Short answer

When designing products that undergo repeated thermal processing, focus on material selection and process control to mitigate aesthetic degradation, as structural integrity is less likely to be compromised.

Field: Final Production
Source: BMC Oral Health (2025)
Method: Experimental
Sample: 180 specimens per material (total 540 specimens)
Evidence: Strong effect

Repeated firing cycles in CAD/CAM ceramic processing significantly compromise color stability, while mechanical properties like flexural strength and microhardness remain largely unaffected. This final production research insight is drawn from a 2025 study published in BMC Oral Health. Using Experimental with 180 specimens per material (total 540 specimens), researchers explored how this design variable affects real-world outcomes. The key design takeaway: When designing products that undergo repeated thermal processing, focus on material selection and process control to mitigate aesthetic degradation, as structural integrity is less likely to be compromised.

Study

Final ProductionNew This WeekStrong effect

Multiple firings degrade color stability of CAD/CAM ceramics, but not strength

Repeated firing cycles in CAD/CAM ceramic processing significantly compromise color stability, while mechanical properties like flexural strength and microhardness remain largely unaffected.

BMC Oral Health · 2025

Key Findings

01Color stability was significantly influenced by both the material type and the number of firing cycles.
02Increasing firing cycles led to a statistically significant increase in color instability for one material (LiSi CAD).
03There was no significant impact on biaxial flexural strength and microhardness from multiple firings.
04Material type significantly affected biaxial flexural strength and microhardness, with IPS e.max CAD showing the highest flexural strength and LiSi CAD showing the highest microhardness.

Application

Design takeaway

How to apply

When specifying materials for CAD/CAM applications, consult data on color stability across multiple firing cycles, especially for visible components where aesthetics are paramount.

Project actions

01Consider the aesthetic requirements of your design and how repeated manufacturing steps might affect them.
02If your design involves multiple heat treatments, research materials known for their color stability under such conditions.

Method & Evidence

AimTo investigate the impact of multiple firing cycles on the flexural strength, microhardness, bond strength, and color stability of different CAD/CAM lithium disilicate-based glass ceramics.

MethodExperimental

ProcedureRectangular specimens of three different lithium disilicate-based glass ceramics were prepared and divided into subgroups based on the number of firing cycles (1 to 5). Color stability was measured using CIEDE2000, followed by biaxial flexural strength and microhardness tests. Shear bond strength was also assessed after bonding the specimens. Fracture surfaces were examined, and data was analyzed using two-way ANOVA.

Sample180 specimens per material (total 540 specimens)

ContextDental prosthetics and CAD/CAM manufacturing

Variables

IV["Material type (IPS e.max CAD, CEREC Tessera, LiSi CAD)","Number of firing cycles (1, 2, 3, 4, 5)"]

DV["Color stability (CIEDE2000)","Biaxial flexural strength","Microhardness","Shear bond strength"]

CV["Specimen dimensions","Wet-sectioning method","Bonding agent (Panavia™ SA)","Testing machine parameters"]

Strengths & Limitations

Strengths

+Investigated multiple critical properties (mechanical and optical).
+Used a statistically robust analysis (two-way ANOVA).

Limitations

The study was conducted in a lab setting, and real-world conditions might differ. Only specific types of ceramics were tested.

Reliability & validity

The study employed standardized testing methods and statistical analysis, enhancing reliability. Validity is supported by the investigation of multiple properties and the use of established measurement techniques.

Think critically

To what extent do the observed color changes in the lab translate to perceptible differences in real-world applications, and how might other environmental factors (e.g., saliva, food staining) interact with these changes?

Design Principles

"Prioritize aesthetic material stability over structural resilience when repeated thermal processing is a known factor in the product lifecycle."

This finding is crucial for designers and manufacturers working with CAD/CAM dental restorations. Understanding that aesthetic qualities are more susceptible to degradation than structural integrity allows for informed decisions regarding material selection, processing protocols, and client expectations.

What This Means for Your Design

Making the same ceramic piece multiple times in the oven can make its color change, but it won't make it weaker.

How to use in your project

1.Reference this study when discussing the impact of manufacturing processes on material properties, particularly color stability, in your design project's analysis or evaluation sections.

Add to My Project

Quick Cite

Paragraph starter

The study by Padunglappisit et al. (2025) highlights that while multiple firing cycles in CAD/CAM ceramic processing do not significantly compromise flexural strength or microhardness, they can lead to notable degradation in color stability, with variations observed across different material types. This suggests that for aesthetic-critical applications, material selection and process optimization to minimize firings are essential to maintain visual integrity.

Source

BMC Oral Health

Effect of multiple firings on mechanical and optical properties of CAD/CAM lithium disilicate-based glass ceramics

journal · 2025

View source

Questions About This Research

What does the research say about multiple firings degrade color stability of cad/cam ceramics, but not strength?: When designing products that undergo repeated thermal processing, focus on material selection and process control to mitigate aesthetic degradation, as structural integrity is less likely to be compromised. Evidence: BMC Oral Health (2025).
Why does "Multiple firings degrade color stability of CAD/CAM ceramics, but not strength" matter for design?: This finding is crucial for designers and manufacturers working with CAD/CAM dental restorations. Understanding that aesthetic qualities are more susceptible to degradation than structural integrity allows for informed decisions regarding material selection, processing protocols, and client expectations.
How can designers apply this research?: When designing products that undergo repeated thermal processing, focus on material selection and process control to mitigate aesthetic degradation, as structural integrity is less likely to be compromised.
What were the main findings?: Color stability was significantly influenced by both the material type and the number of firing cycles.. Increasing firing cycles led to a statistically significant increase in color instability for one material (LiSi CAD).. There was no significant impact on biaxial flexural strength and microhardness from multiple firings.. Material type significantly affected biaxial flexural strength and microhardness, with IPS e.max CAD showing the highest flexural strength and LiSi CAD showing the highest microhardness.
What research method was used?: Experimental with 180 specimens per material (total 540 specimens).
How strong is the evidence?: Evidence strength is rated Strong effect, based on a 2025 journal from BMC Oral Health.
What should I do differently in my next project?: When specifying materials for CAD/CAM applications, consult data on color stability across multiple firing cycles, especially for visible components where aesthetics are paramount.
What are the limitations?: The study focused on specific types of lithium disilicate-based glass ceramics and may not be generalizable to all ceramic materials used in CAD/CAM. The in-vitro testing conditions may not fully replicate the complex oral environment.