REVIEW OF LITERATURE
DEFINING DENTAL CARIES
ROLE OF DENTAL BIOFILM IN ORAL HEALTH & DISEASES
CHEMISTRY OF DENTAL CARIES
DYNAMICS OF TOOTH SURFACE
PROCESS OF DE-MINERALIZATION
THE ORAL ENVIRONMENT
DETECTION & DIAGNOSIS OF DENTAL CARIES
LASER FLUORESCENCE- The DIAGNODent
DETECTION SYSTEM BASED ON ELECTRIC CURRENT MEASUREMENT
THE ICDAS SYSTEM (International Caries Detection and Assessment System) 114
CLASSIFICATION OF DENTAL CARIES
CAMBRA(CARIES MANAGEMENT BY RISK ASSESSMENT)
NON-INVASIVE MANAGEMENT OF DENTAL CARIES
OPTIMAL CARIES PREVENTIVE MEASURES
CHEMO-MECHANICAL METHOD OF CARIES REMOVAL
CHEMOMECHANICAL CARIES REMOVAL Vs. MECHANICAL CARIES REMOVAL
SURGICAL APPROACH TO CARIES MANAGEMENT (THE PRINCIPLE)
MECHANICAL METHODS OF CARIES MANAGEMENT
I am truly blessed for the guidance of my Supervisor Dr Preeti Dhawan MDS Pediatric Dentistry Prof. and Head Dept. Of Pediatric Dentistry Seema Dental College and Hospital and Dr Himanshu Aeran MDS Prosthodontics Director Principal Seema Dental College and Hospital without whose help and guidance this project would not have seen the light of the day.
I dedicate this book to my mom Mrs Indira Singh and Dad (Late) Mr Yogendrapal Singh.
Dental caries is a multifactorial disease that has many contributing factors, including biological, genetic, socioeconomic, cultural, and environmental issues. It’s the localized destruction of susceptible dental hard tissue by acidic by-products from bacterial fermentation of dietary carbohydrates.1
Dental caries is a disease that dates back to antiquity & occurs in populations that have never used sugar or processed food. The prevalence of dental caries appears to increase with civilization, urbanization & affluence. There is presently an alarming rate of increase in prevalence of dental caries in developing countries.2 Although significant caries prevalence has been noted since the time of pre-Neolithic humans (10,000 BC) with reported caries prevalence between 1.4% and 12.1% carious teeth, it was not until the fourteenth and fifteenth century when a sharp increase in caries prevalence was noted. This increase is often ascribed to a sucrose-civilization-caries trinity, with caries prevalence rising above 25%. The sucrose-civilization caries trinity fails to describe the entire picture. At the same time as sucrose consumption increased, so did life expectancy.3
The surgeon General’s report in 2000 labeled Dental caries as a “SILENT EPIDEMIC” that is affecting individuals of all ages, cultures, ethnicities, and socioeconomic backgrounds.4 Caries is the most prevalent disease of children and is epidemic in some populations. In 2000, it was determined that dental caries was the most common chronic disease of childhood, with a rate five times greater than that seen for the next most prevalent disease of childhood: asthma.5
Dental infections are common and usually non-life-threatening in nature, the significance of dental caries in overall health has historically been minimized. However, it is evident from numerous other studies that dental caries continues to affect individuals through childhood and beyond.6
Dental caries is the main reason for placement and replacement of restorations.7,8 The demineralization process occurs because of high consumption of sugary and/or starchy foods and sugared beverages, combined with insufficient fluoride exposure, inappropriate oral hygiene, and/or poor salivary flow.9
The replacement of restorations can result in cavity preparations larger than the predecessors, which leads to weakening of the remaining tooth structure. The longevity of a restoration is attributed to the restorative material properties, the technical quality of the restorative procedure and the patient’s compliance with appropriate maintenance of their oral hygiene.7,8
Much of the dentistry is focused on restoring the symptoms of this transmissible bacterial infection rather than treating its etiologic cause, the infectious cariogenic biofilm in a predominantly pathologic oral environment.
