Background: A reduced residual dentine thickness following crown preparation has a conceivable impact on pulp degeneration by increasing the pulp’s susceptibility to injury. In crown preparations, three different fin...Background: A reduced residual dentine thickness following crown preparation has a conceivable impact on pulp degeneration by increasing the pulp’s susceptibility to injury. In crown preparations, three different finishing lines are used. These are shoulder, chamfer, and knife edge. Each with its comparative advantages and disadvantages. There is inadequate scientific evidence on which of these finishing lines will leave the most amount of residual dentine, after standard crown preparations on mandibular incisors and maxillary lateral incisors to preserve their pulpal health. Objective: To evaluate residual dentine thickness following various cervical finishing lines of anterior crown preparations for zirconia full coverage. Materials and Methods: A prospective comparative study was conducted from September 2<sup>nd</sup> to November 5<sup>th</sup>, 2022, using mandibular incisors and maxillary laterals extracted from individuals between ages 18 to 30. Each of the three groups of teeth was randomly divided into three cervical margin preparations as follows: Shoulder (n = 15), chamfer (n = 15), and knife edge (n = 15). The teeth were disinfected and stored in 10% formalin. Silicone impressions followed by crown preparations were done on teeth mounted on phantom head manikins. The teeth were sectioned 0.5 mm coronal to the cemento-enamel junction using a separating disc and the mesial, distal, buccal, and lingual thickness were measured using a digital caliper. ANOVA analysis was applied to assess the difference in mean residual dentine thickness among the finishing lines and the Tukey test used for mean comparison. Results: Knife edge finishing lines had 2.05 mm of residual dentine thickness, for upper lateral incisors lingually and had an amount of 1.55 mm and 1.47 mm for lower central teeth mesially and distally respectively. Shoulder finishing lines had an amount of 0.58 mm for lower lateral incisors mesially. Interproximal areas had the least amounts of residual dentine for shoulder and chamfer finishing lines of 0.58 mm and 0.78 mm respectively. Conclusions: There was a significant statistical difference in the thickness of residual dentine at the various cervical finishing line margins. The knife edge finishing line was protective enough for zirconia crown preparations.展开更多
Background: Knife edge, chamfer, and shoulder are the three distinct finishing lines utilized in crown preparations. Each finishing line has relative benefits and drawbacks. However, not much scientific data exists re...Background: Knife edge, chamfer, and shoulder are the three distinct finishing lines utilized in crown preparations. Each finishing line has relative benefits and drawbacks. However, not much scientific data exists regarding which of these finishing lines will leave the most amount of residual dentine coronally on maxillary lateral incisors and mandibular incisors. Objective: To assess the coronal residual dentine thickness after different cervical finishing lines for anterior crown preparations. Materials and Methods: A prospective comparative study was conducted including mandibular incisors and maxillary laterals that were taken from subjects from 18 to 30 years old. Teeth in each of the three groups were randomly separated into three cervical margin preparation groups: knife edge, chamfer and shoulder. The teeth were then prepared for single crown coverage using these finishing lines. The teeth were sectioned halfway through the crown preparation, and a digital caliper was used to determine the residual dentine thickness at the buccal, lingual, mesial and distal areas. The Tukey test was used for mean comparison, and ANOVA analysis was used to evaluate the variation in mean residual dentine thickness. Results: For upper lateral incisors, knife edge finishing lines showed the highest amount of remaining dentine thickness—1.5 mm. lingually, while the upper lateral incisors mesially had the least amount of 0.53 mm for shoulder finishing lines. The least residual dentine (0.53 mm for the shoulder and 0.70 mm for the chamfer finishing line) was found in the interproximal portions of all the teeth that were selected. Lower central incisors had the least amount of residual dentine 0.61 mm for shoulder preparations mesially whiles lower lateral incisors had the least amount of residual dentine for shoulder preparations 0.58 mm distally. There was a statistically significant difference of 0.001 across the groups. Conclusion: The thickness of residual dentine seen coronally after the three finishing line preparations showed a statistically significant difference and the knife edge finishing line provided enough coronal protection within the scope of this study.展开更多
Antibacterial dimethylaminododecyl methacrylate （DMADDM） was recently synthesized. The objectives of this study were to： （1） investigate antibacterial activity of DMADDM-containing primer on Streptococcus mutans ...Antibacterial dimethylaminododecyl methacrylate （DMADDM） was recently synthesized. The objectives of this study were to： （1） investigate antibacterial activity of DMADDM-containing primer on Streptococcus mutans impregnated into dentin blocks for the first time, and （2） compare the antibacterial efficacy of DMADDM with a previous quaternary ammonium dimethacrylate （QADM）. Scotchbond Multi-Purpose （SBMP） bonding agent was used. DMADDM and QADM were mixed into SBMP primer. Six primers were tested： SBMP control primer P, P＋2.5% DMADDM, P＋5% DMADDM, P＋7.5% DMADDM, P＋10% DMADDM, and P＋10% QADM. S. mutans were impregnated into human dentin blocks, and each primer was applied to dentin to test its ability to kill bacteria in dentinal tubules. Bacteria in dentin were collected via a sonication method, and the colony-forming units （CFU） and inhibition zones were measured. The bacterial inhibition zone of P＋10% DMADDM was 10 times that of control primer （P〈0.05）. CFU in dentin with P＋10% DMADDM was reduced by three orders of magnitude, compared with control. DMADDM had a much stronger antibacterial effect than QADM, and antibacterial efficacy increased with increasing DMADDM concentration. Dentin shear bond strengths were similar among all groups （P〉0.1）. In conclusion, antibacterial DMADDM-containing primer was validated to kill bacteria inside dentin blocks, possessing a much stronger antibacterial potency than the previous QADM. DMADDM-containing bonding agent was effective in eradicating bacteria in dentin, and its efficacy was directly proportional to DMADDM mass fraction. Therefore, DMADDM may be promisine for use in bonding agents as well as in other restorative and oreventive materials to inhibit bacteria.展开更多
To verify the theoretical models of varying transversely isotropic stress-strain relations of dentin established in the preceding work(Part Ⅰ),we per- form a set of experiments.Because of the very fine tooth size,it ...To verify the theoretical models of varying transversely isotropic stress-strain relations of dentin established in the preceding work(Part Ⅰ),we per- form a set of experiments.Because of the very fine tooth size,it usually seems to be difficult to directly measure the inhomogeneous and anisotropic parameters of dentin.In this paper,by the digital speckle correlation method,tensile experiments are made on the small dentin samples either parallel or perpendicular to the dentin tubules.With the theoretically predicted elastic stress-strain relations,an optimiza- tion method is proposed to fit the strain curve adapted to the experimental data. The results show that the theoretical elastic stress-strain relations coincides very well with the experimental observations.The determined Young's modulus and Poisson's ratio of dentin matrix are 29.5GPa and 0.44,respectively,in the optimization sense.展开更多
