Background: The intensity and duration of speech difficulty inherently associated with lingual therapy is a significant issue of concern in orthodontics. This study was designed to evaluate and to compare the duration of changes in speech between labial and lingual orthodontics.
Materials and methods: A prospective longitudinal clinical study was designed to assess speech of 24 patients undergoing labial or lingual orthodontic treatment. An objective spectrographic evaluation of/s/sound was done using software PRAAT version 5.0.47, a semiobjective auditive evaluation of articulation was done by four speech pathologists and a subjective assessment of speech was done by four laypersons. The tests were performed before (T1), within 24 h (T2), after 1 week (T3) and after 1 month (T4) of the start of therapy. The Mann-Whitney U-test for independent samples was used to assess the significance difference between the labial and lingual appliances. A speech alteration with P < 0.05 was considered to be significant.
Results: The objective method showed a significant difference to be present between the two groups for the/s/sound in the middle position (P < 0.001) at T3. The semiobjective assessment showed worst speech performance in the lingual group to be present at T3 for vowels and blends (P < 0.01) and at T3 and T4 for alveolar and palatal consonants (P < 0.01). The subjective assessment also showed a significant difference between the two groups at T3 (P < 0.01) and T4 (P < 0.05).
Conclusion: Both appliance systems caused a comparable speech difficulty immediately after bonding (T2). Although the speech recovered within a week in the labial group (T3), the lingual group continued to experience discomfort even after a month (T4).
Keywords: Articulation; labial orthodontics; lingual orthodontics; spectrography; speech.