Crown and bridge restorations can be a tricky business. There are a range of problems that dentists must overcome to achieve the best treatment outcome possible. And any inaccuracies in the preparation process can waste time and money — and test your patient’s patience.
That’s why getting crown and bridge preparation right is critical to consistently delivering the treatment outcomes you — and your patients — expect.
Dentists must carefully examine the remaining tooth structure to identify whether a crown or bridge is the appropriate treatment, and understand exactly how to reshape the remaining tooth to avoid creating sensitivity issues.
Patient communication is another important step in crown and bridge preparation, and using an intraoral camera or scanner to show the patient an image of the problem you need to solve is an effective way to build trust.
It’s also important to select the right materials, and using an intraoral scanner for crown and bridge preparation can cut down inaccuracies and avoid remakes that are associated with physical impressions.
Building a good relationship with a digitally-equipped crown dental lab is also vital to enabling consistent results. The use of an intraoral scanner also helps to optimise your workflow and achieve consistent results you can stake your reputation on.
It all begins with understanding when a dental crown restoration is the best option, and when the patient would be better served with a dental implant.
Dr Parsonage says dentists must carefully examine the remaining tooth structure and identify whether any cracking is present to determine if the patient is a suitable candidate for a crown or bridge restoration.
“It’s all about how much tooth is left,” he says. “You can’t just put a crown on any tooth — there has to be at least 1-2 mm of remaining tooth above the gum line. Otherwise an implant may be needed.
“You also need to look at how much cracking there is in the tooth. If there are any cracks that go under the gum line, the tooth is not suitable for a crown or bridge.”
Dr Parsonage says crowns may be used to increase tooth strength, support a false tooth, or to improve teeth aesthetics. However, he suggests dentists take a conservative approach when reshaping the remaining tooth.
“When you are doing a dental crown preparation, you have to change the shape of the tooth and make it a bit smaller. But you can’t over-do that,” he says. “If you do, you can weaken the tooth and it will possibly break under the crown. The patient could end up losing the tooth.”
Dr Parsonage says this is a common pitfall young dentists can fall into, and all dentists should remember that sometimes the dentist can do more damage than good.
“You can create a sensitivity problem for the tooth,” he says. “If the dentist is not using enough cold water to cool down the tooth when using a hot drill, it’s possible to upset the nerve. You essentially start cooking the tooth, which causes serious pain or could even cause the tooth to die.
Dr Parsonage also warns that it’s vital for dentists to understand the equipment they are using, and the key differences between drills that may affect the success of the treatment.
“There is a particular drill some dentists use called a Red Band handpiece. It’s a very good handpiece because it keeps a constant speed up, and when you push on the tooth it doesn’t slow down. But it creates a great deal of heat, and the heat can really cause some damage to the tooth. You have to keep the tooth very cool and give it breaks to cool down.”
Proper communication with the patient is another vital step in the crown and bridge preparation process. Dr Parsonage says while some patients come to him seeking a crown or bridge for aesthetic reasons, others are unaware that they require a crown or bridge. He says communicating with the latter requires a different approach.
“Sometimes patients want a crown or bridge because they are not happy with the appearance of the tooth, other times it’s our job as a dentist to identify that there is a weakened tooth that will start to crumble over time,” he explains.
“If that is the case, I use an intraoral camera to take a photo of the tooth. Then I show the patient on the big screen that the tooth has crack lines starting to appear, and explain that it’s going to be a problem as time goes on if we don’t reinforce the tooth.”
It’s true that a picture paints 1,000 words, and Dr Parsonage says using a visual representation to explain his reasoning for the crown or bridge treatment is an effective way to build trust — particularly with new patients.
“I can show them this is your tooth, this is the crack line, and it’s not going to go away,” he says. “I find this helps patients to accept that there is a problem, and I encourage them to weigh up the greater cost of having to get an implant put in later if they completely lose the tooth.”
Dr Neville adds that an intraoral scanner is also a useful tool for helping patients visualise when a crown is not the right treatment option.
“If someone does have a really big filling or a broken tooth, you can scan it and show the patient,” he explains. “I’d say, ‘Look at this tooth, most of it is missing and I need 60% of the tooth to fit a crown. The patient knows I’m not just upselling to an implant because they can see what the problem is.”
While dental crowns have been a popular dental treatment for around a century, the introduction of new materials over the years has transformed treatment outcomes patients can expect.
