Inner marginal strength of CAD/CAM materials is not affected by machining protocol

Figures & data

Table 1. Summary of CAD/CAM materials used, their descriptions of class, manufacturers, and lot number.

Material	Composition	Manufacturer	LOT	Young’s modulus (GPa)	Biaxial flexural strength (Weibull σ0) (MPa)	Weibull modulus m	KIc (MPa√m)
IPS e.max^® CAD	60.3 vol.% Li2Si2O5 6.8 vol.% Li3PO4 1.0 vol.% Cristobalite	Ivoclar-Vivadent, Liechtenstein	119044	102.5 [10]	647 [11]	17.4 [11]	2.04 [12]
Suprinity^® PC	27.1 vol.% Li2SiO3 14.4 vol.% Li2Si2O5 11.6 vol.% Li3PO4	Vita Zahnfabrik, Germany	66612	102.9 [10]	611 [11]	5.3 [11]	1.39 [12]
Enamic^®	UDMA, TEGDMA (25 vol.%); Aluminosilicate glass (75 vol.%)	Vita Zahnfabrik, Germany	74770	37.4 [10]	195 [11]	19.3 [11]	1.25 [12]
Grandio^® Blocs	UDMA, BIS-EMA, TEGDMA (∼15vol.%); Glass fillers (∼85vol.%)	Voco, Germany	1817685	18 [13]	244 [14]	13.1 [14]	1.42 [14]
Lava™ Ultimate	Bis-GMA, Bis-EMA, TEGDMA, UDMA (∼25 vol.%); Silica and Zirconia fillers (∼75 vol.%)	3M Oral Care, Germany	899630	12.7 [10]	231 [14]	10.8 [14]	1.14 [12]

Bis-GMA: bisphenol A glycidylmethacrylate; Bis-EMA: ethoxylated bisphenol-A dimethacrylate; TEGDMA: triethylenglycol dimethacrylate; UDMA: urethane dimethacrylate; K_Ic: fracture toughness.

Figure 1. (a) Scanned abutment, (b,c) designed sphero-cylindrical shape to be machined, (d) CAD/CAM materials investigated in this study before and after machining (inset shows the burs used in the two different machining protocols), (e) marginal strength test is performed with a laser extensometer, and (f) a view of a fractured specimen [Reprinted with permission from Elsevier].

Figure 2. Scanning electron microscopy images of damaged surface on five different materials tested, in fine and rough protocol machining.

Figure 3. Light retardation illustrated using color scales from blue (0 nm, zero stress) to red (50 nm, high stress). The selected area for measurement is confined here to the region of the specimen in which there is light transmission (the upper region is excluded due to the opacity of the piston as it is inserted into the specimen lumen).

Figure 4. (a) FE Analysis of the maximum principal stress distribution in the sphero-cylindrical model crown for the material IPS e.max^® CAD; (b) principal stress trajectory plots presenting the circumferential stress directions; and (c) cross-section showing the maximum principal stress distribution through the thickness.

Table 2. Weibull parameters were calculated for the inner marginal strength obtained from FE simulation of the obtained fracture forces in the in-vitro test.

Material	Rough-fast machining		Fine-slow machining
	σ0 [90% C.I.]	m [90% C.I.]	σ0 [90% C.I.]	m [90% C.I.]
IPS e.max^® CAD	305.4 [287–324] aA	6.65 [4.9–9.1] aA	306.7 [282–333] aA	4.84 [3.6–6.6] bA
Vita Suprinity^® PC	199.9 [191–209] cA	8.90 [6.6–12.1] aA	214.6 [196–235] cA	4.21 [3.2–5.9] bB
Enamic^®	124.2 [118–130] eA	8.53 [6.3–11.6] aA	118.4 [114–122] eA	11.6 [8.6–115.7] aA
Grandio^® Blocs	256.9 [248–266] bA	11.1 [8.2–15.0] aA	246.5 [236–257] bA	9.11 [6.9–12.4] abA
Lava™ Ultimate	154.3 [147–162] dA	8.31 [6.1–11.2] aA	147.1 [135–159] dA	4.93 [3.7–6.7] bA

Cells with the same uppercase letters in rows are not statistically different at α = 0.05.

Cells with the same lowercase letters in columns are not statistically different at α = 0.05.

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