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Delivery of the MARA
This comes from "A Manual for Orthodontists and Staff" by Paula S. Allen-Noble in partnership with Allesee Orthodontic Appliances (AOA is a subsidiary of Ormco Corporation).
Pre-Insertion Check List
1. Several days before the patient's appointment check to make sure that you have the appliance and its components back from the laboratory. Review the prescription sheet to determine that the appliance has been made to specification and make sure that the work models and appliance identifications match your patient.
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Note: To insure accuracy, AOA laboratory returns all MARA's secured to the original work model with wax. The appliances are advanced to prescription specifications with appropriate adjustments to the lower arms and initial set of upper elbows. A second set of uncut upper elbows that are longer in all dimensions, and shims/bushings of 1mm,2mm,and 3mm lengths are included to accommodate future adjustments and activations. |
Never discard work models until after the appliance has been inserted. If there is a problem, the original work models will need to be returned to the laboratory along with the new models. This procedure insures quality control for both the laboratory and your practice
Note: The MARA is a versatile appliance and is modified depending on the treatment plan and preferences of the clinician. Make sure that the appliance returned to your office meets design specifications as noted on the prescription sheet for that particular patient. Above are random examples of modified MARA designs that were fabricated by AOA laboratory.
MARA Accessory Kit:
Every office should have a MARA Accessory Kit. A kit will give you an ample supply of spare components; upper elbows, advancement shims/bushings, ligature ties and an elbow torquing tool. Component parts can be reordered from AOA.
MARA Demonstration Model:
A demonstration model is always helpful initially when explaining to the patient and parent what the appliance looks like and how it works to correct the malocclusion. And after insertion of the MARA, a model is an extremely effective tool to use during the exit interview for clarification of any questions that may arise.
2. Place the fabricated MARA crowns on the work models with shimmed elbows inserted. Line up the guide- lines on the upper and lower models, or check the pre- scription sheet for the advance- ment requested. Make sure the upper and lower midlines line up over each other.
3. Adjustments will be required if the guidelines do not line up, the upper elbows or lower arms seem too long or short, or there is a problem with the lingual arch, occlusal rests, or removal modifications if present. Corrections should be made at this time.
A. Evaluating and Adjusting the Upper Elbows:
When the upper elbow is too short horizontally, this is an indication that the appliance will not advance the patient properly. From your accessory kit, place a shim/bushing the appropriate length to correct the advancement.
If the elbow is still too short horizontally, you may need to place a new longer elbow in the upper square tube, line up the advance guidelines, and mark the elbow for proper length and then add the appropriate shims to the elbow.
The upper elbows, when engaged into the tube and advanced properly, need to be torqued in close to the lower crowns in order to prevent the patient biting inside the elbows when he retrudes the mandible into a Class II, but do not torque so close that they hit the lower crown when biting in Class I, or the elbows will prevent the patient from fully closing.
Incorrect. Elbow torque too tight. Correct elbow torque.
Various Elbow Adjustments
(Use a heavy duty 3-prong plier)
The upper horizontal and lower sweepback legs of the elbow should not extend too far distally, or they will cause cheek irritation. However, the elbow legs must extend enough distally so that the patient cannot bite behind the sweepback legs and so that there is enough length to accommodate the advancement shim/bushing at the next advancement.
* Alert: If the sweepback leg of the upper elbow is too short distally, the patient could maneuver the arm attached to the mandibular crown into the "interior lumen" space of the upper elbow, causing the patient to lock up on that side.
Horizontal and sweepback
elbow legs too short.Horizontal and sweepback
elbow legs too long.Horizontal and sweepback elbow legs correct lengths.
Check the vertical length of the upper elbow. The elbow should remain engaged with the lower arms as the patient opens and closes. If the vertical leg of the elbow is not long enough the patient may fail to hold the mandible forward, disengaging the lower arm from the desired Class I. They may actually hold their mouth open, letting the mandible retrude, causing them to bite behind the elbow.
Note: If the maxilla is too narrow, the upper elbows may have difficulty staying engaged with the lower arms because the upper elbows are torqued buccally too much and do not have enough vertical engagement. This can be corrected with an additional bend to the medial (direction of the lower teeth) in the vertical leg.
In-out width discrepancies between the upper and lower crowns can be adjusted by placing a horizontal bayonet bend in the horizontal elbow leg to either widen or narrow the position of the vertical leg relative to the lower crown.
The distal slant of the elbow's vertical leg can be varied to correctly engage the lower arm by placing up-down bends in the horizontal leg. Be careful not to allow the lower mandibular arm to bite above the horizontal leg or the patient will lock.
