Some parents swear that the dummy is a lifesaver. But there can be some downsides. Here are some points to consider before introducing a dummy.

Sucking seems to have a soothing and settling effect on babies. Sucking a dummy helps some babies settle.
There is no evidence that dummies cause serious health or developmental problems in infants. Dentists tend to be concerned about dummy use only when a child’s adult teeth are coming through.
Early weaning
There is an association between dummy use and early weaning. But there is increasing evidence that dummies do not cause nipple confusion in breastfed babies and are not the cause of early weaning of babies. It seems more likely that mothers who are experiencing difficulties with breastfeeding use dummies as a weaning tool.
SIDS
Some studies have reported a link between the use of dummies and a lowered risk for SIDS. But the reason for such a link is unknown, and not all researchers believe that the research is conclusive.
Earache
There is a debate among researchers about whether dummy use is associated with a higher incidence of middle ear infections. As yet, the evidence is not strong enough to recommend that parents do not use dummies for this reason alone.
There are downsides to dummies:
Eventually, your child will have to part with the dummy. Children who’ve had their dummies for some time are likely to be very attached to them. This means that giving up the dummy might not be easy.
Sucking the thumb or fingers is normal and common. An advantage over dummies is that babies can find their own fingers easily when they need them. But you can’t ban fingers when your child gets bigger, and some parents prefer the idea of giving up a dummy to the prospect of a finger-sucking habit developing. Luckily, most kids give up finger-sucking all by themselves.
To ensure that dummy-sucking does not interfere with feeding, it’s best to offer it only when you can be sure your baby is not hungry, such as after or between feeds.
American Academy of Pediatrics (n.d.). Thumb Sucking and Pacifiers. Retrieved 8 January 2010 from http://www.healthychildren.org/English/ages-stages/baby/crying-colic/pages/Pacifiers-and-Thumb-Sucking.aspx?nfstatus=401&nftoken=00000000-0000-0000-0000-000000000000&nfstatusdescription=ERROR%3a+No+local+token.
American Academy of Pediatrics, Task Force on Sudden Infant Death Syndrome (2005). Policy statement: The changing concept of Sudden Infant Death Syndrome: Diagnostic coding shifts, controversies regarding the sleep environment, and new variables to consider reducing risk. Pediatrics, 116, 1245-1255.
Callaghan, A., Kendall, G., Lock, C., Mahoney, A., Payne, J., & Verrier, L. (2005). Association between pacifier use and breast-feeding, sudden infant death syndrome, infection and dental malocclusion. International Journal of Evidence-based Healthcare, 3(6), 147-167.
Collins, C. T., Ryan, P., Crowther, C. A., McPhee, A. J., Paterson, S., & Hiller, J. E. (2004). Effect of bottles, cups, and dummies on breast feeding in preterm infants: Randomised controlled trial. British Medical Journal (329)7459, 193-196.
Kramer, M. S., Barr, R. G., Dagenais, S, Yang, H. Jones, P., Ciofani, L., & Jané, F. (2001). Pacifier use, early weaning, and cry/fuss behavior: A randomized controlled trial. Journal of the American Medical Association, 286(3), 322-326.
Niemelä, M., Pihakari, J., Pokka, T., & Uhari, M. (2000). Pacifier as a risk factor for acute otitis media: A randomized controlled trial of parental counseling. Pediatrics, 106, 483-488.
Niemelä, M., Uhari, M., Koepsell, T. D., Johnston, B.D., Grossman, D. C., W. Weiss, P. P. W., Wellington, M., Breese Hall, C., Ebel, B. E., Feinglass, S. R. (2002). Pacifier as a risk factor for acute otitis media. Pediatrics, 109, 351-353.
North, K., Fleming, P., Golding, J. and the ALSPAC Study Team (1999). Pacifier use and morbidity in the first six months of life, Pediatrics, 103, 34-41.
O'Connor, N.R., Tanabe, K.O., Siadaty, M.S., & Hauck, F.R. (2009). Pacifiers and breastfeeding: A systematic review. Archives of Pediatrics & Adolescent Medicine, 163 (4), 378-382.
Olinto, T. A. & Weiderpass, E. (1997). Pacifier use and short breastfeeding duration: Cause, consequence, or coincidence? Pediatrics, 99, 445-453.
SIDS & Kids (2005). Pacifier/Dummy use: Information statement. Retrieved 25 April 2006 from http://www.sidsandkids.org/documents/05Pacifiers2.pdf.