Porcelain Fractures: How To Approach?

Dr.G... Porcelain fractures may occur especialy when opposites tooth are covered by porcelain crown or bridges.When the crowns or bridges are addicionally on implants,fractures can be more possible. Very important is precisious articulations and it can be Your problem. If not.....problem is in Your lab.Change Your technician .It should help. Obviously,I have sometimes this problem,but only sometimes.....not trendy.... Sorry for my english Kris

I have been placing implants and restoring them for nearly 20 years. One of the most frequent complications that occur is the one you have just mentioned. even though it is hardly discussed in the literature. the reasons verify from imbalanced occlusion, fatigue, low technical standards but the main reason is the absence of the compliance that we have with the periodontal ligament. Actually, regardless of the reason to the failure we are often facing the need to replace the prosthetic part or fix it. As we all know, charging the patients in those cases is a major issue. Therefore my recommendations are: Never cement the prosthetic elements permanently. Make sure the metal framework is built correctly and avoid large amounts of unsupported porcelain. The metal framework must be in passive fit. Always prefer a full ceramic zirconia crowns and bridges. When charging the patients for the prosthetic work always take in your considerations the future

Just be thankful that the porcelain broke and not the implants. It is easy for a lab to make the porcelain much too thick on an implant case which along with the previously mentions items can make for failures.

This is a lab quality assurance issue. Stacking 3+mm of porcelain at the cusp tips to save on gold costs is what's the bottom line. Ask them to wax up a coping that somewhat resembles a prepped tooth instead of just covering the abutment or using a premade wax burnout coping. Some labs are just taking the pre-fit wax coping and casting it without any build up whatsoever. And the upcharge for implant labwork is ridiculous, since its less hands on and easier for lab techs to make prosthetics. Like everything else, quality is going downhill and costs are skyrocketing...

I feel compelled to respond to the "If not…..problem is in Your lab.Change Your technician .It should help." Comment. This just too broad a brush stroke and just really not an accurate statement. Yes, a restoration may not have adequate metal substructure, but a trained and knowledgeable technician will support that porcelain. I think the comment about about lack of periodontal ligament is right on the mark. Implants have no shock absorbing ability and will chip and fracture. Good protected and disclusion in posterior working will help protect them but the plain fact is your driving occlusion and antagonists with no shock absorption and the weakest link will give....the porcelain.

As FSOMS has suggested main reason in difference of nos. of porcelain fractures between traditional fixed bridges/crowns/PFM and implant restoration is difference in size of natural teeth abutments and implant abutments.We all know there is no comparison. Implant abutments are too small for size of restorations,specially molars.And as FSOMS pointed out many labs cut corners at the expense of dentists.Lab try to minimise use of precious metal in the fabrication of metal substructure and leave unsupported porcelain. As we know more than 2mm of porcelain is at the mercy of occlusal forces. Best way to avoid this is always try in metal frame to check proper fabrication.Porcelain space should not be more than 2 mm on occlusal and 1 to 1.5 mm on other surfaces.

And, as always, check for parafunctional habits! Particularly in all the situations mentioned above: porcelain against porcelain, thin porcelain, overly thick porcelain, thin copings (we've had a number of Captek failures on natural teeth). If they can break natural teeth, they can split crowns also.

The use of custom cast gold abutments, rather than those prefab parts will allow the laboratory technician to approach the ideal of no more than 2 mm of unsupported porcelain. Very important in a situation where there is no PDL.

There are a couple of possible reasons for fractures in the dental restorations which have been over looked by most clinicians and dental lab technicians,(1) Not evaluating the C/E between the porcelain and alloy used in the fabrication of the substrate. (2) improper coping or bridge designs that do not support the fired dental porcelain by the substrate. If sound prosthodontic techniques are followed remakes should be at a minimum.

GUYS, Remember an implant has no PDL. We place the crown in infra-occlusion for a reason. This is not a lifetime position. Teeth without an opposing contact supraerupt. YEARLY adjustments are needed. Put a new note in your medical history alert in Practiceworks/Dentrix/whatever, and adjust at recall. michaelp

After 7 years I would feel OK to charge patients for a remake.Saying that most of my full-arch rehabs are metall-accrylic,they dont last 7 years anyway,but my patients know that.

