Complications of sinus bone grafting for dental implants in Singapore

I first heard about sinus lift almost thirty years ago when I was student. It was during a conference on dental implants and one of the surgeons present was advocating that all sinus bone grafting operations for dental implants should be done in a hospital operating room. It was a relatively new procedure back then and there were not a lot of long term studies on the potential complications and doing it in the milieu of an operating theatre provided more protection against adverse outcomes. Well, that was thirty years ago. A lot of research have gone into this procedure and much of what works and what does not are well published in the scientific literature. Today, the procedure is routinely done in dental clinics all over the world. However, this does not mean that complications do not happen anymore. As with all surgeries, complications can and will happen.

Complications can be classified as intraoperative or post-operative, depending on when it occurs.

Intra-operative complications

1. Excessive Bleeding.

Sometimes, an artery may be run right across the site where the sinus window is opened and may be cut in the process, giving rise to arterial bleeding. Fortunately, this artery is usually quite small and bleeding can usually be controlled by simple measures such as pressure and in some cases, using electrocoagulation.

2. Fracture of the residual bone

When the window of bone is removed from the sinus wall, the residual bone is weakened. If the bone thin and brittle, it may fracture when the implant is inserted at the same time as the bone graft. If this happens, the implant insertion will have to be done in a separate procedure a few months later. The fractured portion of the jaw may need to be fixated with small plates and screws to ensure that it heals properly. Smaller fragments may be left to heal on their own. Due to the good blood supply to the jaw and sinus, healing is usually uneventful but sufficient time must be given before attempting implant insertion again.

3. perforation of the sinus lining

This is probably the most common complication of sinus bone grafting. Many scientific publications on this subject have reported the incidence of perforation at between 20% and 40%. This is not a surprising figure. The procedure involves the use of a drilling instrument to cut into the bone without cutting the underlying lining. Good pre-operative planning is essential. A CT scan of the sinus will show thickness of the sinus wall that needs to be drilled into, it will also show whether the sinus has septa, ie vertical strutts of bone within the sinus that divide the sinus into compartments. The scan will also give an indication of the thickness of the lining. In addition to having good pre-operative planning, good surgical technique is needed. When I teach sinus grafting courses, one of the teaching aids that I often use is an egg. Opening a sinus window for grafting is like drilling a window on an egg shell without damaging the membrane of the egg inside.

 Fortunately, a membrane perforation does not necessary mean that the surgery must be aborted. If the membrane perforation is not too big, it can be repaired or circumvented. If the perforation can be effectively repaired, bone grafting and implant insertion can proceed as planned. In some cases, the bone grafting can proceed but implant insertion needs to be done separately a few months later. In the worst case scenario, the entire operation is aborted and the surgery repeated a few months later after the sinus lining perforation has healed.

4. Benign paroxysmal positional vertigo

For sinus lifts done via the crestal approach involving the use of osteotomes, there could be disturbance to some calcium crystals in the inner ear. As the inner ear is responsible for our sense of balance, disturbance to the fluid in the inner ear can cause giddiness. If this happens, positioning exercises such as Eppley’s manenvre can help to relieve the vertigo

Post-operative complication: Some complications happens after the surgery is done. These are usually associated infection as bacteria takes some time to work.

5. Infection

As with all surgeries, sinus bone grafting can be affected by infection. The placement of a foreign object such as synthetic bone material can give rise to acute infection. This can manifest as swelling and discharge of pus. If this happens, the graft will need to be removed and antibiotics need to be given to counter the infection. Sometimes, infection can set in in the early post operative period but at other times, it may occur much later. Late onset infection may be due to the bone particles getting through small perforations in the lining and getting stuck at the opening where the sinus connects with the nose. When this opening become blocked by the bone particles, the mucous in the sinus cannot drain into the nose and the stagnant mucous pools in the sinus, giving rise to infection.

Infection of any non-autogenous graft usually require the complete removal of the infected material to clear the infection. Autogenous bone grafts, however, are more resistant to infection and the chances of salvaging the infected graft is much higher.

6. Oroantral fistula

An oroantral fistula is a channel between the oral cavity and the sinus cavity. This happens when the gum flap overlying the window breaks down and cave into the sinus opening. This is usually due to excessive thinning of the flap or a pre-existing discharging sinus tract associated with previsou infection of the molar before it was extracted. If this happens, the bone graft will be exposed to the oral environment and will be contaiminated by food and saliva. The bone graft will need to be removed and the fistula repaired.

The above list is not exhaustive. Other complications can happen but with lower much lower incidence. While most of these complications can be rectified and the bone grafting and implant can still be eventually done, some may give rise to wider problems such as pan-sinusitis whereby the infection spreads to the other sinuses. The best way to manage complications is to prevent them from happening in the first place. This is done by having thorough preoperative assessment, choosing an experience surgeon, and following through the preoperative and postoperative instructions.