Conservative Approach in Restorative Dentistry PDF

Conservative approach in restorative dentistry Operative 501 List of content - Introduction - The modern concepts in Conservative Dentistry A) Understanding the caries nature and process. B) Understanding the sequela of unnecessary cutting of tooth struc...

Conservative approach in restorative dentistry Operative 501 List of content - Introduction - The modern concepts in Conservative Dentistry A) Understanding the caries nature and process. B) Understanding the sequela of unnecessary cutting of tooth structure. C) Seeing the concept of conservation from a different prospective. The medical (Biological) model of treatment 1. Caries diagnosis, risk assessment and control of the causative factor. 2. Minimize demineralization and Enhance remineralization of early lesions. 3. Minimal surgical intervention for cavitated lesions. - Features of a conservative cavity - Mount's classification: (the Si/Sta concept) - Steps of cavity preparation - Recent cavity designs 4. Repair rather than replacement for defective restorations. D) Technological advances in different related aspects. - Recent advances in diagnostic tools - non- invasive cutting tools - Advances in Restorative materials(Bondodontics) 1  Introduction History of tooth preservation: (conservatism) ▪ In the past, extraction of teeth was considered conservatism to avoid spread of caries, then cavity preparation with the concept of extension for prevention was adopted as conservative treatment, then consrvatism was made to minimize cutting of tooth structure. ▪ Nowadays, the modern conservative theory there is a shift to use a medical model and avoid cutting if possible. ▪ This would require the detection and discovery of the lesion in its sub-clinical stage before it initiates any defect that would need repair. ▪ Conservation is the shift to substitute the concept of drilling and filling. That shift in the concept and approach has resulted from: A) Understanding the caries nature and process. B) Understanding the sequela of unnecessary cutting of tooth structure. C) Seeing the concept of conservation from a different prospective. D) Technological advances in different related aspects. A) Understanding the caries nature and process - The knowledge of the caries process gained in recent years can be applied as the first principle in “conservative dentistry”. Specially, the traditional “surgical” approach to the early surface lesion can now be replaced by the medical, “biological” or “therapeutic” approach recognizing also that caries is an infectious disease. - The caries process was thought to be irreversible sequence of events, beginning with enamel demineralization, followed by protein (collagen) degradation. Thus, the logical treatment was surgical excision of the pathological tissue and replacements with the restorative material. 2  - However, it is now recognized that enamel and dentin demineralization is not a continuous irreversible process. Rather, there is a demineralization- reminerlization cycle, in which the tooth structure alternately loses and gains calcium and phosphate ions, depending on micro-environment. When the PH rises again, reminerlization may occur. B) Understanding the sequel of unnecessary cutting of tooth structure - Increased potential to pulpal irritation. - Gingival and periodontal irritation due to plaque accumulation on the margins and surfaces of restorations placed gingival to the gum. - Gross weakening of the remaining tooth structure due to loss of structural continuity which leads to stress concentration and fracture of the restoration. - Structural and marginal failure of the restoration due to increased functional loading. - Increased restorative display and poor aesthetics. - More time, money and effort consumption. - Difficult maintenance of the restorative system. C) Seeing the concept of conservation from a different prospective - In Extension for Prevention concept – G.V. Black: Treating the symptoms rather than the etiology. Extended the cavity preparation to ensure removal of bacterial-infected tooth was done. - In Minimally-invasive Dentistry: Treats the etiology rather than symptoms. Conserves tooth structure as much as possible. - In the modern conservative theory, there is an intention to use a biological model and avoid cutting if possible. 3  The medical (Biological) model of treatment Definition: Respecting the health, function, and aesthetics of oral tissue by preventing disease from occurring or intercepting its progress with minimal tissue loss. This model deals with caries as a disease that should be treated prior to any restorative procedure. It includes the following: 1. Diet and habits modification if required. 2. Salivary flow and buffering capacity adjustment if required. 3. Mechanical preventive measures 4. Use of antimicrobials 5. Remineralization of initial lesions. 6. Fissure sealing for susceptible sites. 7. Close follow up to monitor the healing procedure 8. Perform minimal intervention and preparation for diseased tissues that cannot be remineralized and restore them conservatively The recent medical (Biological) model could be concluded in the following points: 1. Caries diagnosis, risk assessment and control of the causative factor. 