In this era of rapid technological advancement and self-awareness, the demand and market for dental implants have skyrocketed. The only thing that keeps patients from seeking dental implants is the cost. More implants are being placed where cost is not an issue, either due to a better financial position or flexible payment plans through installments. Although implants are easily osseointegrated (95% of cases) with low failure rates, complications, and implant failure can still occur with this technology.
In this blog, I will explain the factors that can lead to implant loosening and its failure.
So, let’s get started:
What is osseointegration?
It’s essential to understand the term osseointegration as it will be used repeatedly in the blog and is central to understanding the implant fixation to the bone. The term osseointegration (Osseo means bone) is a scientific term for healthy bone growth over and into the metal implant.
The implants are made of titanium, a biocompatible material that our body tolerates with no foreign body reaction. They are placed in sterile conditions and are left there for 3 months, during which the bone integrates and grows over the implant. After 3 months, the soft tissues (gums) are incised to expose the osseointegrated implant and a healing abutment is placed. Another 2-6 weeks will be needed for soft tissues healing, followed by the impression for the prosthesis (crown).
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Reason why dental implants fail
There are several reasons for implant failure, and are broadly classified into two categories: Early implant and late implant failure.
4 common Reasons for Early implant failure
The implant that fails before the crown placement and functional loading is an early implant failure. This problem is diagnosed at a 3-month check-up while implant exposure or impression-taking for the crown. The implant feels loose due to a lack of integration with the bone.
The following could be the reasons for the early implant failure:
- Damage to the bone while preparing the socket for implant placement. Inadequate saline irritation or overheating of the bone with the high-speed dental drill can damage the reparative cells in the bone, interfering with the implant’s healing and osseointegration. The damaged bone undergoes necrosis (death of reparative cells) and form a scar tissue around the implant. For the successful osseointegration of the implant, we need to recruit bone-forming cells to form a new bone, not a scar tissue that lacks reparative cells and contains fibrous connective tissue (predominantly collagen).
- It can also occur if you’re immunocompromised, a smoker, and on antidepressants such as SSRIs.
- Unqualified professionals or anatomical complexities (e.g less bone width and height to support the implant) may also interfere with the osseointegration.
- Poor oral hygiene and dental plaque can cause inflammation and impede bone healing.
- Poorly designed, low-quality implants may also fail to fuse with the bone.
Reasons for Late implant failure
Late implant failure can occur at any time after the successful integration (fusion) of the implant with the bone.
Dental plaque-induced Peri-implantitis
Significant bone loss due to peri-implantitis is the primary cause of implant failure. Peri-implantitis is an inflammation around the implant primarily due to plaque accumulation. Peri-implantitis is similar to periodontitis, which occurs around the teeth. Both involve the inflammation of surrounding supporting tissues: bone and gums. Therefore, an implant needs the same care as your natural teeth. They implant body (part embeded in the bone) functions analogous to the root of the teeth. The inflammation around the implant resorbs the surrounding bone, and an uncontrolled plaque accumulation eventually leads to implant failure (loosening of an implant).
Factors that increases the chances of late implant failure
Peri-implantitis is more common in people with periodontitis (advanced gum disease with bone loss around the tooth exposing its roots). Also, oral hygiene maintenance can be challenging with poorly placed and designed implants, so implant selection and an experienced surgeon are key to implant success.
Do implants need more care than natural teeth?
Implants need more care than natural teeth. In natural teeth, collagen fiber bundles from the bone are inserted into the roots of the teeth, gluing them tightly. In the implant-bone interface, the collagen fiber bundles orient themselves parallel or circumferentially to the implant, offering little physical resistance to plaque growing between the bone and implant. Therefore, strict oral hygiene measures are required for the longevity of an implant.
Teeth grinding and late implant failure
Parafunctional habits like teeth grinding can lead to crown or implant fracture. Dental implants are subjected to more stress due to the absence of attachment fibers between the bone and implant. These fibers distribute the stress over the large area of the bone. In implants, the lack of intervening attachment fibres causes stresses to concentrate at the crest of the bone. These continuous stresses beyond the critical limit lead to significant marginal bone loss and microfractures at the bone and implant interface.
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Nanoparticle release and peri-implantitis- raising questions about implant safety
Some scientists believe that the nanoparticle release (titanium and other metal particles) from the implant triggers an inflammatory response, leading to peri-implantitis. The macrophages, white blood cells, engulf these particles but can’t break them down. Instead, these particles disrupt their cellular function and trigger the cell’s natural cell, a process known as apoptosis. To avoid apoptosis, these impaired cells fuse to form giant cells – foreign body giant cells. These foreign body giant cells can potentially resorb bone around the implant, resulting in implant failure.
