Fresh Dentin Research Articles

Effects of gamma irradiation on the measurement of hepatitis B virus DNA in dentin harvested from chronically infected patients.

BackgroundThe manufacturing of the demineralized dentin matrix (DDM) has been proven to extensively reduce the presence of human hepatitis B viral DNA (HBV DNA). This study measured and compared HBV DNA in fresh dentin to that in gamma radiation (GR)-sterilized dentin extracted from HBV-infected patients. The application of GR as a means of terminal sterilization is hypothesized to inactivate or eliminate HBV within the dentin matrix.MethodsDentin from 18 HBV-infected patients was collected and divided into three fragments. The first fragment was unaltered and used as the control group; the remaining two fragments were sterilized with gamma radiation doses of 15 or 25 kGy. DNA was extracted and purified from each fresh (control), and the GR-sterilized (experimental) dentin specimen and HBV DNA copy numbers were evaluated on the basis of the real-time polymerase chain reaction. The copy numbers were used to assess GR efficacy as a means of terminal sterilization for HBV inactivation or elimination.ResultsHBV DNA was detected in 66.67% of the fresh dentin specimens. The differences in HBV DNA levels between the fresh dentin and the GR-sterilized dentin were confirmed by the Wilcoxon signed-rank test for the doses of 15 and 25 kGy with P value of 0.012 and 0.010, respectively. Among the twelve HBV-DNA-positive fresh dentin samples, HBV DNA persisted in eleven after GR sterilization, yet the copy number was reduced to <10 (except for a single sample within each experimental group).ConclusionsThe results suggest that 15 and 25 kGy of GR significantly reduced the HBV DNA levels in the fresh dentin matrix. Expansion of the possible clinical applications of allogenic grafts with the irradiated DDM will require additional studies, including validation of viral load inactivation to prevent infectious transmission and examination of GR exposure effects on the osteoinductivity of the matrix.

Avoidance of Interaction between Impression Materials and Tooth Surface Treated for Immediate Dentin Sealing: An In Vitro Study.

Immediate dentin sealing (IDS) is an advantageous approach for realizing adhesive restorations, but it interferes with the polymerization of impression material due to the oxygen-inhibition layer (OIL), which leaves residues of impression material on the teeth. The aim of this study is to identify a clinical surface cleaning protocol after IDS in order to achieve defect-free impressions. Sixty extracted human teeth were cut to expose fresh dentin and the IDS protocol was performed. Samples were divided into six groups where different surface cleaning protocols were made before taking impressions: G1S and G1P groups, IDS and silicone (S) or polyether (P) impressions; G2S and G2P, treatment with prophy paste and impressions; G3S and G3P, final cleaning phase with surfactant agent and impressions. Teeth were evaluated with a scanning electron microscope to identify the areas (expressed in mm2) where residual impression material was present. The results demonstrate a reduction of residues in the G2 groups and the total disappearance in G3 groups with statistically significant differences between them. Superficial cleaning protocols with the prophy paste and surfactant agent lead to the elimination of the interaction with impression materials and OIL. These results suggest a safe clinical protocol for obtaining defect-free impressions after IDS.

Measurement of hepatitis B virus DNA in fresh versus processed dentin from chronically infected patients

