Use of micro-computed tomography and scanning electron microscopy with energy-dispersive spectroscopy to distinguish natural white spot enamel lesions from sound enamel in human premolars.

PURPOSE: The aim of the present study was to develop a novel method for distinguishing white spot lesions (WSLs) from sound enamel in human premolars using micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and to examine differences in surface morphology, chemical composition, and mineral density (MD) between these two areas. METHODS: Fourteen premolars with natural WSLs on the enamel surface of the crowns were examined. After sectioning the teeth, each specimen containing WSLs adjacent to intact enamel was examined for MD, surface morphology, and atomic percentages (At%) of chemical components using micro-CT and SEM/EDS, respectively. Differences between these areas of the same specimen were analyzed statistically using paired t-test. RESULTS: SEM images highlighted increased roughness and irregularity in the lesion area. EDS analysis revealed significant reductions in calcium (Ca), phosphorus (P), fluorine (F), chlorine (Cl), and sodium (Na) levels at the lesion surface in comparison to intact enamel (P < 0.05). The decreases in the MD of the lesions were statistically significant in comparison to sound enamel (P < 0.05). CONCLUSION: These findings provide standard measurements for evaluating the essential characteristics of WSLs and intact enamel, being vital for assessment of treatment outcomes and development of innovative biomaterials for management of hypo-mineralized enamel lesions.

Effect of proximal box elevation on fracture resistance and microleakage of premolars restored with ceramic endocrowns.

BACKGROUND: Restoration of endodontically treated premolar is in high risk for biomechanical failure, and often presents with subgingival margins. Proximal box elevation (PBE) has been used to relocate subgingival cavity outlines. OBJECTIVE: To evaluate the influence of PBE on fracture resistance and gingival microleakage of premolars with endodontic access cavities following ceramic endocrown. METHODS: Eighty sound maxillary premolars with standardized Class II cavities on mesial surfaces were randomly assigned to four groups (n = 20 in each group). Groups E1, E2 and E3, with proximal margins located in dentin/cementum, 2 mm below the cemento-enamel junction (CEJ), simulated subgingival location. Group E4 (supragingival group), with proximal margins located in enamel, 1 mm above the CEJ, was used as the positive control. For margin elevation of the proximal cavities, bulk-fill Smart Dentin Replacement (SDR), a visible light cured resin composite, was applied in group E1, and conventional resin composite (3M Z350 XT, a light-activated composite) was placed in group E2. Group E3 was only treated with a ceramic crown and served as the negative control. In all groups, computer-aided design (CAD) ceramic endocrowns were adhesively inserted, and fracture resistance, failure mode and microleakage were evaluated. RESULTS: A higher fracture resistance value was observed in PBE groups E1 and E2, regardless of the materials used (P = 0.038, and 0.010, respectively, vs E3), and fracture resistance in group E1 was higher than that in group E2. In teeth without PBE, the percentage of catastrophic failures reached 70%. Compared to group E3, a lower frequency distribution of microleakage was detected in supragingival group E4 (P = 0.031). No increased percentage of microleakage was observed in groups treated with PBE. CONCLUSION: For endodontically treated maxillary premolars restored with ceramic endocrowns, PBE increases fracture resistance but not microleakage.

Effect of matrix metalloproteinase inhibitors on microtensile bond strength of dental composite restorations to dentin in use of an etch-and-rinse adhesive system.

AIM: This study assesses the effect of matrix metalloproteinases on microtensile bond strength (µTBS) of an etch-and-rinse adhesive system. METHODS: This in vitro study evaluated 88 extracted premolars. The teeth were sectioned to expose dentin and were then randomly divided into four groups (n = 22). In group 1 (control), dentin surface was etched, and Adper Single Bond 2 was applied. In groups 2-4, dentin surface was etched and chlorhexidine (CHX), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and dimethyl sulfoxide (DMSO) were applied on the surfaces, respectively, and blotted dry. Next, Adper Single Bond 2 was applied and all teeth were built up with Z350 composite. In each group, half the samples immediately and the other half after 10,000 thermal cycles underwent µTBS test. Data were analyzed using ANOVA and Tukey's test (α = .05). RESULTS: In thermocycled samples, maximum µTBS was noted in CHX group followed by DMSO, EDC, and control group (p < .001). The thermocycled µTBS of composite to dentin was significantly higher in CHX group compared with EDC, DMSO, and control groups (p < .001) but was not significantly different in EDC and DMSO groups (p = .498). CONCLUSION: The thermocycled µTBS obtained by the application of CHX, EDC, and DMSO was significantly higher compared with the value to the control group.

