Fundamentals of Tooth Preparation

Fundamentals of Tooth Preparation

Overview

  • The art and science of diagnosis, treatment, and prognosis of defects in teeth is aimed at restoring proper form, function, and aesthetics.

  • Preventative measures against the progression of disease and tooth loss are critical in operative dentistry.

Reasons for Tooth Intervention

  • Caries Lesion Progression: Progress of decay necessitating restoration due to significant loss of tooth structure.

  • Tooth Pain/Sensitivity: Indications that a tooth requires intervention due to potential underlying issues.

  • Congenital Malformation or Improper Position: Correcting defects to restore form or function.

  • Defective/Failing Restoration: Replacing or fixing previous work that is not functioning correctly.

  • Restorative Work Fulfillment: As a part of broader restorative procedures.

Factors to Consider Before and During Tooth Preparation

Patient Factors

  • Desires: Patient preferences must be considered.

  • Home Care: Understand patient's oral hygiene habits.

  • Risk Status: Assess overall risk for dental issues based on history and lifestyle.

  • Age: Age-related factors affecting dental health and treatment outcomes.

  • Cooperation: Patient's ability and willingness to participate in treatment.

  • Medical/Dental History: Previous conditions or treatments that could affect current procedures.

Anatomical Factors

  • Enamel Rod Orientation: Directionality can influence preparation technique and outcomes.

  • Dentin Thickness: Impacts strength and support of the restoration.

  • Pulp Location: Pulpal proximity affects the choice of restoration and preparation depth.

  • Coronal Contours: The shape and surface features of the tooth.

  • Extent of Previous Restorations: Existing work may affect new preparations.

Lesion/Defect Factors

  • Bone Support: Consideration of the surrounding bone structure in treatment planning.

  • Occlusion: The bite relationship between upper and lower teeth.

  • Gingival/Pulpal Involvement: Assessment of how restorative material will affect gum and pulp health.

Restorative Material Factors

  • Physical Properties: Strength, wear resistance, and other material characteristics.

  • Color Characteristics: Aesthetic considerations for matching natural tooth color.

  • Cost Effectiveness: Financial considerations influencing material choice.

Procedural Factors

  • Operator Skill: The experience and proficiency of the dental professional.

  • Instrument Design: The design of dental tools employed in the preparation.

  • Ability to Isolate: Effective isolation techniques to maintain a dry workspace during preparation.

Tooth Preparation: Basics

Definition and Objectives

  • Tooth Preparation: The mechanical alteration of a defective, injured, or diseased tooth to facilitate the placement of restorative material that corrects its form and function.

  • Objectives of Tooth Preparation:

    • To conserve as much healthy tooth structure as possible.

    • To remove all defects while protecting the pulp-dentin complex.

    • To restore tooth integrity against masticatory forces.

    • To enable the aesthetic placement of a restoration.

Types of Tooth Preparations

Single Tooth Preparation

  • Involves alteration of one tooth surface, typically the occlusal surface.

Compound Tooth Preparation

  • Involves alteration of two surfaces, designated as DO (Distal and Occlusal).

Complex Tooth Preparation

  • Involves alteration of more than two surfaces, noted as MOD (Mesial, Occlusal, Distal).

Types of Restorations

Intracoronal Restoration

  • Definition: A restoration that is placed within the preparation made in the crown of a tooth.

  • Technique: Direct technique of placement.

Extracoronal Restoration

  • Definition: A restoration placed outside the tooth, such as a crown.

  • Technique: Indirect method of restoration.

Cavity Preparation Walls

Internal and External Walls

  • Internal Walls: Include pulp (p), axial, cementoenamel junction (CEJ).

  • External Walls: Include facial (f), lingual (l), distal (d), mesial (m), and gingival walls.

Prepared Walls

  • The prepared wall is generally flat and must be perpendicular to occlusal forces directed occlusogingivally.

  • These walls provide stabilizing seats for restorations, distributing stresses effectively.

Pulpal Floor

  • Definition: The wall located above the pulp chamber.

