Shameena tells us ways to improve our smiles. In the second part of the three-part story, she tells us about dental bonding, teeth whitening and bleaching, along with its advantages and disadvantages, in the weekly column, exclusively in Different Truths.
Last week, we learned about dental veneers. Let’s now understand what dental bonding is. The term bonding is used in dentistry to describe permanently attaching dental materials to your teeth using dental adhesives and a high-intensity curing light.
Direct Composite Bonding
Dentists use tooth-coloured composites (white or natural-looking materials) that they have in their offices to fill cavities, repair chips or cracks, close gaps between your teeth and build up the worn-down edges of teeth. Dentists place the materials in or on the teeth wherever needed.
Because direct composite bonding involves the precise placement of restorative material by the dentist, the direct composite bonding procedure usually is completed in one dental visit. More complicated or extensive treatments may require additional visits. However, there is usually no need for temporaries or waiting days or weeks for laboratory restorations.
The same composite materials also may be directly applied and sculpted to the surfaces of teeth that show most prominently when you smile, for minimally invasive smile makeovers. While dentists call them direct composite veneers, many people just refer to them generically as ‘bonding’. Composite bonding usually is an ideal and less expensive solution for people with chips, gaps between the teeth, staining and discolouration, slight crookedness and misshapen teeth.
Although direct composite veneers typically require minimal preparations, no mould-taking and no temporaries, the artistic skill and precision of the dentist you choose will determine the exact manner in which your direct composite veneers are created. For example, some dentists use putty stents based on an impression of the patient’s teeth and a model of their desired smile to guide them when placing the composite. This helps ensure a satisfactory result.
Adhesive Bonding
Adhesive bonding refers to attaching a restoration to a tooth using an etchant, a bonding agent, an adhesive and a high intensity curing light. This method is typically used for aesthetic and metal-free crowns, porcelain veneers, bridges and inlays/onlays.
The Procedure
Whether your treatment plan calls for direct composite restorations or adhesively bonded restorations, dentists start the process by using a rubber dam to isolate the teeth, to prevent interference from moisture. Depending on the extent of the treatment, anaesthetic injections may be required.
Your dentist would then apply a gentle phosphoric acid solution to the surface of the natural tooth, which won’t hurt. Similar to how roughing up a surface with sandpaper can help paint adhere to it better, acid etching of the tooth surface strengthens the bond between the composite and the adhesive. After 15 seconds the phosphoric acid is removed, and a liquid bonding agent is applied.
For a direct composite restoration
- Your dentist then will place a putty-like composite resin in stages on the natural surface of the tooth, then shape and sculpt it.
- A high-intensity curing light will be used to harden that layer of composite, and the previous step will be repeated, then cured, until the filling or direct composite veneer has reached its final shape.
- Your dentist also will create an appropriate finish to ensure that the bonded resin does not dislodge or cause tooth sensitivity.
For a restoration from a laboratory
- Your dentist will place the appropriate adhesive into the restoration, seat the restoration on the tooth and light-cure it using a high intensity curing light for the appropriate amount of time.
It is not uncommon for a bonded tooth – particularly one that has been filled or on which a crown or inlay/onlay has been placed – to feel sensitive after treatment. This minor sensitivity is often short-lived, but if it persists, see your dentist.
To determine if your dental problems can be solved with direct composite bonding, your dentist first will conduct a thorough examination and evaluation of your teeth and gums. During your consultation, your dentist will discuss the clinical and cosmetic problems that direct composite bonding can resolve, such as cavities, chips, cracks, fractures, gaps and spaces between teeth, and tooth discolouration. However, if
you have teeth that are extensively damaged or your dentist feels other dental issues may affect the success and longevity of direct composite bonding treatment, other options may be presented to you, such as crowns or veneers.
Pre-treatment teeth whitening may be suggested in order to better match the colour of the composite restoration to your natural teeth. If whitening is needed, your dentist may wait anywhere from 14 to 21 days before placing your direct composite restorations to ensure a proper and durable bond to your natural tooth structure.
In instances where bonding materials will be used to lengthen or change the shape of your teeth and alter the appearance of your smile, your dentist may take impressions of your teeth before treatment to create a preview model of what your new smile could look like. If you agree with the proposed changes, your dentist may then use this model as a guide or template when placing the direct composite on your teeth.
Teeth Whitening
Are you looking for a quick, non-invasive way to enhance your smile? Teeth whitening might be the answer.
Universally valued by men and women alike, whitening (or bleaching) treatments are available to satisfy every budget, time frame and temperament. Whether in the form of one-hour bleaching sessions at your dentist’s office, or home-use bleaching kits purchased at your local drugstore, solutions abound.
The long and the short of it is that it works. Virtually everyone who opts for a teeth whitening solution sees moderate to substantial improvement in the brightness and whiteness of their smile. That said, it’s not a permanent solution to discolouration and requires maintenance or ‘touch-ups’ for a prolonged effect.
