Synopsis of new findings
This prospective study evaluated the post-sialendoscopy satisfaction by QOL questionnaire results for 37 sialendoscopies in three years. Few studies have focused specifically on the QOL after sialendoscopies; previous specific questionnaires, like the Chronic Obstructive Sialadenitis Symptoms (COSS) Questionnaire , have retrospectively addressed the severity of sialadenitis symptoms in sialendoscopy submitted patients, in seven years period with only 66 patients enrolled and, different from our study, they evaluated a past month clinical period.
Our study differs in the complete and prospective way in which the topic was addressed by specific questionnaires of sialendoscopy, xerostomia and OHIP, before and after the procedure, with a good correlation of the result with sialendoscopy, with findings similar to another prospective study with forty patients and specific questionnaire  and to date, there are no other comparable studies, despite the growing spread of the technique .
Our cohort included most young female patients: 64.5% had sialolithiasis, 35.4% had post-radioiodine; the periodic painful swelling (4.5 times/week), and a long average time until treatment (23.5 months) could have strongly influenced the poor pre-sialendoscopy QOL, once the pre-VAS was 7.42 (p < 0.001). This was anatomically explained by the sensitive gland innervation from trigeminal V3 branches. Our post-sialendoscopy follow-up (14 months) confirmed the successful viability of the sialendoscopy as an organ function-preserving procedure, with a high satisfaction index.
In our cohort, 64.5% of patients suffered from stones obstruction with an average size of 3.77 mm. Nearly 37% were single stones of which 86.5% were successfully treated with sialendoscopy alone, and the remaining with a combined approach. The average time of 139 min (2 h and 31 min), without complications, was comparable with the literature, in the way that some patients (majority with stones and five others with combined-hybrid procedure), have took more time to retrieve the objective, and they took part of the first cases of the study, being interpreted also as a biases; nowadays it took about forty five minutes [5, 46,47,48]. The post-VAS pain scale was 1.3 after sialendoscopy (p < 0.001). There was major satisfaction with the procedure, as 3.45 was the overall satisfaction score (p < 0.001), which mainly correlated with stone size (p = 0.049) and was comparable with only one other similar article  (Tables 1, 2).
Oral health impact profile and sialendoscopy findings
Overall, 80.6% of patients reported improved symptoms after sialendoscopy in the sialolithiasis clinic (p < 0.001) (Table 3). In the OHIP, the physical pain and psychological discomfort domain scores were mostly impacted by salivary obstruction. As these QOL domains were heavily impacted by obstruction, the sialendoscopy provided relief and truly improved psychological discomfort and physical and psychological deficiencies (p < 0.001) (Table 4), similar to recent studies [32,33,34].
Our study limitations were the relatively small number of patients for this amount of time; questionable conclusions due to the interpretation of subjective data on QOL questionnaires, common in this type of studies; the absence of comparative results in literature to ours of specific questionnaires on sialendoscopy; and patient misinterpretation with different types of questions. Nevertheless, our prospective study on post-sialendoscopy satisfaction found high score QOL correlated with stone size.
In our correlation analysis (Table 4), we found a positive correlation with calculi size, that is, larger sialolithiasis and better sialendoscopy satisfaction (p = 0.049). We found the best correlation with question 46 (unable to enjoy people's company) of OHIP, where r = − 0.660. This negative r-correlation shows, inversely, a greater satisfaction with sialendoscopy, as demonstrated in the QOL questionnaire.
In Table 3, the salivary stone symptom correlated with Good satisfaction (p = 0.022) and overall Good satisfaction with sialendoscopy for obstructive disease (p < 0.001), demonstrating the efficacy of sialendoscopy in relieving pain and an enriching QOL.
In Table 4, other significant Very Good correlations of sialendoscopy included the following: OHIP: questions 3, 21, 25, 36, 45, 47, and total deficiency, meaning that OHIP questions prior to sialendoscopy (such as tooth problems, psychological discomfort, depression, and an unsatisfying life) have a strong correlation with Very Good satisfaction after sialendoscopy procedure. This mainly reflects the patient mental status improvement after relief of pain and resolution of the obstructive salivary problems.
Similar results are shown in Table 5, with respect to the satisfaction answer: Very Good/Good and Satisfying/Bad. The main differences occurred on question 17 (p = 0.041), question 45 (p = 0.014), and question 46 (p = 0.002), implying good correlation after the sialendoscopy, in which the procedure ameliorated in some way the prior symptoms.
Xerostomia and sialendoscopy findings
We found good correlation between sialendoscopy satisfaction in Q5 (p = 0.025), Q6 (p = 0.031), Q10 (p = 0.044), Q14 (p = 0.030), Q15 (p = 0.013), and Q18 (p = 0.003) (Table 4). This showed that worries prior to the procedure were positively associated with resolution and satisfaction after sialendoscopy. These findings lead to conclude that when the patient felling of xerostomia were mainly due stenosis problems of various etiologies, the sialendoscopy are the main mean of treatment, similarly to others studies [33, 49].
However, in Table 5, we found a negative correlation between Xer and sialendoscopy satisfaction, where the total score was 46.5 Satisfying/Bad versus Very Good/Good (p = 0.009). These results demonstrated no correlation in sialendoscopy satisfaction, similar to the literature, specifically on cases of mixture of secondary or main duct stenosis, radioiodine treatment for thyroid cancer, and salivary production deficiency, common findings in auto-immune diseases, diabetes mellitus, tobacco smoker and antidepressant medication users [8, 11, 20, 25, 26, 31].
These contradictory results could be explained by the fact that the main disease that determined the stenosis is the same on salivary tissue and acini destruction. As the Poiseuille’s law, these alterations (quality of saliva as viscosity, volume of saliva production determining the pressure gradient across the tubing, duct length and duct diameter) altogether contribute to decreased salivary production and flow; and since the sialendoscopy is a procedure that ameliorate the diameter of the duct, facilitating the saliva flow, it affects only the flow part of equation . Everything else of the salivary production is not achieved and solved by sialendoscopy, and therefore, the final result is the poor satisfaction expressed by patients along time [30, 33]; other explanations are patient misunderstanding, method limitations and the relatively few subjects on the study.
Our findings support the evident first indication of sialendoscopy for obstructive sialolithiasis treatment and probably a relative time-dependent indication for stenosis/other xerostomia causes due the re-incident nature of the strictures. The positive impact on QOL is clearly evident on the sialolithiasis and barely satisfactory in the stenosis; as result, the surgeon must precisely evaluate the time of each case indication.
The positive satisfaction of sialendoscopy for pain relief in obstructive disease, mainly due to stones while conserving the salivary gland, reaffirms the indication of sialendoscopy as the first alternative for obstructive salivary lithiasis.
Our results can assist clinicians with the appropriate patient selection for sialendoscopy treatment. Additionally, they introduce a new question: When is the best time to indicate sialendoscopy in cases of obstruction due to strictures, where the main cause is inflammation (radioinduced, autoimmune sialodenitis)? Should it only be when they are symptomatic? Or should it be indicated early in the context of the disease? Perhaps more multi-center, prospective studies, with a greater sample size could address this question.
The main goal of the study is to apply these results in our daily clinic, selecting the better temporary moment to perform the procedure and not simply proposing the sialendoscopy act. Our results will help to choose the moment at which sialendoscopy will be indicated as the definitive treatment for obstructions by stones, preserving the gland and getting better QOL, or indicating as "palliative" treatment in cases of inflammatory strictures, expecting a poor improvement on QOL.