A narrative review of cracks in teeth: Aetiology, microstructure and diagnostic challenges

OBJECTIVES

To summarize the available evidence of crack formation in teeth and to discuss the limitations of the current clinical diagnostic modalities for crack detection in teeth.

BACKGROUND

Cracks are a common clinical finding in teeth and yet clinicians still struggle to identify the full extent and orientation of cracks for their appropriate timely management. The biomechanics of crack development can be due to multiple factors and can differ from an unrestored tooth to a restored or endodontically treated tooth.

DATA & SOURCES

This narrative review has been designed following the guidelines published by Green et al. 2006 [1] Published literature in the English language that addresses the objectives of this review up to July 2022 was sourced from online databases and reference lists. The relevance of the papers was assessed and discussed by two reviewers. A total of 101 publications were included in this narrative review.

CONCLUSIONS

The initiation and development of cracks in teeth are likely linked to an interplay between the masticatory forces and fracture resistance of the remaining tooth structure. From the identified literature, the quality and quantity of remaining tooth structure in a restored or endodontically-treated tooth affects the biomechanics of crack development compared to an unrestored tooth. The extent, orientation, and size of the cracks do affect a clinician's ability to detect cracks in teeth. There is still a need to develop reliable diagnostic tools that will accurately identify cracks in teeth beneath restorations to enable effective monitoring of their propagation and provide appropriate interventions.

CLINICAL SIGNIFICANCE

The development and propagation of cracks in an unrestored tooth differ greatly from a restored and endodontically treated tooth; mainly linked to the quantity and quality of the remaining tooth structure and the forces acting on them. Identifying the extent of cracks in teeth remains challenging for early clinical intervention.

Endodontic Periapical Lesion: An Overview on the Etiology, Diagnosis and Current Treatment Modalities

Nonsurgical and surgical endodontic treatments have a high success rate in the treatment and prevention of apical periodontitis when carried out according to standard and accepted clinical principles. Nevertheless, endodontic periapical lesions remain in some cases, and further treatment should be considered when apical periodontitis persists. Although several treatment modalities have been proposed for endodontically treated teeth with persistent apical periodontitis, there is a need for less invasive methods with more predictable outcomes. The advantages and shortcomings of existing approaches for the diagnosis and treatment of endodontic periradicular lesions are discussed in this review.

Electrical Pulp Testing: Sources of Error

INTRODUCTION

Accurate identification and assessment of an inflamed or necrotic tooth is essentialfor endodontic treatment. The purpose of this research was to investigate possible sources of error associated with the use of the electric pulp tester (EPT).

METHODS

Forty-six intact teeth (23 tooth pairs) in 22 patients were evaluated in vivo. For the tooth pairs, one tooth had to have been previously endodontically treated and restored with a class II amalgam restoration. The restoration was required to have proximal contact with a class II amalgam of another vital posterior tooth. EPT was performed on pulpless and vital teeth for experimental groups (enamel, restoration, contacting, or isolated).

RESULTS

The highest rate of false positive responses (82%) was found in the pulpless restored contacting group, suggesting that EPT impulses are able to travel through proximal metallic contacts and stimulate teeth distant from the EPT probe. All vital tooth groups had a high rate of positive responses with no significant diferences.

CONCLUSIONS

If a tested tooth contains an interproximal restoration contacting adjacent restorations or the gingival, the teeth must be isolated (rubber dam) and the EPT probe should be placed in a region suspected to have uninterrupted tubule paths to the pulp.

Management of the pulp in primary teeth--an update

Management of the pulpal tissue in primary teeth is a clinical challenge facing dental practitioners on a regular basis. This article reviews the most common treatments used at the present time in the management of the pulp in deciduous teeth. It gives an overview of treatment options and the indications and contra-indications for the different treatment modalities. The evidence behind the medicaments used, their actions and success rates are discussed. Practical guidelines for choosing to retain or extract deciduous teeth and management of the primary tooth pulp with different clinical presentations are discussed. Areas of future research are highlighted.

Supernumerary lateral incisor

Supernumerary teeth are common in general population and occur frequently in patients with familial trait. However, it is rare to find supernumeraries in individuals with no associated disease or syndrome. Supernumerary teeth are found in any region of maxilla and mandible, with a predisposition for anterior maxilla. A case of endodontically involved supernumerary lateral incisor is described.

A novel diagnostic and prognostic classification for the clinical management of endodontically treated single anterior teeth

The restoration of endodontically treated anterior teeth (ETAT) may pose a significant clinical challenge given the wide variety of therapeutic options available. Accurate analysis of the remaining tooth structure is critical in the diagnostic process, leading to selection of the proper treatment option. A novel, simple, and precise classification that allows the evaluation of ETAT is presented. Important factors related to the crown or abutment such as height, wall thickness, and circumferential integrity and root-related factors such as diameter of the canal, depth of the preparation, and canal shape are discussed. This classification may serve to establish a comprehensive diagnosis and assign prognosis to ETAT, which may be helpful for interclinician communication and standardized comparisons in clinical research.

