Why do my anterior crowns keep breaking?

                                                                       
      

 Often it is desirable to increase the length of a patients anterior teeth. We can have our dental laboratory make a wax up proposal and can often transfer this proposal to the mouth by utilizing a putty matrix made from the wax up. These proposals are very helpful, but they may not be representative of the most desirable shape of the final restorations.

Because the finished crown need to function in the mouth and allow dental excursions and most dentists prefer cuspid guidance. Cuspid guidance means that when a patient moves their lower jaw laterally their canine tooth bears the brunt of the occlusion.

Although other teeth can be used to bear the forces created by lateral jaw movements, most dentists prefer that the cuspid bear the forces involved. Canine teeth are the strongest anterior teeth and have the largest and longest roots of the anterior teeth.

When doing cosmetic make overs on my patients teeth I strongly prefer that the finished result not interfere with cuspid guidance and when I am restoring my patients four incisors but not restoring the canines, I carefully check excursions of the final result. Before my patient leaves with their new smile , I carefully check all their excursions to make sure the movements are smooth and do not allow 'force' concentrations that may eventually create a future breakage of one of the restorations.

In the past , this was  important, since restorations made from feldspathic porcelain were prone to breaking if the forces placed on them were not carefully considered, especially during excursive movements. Currently dentists are more often using lithium disilicate or zirconium restorations that are tougher than feldspathic porcelain restorations, but even these can break if subjected to forces during a 'point contact' during an excursive movement. 

The picture below shows a 73 y/o patients who was experiencing chipping and breakage of his 4 anterior incisors. After he broke #10 I made him a new temporary and discussed what we should do... He and I decided to redo his 4 anterior crowns. Clearly if we had included his canine teeth in his proposed restorations a more ideal smile could have been created, but both he and I thought that a less is more type of case was preferable and below is a photo of his final result taken on the day of insertion. Both He and I were very happy with the result although I may end up shortening #9 a tiny bit more on a subsequent visit.

Before


After






from Ask Dr. Spindel - http://lspindelnycdds.blogspot.com/2026/02/why-do-my-anterior-crowns-keep-breaking.html - http://lspindelnycdds.blogspot.com/

Comments

Post a Comment

Popular posts from this blog

Going for the Gold?

Image
On the left is the older allow, on the right the new one that my lab has chosen to use The cost of a penny weight of pure gold is currently $79.53. The cost of a penny weight of pure palladium is $130.6. It used to be that palladium was added instead of gold to the precious metals often used for pfms, but now laboratories are finding that palladium is no longer affordable. The lab that I am using has just changed the formulation of the metal it's using to one that has more gold than palladium. I really do not mind, but metals with more gold are softer and often easier for a dentist to accidentally polish off delicate margins. It is important when polishing "higher gold" formulations to exert less hand pressure when performing the final polishing of the crown's margins. Other wise there should be no problem with this change. Traditionally labs have chosen alloys with higher gold percentages for optimal esthetics, since alloys with higher concentrations of ...
Read more

Why is my denture loose???

Some Patients may  have shrinkage of their jaw bone(s) after the denture was inserted and experience lack of seal. While bone resorption may play a role, in my experience there are a number of other possible causes.  Uneven bite is at the top of my list. If a dentures occlusion is unbalanced, when a patient closes, their denture may loosen. Another common reason is that a patients muscle attachments are being impinged on. Muscle attachments are little bands of fibers that connect the cheeks, lips, and tongue to the jaws. Over and under extended dentures can also cause dentures to be more likely to come loose. Under extended dentures have less surface area to help develop the adhesion to help keep a denture in place. Over extended dentures tend get dislodged by patients facial muscle movement or opening and closing. A patient with a dry mouth may also find that their denture comes loose easily, since adequate saliva is needed for a denture to develop proper adhesion. De...
Read more

Everythings coming up Roses and daffodils?

Image
 Even though I work hard to do excellent work and send my dental Labs clear impressions, not every lab fabricated restoration fits well in a patient's mouth. Yes, there are times when a restoration does seem to fit without any adjustments needed, but that is not what happens in most cases. Part of a dentist job is to be methodical and check that each restoration is adequate and will actually help preserve a patient's tooth. Our patient may hope that their new crown or filling maybe perfect, but that is not always the case and while it may be true that 'perfection is the enemy of good' , we should not place inadequate restorations in our patients mouth, just because we are afraid to momentarily disappoint a patient or employer. I take a bitewing radiograph when fitting a crown or after I place a new filling. Of course I have my fingers crossed that my new crown or filling fits perfectly, and often it is the case, but sometimes it is not. When this happens, I may try...
Read more