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JADA, Vol. 136 http://jada.ada.org December 2005 1711

Endodontic therapy is amajor part of general

dental practice and asignificant income-producing procedure.

General dentists report thatendodontic therapy is increasingin need. Many practice adminis-

tration courses stress the impor-tance of making endodontic

therapy a fast, easy and effec-tive part of practice, and den-tists are eager to accomplish

endodontic treatment. Althoughreports concerning the long-termsuccess of endodontic therapy

vary, American dentists seem tobe relatively satisfied with theclinical success and pre-

dictability of endodontic treat-

ment. Many adults have bene-fited from at least one

endodontically treated tooth.Few dental maladies are aspainful as a tooth that needs

endodontic therapy, and fewdental patients are as pleased

with their dental therapy as arethose who receive successfulendodontic treatment.

However, why are more teethdying? Why is so much

endodontic therapy needed? Is itbecause more teeth are being

heroically saved, or becausepatients are living longer thanin the past and, therefore,

retaining more teeth that laterneed endodontic therapy? Or arewe inadvertently killing more

pulps with some of the tech-niques, instruments and

materials commonly used today?This article includes some of

the potential ways to kill a

dental pulp, based on observa-tions I have made in visits tomany dental offices, and on my

discussions with thousands ofdentists around the world aboutthe clinical methods they use in

their day-to-day dental practices.

DENTAL TECHNIQUESPOTENTIALLY RELATEDTO PULPAL DEATH

Resin-based composite usedto restore posterior teeth.I have been told by numerous

endodontists that one of themost significant factors relatedto the increase in need for

endodontic therapy has been thepopularity of resin-based com-

posite to restore posterior teeth.Without proper use of dentin

bonding/sealing materials, it iswell-known that Class I and IIresin-based composite restora-

tions cause postoperative toothsensitivity and potential pulpaldeath. Fortunately, this cause of

pulpal death appears to bedecreasing in incidence because

more practitioners are usingdesensitizing liquids containingglutaraldehyde or hydroxyethyl

methacrylate, resin-modifiedglass ionomer liners and self-etching primers instead of total-

etch primers.1 These materialsseal dentinal canals by impreg-nating them with resin or coagu-

late or physically seal dentin.

However, because of resin-basedcomposites known ability to irri-

tate the pulp, there still is resis-tance on the part of some den-tists to using this restorative

material in posterior teethinstead of conventional

amalgam. Resin-based com-posite can be used withoutpulpal sensitivity and subse-

quent pulpal death when properbonding agents, liners and

How to kill a tooth

OBSERVATIONS GORDON J. CHRISTENSEN, D.D.S., M.S.D., Ph.D.

Copyright 2005 American Dental Association. All rights reserved.


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1712 JADA, Vol. 136 http://jada.ada.org December 2005

desensitizing solutions are used.Resin-based composite

cement for indirect restora-tions. In recent years, dentistshave reported that their

patients have experienced unac-ceptable postoperative pulpalsensitivity and some pulpaldeath when total-etch bonding

systems were used before resincements were placed.2 However,some manufacturers continued

to advertise and teach that theirresin cements and bonding sys-tems did not produce such ill

effects. Apparently, the total-etch primer concept used before

placment of resin cement did notpredictably provide the neces-sary dentinal seal to seat crowns

or fixed prostheses without pro-ducing tooth sensitivity andeventual pulpal death. This

unfortunate situation dissuadeddentists from seating restora-tions with resin cements and

from using indirect restorationsrequiring resin cement. Somepopular products, including the

first one introducedPanavia,in its various forms (Kuraray,

New York)had a separatebottle of self-etching primer (inPanavias case, ED Primer) that

had to be used before the resincement component of theproduct was placed on the tooth.

The Panavia concept dominatedthe marketplace for severalyears and was quite successful.

Other companies copied the con-

cept, and although strengthvalues and other properties

were good with these products,improper use caused occasionallingering postoperative sensi-

tivity, and infrequent pulpaldeath occurred. On the advent of

the self-etching primerresincement combination productsMaxcem (Kerr, Orange, Calif.),

RelyX Unicem (3M ESPE, St.Paul, Minn.) and Universal

Resin Cement (Pulpdent, Water-town, Mass.)the dilemma wassolved.

When use of resin cements isindicated for crown cementation,

I suggest that self-etch resincement products should be usedto eliminate the problemsdescribed here.

Deeply cut veneer prepa-rations. There is a growing ten-dency to cut tooth preparations

for veneers deeply into dentin.3

Usually, the veneers are seatedwith resin cement over bonding

agents that are in the total-etchcategory. Because the ceramicveneer can be made thick, this

technique makes matching thedesired tooth color easier than

when the veneer preparationsare cut to a shallow level. How-ever, veneer preparations that

are cut deeply into dentin andthen treated with total-etchprimers can have objectionable

characteristics. These problemsinclude postoperative tooth sen-sitivity, debonding after thermal

changes, occlusal stresses while

eating and pulpal death. I sug-gest that veneer tooth prepara-

tions should be made in enamelwhenever possible. Such prepa-rations do not cause these

problems.Deeply cut tooth prepara-

tions for all-ceramic crownsand fixed prostheses. Thegrowing popularity of all-

ceramic crowns and fixed pros-theses has created an increase

in postoperative tooth sensi-tivity and pulpal death. Often,to change tooth color, contour or

occlusion, these restorations areplaced on nearly virgin teeth

with large pulps or on youngteeth with large pulps and wide-open dentinal canals. Thesetooth preparations must be at

least 1 to 11/2 millimeters deepon all surfaces, except theocclusal surface, where the

reduction should be 11/2 to 2 mm.Such deep tooth preparations onteeth with large pulps require

meticulous care to avoid toothsensitivity or worse effects. For-

tunately, some of the alumina-or zirconia-based all-ceramicrestorations can be seated with

resin-modified glass ionomercement (such as RelyX LutingCement, 3M ESPE, or GC

FujiCEM, GC America, Alsip,Ill.), which reduces or eliminatespostoperative tooth sensitivity.

