• The effect of number and distribution of maxillary implants on the load on the palate under implant-retained overdentures

      Damghani, Sahar; Masri, Radi, 1975- (2011)
      Purpose: to evaluate the effect of the number and distribution of dental implants on the occlusal pressure transmitted to the palate. Material and Methods: eight implant analogs were placed in a replica of maxilla in the areas of teeth number 3, 4, 5, 6, 11, 12, 13 and 14. Locator attachments were attached to the implant analogs. The distances between the centers of implant analogs on each side were 8 mm. Fifteen denture bases with occlusal rims were fabricated to fit on the maxillary replica. Under a load of 245 N, pressure on the palate was measured under each denture base in six different designs of Locator insertions: No Locators, 2 Locators, 4 Locators with distances of 8, 16, and 24 mm and 8 Locators. Data was analyzed using One-Way ANOVA and Tukey's HSD test. A p value of ≤0.05 was considered significant. Results: Pressure transmitted to the palate ranged from 20.67 +/- 16.06 N (mean +/- SD) for overdentures supported by 8 Locators to 85.61 +/- 27.94 N for a conventional denture (control). The amount of pressure transmitted to the palate when the overdentures were supported by 4 Locator attachments, was significantly lower than when no, or when two Locator attachments were used. However, they were not significantly different from each other. When the overdentures were supported by 8 locator attachments, the pressure transmitted to the palate was significantly lower than that of conventional dentures, overdentures supported by 2 Locator attachments and overdentures supported by 4 Locator attachments when the distance between the anterior and posterior implants was 8 mm. Conclusion: Using 4 Locator attachments produced significantly less pressure on the palate, compared to when zero or two Locators were used. When the distance between the 4 Locators was 16 or more mm, the pressure was not significantly lower than 8 Locator design, suggesting that the palate of a 4 implant-retained overdenture with a distance of 16 mm or more, does not contribute significantly to the pressure distribution under the overdenture. Considering the static nature of the load, the results of this study should be interpreted clinically with caution.
    • The Effects of Glossectomy and Palatal Dimension on Activity of the Tongue Muscles: A Quantitative MRI Analysis

      Lim, Ji Youn; Stone, Maureen L. (2016)
      Purpose: The purpose of this study was to compare the tongue muscle activity of glossectomy patients and normal controls and to determine which of the following factors - palate height, palate width, and tumor size (T1 vs. T2) - might influence muscle activity after glossectomy. Methods: Muscle shortening within the hemi-tongue of 12 controls and 9 glossectomy patients was measured during the elevation and retraction of the tongue from /s/ into the /uk/ of the word "a souk" using cine-MRI and tagged-MRI. The muscle length measurements were performed on the following five tongue muscle segments: 1) genioglossus posterior (GGp), 2) geniohyoid (GH), 3) transverse anterior (Ta), 4) transverse middle (Tm), and 5) transverse posterior (Tp). Results: The controls demonstrated significant asymmetric Ta and Tp muscle shortening with the larger side shortening more than the smaller side. The patients showed relatively symmetric muscle shortening on the native and the resected sides. High palate subjects showed greater GH shortening, while wide palate subjects showed greater GH and Ta shortening. No significant interaction was found between the effects of palate dimension and glossectomy on muscle shortening. A significant positive correlation between shortening was found in five pairs of muscles in controls' both sides and in one pair (Ta and Tm) in patients' native side. The T2 patients showed less shortening than T1 patients on both the native and the resected sides for Ta and Tm. Conclusion: There were no statistically significant differences in muscle shortening between the controls and the patients, suggesting that patients were unable to adapt to an easier, asymmetric muscle activity as in controls during multiple repetitions of speech task. The effects of palate height and width were independent of the surgical effects. In controls, the muscles functioned synergistically in order to elevate the tongue by decreasing its length and width. In patients, the Ta and Tm worked in concert to decrease tongue width and create a compensatory behavior during tongue elevation. The lesser muscle shortening in T2 than T1 patients suggested greater impairment and limited muscle activity in T2 patients.
    • The Role of Palatal Sensation during Sucking and Pharyngeal Swallowing in the Infant Pig

      Holman, Shaina Devi; German, Rebecca Z. (2013)
      Swallowing dysfunction in infants can be caused by differences in craniofacial anatomy, neurological disorders or prematurity. These conditions result in difficulty initiating pharyngeal swallow cycles and/or a lack of airway protection during the swallow that can result in aspiration. In order to provide swallowing rehabilitation for these infants, we need to know more about the sensory and motor interactions that occur during the normal infant swallow. The overall aim of this dissertation was to understand how reducing palatal sensation would affect the oral and pharyngeal phase of the swallow. We hypothesized that after a palatal injection of local anesthesia both phases would show significant changes in movements of the tongue, hyoid and epiglottis that may result in less airway protection during the pharyngeal swallow. We also hypothesized we would observe changes in muscle activity to explain the mechanism of the altered kinematics. We used an infant pig model of mammalian feeding to test these hypotheses. Electromyographic (EMG) electrodes were implanted into several hyoid and pharyngeal muscles. We fed the pigs while simultaneously recording EMG and lateral videofluoroscopy captured at 60 frames per second. We evaluated these recordings during feeding sessions with no treatments and compared them to feeding sessions following a palatal anesthesia (0.5% bupivacaine hydrochloride) or saline injection. In order to evaluate airway protection before and after the treatments, we developed the infant mammalian penetration-aspiration scale (IMPAS). A novel method was developed to test local anesthesia duration in infants that proved bupivacaine hydrochloride lasted at least one hour after injection before the return of oral reflexes. Using these methods, we demonstrated that reducing palatal sensation has profound effects on frequency, kinematics and motor function during the oral and pharyngeal swallow. Preliminary data suggests that the infant pharyngeal swallow may also be capable of motor learning. These studies demonstrate an important role for trigeminal sensation in the normal initiation and coordination of the sucking and swallowing CPGs in the brainstem. Future studies are needed to determine if manipulating oral sensory receptors can lead to novel dysphagia rehabilitation strategies in human patients.
    • Tongue Position in Glossectomy Patients vs. Controls in /s/ during Speech with consideration for the effects of Palatal Features

      Rezaei Boroun, Atefeh; Stone, Maureen L. (2020)
      Purpose: This study examines the tongue behavior of glossectomy (N = 8) and control (N =12) speakers using a combination of high-resolution and cine- MRI. The speech task “a geese” phonetically spelled /əgis/, was used to measure anterior tongue displacement, termed “anteriority”, for the /ə/, a neutral vowel, and the /s/. Effects on anteriority due to palate height, arch perimeter, inter-canine width and /s/ type were measured on controls and patients. There are two variants of /s/ in English: apical and laminal. The apical /s/ elevates the tongue tip to contact the palate, create a narrow, grooved constriction, and focus the jet stream of air onto the incisors. The laminal /s/ uses the tongue blade, just behind the tip, to create the grooved constriction, and the tip is kept lower in the mouth.[1, 2]