Without a doubt, the best way to eliminate brown stains in between teeth from smoking is TO STOP SMOKING. When smoking is not an issue, there are many ways to remove these stains. Thorough brushing with a high quality toothpaste can remove most stains. A professional cleaning will remove what you miss. Whitening is not the best solution. It will have an effect, but these whitening products are best suited to lighten overall tooth color. They do in part remove stains, but that is not die true function. Best to quit the habit, you may find the brown in between the teeth disappears
When a tooth is chipped as a result of constantly banging into the opposing tooth, restoration can be a challenge. Bonding material can be carried up to the esthetic edge, but must be reduced to keep it out of the occlusion. If the restoration hyperoccludes, it will fracture. In your case and based on your description, either the bonding can be removed and replaced or the tooth prepared for and a veneer placed.
In general, I do not believe that chipped teeth need to be leveled prior to veneer placement. Sometimes the biting edge of the tooth may be reduced in order to have the veneer wrap over and replace the incisal edge. Minimal surface reduction needs to be balanced with veneer thickness so that enough surface area is preserved to maximize bonding and material strength.
Yes, it is very common to use a "temporary" cement over a "permanent" ement when placing a crown on an implant abutment. Retrievability is one of the most common reasons. The abutment is held onto the implant body by a screw. If the screw breaks, then we would want to have the ability to remove the crown easily so that the screw can be replaced. Most implant cements are closer in formula and strength to temporary cements just for this reason. The tolerance or acuracy of fit of the implant crown to the abutment it sits on superior to that of a standard crown cemented to a prepared tooth. It is this close fit that generally hold the crown, not the cement. In some cases, I have seen water or saliva bind the crown to the implant abutment.
Nothing in life lasts forever! Not even dental veneers. Potential replacement after 20 years, as you suggest, is not a reason to avoid having them done now. You may invest in a car, drive it for 20 years and then decide it is time to replace it. Your new car will be another investment, but not necessarily a reason to forego a car today. High quality veneers prepared and placed by a skilled dental professional will last a long time. The aesthetic results and positive effects on self confidence are well worth the investment for most patients.
