Scanning accuracy of an intraoral scanner according to different inlay preparation designs.

BACKGROUND: The accuracy of intraoral scanning plays a crucial role in the workflow of computer-assisted design/computer-assisted manufacturing. However, data regarding scanning accuracy for inlay preparation designs are lacking. The purpose of this in vitro study was to evaluate the influence of the depth of the occlusal cavity and width of the gingival floor of the proximal box on the trueness and precision of intraoral scans for inlay restoration. METHODS: Artificial teeth were used in this study. Four types of preparations for mesio-occlusal inlay were performed on each #36 artificial tooth depending on two different depths of the occlusal cavity (1 mm and 2 mm) and widths of the gingival floor of the proximal box (1.5 mm and 2.5 mm). Artificial teeth were scanned 10 times each with Cerec Primescan AC, and another scan was performed subsequently with a laboratory scanner as a reference (n = 10). Standard tessellation language files were analyzed using a three-dimensional analysis software program. Experimental data were analyzed using two-way analysis of variance and the Bonferroni multiple comparison test. RESULTS: The narrow shallow group had significantly higher deviation values for trueness than the wide deep group (p < 0.05). The wide deep group had the lowest average deviation value for trueness and there was no significant difference between the narrow deep and wide shallow groups (p > 0.05). For the mean maximum positive deviation, the wide groups had significantly lower values than the narrow groups (p < 0.05). Trueness was affected by both the width and depth(p < 0.05), whereas the mean maximum positive deviation was affected by the width (p < 0.05). The mean maximum negative deviation was affected by all three factors (p < 0.05). Precision was affected by the depth and the interaction between the depth of the occlusal cavity and width of the gingival floor (p < 0.05). CONCLUSIONS: The design of different inlay cavity configurations affected the accuracy of the digital intraoral scanner. The highest average deviation for trueness was observed in the narrow shallow group and the lowest in the wide deep group. With regard to precision, the narrow shallow group showed the lowest average deviation, and the narrow deep group showed highest value.

Evaluation of the intaglio surface trueness and fit of zirconia crowns fabricated using different machining strategies with a chairside CAD/CAM system.

AIM: This study aimed to evaluate the intaglio surface trueness and fit of zirconia crowns depending on the different machining strategies used with the CEREC system. MATERIALS AND METHODS: Thirty duplicate tooth models for a single zirconia crown were randomly assigned to the three groups (n = 10) according to the machining mode used for fabrication: grinding, wet milling, and dry milling. The scan data of the final crowns were compared to their design data to evaluate the intaglio surface trueness. The marginal and internal fits were evaluated using the cross-sectional method. The time required for the machining and sintering processes was measured for each group. RESULT: The wet milling group showed better trueness (RMS, 13.8 ± 1.0 µm) than the grinding and dry milling groups (p < 0.001). The marginal gap was greater in the grinding group (58.6 ± 28.9 µm) than that in the wet milling and dry milling groups (p < 0.001). The dry milling group required the shortest time for the manufacturing process. CONCLUSION: All machining modes fabricated crowns with a clinically acceptable trueness and fit. However, the dry milling mode was advantageous for the chairside CAD/CAM system with respect to time efficiency.

Influence of adjacent teeth on the accuracy of intraoral scanning systems for class II inlay preparation.

OBJECTIVE: This study aimed to evaluate the influence of the presence of adjacent teeth on the accuracy of intraoral scanning (IOS) systems for class II inlay preparation. MATERIALS AND METHODS: The mesio-occlusal inlay preparation was prepared in an anatomical model of the maxillary molar. The prepared tooth was secured to a typodont with the mesial adjacent tooth removed or in situ. Ten digital impressions of the inlay preparation were acquired using three IOS systems (CEREC Primescan, 3Shape TRIOS 3, and Medit i500). A laboratory scanner (3Shape E3) was used to obtain the reference scan data. The mean absolute deviation values were calculated to evaluate the accuracy of the digital models. RESULTS: The group with the adjacent teeth present showed lower trueness and precision compared to that without the adjacent tooth (p < .05). Significant differences were observed among the IOS systems (p < .05). Primescan showed the highest accuracy, irrespective of the presence of adjacent teeth. CONCLUSIONS: The presence of the adjacent tooth negatively affected the accuracy of all the IOSs tested. Although the performance of Primescan was superior to that of TRIOS 3 and i500, each IOS system showed clinically acceptable levels of accuracy for class II inlay preparation. CLINICAL SIGNIFICANCE: The adjacent tooth can be a confounding factor for accurate digital impressions of class II inlay preparation.

