EXPANSION APPLIANCES
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
LOOKING BACK
The earliest cited report is that of E.C .Angell published in the Dental cosmos in 1860. Angell’s thesis was discreditied and it was J.H.Mcquillen who tried to demolish it by arguments that ranged from the specious to fallacious. Four important points were put forth by Angell: 1) lateral maxillary expansion by bony separation 2) use of a jackscrew with contra rotating www.indiandentalacademy.com
Walter Coffin introduced the Coffin Spring in 1881 and was modified by Ricketts in 1973. The design , construction and clinical management of the standard Quad helix has been described by Birnie and Mc Namara in 1980. James and Waters in 1989 derived the behavior of the quad helix theoretically in terms of the properties of the wire used and its dimensions and spatial geometry. Expanding the arch with appliances were not accepted by the orthodontic community in early 1900’s. E.N.T surgeons popularized the technique which they used in treatment of nasal www.indiandentalacademy.com insufficiency and constricted nasomaxillary
Angell’s Appliance
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CLASSIFICATION
According to the rate a) rapid b) slow According to type of expansion a) orthodontic b) orthopedic c) passive e.g Vestibular shield, FR2, Lip bumper According to direction a) anterior b) posterior c) unilateral d) bilateral e) 3-dimensional www.indiandentalacademy.com
According to type of appliance a) removable b) fixed -- banded or bonded 1. Tooth borne e.g. HYRAX , Issacson 2. Tooth and tissue borne e.g Hass According to the jaw a) maxillary e.g Transpalatal arch,HYRAX b) mandibular e.g. Active lingual arch According to the active element a) Screws 1) Dental expansion e.g Sectional screw , Traction screw 2) Skeletal e.g HYRAX www.indiandentalacademy.com
Maxillary Expansion Rapid maxillary expansion or Split Palate
Defintition:
• It is a skeletal type of expansion that involves the
separation of the mid-palatal suture and movement of the maxillary shelves away from each other. ♦ These appliances are the best examples of true orthopedic expansion.
Applied Anatomy: ♦ The maxilla together with the palatine bone forms the hard
palate,floor & greater part of the lateral walls of nasal cavity. It is paired bone that articulates with its opposite www.indiandentalacademy.com
Most of the sutural attachments of the maxilla to the adjoining bones are at its posterior and superior aspects leaving the anterior and inferior aspects free, which makes it vulnerable for lateral displacement .
Sutures: The Inter-maxillary & Inter-palatine sutures are called mid-palatal suture. RME should be initiated prior to the ossification of mid-palatal suture. In infancy, the sutures in vertical coronal section has a ‘Y’ shape and binds the vomer with the palatine processes. www.indiandentalacademy.com
By adolescence, the oro-nasal course of the suture may become so inter-digitated that mechanical inter-locking is as in a jig-saw puzzle and islets of bone are formed. Melsen reports that transverse growth of midpalatal suture continued upto 16 yrs in girls and 18 yrs in boys. Most studies report a broad range of ossification between 15-27 yrs. The suture starts to ossify posteriorly and always shows a greater degree of obliteration posteriorly then anteriorly, while ossification comes very late anterior to Incisive foramen.
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In infancy
In early adolescence
www.indiandentalacademy.com In Late Adolescence
Diagnostic aids
While Considering RME for young adults, occlusal radiographs can be used for analysing the palatal suture status. 1. A radiologically visible midpalatal suture corresponds histologically to a predominantly straight running oronasal suture, which projects largely into the saggital X – ray path. Only small areas of interdigitation, if any are to be expected and the percentage of suture obliteration is low. 2. Radiological invisible suture corresponds histologically to a relatively large area of interdigitation, an oblique running suture course in relation to X ray path or bone structures projecting above the suture course. Percentage of suture obliteration to be expected is also low in this group. 3. A radiologically invisible suture is not www.indiandentalacademy.com
Indications for RME Dental indications: 1. Posterior Cross bite (unilateral/bilateral) 2. Elimination of inter arch tranverse dicrepancies prior to orthopedic intervention in class II malocclusions 3. Activation of the circummaxillary sutural system in treatmentprotocols or Class III . 4. Cleft palate patients with collapsed maxillary arch. 5. In cases requiring face mask therapy. 6. Increase of supplementary arch perimeter to accommodate teeth in patients with tooth size – arch size dicrepancies.
Medical Indications 1. Poor Nasal airway 2. Septal Deformity 3. Recurrent ear, nasal (or) sinus infections www.indiandentalacademy.com
5. Asthma 6. As a preliminary to septoplasty.
Contra - Indications: Absolute: 1. Single tooth cross bites. 2. In patients who are unco-operative. 3. Skeletal asymmetry of maxilla & mandible & Adult cases with severe antero posterior skeletal discrepancies. 4. Vertical growers with steep mandibular plane angle. 5. Anterior open bite.