Deletion or mutation of dentin matrix protein 1 （DMP1） leads to hypophosphatemic rickets and defects within the dentin. However, it is largely unknown if this pathological change is a direct role of DMP1 or an indir...Deletion or mutation of dentin matrix protein 1 （DMP1） leads to hypophosphatemic rickets and defects within the dentin. However, it is largely unknown if this pathological change is a direct role of DMP1 or an indirect role of phosphate （Pi） or both. It has also been previously shown that Klotho-deficient mice, which displayed a high Pi level due to a failure of Pi excretion, causes mild defects in the dentinal structure. This study was to address the distinct roles of DMP1 and Pi homeostasis in cell differentiation, apoptosis and mineralization of dentin and enamel. Our working hypothesis was that a stable Pi homeostasis is critical for postnatal tooth formation, and that DMP1 has an antiapoptotic role in both amelogenesis and dentinogenesis. To test this hypothesis, Dmpl-null （Dmpl-/-）, Klotho-deficient （kl/kl）, Dmpl/Klotho-double-deficient （Dmpl-/-/kl/kl） and wild-type （WT） mice were killed at the age of 6 weeks. Combinations of X-ray, microcomputed tomography （I^CT）, scanning electron microscopy （SEM）, histology, apoptosis and immunohistochemical methods were used for characterization of dentin, enamel and pulp structures in these mutant mice. Our results showed that Dmpl-/- （a low Pi level） or kl/kl（a high Pi level） mice displayed mild dentin defects such as thin dentin and a reduction of dentin tubules. Neither deficient mouse line exhibited any apparent changes in enamel or pulp structure. However, the double-deficient mice （a high Pi level） displayed severe defects in dentin and enamel structures, including loss of dentinal tubules and enamel prisms, as well as unexpected ectopic ossification within the pulp root canal. TUNEL assay showed a sharp increase in apoptotic cells in ameloblasts and odontoblasts. Based on the above findings, we conclude that DMP1 has a protective role for odontoblasts and ameloblasts in a pro-apoptotic environment （a high Pi level）.展开更多
As known, there is a large number of dentin tubules in dentin. These tubules have varying radii and are shaped into radially parallel pattern. The anisotropy of microstructure of dentin shows that dentin should be tre...As known, there is a large number of dentin tubules in dentin. These tubules have varying radii and are shaped into radially parallel pattern. The anisotropy of microstructure of dentin shows that dentin should be treated as a ma- terial of varying transverse isotropy. In this Part, the elastic stress-strain relations and the quadratic strength criterion are established in the form of having varying transverse isotropy, in the framework of micromechanics to take into account of the effect of the microstructures-dentin tubules. Simplified forms for isotropic and ho- mogeneous cases, as well as the corresponding plane stress form of the stress-strain relations are also given. These theoretical models are very well supported by the experiments shown later in the continued paper (Part Ⅱ).展开更多
The morpohologic feature of radicular dentin in sensitive and naturally desensitive area was observed with scanning electron microscopy (SEM). Eight specimens were taken from six patients with periodontal diseases. It...The morpohologic feature of radicular dentin in sensitive and naturally desensitive area was observed with scanning electron microscopy (SEM). Eight specimens were taken from six patients with periodontal diseases. It was established that the orifices of dentinal tubules in hypersensitive areas were much more than those in naturally desensitive areas. The dimension of the orifices in hyperoensitive areas was much larger than that in naturally desensitive areas. The results suggest that theie is relationship between dentin moophology and dentin hypersensitivity. In this article, a new dentin bipopsy technique with hollow drill was reported also.展开更多
Our previous studies showed that biomodification of demineralized dentin collagen with proanthocyanidin（PA） for a clinically practical duration improves the mechanical properties of the dentin matrix and the immedia...Our previous studies showed that biomodification of demineralized dentin collagen with proanthocyanidin（PA） for a clinically practical duration improves the mechanical properties of the dentin matrix and the immediate resin–dentin bond strength. The present study sought to evaluate the ability of PA biomodification to reduce collagenase-induced biodegradation of demineralized dentin matrix and dentin/adhesive interfaces in a clinically relevant manner. The effects of collagenolytic and gelatinolytic activity on PA-biomodified demineralized dentin matrix were analysed by hydroxyproline assay and gelatin zymography. Then, resin-/dentin-bonded specimens were prepared and challenged with bacterial collagenases. Dentin treated with 2% chlorhexidine and untreated dentin were used as a positive and negative control, respectively. Collagen biodegradation, the microtensile bond strengths of bonded specimens and the micromorphologies of the fractured interfaces were assessed. The results revealed that both collagenolytic and gelatinolytic activity on demineralized dentin were notably inhibited in the PA-biomodified groups, irrespective of PA concentration and biomodification duration. When challenged with exogenous collagenases, PA-biomodified bonded specimens exhibited significantly less biodegradation and maintained higher bond strengths than the untreated control. These results suggest that PA biomodification was effective at inhibiting proteolytic activity on demineralized dentin matrix and at stabilizing the adhesive/dentin interface against enzymatic degradation, is a new concept that has the potential to improve bonding durability.展开更多
AIM: To systematically review the literature on the efficacy of noninvasive methods of arresting the progression of non-cavitated occlusal carious lesions in dentin.METHODS: The Medline/Pub Med,LILACS,Sci ELO and Scop...AIM: To systematically review the literature on the efficacy of noninvasive methods of arresting the progression of non-cavitated occlusal carious lesions in dentin.METHODS: The Medline/Pub Med,LILACS,Sci ELO and Scopus databases were searched to identify relevant publications through to November 2013.Only clinical trials evaluating the ability of noninvasive methods to arrest the progression of occlusal non-cavitated carious lesions in dentin were included.Screening,data extraction and quality assessment were conducted independently and in duplicate.RESULTS: Of 167 citations identified,nine full text articles were screened and five were included in the analysis.All papers reported on occlusal fissure sealing using a self-curing glass ionomer(n = 1) or resin-based(n = 4) sealant.Only the use of resin-based sealant to obliterate occlusal fissures arrested the progression of non-cavitated occlusal carious lesions in dentin.CONCLUSION: Occlusal fissure sealing with a resin-based sealant may arrest the progression of non-cavitated occlusal dentinal caries.Further clinical trials with longer follow-up times should be performed to increase scientific evidence.展开更多
