Operative Dentistry 6806
October 14, 2002
Section One
The scope of this paper is to discuss the many topics related to the incipient carious lesion. The problem will be defined, diagnosis protocol and methods will be discussed, as well as the evidence based treatment options available. The research plan was to assign the above topics and related subtopics to group members and use library and internet resources to obtain the most current information available about the topic. After the information was gathered the group developed a clinical protocol for treating the incipient carious lesion.
The patient is a 27 year old white male presenting to the clinic with white spot lesions on the buccal surfaces of his teeth upon drying. After initial visual inspection the doctor has to address some basic questions; Is this incipient decay? Are there other areas of decay that are not being detected by his/her visual inspection? What other detection methods are available to help him detect decay? The first question that needs to be addressed is the definition of incipient decay. According to The Art and Science of Operative Dentistry, the initial carious lesion limited to the enamel is incipient caries and is characterized by a virtually intact surface, but a porous subsurface (1). Clinically it is observed as an opaque chalky region (a.k.a. white spot lesion) which appears chalky only when it is dry. The wet saliva fills in the porous subsurface leaving the tooth translucent and only visually discernable when the surface is dried. The etiology of this carious process is bacterial in nature. Bacteria ferment the sugars found in the oral cavity and the acids produced demineralize the enamel creating carious lesions. The process develops slowly and takes 3-4 years before the lesions become clinically apparent (2).
The interproximal, buccal and lingual surfaces of teeth are placed in the category of smooth surface lesions. These lesions occur where the contour or position of the tooth protect the plaque against the rubbing action of some foods and the toothbrush (1). Gingival to the contact areas (interproximal areas) and gingival to the height of contour on the facial and lingual surfaces of the teeth provide the ideal environment for bacterial plaque to be retained and cause demineralization of the enamel leading to the incipient carious lesion. Every pit and fissure on the posterior teeth can be considered as having its own ecological system. The shape of the pit and fissures protect the bacteria held within them allowing the bacteria to form their own ecosystem which can eventually be detrimental to the tooth. Some pits and fissures end blindly, others open near the dentin, while others penetrate entirely through the enamel. As will be discussed later, it is this morphology of the pits and fissures that makes the detection of the carious lesion in its early stages difficult.
The doctor now needs to use different modes of detection to determine the existence of caries in the dentition. In the past the patient's symptoms had been central to the diagnosis of caries. The main symptom was pulpal pain relatively late in the caries process leading to substantial damage to the tooth structure. A method of early caries detection was needed, therefore, diagnostic techniques were developed to impede the caries process at an earlier step. The classic methods of caries detection included direct and indirect inspection, external illumination, transillumination, detection of the "catch" with the explorer and radiography. These detection modalities separately are insufficient to diagnose caries so one must use many or all of these modalities to determine the presence of the incipient lesion. Using the classic methods to detect incipient decay has been regarded as very effective and is still the main method of caries detection in the University of Minnesota School of Dentistry Dental Clinics. Radiographs are looked at initially to determine the caries status. This can be challenging because 40% of dentin needs to be carious before radiographic detection is possible (2). Since incipient decay only involves demineralization of the enamel, it becomes difficult to diagnose incipient lesions radiographically. The most a clinician can do is look interproximally on the radiograph where caries typically occur between the contact point and the height of the free gingival margin (1-1.5mm below the contact) (2). External illumination and transillumination look for shadowed regions of darkness only if the caries is other than incipient (1), so this method is ineffective in catching the caries process in the beginning stages when it has only damaged the enamel. The difficult location of these caries eliminates the possibility for the clinician to detect them visually. The evidence shows that the classical methods of caries diagnosis are not sensitive enough to diagnose incipient interproximal decay early enough for early intervention.
