Essence and basic principles of preparation
Despite the development of adhesive technologies and calls for minimally invasive intervention (excising only non-viable tissue), classical approaches remain the foundation of standardized treatment. Abandoning them often leads to a misunderstanding of the process and a decrease in the quality of the dentist's work.
Fundamental rules for cavity preparation were formulated by G.V. Black back in 1908. They include four mandatory steps:
- Excision of unsupported enamel margins lacking dentin support (prevents their fracture under masticatory load).
- Total removal of carious dentin.
- Preventive extension ("extension for prevention") — extending cavity margins into immune (resistant) zones of the tooth to protect against recurrence.
- Creation of a box-like cavity — ensures reliable filling retention and crown resistance to masticatory pressure.
Instrumentation
For surgical intervention, a dental unit is used, transmitting energy to cutting instruments through a drive system. The clinician uses different types of handpieces depending on the density of the tissues being treated:
- Turbine handpieces: powered by compressed air, spinning the bur up to 160,000–400,000 rpm. Provide rapid preparation. Used in combination with diamond burs for enamel and intact dentin.
- Contra-angle handpieces: low-speed devices (1,000–40,000 rpm), powered by pneumatic or electric micromotors. Secure carbide burs (via push-button chuck or latch) and are used for gentle excision of necrotic masses.
- Straight handpieces: also low-speed. Allow applying high pressure to the instrument without vibration, but are rarely used—only with ideal surgical access.
Pre-preparation diagnostics
Often, the carious process is occult: the crown looks completely healthy, but the patient complains of pain from thermal and chemical stimuli. In such cases, dentin involvement may reach the pulp chamber. To identify hidden defects before preparation, the following methods are used:
- Radiography: the baseline method. Dense tissues absorb rays and appear light, while destroyed areas let radiation pass and show up as dark spots.
- Transillumination: passing light of a specific wavelength through the tooth. Caries appears as a clearly demarcated dark hemisphere against healthy tissues.
- Luminescent diagnostics: assessing tissue color changes under ultraviolet light (helps find caries and check marginal adaptation of old restorations).
- Electric pulp testing (EPT): assessing the response of pulp nerve endings to current. A healthy tooth responds at 2–6 µA, while at the onset of inflammation, the threshold drops to 20–25 µA.
Specifics in deep and recurrent caries
In deep caries, microorganisms penetrate along the dentinal tubules to the pulp, causing inflammation (pulpitis). Treatment requires extreme caution to preserve tooth vitality. Preparation must be as conservative as possible. The cavity is treated exclusively with warm antiseptic solutions. Calcium hydroxide therapeutic liners are placed on the circumpulpal dentin, and low-toxicity materials (e.g., fluoride-releasing glass ionomer cements) are chosen for restoration.
Special attention is required when treating teeth with previous restorations. The clinician must clearly differentiate between two conditions:
- Recurrent caries: resumption of the process directly beneath the filling due to incomplete removal of infected tissues during the initial treatment.
- Secondary caries: the development of a new lesion on initially healthy enamel adjacent to the filling (most commonly in adjacent fissures).
Briefly: answers to topical questions
What classes of carious cavities exist according to Black's classification?
According to G.V. Black's classification, there are six classes of carious cavities depending on their localization on tooth surfaces.
- Class I — cavities located in natural pits, grooves, and fissures of premolars and molars, as well as blind pits of anterior teeth.
- Class II — cavities on proximal surfaces of premolars and molars.
- Class III — cavities on the proximal surface of incisors and canines without involving the incisal edge and corner of the crown.
- Class IV — cavities on the proximal surface of incisors involving the fracture of the crown angle and incisal edge.
- Class V — cavities in the cervical area of all teeth on the facial or oral surface.
- Class VI — cavities located on atypical surfaces (incisal edges of anterior teeth and cusps of premolars and molars).
What non-mechanical methods of carious cavity preparation are used in modern dentistry?
In modern dentistry, the following preparation methods are used, eliminating the need for burs:
- hydrokinetic preparation;
- laser preparation;
- ultrasonic preparation.
These are modern methods of carious cavity preparation alongside traditional preparation with burs and handpieces.
What antiseptic solutions are used for medical treatment of a deep carious cavity?
Warm antiseptic solutions, particularly saline, are used for the medical treatment of a deep carious cavity. When treating deep caries, treatment is performed with saline, after which the cavity is dried exclusively with sterile cotton pellets and a stream of warm air. At the same time, the use of the following agents is strictly contraindicated:
- Alcohol and ether — reduce the adhesion of composite material to hard tooth tissues.
- Hydrogen peroxide — leads to saturation of dental tissues with oxygen and the formation of an unfavorable inhibited composite layer.
To memorize Black's principles, use the mnemonic: C — Cavity margins (remove unsupported), D — Dentin (excise carious), E — Extension (to immune zones), F — Form (create box-like shape).
Class and exam questions
What is the difference between secondary and recurrent caries?
Recurrent caries develops under an old filling due to incomplete removal of affected tissues during previous treatment. Secondary caries is a new pathological process that begins on healthy enamel adjacent to an existing filling.
Why is "extension for prevention" necessary?
This is the preventive opening of a carious cavity up to the so-called immune zones of the tooth. This step is necessary to prevent recurrent caries in this area.
What handpieces are used for different dental tissues?
Turbine (high-speed) handpieces with diamond burs are used for enamel and healthy dentin. Contra-angle (low-speed) handpieces with carbide burs are used for gentle removal of necrotic tissues.
What else to study on this topic
- G.V. Black's classification of carious cavities (Classes I–VI)
- Assessment of dental lesion intensity (DMF and DFS indices)
- Electric pulp testing (EPT) and pulp vitality indicators
- Non-restorative caries treatment methods (in the white spot stage)
- Modern WHO ICD-10 classification of caries
Master the entire topic in the «Propaedeutics of Dentistry» course
This is a summary. The course covers everything tested in classes and exams.
- Full study guide on "Modern methods of carious cavity preparation" and 868 more pages on the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 65 video lessons on the subject
Other topics in the section "Chapter 6. Operative Dentistry"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.