The Journal of Prosthetic Dentistry

223April 2013

Şakar et alŞakar et al

Clinical ImplicationsWithin the limitations of this clinical study, average closest speaking space values of 1 to 3 mm can be used in the clinical determination of the occusal vertical dimension of prosthetic restorations, regard-less of dental and skeletal classified occlusions; no correlation was found between the amount of vertical overlap and closest speaking space. The use of the Turkish word seyis was appropriate for register-ing the closest speaking space in native Turkish speakers.

Statement of problem. The closest speaking space (CSS) together with the vertical overlap of anterior teeth during the production of the /s/ sound have not been previously investigated with respect to differences in dental and skeletal orthodontic classifications.

Purpose. The purpose of this study was to investigate the CSS in dental and skeletal occlusions and to analyze the cause and effect relationship of the CSS and the amount of the vertical overlap of anterior teeth.

Material and methods. Poly vinylsiloxane interocclusal registration material was placed bilaterally onto the occlusal surfaces of premolar and molar teeth of 155 native Turkish speaking adolescent and young adult dentate participants, who were then asked to pronounce the word seyis. The thinnest point between the maxillary and mandibular teeth was recorded in millimeters as the CSS. The occlusion of each participant was classified according to the Angle dental and Steiner skeletal classifications. The differences in CSS values within each classification were statistically analyzed with the Kruskal-Wallis test, and the correlation between the CSS and the vertical overlap was statistically analyzed with the Spearman Rho Correlation tests (P<.05).

Results. The differences in the CSS were only significant between Angle Class II division 2 and Class III groups (P=.034), while the differences in the CSS between skeletal classes were not significant. The correlation between the amount of CSS and the amount of vertical overlap was not significant.

Conclusions. The results showed that regardless of dental and skeletal occlusions, average CSS values could be used to determine the occlusal vertical dimension of prosthetic restorations. (J Prosthet Dent 2013;109:222-226)

Evaluation of the closest speaking space in different dental and skeletal occlusions

Olcay Şakar, Prof Dr Med Dent,a Canan Bural, Dr Med Dent,b Tonguç Sülün, Dr Med Dent,c Evren Öztaş, Dr Med Dent,d and Gülnaz Marşan, Dr Med Dente

Istanbul University, Faculty of Dentistry, Istanbul, Turkey

aProfessor, Department of Removable Prosthodontics.bAssistant Professor, Department of Prosthodontics.cAssociate Professor, Department of Prosthodontics.dAssociate Professor, Department of Orthodontics.eAssociate Professor, Department of Orthodontics.

Mandibular movements are com-plex and vary in speaking, masticat-ing, and swallowing. Speaking is helpful in the clinical determination of parameters such as occlusal verti-

cal dimension (OVD), tooth position, and anterior guidance.1-8 Pound9 in-dicated that vertical and horizontal overlap, occlusal classification, op-timum OVD, incisal guidance, cusp

height, and the anterior display of mandibular teeth are the key factors in developing clear speech.

In speech, the production of sibi-lant sounds requires a small space

between the teeth. When pronounc-ing these sounds, the occlusal sur-faces and incisal edges of the man-dibular teeth and the maxillary teeth are in their closest relation to each other; this is the closest speaking space (CSS).2,3,5,9-11 The CSS is the minimum distance between the teeth that occurs during the pronunciation of words containing sibilant sounds, particularly those in combination with the vowels /e/ and /i/.12 The CSS identifies and establishes the accept-able OVD so that the teeth do not contact during speech and the anteri-or teeth or occlusal rims are separated by about 2 mm.1,13

The amount of CSS produced by pronouncing words containing sibilant sounds varies with the par-ticipants10,14 depending on anatomic and morphologic factors such as skel-etal variations,8 vertical overlap,10,15-17 increased OVD,18 and the absence of teeth.19 The CSS has been extensively studied and mean values have varied from 0.7 to 3.1 mm in participants with normal occlusion and dentition.3,5,12,13,17

Pound2 described the amount of posterior speaking spaces for oc-clusal classifications with respect to the amount of vertical and horizon-tal overlap of anterior teeth during the production of the sibilants. The amount of posterior speaking spaces should be in a range of 1.5 to 3 mm for Class I and less than 2 mm for Class III occlusions, although this space might controversially be increased up to 10 mm in patients with Class II oc-clusion. This trend was later scien-tifically compared and confirmed in only 2 clinical studies within a broad range of varied findings on CSS.5,20 In both studies, the maxillomandibular relationships were classified accord-ing to the incisor relationship, which was based on the contact of the man-dibular incisors with the palatal sur-face of the maxillary incisors21,22; no orthodontic methods were used to classify the participants.

The CSS has been investigat-ed by using different test materi-als for speech such as the phona-

tion of a phoneme,15,17,23,24 a single word,10,12,17,25-29 a sentence,25,30,31 a passage,5,13,16,20,25,32 or counting.33,34 It can be registered by extraoral (indi-rect) and intraoral (direct) methods by means of manual17 or radiograph-ic measurements,15,17 or electronic kinesiographs.5,10,12,13,16-18,20,23-27,29-34 The limitations of electronic registra-tion methods are the impairment of the orofacial region or difficulty in adjusting the probes, which is time consuming.17 A new technique for the clinical registration of CSS with vinyl polysiloxane interocclusal registra-tion material has been suggested, and only minimal differences compared with kinesiography were noted.12

The purpose of this study was to investigate the CSS in the Angle den-tal and Steiner skeletal Class I, II, and III occlusions and to analyze the cause and effect relationship of CSS with re-spect to the amount of vertical over-lap. The null hypothesis was that the CSS would not differ in different den-tal and skeletal occlusions.

