Tooth bonding for back teeth (Composite Vs Amalgam)

Agustus 24, 2008 pukul 9:31 pm | Ditulis dalam tumpatan/tambal gigi | 2 Komentar

Using tooth bonding to create tooth-colored fillings (composite fillings) for back teeth is a fairly new dental technique. Whereas the use of dental amalgam (the metal dentist use to create “silver” fillings) can be traced back for more than 150 years, the routine use of dental bonding (dental composite) for fillings for back teeth has a history of only about two decades.

What is tooth bonding (dental bonding)?

Generally speaking the term “tooth bonding” refers to a range of dental procedures each of which is similar in the sense that it employs the use of a type of dental restorative dentists call “dental composite.”

As a material dental, composite has a number of characteristics that a dentist can exploit when it is put to use. One of them is the way it creates a strong bond with calcified tooth tissues (meaning tooth dentin and enamel). Another important one is its color. Dental composite comes in a variety of tooth-colored shades so when it is placed it can closely mimic the appearance of natural tooth structure.

Tooth bonding can be used for a variety of purposes ranging from dental procedures that just address cosmetic concerns, to those that replace lost tooth structure (such as that lost due to tooth decay or fracture), to those procedures that provide a combination of both of these functions. Here is a listing of some of the different ways a dentist might put dental bonding to use:

1 Cosmetic tooth bonding – Dental bonding can be used to create cosmetic enhancements for teeth.

Cosmetic applications for dental bonding materials.

a) Dental Veneers
Dentists can place a veneering of dental bonding over the front side of teeth that have become stained or discolored as a way of enhancing their cosmetic appearance.
b)  Closing a dental gap (diastema).
Tooth bonding can be used to fill in gaps that lie between a person’s teeth (dentists call this type of gap a “diastema”). When this technique is employed, dental composite is bonded onto the sides of the two teeth that lie on either side of the gap, so to widen each tooth slightly. The net effect is that the space between the two teeth is narrowed, or even filled in completely.

3) Correcting minor cosmetic imperfections.
Minor to moderate cosmetic imperfections of chipped, disfigured, or misaligned teeth can be masked or corrected by placing dental bonding.

2) Dental composite fillings – Tooth bonding can be used to create white fillings (composite fillings) for teeth.

a)  Dental composite fillings for front teeth.
Dental composite (the restorative that is used with tooth bonding technique) has been the material of choice for creating tooth-colored fillings for front teeth for many decades (since the 1960’s). Because dental composite comes in a wide range of different shades of white, it will typically mimic the color of the tooth on which it is placed very closely.

b) White fillings for back teeth.
In some instances dental composite can be an appropriate restorative for fillings placed in back teeth. Patients often like this option because the white color of composite fillings is much less noticeable than the silver coloration of dental amalgam fillings.

Placing tooth bonding (white fillings) in back teeth is a relatively new type of dental treatment.

Dental composite was first put to widespread use by dentists in the 1960’s but at that time it was not recommended that it be used to create fillings for back teeth. This is because the composites of that era had relatively poor strength and wear properties. Those posterior composite fillings that were attempted in the 1960’s typically deteriorated in relatively short time frames because the dental composite being used could not withstand the forces it was subjected to.

Of course since the 1960’s dental composites have under gone significant change and improvement and their physical properties have been enhanced greatly. As a result now days it is very commonplace that a dentist might use dental composite to create white fillings for back teeth.

Dental composite (the restorative material used with tooth bonding technique) is not always an appropriate filling material for back teeth. There are a number of factors your dentist must take into consideration when making this decision. Here are some of them:

1. Will the size of the filling place demands on the tooth bonding material that will exceed the limits of its physical properties?

Dental composite fillings do not have the combined strength and wear characteristics that dental amalgam fillings or other types of dental restorations do. And for this reason most dentists would probably feel that dental bonding is best suited for use in those circumstances where the filling being placed is somewhat on the small or conservative side.