Smooth surface caries can not seen radiographically but can be detected visually and tactfully. As stated earlier, when smooth surfaces are dried with an air syringe one can see chalky white spots. If an explorer is run over the smooth surface it will feel rough but not soft. The surface feels soft when the caries process has proceeded past the incipient stage. These detection modalities are seen as effective as long as the clinician takes time to dry the teeth and look for the white spot lesions tactfully. With use of the explorer one can detect caries effectively on smooth surfaces (3, 4, and 5).
In 1924 G. V. Black recommended diagnosing caries with a sharp dental explorer - If some pressure was required to remove the explorer, Dr. Black recommended restoring the tooth regardless of any visible sign of disease (6). The bacterial nature of the disease was not considered back then and the progression of the disease, from demineralization → cavitation → progression into the dentin, was not known. The goal was to treat the tooth, not the disease. Detecting pit and fissure caries in the incipient stage is difficult because as stated before, it requires 40% of the dentin to be carious and by that time it is too late. The effectiveness and accuracy of the explorer is approximately 24% in diagnosing pit and fissure caries (6). With the known complex anatomy of the pit and fissure one can see why explorers and radiographs should no longer be our only diagnostic tools for detection of the carious process in the incipient stage. The demineralization zone is better evidenced with desiccation from air if one wants to detect the caries on the occlusal surface but one cannot visually inspect inside the pits and fissures. Since pit and fissures are the first and most susceptible site for carious initiation it is important that better diagnosis tools are available to detect the carious lesion in the incipient stage.
New techniques for caries detection have been developed such as using electrical conductance measurements (EC), Laser Fluorescence (LF) and the DIAGNOdent System. The electrical conductivity of the tooth changes with demineralization, even when the surface remains apparently intact (7). Electrical conductance measurements make use of the increased conductivity of carious enamel in pits and fissures. The entire occlusal surface needs to be covered with a conducting medium and the conductivity from the occlusal surface to the ground electrode is then measured with a probe (7). There is generally high sensitivity with this technique. In one in vivo study, the diagnostic performance of two different commercial electronic devices was superior to that of bite-wing radiography (7). There is some concern with the devices specificity which is below 80%. This translates into a false positive rate of 20% or a 20% risk of unnecessary operative intervention.
Laser Fluorescence is a method that measures the fluorescence of the tooth that is induced after light irradiation to discriminate between carious and sound enamel (7). The term quantitative laser fluorescence (QLF) has been applied to the research method of measuring induced tooth fluorescence after using laser light generally at or near 488 nm rage to quantify tooth demineralization and lesion severity (7). Many studies have shown its usefulness in detecting smooth surface incipient decay but in inaccessible areas the specificity was poorer than visual examination or radiographic examination alone. QLF can only discern enamel demineralization and cannot differentiate between decay, hypoplasia or unusual anatomic features. QLF was not designed to discriminate between lesions restricted to enamel and those extending into dentin. Therefore QLF is not an appropriate diagnostic tool to detect the incipient carious lesion before cavitation.
The DIAGNOdent system is another laser fluorescence system that emits a light at 655 nm wavelength from a fiber optic bundle and directed onto the occlusal surface of a tooth. A second fiber optic bundle receives the reflected fluorescent light beam, and changes caused by demineralization are assigned a numeric value which is displayed on a monitor (7, 8 and 9). The instructions for the system specify that the occlusal area to be diagnosed needs to be clean because plaque, tarter and discoloration may give false values. Numerical values between 5 and 25 indicate initial lesions in enamel and greater values indicate dentinal caries. The reproducibility of the device was high in this study (7) but here was also evidence of different degrees of learning for individual dentists. With experience it has been shown that this system has a high specificity but visual diagnosis remains the method of first choice to be carried out before any other techniques are used (7). This device is helpful in areas of clinical uncertainty, as a second opinion, diagnostic adjunct or in areas were accessibility in a problem.
