No implants for smokers?

You’ve probably heard or read that smoking can be a risk factor for dental implant failure. But does that mean that you will turn away someone who smokes, telling them that they are not a candidate for dental implants?

Are you 100% sure that smoking is a risk factor?

Recently, I had a dental student tell me that smoking is NOT a risk factor for implant failure because of some study that showed that there was no difference in the success rates. I was doubtful, but I checked his reference and…he is right!…sort of.

This article will first describe the biology of how smoking affects bone repair, then briefly cover what the literature says, and finally provide some clinical suggestions for how to modify your treatment.

The Biology Behind it All 

Angiogenesis and osteogenesis are essential to successful osseointegration of a dental implant.

It’s easy to understand why angiogenesis is important. The growth of new blood vessels brings oxygen and growth factors into the implant site, thereby facilitating healing.

It is a well-documented relationship:

Enhanced angiogenesis will lead to enhanced bone healing while inhibited angiogenesis will impair bone healing.

So do you think smoking enhances or inhibits angiogenesis?

According to a study by Ma in 2010 (they performed distraction osteogenesis on poor little rabbits!) smoking actually increased angiogenesis. (My mind was blown!)…but, at the same time, smoking also reduced blood flow.

More blood vessels but less blood flow? This was their hypothesis:

• Nicotine causes vasoconstriction which decreases the delivery of blood to capillary beds, leading to tissue hypoxia.
• This oxygen deprivation stimulates the creation of more blood vessels.
• While there may be more blood vessels, the vasoconstrictive effect of nicotine does not allow this increase in blood vessel density to lead to a higher blood flow.

Just as important is the role of Bone Morphogenic Proteins (BMPs), which are the main osteogenic factors in the body. This study by Ma also showed that nicotine had an inhibitory effect on BMP-2, thereby, inhibiting osteogenic activity.

So smoking basically cripples two of the most important processes in osseointegration: blood flow and growth factors.

But Does it Really Make a Difference?

Remember about the study the student was telling me about? It was written by Wang et al in 1996. They found that success rates for dental implants in smokers and non-smokers were the same.

How could smoking not matter? This contradicts all of this biology we just read about.

It turns out that this study had many limitations that should cause us to take it with a grain of salt:

• Their sample size was small
• They only followed up the patients for 36 months
• They only placed the implants in loose trabecular bone

Not that we should dismiss their findings, but we should view them in the context of a broader review of the literature.

What’s the Literature Say?

A review by Chrcanovic(2015) and another by Klokkevold (2007), help us to demystify what is really the deal with dental implants in smokers. These are the golden bits of information I pulled out of these articles.

Smoking…

1. Does promote greater marginal bone loss.
2. Does not have a big effect on implant failure in good bone sites.
3. Significantly increases failure risk in poor bone sites–especially evident over longer periods of time.
4. Increases risk of post-operative infection.

The Clinical Applications

Because we know that smoking will cause more marginal bone loss, we should take extra measures to maintain bone.Maybe we should be more likely to recommend socket grafting after extractions as well as ridge augmentation during implant placement when indicated.

Because we know that smoking does not have a huge impact on good bone sites, we generally should not be worried about implants in the anterior mandible and, all things equal, we can treat them the same as in a non-smoking patient.

As the bone quality decreases to include more porous bone, it would be prudent to get a little more paranoid and cautious. While immediate placement might still be reasonable in some special situations in the esthetic zone, perhaps we should shy away from immediate placement as the bone quality decreases.

Remember that one way to assess bone quality is via a bone density assessment from a Cone Beam CT. (See: Hounsfield Units for Implant Surgery)

Also, because smokers are at a higher risk for post-operative infection, it would be wise to closely follow them during the healing period. Perhaps, you may want to emphasize the importance of a one-week follow up visit as well as diligent compliance with proper oral hygiene.

I personally, will definitely not be looking to immediately load anything. (except for full arch prostheses because of the cross-arch splinting effect) I know everyone says they do it all the time and have marvelous success, but I am a strong believer in taking every opportunity possible to incrementally improve the outcome. I think that delayed loading protocol in smokers can improve the overall success rate.

Finally, there is one article by Bain, that reports significantly increased success rates in smokers when followed a protocol of smoking cessation 1 week prior to implant surgery and for 8 weeks after.

While your patient’s smoking habit can work against you, by understanding the risks and then managing them accordingly, you can place implants confidently in spite of this risk factor.

References:

Ma Li et al. Uncoupled Angiogenesis and Osteogenesis in Nicotine-Compromised Bone Healing. Journal of Bone and Mineral Research, Vol 25. No. 6, June 2010.

Ma Li et al. Influence of nicotine on the biological activity of rabbit osteoblasts. Clin. Oral Impl Res. 22, 2011; 338-342. 

Wang IC, Reddy MS, Geurs NC, Jeffcoat, MK. Risk factors in dental implant failure. J Long Term Eff Med Implants. 1996;6:103-117.

Chrcanovic, Bruno et al. Smoking and dental implants: A systemic review and meta-analysis. Journal of Dentistry 43(2015)487-498.

Klokkevold Perry, Han Thomas. How do Smoking, Diabetes, and Periodontitis Affect Outcomes of Implant Treatment? Int Journal of Oral Maxillofacial Implants. Volume 22, Supplement, 2007. 

Bain CA. Smoking and implant failure–Benefits of a smoking cessation protocol. Int J Oral Maxillofac Implants; 11:756-759.