Dimensional Accuracy of CAD/CAM Dentures
As technology advances, the dental industry has seen a significant shift towards the use of computer-aided design and computer-aided manufacturing (CAD/CAM) techniques in the fabrication of complete dentures. CAD/CAM dentures offer several advantages over traditional denture processing methods, including enhanced efficiency, improved productivity, and increased accuracy.
One of the key aspects of denture fabrication is the dimensional accuracy of the denture base. The fit between the denture base and the underlying oral tissues is crucial for successful retention and function of the complete denture. Numerous studies have been conducted to investigate the dimensional accuracy of CAD/CAM-fabricated dentures, both before and after aging through thermocycling.
Dimensional Accuracy Before Thermocycling
The CAD/CAM milling process has been shown to produce denture bases with superior dimensional accuracy compared to both 3D-printed and conventional heat-polymerized denture bases. Studies have found that the CAD/CAM milled denture bases exhibit the highest dimensional accuracy, with measurements consistently close to the reference stone cast. This is likely due to the precise control and optimization of the milling process, which minimizes the potential for dimensional changes during fabrication.
In contrast, 3D-printed denture bases have demonstrated the lowest dimensional accuracy among the three methods. The layered nature of 3D printing, along with potential issues such as incomplete bonding between layers and higher residual monomer content, can contribute to the decreased dimensional accuracy observed in these dentures.
Conventional heat-polymerized denture bases fall somewhere in the middle, exhibiting moderate dimensional accuracy. The polymerization shrinkage associated with the traditional denture processing technique can lead to dimensional changes, though not to the same extent as 3D printing.
Dimensional Accuracy After Thermocycling
The effects of aging through thermocycling on the dimensional accuracy of denture bases have also been extensively studied. Thermocycling is a common testing method that simulates the temperature and humidity changes experienced by dentures during long-term use.
The research indicates that thermocycling has a significant impact on the dimensional accuracy of denture bases, with varying degrees of change depending on the fabrication method.
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CAD/CAM Milled Dentures: After thermocycling, the CAD/CAM milled denture bases maintained their superior dimensional accuracy, with minimal changes observed at all measurement locations. The precise control and optimization of the milling process seem to confer a high level of dimensional stability even after aging.
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3D-Printed Dentures: The 3D-printed denture bases experienced the most significant dimensional changes after thermocycling, particularly at specific locations on the denture base. This suggests that the layered structure and potential issues with the 3D printing process may make these dentures more susceptible to dimensional instability over time.
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Conventional Heat-Polymerized Dentures: The dimensional accuracy of conventional heat-polymerized denture bases also decreased after thermocycling, though not to the same extent as the 3D-printed dentures. The polymerization shrinkage and other factors inherent to the traditional denture processing technique can contribute to the observed dimensional changes.
Color Stability of CAD/CAM Dentures
In addition to dimensional accuracy, the color stability of denture materials is another crucial factor in the long-term performance and aesthetics of complete dentures. Discoloration of denture bases can negatively impact the overall appearance and patient satisfaction with the prosthesis.
Color Stability Before and After Thermocycling
Numerous studies have investigated the color stability of CAD/CAM-fabricated denture bases, both before and after thermocycling.
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CAD/CAM Milled Dentures: The CAD/CAM milled denture bases have consistently demonstrated the highest color stability, both before and after thermocycling. The pre-polymerization of the PMMA material under high temperature and pressure conditions during the milling process contributes to the enhanced color stability, minimizing the impact of factors such as water sorption and residual monomer content.
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3D-Printed Dentures: In contrast, the 3D-printed denture bases have exhibited the lowest color stability among the three fabrication methods. The layered nature of 3D printing, along with potential issues such as incomplete bonding between layers and higher residual monomer content, can lead to increased water sorption and discoloration over time.
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Conventional Heat-Polymerized Dentures: The conventional heat-polymerized denture bases fall somewhere between the CAD/CAM milled and 3D-printed dentures in terms of color stability. The polymerization process and inherent material properties of traditional PMMA can contribute to moderate changes in color stability, though not to the same extent as the 3D-printed dentures.
Effect of Denture Cleansers on Color Stability
In addition to the effects of thermocycling, the use of denture cleansers has also been shown to impact the color stability of denture materials. Immersion in denture cleansing solutions can potentially lead to greater color changes compared to the effects of thermocycling alone.
The research indicates that the CAD/CAM milled denture bases demonstrate the highest color stability even after exposure to denture cleansers, while the 3D-printed and conventional heat-polymerized denture bases exhibit more significant color changes. The chemical composition, pH, and oxygenation of the denture cleansing solutions can interact with the denture base materials, leading to increased discoloration.
Conclusion
The advancements in CAD/CAM technology have revolutionized the fabrication of complete dentures, offering several advantages over traditional denture processing methods. The research on dimensional accuracy and color stability of CAD/CAM-fabricated dentures highlights the superior performance of these dentures compared to their 3D-printed and conventional heat-polymerized counterparts.
The CAD/CAM milled denture bases consistently demonstrate the highest dimensional accuracy and color stability, both before and after aging through thermocycling and exposure to denture cleansers. This is attributed to the precise control and optimization of the milling process, as well as the inherent material properties of the pre-polymerized PMMA used in CAD/CAM milling.
In contrast, 3D-printed denture bases exhibit the lowest dimensional accuracy and color stability, likely due to the layered nature of the 3D printing process and the potential issues associated with it, such as incomplete bonding between layers and higher residual monomer content.
Conventional heat-polymerized denture bases fall somewhere in the middle, exhibiting moderate dimensional accuracy and color stability. The polymerization shrinkage and other factors inherent to the traditional denture processing technique contribute to the observed dimensional changes and color instability over time.
These findings highlight the importance of considering the dimensional accuracy and color stability of denture materials when selecting the appropriate fabrication method for complete dentures. The superior performance of CAD/CAM milled dentures in these key areas can lead to improved fit, retention, and long-term aesthetics for the patient, ultimately enhancing the overall success and satisfaction with the prosthetic treatment.
As the dental industry continues to evolve, the ongoing research and advancements in CAD/CAM technology will further improve the quality and reliability of complete dentures, providing clinicians with cutting-edge solutions to better serve their patients.
