Physical properties, marginal adaptation and bioactivity of an experimental mineral trioxide aggregate-like cement modified with bioactive materials.

PURPOSE: To evaluate the effect of adding wollastonite and bioactive glass to an experimental mineral trioxide aggregate-like cement (MTA) on the dimensional stability, compressive strength, solubility, bioactivity, and marginal adaptation by scanning electron microscopy (SEM) and X-ray diffraction (XRD). METHODS: Four groups were evaluated at 7, 14, and 21 days: MTA Angelus, experimental MTA-like cement (MTA Exp), BG10 (MTA Exp+10 wt% bioactive glass), and WO20 (MTA Exp+20 wt% wollastonite). To evaluate marginal adaptation, extracted teeth were endodontically obturated and root-end cavities were prepared and filled with the tested materials. RESULTS: Cements with bioactive materials showed minimal dimensional changes. Adding wollastonite or bioactive glass to MTA Exp reduces the compressive strength but does not affect solubility. Bismite (Bi2O3), larnite (Ca2SiO4), calcite (CaCO3) and carbonated hydroxyapatite (Ca5[PO4,CO3]3[OH]) were identified in the four cements; ettringite (Ca6Al2[SO4]3[OH]12·26H2O) and bismutite ([BiO]2CO3) were only observed in MTA Exp, BG10, and WO20. Cement-dentin interfaces were not observed after 14 days on the BG10 and WO20 cement composites due to the ettringite formation. CONCLUSION: Acicular growing crystals typical of hydroxyapatite were found on the surfaces of all cements. An improved marginal adaptation was observed with the addition of wollastonite or bioactive glass.

Cambios en parámetros masticatorios con prótesis parcial removible para dientes posteriores perdidos / Changes in masticatory parameters with removable partial dentures for missing posterior teeth

Introducción: el reemplazo de dientes perdidos aspira a mejorar la función masticatoria. Aunque hay diferentes opciones para ello, la conveniencia de la prótesis parcial removible (PPR) es su bajo costo. Objetivo: comparar el desempeño masticatorio (DM) después de 20 ciclos masticatorios y al umbral de la deglución (UD) en adultos de 50 a 70 años con dientes posteriores perdidos (DPP), con/sin PPR; y los ciclos hasta la deglución. Material y métodos: estudio transversal en 35 adultos con dientes anteriores y PPR bien ajustadas y utilizadas para comer. El lado de prueba fue el lado con más DPP. El DM se evaluó después de 20 ciclos y al UD utilizando un alimento prueba artificial (Optosil Comfort®) con/sin la PPR en orden aleatorizado. Las partículas se tamizaron para determinar el tamaño medio de partícula (TMP) como medida del DM. Los ciclos se contaron visualmente. Estadística descriptiva y comparaciones con SPSS-v23. Resultados: hubo diferencias significativas (p ≤ 0.05) al masticar con/sin PPR. El TMP fue más pequeño (mejor DM) con la PPR después de 20 ciclos y al UD (3.9 vs 4.4 mm y 3.2 vs 4.2 mm). Los ciclos para llegar al UD disminuyeron con la PPR (40 vs 47). Conclusión: a pesar de una mejora limitada de la función masticatoria, las PPR ayudan a preparar los alimentos en partículas más pequeñas antes de deglutirlas. La mejoría en DM con PPR es de 24% al UD, realizando menos ciclos antes de deglutir sus alimentos (AU)

