The Academy of Dental Materials: Providing roots and wings.

ObjectivesThe long history of the Academy of Dental Materials (ADM) is documented with its strategies (a) to rapidly communicate science among its members, (b) to establish special awards to stimulate new science, and (c) to develop new dental materials scientists.MethodsWe searched the history of the last 35 years of the ADM newsletters, transactions, journals, and officer notes. We document the (a) presidents, (b) meeting history, (c) membership growth, and (d) development of special awards through 2019 with the recent creation of the ADM Marshall Post-Doctoral Award.ResultsThere are 36 years of recent ADM history, 42 international meetings, membership growth to 400 individuals from 15 countries, service of 19 presidents, Paffenbarger annual Awardees since 1989, induction of >200 fellows, and recognition of the first winner of Marshall Post-Doctoral Award in 2018. New directions for recruiting members are suggested. Three potential new thrusts for the organization are presented: artificial intelligence, genetic engineering, and intensive member mentoring.SignificanceThese suggestions for the ADM provide a path for the ADM to continue to adapt to the ever changing scientific landscape

Restorative Dental Materials: Scanning Electron Microscopy and X-Ray Microanalysis

Restorative dental materials include the materials used to repair damaged teeth and/or replace missing teeth. The definition could be extended to include a much broader group of dental materials, but this paper concentrates only on those materials used to restore the crown portion of damaged teeth. Auxiliary materials, materials for removable denture prostheses, and root canal materials are excluded. Progress and recent research utilizing SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectroscopy), and some related methods are presented for the following dental materials: dental amalgam, enamel and dentin bonding agents, dental composites, dental cements, casting alloys for crowns and bridges, and ceramic-metal and ceramic restorative materials. In addition to the basic characterization of these materials by SEM/EDS techniques, examples of replication methods for SEM study of restorative materials in situ are discussed. Some examples are also presented in the direct use of SEM/EDS for characterization of changes and degradation of restorative materials which occur during clinical use

Comparison of Backscattered Scanning Electron Microscopy and Microradiography of Secondary Caries

Carious lesions are usually studied using light microscopy and/or microradiography which require preparation of thin sections. Backscattered scanning electron microscopy (BSEM) has received little attention although it provides information similar to that obtained with microradiographs, with the potential for higher resolution. Recently, microscopes have been introduced that can be used to study wet or nonconducting specimens, offering techniques for studying specimens without desiccation or preparation of thin sections. This investigation sought to determine if secondary carious lesions have the same characteristics when studied by microradiography as when using the wet BSEM mode. Microradiographs were made of thin sections from restored teeth with secondary caries induced in an artificial caries system. The thin sections were also studied by BSEM with a partial pressure in the specimen chamber to prevent specimen charging. Comparisons of the lesion size and shape were made using the two methods. Lesion depth measurements in enamel were the same; lesions that penetrated into dentin appeared to be of similar size and shape, but lesion depths measured by BSEM were slightly greater (paired t-test, p \u3c .05). This was a result of cracks at the carious enamel-dentin interface that probably developed during storage of the samples. Variations in the surface enamel rod structure and the development of subsurface lesions were apparent. Several zones were also apparent in the carious dentin, demonstrating loss of dentinal tubule detail in the depth of the lesion, collapse of tubules, and hypermineralized regions near the advancing front of the lesion. Several additional samples of natural carious teeth were examined. They demonstrated the characteristic structural features of the carious process. This method appears to have considerable promise for the study of such lesions

Influence of fluoride on the mineralization of collagen via the polymer-induced liquid-precursor (PILP) process.

ObjectiveThe polymer-induced liquid-precursor (PILP) mineralization process has been shown to remineralize artificial dentin lesions to levels consistent with those of native dentin. However, nanoindentation revealed that the moduli of those remineralized lesions were only ∼50% that of native dentin. We hypothesize that this may be due to the PILP process having been previously optimized to obtain high amounts (∼70wt%) of intrafibrillar crystals, but without sufficient interfibrillar mineral, another significant component of dentin.MethodsFluoride was added to the PILP-mineralization of collagen from rat tail tendon at varying concentrations to determine if a better balance of intra- versus inter-fibrillar mineralization could be obtained, as determined by electron microscopy. Nanoindentation was used to determine if fluoridated apatite could improve the mechanical properties of the composites.ResultsFluoride was successfully incorporated into the PILP-mineralization of rat tail tendon and resulted in collagen-mineral composite systems with the mineral phase of hydroxyapatite containing various levels of fluoridation. As the fluoride concentration increased, the crystals became larger and more rod-like, with an increasing tendency to form on the fibril surfaces rather than the interior. Nanomechanical testing of the mineralized tendons revealed that fluoride addition did not increase modulus over PILP mineralization alone. This likely resulted from the separated nature of collagen fibrils that comprise tendon, which does not provide lateral reinforcement and therefore may not be suited for the compressive loads of nanoindentation.SignificanceThis work contributes to the development of minimally invasive approaches to caries treatment by determining if collagen can be functionally mineralized

