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SLOW PALATAL EXPANSION- A NOVEL METHOD OF ARCH EXPANSION
Article · January 2019
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Shyamala Naidu
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Anand Suresh Boston University
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SLOW PALATAL EXPANSION- A NOVEL METHOD OF ARCH EXPANSION
Dr. Shyamala Naidu
Lecturer Dr. Anand Suresh
Assistant Professor
One of the most common problems faced by an orthodontist while treating young as well as adult patients is the constricted maxillary arch. Expansion of the maxillary arch has been a topic of debate since centuries. The commonly used methods for constricted arch includes slow maxillary expansion, rapid maxillary expansion and surgically assisted rapid palatal expansion(SARPE). Slow palatal expansion is a procedure to expand the maxillary arch in transverse dimension to correct the constricted maxillary arch with light forces. The following review article provides detailed information of various slow maxillary expansion appliances with their implications in orthodontics.
Keywords: Maxillary expansion, Slow maxillary expansion, Rapid palatal expansion
INTRODUCTION
Expansion of maxillary arch has been studied since centuries. Due to the positive results reported by many studies, clinicians today rely on both slow as well as rapid palatal expansion appliances to correct the constricted maxillary arch by expanding the arch in transverse dimension. The history of expansion dates back to 1860 where Emerson C. Angellreported his first case of successfully splitting the maxilla using a jack screw appliance, thus he was considered as the father of rapid maxillary expansion. Later in the year 1888 Farrarand Clark Godard (1893) stressed the effectiveness of transverse expansion of palate with opening up of the mid palatal suture. Lathamin the year 1971 believed that growth at the midpalatal suture ceases at the age of 3 years which was contradicted in the year 1974 by Bjork and Skiellerwho did a study with implants which proved that growth at mid palatal suture can continue as long as 13 years of age. Slow maxillary expansion can also be termed as dentoalveolar expansion where appliances are used to increase the width of the palate in transverse direction. Although the expansion is purely dental, some amount of skeletal changes are seen. The effect of skeletal versus dental changes purely depends on the age of the patient and the magnitude of force applied. However it was not until 1978 when Hicks with his cephalometric study used a fitted split acrylic plate to expand the maxillary arch and proved the effectiveness of slow palatal expansion.
Classification of Slow Maxillary Expansion Appliances Slow maxillary appliances can be broadly classified as follows:
X
X REMOVABLE
» Coffin spring
» Y plate
» Shwartz appliance
» Active plate
Penang International Dental College, Malaysia
X X FIXED
» Niti palatal expander
» Quad helix
» Minnie expander
» Spring loaded expander
» W arch
» Spring jet
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INDICATIONS OF SME
1. Unilateral or bilateral crossbites
2. To correct minimal crowding by gaining spaces 3. To correct dental crossbite in permanent dentition
4. To correct mild maxillary deficiency in cleft lip and palate patients by providing slow continuous forces
CONTRAINDICATIONS OF SME
1. Adult patients who have completed their growth.
ADVANTAGES OF SME
1. It delivers a constant physiologic force until the required expansion is obtained.
2. There is minimum tipping of anterior teeth.
3. Least strain is exerted on anchored teeth.
4. The appliance is light and comfortable to the patient.
5. It can be used for sufficient retention after the expansion . 6. Relapse tendencies are less.
7. Time required for retention is less.
8. It requires minimal adjustment throughout its use, and allows easy adjustment when necessary.
9. Maintenance of sutural integrity and the reduced stress loads within the tissues 10. Less pain and discomfort due to light forces.
DISADVANTAGES OF SME
1. Longer treatment duration compared to rapid palatal expansion.
AGE FACTOR ON TREATMENT OUTCOME
According to Profitt expansion in younger children can be produced with 1-2lbs of forces. However in adolescents, more dental changes are observed compared to the skeletal changes. Hicks stated that expansion in adults produced more dental changes by tipping of the posterior teeth, increased activation provided minimal expansion whereas aggressive activation lead to tipping of the anchored teeth which are mainly the molars. In his study he used 2 lb force with estimated expansion rates of 0.5 to 1.0 mm per week, however he achieved maxillary arch width increase of 3.8 to 8.7 mm during treatment. According to him the skeletal changes represented 24 to 30 percent of the total arch width increase in 10 to 11-year-old patients whereas in 14-15 years old the expansion rate was 16 percent.
