Clinical Comm

Etiology and treatment of sensitive teethTakao Fusayama. DDS, PhD*

Introduction

A number of techniques for surface-treat ing sensitivetooth roots have been reported but these have notprovided consistent success. Treatment of sensitive,eroded crown and root surfaces has also been prob-lematic. However, the introduction of dual curedbonding agents and chemically adhesive compositeresin has facilitated such treatments. This paper dis-cusses the uses of these materials in the treatment ofthree types of sensitive teeth.

Sensitive root surfaceEliology

Root surfaces often become very sensitive when ex-posed by gingival recession or by gingivectomy (Fig 1 ).Snch root surfaces are sensitive only in isolated areas,usually on the facial surface. This fact suggests theetiology as below.

When a root surface is exposed, the cementum issoon removed by brushing, which further reduces thesuperficial dentin. Mechanical cleansing with sealersean also reduce the root surface. Such reduction canopen some of the peripheral dentina! tubule ends. Theexposure may be at a singie spot initially, but the num-ber of exposed sites increases with further reduction.Beeause a dentinal tubule of vital dentin is filled withthe odontoblastic processes up to the very peripheryas shown by Yamada et al,' the processes thus exposedcan be subjected to external irritation. Cold water orair irritates thermally. The touch of a metallic instru-ment irritates electrochemical ly. Very sweet or saltyfoods irritate by dehydration resulting from osmoticpressure.

Emeritus Professor, Tokyo fvfedical and Dental University; Ad-dress alf correspondence to: Dr T. Fusayama, 4-16-23 Kamiigusa,Stiginamiku. Tokyo 167, Japan.

Figs la and lb Two cases of sensitive root surface treat-ed. Figure la shows incisors with root surface exposed bygum recession (courtesy Dr N. Kurosaki).

F ig ib Resin-splinted anterior teeth with surgiealiy ex-posed roots (courtesy Dr N. Satou].

TreatmentBecause sensitivity is caused by irritation of ihe odon-toblastic processes, closing the opened tubule aper-tures will alleviate the problem. Until recently, ourmethod of treatment was to reduce the root surface.

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b.HtchiriE Ihecleansed surface

.CoatLns with the d,KadiatiQii formins a HlmphQto-cured bond with tags and impregnation

Fig 2 Treatment of a sensifive root surface wifh dual cured bonding agent.

etch the denttn and restore the tooth with an auto-polymerizing adhesive composite resin such as ClearftIFII New Bond (Kuraray Co). The effect was quitedurable, bul reduction of the root surface was re-quired. However, the recent development ofthe dual-cure bonding agents Clearfil Photo Bond (KurarayCo) and Scotchbond (3M Dental Products Div) hasenabled a much simpler and conservative treatment.The result is quite durable, provided the root surfaceis etched, because the coated lilm polymerizes rapidlywithout being disturbed by air inhibition, while theagent penetrating the etched tubules polymerizeschemically. Clearfil in particular impregnates theetched surface.- The technique is as below (Fig 2).

The root surface is cleansed with a cotton pelletsoaked with a hydrogen peroxide solution. The gel-type etchant is then applied for 30 to 60 seconds toopen the dentinal tubule aperture filled with debris orsalivary residues and to slightly roughen the overallsurface. Etching the dentin surface is essential for adurable effect because without etching the eoated filmdisappears within a short period of time. Etchingcauses little or no sensation and protects the pulp.- Itis curious that the manufacturer of one material pro-hibits dentinal etching with the materialwhich iseffective only by etching. As far as the selected chem-ically adhesive resins are concerned, the prohibitionof dentin etching seems to be a rejection of the modernprogress of adhesive dentistry.^

The etched surface must be thoroughly washed witha hard jet spray in order to remove the oversoftened

tissue atid the residual gel etchant. It is then dried]with an air syringe.

The bonding agent is applied and immediately lightlcured for 20 to 40 seconds to form a film with tags|and resin-impregna ted dentin layer. " A delay in curingthe apphed bonding agent may resuh in incompletepolymerization. Apphcation of the bonding agent ibe repeated several times.

Wedge-shaped erosionEtiology

When the root surface is exposed by gingival recessionand the brushing technique is faulty, the root is abradJed, and a wedge-shaped defect is formed. Numerousdentinal tubules are opened, exposing the odonto-jbiastic process ends (Fig 3). The surface can thus be-]come sensitive, although in many cases it will not he|cause the formation of the so-cailed irritation dcntiton the pulp chamber wall blocks the sensory com-]muni cation.

Treatment

Treatment of such sensitive defects comprises resto-ration with an autopolymerizing adhesive compositeresin to close the dentinal tubule apertures. The tech-nique we have been using successfully for several yearsis as described below (Fig 4).

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Ciinicai Comm_

Figs 3a fo 3c Treatmenf of a wedge-shaped defect.

Fig 3a The teeth before treatment. Fig 3b Prepared cavities. Fig 3c Affer restoration.

i.Cuttins trie anlislipslabilizira groove

d.Kestored defect

Fig 4 Preparation of a wedge-shaped defect for chemicaily adhesive composife resin restoration.

Cavity preparation. Because the wedge-shaped de-fecf occasionally has a superficial layer of softened oreontaminated dentin, the surface is slightly redueedwith a round diamond stone at slow speed. The ca-vosurface angle is fhen defined to a 60' to 80" wallinclination with the same stone. Proper definition iscritical because an indistinct cavity margin is apt toproduce an excess resin feather which is liable to peeland retain debris.

