Dental Implant Success & Failure: Risk Factors

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I’m Dr. Joshua Green and today I’m going to talk about dental implants. They are phenomenally successful. Many studies say that they’re 90 plus percent successful on healthy patients, but things can go sideways.

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I’m going to get into some of the things you need to watch if you’re a patient or a practitioner. Local risk factors, systemic issues—some may even surprise you—and infections and biofilms, which can cause rapid losses of implants.

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There was a very interesting paper that came out. It was a Monte Carlo simulation. What this showed is that it’s not a single factor. Certain factors when combined create an increased risk more than the sum of their parts.

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If you have a patient that not just smokes but also has periodontal disease, bone loss, they tend to have a much higher degree of failure. Same thing with short implants combined with periodontal disease—it’s even worse.

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I’ve seen implants placed on the same patient at the same time, right next to each other. One will succeed and one will fail. So a tiny difference in the starting point can create a completely opposite result.

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There are specific genetic traits. One is an Interleukin-1 genotype. This creates a pro-inflammatory cascade that predisposes patients to implant failure and periodontal disease.

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Implant failures tend to be clustered on certain patients. Half of failures occur on a third of patients. If a patient has had a failure before, it greatly predisposes them for additional failures.

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Local risk factors: When you place an implant, it needs to go in the bone. The quality of that bone plays a huge role. The majority of failures occur in soft bone—Type 4 bone, roughly the density of styrofoam.

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Type 4 bone is usually found in the posterior maxilla, the upper jaw. It’s not as vascular and doesn’t have the same blood supply as higher quality bone. The implant may not be as stable.

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You also see increased failures when there’s an infection in the site, if you place an immediate implant, or if there’s a bone graft. Anything that means bone is not highest quality makes it less likely to integrate.

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Short implants have less surface area, so they’re not as stable. Also, the reason short implants are placed is because the bone isn’t thick enough—thin bone means less blood supply.

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Surgical trauma or overheating is a big one. The number always said is 47°C for 60 seconds. But drilling in hard bone with dull burrs can get incredibly hot—over 70° or even 100° in worst cases.

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That’s why it’s best to have copious irrigation. Even chilled irrigation is a good idea. Lack of primary stability means when the implant is placed, it’s not rigidly fixated.

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If it gets loose enough, fibrous scar tissue will form around it instead of bone. Reasons include overpreparation—the site was prepped too wide—or the practitioner became indecisive creating wobble.

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Contamination of the implant doesn’t take much. Staphylococcus is a cause of implant failure and can cause catastrophic results. There could be infection within the site, poor quality bone, or residual granuloma.

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There’s a lot of bacteria in the mouth. That’s why you see improvement in results with measures of sterility, antibiotics, controlling the surgical field, even using a pre-op mouth rinse.

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Operator experience matters. The ability to efficiently create a full thickness flap, deliver the implant quickly, and suture everything closed reduces dry time of the bone and leads to better results.

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Radiation of the site: if somebody receives 50 grays of radiation, it can have a drastic effect on bone marrow. You may need roughly a year and medical consults. This can be an absolute contraindication.

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Systemic risk factors: It’s not only local, but the patient’s ability to respond to the implant. Smoking is a major risk factor—not just dental implants but hip implants, knee implants, all implants.

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History of periodontal disease is absolutely huge. It increases not just early failures but late failures too. Similar bacteria found on failing teeth are also found on those implants.

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Diabetes, especially if poorly controlled, can lead to a huge variety of problems. Implants can be placed very well on healthy folks, but if not healthy, you could have a ton of issues.

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SSRIs have been shown to greatly increase chances of issues, roughly doubling them. The thought is that osteoblasts may use serotonin as a neurotransmitter.

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Proton pump inhibitors—this is surprising—have another doubled risk of inflammation. Osteoporosis and bisphosphonates: IV bisphosphonates are an absolute contraindication.

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High amounts of oral bisphosphonates, especially combined with high-dose steroids and anti-angiogenic medications, can also be contraindicated. Osteoporosis leads to more failures.

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Vitamin D deficiency is another surprising one. I live in a northern latitude so you see this a lot. Elderly folks especially have issues—double or triple your failure risk.

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It’s becoming more common to check vitamin D levels before implant surgery if patients show risk factors. Other systemic factors include immunosuppressive conditions and age.

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Bruxism: people that clench their teeth are more likely to break what you put in their mouth. Poor oral hygiene—very often the same reason that caused tooth loss can cause implant loss.

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Peri-implantitis, bone loss around implants, and long-term failures from biofilms. The surface of implants is hospitable to microbes—it’s very rough and they can live on it extremely well.

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Once a biofilm forms, it’s incredibly difficult to get rid of. During initial healing, it can destroy bone directly and prevent osseointegration. You’ll see pain, swelling, mobility within a month.

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Biofilms are resistant to common antimicrobials. These are hardened fortresses similar to those in periodontal disease. In severe cases, bacteria can resemble osteomyelitis on x-rays.

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How do you avoid this? Have a thorough medical history, thorough evaluation, proper case selection, patient education, and treatment planning. Habit modification—especially smoking cessation.

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Medical management: glycemic control in diabetics, proper nutrition post-surgery, appropriate antibiotic prophylaxis, controlling vitamin D levels, and controlling active periodontal disease.

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Within surgical protocol: aseptic technique, copious irrigation, controlled speed, sharp burrs, chilled liquid, gentle handling. Planning and guiding surgery reduces chair time.

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Grafting when indicated. PRP, PRF can help healing. Osteodensification can compress bone and achieve greater initial stability. These techniques together help achieve success.

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Loading restorations: optimize health first, do surgery perfectly, then determine loading. In some patients, especially immediate cases, you may want to wait additional time.

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Key takeaways: evaluate risk factors—some may surprise you like PPIs and SSRIs. Optimize patient condition. If you’re unable to, you may not want to proceed with the case.

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Never forget occlusion and properly engineering the case. Design appropriate prosthetics based on their bite. Finally, maintain these cases so they can be preserved as time goes on.