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CAVITY PREPARATION Taraivina Qalita BDS 3 Overview • Introduction • History • Objectives of cavity preparation • Factors that determines cavity design • Instrumentation • Dr G. V Blacks classification of caries and steps in cavity preparation • Extension for prevention OVERVIEW Modern Dentistry .Minimally Invasive Dentistry. . Laser cutting of hard tissues . Air Abrasion . Recommendation . Conclusion . Reference Introduction • Cavity preparation as defined by one author, “is the mechanical alteration of a defective, injured or diseased tooth to best receive a restorative material that will establish a healthy state for the tooth, including esthetic corrections where indicated, along with normal form and function.” • The procedure of cavity preparation is the removal of all defective or friable tooth structure because remaining infected or friable tooth structure may result in further caries progression, sensitivity or pain or fracture of tooth and restoration. INTRODUCTION • In the past most restorative treatment was due to caries (decay) and the term cavity was used to describe a carious lesion in a tooth that had tooth structures being destroyed progressed to a point that part of the tooth structure had been destroyed. Thus when the tooth with cavity was repaired, the cutting or preparations of the remaining tooth structure was referred to as a cavity preparation. HISTORY • Dr G V Black referred to as “the father of dentistry”, also a teacher in the first decade of the nineteenth century, developed the classification of carious lesions. • - based his classification on the natural history of caries and the restorative material available • - his work remained unchallenged for than half the century HISTORY • Now with a lot of researches, there are a lot of new materials & there is a better understanding of caries • Until the early part of the nineteenth century , cavity preparation was carried out exclusively by hand instruments. OBJECTIVES OF CAVITY PREPARATION • Remove all defects & provide necessary protection to the pulp. • Extend preparation as conservatively as possible • Form preparation of the cavity so that under masticatory forces the tooth or restoration orboth will not fracture & restoration will not be displaced FACTORS THAT DETERMINES CAVITY DESIGN • Structure and properties of dental tissues. • Disease (eg caries, pathological tooth wear, periodontal disease ) • Properties of restorative material INSTRUMENTATION • Types of instrument – hand cutting, powered cutting • Hand cutting - manufactured from carbon steel & stainless steel. • Carbon steel - harder than stainless steel when not protected it will corrode. • Stainless steel - does not rust or corrode but produces less satisfactory edge than carbon steel. • Best cutting instrument – manufactured from stainless steel with tungsten carbide insert to provide cutting edge. INSTRUMENTATION • Terminology organised by Dr Black in the early century is still being used with minor modification. • Most names used are commonly used item of the day eg. hatchet, hoe, spoon & chisel. • He classified all hand cutting instruments as excavators & referred them as hatchet excavator, spoon excavator etc. • Manufactured in pairs & some are double-ended • Dr Black assigned numeric formulas to instruments using metric system. Millimeter & tenth of a millimeter for instrument dimension INSTRUMENTATION • Centigrades are used in the degree of angulation. • Centigrades are based on a circle divided into 100 units as opposed to the 360 degrees circle • Formula used either 3-number formula or 4-number • Depends on the shape of the blade. • Power cutting instrument - middle of 19th century • Mechanical drills operated by bow strings were used. • Late 19th century – pedal driven engine connected by flexible cable drive to a handpiece. • Towards end of 19th century- first electric motor drill was introduced. DR G V BLACK’S CLASSIFICATION OF CARIES • Based on the site of origin of the carious process. • CLASS 1 – cavities on pits & fissures, mostly on occlusal 1/3 of the crown of molar & premolar teeth • CLASS 2 - cavities on mesial & distal surfaces of molar & premolar teeth. • CLASS 3 – cavities which involve the mesial and distal surfaces of incisors & canine but do not involve the incisal edge. Dr G V BLACK’S CLASSIFICATION OF CARIES • CLASS 4 – same as Class 3 cavities but this time it invoves the incisal edge. CLASS5 – cavities in the cervical third of the buccal & lingual surfaces. • To be more precise on the classification, surfaces of the tooth involved were described eg. occlusal mesial,lingual,buccal, mesio-buccal, mesio-lingual, disto-buccal, disto-lingual etc Dr BLACK’S STEPS IN CAVITY PREPARATION • Establish outline form • Obtain resistance form • Obtain retention form • Obtain convenience form • Remove remaining carious dentin • Finish enamel walls and cavosurface margins • Clean preparation EXTENSION FOR PREVENTION • Dr G V Black’s principle. • Margins of cavities should be extended to areas where caries is least likely to occur. • Should include all deep fissures which are likely to be affected by caries during life of restoration MODERN DENTISTRY- Minimally invasive dentistry • “Minimally invasive” approach to treating dental caries incorporates the dental science of detecting, diagnosing, intercepting & treating dental caries on a microscopic level. • Key concept – dental caries should be treated as an infectious disease, deferring operative intervention. • Main focus is the maximum conservation of demineralized, non-cavitated enamel and dentine. • Once controlled of infection is achieve pt’s caries risk status & evidence of lesion demineralization can be monitored over extended periods. MINIMALLY INVASIVE DENTISTRY • Dentists must engage & involve patients in management of their diseases • All restorative procedures must be carried out only in conjunction with well understood preventive techniques & pt’s education. LASER CUTTING OF HARD TISSUES • Laser – light amplification by stimulated emission of radiation. • Dental laser – medical device that generates a precise beam of concentrated light energy. • Has different wavelength that works on different tissues in the body. • Certain wavelength have an affinity for red pigmented structures which makes them effective for use in oral cavity. LASER CUTTING OF HARD TISSUES • Laser that is used for cavity prep is the ER : YAG with the wavelength of 2940mm. • This wavelength -highly absorbed in water so it is useful for the selective removal of caries & for actual cavity designs in limited situations. • Laser – generated within the machine then guided via a series of gold mirrors along the hand piece to emit from the tip within water jet • It’s the energy released through water that does the cutting & guidance is achieved through a red guide light AIR ABRASION • Air abrasion for restorative preparation removes tooth structure using a stream of alumimium oxide particles generated from compressed air or bottled carbon dioxide or nitrogen gas. • Abrasive particles strike the tooth with high velocity & remove small amounts of tooth structure. • Efficiency of removal is relative to the hardness of the tissue or material being removed and the operating parameters of the air abrasion device AIR ABRASION • Indications • Caries removal • Removal of small existing restorations • Preparation of tooth structure for cutting or etching for the placement of composites, porcelain & ceramics. • Proper evacuation with high-volume suction is needed for the aluminium oxide particles. Good suction & a rubber dam that extends over the nostrils will help to minimise inhalation of particles by pt. RECOMMENDATION • Minimally invasive dentistry is a way to go. • Focus is maximum conservation of demineralized, non-cavitated enamel & dentine. • All restorative procedures must be carried out only in conjunction with well-understood preventive techniques & pt education CONCLUSION • Modern technique of cavity prep is better than Dr G V Black because of the maximum conservation of demineralized and non-cavitated dental tissues and the availability of adhesive materials. REFERENCE 1. Eccles J D Green R M.The Conservation of Teeth.1st ed. London;1973 .p76 2. Roberson TM, Heymann H O, Swift E J. Sturdevant’s ART & Science of Operative Dentistry. 2002. 4th edn.USA.Mosby.Inc [chap 6]: pp 271-74. 3. Kidd E A M, Smith G N, Watson T F. Pickard’s Manual of Operative Dentistry. 4. Walmsley A D, Walsh T I, Burk F J T et al. Restorative Dentistry. 1st edn.2002, Harcount Publishers Ltd. China [chap 8]: pp 65-7.
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