2. Minimize demineralization and enhance remineralization of early lesions. 3. Minimal surgical intervention for cavitated lesions. 4. Repair rather than replacement for defective restorations. 1) Caries risk assessment and control of the causative factor: Caries risk may be defined: as the probability that a specific number of new lesions will develop and / or specific number of existing lesions will progress over a specified period of time. Factors that are to be considered in the caries risk assessment are: 1- The amount of plaque, type of bacteria, 2- Type of diet, 3- Salivary secretion, salivary buffering capacity, 4  4- Amounts of fluorides ingested, 5- Socioeconomic conditions 6- and general patient’s health. It’s based on the fact that for caries to develop, there are several factors that should be present to contribute to its occurrence. By modifying the factor that plays the major, this could successfully prevent the development of the disease. Cariogram: It is a computer program that serves as a risk assessment model for each individual. The Cariogram demonstrates how and what extent the various caries causing factors may affect the patient's risk. It expresses the risk as "Per Cent Chance to Avoid Cavities". The five sectors involved in the cariogram are: Chance (green sector)- The Chance to avoid new cavities in the near future Diet - frequency of eating as well as contents of diet Bacteria - Plaque amount as well as types of bacteria Susceptibility - tooth resistance (fluorides) and saliva characteristics Circumstances - Past caries experience and general diseases and conditions. 5 □ According to this caries risk assessment the patient could be either classified as: 1. No care advised (NCA) and therefore considered dentally fit if he scores a low caries risk value. 2. If he is at risk, therefore preventive care advising (PCA) will be the selected route for treatment. This category of patients could have some initial lesions that require management. Patients are treated by a non-surgical model for treatment, which is also termed biological model or medical model for treatment. Tooth structures would not be cut but rather treated conservatively. 3. When the lesions are not reversible and must be treated by operative intervention, the patient could be classified as operative care advised (OCA). 2) Minimize demineralization and Enhance remineralization of early lesions: Early lesions before being remineralized, it should be diagnosed first using advanced diagnostic tools: A. Approaches to prevent and minimize the demineralization through: 1. Diet and habits modification. 2. Salivary flow and buffering capacity adjustment to enhance the defence mechanisms of the body. The rate of salivary flow is very important, as it can be a contributing factor in the occurrence of caries. The resting flow rate has an average that ranges between 0.3-0.4 ml/min while the stimulated flow rate has an average rate between 1-2 ml/min. These measurements are considered essential as they might modify the line of treatment that could be designed for a patient. Furthermore, the buffering effect of saliva is an important parameter that has to be considered as caries resistant persons show higher capacity to buffer any lowering in the plaque pH. This could again impose a different strategy of treatment. 3. Mechanical preventive measures: a) Plaque control (improve oral hygiene). b) Enameloplasty and fissure sealing using resin material or glass ionomer. 6 Enameloplasty: It is the reshaping of the pits and fissures by rounding or saucering with a round bur or a diamond point to render them non- retentive for bacterial plaque. While in fissure sealing, sealants are in the form of low viscosity resinous materials or glass-ionomers and their modifications. They obliterate pits and fissures that represent good habitats and niches and allow trapping of microorganisms and food substrate. Infiltration method: Caries infiltration has been proposed as an alternative for management of no cavitated enamel caries lesions on the proximal and buccal surfaces. The infiltration concept is based on the penetration of a low viscosity resin material (infiltrant) in the subsurface enamel porosities of the lesion. 4. Chemical preventive methods e.g: Chlorhexidine (home care): This is to attack the cariogenic organisms and deal with caries as a disease rather than dealing with its symptoms. Chlorhexidine or hexitidine mouthwash could be used twice daily for two consecutive weeks. It could also be in the form of gel applied in custom-made trays or applied as a varnish. They reduce substantially and rapidly mutans streptococci for patients with high counts of bacteria and/or high caries activity. Treatment must be repeated at intervals of 1-3 months according to the type of patient but care is to be taken that certain stains occur following this therapy that necessitate polishing of the treated teeth. However certain manufacturers have been trying to incorporate bicarbonates into their formulae to neutralize this staining effect. 