Parametric And Nonparamentric Assessment Of Speech Changes Biology Essay

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The esthetic revolution in dentistry has not left orthodontics untouched. The quest of esthetics has expanded the inventory at the orthodontists disposition- brackets made of plastic and porcelain , coated arch wires and plastic aligners ; all with one aim to make the braces invisible! However, the only true solution to the poor esthetics of conventional fixed orthodontic appliances providing an ultimate in esthetics during the treatment is to attach the appliances to the lingual surfaces of the teeth.

The lingual technique offers the most esthetic orthodontic treatment option. This outstanding advantage over other therapies is, however, eclipsed by the drawback that the bracket placement entails a substantial, albeit temporary, change in the morphology of the lingual tooth surface due to bracket and thus of the second articulation zone. Lingual placement of the brackets hence appears problematic in terms of articulation.1

Since the introduction of the lingual appliance in the late 1970's, research workers have dealt with the technical-clinical aspects of the technique. However, only a few publications have appeared dealing with patient characteristics, acceptance, and motivation. Lingual orthodontic patients are usually informed that there may be some tongue discomfort and speech difficulty associated with the insertion of the appliance. However, the intensity and duration of the problems are not yet entirely clear, and orthodontists are still dubious of the patient's ability to adapt to lingual brackets.2 The severity and duration of this disturbed sound (e.g., /s/ sound) performance and impaired oral comfort are documented with inconsistent data in the literature.3

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The /s/ sound is well suited for evaluating speech performance, because this fricative is considered especially sensitive to morphological changes in the maxillary incisors and is common in most languages.1

In the past, many efforts have been made to standardize treatment protocols to enhance the practicability of lingual orthodontics for the orthodontists and to reduce oral discomfort and speech problems of the patients-e.g., by flattening the bonding technique or the bracket size. Despite these improvements, lingual brackets still cause discomfort and dysfunction in some patients, as do other treatment techniques. If parameters were available to predict the expected inconveniences, they would be helpful to the orthodontist in giving the patient full information and for the patient in deciding to opt for lingual orthodontic treatment.4

This study was first of its kind undertaken to prospectively evaluate and compare the speech changes occurring between the patients treated with labial and lingual fixed orthodontic appliance. Thus, helping the orthodontist to council the patients as for their speech chances during treatment.

Materials & methods

The study aimed at comparing speech performance in labial and lingual orthodontic patients:

Using a software PRAAT version 5.0.47 obtained from www.praat.org.

The auditive analysis was done by two speech, language and hearing pathologist and audiologist.

The subjective evaluation of speech was done by four laypersons.

In a prospective longitudinal study, twelve native Kannada speakers were selected according to convenience and judgement, between 18 to 35 years of age who reported to the Department of Orthodontics, SDM College of Dental Sciences and Hospital, Dharwad, Karnataka, India.

The Exclusion criteria were cleft lip, cleft palate, dialects, a history of speech and hearing disorders and previous elocution training or speech therapy. The potential inclusions were examined by a speech pathologist for the aforementioned and were included only after their clearance.

The subjects were assigned to two different groups -Li (lingual) and La (labial). The brackets used for lingual orthodontics were STB brackets, which were indirectly bonded to the tooth surface (Figure 1). The positioning on the models was done using Torque angulation device and Bracket positioning device(TAD BPD) (Figure 2) from Polydee instruments,Chengmai,Thailand.

The patients undergoing labial orthodontics were treated with preadjusted system using MBT Versatile Plus prescription. These brackets were directly bonded on the tooth surface (Figure 3, 4).

Speech performance was evaluated at the following time:

Immediately before bonding - T1

Within 24 hours after bonding -T2

1 week after bonding -T3

1 month after bonding -T4

The recording was done in a soundproof room using software PRAAT (Figure 5), I-ball electronic microphone and headset and Dell Inspiron 1525 series laptop. The microphone was placed about 1 cm anterior to the mentolabial fold below the breath stream. The patients were not allowed to use relief wax during the recording session.

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Three recordings of each patient was made at all four recording sessions(T1,T2,T3,T4) being:

Each patient was asked to record a short introduction of them that comprised of their name, age, their educational qualification and their address.

