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A radical redesign of the oral implant offers new hope to patients with missing teeth and reduced bone volume. By Tracey Porter
Any oral health professional who has had to contend with a patient with missing teeth and compromised healing is all too familiar with the challenges presented by this type of case.
Forced to choose between undergoing significant grafting procedures or wrestling with unstable removable prostheses, typically neither patient nor practitioner are pleased with the resulting oral health outcome.
Vertical grafting of bone is often described as difficult and unpredictable while alternatives, such as distraction osteogenesis, usually prove prohibitive with few centres offering this course of care.
Help may soon be at hand, however, with a group from the University of Melbourne (UoM) developing a new dental implant that provides a more stable tooth replacement option.
Twelve years in the making, the device—which has been named the rectangular block implant or RBI for short—provides the same surface area for integration, precluding the need for problematic vertical grafting.
UoM Associate Professor (Prosthodontics) Roy Judge, one of the device’s three inventors, says the RBI is constructed from pure titanium and unlike its more traditional contemporaries, is placed in a horizontal orientation.
While traditional dental implants drill straight down into the jaw, the difference with the RBI is that the implant has a long horizontal base to use less vertical height.
As the first of its type to be designed and manufactured in Australia, the secret behind the RBI is that it makes the best use of whatever bone volume the patient still has while minimising the risk to nerves and veins in the patient’s jaw.
It also maximises force distribution to afford patients a better chewing experience.
A conventional cylindrical dental implant requires a finite height and breadth of bone to achieve primary stability. This is not always amenable in situations where the tooth has been lost for a significant period.
A/Prof Roy Judge, co-inventor, RBI
A/Prof Judge says it is particularly effective among patients missing posterior teeth long-term and those with resorbed alveolar ridges.
Ask any oral health expert and they’ll tell you that missing teeth can be replaced in many ways, including with removable partial or full dentures, bridges on prepared teeth, bridges adhered to teeth and dental implants.
But as everyone knows, dental implants—which have been used to replace missing teeth in clinical dental practices since the 1980s—work best when there is a healthy bone into which the implant can be stabilised during the healing phase after placement.
“A conventional cylindrical dental implant requires a finite height and breadth of bone to achieve primary stability,” A/Prof Judge says. “This is not always amenable in situations where the tooth has been lost for a significant period.”
He says that typically 1.5mm of bone is required around all aspects of the implant to ensure stability and blood supply to the healing surfaces.
In situations where there is reduced bone volume the lack of blood supply reduces predictable healing outcomes while the reduced stability means that there is increased micromotion across the bone implant interface resulting in unfavourable fibrous union as opposed to osteointegration of the implant into bone.
“Some patients don’t have enough healthy bone in their jaw as a result of losing it to trauma or disease like oral cancers, while others have a deficit due to having their teeth extracted years ago,” A/Prof Judge says.
Patients with affected bone healing have reduced chances of success, he adds. “These would include patients who currently smoke, have uncontrolled diabetes, have had irradiation to the head and neck or take certain medications to help manage osteoporosis.”
A/Prof Judge says dental implants that have a stable tooth replacement option when placed in posterior regions of the mouth result in patients regaining the ability to chew food effectively thereby improving digestion.
Some patients don’t have enough healthy bone in their jaw as a result of losing it to trauma or disease like oral cancers, while others have a deficit due to having their teeth extracted years ago.
A/Prof Roy Judge, co-inventor, RBI
Implants placed in the anterior regions can support tooth replacements similar in dimension and aesthetic appeal to natural teeth, he says.
“Having confidence in one’s smile is an important part of socialisation plus it helps with job opportunities and other milestone achievements.”
A/Prof Judge explains the RBI came about because he and his fellow inventors, dental surgeon Dr Tim Gazelakis and physicist Joseph Palamara, identified that with one in 10 patients missing teeth unable to be helped by current implants on the market, conventional implants were clearly not an option for everyone.
The RBI team has faced numerous hurdles getting the project to this stage of development, including fallout from COVID-19, as well as the numerous ethics clearances needed to advance both animal and human studies.
Despite this, the design of the rectangular block implant has been stable since initial CAD drawings 12 years ago, A/ Prof Judge says, with the matched surgical tip to provide the rectangular osteotomy the main thing to have changed since the first prototype was developed.
While the sites the team are working on are among the most difficult to treat in terms of both occlusal loads and bone volume, A/Prof Judge says the concept has been “extremely successful in the initial animal studies”. In human trials, it has achieved the same level of success as conventional implants.
To date, the development team have successfully placed implants into two patients, with both having had positive bond and soft tissue responses.
The project has so far attracted funding from the Biomedical Translation Bridge Program as well as a Medical Research Commercialisation grant from the University of Melbourne. An Australian Economic Accelerator Seed Grant from the Department of Education will allow the team to work with Australian manufacturer Signature Orthopaedics.
Proof-of-concept human clinical trials have recently begun, with the trial the first step in making the RBI commercially available.