Relative: 1. Patent mid-palatal suture. 2. Normal buccal occlusion.
Effects of RME: 1.Maxillary skeletal effect: The maxillary posterior teeth are used as handles to apply a www.indiandentalacademy.com
The appliance on activation compresses the periodontal ligament and bends the alveolar process buccally and slowly opens the mid-palatal suture. Opening of mid-palatal suture is triangular with maximum opening at the incisor region and gradually diminishing towards the posterior part of palate. In superior-inferior direction the maximum opening is towards oral cavity with progressively less opening towards the nasal aspects.
Amount of expansion achieved: •
An increase in maxillary width upto 10mm can be achieved by RME. • The rate of expansion is about 0.2 - 0.5 mm per day . • Every mm of posterior expansion produces 0.7 mm of addotional arch perimeter • Effect on Alveolar bone: • The alveolar bone in the area adjacent to the anchor teeth bends slightly due to the resilient nature of bone. • •
Effect on Maxillary anterior teeth:
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♦ Effect on Maxillary Posterior teeth: ♦ these teeth are used as anchors during RME. Theses teeth show buccal
tipping & are also believed to extrude to a limited extent.
♦ Effect on mandible: ♦ most authors have observed a downward & backward rotation of
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♦ ♦
mandible following RME accompanied by a slight increase in M.P. angle. Mandibular rotation is due to extrusion & buccal tipping of maxillary molars. Effect on adjacent cranial bones & sutures: RME not only results in opening of mid-palatal suture but also has far reaching effects on adjacent cranial structure. In addition to effects on those bones directly articulating with the maxilla, bones of the cranium such as parietal & occipital were also found to be displaced. Effects of RME on nasal cavity: The evidence of increased inter-hamular width indicates some widening of choanae. The maxillary air passages are widened throughout their entire lengths from piriform aperture to choanae. This would account for the improved respiratory changes. This increase in nasal cavity width is maximum in the inferior region & decreased towards the superior aspect. Similar gradient is found in A.P direction with the greatest increase in anterior region. www.indiandentalacademy.com
Effect on Face ♦ The measurements of upper lip length, lower lip-chin
length, upper face width, lower face width, upper lip vermilion, and lower lip vermilion demonstrated changes during treatment but showed no significant change from initial values after 1 year of retention. ♦ Overall face height, intercanthal distance, average eye width, and nose length did not change over time. ♦ Soft tissue nasal width increased 2.0 mm during treat-ment.
Effect on pulp ♦ Fibrotic changes occur long after the forces have faded.
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Removable appliances: ♦ Reliability of these appliances in producing skeletal
expansion is highly questionable. ♦ If used during the deciduous (or) early mixed dentition phase produces some effects. ♦ Consists of a split acrylic plate with a midline screw retained using clamps on posterior teeth. ♦ Disadvantages:1. Need for patient co-operation 2. Difficulty in retaining the plate inside the mouth unless activated regularly.
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Bonded RME The bonded expander produces changes in transverse as well as vertical and A-P The acrylic occlusal coverage opens the bite posteriorly facilitating correction of anterior cross bite A slight superior movement of the posterior aspect of the palatal plane occurs with these appliances Clinical Management Two impressons are made,one for wire framework,one for application of acrylic Mandibular impression is taken for fabrication of an invisible retainer to prevent the occlusal wear caused by these appliances www.indiandentalacademy.com
Wire framework These incorporate a Hyrax type screw into a wire framework made of .040 type of ss. Wire framework extends around the buccal and lingual surfaces of the dentition with the wire crossing the occlusion between the upper deciduous canines and the deciduous first molars The wire also curves around the distal aspect of the first molars Screws positioned in the palate with the midline of the screw aligned with the palatal midline and about 2mm away from the surface of the palate The wire extensions of the screw are adjusted to contact the lingual surfaces of the first deciduous molars and the distolingual cusps of first permanent molars www.indiandentalacademy.com
The appliance is bonded with chemical or light cured adhesive Appointment inervals Patient is appointed at two week intervals until expansion is terminated Average amount of expansion with these appliances is 6 to 8 mm which translates to about 28 to 40 expansions that is 4-6 weeks of active expansion treatment The patient is reviewed every 6 weeks for an additional 5 months to allow for reossification and reorganisation of mid palatal suture to occur Retention with a simple palatal plate is given, if deciduous teeth are lost,transpalatal can be used . www.indiandentalacademy.com
Banded RME These are fixed on to the teeth & more reliable & found to produce consistent skeletal effects. These usually involve the banding of first molars and first pre-molars, when preformed bands are used it is advisable to select bands that are one size larger then the normal as it is difficult to seat 4 tightly fitting bands simultaneously. Hass type and Hyrax type of band fall into this category.