5. Close follow up to monitor the healing procedure. 7 B. Approaches to enhance the reminerlization of non-cavitated lesions: Enhance acid resistance, reminerlization and rehardening of the tooth surfaces. a) Increase oral fluoride levels. b) Increase oral calcium and phosphate levels through: For remineralization to occur there are certain rules that should be present; such as the availability of sufficient minerals in saliva and the production of a molecule of carbonic acid that should be near to a mineral molecule. All this is to occur in close proximity to a demineralized spot that requires the exact mineral ion. Additionally, the spot of the tooth has to be clean so that the mineral deficient spot is accessible. 3) Minimal surgical intervention for cavitated lesions. To drill or not to drill?or when to prepare a cavity? Certain data have to be collected prior to decision making about the necessity of operative procedure. These are the diet assessment included in the caries risk evaluation, clinical and radiographic examinations. 1) Diet assessment Estimation of food cariogenicity as well as the frequency of intake of meals and snacks is rather important to allow determination of the problem if there is any. Also, motivation of patients for adopting healthy habits is an essentiality. However, it’s believed that failures are faced due to the difficulty of convincing patients to change their dietary habits. □ A need to adjunct a diet counselor became thus an important issue that is still neglected by dental professionals. 2) Caries risk assessment (as discussed before) 3) Clinical examination: - This step allows the identification of the defect and correlation of previously gathered data with the clinical picture. Upon diagnosis, the defect should be classified as carious or non-carious as it’s dealt with differently. - It tends to become inevitable to perform a cavity rather than to just remineralize the lesion if we require eliminating bacterial traps, relieving patient’s symptoms and restore tooth form and function. 8 Documenting caries and restorative decisions: Shift had been done from the DMF index for documenting dental caries into a more recently described classification system which is termed ICDAS II (International Caries Detection and Assessment System). It can be applied to individual tooth surfaces. ICDAS-II complements the Mount and Hume system by characterizing lesions linked to their histological depth. Studies investigating the ICDAS II methodology confirm its accuracy for predicting the penetration of caries lesions into dentine with histologic validity. Utilizing such classification systems allows appropriate documentation of lesions and provides a sound basis for communication between dentists. The ICDAS-II system distinguishes between a sound tooth surface, the first visual change in enamel (the pre-white spot lesion), the first distinct visual change in the enamel, the occurrence of micro-cavitation and the progression of caries within the tooth to involve various levels of destruction (Table 1). Table (1): ICDAS-II scoring system for enamel 9 3) International Caries Detection and Assessment System (ICDAS) The ICDAS detection codes range from 1 to 6 depending on the severity of the caries lesion. 10 Restorations can be avoided in the following situations: 1. Non-cavitated white spot lesions, such as hidden proximal lesions detected on a bitewing radiograph, if these are confined to within the enamel or are just into dentine (as they are unlikely to be cavitated). 2. Rootsurfacelesions,bothcavitatedandnon-cavitated,ifaccessible for cleaning and application of topical re-mineralizing products. 3. Recurrent lesions adjacent to restorations, if both small and cleansable. 4. Large cavitated lesions accessible to plaque cleansing (no overhanging enamel), where loss of function and aesthetics is acceptable. Minimal surgical intervention for cavitated lesions This can be achieved through the great evolution in materials, tools, instruments and equipment used in dentistry. Features of a conservative cavity should provide the following: 1. Include all defective enamel and dentin. 2. No extension beyond defective areas. 3. Convenient instrumentation and material placement 4. Freeing of all margins with adjacent surfaces. 5. Necessary resistance and retention forms. Mount's classification: (the Si/Sta concept) ▪ Black's classification (I, II, III, IV, and V) which has been serving for a very long time has been challenged as being not specifying the size of the lesion. ▪ A new classification of cavity based on the new concept of minimal intervention has been proposed by Mount & Hume, 1997. ▪ The sites include: Site 1: Pits and fissures and enamel defect on the occlusal surface of posterior teeth and smooth surfaces on anterior teeth.. Site 2: Contact areas between any pair of teeth, anteriors or posteriors. Site 3: Cervical areas related to gingival tissues including exposed root surfaces. 