The list of 59 (Figure 6) words from the Test of Articulation in local language (Kannada) was used as speech stimulus. The words were presented to each patient in a different order at each recording session T1, T2, T3, T4.

Four words 'shartu', 'brush', 'surya' and 'bassu'(Figure 7, 8) were selected from the list of 59 words from the Test of Articulation in Kannada and the patient were asked to speak these words which were then recorded at the four recording sessions .

Objective analysis of articulation using PRAAT

The Four words 'shartu', 'brush', 'surya' and 'bassu'which were selected from the list of 59 words from the Test of Articulation in Kannada were used for this test. The patients in both the group-LA (labial) and LI (lingual) read the standardized text aloud at T1, T2, and T3 andT4. The speech samples were saved and assessed using "PRAAT 5.0.47." The acoustic analysis of the /s/ sound in the initial position of the word "surya" (W1) and the middle position in the word "bassu" (W2) was performed by digital spectrography using this software.

The /s/ sound was selected since it is considered well suited for evaluating speech performance, because this fricative is considered especially sensitive to morphological changes in the maxillary incisors and is common in most languages throughout the world.1

Wide-band spectrography was used to analyze the upper boundary frequency of the fricative sound. This Parameter is defined as the maximum frequency of the band width of the fricative sound, represented in the Wide-band spectrogram as the range of maximum grayness.

Semi objective auditive analysis of the articulation by two Speech Language Pathologist & Audiologist

Two clinical judges trained in speech pathology listened independently to the recording of 59 words, played in a random manner that prevented identification of patients or treatment periods. Each test syllable was judged for imprecision or distortion on a five-point scale ranging from non-pathologic to highly pathologic speech performance. The judges were instructed to grade the entire syllable rather than individual speech sounds. The mean of score of each patient at a given time was used for statistical analysis.

The scale used will have the following classification grades3:

Grade 1-nonpathological speech performance

Grade 2-slightly pathological speech performance

Grade 3-moderately pathological speech performance

Grade 4-pathological speech performance

Grade 5-highly pathological speech performance

Subjective evaluation of speech by four laypersons

Four individuals -two males and two females were randomly selected from the first BDS student of the college. These individuals did not have any training in speech and hearing pathology. They were independently asked to rate the speech performance using the aforementioned scale. A speech stimulus was said to be pathological if it was perceived as less clear. The recordings made at T1, T2, T3, andT4 of both the Li and La groups was played in a random manner.

Statistical methods:

The Wilcoxon signed rank test for related sample was used to evaluate individual articulation changes over T1, T2, T3, and T4 in labial and lingual groups separately.

The Mann Whitney U test for independent samples was used to assess the significance difference between the labial and lingual appliances at T1, T2, T3 and T4.

Comparison of labial and lingual words (W1+W2) at T1, T2, T3, T4 was made by t-test

Results and its interpretation

Objective evaluation of articulation by wide band spectography

/s/ sound in the initial position in the word 'surya'(W1)

In the Labial group, spectrographically the frequency change(table 1a) follows a pattern of falling from an average of 4298.03 Hz. at T1 to 4177.21 Hz. at T2 (T1-T2 p>0.05) and then rising again to 4243.07 Hz. At T3 (T2-T3 p>0.05) to near normal of 4262.99 Hz. At T4 (T3-T4 p>0.05). However, this change in frequency over time is statistically non-significant as revealed by their p values (table1b).

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A similar Comparison made between T1,T2,T3and T4 in lingual group for W1 shows a statistically significant fall in frequency(table 1a) from 4155.96 Hz. At T1 to 4012.86 Hz. At T2 (T1-T2 p<0.05) to 3812.24 Hz. At T3 (T2-T3 p<0.05) there after rising again to 4018.22 Hz. at T4. The frequency at T4 was less than T1, however this difference was not statistically significant (T1-T4 p>0.05) (table1b).