  • Orientation: Usually perpendicular to the long axis of the tooth, with the exception of the mandibular first premolar.

  • Note on Lingual Slanting: The occlusal table slants towards the lingual due to a smaller lingual cusp.

Cavosurface Margins

  • Definition: The junction formed at the transition between a prepared tooth surface wall and the external surface.

  • Preparation Margin: Known as the cavosurface margin, indicating an acute junction.

Line and Point Angles

Definitions

  • Line Angle: The junction formed between two surfaces of different orientations, represented along a line.

  • Point Angle: The intersection point formed by three planes or three line angles of differing orientations.

Schematic Representations

Class I Preparation

  • Line Angles: Examples include faciopulpal (fp), distofacial (df), distopulpal (dp).

  • Point Angles: Examples include distofaciopulpal (dfp).

Class II Preparation

  • Line Angles: include distofacial (df), faciopulpal (fp).

  • Point Angles: Distal-lingual (dl) and others as specified.

Historical Perspective

Greene Vardiman Black (GV Black)

  • Noted as one of the founders of modern dentistry in the U.S. and recognized as the Father of Operative Dentistry.

  • Significant Contributions:

    • 1870: Invented a cord-driven foot engine with a foot motor for dental use.

    • 1871-1877: Patented improvements in dental drills.

    • 1890: Published the first editions of several key works on dental anatomy and operative dentistry.

    • 1891: Standardized cavity preparation and filling methodologies.

    • 1896: Proposed a classification system for dental caries and standardized dental terminologies.

GV Black's Preparation Steps

  1. Outline Form:

    • Definition: The process of defining cavity margins before reduction begins.

    • Determinants: Considerations include lesion location/size, tooth anatomy, restorative material type, and esthetics.

  2. Resistance Form:

    • Definition: The cavity wall's shape and position enable resistance to masticatory forces.

    • Principles: Floors should be flat and at right angles to forces; preparations should limit potential tooth fractures.

    • Considerations for Materials: Materials like amalgam should achieve a 90-degree cavosurface angle.

  3. Retention Form:

    • Definition: The cavity wall shape allows preservation of the restoration against displacement forces.

    • Factors Affecting Retention: Dovetails, converging walls, grooves, pins, and frictional resistance.

  4. Convenience Form:

    • Definition: The preparation's shape allows ease of operation during preparation and restorative phases.

    • Factors: Extension of cavity preparation and instrument approach angle.

  5. Removing Remaining Carious Dentin:

    • Definition: Excavation of any decay beyond basic cavity design.

    • Lesion Categories: Incipient lesions are 0.5 mm or less; extensive lesions are over 0.5 mm.

    • Ideal Depth: Should be 0.5 mm inside the dentino-enamel junction (DEJ).

  6. Finish Enamel Walls:

    • Definition: Smoothing and refining cavity walls for proper margins.

    • Purpose: To achieve a strong seal and prevention of marginal discrepancies.

    • Factors: Quality of Walls: Orientation of enamel rods, material selection, and placement margins.

  7. Cleanse the Preparation:

    • Activities include the removal of debris, drying the preparation, and inspecting for decay.

Classification of GV Black Preparations

Class I

  • Characteristics: Penetrates enamel as a cone with an apex oriented externally, and similarly penetrates dentin with an apex directed towards the pulp.

  • Location: Commonly found in pit and fissure areas of incisors, premolars, and molars.

Class II

  • Characteristics: Involves proximal surfaces of posterior teeth, starting just gingival to the contact area.

  • Approach: Access gained through occlusal methods.

Class III

  • Characteristics: Affects proximal surfaces of anterior teeth.

Class IV

  • Characteristics: Proximal surfaces of anterior teeth, involving the incisal angle.

Class V

  • Characteristics: Affects facial or lingual surfaces in the gingival third of teeth.

Class VI

  • Characteristics: Involves cusp tips of posterior teeth and incisal edges of anterior teeth, often due to enamel developmental issues or functional demands.

References

  • Sturdevant, Clifford M. Sturdevant's Art and Science of Operative Dentistry. Seventh edition.