Minimally Invasive Dentistry and Restorative Techniques -- "Using Technology to Improve Your MInD"

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Minimally Invasive Dentistry and Restorative Techniques -- "Using Technology to Improve Your MInD"
Oral Health Journal
March 2006

By: Ron Goodlin, DDS

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The days of GV Black's "extension for prevention" have long passed us by, and the watchword now is "Enamel is sacred". Of course this has only become a possibility due to the development of modern techniques and materials.

STRUCTURAL INTEGRITY
The reduction of enamel from the surface of the tooth has been shown to weaken the entire tooth complex. The more tooth structure removed the greater the risk of fracture of the tooth regardless of the type of restorative material which is placed to repair the tooth loss.1

It has been long recognized that the flex characteristics of the dentin and the brittle nature of the overlying enamel create a rigid structure which gives the tooth its' inherent strength. Evidence has concluded that with increased force or decreased structural integrity, teeth are more prone to abfraction lesions2 and fractures3 (Fig. 1).

In anterior teeth the greater the amount of enamel that is removed, such as in the case of a an aggressive veneer preparation, the higher the risk of fracture because of the decrease in the holding power of the enamel to prevent dentinal flexion4 (Fig. 2).

It has been researched thoroughly and the results show that there is always a stronger bond to enamel than dentin. So it becomes our responsibility as practitioners to maintain the integrity of the tooth to maximize the enamel remaining so that our restorations are bonded to the tooth in a stronger manner.

In posterior teeth structural integrity is lost due to the removal of enamel and the placement of a restoration, regardless of which type. This will result in an increased risk of fracture when the tooth is placed under occlusal load5 (Fig. 3). The resultant fracture does not necessarily manifest itself as a physically evident broken tooth, but often will be manifested as "Cracked Tooth Syndrome". The resulting internal crack proliferating over time until the tooth becomes endodontically compromised or the tooth in fact splits.6

TRAUMATIC INJURY
It has long been believed by this author, that teeth can only take so much trauma during their lifetime. This trauma is accumulative. We know that some patients have a lower threshold level, and other patients will have a higher threshold level. Once the threshold has been reached, "the straw that broke the camels' back" syndrome takes over and the tooth dies, pulpal necrosis being the result.

Pulpal trauma can come in the form of chemical, bacterial or mechanical means. Mechanical pressure on the dental complex from bruxism, or biting into a hard object creating a moment of traumatic incident or bruising can be enough to reach the maximum traumatic threshold.

Cutting into the tooth using burs which create microfractures, heat buildup, odontoblastic injury, dessication of dentin, vibration which creates shock waves to the pulp, pulp exposure, and bruising can be enough to cause pulpal death from a variety of these factors.8

The deleterious effects of the handpiece on the tooth along with the creation of the smear layer can result in problems with bonding and microleakage. The toxic effects of restorative materials themselves on the pulpal tissue has been well researched.9,10

Bacterial trauma from decay, or infiltration from perio disease reaching open dentinal tubules or a micro-fracture that has opened to the surface resulting in bacterial infiltration can result in the threshold being reached and the bacterial trauma results in pulpal necrosis.11

It is evident therefore, that we must treat the teeth in a compassionate and gentle manner, and it is in the interest of the patient to use the most prudent means possible to reduce and eliminate where possible all forms of trauma to the dentition. This can vary from providing our patients with equilibration and an occlusal bite splint to reduce the effects of traumatic occlusion and bruxism, to early caries detection and removal of that decay by using kinder and gentler methods to reduce the risk of pulpal trauma.

MINIMALLY INVASIVE TECHNIQUES
In clinical practice, as soon as we cut into a tooth we have sentenced that tooth to a lifetime of being repaired, replaced and treated with progressively aggressive and costly techniques. Our goal must be to minimize the structural tooth loss during the restorative process (Fig. 4). When treating our patients in clinical practice, it has become easy to use your MInD (minimally invasive dentistry) techniques, for the early detection, removal of decay, and its' repair, in a manner which will minimize the compromise of the structural integrity of the tooth and reduce the trauma inflicted by iatrogenic sources in the process.12

Early detection of caries
In years gone by, we were taught that amalgam had to be larger to be strong, the tooth prep as championed by GV Black, had to incorporate retention and resistance form to prevent the amalgam restoration from falling out or breaking. Extension for prevention to include all the pits, fissures and grooves of the tooth should be included in the prep to prevent further decay. We all seemed to be concerned about this, so when confronted with a small carious lesion, we would mark OBS (observe) or W (watch) on the chart, until the lesion became large enough that morally we would feel it warranted to remove hefty amounts of tooth structure. In essence we would be watching the cavity get bigger over time.

Laser caries detection using "DIAGNOdent" (Kavo) (Fig. 5) to quantify the amount of organic material in the pits and fissures allow us to differentiate between stain and decay. This early detection allows the practitioner to easily remove the decay before it has compromised the tooth due to increased dentinal decay proliferation and the resulting undermining of healthy enamel and structural compromise.

This newer method of Laser Fluorescence Detection of Dental Caries along with the newer dental materials, allow us to detect decay earlier, without having to rely only on the method of tactile, visual, or radiographic detection techniques which have been shown to be unable to detect carious activity as early as the laser diagnostic procedure.13,14 The early detection will allow us to remove the decay without compromising the structural integrity of the tooth and to restore that tooth with a long lasting, aesthetic and functional material.

Dr. Goodlin is an accredited member of the American Academy of Cosmetic Dentistry and a Fellow of the Academy of General Dentistry. He has a practice limited to cosmetics in Aurora, ON, Canada, and maintains his dental licenses in Ontario, Florida and Texas.

Oral Health welcomes this original article.