The traditional surgical dental caries management philosophy was based on “extension for prevention” and restorative material needs rather than on preserving the healthy tooth structure. This surgical approach, originally developed by G.V. Black and others, has been the standard in dental practice for over 100 years. This technique emphasized large amalgam cavity preparations, which required removal of additional tooth structure in order to provide mechanical retention for the restorative material.10
In the 1970s, the surgical dental paradigm began shifting to a new approach for caries management based on “prevention of extension”. It was a new medical model which emphasizes caries risk assessment, early caries detection, remineralization of tooth structure and especially preservation of tooth structure through minimal intervention in the placement and replacement of restorations. A risk-based approach to managing caries targets those in greatest jeopardy for contracting the disease, as well as provides evidence-based decisions to treat current disease and control it in the future.11
Dr. Miles Markley, who died in 2000, deserves much of the credit for bringing to the profession concepts of minimal intervention. From the 1930s until his retirement from practice in the 1970s, Dr. Markley used many of the preventive strategies available to us today.12 So to better address this highly prevalent disease and conserve tooth structure, dental practitioners started to use these new techniques and adhesive restorative materials in order to meet the caries preventive and restorative needs of children and adults.10
The minimal intervention paradigm emphasizes use of adhesive restorative materials in order to minimize the size of cavity preparation.11 This new medical model, known as Minimally Invasive Dentistry (MID), is a conservative philosophy that reduces restorative procedure time, pain and stress, and results in decreased patient anxiety.11
MID emphasizes that initial caries lesions in the enamel can be repaired by increasing the amounts of calcium, phosphate and fluoride in the saliva. Also, when a lesion needs to be restored, MID emphasizes adhesive restorative techniques, which allow removal of the decay in a way that involves minimal loss of healthy tooth structure.11 The term “minimal intervention” was endorsed by the Federation Dentaire Internationale in a 2002 policy statement and is globally recognized.13
The traditional restorative repair of teeth did little to treat the actual cause & risk factors of the disease; thus by using the risk assessment approach for management of caries(CAMBRA - Caries Management by Risk Assessment) its possible to assess risk of an individual patient & establish evidence based management strategies based on that risk.14,15
With the CAMBRA methodology the clinician identifies the cause of disease by assessing risk factors for each individual patient. Based on the evidence presented, the clinician then corrects the problems (by managing the risk factors) using specific treatment recommendations including behavioral, chemical, and minimally invasive procedures. Both the risk assessment and interventions are based on the concept of altering the Caries Balance. The Caries Balance is a model where pathological factors (bacteria, absence of healthy saliva, and poor dietary habits (i.e., frequent ingestion of fermentable carbohydrates) battle protective factors (saliva and sealants, antibacterials, fluoride, and an effective diet).16
While the paradigm has begun to shift from the G.V. Black surgical approach toward the Minimally Invasive Dentistry philosophy, several articles in the literature continue to suggest that many dental practitioners have not changed their operative strategies to the modern restorative approach which emphasizes preservation of tooth structure.
This evolution of a paradigm shift may take decades & involve several stake holders; however many practitioners are already using this as their current standard approach in patient care. Yet many clinicians still need help getting started with employing these principles in their practice. As Rome was not built in a day similarly changing paradigms in caries management does not happen without global involvement and collaboration from several sources. Despite all the advances made in this arena CAMBRA & MI still fall short of inclusion in main stream dentistry globally. The behavior of the profession must shift from a surgical only approach to caries management towards a system that clearly surpasses traditional methods.
It’s in the best interest of the profession to gear itself for the future & embrace caries management by risk assessment. This means thinking of dental caries as a disease process with the possibility of intervention, arresting the progress of the disease, and even reversing it. Caries risk assessment should become a routine part of the comprehensive oral examination, and the results of the assessment should be used as the basis for the treatment plan. Patients are the first to notice & appreciate this change towards treating the disease by preventing it rather than waiting for the disease to cause significant damage that can be surgically restored. This should motivate more and more clinicians to incorporate CAMBRA & MI in daily practice.
REVIEW OF LITERATURE
Goldstein RE, Parkins FM17 in 1994 reviewed the history, characteristics and clinical approach of air abrasion technology including the advantages and limitations for the removal of stain, enamel, dentin and decay. The authors concluded that air abrasion system offers several advantages over conventional hand pieces like the air abrasion system minimizes heat, vibration and bone conducted noise associated with conventional means of caries removal since the cutting is accomplished by air pressure.
In 1998 Christensen GJ18 made his observations about the air abrasion tooth cutting for smaller restorative situations and concluded that air abrasion tooth cutting has been accepted relatively well by a small segment of the profession. It’s expected to continue to grow in popularity as it is relatively painless, fast, effective and noninvasive compared with rotary cutting and the devices are becoming more refined, and lower-cost air abrasion units are available.
Bryant CL19 in 1999 described the role of air abrasion in preventing and treating early pit and fissure caries and concluded that a key factor in diagnosing pit and fissure decay is recognizing the importance of early detection, and either prevention or treatment of these often small and difficult to detect carious lesions and in such cases air abrasion preparation gives the dental team unequaled flexibility in the treatment of such surfaces.
A study was conducted by Ericson C, Zimmerman M, Raber H, Gotrick B and Bornstein R20 in 1999 regarding the safety and efficacy of a new method for chemo mechanical removal of caries. The results showed that the new method of caries removal causes less discomfort compared to drilling. Also dentin caries was effectively removed using the Carisolv method without any adverse reactions. Thus the author concluded that the method might also be of potential interest for use in combination with atraumatic restorative treatment in developing countries.
Banerjee A, Watson TF and Kidd EAM21 in 2000 discussed some of the techniques available to excavate demineralized dentin clinically. The author concluded that all the techniques will remove carious dentin with different level of efficiency and whether these techniques will discriminate between the soft, outer, necrotic, highly infected zone that needs to be excavated and the inner reversibly damaged, less infected zone which could be retained is still unknown.
A thorough review of of the techniques and latest developments in chemo chemical caries removal was conducted by Beeley JA, Yip HK and Stevenson AG22 in 2000. The authors illustrated that chemo chemical caries removal involves the selective removal of carious dentine and because only carious dentin is removed, the painful removal of sound dentine is avoided and hence the need for local anesthesia is minimized.
