Comparative evaluation of combined amalgam and composite resin restorations in extensively carious vital posterior teeth: An in vivo study.

AIM: The clinical performance of the combined composite - amalgam restorations in posterior teeth was evaluated.
MATERIALS AND METHODS: One hundred carious posterior teeth were randomly divided into four groups of 25 teeth each. In Group A, the teeth were restored with composite Z250 and amalgam FusionAlloy. In Group B, composite Surefil and amalgam were used. In Groups C and D, the teeth were restored with composite Surefil and amalgam FusionAlloy, respectively. The restorations were evaluated at 3, 6, 12, and 15 months, using the Ryge criteria.
RESULTS: Combined restorations and amalgam restorations showed better contact and contour than the composite restorations. No statistically significant difference was observed among the groups. Three amalgam restorations exhibited loss of retention.
CONCLUSION: The combined composite-amalgam restorations performed better for contact and contour and retention than composite and amalgam restorations, respectively.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Restoration of extensively carious teeth to an optimum state of health, function, and aesthetics, continues to be a challenge for all operating dental surgeons. Although numerous restorative materials have been tried in order to achieve adequate strength, restore aesthetics, and conserve the remaining tooth structure, a perfectly ideal restorative material has still eluded researchers.

Dental amalgam is versatile, with clinically acceptable mechanical properties and a long experience associated with its serviceability in the oral environment,[1] although it does not strengthen the remaining tooth structure.[2]

Other restorative materials such as resin-based composites require conservative cavity preparation to increase the fracture resistance of the teeth.[3] However, the material shows an inability to achieve tight proximal contacts in the posterior teeth and polymerization shrinkage.

Thus, many researchers have proposed combined amalgam and composite resin restoration to achieve the advantages of both restorative materials.[4] Presented a clinical case in which a mandibular premolar was restored with composite and amalgam, to mask the unaesthetic buccal surface of the amalgam restoration; keeping proximal contact with the silver amalgam. Another clinical study in which the maxillary posterior teeth were restored with amalgam and composite, reported that 11 out of 12 restorations scored excellently after 6.4 years.[56] A case was reported wherein the mesiobuccal part of the extensively carious premolar was restored with a hybrid composite Z250 and the remainder class II cavity was restored with silver amalgam.

The study evaluated the clinical performance of combined composite – amalgam restorations in extensively carious posterior teeth.

MATERIALS AND METHODS

One hundred carious permanent maxillary and mandibular premolars and molars were randomly divided into four groups of twenty-five teeth each. Informed consent was obtained from all the subjects who participated in the clinical research after the nature of the procedure and possible discomforts and risks had been fully explained.

Materials

Group A: Hybrid composite Filtek Z250 (3M, ESPE) using self-etch adhesive Adper Prompt (3M, ESPE) and silver amalgam FusionAlloy (Heraeus Kulzer).

Group B: Posterior packable composite Surefil (Dentsply) using Prime and Bond NT (Dentsply) and silver amalgam FusionAlloy (Heraeus Kulzer).

Group C: Posterior packable composite Surefil (Dentsply) using Prime and Bond NT (Dentsply).

Group D: Silver amalgam FusionAlloy (Heraeus Kulzer).

The combined amalgam–composite restorations were divided into two groups (A and B), so as to evaluate the self-etch and total-etch techniques of bonding. Therefore, a composite resin was selected, which corresponded to the same manufacturer as that of the bonding agent used.

Study inclusion criteria

Permanent maxillary and mandibular carious molars and premolars involving the proximal surface, along with buccal and / or lingual / palatal surfaces.

Availability for the duration of the study.

Teeth with healthy periodontal status.

Procedure

The tooth was photographed and an intraoral periapical radiograph was taken. The procedure was done under rubber dam isolation.

The cavities were prepared along with the removal of the undermined cusp with carbide fissure burs, at high speed, with water cooling [Figure 1]. The extent and design of the cavity preparation was according to the extent of the carious lesion. The cavity preparation included the occlusal surface, one proximal surface, and buccal and / or lingual / palatal surfaces. The faciolingual width of the cavity was more than one-fourth of the intercuspal distance. The depth of the cavity was determined by the extent of the carious lesion. The gingival margin of the proximal box was kept supragingival. The cavity was not beveled. There was no pulpal exposure in any of the cases. The tooth in which a carious lesion was evident on only one proximal surface was selected. The mesio-occluso-distal cavity was not included in any of the groups. The cusps with undermined enamel were also included in the cavity preparation. However, there was no definite value of depth or intercuspal width of the cavity in any of the cases, because of the complex nature of the cavity design.

