1354

2008;139;1354-1363 J Am Dent Assoc

Chandler Vincent Bennani, Donald Schwass and Nicholas

Versus Teeth: Current StatusGingival Retraction Techniques for Implants

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CLINICAL PRACTICE CRITICAL REVIEW

1354 JADA, Vol. 139 http://jada.ada.org October 2008

Implant dentistry has seenrapid progress in recent years.Its increased use in the treat-ment of partially edentulouspatients has led to two

restorative techniques: screw-retained implant restorations, inwhich the fastening screw providesa solid joint between the restorationand the implant abutment orbetween the restoration and theimplant; and cement-retained resto-rations, in which clinicians do notuse screws but instead cement therestoration on a machined or cus-tomized abutment.

Cement-retained prostheses arethe restoration of choice for manypatients who receive implants forseveral reasons, including esthetics,occlusal stability, overcoming angu-lation problems and the fabricationof a passively fitting restoration.1,2

Some investigators have suggestedthat the intervening cement layercan act as a shock absorber andenhance the transfer of loadthroughout the prosthesis-implant-bone system.3,4

There is, however, limited scien-tific documentation of the cement-retained technique compared withthat for screw-retained technique.5,6

The quest for predictable long-termresults has raised questions about

Dr. Bennani is a senior lecturer, Department of Oral Rehabilitation, School of Dentistry, University ofOtago, 280 Great King St., P.O. Box 647, Dunedin, New Zealand, 9054. Address reprint requests to Dr. Bennani.Mr. Schwass is a postgraduate student in prosthodontics, Department of Oral Rehabilitation, School ofDentistry, University of Otago, Dunedin, New Zealand.Dr. Chandler is an associate professor, Department of Oral Rehabilitation, School of Dentistry, Univer-sity of Otago, Dunedin, New Zealand.

Gingival retraction techniques for implantsversus teethCurrent status

Vincent Bennani, DDS, PhD; Donald Schwass, BSc, BDS; Nicholas Chandler, BDS, MSc, PhD

Background. The authors reviewed and com-pared gingival retraction techniques used forimplants and teeth.Types of Studies Reviewed. The authorssearched the literature using article databases Ovid MEDLINE up to May 2008, PubMED and Google Scholar (advancedsearch) and the following search terms: gingival retraction, implant abut-ment, impressions, cement-retained implant restoration, impressioncoping, peri-implant tissue, emergence profile and tissue conditioning.Results. The authors found insufficient evidence relating to gingivaldisplacement techniques for impression making for implant dentistry.Gingival retraction techniques and materials are designed primarily forperidental applications; the authors considered their relevance to peri-implant applications and determined that further research and newproduct development are needed.Clinical Implications. The use of injectable materials that form anexpanding matrix to provide gingival retraction offers effective exposureof preparation finish lines and is suitable for conventional impression-making methods or computer-aided design/computer-aided manufac-turing digital impressions in many situations. There are, however, limita-tions with any retraction technique, including injectable matrices, forsituations in which clinicians place deep implants.Key Words. Gingival retraction; implant impressions; peri-implanttissue; tissue conditioning.JADA 2008;139(10):1354-1363.

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JADA, Vol. 139 http://jada.ada.org October 2008 1355

the materials used and the techniques followed inclinical practice. One question concerns gingivalretraction techniques and their outcomes inimplant treatment.

Several impression techniques are used inimplant dentistry, and some require gingival dis-placement while making impressions. Others,such as the pickup impression technique, do notrequire any gingival retraction. For screw-retained implant restorations, most systems usemechanical components (impression copings) thatcan be adapted accurately and directly to the fix-ture head on the abutment shoulder. Withcement-retained prostheses that use customizedabutments, the pickup impression techniquecannot be used owing to the unique contour of theabutments. Therefore, clinicians must useanother technique such as the conventional crownand bridge impression or optical impression.