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Wires may be soldered to the buccal aspects of the bands to increase rigidity (or) brackets may be welded & used to attach arch wires for the correction of teeth not covered by RME. Commonly used appliances are 1) Derichsweiler type : Tags are welded & soldered to the palatal aspects of the bands to provide attachments for the acrylic which is also extended to the palatal aspects of all non-banded teeth except incisors.
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2). •
Hass type : A thick stainless steel wire of 1.2mm diameter is soldered on the buccal
and
lingual aspects connecting the premolar and molar bands. •
The lingual wire is kept longer so as to extend past the bands both anteriorly and posteriorly. •These extensions are bent palatally to get embedded in the palatal acrylic
which has a midline screw. • The plate does not extend over the rugae area. •Inflammation of the palatal tissue is an additional complication.
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Isaacson type : •
This is tooth borne appliance without any acrylic palatal covering.
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This design makes use of a spring loaded screw called MINNE expander.
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Metal flanges are soldered on to the bands on the buccal and lingual sides.
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The expander consists of a coil spring having a nut which can compress the spring.
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The coil spring is made to extend between the lingual metal flanges that have been soldered.
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Expander is activated by closing the nut so that spring gets compressed. www.indiandentalacademy.com
Biedermann type or Hyrax type: •
This appliance also required a special screw either Hyrax, Leone 620 or Unitek.
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These have extensions in heavy guage wire which are welded and soldered to the palatal aspects of the bands.
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Mandibular dental decompensation The Schwarz is a horseshoe shaped removable appliance.Inferior border of the appliance extendsa below the gingival margin and contacts the lingual gingival tisue. A midline expansion screw is incorporated into the acrylic and also there a re ball clasps that lie in the interproximal spaces inbetween the deciduous and permanent molars. The appliance is activated ince per week producing about 0.25m of expansion.It is expanded for 3 or 4 months, depending upon the degree of incisor crowding, producing 3-4 mm of arch length anteriorly. Purpose of Schwarz appliance is to produce orthodontic tipping of the lower posterior teeth. www.indiandentalacademy.com
Mandibular passive expansion Lip Bumper ♦ A removable appliance that attaches to buccal tubes located ♦ ♦ ♦ ♦
on the lower first molar bands. A lip bumper is made from .036” SS and available in avariety of preformed sizes. Useful in patients who have very tight buccal and labial musculature. The lip bumper should lie at the gingival margin of the lower central incisors . Increases arch length passively by lateral and anterior expansion and also by distalisation of molars.
Lingual arch Made of .036”SS wire.Extends along the mandibular dentition from first molar to first molar. An adjustment loop can be placed in the lingual arch in the www.indiandentalacademy.com
Acrylic splints : • • •
Made of poly methyl metha-acrylate A wire framework may be adapted around the teeth to reinforce the acrylic. Mondro et al (1977)have described an all acrylic form of cap splints and inter connection with a screw embedded in the midline. These splints are bonded to a teeth using either GIC (or) other bonding adhesive, after adequate etching.
Description of a typical expansion screw : • A typical expansion screw consists of an oblong body divided into two
halves. • Each half has a threaded inner side that receives one end of the double
ended screw. • The screw has a central bossing with four holes. These holes receive a
key which is used to turn the screw.
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Commercial Expansion screws 1. Bilateral symmetrical expansion screws Most commonly used.Can have a double guide pin or a single guide pin. 2. Mandibular bow screw. 3. Encased expansion screw. This restricts accidental recoiling of the screw. 4. Sectional expansion screw. Used for moving single tooth or groups of teeth. 5. Trapezoidal expansion screw. It is used in cases of narrow maxillary arch where the anterior part of the arch is narrower than the posterior. 6. Radial expansion screw Used where anterior region should be expanded more than the posterior region. 7. 3-dimensional expansion screw Brings about movements in 3 directions. www.indiandentalacademy.com
8. Spring loaded expansion screw ble Springs are changed periodically each time with one having more tension. 9. Traction screw Used for closure of extraction space.Works by closing the screw. 10. Telescopic screw 11. Piston spring screw For moving a single tooth in labial or buccal direction. Bala is a lova www.indiandentalacademy.com
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The turning of the screw by 90° (i.e. one turn) brings about a linear movement of 0.18 mm. The pattern of threading on either side is of opposite direction. Thus turning the screw withdraws it from both sides simultaneously.