In 2000 analysis of the different surface characteristics of the dentine cavity floor using five different mechanical and chemo-mechanical methods of excavation was carried out by Banerjee A, Kidd EAM and Watson TF23. The results of the study showed that Carisolv gel was the only method examined that consistently removed the smear layer during excavation to leave exposed dentine tubules at the end of cavity preparation.
A review of newer modalities for tooth preparation- lasers and air abrasion was done by Reyto R24 in 2001.He came to the conclusion that the hard tissue lasers and air abrasion units have a place in the modern dentist’s armamentarium. The author further illustrated that the speed, comfort, ease of approach, public relations, and patient appeal are some of the advantages along with dentist’s own comfort and satisfaction without frightening the already fearful patient.
A comparison of the size and number of air-abraded preparations that extended into dentin in an early treatment group and a control group was conducted by Hamilton JC, Dennison JB, Stoffers KW, and Welch KB25 in 2001. Judged on the basis of the weight of the preparation impression (a surrogate measure of volume), there was no benefit gained from early treatment of questionable carious lesions, so the author’s concluded that early operative intervention should not be recommended until proven clinical benefits have been demonstrated.
Banerjee A and Watson TF26 in 2002 explained about the mode of action of the air abrasive units and discussed some of the clinical uses of these techniques as well as the potential pitfalls and concluded that air abrasion provides a useful addition to the dentist’s armamentarium for operative dental treatment but caution must prevail when recommending its use but adequate practice and training is required before clinical use and in that way air abrasion can be used for maximum clinical benefit now and in the future.
An in vitro evaluation of the effects of air abrasion, acid etching and the combination of both procedures, on the shear bond strength of a composite resin to an enamel surface was carried out by Cristina M, Benitez ABE, Guenka R, Nunes T, Salvitti TN, Aparecida S27 in 2002. The results of the study demonstrated that the application of an aluminium oxide jet in association with the acid conditioning of the enamel presented shear bond strength resistance values statistically similar to those obtained by acid conditioning. Both methods presented better results than the aluminium oxide jet used alone.
Hamilton JC, Dennison JB, Stoffers KW, Gregory WA, and Welch KB28 in 2002 evaluated the efficacy of early treatment of questionable carious lesions in pits and fissures of posterior teeth using air abrasion followed by placement of preventive resin restorations over a period of two years. Based on the results of this study the authors inferred that the preventive resin restorations and sealants placed in the early treatment group performed well after two years.
A study wherein the effects of chloramines used in the Carisolv system on carious dentin mechanical properties and morphology were investigated, using Vickers hardness test and scanning electron microscopy(SEM) was carried out by Ken-ichi T , Araki K, Mataki S and Kurusaki N29 in 2003.The author concluded that the amino acids in tha Carisolv system decrease the aggressive effect of sodium hypochlorite on sound dentin and/or inner layer of carious dentin and also would enhance the disrupting effect on degenerated collagen in carious dentin outer layer.
An assessment of the acceptance and success of the technique in young nervous patients was carried out by Ansari G, Beeley JA and Fung DE30 in 2003. The study achieved a success rate of 90% in acceptance of cavity preparation followed by placement of restoration. Thus the authors came to the inference that chemomechanical caries removal is an effective alternative to conventional mechanical caries removal.
Azrak B, Callaway A, Grundheber A, Stender E and Willerhausen B31 in 2004 compared the efficacy of chemomechanical caries removal with that of conventional excavation in reducing the count of cariogenic flora. The results showed that that the efficacy of chemomechanical removal of carious dentine in children by means of Carisolv is comparable to the results obtained by conventional methods, and thus might serve as a suitable alternative.
Gutkowski S, Berger EK32 in 2004 discussed why and how a noninvasive or minimally invasive protocol can reverse decay before attempting surgery. The author’s further explained concept of remineralization vs. surgical intervention, role of the quantity and quality of saliva in cariogenicity.
In 2004 review of atraumatic restorative technique: a minimal intervention approach to treat dental caries was conducted by Frencken JE, Holmgren CJ33. The authors concluded that the ART approach is very patient-friendly and that it produces good short-term survival results for the treatment of single-surface dentinal lesions in both deciduous and permanent dentitions and also that the ART approach contributes to the improvement of oral health for many the world over and should form an essential part of every dentist’s armamentarium.
Hudson P34 in 2004 explored about the developments occurring in dentistry involving a change in focus from gross mechanical instrumentation of dental caries to early diagnosis and treatment of the bacterial infection that cause caries and concluded that as dentists embrace a new paradigm in the treatment of the Class I lesion they are beginning to acknowledge means to accurately assess the extent and threat of existing disease, provide minimal invasive treatment and clearly describe services rendered.
In 2004 an evaluation of the effectiveness of single-surface ART restorations in the permanent dentition was performed by Frencken JE, Vant Hof MA, Van Amerongen WE and Holmgren CJ35. The results showed that there is no difference in survival results between single surface ART restorations and amalgam restorations in permanent teeth over the first 3 yrs.
