A chemotherapy patient’s experience with dental implants

Dr. Bryan R. Krey and retired engineer Richard G. Dong join forces to facilitate implant placement during cancer treatment

Background
Dental problems of cancer patients are often worsened when the patient undergoes chemotherapy. Dentists and other dental care professionals have seen this. Dental problems definitely worsened for Dr. Richard G. Dong, a retired engineer, during his 3½ years of treatment with the chemo-therapeutic drug Bacillus Calmette-Guerin (BCG), a live bacteria injection used to treat bladder cancer. The problems included persistent infections developing in two existing molar dental implants on teeth Nos. 19 and 30. Dr. Bryan R. Krey is the oral surgeon performing the dental implant procedures and has followed Dr. Dong’s problems and his inventive ways of handling them. This article describes the simple instruments and techniques Dr. Dong developed that saved one of the existing implants and, together with Dr. Krey’s help, extended the life of the other by an estimated 2 years. Conclusions reached by Dr. Dong and Dr. Krey are summarized at the end of the article regarding the handling and designing of implants for individuals on chemotherapy or who had chemotherapy, and who had experienced worsened dental problems while on chemotherapy. Dr. Dong is a nonsmoker, with no diabetes or other systemic disorders. He exercises regularly and eats a healthy diet.

(Left to Right): Fig. 1; Fig. 2
(Left to Right): Fig. 1; Fig. 2

Effects of an altered immune system
The chemotherapy was to train Dr. Dong’s immune system to fight the cancer. The following might or might not be medically established, but from an engineer’s point of view, this means the immune system will be altered; and therefore, various changes in immunity reactions will progressively show up as the alteration increases. This was confirmed by the fact that various forms of immunity reaction came forth one after the other over Dr. Dong’s 3½ years of treatment. This included arthritic auto-immunity reactions, weakened ability to fight off certain bacteria, such as those causing dental problems and those caus-ing cellulitis. Dr. Dong’s last treatment resulted in a severe rash all over his body, as his immune system became sensitized to the drug. Thank goodness it was the last treatment; who knows what else might have arisen next. General tiredness, headache-nausea reactions to weather changes, and allergic reactions to certain foods also developed. The bladder became hyper from three rounds of surgeries and from the prolonged exposure to the chemotherapy drug. Hyper is defined here as constant urgency and frequency to urinate on an hourly basis. Therefore, this is also at least partly an immunity reaction. Besides the immune system becoming more able to fight the cancer, a secondary positive change was that his seasonal hay fever became much milder.

Not everyone would react the same way to this particular chemotherapy, and therefore, not everyone is necessarily going to have the reactions mentioned. Everyone’s immune system is different. This is becoming increasingly clear in general cancer research. Immune systems in individuals could vary widely as revealed in current research using humanized mice. The immune systems of numerous individuals are grown in mice to study their reactions to various cancer-fighting drugs and various cocktails of the drugs. The reactions were found to vary widely among the immune systems.

Ideally, the longer the chemotherapy Dr. Dong received could continue, the more his immune system would be altered to fight the cancer. However, it became apparent to him that the likely reason the standard duration is set at 3½ years is because that is probably what a typical patient could tolerate before the immunity reactions become more intolerable than the cancer. However, at the current level of alteration, Dr. Dong prefers to put up with current reactions than to have his immune system return to how it was, thus allowing the cancer an increased chance of recurring.

Implant failure increases when the implant procedure is timed near or during chemotherapy
Bone formation takes place slowly to fill in the hole left from a tooth extraction. After 4 months, enough bone has usually formed to enable the implant post to be installed. But an X-ray would clearly indicate the bone has not yet reached normal density. Four months after that, the crown is usually installed. An X-ray would indicate the bone density is better but still not at normal level. From an engineer’s perspective, the bacteria could now begin accumulating at the crown-implant junction. The surface transitioning from the crown to the post would not be perfectly smooth, as could be seen on the implant removed from Dr. Dong’s molar tooth No. 30 site. The crown and post are minutely different in diameter and roundness such that a tiny ridge and a tiny shelf are formed there. Tiny gaps likely also exist at various locations where the crown mates with post. Such imperfections are deeply located and somewhat hidden since they are not easily reached during brushing and flossing. Bacteria could accumulate at these imperfections and then migrate to where the post meets the bone to initiate bone loss. Also, as pointed out by Dr. Dong’s regular dentist, the migration is intensified by the “pumping” action during food chewing. There must be reasons why bone loss occurs after the crown is installed, and the factors mentioned seemed logically to be why.

