Restorative Dentistry

Gaining adequate interdentai space with modifiedelastic separating rings: Rationale and techniqueAmi Smidt, DMD, MSc, BmedScVEyal Venezia, DMD, MSc, BmedSc^

Reslcring a tooth with an inadequate contad point and root proximity is a challenge to thG practitioner.Ignoring such situations or making compromises in the treatment plan may hinder a successful treatmentoutcome. Treatment options inciude strategic extractions, sectional orthodontics, and minor orthodonticmovements. The purpose of this articie is to discuss the clinical problems and difticulties arising from thissituation and to present a modified treatment modality through two case reports. Elastic separating rings,which open an interdental space for piacing orthodontic appliances, can be modified to serve as a pre-prosthetio means for solving mesiodistal crowding of teeth in daiiy practice. The classic method is modifiedby the use of eiastic rings in sequentialiy increased thickness, so that the space gained with one ring isfollowed and increased with a thicker one. An orthodontic background and special instruments are notnecessary, (Quintessence int 2002;33:409-414)

Key words: contact point, elastic separating ring, interdental space, minor orthodontics, rool proximity,tooth crowding

Restoring crowded teeth that exhibit root proximitypresents a challenge to the clinician. Whether it is

a restoration, inlay, onlay, or a crown, the prohlemsarising in such cases compromise the results and pre-dictability oí treatment. The objective of this article isto discuss the chnical prohlems of this situation and topresent minor ortbodontic movement as a solution.The importance of developing correct anatomic con-tact points of teeth is emphasized, with special foctjsgiven to the surrotinding supporting tissues in theadjacent area.

CROWDING OFTEETH

Crowded and malpositioned teeth may present one ormore of the foDowing problems:

1, They create difficulty in patient home care, makingdental floss and other cleaning devices instifficientIndividual tooth irregularity, measured as tilting,displacement, and crowding, is statistically signifi-

'Clinical LGCturer, Department of Prostliodontics, Hebrew University-Hadassat!, School of Denfal Medicine, Jerusalem, Piivaie pracfice, Neve-Avfvim, Tel-Aviv, Israel,

^Graduate Student, Departrrent of Periodontics. Hebrew University-Hadassah, Sctiool ot Dental Medicine, Jérusalem; Israel Detense Fofce,Israel,

Reprint requests: Dr Ami Smidt, 6 Levitan Street, Neve-Avivim, Tel-Aviv69204, Israel, E-mail: smidta@md2.liuji,ac,il

cantly correlated with plaque, calctilus, and gingi-val inflammation,'

2, Crowded and malpositioned teeth are predisposedto bone and attachment loss,̂

3, They may result in enlarged contact surfaces andaltered embrasure spaces, the latter bousingsmaller papillae. As the contact point is distorted,the gingival embrasure, an area of abundant plaqueaccumulation, is displaced apically, thus becomingless accessible to self-cleaning and professionalmaintenance,'

4, Uneven marginal ridges, a direct result of tbecrowding, can cause attachment loss,"

5, Crowded teeth may also create abnormal occlusalrelationsbips, transmitting forces in undesirabledirections,^

6, The size of the occlusal table of crowded teeth isreduced and may affect interocclusal contacts,

7, They itnpair esthetic appearance.

Several problems are associated with restoringcrowded teeth without altering their position;

1, Crowded teetb are more prone to pulpal damageduring caries removal or any other restorativeprocedure,

2, The impaired periodontai status is perpetuated, andtbe biologic width is traumatized by tbe introduc-tion of any restoration margins. In such an event,the chance for continued deterioration is increased.

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Fig 1 Radiograph revealing the root proximityof the mandibuiar right moiars The intermoiarcrowding does not favor any pioslhetic proce-dure.

