Acta Odontologica Scandinavica, 2011; 69: 6574

REVIEW ARTICLE

Application of laser technology for removal of caries: A systematicreview of controlled clinical trials

THOMAS JACOBSEN1, ANDERS NORLUND2, GUNILLA SANDBORGH ENGLUND3 &SOFIA TRANUS2,3

1Public Dental Services, Vstra Gtaland District, Skvde, Sweden, and Department of Cariology, Institute ofOdontology, University of Gothenburg, Gothenburg, Sweden, 2Swedish Council on Health Technology Assessment,Stockholm, Sweden, and 3Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden

AbstractObjective. To evaluate the scientic evidence regarding laser technology for removal of carious tissue. Material andmethods. A search for literature on the effect of treatment and on economic aspects of laser technology identied 23 papers.No relevant studies on economic aspects were found. Regarding the effect of treatment, 16 papers were selected for assessmentaccording to established criteria. Results. Cavity preparation and caries excavation by erbium laser were evaluated in threestudies of medium quality. The time required to remove carious tissue was evaluated in ve studies assessed as being ofmedium quality for this outcome. In four studies the effect of laser treatment on the dental pulp was included as an outcomebut, due to the short follow-up time, the quality was assessed as low. Two studies that included the longevity of the restorationas an outcome were also assessed as being of low quality because the follow-up time was inadequate. Patient response wasevaluated in three studies, which were assessed as being of medium quality with respect to this outcome. Conclusions. Thereis limited scientic evidence that laser treatment is as effective as a rotary bur for removing carious tissue. Treatment time isprolonged. There is limited scientic evidence that adults prefer laser treatment. No conclusions can be drawn regardingbiological or technical complications, childrens perception of laser treatment or the cost-effectiveness of the method.

Key Words: Dental caries, economics, erbium YAG, evidence-based dentistry

Introduction

Several techniques for caries excavation are available[1]. The conventional method is the use of a rotarybur. Although this is a highly efcient low-cost tech-nique, it generates considerable noise and vibration.An alternative approach is the application of anerbium laser beam. This is a relatively new methodand to date its application in most countries is notwidespread.When the laser beam encounters the tooth surface,

the light is absorbed by water molecules in the dentalhard tissues. As a result, the water heats up rapidlyand vaporizes. The reaction creates a high localizedpressure and a micro-explosion, which results inablation of dental hard tissue. A comprehensive reporton the basic science and general aspects of lasers indentistry has been edited by Gutknecht [2].

Removal of caries is often a painful procedure andthe pain is more intense in deep lesions close to thedental pulp. Compared to a rotary bur, the laser isquieter and vibrates less [3]. It is claimed that lasertreatment is less painful, reducing the need for localanesthesia [2].Instrumentation of the dental hard tissues can

result in unwanted side effects. The friction developedby rotary instruments raises the temperature and thusincreases the risk of thermal injury to the pulp. Thepeak surface temperature during ablation of enamelwith erbium lasers can vary between 300 and 800C,depending on the laser system [4]. To avoid thermaldamage, continuous water-cooling is required duringtreatment [5,6].The method of excavation may affect the surface

properties of dental hard tissues and compromisebonding with adhesive restorative materials, thus

Correspondence: Soa Tranus, The Swedish Council on Health Technology Assessment, PO Box 3657, SE 103 59 Stockholm, Sweden. Tel: +46 8412 3214.E-mail: Tranaeus@sbu.se

(Received 14 October 2009; accepted 2 September 2010)

ISSN 0001-6357 print/ISSN 1502-3850 online 2011 Informa HealthcareDOI: 10.3109/00016357.2010.536901

Act

a O

dont

ol S

cand

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Gue

lph

on 0

5/04

/13

For p

erso

nal u

se o

nly.

reducing the longevity of the restoration. The bondbetween resin composites and laser-excavated toothstructure has been evaluated in several in vitro studies[713]. However, with respect to potentially detri-mental effects of laser ablation, the results arecontradictory.The aim of the present systematic literature review

of controlled clinical trials was to evaluate the scien-tic evidence in support of laser excavation of carioustissue. The review includes erbium laser equipment ofvarious brands, but with the same wavelengths. At thetime of this review two different laser systems werecommercially available:

. Er:YAG laser (erbium: yttriumaluminumgarnet); wavelength: 2.94 mm.

