Space maintainers

Space maintainers 12/9/20141

DefinitionSpace maintenance can be defined as the provision of an appliance (active or passive )which is concerned only with the control of space loss without taking into consideration measures to supervise the development of dentition.12/9/20142

Space maintainers are appliances used to maintain space or regain minor amounts of space lost, so as to guide the unerupted tooth into a proper position in the arch.(ASDC-J.D. Child 2001)

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Important functions of sound primary teeth:

Efficient mastication of food. Maintenance of a normal facial appearanceFormulation of clear speech. Maintenance of a proper diet (missing / decayed teeth rejection of food difficulty in eating )Maintenance of space and arch continuity for the emergence of permanent teeth. Flared root configuration of molars resists mesial migration and space loss. A most important space maintaining appliance indeed is a properly restored primary teeth. 12/9/20144

Causes of premature loss of primary teethCariesTraumaEctopic eruptionAbnormal root resorptionSystemic disorders or hereditary syndromes Eg.Hypophosphatasia, Rickets, Acrodynia , Histocytosis X, Leukaemia, Cherubism, Juvenile Periodontitis, Dentinal Dysplasia, Cyclic Neutropenia, Papillon Lefevre Syndrome12/9/20145

Premature loss of primary teeth may lead to undesireable tooth movements of primary and or permanent teeth including loss of arch length.Arch length deficiency can produce or increase the severity of malocclusions with crowding, rotations, crossbite, excessive overjet &overbite ,unfavorable molar relationship & occlusal plane discrepanciesTeeth try to retain contact, and when, adjacent contact is missing they usually drift and opposing tooth supraerupts.12/9/20146

Altered tooth position may include symptomatic space deficiency with loss of arch length and circumference, blocked or deflected eruption of permanent teeth, unattractive appearance, food impaction areas, increase caries &periodontal disease.Altered occlusal relationship may evidence traumatic interferences & untoward jaw relationshipsThus, corrective measures such as passive space maintainers, active tooth guidance with space regaining or combination of both may be needed to optimize the normal process of occlusal development after premature loss of primary tooth

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SPACE CLOSURE AFTER PREMATURE LOSS OF PRIMARY TEETHRate of closure: Seipel, Breakspear and Seward found that maxillary space closure is fairly constant, with a slight tendency for the closure rate to slow after first year.

MAXILLAMANDIBLESepiel (1946)D: 1.3mm/yrD: 1mm/yrBreakspear (1951)D: 0.8mm/yrE: 2mm/yrD: 0.9mm/yrE: 1.6mm/yr

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Rate of closureRichardson (1965), maxilla and mandible combined

AMOUNT OF CLOSUREMaxillary spaces close more rapidly than mandibular spaces.(Davey 1967)

First 6 months: 1.35 mm

Second 6 months : 0.86mmThird 6 months: 0.77mm

Fourth 6 months : 0.59 mm

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DIRECTION OF CLOSUREDavid G. Owen (1967) in a literature survey noted that there is complete agreement among clinical investigators that early maxillary extraction spaces close predominantly by mesial movement of teeth posterior to the extraction space. On the other hand mandibular spaces close predominantly by distal movement of the teeth anterior to the extraction space.

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Factors influencing the development of malocclusion after premature loss of primary molarAbnormality of oral musculaturePresence of oral habitsExistence of malocclusionStage of developing dentition12/9/201411

Treatment considerations The following considerations are important to the dentist when space maintenance is considered after the untimely loss of primary teeth- a) Time elapsed since loss- If space closure occurs, it usually takes place during the first 6 months after the extraction. When a primary tooth is removed & all factors indicate the need for space maintenance, it is best to insert an appliance as soon as possible after the extraction.

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b) Dental age of the patient- The chronologic age of the patient is not so important as the developmental age. Gron studied the emergence of permanent teeth based on the amount of root development, as viewed on radiographs, at the time of emergence. She found that teeth erupt when three-fourths of the root is developed, regardless of the childs chronologic age.

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c) Amount of bone covering the unerupted tooth- If there is bone covering the crowns, it can be readily predicted that eruption will not occur for many months, a space-maintaining appliance is indicated. If due to infection bone is destroyed then regardless of root formation status tooth eruption is accelerated.

d) Sequence of eruption of teeth- The dentist should observe the relationship of developing & erupting teeth adjacent to the space created by the untimely loss of a tooth. More space is lost if teeth adjacent to area left by extraction are actively erupting

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Eruption of mandibular second molars before eruption of second premolars tend to decrease space available for second premolars and may lead to its partially blocking out of the arch.Eruption of maxillary canine at the same time of maxillry first premolars tend to dicsplace canine labiallyIn these conditions intervention is needed in form of space maintainer.