11 ▪ The sizes that can be readily identified include: Size 0: Initial lesion at any site but not yet resulted in surface cavitations. It can possibly be healed by remineralization. Size 1: Smallest minimal lesion requiring operative intervention. The cavity is into dentin just beyond healing by remineralization. Size 2: Moderate-sized cavity. There is still sufficient sound tooth structure. Size 3: More than moderate size cavities. The cavity needs to be modified to provide some protection for the remaining tooth tissues. Size 4: The cavity is extensive, following the loss of cusp from a posterior teeth or an incisal edge from an anterior. (Bulk loss)  Steps of cavity preparation: I- The outline form: Obtaining the outline form: There are a number of factors that affect the outline form, which include: 1. The extent of carious lesion. 2. Areas of demineralization which are non- remineralizable. 3. Proximity of the lesion to other defects in enamel. 4. Esthetic considerations. 5. Relationship of approximating and opposing teeth. 6. Type of material used. 7. Operating convenience for preparation and restoration. 8. Patient’s age. 9. Caries index and oral hygiene measures. 10. Tooth positioning. 11. Existing restorations. 12  I. Out line form: According to Black According to the conservatism An extension for prevention concept Caries and convenience dictate the was performed. outline. - Margins are placed in self cleansable - The margins just past the fissure. area. - Till convenience &instrumentation are - The mesial and distal extensions were achieved. midway between the crest of the marginal ridge and depth of the triangular fossa. Buccally and lingually the extensions were midway between cusp tips and central fissures. - In proximal surfaces, the facial and - In proximal surfaces, the facial and lingual margins extended midway lingual margins are extended just beyond between axial line angles and facial or the contact to free it with a clearance of lingual margin of contact area. 0.5 mm. -The gingival margin extended below - The gingival margin is extended just to the crest of the healthy gum margin. include the defect. - In facial or lingual surfaces, the mesial - In facial and lingual surfaces, all and distal walls were extended up to the margins are dictated by the outline of the axial line angles. While incisally or defect occlusally the walls were located above the height of contour. 13 II- Obtaining the resistance and retention forms a- Resistance form According to Black, The cavity width is governed by margin placement midway between the cusptip and depth of the fissure. The cavity depth was about 0.5mm pulpal to the DEJ. Alternatively, the conservative approach allows the cavity widthto be extended just to provide convenience. The cavity depth is located just below the DEJ for amalgam while it can be in dentin or enamel in modified cavities for composite. b- Retention form According to Black, - The retention was mainly macro-mechanical. According the conservative approach: -Bonding offers a micromechanical level of attachment to tooth structure thus minimizing the need for cutting to create retentive features. III- Convenience form: It is the form given to the cavity to be easily seen, reached & restored. According to Black, Cutting of sound tooth structure was sacrificed to improve the visibility &accessibility. 14  According the conservative approach: The recent magnification tools, micro-sized cutting tools & recent cavity designs allow extreme preservation of sound tooth structre. IV- Removal of remaining carious dentin According to Black. All caries must be eliminated completely and if the pulp becomes exposed (called pathological exposure) & then it has to be treated endodontically. According the conservative approach: - Pulp capping can be made in case that the pulp does not show any clinical manifestation of pulpitis or degeneration; by making secondary dentin. - The differentiation between infected dentin and affected dentin is facilitated by the use of Caries detection dyes, which is applied over the deeply seated carious lesion. This is an acid red dye that is painted using a mini brush over the carious tissue then left for a minute then rinsed adequately. If a red stain remains after washing, this indicates that a further removal of this diseased tissue is required; as it denotes that denatured collagen is present and infected dentin needs to be further removed. If no stains are left after washing, this indicates that remaining tissues could be considered; as affected dentin that could be re-mineralized, if left behind, causing no harm to the pulpal tissues. Partial caries removal: A further challenge to the wisdom of conventional caries removal has come from Edwina Kidd, whose work has shown that leaving small amounts of infected dentine in a cavity does not seem to result in caries progression, pulpitis or pulp death, provided the overlying restoration has a perfect seal. 15 There is no clear evidence that it is harmful to leave infected dentine, even if it is soft and wet, prior to sealing the cavity. The issue is the perfect seal of the final restoration. * Another modality of management of deep caries is that of using the chemico- mechanical caries removal approach (Carisolv) to dissolve the required amount. * More recently, the use of Smart prep burs has been advocated. These are designed to brush away decay without disturbing healthy dentin and are made of a malleable polymer material and incorporate small “paddles” that become rounded when they come into contact with hard, healthy dentin. This self-limiting configuration greatly reduces the number of exposed dentinal tubules thus reducing the need for local anesthesia. IV- Finishing of E-mails: the same in both approaches V- Toileting. The same preparation of the substrate tooth surface to receive the restoration. The key principles of minimal invasive cavity design for an adhesive permanent restoration can be summarized as follows: 1. Minimize tooth structure removal so that the preparation follows the shape of the lesion, and is sufficient to achieve visual and instrument access to the caries. 