Comparative evaluation of fracture toughness and marginal adaptation of two restorative materials in nonendodontically and endodontically treated teeth: An in vitro study.

OBJECTIVE: To evaluate and compare the fracture resistance and marginal adaptation of Zirconomer and bulk fill posterior restorative material (Surefil SDR) in nonendodontically and endodontically treated teeth. MATERIALS AND METHODS: The sample consisted of 52 caries-free extracted human premolars which were individually mounted in polyvinyl chloride (PVC) ring filled with acrylic resin up to 1.0 mm below the cementoenamel junction. The teeth were then divided into four groups according to the restorative material used as group I: Zirconomer + Operative only, Group II: Zirconomer + Endodontic treatment, Group III: SDR + Operative, and Group IV: SDR + Endodontic treatment. Fracture strength was tested using a universal testing machine and was expressed in Newtons. The marginal gap was measured at its maximum using a scanning electron microscope and expressed in micrometers. One-way analysis of variance followed by Tukey's post hoc test was used to compare the mean fracture resistance (N) and marginal adaptation (µm) between the four groups. Statistical significance was determined at α = 0.05. RESULTS: Group 3 exhibited significantly highest mean fracture resistance than Group 1 (P < 0.001), Group 2 (P < 0.001), and Group 4 (P < 0.001). Group 4 had significantly higher mean fracture resistance than Group 1 (P = 0.008) and Group 2 (P < 0.001). Group 1 exhibited significantly highest mean marginal gap than Group 3 (P < 0.001) and Group 4 (P < 0.001). Group 2 had a significantly higher mean marginal gap than Group 3 (P < 0.001) and Group 4 (P < 0.001). CONCLUSION: The fracture resistance and marginal adaptation of Zirconomer are significantly lower than Surefil SDR in both nonendodontically and endodontically treated teeth.

Spatial Distributions of Oxygen Stable Isotope Ratios in Tap Water From Mexico for Region of Origin Predictions of Unidentified Border Crossers.

One of the many difficulties associated with identifying undocumented border crossers stems from an inability to narrow down the search area for the region of origin and family members to obtain family reference samples for DNA comparison. While the geography of regions of origins is wide, the biological profiles of the undocumented border crossers often show strong similarities, young and male. The isotopic composition of human bones, teeth, and hair has been demonstrated to be useful biomarkers for tracing locations and movements of individuals and for aiding in the identification of human remains. Data obtained from human remains can be compared to and aligned with various reference sources, such as soils and bedrock, archaeological remains, or cultural data. Here, the spatial deficiency in isotopic reference data for Mexico, specifically for oxygen (δ18 O) isotopes in tap water, is being addressed through the collection and analysis of over 150 water samples and explored with tooth enamel isotopic values from recently identified Mexican nationals. The isoscape was developed using a Spine with Barriers interpolation method and shows sufficient detail to narrow down the regions where specific isotopic values are represented. The individuals were plotted on the developed isoscape using conditional correlations. The methodology was successful in assigning the correct regions of origin for the two individuals, which shows the tremendous potential of the developed isoscape. Nonetheless, there is more research needed to further improve upon this geolocation method, including analysis of multiple isotopes in different tissues, and the development of new isotopic methods.

A Novel Etchant System for Orthodontic Bracket Bonding.

