Dental implant complications: systemic diseases and medication (part 1)

Dr. Diyari Abdah offers an overview of implant complications with a look at how issues with patients’general health can affect treatment

Systemic diseases can have an immediate and long-term effect on the healing process and prognosis of dental implants, but there are some solutions to the problems they pose.

The first rule is to be critical in case selection. Plan the entire case in a specific manner according to the patient’s medical history, and do not apply universal methods of treatment — different individuals may need altered treatment plans according to their individual medical needs. A well thought-out and thorough medical history form can save the clinician and the patient from dealing with complex failures later.

However, some cases yield unexpected outcomes (both good and bad) despite thorough planning and execution of the treatment model. Sometimes the case starts to fail even before the surgeon is aware of it.

Understanding medical conditions and pharmacological implications and interactions is critical for any implant surgeon, and this knowledge needs continuous updating. Every surgery performed, every flap raised, every implant placed, every graft done, and every case restored has to be planned and performed to make it successful and safe for the patient. This article will try to cover some of the main systemic disorders that can influence implant therapy — but further reading is strongly suggested to gain more knowledge and come closer to treating these cases more predictably.

Osteoporosis

Osteoporosis is a decrease in the mineral density of normally mineralized skeletal bone. The assumption that osteoporosis is a risk factor for dental implants is based on the idea that all bone types in the body are similarly affected by decreased bone metabolism. However, the literature suggests that not all bone types are affected in the same way.

Of interest here is that maxilla and mandibular bone mass or density are affected by a diminished bone metabolism, which some suggest is not in line with the rest of the body. There is not enough evidence suggesting that high failure rates of dental implants or complications are related directly to osteoporosis. However, the long-term risk (greater than years) escalates when these patients are treated with bisphosphonates.

Oral bisphosphonates are used to treat osteoporosis and osteopenia, and the risk of bisphosphonate-induced osteonecrosis in the jaw is lower for oral bisphosphonates compared to intravenous therapy.

The process of bone remodeling is different from one area to another; cortical bone remodels differently than trabecular bone. The latter is affected more by metabolic changes, and thus is lost at an annual rate of 1.2% in pre-menopausal females (which increases dramatically after menopause), compared to 0.7% in males.

One fact remains constant, and that is that osteoporotic patients heal as satisfactorily as healthy patients when they have a bone fracture. Consequently, bone healing after implant placement in these patients is comparable to healthy patients.

In conclusion, osteoporotic patients can also benefit from dental implants, and they can initially heal as well as healthy patients. However, if rapid peri-implant bone loss is noted — with no sign of peri-implant disease — after the implant has been in use for some time, the occlusion should be assessed again, and a referral made to the endocrinologist for an updated bone density assessment and re-evaluation of their medication.

Cancer therapy

Chemotherapy and/or radiation therapy of the head and neck for treating cancer can often affect these areas in terms of host defense. Implant therapy is contraindicated when the patient is actively going through chemo- or radiotherapy. High-dose radiation of the head and neck can decrease vascularity of the oral bone, which continues even after the radiation has stopped. The literature suggests that the rate of implant failure is higher in irradiated bone; however, the failure rate reduces when the dose is below 45 Gy.

Surgical resection of oral tumors can lead to a limited amount of bone, making it very difficult to place dental implants even after grafting procedures. These are factors that can increase the failure risks and need to be looked at thoroughly at the treatment planning stage. The literature shows that implant failure rates are usually higher in the maxilla (17.4%) compared to the mandible (4.4%).

In previously irradiated bone, most implant failures occur less than 4-years post placement. In general, the average survival rate of dental implants in irradiated bone (pre- or post-implant placement) is approximately 76%. Implant surgeons and patients should therefore expect lower survival rates if the patient has received radiation therapy.

A major negative effect of radiotherapy is osteoradionecrosis (ORN), which is usually treated with hyperbaric oxygen therapy to increase tissue vascularity and promote angiogenesis. This has led to improved implant survival rates and lower complications in some reports, although not every study shows the same positive results. No conclusive recommendation can therefore be made in this regard.

In conclusion, any dental implant surgery should be delayed while the patient is under chemo- or radiotherapy. Only once the acute phase of chemotherapy has diminished, should one consider such treatment, as during chemotherapy, the risk of hemorrhage, infection, mucositis, and ulceration is much higher.

Antibiotic prophylaxis is usually considered if the patient has had chemotherapy in the immediate past. The surgeon should always consult the patient’s oncologist before planning any implant therapy, especially when radiation therapy was performed, to establish the areas of radiation and the dose used.

If the planned site for the implant placement falls outside the radiation area (i.e., a non-radiated zone of the mouth), an implant success rate comparable with a healthy patient can be predicted. A cancer patient can be a high risk for potential infections, hence why any periodontal diseases, caries, and inflammatory conditions have to be eliminated as soon as possible. Also, consultation with the patient’s oncologist should include projected patient survival, as in some cases the patient can survive for many years post-cancer treatment.

Diabetes

Diabetic patients with good glycemic control can, in theory, be treated like healthy patients when it comes to dental implant therapy. However, one has to be mindful of the changes that occur in the body when the patient is diabetic and bear these in mind when treating with dental implants.