Four-point bending evaluation of dentin-composite interfaces with various stresses

Fracture properties of composite-dentin beams bonded with a self?etching adhesive were tested following short term pretreatments to simulate potential degradation mechanisms (thermal cycling, immersion in 5% NaOCl, or fatigue cycling). Beams of rectangular cross-section were shaped to a size of ~0.87 x 0.87 x 10 mm and placed in a four-point bending apparatus, with the loading points 1.8 and 7.2 mm apart, with the interface centered between the inner rollers. Testing was performed in Hanks? Balanced Salt Solution at 25 ?C . Solid dentin and solid composite beams [n = 6] had bending strengths of 164.4 and 164.6 MPa, respectively, under monotonically increasing loads. Bonded beams [n = 6] had strengths of 56.3 MPa. Thermo-cycling (5? to 55?C), NaOCl solution immersion, or 105 of pre-fatigue cycles did not decrease the strength. Conclusion: Thermal stress, exposure to NaOCL, or 105 cycles of mechanical stress does not decrease bond strength of composite bonded to dentin as tested in four-point bending

Four-point bending evaluation of dentin-composite interfaces with various stresses

Fracture properties of composite-dentin beams bonded with a self?etching adhesive were tested following short term pretreatments to simulate potential degradation mechanisms (thermal cycling, immersion in 5% NaOCl, or fatigue cycling). Beams of rectangular cross-section were shaped to a size of ~0.87 x 0.87 x 10 mm and placed in a four-point bending apparatus, with the loading points 1.8 and 7.2 mm apart, with the interface centered between the inner rollers. Testing was performed in Hanks? Balanced Salt Solution at 25 ?C . Solid dentin and solid composite beams [n = 6] had bending strengths of 164.4 and 164.6 MPa, respectively, under monotonically increasing loads. Bonded beams [n = 6] had strengths of 56.3 MPa. Thermo-cycling (5? to 55?C), NaOCl solution immersion, or 105 of pre-fatigue cycles did not decrease the strength. Conclusion: Thermal stress, exposure to NaOCL, or 105 cycles of mechanical stress does not decrease bond strength of composite bonded to dentin as tested in four-point bending

Effect of mucoprotein on the bond strength of resin composite to human dentin

The final publication is available at Springer via http://dx.doi.org/10.1007/s10266-011-0002-9.The purpose of this study was to test the bond strength and analyze the morphology of the dentin-adhesive interface of two etch and rinse and two self-etch adhesive systems with two kinds of artificial saliva (with and without 450 mg/L mucin) contamination under different conditions of decontaminating the interface. Bonded specimens were sectioned perpendicularly to the bonded surface in 1-mm thick slabs. These 1-mm thick slabs were remounted in acrylic blocks and sectioned in sticks perpendicular to the bonding interfaces with a 1-mm2 area. Nine specimens from each condition were tested after 24 h on a testing machine (Instron) at a speed of 0.5 mm/min for a total of 360 specimens. Mean and standard deviations of bond strength (MPa) were calculated. ANOVA showed significant differences as well as Fisher’s PLSD intervals (p < 0.05). The following values are the results for different groups: Control group 34–60 MPa, saliva without mucin 0–52 MPa, and saliva with mucin 0–57 MPa. Failure sites were mixed and adhesive failure was common for the low bond strength results. P&BNT with ideal conditions and following the manufacturer’s instructions (control) had the highest bond strengths and the dentin-adhesive interface exhibited an ideal morphology of etch-and-rinse system. SEM gave complementary visual evidence of the effect in the dentin/adhesive interface structure with some contaminated conditions compared with their respective control groups. This in vitro artificial saliva model with and without mucin showed that an organic component of saliva could increase or decrease the bond strength depending on the specific bonding agent and decontamination procedure

Bond strength of adhesives to dentin contaminated with smoker\u27s saliva.

