In Conservative Dentistry, a treatment process whereby a minimum of the healthy tooth structure is removed during the restorative process, is inherently a desirable dental objective. Natural enamel and natural dentin are still the best dental materials in existence, and thus, minimally invasive procedures that conserve a greater part of the original, healthy tooth structure must be considered preferable.
Minimally invasive dental procedures are beneficial from a patient’s point of view, as well. There is less discomfort, less need for local anaesthesia, and a real prospect that the repaired natural tooth will last for a lifetime. The replacement of amalgam restorations often leads to even larger restorations that have shorter life spans than their predecessors, and the replacement procedures themselves may cause damage to adjacent healthy teeth.
In many parts of the world, Restorative Dentistry has been called, and taught as, Conservative Dentistry. It has hardly been conservative of tooth structures however, traditional methods and materials have been aggressive and highly invasive, and required the removal of otherwise healthy enamel and dentin for various reasons, including the extension of the cavity for the retention of the final restoration, and the extension of a preparation for the prevention of recurrent decay.
Fortunately, the current era of dentistry has witnessed the development of new materials, new techniques, and new instruments that make conservative dentistry practical and Ultra Conservative Dentistry a reality.
The term minimal intervention is relatively new in dentistry and has been introduced to suggest to the profession that it is time for change in the principles of operative dentistry. This concept brought forward the idea that the disease should be treated first and the surgical approach should be undertaken only as a last resort and also with the removal of as little natural tooth structure as possible. So, according to this concept the treatment should begin with identification and elimination of the disease.
There will then be a need for limited restoration of actual cavitation arising from demineralization of the tooth crown. It is based on the realization of the fact that restorations, per se, will not prevent or eliminate disease. Caries is a bacterial infection and, until the microflora is controlled, all restorations are at risk of further demineralization in remaining tooth structure. This leads to the continuum of restorative dentistry that keeps the profession occupied for much of its productive time. If this cycle is to be broken, the profession must first acknowledge the primacy of prevention.
Dental caries has long been recognized as an infectious disease requiring a susceptible host, a cariogenic microbial flora, and a diet high in refined carbohydrate to sustain that flora. In the presence of all 3 factors, there may be demineralization of dental hani tissues, particularly in those areas in which the microflora can accumulate and mature. A carious lesion can commence in any of the three dental hard tissues-enamel, dentin, or cementum, leading to cavitation of the tooth surface, the ultimate symptom of the disease.
The original approach to the treatment of caries was purely surgical. It was thought that the only effective method of eliminating the disease was to completely remove all of the demineralized areas of tooth structure and rebuild it with an inert restoration that would simply obturate the cavity. The margin of the cavity had to be placed on a so-called caries- free surface to avoid the risks of further plaque accumulation that could lead to recurrence of the disease.
This led to the development of a standardized system of intervention regardless of the size and extent of the original lesion. Even the smallest area of demineralization required the removal of a standard amount of sound tooth structure to prevent progression. Cavity designs were classified and standardized, and sound natural tooth structure was sacrificed in the name of geometric perfection to accommodate the shortcomings of the restorative material.
The logical assumption that if under adverse circumstances a tooth surface can be demineralized, it must be possible for it to be remineralized and healed once the enviromnent has been correctly modified, is the reasoning put forward by the advocates of this theory. Moreover, the considerable research in the last 30 years has confirmed that a carious lesion can in fact be reversed and that prior to cavitation, the tooth surface can be remineralized and returned to health. In fact, it has been shown that, in the presence of fluoride, the healed surface is more resistant to further acid attack and is stronger than it was originally.
The concept of prevntive dentistry was developed along with the early understanding of demineralization, but with the poor understanding of remineralization at that time, the full cycle was not appreciated. Initially, caries control and remineralization was entirely dependent on patient cooperation, and this was hard to achieve on a long-term basis. Subsequently, specific strains of bacteria were identified as being related to cans, the action of the fluoride ion became understood, and patients could be offered a further degree of support in their efforts to control the disease.
The philosophy of minial intervention dentistry has now arisen in an attempt to combine all the present knowledge of prevention, remineralization, ion xchange, healing, and adhesion with the object of reducing carious damage in the simplest and least invasive manner possible. It is obvious that restorative dentistry, based on the surgical restorative approach developed by G.V. Black, is highly destructive and leads to the point where the majority of a dentist’s time is occupied in replacement dentistry.
The potential for minimal intervention operative dentistry is dependent on the following factors:
• The demineralization-remineralization cycle.
• Adhesion in restorative dentistry.
• Biomimetic restorative materials.
The Demineralization-Remineralization Cycle
Due to increase in understanding of the progress of caries over the last 30 years, it is now clear that in a normal, healthy mouth, there is a continuous cycle of demineralization and remineralization of the surface of a tooth. It has also been confirmed in recent years that fluoride plays a significant role in the demineralizationremineralization cycle and the addition of fluoride to the tooth surface will increase resistance to further carious attack. Now it has been observed that the remineralization of the carious surface of the tooth is possible during all stages of the development of a cavity. In the early stages, when only the enamel is involved, attalning remineralization is simply a matter of plaque removal through normal oral hygiene methods in conjunction with the introduction of free fluoride ions by either topical or systemic methods.
