In-Office Milling: Maximizing Aesthetics and Efficiency

Since this article was published, 3M has removed the crown indication for Lava Ultimate CAD/CAM Restorative. The product continues to be indicated for inlays, onlays (with an internal retentive design element), and veneer restoratives, per new instructions for use.

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INTRODUCTION
With an aging population and increasingly high aesthetic demands, today’s dentists face escalating restorative challenges. Fortunately, technology is keeping pace, providing practitioners with tools to offer restorations that are strong, aesthetic, and long-lasting. Intraoral scanning tools, in-office CAD/CAM milling systems, and their accompanying milling materials are among these essential technologies for many practices.

Benefits of Chairside CAD/CAM Systems
The advantages of chairside CAD/CAM systems are significant for modern dental practices. While the initial startup costs can be considerable, dentists who accurately project future use and time investment can determine if the system will be profitable. Many practices reach a break-even point with a relatively low number of monthly restorations when savings in outside laboratory costs outweigh machine ownership or leasing costs.

Beyond financial considerations, there are many other benefits to in-office milling systems. Completing a restoration in one visit can be highly valuable to patients and can help attract and retain patients. The use of intraoral scanning devices can increase patient comfort by eliminating the need for traditional impression materials.1 It also enhances the accuracy of restorations, reducing the need for adjustments or remakes.

Preparing and seating the final restoration in one visit eliminates the temporization process, increasing convenience for both the patient and the dentist.2 Additionally, the milling material itself offers advantages. Regardless of the block material type, these blocks are fabricated using reproducible procedures, producing high-quality, consistently dense blocks without porosities. Traditional laboratory-processed pressed ceramic and hand-layered porcelain restorations can contain porosities due to human error and varying handling conditions.3,4

What Makes a Great Milling Material?
Dentists have several varieties of chairside blocks to choose from. Acceptable block materials should be milled quickly, resist damage from machining, and have simple finishing steps.3 These qualities maximize the efficiency of in-office CAD/CAM systems. Materials should also demonstrate good strength and low wear on opposing dentition.

Although concerns about chairside CAD/CAM restorations have been raised, clinical data has addressed most of these concerns. Initially, postoperative sensitivity was a top concern, but advancements in adhesives and luting techniques have reduced reports of this issue. Additionally, the careful isolation required during the scanning step can reduce the possibility of postoperative sensitivity. Eliminating the temporization step also reduces contamination and subsequent sensitivity.6

Fracturing is a concern for any milling material. Proper design of the preparation and the subsequently fabricated restoration is crucial to prevent fracturing. Inadequate porcelain thickness has been shown to significantly contribute to premature material fractures. Overall, CAD/CAM restorations have demonstrated consistently low fracture rates.6

Helpful Materials
Several milling materials are available for chairside use with notable track records. Vitablocs Mark II (Vident), a feldspathic glass-ceramic material, was introduced in 1991.7 Polished, its strength is approximately 130 MPa, increasing to 160 MPa or more when glazed.3 Lithium disilicate, such as e.max (Ivoclar Vivadent), has gained attention for its aesthetics and flexural strength (360 MPa for the CAD/CAM version and 400 MPa for the pressed version). This material allows restorations to be adhesively bonded with composite resin cements or placed with conventional cements.

A new material, referred to as resin nanoceramic, has recently been introduced (Lava Ultimate Restorative [3M ESPE]). This CAD/CAM block is indicated for aesthetic and strong (200 MPa) single-tooth permanent restorations, including crowns, crowns over implants, inlays, onlays, and veneers. With a matrix consisting of resin and nanoparticles, this material combines properties of composite resin and glass ceramic, making it harder and more resistant to wear while retaining its polish well.

This material offers productivity advantages, as it requires no firing and has composite-like qualities that make it easy to mill, polish, and adjust. It can also be repaired intraorally. The material must be bonded with an adhesive resin cement. The following case report demonstrates the use of this new material to create an aesthetic and strong onlay in a single-office visit.