3. Prosthetic procedures for crown preparation aremore difficult (Fig 1):

a. Tooth preparation (possibility of damage to theadjacent teeth; possibility of pulpal devitaliza-tion; finish line design; multiple abutment paral-lelism).

b. Impression making (tissue retraction; control ofmoisture and bleeding; flow of impression mater-ial; eomplete finish line recording; removai ofthe tray without tearing the impression material).

c. Metal adjustment (adequate metal thickness;verifieation of fit; proper metal design for porce-lain layering),

d. Porcelain adjustment (adequate opaque layers;adequate porcelain layering and thickness; con-tact point design; proper anatomy and contour;ease of color production and esthetics).

4. Professional maintenance and home care are moredifficult.

TREATMENT ALTERNATIVES

The choice of treatment for crowded and malposi-tioned teeth that require restoration may be one of thefollowing:

1. Strategic extractions followed by places.L-rit of afixed partial denture with or without the use ofimplants

2. Sectional orthodontics to open the interproximalspace

3. Separation tools to achieve minor tooth move-ments for space opening

Although the first treatment option is commonlyused in daily praetice, the focus of this article will beon the other two treatment modalities, emphasizingthe feasibility and the importance of these methods forthe elimination of tooth crowding.

CASE REPORTS

Case 1: Sectional orthodontics

A 22-year-old woman was experiencing severe pain inthe mandibular right first molar. Examination revealedpulpal involvement following an extensive carieslesion, as well as loss of interproximal space andcrowding (Fig 2a). After endodontie therapy (Fig 2b)and placement of a provisional restoration, orthodon-fic movement was initiated to regain the lost interden-tal space (Figs 2c and 2d). The movement durationwas 16 weeks, during which the teeth were realignedand the interproximal space was restored, thus allow-ing routine prosthetie procedures.

An immediate post-and-core restoration and a pro-visional acrylic resin crown were made (Fig 2e). Theteeth were splinted for 4 weeks, after which the sontissues, the posifion and relationships of the teeth, andthe interdental separation were evaluated clinicallyand radiographically. The satisfacfory status of theseparameters allowed completion of the prosthefic work(Figs 2f to 2!).

Case 2: Modified elastic separating rings

A 35-year-o!d woman complained of severe pain in theleft side of her mouth. The mandibular left firsf molarwas highly sensitive to percussion. Radiographic exami-nation of that tooth revealed an extensive secondaryearies lesion adjacent to a recently placed amalgamrestorafion (Fig 3a). The crowding compromised treat-ment attempts made by the patient's former dentist. Aspart of the treatment plan, the patient was referred forendodontie therapy in that tooth (Fig 3b). Subsequently,the mandibular left second molar would be tipped dis-tally to separate it from the first molar and to permitplacement of a future crown on the affected tooth.

Elastic separating rings in sequential increasing orderof width were selected for this purpose (Separators

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Fig 2a Mandibular right lirst molar with anextensive caries lesion, loss of interproxi-mal space, and an inadequate conia^'lpoint

Rg 2b Mandibuiar right first molar radio-graph after endodontic therapy, before initi-ation of movement. Note the absence ofthe interdental space between the moiarand premolar.

Figs 2c and 2d Initiation of sectionalorthodontic treatment. Space is gainedmostly from the canine-premolar area andthe distal tipping ot the molars.

Fig 2e End of movement. A provisionaiacrylic resin crovun is used to restore theanatomic contour of the first moiar Ligationof ttie canine and the premolars is per-formed for retention.

Fig 2f fulandibuiar first molar beforeirnpression taking. Noie the healthyappearance of the surrounding soft tissueand the corrected interdentai space.

Fig 2g Final porcelain-fused-to-metalcrown.

Rg 2h Porcelain-fused-to-metal crown inrigtii lateral movement.

Fig 2i Bitewing radiograph of the patient6 mon^s postfreatment.

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Fig 3a Radiograph ot manoibular ieft firstmolar with an extensive secondary carieslesion and ioss of interdental spacebetween the mandibuiar molars.

Fig 3b Periapicai radiograpii afterendodontic therapy.