Orthodontic treatment is widely used to correct irregular teeth and/or jaw discrepancies to improve oral function and facial aesthetics. However, it is frequently associated with enamel damage that include chipping, demineralisation, and white spot formation. So far, current bonding systems that can maintain shear bond strengths (SBS) suitable for clinical performance are unable to limit enamel demineralisation, adhesive remnants and damage caused on removal of brackets after treatment. This study reports a novel "safe enamel etch" clinically viable procedure that was accomplished via application of novel etchant pastes developed with ß-tricalcium phosphate and monocalcium phosphate monohydrate powders mixed with citric acid (5 M) or phosphoric acid (37% PA) to yield BCA and BPA etchants respectively. Although enamel etched with clinically used PA gel yielded higher SBS than the BCA/BPA etchants, it exhibited greater adhesive remnants with evidence of enamel damage. In contrast, the experimental etchants resulted in unblemished enamel surfaces with zero or minimal adhesive residue and clinically acceptable SBS. Furthermore, the BPA etchant caused lower enamel decalcification with extensive calcium-phosphate precipitation. The study conclusively showed that BPA facilitated in vitro enamel adhesion without detrimental effects of the aggressive PA gel with potential for remineralisation and saving time at the post-debonding step.

Effect of radiotherapy on the chemical composition of root dentin.

BACKGROUND: The radiotherapy can directly affect the bond strength of the adhesive materials, interfering in the prognosis of restorative treatments, which may be caused by chemical changes in dentin structure. METHODS: Twenty inferior homologues premolars were distributed in 2 groups (in vitro study) (n = 10): nonirradiated and irradiated. The specimens were submitted to the analysis of phosphate (ν1 PO43- ;ν2 PO43- ;ν4 PO43- ), carbonate (ν3 CO32- ), amide I, CH2 , amide III, and amide I/III ratio by confocal Raman spectroscopy. Data were submitted to statistical analysis (T test, P < .05). RESULTS: In intracanal dentin, the irradiated group had lower ν4 PO43- values (1.23 ± 0.06) compared to nonirradiated group (1.40 ± 0.18) (P < .05), with no difference for ν1 PO43- and ν2 PO43 peaks (P > .05). The irradiated (1.56 ± 0.06) had lower carbonate, amide III (1.05 ± 0.19), and amide I/III ratio values (0.19 ± 0.06) compared to nonirradiated group (1.42 ± 0.10, 1.28 ± 0.24, and 0.31 ± 0.10, respectively) (P < .05). For medium dentin irradiated group (1.30 ± 0.12) had lower phosphate values compared to nonirradiated group (1.48 ± 0.22) (P < .05). In cementum, there was no statistical difference between the groups. CONCLUSION: The radiotherapy was able to cause changes in ν4 PO43- , carbonate, and amide III peaks of root dentin.

Assessing surface characteristics of eroded dentine with optical coherence tomography: a preliminary in vitro validation study.

We conducted the first pilot study to investigate the use of the attenuation coefficient from an optical coherence tomography (OCT) backscattered signal as a measure of surface roughness changes in eroded dentine at an early stage of the erosion process. Ten human premolar root samples were subjected to citric acid treatment before scanning by OCT. The extracted relative attenuation coefficient (µR) from backscattered OCT signals was shown to increase with the duration of acid challenge. Validated against roughness measurements (rSa) from scanning electron microscopy scans, µR is significantly correlated with rSa indicative of severity of erosion (p<0.01, r=0.9195). We conclude that the OCT attenuation coefficient of the immediate subsurface in eroded dentine is a potential surrogate measure for its surface roughness. However, further work should be performed to study how it relates to the surface and immediate subsurface changes effected by other mechanical wear before it could unequivocally be used as a surrogate measurement for surface roughness.

Effect of 2.94 µm Er: YAG laser on the chemical composition of hard tissues.

The aim was to investigate the effect of the Er-YAG laser radiation on morphology and chemical composition of enamel, dentin, and bone. The specimens of the three groups were irradiated with a very long pulse mode (VLP) of 2.94 µm Er-YAG laser with 100 mJ pulse energy and energy density of 8.42 J/ c m 2 for 30 s, at a repetition rate of 15 Hz. The organic and inorganic content of the samples were investigated by Fourier Transforms Infrared spectroscopy (FTIR). The morphological characteristics were investigated with scanning electron microscopy (SEM) and elemental analysis (calcium and phosphorus) with energy-dispersive X-ray spectroscopy (EDX). FTIR data were analyzed with a One-Way ANCOVA test and EDX data with the independent sample t-test. Following the laser radiation, FTIR showed a significant decrease in the organic content of all tissues. The weight percentage (wt %) calcium content of dentin and bone increased significantly following irradiation with a p-value of .002 for both tissues, but the wt % of phosphorus content was not influenced significantly. The morphological alterations expressed signs of fusion in all the samples.