Diabetes, in general, is associated with micro- and macrovascular diseases, an increased risk of infection, and delayed or altered wound healing, which can lead to postoperative complications. When implants are placed in a partially edentulous diabetic patient with periodontally involved dentition, the risk of complications is higher because diabetes is a key risk factor for periodontal disease. This could lead to alteration in the way the implant restorations are loaded over time, with subsequent failures as a result.

The clinician has to perform a thorough periodontal examination in the rest of the dentition with a view to treating and managing any periodontal problems before implant therapy in order to minimize the risks of implant failure later on. Studies have shown that trabecular bone volume is more negatively affected by diabetes (especially type 1) than cortical bone. It is therefore more likely that osseointegration will be negatively affected in areas of predominantly cancellous bone, such as the maxilla.

Areas such as the front region of the mandible with majority cortical bone seem to be less affected. Studies in animal models have also indicated that in type 2 diabetes, there is no significant difference in osseointegration or trabecular bone around implants between diabetic and non-diabetic subjects.

In type 1 diabetes, when insulin therapy is used to control the disease, bone-to-implant contact increases significantly, indicating the importance of good glycemic control for osseointegration. In conclusion, a good knowledge of the patient’s medical history and good glycemic control are critical when planning surgery on diabetic patients. Risk factors, such as infections and postoperative healing, can depend on how well or how poorly the patient is managing the disease.

It is agreed that diabetic patients are at a higher risk of infection (during and after surgery). The use of prophylactic antibiotics has been universally adopted by clinicians to prevent postoperative complications. Chlorhexidine mouth rinse has also shown to increase survival rates in both diabetic and non-diabetic patients when used postoperatively.

It is important that the whole dental team can recognize the signs when the patient seems unwell or about to go into hypo-glycemia, as it can be a life-threatening situation. A full knowledge of patients’ medications, when they took them last, and when they last ate, is important to have before starting surgery.

Valvular prosthesis placement

Valvular heart disease does not directly affect dental implant outcome; however, there is a major need for preventing potential infective endocarditis. As the cardiac tissue can be damaged in these patients, especially valves, the risk of bacteria-induced infective endocarditis can be high.

Preoperative rinses with chlorhexidine can be beneficial together with antibiotic prophylaxis. If any infection persists around dental implants in these patients, necessary steps need to be taken very quickly, such as removing the implants (the infection) under stringent conditions. Patients with valvular prosthesis placement must be vigilant with their oral hygiene to prevent infection.

Myocardial infarction

Patients with cardiovascular disease (CVD) can manifest any form of these conditions: hypertension, vascular stenosis, coronary artery disease, atherosclerosis, and congestive heart failure. These, in turn, can have a negative effect on blood and oxygen supply to the surgical site, thus affecting healing. Ischemic heart disease (coronary artery disease) can manifest itself as angina or myocardial infarction (MI). This can cause severe pain in the jaws, neck, and left arm, and most deaths occur within the first 12 hours. If the patient survives MI, recovery can take months and up to a year; therefore, it is suggested that any planned implant surgery should be delayed by 6 to 12 months, as it may endanger the patient’s overall health.

Some studies suggest that a very well-healed and recovered patient with no further risk of ischemia can undergo surgery by 6 weeks after the event. This has to be in close consultation with the patient’s physician, and a thorough assessment and consent has to be put in place.

Protocols to follow in these cases include the following:

• Blood pressure and heart monitoring
• Administration of oxygen
• Preoperative pain medication
• Stress management
• Deep anesthesia
• Premedication with nitrate

In general, the two main key factors are pain control and stress management. The surgeon must have knowledge of all the patient’s medications, such as anticoagulants and thrombolytic therapies, and understand the risks and benefits of considering implant therapy against interrupting these medications.

Stroke

An interruption in blood flow to the brain tissue can result in diminished levels of oxygen and glucose levels, resulting in neuronal ischemia and neurologic symptoms, and can lead to irreversible brain tissue damage.

The four different phenomena, based on their duration, have been described as follows:

• Transient ischemic attack
• Reversible ischemic neurologic defect
• Stroke in evolution
• Completed stroke

In general, strokes are classified as ischemic and hemorrhagic types based on original pathogenesis. The oral manifestations of strokes include altered or loss of feeling and unilateral paralysis of the face, loss of control over oral structures, leading to increased oral secretion, gag reflex, and an inability to speak clearly. Dysphagia-related problems (trouble swallowing) can also lead to poor fit of appliances due to weight loss.

In addition, oral hygiene is negatively affected, resulting in caries, and periodontal problems. Deferring any implant therapy for the first 6 months is good practice since stroke patients have to cope with a lot during the initial phase of recovery, and their stress and lack of motivation can affect implant therapy greatly.

A preoperative assessment of hemostasis is necessary in patients taking oral anticoagulants. Surgeons have widely accepted that atraumatic surgical techniques should be considered, together with topical hemostatic agents to control bleeding, rather than interrupting the anticoagulation. For international normalized ratios (INR — a measure of blood coagulation) greater than 3.5 and more complex surgery, the patient’s doctor should be consulted prior to performing any surgery. Dental surgeons should be mindful that interaction between oral anticoagulants and certain dental medications (such as metronidazole, tetracycline, and erythromycin) can increase INR. Prescribing alternatives and close monitoring of INR while on certain medication is vital for these patients.

This is not an exhaustive list — the next part of this series will continue reviewing systemic diseases, but further reading is strongly advised on any of these topics.

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