Dentists say not to rinse after brushing, just spit. could this cause excess fluoride intake especially if you have breakfast soon after brushing?

After brushing: Technically it's best not to rinse out after brushing as it washes away more of the fluoride that would remain from the toothpaste. Eating the right foods, avoiding sticky starchy sugary foods and following proper tooth brushing and flossing techniques AFTER meals is probably the best way to avoid cavities. You should use the minimal amount of toothpaste & no then worries about excess fluoride.

Reverse ur technique: Growing body of evidence says acidic food, such as your morning OJ, can slightly demineralize tooth enamel. Suggestion is that you either brush before b'kfast, or wait a full hour after eating, to brush. Use pea-sized portion of t'paste. Spit, don't rinse. Make sure to floss or Water/Pik daily. Fluoride intake will be minimal.