The Marco story – the evolution of full arch immediate loading with WeldOne technology
In the early days of dental implants the founding fathers (in Sweden) decided that after placing an implant it needed to be left hiding in the bone under the gum for 6 months (or more) until the bone around it had attached to the oxide layer on the titanium surface. This process was called Osseointegration. In those early years, this ‘delayed loading’ approach meant that dental implant patients had to be, well, very patient. They waited months for their teeth to be completed. During this period they would have to tolerate dentures or temporary bridges.
The avoidance of dentures was often the reason they were seeking dental implant treatment in the first place so this was a retrograde step! The ‘light at the end of tunnel’/no pain no gain philosophy.
As time passed a few brave pioneers like Dr Marco Degidi and Dr Palo Malo (founder of All on Four) began to research the idea of ‘immediate loading’ on dental implants, that is, surgically placing implants and connecting teeth to them on the very same day.
What patients really wanted is to walk out of surgery with a full set of functioning teeth! These early adopters stumbled upon a remarkable fact: patients can start eating on their implants straight away as long as the implants are not able to move within the bone during mastication. Furthermore the bone around these immediately loaded implants responds very quickly (within weeks) firming up in response to forces transmitted to it via the newly placed implants. It actually grows stronger-faster in these conditions – just so long as the implants aren’t allowed to move during the first few weeks of this process.
Once this bone-response model had been accepted the logical next question was how to keep the implants from moving during the first few weeks after placement. Many implants were lost this way, failure rates for immediately loaded implants in these halcyon days were high.
Probably the best known system for full arch immediate loading is the All On Four system developed by Dr Palo Malo and Nobel Biocare. There have been more full arches immediately loaded using this protocol than any other, the data supporting this system is immense and it is a huge success globally.
All On Four and (it’s many copies) involves placing 4 (or sometimes more) implants and connecting an acrylic set of teeth (usually a cut down denture) to those implants on the same day. It is a system I have used and it works well. However there are some shortcomings with this system
- the patient must return for a new, stronger long term bridge within a few months as these acrylic bridges are inherently weak. They can be made stronger by incorporating stainless steel wire into them which aids rigidity but where this wire is not in direct contact with the implants, fractures still occur
- the temporary implant posts which the temporary acrylic bridge attaches to are simply glued into the bridge, there is no direct metal to metal contact between implants Acrylic has a relatively low modulus of elasticity which allows micro-movement of the implants. In most cases this is not enough to make them fail but with a strong bite failures can and do occur
- Acrylic bridges need to be vertically bulky to overcome their elasticity and fragility The bone around the implants in these cases needs to be quite dense and of good quality. This system does not favour low bone density patients – many of whom end up having a 6 month wait
- In cases where the lip line is high when smiling or where there is ample vertical bone height the implantologist must cut away the bone until there is enough space for a proper thickness of acrylic material and so that the pink margin on the bridge does not reveal itself when the patient smiles
- To my mind this is the biggest issue with All on Four. For years I have held bone to be sacrosanct, a miracle of biology to be maintained at all costs! After all without bone there are no implants! So the idea of taking a drill to a big mass of beautiful bone and cutting it in half simply to work around the shortcomings of a weak temporary bridge design seems counter intuitive to say the least.
While Nobel were developing the All on Four technique, in a little known high end private clinic in Bologna, Italy, Dr Marco Degidi was having other ideas. He refused to accept that the acrylic bridge was the beginning and the end of immediate implant dentistry. He knew that if he could find a way to rigidly splint those implants together using a material with superior physical characteristics (high strength, high modulus of elasticity) then many of the problems described above would be history. A metal of some sort was the obvious choice but at that time the only way to produce a set of teeth with a hidden metal strengthener was to take an impression, send it to a lab, process the framework, add ceramic, etc….a long process which took the ‘immediate’ out of ‘immediate loading’ and would have been a step backwards in time.
Marco chose titanium as the metal of choice for his immediate frameworks. Titanium has a superior modulus of elasticity, (rigidity), is far stronger than acrylic, and its bio-compatibility is widely recognised. Then next question was how to attach it – on the day and at the same time as the implants are placed, reliably, quickly and with enough strength to withstand long term cyclic loading.
Intra oral welding was born. Marco, backed by Dentsply developed a high tech welding machine specifically for welding titanium wire to high precision titanium posts which attach directly to the implants. The welds are practically instantaneous (milliseconds) and the heat produced at the weld dissipates in less than a second. The titanium can be hand held during the welding process. When Marco first demonstrated this to the CEO of Dentsply he refused to believe it until he had held two pieces of titanium between his thumb and forefinger and Marco welded them together!
Having spent time with Marco as this all developed I became the proud owner of the prototypes of this machine and was one of a handful of implant dentists here in the UK to start using it following Marco’s updated immediate loading protocol.
We use acrylic or composite ‘shell’ bridges, remade before the surgery. Once the implants are placed and the titanium frame is welded in place the titanium frame is removed from the mouth attached to the shell, and finished by our on-site technician. The whole process take about 4 hours. Patients walk away with a fully functioning, aesthetic set of teeth designed to last for years not months.
Furthermore
- Implants can be placed in low density bone and once welded together the osseointegration success is no different to implants in high density bone or those that have been placed and left for months before loading.
- Even low density bone patients can begin eating on their new teeth straight away
- The strength of these bridges is such that when the bone is tall or the space available in the mouth is small, they can be fitted with no need for osteoplasty (the drilling away of healthy bone to make room for a bulk of acrylic)
- the reduction in treatment time, together with the ability to produce highly precise, custom titanium frameworks in house (as opposed to outsourcing them to a distant CNC facility to be fabricated) means that the cost of restoring mouths and arches this way is significantly reduced without any reduction in the quality of treatment outcomes
Caveats/Limitations
It should be noted that for ultimate longevity an implant bridge should be constructed using a metal substructure with ceramic teeth laid on top. It is not possible to produce such a bridge and fit it on the same day as the implant surgery. The welded titanium bridges we produce use composite resin teeth (a material with superior aesthetics and wear resistance to acrylic but inferior aesthetics and wear resistance to porcelain/ceramic). We still use acrylic teeth (with an internal titanium welded frame) for patients who need to keep their costs to a minimum. Both acrylic and composite resin teeth will wear and the wear rate is determined by the bite forces in an individual patient’s mouth (ranging from English Rose to Arnold Schwarzenegger) and the condition and type of teeth in the opposing arch or jaw.
For example
If the opposing arch is comprised of multiple ceramic/porcelain crowns and the patient has a heavy bite the wear will be significant over a 12-24 month period necessitating a changeover to ceramic at the end of that period.
If the bite forces are low and the patient is biting on a denture in the opposite jaw then these titanium acrylic/composite resin bridges will last many years without noticeable deterioration.
As for the future?
The future lies in producing off the shelf teeth in a material with similar physical characteristics to ceramic but one that is much easier and quicker to work with. Marco Degidi continues towards this ultimate goal and my experience of him is that he generally achieves those goals that he sets himself. We remain in daily contact.