Influence of different inlay configurations and distance from the adjacent tooth on the accuracy of an intraoral scan.

STATEMENT OF PROBLEM: Clinical guidelines for obtaining accurate scan data during the intraoral scanning of inlay cavities with various configurations and interproximal distances are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of interproximal distance and cavity type on the accuracy of digital scans for inlay cavities, including proximal cavities. MATERIAL AND METHODS: Four artificial teeth with 4 types of inlay cavities designed based on the buccolingual width and gingival level of the proximal box were installed in a mannequin at distances of 0.6, 0.8, and 1.0 mm from the adjacent teeth. Reference scans of the 4 artificial teeth were obtained by using a laboratory scanner. The CEREC Primescan AC was used to acquire digital scan data (each n=10). Standard tessellation language (STL) files were analyzed with a 3-dimensional analysis software program. The mean deviation values were measured with a 3-dimensional best-fit alignment method to evaluate the accuracy of the digital scan data. Statistical analyses were performed by using 2-way ANOVA and the Bonferroni multiple comparison test (α=.05). RESULTS: As per the interproximal distance, the 1.0-mm group showed significantly higher trueness than the 0.6-mm group (P<.05). As the interproximal distance increased, the maximum positive deviation significantly decreased (P<.05). Maximum negative deviation and precision of the scan data were not significantly different among the distance groups (P>.05). Cavity type had a significant influence on the trueness and precision of the scan data (P<.05). In particular, the narrow long cavity type had an adverse effect on the precision and maximum positive deviation of scan data. CONCLUSIONS: During the intraoral scanning of class II inlay restoration, interproximal distance and cavity type affected the accuracy of an intraoral scan. As the interproximal distance increased, the trueness of the acquired digital images increased and the maximum positive deviation significantly decreased. The narrow long cavity type negatively affected the mean maximum positive deviation and precision of scan data.

Endodontic retreatment of a calcified anterior tooth using a 3D-printed endodontic guide.

The treatment of teeth with severely calcified canals is a difficult procedure for clinicians. Procedural accidents such as drill path deviation or perforation of the root canal often occur. 3D-printed directional guides made using CBCT and CAD/CAM can help the clinician to accurately drill in the original root canal direction. Furthermore, chairside operating times and excessive loss of tooth structure are reduced, and the risk of perforation is avoided. The present case report describes two cases of calcified root canals with path deviations that were retreated utilizing a guided endodontic technique.

How light attenuation and filler content affect the microhardness and polymerization shrinkage and translucency of bulk-fill composites?

OBJECTIVES: The purpose of this study was to investigate the microhardness, polymerization shrinkage, and translucency of bulk-fill composites (BFCs) which have different light attenuation properties and filler contents. MATERIALS AND METHODS: Five BFCs [Filtek Bulk Fill (FB), SureFil SDR (SS), Venus Bulk Fill (VB), SonicFill (SF), and Tetric N-Ceram Bulk Fill (TB)] and two resin-based composites (RBCs) [Tetric N-Ceram (TN) and Filtek Z350XT Flowable (ZF)] were chosen. Numbers of transmitted photons, refractive index, microhardness at different thicknesses, polymerization shrinkage, and translucency parameter (TP) were evaluated. RESULTS: Attenuation coefficients (ACs) based on measured photons ranged from -0.88 to -1.90. BFCs, except SF, had lower AC values than TN or ZF, and BFCs, except TN, had smaller refractive index decreases between top and bottom surfaces. Regardless of an exponential decrease in photon counts, microhardness decreased linearly as specimen thickens. Moreover, microhardness of BFCs showed smaller top-to-bottom decreases (11.5-48.8 %) than TN or ZF (57.3 and 71.5 %, respectively). BFCs with low filler contents showed lower microhardness and higher polymerization shrinkage than those of high filler contents. Also, BFCs had significantly higher (p < 0.001) TP values than TN or ZF. CONCLUSION: BFCs attenuated light less than RBCs. However, some BFCs had much lower top surface microhardness and higher polymerization shrinkage than tested RBCs. CLINICAL RELEVANCE: Despite the convenience of bulk filling, careful selection of BFC is advised because some BFCs have worse microhardness and polymerization shrinkage than RBCs due to their lower filler contents.

