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Magnetic Induction Heating (MIH) of magnetite nanoparticles is employed as a novel synthesis procedure of carbon based magnetic nanocomposites. Magnetic nanoparticles (Fe3O4) and fructose (1:2 weight ratio) were mechanically mixed and submitted to a RF magnetic field (305 kHz). The heat generated by the nanoparticles leads to the decomposition of the sugar and to the formation of an amorphous carbon matrix. Two sets of nanoparticles, with mean diameter sizes of 20 and 100 nm, are comparatively analysed. Structural (X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy (TEM)), electrical and magnetic (resistivity, SQUID magnetometry) characterizations confirm the nanoparticle carbon coating through the MIH procedure. The percentage of the carbonaceous fraction is suitably increased controlling the magnetic heating capacity of the magnetic nanoparticles. The procedure enables the synthesis of multifunctional nanocomposites with optimized properties to be applied in different technological fields. Particularly, Cr (VI) removal from aqueous media is presented employing the carbon nanocomposite with 20 nm Fe3O4 nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, room-temperature ferromagnetism and the red-shift of the optical absorption is analyzed in nitrogen doped TiO2 semiconductor nanoparticles. The nanoparticles were synthesized by the sol-gel method using urea as the nitrogen source. Titanium Tetraisopropoxide (TTIP) was employed as the alkoxyde precursor and dissolved in ethanol. The as prepared gels were dried and calcined in air at 300°C. Additionally, post-annealing treatments under vacuum atmosphere were performed to modify the oxygen stoichiometry of the samples. The anatase lattice parameters, analyzed by means of powder X-ray diffractometry, depend on the nanometer grain size of the nanoparticles (increase and decrease, respectively, of the tetragonal a and c lattice parameters with respect to the bulk values). The diffuse reflectance ultraviolet-visible (UV-Vis) absorbance spectra show a clear red-shift as consequence of the nitrogen and the occurrence of intragap energy levels. The samples display ferromagnetic features at room temperature that are reinforced with the nitrogen content and after the post annealings in vacuum. The results indicate a clear correlation between the room temperature ferromagnetism and the shift of the absorbance spectrum. In both phenomena, oxygen vacancies (either induced by the nitrogen doping or by the post vacuum annealings) play a dominant role. However, we conclude the existence of very low concentration of diluted transition metal impurities that determine the room ferromagnetic response (bound magnetic polaron BMP model). The contraction of the c soft axis of the anatase cell structure is outlined as a possible controlling factor of the ferromagnetic response in these metal oxide diluted magnetic semiconductor nanostructures. [ABSTRACT FROM AUTHOR]

Background: Molar-incisor hypomineralization (MIH) is a qualitative enamel defect that is highly prevalent in children. It has been reported that patients with MIH have higher caries occurrence with an increased need and frequency of dental treatment compared to patients without MIH. The objective of this study was to analyze the association between MIH and a series of factors related to maternal health status during pregnancy and children´s medical history in early childhood., Methods: A retrospective study of cases (patients with MIH) and controls (patients without MIH) was designed between 2023 and 2024. A total of 280 children (cases = 140; controls = 140) aged 6 to 14 years (138 boys and 142 girls) were examined according to the European Academy of Pediatric Dentistry (EAPD) criteria for MIH. A survey was carried out with mothers regarding the potential exposure of their children to etiological factors of MIH. Possible prenatal and postnatal etiological factors were obtained through a personal interview with the patients' mothers. The statistical analysis was carried out with the contrast test and the chi-square test., Results: During pregnancy, folic acid consumption, alcohol intake, systemic viral and/or bacterial infections, and gestational diabetes were statistically significantly related to MIH, as were breastfeeding, asthma, and corticosteroid consumption during childhood., Conclusions: Although there are different factors that may have statistically significant relationships with MIH, they cannot be predicted. Therefore, longitudinal studies, with a large sample size, are needed to determine the influence of prenatal and postnatal factors on the prevalence and severity of MIH in children., (© 2024. The Author(s).)