“We started with gold crowns, and I would say in about the 1950s they learned to put porcelain over the gold,” says Dr Parsonage. “Since about the 2000s, we’ve had harder full porcelain crowns that have been getting better and better for the last 20 years. This has changed the way we do the crowns slightly. We don’t have to do as much reduction of the tooth to fit the crowns on.”
But Dr Parsonage believes the more recent development of dental zirconia has changed the game significantly when it comes to dental crown and bridge restorations.
“We’ve been using dental zirconia for the past eight years,” he says. “The zirconia was a little artificial looking to begin with, but more natural looking zirconia is getting very good. It’s a hard material — the hardest material we’ve ever had in dentistry.
“Regular porcelain is not very hard at all and can’t flex like a tooth can. It was common that they would crack and break away from the tooth. Zirconia is much, much stronger. Patients can confidently chew on it knowing it’s not going to crack or break.”
Dr Parsonage also points out that dentists should be aware of how new digital tools such as intraoral scanners are vastly improving dental crown and bridge preparations. He says that while the actual procedure of putting in a crown with dental instruments hasn’t changed much, intraoral scanners have transformed the preparation process.
“We still use dental drills or handpieces to shape down the tooth, but certainly the process of taking the copy of the tooth so a technician can make a crown for us has changed immensely,” he explains. “We’re now using a digital scanner, whereas five to 10 years ago we would have taken a silicone impression.”
He says manual impressions were prone to inaccuracies that could affect the fit of the dental crown and often require costly and time-consuming remakes.
“There’s a problem with getting air bubbles in the impression material, which can affect the bite,” he explains. “The impression can also distort if there is movement before it’s fully set, and you can’t really see if that distortion has occured when you take it out of the mouth.”
Fortunately, Dr Parsonage says digital intraoral scanners have largely solved these problems.
“You don’t get air bubbles, or the user-error you can get when taking impressions in the mouth. All the little inaccuracies that happen with impressions don’t seem to be there with scanners. The bite position is always very good, so there tends to be very few bite adjustments that need to be made with a scanner.”
Dr Neville adds that an intraoral scanner should increase accuracy and improve fit, and will even let you know when occlusal clearance is unsuitable.
“You’re getting measurements and real-time analytics from the scanner while the patient is still in the chair,” he says. “For example, if you’re taking a manual impression and are too minimal with your occlusal clearance, the dental lab technician would either make me a crown that’s not thick enough and will break, or they’ll tell you you have to re-prep.
“That’s a waste of time. You’d have to call the patient back in to do another impression, so they’re already annoyed.”
He says intraoral scanners eliminate that issue with real-time feedback: “The scanner tells me in real time to take another half a millimeter away. That’s a massive advantage for treatment planning.’
Dr Parsonage points out that partnering with a good crown dental lab is critical to any practice’s ability to deliver consistent treatment outcomes.
“We need a team to deliver the best treatment outcomes, and a good digital dental lab is an important member of that team,” he says. “We need to have durable, functional and aesthetic dental crowns consistently made to our specifications. If something comes back from our lab that’s not acceptable to me or my patient, it hurts our efficiency, and our reputation.”
Dr Neville adds that intraoral scanners also give the dentist a lot more control over the final treatment outcome.
“If you’re sending a physical impression to a technician, then the technician is taking the lead in making the crown and you don’t really get any input,” he explains. “Whereas if I’m sending a digital scan to the technician, I will get them to send me the digital design before they mill so I can okay it. That gives me another level of control and ensures I’m happy with everything they’re doing.”
Dr Neville explains that intraoral scanners standardise crown and bridge impression, and enable dentists and dental labs to create much more time and cost efficient digital workflows.
“A scanner cuts out a lot of the steps involved in taking an impression,” he says. “There are about 27 steps involved in taking a standard impression — from the tooth being prepared for the impression, to taking the impression, to getting it bagged up, and sent to the technician. At each one of those steps, something can go wrong. There can be flaws in every part of the process.
“But an intraoral scanner cuts the process down to about five steps. So straight away you’re going to negate any sort of mishap, and it’s going to standardise your crown and bridge preparation a lot more.”
Dr Neville also notes that using an intraoral scanner improves communication between the dentist and the dental lab technician.
“Digital scans are sent almost instantly to the technician, so if you have a really complicated case, you can send the scan and have a conversation with the technician at Avant while the patient is still in the chair. That is very helpful for workflow.”