Once the lesion has advanced to surface cavitation and the dentin is involved, the contents of the cavity can be divided roughly into two layers:
1. An infected layer on the outer surface of the cavity. The tooth structure in this layer is completely denatured and laden with microorganisms.
2. A relatively sterile, softened, demineralized inner layer generally identified as the affected layer. This layer will be demineralized to some degree, depending on the speed and the aggression of the disease process.
In this context, it is important to note that the affected layer at the base of the cavity is relatively sterile. In the past, the surgical approach to the control of caries dictated the removal of all tooth structure that appeared to be involved in the disease. This principle included the removal of the affected layer, on the assumption that it was part of the problem. It has now been demonstrated that this layer can be remineralized as well, provided that it is sealed under a biomimetic restorative material. Therefore, it is suggested that the demineralized layer in the affected dentin be regarded as “precarious” rather than actively carious. This layer should be retained and remineralized under most
Adhesion in Restorative Dentistry
Over this same period of time, there has been considerable research into restorative materials, with the object of replacing gold and amalgam restorative materials. Several major advances have evolved through recent research. There circumstances, thereby reducing the loss of natural tooth structure.
are now materials with biomimetic potential, including the release of fluoride, calcium, and phosphate ions that can be of value in enhancing the remineralization potential of a carious lesion. In addition, it is now possible to develop true adhesion between tooth structure and the restorative material and thus prevent microleakage between the restoration and the cavity walls.
Biomimetic Restorative Materials
The concept of a biomimetic material is very important in restorative dentistry. The term biomimetic suggests “imitation of nature”. It implies that the material will be biocompatible, that is, biologically acceptable to, and not rejected by, adjacent vital tissues. Following placement, such a material may cause a low-grade transitory inflammatory response, but it will not release chemical irritants into the vicinity. Glassionomer cement has been shown to fulfill these requirements upto great extent.
In the past, it has been routine to place a lining under a restoration with the expectation that the lining will lead to some desirable reaction within the pulp and enhance the potential for the tooth to survive. It has recently become apparent that the ability of the pulp to resist insult is in fact very high, provided that it is always protected from bacteria and their byproducts. It has been shown that it is sufficient to remove the bacteria-laden infected layer from the surface of a carious lesion and then seal the tooth; this procedure will allow the pulpal inflammation to subside and, in the absence of further bacterial invasion, the pulp will heal. It has also been shown recently that it is safe to leave the softened, demineralized, affected, but sterile, dentin on the floor of the cavity. If the cavity is then sealed with a biomimetic restoration that releases calcium, phosphate, and fluoride ions in a wet environment, the result will be remineralization and healing of the underlying dentin.
STEPS IN MINIMAL INTERVENTION RESTORATIVE DENTISTRY
The latest minimal intervention restorative dentistry advocates that the following steps to be followed in the case of caries in tooth:
(1) Control the disease.
(2) Remineralize of early carious lesions.
(3) Repair the damage due to carious lesion.
(4) Repair, if possible, rather than replace the defective restorations.
CONSERVATIVE PREPARATION OF THE CAVITY
The goals of ultraconservative preparation are:
1. Recontouring the fissure and pit anatomy for access and visibility.
2. Exploration of the cavity to ensure that no decay remains undetected.
3. Ultra Conservative (but complete) caries removal.
The practitioner has a number of choices of armamentarium in pursuing the UltraConservative treatment approach.
Small Round Burs
While these familiar burs provide a conservative preparation with good explorer access, and require no learning curve, they are slow and inefficient in cutting through enamel.
In recent years many dentists have begun working with air abrasion technology for the preparation of cavities. Air abrasion provides conservative removal of tooth structure, good explorer access into the preparation, and requires minimal local anesthetic. There is however, a learning curve associated with these devices in terms of direction, cutting depth and focus of the spray, since unlike burs, there is no tactile feedback during the preparation process. The equipment may be expensive, and most air abrasion procedures are rather messy as the excessive abrasive dust tends to spread around the operatory.
Excisional Biopsy Burs
The Fissurotomy bur is a new approach to Ultraconservative dental treatment. The Fissurotomy burs, specially designed for recontouring the fissures and accessing the decay with minimal enamel removal, are fast cutting, conservative and inexpensive. In almost all cases, the patient throughout the entire procedure requires no anesthetic. However, the use of the Fissurotomy burs is limited to pits, fissures, and grooves and not indicated for treatment of larger decay.
The shape and size of the bur are designed specifically for the purpose of treating pit and fissure lesions. The head length of the bur is 2.5 mm, allowing the dentist to limit the bur tip to cut to just below the dentino-enamal junction (DEJ), and not further into the dentin. The tapered shape of the bur allows the cutting tip to encounter very few dentinal tubules at any given time, and has been designed to minimize heat build-up and vibration. Since the cutting of the Fissurotomy bur is restricted largely to enamel, patient discomfort is minimized and the need for local anesthetic eliminated in most cases.
It is apparent that it is time for a change in operative dentistry. It is not possible to really imitate natural tooth structure on a long-term basis, so it is best that it be retained as far as possible. Therapeutic methods for the control of the disease are available, and these should be the first line of defense. In the presence of early carious lesions, there is no justification for removal of tooth structure simply to provide a theoretic resistance to further carious attack or to develop mechanical retention for restorative materials.
It is important that the profession embraces modem science and move into the new century. The profession has a responsibility to move away from the maximally interventionist approach.