Esthetic Dentistry

Tray-forming technique for dentist-supervised home bleaching

Sheldon M. Newman*/Paul W, Bottotie^

This article provides a comprehensive and detailed description ofthe technique for makinga custom tray for the deliver)' of bleaching gel in dentist-supervised home bleachingsysteins. Specific recotntnendations about certain steps and materials are made and theadvantages offered by these variations are explained. This information should facilitate tiiepreparation of the tray by the denta! staff in office or provide some guidelities to the dentallaborator}- to improve its sen'ice. The resulting appliance may offer some advantages forpatient comfort during specific treatment regimens. Quintessence Int ¡995:26:447-453.)

Introduction

The concept of bleaching teeth has evolved throughmany techniques over many years. The current tech-nique, in which the dentist supervises the patient in thehome application of the bleaching material, hasprovided a relatively safe,'""' efFtcient. and effective'"^method for providing an esthetic service to the patientand is much easier than previous vital bleachingtechniques,' The materials for this technique ofbleaching teeth currently remain unclassified by theUS Food and Drug Administration, because thequestion of whether they should have the status of acosmetic or drug is unresolved.'" The manufacturersare allowed to continue to sell the product while dataare being collected. The data collection is cotifoundedhy concerns identified from the many sources andtechniques used for bleaching vital and endodonticaliytreated teeth. These techniques range from the use of30% hydrogen peroxide and heat in the in-officebleaching systems for vital teeth, and the placement ofbleach in the pulp chamber for walking bleaching of

' Departmenl of Restorative Dentistry, University ofColorado, Setioolof Dentistry, Denver, Colorado,

*' Denver General Hospital, Clinical Dentistry, Denver, Colorado.

Reprint requests: Dr Siieldon M. Newman, Departmeni of RestorativeDentistry, University of Colorado, Schooi of Dentistry, Campus BoxC-2B4, 4200 East Ninth Avenue, Denver, Colorado ^0262,

nonvital teeth, to the use of over-the-counter materials,which may contain acid-etehing systems and whitepaint.

The dentist-supervised liorne application of a bleach-ing gel (approximately 10% carbamide peroxide) witha tray has been studied sufficiently to allow theconclusion that normal usage over the short term (anumber of weeks) has no lasting detrimental effects onbiologic tissues.'-'""" The treatment can eause acuteirritations to the teeth and gingivae or even gastro-intestinal upset. These symptoms ean be reversedquickly by decreasing quantities of the material,decreasing time ofthe exposure, modifying the tray, ordiscontinuing the usage. Data are insufficient todetermine the safety of long-term usage or recurrentusage over the years,'** it has been suggested that theoxygenating agents have a carcinogenic potential'''^^that is especially synergistic with smoking. Smokingshould be strictly forbidden during treatment. Thecontinued use of these agents by a patient is liteled byseveral issues; (¡) several tnonths of treatment mayeventually resolve some more difficult staining pro-blems-': ('Jasóme rebound to the original coloring canoccur"-"-^ and (3) the patient can deveiop a drive toproduce ever-whiter teeth.

There have been a number of investigations on theeffects of different bleaching agents on restorativematerials, primarily resin composites. Strengths ofthematerial,-'-^' surface roughness and hardness,^^ bond-ing to the teeth and leakage,^'"'''' and color cliatiges""^''

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in the material have been studied. In most cases," apatient dcsiritig esthetic treatment may firtd that theold resiti cotnposite restorations no lottger match hisor her leeth, and they may desire new esthetic resincomposite restorations. It has been recommended thatreplacement of restorations be delayed for severalweeks. The delay would allow some decrease in therelease of absorbed oxygcnatitig agent, which mayititerfere with any bonding process,""'"*- In addition,the dentist would have the opportunity to identify anytendency for rebound in the color of the teeth.

The potential impact on both oral tissues andexisting restorations detnands that; informed consentbe obtained prior to treatment. It is also advisable torecord the tootb color by matching the dentition toshade tabs before, during, and after treatmem. Photo-graphic or video recordings arc helpful.

The efficacy of this method of bleaching teeth hasbeen shown in several articles and accepted by theprofession. '"' The advantage of this supervised methodis the ease and convenience of deliver>' both in thedental practice and for the patient. Flavored gels havemade the applications more palatable for the patient.The thicker gels allow easier and more accurateplacement and may increase the time-released longe-vity of the system,*" The clear gel makes the materialacceptable to wear in public for the longer applicationsto achieve efficient bleaching. The use of a clear andcomfortable tray provides more patient compliance tothe treatment regimen. The nse of spacer resin in trayfabrication alloviis the trays to be customized to theneeds of the patient,"'"'"'-̂

Tray fabrication procedures have been briefly ad-dressed in several articles,̂ ••'̂ ""'* This article is intendedto provide greater detail about the technique, rationalefor some of the steps, and some specific recommenda-tions for material usage. The recommended procedurewill easily produce trays that have appropriate spacingfor the thick bleaching gels: can be individualized tospecific treatment needs; are adaptable to treating botharches simultaneously; and are comfortable and esthet-ically acceptable to the patient.