MATERIAL AND METHODS

Participants

The selection criteria for the par-ticipants were the absence of systemic disease, signs or symptoms of tem-poromandibular dysfunction, speech defects, an anterior open occlusal re-lationship, tongue thrusting, lisping, and the presence of intact first and second premolars in occlusion. A sta-tistical power analysis indicated that a minimum of 165 participants who were accepted for orthodontic treat-ment at Istanbul University, Faculty of Dentistry, Department of Orthodon-tics, (between January 2009 and De-cember 2009) was required. A total of 210 native Turkish speaking, ado-lescent and young adult dentate indi-viduals were included in the study. An informed consent was obtained from each participant or parent before the orthodontic treatment and recording of the CSS.

Recording of CSS

The participants were seated in a dental chair and the recording proce-dures were fully explained. Before re-cordings, participants were asked to re-peat the Turkish word seyis (horse rider in English). Participants were then given a few minutes to become familiar with the word by repeating it aloud while an examiner checked the accuracy of the pronunciation. The participants were asked to repeat the word at a normal conversational rate and volume.

Participants were instructed to sit in an upright position with their heads unsupported. The examiner placed approximately 1.5 cm of vinyl polysi-loxane interocclusal registration mate-rial (Futar-D; Kettenbach GmbH & Co KG, Eschenburg, Germany) bilaterally on the occlusal surfaces of mandibu-lar premolar and molar teeth. Then the participants were instructed to close their lips, swallow, and repeat the word seyis 10 times and then not close or move their mandible for 30 seconds while the material polym-erized. The record material was not placed on the anterior teeth, so as not to interfere with the /s/ sound and to determine that the participant’s pro-nunciation was accurate. After they had polymerized, the interocclusal re-cords were removed from the mouth and identified as the left or right side. The recorded CSSs were measured as suggested by Rizzatti et al.12 The minimum thickness on the occlusal records at the first premolar region was measured with a digital gauge (Guilin; Guanglu Measuring Instru-ment Co Ltd, Shanghai, China) with a 0.01 mm resolution.

The recording material used in the study has been shown to have a vertical discrepancy of about 23 µm 1 hour after setting.35 To minimize dimensional changes, measurements were completed 1 hour after intra-oral recordings, and the resulting value was recorded as CSS in mm. The operator who made the measure-ments was not aware of the partici-pants’ dental or skeletal classification.

The Journal of Prosthetic Dentistry

223April 2013

Şakar et alŞakar et al

Clinical ImplicationsWithin the limitations of this clinical study, average closest speaking space values of 1 to 3 mm can be used in the clinical determination of the occusal vertical dimension of prosthetic restorations, regard-less of dental and skeletal classified occlusions; no correlation was found between the amount of vertical overlap and closest speaking space. The use of the Turkish word seyis was appropriate for register-ing the closest speaking space in native Turkish speakers.

Statement of problem. The closest speaking space (CSS) together with the vertical overlap of anterior teeth during the production of the /s/ sound have not been previously investigated with respect to differences in dental and skeletal orthodontic classifications.

Purpose. The purpose of this study was to investigate the CSS in dental and skeletal occlusions and to analyze the cause and effect relationship of the CSS and the amount of the vertical overlap of anterior teeth.

Material and methods. Poly vinylsiloxane interocclusal registration material was placed bilaterally onto the occlusal surfaces of premolar and molar teeth of 155 native Turkish speaking adolescent and young adult dentate participants, who were then asked to pronounce the word seyis. The thinnest point between the maxillary and mandibular teeth was recorded in millimeters as the CSS. The occlusion of each participant was classified according to the Angle dental and Steiner skeletal classifications. The differences in CSS values within each classification were statistically analyzed with the Kruskal-Wallis test, and the correlation between the CSS and the vertical overlap was statistically analyzed with the Spearman Rho Correlation tests (P<.05).

Results. The differences in the CSS were only significant between Angle Class II division 2 and Class III groups (P=.034), while the differences in the CSS between skeletal classes were not significant. The correlation between the amount of CSS and the amount of vertical overlap was not significant.

Conclusions. The results showed that regardless of dental and skeletal occlusions, average CSS values could be used to determine the occlusal vertical dimension of prosthetic restorations. (J Prosthet Dent 2013;109:222-226)

Evaluation of the closest speaking space in different dental and skeletal occlusions

Olcay Şakar, Prof Dr Med Dent,a Canan Bural, Dr Med Dent,b Tonguç Sülün, Dr Med Dent,c Evren Öztaş, Dr Med Dent,d and Gülnaz Marşan, Dr Med Dente

Istanbul University, Faculty of Dentistry, Istanbul, Turkey

aProfessor, Department of Removable Prosthodontics.bAssistant Professor, Department of Prosthodontics.cAssociate Professor, Department of Prosthodontics.dAssociate Professor, Department of Orthodontics.eAssociate Professor, Department of Orthodontics.