Effects of Additional Acid Etching on the Dentin Bond Strengths of One-Step Self-Etch Adhesives Applied to Primary Teeth.

OBJECTIVES: The aim of this study was to evaluate the bond strengths of one-step self-etch adhesives applied to primary tooth dentin with and without additional acid etching. MATERIALS AND METHODS: In total, 154 specimens were prepared using 50 naturally exfoliated primary molars. Four commercial one-step self-etch adhesives were used in this study: Scotchbond™ Universal, All-Bond Universal™, Adper™ Prompt™ L-Pop™, and Clearfil S3 Bond™. Two etch-and-rinse adhesives, Prime & Bond® NT™ and Scotchbond™ Multi-Purpose, served as controls. Microtensile bond strength tests were performed for specimens treated with the one-step self-etch adhesives with and without additional acid etching and those treated with the two etch-and-rinse adhesives. RESULTS: All one-step self-etch adhesives except Adper Prompt L-Pop exhibited increased microtensile bond strength values (p < 0.05) with additional acid etching. A nonsignificant interaction was observed between the type of self-etch adhesive and additional acid etching (p = 0.056). Bond strength comparisons between the self-etch adhesives used without additional acid etching and the etch-and-rinse adhesives revealed significantly higher values for Prime & Bond NT than for All-Bond Universal® (p < 0.05). However, there were no significant differences between any etch-and-rinse adhesive and self-etch adhesive used with additional acid etching, although Clearfil S3 Bond showed greater strength than Adper Prompt L-Pop. CONCLUSIONS: Our results suggest that additional acid etching increases the bond strength of most one-step self-etch adhesives applied to primary tooth dentin. CLINICAL SIGNIFICANCE: Additional acid etching of enamel and dentin can be recommended to increase the bond strength of one-step self-etch adhesives applied to primary teeth. (J Esthet Restor Dent 29:110-117, 2017).

Effect of two lasers on the polymerization of composite resins: single vs combination.

The selection of a light-curing unit for the curing composite resins is important to achieve best outcomes. The purpose of the present study was to test lasers of 457 and 473 nm alone or in combination under different light conditions with respect to the cure of composite resins. Four different composite resins were light cured using five different laser combinations (530 mW/cm(2) 457 nm only, 530 mW/cm(2) 473 nm only, 177 mW/cm(2) 457 + 177 mW/cm(2) 473 nm, 265 mW/cm(2) 457 + 265 mW/cm(2) 473 nm, and 354 mW/cm(2) 457 + 354 mW/cm(2) 473 nm). Microhardness and polymerization shrinkage were evaluated. A light-emitting diode (LED) unit was used for comparison purposes. On top surfaces, after aging for 24 h, microhardness achieved using the LED unit and the lasers with different conditions ranged 42.4-65.5 and 38.9-67.7 Hv, respectively, and on bottom surfaces, corresponding ranges were 25.2-56.1 and 18.5-55.7 Hv, respectively. Of the conditions used, 354 mW/cm(2) 457 nm + 354 mW/cm(2) 473 nm produced the highest bottom microhardness (33.8-55.6 Hv). On top and bottom surfaces, microhardness by the lowest total light intensity, 354 (177 × 2) mW/cm(2), ranged 39.0-60.5 and 18.5-52.8 Hv, respectively. Generally, 530 mW/cm(2) at 457 nm produced the lowest polymerization shrinkage. However, shrinkage values obtained using all five laser conditions were similar. The study shows the lasers of 457 and 473 nm are useful for curing composite resins alone or in combination at much lower light intensities than the LED unit.

Effect of dentin surface conditions and curing mode of resin cement on the dentin bond strength.