2. Achieve a predictable marginal seal and remove demineralized dentine around the full cavity periphery 3. No flat cavity floor is required 4. Create rounded internal cavity angles; occlusal keys or dovetails are not required. Some internal cavity resistance form or small proximal retention slots can be placed to reduce stresses on the bond to dentine. 16  Conservative cavity designs:  A design based on the shape and extent of the lesion is advocated. Overzealous removal of healthy tooth tissue is considered un- allowed to provide neither flat floors nor squaring out the cavity as in Black’s design.  The finished preparation then very much resembles the shape of the carious lesion it replaces but with refinements to satisfy certain requirements. The concept of extending proximal walls to be localized in self-cleansable areas is subject to controversy as Elderton in 1984 denoted that the so-called self-cleansing areas are virtually non-existent. This was demonstrated readily by disclosing solutions.  He also considered the placement of cervical margin into gingival crevice other features were not recommended as it’s no longer believed to be immune from caries. Upon touching the gingiva, it’s very likely that irritation initiates an acidic- medium and thus becomes vulnerable to future decay.  In proximal caries, a rather rounded design is thought to be suitable for oral hygiene measures accessibility. The cavity is said to have no corners. Thorough condensation of amalgam is difficult with this design but the placement of bonded restoration is substantiated due to better wetting of resin composites on rounded corners rather than sharp ones. It’s also important to emphasize that the depth in which brittle resin-based composites is liable to controversy owing to the properties of the material that have limitations to overcome.  The different examples of conservative designs could be: ❖ Preventive resin restorations (PRR) -Features; 1. No special retentive areas. 2. No extension into sound pits or fissures. 3. It's not necessary to prepare beyond the lesion. 4. When caries is limited to enamel, there's no need to prepare into dentin as is necessary for amalgam restoration. 5. Small cavities could be restored with a flowable composite as a fissure sealant but it is recommended to use filled wear-resistant composites followed by fissure sealants to seal the adjacent fissures. 17  Preventive resin restorations (PRR) ❖ Simple box preparation Indication ▪ It's used to restore small proximal lesion without either occlusal fissures or previous occlusal restoration. ▪ It’s limited to teeth with narrow interproximal contact. It’s mainly used whenever there’s a need to avoid cutting into sound occlusal surfaces. ▪ The outline could have rounded margin as in resinous material or could be in the form of definite walls as in case of amalgam restoration. ▪ Outline: Buccal and lingual walls of the box should be almost facing each other to maximize retention. It’s done without an occlusal step ▪ Preparation: To compensate for the lack of occlusal portion that allows retention; proximal retentive grooves on the expense of facial and lingual walls are done. ▪ Restoration: Using amalgam or resin composite according to the cavity design. Simple box preparation 18  ❖ Slot preparation Indication This type of preparation is used in: 1. Old patients who have gingival recession and cavities are on the proximal exposed cementum on the root surfaces that is gingival to the contact area 2. It is used with wide embrasures that allow easy access to the proximal lesion saving sparing the marginal ridges and the occlusal surfaces. Advantages: 1. It offers better esthetic, 2. It does not alter occlusal relationships, 3. It may preserve a natural proximal contac Preparation 1. The occlusal and gingival walls should be perpendicular to the long axis of the tooth. 2. Two retentive grooves could be placed along the occluso-axial and gingivo- axial line angles if retention is required for non-bonded restoration. Restoration This could be done using amalgam, resin composite or glass-ionomer and its modifications. Slot preparation 19  ❖ Tunnel preparation - This type of preparation is also termed internal fossa, internal oblique preparation, internal occlusal diagonal preparation or simply internal preparation. - The tunnel approach for proximal lesion preparation allows preservation of the marginal ridge without undermining it. - Air-abrasion can perform such a design. Disadvantages 1. Pulp Exposure risk 2. Extension of carious tissues which is different to be seen. 3. Residual carious can be left leading to recurrence & failure of restoration. 