Bleaching vs. Whitening: What’s the Difference?
Bleaching is whitening the teeth beyond their natural colour. This applies strictly to products that contain bleach – typically hydrogen peroxide or carbamide peroxide.
Whitening refers to restoring a tooth’s surface colour by removing dirt and debris. So any product that cleans (like a toothpaste) is technically considered a whitener. Whitening is more frequently used even when describing products that contain bleach.
The Procedure
Most of us start out with sparkling white teeth, thanks to their porcelain-like enamel surface. Composed 
of microscopic crystalline rods, tooth enamel is designed to protect the teeth from the effects of chewing, gnashing, trauma and acid attacks caused by sugar. But over the years enamel is worn down, becoming more transparent and permitting the yellow colour of dentin – the tooth’s core material – to show through.
During routine chewing, dentin remains intact while millions of micro-cracks occur in the enamel. It is these cracks, as well as the spaces between the crystalline enamel rods, that gradually fill up with stains and debris. As a result, the teeth eventually develop a dull, lacklustre appearance.
Teeth whitening removes the stains and debris, leaving the enamel cracks open and exposed. Some of the cracks are quickly re-mineralized by saliva, while others are filled up again with organic debris.
Tooth Discoloration
There are two categories of staining as it relates to the teeth: extrinsic staining and intrinsic staining.
Extrinsic stains are those that appear on the surface of the teeth as a result of exposure to dark-coloured beverages, foods and tobacco, and routine wear and tear. Superficial extrinsic stains are minor and can be removed with brushing and prophylactic dental cleaning. Stubborn extrinsic stains can be removed with more involved efforts, like teeth bleaching. Persistent extrinsic stains can penetrate into the dentin and become ingrained if they are not dealt with early.
Intrinsic stains are those that form on the interior of teeth. Intrinsic stains result from trauma, ageing, exposure to minerals (like tetracycline) during tooth formation and/or excessive ingestion of fluoride. In the past, it was thought that intrinsic stains were too resistant to be corrected by bleaching. Today, cosmetic dentistry experts believe that even deep-set intrinsic stains can be removed with supervised take-home teeth whitening that is maintained over a matter of months or even a year. If all else fails, there are alternative cosmetic solutions to treat intrinsic staining, such as dental veneers.
What Causes Tooth Staining?
Age: There is a direct correlation between tooth colour and age. Over the years, teeth darken as a result of wear and tear and stain accumulation. Teenagers will likely experience immediate, dramatic results from whitening. In the twenties, as the teeth begin to show a yellow cast, whitening may require a little more effort. By the forties, the yellow gives way to brown and more maintenance may be called for. By the fifties, the teeth have absorbed a host of stubborn stains, which can prove difficult (but not impossible) to remove.
Starting colour: We are all equipped with an inborn tooth colour that ranges from yellow-brownish to greenish-grey and intensifies over time. Yellow-brown is generally more responsive to bleaching than green-grey.
Translucency and thinness: These are also genetic traits that become more pronounced with age. While all teeth show some translucency, those that are opaque and thick have an advantage: they appear lighter in colour, show more sparkle and are responsive to bleaching. Teeth that are thinner and more transparent – most notably the front teeth – have less of the pigment that is necessary for bleaching. According to cosmetic dentists, transparency is the only condition that cannot be corrected by any form of teeth whitening.
Eating habits: The habitual consumption of red wine, coffee, tea, cola, carrots, oranges and other deeply-coloured beverages and foods causes considerable staining over the years. In addition, acidic foods such as citrus fruits and vinegar contribute to enamel erosion. As a result, the surface becomes more transparent and more of the yellow-coloured dentin shows through.
Smoking habits: Nicotine leaves brownish deposits which slowly soak into the tooth structure and cause intrinsic discolouration.
Drugs/chemicals: Tetracycline usage during tooth formation produces dark grey or brown ribbon stains which are very difficult to remove. Excessive consumption of fluoride causes fluorosis and associated areas of white mottling.
Grinding: Most frequently caused by stress, teeth grinding (gnashing, bruxing, etc.) can add to micro-cracking in the teeth and can cause the biting edges to darken.
Trauma: Falls and other injuries can produce sizable cracks in the teeth, which collect large amounts of stains and debris.
Teeth Whitening Options
Three major teeth whitening options are available today. All three rely on varying concentrations of peroxide and varying application times.
In-Office Whitening
Significant colour change in a short period of time is the major benefit of in-office whitening. This protocol involves the carefully controlled use of a relatively high-concentration peroxide gel, applied to the teeth by the dentist or trained technician after the gums have been protected with a paint-on rubber dam. Generally, the peroxide remains on the teeth for several 15 to 20-minute intervals that add up to an hour (at most). Those with particularly stubborn staining may be advised to return for one or more additional bleaching sessions or may be asked to continue with a home-use system. Cost: $650 per visit (on average) nationwide.
