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.

Diagnostic and treatment preferences for cracked posterior teeth.

BACKGROUND: Longitudinal cracks in teeth are common and often present challenges in diagnosis and management. This study investigated the preferred diagnostic process and treatment modalities for these cracked teeth. METHODS: Dentists currently registered with Dental Board of Australia and practising within Australia were invited to complete an online Qualtrics-based survey on their perspectives on the presentations, diagnosis, and treatment preferences for cracked teeth. RESULTS: Of respondents, 56.8% chose to place an indirect cuspal-coverage restoration on an asymptomatic cracked vital tooth. When the tooth was mildly cold sensitive, direct cuspal-coverage restoration was favoured (64.9%), while 36.8% preferred placing an orthodontic band in a tooth with biting pain. Respondents had higher odds of recommending indirect restoration when CAD-CAM milling was available on-site or magnification was routinely used, regardless of presenting symptoms. Almost half (46.8%) preferred to extract if the tooth undergoing root canal treatment had a crack with a 5 mm probing pocket depth. Most (71.4%) demonstrated a poor understanding of cracked tooth biomechanics. CONCLUSION: Australian dentists varied in their diagnostic and treatment preferences for cracked teeth, reflecting a need for more well-controlled clinical studies in the diagnostic process, clinical biomechanics and treatment modalities for these teeth. © 2023 Australian Dental Association.

Therapeutic strategy for cracked teeth.

The management of cracked teeth represents a difficulty because their diagnosis is complex and there is no consensus concerning their treatment. The present article explains this pathology within enamel and dentin and also focuses on the clinical consequences of crack development in dental tissue. As cracks have both biologic and mechanical implications, a complete review of the literature on the subject has enabled the development of a comprehensive diagnostic approach to identify cracked teeth and optimize their management. The elements of diagnosis are the bite test, transillumination, the pulp sensitivity test, the periodontal test, radiologic examinations, removal of existing restorations, and the use of quantitative light-induced fluorescence. Finally, the management of biologic and mechanical imperatives relating to the treatment of cracked teeth has allowed the proposal of a reliable and reproducible therapeutic strategy based on two pillars: the arrest of bacterial infiltration using immediate dentin sealing, and the limitation of crack propagation using relative cuspal coverage. In this article, the proposed clinical protocol is explained through the use of a decision map and is illustrated by a clinical case example.

Treatment of cracked teeth: A comprehensive narrative review.

OBJECTIVES: The term "cracked tooth" is used to describe an incomplete fracture initiated from the crown and progressing towards a subgingival direction. Despite the high prevalence of cracked teeth and their frequent association with symptoms and pulpal or periapical pathoses, there is still no consensus in the literature with regard to their restorative and endodontic management. Therefore, the aim of this narrative review was to evaluate the most relevant research and provide an up-to-date comprehensive overview regarding the treatment of cracked teeth. MATERIALS AND METHODS: An electronic literature search was carried out in MEDLINE (via Ovid), Embase (via Ovid), Scopus, and Web of Science as well as several "Grey literature" sources up to February 22nd 2022 using a combination of pre-specified 'free-text' terms (keywords) and "subject headings." The search process was supplemented by handsearching in relevant dental journals and reference lists. This narrative review focused on clinical follow-up studies (observational or interventional studies, case series/reports), laboratory studies and systematic reviews written in English language that reported data on treatment of permanent cracked teeth. The selection of relevant studies was carried out by two reviewers (AK and DG) working independently in two consecutive stages: title/abstract screening and full-text retrieval. Any discrepancies in the study selection were resolved by discussion between the reviewers. RESULTS: In total, 64 articles were selected for inclusion in this narrative review. CONCLUSIONS: Cracked teeth with normal pulp or reversible pulpitis have exhibited high pulp and tooth survival rates by the provision of direct or indirect composite restorations. Besides, recent data favour monitoring, especially in the absence of symptoms or compromised tooth structure. When endodontic intervention is required, current evidence suggests that along with appropriate restorative management, outcomes of cracked teeth may be comparable to those of non-cracked root filled teeth.

A perspective on the diagnosis of cracked tooth: imaging modalities evolve to AI-based analysis.

Despite numerous clinical trials and pre-clinical developments, the diagnosis of cracked tooth, especially in the early stages, remains a challenge. Cracked tooth syndrome is often accompanied by dramatic painful responses from occlusion and temperature stimulation, which has become one of the leading causes for tooth loss in adults. Current clinical diagnostical approaches for cracked tooth have been widely investigated based on X-rays, optical light, ultrasound wave, etc. Advances in artificial intelligence (AI) development have unlocked the possibility of detecting the crack in a more intellectual and automotive way. This may lead to the possibility of further enhancement of the diagnostic accuracy for cracked tooth disease. In this review, various medical imaging technologies for diagnosing cracked tooth are overviewed. In particular, the imaging modality, effect and the advantages of each diagnostic technique are discussed. What's more, AI-based crack detection and classification methods, especially the convolutional neural network (CNN)-based algorithms, including image classification (AlexNet), object detection (YOLO, Faster-RCNN), semantic segmentation (U-Net, Segnet) are comprehensively reviewed. Finally, the future perspectives and challenges in the diagnosis of the cracked tooth are lighted.