Tray systems

In three systems, the tnatiufacturer of the bleaching gelsupplies both tray material and a spacer resin: Night/White (Discus Dental}, Opalescence ( Ultradetit). andKarisma (Confi-dental/Omni), The Night/White systemincludes a green spacer resin atid 0,040-inch ethylvinyl acetate (EVA) tray material. The EVA material isa flexible materiai of the type used for athletic mouth

protectors. Opalescence ( Ultradent) comes wtth a bluespaeer gel and a similar 0,035-inch EVA tray matertal.Measurements with a micrometer could not differen-tiate between the thicknesses oi' the two EVA traymaterials, Karisma is provided with a red spacer geland 0,020-inch low density polypropylene tray mate-rial. The polypropylene tray material is commonlycalled coping material in dentistry. This particularcoping material is slightly translucent as provided atidis stilfer than the EVA materials. The tray materials allcome in S « 5-inch thermoplastic resin sheets. Thespacer resins are all light-cured, strongly colored resiticomposite systems.

Technique

Complete-arch alginate impressions are made of thearches to be bleached, A complete-arch impression isneeded to form a retentive tray. The impression isdisinfected with normal office disinfection proce-dures.

The impression is poured in a buff-colored stone(type 111} ora quick-setting stone. The regular type HIstone is allowed to set for 30 minutes, while with aquick-setting technique, the stone is set within 10minutes. Both casts are trimmed to about 5 mm apicalto the gitigival margin of the teeth. The maxillary eastsshouid be horseshoe shaped and viiithout a palate tointerfere with the efficiency of the vacuum's pull on thehot thermoplastic sheet. The casts are allowed to drycompletely after grinding. This step will allow thespacer resin to penetrate into the porosity of the drystone surface (Eigs la and Ib},

The teeth to be bleached are identified. Thetreatment ean be tailored to the needs of the patient, Asingle tooth ean be painted and the home bleachingsystem used to treat a single, discolored, endodonti-cally treated tooth. It is not necessary to space teeththat iiave complete crowns, Tlie entire arch can betreated, and trays can be fabricated for both archessimultaneously. Directed by the individual smileline ofthepatient, one or more of the most posterior teeth ineach quadrant may be left unspaced to make the tray fitmore securely and to decrease the exposure to thebleaching gel.

The spacer gel is applied to the selected teeth on thecast. It is painted on with a disposable brush or applieddirectly with a disposable syringe tip ( Fig 2}, Tliesyringe tip allows much faster dispensing. Lmd a brushcan be used to smooth the applied material. Only thefacial surface ofthe teeth is painted. The s| jacor gel is notallowed to flow onto the incisai edge or oc>. lii',.,] surface

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Esthetic Dentistr'/

Figs 1a and 1b Slone casts dry and properly trimmed. Fig 1b

Avoiding coverage of occlusal and incisai surfacesallows complete seating of the tray, decreasing anyexposure to excess bleach and preserving the facialspacing for the necessary bleaching agent on the facialaspect. The gel should not be painted within 0,5 to 1,0mm ofthe gingival margin {Fig 3), This seal at thegingivai margin will help to hold the gel in place andprotect the soft tissues. The spacer resin can be applieddirectly from the syringe with a plastic tip and spreadwith a brush,

A light-cnring oven may be used to cure all of theteeth spacers simultaneously within 2 minutes andsignificantly expedite the curing process (Figs 4a and4b), If a light-curing oven is not available, the clinicallight-curing wand can be used for 20 seconds per toothin accordance with instructions from the manufacturerofthe materials. Application of tbe light wand for 10seconds per area may be sufficient. The material is notintended to be a permanent restoration; therefore, amaximum degree of cure may not be necessary, but thematerial has to be sufTiciently set so that no coloringagent is free to stain the resulting tray The surface iswashed or the oxygen-inhibited resin layer is wipedaway from the spacer. The remaining free coloringagent might contaminate and stain the tray to beformed.

The tray material is selected. The systems describedhave either 0,020-inch coping material (Fig 5) or a0,040-inch mouthguard material.

The cast is placed on the suction grid and thethermoplastic material is placed in the retainer frameon the vacuum forming unit (Fig 6), Whereas the0.040-inch EVA simply sags, the 0.020-inch copingmaterial sags some, becomes wavy, and then flattensout again. At this point, the heated coping material is

Fig 2 Direct appiication oí the spacer resin with thesyringe tip.

pulled down for vacuum forming. If the copingmaterial is allowed to sag again, it is overheated andmay be pulled too thin, producing porosities over theteeth. This 0.020-inch coping material does not have atendency to crease as do the EVA material and othercoping materials. The coping material provided withKarisma starts out translucent but turns clear while it isformed. The tray material is allowed to cool oti thecasts.