This study investigates the effects of dentin's drying time, roughness, and curing modes of resin cement on bond strength. Forty human teeth were divided into eight groups based on three experimental factors: dentin's roughness by 240-or 600-grit SiC paper (coarse or fine), dentin wetness with air-drying time (5-s or 10-s), and Single Bond Universal adhesive's curing mode by co-curing with RelyX Ultimate cement or light-curing separately (co-curing or light-curing). The micro-tensile bond strength of fifteen resin-dentin stikcs per groups was measured. Failure mode and adhesive layers were observed using stereoscopic and confocal laser scanning microscopy, respectively. The curing mode of the adhesive layer affected the bond strength of the dentin-resin cement (p<0.05). In particular, the light-curing mode exhibited a significantly higher bond strength than the co-curing one (p<0.05). The bond strength between the resin cement and dentin was improved in the 5-s drying groups than in the 10-s drying groups.

Comparison of the stress distribution in base materials and thicknesses in composite resin restorations.

Resin-based composite materials are commonly used for restorations, but their dimensional changes during the polymerization could cause various clinical problems. This study evaluated the influence of a base of different materials and thicknesses on the stress magnitude and distribution in a second maxillary premolar with an MOD resin composite restoration using three-dimensional finite element analysis. A sound tooth without cavity was considered as the control group (ST), and another group was restored with composite resin without applying a base material in a MOD cavity (CR). The other three groups were restored with composite resin along with the following base materials: glass ionomer cement, low-viscosity resin, and tricalcium silicate, respectively (CR-GIC, CR-LR, and CR-TS). These three groups were further divided into two subgroups according to the thickness of the base layer: thin (0.5 mm) and thick (1.0 mm). The stress distribution was compared using the maximum principal stress after polymerization shrinkage and vertical loading with 600 N on the occlusal surface. Group ST showed the lowest stress value, and its stress propagation was confined to outer enamel surfaces only. Group CR demonstrated the highest stress distribution in the tooth-restoration interface with increased failure risk on marginal areas. The thin and thick subgroups of the three groups with a base layer had lower stress levels than Group CR. The base materials reduced the marginal stress caused by polymerization shrinkage of composite resin in MOD cavities. Different base materials and thicknesses did not affect the stress distribution.

Mechanical properties of composite resins light-cured using a blue DPSS laser.

Lasers have many favorable features as a light source owing to their monochromaticity and coherence. This study examined the mechanical properties of composite resins that were light-cured using a diode-pumped solid state (DPSS) laser. Eight composite resins were light-cured using four different light sources (one quartz-tungsten-halogen (QTH), two light-emitting diodes (LEDs), and one DPSS laser with a wavelength of 473 nm). The light intensity of the DPSS laser and remaining light-curing units were approximately 500 and 900 mW/cm(2), respectively. The microhardness, flexural properties, and compressive properties were evaluated using the Vickers hardness test, three-point bending test, and compression test, respectively. In most cases, the microhardness, flexural properties, and compressive properties of the specimens light-cured using the DPSS laser were similar to those obtained using the other light-curing units. Within the limits of the study, the microhardness, flexural modulus, and compressive strength were linearly correlated with the filler content (in weight percent). The flexural modulus and compressive modulus were also linearly correlated with the microhardness. Even with a much lower light intensity, the DPSS laser with a wavelength of 473 nm can polymerize composite resins and give comparable mechanical properties to those obtained using the other light-curing units.

Incidence of three roots and/or four root canals in the permanent mandibular first molars in a Korean sub-population.

OBJECTIVES: The purpose of this study was to evaluate the prevalence of three-rooted permanent mandibular first molars (PMFMs) with four canals and their morphological characteristics among a Korean population from using cone-beam computed tomography scans (CBCTs). MATERIALS AND METHODS: Among the 705 CBCTs screened, 472 patient cases possessing at least one PMFM were identified. A total of 780 PMFMs were evaluated in axial section series to determine the number of roots and canals. The incidences of three-rooted PMFMs were compared with regard to gender and location. For distal root(s) with two canals, inter-orifice distances (IOD) between distobuccal and distolingual canals were measured at pulpal floor and furcation levels. The difference of IOD between males and females was also analyzed using chi-square tests. RESULTS: Among the 472 CBCTs of 225 females and 247 males, 84 females and 107 males were found to have at least one three-rooted PMFM. Among the 780 PMFMs, 191 PMFMs (24.5%, 89 of 397 left and 102 of 383 right) were found to have three roots. The prevalence of distal root(s) with two canals was 34.2% (267 of 780). From the molars with two distal canals, the mean IOD between distobuccal and distolingual canals at the pulpal floor level was 3.1 mm in males and 2.9 mm in females (p = 0.0428). CONCLUSIONS: The occurrence of three-rooted PMFMs among a Korean population was 24.5% and was higher than other countries and ethnicities. Understanding the prevalence of PMFMs with a distolingual root and/or canal in a Korean population and the IOD between distobuccal and distolingual canals may be useful for successful endodontic treatments. CLINICAL RELEVANCE: Acknowledgment of potential incidence of three-rooted permanent mandibular first molars with four canals and the distance between two distal canals may increase the success rate of root canal treatment by reducing the missing canal untreated.