BackgroundDemineralized dentin matrix (DDM) is commonly used as a bone-graft substitute. This study measured and compared human hepatitis B viruses (HBV) DNA in fresh dentin to that of dentin processed into DDM extracted during dental treatment from HBV-infected patients. The hypothesis was that the processing procedure for DDM would inactivate or eliminate HBV in the dentin matrix obtained from infected patients.MethodsDentin from eighteen HBV-infected patients was collected and each dentin specimen was divided into two fragments. One fragment was used before processing as fresh dentin (control group) and the other was processed into DDM (experimental group). DNA was extracted and purified from each fresh and processed dentin specimen and the HBV DNA copy number quantitated by real time polymerase chain reaction. The HBV DNA copy number in the fresh dentin specimens were compared relative to serologic test results. The second parameter was to evaluate the effectiveness of the processing procedure (defatting, demineralization, freeze-drying, and sterilization) to inactivate or eliminate HBV by comparing the DNA copy number in the processed DDM with that in the matched fresh dentin specimens. All results were analyzed using Mann–Whitney U test to compare numerical measurements between groups and differences were considered statistically significant at P-values less than 0.05.ResultsThe presence of HBV DNA was detected in 55.56% (10/18) of the fresh dentin specimens. For the ten HBV DNA-positive fresh dentin specimens, HBV DNA was detected in two (20%) of the matched processed dentin specimens. The copy number of HBV DNA in the two positive processed dentin specimens was 1.79 and 4.03, which were statistically lower than that of the fresh dentin specimens (P = 0.0167).ConclusionsThe results from this study suggested that fresh dentin may be a carrier of HBV and that the procedure used to generate DDM extensively reduced the levels of HBV DNA. Further studies are needed to evaluate the infectivity of HBV in processed dentin.

Adhesive performance of infiltrating resin bonded on dentin in vitro

To evaluate the adhesive interface and micro-tensile bond strength (μTBS) of infiltrating resin directly bonded to normal dentin. Twenty extracted human molars were collected and ground to expose fresh dentin surface. An infiltrating resin (ICON, DMG, Germany) was served as experimental group and Clearfil SE Bond adhesive (Kuraray, Japan) as control group. Following the application of primer (Kuraray, Japan), the specimens were applied infiltrating resin or adhesive respectively and blocks of composite resin were built up. The adhesive interfaces were observed using scanning electron microscope (SEM) and the μTBS was measured by micro-tensile test before and after thermal cycling. The infiltrating resin could penetrate into micro-structure of dentin created by SE Bond primer. A layer of about 180 μm-long and dense resin tags was observed under SEM in infiltrating resin group. The μTBSs were (35 ± 10) MPa before and (35 ± 9) MPa after thermal cycling respectively in infiltrating resin group, and the difference was not statistically significant (P>0.05). The μTBSs were (38±8) MPa before and (24±7) MPa after thermal cycling respectively in control group, and the difference was statistically significant (P<0.05). After thermal cycling, the μTBS of infiltrating resin group was significant higher than that of control group. The infiltrating resin could penetrate into the micro-structure of dentin created by SE Bond primer. The bond strength and the bonding durability of infiltrating resin were similar to that of SE Bond adhesive.

Discussion: Effects of fresh mineralized dentin and cementum on socket healing: a preliminary study in dogs.

It is impressive to review an article that displays the procedure, outcome, and analysis of the study along with detailed data1. However, existing articles since 1967 have reported that the application of fresh dentin and cementum (DC) to bone defects has little effect on bone regeneration. References 9, 11, and 15 in this article1 illustrate the function of fresh dentin, but other studies have also demonstrated why fresh dentin requires material preparation specific to the defect type2,3,4. This study could also be strengthened by histologically analyzing the data in the figures. The directions of the wall, apex and crestal area could be indicated using the trephine since the reactions differ according to the blood supply potential of each site. Consider adding indicators on the figures to differentiate new bone from the border and to highlight new bone around the dentin powder and connective tissue with vascularization for the objective analysis because dentin promotes new bone formation, especially when located close to native cortical bone, and it may also have potential as a bone augmentation material5,6. Even though the effect of fresh DC on bone regeneration has been repeatedly tested, it is still meaningful to apply fresh DC to extraction sockets. Since many factors could have affected the results of other studies, it is important to periodically confirm this conclusion. This article encourages researchers to investigate new methods to manufacture bone graft material for dental patients with alveolar bone defects.

