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23 Dec 2019

Why can a bone graft fail?

What is a bone graft?

Bone implantation or grafting (bone graft) is the treatment used to increase the size of the maxilla or jaw. The goal is to be able to place dental implants in patients with little bone or insufficient bone. In this way, the patient will be able to improve masticatory function and dental aesthetics.

It is important to take advantage when you have a good bone base. Having an ideal height, width and bone quality shortens the treatment time, reduces discomfort and improves the success rate of dental implant treatment.

Possible problems with a bone grafting

A possible problem for the implant dentist is a reduced anterior or posterior maxillary bone as a result of bone resorption after tooth extraction or trauma.

Prosthetic treatments to recover teeth in edentulous people may require bone augmentation to make the placement and integration of dental implants possible.

This is a complex situation because bone regeneration techniques have failure rates that can reach 25%.

Regeneration techniques

These regeneration techniques depend on:

  • The operator (the surgical technique, training and experience).
  • The patient (general health, smoking, postoperative care).
  • The material chosen (artificial bone grafts are bad substitutes in general).

Types of bone graft

Knowledge of the types of bone grafts and their combinations help and improve the incorporation and preservation of bone grafts.

The bone to be implanted can be taken from the same patient or a bone graft from a human or animal donor can be used.

In the past, it was preferred to use the bone of the same patient whenever possible. In some cases, the human donor bone (allograft) or the animal (cow bone) is used mixed or separately. In part, because they offer total security and optimal results, lengthening waiting times a bit.

While the decision on the graft material to use in each situation will depend on the clinician, before carrying out a bone augmentation several factors must be taken into consideration.

Facts to consider before a bone graft

Treating oral infections such as caries or gingivitis/periodontitis, the position of the nerves, the available inserted keratinized gum, the design of the flap or surgical technique, the antagonist arch and the provisional one on the grafted area after surgery should be evaluated by clinical and radiographic examination.

Many factors can complicate surgery if they are not planned. The patient’s overall health status is a factor to take into consideration at any age.

In which cases should a bone graft be performed?

This bone graft will guarantee a correct bone support for the implants and their subsequent rehabilitation in the mouth. The cases in which it is considered that a bone graft should be done before an implant rehabilitation are the following:

  • Manage to maintain bone height after the extraction of a piece, regenerating at the time of tooth extraction (preservation of the alveolus) in order to place an implant easily and without further regeneration.
  • Gain height or width to rehabilitate later with implants.
  • When maxillary sinus lifting techniques are performed to be able to place implants in the posterior areas of the upper jaw to return lost molars.

 

porque-fracasa-injerto-de-hueso

Placement of bone graft after the loss of a tooth to be able to place an implant after waiting 3-4 months.

 

bone graft

Bone regeneration after placement of a dental implant.

Bone graft techniques:

Increased crest or bone regeneration

A crest augmentation is a frequent intervention in dentistry, performed after a previous extraction or loss of a tooth. It is carried out to help restore the contour, width and height of the bone that may have been lost. The bone of the jaws is reabsorbed predictably after tooth extraction or loss. There are two forms of crest augmentation:

Horizontal (width increase):

In dental terminology, a “horizontal” bone growth or augmentation is one that occurs in the vestibular or lingual sense (from the outer inner part of the teeth), resulting in a more “wide” bone crest.

In most cases this is necessary to allow the placement of an implant inside the bone. Proper planning is essential to success in these procedures.

Horizontal crest augmentation is performed in locations where teeth previously existed, but which have been lost, which has led to a loss of width (and height) as a result of normal bone healing (physiological remodeling).

Horizontal augmentation procedures in most cases involve the following steps:

  • Surgical exposure of the bone in the region to be increased
  • Placement of particulate (bottle) bone graft in deficient areas
  • Placement of a collagen membrane over the bone graft (in some cases, a titanium-reinforced membrane can be used to allow greater stability of the graft material when the need for regeneration is very great).

Vertical (height gain):

In dental terminology, a bone growth or “vertical” augmentation is one that occurs in the coronal direction or height, resulting in a “higher” crest.

This is the most difficult of all bone augmentation procedures in the oral cavity. As a rule, it is difficult to get height above that which exists.

Implant manufacturers have designed implant systems that help compensate for bone height loss since augmentation techniques have a low success rate. In the event that the clinician establishes a vertical augmentation, the steps to follow are similar to those listed for the horizontal augmentation.

In the posterior upper jaw there is also a pneumatization of the maxillary sinus resulting in insufficient bone height to have a good support for the implants.

As a consequence, a maxillary sinus lift surgery is performed generating grafted bone formation in the lower portion of the maxillary sinus to increase the available bone height.

Currently bone grafts are minimally invasive and reliable techniques if properly prepared.

If the graft is placed at the time of tooth extraction, it will wait about 3-4 months to be able to place the implant. If the bone is placed in an area without teeth where bone has already been lost, the waiting time will be extended to 5-6 months.

Dr. José Nart Molina

Dr. Jose Nart received his dental degree in 2001 from Universitat Internacional de Catalunya (UIC), Barcelona, Spain, and his Advanced Certificate in Periodontics and Implant Surgery from Tufts University in 2007. Dr. Nart was awarded Diplomate status by the American Board of Periodontology on May 2008, and he obtained his PhD in Dentistry in 2010 with the highest degree. Currently, he is Professor, Chairman and Program Director at the Department of Periodontology at UIC-Barcelona, and President for the Spanish Society of Periodontology and Osseointegration (SEPA). He maintains, with his family, a well-known multispecialty private practice in Barcelona, Nart Dental Clinic, as medical director. Dr. Nart is author of many international high-impact JCR publications (+110), worldwide speaker and reviewer of the highest impact factor Periodontology and Implant Dentistry journals.

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