Activation schedule: Schedule by Timms : For patients of upto 15 years of age, 90° rotation in the morning and evening. In patients over 15 years, Timms recommends 45° activation 4 times a day. Schedule by Zimring and Isaacson : In young growing patient, they recommended two turns each day for 4-5 days and later one turn each day till the desired expansion is achieved. • In case of non growing adult patients, they recommend two turns each day for first two days, one turn per day for next 5-7 days and one turn every alternate day till the desired expansion is achieved. www.indiandentalacademy.com
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Nearly parallel opening by a rigid appliance is required (or) the dento-alveolar elements will tilt too far buccally and consequently curtail expansion of basal maxilla This undesirable condition arises if the appliances is to flexible (or) teeth held in a manner that allows rotation b/w’n them and the appliance. Rigidity re quirements will generally dictate the type of appliance used and also the choice of many other components (eg., Bands or splints).
2). Tooth Utilization: ( No.of teeth included in appliance) a). Load distribution : • As the entire lower portions of the maxilla are to be moved laterally, it would be best to incorporate as many teeth as possible & thus spread the load over the entire alveolar length instead of applying it only at a few isolated points • Bands can be cemented simultaneously only to a few teeth because of difficulties of multi alignments whereas splints can be adapted to all teeth. b). Appliance retention: • Retention of an appliance against accidental dislodgment during RME depends on a no.of factors, but especially the area of adhesion / interface b/w’n the teeth & appliance, the precision of fit (or) thickness of the adhesive agent & shape of clinical crown www.indiandentalacademy.com
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Bands may be superior to capsplints in view of their closer adaptation. Bands may be pressed into the gingival sulcus where the clinical crowns are very short
3). Expansion : (Dilating unit & action) • • •
The dilating mechanism can be a spring (or) a screw but a spring reduces the rigidity & control. A screw is far better but should have a thread of sufficient length to complete the expansion without interruption. Changing the screw i.e removing the fully open one & replacing it with a new one (or) the same one that as closed, only jeopardises rigidity & wastes time
4). Economy : a). Time : The use of capsplints keep the clinical time to a minimum with good laboratory backup. Chairside work is limited to taking of impressions & bite registration. b). Material : The appliance which makes the least intrusion into the oral space will be best tolerated by patient. Here the banded appliances have a distinct advantage over the bulky capsplints
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5). Hygiene : •
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The form which produces the minimal covering of the dental and palatal mucosal tissues consists of bands and least amount of interconnecting material. But this design as the inherent disadvantage of too much flexibility. The criteria of hygiene given the lowest priority, because any deleterious effects are superficial & reversible and the well manage patient. Cap splints should be fixation of choice, especially where rigidity is important & bands have their place, where there are difficulties in retention.
Clinical Management of RME : a).Fitting the appliance : • The clinician must examine the appliance & satisfy about the quality laboratory work. In the case of Cast cap splints, attention must be paid to cleanliness especially the fitting surface to secure good adhesion. • Check the direction of the screw for opening. it should be backwards when viewed from lingual aspects the appliance should slip on to the teeth with sufficient friction to hold it in place. • Incorrect seating may caused by a high spot on the casting and is revealed by rocking, if the spot can be located it can be removed easily www.indiandentalacademy.com
b). cementation of appliance : • • •
Only when the clinician is satisfied without causing pain (or) discomfort he should then only proceed with cementation. Ames black copper cement is used, in addition to its good adhesive quality, it has a germicidal property which assists oral hygiene. Setting time 20 to 30sec. Allow the cement to become hard for atleast 1/2 hr. to assure complete setting, before strain is imposed by activation
C. Instructions : (Initial) • •
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The parent & child should be told about the appearance of midline diastema which can be disconcerting to them. If the patient has never worn an orthodontic appliance before, the usual inherent difficulties in speech and mastication must be mentioned together with points on oral hygiene. Most expansionists advocate 180° rotation per day, which will provide up to 10mm of expansion in 4 weeks. In order to simplify instructions patients have been classified into 3 age groups. The recommendations must be regarded only as provisional and subject to modification in light of symptoms expressed at subsequent visits. www.indiandentalacademy.com
1). Upto age 15 years : • •
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Includes most patients receiving RME and 180° daily rotation can be met with turn of 90° both morning & evening. The easiest way to rotate the screw is to have to long handled keys to work extraorally. One key is straight and other has a bend of 45° near the end so that 90° is achieved with successive turns of 45 ° from each of keys. While the person responsible for turning the screw is being instructed, the clinician must demonstrate the action precisely & then the person is invited to do it as shown, having first returned the screw to 0. Only when the clinician is sure that the instructions of fully understood, patient to be send and called after one week.
2). Age 15 to 20years : • •
Increasing resistance for maxillary separation may cause a force buildup & pain to patients in this age group with turns of 90°. It is possible to maintain an overall daily rotation of 180° if the total is broken down into 4 turns of 45°. www.indiandentalacademy.com
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Ideally, the divisions should follow 4 equal time lapses but here one may run into difficulties of organization, However, the tension disperses fairly quickly & only a comparatively short break may be needed b/w turns.
