5 months old is far from "extended" use of the bottle! Now that I've seen this question, your other question also makes a lot more sense.
There is evidence that indicates babies fed with breast milk are less likely to develop early childhood caries (cavities), as well as a number of other diseases. Many breast-fed babies also use bottles while mom is away. It is likely the difference is not in the use of the bottle, but in the milk served through the bottle.
However, breast milk is not an option for everyone and since your child has not been on breast milk for this long already, I don't understand why your doctor would be so insensitive as to point that out now and not give you ideas for other kinds of prevention of these issues. Many people will talk about "baby bottle tooth decay" but the problem is not really with the bottle, rather it is with oral hygiene.
There are also problems related to mouth shape and alignment as well as alignment of the teeth the American Academy of Pediatricians points out as possibilities when bottle use is continued after 18 months!! Again, why your doctor would encourage you to do away with the bottle at this point is strange unless there is some special circumstance about your baby with which we are not aware.
I believe in listening to doctor's advice!! However, Doctors are humans and do make mistakes too Therefore, I strongly recommend, getting a second opinion Find a doctor with whom you are comfortable enough to ask questions and who will then give you answers.
In regard to the tooth decay issue:
Pediatric dentists recommend against extra night-time feedings (including with breast milk) or unlimited access to drinks of any kind other than water because:
Frequent night time bottle feeding with milk is associated with, but
not consistently implicated in, ECC. Breastfeed- ing greater than
seven times daily after 12 months of age is associated with increased
risk for ECC.
My Child's dentist and hygienist recommended wiping her teeth and gums with a gauze square after each feeding (even the night-time ones) to wipe away the bacteria that cause decay as well as those that cause gingivitis.
You mention that you use a sterilizer, but humans have bacteria that lives in our mouths and is just there too. Even kissing baby introduces germs into the mouth and so since they are there, good dental hygiene will keep their over-population (and resulting maladies) at bay. The following is an excerpt from the same previously quoted article and also applies.
Oral hygiene measures should be implemented no later than the time of
eruption of the first primary tooth. Cleansing the infant’s teeth as
soon as they erupt with a soft toothbrush will help reduce bacterial
colonization. Tooth- brushing should be performed for children by a
parent twice daily, using a soft toothbrush of age-appropriate size.
Flossing should be initiated when adjacent tooth surfaces cannot be
cleansed with a toothbrush
Because having a relationship with a Dental care professional can be so helpful in a child's dental health and emergence of good habits in this matter the AAPD also recommends finding a "dental home" by the time your child turns one. You aren't at the stage yet, but meeting with a pediatric dentist, may help to put your mind at ease - even now.
The initial visit should include thorough medical (infant) and dental
(parent and infant) histories, a thorough oral examination,
performance of an age- appropriate tooth brushing demonstration, and
prophylaxis and fluoride varnish treatment if indicated. In addition,
assessing the infant’s risk of developing caries and determining a
prevention plan and interval for periodic re-evaluation should be
done. Infants should be referred to the appropriate health
professional if specialized intervention is necessary. Providing
anticipatory guidance regarding dental and oral development, fluoride
status, non-nutritive sucking habits, teething, injury prevention,
oral hygiene instruction, and the effects of diet on the dentition are
also important components of the initial visit. Oral hygiene:
The quotes above are cut from this article.
Finally: One can find discussion about how use of bottles and pacifiers can cause misaligned adult teeth, but all of what I can find online refers to this as a problem for kids that continue use after 18 months at the earliest. Even the AAP doesn't specify what these problems actually are though. The most specific statement in this regard that I found was on the Colgate Page! and said:
During a child's first few years, sucking habits probably won't damage
his or her mouth. But frequent and long-term sucking can cause
problems. This is especially true if the habit continues after baby
teeth start to fall out. Long-term sucking can cause:
The top front teeth to slant out
The bottom front teeth to tilt in
The upper and lower jaws to be misaligned
The roof of the mouth to be narrower side to side
Boldfacing is my addition because I wanted to highlight how late we are talking about here. 5 months is very soon to be worried about sucking habits causing alignment problems down the line.