Remaining dentine thickness of root canals prepared with K-3 and ProTaper rotary systems.

OBJECTIVE: To compare the remaining dentine thickness of root canals prepared with K-3 and ProTaper files.. METHODS: This in-vitro experimental study was conducted from 1st April-30th September 2015 at the dental clinics of Aga Khan University Hospital, Karachi, and comprised human teeth. Extracted human premolars and molars were included in the study using non-probability consecutive sampling. Canals were randomly allocated into two groups i.e. K-3 and ProTaper. Changes in inner and outer walls of canals were measured using Vixwin software at 1mm, 4mm, 7mm and 10mm from the apex. SPSS 20 was used for data analysis. RESULTS: Of the 214 canals, 107(50%) were assigned to each group. No statistically significant difference was found in the remaining dentine thickness at 1mm, 4mm, 7mm and 10mm from the apex of the teeth prepared with in K-3 versus ProTapers system (p>0.05). CONCLUSIONS: The remaining dentine thickness of the root canals prepared with K-3 files was similar to that of canals prepared with ProTaper files.

Investigating human geographic origins using dual-isotope (87Sr/86Sr, δ18O) assignment approaches.

Substantial progress in the application of multiple isotope analyses has greatly improved the ability to identify nonlocal individuals amongst archaeological populations over the past decades. More recently the development of large scale models of spatial isotopic variation (isoscapes) has contributed to improved geographic assignments of human and animal origins. Persistent challenges remain, however, in the accurate identification of individual geographic origins from skeletal isotope data in studies of human (and animal) migration and provenance. In an attempt to develop and test more standardized and quantitative approaches to geographic assignment of individual origins using isotopic data two methods, combining 87Sr/86Sr and δ18O isoscapes, are examined for the Circum-Caribbean region: 1) an Interval approach using a defined range of fixed isotopic variation per location; and 2) a Likelihood assignment approach using univariate and bivariate probability density functions. These two methods are tested with enamel isotope data from a modern sample of known origin from Caracas, Venezuela and further explored with two archaeological samples of unknown origin recovered from Cuba and Trinidad. The results emphasize both the potential and limitation of the different approaches. Validation tests on the known origin sample exclude most areas of the Circum-Caribbean region and correctly highlight Caracas as a possible place of origin with both approaches. The positive validation results clearly demonstrate the overall efficacy of a dual-isotope approach to geoprovenance. The accuracy and precision of geographic assignments may be further improved by better understanding of the relationships between environmental and biological isotope variation; continued development and refinement of relevant isoscapes; and the eventual incorporation of a broader array of isotope proxy data.

A comparative assessment of enamel mineral content and Streptococcus mutans population between conventional composites and composites containing nano amorphous calcium phosphate in fixed orthodontic patients: a split-mouth randomized clinical trial.

OBJECTIVES: The aim of this 'split-mouth design' trial was to evaluate the effect of the nano amorphous calcium phosphate (NACP) containing composite on enamel mineral contents and streptococcus mutans population in fixed orthodontic patients. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION: Randomized, prospective, single-center controlled trial. Twenty-four patients between the ages of 13-18 years participated in this study. The control and test sides were randomly selected by a coin toss (1:1 ratio). On the control side orthodontic brackets were bonded on the buccal surfaces of upper premolars and laterals using an orthodontic composite (Transbond XT), and on the study side NACP-containing composite was used. Outcome measures were the mineral content around the brackets and S.mutans count. The later were calculated in the plaque around the brackets by real-time PCR at 3 months, and 6 months after the initiation of treatment. All stages of the study were blind using coding system. Paired t-test and repeated measurements were used for data analysis. RESULTS: In the third and sixth month, the bacterial population was significantly lower in the study side than the control side (P = 0.01 and 0.000).The mineral content of the study side was significantly higher than the controls, 6 months after brocket bonding (P = 0.004). There were no significant differences between the premolars and lateral teeth for all measurements. LIMITATIONS: This research was performed in a single-center by one experienced clinician. CONCLUSION: NACP-containing composites have the potential to inhibit mineral content loss and S.mutans colonization around orthodontic brackets during fixed orthodontic treatments. TRIAL REGISTRATION: This trial was not registered. PROTOCOL: The protocol was not published before trial commencement.

