Harold E. Goodis

Sterilization of Teeth by Gamma Radiation

Clinical simulations and restorative materials research and development conducted in vitro require the use of large numbers of extracted teeth. The simultaneous need for infection control procedures and minimal alterations of structure and properties of the tissue prompted this study of gamma irradiation as a method to eliminate microbes associated with extracted teeth and their storage solutions. Evaluations of potential change in structure of dentin were conducted in terms of permeability, Fourier transform infrared spectroscopy (FTIR), and optical properties. The dose required for sterilization by gamma irradiation was established by means of a tooth model inoculated with Bacillus subtilis (108 organisms/mL). Sterilization occurred at a dose above 173 krad with use of a Cesium (Cs137) radiation source. Gamma irradiation did not affect permeability of crown segments of dentin. A comparative evaluation of the effects of four sterilization methods on dentin disks was based on FTIR and ultraviolet-visible-near infrared (UV/VIS/NIR) spectra before and after sterilization by (1) gamma irradiation; (2) ethylene oxide; (3) dry heat; and (4) autoclaving. No detectable changes were found with gamma irradiation, but all other methods introduced some detectable change in the spectra. This suggests that common methods of sterilization alter the structure of the dentin, but gamma irradiation shows promise as a method which both is effective and introduces no detectable changes as measured by FTIR, UV/VIS/NIR, or permeability.

Storage effects on dentin permeability and shear bond strengths

The effects of duration of storage and selection of storage solution upon dentin permeability and bond strength were studied over a period of 8 days to 6 mon. Teeth were stored immediately after extraction in one of five commonly used solutions: 70% ethanol (E); 10% formalin (F); distilled water (W); distilled water with thymol (WT); or phosphate-buffered saline with thymol (ST). Permeability and lap shear bond strength measurements were evaluated in a repeated measures design (n = 20) after 8 days, 15 days and 6 mon. Dentin permeability varied with solution type and duration of storage as demonstrated by ANOVA, increasing F, E and the water-based solutions, respectively. Saline storage resulted in large significant decreases in permeability after prolonged storage, suggesting changes in dentin. Bond strengths were unaffected by duration of storage or by solution type, except for saline. Thus, permeability and bond strength values may be affected by storage conditions. The results of this study indicate that saline, the most commonly used solution in dental materials research, may be unsuitable for use as a result of its effect on dentin permeability and bond strength.

Capsaicin-evoked release of immunoreactive calcitonin gene-related peptide from rat trigeminal ganglion: evidence for intraganglionic neurotransmission.

&NA; Chemically‐mediated cross‐excitation has been described between neurons within sensory ganglia. However, the identity and source of the chemical mediators is not known. Ca2+‐dependent release of neurotransmitters from cultured sensory neurons in vitro has been observed, although neurite outgrowth may confound the ability to extrapolate findings from culture systems to in vivo conditions. Thus, the present studies evaluate the hypothesis of capsaicin‐sensitive intraganglionic neuropeptide release from freshly prepared slices of rat sensory ganglia. The ganglionic slice preparation provides an advantage over neuronal cultures, because release may be assessed within minutes after tissue collection (minimizing phenotypic changes) and while maintaining gross anatomical relationships. Trigeminal ganglia (TGG) were quickly removed from male, Sprague–Dawley rats (175–200 g), chopped into 200 &mgr;m slices and placed into chambers within 3 min of collection. Chambers were perfused with buffer, and superfusates were collected and assayed for immunoreactive calcitonin gene‐related peptide (iCGRP) release via radioimmunoassay. After about 90 min of baseline collection, tissue was treated with capsaicin followed by a washout period. Capsaicin (1–100 &mgr;M) evoked concentration‐dependent increases in iCGRP release. A competitive capsaicin receptor antagonist, capsazepine, significantly inhibited capsaicin‐evoked release of iCGRP. In addition, capsaicin‐evoked release of iCGRP was dependent on the presence of extracellular calcium. Furthermore, capsaicin‐evoked release from TGG slices was significantly greater than that from slices of equivalent weights of adjacent trigeminal nerve shown histologically to be free of neuronal somata. These data support the hypothesis that Ca2+‐dependent exocytosis of neuropeptides may occur within the TGG in vivo and that the majority of this release derives from neuronal somata.

Spectroscopic changes in human dentine exposed to various storage solutions - short term

OBJECTIVES Tooth storage conditions in studies of dentine have not been standardized. The objective of this investigation was to determine the effects of storage solution and time on dentine, using spectroscopic methods. METHODS Twenty-seven dentine disks (0.75 mm thick) were prepared from freshly extracted third molars with documented histories. The teeth were sectioned parallel to the occlusal plane using a diamond saw. Specimens were analysed non-destructively for surface chemical changes using specular reflectance infra-red Fourier transform spectroscopy (SRIFTS), and changes in optical properties were measured in the ultraviolet, visible and near-infra-red spectral ranges with an integrating sphere spectrophotometer (UV/VIS/NIR) before and after storage. A minimum of five specimens were stored in distilled water with 0.02% thymol, purified and filtered water, phosphate buffered saline with 0.02% thymol, 70% ethanol or 10% buffered formalin and evaluated at 0, 1, 2, 7, 14, 21 and 28 days. After each measurement, specimens were stored in fresh solutions. IR spectra were obtained from 4400 to 400 wave-numbers (cm-1). Optical properties of reflectance and transmittance were determined from 200 to 2500 nm, and absorbance was calculated. RESULTS Analysis of the IR spectra indicated no significant differences in collagen or mineral peak positions for any solution at any time period. There were significant differences in peak intensities of dentine stored in distilled water, purified and filtered water and phosphate-buffered saline over time in the IR spectra. Furthermore, differences in optical properties of dentine disks were detected by UV/VIS/NIR. CONCLUSION It was concluded that changes in surface chemistry and optical properties of dentine occur as a function of storage solution and time, which must be considered when studying dentine.

