It is not recommended or required to open the place packs such as Contrac Rodent Pellet Place Pacs Rodenticide. Gnawing and chewing paper, cardboards, etc is a natural behavior when rodents are in search of food or nesting supplies. 

Contrac can make a pet sick, but every veterinarian has the antidote.  Contrac is actually a good product if a pet gets into it because the antidote is vitamin K and easily accessible.  You should definitely call your vet immediately and probably have the dog looked at just to be safe.

The size of teeth will vary from mouse to mouse, just like our teeth are all unique.There are four basic steps to eradicating mice. 1.) INSPECTIONMice may live alone or in groups. In order to assess the severity of the problem and to get a better idea of where to bait and trap, you will first need to perform a thorough inspection of the premises. What you'll want to look for are any signs that mice are present, including: droppings, tracks, gnaw marks, urine stains, live or dead mice, and mouse sounds. Take note of where the highest concentration of signs are found so that you can concentrate further preventative and control measures in those areas. 2.) SANITATIONSanitation is probably the most important measure of prevention and control in combating any pest or rodent problem. While good sanitation will not eliminate hosue mice, poor sanitation will certainly attract them and allow them to thrive in great numbers. Remember that the house mouse must have access to a ready supply of food, water, and nesting materials to thrive. Sanitation measures should focus primarily on reducing these stores. To reduce house mouse populations, try the following sanitation measures: Store any bulk food items in large metal containers or other airtight containers with tight fitting lids, rather than bags or boxes that can easily be gnawed through. Remove clutter such as paper and cardboard that mice might use to build their nests Remove undesirable vegetation around your home such as grass clippings and weeds Keep dog food or other pet food stored in a Rubbermaid container overnight. 3) EXCLUSION Mice can enter homes and other structures through openings as small as ¼ inch. They may also enter through ill-fitted doors, windows, or screens, and air vents that are not in sound or working order. While you will not reasonably be able to compensate for every possible entry, you can greatly reduce the ease of entry for mice (and thereby, reduce the population size) by taking the following measures: Seal any openings ¼ inch or larger with caulk, wood, mesh, or other appropriate materials Floor drains and sewer pipes should have tight-fitting grates with openings less than 1/4 inch in diameter. Make sure that all doors, windows and screens fit tightly in their frames and repair those that do not. (It might also prove helpful to cover edges of screens with sheet metal to prevent rats from gnawing around them.) 4) POPULATION REDUCTIONWhile you are preventing future mouse population growth through inspection, sanitation, and exclusion, you will also want to begin working towards elimination of the population that is already present through trapping and baiting. Trapping is the preferred method of control in homes where relatively few mice are present. The following are some advantages of trapping when compared to baiting: 1) Trapping does not require the use of harmful poisons 2) Trapping allows the user to know whether the mouse was killed, whereas with baiting the mouse will wander off and die somewhere else 3) Trapping eliminates odor problems by allowing you to dispose of the carcass. Use enough traps to eliminate the house mice quickly. Traps should be placed flush with walls in areas of highest travel (as determined by Inspection). Baiting. This method uses poisons, or rodenticides, to attract and kill mice. This is a great supplementary treatment to trapping when you are dealing with larger rodent populations, or for outdoor populations. House mice sniff out the bait and return to feed upon it continuously until the poison kills them. A few baits are even strong enough to cause death with a single feeding. You will know the bait is working when the bait is no longer being consumed. This means there are no more mice to feed on it because they are dead. Always be sure that fresh bait is available continuously until mice stop feeding.