Objectives: Rubber dams increase the quality and safety of dental treatment. However, the condition of a rubber dam over an open mouth may also obstruct the route for respiration. We tested whether an open mouth with or without a rubber dam would affect upper airway patency and breathing pattern. Materials and methods: Twenty young healthy volunteers were imaged with a magnetic resonance (MR) system under three conditions: mouth closed, mouth open, and rubber dam with mouth open. Respiration was concurrently monitored with plethysmography. MRI slices of the upper airway were obtained at 5-mm thicknesses, and the size of the cross-sectional area of the upper airway was measured by image analysis software. Respiratory cycle duration and tidal volume were also measured with digital signal analysis software. Results: The volume of the upper airway became significantly decreased with the mouth open. Analysis of each cross-sectional area of the upper airway revealed that while the oropharyngeal area was significantly narrower with an open mouth, the retropalatal and hypopharyngeal areas were not affected. Placing a rubber dam had no additional influence on upper airway patency but was seen to significantly shorten mean respiratory duration and decrease tidal volume. Conclusions: Open mouth position plays the largest role in decreased upper airway patency, and open mouth position with a rubber dam may further disrupt breathing pattern. Clinical relevance: Breathing pattern may become deteriorated by airway obstruction during dental treatments requiring a rubber dam.
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