A-Materials:
Materials used in this study were tabulated according to product names, patch numbers, main composition and manufactures in (Table 1).
Table (1): Material used in this study.
Materials | Product named | Patch numbers | composition | manufactures |
fixture | V Plus Implant 4.2*13 | | Main component: Commercially pure titanium grade 4 | Vitronex, Milano, Italy |
Titanium base | TBASE-MPI | | Main component: Commercially pure titanium grade 4 | Vitronex, Milano, Italy |
zirconia | Ceramill Zolled HT + white 98x18 | 2007001 | Component: Zirconium dioxide (ZrO2) more than 99% by weight. Other contents: Aluminum oxide 0.25 wt % Yttrium oxide (Y2O3) 5.2 wt % | Amann Girrbach, Pforzheim, Germany |
Feldspar hybrid ceramic polymer-infiltrated ceramic network (PICN) | VITA ENAMIC | 91020 | Hybrid ceramic The dominant fine structure ceramic network (86% by weight) is reinforce by an acrylate polymer network (14% by weight) ceramic-network material (UDMA, TEGDMA) with 86 wt% ceramic (Si02, Al203, Na2O, K20, B203, CaO,TiO2, colouring oxides) | Vita, Zahnfabrik, Germany |
Glass ceramic | IPS e.max CAD | Z02FXV | Main component: Lithium disilicate (SiO2). Other contents: Liz0, K20, MgO, AL2O3, P2Os. | Ivoclar-Vivadent, Schaan/Liechtenstein |
Adhesive resin cement | Multilink hybrid abutment | Z03NZG | Main component: Methacrylates, HEMA, barium glass, yttrium, trifluoride and spherical mixed oxide. | Ivoclar-Vivadent, Schaan/Liechtenstein |
Hydrofluoric acid | Porcelain etchant | 2300000134 | 9.5% Buffered Hydrofluoric acid gel | Bisco, Anaheim, CA, USA |
Universal primer | Monobond plus | Z039MX | Alcohol, sulfide dimethacrylate, MDP, gamma-MPTS | Ivoclar-Vivadent, Schaan/Liechtenstein |
Forty two implant fixtures were used and divided into six equal groups (Fig. 7) according to the material of the abutment and height of the titanium base into:
Group (ZS) : hybrid-abutment zirconia crown with short Ti-base, Group (ZL) : hybrid-abutment zirconia crown with long Ti-base, Group (L2S): hybrid abutment glass ceramic crown with short Ti-base, Group (L2L) : hybrid abutment glass ceramic crown with long Ti-base, Group (VS) : hybrid abutment vita enamic crown with short Ti-Base, Group (VL) : hybrid abutment vita enamic crown with long Ti-Base.
The sample size calculation was done using G* (version 3.0.10) to have a sample size of seven spaceman for each group with a 5% disparity and effect size 1.72.
A total of 42 3D-printed PMMA (NextDent, AV Soesterberg, Netherland) boxes with dimensions of 22x12x15 mm were designed and printed using a 3D printer (Mogassam, Cairo, Egypt) to act as a recipient for acrylic material using a marker to represent the off-set point which was 5 mm distal to the center of the box to determine the distally positioned implant (Fig. 1) the Ti-Bases were screwed on the fixtures and fixed in the box using surveyor (Marathon-103, Saeyang, Daegu, Korea), mixing and pouring of acrylic material resin (Acrostone, Alex, Egypt) inside the boxes to insure accurate angulation without deviation form standered position and subsequent be ready for the test. (Fig. 2)
One dental implant system with the same design and dimensions (4.2*13) were used. All materials utilized in the experiment were sterilized inside surgical bags. All sample preparations and all tests were performed by the same operator in a random sequence to avoid any error caused by increase in the operator's skill.
Different ceramic crowns were designed corresponding to lower molar teeth morphology by one dental lab technician for all groups. A scan body was attached to the implant and scanned using Medit i700 intraoral scanner (Medit, Seoul, South Korea). After that, a series of 42 crowns featuring uniform external geometries were meticulously crafted using a CAD software (Exocad dental CAD GmbH, 64293-Darmstadt, Germany) to accommodate two distinct Ti-base (MPI-TBASE, Vitronex, Milano, Italy) abutment heights (n = 42): with two different heights 4 mm short (S) (N = 21) and 7 mm long (L) (N = 21) (Fig. 3). The screw channels were located in a distal position. During CAD-CAM fabrication of all crowns. The offset was placed 5 mm distally (Fig. 4) to mimic the distally-positioned implant. This was standardized to ensure that the implant is placed in the same position in all specimens.
In addition, the main group was further subdivided into two subgroups (n = 7) based on the three ceramic materials employed for the manufacturing of the crowns, namely zirconia (Z), lithium disilicate (L), and Vita Enamic (V).
Three distinct types of machinable ceramics were utilized in this study, namely zirconia (ceramill zolid HT+, Amann Girrbach, Pforzheim, Germany), lithium disilicate (IPS e.max CAD, Ivoclar-Vivadent, Schaan/Liechtenstein), and hybrid ceramic (Vita Enamic, VITA Zahnfabrik, Bad Säckingen, Germany). These ceramics were divided into six groups, denoted as ZL, ZS, LL, LS, VL, and VS, with a total sample size of seven (N = 7). The milling procedure was conducted using a 5-axis milling machine known as the Ceramill Motion 2 (Amann Girrbach AG, Herrschaftswiesen, Germany). (Fig. 4)
Milling of 14 zirconia abutments using the milling machine (Doowonid ARUM, Korea) with a computer controlled five axis simultaneous milling unit. A zirconia block (metoxit Z-CAD) was fixed into its proper place in the milling chamber using special clamps, According to the manufacturer's instructions, the zirconia abutments were sintered on the firing tray of the firing furnace (SinterMax model T1700, SinterMax, USA) then Zirconia non segmented abutments were finished by (Schottlander zirconia finishing kit) (AlleconDental, Canada).
14 hybrid ceramic VE discs were fabricated using CAD/CAM technology. Milling of IPS e.max CAD abutments was done using the milling machine (Doowonid, ARUM, Korea) with a computer controlled five axis simultaneous milling unit. IPS e.max CAD block was fixed into its proper place in the milling machine using special clamps and the order was given to the milling unit. Crowns were milled using 2 milling burs (burs size 2 mm for gross milling. 1 mm for final adjustment) (ARUM, Korea), The crowns were finished using a (Schottlander finishing kit AlleconDental, Canada) finishing kit. Each crowns was inspected for any defects by (EASY view 3D, Renefert, Germany) magnifying screen and finished, According to the manufacturer's instructions, a ceramic furnace (EP 500 Programat, Ivoclar Vivdent) was used for crystallization of the IPS e.max CAD crowns. The crystallization program was selected according to manufacturer's instructions and finally furnace was activated according to manufacture instructions Temperature was elevated from room temperature till 820°C in a heat rate of 60°C per minute.