OK got drink in hand.
Here's your info Lil - I found this in about 5 secs by just typing in some key terms to a search engine - this is a few paras from a paper entitled - "The Influence of Breastfeeding on the Development of the Oral Cavity"
which not only states that dummies can damage the development of the oral cavity but that breastfeeding can assist it (the last para specifically answers your question):
"Legovic, 10 listed the merits of human breast milk as compared to artificial feeds to include ideal nutritional content, better absorption, fewer food-related allergies, more favorable psychological development, better immunologic defenses, and a substantial economic advantage. There is another compelling benefit to exclusive breastfeeding: positive effects on the development of an infant's oral cavity, including improved shaping of the hard palate resulting in proper alignment of teeth and fewer problems with malocclusions. The purpose of this commentary is to stimulate further research as well as to propose the importance of breastfeeding to developing and maintaining the physiologic integrity of the oral cavity.
Cranio-Facial Development and the Etiology of Malocclusions
Shepard,19 noted that the largest increments in craniofacial growth occurred within the first 4 years of life, and that craniofacial development is 90% completed by 12 years of age. The flexible and soft human breast nipple tissue is beneficial in shaping the hard palate because it flattens and broadens in response to the infant's tongue action. As the infant uses a peristaltic-like motion to "strip" milk from the mother's nipple/areolar area, the hard palate is gently shaped by the infant's tongue to a rounded U-shaped configuration. A physiologically and appropriately shaped palate aligns the teeth properly and reduces the incidence of malocclusions.
In the early stages of oral cavity development, the palate is almost as malleable as softened wax. Thus, when any object is pressed against the soft bones of the palate, these bones can be molded into a narrow, unnatural shape. This eventually leads to the poor alignment of teeth, and the "V-shaped" palate found in many people with malocclusions. This dynamic also explains how the upper back teeth are pulled inward to cause a mismatch or "cross-bite." Once a malocclusion develops, it can create a domino effect that can damage the rest of the teeth.
Other infant habits, unrelated to feeding, may contribute to malocclusions. Studies conducted by Larsson21,22 concluded that prolonged finger sucking caused an anterior open bite, proclination and protrusion of the maxillary incisors, a lengthening of the upper arch and the anterior displacement of the maxilla. In addition, studies by Bowden,23 Melsen,24 Paunio25 and Ogaard26 found a positive association between the use of pacifiers and malocclusion. The forms of malocclusion described by these authors included crossbite, reduced arch width, lower anterior facial height, rotation of mandibular plane angle, open bite, and tongue thrust swallow."
for full text see -
www.brianpalmerdds.com/bfeed_oralcavity.htm This is an article authored by Dr. Palmer that was published in the
Journal of Human Lactation, Volume 14, Issue 2, pp 93-98,
copyright 1998 by International Lactation Consultant Association.