Absolute transmitted light plethysmography for assessment of dental pulp vitality through quantification of pulp chamber hematocrit by a three-layer model

After confirming that the gingival circulation had little effect on transmitted light plethysmography measurement in the upper central incisor in both in vivo experiments and numerical Monte Carlo simulation studies, a three-layer model comprising of a pulp chamber sandwiched between two dentin layers has been introduced to quantify the pulp chamber hematocrit (Hctp) from the measured optical density. Two-flux theory was utilized to derive a mathematical equation for transmitted intensity in terms of tooth dimensions, Hctp, and light-source wavelength. Each layer was assumed homogeneous so as to represent its optical properties by the bulk absorption and scattering constants. The mean error between the Hctp estimate based on the three-layer-model equation and the Hctp actual in the extracted model tooth was -0.00115 with standard deviation (SD) of 0.00733 at 522 nm wavelength, while for 810 nm +0.09157 and 0.02493. The Hctp estimate of the upper central incisor in 10 young volunteers at 522 nm using the three-layer model ranged from 0.002 to 0.061 with the mean of 0.032. The Hctp change reflects blood volume shift in the pulp microcirculation to possibly indicate dental pulp vitality.

Comparison of Electrical, Thermal, and Pulse Oximetry Methods for Assessing Pulp Vitality in Recently Traumatized Teeth

Pulse oximeter is a well-established and noninvasive method for measuring vascular health by evaluating oxygen saturation. This study compared the efficacy of a custom-made pulse oximeter dental probe with the electric pulp testing and thermal testing for measuring pulp vitality status of recently traumatized permanent teeth. Readings for pulp vitality for 17 recently traumatized maxillary incisors were taken with custom-made pulse oximeter dental probe (group 1), electrical pulp tester (group 2), and thermal testing (group 3) over a 6-month period. The proportion of recently traumatized teeth showing a positive responsiveness in thermal/electric pulp tests increased from no teeth showing responsiveness on day 0 to 29.4% teeth on the 28th day, 82.35% of teeth at 2 months, and 94.11% teeth at 3 months. However, pulse oximeter gave positive vitality readings that remained constant over the study period from day 0 to 6 months in all patients.

Fundamentals of Endodontics

Endodontic disease is a highly prevalent (>10% of all dogs) and insidiously painful process that can have significant local and systemic effects. The root canal system is a delicate organ and is prone to inflammation, infection, and partial and complete necrosis. Vital pulp therapy must be performed quickly, gently, and meticulously if it is to be effective. The relatively high rate of failure in direct pulp capping makes regular follow-up radiographs of critical importance to ensure patient health. Once a tooth is dead, there are often no obvious clinical signs; therefore, clinicians must be educated in the diagnosis of the disease processes. Once properly educated, the practitioner must remain vigilant for subtle signs of the disease process. Standard root canal therapy is an effective method of removing the inflammation, infection, and associated discomfort of the endodontically diseased tooth while maintaining its function. Endodontic failure most likely remains hidden unless dental radiology is used. Follow-up radiographs at regular intervals throughout the patient's life are critical for ensuring the long-term success of any endodontic therapy.

[Laser Doppler flowmetry for vitality testing of traumatized maxillary incisors]

Pulp sensitivity and vitality changes were evaluated in 69 traumatized maxillary incisors and in 38 control teeth during a follow-up period of 20 months. Examinations included thermal testing using carbon dioxide snow (CO2) and the laser Doppler flowmetry (LDF). These measurements were compared to the clinical and radiological findings. In 47.8% of the traumatized teeth and in 55.3% of the control group the three LDF measurements corresponded with the sensitivity testing using CO2 and with the clinical and radiological findings. In 31.9% of the traumatized teeth and in 7.9% of the control group the LDF-measurements differed from the CO2-measurements, but were in agreement with the other clinical and radiographic findings. The information obtained by laser Doppler flowmetry is of additional importance for the treatment planning. Since the clinical examination of traumatized teeth is sometimes inconclusive, the laser Doppler flowmetry is a further diagnostic tool but it cannot replace the radiological or clinical examination.