Introduction: replacement of missing teeth should improve masticatory function. Although there are different options removable partial dentures (RPD) are used due to their lower cost. Objective: to compare masticatory performance (MP) after 20 chewing-cycles and swallowing-threshold (ST) in 50-70 year-old adults with missing posterior teeth (MPT) with and without their cast-metal RPD; chewing cycles until swallowing were also compared. Material and methods: 35 adults participated in this cross-sectional study. Subjects with anterior teeth and welladjusted RPDs, used for eating were included. The side with more MPT was selected as the test side. MP was evaluated after 20 cycles and ST using an artificial test-food (Optosil Comfort®) with/without the RPD (subject-own-control) (randomized order). Chewed particles were sieved to determine medium-particle-size (MPS) as a measure of MP. Chewing cycles were visually counted. Descriptive statistics and comparisons were run with SPSS v23. Results: there were significant differences (p ≤ 0.05) for all parameters when chewing with/without the RPD. MPS was smaller (better MP) with the RPD (3.9 vs 4.4 mm and 3.2 vs 4.2 mm) after 20 cycles and ST respectively. Cycles required to reach ST were less when chewing with the denture (40 vs 47). Conclusion: despite a limited improvement of masticatory function RPDs help patients prepare their food into smaller particles before swallowing. Improvement in MP with RPDs for patients with MPT is 24% at ST and they perform fewer chewing cycles before swallowing food (AU)

Cell viability and physicochemical effects of different concentrations of bismuth trioxide in a mineral trioxide aggregate cement.

PURPOSE: To evaluate the effect of three concentrations of bismuth trioxide (Bi2O3) on the biological and physicochemical properties of an experimental mineral trioxide aggregate-type (MTA-type) cement at different time points. METHODS: Three experimental groups with white Portland cement containing 15, 20, or 25 wt% of Bi2O3 were assessed. Cellular proliferation in human periodontal ligament fibroblasts was evaluated with an MTT assay. Radiopacity, dimensional stability, pH, and compressive strength were evaluated at different time points. RESULTS: Bismuth trioxide induced cell proliferation in the Bi15 and Bi25 groups in a time-dependent manner; pH was similar in all groups. Compressive strength was associated with time and bismuth concentration. Bi25 had significantly contracted at day 7 and expanded at day 14 (ANOVA P < 0.05, post hoc Tukey test P < 0.05). CONCLUSION: A higher Bi2O3 concentration had a negative effect on the physical properties of the cement at all time points.

Effect of food portion on masticatory parameters in 8- to 10-year-old children.

The objective of this study was to explore differences in bite size and the amount of intraoral processing of four different foods between a reference and a double portion in 8- to 10-year-old children and, also to explore if there were differences depending on the child's weight status. The study was undertaken in 8- to 10-year-old children (n = 89). Body mass index was determined, and weight status was established based on Centers for Disease Control and Prevention(CDC) guidelines. A reference (half a banana, half a large peeled carrot, a slice of loaf cake, and half a salami stick), and a double portion of each food were offered to children in a randomized order in two different sessions. Three consecutive bites were taken and averaged. Variables in this study were bite size (g), number of cycles until swallowing, sequence duration as well as cycles/g. Comparisons were performed with Mann-Whitney, Kruskal-Wallis, and Wilcoxon tests, regressions and correlations were run. Bite size was ≈13% larger with the double portion (p ≤ .05 for salami, banana, and loaf cake). Cycles/g decreased for all foods with the double portion, although only significantly for banana and loaf cake. Normal and obese children had larger bite sizes (p ≤ .05) of banana than overweight children, while only obese had larger bites of loaf cake with the double portion. In conclusion, the bite size of foods in 8- to 10-year-old children increases (13%) when the portion size is doubled and the larger bite size leads to fewer cycles/g (8%). These effects differ among foods. These parameters do not depend on weight status.

Photoelasticity for Stress Concentration Analysis in Dentistry and Medicine.

Complex stresses are created or applied as part of medical and dental treatments, which are linked to the achievement of treatment goals and favorable prognosis. Photoelasticity is an optical technique that can help observe and understand biomechanics, which is essential for planning, evaluation and treatment in health professions. The objective of this project was to review the existing information on the use of photoelasticity in medicine and dentistry and determine their purpose, the areas or treatments for which it was used, models used as well as to identify areas of opportunity for the application of the technique and the generation of new models. A literature review was carried out to identify publications in dentistry and medicine in which photoelasticity was used as an experimental method. The databases used were: Sciencedirect, PubMed, Scopus, Ovid, Springer, EBSCO, Wiley, Lilacs, Medigraphic Artemisa and SciELO. Duplicate and incomplete articles were eliminated, obtaining 84 articles published between 2000 and 2019 for analysis. In dentistry, ten subdisciplines were found in which photoelasticity was used; those related to implants for fixed prostheses were the most abundant. In medicine, orthopedic research predominates; and its application is not limited to hard tissues. No reports were found on the use of photoelastic models as a teaching aid in either medicine or dentistry. Photoelasticity has been widely used in the context of research where it has limitations due to the characteristics of the results provided by the technique, there is no evidence of use in the health area to exploit its application in learning biomechanics; on the other hand there is little development in models that faithfully represent the anatomy and characteristics of the different tissues of the human body, which opens the opportunity to take up the qualitative results offered by the technique to transpolate it to an application and clinical learning.