Phosphophoryn (PP) and dentin sialoprotein (DSP) are the most dominant non-collagenous proteins in dentin. PP is an extremely acidic protein that can function as a mineral nucleator for dentin mineralization. DSP was ...Phosphophoryn (PP) and dentin sialoprotein (DSP) are the most dominant non-collagenous proteins in dentin. PP is an extremely acidic protein that can function as a mineral nucleator for dentin mineralization. DSP was first identified in 1981, yet its functional significance is still controversial. Historically, these two proteins were considered to be independently synthesized and secreted by dental pulp cells into the developing dentin matrix. However, with the identification of the DSP coding sequence in 1994, followed2 years later by the finding that the PP coding sequence was located immediately downstream from the DSP sequence, it became immediately clear that DSP and PP proteins were derived from a single DSP-PP (i.e., dentin sialophosphoprotein, DSPP) transcript.Since DSPP cDNA became available, tremendous progress has been made in studying DSP-PP mRNA distribution and DSP generation from the DSP-PP precursor protein at specific cleavage sites by protease tolloid-related-1 (TLR1) or bone morphogenetic protein 1 (BMP1). The functions of DSP-PP and DSP were investigated via DSP-PP knockout (KO) and DSP knockin in DSP-PP KO mice. In addition, a number of in vitro studies aimed to elucidate DSPP and DSP function in dental pulp cells.展开更多
Objective To investigate the effect of multiple coatings of the one-step self-etching adhesive on immediate microtensile bond strength to primary dentin.Methods Twelve caries-free human primary molars were randomly di...Objective To investigate the effect of multiple coatings of the one-step self-etching adhesive on immediate microtensile bond strength to primary dentin.Methods Twelve caries-free human primary molars were randomly divided into 2 groups with 6 teeth each.In group 1,each tooth was hemisected into two halves.One half was assigned to control subgroup 1,which was bonded with a single-step self-etching adhesive according to the manufacturer's instructions;the other half was assigned to experimental subgroup 1 in which the adhesive was applied three times before light curing.In group 2,the teeth were also hemisected into two halves.One half was assigned to control subgroup 2,which was bonded with the single-step self-etching adhesive according to the manufacturer's instructions;the other half was assigned to experimental subgroup 2 in which three layers of adhesive were applied with light curing each successive layer.Microtensile bond strength was immediately tested after specimen preparation.Results When the adhesive was applied three times before light curing,the bond strength of the experimental subgroup 1(n=33,57.49±11.61 MPa) was higher than that of the control subgroup 1(n=31,49.71±11.43 MPa,P<0.05).When using the technique of applying multiple layers of adhesive with light curing each successive layer,no difference of immediate bond strength was observed between the control subgroup 2 and the experimental subgroup 2(P>0.05).Conclusion Multiple coatings of one-step self-etching adhesive can increase the immediate bond strength to primary dentin when using the technique of light-curing after applying three layers of adhesive.展开更多
The aim of this study is to investigate the change of mechanical properties of human dentin due to aging and spatial variation. Sections of coronal dentin are made from human molars in three groups： young, mid-aged, ...The aim of this study is to investigate the change of mechanical properties of human dentin due to aging and spatial variation. Sections of coronal dentin are made from human molars in three groups： young, mid-aged, and old patients. A nanoindentation test is conducted from regions near the pulp to the dentin-enamel junction （DE J） to evaluate the load-depth indentation response and determine Young＇s modulus and hardness. Based on the loading and unloading load-displacement curves in nanoindentation, a numerical model of plastic damage is used to study the plastic and the damage behaviors and the contribution to the degradation in the unloading stiffness. The experimental results show that Young＇s modulus of the inner dentin is significantly lower than that of outer dentin in each age group. Compared with the young dentin, the old dentin has greater hardness and Young＇s modulus with similar spatial variations. The magnitudes of the yield strength and the damage variable are also affected by aging and vary with spatial locations. In the same age group, the yield strength in inner dentin is lower than those in middle and outer dentin, more damage occurs with similar spatial variations, and the yield strength of young dentin is generally lower and causes more damage compared with those in both the mid-aged and old groups.展开更多
The presence of matrix metalloproteinase-2 （MMP-2） in dentin has been reported, but its distribution and activity level in mature human coronal dentin are not well understood. The purpose of this study was to determ...The presence of matrix metalloproteinase-2 （MMP-2） in dentin has been reported, but its distribution and activity level in mature human coronal dentin are not well understood. The purpose of this study was to determine the MMP-2 distribution and relative activity in demineralized dentin. Crowns of twenty eight human molars were sectioned into inner （ID）, middle （MD）, and outer dentin （OD） regions and demineralized. MMP-2 was extracted with 0.33 mol·L-1 EDTA/2 mol·L-1 guanidine-HCl, pH 7.4, and MMP-2 concentration was estimated with enzyme-linked immunoabsorbant assay （ELISA）. Further characterization was accomplished by Western blotting analysis and gelatin zymography. The mean concentrations of MMP-2 per mg dentin protein in the dentin regions were significantly different （P=0.043）： 0.9 ng （ID）, 0.4 ng （MD）, and 2.2 ng （OD）, respectively. The pattern of MMP-2 concentration was OD〉ID〉MD. Western blotting analysis detected -66 and -72 kDa immunopositive proteins corresponding to pro- and mature MMP-2, respectively, in the ID and MD, and a -66 kDa protein in the OD. Gelatinolytic activity consistent with MMP-2 was detected in all regions. Interestingly, the pattern of levels of Western blot immunodetection and gelatinolytic activity was MD〉ID〉OD. The eoneentration of MMP-2 in human coronal dentin was highest in the region of dentin that contains the dentinoenamel junction and least in the middle region of dentin. However, levels of Western blot immunodetection and gelatinolytic activity did not correlate with the estimated regional concentrations of MMP-2, potentially indicating region specific protein interactions.展开更多
In this study, we employed a nonthermal atmospheric pressure plasma(NTAPP) jet to evaluate the effect of plasma treatment on the durability of resin–dentin bonding under a thermocycling challenge. Furthermore, we ass...In this study, we employed a nonthermal atmospheric pressure plasma(NTAPP) jet to evaluate the effect of plasma treatment on the durability of resin–dentin bonding under a thermocycling challenge. Furthermore, we assessed the degradation resistance of plasma-treated collagen under a sodium hypochlorite(NaClO) challenge. We assessed the beneficial effect of NTAPP treatment on the acid-etched dentin–bonding interface by testing the micro-tensile bond strength and examining the morphology. We found that the immediate bonding strength of the dentin significantly increased after NTAPP treatment. Compared with the control group, NTAPP resulted in a more prominent effect on the bonding durability of the dentin–adhesive interface after treatment for 5 or 10 s. Simultaneously, the mechanical strength of dentin collagen under the NaClO challenge was improved. Our results indicate that, in optimal conditions, NTAPP could be a promising method to protect dentin collagen and to improve the bonding durability between dentin and etch-and-rinse adhesives.展开更多