CASE REPORT
Diagnosis and Treatment Planning
A female patient presented with a large area of interproximal decay on No. 30 and decay on the adjacent tooth No. 28 (Figure 1). Tooth No. 28 was restored with a direct composite restoration using a direct nanocomposite resin (Filtek Supreme [3M ESPE]), then attention turned to the larger caries on tooth No. 30. While removing the decay, it was discovered that the decay ran deeper than initially anticipated. The conservative approach required removing decay from both the buccal and lingual cusps (Figure 2), but the preparation design remained conservative.

Figure 1. The patient presented with a large area of interproximal decay on a first molar. Figure 2. Caries removal was completed. Figure 3. A digital impression using CEREC Bluecam (Sirona Dental Systems) was taken. Figure 4. Margins were drawn electronically using the system’s software.

After preparation, the area was etched with phosphoric acid, and Scotchbond Universal adhesive (3M ESPE) was applied and cured. When using Lava Ultimate Restorative with RelyX Ultimate Adhesive Resin Cement (3M ESPE) and Scotchbond Universal Adhesive, the clinician can use a system that includes primer and adhesive in one bottle. The clinician can choose between self-etch, selective-etch, or total-etch techniques for clinical flexibility.

A felt-tipped syringe (Ultradent Products) filled with alcohol was used to clean the air-inhibited layer of the resin to facilitate the removal of the opaquing medium, and a cord was packed around the preparation margin. A contrast medium (Optispray [Sirona Dental Systems]) was sprayed on the preparation area, and the tooth was scanned with the CEREC (Sirona Dental Systems) wand. Our chairside CAD/CAM system software (CEREC 4.03 [Sirona Dental Systems]) was used to design the restoration (Figures 3 to 6), and an A2-HT/14L Lava Ultimate block was selected and milled.

After sprue removal, the restoration was tried in the mouth to confirm good interproximal contacts and occlusion (Figure 7). The restoration was polished, and the internal aspects were abraded with a surface treatment system, then steam cleaned.

Figure 5. Restoration design. Figure 6. Milling preview displayed. Figure 7. After milling and subsequent removal of the sprue, the restoration was tried-in. Figure 8. The final restoration (Lava Ultimate Restorative [3M ESPE]), after adhesive cementation.

Next, the internal aspects of the onlay were coated with adhesive (Scotchbond Universal), then the restoration was covered to prevent premature photo initiation. An additional application of adhesive was applied to the tooth for 20 seconds and then air-thinned. A dual-cured universal adhesive resin cement (RelyX Ultimate) was then applied to the preparation, and the onlay was seated. Excess material was removed from the margins, and the restoration was fully light-cured (Figure 8).

The patient was very satisfied with the final aesthetic result and pleased that this restoration was completed in only one office visit.

CLOSING COMMENTS
The ability to offer an aesthetic and long-lasting restoration in a single visit is increasingly important for many dental practices. A single CAD/CAM appointment can significantly increase operative efficiency by decreasing the waiting time between preparation and delivery. Depending on the block material or technique, using this newly introduced resin nanoceramic CAD/CAM block can save nearly 20 minutes in a restorative procedure due to its fast milling time and the elimination of the firing step required with conventional ceramics. Advances in materials are helping dentists meet the ever-increasing and sophisticated demands of today’s patients.

References

1. Lowe RA. CAD/CAM dentistry and chairside digital impression making. cnpg.com/Video/flatFiles/-1172/dropbox_pdf/cadent-cadcamlowe.pdf. Accessed August 24, 2012.
2. Klim J, Corrales EB. Innovation in dentistry: CAD/CAM restorative procedures. cadstar.org/category/downloads/cerec-articles. Accessed August 24, 2012.
3. Giordano R. Materials for chairside CAD/CAM-produced restorations. J Am Dent Assoc. 2006;137(suppl):14S-21S.
4. Giordano RA. Building Blocks: An overview of the various types of machinable blocks for laboratory-based CAD/CAM systems. Inside Dental Technology. 2011;2:46-50.
5. Fasbinder DJ. Materials for chairside CAD/CAM restorations. Compend Contin Educ Dent. 2010;31:702-709.
6. Fasbinder DJ. Clinical performance of chairside CAD/CAM restorations. J Am Dent Assoc. 2006;137(suppl):22S-31S.
7. Fasbinder DJ. Chairside CAD/CAM: an overview of restorative material options. Compend Contin Educ Dent. 2012;33:50, 52-58.

