# Oral Impacts of Aligners versus Fixed Self-Ligating Lingual Orthodontic Appliances
## 4 Discussion
The present study demonstrated significantly worse scores in the patients wearing SLLA for discomfort in swallowing, mouth opening, food remaining in the oral cavity and tongue injuries, even three months after the beginning of treatment. The above results are similar to the findings of two other prospective studies which demonstrated that lingual appliances were associated with the greatest oral and general dysfunction [17; 36]. However, after the initial discomfort period, these hindrances persisted only in a small percentage of lingual orthodontic patients [36]. In the above-mentioned studies, the groups and the observation periods were not the same, nor were the types of lingual appliances; thus, the results are not directly comparable. According to a systematic review, eating difficulties were more commonly reported in patients with lingual appliances than in patients with buccal appliances, and mainly during the first month of insertion [31]. An interesting finding, not present in the orthodontic literature, was that aligner patients presented with subtle injuries on the lip and cheeks immediately after the initiation of treatment, although these disturbances ceased at the 3-month re-evaluation. This finding may be associated with the use of power ridges for torque (power ridges were used in 57% of the present aligner sample) or precision cuts for elastics (in 9.5% of aligner patients, precision cuts were used), or in some cases, with sharp or rough edges of the aligners that were not noted at the insertion of the appliances. To date, most studies on aligners have rarely provided data on the presence of power ridges, precision cuts and attachments used; therefore, the comparability between such studies is rendered difficult [37]. Furthermore, sleeping disturbances were more common in the present group of lingual appliances at T0, a finding in agreement with the prospective study of [PERSON] et al. [17]. Sleeping disturbances persisted for up to 3 months in our study; however, results did not differ between the two groups. Similar sleep patterns were reported between patients treated with lingual and buccal appliances [30]. This is the first study to compare speech disturbances between self-ligating lingual appliances and aligners for a medium-term time period. Both groups presented minor speech impairment, which recovered after three months. It has been reported that both aligners and lingual appliances induce alterations in speech, because the contact area of the tongue shifts based on the presence of an unfamiliar appliance on the lingual surface [36; 38; 39]. In the aligner group of the present study, the impairment in some consonants (\"s\" and \"z\") was slightly more pronounced; however, this difference was clinically non-significant. The \"s\" sound was most affected, probably because the alveolar fricative is sensitive to morphological changes in the maxillary incisors [40]. The less pronounced impairments of \"s\" and \"z\" with self-ligating lingual appliances used in this study may be associated with the smooth spring clips. The possible effect of different clips/designs of lingual appliances on speech should be further investigated. The questionnaire used in the present study included a subjective question regarding self-speech assessment. Interestingly, the patients felt that their speech was more strongly affected, compared to the alterations identified by the professionals. Even at T3, 32% of the present sample reported subjective speech difficulties, more often in the lingual appliance group. A recent study reported speech impairment of different degrees of severity in half of a patient sample treated with aligners [39]. Moreover, one-quarter of the lingual patientspresented speech difficulties even after three months [36], and they faced more speech difficulties compared to patients treated with buccal appliances [33]. The present study presents certain limitations.