Figure 1

Steps in restoring 46 DO with combined composite-amalgam restoration

Group A: The cavity preparation was complex and involved more than two surfaces, that is, the occlusal surface, any one proximal surface, and the buccal and / or lingual / palatal surfaces. The faciolingual width of the cavity was more than one-fourth of the intercuspal distance. The depth and design of the cavity was determined by the extent of the carious lesion. The cusps with undermined enamel were also included in the cavity preparation. Type II glass ionomer cement (Fuji II GC Corporation) was used as a base. A self-etch adhesive Adper Prompt was used as per the manufacturer's instructions. Filtek Z250 was placed in increments to restore the tooth. After restoring the tooth to its proper anatomic form, a class II cavity, for amalgam, was prepared. Using a sectional metal matrix band with a Bitine ring (The Palodent System, Dentsply), the cavity was restored with the silver amalgam FusionAlloy. Occlusal interferences if any, were adjusted. The restoration was polished, and the intraoral periapical radiograph and photograph were taken.

Group B: The procedure was similar to Group A, except that the prepared cavity was etched with 37% phosphoric acid for 15 seconds, followed by application of bonding agent Prime and Bond NT, which was light cured for 10 seconds. The tooth was restored with composite Surefil using the incremental technique. Next, a conventional class II cavity for amalgam was made and restored with amalgam FusionAlloy, as in Group A.

Group C: In this Group, the tooth was restored with composite Surefil using the total-etch technique and bonding agent Prime and Bond NT.

Group D: In this Group, the tooth was restored with silver amalgam FusionAlloy.

Postoperative instructions were given to the patients. The restorations were evaluated at baseline and at 3, 6, 12, and 15 months, using the Ryge criteria, for postoperative sensitivity, retention, marginal adaptation, contact and contour, marginal discoloration, and secondary caries [Table 1]. The data was put to statistical analysis using the chi-square test.

Table 1

Ryge criteria rating system

RESULTS

In Group A, [Table 2], at baseline, 21 restorations scored A for contact and contour and postoperative sensitivity, while four restorations scored B. All restorations scored A for marginal adaptation, marginal discoloration, retention, and secondary caries. At 15 months, 17 restorations exhibited excellent contact and contour and marginal adaptation, while one restoration scored B. Sixteen restorations scored A for marginal discoloration and postoperative sensitivity, while two restorations scored B. None of the restorations exhibited loss of retention.

Table 2

Clinical rating of restorations at baseline, 3, 6, 12, and 15 months (Group A)

In Group B, [Table 3] at baseline, contact and contour and marginal adaptation were excellent in 23 restorations, while two restorations scored B. Marginal discoloration, postoperative sensitivity, loss of retention, and secondary caries were absent in all restorations. At 15 months, 18 restorations were available. Sixteen restorations scored A for contact and contour and postoperative sensitivity. Seventeen restorations scored A for marginal adaptation and marginal discoloration, while one restoration scored B. None of the restorations exhibited loss of retention.

Table 3

Clinical rating of restorations at baseline, 3, 6, 12, and 15 months (Group B)

In Group C, [Table 4] at baseline, contact and contour was excellent in 19 restorations, while six restorations scored B. All restorations scored A for marginal adaptation and marginal discoloration. Postoperative sensitivity was absent in 23 restorations. At 15 months, contact and contour and marginal adaptation were excellent in 18 restorations, while two restorations scored B. None of the restorations exhibited marginal discoloration, loss of retention or secondary caries. One restoration scored B for postoperative sensitivity.

Table 4

Clinical rating of restorations at baseline, 3, 6, 12, and 15 months (Group C)

In Group D, [Table 5] at baseline, contact and contour was excellent in 24 restorations, while one restoration scored B. All restorations scored A for marginal adaptation and marginal discoloration. Twenty-three restorations scored A for postoperative sensitivity. None of the restorations exhibited loss of retention or secondary caries. Two restorations fractured at three months and one fractured at six months and these were excluded from the study. At 15 months, 16 restorations scored A for contact and contour, marginal discoloration, and postoperative sensitivity, while one restoration scored B. Marginal adaptation was excellent in 15 restorations, while two restorations scored B. None of the restorations exhibited loss of retention or secondary caries.

