Since digital technologies altered operating flow ten years ago, dentistry has seen enormous changes. With CAD/CAM technology, nearly all fixed and removable prosthetic restorations on natural teeth or implants can be created, starting with essential crowns and inlays.
The way these systems have developed has made an attitude shift necessary. For these systems, switching from analog to digital requires spending money on software, hardware, and training.
To use CAD/CAM technology, a dentist must buy an intraoral scanner and proceed to the digital impression. After that, the data (the STL file) will be sent to a lab, which will do the design and milling work.
However, suppose he wants to spend more money. In that case, chairside CAD/CAM systems will allow him to complete the restoration without the help of the dental technician.
The digital revolution, which provides new materials, techniques, and treatment ideas, greatly benefits digital dentistry.
The development of new attractive materials and CAD/CAM (computer-aided design/computer-aided manufacture) technology is causing a significant transformation in the dental field. The development of technology has drastically changed workflow and operational processes.
Dentistry has advanced and will continue to do so with the introduction of intelligent materials on the market meant to enhance oral health care and, consequently, quality of life.
The transition from manual and error-prone traditional treatment methods to automated ones is now inevitable. Digital technologies have had a notable impact on the majority of dentistry specialties. Dental prostheses, which emphasize using CAD/CAM technology and digital impression techniques, have seen the most remarkable developments in the digital operational process.
Selecting the appropriate material for each distinct scenario is essential to achieving a successful result, which calls for awareness of each material's properties.
The next chapter's goal is to examine the advantages of new techniques and materials to collect information for a therapeutic outcome that is both aesthetically beautiful and long-lasting.
Chairside CAD/CAM Ceramic Material Classification
CAD/CAM chairside ceramic materials can be divided into groups based on composition and features-
Ceramic Blocks Reinforced With Leucite And Feldspathic Ceramics
Feldspathic ceramics (such as CEREC Blocs from Dentsply Sirona and Vitalocs Mark II from Vita Zahnfabrik) are examples of the first generation of chairside CAD/CAM materials.
These materials were first made accessible for commercial use before 1990.
From a lifespan perspective, they were the most researched materials and held a dominant position in the market until the 2000s.
Feldspathic ceramics are among the most transparent and aesthetically beautiful ceramic materials, with a 55-70% glassy phase preponderance.
Blocks Of Lithium Disilicates And Lithium Silicates Reinforced With Zirconia
Developing glass ceramics with improved resistance properties in fixed prostheses represented a significant breakthrough.
Lithium disilicate (IPS e.max CAD Ivoclar Vivadent), introduced in 2006, has a bending resistance of more than 350 MPa, making it superior to prior glass ceramics.
Lithium disilicate is only available in partially crystallized form (purple color) for the CAD/CAM method.
The remaining portion is composed of the crystallized nucleus of lithium disilicate (Li2Si2O5), which offers a "soft" state (with a bending resistance of 140 MPa), and the remainder is composed of lithium metasilicate (Li2SiO3).
This reduces wear on the milling cutters and facilitates block grinding. After milling, the material must undergo a two-stage fire cycle in a ceramic furnace for ten minutes for the metasilicate to fully crystallize and transform into lithium disilicate, which increases the material's bending resistance.
Since 2012, a more recent generation of high-strength CAD/CAM ceramics has been accessible: zirconia-reinforced lithium silicate, or ZLS.
In ZLS, a 10% by-weight tetragonal zirconia component is added to the glass matrix to improve its mechanical properties. The lithium silicate crystals used for reinforcement are 4-8 times smaller than the lithium disilicate crystals.
Zirconium Oxide (Zirconia)
Although zirconium oxide, often known as zirconia, is a heterogeneous polycrystalline ceramic with remarkable mechanical properties (elastic modulus of 210 GPa and flexural strength of 500-1200 MPa), it is resistant to standard acid etching methods.