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Such patients are also asked to return after one week
3). Over age 25 years: •
The mid palatal suture often is opened surgically which relives much of the tension. Here it may not be necessary to reduce the overall rate of expansion in these patients.
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In this age group the clinician is more (or)less feeling his. way and mindful of the probable painful symptoms about which the patient is warned.
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Revisit within 3 -4 days
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Pain to be reviewed during active RME, before continuing with patient management during subsequent visits. www.indiandentalacademy.com
D). Pain during RME: •
Completion of the desired expansion in the short time allotted requires strong forces which often produces painful effects.
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The clinician metering treatment by rate of expansion has only the modality of pain as a monitor and indication of excessive force buildup that may lead to possible tissue damage.
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The threshold levels of pain very among individuals, the cause being the force buildup from resistance to maxillary separation.
2 factors generally are
responsible: 1. Rigidity of facial skeleton 2. Mechanical interlocking and synostosis of mid palatal suture. •
As the facial skeleton becomes progressively stiffer the tension is relieved by dispersion. By the teens, the suture will be interlock mechanically.
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Persistent pain normally is the product of an unyielding suture because the tension disperses and pain disappear as the maxilla separate.
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Suture opening is confirmed by first checking that there has been expansion by the appearance of some of the threaded portion of screw & than noting superior median diastema. www.indiandentalacademy.com
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Only if the clinician is satisfied the suture is opening should RME be continued, never should be the appliance be regularly activated for a period longer than 1 week against an unyielding suture in the hope of achieving maxillary separation.
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The rate can be modified, when patients report episodes which indicate excessive force buildup by the following adjustments to schedule of rotation. 1. Reduce the angle of rotation but increase the frequency . 2. Reduce the rate of expansion, which will stop the accumulation of residue
E). Instructions : (Subsequent) •
First ask the patient & person turning the screw if there were any difficulties. This information may be volunteered as any persistent pain certainly will be.
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Then check the central incisors for diastema.
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Then examine the screw to see how much thread is exposed, which indicates regularity in turning.
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If all is well, ask the patient to continue with the same instructions & return in another week.
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The patients who complaints of pain when the screw is turned should be asked how long it lasts; it generally disappears if the suture is open. Advice that 2nd 45° turn of screw not be made before the pain generated by the first has dissipated.
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With patients overage 20 years it is difficult to differentiate b/w the pain from on unopened suture & that from skeletal rigidity. In event of non opening of suture, surgical freeing should be considered.
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Should difficulties (or) minor illnesses arise during the active expansion phase, it may be stopped & resumed later.
F). How much to expand: The reports from Krebs (1964), Stockfish (1969), Timms (1976) & Linder-Aronson et al (1979) show that b/w one - third & one-half of the expansion was lost before stability was eventually reached. www.indiandentalacademy.com
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General guideline :
Expansion should stop when the maxillary
palatal cusps are level with the buccal cusps of the mandibular teeth. •
During active expansion it is useful to know how much of the screw thread is still available & when the limit is near, so that its is not completely exhausted, the halves of the appliance must not be allowed to disengage, that would lead to collapse.
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At the cessation of active expansion, the patient enters the fixed retention phase & is required to attend only for check-ups once each month.
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During this phase, it should be unnecessary to ligate (or) apply coldcuring acrylic to lock the screw as the angular thrust creates sufficient friction to hold it.
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After 3 months, the fixed appliance is removed & replaced with a removable retainer.
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C. Retention : The objective of retention is to hold the expansion while all those forces generated by expansion have decayed away •
First 2.1/2 years after expansion to be critical & it is essential that in the first 3 months the fixed expansion appliance acts as a retention appliance. Then this can remove and the mouth left without any appliance & without fear of relapse for a few days to permit recovery of palatal mucosa.
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The first removable retention plate is made with patient waiting & delivered with in hour. It consist of fully fiting base-plate of cold cure acrylic with 4 adams clasps (2on 1st molars & 2 on 1st pre molars) In the mixed dentition stage a retention plate with only 2 adams clasps (on 1st permanent molars) is fitted and fixed retention phase is longer, up to 6 months when using an all metal expansion appliance. Long retention period of atleast 2 yrs after removal of expansion appliance is needed. Even with the appliance worn according to instructions there can be slippage & creep it some relapse About 9 months after expansion, wear of retention plate can be reduced from full time to half time (usually evenings & nights)
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A palate covering retainer is satisfactory but may be some what awkward in combination with a fixed appliance to align the teeth as 1st stage of treatment proceeds. An alternative is a heavy labial archwire placed in the headgear, which will maintain the lateral expansion while light resilient archwires are being used to align the teeth (or) lingual arch can be used.
