Dental Research

A clinieal trial of the glass-ionomer cement-composite resin "sandwich"technique in Class II cavities in permanent premolar and molar teethR. Richard Welbury* / John J. Murray'

Glass-ionomer cement has been advocated for use as a base under composite resin resto-rations. Forty-nine restorations were studied over a 2-year period to lest ihe efficiency ofthe glass-ionomer cement-composile resin "sandwich technique" in Class H cavities.The restorations, all plaeed by one clinician, were assessed at 6-month intervals for col-or, anatomic form, marginal adaptation, and surface roughness. Seventeen restorationsfailed during the follow-up period because of progressive loss of glass-ionomer matericd.Despite the good performance of the composite resin at the occlusal surfaces, the sand-wich technique failed to provide acceptable restoration.^ in this clinical trial.(Quintessence Int ¡990:21:507-512.)

Introduction

A glass-ionomer cement (Ketac-Bond. ESPE GmbH)was marketed in 1984 to combine the advantages ofglass-ionomer cement materials with the properties ofan ideal bonding base. The manufacturers recom-mended it for use as a cement base under compositeresin restorations in cavities of all classes and rec-ommended that in the Class II situation the glass-ionomcr cement form the apical 1 to 2 mm of thefinished approximal wall of the glass-ionomer ce-ment-composite resin restoration.

The purpose of this clinicai trial was to test theefficiency of this application of the glass-ionomer ce-ment-composite resin "sandwich" technique.

Method and materials

Patients attending the Department of Child DentalHealth for routine restorative care were admitted tothe trial if they had a carious permanent premolar or

Utturer. Deparlmem of Child Denut Heaith, Univeraly ofNewcastle upon Tyne, The Dental School, F ram I in g ton Place,Newcastle upon Tyne, NE2 4BW. England,Professor, Department of Child Dental Health, University ofNewcastle upon Tyne.

molar that required a Class II cavily design for res-torative purposes. Any cavity was suitable for inclu-sion in the trial, whether it was the result of caries ona previously undamaged site or arose as a consequenceof recurrent deeay or loss of a pre-existing restoration.Between March 1986 and July 1987 a total of 49 res-torations were placed in 23 patients aged 9 to 18 yearsby one chnician (RRW). These restorations were sub-sequently assessed at regular intervals.

All restorations were completed under rubber dam.A Tofflemire matrix holder with thin clear matrixband was piaced around the tooth and wedged inter-proximaliy. A lining of fast-setting calcium hydroxidecement was then placed in deep cavities overlying thepulp. The cavity was then washed with 40% poly-acryiic acid for 10 seconds, rinsed with water for 30seconds, and dried. Ketac-Bond, a no ne neap su la tedglass-ionomer cement, was then mixed according tomanufacturer's instructions and run into the cavitywith the aid of a Thymozin probe to cover the baseof the cavity, the axial wall, and the base of the boxout to the approximal surface. The thickness of ce-ment in the box was at least 1 mm. After 4 minutes,excess glass-ionomer cement was removed with asharp excavator. The surface of the cement and theenamel margins were etched with acid-etchant gel for60 seconds, washed for a further 60 seconds, and driedwith oil-free air, A thin layer of enamel bond was thenpainted over the cernent surface and enamel margins

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Dental Research

Table ! Number of restorations achieving each suc-cessive follow-up period

No, of restorations Foliow-up period

49383111

6 months12 months18 months24 months

Table 2 Cavity sizes of the 49 trial restorations

Occlusal size

Approximal size

Depth of box

No, of restorations

102514

93010

36130

Table 3 Baseline (1-month) assessments of restora-tions (n = 49)

Category Score No, (%)

Color match

Discomfort/sensitivity

Cavomarginal discolorationAnatomic form

Occlusal

Approximal

Marginal adaptationOcciusal

Approximal

Surface roughnessOcclusal

Approximal

454

(92)(8)

A 49 (100)

A 49 (100)