Our group had the opportunity to use the DIAGNOdent system on extracted teeth. The teeth were first examined by some third year dental students first visually and then with the explorer. The DIAGNOdent was then used to get a numeric value. The teeth were finally sectioned and all of the data was compared. While there was a learning curve involved with using the system, our results showed that the system was able to detect incipient lesions before the lesions were detectable by the vision and tactile sense of the dental students. However some lesions that were obviously carious were not detected by the DIAGNOdent as one would expect. This further shows that the DIAGNOdent should only be used in conjunction with good clinical data.
After using the variety of diagnostic techniques available with our patient, the treatment options fall into two categories. One can take the classical invasive approach which removes the demineralized enamel and replaces it with a restorative material or a noninvasive approach can be adopted where no treatment may be done and the prevention of further demineralization with future remineralization may be done. The invasive approach is the approach all dentists are familiar with. Give the patient anesthetic, take away the demineralized enamel with a small round bur, and bond with the composite system of choice. Composites will be considered the incipient lesion invasive technique of choice because it is the conservative preparation technique which keeps the preparation in the enamel and does not involve the dentin. This still works well with interproximal and smooth surface incipient decay but a more conservative invasive technique has been developed for pit and fissure demineralization.
Air abrasion is an alternative to the classical invasive round bur and local anesthetic method. It uses a focused stream of aluminum oxide particles at a pressure of 40-140 psi (10). It allows the "no anesthetic filling" because it eliminates objectionable heat, sound and vibrations. Studies have even shown if the enamel layer is breached and the dentin is exposed, the air abrasion gives the dentin a cooling sensation which is unobjectionable to the patient(10). When the preparation is done in this way you do run the risk of microfracture and microcrazing of enamel margins . After the preparation has been done by opening up the pits and fissures using either invasive method, a preventative resin restoration (PRR) can be placed. It is a resin that will replace the demineralized enamel and bond to the remaining enamel and dentin (if need be). PRR's compare well with amalgams which have a mean survival time being 61.5 months and PRR survival being 63.3 months (11). If caries is left under the restoration it has been shown that the lesion will not progress below the intact restoration (11).
Another approach to treating incipient decay is the noninvasive approach. Most communities are using water fluoridation as a way to prevent decay. For these lesions found by dentists in enamel, treatment consists of improvement in the patients home care preventative methods, application of higher concentration fluorides or using sealants to seal problem areas so the bacteria will have a limited ecosystem to thrive in. Sound fissures or those with arrested lesions require no specific treatment. It has been found that arrested (those that have already remineralized) lesions exhibit a higher degree of resistance to demineralization than uninvolved areas (12). Another technique used by clinicians is termed "watchful waiting," otherwise known as reevaluation at the next appointment. This technique may be combined with topical fluoride treatment and dietary counseling that could provide the opportunity for arrest of the lesion.
Sealants are also placed when an active enamel carious lesion shows signs of progression, when the patient presents high caries risk and cannot control the dental plaque efficiently by tooth-brushing, or when the patient does not cooperate with proposed treatment. A sealant is considered interceptive, rather than preventive, because the carious process in small lesions, and occasionally in larger lesions, may be arrested after sealing. If the sealant is maintained and the nutrients are prevented from entering in the fissure, there is a continual reduction in the viability of the remaining bacteria (12). If the overlying sealant is fully retained then recurrent caries or progression of caries beneath the restoration is negligible. This is consistent with studies of caries progression beneath fissure sealants which indicate that it does not progress beneath intact sealants. Thus, if a sealant restoration is placed, the dentist has a duty of care to ensure that the retention of the sealant is regularly reviewed, repaired or replaced as necessary.
Possible fears over incomplete caries removal appear to be unwarranted, with caries appearing not to progress beneath intact sealants. Potential problems regarding marginal shrinkage of composites and recurrent caries may be addressed by using glass ionomer in the technique. The use of the sealant restoration should be encouraged because it represents a tooth preserving procedure producing a more durable restoration with the added benefit of protecting the remaining fissure pattern from carious attack (12).