We sought to evaluate immediate and delayed micro-tensile bond strength of Panavia F2.0 and Multilink Sprint resin cement to superficial, deep and cervical dentin. Thirty-six freshly extracted non-carious human molars...We sought to evaluate immediate and delayed micro-tensile bond strength of Panavia F2.0 and Multilink Sprint resin cement to superficial, deep and cervical dentin. Thirty-six freshly extracted non-carious human molars were sectioned in the mesiodistal direction to expose three different dentin regions including superficial dentin （1 mm below the dentine-enamel junction）, deep dentin （1 mm above the highest pulp horn） and cervical dentin （0.5 mm above the cemento-enamel junction and 0.5 mm below the dentine-enamel junction）. Resin cements were applied on dentin surfaces and composite blocks were luted under constant seating pressure. Each group was divided into three subgroups according to time intervals. Specimens were sectioned to obtain sticks of 1 mm2 in diameter and subjected to microtensile bond strength testing at a cross head speed of 1 mrn/min. Both resin cements showed higher micro-tensile bond strength to superficial dentin than that to deep or cervical dentin （P 〈 0.001）. Micro-ten- sile bond strengths of Panavia F2.0 were higher than those of Multilink Sprint at different dentin regions （P 〈 0.001）. Immediate ＂micro-tensile bond strengths were higher than those of delayed micro-tensile bond strengths for both resin cements （P 〈 0.001）. It was concluded that resin cements with different chemical formulations and applications yield significantly different micro-tensile bond strengths to different dentin regions.展开更多
The aim of this pilot study was to evaluate the shear bond strength of superficial bovine incisor dentin in different crown regions. Bonding was performed to the incisal, middle and cervical thirds of superficial bovi...The aim of this pilot study was to evaluate the shear bond strength of superficial bovine incisor dentin in different crown regions. Bonding was performed to the incisal, middle and cervical thirds of superficial bovine coronal dentin (n = 20) with a two-step etch-and-rinse adhesive (Optibond Solo Plus) and resin composite (Z100). Shear bond strength was evaluated at 24 h and failure modes of representative specimens wereobserved with FE-SEM. Non-parametric Kruskal-Wallis test with a significance level of 0.05 was used for data analysis. Mean shear bond strength values for the incisal, middle, and cervical thirds were 36.9 (3.1), 42.6 (2.6), and 37.1 (2.1) respectively with no significant differences evidenced between the crown thirds (p = 0.19). Observation of the failure mode of representative specimens demonstrated that specimens with high bond strength values exhibited predominantly mixed-type failures whereas low strength specimens exhibited adhesive failures between the dentin and adhesive. The absence of significant differences in shear bond strength between crown thirds indicate that, regardless of tubule orientation, any crown region can be used when superficial bovine incisor dentin is used for shear bond strength testing.展开更多
The purpose of this study was to evaluate the influence of acid etching on the bond strength of a universal adhesive system (Single Bond Universal, 3M) to caries-affected dentin. Forty permanent third molars were sele...The purpose of this study was to evaluate the influence of acid etching on the bond strength of a universal adhesive system (Single Bond Universal, 3M) to caries-affected dentin. Forty permanent third molars were selected and carious lesions were induced by the microbiological method with?S. mutans?ATCC25175. Teeth were allocated randomly across four experimental designs (n?=?10): PA-I: phosphoric acid etching and application of the adhesive system, followed by immediate microtensile bond strength testing;PA-CC: phosphoric acid etching and application of the adhesive system, followed by microtensile bond strength testing after a 14-day cariogenic challenge;NPA-I: application of the adhesive system without acid etching, followed by immediate bond strength testing and NPA-CC: application of the adhesive system without acid etching followed by bond strength testing after 14-day cariogenic challenge. For microtensile bond strength testing,?a restoration with Charisma composite resin was made and each specimen was sectioned with a cross-sectional area of 1 mm2. Only adhesive and mixed fractures were considered for bond strength calculation. Results were evaluated by the Kruskal-Wallis and Friedman tests. The highest bond strengths were observed in the phosphoric acid etching groups (p??0.05). Cariogenic challenge did not affect bond strength (p?>?0.05). The predominant fracture type was adhesive. We conclude that phosphoric acid increased the bond strength of the Single Bond Universal system to caries-affected dentin, and that cariogenic challenge did not interfere with this bond strength.展开更多
Objective: To evaluate the effect of different irradiation times on the occlusion of dentinal tubules when using Nd:YAG laser. Background data: Dentin hypersensitivity is a frequent problem that has limited treatment ...Objective: To evaluate the effect of different irradiation times on the occlusion of dentinal tubules when using Nd:YAG laser. Background data: Dentin hypersensitivity is a frequent problem that has limited treatment success despite many chemical and physical therapies. Methods: Four coronal dentin disks 2 mm thick were cut with a low-speed diamond saw from four freshly extracted intact first molars. The coronal dentin surface of each disk was divided into four regions, each approximately 2 mm × 3 mm. The dentin surfaces were treated with 27% EDTA then the four regions irradiated separately in a randomized pattern with a Nd:YAG laser (120 mJ, 5 Hz), using irradiation times of 0 s, 20 s, 40 s and 60 s, representing laser energies of 0 J/cm2, 200 J/cm2, 400 J/cm2 and 600 J/cm2, respectively. SEM photomicro-graphs were taken at 1500× and 3000× to calculate the dentinal tubule orifice occlusion rates and to measure the tubule diameters, respectively. Results: For the laser irradiation times of 0 s, 20 s, 40 s and 60 s, the corresponding dentinal tubule occlusion rates were 2.05 (SD 0.29)%, 10.01 (1.71)%, 23.58 (2.51)% and 90.23 (2.24)%, respectively;and the tubule diameters were 4.18 (0.32) μm, 3.46 (0.24) μm, 1.69 (0.32) μm and 0.12 (0.02) μm, respectively. There were significant differences among all groups for both measured variables (p ≤ 0.005). Conclusions: Within the limitations of this in Vitro study, when using a Nd:YAG laser at 120 mJ and 5 Hz, an irradiation time of 60 s achieved the best sealing of the coronal dentinal tubule orifices.展开更多
