Pros and cons of an in-house dental milling machine

Pros and cons of an in-house dental milling machine image

Achieve the right balance between in-house milling and working with your lab

It’s difficult to understate the impact technology has had on dentistry in recent years. From digital smile design to cutting-edge new materials, developing technologies have transformed what the typical suburban dental practice can offer.

With help from a good digital dental lab, the local dentist can now offer sophisticated cosmetic, orthodontic and full-mouth restoration treatments that were once the sole domain of specialised practitioners.

This has changed patient expectations too. A visit to the local dentist is no longer limited to a routine clean and the occasional filling. Patients now see their neighbourhood dentist as a go-to practitioner for everything from teeth whitening and clear aligner treatments to full-mouth restorations.

Many dentists have embraced new technologies to add a competitive edge to their business. And, for many, it has been a successful move. But the rapid pace of technological development also means dental practices run the risk of being left behind.

For example, the recent development of in-house dental milling machines is ushering in the next big play in the dental arena — same-day dentistry.

Dr James Tran

For the patient, that means coming to see the dentist in the morning for a scan, then coming back in the afternoon to have their new crown fitted. The treatment isn’t stretched out across weeks or months. It’s completed in a single day.In-house dental milling machines are enabling suburban dental practices to manufacture crowns, veneers and simple bridges in-house, within hours.

While that’s an attractive proposition for patients, it requires a lot of careful back-end planning, investment and additional work for the dental practice.

Whether a move to same-day dentistry is worth the money you’ll need to put into it is not a simple question. The answer will depend on your individual circumstances, the relationship you have with a good digital dental lab, and where you see your practice going in the future.

We spoke with Dr James Tran, a dentist at Bonnells Bay Dental who has shared some key considerations to think about when weighing up a move to same-day dentistry:

How does a dental milling machine work?

Dr Tran uses an in-house dental milling machine to manufacture crowns, bridges and veneers for his patients. He explains that in-house dental milling machines use computer-aided design (CAD) software and computer-aided manufacturing (CAM) equipment to mill dental products such as crowns, bridges and veneers from oral scans.

“We use an intra-oral scanner to create a picture of the patient’s mouth,” he says. “Instead of sending the scan to a dental lab, we can send it to our milling machine. Then the milling machine grinds down a ceramic block into the shape of a crown or a veneer.”

But that’s not the end of the process. Dr Tran says, depending on the material used, the milled crown then needs to be sintered and glazed in a separate oven and hand polished.

“The patient comes back later in the day, and we’ll check the fit of the crown. If it’s okay, we’ll proceed with putting the permanent cement underneath the crown or veneer. If it’s not perfect, we’d have to start the milling process again.”


Is wet milling or dry milling better?

In the wet milling process, liquid is used to keep the cutting tool and milling material cool and flushes away excess material. A dry milling machine, on the other hand, typically uses pressurised air or a vacuum to remove scrap material.

Whether you choose a dry or wet milling machine really comes down to the materials you want to use.

Some ceramic materials such as lithium disilicate and feldspathic porcelains can only be used in a wet dental milling machine. Some metals like chrome cobalt also require wet milling.

Most wax and acrylic materials can only be dry milled, while zirconia and titanium can typically be either wet or dry milled.

Keep in mind that while most dental milling machines are either wet or dry, some dry mills can also operate as a wet mill when needed.


What can you make on a dental milling machine?

Dr Tran uses his practice’s milling machine to manufacture crowns, bridges and veneers. However, there are some caveats to keep in mind.

“We’re limited to short, three-unit bridges,” he says. “We can’t do long-style crown bridges. The materials we have are not strong enough and the milling machine is not capable enough to get to that length.”

Manufacturing long bridges on a dental milling machine can take up to eight hours. That makes it difficult to offer long bridges as a same-day service. It also significantly reduces the profitability of making long bridges on an in-house milling machine as it requires hours of work from the dentist or technician to complete.

What is a Cerec milling machine?

Cerec stands for ‘Chairside Economical Restoration of Esthetic Ceramics’. This is the type of milling machine you’ll most likely want to use as the in-house mill for a dental practice.

While there are several different brands of Cerec milling machines available from a range of manufactures, most operate in essentially the same way.

A connected oral scanner is used to take a digital scan of the patient’s mouth, and a 3D model is created in the CAD software.

The dentist prepares the restoration site, including any reshaping of the existing tooth that is required, or checks that an abutment has been correctly placed to hold the new crown or bridge.

The crown or bridge is then designed, and the Cerec machine is put to work milling the crown from a ceramic block, which may then be glazed in a separate oven or furnace, and hand polished to achieve the final look.

The dentist then bonds the new crown or bridge to the patient’s existing tooth.


How much does a dental milling machine cost?

A dental milling machine is a serious investment. It can cost anywhere from about $100,000 right up to around $250,000. Dr Tran says it’s important to do a thorough cost evaluation to determine whether the milling machine will deliver a return on your investment.

“It’s difficult to say how long it takes for a dental milling machine to pay for itself because there are so many variables,” he says. “As well as covering the purchase cost, you also need to pay for the materials, and cover the operating and repair costs.”