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E) Delayed eruption of the permanent tooth- In case of impacted permanent tooth, it is necessary to extract the primary tooth, construct a space maintainer & allow the permanent tooth to erupt at its normal position. If the permanent teeth in the same area of the opposing dentition have erupted, it is advisable to incorporate an occlusal stop in the appliance to prevent supraaeruption in the opposing arch.Congenital absence of the permanent toothAmount of space closure maxillary 2nd molar> mandibular 2nd molar>maxillary 1st molar> mandibular 1st molar 12/9/201416

h) Abnormal oral musculature - Strong mentalis muscle patterns may have a pronounced ve effect after loss of 1ry molar or canines with collapse of arch and distal drifting of anterior Segment.i) Patients overall healthJ) Oral hygiene statusK) Patients cooperative abilityl) Eruption 12/9/201417

Space maintainer may not be required if there is

1. Existence of cuspal interference.2. Widely spaced primary dentition.3. If succeeding tooth is expected to erupt within 6 months.

4. If present space is not adequate for the succeeding tooth.5. The possibility of future orthodontic work.6. Where the opposing first molars are locked into a desirable and stable relationship

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Adverse EffectsDislodged, broken, and lost appliancesPlaque accumulationCariesInterference with successor eruptionUndesirable tooth movementInhibition of alveolar growthSoft tissue impingementPain

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Ideal Prerequisites of a Space MaintainerIt should maintain the entire mesio-distal space created by a lost tooth.It must restore the function as far as possible & prevent over-eruption of opposing teeth.It should be simple in construction. It should be strong enough to withstand the functional forces.

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It should not exert excessive stress on adjoining teeth.It must permit maintenance of oral hygiene.It must not restrict normal growth & development and natural adjustments which take place during the transition from deciduous to permanent dentition.12/9/201421

Premature loss of anterior teeth1 Incisors: no decrease in intracanine dimensions if loss after eruption of caninesNeed SM?: Not necessaryExtraction of antimere is suggested to prevent midline shift.

1 Canines: common loss due to ectopic eruption of permanent lateral incisorsNeed SM?: consider LLHA with spur or elective extraction of antimere canine

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Premature loss of posterior teeth?Comprehensive evaluation: determine if space maintainer is indicated for:

a) First primary molarb) Second primary molarc) Multiple tooth loss

Priority: 2nd M > 1st M > Canine > Incisor

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CLASSIFICATION OF SPACE MAINTAINERS1) Acc. To Hitchcock(1973)-Removable or fixed or semi-fixed.With bands or without bands.Functional or non-functional.Active or passive.Certain combinations of the above12/9/201424

2) Acc. To Raymond C.Thurow (1978)-RemovableComplete arch Lingual arch Extra-oral anchorageIndividual tooth

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3) Acc. To Hinrichsen (1962)- Fixed space maintainers- CLASS I (a) Non-functional types- i. Bar type. ii. Loop type. (b) Functional types- i. Pontic type. ii. Lingual arch type. CLASS II Cantilever type (distal shoe, band & loop.)

Removable space maintainers- Acrylic partial dentures12/9/201426

Fixed space maintainers Space maintainers which are fixed or fitted onto the teeth are called fixed space maintainers.ADVANTAGES:1. Bands and crowns are used which require minimum or no tooth preparation.2. They do not interfere with passive eruption of abutment teeth.3. Jaw growth is not hampered.4. The Succedaneous permanent teeth are free to erupt into the oral cavity.5. They can be used in un-co-operative patients.6. Masticatory functions is restored if pontics are placed.12/9/201427

Fixed space maintainersDISADVANTAGES:1. Elaborate instrumentation with expert skill is needed.2. They may result in decalcification of tooth material under the bands.3. Supra eruption of opposing teeth can take place if pontics are not used.4. If pontics are used it can interfere with vertical eruption of the abutment tooth & may prevent eruption of replacing permanent teeth if patient fails to report.