Table 5

Clinical rating of restorations at baseline, 3, 6, 12, and 15 months (Group D)

DISCUSSION

Preservation of the health of the stomatognathic system is the major objective of every dental surgeon. Restoring a damaged tooth to its normal form and function is a continuous challenge for the dental profession, especially when the tooth is extensively damaged by caries. Seventy-three out of 100 restorations were examined after 15 months. Three restorations failed in Group D.

Contact and contour

Combined restorations (Group A - 94.44% and Group B - 88.89%) and amalgam restorations (Group D - 94.11%) showed better results than composite restorations (Group C - 75%), although the difference among the groups was not statistically significant. The findings were concurrent with a study in which the amalgam restorations exhibited an anatomic form (100 and 98%) superior to the composite restorations (79 and 45%) after one and two years.[7] The results concurred with another study in which 6 and 4% of the cases of inadequate proximal contacts with amalgam and composite restorations, respectively, were reported after three years.[8] Due to the viscoelastic properties of the resin composites, condensation of the material into the cavity was impossible.[9]

Marginal adaptation

Combined restorations gave superior marginal adaptation (94.44%), followed by composite (90%) ‘and amalgam (88.23%) restorations. However, the difference among the four groups was not statistically significant. These findings were similar to a study where composite restorations (95.89 and 89.83%) showed superior marginal adaptation than the amalgam restorations (90.4 and 79.66%), after one and two years.[10]

The marginal adaptation of the microhybrid composites was better than that in the packable composite restorations, which could be due to the difficulty in adaptation of the material on the cavosurface margins.

Marginal discoloration

Marginal discoloration was present in 11.11, 5.55, and 5.88% of the restorations in Group A, B, and D, while Group C showed no marginal discoloration after 15 months. However, the difference among the four groups was not statistically significant. These findings were in agreement with the study, which concluded that there was no difference between self-etch adhesive and total-etch adhesive.[11] These findings were concurrent with the study in which no marginal discoloration was reported in packable and microhybrid composite restorations after one year.[12]

The probable reason for marginal discoloration in Groups A and B may be because of the corrosion of silver amalgam; which might have discolored the composite – amalgam interface.

Postoperative sensitivity

Postoperative sensitivity was observed in two, two, one, and one restorations in Groups A, B, C, and D respectively after 15 months, but the difference among the four groups was not statistically significant. The findings of Groups A and B concurred with a study where 100% alfa scores for postoperative sensitivity for posterior composite and microhybrid composite restorations were reported after one year.[12] The occurrence of postoperative sensitivity in composite restorations could be due to the inadvertent etching of the dentin and opening of the dentinal tubules, or polymerization shrinkage of the resin followed by microleakage or hydraulic force on the dentinal tubule fluid.[13]

Retention

None of the restorations of Groups A, B, or C showed any fracture during the 15 months. However, three amalgam restorations in Group D fractured, which were restored, but excluded from the study. There was no statistically significant difference among the groups. These findings concurred with a study in which no composite restorations fractured after two years, while three amalgam restorations fractured after one year and one amalgam restoration fractured after two years.[7] These findings were also similar to those reported by Ralph et al., [14] who reported no case of fracture or loss of composite restorations after three years, while three amalgam restorations fractured after one year of placement. There was no case of tooth fracture in any of the groups.

Secondary caries

None of the restorations showed any secondary caries during the 15 months. The findings concurred with the study where no incidence of secondary caries among composite resin and amalgam restorations was reported after 10 years.[15] These findings concurred with those reported by Fabio et al.,[16] who reported 100% alfa scores for secondary caries in packable and microhybrid composite resin restorations after one year.

The combined composite–amalgam and amalgam restorations showed superior results for contact and contour as compared to the composite restorations. However, no statistically significant difference was observed among the four groups for any of the given criteria. Failure due to loss / fracture of restoration was observed only in amalgam restorations (Group D).

However, the current study included a small sample size. Evaluations still need to be conducted to reveal the long-term clinical performance of combined composite–amalgam restorations in posterior teeth.

SUMMARY AND CONCLUSIONS

No statistically significant difference was observed among the four groups for any of the criteria.

Fifteen percent silver amalgam restorations showed loss of retention during the follow-up. There was no loss of restoration in any other groups.

The combined composite–amalgam restorations performed better than the composite and amalgam restorations for contact and contour and retention, respectively.