(Left to RIght): Left two images: Fig. 3; Middle: Fig. 4; Right: Fig. 5
Left two images: Fig. 3; Middle: Fig. 4; Right: Fig. 5

If bone density were less than normal, the initiation of bone loss would be easier, and continued bone loss would be faster. In addition, if the patient’s immune system’s ability to fight the bacteria were weakened by chemotherapy, the entire bone loss process would progress even faster. Under this condition, the pocket formed by bone loss could quickly grow to where the bacteria would have many corners and crevices in which to hide and colonize. Once colonization occurs, the bacteria would be more difficult to dislodge and eliminate, bone loss might be slowed with extraordinary care but not stopped, and the implant would eventually fail.

Under normal circumstances, with the patient’s immune system well able to fight off the bacteria, bone loss could initiate but would stabilize and essentially stop. The implant would then be successful. An X-ray could show a small amount of bone loss, but that would be considered normal.

Dr. Dong’s experience with implants appears to match the descriptions in the preceding paragraphs. Four of his molars at different times needed to be replaced with implants, and chemotherapy affected all four. The following are the timelines relative to the beginning or ending of chemotherapy.

Molar 19

  • Implant post was installed 1.25 years before chemotherapy began.
  • Crown was installed 0.88 years before chemotherapy began.
  • While chemotherapy affected this implant, the implant was saved by the procedure developed by Dr. Dong.

Molar 30

  • Implant post was installed 1.0 year before chemotherapy began. Crown was installed 0.63 years before chemotherapy began.
  • The implant failed due to effects of chemotherapy, in spite of Dr. Dong and Dr. Krey’s best efforts, and was removed 1.4 years after chemotherapy ended. Thus, the implant lasted 5.53 years after the crown was installed.
  • The implant procedure is currently being repeated. Implant post is not yet installed.

Molar 18

  • Molar 18 was extracted 1.06 years after chemotherapy ended and about 0.06 years after the chemotherapy drug completely left the body.
  • Implant post was installed 1.4 years after chemotherapy ended and about 0.4 years after the chemotherapy drug completely left the body. Crown is not yet installed.

Molar 31

  • Molar 31 was extracted 1.7 years after chemotherapy ended and about 0.7 years after the chemotherapy drug completely left the body.
  • Implant post is not yet installed.
  • The fact that molar 31 went bad quickly could indicate that Dr. Dong’s immune system remains altered and was thus unable to fight the bacteria adequately. His urologist treating the cancer and his primary care doctor indicated his immune system is likely to remain altered for the rest of this life, especially since chemotherapy was done at his somewhat advanced age of 70 years.

Dr. Dong had quite a few dental problems even before he had cancer. According to his dentist, he keeps his teeth so clean; he should not have so many problems. Consequently, it must be in his genes. The need to replace molars 19 and 30 with implants happened before chemotherapy began. However, infections and gum swelling, bleeding, pocket formation, and bone loss started happening soon after chemotherapy began.

The molar 19 implant remains successful while the molar 30 implant failed. Molars 19 and 30 are at the same locations at opposite sides of the lower jaw. Therefore, their environments should be essentially identical. A notable difference is the molar 19 implant had 3 months more to increase bone density than the molar 30 implant had before chemotherapy began. The 3 additional months apparently enabled the bone density for the molar 19 implant to reach a high enough level to prevent the rate of bone loss from becoming unstable.

Molar 18 experienced multiple problems while Dr. Dong was undergoing chemotherapy. The dentist and Dr. Dong did their best to save molar 18, but couldn’t. It seemed that once the bacteria gained a foothold, it is very difficult to stop the destruction when the immune system is unable to fight the bacteria well enough.

An infection occurred at the periapical region of molar 31’s roots, and it led to the molar’s loss. Age-related gum recession exposed the bifurcation point between the roots and allowed bacteria to enter. An earlier root canal eventually resulted in root brittleness, and one root developed a crack that allowed the bacteria to migrate to the lower region of the roots. The entire process happened very quickly and could not be caught even with biannual hygienic cleaning and inspection by the dentist. The process apparently accelerated because the immune system was unable to fight off the bacteria well.

Stopping the 4-week cycling between infections and healing
The gum surrounding molars 19 and 30 implants started getting infected, swollen, and bleeding shortly after chemotherapy began, and worsened as chemotherapy continued. Pockets started to form, and a bit of exudate could be expelled when pressure is applied to the pockets. The problem occurred at the buccal face side of the implants but not at the lingual side. For some reason, this is common. Perhaps the pressure and motions of the tongue kept the bacteria from gaining a foothold at that side of the implants.

Dr. Dong tried handling the problem by brushing, flossing, and using an interdental brush, but none worked. It became apparent that blood clots and other materials the bacteria could cling to or hide in must be removed, and that some method of flushing them out needed to be developed. Therefore, he made some instruments consisting of various shapes of plastic toothpicks, toothpick holders that hold toothpicks at 90º from the handle, an eyedropper, a length of flexible plastic tube 0.05 inches outer diameter, and a covered low container of Listerine®. Plastic toothpicks rather than wooden ones were used because plastic ones would not fray and lose their shape.

