Andries van der Bilt

The relation between saliva flow after different stimulations and the perception of flavor and texture attributes in custard desserts

Salivary flow rates were measured at rest and after three types of stimulation; odor, Parafilm chewing, and citric acid. The highest flow rate was elicited by citric acid followed by Parafilm and odor, while the lowest flow rate was unstimulated. In order to investigate whether and how the amount of saliva a subject produces influences the sensory ratings, the four types of salivary flow rates were correlated with sensory ratings of three different types of vanilla custard dessert. No significant correlation could be found between any of the salivary flow rates and the sensory ratings. A subject with a larger saliva flow rate during eating did not rate the foods differently from a subject with less saliva flow. The same pattern was seen for all types of stimulation. This finding could indicate that subjects are used to their respective amounts of saliva to such a degree that the differences in sensory ratings between subjects cannot be explained by the interindividual difference in saliva flow rate.

Relating particles and texture perception.

Practically all foods contain particles. It has been suggested that the presence of particles in food may affect the perception of sensory attributes. In the present study we investigated the effect of size and type (hardness and shape) of particles added to a CMC based vanilla custard dessert. The two types of particles included in the study were silica dioxide and polystyrene spheres, varying in size from 2 to 230 microm. Eighteen trained adults participated in the study. They rated the sensation of 17 sensory flavour and texture attributes on a 100-point visual analogue scale (VAS). The results indicate that the addition of particles increased the sensation of roughness attributes and decreased the ratings of a number of presumably favorable texture attributes (smoothness, creamy, fatty and slippery) significantly. These effects increased with increasing particle size up to 80 microm. Roughness ratings deceased for larger particles sizes. Surprisingly, even particles of 2 microm had significant effects: they increased perceived rough lip-tooth feel, and decreased slippery lip-tooth feel and smoothness of the product. The affected attributes had previously been related to lubricative properties of foods. Particles added to semi-solid foods with relatively low levels of fat seem to counteract the lubricating effects of the fat resulting in increased oral friction. In a separate study on size perception the silica dioxide particles were used. By sampling the stimuli between the tongue and palate, subjects rated the size of the particles on a 100-point scale in comparison to anchor stimuli containing no particles and particles of 250 microm. The perceived particle size significantly increased for larger particles. Furthermore, perceived particle size was negatively correlated with roughness ratings. Thus, subjects who were sensitive and perceived the particles as being relatively large reported the same stimuli to have less rough after-feel. In conclusion, particles added to a product induce large effects on texture sensations, and texture sensation is related to individual size perception.

Bite force and electromyograpy during maximum unilateral and bilateral clenching

Maximum voluntary bite force has often been studied as an indicator of the functional state of the masticatory system. Bilateral, as well as unilateral, methods have been used to determine bite force. Only a few studies have compared the outcomes of both methods. The aim of this study was to measure bite force and jaw-muscle activity during bilateral as well as unilateral maximum clenching in a large number of healthy subjects, so that the results could be compared. In a group of 81 dentate subjects we observed an average bilateral bite force of 569 N. The average unilateral bite force was significantly lower, being 430 N (right) and 429 N (left). Masseter and anterior temporal muscle activities were also significantly lower during unilateral clenching as compared with bilateral clenching. The masseter muscles showed no difference in activity between the ipsilateral side and the contralateral side during unilateral clenching. In contrast, the activity of the anterior temporal muscle on the ipsilateral side was significantly higher than on the contralateral side. Thus, the change in the forces acting on the jaw during unilateral clenching compared with bilateral clenching leads to a different response in the temporal muscles than in the masseter muscles.