The effect of bolus size on masticatory parameters at swallowing threshold in children using a hard, solid, artificial test food.

The effect of different bolus sizes on food breakdown has been studied in adults, but not in children. The objective of this study was to study median particle size (MPS) and other parameters of masticatory function at swallowing threshold (ST) in 8-10-year-old-children with two different bolus sizes. A randomized crossover trial was undertaken in 89 eight to ten-year-old children. The study was performed with informed consent and ethical approval. The artificial test food used was made of a condensation silicone (Optosil Comfort) following a standardized protocol. Two bolus sizes (three or four quarters of a 20-mm diameter, 5-mm thick tablet) were randomized to avoid an order effect and tested in different sessions. Variables were: MPS (X50 ) at ST, number of cycles until ST, sequence and cycle duration as well as cycles/g. Comparisons were performed with paired t and Wilcoxon tests, regressions and correlations were run. Cutoff for statistical significance was .05. Statistically significant differences were found for all variables; X50 (2.5 ± 0.8 vs. 2.8 ± 0.7 mm, p < .001), cycles until ST (38 vs. 40, p = .022), sequence (25 vs. 27 s, p = .003), and cycle duration (650 vs. 683 ms, p = .015) and cycles/g (27 vs. 21 cycles/g, p < .001), three or four quarters, respectively. In conclusion, in children, as in adults, chewing on a bigger bolus size leads to a larger MPS (X50 ) at ST. When chewing on a larger bolus the number of cycles increases, but not enough to swallow the same particle size since the number of cycles/g is less with a bigger bolus size.

Can Human Oral Mucosa Stem Cells Differentiate to Corneal Epithelia?

Human oral mucosa stem cells (hOMSCs) arise from the neural crest, they can self-renew, proliferate, and differentiate to several cell lines and could represent a good source for application in tissue engineering. Because of their anatomical location, hOMSCs are easy to isolate, have multilineage differentiation capacity and express embryonic stem cells markers such as-Sox2, Oct3/4 and Nanog. We have used SHEM (supplemented hormonal epithelial medium) media and cultured hOMSCs over human amniotic membrane and determined the cell's capacity to differentiate to an epithelial-like phenotype and to express corneal specific epithelial markers-CK3, CK12, CK19, Pan-cadherin and E-cadherin. Our results showed that hOMSCs possess the capacity to attach to the amniotic membrane and express CK3, CK19, Pan-Cadherin and E-Cadherin without induction with SHEM media and expressed CK12 or changed the expression pattern of E-Cadherin to a punctual-like feature when treated with SHEM media. The results observed in this study show that hOMSCs possess the potential to differentiate toward epithelial cells. In conclusion, our results revealed that hOMSCs readily express markers for corneal determination and could provide the ophthalmology field with a therapeutic alternative for tissue engineering to achieve corneal replacement when compared with other techniques. Nevertheless, further studies are needed to develop a predictable therapeutic alternative for cornea replacement.

Masticatory function in children with Down syndrome.