Dr. Fleming is a 1978 graduate of The Ohio State University College of Dentistry. He maintains a full-time practice in Scottsdale, Ariz. Dr. Fleming has spoken to several international groups on CEREC technology and has served on the board of an international academy, furthering the understanding and use of computerized technologies and machinable restorative materials in dentistry. He serves as a consultant to various dental manufacturers, helping in product evaluation and design. Dr. Fleming has been a CEREC user since 2001 and a beta tester for the CEREC software since 2004. He is a faculty member in the CAD/CAM dentistry department at the prestigious Scottsdale Center for Dentistry. Dr. Fleming also serves as faculty on cerecdoctors.com, the largest online CEREC training platform in the world. He is the editor for cerecdoctors.com the Magazine. He can be reached at mjfddsinc@aol.com.

Disclosure: Dr. Fleming received an honorarium from 3M ESPE for this article.

The Fourth Industrial Revolution focuses on greater speed, higher efficiency, and sustainability. Automation will continue to play a key role in manufacturing activities, while modern, data-driven tools and equipment like CNC Lathes and CNC machining will drive innovation.

Precision turned components offer businesses a competitive edge by realizing complex designs, introducing structural benefits, and creating parts that could not be reproduced profitably by other manufacturing methods. Let's explore the advantages of precision-turned components:

CNC Machining Produces Little to No Waste

CNC machines run on software programs that undergo iterative optimization to determine the best way to turn a component without waste. These codes may also be subject to simulations, which check the program's efficacy before implementation.

The final CAD-CAM model produces results and delivers value from the first cycle rather than through trial and error. Since precision milling machines operate on repeatable software programs using fixed tools and routes, they make smart use of the raw material available. Most advanced CNC machines can significantly reduce waste.

Zero Defects and Greater Accuracy

Precision turning machines operate autonomously, eliminating the possibility of human errors leading to defects. Codes and software programs govern the end-to-end process, delivering greater accuracy without flaws. These inputs remain consistent throughout the production process unless deliberately changed, ensuring consistency in the final products. The machines can operate for long hours without breaks, maintaining product quality.

Faster and Efficient Production

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Milling machines can operate on their fastest settings to meet increased demands. These machines can run 24/7 without tiring, taking breaks, or compromising quality. This makes production fast, efficient, and scalable without cost liabilities.

Quicker Assembly

Decoupling production capacity from the number of employees required makes manufacturing units more efficient by moving human resources down the assembly line. Manual assembly lines are known to be more effective in high-production settings and where specialized skills are required. High-precision turning of components allows for seamless fitting of parts, ensuring an uninterrupted assembly line.

Enhanced Personnel Safety

CNC machines isolate machines from humans, mitigating risks. These machines can function without an operator, reducing accidents and risks to life and limb. Modern CNC machines are highly capable, even able to change tools automatically. Design changes can be set in motion by changing the software without direct contact with the machine or person.

Human intervention is limited to a supervisory role for remotely monitoring software execution and preventive or reactive maintenance to avoid breakdowns, enhancing workplace safety.

Reduction in Energy Consumption

Industries such as oil and natural gas, petrochemicals, aerospace, and automotive are already energy-intensive. CNC machines allow scalability and precision without overusing limited resources such as energy and labor. They aim to cut down energy losses due to poor or improper planning, contributing to greater energy efficiency.

CNC Machining Leads to Lower Production Costs

With the above advantages, it's clear that CNC machines for precision turning greatly reduce production costs. They improve efficiency and scalability without contributing to material waste. They also reduce energy consumption and save on recurring operational costs, offloading financial liabilities triggered by accidents and incidents. CNC machining is one of the most efficient ways to make operations cost-effective without compromising quality.

Conclusion

Precision-turned components produced by CNC machines are superior to their manual counterparts. They offer additional benefits, giving companies a competitive edge by leveraging high quality, zero defects, and low environmental impact. For more grinding between centers information, please contact us. We will provide professional answers.