Scientific Session

Iatrogenic Trauma to the Endodontium – Prof. Paul Lambrechts

Abstract: Sometimes the biggest threat to the endodontium comes from the practitioner. Several dental treatment procedures can lead to iatrogenic trauma of the endodontium. All disciplines can be guilty. Poor diagnosis and a lack of respect for biological vital structures are often at the basis of endodontium damage.

Restorative interventions can challenge the endodontium by weakening the tooth structure. Cracks can be induced by invasive restorative or endodontic treatment. Uncontrolled cariesexcavation may lead to pulpirritation and necrosis.

Endodontic mishaps can occurs such as: instrument fracture, instrument inhalation or ingestion, plastination of the apical vascular structure with sealer, coronal or root perforation during access preparation, zipping, ledges, straightening, penetration of irrigants or sealer in the canalis mandibularis with vascular or nerve damage. NaOCl accident can happen with eye irritation, sinus mucosa reaction, emphysema of the soft tissue. Dental tissues can suffer from temperature impacts induced by thermoplastic obturation techniques, ultrasonics, sensitivity testing.

Sinus pathology can be induced by implants, orthognatic screws, extrusion of irrigants and overextension of root canal filling materials inside the sinus.

External cervical resorption (ECR) can be iatrogenically initiated by internal bleaching, cementum damage during periodontal surgery or rootplaning, traumatic intra-ligamentary injection, uncontrolled placement of subgingival rubberdamclamps. Cementumdamage of the neighbouring tooth during elevator extraction. Cementumdamage during subgingival finishing of veneer restorations.

Orthodontics can induce vascular strangling and ischaemic necrosis, apical root resorption, cementum resorption and external cervical resorption.

Orthognatic surgery can cause vascular damage or root damage due to incorrect placement of orthognatic screws.

Incorrect implant placement can inflict apical damage or root damage of the neighbouring tooth.

A more biologic awareness by the dentist can prevent most of the endodontium threats.

Aim: The aim is to increase the biologic awareness of the dentist to prevent most of the threats to the endodontium.

Objectives: Through a clinical scala of iatrogenic mishaps the whole spectrum of potential trauma to the endodontium is given. A mixture of confronting cases should hold a mirror towards the profession without accusing the dental practitioner.


Adventure to Discover the Anatomic, Radiologic and Histological Complexity of External Cervical Resorption. Treatment & outcome – Prof. Paul Lambrechts

Abstract: External cervical resorption (ECR) is an extremely complex periodontal and endodontic pathology. Diagnosis and differential diagnosis with internal resorption or root caries is confusing and the periapical radiographs have several detection limitations. Since the introduction of high resolution Cone Beam CT (CBCT) the prevalence seems to increase but this is due to improved detection power. Also the etiological multifactorial triggers are becoming more evident. Most common causes are: non-vital walking bleach technique, collateral damage induced by orthodontic treatment, cementum damage induced by extraction of neighbouring teeth, cementum abfraction caused by parafunction like bruxing or nail biting, cementum lesions related to eruption collision, chronic irritation caused by cracks or invagination grooves, periodontal pathology and surgery, trauma and even viral infections.

ECR-teeth often keep their vitality for a long time even in the progressed stages of the Heithersay classification. Treatment options are variable depending on the resorption stage and the understanding of the pathology by the practitioner and his ability to approach the lesion in a minimal invasive microscopic way. The pathology outcome and the treatment success are related to the ability to circumscribe the lesion and seal the defect.

The morphological changes during ECR are numerous at the cementum/enamel/dentin/pulp/bone boundaries and the radiographic visualisation is complex. The Heithersay classification needs further improvement in graphical detail because resorption and granulation tissue invasion is only one part of the story. Substitution by osteodentin and reparative processes are as important as well. Also the portal(s) of entry and portal(s) of exit for ECR need to be specified.

Aim: The one over-riding purpose of the lecture.

The aim of the ECR lecture is to unravel the morphological alterations and to increase the understanding of the intriguing biological processes that lead to hard tissue resorption, granulation tissue invasion and formation of osteodentin substitute material. The diagnostic power of CBCT is used to link the image acquisition to the morphological and histological changes and to prepare the practitioner to a controlled watchful waiting approach or therapeutic approach.

Objective: The objective should describe how the aim is achieved.

There are several research tools that help to unravel the ECR pathology and to bring their information together in a 3D understanding of the ECR dynamics.

The synergistic use of clinical surgical microscopy, digital radiography, Cone Beam CT, Micro-CT, Nano-CT, scanning electron microscopy, hard tissue & soft tissue histology and immunohistochemistry helps to visualize the numerous morphological and histological changes in ECR lesions.

The resorption of cementum, enamel and dentin occurs in a dynamic way. Bacterial penetration in dentin tubules and tooth tissue interfaces is becoming evident and can be considered as a maintaining factor in ECR.

The pericanalar root resorption resistant sheet (PRRS), visible as a radiopaque line on digital radiography, is not only composed of a predentin layer, but is thicker than estimated. It includes primary dentin, reactionary dentin and reparative osteodentin.

The formation of intracanalar and intrapulpal reaction calcifications indicate a chronic pulp irritation and is co-responsible for the radiographic cloudy appearance.

