Translated Abstract
Beauty, mastication and pronunciation are three main functions of teeth. In recent years, anterior aestheticrestorationhas becominga trending topic in the field of prosthodontics, while people have paid too much attention to theappearance and occlusion, with the neglecting of pronunciation. Clinical observation found that, some patients are not satisfied with their articulation after the anterior FPD restoration. Besides, it has been reported that there is a significant relationship between increased incisal overjet and acoustic distortions of /S/ sound.
In terms ofpresent prostheses technology, effectivereferences for anterior labial inclination are insufficient. Althoughwe can obtain a descent restoration by the standard of aesthetics and occlusion, it is still difficult to determine the clinical labial inclination design. Obviously, the labial inclination is reflected by incisal overlaps in practice, which is the key factor to affect /S/ sound pronunciation for anteriors. Moreover, there is presently a very limited amount of published informationon the relationship between incisal overlaps with pronunciation and speech movements by now. Therefore, under the premise ofaesthetic restoration, whether we can find more specific associations between insical overlaps with /S/ sound and speech movements is awaiting further exploration. Correspondingly, it will be a possible practical guidancefor determination of anterior overlaps.
Objective:
To measurethe incisal overlaps, the /S/ fricative acoustic parametersand mandibular speech movement trajectory, by means of acoustic spectrum analysis and trajectory tracking of mandibular movement during speech.In order toexplore some possible references to the design of anterior overlaps in future clinical aesthetic restoration cases.
Materials and Methods:
1. Subjects
None of the subjects reported or exhibited speech, language, hearing, or neurological disorder and all were native speakers of Chinese. The criteria for selection: ①No neurological or cognitive deficits, no history of brusixm, and orthodontic treatment, no dentofacial deformities, no dental protheses.②No symptoms of TMD, no periodontal diseases. ③A complete dentition of at least 28 teeth and only third molars could be missing. ④Clinically confirmed by diagnostic casts and radiographys,the occlusion of first premolars were in Class I.
Patients: All patients met the former criteria except ③.8 patients, who required anterior teeth restoration, after clinical examination and adequate communication, agreed received ceramic single crowns or fixed bridges, which include bilateral upper incisors in 2-6 teeth (5 cases for 2 teeth, 1 case for 3 teeth, 2 cases for 4 teeth).
Volunteers:39 healthy individual volunteers (30with normal occlusion, 9 with deep overlaps) participated in this study. All of them were voluntarily agreed to undergo the proposed procedures.
2. Procedures
1) The patients were treated 4 times regularly. During the period,the technician produced 3 resin temporary crowns according to the overjet of 1mm, 2mm, 3mm and the final crowns. The lingual surfaces ofall restorationsshould be smooth, the cingulum, marginal ridge shapes should be the same.
2) All of the subjects were informed of the procedures of the experiment and were familiar with the speech materialswhich were selected from the common phonemes of the Chinese language.
3) The participants were required to read every word three timesat their habitual loudness and speech condition.For recording, there were 10cm from mouth to microphone. Thesound signals were recorded by Cooledit Pro software, then saved as WAV file. Thesampling frequency was 22050Hz; the sampling accuracy was 16 bits. The mandibular speech movement was traced by BioPAKII system- BioEGN, which was used to record the mandibular activity trajectory.
3. Data measurement and analysis
The sound files were analyzed by spectrum analyzing softwarePratt 2.0.The statistical analysis was performed by SPSS19.0 software .Using descriptive statistics for the quantitative variables.Some correlation analysis were used for relating firstly incisal overlaps and /S/ acoustic characteristics, secondly incisal overlaps and perementers of mandibular speech movement trajectory. In addition T-test was used for the differences between groups.
Results:
①1. The descriptive analysis for the /s/ sound characteristics and speech movements are listed as follows: 1.the fricative segment length of /s/ sibilant is 202.54±44.57ms, the spectrum peak is 4052.89±445.80Hz, the spectral center of gravity and average intensity of /s/ frictive are 2452.85±623.50Hz and 40.61±4.99dB respectively. 2. The maximum opening､closing velocity are 113.67±37.07mm/sec,94.87±30.04mm/sec, frontal opening: 12.52±4.00mm; protrusion: 1.48±0.98mm; retrusion: 5.29±2.37mm; translations to the right: 1.67±0.79mm and to the left: 1.54±0.90mm.②Overbite and peak frequency values of /s/ are positively related (r=0.391,P＜0.05) . To Separately discussing, overbite is positively related to the peak frequency of /su/ (r=0.363,P＜0.05 ) and average intensity of /si/ (r=0.405,P＜0.05 ); there is a little positive relation between overjet and average intensity of /si/ (r=0.228, P＜0.05). ③For speech movements: a correlation existed between the maximum closing velocity and overbite (r=-0.355, P＜0.05), between overjet and retrusion: (r=-0.469, P＜0.01).5.Group P2 is the closest to the normal characteristics.
Conclusions: 1. the changes of overlaps may cause variations of /s/ sound acoustic characteristics. Thecharacteristics are different when /s/ is followed by different vowels. 2. The mandibular speech movements of normal subjects are similar, formed by continuoussmooth curve clusters, with a long vertical range, a anteroposterior componentsand lateral translations. 3.The peak frequency values of /s/ sound and the maximum closing velocity should be the prior parameterwhen discussing pronunciation and overlaps. 4./su/､/si/ are the main phonemes we should test in /s/ sound acoustic studies. 5.The overjet of group P2(2~3mm) combining with the previous aesthetic crown dedign experience, will contribute to the three aspects of appearance, occlusion and pronunciation.
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