Cavity preparation - Introduction, history and classification

Definition of cavity:

Is defined as a defect in enamel, dentin or cementum resulting from the pathological processes, mostly the dental caries. Other processes such as abrasion, erosion etc. can also cause such defects.

Cavity preparation:

It is defined as the mechanical and surgical alteration of a defective, injured or diseased tooth in order to best receive a restorative material which will re establish a healthy state for the tooth including aesthetic corrections where indicated along with the normal form and function.

Cavity preparation is the performance of those dental surgical procedures required to expose the carious lesion, permit of removal of affected tissue and so shape the remaining dentin and enamel as to receive a restoration to its original form and function give it strength and prevent re occurrence of decay in the same surface.

History:

Cavity preparation techniques have been known for many centuries. During the ninth century itself cavities have been prepared for dental inlays.

During the early 19th century, cutting was done mainly by hand-operated instruments. Later drills operated by bowstring, Archemedian drives were used. Dr. Samuel Fastlich has suggested that the Mayas used tube drills and bow drills.

During the late 19th century pedal driven engine using flexible cables, hand piece and burs came into existence. Page-Chayas hand piece, the first belt driven angle hand piece to operate successfully at speeds over 100,000rpm was introduced in 1955. In 1957 the first clinically acceptable air turbine hand piece Borden airotor handpiece came into play. Then Air motor, Electric micro motor, straight handpiece, right angled handpiece and contra-angled handpiece were introduced. At the latest, now air abrasion and lasers are being used.

Hamelton Jameson for the first time in the 19th century emphasized the need for organized cavity preparation. He suggested the following steps:

• Removal of soft and infected dentin using hand instruments.
• Sterilization of dentinal surface.
• Retention form using dentinal buttons.

In 1930’s G.V. Black, gave the systemic approach to cavity preparation with special emphasis on retention form. Black’s principles of cavity preparation were specially meant for metallic restorations. Several operators, with the intention of improving aesthetics, had modified some of the original suggestions of Black.
Dr. Charles E. Woodbury suggested that the labial margin of the preparation to be in harmony with the lines of refraction of the labial surface. Henry A. True suggested another inconspicuous type of preparation using a special “slant technique”.
Introduction of new aesthetic restorative materials, particularly during the last two decades have changed the conventional ideas of cavity preparation, probably this is the only area wherein Black’s general principles are becoming obsolute. Conservative cavity designing is done by limiting the preparation of the cavity only to the areas affected.

Classification of cavities:

Based on the type of treatment and the areas involved, Black gave his classification.

CLASS I

All pit and fissure cavities.
IA Cavities on the occlusal surface of molars and premolars.
IB Cavities on the occlusal 2/3rd of the facial and lingual surface of molars.
IC Cavities on the lingual surface of maxillary incisors.

CLASS II

Cavities on the proximal surface of molars and premolars.

CLASS III

Cavities on the proximal surfaces of anterior teeth that do not involve the incisal edge.

CLASS IV

Cavities on the proximal surface of anterior teeth that involve the incisal angle.

CLASS V

Cavities on the gingival third of the facial and lingual surface of all the teeth.

CLASS VI

Cavities on the incisal edge of anterior teeth or the occlusal cusps of posterior teeth.

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