To ensure accuracy with polyvinyl siloxaneimpression materials, clinicians must maintain aminimum bulk of 0.2-millimeter thickness in thesulcus area,7,8 which they can achieve byretracting the gingiva for at least four minutesbefore making the impression.9,10 Rapid reclosureof the sulcus requires that clinicians make theimpression immediately after removing theretraction material.7,10

Larger sulcus spaces than necessary for con-ventional crown and bridge impression tech-niques are needed when making digital computer-aided design/computer-aided manufacturing(CAD/CAM) impressions to ensure accuraterecording of finishing lines.

Direct optical impressions are limited to line ofsight, which is facilitated by performing gingivalretraction to expose finish lines. Artifacts causedby retraction cord fibers that remain in the sulcusmay affect the accuracy of optical impressions.Fifteen percent aluminum chloride in aninjectable kaolin matrix leaves a clean sulcus,reducing the influence of artifact-generatederrors.11 However, the powders used when makingoptical impressions to reduce reflectivity andmake tooth surfaces measurable can influenceimpression accuracy by increasing tooth surfacethickness.12

Clinicians regard the indirect capture of digi-tized information as being potentially more accu-rate; however, the way in which clinicians canacquire data is influenced by the thickness of theimpression material in the sulcus area.11,12 Signifi-cant errors can result from thin impression mar-

gins with a radius less than the contacting probetip.12

Donovan and Chee13 described a variety of gin-gival displacement techniques, but we found noarticles that specifically reviewed gingival retrac-tion techniques in implant dentistry. Since thearchitecture of the gingival crevice surroundingnatural teeth is different biologically from thataround implants, we wanted to know if conven-tional retraction techniques could be appliedsafely to peri-implant tissue. In this article, wereview the advantages and disadvantages of dif-ferent gingival retraction techniques on peri-implant and peridental tissues.

METHODS

We conducted a literature search for articlesabout gingival retraction techniques used whenmaking impressions of implant restorations. Wenoted that there was no literature on this subject,so we widened our search to include soft-tissueretraction techniques applicable to natural teeth.

We conducted the search using Ovid MED-LINE up to May 2008. The key words we usedand the number of articles they generated wereas follows: “gingival retraction” (130), “implantabutment” (237), “impressions” (7,242), “cement-retained implant restoration” (one), “impressioncoping” (22), “peri-implant tissue” (141), “emer-gence profile” (76) and “tissue conditioning” (326).Combinations of key words that yielded zero arti-cles were “impressions” plus “cement retainedimplant restoration” and “peri-implant tissue”plus “emergence profile” plus “tissue condi-tioning.” We searched further for relevant articlesby using PubMED and Google Scholar (advancedsearch).

Considering the relative paucity of informationon this subject, we considered all references to bea relevant contribution. If we had implemented amore rigorous selection protocol with tighterstudy inclusion criteria, we would have had fewresults.

COMPARISON OF PERIDENTAL AND PERI-IMPLANT TISSUE

There are substantial differences between theconnective tissue structures surrounding teeth

ABBREVIATION KEY. CAD/CAM: Computer-aideddesign/computer-aided manufacturing. CO2: Carbondioxide. Er:YAG: Erbium:yttrium-aluminum-garnet.Nd:YAG: Neodymium:yttrium-aluminum-garnet.



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and implants that affect the robustness of gin-gival tissues (Table 114 and Figure 1).

Peri-implant mucosa lacks keratinized epithe-lium at the base of the sulcus, which forms thejunctional epithelium and has a hemidesmosomalattachment and internal basal lamina in thelower regions of the interface.15,16 It adherespoorly to implant surfaces, is more permeable andhas a lower capacity for proliferation and regener-ation than does the junctional epithelium around

teeth.17

Peri-implant mucosa consists of circumferen-tially running fiber bundles and fibers that runlongitudinally to the implant surface. Most con-nective tissue fibers that surround smoothimplants run parallel to the implant surface. Theuse of rougher implant surfaces encourages theattachment of fibrils to the implant surface,affecting the orientation of fibers adjacent toimplants at varying angles.15,16 The junctionalepithelium is longer adjacent to machinedimplant surfaces (a mean of 2.9 mm) than it is toacid etch–conditioned implant surfaces (a mean of1.4 mm) or oxidized surfaces (a mean of 1.6 mm).15

The junctional epithelium associated with nat-ural teeth has a high rate of cell turnover, whichoccurs rapidly during the wound healing thattakes place after penetration by a dental probe orwhile recovering from infection.17 The rate of junc-tional epithelium cell turnover is twice that oforal gingival epithelium. At the base of thesulcus, the rate of exfoliation is as much as 50times that of oral gingival epithelium, which, ineffect, hinders bacterial colonization of the sulcus.