Fig 3c Introduction of a separating ring tothe mouth {in a different patient). The tips ofthe instrurrent are directed in a coronaidirection to ease the maneuver.

Fig 3d Elastic separating nng in place (in Fig 3e Radiograph showing adequate Fig 3f Prepared mandibular left first molara different patient]. interdental spaoe after use of the separat- before impression taking.

ing rings.

Fig 3g (ieft) Final porcelain-fused-to-metal crown.

Fig 3h (rigiit) Bitewing radiograph of thepatient 6 years posttreatment.

designed for research, American Orthodontics), Thethinnest separator band (No-1) was inserted in the con-tact point with the help of a clamp holder f Stotna) (Figs3c and 3d), A wooden anatomic wedge insertedbetween the teeth, below the contact point, assistedduring placement of the separating ring. After 1 week,ring 1 was replaced with ring 2, which was replaced thefollowing week with ring 3, After 3 weeks, an immedi-ate post-and-core restoration was prepared, and a pro-visional acrylic resin crown was made to fit the gainedinterproxitnal space. The tipping movement continuedin the same way, starting with ring 2, which was

replaced after 3 days with ring 3, which was replaced 1week later with ring 4,

The possibility of modifying the provisional acryliccrown allowed the acquisition of a tight contact pointwhen movement was fottnd to have opened sufficientinterdental space (Fig 3e). Four weeks later, after thisminor orthodontic movement, the stability and peri-odontal status of these teeth were found to be satisfac-tory. The crown on the mandibular left second molarwas clinically acceptable. At this stage, a final porce-lain-fused-to-metal crown was fabricated for the firstmolar (Figs 3f to 3h}.

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DISCUSSION

The most common type of malocclusion is crowdedteeth^; these cause problems witb many restorativeprocedures in dental practice. Rotifine bome care andprofessional maintenance are always more difficult inthe interproximal area, whether the tooth is intact orrestored. The interface of tooth structure and restora-five material is less resistant to recurrent pathosis, par-ticularly in the proximal area, where no direct vision,finishing, or effective polishing is possible once arestoration is completed. This situation is furtheraggravated when the interdental space is fully or par-tially lost due to crowding. There are several reasonsfor this problem, including untreated extensive carieslesions with loss of proximal walls and open contactpoints, old faulty restorations, and disturbed order oftooth erupfion and alignment.

Wben a restoration is to be piaced proximally andthe interdental space is compromised, tbe solution isto regain adequate interproximal space. This wouldallow the placement of any proximal restoration mar-gin without insuhing the biologic width and wouldenstire proper quality control.

Restoring a tooth without eliminating the crowdingperpetuates the situation. The roots of crowded andmalpositioned teeth may be in close approximation.These teeth will have a poor prognosis because of thesmall volume of bone between the roots and becauseof the abnormal tootb relationship to one another andto the soft tissue. A crown-lengthening procedure ivillundoubtedly fail, because the cause of the problem isnot treated. Surgical reduction of the thin interradicu-lar bone and changing the local architecture is thewrong approach. This may lead to unnecessary rootand furcation exposure, reverse bone and soft tissuearcbitecture, and the unnecessary sacrifice of support-ing bone from adjacent teeth.

As previously stated, there are three main treatmentalternatives for crowding. Strategic extraction is acommonly used treatment modality. Extraction is foi-lowed by placetnent of a multiple-unit fixed partialdenture or an implant-supported restoration. Even ifextraction is tbe treatment of cboice, opening of tbeinterdental space is sometimes recommended, fol-lowed by a réévaluation of tbe situation. The topo-graphic improvements gained by such a movement'cotild be beneficial not only for future implant place-ment (increased mesiodistal measurements) but alsoas an attempt to save the tooth from extraction.

Sectional orthodontics is a highly predictable treat-ment modality but requires skills and instrumentationthat not all general practitioners possess. It also ismore time consuming and requires more anchoragethan does the alternative technique that uses modified

elastic separating rings. Moreover, a specialist is oftenneeded for sectional orthodontics.