4. The solubility of the glass ionomer is doubtful even with the enhanced physical properties "Partial tunnel" "Total tunnel" This preparation when this proximal This occurs when enamel has been enamel is left intact as it's neither perforated by the carious lesion and carious nor cavitated but left supported removed during the preparation. by sound dentin. Restoration: Restoration: Closed sandwich technique Open sandwich technique 20  Tunnel preparation D)-Technological advances in different related aspects I. Advanced diagnostic tools to detect incipient lesions: - Up to date, no diagnostic tool could make caries detection full proof. - The earliest possible lesion detection will provide the facility of condition reversal. It could also provide for a minimum tooth structure removal and consequently a much conservative restoration. - The use of sharp explorer and the analysis of high-quality bitewing radiographs have been the mainstays of the dentist up to the present day. But this was proved that, probing may disrupt the tooth surface and predispose to cavitation or may incorrectly result in misdiagnosis because stickiness may be due to fissure morphology or probe pressure. - This led to the development of several techniques that help the operator to reach an accurate diagnosis. Amongst which is the use of intraoral camera, digital radiography, the laser-based device (DIAGNOdent), the fiber optic trans-illumination and the electric caries monitor. Magnification technology: 1. Loupes Extension of eye glasses with magnification power 2X-5X. They are sometimes associated with lighting by single spot halogen or fiberoptic lamps but this adds to them more weight. 21 2. Microscopes Magnification power is 10X-25X. Either fixed (wall-mounted or ceiling-mounted) or mobile to serve in several workstations. The intraoral camera: -It’s a camera placed inside the oral cavity to allow display of intraoral images of exceptional quality on a computer. -It serves to communicate and demonstrate to patients the need for treatment. -It also allows to increase the quality of care dentists provide because they offer improved visual access to the dental cavity, improved lighting, and magnification. Advanced diagnostic tools to detect incipient lesions: Digital radiography Advantages: 1. Lower exposure of radiation for patients, 2. Absence of darkroom and processing solution 3. Convenience of image enhancement, magnification, density assessment,.etc 4. Used in diagnosis of initial proximal caries lesions while it possesses minimal diagnostic value for detection of occlusal enamel caries and superficial dentinal caries. Disadvantage: 1. It underestimates the size of the lesion considerably. 2. Provides high false positive results when used for occlusal caries detection. The radiographic classification for proximal caries lesions is as follows: 0= radiographically sound surface. E1 = lesion in the outer half of the enamel 22 E2 = lesion in the inner half of the enamel D1 = lesion in the outer third of dentin D2 = lesion in the middle third of dentin D3= lesion in inner third of dentin - Sub-clinical lesions of values E1 and less than E1 - Clinical lesions of values E2 and more, could be detected by clinical examination. - The importance of this classification in line of treatment as values E1, E2 and possibly D1 could be subjected to a medical model by remineralization only while other values will be operatively treated. Traditional dental practice generally adopts the criterion that restorations should be placed when a proximal radiolucency is observed. Using the minimal intervention approach restorations are not indicated if the lesion has extended to D2 region, that is, where the probability of cavitation in the enamel is between 10% and 41%. Laser-based device (DIAGNOdent) - The device works on the fluorescing nature of bacterial, (streptococci mutants) metabolic by-products. - This fluorescence is detected into numerical figure that can be used in the diagnostic protocol. It thus allows measuring the level of cariogenic bacterial activity. - In other words, it detects caries-induced changes in the tooth. - Advantage the quantitative nature of its readings gives a basic guideline that could be followed up longitudinally to monitor the decay extent. 