(Table1a) Change in frequency of W1 over time

W1

T1

T2

T3

T4

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Labial

4298.03

368.37

4177.21

295.30

4243.07

309.68

4262.99

342.33

Lingual

4155.96

326.50

4012.86

316.54

3812.24

250.21

4018.22

346.36

(Table1b) Comparison of T1, T2, T3, T4 in W1 of Labial and lingual by Wilcoxon Matched Pairs Test

Labial

N

T-value

Z-value

p-level

signifi.

T1 & T2

6

6.0000

0.9435

0.3455

NS

T1 & T3

6

10.0000

0.1048

0.9165

NS

T1 & T4

6

9.0000

0.3145

0.7532

NS

T2 & T3

6

7.0000

0.7338

0.4631

NS

T2 & T4

6

7.0000

0.7338

0.4631

NS

T3 & T4

6

6.0000

0.9435

0.3455

NS

Lingual

T1 & T2

6

1.0000

1.9917

0.0464

S

T1 & T3

6

0.0000

2.2014

0.0277

S

T1 & T4

6

3.0000

1.5724

0.1159

NS

T2 & T3

6

0.0000

2.2014

0.0277

S

T2 & T4

6

10.0000

0.1048

0.9165

NS

T3 & T4

6

4.0000

1.3628

0.1730

NS

/s/ sound in the middle position in the word 'bassu'(W2)

Spectrographic frequency change in the labial group again followed a pattern of falling from an average of 3997.32 Hz. at T1 to 3922.80 Hz (table 2a) at T2 (T1-T2 p>0.05) and to 3872.33Hz. At T3 (T2-T3 p>0.05) and rose again to 3928.86 Hz. At T4 (T3-T4 p>0.05). However, this change in frequency over time was again statistically non-significant as revealed by their p values (table 2b).

A similar Comparison made between T1,T2,T3and T4 in lingual group for W2 shows a statistically significant fall in frequency from 4456.67 Hz. at T1 to 4267.27 Hz. at T2 (T1-T2 p<0.05) to 4182.98 Hz. at T3 (T2-T3 p<0.05) there after rising again to 4352.36 Hz. at T4 . The frequency at T4 was less than T1, however, unlike the /s/ sound in the initial position a statistically significant difference was noted this time (table 2b).

(Table2a) Change in frequency of W2 over time

W2

T1

T2

T3

T4

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Labial

3997.32

275.23

3922.80

303.48

3872.33

317.97

3928.86

315.16

Lingual

4456.67

249.93

4267.27

212.87

4182.98

325.59

4352.36

269.60

(Table 2b) Comparison of T1, T2, T3, T4 in W2 of Labial and lingual by Wilcoxon Matched Pairs Test

Labial

N

T-value

Z-value

p-level

signifi.

T1 & T2

6

0.0000

2.2014

0.0277

S

T1 & T3

6

0.0000

2.2014

0.0277

S

T1 & T4

6

0.0000

2.2014

0.0277

S

T2 & T3

6

0.0000

2.2014

0.0277

S

T2 & T4

6

3.0000

1.5724

0.1159

NS

T3 & T4

6

7.0000

0.7338

0.4631

NS

Lingual

T1 & T2

6

0.0000

2.20139813

0.027715

S

T1 & T3

6

0.0000

2.20139813

0.027715

S

T1 & T4

6

0.0000

2.20139813

0.027715

S

T2 & T3

6

0.0000

2.20139813

0.027715

S

T2 & T4

6

8.0000

0.52414244

0.600183

NS

T3 & T4

6

0.0000

2.20139813

0.027715

S

An inter group comparison made between the labial (LA) and the lingual (LI) group by Mann Whitney U test at the four time interval showed that there was no statistically significant difference between the change in frequency in the two groups at one given time (eg: T2 of labial compared with T2 of lingual) at any of the time interval (table 3a) for the /s/ sound in the initial position in the word 'surya'.

This same comparison when made for the /s/ sound in the middle position in the word 'bassu'(W2) shows a frequency difference at T3 between the labial and the lingual group to be statistically highly significant(p<0.01) (table 3b)

(Table 3a) Comparion of labial and lingual of W1 at T1, T2, T3, T4 by Mann Whitney U-test

Rank Sum

Rank Sum

Time

Labial

Lingual

U-value

Z-value

p-level

signifi.