Tooth development is a complex process that involves precise and time-dependent orchestration of multiple genetic, molecular,and cellular interactions. Ameloblastin(AMBN, also named "amelin" or "sheathl...Tooth development is a complex process that involves precise and time-dependent orchestration of multiple genetic, molecular,and cellular interactions. Ameloblastin(AMBN, also named "amelin" or "sheathlin") is the second most abundant enamel matrix protein known to have a key role in amelogenesis. Amelogenesis imperfecta(AI [MIM: 104500]) refers to a genetically and phenotypically heterogeneous group of conditions characterized by inherited developmental enamel defects. The hereditary dentin disorders comprise a variety of autosomal-dominant genetic symptoms characterized by abnormal dentin structure affecting either the primary or both the primary and secondary teeth. The vital role of Ambn in amelogenesis has been confirmed experimentally using mouse models. Only two cases have been reported of mutations of AMBN associated with non-syndromic human AI. However, no AMBN missense mutations have been reported to be associated with both human AI and dentin disorders.We recruited one kindred with autosomal-dominant amelogenesis imperfecta(ADAI) and dentinogenesis imperfecta/dysplasia characterized by generalized severe enamel and dentin defects. Whole exome sequencing of the proband identified a novel heterozygous C-T point mutation at nucleotide position 1069 of the AMBN gene, causing a Pro to Ser mutation at the conserved amino acid position 357 of the protein. Exfoliated third molar teeth from the affected family members were found to have enamel and dentin of lower mineral density than control teeth, with thinner and easily fractured enamel, short and thick roots, and pulp obliteration. This study demonstrates, for the first time, that an AMBN missense mutation causes non-syndromic human AI and dentin disorders.展开更多
文摘Background: A reduced residual dentine thickness following crown preparation has a conceivable impact on pulp degeneration by increasing the pulp’s susceptibility to injury. In crown preparations, three different finishing lines are used. These are shoulder, chamfer, and knife edge. Each with its comparative advantages and disadvantages. There is inadequate scientific evidence on which of these finishing lines will leave the most amount of residual dentine, after standard crown preparations on mandibular incisors and maxillary lateral incisors to preserve their pulpal health. Objective: To evaluate residual dentine thickness following various cervical finishing lines of anterior crown preparations for zirconia full coverage. Materials and Methods: A prospective comparative study was conducted from September 2<sup>nd</sup> to November 5<sup>th</sup>, 2022, using mandibular incisors and maxillary laterals extracted from individuals between ages 18 to 30. Each of the three groups of teeth was randomly divided into three cervical margin preparations as follows: Shoulder (n = 15), chamfer (n = 15), and knife edge (n = 15). The teeth were disinfected and stored in 10% formalin. Silicone impressions followed by crown preparations were done on teeth mounted on phantom head manikins. The teeth were sectioned 0.5 mm coronal to the cemento-enamel junction using a separating disc and the mesial, distal, buccal, and lingual thickness were measured using a digital caliper. ANOVA analysis was applied to assess the difference in mean residual dentine thickness among the finishing lines and the Tukey test used for mean comparison. Results: Knife edge finishing lines had 2.05 mm of residual dentine thickness, for upper lateral incisors lingually and had an amount of 1.55 mm and 1.47 mm for lower central teeth mesially and distally respectively. Shoulder finishing lines had an amount of 0.58 mm for lower lateral incisors mesially. Interproximal areas had the least amounts of residual dentine for shoulder and chamfer finishing lines of 0.58 mm and 0.78 mm respectively. Conclusions: There was a significant statistical difference in the thickness of residual dentine at the various cervical finishing line margins. The knife edge finishing line was protective enough for zirconia crown preparations.
文摘Background: Knife edge, chamfer, and shoulder are the three distinct finishing lines utilized in crown preparations. Each finishing line has relative benefits and drawbacks. However, not much scientific data exists regarding which of these finishing lines will leave the most amount of residual dentine coronally on maxillary lateral incisors and mandibular incisors. Objective: To assess the coronal residual dentine thickness after different cervical finishing lines for anterior crown preparations. Materials and Methods: A prospective comparative study was conducted including mandibular incisors and maxillary laterals that were taken from subjects from 18 to 30 years old. Teeth in each of the three groups were randomly separated into three cervical margin preparation groups: knife edge, chamfer and shoulder. The teeth were then prepared for single crown coverage using these finishing lines. The teeth were sectioned halfway through the crown preparation, and a digital caliper was used to determine the residual dentine thickness at the buccal, lingual, mesial and distal areas. The Tukey test was used for mean comparison, and ANOVA analysis was used to evaluate the variation in mean residual dentine thickness. Results: For upper lateral incisors, knife edge finishing lines showed the highest amount of remaining dentine thickness—1.5 mm. lingually, while the upper lateral incisors mesially had the least amount of 0.53 mm for shoulder finishing lines. The least residual dentine (0.53 mm for the shoulder and 0.70 mm for the chamfer finishing line) was found in the interproximal portions of all the teeth that were selected. Lower central incisors had the least amount of residual dentine 0.61 mm for shoulder preparations mesially whiles lower lateral incisors had the least amount of residual dentine for shoulder preparations 0.58 mm distally. There was a statistically significant difference of 0.001 across the groups. Conclusion: The thickness of residual dentine seen coronally after the three finishing line preparations showed a statistically significant difference and the knife edge finishing line provided enough coronal protection within the scope of this study.
基金supported by NIH R01 DE17974 (Hockin HK Xu)a scholarship from West China School of Stomatology (Chen Chen)+3 种基金Program for New Century Excellent Talents in University (Lei Cheng)Youth Grant of Science and Technology Department of Sichuan Province China (2014JQ0033) (Lei Cheng)a bridge fund from University of Maryland Baltimore School of Dentistry (Hockin HK Xu)a seed grant from University of Maryland Baltimore (Hockin HK Xu)
文摘Antibacterial dimethylaminododecyl methacrylate （DMADDM） was recently synthesized. The objectives of this study were to： （1） investigate antibacterial activity of DMADDM-containing primer on Streptococcus mutans impregnated into dentin blocks for the first time, and （2） compare the antibacterial efficacy of DMADDM with a previous quaternary ammonium dimethacrylate （QADM）. Scotchbond Multi-Purpose （SBMP） bonding agent was used. DMADDM and QADM were mixed into SBMP primer. Six primers were tested： SBMP control primer P, P＋2.5% DMADDM, P＋5% DMADDM, P＋7.5% DMADDM, P＋10% DMADDM, and P＋10% QADM. S. mutans were impregnated into human dentin blocks, and each primer was applied to dentin to test its ability to kill bacteria in dentinal tubules. Bacteria in dentin were collected via a sonication method, and the colony-forming units （CFU） and inhibition zones were measured. The bacterial inhibition zone of P＋10% DMADDM was 10 times that of control primer （P〈0.05）. CFU in dentin with P＋10% DMADDM was reduced by three orders of magnitude, compared with control. DMADDM had a much stronger antibacterial effect than QADM, and antibacterial efficacy increased with increasing DMADDM concentration. Dentin shear bond strengths were similar among all groups （P〉0.1）. In conclusion, antibacterial DMADDM-containing primer was validated to kill bacteria inside dentin blocks, possessing a much stronger antibacterial potency than the previous QADM. DMADDM-containing bonding agent was effective in eradicating bacteria in dentin, and its efficacy was directly proportional to DMADDM mass fraction. Therefore, DMADDM may be promisine for use in bonding agents as well as in other restorative and oreventive materials to inhibit bacteria.