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Band and loop appliancesIndications (Methewson): In case of premature loss of any primary molar in primary dentition or primary maxillary molar in transitional dentition with permanent successor not erupting clinically for the next 2 years and its root length is less than one third mature. Premature loss of a primary second molar as the permanent first molar is erupted clinically. Bilateral loss of single primary molar before eruption of permanent incisors.

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Band and loop appliancesCONTRAINDICATIONSAn occlusion that is extremely crowded or already exhibits marked space loss. High dental caries activity

Replacement of primary anterior teeth. Replacement of primary second molars in transitional dentition with the permanent molar not erupted. 12/9/201430

Band and Loop DisadvantagesMasticatory function.Not restored

Extrusion of opposing dentition.Not prevented

Normal distal movement of primary cuspids during eruption of permanent lateral incisorNot allowed if placed for the early loss of mand 1st primary molar

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Band and Loop ConstructionBand: stainless steel material 0.1800.005 inches in thickness

Crib: portion of the wire spanning the edentulous space

Loop: portion of the wire contacting the abutting tooth 0.036 inches in diameter.

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Band and loop. The loop should be parallel to the edentulous ridge 1mm off the gingival tissue and should rest against the adjacent tooth at the contact area. The faciolingual dimension of the loop should be approximately 8mm. The distal free end of the loop should lie on both sides and in the middle of band. This allows occlusal clearance and adequate strength of the soldered joints.

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Bilateral fixed space maintainersFIXED LINGUAL ARCHThe lingual arch is the most effective appliance for space maintenance and minor tooth movement in the lower arch. The classical mandibular arch wire consists of two bands cemented to the first permanent molars or sometimes 2nd deciduous molars, which are joined by a stainless steel wire butting against four incisors.

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LINGUAL ARCH INDICATIONSMaintainence of arch perimeter , because of premature loss of 1ry teeth after permanent incisor eruptionMaintainence or prevention of mandibular changes in arch length, overjet &overbite from incisor repositioning in transitional dentition.Retention of position of mandibular incisors after tooth movement to prevent relapse in mand. Ant. Crowding and changes in bite depth. Base for aesthetic restoration in loss of anterior teeth(hollywood appliance) and as a base for habit appliance.

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LLHA CONTRAINDICATIONSAnything that require frequent adjustments, eg tooth movement or space regainingRampant dental caries, high plaque scores and poor patient co-operationAnt. Or posterior crossbiteExtreme mand. Ant. Crowding or lingually erupting succedenaous teeth12/9/201436

Lingual ArchAdvantages Disadvantages1. Maintains established arch form.

2. Allows eruption of perm teeth w/o interference.

3. Not easily displaced.

4. Ease of cleaning for proper oral hygiene.

5. Can be modified easily to serve in many situations.

6. Patient comfort.

1. Does not prevent extrusion of opposing teeth.

2. Not advisable to band teeth which are:HypoplasticHypocalcifiedHighly prone to caries.

3. Can promote decay in non-compliant patients.

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Fixed Lingual Arch ConstructionBand: Stainless steel material 0.005 inches in thickness (ortho bands)

Lingual arch wire: Stainless steel round wire 0.036 inches in thickness

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. The arch wire should contact the erupted permanent incisors at the cingulum.

PASSIVATION- The lingual arch wire should be completely passive. This is done by heating the wire to a dull brownish appearance, while keeping the wire gently in place on the cingula with an old instrument.

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Nance ApplianceThe Nance arch is simply a maxillary lingual arch that does not contact the anterior teeth, but approximates the anterior palate. The palatal portion approximates an acrylic button that contacts the palatal tissue, which theoretically provides resistance to the anterior movement of posterior teeth.Indications:The same as for fixed lingual arch

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Construction:Bands: Stainless steel material 0.005 inches in thicknessPalatal wire: Stainless steel round wire 0.036 inches in thickness. At the rugae area, a small U-shaped bend should be incorporated in the wire, which is approximately 1-2 mm away from the soft tissue. The acrylic button is placed usually on the descending portion of the palatal vault. The button is about 0.5 inch in diameter, rests against the palatal tissues.