The steps in the procedure Dr. Dong developed are as follows:

Step 1:

  • He used the smooth, round blunt end of a toothpick holder to gently rub against the pockets to expel the exudate accumulated in the pockets.
  • The exudate would be a larger amount and a bigger concern when infection exists. If infection does not exist, the exudate would be a smaller amount and of minor concern.

Step 2:

  • A blunt toothpick was used to scoop up the exudate.
  • The mouth was rinsed with plain water before performing the next step.

Step 3:

  • The reason for omitting this step here will be explained later in the article.

Step 4:

  • A more sharply pointed toothpick is used to slightly enlarge the front and rear openings of the pocket and to mechanically gently dislodge the bacteria from the surfaces of the pocket. The center edge of the pocket is usually still attached to the post, and this part of the pocket is not to be forced open. Otherwise injury would occur leading to infection. Step 4 is performed only if the openings of the pocket are large enough to allow the toothpick to easily enter, as was the case for the molar 30 implant.
  • If the openings of the pocket are very small, as is the case for the molar 19 implant, Step 4 is omitted, and Step 5 would still be effective.
  • The mouth is rinsed before going to Step 5.

Step 5:

  • The syringe made with an eyedropper with a length of 0.05-inch outer diameter flexible plastic tube fastened to it with a glue gun. This is used to squirt Listerine into the pocket to flush out the bacteria and any other materials. The tube is inserted into one of the two openings widened in Step 4, and that part of the pocket is flushed. This procedure is repeated with the other openings. Flushing is repeatedly alternated between the two openings until all the Listerine in the eyedropper is used up.
  • If the pocket was bleeding to begin with, Step 5 was performed three times to stop the bleeding. A blood clot must not be allowed to form in the pocket. Listerine apparently has an ingredient that helps stop the bleeding.
  • As explained, Step 4 is omitted for the molar 19 implant. Squirting the Listerine into the pocket through openings as they already exist without being further opened by Step 4 seems to work adequately for the molar 19 implant.
  • The mouth was rinsed, and the usual teeth brushing was then performed for the entire mouth.
  • A flexibility syringe made as explained works better and safer than using a standard rigid syringe. The plastic tube was held at the opening of the pocket with one hand, while the other hand squeezed the eyedropper. The flexibility of the plastic tube enabled the tube to be easily and safely held at the opening of the pocket. This is likely to be much more difficult to do using a standard rigid syringe.

Step 3 is left blank in the above list for the following reason. The four steps listed would dislodge and flush out the bacteria and thus promote healing. However, as healing progresses, the gum would tighten against the post. Steps 4 and 5 would then become more difficult and less effective to perform. Consequently, the bacteria begins to re-establish in the pocket. This caused infection to start again. The infection and swelling would cause the openings of the pocket to enlarge. This then enables Steps 4 and 5 to be more easily and effectively performed. Healing would then be promoted again. The net result is we get 2 weeks of healing followed by 2 weeks of infection, swelling, and bleeding. This 4-week cycle continues to repeat with only the four steps listed above.

Dr. Dong discovered that by adding a Step 3, the 4-week cycle would be stopped. In Step 3, he uses a toothpick, not quite as pointed as the one used in Step 4, to clean the gum line around the post where brushing and flossing would not reach. This would be where a tiny trough is formed over the length of the edge of the pocket that remains attached to the post. This is the length of the edge of the pocket that is not to be opened in Step 4. Apparently, this trough provides a lodging site for the bacteria. When the pocket could not be flushed out very well, these bacteria would migrate into the pocket and add to those not flushed out. The total would reach a level that would cause infection to start. Step 3 is as follows:

Step 3:

  • Use a toothpick not quite as pointed as the one used in Step 4, and clean along the gum line at the face side and the tongue side of the implant. While cleaning the tongue side is probably not necessary, you might as well do it just in case.
  • The mouth is rinsed before performing Step 4.

By adding Step 3, the 4-week cycle was stopped. Bone loss in the molar 19 implant was stabilized, and the implant was saved.

Unfortunately, the addition of Step 3 was unsuccessful in saving the molar 30 implant. The pocket there had become so large and deep with so many corners and crevices in which bacteria could hide that while the 4-week cycle was stopped, enough bacteria remained in hiding to cause continued bone loss even without apparent infection. Dr. Krey tried cleaning out the pocket to minimize the places where bacteria could hide, but as he later explained, once the bacteria colonized within the pocket, they were very difficult to completely dislodge and flush out. In this case, “colonization” means the bacteria became established in some hard-to-clean and flush locations in which to hide and breed. Nevertheless, by stopping the 4-week cycle and thus slowing the rate of bone loss, the molar 30 implant’s life span was extended by 2 years, by Dr. Dong’s estimate.