The third treatment option, using modified elasticseparafing rings for interdental space opening, is easyto achieve and can be performed by general practition-ers without the use of fixed orthodontic appliances. Interms of prosthetic results and overall prognosis, bothorthodontic modalities are preferable to tbe firstchoice, because teeth are saved from extraction.

The main methods used to separate posterior teethin orthodontic treatment are^ (1) soft brass wire,whicb is twisted tigbtly around the contact point andleft in place for several days; (2) a separafing spring,which exerts a scissors action above and below thecontact point; and (3) elastic separating rings, whichsurround the contact point and separate the teeth overa period of several days. Tbe modified elastic separat-ing ring technique ufilizes tbe increasing space by stip-ulafing that each ring be replaced with a consecutivelythicker one until the desired space is obtained. Wbena provisional acrylic resin crown is combined in tbeseparation action, the space gained may be furtberincreased. Tbis is achieved by adding self-poiymerizingacrylic resin to the proximal side, increasing thecrown dimension before eacb ring replacement.

In minor tooth movement, tbe issue is wbere todirect tbe movement. In tbe posterior areas of tbemoutb, space is gained by tipping the most posteriortooth in tbe arch. In other areas, to avoid crowding inadjacent areas, movement must take into accountpresently available spaces.

The presented technique is performed to enable betterprosthetic results. Thus, it is cruciai that tbe gained spacebe retained once movement is completed. Retention maybe accomplished with a provisional acryiic resin crownwith tight contact points. After a reasonable period ofretention, prostbetie procedures may be completed.

For the patient, this technique is easy to tolerate,although pain and inconvenience might be experi-enced. The rings, especially the thicker sizes, coulddisturb occlusion in the area, but clinical experienceindicates tbat tbis bas no clinical significance.

The main disadvantage of the elastic separating rings isthat they may become loose and fall out as they accom-plish their purpose. Therefore, the rings should remain inplace only for a few days. A ring lost in the interproximalspace may cause serious, irreversible periodontal damage(less probable with thicker rings). The patient should beadvised to immediately report any ring displacement.

Appointments sbould be set at intervals of severaldays. Under no circumstances should the separatorsbe left in place for more than 2 weeks.̂ The decisionto cease treatment is based on clinical and radi-ographie evaluation to determine if the restorativerequirements have been met

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The biologic basis for this technique is the 0,25 mmplus 50% of space tbat occupies the periodontai liga-ment,* Although there are many varieties of separa-tors, the principle is the same for each: A device toforce or wedge the teeth apart is left in place longenough for initial tooth movement to occur. In tbepresent tecbnique, tbe separators are replaced insequentially increasing tbickness to create a largerinterproximal space than is created by a one-sizesingle separating ring.

CONCLUSION

Prostbetic failure is frequently related to inadequateoral hygiene measures and infrequent professionalmaintenance. Many of tbese failures can also be attrib-uted to an inadequate contact point and close proxim-ity of teeth. The main goal of prosthodontics is torestore lost anatomic structures. Use of modified elas-tic separating rings enhances treatment resitlts. Thetipping action improves tbe interproximal topographyand facilitates prosthetic procedures,

The two case reports showed tbat the use of modi-fied elastic separafing rings is easy and simple and thatthe procedure ean be used by the general practitionerin daily pracfice. The technique is more convenient tothe pafient, is less time consuming, is less expensive,and does not require referral out of the clinic.Therefore, patient compliance is likely to be better tbanmay occur witb conventional orthodonfic appliances.

ACKNOWLEDGMENTS

The authors wish to thank Dr Naplitali Brezniali ¡"i lii'' support andadvice.

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3. Carranza FA Jr, Clinical Peri odontology, ed 8, Philadelphia:Saunders, 1996:559,

4. Pihlstrom BL, Anderson KA, Aeppli D, Schaffer EM.Association hetween signs of trauma from occlusion andperiodontitis, I Periodontol 1986;57:l-6,

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