Background: This study aimed to characterize dentistry, medicine and pharmacy students in terms of emotional intelligence (EI) and personality traits (PTs). It also sought to identify whether differences existed according to gender and degree program and the relationship between them., Methods: Students enrolled in dentistry (115), medicine (85) and pharmacy (57) degree programs participated voluntarily in the research, including 59 men and 198 women. The following questionnaires were used: (1) the Trait Meta-Mood Scale (TMMS-24) to evaluate EI; (2) the NEO Five-Factor Inventory (NEO-FFI) to assess PT. The Qualtrics XM platform was used for data collection., Results: There were no statistically significant differences between three components of EI, either according to gender or degree program. The only difference in PTs was found in neuroticism, where women scored higher than men. There were statistically significant differences between students on different degree programs in openness to experience and responsibility. The five PTs correlated significantly with the three components of EI, except responsibility and emotional attention. The strongest associations were found between neuroticism and emotional repair (-0.439)., Conclusions: High percentages of the student population were observed to have weaknesses in emotional clarity and emotional repair. Neuroticism is a personality trait that seems to occur more frequently in women.

The roughness of the intra-oral surfaces significantly influences the initial adhesion and the retention of microorganisms. The aim of this study was to analyze the surface texture of four different CAD-CAM materials (two high-performance polymers and two fifth-generation zirconia) used for complete-arch implant-supported prostheses (CAISPs), and to investigate the effect of artificial aging on their roughness. A total of 40 milled prostheses were divided into 4 groups ( n = 10) according to their framework material, bio.HPP (B), bio.HPP Plus (BP), zirconia Luxor Z Frame (ZF), and Luxor Z True Nature (ZM). The areal surface roughness "Sa" and the maximum height "Sz" of each specimen was measured on the same site after laboratory fabrication (lab as-received specimen) and after thermocycling (5-55 °C, 10,000 cycles) by using a noncontact optical profilometer. Data were analyzed using SPSS version 28.0.1. One-way ANOVA with multiple comparison tests ( p = 0.05) and repeated measures ANOVA were used. After thermocycling, all materials maintained "Sa" values at the laboratory as-received specimen level ( p = 0.24). "Sz" increased only for the zirconia groups ( p = 0.01). B-BP exhibited results equal/slightly better than ZM-ZF. This study provides more realistic surface texture values of new metal-free materials used in real anatomical CAISPs after the manufacturing and aging processes and establishes a detailed and reproducible measurement workflow.

No gingival shade guide exists that can be used as a 'gold standard' in gingival shade selection. This research, therefore, aimed to determine whether comparable results in subjective gingival shade selection can be achieved using basic gingival colours produced by distinct manufacturers. It also aimed to explore how coverage of the colour space is affected by mixing these basic colours to create additional shades. To achieve these objectives, the basic gingival colours of three ceramic systems (Heraceram, Kulzer, Madrid, Spain; Vita VM9, Vita Zahnfabrik, Bad Säckingen, Germany; IPS Style, Ivoclar, Schaan, Liechtenstein) were analysed. The colour systems were expanded by creating porcelain gingival samples, whose colours were obtained by mixing the basic colours, altering each mixture by increments of 10%, and respecting the numerical order used by manufacturers to identify the colours. The colour coordinates of the basic and additional colours were recorded using spectrophotometry, and the intra- and inter-system colour differences were calculated using the Euclidean (ΔE ab ) and CIEDE2000 (ΔE 00 ) formulae. None of the basic colours in the three systems, despite their similar nomenclature, were found to be interchangeable (the colour differences exceeded the gingival acceptability threshold: ΔE 00 2.9 units). The expanded gingival colour systems, with mixtures altered by 10% increments, notably increased the gingival colour space covered by the original systems. The authors concluded that there are clear differences between the basic gingival colours produced by distinct manufacturers using the same nomenclature. Ceramic samples produced by mixing basic gingival colours are a resource with the potential to improve subjective gingival shade matching.