ABAB

ABAB

ABABCD

8 (98)1 (2)8 (98)1 (2)

146

3

481

45211

(98)(2)

(94)

(6)

(98)(2)

(92)(4)(2)(2)

and light cured for 15 seconds. Occlusin (Pot-Univer-sal shade) composite resin (ICI Dental) was thenpacked incrementally into the cavity with an amalgamburnisher dipped in enamel bond to prevent the com-posite resin from sticking to the instrument. No morethan 2 mm of composite resin was light cured (60seconds) at any one time, and during packing a pre-cured ball of composite resin was packed into the ap-proximal box to help estabhsh a contact point withthe next tooth.' To minimize finishing by rotary in-struments, restorations were preshaped and formedwith burnishers of different shapes lightly dipped inenamel bond before the restorations were cured. Aftercuring, the restorations were finished with slow- andfast-speed diamonds and abrasive disks. A final glazewas achieved by light curing a thin layer of enamelbond to the surface ofthe restoration.

After the restoration was placed, three assessmentswere made. First, the size ofthe cavity was classifiedunder the following scoring system:

Occlusal

1. Cavity extended up the cuspal incline less than onefourth of the distance from the depth of the fissureto the cusp tip

2. Cavity extended between one fourth and one thirdof the way up the cuspal incline

3. Cavity extended greater than one third of the wayup the cuspal incline

Approximal

1, Cavity just cleared contact point areas and extend-ed into embrasures

2, Cavity extended well into embrasure areas3, Cavity extended onto the buccal and palatohngual

walls

Depth of box

1, Above cementoenamel junction2, At cementoenamel junction3, Below cementoenamel junction

Second, a postoperative bite-wing radiograph wastaken, and, third, a clinical photograph was taken.

The restorations were assessed at baseline (] monthpostplacement) and at each subsequent 6-month re-view appointment by one clinician (RRW), They werescored using a modification of US Pubhc Health Serv-

508 Ouintessence-Uiii 6/1990

Dentai Research

ice (USPHS) criteria- for posterior composite resinrestorations. Bite-wing radiographs and clinical pho-tographs were taken annually or more frequently if theneed arose.

Results

A total of 49 Class IT restorations in 24 patients aged9 to 18 years were assessed regularly between July 1986and July 1988. Of the 49, 43 were mesio-occlusal ordisto-occlusal and six were mesio-occlusodistal res-torations; 29 were placed in molars and 20 in pre-molars. All the patients attended each subsequent 6-month recall, except for two (three restorations), whoonly returned for the first 6-month recall. The numberof restorations achieving each successive 6-month re-view appointment is shown in Table 1, and the cavitysizes of the 49 restorations are shown in Table 2. Noneof the restorations had an approximal box that ex-tended apically below the cementoenamel junction.

Modified USPHS criteria were used to assess ana-tomic form, marginal adaptation, and surface rough-ness on both occlusal and approximal surfaces andcavomarginal discoloration and eolor match on theoeclusal surface only. Baseline (1-month) assessmentsand results are presented in Table 3, and the resultsof the 6-, 12-, 18-, and 24-month examinations arepresented in Table 4.

Color match was good throughout; only a smallpercentage of restorations was graded B and thoserestorations were readily apparent at baseline. No dis-comfort or sensitivity was reported by the patients atany time in the trial.

At the 6-month recall, 3% of the restorations weregraded B for eavomarginal discoloration, but by 24months this amount had increased to 36%. The prox-imal margins of the Class II restoration were foundto be relatively free of cavomarginal discoloration. De-terioration was most commonly found in relation toareas of complex morphology and marginal defectson stress-bearing areas.