Among the several integrated ceramics, it has the lowest rate of wear against the antagonist, lower plaque retention than titanium, and excellent biocompatibility both in vivo and in vitro.
Pre-sintered zirconia can be processed with simple soft machining using the zirconia blocks for chairside CAD/CAM systems.
Zirconia restorations are machined with a 25% oversized final volume to ensure the ideal fit during sintering. Using chairside blocks, this material can be utilized to create single crowns, implant abutments, and bridges with up to three pieces.
The Materials Made Of Resin Matrix Ceramics Or Hybrid Ceramics
A brand-new class of CAD/CAM chairside materials called hybrid ceramics was developed to combine the unique aesthetics of ceramic materials with the stronger fracture resistance and decreased fragility of composite resins.
In industrially produced nanoceramic resin blocks, a high-temperature, high-pressure process couples a ceramic filler (up to 80% by weight) with a composite resin such as Bis-GMA, UDMA, UTMA, and Bis-EMA.
In polymer-infiltrated-ceramic network (PICN) blocks, the ceramic structure, which comprises 86% of the block's bulk, has been artificially infused with composite resin (14% by bulk).
It has been demonstrated that hybrid ceramics require no or few heat cycles and are more accessible to mills. They can still be used at thinner thicknesses and have strong bending resistance.
In the last ten years, many new components with improved mechanical properties have been developed for CAD/CAM technology.
With the development of novel nanomaterials, dental care standards have significantly improved. Nano-dentistry is expected to dramatically impact therapeutic dentistry science since it will allow customized therapy.
Nanoparticles have been used to improve the mechanical properties of dental composites, strengthening bonding and minimizing wear.
Smaller particles can lower the porosity of dental composite for enhanced toughness and more efficiently penetrate deeper lesions.
Acrylic Resin
Polymers based on polymethyl methacrylate (PMMA) are stored until needed after being pre-polymerized without the use of fillers.
Their mechanical properties are determined mainly by their chemical composition and cross-linked structure. Mechanical properties are significantly influenced by the lack of voids and the reduced shrinkage from polymerization during mixing, packing, and setting.
Temporary prosthesis can be made with less chairside time. These PMMA CAD/CAM blocks could also create long-term temporary prostheses.
The Properties Of Chairside CAD/CAM Materials
The attention to detail used in choosing the unique characteristics and attributes of the various CAD/CAM material types is directly associated with the outcomes of clinical treatments.
Chairside restoration success depends on several factors: cementation, occlusion, restoration design, and material selection.
Even though the functional elements of CAD/CAM materials have been thoroughly researched and used, attention to their aesthetics is still urgently needed.
Aesthetics is critical in several fields, including dentistry, where natural-looking prostheses and restorations are highly sought.
Investigations On Esthetic Properties
Given that oral restorations are subjected to various intricate oral circumstances throughout their lifetimes, it is imperative that the material chosen for the restorations mirrors the natural tooth structure in terms of both mechanical qualities and aesthetic appeal.
A restoration that seamlessly integrates with the surrounding natural teeth is essential to creating a smile that looks natural. Visual attributes, including color, texture, and transparency, play a significant role in this process.
The resilience of dental materials to chemical deterioration is essential for intraoral use and a determining factor when choosing the kind of restoration.
Temperature, acid concentration, and immersion duration are all factors that influence how acid is simulated in vitro on dental ceramic surfaces. Based on other study articles in the literature, there needs to be more consensus on how to recreate stomach acid and how long it takes to duplicate it in an in vivo model.
Based on ISO standard 6872, which addresses the solubility test for dental materials, two years of clinical exposure is equal to using 4% acetic acid and a 16-hour exposure period at 8°C.
An additional in vitro study was conducted to examine the color stability of chairside CAD/CAM ceramic blocks composed of leucistic, feldspathic, and disilicate after exposure to typical liquids.
The investigation results indicate that all materials had color changes when immersed in red wine that were just marginally above the acceptable and perceptible thresholds.
