188 GENERAL DISCUSSION ligatures were used required additional treatment after 2-DL. However, these numbers are too small to draw definitive conclusions, and it should be noted that recurrence was also observed after 2-DL with vascular clips instead of ligatures. Another potential route for alternative salivary pathways is backflow through the duct of Bartholin. When the submandibular duct is clipped distally to the duct of Bartholin, one could expect submandibular saliva to find its way into the duct of Bartholin and eventually drain into the floor-of-mouth via the ductuli of Rivini.31, 52 There is, however, also an argument to be made against the ‘alternative salivary pathway’. Namely, chapter 8 showed only little effect of submandibular gland extirpation (SMGE) after unsuccessful 2-DL. Recurrence and treatment failure could alternatively depend on multiple, yet unidentified, clinical variables like epilepsy, poor gross motor function, lack of speech, anterior open bite, poor posture, head balance, dysfunctional oral motor control, or gross motor function. This thesis shows that age (younger), anteflexion (poor posture), and a very severe speech disorder increase the risk of 2-DL treatment failure. Moreover, there were significantly more cases with severe dental malocclusion and serious speech disorders who required reintervention after submandibular duct surgery compared to a reference cohort in chapter 8. Furthermore, rat studies have shown contralateral salivary gland hypertrophy after unilateral parotid duct obstruction.58 This suggests that 2-DL treatment failure could be a result of compensatory hypersalivation.56, 59-61 Obviously, in bilateral treatment this compensatory hypersalivation would have to arise from the parotid or accessory salivary glands. This, however, would fail to explain why similar recurrence is more rarely seen following gland excision than after ligation. Contralateral compensatory submandibular salivation is not expected to contribute to recurrence rates of successful bilateral submandibular duct ligation. Yet, there may be compensatory salivation from other salivary glands (parotid, sublingual, or minor salivary gland), which leads to recurrence after submandibular 2-DL. This, however, does not explain why a similar degree of recurrence is not seen after submandibular gland excision.
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