Influence of the radius of Monson's sphere and excursive occlusal contacts on masticatory function of dentate subjects.

OBJECTIVE: To determine the influence of the radius of Monson's sphere, the number of posterior laterotrusive, mediotrusive, and protrusive contacts, and the chewing rate on food comminution. DESIGN: Sixty healthy dentate subjects, aged 21.22 ± 2.30 years, were selected. The three-dimensional coordinates of the cusp tips of the lower canine, premolar, and molar teeth were identified from the subjects' digital models. Monson's sphere was designed using the simplex method for function minimisation by adjusting the coordinates on its surface. The contacts were verified using 12 µm metal strips in jaw excursions at 0.5, 1.0, 2.0, and 3.0 mm. The masticatory performance and efficiency, swallowing threshold, and chewing rate were assessed through particle size fractionation. Data were analysed with multiple linear regression (α = 0.05). RESULTS: The sphere's radius, laterotrusive and protrusive contacts at 0.5 mm, and chewing rate were found to be negative predictor variables for masticatory performance until 20 chewing cycles (R2 = 0.429). For 40 cycles, the radius and total contacts (0.5 mm) were also explanatory factors (R2 = 0.223). Only the radius (R2 = 0.176) and the chewing rate (R2 = 0.082) were found to be significant for 60 cycles and swallowing threshold, respectively. Masticatory efficiency was influenced by masticatory performance until 40 and 60 cycles, as well as the radius and total contacts at 2.0 and 3.0 mm (R2 = 0.958). CONCLUSION: A larger radius of Monson's sphere and a greater number of posterior excursive contacts were found to be related to better masticatory function.

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)

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.

Relationship Between Masticatory Function Impairment and Oral Health-Related Quality of Life of Edentulous Patients: An Interventional Study.

PURPOSE: To investigate the influence of impaired masticatory function on the oral health-related quality of life of conventional complete denture wearers before and after the transition to implant-retained mandibular overdentures. MATERIALS AND METHODS: Masticatory function and oral health-related quality of life were evaluated in 40 edentulous patients after 3 months of adaptation to complete dentures and after transition to implant-retained mandibular overdentures. Masticatory function was evaluated through the swallowing threshold test with a standardized portion of an artificial test food (Optocal) to determine median particle size (×50) and homogenization index (B). After the test, the masticatory function outcomes were used to categorize patients in 2 groups according to chewing performance: (i) satisfactory or (ii) unsatisfactory. The cutoff value for ×50 was based on a preestablished value of 3.68 mm, whereas for the B index, median values were adopted for categorization. The oral health-related quality of life was analyzed via the Oral Health Impact Profile for Edentulous Adults (OHIP-EDENT) questionnaire. The Mann-Whitney test was used to compare masticatory function outcomes and OHIP-EDENT scores, and associations were checked using the Spearman correlation test and multiple linear regression. RESULTS: Masticatory function was significantly correlated with functional limitation (p = 0.02) and physical disability (p = 0.04) for complete denture wearers with unsatisfactory masticatory function. After the transition to implant-retained mandibular overdentures, only the psychological discomfort domain (p = 0.02) was influenced by the masticatory function category. Multiple linear regression analysis revealed that only the functional limitation domain (p < 0.001) of the complete denture wearers was associated with masticatory function outcomes. CONCLUSIONS: Implant-retained mandibular overdentures eliminate the problems that lead to functional limitations, consequently improving masticatory function and oral health-related quality of life of these individuals; however, patients with unsatisfactory masticatory function after transition to implant-retained mandibular overdentures still experience more psychological discomfort.

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.