After being immersed in coffee, the feldspathic CAD/CAM ceramic blocks displayed the most noticeable color changes. Within the constraints of this investigation, it is possible to deduce that common beverages could affect the color stability of the CAD/CAM ceramic blocks, thereby endangering the aesthetics of the restorations.
Read more: Revolutionize Design with CAD/CAM Software Efficiency
Investigations On Mechanical Properties
The mechanical properties of materials produced by CAD/CAM technology demand particular attention. Understanding the mechanical properties of restorative materials is essential for researchers and doctors because severe fracture is the leading cause of failure in these materials.
A single in vitro investigation assessed the surface and fracture resistance of complete contour Vita Enamic CAD/CAM crowns in a range of thicknesses.
The investigation showed that the compression load of crowns with a 1.5 mm thickness was higher than those with a 0.5 or 1.0 mm thickness.
There was no discernible difference in the fracture loads between the groups with occlusal thicknesses of 0.5 and 1.0 mm. PINC distributes more significant stress to the abutment than stiffer materials like zirconia-reinforced glass ceramic and high-translucency zirconia.
Some researchers found that extended tooth preparation may harm the remaining tooth structure and result in permanent failure.
Therefore, they concluded that a thicker restorative material would strengthen the fracture resistance of the restoration. The results of this study demonstrate that restored teeth employing PICN CAD/CAM crowns can achieve compression load values between 700 and 2500 N, irrespective of the crown's thickness.
These values are higher than the human masticatory forces (600-800 N), even in bruxism patients developing masticatory forces of 780 to 1120 N during mastication.
The force produced by the physiologic masticatory process was smaller than the load applied to ceramic network restorations with polymer infiltration. CAD/CAM hybrid ceramic materials can provide sufficient load capacity and fracture strength for posterior area restorations.
Research On CAD/CAM Materials' Biocompatibility
The biocompatibility of these CAD/CAM restorative materials has yet to be extensively studied and reported in the scientific literature.
For example, Vita Enamic (EN), Cerasmart (CS), and Brilliant Crios (BC) are three types of ceramics whose biocompatibility and sustainability were examined in a recent study.
The scientists concluded no discernible difference in surface roughness between the analyzed CAD/CAM blocks based on studies of biofilm formation, cytotoxicity, genotoxicity, and cellular changes using transmission electron microscopy (TEM).
Moreover, there is no connection between surface roughness and biofilm formation.
BC had the highest values when cytotoxicity was considered, followed by CS and EN. Thus, it was concluded that EN was the most biocompatible material among the materials under evaluation.
Daguano and associates developed a novel lithium silicate glass ceramic and examined its biocompatibility in vitro. The new lithia-silica glass ceramic is bioactive, unlike existing glass ceramics of the same family currently in use.
The most important finding is this one. It promoted the MG-63 cells' production of a bone-like matrix, which may be essential for dental applications and bone regeneration.
It also encouraged the proliferation and adherence of cells. Long-term oral exposure to the hybrid tooth-restoration system requires consideration of the effects of both intrinsic and extrinsic chemicals on these surfaces, as the preciouses' investigations pointed out.
Patients suffering from gastroesophageal reflux disease are particularly susceptible to this situation because stomach acid frequently refluxes into the oral cavity.
Conclusion
Chairside CAD/CAM restorative materials offer numerous benefits, including simplicity of preparation, polishing, and reparability.
However, further studies are needed to determine the compounds emitted from these materials and their consequences.
Although employing the digital approach has many benefits, some things can affect how accurate a digital impression is.
Variables like ambient light, fluid isolation, scanning pattern, and distance, or repeat scanning of the same surface can all result in a less precise digital impression.
Since different research produced different results on ambient light, there is no agreement on the ideal lighting settings.
However, it is safe to presume that high illumination sources may oversaturate the scanned areas, resulting in artifacts in the digital model.