Clinical Communication

The 2-minute impression technique

S. Rand Werrin*

Abstract Finding an impression technique ihai provides a quick and accurate dentalimpression van be an elusive goal. The combination ofa rigid, fast-settingpoly(vinyl siloxane) bite registration paste atid a disposable closed-mouthimpression Irayfttlfills this goal. The comfort of the patient is enhanced becausea minimal amount of the itnpresslon material, which is tasteless, is necessary.The technique etmbles the dentist to record habilitai centric occlusion, the preparedtooth or teeth, and the opposing arch accurately and simultaneously.(Quintessence Int 1996:27:179-18}.)

Introduction

Wth the advent of more accurate impression materials,the closed-mouth impression technique has become amost advantageous method of constmcting simple castrestorations free of occiusal disharmony. The TripleTray (Premier) allows the dentist to take an impressionof the prepared toolh, the opposing teeth, and thehabitual centric occlusion all at once. This techniquereduces chair time, expense, effort, and error because itrequires fewer steps. Patients also report that gaggingis reduced and comfort is increased with this method.The technique described in this article also has theadvantages of reduced armamentarium and it takesonly 2 minutes to perform.

Tray

The disposable Triple Tray is available in posterior,quadrant, anterior, and sideless designs. Evaluatorshave stated that the size, strength, and comparativelylow cost of Triple Trays are improvements over otherdouble-arch trays.' Because the plastic framework ofthe Triple Tray is curved from mesial to distal toconform to the dental arch, this design is more

* Pnvate Practice. Pittsburgh, Pennsylvania,

Reprint requests: Dr S. Rand Werrin, 3506 Filth Avenue, Pittsburgh.Pennsyivania 15213,

comfortable for the patient. The Triple Tray is alsolonger than some trays, enhancing the stability ofarticulated casts. The new sideless design eliminatescontact with the gingiva, palate, mandible, and otherstructures and does not restrict the impression mate-rial, increasing the overall accuracy of the impression.The pliable and permeable webbing of the Triple Traypermits complete closure in centric occlusion withoutdrawing in the sides of the tray.

Triple Trays are disposable, reducing the risks ofcross contamination and eliminating the need forcleaning. They cost less than do custom trays and useless material than do stock trays.

Impression material

For this technique, a fast-setting, automixing biteregistration material with a setting time of 2 minutes,such as Regisil 2X or Stat BR, would be ideal. Biteregistration materials have been recommended fordouble-arch impressions because their rigidity rein-forces the tray. The initial unset bite registration pastehas the property of pushing away tissue fluid, blood,and gingivae. The final stiff, solid set enhances theaccuracy of the final impression. The ease of removalof bite registration materials and their dimensionalstability make them ideal for this technique.

Any poly(vinyl siloxane) or polyether impressionmaterial could also be used, but the setting time for

fircf! International Vnli imn ;i7T')lumber 3/1996 179

Werrin

Fig 1 "The I p ot the mix lube is cut to ailow fast-setting,automixing bite registration material to be injected into tineTriple Tray and around the preparation.

Fig 2 The bite registration materiai is quickiy injected ontoboth sides of the Tripie Tray.

these materials is significantly longer than is the settingtime of a bite registration material. The neutral tasteand absence of odor of poly(vinyl siioxane) biteregistration materials increase patient acceptance andcomfort.

The automix gun of most bite registration materialsreduces the occurrence of voids and air entrapment.Because only one viscosity is used, only one gun isused, thereby reducing armamentarium, waste, set-uptime, and clean-up time. The gun can be coldsterilized, and the tips are disposable, reducing risks ofcross contamination. This streamlined armamentariumreduces cost as well as chair time.

Patient selection

As with all impression techniques, the decision to usethe double-arch impression technique must be basedon sound physical principles. This technique is usefulfor single-unit restorations or short-span fixed partialdentures with clear, not deep, margins. The patientmust also exhibit a nonpathologic occlusion; a caninerise with incisai guidance is preferred.^

Technique

During onset of anesthesia, the Triple Tray should betested in the patient's mouth for passivity of fit. Passivetray fit is necessary to gain an accurate impression, so itis imperative that the operator choose the type of traythat is appropriate. Posterior, anterior, quadrant, andsideless trays are available. If the dentist is concernedthat unusual oral anatomy will cause impingement, thistechnique should not be used.

The tray should be checked for signs of impinge-ment on the tray walls, and the operator should makesure the crossbar is distal to the last tooth. Any minorimpingement of the sidewalls or crossbar can beadjusted with a laboratory carbide bur, or a sidelesstray can be used. The sideless tray can also be curvedslightly to match the curve of Spee. The tray can bemade slightly wider, if necessary, by tugging on thesides and stretching the gauze mesh.

The patient should be instructed to close intohabitual centric occlusion with the unloaded tray inplace. This position on both sides of the arch should benoted.

After tooth preparation and tissue management areaccomplished through standard techniques, impres-sion material is loaded into the gun. The tip of the gunis then trimmed (Fig 1 ), and the tray is loaded on bothsides to a depth of approximately 5 mm (Fig 2). Theretraction cord is removed, and impression material isinjected around the prepared teeth (Fig 3).

The loaded tray is carefully positioned in the mouth,and the patient is instructed to close into centricocclusion. Complete interdigitation should be verifiedby checking the opposite side of the arch (Fig 4). Thedentist should tap gently under the patient's chin orguide the chin to assure complete closure.

When the material is set, approximately 2 minutesafter the start of the mix if a fast-setting bite registrationmaterial is nsed, the impression is removed with equalbilateral pressure applied to the flanges of the tray. Theimpression is inspected for accuracy and signs ofimpingement (Figs 5 and 6).

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Fig 3 Tbe bite registration material is injected around theprepared tooth.

Fig 4 The -i i - il i= 3 [-^a .j i.luse into habitual centricocclusion. Teeth on Ihe other side of the mouth are checkedto verity the position.

Fig 5 Counterside oi the Trtple Tray final impression. Fig 6 Final impression and automixing gun with modifiedmixing tip.

Discussion

The donble-arch techtiique and the Triple Tray havebeen found to be fast, easy, and accurate in clinicalcases around the world,'' The increased pace of thechanges in dental reimbursement mandates that mem-bers of the profession become more efficient with thevarious restorative systems that they choose. Manypractitioners complain that single-unit restorationsproduce minimal income because of the excessive timerequired to produce higb-quaiity single-unit cast res-torations,' The closed-mouth impression techniqueempowers the dentist to produce accurate inlays,onlays, crowns, short-span fixed partial dentures,veneers, provisional restorations, resin-bonded pros-theses, space maintainers, and single-tooth implantcrowns with a time-saving and easy approach. The

synergy of the newer accurate bite and impressionmaterials and the innovative, disposable impressiontrays are the keys to the technique's popularity andsuccess.

References

1. Chrislensen G. A new simple double arch impression iray. Clin ResAssoc Newstetter 19Bt:5(5];4.

2. Farah JW, et al. Impressions and accessories. Dent Advisor t992;9:4,

3 Witson EG, Werrin SR. Dotible arch impressions for simplifiedrestorative dentistry. J Prosthet Dent 1983;49;2.

4, Chnsteiiien G. Special report—Products CRA evaluators 'can't livewithout." Clin Res Assoc Newsletter, I993;17(S):4.

5. Cliristensen G. Day to day fixed prosthodontics. J Atn Dent Assoc, D

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