. Er,Cr:YSGG laser (erbium, chrome: yttriumscandiumgalliumgarnet); wavelength: 2.79 mm.

The review addresses the following primaryquestions:

. Is laser an effective method for removing carioustissue? (Outcome: complete caries removal.)

. Are there potential biological complications asso-ciated with the method? (Outcome: pulpal injury.)

. Is the longevity of the restorations affected by themethod of caries removal (laser versus bur)? (Out-come: longevity of the restoration.)

. Do patients respond more favorably to laser treat-ment than conventional caries excavation? (Out-come: comfort or subjective perception duringtreatment, patient preference for laser/bur, needfor local anesthesia.)

. What is the cost of the laser treatment? Is themethod cost-effective?

The review was initiated by the Swedish Councilon Technology Assessment in Health Care(SBU) [14].

Material and methods

Effect of treatment

Search strategies. In January 2009, in consultation withan information specialist, a search for relevant liter-ature on the effect of treatment was conducted usingthe following databases: PubMed, Cochrane Library,Embase and Inspec (Table I). The reference lists ofthe selected articles were then manually searched foradditional relevant articles. Original studies publishedin any language, but with an abstract in English,German, French or any of the Scandinavian lan-guages, were accepted. Grey literature, such as text-books, abstracts, letters, editorials and proceedings,were not taken into account. Animal studies were alsoexcluded. The literature search resulted in retrieval of766 unique abstracts. Two reviewers independentlyevaluated the abstracts for potential inclusion.

A full-text version of an article was ordered if at leastone of the reviewers considered it potentially relevantaccording to the following basic inclusion criteria:

. Study aim in agreement with the main researchquestion.

. Prospective clinical study.

. At least two experimental groups in which theoutcome of laser ablation was compared withthat of conventional excavation with a rotary bur.

. At least 20 patients in each study group.

. Follow-up of at least 3 years for evaluation of long-term pulpal effects and longevity of restorations.

The papers did not have to address all the researchquestions in order to be selected.

Quality assessment. The two examiners read the papersindependently. The quality and relevance of eachstudy were graded as high, medium or low using astudy-quality checklist. The questions focused on

Table I. Search strategies: effect of treatment.

PubMed 19502009 (January)

Er yag (TW)Erbium yag (TW)Er, cr ysgg (TW)Er cr ysgg (TW)

AND Caries (TW)Carious (TW)Teeth (TW)Tooth (TW)Dentin(e) (TW)Dental (TW)Enamel (TW)

Cochrane Library version 1, 2009

Er yag (ti, ab, kw)Erbium yag (ti, ab, kw)Er, cr ysgg (ti, ab, kw)Er cr ysgg (ti, ab, kw)

AND Caries (ti, ab, kw)Carious (ti, ab, kw)Teeth (ti, ab, kw)Tooth (ti, ab, kw)Dentin(e) (ti, ab, kw)Dental (ti, ab, kw)Enamel (ti, ab, kw)

Embase 1974-2009 (January)

Er yag (TW)Erbium yag (TW)Er, cr ysgg (TW)Er cr ysgg (TW)

AND Caries (TW)Dental caries/expCarious (TW)Teeth (TW)Tooth (TW)Tooth/expDentin(e) (TW)Dentin/expDental (TW)Enamel (TW)Enamel/exp

Inspec 19872009 (January)

Er yag (TW)Erbium yag (TW)Er, cr ysgg (TW)Er cr ysgg (TW)

AND Caries (TW)Carious (TW)Teeth (TW)Tooth (TW)Dentin(e) (TW)Dental (TW)Enamel (TW)

TW = text word; ti = title; ab = abstract; kw = keyword; exp =explode.

66 T. Jacobsen et al.

Act

a O

dont

ol S

cand

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Gue

lph

on 0

5/04

/13

For p

erso

nal u

se o

nly.

external validity, internal validity (e.g. study popula-tion, distribution of treatment, comparability ofgroups, blinding, loss to follow-up, compliance,reporting of effectiveness and side effects), and studyprecision (whether the factors and calculations usedto determine the minimum number of participantswere acceptable, e.g. power calculation). An overallassessment of the different quality items was thenused as a basis for the intellectual discussion involvedin grading the study quality. In case of disagreementbetween the reviewers, the paper was discussed by allauthors until a consensus was reached. Studies withseveral endpoints could be awarded different qualitygradings for each endpoint.