When the defect is very deep, the operator must beparticularly careful because bacteria in the residualouter carious dentin left close to the pulp can multiply,robbing the pulp of nutrition and eventually reach thepuip, causing serious purulent pulpitis,' Carious tissue

is evaluated with 0.5% basic fiichsin or 1.0% acid red52 solution in propylene glycol* and removed by asmall round bur.

In addition, a stabilizing groove is cut inside thecavosurface margin, because if the packed compositeresin slips along the even cavity floor on insertion, theresin tags penetrating the dentinal tubules may be bro-ken before polymerization, considerably weakeningthe bond,'' This groove is made with the smallest roundbur available (No, 1/2). When Ihe tooth is sensitive,this preparation is performed under anesthesia; how-ever, most wedge-shaped defects are not so sensitive.

Capping the putp. Lining the dentin wall is undesir-able because this weakens retentive stability and gin-

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Figs 5a to 5o Crown surface erosion.

Fig 5a Before freatment. Fig 5b Prepared cavity. Fig 5c After restoration.

gival marginal seal, exposing the pulp to danger. Whenthe excavated cavity reaches or very closely approachesthe pulp, a spot lining is placed in the deepest area.The spot must be of the smallest necessary area toleave the maximal area of dentin wall exposed foradhesion, A calcium hydroxide cement is recommend-ed because it promotes formation of protective dentin.The physical strength of cement is not important be-cause it is used in a very sniLill spot.

Eleliing lie cavity wall. The entire cavity wall, bothenamel and dentin, is totally etched with 40% phos-phoric acid gel etchant. This etching i,v essential fordurable retention and tight seal of the tubule apertureand gingival margin of dentin.^ Etching dentin causeslittle sensation and better protects the pulp by adhe-sion, provided an autopolymerizing adhesive compos-ite resin is used," After 30 to 60 seconds, the etchedcavity preparation is thoroughly washed with a jetspray and dried with an air syringe.

Placement oj the selj-ciired composite resin. After thebonding agent is applied, the autopolymerizing ad-hesive composite resin is placed in the cavity prepa-ration, A light cured composite resin is not recom-mended because it cannot secure a stable seal at thegingival margin of dentin,^

Facial crown fnision

FtiologyThe facial crown surface of a patient fond of tart fruitsor drinks is sometimes eroded because enamel is easilyweakened by citric acid, which is apt to be retained

in the vestibule after consumption. When the erosionreaches the dentinoenamel junction forming commu-nication to some odontoblastic process ends, the toothbecomes sen,';itive (Fig 5}.

Treatment

A chemically adhesive composite resin is used to closethe dentinal tubule apertures (Fig 6). A light curedcomposite resin may be preferred, although the au-topolymerizing adhesive composite resins are also use-ful.

Ciiritvpreparation. The operator must be most care-ful in determining the outline of the cavity preparationbecause the peripheries of such a defect are very in-distinct, with no defmile cavosurface angle, and theoutline is often likely to be too small. This will resultin an underfilled restoration. The cavity preparationmust therefore be sufficiently extended so as not toleave any concave surfaces. The cavity margin is pre-pared at a wall inclination of 60" to 80", the marginalenamel being reduced with a round diamond. If thedefect exposes dentin, a stabilizing groove should hecut in the peripheral dentin surface. If some cariousdentin is found, it must be removed, preferentially us-ing a caries-disclosing solution as a guide. Preparationusually requires anesthesia because eroded dentin isvery sensitive.

Etching the cavity wall. The entire cavity wall, bothenamel and dentin, is totally etched by the 40% phos-phoric acid-etching gel. This is essential for stable re-tention and pulp protection. The dentin wall shouldnot be lined because hning inhibits retention.^

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tj,Form ing ihe c.Cutling tne antisllp d.Reslared defect

Fig 6 Preparation of a crown surtace erosion for chemically adhesive composite resin restoration.

Placement of the adhesive composite resin. After ap-plication of the bonding agent, the cavity preparationis tilled with the adhesive composite rcsin. The lightcured composite resin may he preferred to the auto-polymerizing resin for such a shallow,, extensive cavitywith a wide enamel floor.

References1, Yamada T, Nakamura K, Iwaku M, et al: The extenl of the

oiluntoblasi process in normal and canus human dentin, J DenlRes my. 62:798-802,

2, Fusayama T: Factors and prevention of pulp irritation by ad-hesive composite resin restorations. Quimessence Int 1987;1B:633-641.

3, Fusaiiamu T: Problems preventing progress in adhesive restora-tive dentistry, AJ- Dem Res 1988; 2(1):15S-161,

4, Fusayama T: Gingival irritation of restoration margins, Quin-tc.'^sence Inl 1987: 18:215-222,

5, Iwaku M, et al: Conservative dentistry with a caries detector anda chemically adhesive composite, a longitudinal study of a newsyslem, Br Dem J 1983; 155:19-22,

6, Fusayama T: New Concept.': in Operative Demi.itry. Chicago,Quintessence Publ Co Inc, 19R0, pp 44-59, 84-85,

7, Fusayama T: A study on marginal closure of composite resin.Jap J Ci>nser\i Dent 1985; 29:177-186,

8, Iga M, et al: Effect of irradiation methods on the marginal sealingof Class V light-cured composite resin restorations, Jap J Ci>n.iervDem 1987; 30:1407-1413,

9, (Citation to follow)

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