RME in cleft palates RME is carried out only in those cases where cleft has been closed surgically.
Appliances : The basic principles of design apply equally to clefts, the idiosyncrasies of these malocclusions usually call for more complicated forms. www.indiandentalacademy.com
The most common problem, is the anterior collapse, so that parallel (or) near parallel expansion is undesirable •
To restrict the posterior expansion, the left and right, portions of the appliance should be tethered at the back, leaving the anterior aspects to expand fully. This may be done with a hinge (or) omega spring, the latter is probably better as this puts the point of rotation well back in the pharynx.
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Differential expansion puts considerable flexural strain on the screw in the horizontal plane & there are limits which if exceeded, will result in fracture of the screw (or) displacement of the appliance.
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If an appliance is required to provide a vastly greater expansion anteriorly than posteriorly, some form of articulation b/w’n the left & right sides is advised
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Unfortunately very few articulated screws are available and these seem to have neither the length (nor) the strength for much of this work.
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The greater the collapse, the less space available for the screw, where the longest possible length of thread is needed www.indiandentalacademy.com
• As the palate in cleft palate patients is usually flat, the screw
can be mounted near the level of crowns & due to limited availability of clinical crowns, bands are preferred to cap splints. •
RME in young children, springs might be easier to use eg: ‘W’ Porter (or) Quad helix
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Normally RME is done before extraction (or) other forms of appliance therapy. Often some alignment of incisors is done early. Eg., at age 7-8 yrs & RME b/w’n 12-15yrs.
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RME usually produces less discomfort then in normal palate subjects of equivalent age.
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No mid palatal suture, & less force is required to separate the maxilla.
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The usual 3 months of fixed retention phase with expansion appliance left insitu is advised.
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The only undesirable situation which may arise from RME is the opening of oro-nasal fistula, which can be so find that inter collapsed state of the maxillae they do not readily pass fluids but can cause inconvenience when opened by RME.
• RME IN CLASS III Treatment with RME /FM therapy for 10 months induces a significant response of the craniofacial skeleton in terms of forward movement of the and downward and backward movement of the mandible. Although Class III craniofacial characteristics were re-established in the posttreatment period, postpro-traction www.indiandentalacademy.com
Overall, RME/FM therapy has been shown to be an effective treatment for correcting skeletal Class III malocclusion in the long term The favorable skeletal effects induced before the puber-tal growth spurt with orthopedic facemask therapy led to the establishment of a positive overbite and overjet relationship. The occlusal relationships gen-erally withstood subsequent Class III craniofacial growth throughout attainment of skeletal maturity as assessed by the CVM method. •
SURGICALLY ASSISTED RAPID PALATAL EXPANSION
Surgical freeing of the maxilla 1)
Age at surgery :
Resistance in the maxilla to separation may be traced to 3 causal factors 1. Mid palatal synostosis www.indiandentalacademy.com 2. Mid palatal inter locking
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Generally the commencement of synostosis corresponds with the cessation of growth in the middle to late teens, as spicules of bone appear b/w’n the palatal processes.
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These thin early bridges may be removed by osteoclasts to suit local physiological needs. There after this rather slow sutural obliteration increases more rapidly in the twenties.
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All RME patients of age 25 yrs & over are to be supported with surgery. B/w’n 20-25 yrs must be treated with utmost respect for early sutural closure.
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Surgical option cannot be dismissed fully in 15-20 yrs range, because the force buildup can be quite high & produce some pain with sutural opening.
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Some overexpansion is suggested to counteract the relapse effect of buccal tipping of the posterior teeth
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that takes place during Surgically assisted rapid maxillary expansion treatment in the mixed dentition.
SLOW EXPANSION Defn.: It is a form of expansion which involves increase of arch width by movement of few teeth (or) many teeth. • •
Slow expansion has traditionally been termed dento-alveolar expansion, although some skeletal changes can be observed. Expansion is at a rate of 0.5-1mm per week. www.indiandentalacademy.com
Differences between slow expansion and RME Properties Slow Expsn RME 1. Bio Mechanical Orthodontic Effect Effect 2. Type & Amount of Light force force applied (400-500gms) 3. Effects on tissues Dental mild 4. Results Stable more 5. Duration of 2-4 months Treatment 6. Arch Perimeter changes Lesser
Orthopaedic Effect
7. Inter- canine width
0.60 times the posterior expansion 8. Mandibular rotation nil
Heavy force (2000-5000gms) Skeletal mainly & Dental effects Relapse tendency One month Significantly greater
9. ANB
Lesser than RME
0.65 times the posterior expansion downward and backward Significant increase
10.decrease in
nil
Significant
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11. N-Pg-A
not significant
Using Jack screws Using Functional Appliances Ni-Ti palatal expander Coffin Spring ‘W’ Arch Butterfly Expander
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Significant change
Fan Shaped Expander Light Continous Force Expander By Arch Wires Jack screws: •
The various jack screws incorporated in the appliances described for rapid expansion can be used for slow expansion, but with a more spread out activation schedule.