However, to provide adequatestrength for pressed ceramicindirect restorations, and to

avoid the hygroscopic expansionof the resin-modified glass

ionomer cements on these some-what weaker restorations, therestorations should be cemented

with resin-based compositecements. I suggest that pressedceramic restorations should be

cemented with the self-etchprimerresin cements suggestedpreviously in this article to

reduce or eliminate postopera-

tive problems.Occlusion too high on res-torations. Fixed prosthodonticprocedures are carried out farmore frequently now than they

were in years past. On manyoccasions in my practice, I have

observed crowns and fixed pros-theses, placed elsewhere, thatwere left in supraocclusion after

cementation. I have seen den-tists seat fixed prostheses

O B S E R V A T I O N S

When use of resin

cements is indicated

for crown

cementation, self-etchresin cement products

should be used.



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without checking and correctingocclusal contacts, with the resultthat the affected tooth or teeth

soon become highly sensitive. Toavoid the high occlusion, the

teeth move in the bone to loca-tions that do not have the samehigh occlusion. Often, theaffected teeth cannot move far

enough to get out of the zone ofocclusal trauma. The clinicalresult is a widened periodontal

ligament, mobile teeth, painfulteeth, open contact areas,chipped ceramic, loosening of

implants or implant abutments,and eventual pulpal death of the

restored or opposing teeth. Inmy opinion, clinicians must paymore attention to correcting

occlusion when seating compre-hensive restorations.

Aggressive or dry toothcutting and dull rotaryinstruments. High-speed airrotor handpieces, and especially

electric high-speed handpieces,cut extremely rapidly and cancause significant vibration in

the teeth being prepared. Also,many dentists do not use signifi-

cant water lavage when cuttingteeth. I have seen teeth developblack burn marks as high-speed

handpieces and dull burs orworn-out diamond rotary instru-ments are used with too much

pressure while cutting. Howmuch trauma can a dental pulptake before dying, and how long

after cutting a tooth preparation

does the pulp die? We dontknow. I suggest using new car-

bide burs for each patient when-ever possible and new, single-use rotary diamond instruments

for every patient. When usingnew rotary instruments each

time, the clinician has no doubtthat the instruments are sharp

and concentric. Additionally, Isuggest using careful low-loadcutting with either air rotors or

electric handpieces. These hand-pieces cut fast and well, even if

high cutting load is not used onthem.

High exothermic activityin provisional restorations.Try holding an unset piece ofpolymethyl methacrylate orpolyethyl methacrylate in your

hand while the specimen sets.You will have to release it as itgoes through its exothermic set-

ting reaction. Imagine that samehigh temperature on a deeply

prepared tooth. Pulpal damageis unavoidable with improperlyused provisional materials.

These materials must be cooledas they are polymerizing. Dentalassistants making these types of

provisional restorations need toknow the significance of highexothermic activity and high

pulpal temperatures. I suggestusing bisacryl provisionalmaterials for one unit or short

fixed prosthodontic situations.These materials do not have a

significant exotherm. When thestrength and color stability ofpolymethyl methacrylate is

needed, I suggest using alaboratory-made polymethylmethacrylate shell for the

exterior of the provisional resto-ration and a liner made ofpolyethyl methacrylate, which

gives off a lower exotherm, in

the mouth for the shell.Dentist error. In addition tothe problems I already havedescribed, numerous other com-monly occurring clinical situa-

tions could be described that log-ically should injure or kill the

dental pulp. Perhaps we den-tists are our own enemies. Per-

haps we are one of the majorreasons for the increased needfor endodontic therapy by virtue

of creating deep preparations,leaving dentinal canals

unsealed, carrying out trau-matic preparations and prema-turely abandoning occlusaltreatment of restored teeth. Per-

haps we are too hasty in accom-plishing endodontic therapy onteeth that are sensitive but may

become nonsymptomatic ifallowed to rest withoutendodontic therapy for a few

more weeks. I feel that is thecase.

SUMMARY

Many dentists report increased

activity in endodontic therapy.Although retention of teeththrough most of life by many

patients and the aging popula-tion are potential reasons forthis increase, it is possible that

some of the new dental pro-cedures, instruments ormaterials that have become pop-

ular in recent years also are sig-nificant causative factors. Sev-

eral potential preventablereasons for increased pulpaldeath and the resultant need for

endodontic therapy arediscussed in this article. s

Dr. Christensen is co-founder and seniorconsultant, Clinical Research Associates, 3707N. Canyon Road, Suite 3D, Provo, Utah 84604.Address reprint requests to Dr. Christensen.

Bibliography1. Christensen GJ. Preventing postoperative

tooth sensitivity in Class 1, 2 and 5 restora-tions. JADA 2002;133:229-31.2. Clinical Research Associates. Artglass,

belleGlass, and Targis System crowns com-pared at one year. CRA Newsletter 1998;22(10):1-3.

3. Christensen GJ. What is a veneer? JADA2004;135:1574-6.

JADA, Vol. 136 http://jada.ada.org December 2005 1713

O B S E R V A T I O N S


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