Development of dental inspection method: Nondestructive evaluation of an adhesive interface by ACTIVE acoustic emission.

PURPOSE: This study aims to confirm the usefulness of active acoustic emission (Active AE) for reproducible and non-invasive generation of physical external force which is required for conventional AE. METHODS: Experiment 1: A root dentin-resin adhesive interface was observed. The post space was filled with a dual-cure resin composite core material with and without adhesive. The vibration characteristics of the data obtained from the time-frequency analysis were evaluated. Experiment 2: A crown-abutment tooth adhesive interface was observed. Adhesive resin cement was used for luting the crown and adhesion states in the same specimen over time were analyzed with three measurements: at trial-fitting, immediately after luting, and 2 weeks after luting. Data were subjected to time-frequency analysis and relationships between amplitude (indicating loudness) and frequency (indicating the sound component) were analyzed. RESULTS: Experiment 1: Time-frequency analysis confirmed multiple peak frequencies for each specimen without adhesive and monomodal peak frequency in all specimens using adhesive. Experiment 2: Two weeks after luting, all specimens showed a single major peak except one which showed multiple weak peaks. The three-dimensional visualization of time-frequency analysis revealed one specimen with multiple weak peaks while all others displayed a single, low-amplitude band at 2 weeks after luting. CONCLUSION: The state of the adhesive interface can be evaluated using active AE. This basic technique may prove useful to evaluate changes in the adhesive interface of prostheses over time.

Diastereoselective Methylation at the Congested ß-Position of a Butenolide Ring: Studies toward the Synthesis of seco-Prezizaane-Type Sesquiterpenes.

We established a method for installing a methyl group at the ß-position of a butenolide ring. The methylated position is located at the congested ring juncture of a 5,6,5-tricyclic lactone, which is common to neurotrophic seco-prezizaane-type sesquiterpenes. The samarium(II)-mediated conjugate addition of the halomethylsilyl ethers tethered to the proximal hydroxy groups efficiently formed the desired C-C bond. Subsequent fluoride-free Tamao oxidation and Barton-McCombie deoxygenation converted the resultant cyclic silyl ether into the corresponding methyl group.

Ultrasonic measurement of bone thickness for spinal surgery.

We measured the thickness of the transverse structures associated with the bovine coccygeal transverse processes (bone specimen) by using ultrasonic waves and examined the reliability of this measurement for use in spinal surgery. We first measured the velocity of ultrasonic waves propagating in the spinous process. We then made a hole in the transverse process with an air drill and placed an ultrasonic transducer with a center frequency of 10 MHz in the hole. The time of reflection of the ultrasonic wave from the underside of the transverse process was detected to estimate the remaining bone thickness. The thickness estimated by using ultrasound was compared with the thickness measured by microscopic examination. We could detect reflection waves from the underside of the transverse process in 91.7% of cases (i.e., 22 of 24 measurements using 6 bones from 3 cows). The thickness of the transverse processes in which we detected the waves varied from 0.24 to 6.8 mm. The 95% limit of agreement between ultrasonic and histological measurement was 0.71 mm. Pearson's correlation coefficient showed a strong and positive relationship between the two measurements (r = 0.97, n = 22, P <0.0001).