基金The project supported by the National Natural Science Foundation of China(19525207)
文摘To verify the theoretical models of varying transversely isotropic stress-strain relations of dentin established in the preceding work(Part Ⅰ),we per- form a set of experiments.Because of the very fine tooth size,it usually seems to be difficult to directly measure the inhomogeneous and anisotropic parameters of dentin.In this paper,by the digital speckle correlation method,tensile experiments are made on the small dentin samples either parallel or perpendicular to the dentin tubules.With the theoretically predicted elastic stress-strain relations,an optimiza- tion method is proposed to fit the strain curve adapted to the experimental data. The results show that the theoretical elastic stress-strain relations coincides very well with the experimental observations.The determined Young's modulus and Poisson's ratio of dentin matrix are 29.5GPa and 0.44,respectively,in the optimization sense.
基金supported by NIH grants Jian-Quan Feng (DE018486) and to Chun-Lin Qin (DE005092)State Key Laboratory of Oral Diseases Open Funding (SKLODOF2010-03) to Jian-Quan Feng
文摘Deletion or mutation of dentin matrix protein 1 （DMP1） leads to hypophosphatemic rickets and defects within the dentin. However, it is largely unknown if this pathological change is a direct role of DMP1 or an indirect role of phosphate （Pi） or both. It has also been previously shown that Klotho-deficient mice, which displayed a high Pi level due to a failure of Pi excretion, causes mild defects in the dentinal structure. This study was to address the distinct roles of DMP1 and Pi homeostasis in cell differentiation, apoptosis and mineralization of dentin and enamel. Our working hypothesis was that a stable Pi homeostasis is critical for postnatal tooth formation, and that DMP1 has an antiapoptotic role in both amelogenesis and dentinogenesis. To test this hypothesis, Dmpl-null （Dmpl-/-）, Klotho-deficient （kl/kl）, Dmpl/Klotho-double-deficient （Dmpl-/-/kl/kl） and wild-type （WT） mice were killed at the age of 6 weeks. Combinations of X-ray, microcomputed tomography （I^CT）, scanning electron microscopy （SEM）, histology, apoptosis and immunohistochemical methods were used for characterization of dentin, enamel and pulp structures in these mutant mice. Our results showed that Dmpl-/- （a low Pi level） or kl/kl（a high Pi level） mice displayed mild dentin defects such as thin dentin and a reduction of dentin tubules. Neither deficient mouse line exhibited any apparent changes in enamel or pulp structure. However, the double-deficient mice （a high Pi level） displayed severe defects in dentin and enamel structures, including loss of dentinal tubules and enamel prisms, as well as unexpected ectopic ossification within the pulp root canal. TUNEL assay showed a sharp increase in apoptotic cells in ameloblasts and odontoblasts. Based on the above findings, we conclude that DMP1 has a protective role for odontoblasts and ameloblasts in a pro-apoptotic environment （a high Pi level）.
基金The project supported by the National Natural Science Foundation of China (19525207).
文摘As known, there is a large number of dentin tubules in dentin. These tubules have varying radii and are shaped into radially parallel pattern. The anisotropy of microstructure of dentin shows that dentin should be treated as a ma- terial of varying transverse isotropy. In this Part, the elastic stress-strain relations and the quadratic strength criterion are established in the form of having varying transverse isotropy, in the framework of micromechanics to take into account of the effect of the microstructures-dentin tubules. Simplified forms for isotropic and ho- mogeneous cases, as well as the corresponding plane stress form of the stress-strain relations are also given. These theoretical models are very well supported by the experiments shown later in the continued paper (Part Ⅱ).
文摘The morpohologic feature of radicular dentin in sensitive and naturally desensitive area was observed with scanning electron microscopy (SEM). Eight specimens were taken from six patients with periodontal diseases. It was established that the orifices of dentinal tubules in hypersensitive areas were much more than those in naturally desensitive areas. The dimension of the orifices in hyperoensitive areas was much larger than that in naturally desensitive areas. The results suggest that theie is relationship between dentin moophology and dentin hypersensitivity. In this article, a new dentin bipopsy technique with hollow drill was reported also.
基金supported by research funds from the Natural Science Foundation of China (No. 81130078 and No. 81000458)Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13051)
文摘Our previous studies showed that biomodification of demineralized dentin collagen with proanthocyanidin（PA） for a clinically practical duration improves the mechanical properties of the dentin matrix and the immediate resin–dentin bond strength. The present study sought to evaluate the ability of PA biomodification to reduce collagenase-induced biodegradation of demineralized dentin matrix and dentin/adhesive interfaces in a clinically relevant manner. The effects of collagenolytic and gelatinolytic activity on PA-biomodified demineralized dentin matrix were analysed by hydroxyproline assay and gelatin zymography. Then, resin-/dentin-bonded specimens were prepared and challenged with bacterial collagenases. Dentin treated with 2% chlorhexidine and untreated dentin were used as a positive and negative control, respectively. Collagen biodegradation, the microtensile bond strengths of bonded specimens and the micromorphologies of the fractured interfaces were assessed. The results revealed that both collagenolytic and gelatinolytic activity on demineralized dentin were notably inhibited in the PA-biomodified groups, irrespective of PA concentration and biomodification duration. When challenged with exogenous collagenases, PA-biomodified bonded specimens exhibited significantly less biodegradation and maintained higher bond strengths than the untreated control. These results suggest that PA biomodification was effective at inhibiting proteolytic activity on demineralized dentin matrix and at stabilizing the adhesive/dentin interface against enzymatic degradation, is a new concept that has the potential to improve bonding durability.
文摘AIM: To systematically review the literature on the efficacy of noninvasive methods of arresting the progression of non-cavitated occlusal carious lesions in dentin.METHODS: The Medline/Pub Med,LILACS,Sci ELO and Scopus databases were searched to identify relevant publications through to November 2013.Only clinical trials evaluating the ability of noninvasive methods to arrest the progression of occlusal non-cavitated carious lesions in dentin were included.Screening,data extraction and quality assessment were conducted independently and in duplicate.RESULTS: Of 167 citations identified,nine full text articles were screened and five were included in the analysis.All papers reported on occlusal fissure sealing using a self-curing glass ionomer(n = 1) or resin-based(n = 4) sealant.Only the use of resin-based sealant to obliterate occlusal fissures arrested the progression of non-cavitated occlusal carious lesions in dentin.CONCLUSION: Occlusal fissure sealing with a resin-based sealant may arrest the progression of non-cavitated occlusal dentinal caries.Further clinical trials with longer follow-up times should be performed to increase scientific evidence.