The objective was to study masticatory function of 8 to 10-year-old children with Down syndrome (DS) through the evaluation of maximum occlusal force and masticatory performance (via medium particle size) and compare it to that of children of the same age without DS. METHODS: A convenience sample of eight, 8-10-year-old children with DS were included in this cross-sectional study. The study had ethical approval and parents provided informed consent. Exclusion criteria were large carious lesions, dental pain or previous orthodontic/orthopedic treatment. Masticatory performance was evaluated with an artificial test food (Optosil Comfort®) after 20 cycles and at swallowing threshold. The chewed material was collected, dried and sieved. The material on each sieve was weighed; the weights were used to calculate medium particle size. Maximum occlusal force (1st permanent molars) was determined using the GM10 Nagano Keiki Co.™ portable transducer. The number of cycles until swallowing threshold, cycle and sequence durations were also compared. The data for the reference group (n = 32) came from a previous study in children of the same age. Descriptive statistics as well as comparisons with Mann-Whitney tests and simple and multiple regression analysis were performed. Cutoff was set at p≤.05. RESULTS: Medium particle size is larger by 44% after 20 chewing cycles and 75% at swallowing threshold (p<.05) in children with DS. Median maximum occlusal force was 254 kN in DS children and 499 kN in children without the syndrome (p<.001). 48% of the variance in maximum occlusal force is explained by having DS. There were also significant differences in sequence and cycle durations. All significant differences had large effect sizes (˃1). Although the children with DS chewed more cycles before swallowing threshold the difference was not significant. CONCLUSIONS: Children with DS have approximately 50% of the masticatory performance and maximum occlusal force of children of the same age without DS. These findings can be associated to the feeding problems reported in children with DS.

Masticatory performance parameters for young adults with "normal" occlusion.

Objective To develop reference data for young men/women on the variability of parameters used for the evaluation of masticatory function with an artificial test food. Methods Subjects included were 200 18-25-year olds with complete dentition and "normal" occlusion. An artificial test food was chewed in two tests (20 cycles and swallowing threshold), during which sequences/cycles were counted and timed. Medium-particle-size (MPS) and broadness of particle distribution were calculated evaluating the chewed material. Reference data was based on order statistics. Sex-specific 95% reference limits with 90% confidence intervals were calculated with RefVal-v2.1-software. Coefficients of variation were also obtained. Results Tables with reference data for young men/women chewing an artificial test food were constructed with the data collected displaying ample variability: MPS after 20 cycles anywhere between 0.7-3.5 mm or 14-84 cycles to deem the test food ready to be swallowed (C.V. 43% males/34% females). Conclusion There is much variability in masticatory parameters for young adults with good oral health.

Bolus size for the evaluation of masticatory performance in 8-10-year-old children: a pilot study.

OBJECTIVE: To study bolus-size of different foods in 8- to 10-year-olds and appraise if 1.7-2 g of condensation silicone (Optosil®) is an adequate size to study masticatory performance in children. METHODS: Bolus-size of seven foods (carrot, almonds, sausage, banana, cookie, gummy bears, raisins) (placed in random order on a scale) was studied in 20 children, aged 8-10 years. Children picked up the amount they would normally take of each, and chewed and swallowed it (three repetitions/each). STATISTICAL ANALYSIS: Descriptive; comparisons with ad hoc tests. RESULTS: There are no gender differences in bolus-size. Bolus-size was constant but different for each food.There is no pattern of bolus-size depending on hardness. Bolus-size was largest for banana; smallest foralmonds. Bite-size for carrot (food most similar to Optosil®) is 2.6 times larger than the size used for Optosil®. DISCUSSION: The results support using this bolus-size of the artificial-test-food to further study masticatory function in children.

Toward a Comprehensive Instrument of Oral Health Literacy in Spanish.

To develop and assess the Spanish Oral Health Literacy Scale (SOHLS) in a Mexican adult population, a repeated survey was undertaken in 227 adults. Participants were interviewed and asked to complete the SOHLS on the basis of the Health Literacy Test developed by the Educational Testing Service. The SOHLS covered literacy skills: location, integration, generation, calculation and return. Cronbach's α was obtained for internal consistency and intraclass correlation coefficient for test-retest reliability. Construct validity was obtained comparing the test score with self perceived oral health and the Oral Health Impact Profile-14 (OHIP-14). Mean age was 47.2 years (SD = 14.3 years). Average time for test completion was 24.6 ± 11 minutes; mean score was 24.2 ± 3.8 and Cronbach's α was .748; the intraclass correlation coefficient was 0.766. Spearman's correlation was 0.426 between the test and self perceived oral health. Pearson's correlation was -0.336 between the total test score and the OHIP-14. The instrument has good values of reliability; construct validity is significant but could be improved.

