The ÇƒÚthird lawÇƒÙ

The ÇƒÚthird lawÇƒÙ
March 15,2003
The Statesman
Scientists have detected a ÇƒÚthird dentitionÇƒÙ and developed a sophisticated mode of surgery called Oral Implantology that can not only correct your jaw bones but will also light up your face. Montey Garg reports
HUMANS have two dentitions ÇƒÓ milk (primary) and permanent (secondary) dentition. But todayÇƒÙs medical technologies found a third dentition through device called oral implantology, an Çƒ?oral implantÇƒ?. ItÇƒÙs a surgery that requires a a titanium screw anchored to the jaw bone to Çƒ?hold the replacement tooth or bridge in placeÇƒ?.
This screw acts as an artificial tooth root and supports a Çƒ?dental prosthesisÇƒ? constructed over it and they donÇƒÙt really depend on its neighbouring teeth for support. They are Çƒ?permanent and quite stableÇƒ? and can replace any number of teeth, even its entire jaw.
An Çƒ?implantÇƒ? preserves bones in the areas without a tooth and there is absolutely no problem chewing, swallowing, speaking, kissing, laughing or even moving the tongue.
Usually, oral implants are of three types It is much like the nut and bolt arrangement in ordinary wood carpentry.
The success of Çƒ?implantÇƒ? depends largely on the fusion of the surface with the bone, a phenomenon that is called osseointegration that an orthopaedic surgeon, Per-Ingvar Branemark, discovered in 1952 at Lund University Çƒ?by accidentÇƒ?.
Branemark and his team were diligently working on how the bones of rabbits could be healed by using an optical chamber housed in a titanium metal cylinder that could be Çƒ?screwedÇƒ? into its thigh bones. Even several monthsÇƒÙ of hard work and research failed to remove the titanium cylinders from the bone and the scientists believed that the cylinder had been biologically ÇƒÚfusedÇƒÙ with it. Then what followed was a series of trials that involved titanium appliances tried for healing human bones as well. In fact, the titanium screws acted as bone anchors to make up for the lost teeth. The first clinical dental osseointegration surgery was performed in 1965 on an Çƒ?edentulousÇƒ? female patient. And thereÇƒÙs been continuous work on implantology since. In fact, the success rates of implants are increasing phenomenally.
Today, two types (metals and ceramics) of materials are used for implants either in a pure form or the hybrid type. There are six types of titanium-based materials used for it. They include four types of commercially pure titanium and two titanium alloys.
Pure titanium is found in four grades. It is tensile strength and the amount of oxygen that determine its grades.
Titanium implants are resistant to corrosion, biocompatible, relatively lightweight and can be coated with a thin layer of hydroxyapatite or tricalcium phosphate. These bio-active or bioresorbable ceramic materials not only form an intimate bond to the bone but also can be replaced by tissues over a period of time. Tricalcium phosphate and hydroxyapatite, rich in calcium and phosphorus, produce a surface that is bio-active and greatly induces bone growths.
Compared to titanium, ceramic materials (made of aluminum or zirconium oxides) are brittle and not quite suited for implants. In fact, they are used for replacement of just one tooth. Such materials do not help in bone formations, but with its biocompatibility allows bone to grow closely on its surface. The ceramic materials that are relatively inert but fully oxidised and, chemically stable, as a result, has a very high compressive value but helps little to Çƒ?bend the tensile forcesÇƒ?.
Çƒ?Implant placementÇƒ? require extraordinary surgical skills. The jaw that in medical parlance called the Çƒ?recipient siteÇƒ? is picked and an oestotomy is done either with a drill or a hand instrument, depending on how a surgeon chooses to do his job.
The surgeon also creates an area for Çƒ?implantÇƒ? that usually takes about three to six months to heal the jaw bone before it gets Çƒ?fusedÇƒ?. Each jaw bone has different densities, in different areas. The denser the bone the shorter the briefer time.
The surgeons now do their jobs by Çƒ?inserting an implantÇƒ? into an Çƒ?already prepared bone socketÇƒ? soon after a tooth is extracted. The whole process takes place in a very quick time. The voids that remain between the Çƒ?implantÇƒ? and the bone socket are filled with a graft material like tricalcium phosphate but even in Çƒ?quick implantsÇƒ?, teeth are loaded only after the Çƒ?healing periodÇƒ? is over. The most recent treatment that revolutionised implantology is Çƒ?immediate loadingÇƒ? that is commonly called the Çƒ?same-day teethÇƒ?.
So, your worries about decaying teeth is over. You just visit a dental surgeon and get a tooth extracted and return with a brand new one in the form of an implant, the third dentition.
In the past, bone grafting would be performed on people who didnÇƒÙt have strong structures which were considered very important for performing Çƒ?implantÇƒ?.
But now, bone grafting has given way to thing called distraction osteogenesis, a modern technique of forming new tissues by gradually expanding the existing ones. In fact, human bodies have their own mechanisms heal themselves. Even new tissues are created. In this technique, bone growths can be induced by applying tension forces across the osteotomy site and the technique is becoming enormously popular across the world.
The success rates of this state-of-the-art oral implant treatment are about 95 and 90 per cent with the lower (mandible) and upper jaws (maxilla) respectively. The figures are based on study conducted over the past five years. Finally, oral implantology promises a potent and sound option for both biomaterial science and bio-mechanics, and itÇƒÙs here to stay!
(The author, a final-year dental student, is a freelance science writer and can be contacted at montey@rediffmail.com.)