Clinical applications of a quantitative light-induced fluorescent (QLF) device in the detection and management of cracked teeth: A case report.

INTRODUCTION: The aim of this case report was to discuss the clinical application using a quantitative light-induced fluorescent (QLF) device for the diagnosis and treatment of a cracked tooth as visualizing the tooth's crack. CASE REPORT: A 39-year-old woman visited a dental hospital complaining of throbbing pain on tooth #36. Observation of the tooth with naked eyes showed that tooth had a ceramic restoration with no specific findings. QLF device's images around the restoration, and after removal of the restoration were taken. In the QLF image after removal of the restoration, clear red-fluorescent crack line was shown, indicating that microorganism had penetrated along the crack path. During root canal treatment, the QLF image of the inside of the pulp chamber showed a pattern in which the crack line progressed into the tooth. During the treatment of the cracked tooth, the crack line was removed as much as possible using the fluorescent information obtained by the QLF device, and crack lines of fluorescence images quantitatively analyzed using a QLF's software. CONCLUSION: Images acquired with the QLF device can provide useful information for detecting crack lines, recording the treatment process, and restorative management of cracked teeth.

Influence of Dentin Surface Roughness, Drying Time, and Primer Application on Self-adhesive Composite-Cement Bond Strength.

PURPOSE: To investigate the effect of roughness and drying time of dentin as well as the number of coats of a self-adhesive composite-cement primer on the bond strength of self-adhesive composite cement. MATERIAL AND METHODS: Sixty human teeth were prepared and assigned to 12 groups (n = 5), according to three experimental factors: 1) dentin surface roughness, rough or fine, as achieved by 250- and 600-grit silicon carbide papers, respectively; 2) dentin wetness based on air-drying time (5 or 10 s); and 3) the self-adhesive composite-cement primer applications (no-coat, 1-coat, and 2-coat). Composite resin blocks were made with hybrid composite resin (M1 GraceFil) and cemented with G-CEM ONE (both GC). Cement-dentin sticks (12) were prepared, and the microtensile bond strength (µTBS) test was performed. Failure modes were observed with a stereomicroscope (40X), and bonding interfaces were evaluated with confocal laser scanning microscopy (CLSM). Statistical analysis was performed using three-way ANOVA and Tukey's post-hoc comparisons test (α = 0.05). RESULTS: Dentin roughness (250-grit > 600-grit, p = 0.000), drying time (5-s drying > 10-s drying, p = 0.000), and primer application (no-coat < 1-coat = 2-coat, p = 0.000) had significant effects on bond strength. These factors also showed significant interactions with each other (p = 0.003). The highest µTBS (31.8 ± 3.1 MPa) was observed in the 1-coat/fine roughness/10-s drying group and the lowest µTBS (13.4 ± 2.7 MPa) in the no-coat/coarse roughness/5-s drying group. CLSM showed higher penetration of cement in the primer-coated groups compared to that in the no-coat groups. CONCLUSION: Bond strength between the self-adhesive composite cement and dentin was higher in the fine-roughness dentin group than in the coarse-roughness dentin group, and in the 5-s drying group compared to the 10-s drying group. Applying a primer to dentin improved bond strength of the self-adhesive composite cement.

The Effectiveness of a Quantitative Light-induced Fluorescent Device for the Diagnosis of a Cracked Tooth: A Case Report.