Review of Cracked Tooth Syndrome: Etiology, Diagnosis, Management, and Prevention.

Cracked tooth syndrome refers to a series of symptoms caused by cracked teeth. This article reviews the current literature on cracked tooth syndrome from four aspects, etiology, diagnosis, management, and prevention, to provide readers integrated information about this. The article begins with an introduction to the odontiatrogenic factors and then covers the noniatrogenic factors that induce cracked tooth syndrome. While the former discusses inappropriate root canal therapy and improper restorative procedures, the latter covers the topics such as the developmental and functional status of cracked tooth syndrome. This is then followed by the description of common clinical diagnosis methods, the prospects of new technologies, and summaries of current clinical management methods, including immediate management and direct and indirect restoration. In the final section, preventive methods and their importance are proposed, with the aim of educating the common population.

A method of crack detection based on digital image correlation for simulated cracked tooth.

BACKGROUND: Early clinical cracked tooth can be a perplexing disorder to diagnose and manage. One of the key problems for the diagnosis of the cracked tooth is the detection of the location of the surface crack. METHODS: This paper proposes an image-based method for the detection of the micro-crack in the simulated cracked tooth. A homemade three-axis motion platform mounted with a telecentric lens was built as an image acquisition system to observe the surface of the simulated cracked tooth, which was under compression with a magnitude of the masticatory force. By using digital image correlation (DIC), the deformation map for the crown surface of the cracked tooth was calculated. Through image analysis, the micro-crack was quantitatively visualized and characterized. RESULTS: The skeleton of the crack path was successfully extracted from the image of the principal strain field, which was further verified by the image from micro-CT. Based on crack kinematics, the crack opening displacement was quantitatively calculated to be 2-10 µm under the normal mastication stress, which was in good agreement with the value reported in the literature. CONCLUSIONS: The crack on the surface of the simulated cracked tooth could be detected based on the proposed DIC-based method. The proposed method may provide a new solution for the rapid clinical diagnosis of cracked teeth and the calculated crack information would be helpful for the subsequent clinical treatment of cracked teeth.

Management of cracked teeth: Perspectives of general dental practitioners and specialists.

OBJECTIVES: The main aim of this study was to compare how general dental practitioners (GDPs), endodontists and prosthodontists diagnose, prognosticate, and treat cracked teeth. The secondary aim was to highlight factors influencing GDPs' referral practices of cracked teeth to specialists. MATERIALS AND METHODS: Questionnaires were used to collect information from GDPs, prosthodontists, and endodontists, on their use of diagnostic methods to identify cracked teeth, prognostication, and their management and referral practices for cracked teeth. Descriptive statistics were used to summarize the quantitative data. Pearson's Chi-Square test or Fisher's Exact test was applied to categorical variables while Kruskal-Wallis or Spearman's correlation coefficient was applied to continuous variables (p <0.05). Content analysis was performed for qualitative data. RESULTS: 207 dentists responded, resulting in a response rate of 83.5%. Endodontists used more diagnostic tools as compared to prosthodontists and GDPs. For pulpally involved cracked teeth, endodontists were more likely to recommend root canal treatment (RCT) and cuspal coverage compared to extraction, followed by prosthodontists then GDPs. Main reasons for referral of cracked teeth to specialists include uncertainty in diagnosis, difficulty in crack visualization after endodontic access, and cracked teeth indicated for RCT. CONCLUSION: GDPs, prosthodontists, and endodontists differ in terms of their diagnosis, prognostication, and treatment of cracked teeth. GDPs refer cracked teeth to specialists due to challenges faced in diagnosis and treatment. Future research and education are required to provide evidence-based guidelines in the management of cracked teeth so that patients with cracked teeth can receive standardized care.

The Effectiveness of a Quantitative Light-induced Fluorescent Device for the Diagnosis of a Cracked Tooth: A Case Report.

Diagnosing a cracked tooth is a challenge for dental clinicians. This report describes the use of a quantitative light-induced fluorescent (QLF) device that detects fluorescence reactions with visible light (405 nm) to visually identify microscopic tooth cracks during the diagnosis and treatment of cracked teeth that caused pulp disease. Fluorescence images of the occlusal surface, before and after removal of the restoration, and inside of the access cavity for root canal treatment were obtained using an intraoral capture-type QLF device (Q-ray penC; AIOBIO, Seoul, Korea). The device provided visual information such as enhanced magnification and fluorescent images to identify cracks on the exterior of the tooth, around restorations, and inside the cavity after removal of the restoration by a simple image capture process. The device was able to demonstrate the existence of the crack line and to predict the depth of cracks during treatment.The QLF device showed a potential benefit in the diagnosis and characterization, including the location and depth, of tooth cracks.

