How can alterations

There are several books you can look at. 

'Change Your Smile' by Ronald E Goldstein DDS (Quintessance) can be bought from Amazon - it is full of amazing photos of before and after every type of treatment, showing what is possible. 

Amazon has lots of other titles which we have not looked at:- 

The Perfect Smile:  The Complete Guide to Cosmetic Dentistry by James Doundoulakis

Atlas of Cosmetic Dentistry: A Patient's Guide by Mark Landau

Billion Dollar Smile: A Complete Guide to your Extreme Smile Makeover by Bill Dorfman, Paul Lombardi

to name three

regards, the Allaboutteeth Team

Colour

Tooth colour is most commonly what people see first. As you get older, your teeth get darker. Darker teeth are associated with older age. The easiest way to correct this is by tooth whitening. But over bleaching can create an unnatural-looking appearance.

Size and Shape (also look at occlusion)

Size and shape of teeth change over time. This is usually tooth wear, from tooth-to-tooth contact, or grinding. This can change your tooth to lip ratio and you stop seeing your teeth at lip rest. 

If the cause is due to wear of the teeth, dental veneers or dental crowns can be used to regain the lost length and fill out the smile. The treatment can vary from teeth bleaching to dental crowns or dental veneers.

Depending on the severity, other forms of treatment such as braces, implants and gum surgery also may be used to enhance the appearance and function of your teeth.  Supporting soft tissues can be replaced in the correct areas in your mouth improving your smile hugely.  (This can be done by surgical grafting as well).