Christensen GJ36 in 2005 summarized the advantages of minimal invasive dentistry by illustrating various examples of minimally invasive oral procedures.
In 2005 a comparison of the efficacy of chemomechanical and mechanical methods of caries removal in the reduction of Streptococcus mutans and Lactobacillus in carious dentin removal was made by Tobias GQ, Oliviera EG and Neto M37. The authors thereby concluded that the two methods are comparable in reducing Lactobacillus but Carisolv is more effective in elimination of S. Mutans.
Lopez N, Simpser- Rafalin S, and Berthold P38 in 2005 evaluated the acceptability and effectiveness of atraumatic restorative treatment to prevent and treat caries in an underserved community in Mexico & inferred that atraumatic restorative treatment is acceptable and effective to control and prevent decay in a socioeconomically deprived community.
A two year clinical study to evaluate whether sealant retention increased when fissures were prepared using an air abrasion system followed by acid etching at 6, 12 and 24 month recall appointments was done by Yazici R, Kiremitci A, Celik C, Dayagac B39 in 2006. The authors inferred that molar retention rates were significantly less than those for premolars at each evaluation.
Frencken JE, Taifour D, and vant Hof MA40 in 2006 compared the survival of ART and amalgam restorations in permanent teeth of children after 6.3 years. The authors concluded that the restorations produced with the ART approach, with high-viscosity glass ionomer, survived longer than those produced with the traditional approach, with amalgam, in the permanent teeth of young children.
Bresciani E41 in 2006 presented a review on clinical trials with Atraumatic Restorative Treatment. The author concluded that available scientific literature is encouraging in terms of management of dental caries by this approach, especially for one-surface lesions.
Van Gemert-Schriks MCM, van Amerongen WE, Ten Cate JM & Aartman IHA42 in 2007 compared the Three-year survival of single- and two-surface ART restorations in a high-caries child population. The results showed extremely low survival rates for single and two-surface ART restorations in the primary and permanent dentitions.
An evaluation of the efficiency of air abrasion alone and associated with phosphoric acid etching bond strength of a single-bottle adhesive/indirect composite restorative system was carried out by Silva PSG, Goncalves M, Nascimento TN, Centola ALB43 in 2007. Based on the results the authors put forth that the use of air abrasion alone or associated with a bonding agent yielded the lowest tensile bond strength of the resin to enamel which confirmed the use of or need of conventional acid etching as the treatment of choice for enamel.
Pandit IK, Srivastava N, Gugnani N, Gupta M, Verma L 44 in 2007 compared the different methods of caries removal was done in children of age group 6-9 years. The author concluded that the kinetic preparation technique in conjunction with the operating microscope solves the problem inherent in traditional preparation including obstruction of the operating field due to water sprays and microcracks created by traditional burs. The author further illustrated that the technique is nearly painless and silent while also eliminating heat, vibration and pressure. It provides the clinician a direct view of the preparation and the highest possible precision along with a stress free treatment and excellent results.
The influence of papain based gel for chemo-mechanical caries removal and on microtensile bond strength to dentin was studied by Piva E, Ogliari FA, de Moraes RR, Corá F, Sandrina Hen S, Correr-Sobrinho L45 in 2008. According to the results of this study, the authors drew the conclusion that the papain-based gel reduced the microtensile bond strength to carious dentin.
Motta LJ, Martins MD, Porta KP, Bussadori SK46 in 2009 presented a clinical case of aesthetic restoration of deciduous anterior teeth after removal of carious tissue with Papacarie. The author’s concluded that the use of Papacarie for the removal of carious tissue represents an alternative for dental cavity preparation as it promotes better preservation of healthy tissue and reduces the disadvantages of conventional methods using dental drills and excavators that induce discomfort and pain.
Topaloglu AK A, Eden E, Frencken JE, Oncag O47 in 2009 studied the two years survival rate of class II composite resin restorations prepared by ART with and without a chemomechanical caries removal gel in primary molars. The results indicated that ART with chemomechanical gel might not provide an added benefit increasing the survival percentages of ART class II composite resin restorations in primary teeth.
Hegde VS, Khatavkar RA48 in 2010 has reviewed the development of air abrasion, its clinical uses, and the essential accessories required for its use. The authors concluded that air abrasion dentistry has evolved over a period of time from a new concept of an alternative means of cavity preparation to an essential means of providing a truly conservative preparation for preservation of a maximal sound tooth structure.
A review of the concepts, methods & clinical incorporation of microdentistry has been carried out by Murel Carlos49 in 2010 where he has summarized the factors to consider when transitioning from traditional treatment to the practice of microdentistry with the operating microscope. He has propagated the use of microdentistry as a practice of minimal invasive dentistry with the aid of any optical device that magnifies the operating field.
Gugnani N, Pandit IK, Srivastava N, Gupta M, Gugnani S 50 in 2011 described a few cases that explain the clinical applicability of Soprolife camera. They further inferred that auto fluorescence was found to be helpful in caries detection; & the red fluorescence in the treatment was found in deciding when to stop excavating the carious lesion.