Mandibular movements are com-plex and vary in speaking, masticat-ing, and swallowing. Speaking is helpful in the clinical determination of parameters such as occlusal verti-

cal dimension (OVD), tooth position, and anterior guidance.1-8 Pound9 in-dicated that vertical and horizontal overlap, occlusal classification, op-timum OVD, incisal guidance, cusp

height, and the anterior display of mandibular teeth are the key factors in developing clear speech.

In speech, the production of sibi-lant sounds requires a small space

between the teeth. When pronounc-ing these sounds, the occlusal sur-faces and incisal edges of the man-dibular teeth and the maxillary teeth are in their closest relation to each other; this is the closest speaking space (CSS).2,3,5,9-11 The CSS is the minimum distance between the teeth that occurs during the pronunciation of words containing sibilant sounds, particularly those in combination with the vowels /e/ and /i/.12 The CSS identifies and establishes the accept-able OVD so that the teeth do not contact during speech and the anteri-or teeth or occlusal rims are separated by about 2 mm.1,13

The amount of CSS produced by pronouncing words containing sibilant sounds varies with the par-ticipants10,14 depending on anatomic and morphologic factors such as skel-etal variations,8 vertical overlap,10,15-17 increased OVD,18 and the absence of teeth.19 The CSS has been extensively studied and mean values have varied from 0.7 to 3.1 mm in participants with normal occlusion and dentition.3,5,12,13,17

Pound2 described the amount of posterior speaking spaces for oc-clusal classifications with respect to the amount of vertical and horizon-tal overlap of anterior teeth during the production of the sibilants. The amount of posterior speaking spaces should be in a range of 1.5 to 3 mm for Class I and less than 2 mm for Class III occlusions, although this space might controversially be increased up to 10 mm in patients with Class II oc-clusion. This trend was later scien-tifically compared and confirmed in only 2 clinical studies within a broad range of varied findings on CSS.5,20 In both studies, the maxillomandibular relationships were classified accord-ing to the incisor relationship, which was based on the contact of the man-dibular incisors with the palatal sur-face of the maxillary incisors21,22; no orthodontic methods were used to classify the participants.

The CSS has been investigat-ed by using different test materi-als for speech such as the phona-

tion of a phoneme,15,17,23,24 a single word,10,12,17,25-29 a sentence,25,30,31 a passage,5,13,16,20,25,32 or counting.33,34 It can be registered by extraoral (indi-rect) and intraoral (direct) methods by means of manual17 or radiograph-ic measurements,15,17 or electronic kinesiographs.5,10,12,13,16-18,20,23-27,29-34 The limitations of electronic registra-tion methods are the impairment of the orofacial region or difficulty in adjusting the probes, which is time consuming.17 A new technique for the clinical registration of CSS with vinyl polysiloxane interocclusal registra-tion material has been suggested, and only minimal differences compared with kinesiography were noted.12

The purpose of this study was to investigate the CSS in the Angle den-tal and Steiner skeletal Class I, II, and III occlusions and to analyze the cause and effect relationship of CSS with re-spect to the amount of vertical over-lap. The null hypothesis was that the CSS would not differ in different den-tal and skeletal occlusions.

MATERIAL AND METHODS

Participants

The selection criteria for the par-ticipants were the absence of systemic disease, signs or symptoms of tem-poromandibular dysfunction, speech defects, an anterior open occlusal re-lationship, tongue thrusting, lisping, and the presence of intact first and second premolars in occlusion. A sta-tistical power analysis indicated that a minimum of 165 participants who were accepted for orthodontic treat-ment at Istanbul University, Faculty of Dentistry, Department of Orthodon-tics, (between January 2009 and De-cember 2009) was required. A total of 210 native Turkish speaking, ado-lescent and young adult dentate indi-viduals were included in the study. An informed consent was obtained from each participant or parent before the orthodontic treatment and recording of the CSS.

Recording of CSS

The participants were seated in a dental chair and the recording proce-dures were fully explained. Before re-cordings, participants were asked to re-peat the Turkish word seyis (horse rider in English). Participants were then given a few minutes to become familiar with the word by repeating it aloud while an examiner checked the accuracy of the pronunciation. The participants were asked to repeat the word at a normal conversational rate and volume.

Participants were instructed to sit in an upright position with their heads unsupported. The examiner placed approximately 1.5 cm of vinyl polysi-loxane interocclusal registration mate-rial (Futar-D; Kettenbach GmbH & Co KG, Eschenburg, Germany) bilaterally on the occlusal surfaces of mandibu-lar premolar and molar teeth. Then the participants were instructed to close their lips, swallow, and repeat the word seyis 10 times and then not close or move their mandible for 30 seconds while the material polym-erized. The record material was not placed on the anterior teeth, so as not to interfere with the /s/ sound and to determine that the participant’s pro-nunciation was accurate. After they had polymerized, the interocclusal re-cords were removed from the mouth and identified as the left or right side. The recorded CSSs were measured as suggested by Rizzatti et al.12 The minimum thickness on the occlusal records at the first premolar region was measured with a digital gauge (Guilin; Guanglu Measuring Instru-ment Co Ltd, Shanghai, China) with a 0.01 mm resolution.