When the junctional epithelium that surroundsimplants is exposed totrauma (such as duringgingival retraction pro-cedures), it is at greaterrisk of experiencingpenetration damagethan is the more robustsulcus of natural teeth.Pressure that is appliedwhen clinicians applyretraction materialsinto the sulcus maycause considerable dis-comfort in patients; thisis particularly true forpatients with more vulnerable implant situations.

Another consideration that has a bearing onthe ability of epithelial tissues to withstandchemomechanical manipulative procedures is theinfluence of the natural soft tissue biotype. Intissue hierarchy, teeth act as protagonists fol-lowed by soft tissue and bone topography. Clini-cians associate a thin periodontal biotype withfragility that requires delicate management toavoid recession owing to tissue damage. Thickfibrotic biotypes are more resilient, and they have

Figure 1. Comparison of peridental biological width and peri-implant biological width. mm: Millimeters.

TABLE 1

Comparison of peridental and peri-implant tissues.PERIDENTAL TISSUE PERI-IMPLANT TISSUE

Free gingival margin with buccal keratinizedepithelium

Free gingival margin withbuccal keratinized epithe-lium

Gingival sulcus apicallylimited by the junctionalepithelium

Gingival sulcus apicallylimited by the junctionalepithelium

Keratinized epitheliumat the base of gingivalsulcus

No keratinized epithelium at the base of gingival sulcus

Junctional epitheliumadherent, less permeable,high regenerativecapacity

Junctional epitheliumpoorly adherent, morepermeable, low regenerative capacity

Cementum No cementum

Gingival fibers insertingperpendicularly in thecementum

Gingival fibers runningparallel to the implantcollar

Biological width of atleast 2.04 millimeters

Biological width of 2.5mm ± 0.5 mm*

Periodontal ligament No periodontal ligament

No direct contactbetween tooth and bone

Direct contact of implantto bone

* As shown in Ericsson and Lindhe.14



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a tendency to form pockets rather than recede.Thus, a thick biotype is more conducive forimplant placement.14,18

GINGIVAL RETRACTION TECHNIQUE

When making impressions for fixed prostheses,clinicians need to expose, access and isolate theabutment margins. Clinicians can record goodimpressions only if they meet these requirements.The precise reproduction of the abutment pro-vides clinicians with crucial clinical informationthat allows them to fabricate exact-fitting, bio-integrated restorations.19 The aim of gingivalretraction is to atraumatically allow access for theimpression material beyond the abutment mar-gins and to create space so that the impressionmaterial is sufficiently thick so as to be tear-resis-tant.20 In peridental tissue, the fiber-rich, highlyorganized periodontal complex surrounding nat-ural teeth provides support for gingival tissueswhen they are retracted, mitigating the collapseof the tissues when the retraction agents areremoved before making the impression. The peri-implant fiber structure, however, does not providethe same level of support and is not able to pre-vent the collapse of retracted tissues to the sameextent, which complicates attempts to success-fully make impressions. This is particularly truein situations in which the depth of sulcus isgreater than average, such as when an implanthas been placed deeply.

Clinicians prefer that patients have a greaterdegree of soft-tissue support than that foundaround natural teeth when they retract soft tis-sues surrounding implants. Yet at the same time,clinicians need to ensure that the retractionforces are gentle since patients’ peri-implant junc-tional epithelium is more fragile.

Deformation of gingival tissues during retrac-tion and impression procedures involves fourforces: retraction, relapse, displacement and col-lapse21 (Figure 2).

Retraction is the downward and outward move-ment of the free gingival margin that is caused bythe retraction material and the technique used.