Best to repeat the procedure every 12 hours
Based on Dr. Dong’s experience, the procedure described is best repeated every 12 hours. This enables the openings of the pocket, in the case of the molar 30 implant, to remain reasonably open so that Steps 4 and 5 could be performed effectively. If more than 12 hours have passed, the openings would decrease to where Steps 4 and 5 could be more difficult or impossible to perform. Then infection could start again. If the procedure were performed more frequently than every 12 hours, injury and inflammation could occur leading to infection.

Every step of the procedure must be done not too gently or too forcefully, even while squirting Listerine into the pocket. Enough force is needed to dislodge or flush out the bacteria, but too much force can cause injury followed by infection. The tissue inside the pockets is very tender and fragile since it is well protected and not toughened by exposure during brushing, flossing, and contact with foods.

Conclusions

Based on the differences in the behaviors of the molars 19 and 30 implants, and how installing the crown on the post could initiate bone loss, Drs. Dong and Krey came up with two conclusions. If the patient is under chemotherapy or had chemotherapy in the past, and if dental problems significantly worsened while on chemotherapy, then Conclusion 1 would apply.

Conclusion 1
Installing the crown onto the post should be delayed to allow more time for the bone density to reach a high enough level to prevent easy initiation of bone loss followed by a fast rate of bone loss. How much delay time is required to achieve this is not known at this time. However Dr. Dong’s experience indicates waiting 1.25 years after the post is installed would most likely achieve the desired result. But waiting 1.25 years is probably longer than really necessary. According to Dr. Dong’s experience, an increase of 0.25 years in doing the implant procedure before chemotherapy commenced was enough to make a significant difference. While this is not the same as waiting 0.25 years before installing the crown onto the post, it does confirm that allowing extra time for the bone density to increase before chemotherapy begins is beneficial. Therefore, instead of waiting 1.25 years to install the crown, we could try doubling or tripling the standard waiting time of 4 months after the post is installed before installing the crown and see if that is enough to achieve the desired result. Dr. Dong plans to try this for the molars 18, 30, and 31 implants and could report on the results at a later time.

The post installed at the molar 18 site has a new design to help hinder the migration of bacteria to where the post meets the bone. The new design has the same overall proportions as the preceding design except a location that is a short distance below the top has a smaller diameter. This forms a circumferential grove for the gum tissue to grow into. This makes the path more difficult for the bacteria to negotiate to reach where the post meets the bone. In Conclusion 2, Drs. Dong and Krey present another possible new design for the implant post following a different approach to preventing bacteria from migrating to where the post meets the bone.

Conclusion 2
As stated earlier, tiny imperfections, such as a ridge, a shelf, and gaps, formed where the crown meets the post are possible sites for the bacteria to accumulate. These sites are not easy to reach during brushing and flossing. The bacteria could accumulate there and then migrate to where the post meets the bone to initiate bone loss. This chain of events could be avoided if the post and crown were reconfigured. The crown-post assembly has the shape of a wine glass with a very stout stem minus the base. The tiny imperfections would be located where the cup meets the stem. If the imperfections were relocated higher up onto the cup, then any bacteria accumulated there would be more exposed and more easily removed by brushing and flossing. This would eliminate the imperfections as sites where bacteria could accumulate, and from which to migrate to where the post meets the bone. The post would have a head similar to how a flat-head wooden screw has a head. The crown would be flatter to accommodate the head on the post. The appearance might not be desirable if the base of the implant is visible to others.

The implant post design presented would benefit any dental implant recipient regardless of whether or not the recipient is going through chemotherapy or had worsened dental problems while on chemotherapy in the past.

Richard G. Dong, PhD, was born and raised in Sacramento, California. He earned his BS and MS degrees in Mechanical Engineering at the University of California in Berkeley, California. He worked for 2 years at the Aerojet-General Corporation in Sacramento, California. He returned to the Berkeley campus and earned his PhD in Structural Mechanics. He then worked at the Lawrence Livermore National Laboratory in Livermore, California, as a research engineer and as one of the technical reviewers for the laboratory’s Nuclear Test Program. He retired in 1993. He lives in Danville, California, where he and his wife raised two children.

Bryan R. Krey, DMD, was born and raised in Brentwood, California. He earned his dental degree at Oregon Health and Science University in Portland, Oregon, in 1993. He completed his Oral Surgery residency at Highland Hospital in Oakland, California, and later completed his board exams and is a Diplomate of the American Board of Oral and Maxillofacial Surgery. He is in private practice with offices in Berkeley and Orinda, California. He lives in Lafayette, California, with his wife and four children.

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