One school of thought is that the width of a composite filling should be less than about one third of the distance between the tooth’s cusps. And no tooth to filling junctions should lie at that point where the cusps of opposing teeth strike.

If the planned restoration does not conform to these guidelines, and especially in those cases where the dental bonding will be used to rebuild entire tooth cusps, you and your dentist may still decide to place a dental composite restoration but the longevity of the filling might be expected to be comparatively compromised.

2. Will the dental composite be exposed to heavy biting and chewing forces?

Dental composite fillings do not have the pronounced wear and strength characteristics that many other types of dental restorations do. In those situations where a dental patient is known to clench or grind their teeth (dentists call this activity “bruxism”), most dentists would probably not consider a composite filling to be the best choice. Bruxing habits can easily subject composite fillings to forces that exceed the limitations of their physical properties and therefore result in premature failure.

3. Does the dental patient have any known metal allergies?

While rare, people can have allergic reactions to some of the metals dentists use to create dental restorations. In these situations dental composite may be (out of necessity) the dental restorative that is chosen. (In the dental literature there are fewer than 100 documented cases of localized allergic reactions associated with the use of dental amalgam.)

4. Does the dental patient want to avoid the use of dental amalgam in their mouth?

One of the components of dental amalgam is mercury. Over the past few decades there has been some debate (more so in the popular press than in bona fide dental research publications) as to the ill effects of this mercury content on a person’s health.

In defense of dental amalgam, we would like to bring to your attention that dental amalgam has been in use in dentistry for more than 150 years. During this time period literally billions of amalgam fillings have been placed. One would anticipate that if a problem did exist that by now there would be ample epidemiological evidence demonstrating any ill effects caused by dental amalgam on the health of dental patients (or on the health of the dentists who work with this metal every day). To the contrary, however, there is not. In the time frame of the last two decades (a time period during which the popular press has hyped this topic and a time frame during which you would expect that any and all peer reviewed scientific studies identifying any problems associated with dental amalgam would be pushed rapidly to the forefront) no ground swell of dental research has demonstrated a health problem associated with the mercury found in amalgam fillings.

Several national and international health organizations have reviewed the available literature evaluating health concerns associated with the use of dental amalgam. None of the following organizations have found a demonstrable risk associated with the use of dental amalgam: U.S. Public Health Service, The American Dental Association, Food and Drug Administration, World Health Organization, FDI World Dental Federation.

However, in those cases where a person has for whatever reason decided that they do not want to have their teeth restored with dental amalgam, then a composite filling may be chosen out of necessity.

5. Do cosmetic considerations necessitate that a white filling should be placed?

Since white fillings created using dental bonding can mimic the color of tooth structure, whereas fillings made from dental amalgam clearly cannot, many people prefer that their dentist place composite fillings. And in those cases where either type of filling material can provide a satisfactory alternative, the white color of a composite filling can make it an easy choice for the patient.

There can be other concerns associated with cosmetic appearances other than just the direct visualization of the filling itself. Dental amalgam fillings can, at times, show through (or with time even cause staining of) the tooth structure that surrounds them. As a consequence, even though the filling itself may not be readily visualized another untreated portion of the tooth can take on a grayish tint. In many cases this may not be much of a cosmetic concern but some back teeth (especially upper ones) can show prominently when a person smiles. If this is the case then placing a white composite filling might prove to be a good choice. You simply need to ask your dentist and let them advise you on this issue.

Advantages / disadvantages of choosing dental bonding (white fillings) for posterior teeth.

Dental composite fillings and amalgam fillings each have unique characteristics that offer distinct advantages and disadvantages. Since in every case each person’s specific situation and needs will vary, it is only appropriate that their dentist is the one who addresses their concerns associated with the use of each of these types of fillings. We do however list many of the advantages and disadvantages of both of these types of restorations here so to help you formulate your questions for your dentist.

Advantages of tooth bonding (white fillings) over dental amalgam fillings.

A) The tooth-colored appearance of composite fillings is more cosmetically appealing than dental amalgam.