Diagnosing a cracked tooth is a challenge for dental clinicians. This report describes the use of a quantitative light-induced fluorescent (QLF) device that detects fluorescence reactions with visible light (405 nm) to visually identify microscopic tooth cracks during the diagnosis and treatment of cracked teeth that caused pulp disease. Fluorescence images of the occlusal surface, before and after removal of the restoration, and inside of the access cavity for root canal treatment were obtained using an intraoral capture-type QLF device (Q-ray penC; AIOBIO, Seoul, Korea). The device provided visual information such as enhanced magnification and fluorescent images to identify cracks on the exterior of the tooth, around restorations, and inside the cavity after removal of the restoration by a simple image capture process. The device was able to demonstrate the existence of the crack line and to predict the depth of cracks during treatment.The QLF device showed a potential benefit in the diagnosis and characterization, including the location and depth, of tooth cracks.

Effect of Silane-Containing Universal Adhesives on the Bonding Strength of Lithium Disilicate.

The purpose of this study was to investigate the effect of silane-containing universal adhesives on the bonding strength of lithium disilicate. Two-hundred-and-forty lithium disilicate blocks were divided into 16 groups according to the following surface treatments: hydrofluoric acid (HF)-treated or not, silane-treated or not, and the type of universal adhesive used (All-Bond Universal (ABU); Prime & bond (PB); Clearfil Universal Bond (CU); Single bond Universal (SBU)). After surface treatment, resin discs were bonded to each lithium disilicate using dual-cure resin cement. Bonded specimens were stored in distilled water for 24 h and then subjected to microtensile bond strength (µTBS) test. Failure modes were examined under stereomicroscope. Microscopic observation of bonded interfaces was analyzed using scanning electron microscopy. The µTBS data were statistically analyzed. Regardless of silane treatment, all groups treated with HF showed higher bonding strengths compared to those that were not treated with HF (p < 0.05). In groups treated with HF, the bonding strength increased after silane application (p < 0.05) except PB and CU (p > 0.05). Adhesive failures were dominant in all groups, but some mixed failures were observed in ABU treated with HF and silane. While most of the specimens that were not treated with silane after HF application only showed loose bonding between the ceramic and resin cement due to partial gaps, the specimens treated with silane application after HF showed a tight ceramic-resin interface. In conclusion, the silane in universal adhesives did not effectively improve the bonding strength between lithium disilicate and resin cement.

In vitro analysis of intraoral digital impression of inlay preparation according to tooth location and cavity type.

Purpose This study aimed to evaluate the influence of tooth location and inlay cavity type on the accuracy of intraoral digital impressions.Methods Class II inlay preparation was performed on anatomical models of the maxillary first molar (16) and mandibular first molar (46). Mesio-occlusal and disto-occlusal cavities were prepared, such that the axial wall of the proximal box measured 1 mm or 2 mm in height. Thus, four types of inlay cavities were prepared in 16 and 46, respectively. Ten digital impressions of each cavity were obtained using Cerec Primescan (Sirona). Reference scans were obtained with a laboratory scanner (E3, 3Shape). All scan data were exported for comparative analysis of the three-dimensional models. Mean absolute deviation values were calculated to evaluate the trueness and precision of the digital models. Color-coded maps were used for the qualitative analysis of deviations.Results The overall results showed that the trueness for 16 (10.43 ± 0.39 µm) was higher than that for 46 (12.42 ± 0.59 µm) (p < 0.05), while the precision was similar between 16 (3.08 ± 0.92 µm) and 46 (3.08 ± 0.76 µm). The cavity type affected the accuracy of the digital impressions. The highest deviation was observed in positive directions at the margins of the proximal boxes regardless of the cavity type.Conclusions Tooth location and cavity type affected the accuracy of intraoral digital impressions. Positive deviations were observed at the margins of the proximal boxes.

Effect of Exclusive Primer and Adhesive on Microtensile Bond Strength of Self-Adhesive Resin Cement to Dentin.

The aim of this study was to investigate the effect of G-CEM One Primer (GCOP) and self-etching adhesive on the microtensile bond strength (µTBS) between self-adhesive resin cement G-CEM One (GCO) and dentin. Teeth were sectioned to expose the flat dentin surface and randomly assigned into five groups (n = 15) according to the dentin surface treatment: 1) no surface treatment, 2) GCOP, 3) All-Bond Universal (ABU), 4) GCOP followed by ABU (GCOP/ABU), 5) ABU followed by GCOP (ABU/GCOP). The composite resin blocks were bonded to the dentin surface using GCO. The specimens were stored in distilled water at 37 °C for 24 h, then sectioned into sticks (1 mm × 10 mm). The µTBS values were statistically analyzed using 1-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test (α = 0.05) and failure mode was examined under a stereomicroscope. The bonding interface of each specimen was evaluated using confocal laser scanning microscopy. The GCOP group exhibited the highest µTBS value and there were no significant differences observed between GCOP, GCOP/ABU, ABU/GCOP groups (p > 0.05). The use of GCOP with GCO results in the improved µTBS between GCO and dentin. In conclusion, using only GCOP with GCO for bonding of indirect restoration is extremely simple and increasing bond strength.

