Crestal bone loss in mandibular telescopic implant retained overdenture with milled titanium and milled poly-ether ketone ketones secondary copings. (A randomized clinical trial)
This randomized clinical trial found that after one year, mandibular telescopic implant-retained overdentures using milled PEKK secondary copings resulted in crestal bone loss comparable to those using milled titanium copings, establishing PEKK as a viable alternative treatment option.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
For millions of people, the loss of all teeth in the lower jaw is a quiet crisis. Without teeth, the jawbone slowly shrinks, the face loses its shape, and chewing becomes a struggle. While modern dentistry offers implants to replace lost roots, fitting a full set of false teeth onto just two tiny metal posts is a delicate balancing act. The teeth must stay firmly in place when biting, yet they cannot press so hard on the bone that it cracks or dissolves away. For decades, the standard solution has been a double-layered crown system: a metal cap fixed to the implant, and a second cap inside the denture that snaps over it. This friction holds the teeth in place. However, the metal-on-metal contact can sometimes irritate sensitive patients, and the rigid nature of metal does not always distribute chewing forces gently enough to protect the underlying bone.
Researchers have long wondered if a different material could solve this problem. A newer class of high-performance plastics, known for being strong yet slightly flexible, has emerged as a potential alternative to metal. The question was simple: could these plastic caps hold the denture just as well as metal, but without the harshness that might damage the bone? To find out, a team of scientists in Egypt conducted a careful, year-long experiment involving elderly patients who had lost all their lower teeth. They wanted to see if swapping the traditional metal caps for these advanced plastic ones would change how much bone was lost around the implants over time.
The study began with twenty patients, all between the ages of sixty and sixty-five, who had already lost their lower teeth. Each person received two dental implants, small titanium screws placed into the jawbone at the locations where the canine teeth used to be. Once the implants had settled into the bone, the patients were randomly assigned to one of two groups. One group received the traditional treatment: a secondary cap made of milled titanium, the gold standard material in dentistry. The other group received a secondary cap made of a material called poly-ether ketone ketone, or PEKK. This material is a tough, tooth-colored polymer that is stiffer than standard plastics but softer than metal.
The researchers did not just guess which material was better; they measured the results with precision. Every three months for a full year, they took highly detailed X-rays of the patients' jaws. These images allowed them to measure the height of the bone right next to the implants. They were looking for a specific sign of trouble: if the bone level dropped, it meant the implant was losing its grip on the jaw, a common issue that can eventually lead to failure. The team compared the bone loss in the metal group against the bone loss in the plastic group at every single check-up, from the moment the dentures were first loaded with chewing force up to the twelve-month mark.
The results were clear and reassuring. After a full year, there was no meaningful difference in the amount of bone lost between the two groups. Whether the patients had metal caps or PEKK caps, the bone around their implants remained stable. In fact, the average bone loss for both groups was less than one millimeter over the entire year, a figure that falls well within the range dentists consider healthy and acceptable. The data showed that the plastic caps did not cause extra damage, nor did they fail to hold the teeth in place. The bone loss patterns were nearly identical, suggesting that the new material performs just as well as the traditional metal in protecting the jaw.
Beyond the numbers, the study highlighted a practical advantage for the patients. While the bone health was the same, the plastic caps offered a cosmetic benefit that metal could not. Because PEKK is tooth-colored and does not show through the gums, it provided a more natural look. Patients in the study who received the plastic caps expressed a preference for them, appreciating that they did not have the grayish tint of metal. The researchers concluded that for patients needing a lower denture held by two implants, this advanced plastic is a completely viable and safe alternative to metal. It offers the same protection for the jawbone while providing a more comfortable and aesthetically pleasing option, proving that sometimes the best solution is not to stick with the old standard, but to embrace a material that is both strong and gentle.
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