The formation of vascularised osteodentin as a substitute for the resorbed enamel, cementum, dentin and PRRS tissue is extremely complex and only histology linked to Nano-CT clarifies the real nature of the dynamic ECR process.

Also the bone turnover of the osteodentin can be proven and is a regular process occurring in hard tissue biology.

Key Learning Points:

    • Cone beam CT is essential in the diagnosis of ECR
    • Histological and histochemical imaging of the granulation tissue highlights the resorption process.
    • SEM-analysis provides a better insight in activity of clastic cells and osteodentin formation.
    • The root canal is surrounded by a pericanalar resorption resistant sheet (PRRS).
    • Osseoid tissue formation and osseodentin apposition in a coral like manner makes the pathology even more complex.
    • The outcome of the minimal invasive treatment is significantly enhanced by better diagnosis.
    • Increase understanding when to treat and how to treat.
    • Obtaining confidence in the decission making how to determine treatment strategies for ECR.

From Root Canal to Crown – Unibody Concept for Endodontically Treated Teeth – Prof. Pekka Valittu

In dentistry typically isotropic materials, such as metals, ceramics and polymers are used. Their properties are not related to the any specific direction of the material´s microstructure. There is a trend towards non-metallic, adhesive and minimally invasive dentistry. In modern adhesive prosthetic and restorative dentistry, structures of remaining tooth substance and the artificial material forms unibody designs enabling preservation of tooth substance and repairable failures to occur in the worst-case scenario. This differs from the traditional prosthodontic thinking where devices like fixed dental prostheses are bearing the load as such and only mechanically locked to the underlying teeth. In recent years, more attention has been paid to mimicking fibrous structures of dental hard tissues by synthetic fiber-reinforced composites. This lecture is reporting existing knowledge of structural fibrous design elements and finding out how much they are utilized in prosthetic and restorative dentistry. Special attempt is put to the aspects of interfacial adhesion of restorative materials, and their role in unibody design of tooth-restoration system. Practical examples of unibody restorations are direct and indirect endocrowns which utilize toughened materials and durable adhesive interfaces.


Root Canal Preparation Errors and Their Impact on Endodontic Outcomes – Prof. Ové Peters

Complications in root canal therapy, while varying in degree, are not rare. More discreet issues in canal preparation are the formation of well-described errors such canal transportation and ledge formation. These may extend to more overt forms such as perforation and canal blockage, which are often clearly visible on radiographs. Likewise, instrument fracture during shaping results in a distinct appearance.

This presentation will describe the nature of the most common canal shaping errors, as well as strategies to avoid and rectify them when present. This is clinically particularly relevant since these errors may be associated with the perception or inferior outcomes.

Specifically the course with include the following information:

  • An assessment of current preparation instruments and their relationship to shaping errors
  • Practical hints to resolving canal blockage and ledge formation
  • Information to assess clinically the effect of shaping errors and case outcomes

Root Canal Preparation Errors and Their Impact on Endodontic Outcomes – Prof. Ove Peters

Complications in root canal therapy, while varying in degree, are not rare. More discreet issues in canal preparation are the formation of well-described errors such canal transportation and ledge formation. These may extend to more overt forms such as perforation and canal blockage, which are often clearly visible on radiographs. Likewise, instrument fracture during shaping results in a distinct appearance.

This presentation will describe the nature of the most common canal shaping errors, as well as strategies to avoid and rectify them when present. This is clinically particularly relevant since these errors may be associated with the perception or inferior outcomes.

  • Specifically, the course with include the following information:
  • An assessment of current preparation instruments and their relationship to shaping errors
  • Practical hints to resolving canal blockage and ledge formation
  • Information to assess clinically the effect of shaping errors and case outcomes

Art of retrieval of fractured instrument from the root canal – Dr. Yoshi Terauchi

One of the iatrogenic accidents in endodontic treatment is an instrument fracture within the root canal system.

More than 80% of instruments fractured in root canals are reported to be NiTi. A NiTi instrument fractures mostly in the apical one-third or beyond a curve in the canal because of the superelastic property.

An instrument fracture is very frustrating and instrument retrieval is considered to be even more challenging in endodontics than any other part of endodontic procedure. In addition, the instrument fracture immediately hinders the clinician from performing further treatment, and thus the outcome of the treatment will be compromised. Although the success rates of instrument retrieval with ultrasonics are in the range of 80 to 90 %, ultrasonic retrieval has never been 100 % successful and it is deemed to be unpredictable. Ultrasonic removal attempts especially from the apical one third of a curved canal often result in a significant amount of dentin sacrifice.

On top of that, aggressive use of ultrasonics could lead to perforation and secondary fracture especially around a curve.

To date no standardized technique for successful instrument removal has been established. It is very crucial to safely remove a fractured instrument. Now a novel instrument retrieval kit (TFRK) has been developed to both minimize dentin sacrifice and the time required to remove a fractured instrument and maximize the success without causing iatrogenic events. The recent literature has shown that the instrument retrieval with TFRK was predictable and was significantly shorter than that with ultrasonics.

The unique procedures in combination with CBCT for instrument retrieval will be shown and discussed using contemporary concepts.