During the eruption of new teeth, a baby is said to be cutting new teeth or {teething}. Whilst teething, children are often irritable, fretful, they may develop flushed cheeks, dribble & want to gnaw on hard objects. The lower middle or front {incisor} teeth are the 1st to appear, usually at 6mths. The last baby teeth have erupted usually by 3yrs.
Most dentists agree it's not {teething} causing problems. At 6mths, when front teeth appear, a baby loses infection immunity received from mother prior to birth. For a short time (coinciding with teething), a baby is prone to minor infections, until its own immunity develops. Babies rarely suffer teething problems when back teeth erupt, as their immune system has started operating.
Teething can be painful, & gums & oral cavities may become inflamed. However, teething gels are available which contain an {antiseptic} & {local anesthetic} which can provide rapid relief. It's important to ensure such gels are free from sugar. Your dentist will advise on a suitable product. Solid teething rings can also provide relief for a teething baby. If in doubt seek medical advice.