The recording material used in the study has been shown to have a vertical discrepancy of about 23 µm 1 hour after setting.35 To minimize dimensional changes, measurements were completed 1 hour after intra-oral recordings, and the resulting value was recorded as CSS in mm. The operator who made the measure-ments was not aware of the partici-pants’ dental or skeletal classification.

224 Volume 109 Issue 4

The Journal of Prosthetic Dentistry

225April 2013

Şakar et al Şakar et al

Dental and skeletal classifications

Each participant’s occlusion was evaluated by means of casts accord-ing to the Angle classification meth-od.36 The skeletal classification was performed by means of cephalomet-ric radiographs made with the same machine (Orthophos XG Plus; Sirona Dental Systems, Bensheim, Germa-ny) according to ANB angle (Steiner cephalometric analysis), which is the angle between point A (Subspinale, the most posterior midline point in the concavity between the anterior nasal spine and the prosthion), na-sion (the most anterior point on the frontonasal suture in the midsagittal plane), and point B (Supramentale, the most posterior midline point in the concavity of the mandible be-tween the pogonion and infradentale) in the maxilla. It is the most common-ly used measurement for evaluating anteroposterior disharmony of the jaws.37 Participants were classified as Class I: 0≤ANB≤5 degrees, Class II: ANB>5 degrees, Class III: ANB<0 de-grees. The vertical overlap was mea-sured as the vertical overlap from the labio-incisal edge of the right maxil-lary central incisor with the greatest overlap to the labio-incisal edge of the corresponding mandibular right central incisor and was expressed as a percentage (%).

Descriptive analysis was per-formed to calculate the mean and standard deviation (SD) values for the CSS and the vertical overlap for dental and skeletal occlusions. The Wilcoxon test was used to determine whether a difference between the 148 right and 144 left interocclusal records existed. To test interobserver and intraob-server reliability, a total of 40 occlusal records were measured twice, with a 1-week interval by 2 different observ-ers and analyzed with the Spearman Rho test. Gender differences in the CSS were analyzed with the Mann Whitney U test, and the differences in the CSS within dental or skeletal classifications were analyzed with the Kruskal-Wallis test. Comparisons of

the CSS or vertical overlap among groups within the classifications were analyzed with the Mann Whitney U test, and the correlation between the CSS and the amount of vertical over-lap was analyzed with the Spearman Rho Correlation test. The significance level was set at α=.05. All statistical analyses were performed with SPSS software (SPSS for Windows, v11.5; SPSS Inc, Chicago, Ill).

RESULTS

Of 210 participants, 35 had some difficulties (inaccurate pronunciation while recording with the registration material in the mouth, gagging) while making the records, and 30 had inter-occlusal records with no exact thick-ness or measurable area around the premolar region. Therefore, the re-cords of 65 participants were discard-ed and the data obtained by measur-ing the records of 155 participants (100 females, 55 males) were used. Also, 7 right and 11 left records of par-ticipants in the final group could not be measured because of the lack of neces-sary thickness. As a result 148 right and 144 left interocclusal measurements were performed and evaluated.

The Spearman Rho test found that the measurement of the CSS was

statistically reliable. Interobserver (r =0.89, P<.001) and intraobserver (r=0.91, P<.001) reliability rates were high. The mean and SD of the CSS were 2.27 ±1.17 mm for the 148 right interocclusal records and 2.15 ±1.06 mm for the 144 left interocclusal re-cords. The difference between the 2 sides was not statistically significant (P=.737), and so data belonging to the 148 right interocclusal records of the 155 (100 females, 55 males) par-ticipants were used in the further sta-tistical analysis.

The mean age of the 55 males was 14.96 years (range 11 to 22 years), and the mean age of the 100 females was 15.50 years (range 10 to 28 years). The overall mean and SD of the CSS (range 0.11 to 5.85 mm) was 2.27 ±1.17 mm. The difference in the CSS between males and females was not significant (P=.747).

The mean and SD of the CSS of Angle Class I (55 participants) was 2.28 ±0.89 mm, of Class II division 1 (44 participants) 2.16 ±1.49 mm, of Class II division 2 (29 participants) 2.66 ±1.16 mm, and of Class III (20 participants) 1.92 ±0.95 mm. The mean and SD of the amount of verti-cal overlap (%) was 20.13 ±18.02 for Angle Class I, 42.37 ±26.90, for Class II Division 1, 48.75 ±35.90 for Class II

CSS

Vertical overlap (%)

CSS

Vertical overlap %

2.28

20.13

Class I (n=55)

Angle Dental Classification

Mean

0.89

18.02

SD

2.16

42.37

Class II Div 1 (n=44)

Mean

1.49

26.90

SD

2.66*

48.75

Class II Div 2 (n=29)

Mean

1.16

35.90

SD

2.24

26.60

Class I (n=77)

Steiner Skeletal Classification

Mean

1.07

23.18

SD

2.46

47.48

Class II (n=46)

Mean

1.44

31.63

SD

2.00

13.75

Class III (n=25)

Mean

0.84

21.02

SD

1.92*

16.25

Class III(n=20)

Mean

0.95

24.03

SD

* Indicates statistically significant differences among groups (P<.05).