Lock Up: Lower Arm Locks into Upper Elbow:
A patient may lock up the MARA by slipping the lower arm into the opening of the upper elbow's interior lumen space. There are several factors that contribute to this problem. The first is that the opening to the interior lumen space is too large and needs to be closed more; second the sweepback leg of the elbow is too short; third the patient is usually a "sleep bruxer," and clenches so hard that they flex the elbow buccally until it snaps over the lower arm; fourth the elbows are not torqued tightly enough against the buccal surface of the lower crown, fifth the lower arm loop is too small of a radius and fits inside the interior of the elbow.Unlocking a patient:
Should a patient lock up, see them as soon as possible, as they get anxious not being able to open their mouth. Tell them not to try to force the mechanisms apart. Unlocking the MARA can be done easily in the orthodontic office by simply cutting the ligature wire and sliding the elbow forward. Once either elbow is removed, they unlock easily from the other side.
The distal tail end of the elbow's sweepback leg should be adjusted so it remains close to the buccal surface of the mandibular crown in order to avoid cheek irritation and cheek biting, but not so close to the buccal surface of the mandibular crown that it locks under the archwire tube.
B. Evaluating and Adjusting the Lower Mandibular Arms
It is very important to check for and correct lower arm problems before cementing your appliance. If you notice a problem correct it and recheck once again when you trial-fit the MARA on the patient before cementation. Once the appliance is cemented you would most likely have to remove the lower crown and mechanism to adjust it, involving discomfort, loss of patient confidence, time, money, and possible appliance damage.
Adjustments to the mandibular arms are usually made with small beak three prong pliers. Any up-down, in-out or forward backward corrections should be made at this time.
If the lower arm on the mandibular crown is too long (width), it will impinge on the soft tissue of the cheek. The lower arm when articulated against the upper elbow should not extend any further than 2mm wider than the upper elbow, yet it must extend about 2mm wider in order to prevent lockup when biting in retruded Class II.
To shorten the width of a lower arm, hold the crown in a strong plier: first open the lower arm loop with a bird beak plier, then squeeze the lower arm with a small beak 3-prong plier to reduce the buccal projection.
If the lower arm is too short (width), you may correct the length (width) by unfurling it, holding the crown with a strong plier and opening the curve of the arm with a bird beak plier.
The up-down (height) position of the lower arm should be checked to verify engagement with the vertical leg of the upper elbow, even when the mouth is partly open, and to make sure the lower arm does not bite above the elbow when closed, or the patient will lock.
C. Evaluating and Adjusting Midline
Adjusting midline discrepancy by shimming the upper elbow.
If the work models show a deviation and the midlines are off you can add a shim, of the appropriate length to the appropriate elbow, to correct the discrepancy. In the photos below, note that the lower midline is off. A shim / bushing has been added to the upper elbow on the right side shifting the mandible towards the left, correcting the midline. Patients will occasionally present with this problem at delivery, as well as later during treatment. Correction is easily made at the chair.
Adjusting lower arms to correct midline discrepancy.
The mandibular lower arms can also be bent mesially or distally in order to adjust the space for the midline.
arm and upper elbow
D. Evaluating and Adjusting Lower Lingual Arch, if present.
(Not expansive.)
If a lower lingual arch is present , check that the lingual arch is the correct width and is not expansive, nor narrowing to the lower molars. The lingual arch should rest on the cingulums of the lower incisors.
If a lingual arch was not requested and is desired, you can make one in the office using your work model. Form, adjust, solder. This can also be done right before delivery if you prefer to check the lingual arch form in the patient's mouth before soldering it to the lower crowns.
Pearl: Incorporating a small omega adjustment loop into the lingual wire during construction can simplify lower lingual arch adjustments.
E. Evaluating Occlusal Rests, if present.
If occlusal rests are incorporated into the MARA they need to be checked for their approximation to the teeth. This particular procedure will need to be re-checked at the trial fit of the appliance.
Rests vary in design and function. Occlusal rests are sometimes placed on second molars to ensure that there is no super eruption of those teeth during Class II correction. Occlusal rests may be placed on pre-molars just as seen with the Herbst, as well as off the lingual arch to help with stabilization. Occlusal rests are sometimes used in conjunction with expanders to control the molars from tipping and enmasse expansion of the entire arch.