Scientic evidence. The scientic evidence was there-after assessed on the basis of studies with high ormedium quality/relevance. The level of evidence wasset according to predetermined SBU criteria usedat the time for the present study, as presentedin Table II.

Health economics

In consultation with an information specialist, asearch for relevant literature which included eco-nomic aspects of caries excavation by erbium laserwas conducted in January 2009, using the followingdatabases: PubMed, Cochrane Library and HEED(Table III). The Drummond checklist was used forquality assessment of the studies [15]. The searchdisclosed no relevant published studies.

Results

In all, 16 papers were selected for assessment in full-text format. Nine papers were excluded [1624].

Agreement between the two examiners was good(k = 0.71). The studies included are summarizedin Table IV [2531]. Because the studies were soheterogeneous, no meta-analyses were performed.

Cavity preparation and removal of caries

Cavity preparation and caries excavation by erbiumlaser were evaluated in three studies of mediumquality [2526,28].Den Besten et al. [25] compared laser ablation and

rotary bur preparation of one cavity per subject in124 children and adolescents (age 418 years). Thesubjects were randomized 2:1, i.e. 82 teeth wereprepared by erbium laser and the remaining 42 byrotary bur. The operator and a calibrated, indepen-dent evaluator assessed the cavities for caries-free status using a tactile probe. If the status wasquestionable, the operator repeated the procedure.No information is available as to how often thisoccurred, but ultimately 81/82 cavities ablated bylaser and all 42 cavities excavated by bur wereaccepted.A randomized clinical trial by Dommisch et al. [26]

used a split-cavity design to compare the efcacy of auorescence-controlled laser and conventional exca-vation. There were 26 subjects (age 2256 years) witha total of 102 lesions. All lesions were opened withrotary instruments. Each lesion was divided into twoareas. Carious tissue from one half of the cavity wasremoved by laser and from the other half by a rotarybur. The diagnostic laser (uorescence feedback) wasset at threshold values between 7 and 10. The exca-vation was re-evaluated by a blinded, independentevaluator using a tactile probe. After treatment, den-tin samples were collected from the different locationsand analyzed for potential growth of Streptococcusmutans and Lactobacillus. At the threshold levels of7 and 8 the laser removed carious tissue as effectivelyas the bur. The bacteria remaining after cavity prep-aration were regarded as clinically irrelevant.Hadley et al. [28] compared caries excavation by

laser and bur in a randomized clinical trial using asplit-mouth design. The subjects comprised 68 adultsaged 2084 years, with 75 pairs of teeth. Two cali-brated operators and three blinded evaluators wereengaged in the trial. The cavities were assessed by theoperator and an evaluator. If the outcome wasregarded as unacceptable, the operator repeated theprocedure until the cavity was caries-free and thepreparation was satisfactory. No information is avail-able as to how often this occurred. No signicantdifference was found between laser and bur for thetwo outcomes: caries removal and cavity preparation.Caries removal and cavity preparation were

also assessed in a study of low quality byPelagalli et al. [31].

Table II. Criteria for grading of scientic evidence.

Evidence grade 1(strong scienticevidence)

The conclusion is corroborated byat least two independent studies ofhigh quality, or a goodsystematic overview

Evidence grade 2(moderately strongscientic evidence)

The conclusion is corroboratedby one study of high quality, andby at least two studies of mediumquality

Evidence grade 3

Limited scienticevidence

The conclusion is corroboratedby at least two studies of mediumquality

Insufcient scienticevidence

No conclusions can be drawn whenthere are not any studies that meetthe criteria for quality

Contradictory scienticevidence

No conclusions can be drawn whenthere are studies with the samequality whose ndingscontradict each other

Laser excavation of caries 67

Act

a O

dont

ol S

cand

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Gue

lph

on 0

5/04

/13

For p

erso

nal u

se o

nly.