The effects of storage after extraction of the teeth on human dentine permeability in vitro

Freshly extracted third molars were stored for one week in one of four solutions: 70% ethanol, 10% formalin, distilled water with thymol and phosphate-buffered saline with thymol. Crown segments were prepared and initial permeability measurements taken. Each specimen was placed in a fresh preparation of its original solution, and permeability was measured over two periods: 1, 4, 6 and 8 days or 1, 8, 15 and 22 days. Ten crown segments were used for each solution for each time sequence. Permeabilities were lower for those specimens stored in ethanol and formalin than in water/thymol and saline/thymol, but most specimens showed increased permeability with time. Both storage solution and storage time had statistically significant effects (p less than 0.05), with significant differences between specimens stored in water/thymol and saline/thymol and those stored in ethanol and formalin. Thus, type of storage solution effects dentine permeability over time.

Measurement of temperature generated by visible-light-cure lamps in an in vitro model.

The dental pulp is vulnerable to cavity preparation and restoration procedures. This vulnerability may be a result of the temperature rise generated by those procedures. When visible-light-cure lamps are used to place composite restorations, they cause the temperature in the pulp to rise. This study measured the temperature rise recorded when six visible-light-cure lamps were tested for 20- and 60-second exposure times. They were also tested in conjunction with an air current passed along the face of the lens in order to lower the temperature. Analysis of the data indicates that the lamps do cause a temperature rise within the pulp chamber--a higher rise the longer the lamp is used. Dentin thickness is important, and air lowers the temperature generated.

Prostaglandin E2 Enhances Bradykinin-evoked iCGRP Release in Bovine Dental Pulp

Mediators produced during inflammation are responsible for hyperalgesia and expression of neurotransmitters and receptors in the nervous system. The production of bradykinin (BK) and the prostaglandins (PGs) may regulate initiation of pain. This study tested the hypothesis that BK and prostaglandin E2 (PGE2) have a positive interaction in evoking neurosecretion of immunoreactive calcitonin gene-related peptide (iCGRP). Bovine dental pulp was prepared and stimulated by the superfusion method with BK alone and in combination with PGE2. Kinin receptor antagonists to bradykinin-evoked release of iCGRP were also tested. Also tested was the hypothesis that dental pulp contains cither the B, or B2 or both BK receptors. Results showed that PGE2 enhanced BK-evoked iCGRP release by more than 50%. Western immunoblots revealed detectable B, receptor protein with no detectable B1 receptor protein. We conclude that BK evokes iCGRP release from bovine dental pulp which is enhanced by a positive interaction with PGE2. Neurosecretion is evoked from isolated terminals of dental pulp fibers via the bradykinin B2 receptor-dependent mechanism.

Effects of Nd: and Ho:yttrium-aluminium-garnet lasers on human dentine fluid flow and dental pulp-chamber temperature in vitro

Dentine specimens were prepared from freshly extracted third molars and initial permeability measured. Each specimen was subjected to Nd:yttrium-aluminium-garnet (YAG) (1.06 or 1.32 microns wavelength) or Ho:YAG (2.10 microns wavelength) laser energy while temperatures in the pulp chambers were recorded. Permeability was again measured and the surfaces examined by scanning electron microscopy. Six crown segments were used for each laser variable and eight permeability measurements were taken before and eight after laser exposure, while temperature was recorded during treatment. All wavelengths reduced permeability but temperature rises were high enough to have caused pulpal damage, indicating that shorter treatment times and lower power settings may be necessary if used in vivo.

Identify and Determine the Metrics, Hierarchy, and Predictive Value of All the Parameters and/or Methods Used During Endodontic Diagnosis

A Consensus Conference on Terminology was convened by the American Association of Endodontists in Chicago on Oct 3, 2008 to review solicited papers on focused questions. This paper addressed the question: Identify and determine the metrics, hierarchy, and predictive value of all the parameters and/or methods used during endodontic diagnosis. The best available clinical evidence was used to determine the sensitivity, specificity, and predictive value of pulpal and periapical testing methods and imaging technologies. Diagnosis of dental pulp diseases suffers from operators inability to test/image that tissue directly due to its location within dentin. In general, current pulp tests are more valid in determining teeth that are free of disease, but less effective in identifying teeth with pulp disease. Radiographic imaging is probably the most commonly used diagnostic tool to determine the status of root-supporting tissue, although interpretation of structural changes in the periradicular tissues is still considered unreliable.

Pulp chamber temperature changes with visible-light-cured composites in vitro

Due to the low compliance nature of the dental pulp, it is vulnerable to cavity preparation and restoration procedures. The vulnerability may be due to temperature increases within the pulp tissue generated by those procedures. Placement of composites includes the use of visible-light-cure lamps which emit heat and cause a temperature increase in the pulp. This study measured the temperature increase occurring in the pulp chamber with the placement of a two-surface posterior composite using six visible-light-cure lamps. The data indicate that the lamps vary in the amount of temperature increase generated from one to another; that the greater portion of the temperature increase occurred during the placement of the first layer of composite; and that one lamp caused significantly lower temperature increases.