CAVITY PREPARATION

							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[1], “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.