Together with diagnosis and treatment planning, a good knowledge of the root canal system and its frequent variations is a necessity for successful root canal therapy. The selection of instrumentation techniques for variants in internal anatomy of teeth has significant effects on the shaping ability and cleaning effectiveness. The aim of this study was to reveal the differences made by including variations in the internal anatomy of premolars into the study protocol for investigation of a single instrumentation technique (hand ProTaper instruments) assessed by microcomputed tomography and three-dimensional reconstruction.
Recently, microcomputed tomography (micro-CT) has emerged as a powerful tool for the evaluation of root canal morphology [15]. Micro-CT technology allows noninvasive evaluation of both the external and internal morphology of a tooth in a detailed and accurate manner [2, 3]. Though micro-CT is expensive and time-consuming and not suitable for clinical use, it would be an effective way to examine the shape of the root canal after preparation [16, 17] and obturation [18]. In comparison, the cone-beam computed tomography (CBCT) designed for dental use can provide the clinician with an imaging modality that is capable of providing a 3D representation of the maxillofacial region with minimal distortion, and it can also enhance detection and mapping the root canal system with the potential to improve the quality of root canal therapy [5, 19, 20].
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Thirty single-root premolars were randomly selected from a collection of extracted human teeth from a Chinese population sample based on mature apices without visible apical resorption and no prior endodontic treatment. These teeth were extracted because of periodontitis or orthodontic need. After understanding and written consent was obtained from patients, the extracted teeth were collected by the West China Hospital of Stomatology for teaching and research. The present study was approved by the Ethics Committee of the West China Hospital of Stomatology, and the premolars were selected from the teeth bank of the hospital. After extraction, tissue fragments and calcified debris were removed from the teeth by scaling and the teeth were stored in 0.1% thymol until used.
The present study aimed to reveal the differences made by including variations in internal anatomy of premolars into the study protocol for investigation of a single instrumentation technique (HPT) using micro-CT and 3-D reconstruction technology. Because of the diversity of clinical cases in endodontic therapy, we wanted to develop a study protocol that integrates the canal system classification with various instruments to evaluate the preparation efficacy using 3-D reconstruction techniques. As a pilot study, only five teeth of different categories of root canal configuration (one each of types I, II, III, IV and V) were selected. The results showed the difference of morphological changes in the five types of root canal systems shaped with the same hand instrumentation technique. However, because of the limited numbers of teeth and techniques, no statistical evaluation could be made concerning the instrumentation technique.
In daily clinical practice, there are some cases in which conventional intraoral radiography and/or panoramic radiography alone do not provide enough information on the pathologic condition [43]. It is important to visualize and to have knowledge of the internal tooth anatomy before undertaking endodontic therapy [4]. Micro-CT has emerged as a powerful tool for evaluation of root canal morphology. Unfortunately, this technique is not suitable for clinical use, but cone-beam computed tomography (CBCT) systems have now been introduced for 3-D imaging of hard tissues of the maxillofacial region, with minimal distortion [44]. When encountering a case with a complicated canal system (such as type II or V) by radiographic evaluation, CBCT may be a good choice to allow appropriate management of the endodontic problem for endodontists [19, 44].
From 3-D color-coded images, we discovered obviously different morphological changes in the five types of root canal systems shaped with the same hand instrumentation technique. These results provide further information that premolars are among the most difficult teeth to be treated endodontically and that instrumentation techniques for the root canal systems of premolars should be judged individually depending on the 3-D canal configuration of each tooth. Further study is needed to demonstrate the differences made by including variations in internal anatomy of teeth into the study protocol for investigation of various instrumentation techniques.
Cracked tooth is a distinct type of longitudinal tooth fracture which occurs very commonly and its diagnosis can be challenging. This type of fracture tends to grow and change over time. Clinical diagnosis is difficult because the signs and symptoms are variable or nonspecific and may even resemble post-treatment disease following root canal treatment or periodontal disease. This variety and unpredictability make the cracked tooth a challenging diagnostic entity. The use of cone beam computed tomography (CBCT) in diagnosis of complex endodontic cases has been well documented in the literature. In this paper we present two cases of cracked tooth and emphasise on the timely use of cone beam computed tomography as an aid in diagnosis and as a prognostic determinant.
