Microleakage at Implant Abutment and Prosthesis Interface in Cemented Implant-Supported Prosthesis.

BACKGROUND: Dental implants have an important role in mainstream dental practice today to restore esthetics. The present study was conducted to evaluate the microleakage at implant abutment and prosthesis interface in cemented implant-supported prosthesis.
MATERIALS AND METHODS: The present study comprised sixty replicas of abutment analog with length 5 mm, width of platform 4.8 mm, and taper 6° which were milled and divided into three groups. In Group I, nickel-chromium copings were fabricated; marginal gap was evaluated with optical microscope and luted with zinc oxide noneugenol cement, Group II with zinc polycarboxylate cement, and Group III with zinc phosphate cement. Microleakage was scored by the method used by Tjan et al.
RESULTS: The mean microleakage score in Group I was 2.5, in Group II was 1.9, and in Group III was 1.05. The difference was significant (P < 0.05).
CONCLUSION: All cements showed microleakage. Minimum microleakage was seen with zinc phosphate cement than zinc oxide noneugenol cement and zinc polycarboxylate cement. Copyright:

INTRODUCTION

Dental implants have an important role in mainstream dental practice today to restore esthetics, contour, occlusion, function, comfort, speech, and health.[1] The fabrication of cement-retained restorations is easier than that of screw-retained restorations because conventional laboratory and clinical prosthodontic techniques are used for making cemented restorations.[2]

The screw-retained restorations are usually more expensive because of the extra components needed such as plastic sleeves, laboratory fixation screws, and the fixation screws themselves.[3]

Nevertheless, the increased cost of the screw-retained restoration that allows for predictable retrievability must be compared to the potential costs of damaging the cemented restoration if biologic or technical complication occurs.[45]

The benefits of screw-retained prosthesis are satisfactory crown retention, cement-free gingival sulcus area, and crown retrievability.[6] There are some complications which include abutment screw loosening, fracture of fastening screw, optimum location of the access hole for precise placement, ceramic chip off around access hole, and fracture of the abutment.[7]

Microleakage is crucial consideration while selecting luting cements.[8] Leakage around crown margins is directly proportional to cement solubility, film thickness, adherence to substrate, dimensional changes, and poor adaptation of the prosthesis with abutment.[9] The present study was conducted to evaluate the microleakage at implant abutment and prosthesis interface in cemented implant-supported prosthesis.

MATERIALS AND METHODS

The present study comprised sixty replicas of abutment analog with length 5 mm, width of platform 4.8 mm, and taper 6° which were milled and divided into three groups. The study got approval from the institutional review board.

In Group I, nickel–chromium copings were fabricated; marginal gap was evaluated with optical microscope and luted with zinc oxide noneugenol cement, Group II with zinc polycarboxylate cement, and Group III with zinc phosphate cement. After thermocycling, cemented specimens were placed into 0.5% aqueous solution of basic fuchsin solution for 24 h for dye penetration. Copings were longitudinally sectioned, and microleakage scores were evaluated. Microleakage was scored by the method used by Tjan et al. Microleakage scores used were 0 – no microleakage seen on the axial wall of the sectioned specimen, 1 – microleakage seen up to one-third the length on the axial wall of the sectioned specimen, 2 – microleakage seen up to two-third the length on the axial wall of the sectioned specimen, 3 – microleakage seen along the full length of the axial wall of the sectioned specimen, and 4 – microleakage seen on the occlusal surface of the sectioned specimen. Results thus obtained were subjected to statistical analysis using Mann–Whitney U-test. P < 0.05 was considered statistically significant.

RESULTS

Table 1 shows the distribution of replica of abutment analog in different groups based on the type of luting agent used.

Table 1

Distribution of groups

Groups	Group I	Group II	Group III
Luting agent	Zinc oxide noneugenol cement	Zinc polycarboxylate cement	Zinc phosphate cement
Number	20	20	20

Table 2 and Graph 1 shows that the mean microleakage score in Group I was 2.5, in Group II was 1.9, and in Group III was 1.05. The difference was significant (P < 0.05).