Relapse is the tendency of the gingival cuff togo back to its original position. It is influenced bythe elasticity or memory of the gingival cuff andby the rebound forces of adjacent attached gingivathat was compressed during retraction. Whenclinicians removed plain mechanical retractioncords, an inspection of the sulci using a miniaturevideo camera determined that the sulci closed

within one minute of removal.10 Sulci that havebeen retracted with medicated cords tend toremain open longer. A 0.2-mm sulcular width isnecessary for there to be sufficient thickness ofmaterial at the margins of impressions so theycan withstand tearing or distortion on removal ofthe impression.7 The results of another miniaturecamera study showed that to achieve 0.2-mmcrevicular width, the retraction cords needed tobe in place for four minutes before making theimpression.9 Placing retraction cords for longerthan this amount of time gained no furtheradvantage, but placing the retraction cords forless time caused a significant effect. For example,if the clinician placed the cord for only two min-utes, the sulcus width closed to 0.1 mm within 20seconds after it was removed. Low-viscosityimpression materials such as light-bodied “wash”type materials do not provide sufficient support toprevent this relapse.22

Displacement is a downward movement of thegingival cuff that is caused by heavy-consistencyimpression material bearing down on unsup-ported retracted gingival tissues.

Collapse is the tendency of the gingival cuff toflatten under forces associated with the use ofclosely adapted customized impression trays.22

Depending on the amount and duration ofthese forces, the gingival tissue may or may notrebound to its original position. The gingivaltissue responds viscoelastically, and recoverytime is much longer than the duration of thedeforming force application. If too much traumaoccurs and if the gingival tissue is too thin, irre-versible alteration will take place.

Clinicians have adopted techniques that origi-

Figure 2. Force involved with retraction of peridental and peri-implant tissues.



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nally were designed for natural teeth for use inimplant restoration situations despite significantdifferences between the tooth biosystem and theimplant biosystem. Techniques that clinicianshave refined to work well for teeth may notaddress the challenges faced by clinicians inimplant dentistry. The following sections reviewthe available retraction techniques for naturalteeth and their potential application for implantrestorations (Table 2).

Mechanical retraction. Cord. Cliniciansplace retraction cords by using cord-packinginstruments; however, many commonly usedhand instruments (such as the Hollenbach carvertip) were not designed for this application. Theforces generated by pointed or wedge-shapedinstrument tips may be traumatic to the rela-tively fragile junctional epithelium aroundimplants, whereas gingival tissues may be moreforgiving of this type of force. Some manufac-turers make purpose-designed packing devicesthat have smooth, nonserrated circular headsthat can be used to place and compress twistedcord with a sliding motion. Other manufacturersmake devices with serrated circular heads for usewith braided cords. The thin edges of these ser-rated circular heads sink into the braided cord,and the fine serrations keep it from slipping offand cutting the gingival attachment. There is noliterature describing the use of cord-packinginstruments, and the forces involved with cordplacement remain undetermined.

Single-cord versus dual-cord technique. Retrac-tion cords were developed for use with naturalteeth. They provide more effective control of gin-gival hemorrhage and exudate when used in con-junction with medicaments than when used withno medicaments. The use of a single retractioncord often provides inadequate gingival retrac-tion. The dual-cord technique in which the firstcord remains in the sulcus reduces the tendencyfor the gingival cuff to recoil and partially dis-place the setting impression material.23 Resultsfrom one survey showed that 98 percent ofprosthodontists use cords, with 48 percent using a dual-cord technique and 44 percent using asingle-cord technique.24

Placement of retraction cords can cause injuryto the sulcular epithelium and underlying connec-tive tissues,25 as shown by the results of experi-ments involving dogs’ teeth.26 The filaments orfibers of conventional cords also may causeresidual contamination of sulcal wounds, creating

foreign body reactions and exacerbating inflam-mation.27 Healing of the sulcus can take seven to10 days.26,28 Use of minimal force is necessarywhen packing cords to protect Sharpey fibers,29

and application of excessive force is inappropriatebecause it may cause crevicular bleeding, gingivalinflammation30 and shrinkage of marginaltissues.31

Clinicians may place untreated plain cordsafely in the sulcus for periods of five to 30 min-utes,26 but the pressure of cords alone will notcontrol sulcular hemorrhage.25 On removal, plaincords are associated with bleeding in more than50 percent of situations, although wetting thecords before removal may help control thebleeding.32

Clinicians should question the use of cordsaround implants since the junctional epitheliumis not as adherent, is more permeable and has alower regenerative capacity than the junctionalepithelium around teeth.

