Thomas Clifford

Closest Speaking Space During the Production of Sibilant Sounds and its Value in Establishing the Vertical Dimension of Occlusion

The purpose of this investigation was to determine whether the production of sibilant sounds involved adopting a jaw position that corresponded to the closest vertical speaking space (CSS), by analysis of the smallest vertical excursion of the mandible during the performance of different phonetic exercises. A further objective was to establish the variability in the-CSS produced by individual sibilant phonemes. Thirty young adult subjects had their CSS determined during three separate phonetic tests, using a kinesiograph (Sirognathograph, Siemens A.G., Benshiem, Germany) and a Bio-Pak (BioResearch Associates Inc., Milwaukee, WI) jaw-tracking software program. The first test was a general phonetic articulation test containing all the sounds of the English language and specifically including all six sibilant word sounds. The second phonetic test contained the six sibilant sounds making up a short sentence. The third test included six single words, each expressing a different sibilant sound. No statistically significant difference among the mean CSS determined in each of the three exercises was demonstrable. A phonetic test containing all sibilant sounds produced a CSS equivalent to that of a test containing all speech sounds. The vertical component of the CSS was also independent of the form or duration of the phonetic tests containing the sibilant word sounds used in this investigation. The CSS determined for 5 of the individual sibilant phonemes in the third exercise differed (p < 0.05) from that calculated for the three complete exercises. It was concluded that voicing sibilant phonemes, or word sounds, does cause the subject to adopt the CSS. When a phonetic test is used in the determination of the vertical dimension of occlusion, one of short duration containing all the sibilant sounds appears to give a reliable guide to the CSS. It was also concluded that subjects varied with respect to which of the group of sibilant sounds produced the CSS, and that a single sibilant word sound does not give a reliable indication of the smallest speaking vertical dimension.

Quantification of tooth wear: Conventional vs new method using toolmakers microscope and a three-dimensional measuring technique

OBJECTIVES This study aimed to evaluate the reliability of a new CAD-CAM Laser scanning machine in detection of incisal tooth wear through a 6-month period and to compare the accuracy of using this new machine against measuring tooth wear using tool maker microscope and conventional tooth wear index. METHODS Twenty participants (11 males and 9 females, mean age=22.7 years, SD=2.0) were assessed for incisal tooth wear of lower anterior teeth using Smith and Knight clinical tooth wear index (TWI) on two occasions, the study baseline and 6 months later. Stone dies for each tooth were prepared and scanned using the CAD-CAM Laser Cercon System (Cercon Smart Ceramics, DeguDent, Germany). Scanned images were printed and examined under a toolmaker microscope (Stedall-Dowding Machine Tool Company, Optique et Mecanique de Precision, Marcel Aubert SA, Switzerland) to quantify tooth wear and then the dies were directly assessed under the microscope to measure tooth wear. The Wilcoxon Signed Ranks Test was used to analyse the data. RESULTS TWI scores for incisal edges were 0, 1, and 2 and were similar at both occasions. Scores 3 and 4 were not detected. Wear values measured by directly assessing the dies under the tool maker microscope (range=517-656microm, mean=582microm, and SD=50) were significantly more than those measured from the Cercon digital machine images (range=132-193microm, mean =165microm, and SD=27) and both showed significant differences between the two occasions. CONCLUSIONS Measuring images obtained with Cercon digital machine under tool maker microscope allowed detection of wear progression over the 6-month period. However, measuring the dies of worn dentition directly under the tool maker microscope enabled detection of wear progression more accurately. Conventional method was the least sensitive for tooth wear quantification and was unable to identify wear progression in most cases.

A preliminary investigation into the effect of increased occlusal vertical dimension on mandibular movement during speech

Current methods of determining whether a patient will accommodate to an increased occlusal vertical dimension rely on a largely subjective assessment of the mandibular rest position and capacity to adapt whilst wearing a temporary appliance. The purpose of this preliminary study was to establish if mandibular movement during speech may provide an objective criterion in the assessment of adaptation to increases in occlusal vertical dimension. The closest speaking space, measured as the vertical distance between an incisor point and centric occlusion, as determined during pronunciation of sibilant speech sounds was chosen to depict mandibular movement. The closest speaking space was determined using a Sirognathograph for six young adult subjects and varied from a mean of 1.0 to 3.3 mm. An acrylic splint covering the entire occlusal surface of the lower arch, designed to increase the occlusal vertical dimension by 4 mm in the incisor region, was then cemented on each subjects mandibular arch. The closest speaking space was again determined after 5 days continuous wear of the splint and the mean values found to have decreased to a range of 0.0-1.0 mm. The differences between the mean values for the closest speaking space for each subject before and after splint wear were statistically significant. It was postulated that this method may lead towards an objective basis for deciding if patients will adapt to an increase in occlusal vertical dimension.

Migraine and masticatory muscle volume, bite force and craniofacial morphology

The purpose of this investigation was to compare the masticatory muscle volume, bite force, and craniofacial morphology of migrainous subjects with age‐ and sex‐matched controls. Ten adult dentate migraineurs were matched with 10 dentate age‐ and sex‐matched controls. The groups consisted of nine women and one man (mean age, 43 years; range, 29 to 51 years). Volumetric analysis of the masseter and medial pterygoid muscles was performed using magnetic resonance imaging. Craniofacial morphology was analyzed from standard cephalometric radiographs using 30 angular and linear variables. Recordings of bite force were made using a strain gauge transducer. There was a significant difference in the volume of both masseter and medial pterygoid muscles between the two subject groups (P<.0001), with the muscles of the migraineurs nearly 70% larger. The migraineurs recorded significantly higher maximal bite forces (P<.0001) than did the controls. No significant differences for any craniofacial morphological measurement were demonstrated between the two groups. It was concluded that the migraineurs had larger masseter and medial pterygoid muscle volumes, and greater bite forces than the controls, which could not be explained by any change in craniofacial morphology.