There is no question that the tooth-colored appearance of composite fillings is more cosmetically pleasing than the silver coloration of dental amalgam fillings. And in those cases where the use of either restorative is appropriate it is easy to see why a dental patient would prefer a white composite filling. However, in those cases where the cosmetic appearance of dental composite is placed ahead of a consideration of its (possibly less than optimal) physical properties, dental composite can be a poor choice.

B) A completed dental composite filling will often be smaller in size than a comparable dental amalgam filling.

When placing a dental filling a dentist will first use their drill and shape the tooth. Some aspects of this shaping are dictated by requirements associated with the type of dental filling material being used. Comparatively speaking, the required shape for a dental composite filling can typically be smaller than that shape required for a dental amalgam filling.

The flip side to this argument however could be as follows. Most dentists would probably feel that one of their primary treatment goals is to conserve as much natural tooth structure as is possible. In light of this statement you might anticipate that in most cases a dentist would likely recommend the placement of a composite filling rather than a dental amalgam restoration since the size of the cavity preparation can be minimized when dental composite is placed.

A point to the contrary could be made however. Since a composite filling quite possibly won’t last as long as a dental amalgam filling and because each time a dental filling is replaced the overall size of the filling typically increases, placing dental composite may not be as conservative a treatment as one might have initially anticipated. Clearly it would take your dentist’s evaluation and judgement to make a determination regarding this argument.

C) Dental bonding can possibly have a strengthening effect on teeth.

Some dentists feel that teeth restored with dental amalgam fillings are more likely to experience cusp fracture than those teeth restored with tooth bonding (a composite filling). The thought is that the adhesive nature of the bond between the dental composite and the tooth serves to strengthen the tooth being repaired, as opposed to the typical dental amalgam filling where a bond with the surrounding tooth structure does not exist.

This conventional wisdom is not necessarily confirmed by dental research. One study (Wahl, 2004) evaluated the rate of tooth cusp fracture in more than 10,000 teeth that had either a dental amalgam or dental composite filling. The study’s findings were that overall there was no significant difference in the rate of tooth cusp fracture in regards to either type of filling. As a conclusion, this study stated that when choosing between a dental amalgam filling and a dental composite filling (in regards to the likelihood of a future cusp fracture) that either type of filling should be considered acceptable.

To continue this discussion further, we would like to bring to your attention that even though conventional dental amalgam fillings do not create a bond with tooth structure there is a technique of using a bonding protocol with dental amalgam where such a bond is created. Two of our references (Rasheed, 2005 and Zidan, 2003) evaluated the use of bonded dental amalgam fillings as a means to reinforce weakened teeth and both studies found that this bonding technique did provide a benefit. More specifically, the Zidan study evaluated the effect of bonding technique on the stiffness of teeth. The study found that a dental amalgam filling alone did not provide a stiffening effect whereas bonded dental amalgam fillings and dental composite fillings both did. Bonded dental amalgam fillings on average restored teeth to 62% of their original stiffness whereas tooth bonding (composite fillings) on average restored teeth to 77% of their original stiffness.

A review of just these three studies is hardly conclusive (and we admit that comparisons of their individual findings are even somewhat contradictory) but these studies would lead us to believe that the tooth strengthening argument attributed to the use of dental composite is not as strong as some would claim. It seems just as valid to suggest that a bonded amalgam filling might provide the best choice in regards to tooth strengthening, since this technique can offer the more durable type of filling material and also the benefits of bonding technique. Clearly your dentist’s evaluation of your specific situation should weigh heavily when making a decision regarding what type of filling is best for your tooth.

D) Tooth bonding usually creates less post treatment thermal sensitivity.

Dental amalgam is a metal and therefore is an efficient thermal conductor. This means that after amalgam fillings are placed (especially relatively large ones) it is common that people will experience a sensation in their tooth when they consume hot or cold foods and beverages. In most cases this thermal sensitivity will subside as days and weeks pass but for some people it most certainly can be a nuisance.

