In the context of this series, a cavity is a metaphor for harbored emotions rooted in memories. Inside the cavity is a broken watch, an object taken from a specific memory of mine, it also acts as a symbol for exclusive insecurities.  Our personal childhood narratives are a part of all of us and often shape who we may become.  Although, we do positively grow out of some of the events and memories, others become permanent and solidify into our consciousness often affecting our attitudes and behaviors. 
Personal mental growth and health relies heavily on social interaction. Our mouths are a main vehicle for which social interaction can occur.  Attachment issues are conveyed through the depiction of opening ones mouth.