Evaluation of the relationship between non-caries cervical lesions and the tooth and periodontal tissue: An ex-vivo study using micro-computed tomography.

The purpose of this study was to analyze the relationship between the height and depth of buccal non-carious cervical lesions (NCCLs) and the relationship between the size of buccal NCCLs and clinical crown-root ratio of both buccal and lingual (palatal) sides using micro-computed tomography (micro-CT) images of the teeth and periodontal tissues from the cadavers. The micro-CT images of 56 teeth and their supporting tissues were obtained from 17 cadavers. From these images, the height and depth of NCCLs and the length of the buccal and lingual (palatal) clinical crowns were measured, and the conventional/modified clinical crown-root ratios were calculated. The height and depth ratio of NCCLs were analyzed statistically with the conventional/modified crown-root ratios by Pearson's correlation and multiple regression. According to the Pearson's correlation, the height and depth of buccal NCCLs were positively correlated with the modified buccal clinical crown-root ratio (p < 0.001 and p = 0.013, respectively). The regression model composed of variables of crown-root ratios explained the height of buccal NCCLs, and the prominent factor of the model was the modified buccal clinical crown-root ratio (p < 0.001). Moreover, the depth of buccal NCCLs was also explained by the regression model, and its prominent factor was the proportion of modified buccal and lingual (palatal) clinical crowns (p = 0.004). The buccal NCCLs were related to the crown-root ratios; particularly, the level of buccal gingival margin could be associated with the formation of buccal NCCLs.

Mesoporous Bioactive Glass Combined with Graphene Oxide Quantum Dot as a New Material for a New Treatment Option for Dentin Hypersensitivity.

Dentin hypersensitivity is one of the most common clinical conditions usually associated with exposed dentinal tubules. The purpose of this study was to identify the potential of a graphene oxide quantum dot coating for mesoporous bioactive glass nanoparticles as a new material for the treatment of dentin hypersensitivity by investigating its mineralization activity and dentinal tubules sealing. Mesoporous bioactive glass nanoparticle was fabricated by modified sol-gel synthesis. X-ray diffraction was performed to characterize the synthesized nanoparticle Fourier transform infra-red spectroscopy investigated the functionalized surfaces. The distribution of the specific surface area and the pore size was measure by Pore size analysis. The morphology of sample was observed by Field Emission Scanning Electron Microscope (FESEM) and Field Emission Transmission Electron Microscope (FETEM). After disk-shaped specimens of mesoporous bioactive glass nanoparticles and graphene oxide quantum dot coated mesoporous bioactive glass nanoparticles (n = 3) were soaked in the simulated body fluid for 0, 1, 5, 10,and 30 days, the amount of ions released was observed to confirm the ionic elution for mineralization. Sensitive tooth model discs (n = 20) were applied with two samples and evaluated the dentinal tubule sealing ability. The spherical mesoporous bioactive glass nanoparticles and graphene oxide quantum dot coated mesoporous bioactive glass nanoparticles with a diameter of about 500 nm were identified through FESEM and FETEM. The ion release capacity of both samples appeared to be very similar. The amount of ion released and in vitro mineralization tests confirmed that graphene oxide quantum dot coating of mesoporous bioactive glass nanoparticles did not inhibit the release of calcium, silicon and phosphate ions, but rather that graphene oxide quantum dot promoted hydroxyapatite formation. In the FESEM image of the sensitive tooth disc surface, it was observed that graphene oxide quantum dot coated mesoporous bioactive glass nanoparticles sealed tightly the dentinal tubules. The graphene oxide quantum dot coating of mesoporous bioactive glass nanoparticles not only showed the excellent dentinal sealing ability but also rapidly promoted mineralization while minimizing the size increase by coating the mesoporous bioactive glass nanoparticles.