An in vitro study of influence of resin infiltration system on enamel microhardness & surface roughness was done by Taher NM, Alkhamis HA, Dowaidi SM51 in 2012.The authors showed that enamel treated with resin infiltrate had approximately the same microhardness & surface roughness as that of sound enamel therefore it can be used for treating enamel subsurface carious lesion.
The effect of different surface preparation techniques on long term bonding effectiveness of eroded dentin was analyzed by Zimmerli B, Munck JD, Lussi A, Lambrechts P & Meerbeek BV52 in 2012.The authors recommended that superficial preparation of eroded dentin should be done with diamond bur for long term bonding to eroded dentin.
A comparison between the clinical efficiency of chemomechanical caries removal agents Carisolv & Papacarie was studies by Kumar J, Nayak M, Prasad KL, Gupta N53 in 2012, following which they concluded that they both had similar clinical efficiency as chemomechanical agents for dentinal caries removal.
An invitro study that analyzed the use of visual inspection using ICDAS II , Laser fluorescence , fluorescence based camera, & radiographic examination for detection of caries & for treatment decision was performed by Momeni AJ, Stucke J, Steinberg T & Gutenbrunner MH54 i n 2012. The authors inferred that ICDAS II has higher potential for detection & treatment planning of caries , & other devices can substantially add to it thereby enabling the examiners plan treatment more accurately.
Thaman D & Sood P55 reviewed applications of ozone therapy in Conservative Dentistry & Endodontics in 2012.They highlighted the benefits of ozone therapy in treating dental caries.They further emphasized that if ozone is judicially used according to precisely defined guidelines causes neither acute nor chronic side effects.
Frencken JE,Peters CM, Manton DJ, Leal SC, Gordan VV, Eden E56 reviewed the minimal intervention techniques for managing dental caries in 2012 & presented evidence for various carious lesion detection devices for preventive measures, for restorative and non-restorative therapies as well as for repairing rather than replacing defective restorations.
A clinical research was carried out by Fernandez MEJ, Estay J, Gordan VV, Mjor IA, Moncada G57 in 2013 on minimal invasive treatment for defective restorations using sealants .The authors demonstrated that marginal sealing of restorations is a minimally invasive treatment that may be used instead of the replacement of restorations with localized marginal defects.
Clinical evaluation of a modified silver fluoride application technique designed to facilitate lesion assessment in outreach programs was carried out by Craig GG, Powell KR & Price CA58 in 2013. The authors concluded that the retention of a black surface on an open carious lesion following treatment with silver fluoride followed by stannous fluoride was a reliable visual indicator of lesion stasis.
Geetha Priya PR, Asokan S , John JB, Punithavathy R, Karthiek K59 evaluated & compared the behavioral & physiologic responses to chemomechanical caries removal & conventional drilling method in 2014. They found out that chemomechanical method of caries removal was effective in caries removal & ensured excellent patient comfort. Even if the time duration was more in this method it did not seem to affect the child’s behavioral response.
The earliest attempt to remove caries involved the use of a hand drill, which was soon surpassed in 1871 by James Morison’s treadle instrument developed from the mechanism of Isaac singer’s sewing machine.60
In 1908 G.V Black put forth the concept of “extension for prevention” where he propagated that healthy tooth structure should be sacrificed to create large tooth cavities which can retain the restorations like silver amalgam effectively thereby preventing further tooth decay. Treatment decision was deceptively simple then as dental caries was equated to just a cavity in the tooth & treatment was equated to just filling the cavity. The intense focus was on the ‘art’ of creating good restorations.61
Material science advancement & technical revolution in high speed cutting gadgets though improved the quality of restorative treatment ironically sidelined the disease nature of dental caries. For centuries this mechanical solution for a biological problem prevails.61
Currently, the conventional treatment of caries is usually carried out with a high-speed hand piece to access the lesion and a low speed hand piece to remove the caries. This method involves quick and efficient caries removal, however it may result in unnecessary removal of the healthy or even the affected dentine that shows the ability for remineralization60.
Caries removal utilizing the conventional technique is usually associated with pain and patient’s discomfort. The bone- conducting noise and vibration and the possibility of producing thermal and mechanical injuries to the dental pulp are also considered as the major shortcomings of the drilling approach.
In the last few decades and as a result of the former drawbacks, a growing interest has been noticed to develop alternative minimally invasive techniques . Air- abrasion was originally developed by Robert Black in 1945 as an alternative pseudo-mechanical method for dental tissue removal. This technique involved bombarding the tooth surface with high velocity aluminum oxide particles (Alumina) carried in a stream of air. Recently, several new air-abrasive cutting instruments have been introduced; such systems utilize air pressure of 7-11 atm with alumina powder ranges 20-50 µm to cut dental tissue. This method of cutting is relatively painless when compared with dental drills. However, the total loss of tactile sensation, and the ability of alumina particle to remove sound tooth structure rather than the carious substrate in addition to the potential risk of inhalation problem should also be considered at the time of selection62.
