An In vitro Assessment of Retention Force of ZrO2, Polyether Ether Ketone, and ZrO2-Polyether Ether Ketone Telescopic Attachment for Mandibular Overdentures.

Objectives: The objective of this study was to compare ZrO2, polyether ether ketone (PEEK), and ZrO2-PEEK telescopic attachments in terms of retention of overdenture. Methodology: Forty-five acrylic resin models of the lower arch were divided into 3 groups of 15 each. In Group I, primary and secondary crowns were constructed from all zirconia (ZrO2), whereas all PEEK was used for Group II and Group III was made up of ZrO2 PEEK.
Results: The mean retention value in Group I was 14.12 ± 3.4 N, in Group II was 15.86 ± 5.1, and in Group III was 22.40 ± 10.3 N. The mean final initial retention value in Group I was 14.50 ± 6.1 N, in Group II was 14.97 ± 8.2, and in Group III was 17.21 ± 9.3 N. A significant difference was observed in intergroup comparison (P < 0.05).
Conclusion: Zirconia resulted in maximum retention as compared to other telescopic crown materials. Copyright:

INTRODUCTION

Implant-supported denture has revolutionized the field of prosthodontics.[1] Severely resorbed ridges where conventional complete denture poses difficulties may be well managed with implant-supported denture.[2]

Resilient telescopic attachments are prepared from multiple materials available in the market. Zirconia is the material of choice for primary and secondary copings.[3] The high resistance to mechanical and tensile forces makes it superior as compared to other materials. Polyether ether ketone (PEEK) is another useful material widely used for resilient telescopic attachments. It is a thermoplastic polymer with sufficient biocompatibility. Implant-supported overdentures with three to four implants are sufficient in offering desired results.[4] This in vitro study compared ZrO2, PEEK, and ZrO2-PEEK telescopic attachments in terms of retention of overdenture.

METHODOLOGY

The approval for the present study was obtained from the Institutional Ethical and Review Committee. We selected 45 acrylic resin models of the lower arch for the study. Two Nobel care dental implants with the dimensions 11.5 mm × 4.2 mm were placed in the canine region of all models, and two dual models of 4.2 mm (width) × 4.2 mm (length) and 1.5-mm gingival length were screwed in dental implants.

Following this, models were divided into 3 groups of 15 each. Group I was those in which primary and secondary crowns were prepared from all zirconia (ZrO2), Group II was made up of all PEEK, and Group III was made up of ZrO2-PEEK.

Resilient telescopic attachment having occlusal height (3 mm) and gingival height (2 mm) was prepared and scanned with CAD/CAM technology. A four-degree taper was given along with maintaining the parallelism. Semi-sintered ZrO2 blanks were used for milling the primary ZrO2 crowns and BioHPP blanks for primary PEEK crowns. Cementation of primary crowns was aided with zinc phosphate cement.

Primary crowns along with all models were scanned with maintaining parallelism of walls along with occlusal space (0.3 mm) and wall thickness (0.5 mm). Secondary ZrO2 crowns and PEEK crowns were milled. Following the same insertion path, secondary crowns were fitted on primary crowns and to the fitting surface of overdenture with auto-polymerized acrylic resin. Universal testing machine using crosshead speed of 60 mm/min and load cell of 3.5 KN was used for measuring the retention forces. Initial retention (maximum retention) force was recorded. Overdenture (with primary and secondary crowns) undergoes 540 cycles of placing and taking away considered as final retention. Results were analyzed statistically using Fisher's exact test.

RESULTS

Table 1 shows that the mean retention value in Group I was 14.12 ± 3.4 N, in Group II was 15.86 ± 5.1, and in Group III was 22.40 ± 10.3 N. A significant difference was observed in intergroup comparison (P < 0.05).

Table 1

Assessment of initial retention values

Groups	Mean±SD	P
Group I	14.12±3.4	0.021
Group II	15.86±5.1
Group III	22.40±10.3

SD: Standard deviation

Table 2 shows that the mean final initial retention value in Group I was 14.50 ± 6.1 N, in Group II was 14.97 ± 8.2, and in Group III was 17.21 ± 9.3 N. A significant difference was observed in intergroup comparison (P < 0.05).

Table 2

Assessment of final retention values

Groups	Mean±SD	P
Group I	14.50±6.1	0.05
Group II	14.97±8.2
Group III	17.21±9.3

SD: Standard deviation

DISCUSSION

Prolonged edentulism leads to progressive alveolar bone loss resulting in failure in complete denture treatment modality.[5] It was observed that stability and retention capacity of implant-supported overdenture is more in comparison to conventional denture.[6] Bar–clip constructions or nonsplinted concept attachments are used for retaining these overdentures.[7] Literature demonstrated the use of telescopic attachments as a retentive aid in implant-supported overdentures. The main effect of these attachments is transmission of occlusal forces along the long axis of abutment, and hence ensures the long life of prostheses.[8]

Hegazy et al.[9] observed higher mean stress on distal, labial, and mesial surfaces of the implants in the rigid design model in comparison to resilient design models I and II. Debis et al.[10] observed that metallic bar attachments Overdentures indicted considerable plaque builds up than zirconium bar attachment Overdentures.

Further in vivo studies are needed to verify the results.

CONCLUSION

The results of our study showed that zirconia resulted in maximum retention as compared to other telescopic crown materials.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.