EFFECTS OF SME ON MID-PALATAL SUTURES
According to Storey et al in 1973 stated that the opening of the mid-palatal suture occurs when sutural integrity is maintained during remodelling of maxilla. Ekstrom et al in 1977 proved that with SME there is less traumatic disruption, a greater reparatory reaction, and greater sutural stability than rapid expansion of sutures. According to Bell et al in 1982 the rate of midpalatal suture separation by slow expansion systems apparently allows
a more physiologically tolerable response by the sutural elements than the disruptive nature of rapidly expanded maxillary segments. Moyers et al in 1974 mentioned that slow expansion procedures increase the percentage of orthodontic movements as the tensile strength of the suture elements is not overwhelmed. Zachrisson et al in 1982 did a comparative study on slow and rapid palatal expansion and concluded that periodontal breakdown on the buccal aspects of the posterior teeth occurred in both the groups however the groups which were treated with rapid palatal expansion the occurrence of attachment loss was higher.
APPLIANCES USED TO PRODUCE SLOW MAXILLARY EXPANSION
1. COFFIN SPRING
The coffin spring was introduced by Sir Walter Coffin in the year 1875.The appliance consists of adam’s clasp in the first premolars and first molars of both sides with an omega shaped wire placed in the mid-palatal region. The appliance is made up of 1.2 mm stainless steel wire and the components of the appliance are embedded into an acrylic base plate. The appliance is mainly indicated to bring about dentoalveolar changes in cases of unilateral or bilateral crossbite, Cases where lateral expansion is indicated, Cases requiring antero-posterior expansion, and when space requirement is less than 3 mm..
However some amount of skeletal changes can also be brought about in mixed dentition period if proper retention protocol is maintained.(Figure 1)
Figure 1
2. Y Plate
It is an active type of removable expansion appliance which is similar to that of the bite plate with Adams clasps serving as an anchorage or retentive component in the premolars and molars region.The labial bowis fitted in the anterior region and the retentive arm is embedded in the acrylic. The acrylic plate is splitted into Y shaped and has two jack screws placed between the anterior and posterior half of the acrylic plate which exerts a distalizing force.
The jackscrews on activation exerts a distalizing force on the buccal segment teeth and a reciprocal force is delivered to the anterior palatal contour and maxillary incisors. To avoid the incisors to tip labially and dislodge the entire appliance the jackscrews are activated alternatively.The Y plate is indicated
Orthodontics Orthodontics O rthOdOntics Jan 2019
in patients with first premolars erupted, giving increased anchorage, upright incisors and where no extensively bodily movement are required. (Figure 2)
Figure 2
3. SHWARTZ APPLIANCE
The Shwartz appliance was introduced by Shwartz in 1966. It is a removable expansion plate mainly given in the mandible. The appliance is indicated during the mixed dentition phase. The appliance basically consists of an acrylic plate with a midline split incorporating one or two expansion screws, the acrylic does not cap the occlusal surface or incisal edges. The appliance in addition has a labial bow & is retained by means of Adam’s or ball end clasps. The Schwarz appliance can be used in patients who have arch length deficiencies and/or posterior teeth that have an abnormal lingual inclination.
The gradual expansion of Schwarz appliance produced by activation of midline screw, simply tips the posterior teeth in a lateral direction .This is followed by rapid maxillary expansion which would stabilize mandibular dentoalveolar position during the retention period. (Figure 3)
Figure 3
4. ACTIVE PLATE
The concept of active plate was introduced by Pierre robin in 1902. He constructed a split acrylic platewith a screw incorporated in the midline for arch expansion.The active plate consists of acrylic base which serves as a base in which screws or springs are embedded and to which clasps are attached.
The expansion screws are the active components of this removable appliance.
According to Proffit most screws open 1mm per complete revolution, so that a single quarter turn produces 0.25mm of tooth movement.The active plate are most useful when few millimetres of space is required (1.5-2mm per side).(Figure 4)
Figure 4
5. NITI PALATAL EXPANDER
The appliance was introduced by Wendell.V,Arndt in the year 1993. It is a tandem-loop, nickel titanium palatal expander which is activated by temperature that produces light, continuous pressure on the midpalatal suture which simultaneously helps in uprighting, rotating, and distalizing the maxillary first molars. The adjustable stainless steel extensions which are inserted into standard horizontal lingual sheaths are spot- welded to the molar bands.A locking indent on the lingual attachment holds the expander to the molar band for patient safety.The nickel titanium expander has a transition temperature of 94°F. When chilled before insertion, it becomes flexible and can easily be bent to facilitate placement. 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 and the midpalatal suture. Nickel titanium expanders are available in eight different intermolar widths, ranging from 26mm to 47mm, and generates forces of upto 180-300g. The 26-32mm sizes have softer wires that produce lower force levels for younger patients. Marzban et al in 1999 stated that it delivers a uniform, slow, continuous force for maxillary expansion, molar rotation and distalization, and arch development.This appliance expands at a rate that maintains tissue integrity during repositioning and remodeling of the teeth and bone.(Figure 5)
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Figure 5
6. QUAD HELIX
Quad helix was introduced by Robert Ricketts in 1975.It is a modification of W arch appliance.The indications include a) All crossbites needing upper arch expansion b) Crowding cases needing mild expansion c) Class II cases needing molar distal rotation d) Class III cases with constricted maxillary arch e) Tongue thrusting cases f)Cleft lip with cleft palate patients. The quad helix is made up of 038 Elgiloy or No.4 Gold or 1 mm S.S. The anterior bridge is at the level of distal surfaces of canines. The anterior helices are towards the palate. The posterior helices are placed distal to the first molars.