Chemomechanical retraction. Chemicalswith cord. Epinephrine commonly is used to med-icate retraction cords since it provides effectivevasoconstriction and hemostasis during retrac-tion.33 It is, however, associated with significantlocal and systemic side effects, which investiga-tors have reported occurring during 33 percent ofapplications.24 Absorption at the sulcus interfaceis dependent on patients’ gingival health.34

Healthy gingiva acts, to some extent, as a barrierto absorption of epinephrine.35 This may be whythe theoretical overdose levels are not observedclinically. Absorption varies with the degree ofvascular bed exposure, the length of cord used,the concentration of cord impregnation and thelength of application time.36 Clinicians shouldavoid applying high concentrations of epinephrineto large areas of lacerated or abraded gingival tis-sues.37 Patients who are susceptible to the effectsof epinephrine may develop “epinephrine syn-drome,” which includes tachycardia, rapid respi-ration, increased blood pressure, anxiety andpostoperative depression.34,36

A number of alternatives to epinephrine areused clinically, with varying benefits and draw-backs. Synthetic sympathomimetic agents thatmimic the actions of epinephrine are more effec-tive and safer than epinphrine.38

Aluminum sulfate and aluminum potassiumsulphate act by precipitating tissue proteins withtissue contraction, inhibiting transcapillary move-ment of plasma proteins and arresting capillary



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TABLE 2

Gingival retraction techniques and their application to implant dentistry.RETRACTIONMETHODS

ADVANTAGES DISADVANTAGES USE INIMPLANT

DENTISTRY

MechanicalCord (may betwisted, knitted or braided)Single-cord techniqueDual-cord technique

InexpensiveAchieves varying degrees of retractionCan be used with chemical adjuncts

PainfulRapid collapse of sulcus after removalRisk of traumatizing epithelial attachmentNo hemostasisPlacement is time-consumingRisk of sulcus contamination

Yes/No*

Chemomechanical

Chemicals with cord

Epinephrine HemostaticVasoconstrictive

Systemic effects “epinephrine syndrome”Risk of inflammation of gingival cuffRebound hyperemiaRisk of tissue necrosis

No

Synthetic sympathomimeticagents

HemostaticVasoconstrictiveMore effective than epinephrine withthe absence of systemic effects

Rebound hyperemiaRisk of inflammation of gingival cuffRisk of tissue necrosis

No

Aluminum sulphateandaluminum potassiumsulphate

HemostasisLeast inflammation of all agents usedwith cordsLittle sulcus collapse after cord removal

Offensive tasteRisk of sulcus contaminationRisk of necrosis if in high concentration

Yes/No

Aluminum chloride No systemic effectsLeast irritating of all chemicalsHemostasisLittle sulcus collapse after cord removal

Less vasoconstriction than epinephrineRisk of sulcus contaminationModifies surface detail reproductionInhibits set of polyvinyl siloxane and polyether impressions

Yes/No

Ferric sulphate Hemostasis Tissue discolorationAcidic tasteRisk of sulcus contaminationInhibits set of polyvinyl siloxane and polyether impressions

Yes/No

Chemicals in aninjectable matrixAluminum chloride with kaolin

Reduced risk of inflammation(injectable form)Nontraumatizing to junctional epitheliumHydrophilicEase of placementPainlessNo adverse effects

Inhibits set of polyvinyl siloxane and polyether impressionsMore expensiveLess effective with very subgingival margins

Yes

Inert matrixPolyvinyl siloxane No risk of inflammation or irritation

NontraumatizingEase of placementPainlessNo adverse effects

Limited capacity for hemostasis (no activechemistry)Less effective with subgingival margins