Treatment time

The time required to remove carious tissue has beenevaluated in ve studies assessed as being ofmedium quality for this outcome [2527,29,30].Dommisch et al. [26] showed that the laser methodtook three times longer than a rotary bur to removecarious tissue. Keller et al. [29] and Liu et al. [30]reported that the laser procedure took twice as long.In the study by Den Besten et al. [25] there was nosignicant difference in treatment time between thegroups. Evans et al. [27] reported only that length ofappointment for laser treatment was signicantlylonger than for the rotary bur. Treatment timewas also evaluated in one study assessed as being oflow quality regarding this outcome [31].When calculating the total treatment time it is

essential to take into account the need for localanesthesia. Hypothetically, if anesthesia is notrequired the treatment time could be reduced by510 min. In the study by Den Besten et al. [25],fewer patients in the laser group than in the rotary burgroup requested anesthesia.

Effect on the dental pulp

If dental treatment causes a rise in pulpal tempera-ture, the risk of pulpal damage increases. Four studiesthat included an evaluation of the effect of lasertreatment on the dental pulp were identied[25,28,29,31]. However, the quality with respect tothis outcome was assessed as low because the follow-up time was short and the presentation of the resultsunclear.

Longevity of restoration

If a treatment compromises the potential for restor-ative material to adhere to the prepared tooth surfacethen there is an increased risk of failure or loss of therestoration. Two studies which included the longevityof the restoration as an outcome were identied[25,28]. The studies were assessed as being of lowquality for this outcome because the follow-up timeswere only 3 and 6 months, respectively.The scientic evidence is insufcient to determine

whether cavity preparation by laser compromises thelongevity of a restoration.

Patient perception

Patient perception has been evaluated in three studies,which were assessed as being of medium quality withrespect to this outcome [25,27,29].In the study by Den Besten et al. [25] signicantly

fewer subjects in the laser group needed local anes-thesia. In another study [29], 6/103 patients requiredlocal anesthesia for laser treatment and 11/103 forconventional treatment. This difference was not sta-tistically signicant. However, a majority of thepatients reported greater discomfort when a burwas used, irrespective of the use of local anesthesia.The third study [27] showed that a statistically

signicant number of adult patients preferred laser toconventional technique. This study also includedchildren (age

Patient perception has also been evaluated in fourstudies assessed as being of low quality with respect tothis outcome [26,28,30,31].

Discussion

A systematic search of the literature followed by dataextraction and quality assessment is today a well-established component of evidence-based medicineand dentistry. Health service staff must work in accor-dance with scientic knowledge and accepted stan-dards of practice. Assessing an intervention involvesevaluating its benets and harmful effects. Relevantinformation about the intervention is systematicallycollected, and the intervention is compared with otherinterventions or with the absence of any intervention.When weighing different options, decisions on thebest alternative can be informed by solid evidence.Thus, assessment results form a base for decisionmaking.Research results and comprehensive clinical expe-

rience should guide the delivery of healthcare [32].The methodology used in this paper was based on theguidelines developed by the SBU. The principalobjectives were to examine the feasibility of laserinstrumentation for removing carious tissue, therisk of biological and technical complications, patientresponse to laser treatment, and the cost-effectiveness of the method. The selected literatureconsisted of clinical prospective studies with at leasttwo experimental groups. The main reason forexcluding papers assessed in full-text format wasthe lack of a comparison group.Comments regarding the quality of the included

studies are presented in Table IV.Three studies of medium quality [2527] con-

cluded that a laser is as effective as a bur to removecarious tissue. An independent evaluator checked theresults in all three studies. Laser ablation of dentalhard tissues generates a different surface texture thancaries excavation by a conventional rotary bur. Sincecaries removal was conrmed by tactile examination,one cannot rule out that this might have inuencedthe evaluation. The validity of blinded evaluationmust be questioned.In two of the studies [25,28], laser ablation was

repeated if necessary in order to complete cariesremoval, but it was not stated how often thatoccurred. It is reasonable to assume that both laserand bur can generate a caries-free surface but it is notpossible to evaluate to what extent repeated laserablation and evaluation affected/prolonged the treat-ment time.None of the selected studies fullled the basic

inclusion criteria for evaluation of long-term pulpal effects and longevity of restorations.For both outcomes, an observation period of at least

3 years was required. Thus, the scientic evidence isinsufcient to determine whether laser treatmentmay be harmful to the pulp, or whether cavitypreparation by laser compromises the longevity ofa restoration.Patient perception was evaluated in seven studies