Effect of exposure time of zinc oxide eugenol restoration on microtensile bond strength of adhesives to dentin

ObjectiveThe purpose of this study was to evaluate the influence of different exposure times (24h, 7 days and 45 days) of zinc oxide eugenol cement (ZOE) on microtensile bond strength (μTBS) of etch-and-rinse and self-etch adhesives. MethodsOcclusal enamel of 40 human molars was removed. Zinc oxide eugenol restoration was placed on the dentin surface and left for different times (24h, 7 days or 45 days). After ZOE removal or over fresh dentin (control) were restored using Adper Single Bond 2 (SB2) or Clearfil S3 Bond (CS3). After 24h, each tooth was longitudinally sectioned, to obtain bonded sticks that were tested under tension (0.5mm/min). Two-way ANOVA and Tukey's test (α=0.05) were used to compare μTBS. ResultsA decrease in μTBS was observed for SB2 after 24h (46.8±3.4MPa) when compared to the control (60.4±5.2MPa, p<0.05). Similarly, a decrease was observed for CS3 after storage for 24h (20.4±2.2MPa) and 7 days (18.1±2.1MPa), when compared with a control group (39.1±4.2MPa, p<0.05). After 45 days, both adhesives SB2 and CS3 show the same μTBS compared to controls. Under all conditions, SB2 showed higher μTBS values than CS3 (p<0.001). ConclusionThe results suggest that ZOE has negative effects on microtensile bond strength after 24h.

The effects of desensitizing resin, resin sealing, and provisional cement on the bond strength of dentin luted with self-adhesive and conventional resincements

Self-adhesive resin cements were designed to bond without any pretreatment of dentin. However, pretreatments such as the application of desensitizing resin or the resin sealing of dentin with priming/bonding solutions might influence the bonding quality of these self-adhesive resin cements. Little is known about the effect of dentin pretreatment on the bond quality of self-adhesive resin cements. This study evaluated whether dentin desensitizing or sealing methods influenced the shear bond strength of 1 self-adhesive and 2 conventional resin cements. One-hundred and eighty human molars were assigned to 5 different pretreatment groups: 1) freshly ground dentin, 2) glutaraldehyde/hydroxyethylmethacrylate (HEMA) desensitized dentin (Gluma), 3) contamination of desensitized dentin with provisional cement, 4) sealed dentin (dual bonding technique), and 5) contamination of sealed dentin with provisional cement. The shear bond strength of a self-adhesive resin cement (RelyX Unicem; RXU) and 2 conventional resin cements (Variolink II; VAR, Panavia 21; PAN) was assessed for each pretreatment group (n=12 per cement types). Two-way ANOVA and 1-way ANOVA together with the post hoc Tukey multiple comparison (α=.05) were performed. On freshly ground dentin, PAN exhibited the highest shear bond strength values (P<.001). The use of the glutaraldehyde/HEMA resulted in a significant increase in the bond strength of RXU as compared to fresh dentin (P<.001). Resin sealing of dentin increased the bond strength of RXU but had no significant effect on VAR or PAN. RXU exhibited the highest mean bond strength after the contamination of resin-sealed dentin by provisional cement. Glutaraldehyde/HEMA treatment and resin sealing of dentin have a beneficial effect on the shear bond strength of self-adhesive resin cement (RXU). Contamination of dentin with provisional cement has no influence on the bond strength of the self-adhesive resin cement (RXU) or VAR but lowered the bond strength of PAN.

EXPERIMENTAL IN VITRO DISSOLUTION OF THE DENTINE OF TEETH OF SUS SCROFA (MAMMALIA, SUIDAE): CHEMISTRY AND MICROSTRUCTURAL ALTERATIONS*

Alterations induced during the first step of fossilization are examined. Molars and premolars of a modern large mammal were crushed to expose fresh dentine. Fragments were placed in solutions of acids present in humus for 2 months. Changes in composition of the solutions were analysed. Micro‐ and nanostructural changes of fresh and etched dentine were observed with scanning electron and atomic force microscopes. The ion contents of the acetic acid solution are higher than those of oxalic and oxalic plus acetic acid solutions. Oxalic acid etching results in secondary deposits of oxalates on the exposed dentine. The composition of the soil in natural fossilization processes is a main factor in fossil preservation.

