Keith B. Wong, DDS, MS

Invisalign and braces both deliver specific force vectors on teeth to elicit particular movements of teeth.  There are notable differences though, here's a few:

1-Invisalign involves a sequence of clear, removable aligners where as braces involve non-removable brackets/bands in conjunction with archwires that are changed.  This makes Invisalign, for many people, more attractive to their lifestyle.

2-Invisalign delivers specific forces via the elastic nature of the aligner material, however, that material is relatively uniform thickness throughout the aligner, so the range of the various force levels from one area of the aligner to another is relatively small. In other words, you cannot have a very light force in one area and a much higher force in another in the way braces can.  This is because braces lend themselves to more variations in the ways force is delivered (very different archwires can be used, even at the same time).  Also, other types of force modules can be used (elastic modules can move teeth efficiently over longer distances in a given amount of time).  
   The reason it is helpful to be able to vary forces is that different tooth movements need different force magnitudes.  For instance, pushing teeth into (intrusion) or out of (extrusion) the bone requires light force compared to trying to move a molar sideways without letting it tip (translation/bodily movement), which needs much more force.  The fact Invisalign aligners are designed to be removed by the patient also limits how much force they can impart (not too much or you wouldn't be able to get them off), therefore they have difficulty translating teeth efficiently.

3-Invisalign aligners cover the majority of the exposed crown, which gives them a lot of control in three dimensions.  This is great in a case where a front tooth in missing and the space needs to be prepared to be exactly 7.2mm to be ideal functionally and aesthetically relative to the other teeth; this is, however, rather tricky in braces.  Also, Invisalign is superior if you want to move certain teeth and not others.
    This control also has problems.  When it comes to rotating teeth, Invisalign is very slow compared to braces.  For instance, I had a patient with a very rotated lower bicuspid (60 degrees) that Invisalign would have taken 88 weeks to correct.  Instead, we first used three brackets and some elastic modules to correct the rotation in 6 weeks and then started her Invisalign treatment, which took 40 weeks (reducing treatment time by 42 weeks).

    This brings up an important point:  Invisalign and braces are not mutually exclusive.  In fact, it is more useful to think of them as different tools in your orthodontist's toolbox.  Consider a hammer and a screwdriver.  They are both involved in applying connectors (nails and screws, respectively).  In some cases you could use either (making a birdhouse).  In some cases you would definitely prefer one over the other (finish nails over screws for stained wood trim).  But in a complex situation where strength, functionality, and aesthetics are all important (building a custom home with hardwood floors, custom cabinets, beautiful trim details), both screws and nails have their uses.
    This is true in many orthodontic cases.  There are numerous cases that would be "poor candidates" for Invisalign-only treatment, however, only due to one or two teeth that require movements that are difficult for Invisalign to accomplish effectively/efficiently (such as the aforementioned case with the 88 week rotation).  This type of case can be treated ideally using a combination of braces and Invisalign.  In these situations, one can achieve the highest-quality result while still enjoying the aesthetic/lifestyle benefits of Invisalign.

The differences between braces and Invisalign have only been touched upon.  There are many, many more--but you get the point.

Finally, let me acknowledge that there are many cases that, in my opinion, are better treated with braces only; but then again, there are others that would be better treated with Invisalign.

The bottom line:  If you are interested in the possibility of Invisalign, seek out an experienced orthodontist that is also experienced in the specific use of Invisalign, and even better, experienced in the integrated use of Invisalign and fixed appliances (braces) to see what might be the best approach to your particular situation.

Invisalign aligners need to conform to the crowns of the teeth to 1) effect tooth movements, and 2) to stay on the teeth.  The palatal expanders that most orthodontists use need to be connected via bands around teeth or by large surfaces that are bonded to the chewing surface of teeth, making the simultaneous wear of aligners impractical.

I often use palatal expansion devices directly prior to Invisalign aligner treatment, in cases that would benefit from them, however.  This allows the lateral transverse dimension of the upper arch to be increased predictably and much more quickly than using the aligners to do this (thus, the overall treatment length is reduced).  In other cases, I will use the aligners to do this expansion.  Each case has many factors to consider.

The main point:  Invisalign aligner treatment can be supplemented with other treatment modalities in many cases to improve outcomes and reduce treatment length.

In general, it would be a bit rash to say that you are definitively a good Invisalign candidate based upon the very limited information contained in that single photo.  For instance, one cannot see the anteroposterior relationships of your posterior teeth (bicuspids and molars), etc.

It is true that Invisalign is predictably effective in cases with mild dental spacing, mild misalignments (without severe rotations), mildly excessive vertical overlap of the incisors, etc.

I would suggest that you find an experienced orthodontist (that is experienced in Invisalign specifically) near you and contact them for an in depth consultation.  They would then be able to look at your dental alignment in three dimensions,in the context of your facial/smile aesthetics, in relation to your supporting periodontium (gums and bones), and in context to the dynamic movements of your jaw.

Moreover, you could discuss your goals for treatment and they could bring up aspects of treatment that you may not have thought of.

Costs vary between regions and between offices, so I would suggest that you do some local research.  The key is to work with an orthodontist that is experienced with Invisalign and that you feel is interested and aware of your particular goals--someone with whom you can communicate well.

Typically, Invisalign treatments are designed with tooth-movement velocities based on wearing each set of aligners 14 days  Now, orthodontists can modify this as needed case by case.

Assuming that is true in your case, you would finish set 16 on 3/11/14 and then finish set 49 on 6/16/15.  

Please keep in mind that is assuming you are on the "2 week" schedule.  If that seems like a long time, you could always ask your orthodontist about ways to enhance your "tooth movement biology" with technologies such as Acceledent or Propel, which tend to reduce treatment times by 33-50% (depending upon the particulars of your case).  Of course there are pros and cons to consider, such as cost or what the procedures entail, that you would need to evaluate for yourself.

Also, be aware that some cases are best treated with detailing sequences of aligners after the main set, known as refinements.  It is usually the case that indications for refinements are not determined until one sees how the main set of aligners expressed in your mouth (because everyone's bodies react slightly differently).

Retainers are designed to help keep the dental alignment in the desired position.  This includes all three dimensions.  Often, if there is plastic that is made to contact only some teeth but not others, there is some type of vertical control designed into the retainer; you may want to ask your orthodontist if this is the case.

That being said, it is very important that the retainer be comfortable to wear. This is because 1) discomfort may indicate some kind of imbalance of forces on the teeth, 2) will tend to discourage consistent use, which is key to effectiveness of retainers, in general, and 3) we really do not want to cause discomfort when it can be helped!

All in all, the best course of action is to let your orthodontist know about the discomfort, and your questions, then let them address them.