Iatrogenic dental injuries
I/ Definition/ “Iatrogenic” is a medical term which describes a pathology caused by a treatment or a medical act.
In dentistry, itarogenic lesions are lesions of the tooth and structures associated with the dental system, caused involuntarily by the dental surgeon. These lesions are due to physicochemical and mechanical aggressions following restorative and endodontic treatments.
The direct effects of operational results vary considerably depending on the quality and evolutionary state of the structures to which they are applied.
So, it is useful to know some basic facts which condition the pulp prognosis and which are:
Dentin permeability; the thickness of residual dentin remaining between the bottom of the cavity and the pulp, expresses pulp proximity in a numerical manner.
If this measurement equals or exceeds 1.5 mm, the dentin in principle constitutes a sufficient protective barrier.
From 0.5 mm, the thinness of residual dentin reaches the critical threshold allowing, among other risks, the passage of irritants into the pulp.
Dentin permeability may vary due to factors resulting from cavity preparations as well as the nature of the solute brought into contact with the dentin.
Cavity preparations induce:
The formation of a viscous coating composed of microcrystalline debris mixed with saliva and bacteria: this is the dentin smear. It is a real plug which greatly reduces permeability and which opposes the processes of dentin adhesion.
The formation of reactional dentin: this pulp-dentin response is extremely varied both in its location and in its structure.
II/ the agents that attack the pulp-dentin complex. During the various dental procedures, the practitioner can, and sometimes inevitably, cause a certain number of traumas at the level of the pulp-dentin complex.
The attacks are caused both during the surgical procedures and during the obturation.
They are often multifactorial and can be dissociated into physical, chemical and bacterial stimuli.
Iatrogenic dental injuries
1/ physical attacks : Are for the most part transmitted through the dentine, and we distinguish:
a-Mechanical aggression: can be produced by the vibrations of rotating instruments in contact with the dentinal walls.
These vibrations alter the odontoblastic layer
would transiently increase permeability
dentin and filtration of the fluid to the outside.
So, whether it is grinding or milling, when it affects the dentin, it creates a wound at the level of the pulp-dentin complex, comparable to a skin incision.
This will have a particular impact on the pulp and we see traumatic inflammation ranging from small reversible damage to irreparable lesions (necrosis).
b-Thermal aggression: is classically caused by the friction of the instrumentation on the dentinal wall, this contact causes, if there is no cooling, heating of the tissue but also evaporation of the fluid on the surface.
The emptied tubules in turn call upon the fluid from the pulp compartment which will come to the surface before being evaporated again in turn.
The installation of irreversible lesions is admitted as soon as the local temperature exceeds 46°C.
In addition, milling without cooling causes dentin burns and intrapulpal temperature increases that can lead to irreversible lesions. This critical threshold is reached after 25 seconds of dry milling.
c-Hydraulic aggression or dehydration of cavities: takes several forms, and is transmitted by the movement of the fluid contained in the tubules.
Any situation which causes an increase in intra-tubular pressure in the periphery, such as the sealing of a crown, results in a liquid movement towards the pulp which will be all the more significant and rapid as the dentine is permeable.
For example, one minute of exposure to the air jet can be enough to eliminate several times the volume of the pulp chamber.
2/ chemical attacks
chemical attacks progress through the dentin.
In fact, diffusion in the tubules reduces the concentration of substances that diffuse towards the pulp. This dilution is a function of the thickness of the dentin layer.
3/ microbial attacks:
Given their assembly complexity, the heads of the turbines and contra-angles and the anti-corrosion oil are factors in the retention of microbial agents, a source of contamination during milling.
Furthermore, during operation, the friction of the moving parts against each other allows the mechanical transport of infected fluids inside the cavity: blood, saliva and water. This is septic inoculation.
4/Other aggressions
STENLEY and SWERDLOW have shown that the intensity of the pulp reaction increases at the same time as the cavity-pulp distance decreases and this in varied experimental conditions.
Hard tissues provide mechanical, thermal and chemical protection.
The deeper or more extensive the dentin resection, the more there is formation of anarchic fibrous reaction dentin and calcification accompanied by pulp retraction and premature aging of the pulp.