Dentoalveolar trauma in a patient with chronic idiopathic thrombocytopenic purpura: a case report

A case is presented of a 13-year-old boy with chronic idiopathic thrombocytopenic purpura (ITP) who sustained traumatic labial luxation of both lower central incisors, with partial alveolar fracture resulting in displacement of the labial alveolar plate. Intravenous immunoglobulin (Fleibogamma, 1 g/kg body weight x 2 days) was administered, resulting in the patient's platelet count rising from 15,000/mm3 to 70,000/mm3. Under general anesthesia, the displaced lower labial alveolus and luxated teeth were repositioned and splinted 2 days following trauma. Healing was uneventful. Subsequently, both lower central incisors became nonvital and were endodontically treated. The dental treatment of this patient with ITP is discussed in terms of emergency management, and subsequent care.

Quantitative analysis of MRI signal intensity as a tool for evaluating tooth pulp vitality

OBJECTIVES

To assess whether it is possible to measure tooth vitality using magnetic resonance imaging (MRI).

METHODS

Signal intensity measurements were conducted using T(1) and T(2) sequences at the region of interest in 211 teeth (35 patients).

RESULTS

Clinical findings showed that 17.3% of the teeth were avital, whereas 82.7% were found to be vital. Neither the T(2) sequence nor the non-contrast-enhanced T(1) sequence showed significant differences between vital and avital teeth. However, the contrast-enhanced sequence and, in particular, a comparison of signal intensities between the non-contrast-enhanced T(1) sequence and the contrast-enhanced sequence showed a significant difference between vital and avital teeth.

CONCLUSION

Contrast-enhanced MRI enables us to draw conclusions on pulpal perfusion in vivo.

[Evaluation of pulpal blood flow by laser doppler flowmetry as a test of tooth vitality in long-term follow-up: case report]

The reliability of laser Doppler flowmetry in a 2-probe assessment of pulpal blood flow is well known. The purpose of this case report was to determine its use as an exclusive and reliable tool for tooth vitality diagnosis in a long-term follow-up. As a result of a traumatic injury to a 24-years old Caucasian female, tooth pulp vitality was studied in 6 maxillary front teeth over 30 weeks through use of 2-probe laser Doppler flowmetry and current sensitivity tests. A similar assessment was repeated after 228 weeks. Confronted with an alveolar bone fracture with a tooth in the fracture line, one intrusion and several luxated teeth, current sensitivity tests are found not to be so reliable indicators of revascularisation as significant results are given later (7 weeks) compared to laser Doppler flowmetry tests (1 week). A pathway with ischaemia (3 weeks), hyperaemia (7 weeks) and restored blood supply in the pulp measured by laser Doppler flowmetry tests was found and avoided endodontic treatment. Teeth vascularisation evolved normally (228 weeks). Despite a high indication in all sensitivity tests for endodontic treatment, the use of laser Doppler flowmetry tests was clear, more reliable than sensitivity tests and exclusive as denervation was postponed and pulp vascularisation was evident.

Comparison of carbon dioxide versus refrigerant spray to determine pulpal responsiveness

There is little evidence for which cold delivery method is most accurate in determining pulp responsiveness. This study compared carbon dioxide dry ice sticks (CO2) versus refrigerant spray (RS) to generate a patient response from different types of teeth restored to varying degrees. Fifteen human patients were selected. In each quadrant, three teeth were identified and the restoration type recorded. Blindfolded patients were randomly tested with either CO2 or RS in a crossover design at two different sessions. Responsiveness was recorded as yes/no and the interval (in seconds) from application to response was determined. Results showed that (a) CO2 and RS were equivalent in producing a pulpal response regardless of tooth and presence of restoration, and (b) CO2 took significantly (p < 0.05) longer to evoke a response than RS using paired t tests. In conclusion, RS and CO2 were equivalent in determining pulpal responsiveness, but the elicited response from RS was faster.

Periapical central giant cell granuloma: a potential endodontic misdiagnosis

This retrospective study ascertained the incidence and clinicopathologic features of central giant cell granulomas (CGCGs) associated with teeth with necrotic pulps or teeth that had received previous endodontic treatment and determined whether periapical CGCGs can result in endodontic misdiagnosis. Clinical and histopathologic data of biopsy specimens diagnosed as CGCG were collected from the archives of the Oral Pathology Laboratory, Temple University, and were reviewed. Over the 9-year period, 16 of 79 cases (20%) of CGCG were associated with a tooth that had a history of pulp necrosis. Of those, 14 (88%) were associated with previous root canal treatment. The data from this series of 79 cases of CGCG also showed that CGCGs were less common in women, less common before age 30, and did not cross the midline of the jaw as often as previously reported. Clinical and histopathologic data were compared from (1) CGCGs associated with teeth with vital pulps or that occurred in edentulous areas; (2) CGCGs associated with teeth with necrotic pulps; and (3) 194 cases of periapical granulomas and radicular cysts. These data strongly suggest that CGCGs associated with teeth with necrotic pulps are not directly related to periapical inflammation and may be misdiagnosed as endodontic lesions. Posttreatment follow-up and routine submission of periapical surgical specimens are emphasized.

