March 1, 2000
by Gerald R. Ross, DDS
Fluoride has changed the nature of decay that dentists see every day. This has made the diagnosis of fissure caries much more difficult. Before the widespread use of fluoride, caries started with the decalcification and cavitation at the surface, which was easy to diagnose visually or with an explorer.
With fluoride, the start of a caries lesion has changed. The caries track through defects in the enamel surface and begins at the base of the defect, which is often in the dentin. The explorer is extremely poor in diagnosing this type of lesion. Numerous articles support this.1-12
In addition, the fluoride has also affected the dentin, causing less lateral spread of the carious lesions and making radiographic diagnosis very difficult.
To diagnose caries in our patients new tools are needed; probes, magnification, x-rays and caries detectors do not tell us what is happening under the surface enamel.
KaVo has introduced a 655-nanometer diode laser (Figure 2) in an attempt to create an accurate diagnostic tool for the changing pattern of caries. The diagnosis occurs as follows:
A laser diode provides a pulsed 655 nm laser beam, which is directed into the tooth. When the incident light meets a change in tooth substance, it stimulates fluorescent light of a different wavelength. This translated through the hand piece into a number from 0 to 99. The laser light is transported to the tip within a central fibre. Around this central fibre additional fibres are concentrically arranged to collect the fluorescent light from dental hard tissue. As well, it produces an audio signal with a frequency that increases as the number gets higher.
This device has the potential that, for the first time, dentists may be able to diagnose the caries more accurately and it may enable us to make a quantitative decision rather than a subjective one.
On the screen there are two readings. The left one is the moment; this is a reading taken at any instant in time. As the hand piece moves across the tooth this number is constantly moving up and down. The right number is the peak; it gives the highest number registered before the unit is reset.
There are also indicators for A, B and C tips. The A tip is used in pits and fissures; the B tip is for smooth surface use and at present there is no C tip.
There is also a calibration button. I calibrate each of my tips on a weekly basis, as any damage to the fiber-optic bundles in the tips would change the accuracy of the diagnosis.
In 1998, I did a clinical research project that was published in Ontario Dentist in March of 1999.13 In the research I found the unit to be 98% accurate when it read no caries. In the clinical portion of the research I found the unit gave a reading that correlated with the clinical situation 92% of the time.
In addition there have been a number of other studies (many by Lussi) with results in the 85% to 95% range. All the studies concluded that it was a very effective diagnostic tool.
The first step is always the same; to explain to the patient and/or parent what you are going to use and what the numbers and sounds mean. The unit is then set for the individual patient by applying the tip to the healthy labial enamel of a front tooth. This gives the reading for healthy enamel and it is usually in the range of -5 to +2. The unit is then placed in front of the patient (I often have them hold the unit) and the unit is moved across the grooves in a pendulum motion. Laser light reads at only one angle so it is necessary to read at all angles, thus the back and forth pendulum motion as the unit is walked across the teeth.
Below is what I found the numbers to mean in the clinical situation:
0-10: There was no caries or it was just starting in the enamel. In these teeth there is no treatment and the number is not even recorded on the patient’s chart.
10-20: The caries was in the enamel or just into the outer layer of the dentin. I feel that arrested caries would be in the 5 to 20 range. In these teeth I do no restorative treatment but record the number on the patients chart to allow me to know if the caries is getting worse at future recalls. In these cases, preventative measures can be undertaken.
20-30: The caries was well established in the dentin and some lateral spread had started to occur. I restore these teeth and in most cases I can complete the preparation using air abrasion without any anesthesia. These will not be visible on radiographs.
>30: The severity increased as the numbers rose and in almost all cases air abrasion was not indicated and it was necessary to use local anesthetic. These cases will often show up on radiographs. In all restorative cases I record the DIAGNOdent readings in the patient’s chart. This accurately describes why the restoration was necessary. In Lussi’s study,14 which was an in-vitro study with histological section, he found the same results except his number for serious dentin caries was 18 rather than 20. The unit is primarily used in the hygiene department.
In the following situations I found the unit did not work: 1) Around the margins of existing composite restorations. I found that even the smallest lesion gave a very high number. The crystalline structure of the composite changes the fluorescence of the laser beam. 2) Under sealants. The sealant must be removed before stains under sealants can be accurately diagnosed. 3) Incipient inter-proximal lesions. 4) The unit also cannot be used to replace caries detection dye during preparation.
ADVANTAGES OF THE DIAGNOdent:
1.Quantitative, not subjective. The dentist can record a number when the patient is seen and, at a later date, the number allows the practitioner to know if the lesion is staying the same or getting worse.
2.Know when to treat and when to watch. As the study shows, the DIAGNOdent is very accurate (>90 percent) in diagnosing the severity of a lesion.
3.Know amount of caries to treat. The DIAGNOdent allows the dentist to map the caries in a tooth, allowing greater preservation of the tooth, therefore resulting in a stronger tooth. This is the ultimate principle in the practice of Microdentistry. For those dentists using air abrasion, this may be very helpful.
4.Increased Patient Confidence. When the patient can hear the audio sound and see the digital readout, they can readily accept the dentist’s treatment plan.
5.Ability to monitor the effect of preventative measures.
6.More accurate record keeping. In our current practice environment this is becoming increasingly important.
7.Ability to check a tooth for any caries before a sealant is placed.
We are all finding that diagnosis of occlusal caries is becoming more difficult. We have all faced the situation where we start to restore what we believe to be a very small restoration only to find that the whole inside of the tooth is carouse and when we go back to the x-ray, we still cannot see it. I have found the DIAGNOdent to be an irreplaceable tool in my diagnostic armamentarium.
r. Gerald R. Ross, DDS, has a private practice in Tottenham, ON. He has had several articles published on air abrasion, lasers and caries research.
References available upon request from the managing editor.
Oral Health welcomes this original article.