Cracked tooth is common and challenging [4]. It may be caused by excessive forces from mastication or occlusion, either large forces on a normal tooth or normal forces on a weakened tooth [1]. Complex restorative and endodontic treatments that remove dentin compromise the internal strength of the tooth making it susceptible to fracture [3]. The detection of non-displaced longitudinal fractures, such as a cracked tooth, is a significant challenge in clinical practice [4]. Clinical diagnosis is difficult because the signs and symptoms are variable or nonspecific and may even resemble post-treatment disease following root canal treatment or periodontal disease [5]. Radiographic signs are usually absent when the orientation of the X-ray beam is not parallel to the plane of the fracture making the diagnosis even more challenging [6]. Moreover superimposition of other structures further limits the sensitivity of radiographs for the detection of fractures.
Cracked tooth by itself is not a diagnosis, but is a finding. A cracked tooth can act as a pathway for bacteria that may induce pulpal and/or periapical inflammation or disease. The relationship between cracks in teeth and endodontic diagnosis depends upon the extent of the fracture. If the fracture is in or in close proximity to the pulp and allows bacterial byproducts or frank bacteria to communicate with the pulp, then inflammation and pulpal degeneration occurs. If the fracture is not in close proximity to the pulp and bacterial byproducts are neutralized in the dentinal tubules, then no pulpal inflammation or degeneration should be expected [7]. The prognosis of a tooth depends on extent of the fracture. The prognosis of cracked tooth that is not treated will progressively deteriorate and may evolve into a split tooth or result in severe periodontal defects [1]. Eventually the tooth may be lost. Therefore early diagnosis and treatment are essential in saving these teeth.
A female patient aged 49 years reported with pain on upper left second premolar, that is, 25, for the past two weeks. Pain was severe, throbbing in nature, and radiating towards the temporal region and the neck. It was aggravated on taking cold and hot drinks and relieved with pain killers (NSAIDs). No caries or fracture was detected nor was restoration present. The tooth was tender on percussion and no mobility was detected. Electric pulp test showed delayed response. Radiograph revealed no significant findings. Based on the history and clinical presentation it was diagnosed as apical periodontitis. Root canal treatment was performed with amalgam as post-endodontic restoration (Figure 1(c)). Thereafter, the patient failed to report for a crown restoration.
Fifteen months later, the patient returned with severe pain in the same tooth, that is, 25. Pain was radiating and aggravated on chewing and biting. Patient could recall episodes of dull aching pain even after the root canal therapy, for which she was taking pain killers for relief. Clinical examination revealed a fracture on the centre of occlusal surface running mesiodistally and over the marginal ridges onto the proximal surface (Figure 1(a)). A diffuse swelling was present on the buccal gingiva involving the marginal and attached gingiva (Figure 1(b)). Tooth was tender on percussion and exhibited grade II mobility. The fracture could not be separated by using wedging forces. Periodontal probing revealed deep isolated narrow pockets on both proximal sides. Radiograph did not reveal the fracture as it was mesiodistally oriented, but showed angular bone loss on both mesial and distal proximal aspects and generalised widening of periodontal ligament space (Figure 1(d)). Prognosis was considered poor and extraction was performed.
Cracked tooth is a distinct type of longitudinal fracture of the tooth and studies have indicated increased incidence of cracked tooth [8, 9]. This type of fracture is not only associated with complex and long standing restorations but also with minimally restored teeth and teeth without any restorations as noticed in case report 2. The teeth usually involved are mandibular molars (restored and nonrestored) followed by maxillary premolars and then by maxillary first molars [1, 10, 11]. Cracks in teeth are almost invariably mesiodistal fractures [12] although mandibular molars may occasionally fracture toward the facial or lingual surface. Longitudinal fractures are common in root canal-treated teeth, because the strength of root canal treated tooth has already been compromised by caries, restorations, or overextended access preparations [13] making it vulnerable to fracture. Crown restorations given in posterior teeth after endodontic therapy provide bracing effect and prevent crack initiation and propagation. In case report 1, failure to deliver crown restoration after root canal therapy may have led to the propagation of crack over a period of time leading to devastating results and finally extraction of tooth. 2ff7e9595c
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