This in vitro study aimed to assess the presence of microgaps at the implant-abutment interface in monolithic zirconia partial implant-supported fixed prostheses on transepithelial abutments versus Ti-base abutments., Methods: Sixty conical connection dental implants were divided into two groups ( n = 30). The control group consisted of three-unit bridge monolithic zirconia connected to two implants by a transepithelial abutment. The test group consisted of monolithic zirconia three-unit restoration connected to two implants directly by a titanium base (Ti-base) abutment. The sample was subjected to thermocycling (10,000 cycles at 5 °C to 55 °C, dwelling time 50 s) and chewing simulation (300,000 cycles, under 200 N at frequencies of 2 Hz, at a 30° angle). The microgap was evaluated at six points (mesiobuccal, buccal, distobuccal, mesiolingual, lingual, and distolingual) of each implant-abutment interface by using a scanning electron microscope (SEM). The data were analyzed using the Mann-Whitney U tests ( p > 0.05)., Results: The SEM analysis showed a smaller microgap at the implant-abutment interface in the control group (0.270 μm) than in the test group (3.902 μm). Statistically significant differences were observed between both groups ( p < 0.05)., Conclusions: The use or not of transepithelial abutments affects the microgap size. The transepithelial abutments group presented lower microgap values at the interface with the implant than the Ti-base group in monolithic zirconia partial implant-supported fixed prostheses. However, both groups had microgap values within the clinically acceptable range.

The aim of this study was o determine the relationship between sleep bruxism (SB) and sleep apnea-hypopnea syndrome (SAHS) at the pathophysiological level, the risk factors, as well as the common signs and symptoms. A search was carried out using the databases PubMed, Web of Science, Scopus, and the Cochrane Library together with the Boolean equation "bruxism" AND "sleep apnea" AND "relation*"; the systematic search strategy limited the results to English language articles published from 2013 until December 2021. This review was conducted in accordance with the PRISMA statement. Nine articles were reviewed to relate SAHS and SB at different levels: two were systematic reviews (22%) and seven were research studies (78%). According to the literature reviewed, SB and SAHS occur simultaneously in 21.0% to 41.3% of cases. There are signs and symptoms that are common to both SAHS and SB. Rhythmic masticatory muscle activity (RMMA) precedes an SAHS event in 25% of subjects with SB, in contrast to 55% of the general population. SB and SAHS seem to have a certain concomitance, ranging between 20% and 40%, and they also share some risk factors such as advanced age, obesity, smoking, and alcohol consumption. Dentists should be aware of this relationship, as part of a multidisciplinary team, for early diagnosis.

Magnetic carbon nanocomposites (α-Fe/Fe 3 C@C) synthesized employing fructose and Fe 3 O 4 magnetite nanoparticles as the carbon and iron precursors, respectively, are analyzed and applied for the removal of Cr (VI). Initial citric acid-coated magnetite nanoparticles, obtained through the co-precipitation method, were mixed with fructose (weight ratio 1:2) and thermally treated at different annealing temperatures ( T ann = 400, 600, 800, and 1000 °C). The thermal decomposition of the carbon matrix and the Fe 3 O 4 reduction was followed by thermogravimetry (TGA) and Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, Raman spectroscopy, SQUID magnetometry, and N 2 adsorption-desorption isotherms. A high annealing temperature ( T ann = 800 °C) leads to optimum magnetic adsorbents (high magnetization enabling the magnetic separation of the adsorbent from the aqueous media and large specific surface area to enhance the pollutant adsorption process). Cr (VI) adsorption tests, performed under weak acid environments (pH = 6) and low pollutant concentrations (1 mg/L), confirm the Cr removal ability and reusability after consecutive adsorption cycles. Physical adsorption (pseudo-first-order kinetics model) and multilayer adsorption (Freundlich isotherm model) characterize the Cr (VI) absorption phenomena and support the enhanced adsorption capability of the synthesized nanostructures.