Air-polishing is another technique utilizing a mixture of water-soluble sodium bicarbonate and tricalcium phosphate particles that is applied onto the tooth surface using air pressure and shrouded in a concentric water jet. The water jet helps the abrasives not to escape far from the operating field; however the detrimental surface attack of such restoration and sound tooth structure could be the result of non- selective abrasion characteristic of this method. Relative to this fact, several researchers suggested the use of that technique only for removing carious dentine at the end of cavity preparation.63
Ultra - sonic instrumentation has also been tried. This method depends on transferring the kinetic energy of water molecules to the tooth surface via the abrasives in presence of high speed oscillations of the cutting tip. The ultrasonic procedure has the advantage of minimizing or eliminating noise, vibration, heat and pressure. The limited availability of instrument tips, slowness of action and the inability to remove soft carious dentine were the main limiting factors regarding the acceptance of that technique.
Recently, sono-abrasion was developed as a modification of the original ultrasonic technique. This technique utilizes high frequency, sonic air- scalers with modified abrasive tips which describe an elliptical motion with a transverse distance of 0.08- 0.15 mm and a longitudinal movement ranges from 0.055 to 0.135 mm. These tips are diamond- coated on the cutting side, cooled using water at a flow rate of 20-30 ml/min and operated by 305 bar air pressure for cavity finishing. Other tips shaped length ways halved torpedo, small hemisphere and large hemisphere are currently available. Using the different shapes of the tips helps in preparing predetermined cavity outlines, and also works well in removing softened, carious dentine. On the other hand, the relatively low abrasion and high hub excursion (0.4 mm) of the tips were known as disadvantages of this system. The limited application and the weakening of enamel rods with the associating cracks adjacent to the prepared sites were also reported. 64
Another approach was postulated with the development of the first ruby laser by Maiman in the 1960s. However, early studies had found that the ruby laser produced significant heat that caused damage to the pulp. In spite of the drawbacks of that beginning, new types of laser are now available to cut dental hard tissues with the priority of selecting Excimer Lasers (Ultraviolet emission of 337 nm) for ablating carious dentine. The non- touch application of energy impulse (Lasing) seems advantageous to regular drilling as it provides less pain, noise and pressure. Moreover, it is believed to have minimal vibration and the ability to produce a sterile cut surface. In spite of these benefits, still there is a risk of heat generation with its subsequent effect on the tooth structure (carbonization, melting and cracking) and dental pulp (inflammation and necrosis). Moreover, the high price and the disability to use laser in the presence of intraoral metal restorations are additional limiting factors65..
During the last few years, reversal of caries using Ozone has also been suggested based on the fact that the remineralized tooth tissues are known to be more resistant to decay than sound tooth structure. The technique uses laser detection of caries and Ozone treatment for less than 2 minutes. Ozone readily penetrates through decayed tissue, eliminating the ecological niche of cariogenic microorganisms as well as priming the carious tissue for remineralization. The remineralization process will then take place with the aid of a topically applied remineralizing solution and the recommended patient’s maintenance kit. This simple fast novel approach avoids the need for local anesthesia, drilling and filling, however its application is restricted to treat the superficial enamel and root caries, and the use of conventional drilling and filling are still recommended to treat deep carious lesions. It is obvious that most of the proceeding trials are trying to achieve a conservative approach for removing dental caries.
The issue stimulated the development of the currently known Atraumatic restorative treatment (ART) approach . This method includes excavation and removing of the caries with hand instruments only and subsequently restoring the cavities with such adhesive restorative material. However, a potential risk of leaving infected carious dentine still exists.
Goldberg and Keil in 1989 discovered the efficacy of collagenase enzyme , released from Achromobacter bacterial species , in removing soft carious dentine 2-5 hours after its application. A residual sound layer of dentine resulted with no bacteria seen within the exposed collagen of the dentinal floor.
Another enzyme named Pronase has also been discovered for the same application. In spite of the potential effectiveness, the slow action of this approach for caries removal limits its clinical application. Combining the last two approaches resulted in the development of chemo-mechanical caries removal66.
Chemochemical caries removal involves the selective removal of carious dentine. The reagent is prepared by mixing solutions of amino acids and sodium hydrochlorite. N-monochloroamino acids are formed which selectively degrade demineralised collagen in carious dentine. The procedure requires 5–15 minutes but avoids the painful removal of sound dentine thereby reducing the need for local anesthesia. It is well suited to the treatment of deciduous teeth, dental phobics and medically compromised patients.