Professionally Dispensed Take-Home Kits
Many dentists are of the opinion that professionally dispensed take-home whitening kits can produce the best results over the long haul. Take-home kits incorporate an easy-to-use lower-concentration peroxide gel that remains on the teeth for an hour or longer (sometimes overnight). The lower the peroxide percentage, the longer it may safely remain on the teeth. The gel is applied to the teeth using custom-made bleaching trays that resemble mouth guards. Cost: $100 to $400.
Over-the-Counter Products
The cheapest and most convenient of the teeth whitening options, over-the-counter bleaching involves the use of a store-bought whitening kit, featuring a bleaching gel with a concentration lower than that of the professionally dispensed take-home whiteners. The gel is applied to the teeth via one-size-fits-all trays, strips or paint-on applicators. In many cases, this may only whiten a few of the front teeth, unlike custom trays that can whiten the entire smile. Cost: $20 to $100.
Hydrogen Peroxide vs Carbamide Peroxide
The bleach preference for in-office whitening, where time is limited, is powerful and fast-acting hydrogen peroxide. When used in bleaching teeth, hydrogen peroxide concentrations range from approximately nine percent to 40 percent.
By contrast, the bleach of preference for at-home teeth whitening is slower acting carbamide peroxide, which breaks down into hydrogen peroxide. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15 percent solution of carbamide peroxide is the rough equivalent of a five percent solution of hydrogen peroxide.
Guidelines to Whiten
Results are subjective, varying considerably from person to person. Many are immediately delighted with 
their outcome, while others may be disappointed. Before you embark on any whitening treatment, ask your dentist for a realistic idea of the results you are likely to achieve and how long it should take to achieve them.
In the dental office, before-and-after tooth colour is typically measured with shade guides. These are hand-held displays of a wide range of tooth colours. (Dentists also use them in choosing crown and other restoration shades.)
The standard-setter among them has long been the Vitapan Classic Shade Guide. This shade guide standard incorporates 16 shades, systematically arranged from light to dark into four colour groups, and provides a universal tooth-colour terminology.
While whitening can occasionally lighten tooth colour by nine or more shades, most of those who bleach their teeth are likely to see a change of two to seven shades.
Disadvantages
Teeth whitening treatments are considered to be safe when procedures are followed as directed. However, there are certain risks associated with bleaching that you should be aware of:
- Sensitivity: Bleaching can cause a temporary increase in sensitivity to temperature, pressure and touch. This is likeliest to occur during in-office whitening, where higher-concentration bleach is used. Some individuals experience spontaneous shooting pains (“zingers”) down the middle of their front teeth.
Individuals at greatest risk for whitening sensitivity are those with gum recession, significant cracks in their teeth or leakage resulting from faulty restorations. It has also been reported that redheads, including those with no other risk factors, are at particular risk for tooth sensitivity and zingers.
Whitening sensitivity lasts no longer than a day or two, but in some cases may persist up to a month. Some dentists recommend a toothpaste containing potassium nitrate for sensitive teeth.
- Gum irritation: Over half of those who use peroxide whiteners experience some degree of gum irritation resulting from the bleach concentration or from contact with the trays. Such irritation typically lasts up to several days, dissipating after bleaching has stopped or the peroxide concentration lowered
- Technicolor teeth: Restorations such as bonding, dental crowns or veneers are not affected by bleach and therefore maintain their default colour while the surrounding teeth are whitened. This results in what is frequently called ‘technicolour teeth’.
Caveats
To extend the longevity of newly whitened teeth, dentists are likely to recommend:
- At-home follow-up or maintenance whitening – implemented immediately or performed as infrequently as once a year.
- Avoiding dark-coloured foods and beverages for at least a week after whitening.
- Whenever possible, sipping dark-coloured beverages with a straw.
- Practicing excellent oral hygiene – brushing and flossing after meals and at bedtime.
- No amount of bleaching will yield “unnaturally” white teeth.
- Whitening results are not fully seen until approximately two weeks after bleaching. This is an important consideration if you are about to have ceramic restorations and want to be sure the colour matches that of your newly bleached teeth.
- If cosmetic bonding, porcelain veneers or other restorations are part of your treatment plan, they should not be placed until a minimum of two weeks following bleaching to ensure proper adhesive bonding, function and shade matching.
- To avoid the technicolour effect, tooth-coloured restorations will likely need replacement after bleaching.
- Recessed gums often reveal their yellowish root surfaces at the gum line. That yellow colour has proven difficult to bleach.
- Pregnant or nursing women are advised to avoid teeth whitening. The potential impact of swallowed bleach on the foetus or baby is not yet known.
(To be continued)
©Shameena Abdurahiman
Photos sourced by the author from Internet
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