(1) Background: This study compared the clinical and esthetic results of the double lateral sliding bridge flap (DLSBF) and the laterally closed tunnel (LCT) techniques, with a subepithelial connective tissue graft (SCTG), for the treatment of single Miller class II-III recessions in the mandibular anterior teeth. (2) Methods: This pseudorandomized clinical trial evaluated 14 patients, 7 of whom were part of the DLSBF + SCTG group, with an average follow-up of 58.7 ± 24.0 months, and 7 of whom were in the LCT + SCTG group, with an average follow-up of 16.7 ± 3.3 months. Clinical and esthetic evaluations of the following parameters were performed and the results for the two groups were compared: gingival recession depth, probing depth, keratinized tissue width, gingival thickness, percentage of root coverage and root coverage esthetic score. (3) Results: After the follow-up period, each technique provided evidence of a reduction in recession depth and clinical attachment level, as well as increased keratinized tissue width and gingival thickness, with statistically significant differences (p < 0.05). The analysis showed that gingival recession depth decreased less in the DLSBF group (4.3 ± 1.2 mm to 0.6 ± 1.1 mm) than it did in the LCT group (4.9 ± 1.1 mm to 0.1 ± 0.4 mm), but no significant difference was found between the two groups. Similarly, a greater reduction in the clinical attachment level parameter was observed in the LCT group, while a greater increase in gingival thickness was observed in the DLSBF group. The presence of scars was the only parameter for which statistically significant differences (p < 0.05) between the two study groups were found. (4) Conclusions: Within the limitations of the study, it indicates that the LCT + SCTG technique may be considered an optimal technique in terms of reducing gingival recession depth, complete root coverage and esthetic results for the treatment of single gingival recessions in the mandibular anterior teeth.

Background and Objectives: To study the validity and the degree of representability of the toothguide 3D Master, with 26 physically shade tabs, on the natural tooth colour on a sample of the Spanish population. Materials and Methods: Natural tooth colour was measured in a sample of 1361 Spanish participants of both genders distributed within an age range of 18 and 89 years of age. The colour coordinates were calculated and the frequency of the 26 physically shade tabs of the toothguide as well as the "intermediate shades" (without physical representation in toothguide) through the Easyshade Compact (Vita-Zahnfabrik) spectrophotometer using the 3D Master System nomenclature. The colour differences between the "intermediate shades" were calculated using the Euclidean formula (ΔEab*). The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. Results: A total of 49 "intermediate shades" were registered in 816 participants (60%). The colour coordinates of the 49 'intermediate shades' cover colour coordinates ranging from 0M1.5 (L* 100.0, C* 7.70, h* 112.2) to 5M2.5 (L* 56.8, C* 35.8, h* 78.5). Not all possible 3D Master System's "intermediate shades" were registered in the population studied. 82.4% of the colour differences among the "intermediate shades" were clinically unacceptable (ΔEab* ≥ 5.5 units). Conclusions: Only 40% of the population studied presented a natural tooth colour belonging to the 3D Master Toothguide's physical shade tabs.

The aim of this work is to study the personality factors and coping styles of Spanish dentists when facing burnout syndrome, through epidemiological work. An epidemiological study of 1928 Spanish dentists was undertaken through an online survey, which registered the age and gender, and three questionnaires: NEO-FFI (personality traits), Brief COPE (coping styles), and MBI-HSS (burnout questionnaire). A multivariate analysis and an explanatory binary logistic regression model were used to estimate the presence of burnout. Neuroticism turned out to be the strongest indicator (OR 1.10; IC 95% 1.09-1.14), while extraversion (OR 0.93; IC 95% 0.91-0.95) and agreeableness (OR 0.94; IC95% 0.92-0.98) showed an inverse relationship with the occurrence of burnout, as did age (OR 0.9; IC95% 0.96-0.99). Conscientiousness (OR 1.0; IC95% 1.00-1.06) had a direct relationship with the presence of burnout. An avoidant coping style was the only indicative coping style (OR 1.04 IC95% 1.02-1.06). Approximately 70% of the dentists scored high on one of the three dimensions of burnout. No differences were found in the degree of burnout according to gender. Certain personality factors (neuroticism, extraversion, agreeableness, and conscientiousness), the avoidant coping style, and age are powerful indicators to attempt to forecast the presence of burnout syndrome in dentists.