DEFINING DENTAL CARIES
Dental Caries is the localized destruction of susceptible dental hard tissue by acidic by-products from bacterial fermentation of dietary carbohydrates Thus, it is a bacterial driven, generally chronic, site-specific, multifactorial, dynamic disease process that results from the imbalance in the physiologic equilibrium between the tooth mineral and the plaque fluid; that is, when the pH drop results in net mineral loss over time. The infectious disease process can be arrested at any point in time.67
Lufkin reported a Neanderthal skull from the Paleolithic era (40,000 to 25,000 year ago) with major alveolar bone loss, missing teeth, and various levels of decay in the remaining teeth thereby emphasizing that dental decay was recognized as a widespread disease even in the prehistoric race.68
In 384-322 BC Aristotle A Greek philosopher observed that sweet foods such as soft figs and dates caused a sticky film on the tooth that led to putrification and tooth decay. In 1300–1368 AD Guy de Chauliac believed the tooth worm existed and was responsible for tooth decay. He suggested fumigation with leek, onion, and Henbane to cure the persons tooth pain.68
The worm theory was very much accepted until 1780 when it was discarded & John Hunter preferred the term mortification to caries, and believed the source of decay was due to an imbalance of internal forces that caused inflammation and pulp disease. In 1878 AD T. Leber and J.W. Rottenstein proposed that caries was due to bacterial fermentation of food debris, and oral fluids that led to the presence of bacteria in dentin tubules. 1881 AD G. A. Milles and A. S. Underwood believed that caries was most likely due to demineralization by organic acids produced by bacteria. 1884 AD Greene Vardiman Black was the first to assemble the caries puzzle that involved food debris, gelatinous debris, and acids, which caused demineralization leading to the initial caries lesion.68
Then in 1890 Dr W.D. Miller put forward the ‘‘chemico-parasitic’’ theory of caries disease, in which he proposed that oral microorganisms can break down dietary carbohydrates to acids which demineralize enamel.69 Microbiology was in its infancy, however, and it was not possible to determine which bacteria were involved. In 1924, Clarke isolated streptococci from human caries lesions and named them S mutans.69 This finding was overlooked, however, for several decades, and it was not until the 1960s that further substantial progress was made when gnotobiotic animal studies were feasible and it could be shown categorically that
(1) Caries disease was a transmissible,
(2) Fermentable carbohydrates in the diet played a critical role,
(3) Oral streptococci (and other bacteria) from humans could cause caries lesions in rodents fed a high sugar diet, and
(4) Interventions, such as antibiotics targeted against these bacteria, prevented caries lesions69.
The most cariogenic species in these animal studies were what are now termed mutans streptococci, in particular S mutans and S sobrinus. These studies laid the foundation for epidemiologic studies in humans in which the prevalence and proportions of selected bacteria or the whole plaque microflora were compared at caries versus healthy surfaces.69
Dental plaque is a diverse community found on the tooth surface embedded in a matrix of polymers of bacterial and salivary origin. A small sample of dental plaque contains, on average, between 12 and 27 species. These biofilms develop in a specific pattern.69
Marsh, Bradshaw (1995) describes the process of developing a mature biofilm as:
1. The formation of a conditioning film (acquired pellicle) on the tooth surface;
2. The interaction between salivary bacteria and the acquired pellicle (non-specific, followed by primary colonizers);
3. The attachment of secondary colonizers to the primary colonizers;
4. The development of horizontal and vertical stratification;
5. The growth and formation of a climax community.70
Within seconds of eruption, or after cleaning, tooth surfaces become coated with a conditioning film of molecules (biologically active proteins and glycoproteins) derived mainly from saliva (and also from gingival crevicular fluid and from the bacteria themselves).69 Initially, only a few bacterial species are able to attach to this film, which is also termed, the acquired pellicle. Cells are held reversibly near to the surface by weak, long-range physicochemical forces. Molecules (adhesins) on these early bacterial colonizers, mainly streptococci (eg, Streptococcus mitis and S oralis) can bind to complementary receptors in the acquired pellicle to make the attachment irreversible and then these pioneer species start to multiply.69 The metabolism of the early colonizers modifies the local environment, for example, by making it more anaerobic after their consumption of oxygen.69 As the biofilm develops, adhesins on the cell surface of more fastidious secondary colonizers, such as obligate anaerobes, bind to receptors on already attached bacteria by a process termed, coadhesion or coaggregation, and the composition of the biofilm becomes more diverse (microbial succession).69 The attached bacteria produce extracellular polymers (the plaque matrix) that consolidate attachment of the biofilm. The matrix is more than a mere scaffold for the biofilm; the matrix can bind and retain molecules, including enzymes, and also retard the penetration of charged molecules into the biofilm.69
Biofilms are spatially and functionally organized, and the heterogeneous conditions within the biofilm induce novel patterns of bacterial gene expression, while the close proximity of different species provides the opportunity for interactions.69
Thus, dental plaque is a classic example of a biofilm and a microbial community, in which bacteria interact and the properties of the whole consortium are more than the sum of the constituent species.69
The microbial composition of the biofilm varies at distinct sites on a tooth (fissures, approximal surfaces, and gingival crevice) and reflects the inherent differences in their anatomy and biology.69 The normal microflora of fissures is sparse and the organisms present have a saccharolytic metabolism (ie, their energy is derived from sugar catabolism); the predominant bacteria are streptococci and there are few gram-negative or anaerobic organisms. In contrast, the gingival crevice has a more diverse microflora, including many gram-negative anaerobic and proteolytic species, whereas approximal surfaces have a microflora that is intermediate in composition.69
