Inlay augmentation is a technique used in bone re-building operations, in which the height of the alveolar ridge remains unchanged.

In the animation you can see how after tooth loss, lack of sufficient pressure causes bone to recede. Our body is very economical, use it – or lose it! After a while there is no longer enough bone for an implant, and the implant would stick out into the maxillary sinus (shown by the blinking light).

The missing bone is replaced using inlay surgery, in which bone material is inserted between a patient’s own bone and the maxillary membrane – this technique is also known as a sinus lift operation. After a few weeks the bone heals and it is possible to insert an implant.

Another technique is onlay augmentation, in the animation you can see how the missing bone is replaced using onlay surgery, meaning that the bone used (coming either from a donor or the patient’s own body, for example the chin) is screwed onto the desired spot, and the maxillary ridge is raised. After some weeks the replacement bone has healed and become attached to the bone and an implant is then possible.
This is the main difference between inlay- and onlay surgery. In inlay surgery, the height of the alveolar ridge is not changed, in the case of onlay surgery it is. If there are still teeth left and there is only some bone and a few teeth missing in the back, then in general it is better to perform onlay surgery, since this leads to more aesthetically pleasing results. If there are no more teeth left and the alveolar bones have receded evenly, then inlay surgery of the sinus lift type is usually the way to go. Sometimes these two techniques are combined.

As you can see, nowadays there are many different surgical techniques which can be used to build up jaw-bones. The material used to replace bone can be either human bone or bone from animals such as cattle or it can be synthetic.

Human bone heals best, while synthetic materials heal worst. With human bone, it is possible to use either purified bone from donors – or else one’s own – by means of a bone transplant.

When using a patient’s own bones, care should be taken to ensure that the transplanted chunk does not exceed a certain size. The reason for this is that the transplanted bone contains various cells. Once the block is removed, the cells in it are cut off from the supply of nutrients. If a chunk is small, then after transplantation the cells are once again supplied with nutrients from the side by the process of diffusion. If the chunk of bone is too big, then diffusion is not enough, it takes days for new blood vessels to reach the interior. For the cells inside the chunk this takes too long – the cells die. This triggers an immune reaction, in which the immune system removes the dead cells, which in turn leads to bone absorption. This is why larger chunks of bone are transplanted using the microvascular method, meaning that the bone is removed along with the supplying vessel which is then connected to another vessel in the area to which it is transplanted, which ensures the supply of nutrients to the inside of the transplant.

Microvascular transplants are not usually necessary in dentistry, small chunks of bone are usually enough – which is also why it is pointless to spend a lot of money on growing bone chunks using cells in test tubes under the right conditions, because the moment that the bone is removed from this „optimum“ incubator – and transferred to a human body, it already begins to „melt away“ for the above-mentioned reasons. This method is very interesting and sounds very nice, but it’s also expensive and pointless.