[2531], and in three of them this outcome wasassessed as being of medium quality. The assess-ment was affected by the interaction between reportsof pain during treatment and administration oflocal anesthetics. Information about how often anes-thetics were administered was often inadequatelyreported, thus it is difcult to experience painfrom a more comprehensive overview of the patientsperception of treatment. With respect to assess-ment of pain there is also an ethical aspect, especi-ally when treating children. Best practice must beto prevent pain in every situation where it mightoccur.In the paper by Evans et al. [27], the dentists

preference of laser or bur for preparation and cariesexcavation was evaluated and a majority of the den-tists preferred a conventional bur. However, the par-ticipants had limited experience of laser ablation priorto the trial.The cost of resource utilization is one of several

parameters to be considered in the planning of dentalcare. The provision of erbium laser capacity increasesthe total cost of establishing and running a dentalclinic. However, an important aspect is whether thepatients preference for treatment with minimal dis-comfort is such that additional costs are acceptable.With the present uncertainty about potential treat-

ment complications, e.g. pulpal survival, the questionarises as to whether caries excavation by laser isethically acceptable.The evidence ranged from insufcient to low for all

outcomes. Further research is therefore warranted. Itmust also be stressed that the results of this reviewcannot be extrapolated directly to every clinical situ-ation involving removal of carious tissue. Much clin-ical time is spent on removing old restorations. As thelaser is not effective on metals, a combination of burand laser must often be used.Based on our results, the following conclusions

have been made according to the guidelines of theSBU. A laser is as effective as a rotary bur forremoving carious tissue (evidence grade 3). Removalof carious tissue by laser takes longer than by rotaryinstruments (evidence grade 3). The scientic evi-dence is insufcient to determine whether lasertreatment may be harmful to the pulp. The scienticevidence is insufcient to determine whether cavitypreparation by laser compromises the longevity of arestoration. Adults prefer laser treatment to rotaryinstrumentation (evidence grade 3). The scienticevidence is insufcient to draw conclusions aboutthe response of children to laser treatment.

Laser excavation of caries 69

Act

a O

dont

ol S

cand

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Gue

lph

on 0

5/04

/13

For p

erso

nal u

se o

nly.

TableIV.Clinicaltrialswithcavitypreparationandremovalof

caries

bylaser.

Authors,year,

reference,

country

Study

design

No.ofpatientsin

intervention

and

controlgroups

Aims

Results

Qualityassessment

Com

ments

Den

Besten

etal.2001

[25]

USA

RCT(twoclinics)

Er:YAG

(I)

andbur(C)

124patients

(418

yearsof

age)

I:82

C:42

Dropoutsa

No.

ofdropoutsat

3-month

check-up:

12/124

Cariesremovaland

cavitypreparation

Timeconsum

ption

Patient

andparental

perception

(pediatricscale)

Restoration

longevity

Treatmentadverseeffects

Cariesremoval/

cavity

preparation

I:81/82acceptable

C:42/42acceptable

Tim

econsumption

Nodifference

between

groups

(P=0.299)

Patientperception

Needforlocalanesthesia

I:4/82

(5%)

C:11/42(26%

)(P

=0.002)

Com

fortduring

treatm

entor

subjectiv

eperceptionof

treatm

ent

Nodifference

between

groups

Sym

ptomsafter

treatm

ent

Nodifference

between

groups

Pulpal

effects

Nodifference

between

groups

after3months

Cariesremoval/cavity

preparation

Medium

Tim

econsumption

Medium

Patientperception

Medium

Restoration

longevity

(3months)

Low

Pulpal

effects(3

months)

Low

Randomizationnotclearlydescribed

Unclear

descriptionof

results.Not

stated

towhatextent

treatm

entswererepeated

inorderto

completecaries

removalor

adjustcavity

preparation

Treatmentevaluatedby

independent,

calibratedevaluator

Difference

inlasersettings

between

thetwoclinicsanddifference

intime

consum

ption

Parentalperception

notstated

Dom

misch

etal.2008

[26]

Germany

RCT

Splitcavity

One

operator

andone

independent

blindedcalibrated

exam

iner

Er:YAG(I)andbur

(C)

26patients

(2256

years)

102teeth

I:26

C:26

Dropoutsa

Nofollow-upNo

dropouts

Cariesremoval

Timeconsum

ption

Patient

perception

(VAS)

Bacterialinfection

Rem

oval

ofcaries

atuorescence

feedback

thresholdlevels7and8

I:94%Tim

econsumption

Three

times

longer

with

laser(P