Many good points presented in this discussion. It is of course incorrect to generalize motivation or condemn a group, i.e. technicians. There are myriad causes for porcelain fracture as explained above. However we must admit that restoration of implants is an extrapolation of technique and material for the restoration of teeth; this is an error at the basic level. Without the built in shock absorbing PDL and the significant decrease in proprioception it is reasonable to deduce that the porcelain will be subjected to far greater functional stresses. Altering the design of the restoration is an important conclusion however the modification is not easily accomplished. Simply increasing the thickness of the metal to reduce the porcelain depth may induce stress/strain in the ceramic due to altered heating and cooling rates of the alloy during firing. Design of custom abutments may reduce this particular problem but risks escalation in treatment cost, particularly with the rising cost of gold. In twenty years of prosthodontic practice I have my share of fractured porcelain, typically distal marginal ridges. Most, but not all were due to unsupported porcelain; restorations designed as if on teeth. We require methods and/or materials developed specifically for implant dentistry; CAD/CAM milled frames and abutments is a start, pressing ceramics onto metal substructures is promising, we need more. Until then, advise patients before initiating treatment and inform them that with increasing esthetics comes greater risk of breakage and consider employing a pro-rating cost of replacement . For example, one year breakage means free replacement, five years is 50/50 shared cost, etc,

Excellent post. In this age of all ceramic dare I say that a metal occlusion might be a good scenario for molars? When I explain to patients that metal will almost never break they seem to prefer it in non esthetic areas.

Hello My fellow colleagues, Great Discussion. however stress and strain on porcelain implant restorations can never be measured intra-orally. SO therefore stop blaming the labs, the porcelain, the implant, the lack of PDL. We really never know why it breaks and it's no one's fault. 2 Issues. 1) Our patients are told after their insert visit ( temrex cement usually never perm cem.) that they will never be charged for our services on these restoration for the first 24 months. They may have some lab charges to re-do any crowns, screws, etc.. After 24 mos it is our discretion what the fees will be according to compliance of patients and hygeine, adjustments, etc. So I try to coach my colleague to have some policy dealing with failures and re-dos. Also ask your labs what their policy is on re-dos so at least you know your cost from the beginning. 2nd issue is Occlusion. I have seen many cases while helping and teaching many clinicians and what we see is some of the following: Canine guided protection was not there. we suggest that is the safest occlusion scheme for implants. If the opposing teeth are flat then we restore the guidance with those teeth, If the VDO is collapsed it must be addresses before implants are placed. Group function is not indicated. Centric position should be checked on insertion and 2 weeks and 3 months later. There is shifting and remodeling of bone all the time. We have seen teeth and implant shift 1, 2 even 3 years out. We suggest bite plates on patients that exhibit any bruxism and grinding habits. Also complicance for these appliances you know is never what it should be. So we warn them they may have failures and breaks if they are not compliant with their bite plates. Also other than minor repairs we have been succesful VENEERING porcelain over implant units to avoid removal and any undo stress taking old crowns off ( ei Back action appliances) If anyone would like to see some photos of this let me know at drdean17@aol.com . I hope this helps.

Dear dr. Dean, As you know I always respect your knowledge and admire your skill,but in this case I have to respectfully disagree with you on the notion that poorly supported thick cuspal porcelain has no bearings on fracture incidences in implant restorations. When patient bites on hard candy or chew bone, 4 mm of cuspal porcelain on .5 mm metal is more prone to fracture than 2 mm of porcelain on 2.5 mm of metal regardless of cuspid guidance occlusion or better compliance from patient.

Dr Dean What you are saying is not right If the porcelain is not designed correctly on the crown and does not respect the priciples of bonded ceramics ..then it will fail This is nothing new and has been understood for decades If the tech stacks 3mm plus porcelain on metal ..he is wrong and the GDP wrong to accept it ..otherwise roll the dice Ask any CDT on this forum they will not disagree they have not been taught otherwise It does not take a bruxist to crack 3mm of porcelain in a molar area implant ..this is hardly a point of discussion michaelp march 25th you are NOT supposed to place implant crowns in infra occlusion Please look this up ! Adjusting regularly for the errupting tooth is not implant dentistry ..you are misleading novices on this forum In breif the implant crown does not make initial light contact It does however make contact when the teeth are clenched ie the other teeth are depressed into pdl ...then the implant connects This is not infra occlusion.. there is specific protocol to acheive this for Implant dentistry we should all be very familiar with it

There alot said on the thickness of porcelain and the metal substructure, I would agree that if you have unsupported porcelain will fracture regardless of implants or no implants. I have found that a properly designed occlussal guard has kept my porc fractures to a minimum.

All very interesting discussion and most all of it is accurate but one point must be stressed more than any other when we talk about crowns on implants. I am a technician but not a ceramist I was trained as a engineer and the first thing you learn in engineering is to calculate loads. In designing copings we are able to cheat with prepped teeth because of the PDL and get by most of the time without fractures (we still have them don't we). In implants we have to give more consideration to occlusal forces and how they are being directed during function. I can build a beautiful crown on a well designed coping cemented to the perfect custom abutment and have porcelain fracture if I do not take into account directional loading; that is the direction that opposing dentition is exerting force on the porcelain. I wish I could draw pictures here - it would make it so much more simple - but you have to look at distribution of forces in function and this requires full arch impressions and adjustable articulation and patience. I could not agree more with the doctor who said light occlusal contact is not implant dentistry; doctors and patients must understand that design must sometimes compromise esthetics but with ceramic copings I see very little compromise if any in most cases. You can avoid most fracture problems on crowns cemented to implants with proper coping design, but not all. I still don't have an answer for the 3.5 mm implant in the #30 position 20 degrees off axis. lol Joe