T1

41.0000

37.0000

16.0000

-0.3203

0.7488

NS

T2

44.0000

34.0000

13.0000

-0.8006

0.4233

NS

T3

49.0000

29.0000

8.0000

-1.6013

0.1093

NS

T4

45.0000

33.0000

12.0000

-0.9608

0.3367

NS

(Table 3b) Comparion of labial and lingual of W2 at T1, T2, T3, T4 by Mann Whitney U-test

Rank Sum

Rank Sum

Time

Labial

Lingual

U-value

Z-value

p-level

signifi.

T1

49.0000

29.0000

8.0000

-1.6013

0.1093

NS

T2

47.0000

31.0000

10.0000

-1.2810

0.2002

NS

T3

57.0000

21.0000

0.0000

-2.8823

0.0040

HS

T4

50.0000

28.0000

7.0000

-1.7614

0.0782

NS

A comparison of /s/ (W1+W2) sound made between the labial and lingual group revealed a highly statistically significant difference to be present after one week at T3 (p<0.01) (table4). While in the labial group the speech had started improving, the lingual group showed the worst speech performance at this time.

(Table 4) Comparison of labial and lingual (W1+W2) at T1, T2, T3, T4 by t-test

Variable

Group

n

Mean

SD

t-value

p-value

Signify.

T1

Labial

12

4298.03

368.37

0.9999

0.3283

NS

Lingual

12

4155.96

326.50

T2

Labial

12

4177.21

295.30

1.3152

0.2020

NS

Lingual

12

4012.86

316.54

T3

Labial

12

4243.07

309.68

3.7486

0.0011

HS

Lingual

12

3812.24

250.21

T4

Labial

12

4262.99

342.33

1.7411

0.0956

NS

Lingual

12

4018.22

346.36

Semi objective auditive analysis of the articulation by two Speech Language Pathologist & Audiologist

A mean increase in score on the Likert scale for the patient in labial group(table 5a) from 1.00 at T1 to 1.08 at T2 was observed which was highly statistically significant(p<0.01)(table 5b). The scores decreased thereafter being 1.04 atT3 to1.02 at T4 showing a statistically significant (p<0.05) improvement in the clarity of the patient's speech over a period from T2 to T4. The mean score at T4 was however lower than T1 , the difference being statistically significant(p<0.05)

The mean scoring on the Likert scale by the speech pathologist for the lingual group (table 5a) increased from 1.00 at T1 to 1.10 at T2 to 1.28 at T3 and then improving to 1.09 at T4. Thus, a highly statistically significant deterioration in articulation occurred from T1 to T2, further worsening until T3 thereafter improving at T4. The difference of score between T1 and T4 in the lingual group remained statistically highly significant (p<0.01) (table 5b).While in labial group a significant improvement in articulation was noted at T4 the mean score of articulatory performance in the lingual group remained far from normal.

(Table 5a)Change in score on Likert scale by speech pathologist

T1

T2

T3

T4

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Labial

1.00

0.01

1.08

0.05

1.04

0.02

1.02

0.03

Lingual

1.00

0.00

1.10

0.06

1.28

0.14

1.09

0.07

(Table 5b) Assessment by speech pathologist

Comparison of T1, T2, T3, T4 in Labial byWilcoxon Matched Pairs Test

Labial

N

T-value

Z-value

p-level

signifi.

T1 & T2

12

0.0000

3.0594

0.0022

HS

T1 & T3

12

0.0000

2.9341

0.0033

HS

T1 & T4

12

0.0000

2.0226

0.0431

S

T2 & T3

12

1.0000

2.5471

0.0109

S

T2 & T4

12

0.0000

3.0594

0.0022

HS

T3 & T4

12

2.5000

2.7118

0.0067

HS

Lingual

T1 & T2

12

0.0000

3.0594

0.0022

HS

T1 & T3

12

0.0000

3.0594

0.0022

HS

T1 & T4

12

0.0000

3.0594

0.0022

HS

T2 & T3

12

3.5000

2.6229

0.0087

HS

T2 & T4

12

35.5000

0.2746

0.7837

NS

T3 & T4

12

0.0000

3.0594

0.0022

HS

An inter group comparison made between the labial(LA) and the lingual(LI) group by Mann Whitney U test at the four time interval showed that there was a highly statistically significant difference between the Likert scale scoring in the two groups at T3(p=0.00) and T4(p=0.01) , the lingual group scoring poorly on the scale and having more misarticulations than the labial group at T3 and T4 (table 5c).

