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- Håkansson, Bo, et al.
(författare)
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Resonance frequencies of the human skull in vivo
- 1994
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 95:3, s. 1474-1481
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Tidskriftsartikel (refereegranskat)abstract
- Patients with skin penetrating titanium implants in the temporal bone, for attachment of bone-anchored hearing aids, have made it possible to investigate the free-damped natural frequencies (resonance frequencies) of the human skull in vivo. The resonance frequencies of the skull of six subjects were investigated. Teh resonance frequencies were extracted from two frequency response functions (acceleration/force) measured on each subject: One point measurement where the force and acceleration were both measured at the same point, and one transcranial measurement where the acceleration was measured contralaterally. Between 14 and 19 resonance frequencies were identified for each subject in the frequency range 500 Hz to 7.5 kHz. The two lowest resonance frequencies were found to be on the average 972 (range 828-1164) and 1230 (range 981-1417) Hz. The relative damping coefficients of all resonances were found to be between 2.6 and 8.9%. Due to the relatively high damping coefficients, it is assumed that the resonance frequencies do not significantly affect bone conducted sound. In the transcranial measurements, however, a few large antiresonances were found which may affect bone-conducted sound. Intersubject variations were large, probably due to individual variations in skull geometry and in mechanical parameters. The results were shown to be consistent with previous results obtained on dry skulls. No obvious correlation between lowest resonance frequency and skull size was found.
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| 7. |
- Eeg-Olofsson, Måns, 1967, et al.
(författare)
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Transmission of bone-conducted sound in the human skull measured by cochlear vibrations.
- 2008
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Ingår i: International journal of audiology. - : Informa UK Limited. - 1708-8186 .- 1499-2027. ; 47:12, s. 761-9
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Tidskriftsartikel (refereegranskat)abstract
- One limitation with the Bone Anchored Hearing Aid (Baha) is too poor amplification for patients with moderate to severe sensorineural hearing losses. Therefore, we investigated if bone conducted (BC) sound transmission improves when the stimulation approaches the cochlea. Also the influence from the squamosal suture on BC sound transmission was investigated. Both sides of the heads on seven human cadavers were used and vibrational stimulation was applied at eight positions on each side with a frequency range of 0.1-10 kHz. A laser Doppler vibrometer was used to measure the resulting velocity of the cochlear promontory. It was found that the velocity of the promontory increases as the stimulation position approaches the cochlea; this was especially apparent at distances within 2.5 cm from the ear canal opening and when the stimulation position was in the opened mastoid. At frequencies above 500 Hz there was on average 10 to 20 dB greater vibrational response at the cochlea when the stimulation was close to the cochlea compared with the normal Baha position. Moreover, even if there were general indications of attenuation of BC sound when passing the squamosal suture, an effect from the suture could not be conclusively determined.
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| 8. |
- Granström, Gösta, 1950, et al.
(författare)
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Sleeping implant in the temporal bone: report of a case with 20-year follow-up.
- 2012
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Ingår i: Clinical implant dentistry and related research. - : Wiley. - 1708-8208 .- 1523-0899. ; 14:2, s. 236-40
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is limited knowledge of the long-term fate of “sleeping” or nonloaded implants in the temporal bone. Purpose: This article describes the fate of a fixture installed in the temporal bone that remained unloaded for 20 years. Patient and Methods: A 25-year-old male with hemifacial microsomia had three osseointegrated implants installed for an auricular episthesis and bone-anchored hearing aid (BAHA) in the left temporal bone in 1988. Two of the implants for the ear episthesis were activated the same year, but the fixture for the hearing aid was not uncovered until 2008. When the patient experienced hearing problems at his office, he wanted to reactivate the sleeping implant. An audiogram showed a maximum conductive hearing loss with good preserved cochlear function. Before reactivation, an Accuitomo three-dimensional, cone beam computed tomography was performed. Resonance frequency analysis (RFA) using the Ostell technique was done when the implant was uncovered. Results: Preoperative x-ray investigation showed the sleeping implant to be well integrated in the temporal bone, covered with 1 mm bone, and with no signs of resorption. Geometric measurements correlating to the two loaded implants showed the sleeping implant to be positioned too close to these to be able to anchor a BAHA without interference with the episthesis. Surgical exploration was done to analyze the implant. The clinical status correlated well to that diagnosed from the x-ray investigation. RFA revealed the implant to be well integrated. A new fixture and abutment for BAHA was installed in the temporal line and activated 2 months after surgery. The patient is today supplied with a BAHA. Conclusion: It seems possible to use sleeping implants in the temporal bone even 20 years after installation.
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| 9. |
- Heo, S J, et al.
(författare)
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Stability measurements of craniofacial implants by means of resonance frequency analysis. A clinical pilot study.
- 1998
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Ingår i: The Journal of laryngology and otology. - : Cambridge University Press (CUP). - 0022-2151 .- 1748-5460. ; 112:6, s. 537-42
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Tidskriftsartikel (refereegranskat)abstract
- Nineteen patients previously treated with 52 implants for anchorage of craniofacial prostheses were subjected to implant stability measurements by means of resonance frequency analysis (RFA), six months to 15 years after implant placement. The resonance frequency (RF) of a transducer attached to the implant abutment was measured by using a frequency response analyser, a personal computer (PC) and dedicated software. Statistically significant higher RF values were seen for implants in the temporal bone as compared to implants in the nose and periorbital regions. There was a positive correlation with time since implant placement for the period from six months up to seven years. It was concluded that the preliminary results suggest that implant stability increases with time and that implants in temporal bone are more stable than implants in the bone in the nose and periorbital regions, probably reflecting differences in bone density.
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