Release of fluoride from orthodontic adhesives and penetration into enamel.

OBJECTIVE: The purpose of this work was to compare fluoride release from three orthodontic adhesives and fluoride penetration into the enamel surface. MATERIALS AND METHODS: A total of 156 extracted human premolar teeth were randomly assigned to three experimental groups and one control group (without bonding) with 39 teeth per group. Brackets were bonded to teeth using Fuji Ortho LC®, Illuminate®, or Light Bond®. The amount of fluoride released (ppm) into artificial saliva was measured by a fluoride ion-selective electrode connected to an ion analyzer on days 1, 3, 7, and 30. Fluoride penetration was investigated after 1, 2, and 3 months; 13 teeth of each group were randomly selected at every period of study and sectioned across the center of the bracket. The surface of the cross-section was studied under the scanning electron microscope, and the fluoride concentration (weight%) at 1, 2, and 3 µm below the outer enamel surface was determined by energy-dispersive X-ray microanalysis. RESULTS: On days 1, 3, 7, and 30, the mean cumulative fluoride release from the three orthodontic adhesives were significantly different (p < 0.05). Illuminate® released the greatest fluoride, followed by Fuji Ortho LC® and Light Bond®. After 1, 2, and 3 months, fluoride penetration into enamel was only found from Fuji Ortho LC®. The fluoride concentration decreased with depth but there were no significant differences (p > 0.05) over time at all depths. CONCLUSIONS: The in vitro study indicated that fluoride release is a common property of the three fluoride-releasing orthodontic adhesives: Illuminate®, Fuji Ortho LC®, and Light Bond®. However, detectable fluoride penetration is a specific property of Fuji Ortho LC®. Further clinical studies should be undertaken to investigate the benefit of the two adhesives Illuminate® and Fuji Ortho LC® on protection of enamel demineralization.

A Comparison of the Discoloration Potential for EndoSequence Bioceramic Root Repair Material Fast Set Putty and ProRoot MTA in Human Teeth: An In Vitro Study.

OBJECTIVE: To compare the discoloration potential of Endosequence Bioceramic Root Repair Material fast set putty (ERRMF) and ProRoot MTA (PMTA) when placed coronally in human extracted teeth over a 4-month period. METHODOLOGY: Forty-eight premolars were sectioned 2 mm below the cementoenamel junction. The pulp chambers were cleaned chemo-mechanically. The specimens were randomly assigned to three groups: PMTA, ERRMF, and no fill (control). Tooth color was measured spectrophotometrically at six time points: after material placement, after 2, 4, 8, 12, and 16 weeks. Data were transformed into Commission Internationale de l'éclairage (CIE) L*a*b* system and color difference values (ΔΕ) were calculated. Specimen images were recorded for each time point. Three random specimens from experimental groups were sectioned longitudinally and examined under a stereomicroscope. For data analyses, we used one-way analysis of variance with repeated measurements and Tukey's test (α = 0.05). RESULTS: At 2 weeks, the ΔE means did not differ significantly between the groups. At 4, 8, 12, and 16 weeks, PMTA group exhibited a significantly higher ΔE compared with the ERRMF and control groups. The ΔE did not differ significantly between the ERRMF and control groups. Teeth restored using PMTA exhibited a visually progressive dark discoloration. The control and ERRMF group specimens exhibited color stability. Sections of PMTA specimens revealed grayish discoloration of the material with dark dentinal staining that was not visible in the ERRMF specimens. CONCLUSION: Teeth restored using PMTA exhibited progressive discoloration, whereas teeth restored with ERRMF maintained color stability over a 4-month period. CLINICAL SIGNIFICANCE: The results found in the present study suggest that PMTA produces tooth discoloration over time, whereas ERRMF does not induce tooth discoloration. Therefore, ERRMF might be an alternative to PMTA, especially for coronal restoration in aesthetic zone teeth. (J Esthet Restor Dent 29:59-67, 2017).

