Prosthetic teeth prove to be effective vibration carriers that are suitable as potential hearing aids.
In a research paper entitled “Bone conduction sensitivity for dental implants‘ published earlier this month in the Journal of the Acoustical Society of America, Eggheads at Tongji University in Shanghai describe tests to determine how well implanted teeth conduct sound.
Authors Fengxuan Ren, Yutong Li, Lidan Chen, Jiaqi Huang, and Jianxiang Tao explain how this is known bone conduction through natural teeth can produce a hearing effect. But sound transmission through artificial teeth has not been studied that much.
So the researchers gathered 38 subjects who met the desired criteria and had them listen to a signal sent by a vibrating device placed on either a dental implant, a natural tooth, or the mastoid bone (just behind the ear). The stimulus was in the form of tones with frequencies between 250 Hz and 4000 Hz at 30 dB and at lower decibel levels when participants signaled that they heard the tone.
The results suggest that “dental implants were more sensitive [bone conduction] than natural teeth and mastoids at some frequencies,” the authors note.
The study results also indicate that implants in anterior teeth have a lower threshold for detecting vibration than posterior teeth. “[A]anterior dental implants performed better [bone conduction] sensitivity than posterior,” the authors note, suggesting that this may be due to differences in bone density in the anterior and posterior jaws.
The first bone anchored hearing aid (BAHA) was implanted by Anders Tjellstromat Gothenburg University, in 1977. Currently, these devices are taking the form of products including the Cochlear Baha System, Oticon Pontoand Medtronics Alpha 2 MPO ePlus. Some are non-surgical—they are worn on a headband—and others, depending on the condition being treated, require surgical implantation of a metal stud or magnet that carries an external sound processing unit.
BAHAs and cochlear implants are both options for treating profound hearing loss. BAHAs can be either surgical or non-surgical and rely on vibrations to transmit sound waves to the inner ear and auditory nerve. Cochlear implants are always surgically placed and transmit sound directly to the auditory nerve via electrical impulses.
The development of conductive hearing technology has faced some obstacles – for example, US federal regulations for Medicare reimbursement. About a decade ago, a company called Sonitus Medical raised $80 million to develop its non-surgical SoundBite hearing aid, “a prosthetic device that uses the established principle of bone conduction in a novel way by transmitting sound through teeth.” and thereby the function of replaces the damaged ear.”
Three years later the company filed for bankruptcy following a decision by the Centers for Medicare & Medicaid Services (CMS) not to reimburse patients for SoundBite hardware — a tooth-fitted mouthpiece and microphone receiver. The federal agency that oversees Medicare classified the device as a hearing aid rather than a prosthesis as no surgery was required.
So it may be that vibrating denture teeth survive the bureaucracy of the American healthcare system because they are implanted rather than worn.
“Because dental implants performed extremely well [bone conduction] Properties, dental implants could be used as a potential [bone conduction] Hearing aids in the mouth,” the researchers conclude. “Suppose these devices could be included in the abutments of dental implants. In this case, dental implant hearing aids offer unique advantages in practical use, such as excellent coverage, good comfort and improved sound quality.” ®
https://www.theregister.com/2022/10/01/prosthetic_teeth_hearing_aid/ Vibrating dentures could be used as hearing aids • The Register