Stem Cells in Dentistry ?!?

Absolutely !!  Oral Surgery in general and bone grafting in particular are starting to make a transition.  More and more bone grafting scenarios employ cell-based or growth factor-enhanced grafting material.  Four items are absolutely essential in bone regeneration if predictable results are sought.

  • A matrix or scaffolding (collagen, bone mineral, synthetic grafts)
  • Cells (stem cells, platelets, osteoblasts)
  • Signaling molecules (growth factors, morphogens, adehsion molecules)
  • Time (often underestimated)

Within minutes after an “injury” to the bone structure, platelets aggregate in the area and release PDGF (Platelet Derived Growth Factor) and a variety of TGF-beta (Transforming Growth Factor – beta) molecules, to which BMPs (Bone Morphogenic Proteins) belong.  Some of the BMPs signal the Mesynchemal Stem Cells (MSCs) to “morph” into bone-precursor cells (osteoprogenitor cells).  Subsequently, PDGF signals these precursor cells to divide rapidly, in order to increase their number.  Once their number has increased (usually by an order of magnitude), a different set of BMPs will signal the precursor cells to “morph” again into mature bone-building cells (osteoblasts).

From this somewhat simplified molecular “injury cascade”, we can certainly appreciate the importance of stem cells.

A quick word on stem cells, because it has brought up some ethical and political issues in the past.  There are three types of stem cells in our body:

  • Embryonic Stem Cells (most potent, can form every tissue in our body)
  • Fetal Stem Cells (almost as potent, but somehwat more restricted in what they can become.  Often harvested from the umbilical cord and cryogenically frozen)
  • Adult Stem Cells (a.k.a. mesynchemal stem cell.  This cell is already committed to form only tissues of mesynchemal origin, i.e. bone, muscle, cartilage tissue, etc.).

The embryonic stem cells are the ones wich caused all the ethical controversy and to this day we can not perform any experiments with this cell lineage here in the U.S.  This cell line is extremely potent and can form any kind of tissue from all three primitive germ layers.

Our interest, however revolves around the Adult or Mesynchemal Stem Cells.  It stands to reason that an increased number of such stem cells during an “injury” or bone surgery can not only improve but also accelerate the bone healing.  It is now possible to use stem cell-fortified bone graft material (several thousand times the cell concentration of the human body), for various grafting procedures.  This graft material is very expensive and must be delivered within a day of surgery.  Initial results look very promising across several research studies.

Bookmark and Share


How many dental implants do I need to get rid of my denture?

This can be a tricky question.  First, I am going to assume that you want a fixed appliance or at least an appliance that gives you the same chewing power as a fixed appliance.  There are many people that do fine with removable dentures (plates), but then there are others, who really suffer with their dentures.  The empirical fact, however is this:  With a very well fitting pair of dentures (and that is very rare !!) a patient can achieve at most about 15% of their original biting power.  As you can imagine, this can severely limit your nutritional intake as well as your food enjoyment.  Dentures typically cover the whole palate.  Well, it just so happens that a great deal of taste buds are located in the palate, which are suddenly excluded from the tasting experience.

Now, in order to restore such a case to full functionality, we need several implants to gain enough bone anchorage in order to get the patient back to about 90% of their original biting force.  At a minimum 8 implants are recommended in the upper jaw and at a minimum 6 implants are recommended in the lower jaw (the bone is generally denser in the lower jaw !).

Additionally, the upper jaw may still need to be somewhat removable for the patient, so that he or she can clean the support structures for the appliance or prosthesis better.  This is not as often the case in the lower jaw.  The reason for this is that there is usually a flange on the lip side of the upper jaw prosthesis (see pictures below) and a little extension on the palatal side, to assure a good phonetic seal.  It is impossible to clean underneath this type of appliance if it was fixed.  We therefore often make “Fixed-Removable” appliances, which give you the same biting power as a completely fixed appliance, but can be removed for cleaning purposes.  Below are a series of images, which illustrate a “Fixed-Removable” appliance for the upper jaw.

X-ray of 8 implants in the upper jaw

X-ray of 8 implants in the upper jaw

Here we see an x-ray image of implants placed into the upper jaw.  We chose 8 implants to give the patient enough support to be able to chew “steaks” again.  In this image one can see that the lower teeth need some extensive work too, but the patient wanted to get started with the upper arch first, because he could not tolerate his denture anymore.