Evaluation of the coefficient of thermal expansion of human and bovine dentin by thermomechanical analysis

The mismatch of thermal expansion and contraction between restorative materials and tooth may cause stresses at their interface, which may lead to microleakage. The present work compared the coefficient of thermal expansion (CTE) with the thermomechanical behavior of human and bovine teeth and determined if the CTE is a suitable parameter to describe tooth behavior. Fifteen human third molar and 15 bovine incisor tooth slices (6×5×2 mm) were allocated to 3 groups according to the test environment: G1 - room condition, G2 - 100% humidity, G3 - desiccated and tested in dry condition. Each specimen was weighed, heated from 20 to 70ºC at 10ºC min-1 and reweighed. The CTE was measured between 20 and 50ºC. Fresh dentin (human -0.49% ± 0.27, bovine -0.22% ± 0.16) contracted on heating under dry condition. Under wet conditions, only human teeth (-0.05% ± 0.04) showed contraction (bovine 0.00% ± 0.03) accompanied by a significantly lower (p<0.05) weight loss than in dry specimens (human 0.35% ± 0.15, bovine 0.45% ± 0.20). The desiccated dentin expanded on heating without obvious weight changes (0.00% ± 0.00). The CTE found was, respectively, in dry, wet and dissected conditions in ºC(-1): human (-66.03×10(-6), -6.82×10(-6), 5.52×10(-6)) and bovine (-33.71×10(-6), 5.47×10(-6), 4.31×10(-6)). According to its wet condition, the dentin showed different CTEs. The thermal expansion behavior of human and bovine dentin was similar. A simple evaluation of the thermal expansion behavior of tooth structure by its CTE value may not be appropriate as a meaningful consideration of the effects on the tooth-material interface.

Notch signalling pathway in tooth development and adult dental cells

Notch signalling is a highly conserved intercellular signal transfer mechanism that includes canonical and non-canonical pathways. It regulates differentiation and proliferation of stem/progenitor cells by means of para-inducing effects. Expression and activation of Notch signalling factors (receptors and ligands) are critical not only for development of the dental germ but also for regeneration of injured tissue associated with mature teeth. Notch signalling plays key roles in differentiation of odontoblasts and osteoblasts, calcification of tooth hard tissue, formation of cusp patterns and generation of tooth roots. After tooth eruption, Notch signalling can also be triggered in dental stem cells of the pulp, where it induces them to differentiate into odontoblasts, thus generating fresh dentine tissue. Other signalling pathways, such as TGFβ, NF-κB, Wnt, Fgf and Shh also interact with Notch signalling during tooth development.

Effects of saliva contamination and decontamination procedures on shear bond strength of self-etch dentine bonding systems: An in vitro study