The molar region is where fracture of porcelain happens mosts frequently because of the greater forces which are generated closer to the jaw hinge fulcrum. Design extension of the sub-veneer scaffold is therefore of the utmost importance because of the poor fracture toughness of porcelain. The same is true of composite and even enamel which collectively have poor fracture toughness in the range of 1.1 - 1.4 Mpa compared to metals which are over 100. Ideally, a complete form wax-up should be made and then cut back to establish the support scaffold. Consider additionally the bruxer plus the loss of resiliency of the PDL and the use of porcelain on occlusal surfaces in the second molar region where aesthetics are least critical should come into question. I have never seen a gold crown fracture. A patient who is informed and who insists on porcelain in the second molar area should accept the consequences of their decision when it comes time for revision.

All good points. These are not addressed in general as there is no financial incentivce on part of implant co's etc to bring them up. This is our problem because as practitioners and the one with the relationship and responsibility to the patient in rightfully belongs here. We are the ones who have to deal with the physical, emotional, and financial aspects of the problem when it arises. No one else in the food chain.

Guys are we missing the point? The question here is not about reasons for porcelain fractures in general. The question is about reasons for MORE porcelain fractures in implants than regular crown and bridge work. Most of us were taught and know the reasons for porcelain fractures:Like too thick/too thin porcelain,type of occlusion,lack of guidance,parafunction,opposong dentition,collapsed bite,temprature of porcelain firing,type of metal( precious/non precious), and more. Dr.satesh Joshi is on target. The main reason for MORE porcelain fractures in implant crowns is smaller size of abutments leading to thin metal and thick porcelain (very pretty looking crown). The secondary reasons are 1,lack of propeoception and at a certain degree 2,lack of elastcity of PDL.

To often we blame the lab. Most of the time its not the lab. They work for many practioners of differing skills. They have developed a wealth of knowledge of what works and what dosent. MOST OF THE TIME THEY VIEW OUR CASES IN A KINDER ENVIRONMENT, THE LAB BENCH, AND SEE THINGS THAT WE DONT SEE AT ALL. iN SO DOING MANY TIMES PROTECTING US FROM FAILURE WITHOUT OUR KNOWLEDGE. With out them I would be lost since these pieces of ceramic do not come in the shapes I need in stock supply. Its is irressponsible to just blame the lab. If we adjust the ceramic in the mouth prior to delivery and dont take appropriate steps to deal with the microcracks then we will see ceramic failure down the road due to hydrolic pumping and crack propagation. Also, when using the term proprioception in relation to the PDL its not proprioception. There are no such fibers in the PDL histology. We mean to say MECHANOCEPTION or load perception. Forthermore, did we for a moment forget the patient? How did it fracture in the first place. What do they do with their teeth. When they call or come in, first question up front is how did you do this? We ask this when they call when they dont fabricate that it occurred on soft bread... Which it could have, by the way, but the fracture or cone crack was done way before the soft bread. Thanks

I'am a dental tech for 26 Years and still have porcelain cracks once in a while even after doing the best framework design i can and most of the time they are on pontics on implant cases only!i think it comes from tension between metal and porcelain and or thermal shock because of some areas being thin around implants and pontics being thicker metal;i'm am using shofu vintage pocelain does anyone have suggestions for another brand of porcelain that is less subject to tensions??

I gave a leture on this topic a while ago, and it is free today....take my knowledge away if you deemed suitable. I love this forum... Re: management aspect of implant porcelain fracture Given the facts: 1. implants have no PDL. 2. Porcelain is glass-like Summary: Implant porcelain will fracture, it is only a matter of time. if your patient live no enough. it is no a matter of your tech or your lab (most of the cases)... Solution: 1. Written, sign contract between the patient and the Dentist. just like electronic appliances. Give your warranty. 5 years is what I set. no questions asked. after that fees will be charged. 2. Metal crown, metal occlusion can make your days easier. explain to the patient. sure they can understand or be informed. 3. Single crown the implants, splinting is wonderful (good for the implants but bad the glass crowns) , have you notice splinting adjacent implants increases the chance of porcelain fracture..... personal observation. unless your design is implant supported bridge and then there is no a lot you can do. by not splinting the crowns, you may lose some " implant support", but when porcelain does fracture, you only need to face them one at a time. 4. Night guard, explain to the patient, charge the patient if you want to, or give it as a present if the total bill is big enough. 5. i am not going to focus on the tech part of coping design nor am I going to focus on the occlusion. After many many years of placing them, restoring them. they will fracture if your pt live long enough. 6. have a 24 or 36 hours post insertion check, may be you will pick up high spot that was missing during insertion date. 7. P.S. I know i said i was not going to focus on occlusion, but if you are doing posterior restoration, and you have healthy canine, let most of the movement ride on canine ( remember, canine protection... use it to protect your precious posterior porcelain). love you all