How does particle release from the implant occur?
The particles may be released during the placement of implant fixtures, probably owing to surface friction, and later on, wear between the abutment and implant fixture due to functional loading. Progressive implant surface degradation and corrosion may also cause particle release. Although titanium is corrosion-resistant at a healthy oral pH (6.3-7), the acidic environment (pH below 3.5), such as chronic (long-standing and low-grade) inflammation and acidic foods, may trigger its release.
The studies show that a significantly higher number of particles have been isolated at the peri-implantitis sites than at the healthy sites, suggesting that bacterial infection might have caused the release of nanoparticles from the implant.
Nanoparticles distributed to diffent organs
You’ll be surprised to know that titanium particles have not only been found in the mouth in the peri-implant bone, gums, and plaque but also at distant sites such as lymph nodes, lungs, kidneys, liver, and spleen. The macrophages or plasma proteins (transport proteins in the blood) might have transported them to a distant location through circulation. The systemic implications of these nano-particles are yet unknown.
Common implants types, their composition and how they interact with human tissues
Several different types of implants are used to replace a missing tooth. The common ones are grade 4 commercially pure titanium (4-CP), the alloyed grade 5 (contains 90% titanium, 6% aluminum, and 4% vanadium (Ti-6Al-4V), and alloyed Roxolid® (Straumann, Crawley, UK, made with 85% titanium and 15% zirconium (Ti-15Zr).
Several lab studies suggest that Grade 5 implants release significantly more nanoparticles at placement than the other varieties. Vanadium and aluminum in the implants are known to cause an inflammatory reaction.
Titanium dioxide nanoparticles can potentially cause inflammatory reactions and DNA damage. They also promote the replication of disease-causing bacteria in plaque, increasing the risk of peri-implantitis. There is a complex link between the implant material, plaque, and the body’s immune response, which warrants further research.
Nanoparticle-induced inflammation and giant cell formation often take years to cause recognizable bone loss and implant failure. This might also explain implant failure several years after implant placement in people with no apparent risk factors.
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Hypersensitivity reaction – an uncommon factor for implant failure
Dental implants contain impurities and trace metals, including iron, nickel, cobalt, and chromium, which can be toxic and trigger an allergic reaction, leading to implant failure.
Improper packaging can contaminate the implant and trigger a delayed allergic reaction. Therefore, the International Organization for Standardization (ISO 5832) and the American Society for Testing and Materials (ASTM F67-13) have set standards for dental implant manufacturing. The standards list the required composition of elements in the implants with ASTM grades 1-5 (commercially pure grades 1-4 and Ti-6Al-4V alloy grade 5).
Despite the ISO and ASTM standards for 1-5 grade implants, trace metals such as chromium, nickel, iron, lead, arsenic, and radioactive elements such as thorium 232 and uranium 238 in zirconia implants may be introduced in the implants during surface treatments such as abrasion, etching, and anodization.
Although most people tolerate titanium, a few cases of titanium hypersensitivity have also been reported. Similar to nanoparticle release, hypersensitivity reactions may take years to surface, explaining why some people with no risk factors may experience implant failure.
Tissue reaction to different implant systems and their contaminants makes analysis difficult because different implant systems and discrepancies in the batches of the same system are involved.
My thoughts and expertise
Nothing can replace natural teeth, so it’s best to keep them healthy as long as possible. As for tooth replacement options, dental implants are by far the best option for replacing a missing tooth, but everything comes with a risk.
Dental implants have an oxide surface coating to protect them from corrosion, but nanoparticles can still be released over time. These nanoparticles cause low-grade chronic inflammation and can lead to implant failure years after placement. Their release can be minimized by selecting a high-quality implant, less traumatic surgical technique, an experienced surgeon, avoiding low pH foods and plaque build-up.
Implant standardization, sterile packaging, and high-quality pure titanium make implants costly. If a dental practice offers an implant at a low cost, ask about the type of implant and the dentist’s expertise to ensure you’re getting the right thing.
If you choose to get an implant, good oral hygiene is the key to unlocking most mouth-related problems, including implant failure. Another factor you need to remember is choosing a reputable dental clinic that provides the best care.
Also, if you’re under stress, have a habit of clenching or grinding teeth, have allergies or are on certain medications, discuss this with your dentist. You may be given a mouth guard to prevent excessive pressure on the implant and its failure.
Conclusion
There is a 90-95% success rate in dental implants over ten years, but if they are not taken care of, they can fail. The most common reasons for early and late implant failure are bone resorption due to inadequate oral hygiene, premature implant loading, poor implant design, unqualified surgeons, existing periodontitis, lower immunity, and smoking.
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