Enamel shear bond strength of two orthodontic self-etching bonding systems compared to Transbond™ XT.

OBJECTIVE: The aim of this in vitro study was to compare the shear bond strength (SBS) and Adhesive Remnant Index (ARI) scores of two self-etching no-mix adhesives (Prompt L-Pop™ and Scotchbond™) for orthodontic appliances to the commonly used total etch system Transbond XT™ (in combination with phosphoric acid). MATERIALS AND METHODS: In all, 60 human premolars were randomly divided into three groups of 20 specimens each. In group 1 (control), brackets were bonded with Transbond™ XT primer. Prompt L-Pop™ (group 2) and Scotchbond™ Universal (group 3) were used in the experimental groups. Lower premolar brackets were bonded by light curing the adhesive. After 24 h of storage, the shear bond strength (SBS) was measured using a Zwicki 1120 testing machine. The adhesive remnant index (ARI) was determined under 10× magnification. The Kruskal-Wallis test was used to statistically compare the SBS and the ARI scores. RESULTS: No significant differences in the SBS between any of the experimental groups were detected (group 1: 15.49 ± 3.28 MPa; group 2: 13.89 ± 4.95 MPa; group 3: 14.35 ± 3.56 MPa; p = 0.489), nor were there any significant differences in the ARI scores (p = 0.368). CONCLUSIONS: Using the two self-etching no-mix adhesives (Prompt L-Pop™ and Scotchbond™) for orthodontic appliances does not affect either the SBS or ARI scores in comparison with the commonly used total-etch system Transbond™ XT. In addition, Scotchbond™ Universal supports bonding on all types of surfaces (enamel, metal, composite, and porcelain) with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures.

Transmission of Curing Light through Moist, Air-Dried, and EDTA Treated Dentine and Enamel.

Objective. This study measured light transmission through enamel and dentin and the effect of exposed dentinal tubules to light propagation. Methods. Light attenuation through enamel and dentin layers of various thicknesses (1 mm, 2 mm, 3 mm, and 4 mm) was measured using specimens that were (1) moist and (2) air-dried (n = 5). Measurements were repeated after the specimens were treated with EDTA. Specimens were transilluminated with a light curing unit (maximum power output 1869 mW/cm(2)), and the mean irradiance power of transmitting light was measured. The transmission of light through teeth was studied using 10 extracted intact human incisors and premolars. Results. Transmitted light irradiance through 1 mm thick moist discs was 500 mW/cm(2) for enamel and 398 mW/cm(2) for dentin (p < 0.05). The increase of the specimen thickness decreased light transmission in all groups (p < 0.005), and moist specimens attenuated light less than air-dried specimens in all thicknesses (p < 0.05). EDTA treatment increased light transmission from 398 mW/cm(2) to 439 mW/cm(2) (1 mm dentin specimen thickness) (p < 0.05). Light transmission through intact premolar was 6.2 mW/cm(2) (average thickness 8.2 mm) and through incisor was 37.6 mW/cm(2) (average thickness 5.6 mm). Conclusion. Light transmission through enamel is greater than that through dentin, probably reflecting differences in refractive indices and extinction coefficients. Light transmission through enamel, dentin, and extracted teeth seemed to follow Beer-Lambert's law.

Cuspal Deflection of Premolars Restored with Bulk-Fill Composite Resins.