This study aims to assess the treatment outcomes (functional and subjective) of full-arch fixed hybrid rehabilitations made of PEEK (poly-ether-ether-ketone) with milled crowns of nano-filled composite (NFC) supported on four to six implants. In this randomized clinical trial, 34 edentate patients in the upper and/or the lower jaws were treated with the fixed hybrid dentures. In 16 patients (47.1% of the sample), the implants were loaded immediately (IL) by means of a provisional fixed rehabilitation made of PMMA (polymethylmethacrylate) screwed on Multi-Unit (MU) abutments connected after emplacement of the implant; however, in the counterparts ( n = 18) these MU abutments were covered by healing caps and were left unloaded during two months (conventional loading protocol-CL), when all patients received a fixed hybrid PEEK-NFC rehabilitation on the upper and/or the lower jaw. Treatment outcomes were assessed 12 months after prostheses delivery. Functional outcomes were calculated according to masticatory performance, estimated by mixing ability tests of two colored chewing gums after ten chewing strokes, by the occlusal force/area recorded by pressure-sensitive sheets, and by electromyography of masseters and temporal muscles at maximum biteforce. The subjective outcomes of the treatment were assessed using both the oral satisfaction scale (visual analog scale) and the Spanish version of the Oral Health Impact Profile (OHIP-20). The findings of the present study showed that treatment with fixed PEEK-NFC hybrid prostheses significantly improved the masticatory performance, bite force, occlusal pattern, quality of life, and satisfaction, with the IL group being those with significantly higher occlusal bite forces and greater satisfaction in comparison with CL group. It should be concluded that PEEK-NFC hybrid prostheses can improve several patient-centered outcomes and that loading protocol significantly affects the patient's self-rated satisfaction.

This study aims to assess the treatment outcomes (functional and subjective) of mandibular overdentures retained on two implants with or without an immediate loading protocol. In this randomized clinical trial, twenty fully edentulous patients were treated with a mandibular two-implant-retained overdenture and a complete new maxillary denture. In half of the sample, the implants were loaded immediately by means of VulkanLoc ® abutments after emplacement of the implant, but in the counterparts, these VulkanLoc ® abutments were connected to implants two months after the surgery (conventional protocol), and until that time the dentures were retained by healing abutments. Treatment outcomes were assessed at two, six, and twelve months after surgery. Functional outcomes were calculated according to masticatory performance, estimated by the mixed fraction of a two-coloured chewing gum after five, ten, and fifteen chewing strokes, by the occlusal force recorded by pressure-sensitive sheets, and by the bioelectrical muscular activity. The subjective outcomes of the treatment were assessed using both the oral satisfaction scale (visual analogue scale) and the Spanish version of the Oral Health Impact Profile (OHIP-20). The findings of the present study show that new complete dentures resulted in significant improvements in chewing ability, patient satisfaction, and oral health-related quality of life and that subsequent implant-retained overdentures produced further and faster significant improvements. The loading protocol may influence those positive self-reported outcomes rather than the objective functional evaluations.

Clinicians should appreciate the effectiveness of virtual reality (VR) headsets for managing both the anxiety and the behaviour of non-cooperative paediatric patients who require treatment over several dental appointments. The aim of this study was to assess the effectiveness of using a VR headset as a distraction for managing the anxiety and behaviour of paediatric patients during their dental treatment. Eighty patients, aged between five and ten years old and who required dental treatment over three or more appointments, were randomly allocated into two groups. One group used a VR headset during all their appointments, and the other one did not use any distraction technique. The patients were asked to take a Facial Image Scale Test during their first and last appointments to assess their level of anxiety. Additionally, the dentist completed the Frankl Test to quantify the child's behaviour at the beginning and the end of their treatment. The results obtained, both from the group using the VR headset and from the control group, were compared using the chi-square test. The use of a VR headset during dental treatment significantly reduced anxiety (95% of the children were happy) and improved behaviour (100% positive behaviour) as compared with the control group (40% and 57.5%, respectively). A VR headset can effectively distract a paediatric patient, helping to reduce anxiety and manage behaviour during dental treatment.