文摘Phosphophoryn (PP) and dentin sialoprotein (DSP) are the most dominant non-collagenous proteins in dentin. PP is an extremely acidic protein that can function as a mineral nucleator for dentin mineralization. DSP was first identified in 1981, yet its functional significance is still controversial. Historically, these two proteins were considered to be independently synthesized and secreted by dental pulp cells into the developing dentin matrix. However, with the identification of the DSP coding sequence in 1994, followed2 years later by the finding that the PP coding sequence was located immediately downstream from the DSP sequence, it became immediately clear that DSP and PP proteins were derived from a single DSP-PP (i.e., dentin sialophosphoprotein, DSPP) transcript.Since DSPP cDNA became available, tremendous progress has been made in studying DSP-PP mRNA distribution and DSP generation from the DSP-PP precursor protein at specific cleavage sites by protease tolloid-related-1 (TLR1) or bone morphogenetic protein 1 (BMP1). The functions of DSP-PP and DSP were investigated via DSP-PP knockout (KO) and DSP knockin in DSP-PP KO mice. In addition, a number of in vitro studies aimed to elucidate DSPP and DSP function in dental pulp cells.
文摘Objective To investigate the effect of multiple coatings of the one-step self-etching adhesive on immediate microtensile bond strength to primary dentin.Methods Twelve caries-free human primary molars were randomly divided into 2 groups with 6 teeth each.In group 1,each tooth was hemisected into two halves.One half was assigned to control subgroup 1,which was bonded with a single-step self-etching adhesive according to the manufacturer's instructions;the other half was assigned to experimental subgroup 1 in which the adhesive was applied three times before light curing.In group 2,the teeth were also hemisected into two halves.One half was assigned to control subgroup 2,which was bonded with the single-step self-etching adhesive according to the manufacturer's instructions;the other half was assigned to experimental subgroup 2 in which three layers of adhesive were applied with light curing each successive layer.Microtensile bond strength was immediately tested after specimen preparation.Results When the adhesive was applied three times before light curing,the bond strength of the experimental subgroup 1(n=33,57.49±11.61 MPa) was higher than that of the control subgroup 1(n=31,49.71±11.43 MPa,P<0.05).When using the technique of applying multiple layers of adhesive with light curing each successive layer,no difference of immediate bond strength was observed between the control subgroup 2 and the experimental subgroup 2(P>0.05).Conclusion Multiple coatings of one-step self-etching adhesive can increase the immediate bond strength to primary dentin when using the technique of light-curing after applying three layers of adhesive.
基金supported by the National Natural Science Foundation of China(Nos.11172161 and11372173)the Innovation Program of Shanghai Municipal Education Commission(No.12ZZ092)+1 种基金the China Postdoctoral Science Foundation(No.2013M541504)the Shanghai Leading Academic Discipline Project(No.S30106)
文摘The aim of this study is to investigate the change of mechanical properties of human dentin due to aging and spatial variation. Sections of coronal dentin are made from human molars in three groups： young, mid-aged, and old patients. A nanoindentation test is conducted from regions near the pulp to the dentin-enamel junction （DE J） to evaluate the load-depth indentation response and determine Young＇s modulus and hardness. Based on the loading and unloading load-displacement curves in nanoindentation, a numerical model of plastic damage is used to study the plastic and the damage behaviors and the contribution to the degradation in the unloading stiffness. The experimental results show that Young＇s modulus of the inner dentin is significantly lower than that of outer dentin in each age group. Compared with the young dentin, the old dentin has greater hardness and Young＇s modulus with similar spatial variations. The magnitudes of the yield strength and the damage variable are also affected by aging and vary with spatial locations. In the same age group, the yield strength in inner dentin is lower than those in middle and outer dentin, more damage occurs with similar spatial variations, and the yield strength of young dentin is generally lower and causes more damage compared with those in both the mid-aged and old groups.
文摘The presence of matrix metalloproteinase-2 （MMP-2） in dentin has been reported, but its distribution and activity level in mature human coronal dentin are not well understood. The purpose of this study was to determine the MMP-2 distribution and relative activity in demineralized dentin. Crowns of twenty eight human molars were sectioned into inner （ID）, middle （MD）, and outer dentin （OD） regions and demineralized. MMP-2 was extracted with 0.33 mol·L-1 EDTA/2 mol·L-1 guanidine-HCl, pH 7.4, and MMP-2 concentration was estimated with enzyme-linked immunoabsorbant assay （ELISA）. Further characterization was accomplished by Western blotting analysis and gelatin zymography. The mean concentrations of MMP-2 per mg dentin protein in the dentin regions were significantly different （P=0.043）： 0.9 ng （ID）, 0.4 ng （MD）, and 2.2 ng （OD）, respectively. The pattern of MMP-2 concentration was OD〉ID〉MD. Western blotting analysis detected -66 and -72 kDa immunopositive proteins corresponding to pro- and mature MMP-2, respectively, in the ID and MD, and a -66 kDa protein in the OD. Gelatinolytic activity consistent with MMP-2 was detected in all regions. Interestingly, the pattern of levels of Western blot immunodetection and gelatinolytic activity was MD〉ID〉OD. The eoneentration of MMP-2 in human coronal dentin was highest in the region of dentin that contains the dentinoenamel junction and least in the middle region of dentin. However, levels of Western blot immunodetection and gelatinolytic activity did not correlate with the estimated regional concentrations of MMP-2, potentially indicating region specific protein interactions.
基金supported by grants from National Natural Science Foundation of China(Nos.81701014,81801310,31700076)the Basic Research of Natural Science Project funded by the Department of Science and Technology of Shaanxi Province(No.2017JM8038)the Science and Technology Project funded by the Science and Technology Bureau of Weiyang District,Xi’an city(No.201846)。
文摘In this study, we employed a nonthermal atmospheric pressure plasma(NTAPP) jet to evaluate the effect of plasma treatment on the durability of resin–dentin bonding under a thermocycling challenge. Furthermore, we assessed the degradation resistance of plasma-treated collagen under a sodium hypochlorite(NaClO) challenge. We assessed the beneficial effect of NTAPP treatment on the acid-etched dentin–bonding interface by testing the micro-tensile bond strength and examining the morphology. We found that the immediate bonding strength of the dentin significantly increased after NTAPP treatment. Compared with the control group, NTAPP resulted in a more prominent effect on the bonding durability of the dentin–adhesive interface after treatment for 5 or 10 s. Simultaneously, the mechanical strength of dentin collagen under the NaClO challenge was improved. Our results indicate that, in optimal conditions, NTAPP could be a promising method to protect dentin collagen and to improve the bonding durability between dentin and etch-and-rinse adhesives.