Digital plaque imaging evaluation of a stabilized stannous fluoride dentifrice compared with a triclosan/copolymer dentifrice.

PURPOSE: To compare the relative plaque control efficacy of a marketed 0.454% stabilized stannous fluoride (SnF2) dentifrice relative to a triclosan/copolymer dentifrice using digital plaque imaging analysis (DPIA). METHODS: This was a randomized, two-treatment, double-blind, parallel group design study that compared SnF2 and triclosan/copolymer dentifrices over a period of 3 weeks. DPIA was used to capture a digital image of the maxillary and mandibular anterior facial surfaces of 12 teeth and to calculate plaque area coverage. Overnight DPIA images were taken at a baseline visit after which subjects were randomly assigned to one of the two treatment groups and were required to brush with their assigned dentifrice according to each manufacturer's instructions. Subjects had DPIA assessments on two separate days at the end of Week 3. RESULTS: 96 subjects were randomized to treatment. Plaque area data for 47 subjects per treatment group were compared at Week 3 using ANCOVA. The SnF2 group demonstrated a statistically significant reduction in overnight plaque at Week 3 compared to baseline (P= 0.002). The reduction for the triclosan group at Week 3 compared to baseline was not statistically significant (P= 0.24). At Week 3, the SnF2 group demonstrated a 17% lower adjusted mean for overnight plaque relative to the triclosan group with a mean difference that was statistically significant (P< 0.05). The Week 3 adjusted mean change from baseline in overnight plaque for the SnF2 group was 3 times greater versus that of the triclosan group (P< 0.05).

Effects of bolus size and hardness on within-subject variability of chewing cycle kinematics.

This study analysed how bolus hardness and size affect within-subject variability of chewing cycle kinematics. Two independent prospective studies were performed; both tracked chin movements using an optoelectronic recording system. Computer programs identified each subject's ten most representative cycles, and multilevel modelling procedures were used to estimate variances. One study evaluated 38 subjects who chewed 1, 2, 4 or 8 g of gum presented in random order. The second study evaluated 26 subjects who chewed approximately 2.5 g of harder (670 g) or softer (440 g) gum, also presented in random order. In terms of bolus size, the 2g and 1g boluses produced the least and greatest relative within-subject variability, respectively; the largest differences were found for cycle duration and excursions. Within-subject variability when chewing the harder gum was consistently greater than when chewing the softer gum, except for lateral movement towards the balancing side. Because bolus hardness and bolus size influence within-subject variability differently, they must be taken into consideration when designing experiments to study masticatory kinematics. We conclude that a 2g bolus of soft gum should be used in studies of chewing cycle kinematics in order to reduce within-subject variability and increase statistical power.

Chewing cycle kinematics of subjects with deepbite malocclusion.

INTRODUCTION: The notion that chewing cycle shape and cycle dynamics differ between subjects with and without malocclusion is largely based on qualitative studies that combined various types of malocclusion. The purpose of this prospective study was to determine whether chewing cycle kinematics of untreated young adults with deepbite malocclusion differ from those with normal occlusion. METHODS: Twenty-three deepbite subjects (>50% overbite) and 24 controls with normal occlusion chewed gum (right side only) while their jaw movements were recorded at 100 Hz by using an optoelectric jaw tracking system. RESULTS: Differences in cycle duration between deepbite and control subjects were small and not significant (P >.05). The deepbite subjects showed significantly (P <.05) less maximum inferior excursion (7.7 vs 9.0 mm) and significantly greater maximum posterior excursion (5.1 vs 4.0 mm) than subjects with normal occlusion. In addition, the deepbite subjects had significantly smaller maximum vertical velocities than subjects with normal occlusion (49.2 vs 60.8 mm per second). Deepbite subjects also showed significantly (P <.05) less cycle-to-cycle variability in maximum velocities and excursions to the balancing side but significantly (P <.05) greater variability in cycle duration and maximum posterior excursions. CONCLUSIONS: A deepbite malocclusion alters the shape of chewing cycles and the consistency of chewing cycle kinematics.