Depending on the manufacturer of the milling machine, Dr Tran says you may also need to pay annual servicing and/or support fees.

“You have to really be churning through a lot of crowns and veneers to realistically be able to pay the milling machine off within five years.”

Dr Tran also says you need to consider whether the dentist will run the milling process, or whether you’ll employ a technician to handle it.

“Some dentists want to take full control over the milling process, and others will outsource the milling work to their assistants or a technician,” he explains.

“If the dentist is doing the milling work, they will have to take time out of their day to design, mill and polish the crown, or they have to pay someone to do it.”

Either way, in-house milling will require the dentist to take time away from the chair and potentially see fewer patients in a day, or come with the added cost of employing an assistant or technician to run the milling process. Both options have an impact on the overall profitability of an in-house milling machine, and should be carefully considered as part of your cost analysis.

Dr Tran also advises that dentists should have a high volume of existing crown, bridge and veneer work before even considering investing in an in-house milling machine.

“If you’re not already doing a lot of crown and veneer work, then an in-house milling machine may not be worth it,” he warns.


What are the advantages of CAD/CAM milling for dentistry?

Dr Tran says the obvious advantage of an in-house CAD/CAM dental milling machine is that it enables the dental practice to provide same-day dentistry. This can help to give your dental practice a competitive edge over other practices that may require multiple patient appointments over a period of weeks to provide the same crown, bridge or veneer treatment you can in a single day.

“Same-day dentistry is becoming much more popular,” Dr Tran explains. “It’s more convenient for the patient than waiting for a two-week turnaround on their crown or veneer from a lab. Instead of taking two days off work, they only need to take one day off.”

There are also savings to be made. Dr Tran says the practice is only paying for the ceramic block, which is cheaper than sending a job out to a dental lab. However, this should be considered in terms of overall profitability.

For example, the purchase cost of the milling machine and associated maintenance, repair, operating and staff costs need to be factored in to determine the average cost of each crown made on an in-house milling machine. It’s this number that you then want to compare to the cost of having a dental lab manufacture the crown.

An in-house milling machine can also assist patient education. Some practices allow patients to see their new crown in production, which adds to the patient experience.


What are the challenges of CAD/CAM milling for dentistry?

Adopting in-house milling comes with a pretty steep learning curve, and the dentist or technician will need to factor in training time — and consider the cost of remakes as you work to master the milling process.

Dr Tran also points out that in-house milling machines come with certain limitations. “We have to design our tooth preparation to make sure the cutting burr can cut the crown without chipping the material. That thickness we can achieve will be different depending on the material we’re using, so we need to know more about the materials than if we were sending the crowns to be manufactured by a dental lab.”

For example, when using E-Max on his in-house milling machine, Dr Tran needs to allow 1.5mm thickness around the tooth. That means he needs to grind more of the patient’s tooth down.

“However, if I was to send the same job to a lab, I could go down to 0.5mm thickness and grind less tooth,” he says. “To do that myself, I’d have to over-mill the crown on the machine then cut it back by hand manually. That takes time.”

Maintenance of the machine is also an ongoing issue. “The staff have to be trained to keep the milling machine absolutely as new as possible,” Dr Tran explains. “If any powder gets caught in the machine, you’re in big trouble.

“You’re also reliant on the power supply to the practice, and you have to make sure your computer is updated. We recently had to upgrade our computer because it was too slow to handle the new software updates. We also had a power outage to the practice recently, and we had to cancel all the patients for the day because we couldn’t mill.”

How can a dental lab help with in-house milling?

Dr Tran is quick to point out that an in-house milling machine does not replace your relationship with a dental lab. While he may choose to mill simple crowns, bridges and veneers on his practice’s in-house machine, he still sends more complex jobs out to Avant.

“For anything that requires a finishing touch by hand, I’d prefer to send it out to the lab,” he says. “Otherwise I’d have to spend my time after hours doing it.

“I also send out any complex cases that consist of more than a few crowns at a time. With same-day crowns, it’s effective to do two or three in-house at most. But if someone needs more than that, it’s quite a push.”

Dr Tran also favours Avant when high-level aesthetic outcomes are required.

“If we need a really high-level aesthetic, like front veneers, I’d rather send scans and photos to the lab so they can do more accurate colour matching,” he says.

“We’re also not capable of doing denture work on the in-house machine, so we’d send that to the lab too. If we set up the right workflow, we could do clear aligners in-house, but I don’t like the quality. I prefer the lab’s work on aligners.”

In-house dental milling machines are also typically incapable of manufacturing splints, castings, bleaching trays, sports mouth guards, diagnostic wax-ups and smile design-related products. However, this can be easily remedied with an intraoral scanner connected to a digital dental lab. Avant, for example, can automatically receive digital scans straight from your connected intraoral scanner software, and manufacture all of the above on short turn-around timelines.

“Generally our machine has been okay,” Dr Tran concludes. “We’ve just needed to figure out the quirks. If you can live through that, then you’ll be okay.”


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