A cautionary tale. Case report

A healthy 26 year old female underwent unsuccessful surgery for an incorrectly diagnosed sebaceous cyst in the cheek. Eventually the problem was traced to a non-vital tooth 24. When the tooth was treated endodontically, the situation resolved in one week.

A comparison of laser Doppler flowmetry with other methods of assessing the vitality of traumatised anterior teeth

Laser Doppler flowmetry is a non-invasive electrooptical technique which allows the semi-quantitative recording of pulpal blood flow. This study aimed to determine the reliability (measured as the sensitivity and specificity) of laser Doppler flowmetry as a method of assessing the vitality of traumatised anterior teeth, and to compare it with standard pulpal diagnostic tests. Recordings of pulpal blood flow were taken from 67 non-vital anterior teeth (55 patients), where the pulpal status was confirmed by pulpectomy. For comparison, recordings were also taken from 84 vital anterior teeth (84 patients). Analysis of the recordings allowed diagnostic criteria to be developed which gave the technique a sensitivity and specificity of 1.0 for this sample. None of the other standard pulpal diagnostic methods tested was as reliable. This was usually due to low sensitivities, which ranged between 0.92 for sensibility testing with ethyl chloride down to 0.36 for periapical radiolucency and 0.16 for a history of pain. Laser Doppler flowmetry was found to be a reliable method of assessing the pulpal status of traumatised anterior teeth, although it is technique-sensitive and time-consuming to use.

Evaluation of the ability of thermal and electrical tests to register pulp vitality

The aim of the present study was to evaluate the ability of thermal and electrical tests to register pulp vitality. Sensitivity, specificity, negative predictive value and positive predictive value were calculated by comparing the test results with a "gold standard". The thermal tests studied were a cold test (ethyl chloride) and a heat test (hot gutta-percha). For the electrical test, the Analytic Technology Pulp Tester was used. The examined teeth were 59 teeth with unknown pulpal status in need of endodontic treatment and 16 intact teeth, all with radiographically normal periapical bone structures. In total 46 teeth with vital pulps and 29 teeth with necrotic pulps were tested. This gave a disease prevalence of 39%. The gold standard was established by direct pulp inspection of the 59 teeth in need of endodontic treatment. In the 16 intact teeth the pulp was judged as vital. The number of true positive (TP), false positive (FP), true negative (TN) and false negative (FN) test results was calculated for each method as compared to the gold standard. Based on this, the sensitivity, specificity, positive predictive value and negative predictive value were calculated for each method. The sensitivity was 0.83 for the cold test, 0.86 for the heat test and 0.72 for the electrical test. The specificity was 0.93 for the cold test, 0.41 for the heat test and 0.93 for the electrical test. The positive predictive value was 0.89 for the cold test, 0.48 for the heat test and 0.88 for the electrical test, and the negative predictive value was 0.90 for the cold test, 0.83 for the heat test and 0.84 for the electrical test. This indicated that the probability of a non-sensitive reaction representing a necrotic pulp was 89% with the cold test, 48% with the heat test and 88% with the electrical test. It also indicated that the probability of a sensitive reaction representing a vital pulp was 90% with the cold test, 83% with the heat test and 84% with the electrical test.

Subjective sensation and objective neural discharges recorded from clinically nonvital and intact teeth

The aim of this study was to compare subjective sensation with objective neural discharges recorded by microneurography. We examined human teeth that did not respond to pulp vitality testing, but that responded to cavity preparation for endodontic treatment (pathophysiological). Intact teeth and endodontically obturated teeth were used as controls. Pulpal blood flow in the clinical crown and histological examination were also used. Most teeth, both in normal and pathophysiological conditions, did not respond to all pulp vitality tests. Even when teeth in the pathophysiological group showed spike discharges evoked by pulp vitality tests or from spontaneous activity no sensation was elicited. These results confirmed the usefulness of microneurography for research on pulpal sensation and the significance of summation in the perception of sensation in chronically inflamed tooth pulp.

The odontogenic keratocyst: a potential endodontic misdiagnosis

Odontogenic keratocysts manifest themselves as radiolucencies that can appear anywhere in the maxilla or mandible, including periradicular areas; they may thus masquerade as lesions of endodontic origin. This retrospective study examined 239 odontogenic keratocysts received by the Oral Pathology Laboratory at Temple University School of Medicine over a 3-year period. Twenty-one (9%) of the cysts received were located periradicularly; of these 21, 12 (57%) were associated with nonvital or endodontically treated teeth and thus mimicked lesions of endodontic origin. Because of its aggressive nature and tendency to recur, the periradicular odontogenic keratocyst should be included in the differential diagnosis of lesions that are refractory to endodontic treatment.