Below is a basic script to lockout Content Database for new site collections.  It sets the max to current sites count and warning to less than 1 of count.  May help someone.

$ALLDB = Get-SPContentDatabase
foreach($DB in $ALLDB)
{
    $Count = $DB.Sites.Count
    if($Count -gt 0)
    {
        $CountWarnining = $Count – 1
        Set-SPContentDatabase $DB.Name -MaxSiteCount $Count -WarningSiteCount $CountWarnining
    }
}

Get-SPContentDatabase | Select Name, Current*, Max*, WarningSiteCount | Out-GridView