A comparison of the effects of added saliva, α-amylase and water on texture perception in semisolids

The effect of adding saliva or a saliva-related fluid (alpha-amylase solution and water) to custard prior to ingestion on the sensory ratings of odour, flavour and lip-tooth-, mouth- and after-feel sensations was investigated. Saliva had previously been collected from the subjects and each subject received his/her own saliva. Sixteen subjects from a trained panel assessed 17 flavour and texture attributes of soy- and milk-based custard desserts. Immediately prior to administration, two different volumes (0.25 and 0.5 ml) of three different saliva-related fluids (saliva, alpha-amylase solution and water) were added to the product. The added volumes represented an approximately 33% and 66% increase of the volume of saliva present in the mouth during ingestion. The results show that addition of a fluid affected the mouth-feel attributes of melting, thickness and creamy. Melting was the only attribute on which the type of fluid had an effect, where saliva elicited a stronger melting effect than the alpha-amylase solution and water. The volume of the added fluid affected a number of attributes (thick and creamy mouth-feel and fatty after-feel). It can be concluded that in general the sensory attributes of semisolids were relatively stable. Mouth- and after-feel sensations were partly affected, while odour, flavour and lip-tooth-feel sensations were not affected by an increase in volume of saliva or other saliva-related fluid during ingestion.

Mandibular implant‐supported overdentures and oral function

OBJECTIVES Oral rehabilitation by means of implant-retained mandibular overdentures is known to improve oral function. The aim of this study was to evaluate the long-term effects of mandibular implant treatment on oral function. We quantified maximum bite force and masticatory performance 10 years after implant treatment. It was hypothesized that these outcome measures would not change in this period. MATERIALS AND METHODS Eighteen edentulous patients were scheduled for re-evaluation of their oral function 10 years after they had participated in a randomized cross-over clinical trial. In that trial, they had received two mandibular implants and a new denture with successively magnet-, ball-socket, and bar-clip attachments. RESULTS At the 10-year follow-up, 14 of the initial 18 patients participated in the evaluation. As a result of the implant treatment, the average maximum bite force more than doubled, from 162 to 341 N, whereas the average number of chewing cycles to halve the initial particle size decreased from 55 to 27 cycles. No significant changes in maximum bite force and masticatory performance were observed after 10 years. However, the average maximum bite force obtained with implant-retained overdentures is still significantly lower than that of dentate subjects (569 N). CONCLUSION Maximum bite force and masticatory performance significantly increased after implant treatment and remained unaltered during the following 10-year period. Thus, implant treatment greatly improves oral function for a long period of time.

Free Vascularized Flaps for Reconstruction of the Mandible: Complications, Success, and Dental Rehabilitation

PURPOSE To evaluate complications and success of mandibular reconstruction with free fibula flaps, iliac crest flaps, and forearm flaps with reconstruction plates and to evaluate dental rehabilitation after these reconstructions. PATIENTS AND METHODS Eighty-three patients with segmental mandibular defects were included. Correlation analyses were used to determine the relationship between reconstruction type and clinical parameters with recipient-site complications and success. The dental rehabilitation was evaluated in successfully reconstructed survivors. RESULTS Multivariate analyses showed significant correlations between flap type and success (P < .0001). Of the patients, 51 (61%) were alive 2 years after the reconstruction. Mandibular reconstruction with a free forearm flap and reconstruction plate was associated with higher complication rates at the recipient site and higher failure rates compared with reconstruction with free vascularized bone flaps. Of the 32 successfully reconstructed survivors, 14 (44%) had a complete dental rehabilitation, of which 10 had dental implants and 4 did not. Only 6 (29%) of the edentulous survivors ultimately had an implant-supported prosthesis. CONCLUSIONS Reconstruction of the mandible with a free vascularized bone flap is superior to reconstruction with a free forearm flap with a reconstruction plate. Complete dental rehabilitation was reached in fewer than half of the surviving patients.

Mastication and swallowing: influence of fluid addition to foods

Introduction: The production of sufficient saliva is indispensable for good chewing. Recent research has demonstrated that salivary flow rate has little influence on the swallowing threshold. Objectives: The hypothesis examined in the present study was that adding fluids to foods will influence chewing physiology. Materials and Methods: Twenty subjects chewed on melba toast, cake, carrot, peanut and Gouda cheese. They also chewed on these foods after addition of different volumes of water or α-amylase solution. Jaw muscle activity, number of chewing cycles until swallowing and chewing cycle duration were measured. Repeated measures analysis of variance was applied to test the null hypothesis that there would be no statistically significant difference among the results obtained for the various food types and fluids. Subsequently, contrasts were determined to study the levels of intra-subjects factors (food type and fluid volume). Linear regression was used to determine the changes in muscle activity and cycle duration as a function of the chewing cycles. Results: Fluid addition significantly decreased muscle activity and swallowing threshold for melba, cake and peanut (p<0.05). The effect of α-amylase in the solutions was similar to that of water (p>0.05). Doubling the volume of tap water had a greater effect. Conclusions: Fluid addition facilitated chewing of dry foods (melba, cake), but did not influence the chewing of fatty (cheese) and wet products (carrot). This study is relevant to improve patients’ life quality and the management of chewing and feeding disorders caused by hyposalivation.