Clinicians should be aware of the main methods and materials to face the challenge of bone shortage by manufacturing customized grafts, in order to repair defects. This study aims to carry out a bibliographic review of the existing methods to manufacture customized bone scaffolds through 3D technology and to identify their current situation based on the published papers. A literature search was carried out using "3D scaffold", "bone regeneration", "robocasting" and "3D printing" as descriptors. This search strategy was performed on PubMed (MEDLINE), Scopus and Cochrane Library, but also by hand search in relevant journals and throughout the selected papers. All the papers focusing on techniques for manufacturing customized bone scaffolds were reviewed. The 62 articles identified described 14 techniques (4 subtraction + 10 addition techniques). Scaffold fabrication techniques can be also be classified according to the time at which they are developed, into Conventional techniques and Solid Freeform Fabrication techniques. The conventional techniques are unable to control the architecture of the pore and the pore interconnection. However, current Solid Freeform Fabrication techniques allow individualizing and generating complex geometries of porosity. To conclude, currently SLA (Stereolithography), Robocasting and FDM (Fused deposition modeling) are promising options in customized bone regeneration.

This study aimed to analyze a novel technique to make screws with greater untightening resistance and to solve screw loosening in implant-supported single crowns. Thirty grade IV titanium straight abutments were screwed onto 30 external hex implants using grade IV titanium screws (30 Ncm). They were exposed to cyclic loading (300,000 cycles, 200 N). Samples were divided into 4 groups (15 samples per group): new screws (SCREW group) (control), reused screws (rSCREW group), new screws wrapped with polytetrafluoroethylene (PTFE) tape (PTFE group), and reused screws wrapped with PTFE tape (rPTFE group). Reverse torque values (RTVs) were recorded with a digitally calibrated implant motor. Mean RTVs observed were 14.46 N (±1.10 N) for the control group, 14.42 N (±1.22 N) for the rSCREW group, 19.97 N (±1.16 N) for the PTFE group, and 19.13 N (±2.38 N) for the rPTFE group. Statistically significant differences were found between RTVs of both groups employing screws without PTFE tape (SCREW and rSCREW groups) compared with those using screws wrapped with PTFE tape (PTFE and rPTFE) ( p < 0.001). These results suggest that wrapping the implant-abutment screw with PTFE tape may effectively lower the risk of loosening and even constitute a solution when this complication occurs in implant single crowns.

Soft magnetic amorphous alloys obtained via rapid quenching techniques are widely employed in different technological fields such as magnetic field detection, bio labeling, non-contact positioning, etc. Among them, magnetoelastic applications stand out due to excellent mechanical properties exhibited by these alloys, resulting from their amorphous structure, namely, their high Young modulus and high tensile strength. In particular, the giant stress impedance (GSI) effect represents a powerful tool to develop highly sensitive magnetoelastic sensors. This effect is based on the changes in the high-frequency electric impedance as the result of the variation in magnetic permeability of the sample under the action of mechanical stresses. In this work, the GSI effect is analyzed in two soft magnetic ribbons ((Co 0.93 Fe 0.07 ) 75 Si 12.5 B 12.5 and (Co 0.95 Fe 0.05 ) 75 Si 12.5 B 12.5 ) for the subsequent development of two practical devices: (i) the characterization of the variations in the cross-section dimensions of irregularly shaped elements, and (ii) the design of a flow meter for measuring the rate of flow of water through a pipe.