文摘We sought to evaluate immediate and delayed micro-tensile bond strength of Panavia F2.0 and Multilink Sprint resin cement to superficial, deep and cervical dentin. Thirty-six freshly extracted non-carious human molars were sectioned in the mesiodistal direction to expose three different dentin regions including superficial dentin （1 mm below the dentine-enamel junction）, deep dentin （1 mm above the highest pulp horn） and cervical dentin （0.5 mm above the cemento-enamel junction and 0.5 mm below the dentine-enamel junction）. Resin cements were applied on dentin surfaces and composite blocks were luted under constant seating pressure. Each group was divided into three subgroups according to time intervals. Specimens were sectioned to obtain sticks of 1 mm2 in diameter and subjected to microtensile bond strength testing at a cross head speed of 1 mrn/min. Both resin cements showed higher micro-tensile bond strength to superficial dentin than that to deep or cervical dentin （P 〈 0.001）. Micro-ten- sile bond strengths of Panavia F2.0 were higher than those of Multilink Sprint at different dentin regions （P 〈 0.001）. Immediate ＂micro-tensile bond strengths were higher than those of delayed micro-tensile bond strengths for both resin cements （P 〈 0.001）. It was concluded that resin cements with different chemical formulations and applications yield significantly different micro-tensile bond strengths to different dentin regions.
文摘The aim of this pilot study was to evaluate the shear bond strength of superficial bovine incisor dentin in different crown regions. Bonding was performed to the incisal, middle and cervical thirds of superficial bovine coronal dentin (n = 20) with a two-step etch-and-rinse adhesive (Optibond Solo Plus) and resin composite (Z100). Shear bond strength was evaluated at 24 h and failure modes of representative specimens wereobserved with FE-SEM. Non-parametric Kruskal-Wallis test with a significance level of 0.05 was used for data analysis. Mean shear bond strength values for the incisal, middle, and cervical thirds were 36.9 (3.1), 42.6 (2.6), and 37.1 (2.1) respectively with no significant differences evidenced between the crown thirds (p = 0.19). Observation of the failure mode of representative specimens demonstrated that specimens with high bond strength values exhibited predominantly mixed-type failures whereas low strength specimens exhibited adhesive failures between the dentin and adhesive. The absence of significant differences in shear bond strength between crown thirds indicate that, regardless of tubule orientation, any crown region can be used when superficial bovine incisor dentin is used for shear bond strength testing.
文摘The purpose of this study was to evaluate the influence of acid etching on the bond strength of a universal adhesive system (Single Bond Universal, 3M) to caries-affected dentin. Forty permanent third molars were selected and carious lesions were induced by the microbiological method with?S. mutans?ATCC25175. Teeth were allocated randomly across four experimental designs (n?=?10): PA-I: phosphoric acid etching and application of the adhesive system, followed by immediate microtensile bond strength testing;PA-CC: phosphoric acid etching and application of the adhesive system, followed by microtensile bond strength testing after a 14-day cariogenic challenge;NPA-I: application of the adhesive system without acid etching, followed by immediate bond strength testing and NPA-CC: application of the adhesive system without acid etching followed by bond strength testing after 14-day cariogenic challenge. For microtensile bond strength testing,?a restoration with Charisma composite resin was made and each specimen was sectioned with a cross-sectional area of 1 mm2. Only adhesive and mixed fractures were considered for bond strength calculation. Results were evaluated by the Kruskal-Wallis and Friedman tests. The highest bond strengths were observed in the phosphoric acid etching groups (p??0.05). Cariogenic challenge did not affect bond strength (p?>?0.05). The predominant fracture type was adhesive. We conclude that phosphoric acid increased the bond strength of the Single Bond Universal system to caries-affected dentin, and that cariogenic challenge did not interfere with this bond strength.
文摘Objective: To evaluate the effect of different irradiation times on the occlusion of dentinal tubules when using Nd:YAG laser. Background data: Dentin hypersensitivity is a frequent problem that has limited treatment success despite many chemical and physical therapies. Methods: Four coronal dentin disks 2 mm thick were cut with a low-speed diamond saw from four freshly extracted intact first molars. The coronal dentin surface of each disk was divided into four regions, each approximately 2 mm × 3 mm. The dentin surfaces were treated with 27% EDTA then the four regions irradiated separately in a randomized pattern with a Nd:YAG laser (120 mJ, 5 Hz), using irradiation times of 0 s, 20 s, 40 s and 60 s, representing laser energies of 0 J/cm2, 200 J/cm2, 400 J/cm2 and 600 J/cm2, respectively. SEM photomicro-graphs were taken at 1500× and 3000× to calculate the dentinal tubule orifice occlusion rates and to measure the tubule diameters, respectively. Results: For the laser irradiation times of 0 s, 20 s, 40 s and 60 s, the corresponding dentinal tubule occlusion rates were 2.05 (SD 0.29)%, 10.01 (1.71)%, 23.58 (2.51)% and 90.23 (2.24)%, respectively;and the tubule diameters were 4.18 (0.32) μm, 3.46 (0.24) μm, 1.69 (0.32) μm and 0.12 (0.02) μm, respectively. There were significant differences among all groups for both measured variables (p ≤ 0.005). Conclusions: Within the limitations of this in Vitro study, when using a Nd:YAG laser at 120 mJ and 5 Hz, an irradiation time of 60 s achieved the best sealing of the coronal dentinal tubule orifices.
基金partially supported by a grant from the National Natural Science Foundation of China 31371279 (to Fu Xiong)the National Natural Science Foundation of China 81371137 (to Bu-Ling Wu)the Science and Technology Program of Guangzhou 201707010301 (to Fu Xiong)
文摘Tooth development is a complex process that involves precise and time-dependent orchestration of multiple genetic, molecular,and cellular interactions. Ameloblastin(AMBN, also named "amelin" or "sheathlin") is the second most abundant enamel matrix protein known to have a key role in amelogenesis. Amelogenesis imperfecta(AI [MIM: 104500]) refers to a genetically and phenotypically heterogeneous group of conditions characterized by inherited developmental enamel defects. The hereditary dentin disorders comprise a variety of autosomal-dominant genetic symptoms characterized by abnormal dentin structure affecting either the primary or both the primary and secondary teeth. The vital role of Ambn in amelogenesis has been confirmed experimentally using mouse models. Only two cases have been reported of mutations of AMBN associated with non-syndromic human AI. However, no AMBN missense mutations have been reported to be associated with both human AI and dentin disorders.We recruited one kindred with autosomal-dominant amelogenesis imperfecta(ADAI) and dentinogenesis imperfecta/dysplasia characterized by generalized severe enamel and dentin defects. Whole exome sequencing of the proband identified a novel heterozygous C-T point mutation at nucleotide position 1069 of the AMBN gene, causing a Pro to Ser mutation at the conserved amino acid position 357 of the protein. Exfoliated third molar teeth from the affected family members were found to have enamel and dentin of lower mineral density than control teeth, with thinner and easily fractured enamel, short and thick roots, and pulp obliteration. This study demonstrates, for the first time, that an AMBN missense mutation causes non-syndromic human AI and dentin disorders.
