Porcelain Fractures: Is This Very Common?

porcelain fracture is the first most prosthetic complication occuring in implants...that may be frequent especially if your lab is not planning your crown the best way... the metal infrastructure should have the design of the crown so that there will be no unsupported porcelain and no more than 2 mm thickness of porcelain at the most... your lab is right that screw retained is better for repairing...Occlusion is a factor also with parafunction...Can you please tell us where the porcelain break and if the patient had parafunction?

Big Question The lab should attempt to take implants crows out of occlusion by 40 UMS in compressed centric and that should be maintained throughout the crown life since natural adjacent teeth have a periodontial ligament that allows compression and closing of the bite. Some cases have more movement and some less depending on the parafunctional habits and stability of the adjacent teeth. This problem is rearing its ugly haed in Zirconia as the eariler copings that were made were generally not made with support as the design capabilities were not there in eariler programs. It will be a BIG problem for the cases of the past. The newer CAD systems have better programs and the knowlege now of the labs is moving slow so even today the problem exists. Many PFM 's are the same. All understructures should be made with support but that raises the cost for gold alloy. Another view is where the poccelian fractured. Is it on a holding cusp? is it a clean fracture to the metal suggesting that a porr bond was ecvident? Doing a screwed crown is not necessarly the answer as if the holding cusp is on the area of the acces hole, youy can get chipping there or possible more mechniacl failures . All systems are not equal. Some have better tollorance and some are very poor with the fit and sometimes the lab destroys the fit through fabrication. Some times the clinician does not torque the abutment properly and a few times the screw seat is damaged. I hope this helps a bit.

We can discuss and discuss and discuss the issue..... it is not very frecuent but happens.... main reason in my opinion is occlusion. A great dentist told me 12 years ago "oclussion is of paramount importance but disclussion is vital". I understood that and since then i dont really have problems(a few are expected). In terms of screwing down crowns... i do 50/50 cemented and screw reatined and i dont really see a difference in terms of fractures. So good incisal and canine guidance, only small and light contacts in centric occlusion and you should be fine.

In my experience of restoring the implants for 19 years the fractures of porcelain happened both on single units and on bridges. From the literature, expert opinions and my understanding among the reasons could be : 1) abscence of proprioception on implants, leading to occlusal overload; 2)technical mishaps; 3)considering previously widely used Al2O3 metal free substructures, they often did not take the posterior occlusal load; 4)in partially edentulous cases I as a rull reduce the occlusion on implant supported crowns using the shim-stock foil.

Abe is correct. I have also seen fractures with the use of porcelain abutments. Remember, there is no periodontal ligament about the implant. Occlusal force is a big factor.

One of the most common causes of tooth loss is bruxism either through tooth fracture or loss of periodontal support. The habit does not often disappear after implant placement. Bruxism appliances are a big help in preserving tooth structure whether natural or artificial. Of course delivering a well developed occlusal scheme for centric,lateral and protrusive positions and movements will help tremendously. I don't mean to belabor the obvious but attention to detail is critical to long term success.

Dr. Callan is correct!

Just back from a seminar on occlusion and implants I think I have derived some moral authority to answer this question. The excursive movements of the jaws is very critical when it comes to Prostheses, Implants and Periodontics. Often while selecting cases for implants we are glad that we have one more implant case and we take up a case with obvious Occlusion related issues like clenching, bruxing and extreme canine wear for eg. These circumstances produce extreme loads on the ceramic leading to Ceramic chipping. A lab may go wrong once but not as often as you have mentioned. When the crown comes in for the biscuit bake trial always check whether the ceramic interferes with the opposing tooth's cusps as the jaw makes it's usual anterior and side to side movement (Guidance). Finding it out after the crown is delivered isn't good practice. Especially since it is you who may get pressurized into giving a new crown at half the price. Checking excursive movements will save you money and your patient some trouble. Also check for abutment shapes whether they are anti rotatory and whether your lab follows standard practices and materials. Occlusion is the basis of all dentistry. Spare time and read all you can, attend lectures and workshops on Occlusion.