Objective:This study aims to evaluate the effect of saliva contamination on the shear bond strength of two self-etch dentine bonding systems and also investigate the effect of decontamination procedure on the recovery of bond strength.Materials and Methods:Sixty premolars extracted for orthodontic reason were obtained and the buccal surfaces of teeth were reduced to create a flat dentine surface. The samples were randomly divided into three sub-groups for AdheSE (ASE) (Ivoclar – Vivadent, Schaan, Liechtenstein) and three sub-groups for Adper Prompt Self-Etch Adhesive (ADP) (3M ESPE, St Paul, MN, USA) of 10 each. For AdheSE (ASE); ASE-I was the control group (primer applied to fresh dentine surface), ASE-II was the contamination group (primer applied, followed by saliva contamination and then air dried) and ASE-III was the decontamination group (primer applied, followed by saliva contamination, air dried and then primer reapplied). For Adper Prompt (ADP); ADP-I was the control group (self-etch adhesive applied to fresh dentine surface), ADP-II was the contamination group (self-etch adhesive applied, followed by saliva contamination and then air dried) and ADP-III was the decontamination group (self-etch adhesive applied, followed by saliva contamination, air dried and then self-etch adhesive reapplied). Followed by the bonding procedure, a 5 mm composite resin block with Filtek P-60 (3M ESPE, St Paul, MN, USA) was built on the substrate. Shear bond strength (SBS) was tested with Instron Universal testing machine (Instron Corporation, Canton, MA, USA) with a cross head speed of 1 mm per minute. Data obtained was subjected to one way ANOVA test, while the inter group comparison was made using Tukey’s multiple comparison and Unpaired t-test.Results:In AdhSE group (ASE), the sub-group ASE-II (contamination group) [5.4 ± 2.2 MPa] showed lower SBS than ASE-I [11.8 ± 2.6 MPa] and ASE-III [8.9 ± 3.3 MPa], which was statistically significant. There was no significant difference in the bond strength between the ASE-I (control group) and ASE-III (decontamination group). In Adper Prompt group (ADP), there was a severe decrease of bond strength in ADP-II (contamination group) [4.6 ± 1.1 MPa] when compared to ADP-I (control group) [7.4 ± 1.4 MPa] and ADP-III (decontamination subgroup) [14.1 ± 2.2 MPa] which was statistically significant. The bond strength of ADP-III wherein Adper Prompt bonding agent was reapplied after salivary contamination was found to be statistically significant than ADP-I and ADP-II.Conclusion:Saliva contamination reduces the dentine bond strength of both the self-etch systems; AdheSE and Adper Prompt. Re-application of the primer for the AdheSE and re-application of the adhesive for the Adper Prompt after air drying the saliva off can recover the dentine bond strength. In the Adper Prompt group, the added application of adhesives to decontaminate saliva not only recovered the bond strength but also improved it significantly.

The bonding durability of total etching adhesives on dentin

The purpose of this study was to evaluate the effect of different etching times on microtensile bond strength (μ TBS) to dentin both initial and after thermocycling with 3 different types of total-etching adhesives. Fifty four teeth were divided into 18 groups by etching times (5, 15, 25 sec), adhesives types (Scotchbond Multipurpose (SM), Single Bond (SB), One-Step (OS)), and number of thermocycling (0, 2,000 cycles). Flat dentin surfaces were prepared on mid-coronal dentin of extracted third molars. After exposed fresh dentin surfaces were polished with 600-grit SiC papers, each specimen was acid-etched with 35% phosphoric acid (5, 15, 25 sec) and bonded with 3 different types of total etching adhesives respectively. Then, hybrid composite Z-250 was built up. Half of them were not thermocycled (control group) and the others were subjected to 2,000 thermocycle (experimental group). They were sectioned occluso-gingivally into 1.0 × 1.0 ㎟ composite-dentin beams and tested with universal testing machine at a crosshead speed of 1.0 ㎜/min. Within limited data of this study, the results were as follows 1. There was no statistically significant difference in μ TBS between the thermocycled and non-thermocycled groups, except for both SM and SB etched for 25 sec. 2. In thermocycled SM and SB groups, bond strength decreased by extended etching time. In total etching systems, adhesive durability for dentin could be affected by type of solvents in adhesive and etching time. Especially, extended etching time may cause deteriorate effects on bond strength when ethanol-based adhesive was used.