Table 2

Comparison of microleakage

Groups	Mean±SD	P
Group I	2.5±0.67	0.01
Group II	1.9±0.52
Group III	1.05±0.38

SD: Standard deviation

Graph 1

Comparison of microleakage

DISCUSSION

In implant dentistry, there is a adhesion between two metallic components instead of the tooth to the metal as in conventional fixed prosthodontics.[10.11] Thus, the selection of luting cements is more diverse and extensive than natural teeth. In addition, the resistance and retention form of implant abutments is much more favorable than natural tooth preparations.[12] Ideal and stable occlusal contacts can be established with cement-retained restorations because there are no occlusal screw access holes.[13] These screw access holes will also interfere with protrusive and lateral excursions, and therefore, anterior guidance may be compromised.[14] The screw-retained restorations where the screw access hole occupies more than 50% of the intercuspal occlusal table require an occlusal restorative material to cover the screw access channel; these restorative materials are susceptible for wearing under functional forces, and so the occlusal contacts will be less preserved than when using cement-retained restorations with intact occlusal surface. Moreover, the difficulty in achieving stable occlusal contacts when using screw-retained restorations because of the presence of restoration material will affect the direction of occlusal loads which will be distributed as lateral forces to the implant instead of being axially directed.[15] The present study was conducted to evaluate the microleakage at implant abutment and prosthesis interface in cemented implant-supported prosthesis.

In the present study, the mean microleakage score in Group I was 2.5, in Group II was 1.9, and in Group III was 1.05. Handa et al.[16] evaluated the microleakage of metallic copings luted with three different commercially available luting cements. The mean microleakage score was least for zinc phosphate cement (1.075 ± 0.85), followed by zinc polycarboxylate cement (1.80 ± 0.23) and most for zinc oxide noneugenol (2.1 ± 0.37). The results of the study were statistically significant. Wenner et al.[14] found evaluated the microleakage of various restorative materials placed in root surfaces. A minimum of twenty freshly extracted single-rooted teeth were used for each combination of restorative materials. Four preparations were made on the root surface and each restored with a different material. After thermocycling in dye, the root was cut transversely in several sections through the restoration, and microscopically examined to record the microleakage at the interface between restorative materials and tooth. Results indicated that fewer composite resin specimens allowed microleakage into dentin as compared with either amalgam or glass ionomer materials.

Bhatnagar et al.[17] assessed, compared, and evaluated the microleakage at the margins of cast metal copings cemented with three luting agents. A comparative study was done to evaluate the ability of three contemporary luting agents to resist microleakage in cemented nickel–chromium complete metal copings cast on prepared molars. The copings were placed back on the respective prepared teeth to check the fit, and marginal adaptation was observed under an optical microscope. Copings with marginal discrepancies of more than 39 μm were rejected, and castings were repeated for accurate marginal fit. The castings were cemented with the three luting agents under study, namely, glass ionomer cement, resin-modified glass ionomer cement, and resin cement under ideal conditions. The cemented specimens were thermocycled after 24 h between 5°C and 50°C. After thermocycling, the teeth were treated with 50% of silver nitrate solution for 60 min, placed under a 150 watt flood lamp for 5 min to allow complete fixation of any unfixed stain, embedded in clear epoxy resin, and sectioned twice longitudinally. It was concluded from the study that the glass ionomer cement, Ketac Cem showed less microleakage than the resin-modified glass ionomer cement, RelyX Luting 2 and the resin cement, RelyX ARC. The resin cement was associated with a higher degree of microleakage than the glass ionomer cement and the resin-modified glass ionomer cement.

CONCLUSION

Authors found that all cements showed microleakage. Minimum microleakage was seen with zinc phosphate cement than zinc oxide noneugenol cement and zinc polycarboxylate cement.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.