Effects of added fluids on the perception of solid food

The production of sufficient saliva is indispensable for good chewing. Recent research has demonstrated that salivary flow rate has little influence on the swallowing threshold. We examined the hypothesis that adding fluid to a food will influence the chewing process. Twenty healthy subjects chewed on melba toast, breakfast cake, carrot, peanut and Gouda cheese. In addition they chewed on these foods after we added different volumes of tap water or a solution of alpha-amylase. We measured jaw muscle activity and the number of cycles until swallowing. Furthermore, we obtained visual analogue scale (VAS) scores for texture and sound attributes for all foods and fluid conditions. The additional fluids significantly lowered muscle activity and swallowing threshold for melba, cake and peanut. The effect of alpha-amylase in the solutions was rather limited. Doubling the volume of tap water had a larger effect. Several texture and sound attributes of melba, cake and peanut were also significantly affected by the additional fluids. For melba, cake, and peanut we observed significant correlations between the physiology parameters and several attributes for the various fluid conditions. This indicates that the added fluid affects both the physiology (muscle activity and number of cycles) and the sensory perception of a number of texture and sound attributes. Adding fluid facilitates the chewing of dry foods (melba, cake), but does not influence the chewing of fatty (cheese) and wet products (carrot).

Quantitative dynamic contrast-enhanced MRI for the assessment of mandibular invasion by squamous cell carcinoma

The objective of this study was to determine the value of dynamic contrast-enhanced MRI (DCE-MRI) for the preoperative assessment of mandibular invasion in squamous cell carcinomas (SCC), adjacent or fixed to the mandible. DCE-MRI was performed with gadolinium diethylene triamine pentaacetic acid (Gd-DTPA). Data were obtained from 25 patients. From pharmacokinetic analysis of the tissue uptake of Gd-DTPA, the DCE-MRI parameters (k(ep), K(trans) and v(e)) were determined, with k(ep) representing the exchange rate constant, K(trans) the volume transfer constant and v(e) the volume of extracellular space per unit volume of tissue. The histology of the resection specimens was used as gold standard for the extent of mandibular invasion. SCC with medullary invasion showed higher mean k(ep) and K(trans) compared with SCC without medullary invasion (ANOVA, p<0.001). ROC analysis of k(ep) and K(trans) revealed reliable threshold values for medullary invasion. In conclusion, DCE-MRI can discriminate SCC with medullary invasion from SCC without medullary invasion and may serve as a valuable tool in preoperative tumour staging with regard to the delineation of medullary invasion.

Oral Function After Oncological Intervention in the Oral Cavity: A Retrospective Study

PURPOSE To assess self-perceived oral function of patients with oral cavity cancer at different stages of treatment, ie, before oncologic intervention, 5 weeks after intervention, and 5 years after intervention. PATIENTS AND METHODS A cohort of 158 patients with malignancy in the oral cavity treated by surgery in 1999 or 2000 was included. From this cohort we interviewed 69 patients by telephone in 2005 and collected data on dental status, disorders of chewing and swallowing, xerostomia, preference of food consistency, tube nutrition, weight loss, and speech for different stages of treatment. RESULTS For patients treated in the maxilla region we observed a significant (P < .05) recovery of perceived chewing ability after 5 years to the level experienced before oncologic intervention. Patients treated in the mandible region reported a deteriorated dental state, chewing ability, lip competence, and xerostomia after 5 years. Patients treated in the tongue and mouth-floor region experienced deterioration for dental state, chewing ability, and xerostomia after 5 years compared with the level before the oncologic intervention. CONCLUSIONS Our telephone interview on oral function provided supplementary information on how patients experienced their problems with oral function during various phases of oncologic treatment. A retrospective interview may thus help to add information to incomplete retrospective data.