(Table 5 c) Comparison of labial and lingual at T1, T2, T3, T4 by Mann Whitney U-test

Rank Sum

Rank Sum

Time

Labial

Lingual

U-value

Z-value

p-level

signifi.

T1

151.5000

148.5000

70.5000

-0.0866

0.9310

NS

T2

141.0000

159.0000

63.0000

-0.5196

0.6033

NS

T3

78.0000

222.0000

0.0000

-4.1569

0.0000

HS

T4

93.5000

206.5000

15.5000

-3.2620

0.0011

HS

Subjective evaluation of speech by four laypersons

A mean (table6a) increase in score on the Likert scale for the patient in labial group from 1.08 at T1 to 2.42 at T2 was observed which was highly statistically significant (p<0.01) (table 6b). The scores decreased thereafter being 2.00 atT3 to1.13 at T4 showing a statistically significant (p<0.05) improvement in the clarity of the patient's speech over a period from T2 to T4.

The mean rating (table6a) on the Likert scale by the layperson for the lingual group increased from 1.13 at T1 to 2.63 at T2 to 3.04 at T3 and then decreased to 2.00 at T4. Thus, a highly statistically significant deterioration in speech occurred from T1 to T2, further worsening till T3 thereafter improving atT4. The difference of score between T1 and T4 in the lingual group remained statistically highly significant (p<0.01) (table 6b).

(Table 6a)Change in score on Likert scale by layperson

T1

T2

T3

T4

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Means

Std.Dev.

Labial

1.08

0.28

2.42

0.58

2.00

0.59

1.13

0.34

Lingual

1.13

0.34

2.63

0.65

3.04

0.62

2.00

0.72

(Table 6b).Layperson assessment of speech

Comparison of T1, T2, T3, T4 in Labial byWilcoxon Matched Pairs Test

Labial

N

T-value

Z-value

p-level

signifi.

T1 & T2

24

0.0000

4.1973

0.0000

HS

T1 & T3

24

0.0000

3.8230

0.0001

HS

T1 & T4

24

2.0000

0.5345

0.5930

NS

T2 & T3

24

38.0000

2.0686

0.0386

S

T2 & T4

24

0.0000

4.1069

0.0000

HS

T3 & T4

24

0.0000

3.8230

0.0001

HS

Lingual

T1 & T2

24

0.0000

4.2857

0.0000

HS

T1 & T3

24

0.0000

4.1069

0.0000

HS

T1 & T4

24

28.5000

3.1816

0.0015

HS

T2 & T3

24

42.5000

1.8727

0.0611

NS

T2 & T4

24

26.5000

2.3669

0.0179

S

T3 & T4

24

9.0000

3.8147

0.0001

HS

An inter group comparison made between the labial(LA) and the lingual(LI) group by Mann Whitney U test as assessed by the layperson at four time interval showed that there was a highly statistically significant difference between the Likert scale scoring in the two groups at T3(p=0.00) and T4(p=0.00) (table 6c). The speech in the labial group showed a marked improvement over time than the lingual group.

(Table 6c) Comparison of labial and lingual at T1, T2, T3, T4 by Mann Whitney U-test

Rank Sum

Rank Sum

Time

Labial

Lingual

U-value

Z-value

p-level

signifi.

T1

576.0000

600.0000

276.0000

-0.2474

0.8046

NS

T2

547.5000

628.5000

247.5000

-0.8351

0.4037

NS

T3

378.0000

798.0000

78.0000

-4.3301

0.0000

HS

T4

390.0000

786.0000

90.0000

-4.0827

0.0000

HS

Discussion

This study is the first of its kind to prospectively compare the change in articulation in a group of patients treated with labial and lingual brackets using objective evaluation of speech performance by PRAAT combined with semi objective and subjective auditive analysis.