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Transpalatal arch The construction of transpalatal arch was described by Hill et al (1975) and Tsamtsouries and George E. White (1977). The transpalatal arch runs directly across the palatal vault avoiding contact with the soft tissue.When permanent maxillary molars move anteriorly , they rotate mesiolingually around the large palatal root.transpalatal arch reduces ant. Molar movement by preventing this rotation.12/9/201442

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INDICATIONS:The best indication for transpalatal arch is when one side of the arch is intact, and several primary teeth on the other side are missing.When primary molars are lost bilaterally , it cannot be used as both permanent molars may tip anteriorly despite the transpalatal arch, and in these cases a conventional lingual arch or Nance palatal holding arch is preferred. ADVANTAGELack of acrylic button so less tissue irritation and more cleansable.12/9/201444

DISADVANTAGE:Failure of the appliance to remain passive.If appliance is not passive , unexpected vertical & transverse movement of the permanent molars can occur. CONSTRUCTION: 0.036 inch standard round wire is bent to confirm to the palatal contour and extending toward the palatal surface of the bands. As it approaches the mesial part of the palatal site of the band, the wire should be bent to the distal part of the band to assure a better joint. After soldering the wire should be heat treated in order to make it passive.

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Various Changing Trends In Use Of Space Maintainers Glass Fibre Reinforced composite resins as space maintainers. FABRICATION1 After Extractions & impression: diagnostic casts are made. The amount of ribbond to be placed is measured with Vernier calliper 2 Placement of Ribbond: The abutments on which Ribbond is to be placed is cleaned with pumice. 12/9/201446

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The area is isolated with rubber dam acid etched with 37% orthophosphoric acid ,washed with water and then dried. The bonding agent is applied and cured for 10 seconds according to manufacturers instructions.A thin layer of flowable composite is applied on distal surface of the mesial tooth and on the mesial surface of the distal tooth of the created space without light curing where Ribbond is intended to be placed.

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Ribbond is placed on the abutment teeth. After preliminary curing on both the teeth, additional restorative composite is further placed & cured for 40 seconds to completely bond the space maintainer with the abutment.

The space maintainer is checked for any occlusal and gingival interferences.Finishing is done with composite finishing burs.

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INTRA ALVEOLAR (DISTAL SHOE) APPLIANCEUsed to maintain the space of a primary second molar that has been lost before the eruption of the permanent first molar.An unerupted permanent first molar drifts mesially within the alveolar bone if the primary second molar is lost prematurely. The result of the mesial drifts is loss of arch length & possible impaction of the second premolar.Introduced by willets (1932) with bar type gingival extension and modified by Roche (1942) with a V shaped gingival extension.

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APPLIANCE DESIGNThis appliance consists of a metal or plastic guide plane along which the permanent molar erupts. The guide plane is attached to a fixed or removable retaining device When fixed, the distal shoe is usually retained with a band instead of a stainless steel crown so that it can be replaced by another type of space maintainer after the permanent first molar erupts.To be effective, the guide plane must extend into the alveolar process so that it contacts the permanent first molar approximately 1 mm below the mesial marginal ridge, at or before its emergence from the bone.

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APPLIANCE DESIGNIf primary first and second molars are missing, the appliance must be removable because of the length of the edentulous span and the guide plane is incorporated in a partial denture. This type of appliance can provide some occlusal function. Careful measurement and positioning are necessary to ensure that the blade will ultimately guide the permanent molar.

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DISTAL SHOEDISADVANTAGEUnfortunately, this design limits the strength of the appliance and provides no functional replacement for the missing tooth CONTRAINDICATIONSHopelessly damaged abutmentPatients who are at risk for subacute bacterial endocarditis or who are immunocompromised, because complete epithelialization around the intra-alveolar portion has not been demonstrated. 12/9/201453

DISADVANTAGESFabrication and placement can be quite complicated especially as patients in need of such appliances are usually very young and often uncooperative.Radiographs are needed to determine the position of the distal intragingival extension in relation to the tooth bud of the permanent first molar, multiple impressions may be required (study and working models), at placement local analgesia is needed in order to force the sharpened distal extension through the ridge (unless it is placed at the time of extraction). Due to its cantilever design and its cementation on the occlusally convergent crown of the first permanent primary molar, the appliance is somewhat fragile. 12/9/201454

DISADVANTAGESInflammation of the soft tissue surrounding the extension may occur, a metallic tattoo may result, and a chronic inflammatory response may be expected thus making this appliance contraindicated in any patients who may be at greater risk and are medically compromisedBlood dyscrasias, Congenital heart defects, A history of rheumatic fever, Diabetes or generalized debilitation [hicks, 1973]. Another contraindication is multiple loss of the first and second primary molars. The distal shoe appliance can replace only one tooth. Healthy patients with poor oral hygiene are also contraindications.