Effect of temporary cements on the bond strength of ceramic luted to dentin

Objectives The purpose of this study was to evaluate the effect of either eugenol-containing or eugenol-free temporary cement removal by excavator or sandblasting on the shear bond strength of ceramic luted to dentin. Methods A self-etching primer system, Panavia F 2.0, Kuraray Medical (PF2), and a total-etch bonding system, Excite/Variolink II, Vivadent (EXV), were used. One hundred forty human molars, ground to expose dentin surfaces, were divided into 14 groups (7 groups for each adhesive system). For each adhesive system, either a eugenol-containing (Temp bond) or a eugenol-free (Temp bond NE) temporary cement was applied to the dentin surface for 7 days, then removed by an excavator or sandblasting (4 groups). Three control groups were studied where fresh dentin was either scratched by excavator or sandblasted, or underwent no surface treatment. After application of the adhesives, ceramic cones (Cerafil inserts) were adhesively luted to standardized dentin areas. After 24-hour storage in distilled water, the shear bond strengths were determined at a cross-head speed of 0.75 mm/min. Results For each adhesive system, neither the method of temporary cement removal nor the type of temporary cement affected the bond strength significantly (P≤0.05). EXV showed statistically higher bond strengths (26.6-31.6 MPa) than PF2 (8.6-12.9 MPa) within all groups. Significance The use of temporary cements, either containing eugenol or not, does not alter the retentive strength of ceramic restorations luted to dentin using the tested adhesive systems, whether the temporary cements are removed by excavator or sandblasting.—Reprinted with permission of The Academy of Dental Materials. The purpose of this study was to evaluate the effect of either eugenol-containing or eugenol-free temporary cement removal by excavator or sandblasting on the shear bond strength of ceramic luted to dentin. A self-etching primer system, Panavia F 2.0, Kuraray Medical (PF2), and a total-etch bonding system, Excite/Variolink II, Vivadent (EXV), were used. One hundred forty human molars, ground to expose dentin surfaces, were divided into 14 groups (7 groups for each adhesive system). For each adhesive system, either a eugenol-containing (Temp bond) or a eugenol-free (Temp bond NE) temporary cement was applied to the dentin surface for 7 days, then removed by an excavator or sandblasting (4 groups). Three control groups were studied where fresh dentin was either scratched by excavator or sandblasted, or underwent no surface treatment. After application of the adhesives, ceramic cones (Cerafil inserts) were adhesively luted to standardized dentin areas. After 24-hour storage in distilled water, the shear bond strengths were determined at a cross-head speed of 0.75 mm/min. For each adhesive system, neither the method of temporary cement removal nor the type of temporary cement affected the bond strength significantly (P≤0.05). EXV showed statistically higher bond strengths (26.6-31.6 MPa) than PF2 (8.6-12.9 MPa) within all groups. The use of temporary cements, either containing eugenol or not, does not alter the retentive strength of ceramic restorations luted to dentin using the tested adhesive systems, whether the temporary cements are removed by excavator or sandblasting.—Reprinted with permission of The Academy of Dental Materials.

A comparison between a smooth wire and a K‐file in removing artificially placed dentine debris from root canals in resin blocks during ultrasonic irrigation

To compare the efficacy of a smooth wire with a conventional K-file, in removing dentine debris from grooves in root canals made in resin blocks, during ultrasonic irrigation. Each resin block containing a standard simulated canal was split longitudinally through the canal, forming two halves. In one canal wall, a standard groove 4 mm in length, 0.2 mm in width and 0.5 mm in depth was cut 2-6 mm from the apical end of the canal, to simulate uninstrumented canal extensions. Each groove was filled with fresh dentine debris mixed with 2% NaOCl to simulate a situation when dentine debris accumulates in uninstrumented canal extensions. Each canal was reassembled by joining the two halves of the resin block by means of wires and sticky wax. In each canal ultrasonic irrigation was performed for 3 min using 2% NaOCl as irrigant. In one group (n = 20) a conventional K-file size 15 was used. In the other group (n = 20) a smooth wire was used which had the same length and diameter as the size 15 K-file. Before and after irrigation, images of each half of the canal with a groove were taken, using a microscope and a digital camera, after which they were scanned into a PC as TIFF images. The quantity of dentine debris in the groove was evaluated using a scoring system: the higher the score, the larger the amount of debris remaining. The score data were analysed by means of the Mann-Whitney U-test. After ultrasonic irrigation, the debris was completely removed from the groove in 35 canals (87.5%), and there was no significant difference between the groups (P = 0.429). Using a smooth wire during ultrasonic irrigation is as effective as a size 15 K-file in removal of artificially placed dentine debris in grooves in simulated root canals in resin blocks.