The occlusal surface of the restoration, that is, the"composite resin only" surface, after 18 months ofservice achieved A scores for anatomic form (87%),marginal adaptation (94%), and surface roughness(87%), However, when the approximal surfaces wereconsidered, the corresponding A scores at 18 monthsof service were anatomic form (68%), marginal ad-aptation (58%), and surface roughness (58%). Thediscrepancy between the two surfaces was due to thesmall, 1- to 2-mm layer of glass-ionomer cement m

the base of the box, which, in a number of cases,continuously lost material. Even after 1 month, at thebaseline assessments, 6% of restorations were gradedB for marginal adaptation and B, C, or D for surfaceroughness in the approximal box, indicating early de-terioration in the region of glass-ionomer cement.

To date, Í7 restorations have failed during the fol-low-up period- A restoration was regarded as failed ifit had a score of C for anatomic form or marginaladaptation or if recurrent caries was found beneaththe restoration. Ten of the failures were due to loss ofglass-ionomer cement from the base of the box, re-sulting in cervical gap formation (mean time to failure13.2 + 6.8 months). Seven of these failures were inmolars and three in premolars. Five restorations faileddue to fracture or loss of composite resin (mean timeto failure 8.0 ± 3.7 months). Eour of these failureswere in molars and one was in a premolar. One res-toration was a combined failure in a molar tooth withfracture of composite resin and loss of glass-ionomercement at 18 months, and one restoration was replacedbecause earies was found elsewhere in the tooth at 24months.

The number of failures involved was too small tobe able to interpret any significance test comparingfailure to original cavity size. However, the teeth re-stored with the Class II sandwich restorations de-scribed in this trial required careful radiographie inter-pretation. Fig la shows a maxillary left first molarimmediately after placement of a mesio-oeelusal res-toration. The base of the box. was within enamel ap-proximately 1 mm above the cementoenaniel junction,Glass-ionomer cement occupied 1 to 2 mm of the fin-ished approximal wall of the restoration and was al-most identical in radiopacity to enamel. The occlusalsurfaee and the remainder of the approximal toothsurface were restored with the more radiopaque com-posite resin. The restoration is shown in Fig lb after18 months, when it achieved a score of A on all sur-faces for anatomic form, marginal adaptation, andsurface roughness.

Fig 2a shows a mandibular left first molar imme-diately after placement of a disto-occlusal restoration.After 18 months, there was some loss of glass-ionomercement at the composite resin-glass-ionomer cementbox junction, and this tooth, although achieving gradeA on its occlusal surface, was graded B for anatomicform and marginal adaptation and C for snrfaceroughness on its approximal surface (Fig 2b).

Fig 3 shows a disto-occlusal restoration in a max-illary right second premolar after 12 months. Al-

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Dental Research

Table 4 Assessments of restorations over

Category

Color match

Discomfort/sensitivity

Cavomarginal discoloration

Anatomic formOcclusal

Approximal

Marginal adaptationOcclusal

Approximal

Surface roughnessOcclusal

Approximal

6 months (n

Score

AB

A

AB

ABCABC

ABCDABCD

ABCDABCD

No.

454

49

463

4342

4045

44113

37444

43303

38164

titne

= 49)

(%)

(92)

m(100)

(94)(6)

(88)(8)(4)

(82)(8)

(10)

(90)(2)(2)(6)

(76)(8)(8)(8)

(88)(6)(0)

(6)(78)(2)

(12)(S)

Î2 months (n

Score

AB

A

AB

ABCABC

ABCDABCD

ABCDABCD

No.

353

38

344

3242

2963

34103

26813

33203

28163

- 38)

(%)

(92)(8)

(iOOt

(89)(11)

(84)(11)

(5)(76)(16)

(8)

(89)(3)(0)(8)

(68)(21)

(3)(8)

(87)(5)(0)(8)

(74)(2)

(16)(8)

18 months (n

Score

AB

A

A

B

ABCABC

ABCDABCD

ABCDABCD

No.

292

31

229

2731

2155

29101

18841

27211

180

n1

= 31) 24 months (n

(%)

(94)(6)

(100)

(71)(29)

(87)(10)

(3)(68)(16)(16)

(94)(2)(0)(2)

(58)(26)(13)

(3)

(87)(7)(3)(3)

(58)(0)

(39)(3)

Score

A

A

AB

A

ABC

A

AB

A

AB

No.