It was observed in this study that the frequency changes followed a pattern in both labial and lingual treatment groups.

In the labial group, the frequency dropped to the lowest level immediately after placement thereafter rising again towards normal over a month period. This spectrographic frequency change also was in agreement with:

The change in misarticulation as noted by the speech pathologist, that is, the maximum misarticulations were made immediately after bracket placement reducing thereafter.

The changes in speech as rated by the laypersons. The pathologic speech being defined as being less clear. The speech after the bracket placement being rated the poorest.

In the lingual group, the sound frequency of the /s/ sound decreased immediately after bracket placement, continued to drop further, and was observed to be at the lowest one week after bracket placement .This finding was corroborated by the semi objective and the subjective observations made:

The speech pathologist reported the misarticulations to be at their maximum after one week of bracket placement and then lowering after one month.

The layperson also reported a similar finding that the speech was least clear after one week, improving thereafter. However, it was still statistically far from normal even after a month.

The speech problems encountered by the LA (labial) group patients may be attributed to the transpalatal arch and the lingual arch used in combination with labial orthodontic appliances to reinforce anchorage. This finding confirms the results of the studies by Caniklioglu2, Haydar et al7,and Strutton and Burkland.9 They all reported that dental appliances (orthodontic or prosthetic) can cause articulation disorders. Patients with these appliances experienced articulation problems at the beginning of treatment, which gradually decreased with time.

When considering the LI (lingual) group, comparison with the literature showed a similar reduction in the upper boundary frequency of the fricative sound to that recorded in our study when the maxillary incisor crown of dentures were tipped 30° palatal 10 . This suggests a patho- mechanism similar to that recorded in our study, because the contact area of the tongue is also shifted farther palatal by the lingual brackets.

The patients in our study described "hurting of tongue" as the main cause of speech difficulty since they were not allowed to use relief wax during recording sessions and reported that they felt considerably better when speaking with the wax, however had to speak slower than their pre treatment pace to speak clearly .

In a study by Sinclair et. al. 5 speech professionals using a method comparable with that in the present study diagnosed significantly more speech errors 10 minutes after placing the lingual brackets than before. The single biggest problem reported in his study was tongue soreness, especially at the tip and the lateral surfaces in the canine-bicuspid area. The discomfort lasted between one and two weeks for most patients, and some reported problems even after a month of treatment. This study also described tongue soreness as the main contributor to speech problems. This study concluded that the lingual appliance is a complex challenge to the speaking mechanism because patients' tongues automatically aim for their customary alveolar targets thus striking the sharp edges of the appliance.

Spectrographic evaluation confirmed that most distortions could be accounted for by four abnormal articulatory modifications:

1. Breaking of consonant airflow (frication) as the tongue tip encountered the unfamiliar appliance. This modification started immediately after appliance placement.

2. Lowering of the noise frequency band that contained most of the consonant energy, producing a sound with lower resonance. This probably resulted from a posterior shifting of the tongue tip's point of articulatory contact along the roof of the oral cavity (from linguo-alveolar to linguo-palatal).

3. Reduction in overall intensity of consonants, maximally seen one week after placement probably related to avoidance of contact during the period of most pronounced tongue soreness.

4. Prolongation or slowing of the production of individual speech sounds as patients reorganized their patterns of articulation. This adaptation seemed to be nearly complete after a month as most patients got relatively accustomed to their lingual brackets and were able to speak at their pretreatment pace with minimal effort.

The increase in misarticulations as noted by the speech pathologists increased considerably immediately after bracket placement in the labial group decreasing thereafter to a statistically insignificant level after one week while in the lingual group the worst speech performance was noted at one week time interval. The misarticulations noted in both the groups were mainly in the alveolar consonants-/s/(fricative), /d/(stops) and /l/(liquids). These may be attributed to the posterior shift of tongue contact as it encountered the foreign object. This significant change in /s/ sound production registered for a 1-month period by the speech professionals in this study was confirmed in the study by Sinclair5 ,Fujita11 and Fillion 12.