Crown-and-bridge scissors or any supermarketscissors are used to begin to cut the excess materialaway ( Fig 7). Curved iris scissors are used to begin tocut the material from both heals (most posteriorextensioti) ofthe cast. The excess material is trimmedfrom undercut areas ofthe cast that may retain the trayand make it difficult to remove the tray withoui:distortion.

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Fig 3 Spreading the resin to the appropriate limits on the Figs 4a and 4b Light box with the casts on a rotating tablefacial aspect of the teeth. ciose to the curing iight.

Fig 4b Fig 5 Sheet of tray material (0.020-inch coping material,which appears frosty before vacuum forming).

Fig 6 Coping matenal and stone cast in place on thevacuum forming unif

Fig 7 Trimming excess material from around the castNote the clear appearance of the materiai after vacuumforming.

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Esthetic Dentistry

Fig 8 Scalloping the tray to the gingival margin. Fig 9 Linguai views of mandibular and maxillary Irays,showing the lingual aspect of the maxillary tray scalloped tothe gingival margin and the lingual aspect of the mandibulartray unsoalloped.

Fig 10 Trays comtortably seated in the mouth. Fig 11 Completed tray well adapted on the stone cast.

The tray is removed from the cast and cut to thedesired level. The tray is carefttlly teased from the castto minimize the distottion and improve the final fil ofthe tray. The curved iris scissors are used to access theinterproximal areas for scalloping the tray to thegingival margin ofthe teeth (Fig 8), Extending the traybeyond the gingival margin on the facial aspect tnaytrap the bleaching agent against the tissue, increasingthe risk of burning.

The lingual aspect of the anterior segment of themandibular tray should probably not be scalloped (Fig9). The tissue coverage is minimal because of theembrasure size, and thus soft tissue exposure would beminimal. The straight, smooth surface is less likely tocause irritation to the tongue or to induce parafunc-tional activity.

At delivery to the patient, the trays are checked forfit and comfort (Fig 10). If adjustfnents are necessaty,the finished trays can be replaced on the casts. Thegingival marins are readapted to the casts by using alight flame to heat them and a wet paper towel tocompress them. Figttre 11 shows a maxillary tray welladapted to the cast.

Discussion

The spacer resins used in these systems are based onresin composite technology. They can quickly providesufficient thickness of spacing in the tray for thebleaching agenf. They are easily controlled for place-ment within the design of desired spacing but fioweasily to produce a smooth, uniform coating. The greenresin provided with Night/White is thicker than that

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Esthetic Dentistry

provided with the other two bleaching systems. TheKarisma spacer resin has some minor translucence thatallows for easier differentiation of the thickness ofthegel. None of the spacer gels Hows after placement,unless the casts are vibrated. Paints used in theprosthodontic die spacer technique do not producesufficient spacing for the bleaching gel. Nail polish andmodel paints also produce a layer that is too thin andtakes a long time to set.

The tray material most commonly provided withsuch bleaching systems appears to be 0.040-inch HVA.This material has been used without widespreadproblems for single-arch applications. The materialrecommended for this procedure, however, is the0,020-inch eoping material, Garber et al"* suggestedthat the coping material offers greater patient comfort,whether one or two trays are worn, because it producesthe least interarch opening. There would be lesspotential for temporomandibular joint problems. Itappears frosty in the sheet as provided but turns clearafter thermal processing. Once seated in the mouth,the 0,020-inch coping material is almost undetectableand thus acceptable for wearing in public. The greaterstiffness could provide a more secure fit, but thatdifference may not be clinically significant.

The EVA material may be too thick for somepatients to use comfortably, particularly if both archesare treated simultaneously. The EVA material gener-ates more friction when wom on opposing arches atthe same time. This binding can trigger more grindingand clenching in the patient. The EVA material seemsto wear faster than the coping (po i y prop y lene)material.

Thicker coping materials that provide more rigidityto the tray are available, but that is unnecessary. Thereare also thicker, 0,080-inch EVA materials that offerfew advantages and produce more interocclusal di-stance. Other 0,020-inch clear, rigid materials, whichtnay be called splint materials or provisional crownfabrication materials, are polyvinyl chloride-derivativematerials and do not make acceptable trays.

Summary

A technique for preparing a custom tray for thedelivery of carbamide peroxide bleaching gel has beendescribed. The preferred material for making the tray isa 5 >: 5-inch sheet of frosty 0,020-inch coping material(polypropylene). The technique used with this mate-rial is efficient and reliable and provides an estheticand comfortable tray for the patient.

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