Rests on the occlusal surface of upper or lower pre-molars are usually secured with a light cure composite. As with crowns, occlusal rests should be micro etched to ensure a good bond. (AOA lab routinely micro etches crowns and occlusal rests).
Note: Adjustments to occlusal rests are easily made with How or bird beak pliers. However, caution should be taken when adjusting rests as they can break if annealed too much.
Alternative to occlusal rests when super eruption is of concern:
An alternative to occlusal rests is an occlusal buildup with composite/acrylic, fixed with the acid etch technique. This is usually placed on the lower second molars. Also, if intrusion of the first molars is not desired, as in deep bite cases, then lingual plateaus (bite turbos) can be fixed on the upper anterior teeth.
4. Crown Removal Design Modifications: (Optional) Adding occlusal removal holes, horizontal removal slits, or vertical removal notches to the crowns can simplify crown removal.
Occlusal Removal
Holes:
Occlusal removal holes are placed in the occlusal surface of the crowns to aid
in removal of the appliance, especially if a crown removal plier is going to
be used. This hole can be made by the clinician at the time of MARA removal,
but some clinicians find it easier to have them placed by the laboratory technician
during fabrication. An occlusal crown removal hole is about 1/8" in diameter.
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Maxillary occlusal removal hole.
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Mandibular occlusal removal hole.
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Note:
1. Do not confuse an occlusal removal hole with a "vent hole." Occlusal removal holes are often misnamed as "vent holes." Vent holes are much smaller and are requested to help extra cement escape from the crown. Venting is not a necessary feature of cementation, but the name developed because of the venting observed during cementation, and is usually enlarged chairside later to facilitate crown removal.
2. Do not use Vaseline of Chap Stick on the teeth if a crown removal hole or vent has been pre-cut in the occlusal surface of the crown. If there is a hole, the cement should set or cure before cleaning. Check for voids around the margins of the holes to avoid decalcification. Provided that a barrier shield (Vaseline of Chap Stick) is ot used with occlusal holes, caries is virtually nonexistent. When using glass ionomer cement with fluoride in it.
Horizontal Removal
Slit:
Horizontal removal slits are normally placed only on the mesial lingual corner
of maxillary first molar crowns. They act as a purchase point for use with the
Ormco "Chastant" crown removal pliers. The slit should be placed half way from
the gumline to the occlusal surface.
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Horizontal
removal slit.
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Vertical Removal
Notch:
The upper crowns may be notched approximately 1.5 -2mm on the mesiopalatal gingival,
while the lower crowns may be notched 1.5 - 2mm on the mesiobuccal gingival
just lingual to the lower arm. These notches will eliminate the need to use
a bur subgingivally if the crowns are to be sectioned. The notches also aid
in the removal of crowns when using the Ormco crown slitting plier.
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Maxillary
crown vertical removal notch.
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Mandibular
crown vertical removal notch.
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Note:
To add vertical notches to the crowns yourself, rotate disc so any burs will be inside the crown. Be careful to stay within suggested guidelines. If the crown is notched too much it could weaken and split over time. It is also suggested to re-micro etch the inside of the crown following this procedure. |
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Upon request, AOA laboratory will add crown modifications: horizontal slits, vertical notches and occlusal removal or vent holes to crowns during fabrication.
5. Final Review of MARA on work model:
Test the appliance with the lower model forward in Class I position.
The lower arms should stick out wider than the elbows but not so excessively
that they will irritate the cheek. The prominence of the lower arm is adjustable
using a small beak 3-prong plier and bird beak. The elbow horizontal leg should
extend around 4mm distal to the large square tube, to allow tiebacks and the
addition of shims later, but not longer or it may poke the cheek. The elbow
vertical leg should be long enough to engage the lower arm even if the patient
opens a few millimeters. It should be torqued lingually enough to touch the
buccal of the lower crown.
The sweepback leg of the elbow should not impinge on the lower gum tissue, nor should it flare out into the cheek. It needs to extend distally enough to prevent the patient from biting behind it, yet not so far distally that it pokes the cheek.
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Front
View
MARA on lower model forward in Class I position. |
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Buccal View
MARA with lower model forward in Class I position. |
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Test the appliance with the lower model retruded in the Class II position.
The lower arms should stay engaged on the sweep back arms of the elbows, and
should not drop behind them or bite inside them. For this to be true, the lower
arms must be long enough and the elbows must be torqued in tight enough to the
buccal surface of the crowns.
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Front
View
MARA on lower model retruded in Class II position. |
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Buccal View
MARA with lower model retruded in Class II position. |
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Coming soon:
Clinical Insertion 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
