Hey...uh, I saw you posted this in two different threads....kinda, but I'm just gonna answer here. I volunteered at Kaiser eons ago, and they aren't big on one month volunteerism, and yes that does look a bit weird.
I didn't say volunteering doesn't matter at all. Some schools, like Arizona and UMASS, are really attracted to students with a truly altruistic background. So it depends on the school how much they choose to emphasize it. However, in general among dental schools...
(warning...generalization coming)
...whether you volunteer 50 hours total or 250 hours total, isn't going to make or break you as a applicant. Given two identical, separated, siamese twin applicants...down to personality and personal statement...then the added 200 hours might make a difference. The type of volunteering can also make a difference. Some schools might think volunteering at a homeless shelter for 500 hours isn't something they find interesting in candidates and would have preferred you volunteered 40 hours at a local dentist office. Some might think 40 hours at a dental office isn't really any time at all and might prefer you worked 150 hours with the red cross...who knows. All I know is that most of the friends who have gone to interviews have said that they didn't ask much about their volunteer experiences unless it really stood out (like they spent 2 years to set up the first grant-run, 800 chair, non-profit, dental clinic in Namibia)
However, some schools do have minimum requirements on dental observation hours. UOP says 20+, and others have other varying degrees of hours they feel you should have been exposed to dentistry, so volunteering in a dental office or clinic can be a good way to rack up observation hours that are required. I volunteer at offices and it works great. I couldn't imagine standing over a dentist's shoulder for 20 hours watching crown prep after crown prep. Instead I volunteer in the office and help out with filing, seating patients, sterilizing, x-rays, cutting trays etc. And when an interesting case comes into the office, the dentist grabs me and says "Hey Jeff, wanna see something kinda cool you might not ever see in dental school?" and sometimes he lets me assist even though he's then paying his assistant to just stand there and watch me do her job. I've easily racked up enough observation hours to satisfy any school and also learned a lot about the ins and outs of small dental practices to boot.
I realize this isn't everyone's case. A lot of predents grew up with close family friends who were dentists and have worked in offices all their lives, but I'm a career changer. I have no family in dentistry and had no prior experience in dentistry before deciding to become a dentist, so I just went out and started asking to help out to see what the field was like and help out my application as well. It's worked out cause now I have a paid job in a dental office...albeit a lot less well paid than my last career, but that job totally sucked ba;;s like a two dollar *****.