Can a new dentist be untruthful to you when showing you your dental xrays, saying that you have 10 small cavities, when 6 months ago only had one.

Likely have 10: Anyone can lie. Dentists as a profession are ranked as one of the most trustworthy and honest. Sight unseen you probably have all those cavities. Sometimes it's subjective when to fill small ones. It's aways better to be proactive!, than to let small ones go and have big problems later on.

???: I assume there is always the possibility that a person, including a dentist could be misleading you. Ask for a copy of your x-rays and get a second opinion. Good luck.

Perhaps: I'd prefer to think that this is more a difference of opinion. You may have some incipient cavities (very small, only in enamel). Some dentists monitor these while others prefer to restore these to prevent them from getting bigger (in their opinion). There's a new procedure whereby these incipient cavities can be sealed with a resin to remove the "softer" enamel and seal the tooth.

Early Detection: New technology enables dentists to detect decay earlier then in the past. It is possible that the dentist with the newer equipment is actually going to preserve more tooth structure by early intervention (smaller hole). Laser detection (diagnadent) and sopra fluoresence are some of the newest tools I have in my practice for early intervention. If very early, Fluoride mineralization is best.

Cavity Detection : The models of how decay forms have changed. Before fluoridation, decay formed at the tooth surface and progressed inward making it easier to feel a difference in hardness of the tooth surface as the enamel softened from decay. However, since fluoride, decay forms from the bottom of the tooth grooves and moves pward. Harder to detect. A laser cavity detector you will find 70 % of cavities missed.