8 implants in the upper jaw with abutments connected

8 implants in the upper jaw with abutments connected

This image shows the implants in the patient’s mouth.  actually what is visible are the abutments, which are connected to the implants.  The implants themselves are buried in the bone and underneath the gum tissues and are therefore not visible.  These abutments, however are custom milled abutments which exhibit a 3-degree taper.  This is necessary, because the appliance will attach to these abutments via simple friction fit.
Fixed-Removable Appliance

Fixed-Removable Appliance

In this image we can see the appliance itself.  As you can see, it has only minimal extensions of acrylic and no palatal coverage.  The amount of pink acrylic necessary will largely depend on the amount of bone and gum tissue loss that has happened prior to the implant placements.  Once teeth are extracted, bone and gum tissue will shrink away.  That is an inevitable fact.  The less tissue loss we have, the less pink acrylic we have to use.
Palatal side of the Fixed-Retrievable appliance

Palatal side of the Fixed-Retrievable appliance

This image shows the flip side ( the palatal side) of the “fixed-retrievable appliance.  You can clearly see that it is metal re-enforced, in order to give it good stability and fracture resistance.  Furthermore, you can appreciate the “golden” metal caps.  These are the “female” friction components to the custom abutments shown above.  The patient will be able to positively seat the appliance without any rocking and will also be able to “wiggle” it back out.  The chewing power the patient gains is similar to that of a completely fixed bridge.  Additionally, the bone and gum tissue resorption has been arrested.  Since the dental implants are bone anchored devices, they transmit enough of a “stimulus to the bone, to maintain itself rather than resorb.
Please keep in mind that this represents only one out of many appliance options that could have been used in this scenario.  The one which is depicted here is a result of what worked best for this particular patient along several parameters.

Bookmark and Share

Can I get a dental implant if I take Coumadin?

Coumadin is an anticoagulant (blood thinner), which reduces the formation of blood clots. It does so by blocking the synthesis of certain clotting factors. A reduction in clotting factors will also reduce the chance of any blood clot formation.

Coumadin is predominantly used to prevent heart attacks, strokes and blood clots in veins and arteries as well as around prosthetic devices, such as artificial heart valves. The down side of Coumadin are the prolonged bleeding times. This is of great concern to anyone who needs to undergo minor surgery.
Many patients who take Coumadin get their INR (International Normalized Ratio) and PT (Prothrombin Time) tested on a regular basis. The Prothrombin time (PT) evaluates the ability of blood to clot properly, whereas the International Normalized Ratio (INR) is used to monitor the effectiveness of blood thinning drugs such as Coumadin (or also Jantoven, Marevan and Waran, which are all brand names for the generic Warfarin).

Most dental surgeons will look for the INR assessed a day prior to surgery, to determine whether it is safe to perform any minor oral surgical procedure, however some also consider the PT time along with the INR. Your cardiologist is always the final decision maker, however. Sometimes they will take you off the Coumadin and switch you over to Heparin a few days prior and after the surgery, sometimes they may just take you off for a couple of days. This will really depend on how high your risk of clot formation is and only your cardiologist can make this decision.

So to answer the original title question: As long as you are carefully monitored and prepared by your cardiologist just prior and after the dental implant surgery, you can get dental implants. There are no published studies showing an decrease in success rates of dental implants in patients taking any of the Warfarins.

Bookmark and Share

How Cold Lasers Work…

“Cold Lasers” seem to be the latest Buzz Word in Laser Dentistry. Cold Lasers are also known as “Soft Lasers” or, more scientifically, Biostimulatory Lasers.  As already mentioned in previous posts, these lasers do not cut or vaporise any tissue.  Although often very powerful, these lasers are defocused enough so that the tissue interaction is that of biostimulation and not thermal.

As we have seen earlier, cold lasers can be used for a variety of applications not only in dentistry, but also in medicine.  Their typical application field is that of tissue healing (Well, lately the application of hair re-growth has also been added and actually FDA approved, but there is little if any scientific substantiation to this at this point).

In order for laser light to be absorbed, there must be receptors.  Such receptors are well known in plants, but there are human light receptors other than those in the eyes and the skin.  In fact, to date more than three hundred photochemically reactive proteins, capable of harvesting low light energy, have been identified in both prokaryotic and eukaryotic organisms.  In humans, the most commonly known photochemically active receptor proteins are the rod and cone pigments in the eye.  However, other human photoreceptors have been discovered in recent times.  In fact today, we know that the majority of our cells have photoreactive molecules in them and we call those CHROMOPHORES.

It has been observed that if laser light is administered in the right dose, certain cell functions are being stimulated, and this is particularly evident if the cell in question has an impaired function.  It is known that laser light will cause certain chromophores in our cells to allow the build-up of radical oxygen species (singlet oxygen, instead of O2), which in turn influences the the formation of ATP (Adenosine Tri-Phosphate), which is the cells basic energy and fuel molecule.  Now, if the production of ATP reaches a certain level within cells, this will lead to a host of secondary effects, which have been studied and measured in several contexts:

  • increased cell metabolism and collagen synthesis in fibroblasts
  • increased DNA and RNA formation in the cell nucleus
  • increased cell division cycles
  • increased cell differentiation cycles of primitive cells (stem-type cells)

All of the above cellular effects will translate into faster healing by virtue of an increased population of cells which are involved in the inflammatory and healing cascades of the body.  Bone and soft tissue tend to heal faster and better after surgery, nerve cells can regenerate themselves at higher rates and pain is often reduced due to a laser-induced block of the pain receptor cells.