Furthermore, curetting a cavity that is too deep can cause accidental pulp exposure. This is also the case when finishing a deep cavity, or when a sharp rotary or manual instrument slips, or when there is an anatomical variation such as a protruding pulp horn.
v/pulpo-dentin complex reactions to therapeutics
In dentistry, any therapeutic action at the level of the dentin has repercussions on the pulp.
Pulpo-dentin reactions will vary because several factors come into play, ranging from reversible pulp hyperemia to an irreversible inflammatory state or even pulp necrosis.
Atraumatic milling with rotary instruments during cavity preparation or peripheral preparation produces vibration, pressure and heat and has deleterious effects on odontoblasts and pulp health.
The severity of these effects depends on the degree of heating of the dentin and pulp and the intensity of intradentin fluid movements.
The lesions induced by milling are explained by the hydrodynamic movements within the canaliculi, and this in both directions, in the form of inflow and outflow.
The heat generated by the friction of poorly irrigated strawberries first causes an inflow, then a loss of water by evaporation which induces an outflow.
VI/ Clinical forms of iatrogenic lesions
Postoperative sensitivities : After placement of a restoration, postoperative sensitivities decrease within a few days or weeks and disappear completely.
Remargination of the edges of the restoration and sealing them with a fluid covering resin is a simple palliative solution to implement and which can prove very effective in reducing patient discomfort.
Micro-infiltrations and secondary carious lesions : Carious lesions that develop after the placement of restorations should be considered as iatrogenic lesions. The marginal deterioration of the restorations increases over time, leaving room for bacterial growth in the gap thus created. Recurrent caries can be treated by performing a partial repair of the restoration, if the carious defect is accessible. They often require complete removal of the restoration and its replacement.
Fracture of restorations:
Fractures occurring in the mass of the restorative material are the second most common cause of replacement of direct and indirect restorations, after recurrent caries and before marginal deficiencies.
These fractures can result from chewing accidents , but they are most often linked to design defects leading to reduced mechanical resistance.
Pulp necrosis and complications:
Pulp necrosis can occur under inadequate restorations that leave exposed areas of dentin unprotected and have a poor seal that leads to bacterial infiltration. Root canal treatment is then indicated. Necrosis is mainly observed under large and deep restorations or under crowns due to the large dentinal surfaces exposed by peripheral preparations. With regard to composite restorations, the absence of conventional pulp protection (calcium hydroxide) is not responsible for pulp complications, even in deep cavities where a self-etching adhesive has been used.
Iatrogenic pulp exposure :
Iatrogenic pulp exposures consist of accidental denudation of the pulp by rotary or manual excavation and milling instruments, during carious excision and/or during cavity or peripheral preparation.
False passages and perforations: These are iatrogenic damages crossing the mineralized coronal and/or radicular structure .
Perforations are procedural errors that result jointly from a lack of knowledge of anatomy, a poor appreciation of the local situation and an inappropriate use of rotary instrumentation. Iatrogenic perforations are among the complications of endodontic procedures and still too often lead to tooth extraction.
Prevention of iatrogenic pulp exposures and their complications involves:
a good knowledge of the thicknesses of coronal dental tissues
a preliminary radiographic assessment of the depth of the cavity and its relationship to the pulp ceiling
visual and tactile control of altered or healthy dentin areas during milling
non-elimination of suprapulpal carious dentin in deep lesions
the application of tissue economy principles in adhesive cavity preparations
work under a dam which allows in the event of pulp exposure to avoid contamination of the pulp by saliva
the immediate placement of a definitive restoration protecting the dentino-pulpal area covered by the capping from bacterial infiltration.
CONCLUSION.
Iatrogenic injuries should not be considered a minor problem in OCE. Iatrogenic practices cause dental injuries with immediate repercussions on pulpal and periodontal health, contributing in the long term to functional deficiencies of these structures. They also have a direct impact on the results of restorations by altering their duration and effectiveness and promoting relapses.
The prevention of iatrogenic pathologies must be a constant concern of the practitioner, both in the therapeutic approach and in his operator behavior. Clinical precision in the service of a biological and more preventive approach to restorative OC essentially makes it possible to avoid these iatrogenic lesions.
Iatrogenic dental injuries
Iatrogenic dental injuries
Iatrogenic dental injuries