Table I. Means and SDs of CSS (mm) and vertical overlap (%) in dental and skeletal Class I, II, and III classification

division 2, and 16.25 ±24.03 for Class III occlusions. The differences in CSS were only significant between Angle Class II division 2 and Class III occlu-sions (P =.034) (Table I).

The mean and SD of the CSS was 2.24 ±1.07 mm for skeletal Class I (77 participants), 2.46 ±1.44 mm for Class II (46 participants), and 2.00 ±0.84 mm for Class III (25 par-ticipants). The mean and SD of the amount of vertical overlap (%) was 26.60 ±23.18 for skeletal Class I, 47.48 ±31.63 for skeletal Class II, and 13.75 ±21.02 for skeletal Class III occlusions. The differences in CSS within skeletal Class I, II, and III occlu-sions were not statistically significant (P =.452) (Table I).

The correlation between the CSS and the amount of vertical over-lap was not statistically significant (Spearman r=.110, P=.249).

DISCUSSION

The null hypothesis that the CSS would not differ in different dental and skeletal occlusions was not rejected. CSS is one of the methods used to de-termine OVD and the esthetics of pros-thetic restorations. This clinical study aimed to test the amount of CSS with respect to the differences in dental and skeletal orthodontic classifications.

Rizzatti et al12 recommended the use of vinyl polysiloxane interocclusal registration material over the kinesio-graphic method to determine the CSS because it is simple and less expen-sive. In the present study, it was also observed that the majority of the par-ticipants easily pronounced the word seyis with the interocclusal registration material between the posterior teeth. It should be noted that 16% of the participants (35 participants out of 210) were not successful in recording the CSS perhaps because of atypical situations,20 personal skills, or reac-tion to a foreign material in the oral cavity (vomiting, gagging, or diffi-culty in speech). On the interocclusal records, of 14% of the participants (30 participants out of 210), no exact

thickness or area around the premolar region was identified, so these records were discarded. These observations can be regarded as the limitations of this method.

The present finding that the CSS did not differ between genders sup-ports the finding20 for participants with mean age of 20 years. This result might indicate that CSS is similar in adolescents and young adult partici-pants without gender differences.

Common qualitative methods of recording occlusal traits include the British Standard Institute (BSI) classi-fication for incisors and the Angle clas-sification for molar relationships.21,22 The present findings indicate that the amount of CSS did not differ between the Angle dental and cephalometric skeletal classifications. The previous studies of Burnett and Clifford5 and Howell,20 however, used the incisor classifications. Burnett and Clifford5 reported that the difference in the CSS between occlusions was only sig-nificant for Class III, which showed the lowest CSS value, and emphasized that the CSS should be interpreted with the low number (n=5) of Class III participants in mind. However, with a higher number of participants, How-ell20 reported no significant differenc-es among classes. The CSS findings of these studies were close for only Class III participants, while the other find-ings were quite different.5,20 The same trend for Class III participants was also observed in the present study, but for the Angle Class II participants, the CSS findings for Class II division 1 and division 2 participants conflicted. This result might be due to the differ-ence in the Angle and incisor classifi-cation systems.

The results of this study indicate that the CSS does not significantly differ when a skeletal classification is considered. However, when the Angle classification was analyzed, a signifi-cant difference in the CSS was ob-served between the Class II division 2 and Class III, in which the mean CSS finding was lower than in Class II divi-sion 2. The increased vertical overlap

in Class II division 2 and the decreased overlap in Class III occlusions might have resulted in this apparent signifi-cant difference. This finding suggests the vertical overlap of the anterior teeth affected the CSS. However, a correlation suggesting a cause and ef-fect relationship between the CSS and vertical overlap was not found in the present study. Thus the null hypoth-esis of this study was confirmed.

Most clinical research on the CSS has been performed by using Eng-lish words containing sibilants to register the /s/ sound, for example, Mississippi, sixty-six, and yes25 and non-English words such as sessantasei12 and seis,23,26,27 or complete sentences.30 However, as no available study ex-ists investigating the CSS in native Turkish speakers, the findings of this study cannot be compared. The av-erage CSS of 2.27 mm in the present study was close to the previous find-ings pertaining to dentate partici-pants.5,16,17,20,25,26,32,33 The word seyis was chosen as a test for speech be-cause translated in English the word ‘horse rider’ is easily understood and that, its pronunciation in Turkish is similar to its original pronunciation in Spanish, starting and ending with an /s/ sound.26 Depending on the av-erage value and the general trend in CSS values within the classes of mal-occlusion, the use of the word seyis in the evaluation of the CSS in native Turkish speakers seems appropriate. Although it is held that the CSS is con-stant throughout life,3 further investi-gations of the CSS in native Turkish speakers of different ages and denti-tions are necessary.