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A simplified chair side-fabricated distal shoe appliance [Brill, 2002] has been described as being an efficient and cost effective appliance with success rates approximately equal to those of other space maintainers.

The only treatment alternative to the distal shoe space maintainer is a removable appliance. Carrol and Jones [1982] included in their appliance design acrylic pressure ridges, created by making 2mm deep x 2mm wide grooves in the plaster model in the area of the unerupted first permanent molar. They also adapted lead foil around the distal end of the appliance so that it could be viewed radiographically.12/9/201456

An acrylic partial denture with a distal extension to guide first permanent molars into position may be used .The teeth to be extracted are cut away from the stone cast and a depression is cut into the stone model to allow the fabrication of the acrylic extension. The acrylic will extend into the alveolus after removal of the primary teeth. The extension may be removed after eruption of the permanent tooth.12/9/201457

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C, The primary teeth have been extractedin preparation for the placement of the partial denture. D, The acrylic distal shoe extension. E, Lead foil has been placed over the tissue extension to determine, with the aid of a radiograph, whether the acrylic is positioned properly to guide the eruption of the first permanent molar.CDE

DISTAL SHOE

Should be evaluated with radiograph prior to cementationLengthPosition

Will be replaced with another space maintainer when permanent teeth erupt. FAULTY POSITIONING IS THE MOST COMMON PROBLEM WITH THIS APPLIANCE12/9/201459

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A modified distal shoe pressure appliance to provide bilateral space maintenance and eruption guidance for the first permanent molars.

Decalcification beneath bandsPoor band fit or defective cement may serve as a locus for debris accumulation and subsequent decalcification. Steps to prevent this include :Adapting a band that contours tightly to the tooth surface and extends beneath the gingival margins.Providing a thorough prophylaxis before cementation.Keeping the tooth thoroughly dry during cementation.Using glass ionomer cements.Teaching the child and parent proper oral hygiene practices to include the use of fluoride rinses.12/9/201461

Removable space maintainersThey are space maintainers which can be removed and reinserted into the oral cavity by patientThe partial denture is most useful for bilateral posterior space maintenance when more than one tooth has been lost per segment and the permanent incisors have not yet erupted.TYPES;FunctionalNon functional12/9/201462

Removable space maintainersADVANTAGES 1. Easy to clean and permit maintainance of proper oral hygiene.2. Maintain or restore the vertical dimension.3. Can be worn part time allowing circulation of the blood to the soft tissues.4. Room can be made for permanent teeth to erupt without changing the appliance.5. Stimulate eruption of permanent teeth.6. Help in preventing development of tongue thrust habit into the extraction space.

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Removable space maintainersDISADVANTAGES:1. May be lost or broken by the patient.2. Un-co-operative patients may not wear the appliance.3. Lateral jaw growth may be restricted, if clasps are incorporated.4. May cause irritation of the undrelying soft tissues.

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Removable space maintainersINDICATIONS:1.When aesthetics is of importance. 2.In case the abutment teeth cannot support a fixed appliance.3.In cleft palate patients who require obturation of the palatal defect.4.In case the radiograph reveals that the unerupted permanent tooth is not going to erupt in less than five months time.5.If the permanent teeth have not fully erupted it may be difficult to adapt bands.6.Multiple loss of deciduous teeth which may require functional replacement in the form of either partial or complete dentures.

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Removable space maintainersCONTRAINDICATIONS-1.Lack of patient co-operation.2.patients who are allergic to acrylic material.3.Epileptic patients.

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12/9/201467A, Primary teeth with rampant gross caries and pulpal involvement. B, Complete dentures in placeafter the extraction of all primary teeth.

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C, Modification of the dentures after eruption of upper first permanent molars andlower permanent incisors.