Yes

SurgicalLaser Excellent hemostasis–carbon dioxide

(CO2) laser safe for implants asreflected by metalReduced tissue shrinkageRelatively painlessSterilizes sulcus

Neodymium:yttrium-aluminum-garnetlaser contraindicated with implantsErbium:yttrium-aluminum-garnet laserreflected by metal but not as good at hemostasis as CO2 laserCO2 laser provides no tactile feedback,leading to risk of damage to junctionalepithelium

Yes/No

Electrosurgery Efficient precise hemostasis Contraindicated with implant (risk ofarcing)Gingival sulcus too small for two elec-trodes, impractical in implant dentistry

No

Rotary curettage FastAbility to reduce excessive tissueAbility to recontour gingival outline

Causes considerable hemorrhageContraindicated with implantsHigh risk of the bur damaging the implantsurfaceRisk of tissue retraction exposing implantthreadsHigh risk of traumatizing the epithelialattachment

No

* Yes/No: Method could be used but is not recommended.



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bleeding.39 Both are hemostatic and retractive,which causes minimal postoperative inflamma-tion at therapeutic concentrations,33 although con-centrated aluminum potassium sulphate solu-tions can cause severe inflammation and tissuenecrosis.40

The action of aluminum chloride is similar tothat of aluminum sulfate, which is an astringentthat causes precipitation of tissue proteins29 butless vasoconstriction than epinephrine.35 Alu-minum chloride is the least irritating of themedicaments used for impregnating retractioncords,41 but it disturbs the setting of polyvinylsiloxane impression materials.42

Aluminum potassium sulphate– and aluminumchloride–medicated cords are more effective inkeeping the sulcus open after clinicians removethe cord (10-20 percent of original opening eightminutes after the cord is removed) than are epinephrine-medicated cords (50 percent closureof sulcus observed over a similar time).10 After 12minutes, only sulci packed with aluminum chlo-ride remained open at 80 percent of the originalspace created.10

Owing to its iron content, ferric sulfate stainsgingival tissues a yellow-brown to black color forseveral days after a clinician has used it as aretraction agent.20 The accuracy of surface detailreproduction during impressions can be modifiedby ferric sulfate, as it disturbs the setting reac-tion of polyvinyl siloxanes. Thus, it is importantfor clinicians to remove all traces of medicamentfrom the tissues carefully before recording theimpressions.42

The two main drawbacks of using chemicalswith retraction cords are the occurrence ofrebound hyperemia that often occurs after cordremoval, which affects how effectively clinicianscan make impressions,43,44 and inflammatory reac-tions induced by these chemicals, which can affectthe subepithelial connective tissue.45 When clini-cians consider all of these factors, they may ques-tion whether retraction cords are appropriate foruse around implants, given the vulnerability ofthe junctional epithelium.

Chemicals in an injectable matrix. Injecting 15percent aluminum chloride in a kaolin matrixopens the sulcus, providing significant mechan-ical retraction.46,47 When compared with having acord packed into the sulcus, an injection of 15 per-cent aluminum chloride in a kaolin matrixresulted in less pain for patients and was easierand quicker to administer.48 Furthermore, its



effectiveness in reducing the flow of sulcular exu-date is similar to that of epinephrine-soakedcords.49

The use of 15 percent aluminum chloride in aninjectable kaolin matrix is effective.50 It also issafe, with the results of one study showing noreports of adverse effects.51 Gingival recessionassociated with an injection of aluminum chlorideinto the gingival sulcus is almost undetectable.52

The injectable matrix is hydrophilic and can beflushed away relatively easily from the gingivalcrevice.46 As with any foreign materials intro-duced into the oral cavity, there remains a smallrisk of residues’ persisting in the gingival crevice.The viscosity of the injectable matrix may not beenough to provide sufficient retraction for deepersubgingival preparations,53 and aluminum chlo-ride can inhibit the set of polyether and polyvinylsiloxane materials if clinicians do not rinse itaway properly before making impressions.

The delivery of chemicals via an injectablematrix shows promise for peri-implant tissueretraction, because it preserves the gingival tis-sues with no risk of lacerating or inflaming thejunctional epithelium. In patients who havedeeply placed implants with subgingival margins,however, its value may be somewhat limited bythe extent to which such matrices are able toretract effectively.