Effect of temporary cements on the bond strength of ceramic luted to dentin

The purpose of this study was to evaluate the effect of either eugenol-containing or eugenol-free temporary cement removal by excavator or sandblasting on the shear bond strength of ceramic luted to dentin. A self-etching primer system, Panavia F 2.0, Kuraray Medical (PF2), and a total-etch bonding system, Excite/Variolink II, Vivadent (EXV), were used. One hundred and forty human molars, ground to expose dentin surfaces, were divided into 14 groups (seven groups for each adhesive system). For each adhesive system, either a eugenol-containing (Temp bond) or a eugenol-free (Temp bond NE) temporary cement was applied to the dentin surface for 7 days, then removed by an excavator or sandblasting (four groups). Three control groups were studied where fresh dentin was either scratched by excavator or sandblasted, or underwent no surface treatment. After application of the adhesives, ceramic cones (Cerafil inserts) were adhesively luted to standardized dentin areas. After 24 h storage in distilled water, the shear bond strengths were determined at a cross-head speed of 0.75 mm/min. For each adhesive system, neither the method of temporary cement removal nor the type of temporary cement affected the bond strength significantly (P<or=0.05). EXV showed statistically higher bond strengths (26.6-31.6 MPa) than PF2 (8.6-12.9 MPa) within all groups. The use of temporary cements, either containing eugenol or not, does not alter the retentive strength of ceramic restorations luted to dentin using the tested adhesive systems, whether the temporary cements are removed by excavator or sandblasting.

Storage effect on dentine structure and on resultant composite bond strengths.

This study evaluates the effects of a food simulating solution (75 vol% ethanol/water) and an artificial saliva (Moi-Stir) on dentine structure and chemistry, using scanning electron microscopic examination and Fourier transform infra-red (FTIR) microscopic characterization. The effect on the bonding of composites to the conditioned dentine were evaluated by shear bond strength (SBS) tests. Three adhesive/composite systems were examined: Tenure/Marathon One, Scotchbond Multi-Purpose/Z100, and Optibond/Herculite XRV. Control specimens were stored in either distilled water or tested without storage. Dentine surface exposure to ethanol resulted in partial loss of the smear layer and of plugs, as well as possible perturbation of collagen. Dentine surfaces exposed to artificial saliva or to distilled water had no evidence of any change from normal appearance of the smear layer. The measured FTIR spectra for most specimens conditioned in these two liquids appeared to be similar to those obtained from fresh dentine. SBS data were analysed using ANOVA and the Tukey LSD test. The SBS value for the non-preconditioned control (23.0 +/- 3.7 MPa) or for the dentine preconditioned in distilled water (22.9 +/- 4.2 MPa) was significantly higher (P < 0.05) than that for dentine pre-conditioned in ethanol (20.0 +/- 3.5 MPa). The SBS (13.3 +/- 3.4 MPa) of all bonding systems was reduced by 40-50% (P < 0.001) when artificial saliva pre-conditioned dentine was used. The failure mode at the dentine-bonding agent interface for the artificial saliva group was adhesive in nature. This is in contrast to the complex cohesive fracture mode found in the control groups and in most ethanol conditioned groups. Dentine structure and chemistry, shear bond strength, and the subsequent debonded mode can be significantly affected by exposure to oral environment prior to conditioning.