Effect of an auditory cue on chewing cycle kinematics.

OBJECTIVES: This study analysed the systematic and random effects of a rhythmic auditory cue on chewing cycle kinematics. METHODS: The chin movements of 25 subjects (19-35 years of age) with normal class I occlusion were recorded at 100Hz (Optotrak) Northern Digital) during two natural gum chewing (2.5 g) sequences to determine the chewing rate of each subject. Another sequence was recorded with the subjects chewing at their natural rate following an audible cue. Multilevel modeling procedures were used to evaluate differences between natural chewing with and without an audible cue. RESULTS: Differences were found between experimental conditions for excursions, velocities and cycle shape. When chewing with the audible cue velocities were slower and there was less excursion of the chin marker, with the exception of initial lateral movements toward the balancing side. No differences in between-subject variability were found when chewing with or without an audible cue. Within-subject variability was 44% smaller for total cycle duration and 53% smaller for total 3D excursion when chewing with the auditory cue. CONCLUSIONS: Chewing at one's normal rate while following an auditory cue produces more consistency in chewing cycle kinematics. This method may be applicable, with some limitations, to reduce within-subject variability in chewing cycle kinematics.

Variation in Class II malocclusion: comparison of Mexican mestizos and American whites.

This study compared the skeletal and dental characteristics of Class II Division 1 white Americans and Mexicans. It was designed specifically to the evaluate ethnic, age, and sex differences of 101 whites and 107 Mexican mestizos, with approximately equal numbers in each subgroup. Three-way analyses of variance were used to simultaneously evaluate the effects of age, sex, ethnicity, and their interactions. Although Mexicans and whites in the United States had similar maxillomandibular relationships, Mexicans showed greater protrusion of the jaws and teeth. Mexican subjects with Class II malocclusions also showed less divergence of the cranial base (SN-FH angle) and greater vertical tendencies (MPA, Y-axis, and palatal plane angle) than their white counterparts. In comparison with children (mean age 9.0 years), young adults (mean age 20.1 years) had significantly larger craniofacial dimensions, jaws that were positioned more forward, and teeth that were more protruded. Sex differences pertained only to size (men were larger) and maxillary incisor angulation (men were more protrusive). The findings pertaining to the ethnic differences have important clinical implications regarding treatment decisions for Mexican and white patients. In addition, this study provides a foundation for future studies pertaining to Class II malocclusion in Mexicans.

Transforming growth factor-beta 3(Tgf-beta3) in a collagen gel delays fusion of the rat posterior interfrontal suture in vivo.

Postnatal expansion of the intramembranous bones of the craniofacial skeleton occurs as bone growth at sutures. Loss of the bone growth site occurs when the suture fails to form, or when the newly formed sutures become ossified, resulting in premature obliteration. Previous experiments demonstrated that removal of dura mater from fetal rat coronal sutures, or neutralizing transforming growth factor-beta 2 (Tgf-beta2) activity using antibodies resulted in premature obliteration of the suture in vitro. Conversely, addition of Tgf-beta3 to coronal sutures in vitro rescued them from osseous obliteration. To examine whether Tgf-beta3 rescues sutures from obliteration in vivo, a collagen gel was used as a vehicle to deliver Tgf-beta3 to the normally fusing rat posterior interfrontal (IF) suture. Surgery was done on postnatal day 9 (P9) rats, in which collagen gels containing 0, 3, or 30 ng Tgf-beta3 were placed above the IF suture, underneath the periosteum for 2 weeks. By P24, 75-100% of animals in control unoperated, sham-operated, and collagen gel-only groups had fused IF sutures. In contrast, 40% of sutures exposed to 3 ng Tgf-beta3 remained open, while sutures exposed to 30 ng Tgf-beta were similar to controls. By immunohistochemistry, sutures rescued from obliteration by Tgf-beta3 had the same Tgf-beta receptor type II (Tbetar-II) distribution as controls. However, Tgf-beta3-treated sutures had altered Tgf-beta2 and Tbetar-I distribution compared to controls.