Dear Dr. J., That´s why basic principles on metal-ceramic systems will never be old-fashioned. The risk of fracture exists in metal and metal-free systems and simply, there is no "magic trick" to overcome a short interocclusal distance with all-ceramic implant-supported crowns. Basically, bruxism and parafunctional habits must be considered, but occlusion is the key factor (how you distribute the stress over the abutments). you can check all the top quality literature and no one says that "dental porcelains fracture-proof" even in zirconia cases. a simple checklist is: - good occlusal scheme - take care with limited interocclusal space (check you wax-up in the laboratory) - do not make "magic" : if the patient is candidate to a metal-ceramic, do it and avoid all-ceramic systems - adjusting contacts before glazing - recommend an acrylic appliance for patient during sleep - schedule 3-month time interval recalls - even with all the aforementioned, all-ceramic can fracture. the secret is "your patient must know the risks" - don´t be ashamed!!! we have many colleagues with cases of fractured all-ceramic implant-supporte crowns

What ever happened to good old fashioned flat-plane occlusion in the posterior or metal centric stops? Although not extremely esthetic, they sure have kept my incidence of procelain fracture down over 20 years. TB

Fully agree wih above reasons only thing is how to remove cemented crowns?[Esp. in a multi Unit Implant cemented Prosthesis] Dr Ashish www.drashish.com

Did you always have this problem? Or is it just with the implants? I keep my posterior implants in very light or no occlusion if they are opposed by implants posteriorly. During a bitemark research I was doing,I found that people with anterior open bites had no trouble eating.I measured my bite force with a machine I made an it was 100 lbs.That was the limit of the scale.So that means if I choose a point between the joint and my ant teeth the force would be 200lbs. I used a protrusive bite and a bite that I had a pt open as far as he could to determine the condylar guidance on my Hanau semiadjustable articulator.With the latter I discovered he had a parafunctional habit that was responsible for the loosening of two post molars that were in hyperocclusion.All the occl adjs I did in lateral movements were of no avail. In one of the first chapters of Dawson's text he stresses that in protrusive the post teeth shouldn't occlude.Disoccluson.

As a lab we have eliminated porcelain fractures associated with zirconia. We are an all Procera lab and experienced fractures because the copings were not designed to properly support the porcelain. We have created custom zirconia copings to support the porcelain throughout the entire restoration. We build these crowns like well made PFMs. You no longer have to sacrifice strength for esthetics. Whatever is done with metal, we can do with zirconia: lingual, interproximal, and buccal collars; zirconia occlusion, etc, and it is hardly visible in the posterior. We can be reached at (602) 298-1388

Good discussion. I am wondering what experience forum users have had with porcelain full arch fixed implant restorations - particularly with regards to metal vs. zirconia frameworks, porcelain fractures, and occlusal protocol used...

OCCLUSION is the key! Guidelines for the management of occlusal forces in function and parafunction. I recommend Dr Terry Tanaka courses and DVD`s

I have had an in-office dental lab for over 30 years which affords us the hands-on ability to control quality and technique issues. We have been using Zirconia copings and layering porcelain builds over Zirconia for over three years . At first we were supporting the build-on porcelain with the same degree of coping extention that we were using for our PFM's and like the other people reporting, we experienced a significantly greater porcelain chipping incidence compared to our PFM's, particularly on implant units but not only with implant units. We revised our coping extentions to provide the maximum degree of support. While this diminished the chipping incidence it certainly did not eliminate it. As with all new technologies there is a learning curve and I believe that we have not yet as an industry learned how to properly fire the veneer material to the Zirconia substructure which I believe disipates heat quite differently than does a metal coping or frame. For the time being I have reverted back to the PFM structure particularly for the second molar region and many times with gold occlusions. We have been working with increasing our ramping and hold temperatures and feel that there is some improvement. PDL's and occlusion notwithstanding, I believe that the metal substructure may also provide some minute amount of resiliency that Zirconia does not. Time will tell as it usually does.

Hi i face the same problem but i sorted out by going to my lab and checking on my tech and i found that they were touching the coupings with there bear fingers and contaminating the couping before placing the porcelain as a result there was lots of chip off and i stopped using ips material and switched to ceramco 3 and since then things have cooled off ,but main factor still remains occlusion

I do both cement and screw retained and do not notice one causing more porcelain fracture than the other. The main problem is occlusion. Second is porcelain quality by the lab.

Management and understanding of occlusion and parafunction is key to preventing porcelain fractures.

There are numerous ways that can prevent these fractures from occuring such as rounding the line angles both on the implant abutment and the coping, having proper substructure design, ensuring proper adheshion between the opaque/liner and substructure and also from proper functional guidelines. Hopefully in following the formula for each of these you will have success however there can be other factors that influence an implant case as well as other restorative cases. Are the porcelain fractures occuring in the lab and then being anhealed before they are sent to your office, are the subtructures being prepared correctly to accept the porcelain? The types of issues you are having can be corrected and aesthetics don't need to be compromised in fabricating restorations for your patient. Vernice Griffin, CDT Griffin Dental Laboratories, LLC Louisville, KY 40223 Receive your first zirconia crown for free a great opportunity to cut the cost of your next implant restoration and invest more in a custom milled zirconia abutment which can be done inhouse at Griffin Dental Laboratories.