An inert matrix. A polyvinyl siloxane materialfor gingival retraction was introduced in 2005. Itworks by generating hydrogen, causing expansionof the material against the sulcus walls duringsetting. The manufacturer has reported advan-tages including gentle placement without need forlocal anesthetic, visibility in the sulcus due to itsbright color, ease of removal and absence of theneed for hemostatic medicaments. Potentialdrawbacks are that it may not improve the speedor quality of retraction obtained and that it likelyis less effective with subgingival margins. Clini-cians place deep implants with subgingival mar-gins relatively frequently since implant place-ment is dictated largely by the location ofavailable bone.

Surgical retraction. Lasers. Compared withother retraction techniques, diode lasers with awavelength of 980 nanometers and neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers with awavelength of 1,064 nm are less aggressive, causeless bleeding and result in less recession aroundnatural teeth (2.2 percent versus 10.0 percent).54

Lasers’ properties largely depend on their



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wavelength and waveform characteristics. Theuse of Nd:YAG lasers is contraindicated nearimplant surfaces, because they tend to absorbenergy, which causes them to heat up andtransmit the heat to bone, owing to the effects ofthis laser’s wavelength on metal.55 There is also atendency for Nd:YAG lasers to damage the fragilesubjunctional epithelium at the sulcus basearound implants.

Erbium:yttrium-aluminum-garnet (Er:YAG)lasers with a wavelength of 2,940 nm arereflected by metal implant surfaces and mini-mally penetrate the soft tissues, so they are rela-tively safe to use. The hemostasis achieved withthe Er:YAG laser, however, is not as effective asthat achieved with the carbon dioxide (CO2)laser.55

The prime chromophore of the CO2 laser, whichhas a wavelength of 10,600 nm, is water, and itreflects off metal surfaces. When used near metalimplant surfaces, CO2 lasers absorb little energy,with only small temperature increases (< 3oC) andminimal collateral damage. CO2 lasers do notalter the structure of the implant surface.55

Surgical wounds created by lasers heal by sec-ondary intention, and incision lines show disorga-nized fibroblast alignment. This reduces tissueshrinkage through scarring, which helps preservegingival margin heights.31

Visualizing the action of laser beams is diffi-cult, owing to the plume of coolant water. So,there is the potential for attached gingiva to beobliterated when lasers are used for retractionpurposes, since clinicians receive virtually no tac-tile feedback. Although there is a hemidesmo-somal attachment around implants that creates abiological seal, the attached gingiva serves as abarrier that prevents exposure of the implantbody over time through recession.

There are many advantages to using CO2

lasers, but their method of exposing implant mar-gins is to create a trough by excision rather thanby displacing soft tissue. Therefore, their use maynot be practical around deeply placed implant fix-tures where a large defect could result. In addi-tion, in anterior applications in which esthetics iscritical, it may not be desirable to create a trougharound the margins, as it may have a detrimentaleffect on patients’ appearances.

Although CO2 lasers may be significantlyuseful in some implant impression situations,they are invasive, thus failing to meet the idealobjective of a truly conservative technique.



Electrosurgery. Clinicians can use electro-surgery effectively to widen the gingival sulcusaround natural teeth before placing the cord andto provide hemostasis by coagulation. However,electrosurgery is not recommended aroundimplants because there is significant risk that thecontacting electrode may arc by conducting elec-tric current though the metal implant structureto the bone rather than via the more dispersivegingival tissue pathway. The concentrated elec-trical current at the tip of electrodes can generateheat, which may cause osseous or mucosalnecrosis.56

Rotary curettage. Rotary curettage involves theuse of a high-speed turbine to excise the gingivaltissue quickly and create a trough around themargins. For healthy, disease-free tissue aroundnatural teeth, rotary curettage has little effect ongingival margin heights if adequate keratinizedgingiva is present,57 although slight deepening ofthe sulcus may result.58 However, rotary curet-tage is inappropriate for use around implant res-torations because of poor tactile control when cut-ting soft tissue, which could lead to bur contactdamage to the implant surface and overinstru-mentation. The absence of keratinized gingiva atthe base of the gingival sulcus surrounding theimplant could lead to an exaggerated response torotary curettage, including deepening of thesulcus and gross recession.

