Now consider that the same fate may befall a number of genes during an inbreeding program. There is no magic formula for regaining what you have lost. You must start again. About the only animals that are routinely inbred to a high level are laboratory mice and rats. There, the breeders start breeding many lines simultaneously in the expectation that the majority will die out or will suffer significant inbreeding depression , which generally means that they are smaller, produce fewer offspring, are more susceptible to disease, and have a shorter average lifespan.
Dogs are no different.
However, dog breeders generally don't have the resources to start several dozen or more lines simultaneously. If that is not sufficient to discourage you, then consider the following. During the past 25 years, geneticists have been going out and measuring genetic diversity in natural populations directly by looking at the DNA or proteins, rather than at the phenotype. The have found that many individuals that cannot easily be distinguished by their phenotypic appearance nevertheless have considerable differences in their genotype. This came as a considerable surprise, as the expectation was that even those alleles that only reduce function marginally should, over time, be selected against in the real world.