Several studies have shown that fluoride is effective in remineralizing and arresting early carious lesions in the permanent dentition. Remineralization is the theory behind fluoride varnishes which are applied to the patients teeth. One study showed that in the varnish group, 81.2 percent of active enamel lesions were inactive after nine months, compared with 37.8 percent of active enamel lesions in the control group (13). In the control group, 36.9 percent of all active enamel lesions were still active at nine months, whereas only 8.2 percent of all active enamel lesions in the varnish group were still active. Significantly more inactive lesions were found in the varnish group after nine months on all surfaces than were found in the control group. Clearly, remineralization in the control group was less evident. The results of this study indicate that two applications of fluoride varnish may be effective in arresting early active enamel lesions in the primary dentition (13). Biannual application of fluoride varnish Duraphat was shown to arrest early enamel lesions. The ease, safety, and practicability of the fluoride varnish application technique and the reduced dependence on patient cooperation are substantial advantages to this non-invasive technique (14).
The modern concept of prevention entails monitoring of caries sites over time, not just to detect progression as in the past, but also to observe evidence of remineralization-an important goal of caries prevention procedures. For patients who have been shifted to a "low-caries-risk" status and those who have no evidence of caries progression in 12 months treatment should include: continued monitoring of arrested lesions and replacing caries control restorations with definitive restorations as needed. For patients who have noncavitated lesions that have penetrated less than one third through the outer dentin, continue fluoride treatments with office topical fluoride and/or fluoride varnish applied interproximally plus periodic rinses with chlorhexidine (once a week for six weeks). In these cases, radiographic bitewing analyses should be performed after six to nine months. If no change is detected in lesions depth, subsequent radiographic and clinical exams can be extended to 12 months for adolescents and 18 months for adults (15). The twelve-month data confirm that it is possible to keep initial lesions of occlusal caries under control through the implementation of non-invasive strategies.
To deal with the real question of how to deal with our patient and what methods will be incorporated into our future practices: Incipient decay is difficult to diagnose using just the classical methods of detection. The new DIAGNOdent system has shown to be a valuable adjunct to the diagnosis of incipient decay. It can detect caries in its earliest stages interproximally and occlusally which allows the practitioner to treat the lesions using a treatment plan with a noninvasive direction. The DIAGNOdnet system should not be used alone but should be used with the classical detection techniques.
Treatment is focused to the patient first, the teeth second. The patient mentioned earlier in the paper has a handful of incipient lesions on his teeth but does not have a history of decay with minimal restorations in his mouth. In his case we would tend to use a topical in office fluoride and use oral hygiene instruction to supplement his home care. If in six months there has been remineralization of the lesions we will consider the "watchful waiting" technique successful. If there has been greater demineralization an invasive technique may be warranted depending on the extent of demineralization. This treatment protocol will be used in our practices. In low risk caries patients the watch and wait protocol along with the placement of fluoride varnishes will be implemented while with moderate to high risk patients sealants and invasive techniques will be used more often. Patient motivation is also a factor. If the patient only visits your practice when something hurts, the invasive approach will be followed more often because without sufficient recall appointments and maintenance of varnishes and sealants the noninvasive approach is doomed to failure.
It is important to become the complete Dentist, to use all of the diagnostic and treatment modalities at ones disposal in an intelligent way. Clinicians are there to treat the patient and not just the tooth. This is important because if one cannot detect and control the early phases of the disease, prognosis for the patient is poor. This is true in most diseases where early detection is imperative to an effective treatment. In the clinics at the University of Minnesota School of Dentistry the diagnosis only involves the classical methods of diagnosis and the treatment is almost always invasive. Granted most of the patients are in moderate to high caries risk categories but the possibility of watching incipient lesions throughout a 6 month treatment has not been recommended by most clinicians. It is important for us, as students, to be aware of using new and old technologies and treatments to treat our patients in the best possible way. It has been taught to dental students in every class that there is no restorative material better than the original tooth structure, therefore through dentist and patient participation, and intelligent use of diagnostic and treatment techniques, proper management of the patient is assured.
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