11

11

74

11

911

11

101

11

101

= 11)

(%)

(100)

(100)

(64)(36)

(100)

(82)(9)(9)

(100)

(91)(9)

(100)

(91)(9)

though the restoration was graded A on its occlusalsurface, it had lost sufficient glass-ionomer cement atthe base of the box to receive a C for anatomic form,marginal adaptation, and surface roughness and thusrequired replacement.

Fig 4 shows a rnesio-occlusal restoration in a tnan-dibular right second molar and mesio-occlusodistalrestoration in a mandibular right first molar just 6months after placement. There was severe loss ofglass-ionomer cement from the distal box of the first

molar and the mesial box of the second molar. Inaddition, the marginal ridge of the second molar hadfractured. Both restorations required replacement.

Discussion

No previous clinical trials have been reported in theliterature concerning this application of the glass-io-nomer eement-composite resin sandwich re.'; to ration.

510

Dental Research

Fig la Tooth 26 immediately atter placement of mesio-occlusal restoration.

Fig l b Restoration at 18-month recall, showing no dete-rioration ot glass-ionomer cement.

Fig 2a Tooth 36 immediately after placement of dlsto-Qcclusal restoration.

Fig 2b Restoration at 18-month recall, showing some lossof glass-ionomer cement from the box.

Fig 3 Disto-occlusal restoration in tooth 15 after 12monlhs, showing appreciable loss of glass-ionomer cementfrom the box.

Fig 4 Mesio-occlusal restoration in tooth 47 and mesio-ooclusodistal restoration in tooth 46 after 6 months. Severeloss of glass-ionomer cement In the mesial box of tooth 47and the distal box of tooth 46.

Quintessence Internafionaf Volume'îi^, Number 6/1990 511

Dental Research

Despite meticulous attention to moisture control andthe manufacturer's recommendations for the materialsinvolved, 11 restorations (22%) had to be replacedwithin 18 months because of failure of glass-ionomercement at the base of the approximal box. This oc-curred despite the fact that no box extended below thecementoenamel junction. Failure always took the formof progressive loss of glass-ionomer material and wasrevealed by adjacent erythema and swelling at the in-terdental papilla before being confirmed by dentalprobe and radiography.

Six restorations ofthe original 49 had to be replacedbecause of "composite resin only" failures. This rateis similar to the failure rate for Occlusin after 2 yearsreported by Wilson et al' in 1986, Scores for anatomicform, marginal adaptation, and surface roughness onthe occlusal surface were also similar to those reportedby Wilson et al.̂ However, for comparisons betweenthe two studies, the small number of restorations com-pleting the 2-year review in the present study (11),compared to the larger number in the study by Wilsonet aP (52), should be considered.

Conclusions

Regardless of the performance of the composite resinin the more coronal part of the cavities, this trial wasdesigned to investigate whether a sandwich restorationincorporating 1 to 2 mm of glass-ionomer cement atthe base of the finished approximal surface in ClassII boxes would overcome the problem of cervical con-traction gaps in Class II composite resin restorations.The sandwich restoration failed to achieve this aimwith the materials used under the conditions reportedand cannot be advocated as an alternative method ofrestoration in the approximal box situation.

References

1. Wander P. Paul E: Posterior composites: "guaranleed way forsuccess." Dem Fract 1986;24:17-19.

2. Cvar JF, Ryge G: Criteria for the Clinicai Evaluation of DentalRestorative Materials. USPHS publication No. 790-244. SanFrancisco, US Goverment Printing Office, 1971.

3. Wilson MA. Wilson NHF, Smilh GA: A Clinical trial ofa visiblelighi-cured pos I eri or composite resin restorative: two-year lesul Is,Quintessenee Int 1986;]7:]51-I55, D

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