23 - Red light with a wavelength of 655nm is transported to an angulated tip of the device by a central fiber. Additional light fibers are concentrically arranged around the central fiber and a filter eliminates ambient light. - A photodiode measures the amount of fluorescent light passing through the filter and a digital display shows numerical values. - Two fiber-optic tips, a tapered one for the fissure caries and a flat one for smooth surface caries area are supplied with the system. Digital Imaging Fiber Optic Transillumination tool (DIFOTI): - It is based on the fact that carious enamel has a lower index of light transmission than sound enamel. - It allows the capture and view of real-time digital images on the computer monitor. - Its mouthpieces enable dentist to view: a) Decay on occlusal surfaces, b) Around restorations, & c) Facial and lingual surfaces. - It detects incipient caries & fractures. - A high-intensity light is passed through the tooth and the transilluminated image of the tooth is captured on a charge -coupled device (CCD), then analyzed by computer software and displayed on a computer screen for diagnosis. Electrical caries monitor (ECM) - It's based on the electrical conductivity differences between sound dental tissues and carious dental tissues in absence of liquid (saliva). 24 - It works effectively for detection of occlusal caries and measures the electrical conductivity of a site on the tooth during controlled drying. The conductivity should be recorded in the absence of liquid (saliva). - Low conductivity measurements indicate well-mineralized tissue while high conductivity values indicate demineralized tissue. - It has the ability to: ▪ Detect demineralization even when the surface remains macroscopically intact. ▪ Monitor lesion progression, in remineralization. II. Non-invasive cutting tools: Requirements of the ideal cutting instrument: 1. Comfort 2. Ease of use 3. Ability to discriminate and remove diseased tissues only 4. Painless, silent, requires minimal pressure for optimal use 5. Does not generate heat or vibration during work 6. Affordable and easy to maintain 1- Air-abrasion technology Air abrasion equipment has been produced and used since 1950. In spite of showing promising results, the concept did not gain popularity due to three major factors. 1. Firstly, air abrasion was not able to prepare cavities with well-defined walls and margins, and the materials during that time (mostly amalgam and direct or indirect gold) demanded such preparations since the concept of bonding had not been introduced. 25 2. Secondly, the introduction of the air turbine handpiece in the late 1950s made conventional cavity preparations less time consuming. 3. Thirdly, as high-velocity suction had not been developed, evacuation of the powder was difficult. - Nowadays bondodontics have solved the problem by using resinous material to restore cavities prepared by air abrasion. - Mode of action This technique allows the flow of a stream of compressed air (40-140psi) that carries aluminum oxide particles (20- 50µm) which strike the tooth surface. Today Applications: Specific indications for use of air abrasion include caries removal; removal of small existing restorations; preparation of tooth structure for cutting or etching for the placement of composites, porcelain and ceramics; and as an adjunct to the conventional handpiece bur. Some of the situations where the air abrasion has particularly proved a boon include: 1. Removal of superficial enamel defects – these are much easier with the air abrasives since they result in removal of less tooth structure than the drill. 2. Air abrasion can also be used for the removal of pit and fissure surface stain on enamel before placement of a resin-based composite restoration or porcelain veneers 3. Teeth where the caries is restricted only to a small section of the tooth can also be prepared using air abrasives for conservation of sound tooth structure. Box- preparations for Class II cavities can also be prepared. 4. Surface preparation of abfractions and abrasions – air abrasion breaks the glaze of the highly polished surface that is not suitable for bonding and produces a highly textured surface that is excellent for the wet dentin-bonding technique. 5. Removal of existing restorations – the particles of the air abrasives can be used at higher pressures for removal of old amalgam restorations for replacing 26  them or for removal and repair of composites, glass ionomers, and porcelain restorations 6. The use of local anesthesia while working in dentin may be avoided because of their cooling action through high pressure air It has shown its safety concerning: ❖ Tooth vitality ❖ Not hazardous to the patient nor to the operator so long that the protective measures are taken into consideration during its use. These essentials are the use of a rubber dam, high velocity suction unit and face shields or protective facemasks to control the messy procedure. 2- Chemico-mechanical removal of tooth tissues (CARISOLV) - The aim of micro dentistry is to identify diseased tooth structure, and then remineralize those structures with minimal disruption of the surrounding tooth structure. Mode of action - Chemical methods of caries dissolution were based on the combined use of an organic acid and sodium hypo-chlorite. Now they use the combination of amino acids and a weak solution of sodium hypo-chlorite in a gel form. - Apply the gel over the diseased tissue for several minutes until it performs its action then gentle scrapping is done using specially designed instruments that resemble excavators. - This gel focuses on diseased tissue only and selectively reacts by chemically disrupting denatured collagen in demineralized zone. The specially designed instruments are used then to remove the unsupported mineral in the softened materials. 