The present study was conducted on young adult dentate participants with dental and skeletal malocclu-sions needing orthodontic treat-ment. However, a direct relationship between the severity of malocclusion and misarticulation has not yet been scientifically proved. Further evalu-ation and comparison of the CSS of the same participants are suggested after correcting the vertical overlap, incisors, premolar and molar teeth

224 Volume 109 Issue 4

The Journal of Prosthetic Dentistry

225April 2013

Şakar et al Şakar et al

Dental and skeletal classifications

Each participant’s occlusion was evaluated by means of casts accord-ing to the Angle classification meth-od.36 The skeletal classification was performed by means of cephalomet-ric radiographs made with the same machine (Orthophos XG Plus; Sirona Dental Systems, Bensheim, Germa-ny) according to ANB angle (Steiner cephalometric analysis), which is the angle between point A (Subspinale, the most posterior midline point in the concavity between the anterior nasal spine and the prosthion), na-sion (the most anterior point on the frontonasal suture in the midsagittal plane), and point B (Supramentale, the most posterior midline point in the concavity of the mandible be-tween the pogonion and infradentale) in the maxilla. It is the most common-ly used measurement for evaluating anteroposterior disharmony of the jaws.37 Participants were classified as Class I: 0≤ANB≤5 degrees, Class II: ANB>5 degrees, Class III: ANB<0 de-grees. The vertical overlap was mea-sured as the vertical overlap from the labio-incisal edge of the right maxil-lary central incisor with the greatest overlap to the labio-incisal edge of the corresponding mandibular right central incisor and was expressed as a percentage (%).

Descriptive analysis was per-formed to calculate the mean and standard deviation (SD) values for the CSS and the vertical overlap for dental and skeletal occlusions. The Wilcoxon test was used to determine whether a difference between the 148 right and 144 left interocclusal records existed. To test interobserver and intraob-server reliability, a total of 40 occlusal records were measured twice, with a 1-week interval by 2 different observ-ers and analyzed with the Spearman Rho test. Gender differences in the CSS were analyzed with the Mann Whitney U test, and the differences in the CSS within dental or skeletal classifications were analyzed with the Kruskal-Wallis test. Comparisons of

the CSS or vertical overlap among groups within the classifications were analyzed with the Mann Whitney U test, and the correlation between the CSS and the amount of vertical over-lap was analyzed with the Spearman Rho Correlation test. The significance level was set at α=.05. All statistical analyses were performed with SPSS software (SPSS for Windows, v11.5; SPSS Inc, Chicago, Ill).

RESULTS

Of 210 participants, 35 had some difficulties (inaccurate pronunciation while recording with the registration material in the mouth, gagging) while making the records, and 30 had inter-occlusal records with no exact thick-ness or measurable area around the premolar region. Therefore, the re-cords of 65 participants were discard-ed and the data obtained by measur-ing the records of 155 participants (100 females, 55 males) were used. Also, 7 right and 11 left records of par-ticipants in the final group could not be measured because of the lack of neces-sary thickness. As a result 148 right and 144 left interocclusal measurements were performed and evaluated.

The Spearman Rho test found that the measurement of the CSS was

statistically reliable. Interobserver (r =0.89, P<.001) and intraobserver (r=0.91, P<.001) reliability rates were high. The mean and SD of the CSS were 2.27 ±1.17 mm for the 148 right interocclusal records and 2.15 ±1.06 mm for the 144 left interocclusal re-cords. The difference between the 2 sides was not statistically significant (P=.737), and so data belonging to the 148 right interocclusal records of the 155 (100 females, 55 males) par-ticipants were used in the further sta-tistical analysis.

The mean age of the 55 males was 14.96 years (range 11 to 22 years), and the mean age of the 100 females was 15.50 years (range 10 to 28 years). The overall mean and SD of the CSS (range 0.11 to 5.85 mm) was 2.27 ±1.17 mm. The difference in the CSS between males and females was not significant (P=.747).

The mean and SD of the CSS of Angle Class I (55 participants) was 2.28 ±0.89 mm, of Class II division 1 (44 participants) 2.16 ±1.49 mm, of Class II division 2 (29 participants) 2.66 ±1.16 mm, and of Class III (20 participants) 1.92 ±0.95 mm. The mean and SD of the amount of verti-cal overlap (%) was 20.13 ±18.02 for Angle Class I, 42.37 ±26.90, for Class II Division 1, 48.75 ±35.90 for Class II

CSS

Vertical overlap (%)

CSS

Vertical overlap %

2.28

20.13

Class I (n=55)

Angle Dental Classification

Mean

0.89

18.02

SD

2.16

42.37

Class II Div 1 (n=44)

Mean

1.49

26.90

SD

2.66*

48.75

Class II Div 2 (n=29)

Mean

1.16

35.90

SD

2.24

26.60

Class I (n=77)

Steiner Skeletal Classification

Mean

1.07

23.18

SD

2.46

47.48

Class II (n=46)

Mean

1.44

31.63

SD

2.00

13.75

Class III (n=25)

Mean

0.84

21.02

SD

1.92*

16.25

Class III(n=20)

Mean

0.95

24.03

SD

* Indicates statistically significant differences among groups (P<.05).

Table I. Means and SDs of CSS (mm) and vertical overlap (%) in dental and skeletal Class I, II, and III classification

division 2, and 16.25 ±24.03 for Class III occlusions. The differences in CSS were only significant between Angle Class II division 2 and Class III occlu-sions (P =.034) (Table I).