Localized Space Loss (3 mm or Less):Space RegainingSpace is easier to regain in the maxillary arch than in the mandibular arch because of the increased anchorage for removable appliances afforded by the palatal vault and the possibility for use of extraoral force (headgear).MAXILLARY SPACE REGAINING.Permanent maxillary first molars can be tipped distally to regain space with either a fixed or removable appliance, but bodily movement requires a fixed appliance.12/9/201469

For tipping one molar , a removable appliance retained with Adams' clasps and incorporating a helical finger spring adjacent to the tooth to be moved is very effective. One posterior tooth can be moved up to 3 mm distally during 3 to 4 months of fulltime appliance wear. The spring is activated approximately 2mm to produce 1 mm of movement per month. The molar generally will derotate spontaneously as it is tipped distally. If bodily movement of one or both permanent maxillary first molars is necessary in regaining space, it sometimes can be accomplished by using headgear or an arch wire with excellent anchorage12/9/201470

A removable appliance with a fingerspring is used to regain space by tipping a permanent first molar distally. A, The appliance incorporates multiple Adams' clasps and a 28mil helical spring that is activated 1 to 2 mm per month. B, Premature loss of the primary second molar has led to mesial drift and rotation of the permanent first molar.12/9/201471

12/9/201472After space is regained, fixed space maintainer is recommended, rather than trying to maintain the space with the removable appliance that was used for space regaining.

A removable appliance with a fingerspring is used to regain space by tipping a permanent first molar distally. A, The appliance incorporates multiple Adams' clasps and a 28mil helical spring that is activated 1 to 2 mm per month. B, post operative space is regained . After space regaining, the space should be maintained with a band and loop or lingual Arch if the permanent incisors have erupted.

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A, A fixed appliance also can be used to regain space in the maxillary posterior regions, with a coil spring generatingthe distalizing force.B , Palatal anchorage was gained using a Nance arch and the erupted teeth.

Mandibular Space Regaining.If space has been lost on one side of the mandibular arch, the appliance of choice is a removable lingual arch incorporating a loop that can be opened to provide the necessary distal force.It is important to activate the lingual arch so that the molar is tipped up and back, while the reaction force is expressed largely downward on the cingulum area of the lower incisors. DISAVDANTAGE:Incisors may tip forward.An alternative for unilateral mandibular space regaining is a fixed appliance and an arch wire, which provide excellent anchorage12/9/201474

Space regaining in a child with space loss in the upper and lower arches.A, Casts demonstrating loss of space as a result of caries and early loss of a primary molar.B, Bitewing radiograph shows space loss caused by mesial tipping of upper and lower permanent first molars. C, An active lingual arch, inserted from the distal in this case, was used for mandibular space regaining.12/9/201475

D, When an active lingual arch is inserted from the mesial, the welded attachment on the band should be tipped up on the mesial to allow easy placement and removal.E, Note that when the lingual arch is fully seated, the dimple on the distal of the sheath into which it inserts serves as a lock to retain the arch wire. F, Casts of this patient after treatment with a mandibular lingual arch and maxillary headgear, showing the space regaining that was achieved.12/9/201476

Bilateral space loss in mandibular archLip bumper: it is a labial appliance fitted to the tubes on molar teethIt creates distal force to tip the molars distally.DISADVANTAGELip bumper also alters the equilibrium of forces against the incisors, removing any restraintfrom the lip on these teeth. The result is forward movementof the incisors12/9/201477

Moving molar distally in mandibular Arch is quite challenging and requires support from a number of teeth. Using a lingual arch, to incorporate anchorage from the permanent and primary molars as well as the incisors and force from a coil spring can be effective.12/9/201478

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Jackscrew ApplianceIt is designed to regain space without tipping or rotating the teeth. Reciprocal movement of the molar distally and the bicuspid mesially will be effected by the proximity of the adjacent teeth

Ectopic Spring DistalizerDesigned in principle to function the same as the Elastic Halterman, this appliance features a recurved wire spring to achieve the distal movement of the six-year molar that iscaught under the distal edge of a primary second molar

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Looped Coil Space RegainerThis appliance is used to gain space for an un-erupted bicuspid, but it can move more than one tooth or move a molar distallyElastic Halterman ApplianceThis design is indicated when the erupting first permanent molar is caught under the distal edge of a primary second molar. A mushroom-shaped button is bonded to the occlusal surface of the erupting molar. A band with a hook that extents distal to the molar is cemented to the primary second molar. Chain elastic is used between the hook and the button to provide the distal force needed to move the first permanent molar

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Sliding Distal ShoeThis expanding distal shoe engages a mesially erupting six-year molar and guides it distally when the primary second molar has been lost prematurely. Light coil springs over the loop wire provide the needed pressure for distalization.

Removable space regainer with expansion screw

12/9/201482Thank you