These are sloped parallel to the palatal surface. The activation is done before cementation. Ricketts prescribes 500 gm force to separate the midpalatal suture. A six weeks interval is observed before further activation. 1 cm each side in molar region & 1.5 mm anteriorly is preferred. Anterior helices are opened for intermolar expansion then posterior helices adjusted to counteract mesial molar rotation.(Figure 6)
Figure 6
7. MINNE EXPANDER
Minne Expander is a fixed, slow maxillary expansion appliance cemented to the first permanent molars and first premolars.It is used to increase maxillary width by activating the palatal compressed-coil spring. According to Hicks 1978, the Minne-expander appliance spring applies forces of up to 10 N which is upto 2 pounds. Each incremental activation of the Minne-expander produces 0.125mm of expansion .It has lessened effect to the maxillary sutures and the
consequent healing and repair of the latter during the expansion procedure makes it more physiologic in nature. The disadvantage of this appliance includes poor oral hygiene maintenance.(Figure 7)
Figure 7
8. SPRING LOADED EXPANDER
The spring loaded expander (SLE) was introduced by Leone in 2003. The SLE is a new expansion device that produces slow palatal expansion with light continuous forces.The appliance is indicated in patients whose growth is completed. They produce accurate force levels due to the control on the spring. Depending on the need of expansion SLE can produce either a 500g or a 800g of force. The appliance consists of bands surrounding the molar with screw attached to the centre. The spring provides a continuous force, sufficient to promote a dentoalveolar remodelling that is biologically ideal and biomechanically controlled. The screw has a self-stop mechanism at the end of expansion to prevent it from disassembling in case of excessive activation. The device is activated on average, 4-8 activations (0, 4-0, 8 mm) every 6 weeks.A different number of activations will not alter the intensity of the force delivered to the dental structures, as this stays constant (500 or 800g.).There is no risk of over-expansion as the screw, upon reaching the pre-determined expansion, will become passive. However, by changing the activation pattern, rapid maxillary expansion can also be achieved using SLE.
(Figure 8)
Figure 8
GUIDENT
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Your Guide on the path of Dentistry42
Orthodontics O rthOdOntics Jan 2019
9. W ARCH
The W arch appliance was introduced byRicketts in the year 1975. It is a fixed horseshoe shaped appliance soldered to the molar bands on either side.
It is indicated in maxilla and mandible where mild expansion is preferred. To avoid causing any damage to the soft tissues the lingual arch is constructed 1-1.5mm away from the palate. The activation of W arch appliance is by simply by opening the apices of the appliance. Depending on whether anterior or posterior expansion is needed the arch is adjusted. To deliver appropriate force levels the appliance is preactivated before insertion by opening up of apices by 3mm. The appliance is activated at the rate of 2mm per month until the cross bite is mildly overcorrected. (Figure 9)
Figure 9
10. SPRING JET APPLIANCE
Spring Jet is a prefabricated appliance consisting of an active component which is Niti coil spring and supporting components are made up of stainless steel wire. The Niti spring is soldered to the molar bands place on each molar.A nickel titanium spring is attached with a lock screw which acts as a telescopic unit. Activation of the coil spring is achieved simply by moving the lockscrew horizontally along the telescopic tube. A ball stop is attached to the wire to allow the spring to be compressed. The telescopic unit is placed 5mm above the palate so that the application of forces is passed through the centre of resistance of the maxillary teeth.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. The spring jet offers a lighter consistent force transferred through the use of NiTi springs. The Niti coil spring delivers approximately 400 gms of force to correct the crossbite.The spring jet is activated by turning the lockscrew by 90 degrees every two weeks to keep the spring compressed for slow palatal expansion. (Figure 10).
Figure 10
CONCLUSION
Previously tooth extraction was considered as an ideal method of gaining space. However since centuries the debate on the stability of dentition and surrounding structures after tooth extraction have been questioned. Arch expansion is considered one of the safe and ideal means of gaining space.
Although both rapid as well as slow maxillary arch expansion have proven to produce long term stability, due to the aggressive nature of rapid palatal expansion on tissues , researchers are inclined towards both skeletal and dental effects of slow maxillary palatal expansion. However further clinical trials have to be carried out to discuss the effects of SME on dentition.
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