The mean and SD of the CSS was 2.24 ±1.07 mm for skeletal Class I (77 participants), 2.46 ±1.44 mm for Class II (46 participants), and 2.00 ±0.84 mm for Class III (25 par-ticipants). The mean and SD of the amount of vertical overlap (%) was 26.60 ±23.18 for skeletal Class I, 47.48 ±31.63 for skeletal Class II, and 13.75 ±21.02 for skeletal Class III occlusions. The differences in CSS within skeletal Class I, II, and III occlu-sions were not statistically significant (P =.452) (Table I).

The correlation between the CSS and the amount of vertical over-lap was not statistically significant (Spearman r=.110, P=.249).

DISCUSSION

The null hypothesis that the CSS would not differ in different dental and skeletal occlusions was not rejected. CSS is one of the methods used to de-termine OVD and the esthetics of pros-thetic restorations. This clinical study aimed to test the amount of CSS with respect to the differences in dental and skeletal orthodontic classifications.

Rizzatti et al12 recommended the use of vinyl polysiloxane interocclusal registration material over the kinesio-graphic method to determine the CSS because it is simple and less expen-sive. In the present study, it was also observed that the majority of the par-ticipants easily pronounced the word seyis with the interocclusal registration material between the posterior teeth. It should be noted that 16% of the participants (35 participants out of 210) were not successful in recording the CSS perhaps because of atypical situations,20 personal skills, or reac-tion to a foreign material in the oral cavity (vomiting, gagging, or diffi-culty in speech). On the interocclusal records, of 14% of the participants (30 participants out of 210), no exact

thickness or area around the premolar region was identified, so these records were discarded. These observations can be regarded as the limitations of this method.

The present finding that the CSS did not differ between genders sup-ports the finding20 for participants with mean age of 20 years. This result might indicate that CSS is similar in adolescents and young adult partici-pants without gender differences.

Common qualitative methods of recording occlusal traits include the British Standard Institute (BSI) classi-fication for incisors and the Angle clas-sification for molar relationships.21,22 The present findings indicate that the amount of CSS did not differ between the Angle dental and cephalometric skeletal classifications. The previous studies of Burnett and Clifford5 and Howell,20 however, used the incisor classifications. Burnett and Clifford5 reported that the difference in the CSS between occlusions was only sig-nificant for Class III, which showed the lowest CSS value, and emphasized that the CSS should be interpreted with the low number (n=5) of Class III participants in mind. However, with a higher number of participants, How-ell20 reported no significant differenc-es among classes. The CSS findings of these studies were close for only Class III participants, while the other find-ings were quite different.5,20 The same trend for Class III participants was also observed in the present study, but for the Angle Class II participants, the CSS findings for Class II division 1 and division 2 participants conflicted. This result might be due to the differ-ence in the Angle and incisor classifi-cation systems.

The results of this study indicate that the CSS does not significantly differ when a skeletal classification is considered. However, when the Angle classification was analyzed, a signifi-cant difference in the CSS was ob-served between the Class II division 2 and Class III, in which the mean CSS finding was lower than in Class II divi-sion 2. The increased vertical overlap

in Class II division 2 and the decreased overlap in Class III occlusions might have resulted in this apparent signifi-cant difference. This finding suggests the vertical overlap of the anterior teeth affected the CSS. However, a correlation suggesting a cause and ef-fect relationship between the CSS and vertical overlap was not found in the present study. Thus the null hypoth-esis of this study was confirmed.

Most clinical research on the CSS has been performed by using Eng-lish words containing sibilants to register the /s/ sound, for example, Mississippi, sixty-six, and yes25 and non-English words such as sessantasei12 and seis,23,26,27 or complete sentences.30 However, as no available study ex-ists investigating the CSS in native Turkish speakers, the findings of this study cannot be compared. The av-erage CSS of 2.27 mm in the present study was close to the previous find-ings pertaining to dentate partici-pants.5,16,17,20,25,26,32,33 The word seyis was chosen as a test for speech be-cause translated in English the word ‘horse rider’ is easily understood and that, its pronunciation in Turkish is similar to its original pronunciation in Spanish, starting and ending with an /s/ sound.26 Depending on the av-erage value and the general trend in CSS values within the classes of mal-occlusion, the use of the word seyis in the evaluation of the CSS in native Turkish speakers seems appropriate. Although it is held that the CSS is con-stant throughout life,3 further investi-gations of the CSS in native Turkish speakers of different ages and denti-tions are necessary.

The present study was conducted on young adult dentate participants with dental and skeletal malocclu-sions needing orthodontic treat-ment. However, a direct relationship between the severity of malocclusion and misarticulation has not yet been scientifically proved. Further evalu-ation and comparison of the CSS of the same participants are suggested after correcting the vertical overlap, incisors, premolar and molar teeth

226 Volume 109 Issue 4

The Journal of Prosthetic Dentistry Asavapanumas and LeevailojŞakar et al

positions, and the occlusion with orthodontic treatment; this is espe-cially true of Class II divisions 1 and 2 and Class III malocclusions.

CONCLUSION

Within the limitations of this clini-cal study, the following conclusions can be drawn:

1. The CSS does not differ be-tween males and females.

2. The CSS does not differ accord-ing to the skeletal classification.

3. The difference in the CSS was only significant between Angle Class II division 2 and Class III occlusions.

4. No correlation was found be-tween the amount of vertical overlap and the CSS.

5. The use of the Turkish word seyis is appropriate for registering the CSS in native Turkish speakers.

6. Irrespective of dental and skel-etal classified occlusions, average CSS values can be used to determine the OVD of prosthetic restorations.