Bookmark and Share

Bone resorption of the Jaw

Continue reading

A 100 Watt Laser – And My Doctor Says It Won’t Hurt?!?!

It is an unfortunate business practice, but the sale of medical lasers is largely being promoted by their hardware profile: “X” number of watts, “Y” number of pulses at “Z” nanometers etc.  What is unfortunate about this is that it does not really paint a good picture on what the clinical qualities of a laser really are, because this type of advertising does not really address what kind of “tissue interaction” it produces.  This however is ultimately the most important quality of any laser.  I’ll explain…

First and foremost, the power of the laser (usually displayed in Watts) is the true output power in terms of light energy emitted.  This is in direct contrast to a light bulb for instance.  A 60-Watt light bulb will draw 60 Watts of power out of the socket, but only deliver a fraction thereof as light energy, because most of the power drawn gets converted to heat energy.  In a laser the power rating is NOT what it draws out of the electric socket, but rather the light energy it produces.

Another concept that needs to be addressed is that this power claim describing a laser, can often be misleading.  More often than not, a “high-powered” healthcare laser in the 20 – 100 Watt range achieves this kind or output power mostly in a “pulsed” mode.  This means that the laser will be “on” and “off” several hundred or even several thousand times a second and every time it is “on” it emits 100 Watts.  Since this is a pulse train of laser light, it is important to note that the AVERAGE power may only be in the milliwatt range, so there is effectively only less than 1 Watt being absorbed by the tissues.

The last and most important concept which needs to be addressed is that of the power density at the output tip (aka “fluence”).  A 50-Watt laser with an output diameter of 1 cm will have an entirely different effect on tissues than a 6-Watt laser with an output diameter of only a few hundred microns.  The former will have a biostimulatory effect, whereas the latter will be able to cut tissue.

So, as we can see, the advertising profiles of lasers do not really always reflect the clinical relevance.  It is my opinion that this needs to change eventually, so that the tissue interaction is placed into the foreground and not the hardware profile.

Bookmark and Share

Sinus Augmentation or Sinus Lift Procedure

The Sinus Augmentation of Sinus Lift Procedures are very common bone grafting procedures within the realm of implant dentistry.  Patients are often not quite clear what these procedures actually are, so I would like to

The maxillary sinus on a CT scan 3-D image

The maxillary sinus on a CT scan 3-D image

shed some light on these grafting procedures.  The maxillary sinus is the largest of all sinuses in the head-and-neck area.  It is located just to the inside of the bone in the upper cheek area.  The maxillary sinus starts out as a small air cavity in children and then expands and gets bigger as we grow older.  Once teeth are missing in the back areas of the upper jaw, the sinus will expand even further down towards the jaw ridge from the inside of the jaw bone.  This can be seen on the images on the right, especially the very bottom image, which shows a cross-sectional CT scan slice through the alveolar process of the upper jaw bone.

Now, as the sinus expands, and encroaches upon the alveolar ridge from the inside, you can appreciate that there is a diminishing distance of bone left between the top of the ridge and the floor of the sinus.  If this distance is too small to place one or several dental implants of proper length, we need to perform a sinus lift or sinus augmentation procedure, in order to re-gain this distance.

What is the difference between a “Sinus Augmentation” and a “Sinus Lift Procedure”?  Well, many will use these two terms

A CT Scan Slice through the sinus and alveolar process

A CT Scan Slice through the sinus and alveolar process

interchangeably, however there is a little difference between these two terms.  A “Sinus Augmentation” is a slightly more aggressive procedure, where a window is cut into the bony cheek side wall of the sinus and the sinus membrane is then gently lifted off the sinus floor, until a bone graft is finally placed underneath the lifted membrane.

A Sinus Lift procedure, on the other hand is usually performed right through the hole which is drilled for the implant(s).  No window is cut on the cheek side of the bone.  The Augmentation is usually done, for bigger lifts and the Lift procedure is usually done for smaller lifts.

So when the sinus membrane is finally lifted in either procedure, a bone graft is placed underneath the membrane, which keeps the membrane “tented” up.  For more detailed information on bone grafts see my bone graft post or link to Robert Gougaloff ‘s website.  This bone graft will then “mature” over the next six to 24 months (depending on the type of graft used).  What this

A CT Scan Cross sectional slice from the above image

A CT Scan Cross sectional slice from the above image

has accomplished however, is that the floor of the sinus was effectively “raised” and has thus given us enough room to place one or more dental implants of proper length.

Sinus Augmentations and dental implants can be done in one stage or in two stages, depending on how much residual alveolar bone was left to stabilize the implant.  If it is done in two stages, then the dental implant is usually placed 6 to 12 months following the sinus augmentation, depending on the graft material used.

Sinus Lift Procedures and the placement of dental implants are usually done at the same time, which obviously shortens the treatment time dramatically.  However this can usually be only done if the amount of lift needed is not too excessive.

A video of a Sinus Augmentation procedure can be seen on the following video link: Robert Gougaloff ‘s Sinus Augmentation Video.

Bookmark and Share