27 - It does not affect healthy dentine or soft tissue nor does it affect enamel. Consequently, it should be used in combination with other cutting techniques. - Used: in root caries, coronal caries with open access and in deep caries approaching the pulp. 3- Ultrasonic cutting The early generations SonicSys could not preserve tooth structure and tend to dictate a wider cavity preparation owing to their large sizes. Later on SonicSys micro with oscillating working tips was introduced. It permits extremely precise preparation without damage to healthy tooth substance owing to its smaller sizes. 4- Laser technology - The most commonly used types are excimers, which are special ultraviolet lasers. - CO2 and Nd: YAG lasers: have also shown to be promising. The use of laser beam is focused to deliver a total energy to the subjected substrate. Lasers are used with caution for cavity preparations, as they are inefficient at removing large amounts of enamel and dentin and result in generating extensive amounts of heat. 5- Enzymes - This approach is still surrounded with extensive researches. - Pronase enzyme successfully disintegrates decayed dentin. Mode of action: It said to perform digestion of carious dentin. Pronase does not attack sound dentin but solubilizes more than 90% of the nitrogen present in carious dentin. It has no ability to remove sound or carious enamel. 28 6- Ozone Technology Advantages: 1. Simple, time saving, effective and efficient approach. 2. No cutting is performed. 3. It rapidly penetrates the bacteria and kills them in their protected niches. 4. It could alter the metabolic products of bacteria that inhibit remineralization and thus allows clinical reversal of the lesion. 5. It used in treatment of root and occlusal caries. The production of pure ozone in the spot that is to be treated by means of probes, reduces and eliminates the pathogen either bacteria, viruses or fungi. - It’s supplied through a medical device known as HealOzone that produces ozone in the unit by passing air through high voltage. Ozone reaches the lesion via a handpiece covered by a cup that is placed on the lesion for a period of 10 seconds. This results in deactivation of 99% of bacteria, fungi and viruses. - This is followed by suction to eliminate any ozone remnants. A time lapse should be allowed for remineralization of treated tissues which are rather soft before any restorative procedure. - This takes about 3 months and is done using an at-home care kit containing dentifrice and mouthrinse. No amputation is thus done before the placement of any restorative procedure. This methodology, if becomes widespread after its success, would be revolutionary as it means that tooth tissues even if diseased would not be excised. 7- Smart prep burs These are designed to brush away decay without disturbing healthy dentin and are made of a malleable polymer material and incorporate small “paddles” that become rounded when they come into contact with hard, healthy dentin. This self-limiting configuration greatly reduces the number of exposed dentinal tubules, thus reducing the need for local anesthesia. 29 III. Bondodontics: ▪ With the advent of minimally invasive Dentistry, there has been a paradigm shift, moving away from metal restorations and toward adhesive dentistry and the conservation of tooth structure. ▪ The first idea of bonding to tooth structures was introduced by Michael Buonocore in 1960s by etching of enamel and results in terms of minimizing the interfacial gaps at this critical interface. ▪ Bonding is better than adhesion as true adhesion does not actually occur to the oral tissues. ▪ Adhesion means chemical-based bonding by strong interatomic or intermolecular attraction forces along the interface between an adhesive and a structurally different substrate surface at microscopically gap-free interfacial contact. ▪ Micromechanical bonding depends on formation of an intermediary joint consisting of numerous resin micro tags and resin tooth hybrid layer created in the top 2-5 pm layer of substrate tooth. ▪ Adhesion is thus different from micromechanical bonding. ▪ By correlating the above interpretation, it seems essential to substitute the term adhesion by bondodontics to be more precise in description of this science. Bonding thus allows maximum preservation of tooth structure and hence maximum conservation. ▪ Clinical significance of bonding: 1. Ultra-conservation of tooth structure: through elimination of undercuts, groovesand pinholes. 2. Long term restoration retention: strong bond provides longevity of the restoration and prompted patient acceptance. 30 3. Decrease microleakage and its sequels which are: postoperative hypersensitivity, recurrent caries, cytotoxic pulp reaction, discoloration, fracture or dislodgment. 4. Reinforcement of the remaining tooth structure: (still a controversy) due to the ability of bonding between the restoration and tooth that participate in its load carrying ability. 5. Wide application of tooth-colored restoratives. 6. Better transmit and distribute functional stresses across the bonding interface to the tooth thus provide better resistance. 31