ROLE OF DENTAL BIOFILM IN ORAL HEALTH & DISEASES
The biofilm, related to dental caries, functions in several ways. It is a site of bacterial proliferation and growth, as mentioned above, a location of acid/ base regulation at the tooth surface, and a reservoir for calcium ion exchange between the tooth and the saliva.71
Hannig et al.(2003) demonstrated that pellicle formation, even as early as 2 hours, imparts significant resistance to enamel demineralization.72
Hannig et al.(2003) demonstrated that a salivary pellicle only 3 minutes old conferred protection to enamel against citric acid attack. They demonstrated that the pellicle is 20-500 nm thick within the first two hours of exposure to saliva, depending on location, and is resistant to removal by a toothbrush (without toothpaste) and masticatory forces. The protein-rich biofilm layer, salivary pellicle, is the interface that regulates the reaction between tooth surface, saliva and erosive acids.72
However the pellicle offers little resistance to erosive changes in dentin73.This could be mainly due to the fact that a) dentin is more soluble than enamel and b) the pellicle could not resist the acid attack.7 It was speculated that greater protection of dentin could be expected if the pellicle was allowed to mature for more than two hours.73 The pellicle/ biofilm interaction in protecting dentin from erosive challenges requires further investigation.71 The ability of the biofilm to neutralize acid attack as well as to initiate and support remineralization of the dentin surface appears to be a critical step in determining if it demineralizes.71
As the plaque is a mixed culture containing many bacteria, an increased amount of saliva serves to bring the plaque other nutrients such as the amino acid arginine and urea. Both of these compounds serve as substrates for bacteria that create base as a metabolic byproduct. The biofilm is rich in arginolytic bacteria that produce base in response to the exposure to saliva, helping neutralize the acid produced.71
Saliva is critical to the protection of the teeth against the acidic pH changes that result in dental plaque when its bacteria degrade fermentable carbohydrates. Adequate amounts of healthy saliva supply all the necessary ingredients for successful remineralization, and the lack of it severely handicaps the natural repair process.71
CHEMISTRY OF DENTAL CARIES
DYNAMICS OF TOOTH SURFACE
Not all mineral loss from tooth structure is part of a pathologic process such as dental caries disease. Crystals at the tooth surface regularly go through natural periods of mineral loss (demineralization) and mineral gain (remineralization), particularly in surfaces covered by undisturbed (stagnant) biofilms (ie, dental plaque).Immediately after eruption into the oral cavity, teeth are colonized by oral bacteria that create conditions that, in combination with saliva, modify the composition of teeth surfaces, making them more resistant to dental caries. This process has been called post eruptive enamel maturation 74.A similar post eruptive maturation process is expected to occur on exposed root surfaces when the cementum or dentin is exposed to the oral environment after gingival recession.
Crystals at the enamel and dentin/cementum surfaces covered by undisturbed biofilms are likely to continue having mineral exchanges for as long as the covering biofilms are able to create conditions of undersaturation and supersaturation with respect to the crystals. During the period of supersaturation, minerals can remineralize partially demineralized enamel crystals and, when supersaturation occurs for long periods of time, dental calculus can form, although protein inhibitors tend to prevent this from happening.75 Therefore, although pH is the strongest determinant for saturation level leading to demineralization or remineralization under clinical conditions, it is not the only important factor because saturation is significantly affected by other factors such as the concentration of calcium and phosphate ions and the total ionic strength of plaque fluid.76 This is clinically relevant because patients with significant decrease in salivary flow would have difficulty supplying enough minerals and buffering the fluid to maintain adequate saturation levels to maintain tooth surface integrity.
There are other clinically relevant factors, such as the presence of calculus nearby, that also affect this process. Calculus crystals are less stable than those in tooth structure and therefore demineralize at higher saturation levels, releasing minerals into the plaque fluid protecting the tooth structure.(fig.1)
PROCESS OF DE-MINERALIZATION
Stephan (1944) put forth the changes in pH occurring within dental plaque when it is subjected to a challenge, typically with a foodstuff. He showed that with a fall in pH below the critical level of pH 5.5, demineralization of enamel occurs following the intake of fermentable carbohydrates, acidic liquids, or sugar in the presence of acidogenic bacteria. After consumption, there is an elimination of the acid and a return to normal saliva or plaque pH, at which point repair of any destruction of the enamel structure takes place (remineralization). Repeated intakes of fermentable carbohydrates cause the low pH to be maintained for longer periods, thereby not allowing remineralization to take place. Factors affecting the shape of the Stephan Curve include the microbial composition of the plaque; the nature of the fermentable substance; the rate of diffusion of bacterial metabolites, salivary components such as bicarbonate and the fermentable substance; salivary access to the plaque; saliva flow rate (Fig:2)77
Crystals at the tooth surface become more resistant to demineralization through the posteruptive maturation process and the formation of the lesion itself, leaving the subsurface crystals more susceptible to undersaturation conditions being created by the diffusion of hydrogen ions from plaque fluid. Moreover, the surface layer has better saturation conditions because, in addition to having access to ions coming from the body of the lesion and plaque fluid/saliva, it is also covered by the salivary pellicle, which acts as a diffusion barrier slowing down the outward diffusion of ions. These conditions allow the caries lesion (demineralization secondary to acid penetration) to develop well into dentin without breakage of the surface, and it is probably bacteria free in most cases because bacteria are physically too large to fit into the diffusion spaces of a seemingly intact surface layer.
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