The layperson assessment of speech showed a similar trend as the speech professional with the labial group performing the worst at T2 and the lingual group at T3. A statistically insignificant difference was noted between T1 and T4 when an intragroup comparison was made .A similar intragroup comparison made between T1 and T4 in lingual group showed a highly statistically significant poor speech performance to be present at T4 when compared with T1 . This could again be attributed to the adaptability of the tongue to the appliance and the amount of tongue soreness encountered in the lingual group unlike the labial group that shows fast recovery towards normality.

In studies conducted by Hohoff 1 and Fujita13 that compared the speech assessment as done by the patient and their close contact showed that the patients' close contacts gave their speech a slightly better mean evaluation than the patients themselves did after the start of treatment. This might suggest a tendency for patients to be preoccupied with their speech 13 .

The subjectively perceived disturbances in sound formation caused by labial brackets was 22.5% and lingual brackets was 40% after one month. Similar results were reported in studies by Marioti8 and Fillion12 for lingual brackets ,although varying in information on the duration of the disturbances and the number of patients affected.. The data range from subjectively perceived speech disturbances in approximately 20% of patients a month after placement of lingual brackets 5,12 to subjectively perceived speech disturbances in more than 37% of patients until the lingual brackets were removed.6 These differences might be due to variations in the study design (prospective versus retrospective), subjective evaluation of sound formation, different bracket surfaces, and varying degrees of tongue soreness.

Concluding from the psychological evaluation done Sinclair et. al. 5 suggest that those who did not handle stress well might have exaggerated adverse responses to lingual treatment. Such patients may feel blocked from normal eating and talking habits and may respond by becoming angry and aggressive, thus prolonging the initial adaptation phase.

It is also conceivable that different bracket positioning techniques could play a role1. With the BEST positioning technique used, the brackets project further palatal than with the transfer optimized positioning (TOP) system. For example in the TOP system, where a target setup is used for the 3-dimensional orientation of each tooth, all brackets have at least a 1-point contact with the teeth and are bonded on the malocclusion model with the least possible positioning thickness, resulting in a slimmer appliance design than any other positioning procedure.

This could imply that the space for the tongue is restricted more than necessary at some sites with the BEST technique, because the tooth defines the general distance of the slot from the labial surface with the greatest positioning thickness. No committed remark could be made on this as no published data was available comparing the speech performance in patients bonded using TAD BPD with other bracket positioning system. However, the possibility of such difference existing cannot be ruled out.

The size of lingual appliances used also plays a role in deciding the amount of discomfort perceived by the patient. In the subjective evaluation of articulation and oral comfort of the patient it was proven that the smaller the dimensions of the lingual appliance, the less pronounced the impairments in sound performance.3 The lower profile design of the customized bracket's thin bracket bases of 0.3 mm thick which adapted directly to tooth morphology, thus minimizing the filler spaces when compared with the prefabricated brackets. The customized lingual brackets project less far into the mouth than do the prefabricated lingual brackets hence being less impairing in speech production.

Gender related difference in speech performance was not evaluated in this study since a review of literature failed to show any influence of gender on the sterognostic ability in young individuals. Gender and age related influence on stereognostic abilities was found only after the age of 80 years in Dahan and Lelong's study.14The results of Hohoff's1 study also supported this view that gender has no impact on speech performance of subjects with lingual brackets, and age has no impact up to 57 years of age.

In our investigation, lingual brackets were bonded on both arches during the same appointment. However, placing the lingual appliance in the upper and the lower jaw during two different sessions would enhance patient comfort.2, 12

The level of speech difficulty was more bothersome in LI patients when compared with LA patients. Speech problems decreased significantly within a week after appliance placement in all patients in the LA group however, in a majority of the subjects in the LI group speech did not return to normal even in a month's time. This finding is in agreement with Sinclaire 5 and Artun15 .However, the patient's assessment for speech disturbance in this study appears more negative compared with that in the studies by Marioti.8 Fillion, 12and Fujita, 13 Pronunciation of different languages may be the reason for this difference.

