Polymerization of the filling using a compact light source (wavelength - 400–500 nm).
Seals made of various materials are good for everyone when used according to indications. And the indications of fillings are limited by the volume of the defect to no more than 40% of the hard tooth tissue. In practice, this means approximately average caries: usually the damage to the tooth is amphora-like, that is, in the form of a cavity with a narrow neck. From the outside, it is very difficult for the patient to assess the true volume of the lost tissue. There is a stereotype that you can just put a seal on top, and that's okay. Dentists are in no hurry to dispel these thoughts and, for their own reasons, often expand the indications for fillings. For example, because of conservatism or because it is better to close this cavity with something than not to touch it at all or to perform more complex operations that the patient may not go to because of their cost.
In short: large fillings were a makeshift until there were more reliable ways to close a tooth cavity. They cannot be played, but they are still being played.
What's wrong with the large expansion seal? It is very simple: its material (most often a polymer) shrinks by 2–6% by volume during hardening. This means that it does not fit snugly against the tissues of the tooth. When the load is transferred to the tooth in the correct situation, it is distributed along the axis evenly both to the filling and to the remaining hard tissue, and then to the root of the tooth. In the case of a large filling, the load falls on the hard tissues (and there are less than 60% of them left by the expansion of the indications). In practice, this means a broken tooth five to eight years after filling. It will be lucky if it is broken above the gum level: we will restore it with a crown. No luck if it is lower: removal will be required, most likely, bone augmentation, and only then - expensive implantation.
The solution is ceramic inlays. It's almost like fillings, only something completely different. The main difference is that they are introduced not in the form of a layer-by-layer polymer, but in the form of a single piece prefabricated on a CNC mill (or other device). They require a laboratory and a machine for their manufacture, photogrammetry of the oral cavity, a 3D image and software for accurate design for the patient. It turns out ten times better, but more expensive.
What are the fundamental differences between ceramic inlays and fillings?
The filling is created by layer-by-layer filling of the material and processing it with a lamp. This means that "narrow-necked" amphorae cavities can be filled without expanding the neck. In the case of small fillings, the technology is good enough to change something in it, apart from generations of materials. In the case of large fillings, the shrinkage of the material creates a cavity (long gap) between the filling and the tooth tissues. The filling almost does not begin to "dangle" in the amphoraoid cavity, but this gap is a large enough opportunity for bacteria to enter this space and cause a recurrence of caries. Recurrence of caries under a large filling is the most common complication and the most common problem with large fillings. In this case, the filling cannot come out of the cavity, because the neck is narrow. At the same time, the distribution of the load on the tooth suffers,therefore, further chipping can be expected - a broken tooth due to the lack of sufficient structural strength of the remaining tissues.
Here is an example of a large seal depressurizing and replacing it with a tab:
Before.
At the stage of treatment.
After.
The inlay is machined for a specific cavity and inserted into it with an accuracy of 1/10 millimeter. It is fixed in principle with the same material from which the filling is made, but this layer is very thin and acts as an adhesive. Its shrinkage has almost no effect on the strength of the joint. The bond strength is practically comparable to chemical bonds (but in practice these are micromechanical bonds). You can remove the tab only by cutting it out, while the filling is often removed with tweezers after five to six years. The service life of the seal is only up to eight years, with the expansion of the readings and the gap - two to three times less. The service life of the tab is up to 25 years, and it is very easy to extend it. In practice, I glued inlays planted on early polymers just about that old. Modern materials should provide lifelong service, but it has not yet been verified.
The inlay is often more aesthetically pleasing, since it allows for much more precise design of the shape of the tooth, and ensures minimal differences in the appearance of the material.
The inlay is fixed in the same way as a filling: the monomeric material polymerizes under the influence of light at a wavelength of about 400–500 nm. The ceramic inlay is partially transparent, like a natural tooth, but is inserted as a whole product, which requires a different lamp power to polymerize the lower layers of the fastening material. This is another reason why they are rarely used in a regular clinic: you need a lamp not for 200–350 dollars, but for 1,000–2,000 dollars. On the other hand, if the tab is thick enough, then you can use double-cured cements and do without the emitter.
