)

Pearl: #1 Common Cause of Incorrect Crown Adaptation: is the presence of the operculum tissue over the distal of the lower first molars. In this situation it is recommended that the lower first molars be sized with bands allowing the lab technician to use them as an aid in identifying the molars' distal cusps being hidden under the tissue. Thus crown adaptation accuracy is greatly enhanced. But lower molars this poorly erupted may mean there is insufficient room in the back of the mouth for the elbows. In certain cases, it is recommended that an operculumectomy be performed before fitting crowns or bands.

Fitting your own crowns will require keeping an inventory of crowns. There are seven sizes of molar crowns of which four are used regularly. Most staff are accustomed to fitting bands, which are available in many sizes; however because of the sizing limitations, crowns will not fit precisely. There will be a little play in them when seated.

1. Crowns to be incorporated into the work model will require that the impressions to be taken with the crowns seated on the teeth. Remove crowns, place in impressions securing with wax, glue, or preferably a pinning technique to ensure that the crowns do not move while pouring the stone.

*Alert: Due to the smooth form of crowns they can easily be placed in the impressions backwards, or switched from right to left.

Pearl: Before pouring the impression in orthodontic stone, wax can be generously wiped (inside) the crown or band in the area where soldering is to be done on the buccal (outside) of the crown/band. This prevents the plaster from taking away heat from the crown/band during soldering. This way the crown/band material will not be overheated when soldering attachments. Overheating when soldering causes breakage.

2. Your direct-fit crowns or bands to be placed indirect on the work models:

This procedure will require that the impressions be taken with the crowns/bands removed from the teeth. Crowns/bands to be re-fit on the work models by the laboratory should be sterilized, identified, b

agged and the bags stapled to the prescription sheet. Work model should be poured in hard orthodontic stone.

Coming soon: Delivery of the MARA

About the Author:

Paula is the clincal liason for Allesee Orthodontic Appliances (AOA). Many of you know Paula from her 30 years in the industry. She worked in an orthodontic practice for fourteen years and has attended and lectured at continuing education seminars, presented staff and doctor's clinics at the Great Lakes, Midwest, Southern, and Mid-Atlantic constituent meetings, as well as, for the American Association of Orthodontists. Paula has visited and interacted with hundreds of orthodontic offices. Her experience in orthodontics covers a wide range of areas.

She can be reached at: p-allen-noble@mindspring.com or 1-800-990-3485

Paula S. Allen-Noble
Clincal Liason Allesee Orthodontic Appliances (AOA)
13931 Spring Street Sturtevant
WI 53177 USA

or more directly:

Paula S. Allen
Clincal Liason (AOA)
463 Club View Drive
Lawrenceville, GA 30043 USA