An energy harvesting device combined with a giant magnetoimpedance (GMI) sensor is presented to analyze low frequency vibrating systems. An electromagnetic harvester based on magnetic levitation is proposed for the electric power generation. The device is composed of two fixed permanent magnets at both ends of a cylindrical frame, a levitating magnet acting as inertial mass and a pick-up coil to collect the induced electromotive force. At the resonance frequency (10 Hz) a maximum electrical power of 1.4 mW at 0.5 g is generated. Moreover, an amorphous wire was employed as sensor nucleus for the design of a linear accelerometer prototype. The sensor is based on the GMI effect where the impedance changes occur as a consequence of the variations of the effective magnetic field due to an oscillating magnetic element. As a result of the magnet's periodic motion, an amplitude modulated signal (AM) was obtained, its amplitude being proportional to mechanical vibration amplitude (or acceleration). The sensor's response was examined for a simple ferrite magnet under vibration and compared with that obtained for the vibrational energy harvester. As a result of the small amplitudes of vibration, a linear sensor response was obtained that could be employed in the design of low cost and simple accelerometers.

The final color of a ceramic restoration is influenced by both the ceramic thickness and the cement shade. This study aims to evaluate the color stability according to the 3D Master System of e.max ceramic discs after bonding with different shades of luting agents. A total of 120 e.max.Press 2M1 HT ceramic discs (60 discs of 1-mm thick and 60 discs of 0.5 mm thick) and three different values of Variolink Veneer cement were used (-3, 0, +3) for the cementation process. An Easyshade compact device was used to measure color shade tabs, according to the 3D Master System, on the discs both before and after the cementation protocols. Bivariate and multivariate analyses were carried out with the spss v.21. After bonding with the different luting agents, only 30% remained as 2M1: specifically, 22% of the thinner discs and 37.3% of the thicker discs. In general, the effect of bonding increased the value and the chroma of the shade to a significant extent. Regression analyses revealed that the most significant predictor for all color parameters was cement shade, the thinner disc group bonded with -3 cement being the most unstable subgroup. According to the 3D Master System, the shade of the luting agent was the main predictor of the final color. However, the final color seems to be somewhat unpredictable, at least according to the modulating factors evaluated in the present study.

Purpose: To identify the most frequent natural tooth colors using the Easyshade Compact (Vita -Zahnfabrik) spectrophotometer on a sample of the Spanish population according to the 3D Master System., Materials and Methods: The middle third of the facial surface of natural maxillary central incisors was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Caucasian Spanish participants aged between 16 and 89 years. Natural tooth color was recorded using the 3D Master System nomenclature. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3., Results: The results show that the most frequent dental color in the total sample studied is 3M1 (7.05%), followed by the intermediate shade 1M1.5 (6.91%) and 2L1.5 (6.02%)., Conclusion: According to the research methodology used, and taking into account the limitations of this study, it can be proposed that the most frequent color among the Spanish population is 3M1; the most common lightness group is 2; the most frequent hue group according to the 3D Master System is M and the most frequent chroma group is 1.5.

Objectives: To analyse natural tooth colour in the Spanish population according to the colour coordinates lightness (L*), chroma (C*), hue (h*), red-green axis (a*) and yellow-blue axis (b*) in order to quantify the correlation and changes of tooth colour with age and sex., Methods: Natural tooth colour was measured in a sample of 1,361 Spanish participants of both sexes distributed within an age range of 16 to 89 years. The Easyshade Compact spectrophotometer was used and the CIELAB and CIELCh systems were followed., Results: Pearson's bivariate correlations between age and colour coordinates were highly significant for L* (r=-0.674, P≤0.001), h* (r=-0.468, P≤0.001) and C* (r=0.417, P≤0.001). The correlation between age and colour coordinates was stronger for men than for women, for all colour coordinates. The results showed that C*, b* and a* increased by 0.60, 0.56 and 0.26 units/year on average, respectively, whereas L* and h* decreased progressively with age (by 0.60 units/year, on average), and colour differences increased in a systematic way as the gap between the ages being compared grew wider., Conclusions: The strongest correlation was found between age and L*, then between age and h* (both inverse relationships) and then between age and a*, C* and b* (direct relationships). In addition, a similar degree of change in the colour coordinates L*, C* and h* (of 0.60 units/year on average) was observed for natural tooth colour. Knowledge of the chromatic range of natural teeth may help to choose colour for the replacement of missing elements., (© 2015 FDI World Dental Federation.)