Preparation techniques and their consequences in hard dental tissues.


Pressure

Vibration

Heating


Increasing of temperature in dental pulp – 5° is fatal.

Hand preparation

Pressure high

Vinration and heating no


Rotary preparation

Friction – heating

Rotation – vibration

Pressure


Electromotors:

Max 40.000 rpm, handpiece with gear to fast – till 200.000 rpm.

Gear to slow : 1:2,7, 1: 7,5

Pressure

Vibrations


Turbine handpiece -300.000 rpm

No pressure

Vibrations – very hihg, their perception disappeares

Heating.

Water cooling – water spray

50ml/min.


Preparation trauma:


Enamel

Cracs in enamel

Less by preparation with diamonds


Dentin

Overheating causes burning of collagen in dentin.

Dental pulp

Pulpitis – inflammation

Necrosis

Prevention:

Careful praparation with interruption and sufficient water cooling.


Alternative techniques of preparation:

Ultrasonic or sonic instruments  - hihger effect in enamel ., less in dentin, smoother borders of
cavities, excavation of carious dentin insufficient.


Laser preparation

Selective preparation, can penetrate into dental pul. .


Kinetic preparation

Irregularities on surface, insufficient in soft (carious) dentin.