DISCUSSION

The mechanical retraction of gingival tissues byusing cords around implant restorations can leadto ulceration of the junctional epithelium. Retrac-tion cords were developed for application aroundnatural teeth where the junctional epithelium isrobust. The forces used in cord placement arelikely to exceed peri-implant tissues’ capacity toresist them. The resulting laceration of the sulcalepithelium will break down, causing ulcerationswith delayed healing. Once patients’ gingivalepithelial structure is damaged, there is signifi-cant risk of permanent recession and loss ofattachment developing. Thus, the use of mechan-ical retraction with cords may be contraindicatedaround implants, except in situations in whichpatients’ sulcus depths are shallow, their mucosalhealth is impeccable and a robust, thick perio-dontal biotype is present.

The addition of chemical adjuncts to retractioncords further complicates the situation and maylead to increased inflammation of the subsulcular



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tissues. If the delicate junctional epitheliumaround the implant restoration becomes damagedduring cord placement, the lacerated sulcus pro-vides reduced protection against the penetrationof chemicals into deeper subepithelial cell layersand against systemic dissemination when thevascular bed is exposed. All chemical agents usedfor gingival retraction are irritants, and studyresults demonstrate their adverse effects on peri-dental tissues.26,32,36,37,40,51 Little is known about theeffects of these same chemicals when they areplaced into peri-implant tissues.

Clinicians often choose to perform surgical pro-cedures because they are able to, the procedurecan be performed rapidly and hemostasis isachievable. Surgical retraction procedures, how-ever, are destructive and involve excision oftissue. This may be acceptable around naturalteeth, as the results of studies have supportedusing electrosurgery, lasers and rotary curet-tage.54,56-58 Evidence does not support the use ofsuch destructive procedures in the implant situa-tion.31,55 Peri-implant mucosa does not have thesame capacity for regeneration as peridentalmucosa. The correct use of lasers with appro-priate wavelengths may be applicable in some,but not all, implant situations during retractionand when making impressions.

Using an injectable matrix for gingival retrac-tion offers clinicians the opportunity to performan atraumatic procedure. There is no risk of lac-eration when clinicians introduce materials suchas 15 percent aluminum chloride in a kaolinmatrix into the sulcus surrounding natural teeth.With no damage to the junctional epithelium atthe base of the sulcus or to the sulcus walls, therisk of inflammation caused by chemicals deliv-ered in the matrix is reduced significantly.Inflammation results from the use of chemicalagents, but the aluminum chloride in theinjectable matrix offers the best outcome of thechemical choices to date.48,52

The atraumatic application of an injectablematrix is not without its limitations. The viscosityof the injectable matrix limits the force of retrac-tion offered, and, while this protects the implantsulcus from the trauma of overpacking, it may notoffer sufficient retraction for situations that areunique to implant dentistry in which therelapsing and collapsing forces are important.Deeply placed implants often are associated withan increased sulcus depth compared with thatfound around natural teeth; this is reflected by



the greater “biologic width” that is observed. It isnot always possible to avoid deep placement ofimplants as this is dictated by patients’ bone morphology.

Although injectable matrices are promising asa gingival retraction technique for implant situa-tions, further development is needed. Comparedwith research on implant fixtures, there is rela-tively little research to guide clinicians regardinghow to restore implants59 and about which gin-gival retraction techniques to use around implantabutments.

In the meantime, the use of techniques devel-oped by clinicians for natural teeth will continue.Further research exploring the uniqueness of theimplant restoration situation and investigatingthe effect of these conventional techniques on theperi-implant tissue is needed.

CONCLUSION

The literature concerning gingival retraction forimpressions in fixed prosthodontics is extensive.By contrast, little has been published about thechallenges presented by the unique anatomy sur-rounding implants. As implants become main-stream treatments for tooth loss, this topic willwarrant further research. �

Disclosures. None of the authors reported any disclosures.

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