Storage effect on dentine structure and on resultant composite bond strengths

summary This Study evaluates the effects of a food simulating solution (75 vol% ethanol/water) and an artificial saliva (Moi‐Stir) on dentine structure and chemistry, using scanning electron microscopic examination and Fourier transform infra‐red (FTIR) microscopic characterization. The effect on the bonding of composites to the conditioned dentine were evaluated by shear bond strength (SBS) tests. Three adhesive/composite systems were examined: Tenure/Marathon One®, Scotchbond Multi‐Purpose/ Z100®, and Optibond/Herculite XRV®. Control specimens were stored in either distilled water or tested without storage. Dentine surface exposure to ethanol resulted in partial loss of the smear layer and of plugs, as well as possible perturbation of collagen. Dentine surfaces exposed to artificial saliva or to distilled water had no evidence of any change from normal appearance of the smear layer. The measured FTIR spectra for most specimens conditioned in these two liquids appeared to be similar to those obtained from fresh dentine. SBS data were analysed using anova and the Tukey LSD test. The SBS value for the non‐preconditioned control (23.0 ± 3.7 MPa) or for the dentine pre‐conditioned in distilled water (22.9 ± 4.2 MPa) was significantly higher (P &lt; 0.05) than that for dentine pre‐conditioned in ethanol (20.0 ± 3.5 MPa). The SBS (13.3 ± 3.4 MPa) of all bonding systems was reduced by 40–50% (P &lt; 0.001) when artificial saliva pre‐conditioned dentine was used. The failure mode at the dentine‐bonding agent interface for the artificial saliva group was adhesive in nature. This is in contrast to the complex cohesive fracture mode found in the control groups and in most ethanol conditioned groups. Dentine structure and chemistry, shear bond strength, and the subsequent debonded mode can be significantly affected by exposure to oral environment prior to conditioning.

A new saw technique improves preparation of bone sections for light and electron microscopy.

A newly developed saw technique was developed to produce sections circa 10 microns or thicker from fresh bone or dentine and from plastic embedded undecalcified bone tissue with or without implant materials. The method comprises only one step because grinding or polishing to make the sections thinner is not necessary. The bone slices can be decalcified rapidly without using aggressive solvents and used for making ultrathin sections for electron microscopy. Sections of fresh dentine of 15 to 30 microns are transparent which makes it possible to study osteoclastic resorption in vitro. Sections, 10 microns thick, with an intact interface of bone and implant material can be observed for biocompatibility studies.

Influence of dentin on bonding of composite resin. Part 1. Effect of fresh dentin and storing conditions.

The effects of preserving conditions and time after extraction of human teeth, as specimens for bond strength of composite resin to the dentin, were investigated by the tensile test method and scanning electron microscopy (SEM).When the teeth were stored in physiologic saline solution, bond strength at 15 minutes after extraction showed the lowest value (13kg/cm2), and at 1 to 12 weeks it was elevated to about 35kg/cm2. However pretreatment with citric acid-FeCl3 solution of dentin surface increased the bond strength 3-fold. The teeth stored in formalin for 6 months had the highest bond strength (80kg/cm2). On SEM observation of the dentin and resin surfaces following the tensile test, a clear correlation was found between range of bond strength and appearance of resin tags.

Changes in the dentine of human teeth following extraction and their implication for in-vitro studies of adhesion to tooth substance

The change in bond strength, measured in shear, which can be achieved between polycarboxylate cement and human dentine at various times after tooth extraction is described. Four stages of change were noted at 25 °C; a rapid fall in strength, of up to 50 per cent, in bonds made in the first 250 min after extraction, followed by a slow rise for 25 days, then a rapid fall between 25 and 30 days to a plateau at 45 per cent of the original value. This final bond strength showed little further change 35 days later. The ability of dentine to form bonds is thus closely dependent on its freshness; some possible explanations of the tissue changes responsible are given. It is concluded that physical testing and chemical assay of stored human dentine is likely to yield unreliable data. Ideally, experiments should be conducted in vivo, or fresh dentine used within 20 min of tooth extraction.