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One time probably didn't do a lot of damage but the general recommendation for the future is to wait around 40 minutes or more after having acidic food before brushing. Noticable damage occurs with chronic use. We see damage in people who suck on lemons, and grapefruit, and also people who have chronic reflux with stomach acid coming into the mouth. Having more acid is not the way to get rid of reflux. I am not an MD but I have reflux and Ranitidine/Zantac is good for flare ups as well as Tums/Rolaids. If it is a chronic issue your MD or Gastro may want to put you on a Proton Pump Inhibitor like Nexium or Prilosec.
Months or years of doing it depending on susceptibility of your teeth. Enamel loss cannot be recovered but I doubt you have made significant difference after one time. Sensodyne or similar toothpastes with Potassium Nitrate will help with sensitivity. FYI It takes 2 weeks to have full effect and has a bad aftertaste. If the rough feelings continues I suggest a cleaning at a dental office. Everyone should have a yearly dental exam
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