More examples
Example 1:
There is a crack in a tooth due to a large filling.
Example 2: filling with normal indications
Given:
Correct fillings:
Are tabs better than fillings?
As with any type of treatment, this is neither good nor bad in general, but there is always a choice according to the indications. Historically, in Russia, composite filling materials are used very widely, and there are doctors with excellent manual skills who can make anything out of them. Formally, you can even build a house from a composite, illuminated by a lamp. This allows the reading to be expanded. This is more than justified in regional clinics, when the patient is limited in funds or there is simply no access to the necessary equipment. In clinics with access to intraoral scanners and an in-house or independent laboratory for the manufacture of ceramics, the expansion of indications is medically unacceptable. From the economic point of view, let's say - borderline cases.
Our CNC router.
Why precision is needed in the design of the tab?
For small interventions, manual precision of work with a filling and additional correction is sufficient. In large reconstructions, it is often necessary to restore the bumps on the teeth that provide correct contact. We build an occlusal compass in order to model the oral cavity so that movement is limited, that is, to ensure the correct mechanics of teeth closing. In principle, it is impossible to do the same in the mouth with filling material. Yes, it is possible to achieve aesthetics on fillings, but the correct mechanics for large interventions with several teeth is almost never.
When a filling is required not from above, but on the lateral surface of the tooth, it is necessary to restore the contact point (so that the thread passes with a click): this is necessary so that food does not pass down and does not injure the periodontal papilla. It is very difficult to restore the contact point with the correct anatomy. In addition to the contact point itself, there is an approximal ridge with a triangular fossa. He rolls the food lump not between the teeth, but towards the chewing surface of the tooth:
On a filling it is often difficult to do this manually. And one more difficulty is when we have a defect on the side, and it is critically important that the restoration or filling is flush with the level of the tooth: if it is wider, then food will get there, there will be caries below. If already, there will be a step that will create mechanical difficulties.
Are inlays better than crowns?
When it is impossible to place a filling (with little preservation of hard tissues) without access to the inlays, the recommended protocol is the installation of a crown. But this often requires additional cutting of tissue. Often, the inlay allows you to save more tissue, that is, it is suitable for gentle restoration protocols.
What does tab design look like?
Like this:
What else do you need to know about tabs?
By themselves, ceramic products will be found in the excavations of your home unchanged. Most likely, the teeth remaining from you will degrade, but the tabs will remain the same. But the material that creates micromechanical bonds with the hard tissues of the tooth degrades and accumulates mechanical fatigue. Research is currently underway to improve its qualities. Of the important, a composite based on glass-ionomer cements has been widely used for a long time. They are very dentin friendly and release fluoride, which is a cellular poison for bacteria. It is impossible to make a filling entirely from such cements: it will turn out to be mechanically unstable and of low aesthetics. We use this material if there are deep cavities or if we are worried about possible pulp inflammation. We put a layer of this material under the inlay: we get the whole structure,good in relation to tooth tissues and sufficiently stable to withstand stress. By itself, glass-ionomer cement without a liner cannot withstand the load.
Inlays protect against hidden tooth defects. If a tooth with a filling is cracked, then this often means almost the same nature of damage as when triplex glass is damaged: the place of fracture and many microcracks are visible. Many of them are difficult to track, but in general the material degrades. If such cracks reach the root, they become there a gateway for infection and cause a purulent inflammatory process. This means much more complex consequences, including the rapid loss of bone tissue: a defect is formed in the bone tissue, and then there is nothing to put the implant into. We will have to remove the tooth, do augmentation with xenogeneic bone or mixed with autogenous material.
From scanning to the finished restoration, the patient waits at least 40 minutes - this is design and milling. In difficult cases, it is two hours, the median case in the practice of the clinic, taking into account the preparation of the cavity, is about 90 minutes. An insert for one tooth costs from 44,000 rubles, while as a filling for one tooth we have from 9,000 rubles.
PS If you get to our clinics, then say that you are from Habr, there will be a 5% discount.