The purpose of this study was to determine the effects of contamination with smoker\u27s and non-smoker\u27s saliva on the bond strength of resin composite to superficial dentin using different adhesive systems. The interfacial structure between the resin and dentin was evaluated for each treatment using environmental scanning electron microscopy (ESEM). Freshly extracted human molars were ground with 600-grit SiC paper to expose the superficial dentin. Adhesives [One-Up-Bond-F-Plus (OUFP) and Adper-Prompt-L-Pop (APLP)] and resin composite (TPHSpectrum) were bonded to the dentin (n = 8/group, 180 total specimens) under five surface conditions: control (adhesive applied following manufacturers\u27 instructions); saliva, then 5-s air dry, then adhesive; adhesive, saliva, 5-s air dry; adhesive, saliva, 5-s water rinse, 5-s air dry (ASW group); and adhesive, saliva, 5-s water rinse, 5-s air dry, reapply adhesive (ASWA group). After storage in water at 37 degrees C for 24 h, the specimens were debonded under tension at a speed of 0.5 mm/min. ESEM photomicrographs of the dentin/adhesive interfaces were taken. Mean bond strength ranged from 8.1 to 24.1 MPa. Fisher\u27s protected least significant difference (P = 0.05) intervals for critical adhesive, saliva, and surface condition differences were 1.3, 1.3, and 2.1 MPa, respectively. There were no significant differences in bond strength to dentin between contamination by smoker\u27s and nonsmoker\u27s saliva, but bond strengths were significantly different between adhesive systems, with OUFP twice as strong as APLP under almost all conditions. After adhesive application and contamination with either smoker\u27s or nonsmoker\u27s saliva followed by washing and reapplication of the adhesive (ASWA group), the bond strength of both adhesive systems was the same as that of the control group

Bond strength of adhesives to dentin contaminated with smoker’s saliva

The final publication is available at Springer via http://dx.doi.org/10.1007/s10266-009-0109-4.The purpose of this study was to determine the effects of contamination with smoker’s and non-smoker’s saliva on the bond strength of resin composite to superficial dentin using different adhesive systems. The interfacial structure between the resin and dentin was evaluated for each treatment using environmental scanning electron microscopy (ESEM). Freshly extracted human molars were ground with 600-grit SiC paper to expose the superficial dentin. Adhesives [One-Up-Bond-F-Plus (OUFP) and Adper-Prompt-L-Pop (APLP)] and resin composite (TPH-Spectrum) were bonded to the dentin (n = 8/group, 180 total specimens) under five surface conditions: control (adhesive applied following manufacturers’ instructions); saliva, then 5-s air dry, then adhesive; adhesive, saliva, 5-s air dry; adhesive, saliva, 5-s water rinse, 5-s air dry (ASW group); and adhesive, saliva, 5-s water rinse, 5-s air dry, reapply adhesive (ASWA group). After storage in water at 37°C for 24 h, the specimens were debonded under tension at a speed of 0.5 mm/min. ESEM photomicrographs of the dentin/adhesive interfaces were taken. Mean bond strength ranged from 8.1 to 24.1 MPa. Fisher’s protected least significant difference (P = 0.05) intervals for critical adhesive, saliva, and surface condition differences were 1.3, 1.3, and 2.1 MPa, respectively. There were no significant differences in bond strength to dentin between contamination by smoker’s and non-smoker’s saliva, but bond strengths were significantly different between adhesive systems, with OUFP twice as strong as APLP under almost all conditions. After adhesive application and contamination with either smoker’s or nonsmoker’s saliva followed by washing and reapplication of the adhesive (ASWA group), the bond strength of both adhesive systems was the same as that of the control group

Tissue-specific calibration of extracellular matrix material properties by transforming growth factor-beta and Runx2 in bone is required for hearing

Publisher version: http://www.nature.com/embor/journal/v11/n10/full/embor2010135.htmlDA - 20100917 IS - 1469-3178 (Electronic) IS - 1469-221X (Linking) LA - ENG PT - JOURNAL ARTICLEDA - 20100917 IS - 1469-3178 (Electronic) IS - 1469-221X (Linking) LA - ENG PT - JOURNAL ARTICLEDA - 20100917 IS - 1469-3178 (Electronic) IS - 1469-221X (Linking) LA - ENG PT - JOURNAL ARTICLEPhysical cues, such as extracellular matrix stiffness, direct cell differentiation and support tissue-specific function. Perturbation of these cues underlies diverse pathologies, including osteoarthritis, cardiovascular disease and cancer. However, the molecular mechanisms that establish tissue-specific material properties and link them to healthy tissue function are unknown. We show that Runx2, a key lineage-specific transcription factor, regulates the material properties of bone matrix through the same transforming growth factor-beta (TGFbeta)-responsive pathway that controls osteoblast differentiation. Deregulated TGFbeta or Runx2 function compromises the distinctly hard cochlear bone matrix and causes hearing loss, as seen in human cleidocranial dysplasia. In Runx2(+/-) mice, inhibition of TGFbeta signalling rescues both the material properties of the defective matrix, and hearing. This study elucidates the unknown cause of hearing loss in cleidocranial dysplasia, and demonstrates that a molecular pathway controlling cell differentiation also defines material properties of extracellular matrix. Furthermore, our results suggest that the careful regulation of these properties is essential for healthy tissue functio