By combining three semi objective or subjective methods to evaluate speech performance with all of them showing similar results, bias due to patient- or investigator-related misinterpretation can be largely dismissed in this study. Method 1 (spectrography), of course, is a very sophisticated means of evaluating speech performance and cannot be applied in everyday practice. On the other hand, it verifies that the speech changes observed or reported by speech professionals exist and are not based only on subjective perceptions.

The assessment of speech by blinded raters is an established means of assessing the changes in sound performance induced by lingual appliances.1,5 The /s/ sound is well suited for evaluating speech performance, because this fricative is considered to be especially sensitive to morphological changes in the maxillary incisors and is common in most languages.3,16

Conclusion

Clinical recommendations:

Patients must understand before treatment that there will be some inconvenience and discomfort with the lingual appliance. However, too much pretreatment emphasis on potential problems can become a self-fulfilling prophecy.

Questions about possible anxiety may help identify patients with low tolerance thresholds. It helps if the appliance can be placed at a time of relatively low stress, so the patient has at least a week to adapt. Follow-up telephone calls are very useful in allowing the patient to ask questions and gain reassurance.

Tongue soreness can be alleviated by using plastic bumper sleeves to span long spaces and minimize the amount of sharp surface presented to the tongue. Soft wax can also be used to cover arch wires and brackets, but prolonged use should be avoided because the wax acts as a food trap and seriously hinders brushing of the gingival margins. Extra care should be taken not to leave sharp wire ends protruding from distal tubes and ligature ties.

Hot or spicy foods should be avoided for the first few days, because they can further irritate sensitive tongue surfaces. Firm, fibrous foods should also be avoided, at least initially. Other foods should be eaten slowly at first, and perhaps should be cut into smaller pieces until the patient adapts to the appliance.

The orthodontist should closely evaluate the patient's speech immediately after appliance placement, because patients with severe speech distortions at this point often take the longest to adapt. These patients will need the most counseling and perhaps the assistance of a speech pathologist.

Considerable counseling may be required during the first days and weeks. Patients should be forewarned about the initial difficulty of making telephone calls and giving verbal presentations.

Patients should be advised to be forgiving of their own speech problems at the beginning of treatment. They should speak more slowly and accept that some sounds such as /s/,/d/,/l/ and /z/ will be hard to communicate clearly for a few days.2,3,6,12

Reading aloud from a newspaper can be helpful, but only if there has not been successful natural adaptation after one week. Excessive practicing too early will aggravate tongue soreness and can make the situation worse.2

Patients should recognize that listeners will notice only a few speech distortions-far fewer than they think they are producing.3

Transpalatal bars and Nance appliances may be needed to reinforce anchorage in some lingual patients. The nature of the lingual technique is uncomfortable for patients. Therefore, one should avoid the use of auxiliaries such as transpalatal arch and Nance appliances along with lingual brackets as far as possible. Mini screws and implants should be considered more often to reinforce anchorage when using this technique.2,17

Bonding of brackets in the upper and lower arch at different appointment can be considered yet another mean of improving patient comfort and the concomitant voice changes.2,12

The smaller the dimensions of the lingual appliance, the less pronounced the impairments. By using lower-profile customized brackets, the orthodontist can significantly enhance patient comfort and reduce impairments of sound performance compared with prefabricated brackets with larger dimensions. However, longitudinal studies comparing the treatment success achieved with customized brackets with that of prefabricated lingual brackets have yet to be published.3

Successful lingual therapy requires considerable attention by both doctor and staff to the patient's personality, pain tolerance, diet, oral hygiene, and speech.All lingual appliances investigated until date has led to significant impairments in sound performance and oral comfort, but with interappliance differences in the degree of impairment.

This study shows that the lingual technique is indeed more demanding on the patients part when compared to its lingual counterpart with respect to speech performance. It thus becomes the responsibility of the orthodontist to inform the patient about the initial difficulties and be sympathetic and supportive during the adaptive phase. "A journey of thousand mile begins with a single step." A good rapport build with the patient at this supporting time will go a long way in deciding the success of the treatment. The clinician must remember that the "TLC"(tender, loving and caring) approach towards the patient never goes unrewarded!