Answer: You'll first want to determine just why it died. Is it possible that dog urine has killed it? Or might it be under or over-watering? Or, it could be diseased. Without knowing what the hedge plants are and whether or not they've been exposed to salts from dog urine, it's difficult to make any recommendations. If you submit another question through this forum with more details, we may be able to make some suggestions.
Best wishes with your landscape!
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