Since dental composite is a plastic it is a comparatively poor thermal conductor. This means that a strong sensitivity to hot and cold stimuli is usually not a problem with composite fillings. This is not to say that post treatment sensitivity is never occurs with composite fillings. In fact, especially during that era when creating an effective bond with tooth dentin was less well understood by dentists, sensitivity with dental bonding could at times be very problematic. Now days however, subsequent to the development of new dental bonding materials and protocols, the potential for post treatment sensitivity with dental bonding has become less of a concern.

E) Dental composite fillings are ready to be used immediately after the dental appointment has been completed.

As a matter of convenience, a dental patient may be pleasantly surprised to find that the composite filling they have just had placed is fully cured (hardened) and ready for use. In comparison, dental amalgam fillings need several hours before they approach full strength.

Disadvantages of tooth bonding (white fillings) as compared to dental amalgam fillings.

A) Composite fillings usually cost more than dental amalgam fillings.

As a basis of comparison, the cost of a dental amalgam filling will usually be on the order of about 25% to 30% less than the cost of a comparable dental composite filling. This price difference reflects the relative cost of the materials involved and the relatively greater amount of time it takes the dentist to place a white filling as compared to a dental amalgam filling.

If cost is much of a concern, and you have dental insurance, you should be sure to ask your dentist’s office staff about the specific details of your coverage. In some cases dental insurance plans do cover the cost of white fillings (composite fillings) but only up to that amount an equivalent dental amalgam filling would cost. This means that you, the dental patient, would pay the difference.

B) The life span of white fillings may be less than dental amalgam fillings.

The combined strength and wear characteristics of dental amalgam are typically considered to be superior to those of dental composite. This in turn implies that one would expect that an amalgam filling will last longer than a comparable composite filling. Of course there are a number of variables that become involved with any particular filling’s longevity. In some applications (such as very small filling placed on a tooth surface not subject to direct chewing forces) for all practical purposes the anticipated life expectancy of both types of fillings might be very similar.

There have been a number of studies that have tried to evaluate the relative longevity of different types of dental fillings placed in back teeth. One study (Van Nieuwenhuysen, 2003) evaluated more than 100 dental composite fillings and 700 dental amalgam fillings. They found an average life span of 12.8 years for amalgam fillings and 7.8 years for composite fillings. Another study (Forss, 2001) calculated an average life span of 12 years for amalgam fillings and about 5 years for composite fillings. An evaluation of a dental insurance claims database (Bogacki, 2002) concluded that composite fillings in back teeth do not last as long as dental amalgam fillings.

To the defense of dental composite, not all studies have come to these same conclusions. Some studies have felt that they found little difference in the life span of dental amalgam and dental composite fillings. Certainly one might anticipate that as research and development continues to further improve the physical properties of dental composites that the discrepancy that exists between the longevity of dental amalgam and dental composite fillings will diminish. And probably most important, since there is a myriad of factors that come into play regarding the life span of a dental filling, it’s probably best to rely on your dentist’s judgement and experience when making a decision between the two.

C) It takes more time for a dentist to place a bonded restoration.

Placing composite fillings is much more technique intense than placing dental amalgam fillings. This means it will take comparatively longer for your dentist to place a composite filling. The specific time difference will depend upon many factors such as the size and location of the filling but as a ballpark estimate it might take your dentist only about two thirds to half as long to place a dental amalgam restoration as opposed to a white composite filling.

D) A tooth must be adequately isolated when a dental composite filling is placed.

The process of placing composite fillings is fairly technique sensitive and certain steps of this technique do require that the tooth is isolated in a manner where it can be kept free of contamination by oral fluids. There can be instances where the location of a filling is such that it is essentially impossible for the dentist to adequately isolate the tooth. In these cases dental amalgam can often be placed and create a serviceable filling whereas dental bonding cannot.

E) White fillings will stain and discolor over time.

Dental composite fillings will characteristically pick up staining over time. However, when compared with the silver appearance of dental amalgam, it seems unlikely that the potential staining of a composite filling in a back tooth would be a reason not to place one.


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