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11.The Glossary of Prosthodontic Terms. J Prosthet Dent 2005;94:24.

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13.Howell PGT. Incisal relationships during speech. J Prosthet Dent 1986;56:93-9.

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16.Burnett CA, Clifford TJ. The mandibular speech envelope in subjects with and with-out incisal tooth wear. Int J Prosthodont 1999;12:514-8.

17.Meier B, Luck O, Harzer W. Interocclusal clearance during speech and in mandibular rest position. A comparison between differ-ent measuring methods. J Orofac Orthop 2003;64:121-34.

18.Burnett CA, Clifford TJ. A preliminary investigation into the effect of increased occlusal vertical dimension on man-dibular movement during speech. J Dent 1992;20:221-4.

19.Agnello JG, Wictorin L. A study of phonetic changes in edentulous patients following complete denture treatment. J Prosthet Dent 1972;27:133-9.

20.Howell PG. The variation in the size and shape of the human speech pattern with incisor-tooth relation. Arch Oral Biol 1987;32:587-92.

21.Angle EH. Classification of malocclusion. Dental Cosmos 1899;41:248-64.

22.British Standard Institute. British Standard Incisor Classification. Glossary of Dental Terms BS 4492. London: British Standard Institute; 1983

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Corresponding author:Dr Canan BuralIstanbul University, Faculty of DentistryDepartment of Removable Prosthodontics Capa, 34390, IstanbulTURKEYFax: +90212-525-35-85E-mail: cbural@istanbul.edu.tr

Copyright © 2013 by the Editorial Council for The Journal of Prosthetic Dentistry.

Clinical ImplicationsFor ceramic restorations, preparations with higher degrees of abutment finish line curvature should be avoided. Supragingival margin design may be considered in an effort to reduce the degree of finish line curvature of abutment teeth.

Statement of problem. As a result of natural tooth anatomy or gingival recession, anterior teeth are more likely to present increased abutment finish line curvature.

Purpose. The purpose of this study was to investigate the influence of the curvature of the finish line on the marginal gap widths of ceramic copings.

Material and methods. An ivorine maxillary central incisor was prepared for 3 different abutment finish line curva-tures (1, 3, and 5 mm). Thirty-six copings were fabricated for each of these curvatures by using Cercon, IPS e.max, and Lava systems. The marginal gap width was measured by using a stereomicroscope, and the data were subsequent-ly analyzed by means of a 2-way ANOVA and a 1-way ANOVA (α=.05).

Results. A significantly higher mean marginal gap width was found for the 5-mm curvature group (Cercon, 76.59 ±23.01 µm; IPS e.max, 106.44 ±18.48 µm; Lava, 128.34 ±20.79 µm) than for both the 3-mm curvature group (Cer-con, 60.18 ±9.74 µm; IPS e.max, 81.79 ±16.20 µm; Lava, 99.19 ±15.32 µm) and the 1-mm curvature group (Cercon, 38.3 ±6.85 µm; IPS e.max, 52.22 ±10.66 µm; Lava, 69.99 ±6.77 µm).

Conclusions. The greater the finish line curvature, the wider the marginal gap widths for the 3 ceramic systems. (J Prosthet Dent 2013;109:226-233)

The influence of finish line curvature on the marginal gap width of ceramic copings

Chutima Asavapanumas, DDSa and Chalermpol Leevailoj, DDS, MSDb School of Dentistry, Chulalongkorn University, Bangkok, Thailand

Supported by the Graduate School Thesis Grant, Chulalongkorn University.

aGraduate student, Esthetic Restorative and Implant Dentistry, Faculty of Dentistry. bAssociate Professor, Program Director of Esthetic Restorative and Implant Dentistry, Faculty of Dentistry.

The natural appearance of ceramic restorations has made them the treat-ment of choice for anterior teeth. How-ever, this advantage must be consid-ered against the possible lack of good marginal adaptation, which is essential for the clinical success and quality of a ceramic restoration.1,2 Insufficient ad-aptation of restorations may result in an increase in plaque accumulation, ultimately leading to periodontal dis-ease3,4 and secondary caries, which can result in pulpal inflammation.2 Furthermore, exposure of the dental

luting agent at the marginal gap to the oral environment also leads to a rapid increase in cement dissolution,5 a situ-ation which is widely recognized as a major cause of restoration failure.

Christensen6 found that in the vi-sually accessible surfaces of a cast restoration, subgingival marginal openings in the range of 39 to 119 µm and supragingival margins of 2 to 51 µm were judged to be clinically acceptable. McLean and von Fraun-hofer7 subsequently undertook a 5-year clinical study of 1000 restora-

tions and concluded that 120 µm was the maximum acceptable marginal opening (ranging from 100 to 120 µm); however, Byrne et al8 reported that discrepancies of less than 10 µm were routinely possible.

There are several studies report-ing the marginal gap widths in differ-ent ceramic systems. Balkaya et al9 reported a value of 57 µm as a mean marginal gap widths of In-Ceram Alumina coping. Cho et al10 demon-strated a mean marginal opening of 27.5 µm for IPS e.max Press (Ivoclar