OBJECTIVE: This in vitro study compared cuspal deflection of premolars restored with three bulk-fill composite resins to that of incrementally-restored ones with a low-shrinkage silorane-based restorative material. MATERIALS AND METHODS: Forty freshly-extracted intact human upper premolars were used. Reference points at buccal and palatal cusp tips were acid-etched and composite rods were horizontally bonded to them (TPH-Spectra-HV, Dentsply). Two acrylic resin guiding paths were made for each premolar to guide beaks of a digital micrometer used for cuspal deflection measurements. Standardized MOD cavities, 3 mm wide bucco-lingually and 3.5 mm deep, were prepared on each premolar. Prepared teeth were then equally divided into four groups (n = 10) and each group was assigned to one of four composite resin (QuiXX, Dentsply; X-tra fil, Voco; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent; low-shrinkage Filtek LS, 3M/ESPE). Adper Single Bond-Plus, 3M/ESPE was used with all bulk-fill restoratives. LS-System Adhesive, 3M/ESPE was used with Filtek LS. For each prepared premolar, cuspal deflection was measured in microns as the difference between two readings between reference points before and after restoration completion. Means and SDs were calculated and data statistically-analyzed using One-way ANOVA and Tukey's test. RESULTS: Filtek LS showed the lowest mean cuspal deflection value 6.4(0.84)µm followed by Tetric EvoCeram Bulk Fill 10.1(1.2) µm and X-tra fil 12.4(1.35)µm, while QuiXX showed the highest mean 13(1.05)µm. ANOVA indicated significant difference among mean values of groups (p < 0.001). Tukey's test indicated no significant difference in mean values between QuiXX and X-tra fil (p = 0.637). CONCLUSIONS: Tetric EvoCeram Bulk Fill had significantly lower mean cuspal deflection compared with the two other bulk-fill composite resins tested. Filtek LS had the lowest significant mean cuspal deflection in comparison to all tested bulk-fill restoratives. CLINICAL SIGNIFICANCE: The use of Tetric EvoCeram Bulk fill composite resin restorative for class II MOD cavities resulted in reduced cuspal deflection in comparison to the two other bulk-fill composite resins tested. The silorane-based Filtek LS restorative resulted in the least cuspal deflection in comparison to all tested bulk-fill composite restoratives.

Comparative evaluation of tooth substance loss and its correlation with the abrasivity and chemical composition of different dentifrices.

CONTEXT: In India, teeth cleaning with tooth powder is common in rural and semi-urban areas. These dentifrices may contain low-quality abrasives, which may have a deleterious effect on dental hard tissues. AIMS: This study aims to evaluate the tooth substance loss caused by different dentifrices and to correlate it with chemical composition, size, and shape of abrasives used. SETTINGS AND DESIGN: An indigenously made automated machine was used for brushing the specimens. MATERIALS AND METHODS: Sixty-four freshly extracted premolars were allocated to eight groups (n = 8). Colgate toothpaste was used as the control group. Each specimen was brushed in a vertical motion for 2½ h at 200 strokes/min with a constant applied load of 200 g corresponding to 6-month brushing. The difference in weight (pre- and post-brushing) was determined by an analytical weighing machine. Chemical analysis was done to determine the presence of iron oxide by Inductively Coupled Plasma Mass Spectrometry method. Shape and size of the abrasive particles was evaluated under scanning electron microscopy (SEM). STATISTICAL ANALYSIS USED: One-way analysis of variance and Paired t-test were used to analyze the data. RESULTS: Tooth substance loss was maximum in the group brushed with red tooth powder, which was shown to contain the highest amount of iron oxide and also exhibited large, irregularly shaped abrasive particles under SEM. CONCLUSIONS: Tooth substance loss was documented to be correlated with chemical composition (iron oxide) and the size and shape of abrasive particles used in dentifrices.

Wettability modification of human tooth surface by water and UV and electron-beam radiation.

The wettability of the human tooth enamel and dentin was analyzed by measuring the contact angles of a drop of distilled water deposited on the surface. The samples were cut along the transverse and longitudinal directions, and their surfaces were subjected to metallographic mirror-finish polishing. Some samples were also acid etched until their microstructure became exposed. Wettability measurements of the samples were done in dry and wet conditions and after ultraviolet (UV) and electron beam (EB) irradiations. The results indicate that water by itself was able to increase the hydrophobicity of these materials. The UV irradiation momentarily reduced the contact angle values, but they recovered after a short time. EB irradiation raised the contact angle and maintained it for a long time. Both enamel and dentin surfaces showed a wide range of contact angles, from approximately 10° (hydrophilic) to 90° (hydrophobic), although the contact angle showed more variability on enamel than on dentin surfaces. Whether the sample's surface had been polished or etched did not influence the contact angle value in wet conditions.