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The screws used for slow expansion have a smaller pitch than those used in RME.
Coffin spring : •
This appliance was designed by Walter Coffin around the beginning of this
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century.
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It is a removable appliance capable of slow dento-alveolar expansion.
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The appliance consists of an omega shaped wire of 1.25mm thickness, placed in the mid palatal region.
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The free ends of the omega wire are embedded in acrylic covering the slopes of the palate.
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The spring is activated by pulling the two sides apart manually (or) by 3 prong pliers.
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Coffin spring is believed to bring about a dento-alveolar expansion. However use of this appliance in younger patients is believed to bring about some amount of skeletal expansion. www.indiandentalacademy.com
‘W’ arch : •
Use to correct the bilateral constriction in primary dentition.
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Made of 36mil steel wire soldered to molar bands.
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The lingual wire should contact the teeth involved in cross bite & extend not more than 1-2mm distal to banded molars to eliminate soft tissue irritation.
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Lingual wire should remain 1-1.5 mm away from marginal gingival & the palatal tissue.
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Accelerates the rate of normal expansion of the mid palatal suture in a young child.
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The appliance delivers proper forces levels when opened 3-4 mm wider than passive width & should be adjusted to this dimension before being inserted.
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Quad helix : •
It is said to have evolved from the original Coffin loop.
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It exerts a palatal suture widening effect.
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It is slower, but separate the suture in pace with the speed of new formation of bone.
Appliance design •
It consist of 4 helices that increase the wire length. Therefore the flexibility and range of action of this appliance is more.
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The appliance is constructed using 0.038 inch Elgialloy wire and is soldered to bands on the first molars.
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The quad helix consists of a pair of anterior helices and a pair of posterior helices. The portion of wire b/w’n the two anterior helices is called the anterior bridge.
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The wire b/w’n the anterior and posterior helices is called the palatal bridge.
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The free wire ends adjacent to the posterior helices are called outer arms. They rest against the lingual surface of the buccal teeth and are soldered on to the lingual aspect of the molar bands. www.indiandentalacademy.com
Activation : It can be pre activated by stretching the two molar bands apart prior to cementation or by using three prong pliers after cementation.
Indications : 1). All cross bite in which upper arch needs to be widened. 2). Cases needing mild expansion in the mixed / permanent dentition which will frequently exhibit lack of space for upper laterals & in which long range of forecast is available. 3). Cases of class II in which upper arch needs to be widened & upper molars rotated distally. 4). Class III conditions in which upper arch needs to be widened & advanced with class III elastics. 5). Cleft palate conditions either unilateral (or) bilateral.
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Nickel Titanium palatal expander : (JCO Mar 1993). •
To overcome the limitations of conventional expansion appliances Wendell V .Arndt, developed a tandem- loop, Ni-Ti temperature activated palatal expander.
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It has the ability to produce light, continuous pressure on mid palatal suture while simultaneously uprighting, rotating & distalizing the maxillary 1st molars.
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This fixed removable appliance has adjustable stainless steel extensions and is inserted into standard horizontal lingual sheaths that are spot welded to the molar bands.
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Action of appliance is consequence of Ni-Ti shape memory & transition temperature effects.
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Expanders come in 8 different intermolar widths ranging from 26mm-47mm that generate forces of 180 - 300gms.
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The clinician determines the appropriate size by measuring the amount of expansion needed & then adding 3mm for over correction.
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♦ Freeze -gel packs, provided in the expander kits, can be placed around the
expander assembly while the band cement is being prepared. This will cool the appliance enough to allow easy insertion into lingual sheaths •
Expander should be handled by molar attachments during placement to avoid warming the Ni-Ti.
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When appliance begins to stiffen in mouth, it may cause some discomfort at first. The patient can alleviate this by sipping a cold liquid, which will temporarily make the Ni-Ti slightly more flexible.
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It can be alloyed to produce a metal with specific transition temperature. At temperatures below the transition temperature interatomic forces weaken, making the metal much more flexible & above the transition temperature the interatomic forces bind the atoms tighter & metal stiffens.
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Ni-Ti as transition temperature of 94°F, when it is chilled before insertion, it become flexible & can easily be bent to facilitate placement.
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As the mouth begins to warm the appliance, the metal stiffens, the shape memory is restored and the expander begins to exert a light continuous force on the teeth & mid palatal suture.
