Fracture Resistance and Retention of Metal-Free Inlay Retained Fixed Partial Dentures

Abstract

Statement of the problem: Conservative esthetic restorative dentistry has become an essential component in modern clinical practice. However, the inlay retained fixed partial dentures (IRFPDs) have a higher risk of fracture and dislodgement due to minimal preparations. Purpose: to compare fracture resistance and retention of Lithium disilicate (IPS e.max) and Polyetheretherketone (BioHPP) IRFPDs fabricated with heat-press technique and CAD/CAM system. Materials and Methods: Forty models, each including extracted mandibular 2 nd premolar and 2 nd molar embedded in an epoxy resin block with 10 mm intra-abutment distance representing missing mandibular 1 st molar were constructed. The premolar and molar of each model received standardized class II inlay preparations. The constructed models were randomly divided into four groups; Group (1): IPS e.max Press IRFPDs, Group (2): IPS e.max CAD IRFPDs, Group (3): BioHPP Granulates IRFPDs, and Group (4): breCAM.BioHPP IRFPDs. All IRFPDs were cemented using RelyX Ultimate adhesive resin cement. Samples were stored for 24 hours in distilled water at 37°C, and then thermocycled for 5000 cycles. Universal testing machine was used to measure fracture and dislodging loads. Samples were examined for determination of failure mode using a magnifying lens. Results: The statistically significant highest mean dislodging load value was obtained in IPS e.max Press IRFPDs, followed by IPS e.max CAD, with the least value recorded in breCAM.BioHPP. In contrast, breCAM.BioHPP IRFPDs revealed the statistically significant highest mean fracture load value, followed by BioHPP Granulates, while the least mean fracture value was recorded in IPS e.max Press. Most failure occurred in IPS e.max groups was connector fracture, while in BioHPP groups was plastic deformation. Conclusions: Retention and fracture resistance of metal-free inlayretained bridges are significantly affected by both; material type and construction method. BioHPP has significant advantages for dental applications because of higher fracture resistance and better stress distribution. The bond strength at IPS e.max/ resin cement interface is considered a reliable bond presenting better retention to IRFPDs. Being a brittle material, connector fracture is the predominant failure mode of IPS e.max IRFPDs; however, BioHPP has low elastic modulus showing plastic deformation as a predominant failure mode.

COMPARISON OF THE FRACTURE RESISTANCE BETWEEN INLAY RETAINED FIXED PARTIAL DENTURES FABRICATED FROM MILLED PEEK (BIOHPP) AND MONOLITHIC ZIRCONIA (In vitro study)

“…Each epoxy resin model was scanned to confirm accurate seating of the restorations over their corresponding models, which was in agreement with Gumus et al (2018) (5) and Al Assar et al (2017) (17) .…”

“…Regarding P/C group, our results were in consistence with Nagas et al (2018) (11) , who reported that PEEK IRFPDs veneered with composite have mean load bearing capacity of (995.5±78.1N), and contradicting to Al Assar et al (2017) (17) , who stated that PEEK IRFPDs had a lower fracture resistance (600 N for BioHPP granules and 684 N for BreCAM BioHPP), which could be attributed to cementing samples to natural teeth, rather than epoxy models. (19) , who reported similar fracture resistance values for zirconia IRFPDs (1749N) when centric load was applied.…”

“…Chi square test was performed between failure mode patterns. Sample size (n=7) was large enough to detect large effect sizes for main effects and comparisons, with the satisfactory level of power set at 80% and a 95% confidence level (16,17) .…”

Effect of Material Selection and Different Fabrication Techniques on Marginal and Internal Fit of Metal Ceramic and All Ceramic Crowns (In vivo and In vitro study)

“…Investment ring was preheated within conventional preheating furnace (Vulcan 3-550, Degussa-Ney Dental, NDI Inc) according to manufacturer's instruction. The investment ring with the ingot and plunger were placed in center of press furnace ( EP600, Ivoclare Vivadent Schaan, Liechtenstein Germany) (14) .…”

“…Samples were placed for 24 hours in distilled water at 37°C, after that exposed to routine thermocycling in automatic thermal-cycling device (Thermo-cycler, SD Mechatronik GMBH,Germany) for 5000 cycles in two water bath at 5 and 55°C. The settle time at each temperature was 30 seconds and the move time from one bath to the other was 2 seconds (14) .…”