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The Spring Jet for Slow Palatal Expansion (JCO Sep 1999) It is a new appliance designed to achieve fully controllable mechanics for slow maxillary expansion.
Appliance Design : •
The active components of the spring Jet are soldered or attached to the molar bands as with any traditional expander.
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The transpalatal arch is replaced by a telescopic unit with a nickel titanium coil spring and a lock screw.
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Activation of the coil spring is achieved simply by moving the lockscrew horizontally along the telescopic tube.
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A ball stop on the transpalatal wire allows the spring to be compressed.
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The telescopic unit is placed high in the palate, about 5mm up from the center of the molar bands, so that the line of force passes close to the center of resistance of the maxillary teeth.
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While the higher placement avoids irritating the tongue, the Spring Jet should be kept atleast 1-1.5mm away from the palatal soft tissue as well. www.indiandentalacademy.com
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Two different coil springs are available 1). using the 240g spring in the mixed dentition and 2). the 400g spring in the permanent dentition.
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Because the force level of the spring tends to decrease as it opens, the lockscrew is designed to maintain full spring compression, assuring a constant level of force throughout expansion.
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Unfortunately, with previously available appliances, whether stainless steel or nickel titanium, it has been virtually impossible to maintain a constant force of expansion as the palatal arch rebounds to its passive shape.
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The simple and comfortable Spring Jet allows a constant expansion force to be applied as long as necessary. After correction, the appliance can easily be inactivated and kept in place as a retainer. www.indiandentalacademy.com
Butterfly Expander for Use in the Mixed Dentition (JCO Oct 1999) RPE have been shown to create undesirable side effects such as dental extrusion and tipping. A new RPE appliance, called a “butterfly expander”, that is used to treat patients in the mixed dentition was devised.
Appliance Design : •
The butterfly expander follows the basic design of Hass, with a few modifications.
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A high midpalatal jackscrew (A0620) is attached to a butterfly-shaped stainless steel framework that extends forward to the palatal surfaces of the deciduous canines.
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The appliance is soldered to bands on the second deciduous molars.
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A high -powered laser is used to weld the two arms to the screw housing, ensuring perfect, one-piece joints and eliminating any possibility of detachment.
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The rigidity of the appliance and its location high in the palatal vault allow the transverse force to be delivered closer to the center of resistance of the posterior teeth than with conventional expander. www.indiandentalacademy.com
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The butterfly design thus minimizes posterior tipping and extrusion.
Activation : •
Activation of the screw is begun with a complete turn (four quarter -turns) immediately after cementation of the appliance.
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The parents should be instructed to activate the screw a quarter-turn three, times a day (morning, afternoon, and evening).
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Active expansion takes seven to nine days, depending on the degree of maxillary constriction.
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Transverse expansion is usually deemed sufficient when the posterior crossbite is over corrected by 2-3 mm.
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Screw is then blocked, and the appliance is left in place as a passive retainer.
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Occlusal and anteroposterior x-rays should be taken at this point to confirm the expansion.
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♦ It allows early treatment of a skeletal problem that commonly manifests itself in
the primary dentition and will not-self-correct. Because the butterfly expander is applied to the primary molars, it will not cause root resorption of anchored premolars and permanent molars after RPE
Fan-shaped Maxillary Expander
(JCO Nov. 1999
)
Patients with narrow maxillae, sometimes require differential expansion of the anterior and posterior segments, as in cleft lip and palate cases. Schellino & Modica have designed a “ spider screw” that works asymmetrically to produce differential expansion.
Mechanism: •
The expander is made of medical -grade stainless steel, with the spider screw as the active component.
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There are three pivot points; a posterior one, which allows the “fan” opening, and two anterior ones, which counteract the torquing forces produced during expansion.
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Four arms, two mesial and two distal, are welded to the expander and to bands on the teeth. The type of expansion produced depends on the angulation and www.indiandentalacademy.com length of the arms.
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If the arms are mesially inclined (acute anterior angles with respect to the screw), the interarm distance will increase both anteriorly and posteriorly during expansion, but more in the anterior region.
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If the arms are perpendicular, only the anterior interarm distance will increase , with no appreciable change in the posterior dimension. •With distally directed arms (obtuse anterior angles with respect to the
screw), there will be a contraction in the posterior interarm distance, with no anterior change. • Shortening the arms will decrease any of these effects.
•Placement of the fan-shaped expander is similar to that of the traditional
rapid palatal expander.
• After a bite registration is taken with the bands in place, the screw is
adapted and welded to the bands by the laboratory technician.
• A screw with asymmetrical action can produce expansion, contraction,
or conservation of the anterior or posterior transverse dimensions. www.indiandentalacademy.com
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