Cracked Tooth Syndrome: Assessment, Prognosis and Predictable Management Strategies.

Cracked tooth syndrome (CTS) is a common presentation in general practice. The diagnosis and management of teeth with CTS may be difficult due to the unknown extent of the crack. This article reviews the aetiology, diagnosis, management and prognosis of teeth with CTS. A thorough examination is required to effectively assess CTS. Intervention should aim to relieve symptoms and brace the remaining tooth structure effectively against further flexion. Restored teeth with CTS have a guarded prognosis due to the risk of further crack propagation, but the chances of survival at 5-years is acceptable (74.1-96.8%).

Facts About Cracks in Teeth.

Examining the nature of stress distribution within the intact tooth can aid in understanding how natural tooth structures are able to resist mechanical forces during masticatory function. Identification of potential fractures in teeth on clinical examination is essential for correct diagnosis, particularly if there is pulpal involvement. This discussion will consider the different types of fracture, their identification and management. This paper will highlight management of tooth fractures, including identifying prognostic indicators, which are largely dependent on the extent of the fracture within the tooth structure.

Indocyanine green-assisted dental imaging in the first and second near-infrared windows as compared with X-ray imaging.

Indocyanine green (ICG) has been widely used in medical imaging, such as in retinal angiography. Here, we describe a pilot ex vivo study of ICG-assisted near-infrared fluorescence (NIRF) dental imaging in the first (700-950 nm for ICG-NIRF-I) and second (1000-1700 nm for ICG-NIRF-II) NIR windows using human extracted teeth; our study is compared with the traditional prevalent X-ray imaging and NIR II illumination (NIRi-II, 1310 nm) without ICG enhancement. The results show that ICG fluorescence has much better imaging contrast in both windows compared with NIRi-II (by quantitatively comparing NIR intensity of the critical neighboring structures, such as enamel and dentin). Cracked teeth, notoriously hard to diagnose by dental X-ray and computed tomography, were clearly profiled in NIRF dental imaging. An insidious occlusal caries, missing in X-ray imaging, became a bright dot that was readily observed in ICG-NIRF-I images. For dental decay, NIRF imaging with ICG enhancement could clearly delineate the decay boundary. NIRF in both windows distinguished interproximal and occlusal superficial caries. Overall, ICG-assisted NIRF dental imaging has unique advantages in identifying cracked teeth and insidious caries. The two NIR imaging windows used in our study might one day serve as noninvasive and nonionizing-radiation methods for the diagnosis of critical dental diseases in situ.

Biting pain reproduced by the Tooth Slooth: an aid for early diagnosis of cracked tooth.

OBJECTIVE: The purpose of this study was to find a reliable method to reproduce biting pain to facilitate an early diagnosis of cracked tooth and to verify the feasibility of the Tooth Slooth in diagnosing a cracked tooth. METHOD AND MATERIALS: In this study, 46 intact teeth diagnosed as cracked teeth were selected. Patients were asked to bite wet cotton rolls and the Tooth Slooth, and clinical findings were recorded. The difference in the relevance ratio between these two bite test methods was determined. RESULTS: The relevance ratio of biting pain by the Tooth Slooth and wet cotton rolls was 91.3% and 32.6%, respectively. There was a statistically significant difference between these two bite tests (P < .001). CONCLUSIONS: Within the limitations of this study, the relevance ratio of biting pain by the Tooth Slooth was significantly higher than that of the wet cotton rolls. The Tooth Slooth was a reliable method to reproduce biting pain and was useful for early diagnosis of cracked teeth.

Analysis of the characteristics of cracked teeth and evaluation of pulp status according to periodontal probing depth.

BACKGROUND: The purpose of this study was to analyze the characteristics of cracked teeth and to evaluate pulp status according to periodontal probing depth (PPD). METHODS: A total of 182 cracked teeth were included. The location and type of the cracked teeth, age and gender of the patients, restoration type, pulp status, PPD, and radiographic findings were analyzed. RESULTS: Mandibular second molars (25.3%) were the most frequently involved teeth, followed by mandibular first molars (22.5%), maxillary first molars (22.0%), and maxillary second molars (17.6%). The patient age was most frequently 50-59 years. Cracks occurred mainly in nonbonded restorations, such as gold (26.9%), and were usually found in intact teeth (37.9%). A total of 103 teeth (56.6%) had an initial PPD of less than 3 mm, while 40 (22.0%) had a PPD of 4-6 mm, and 39 (21.4%) had PPD of 7 mm or more. A total of 33 cracked teeth (18.1%) were diagnosed with pulp necrosis, 40 (22.0%) with irreversible pulpitis, and 97 (53.3%) with reversible pulpitis. The incidence of pulp necrosis was 31.8% among cracked teeth with a PPD of 4-6 mm, and 28.6% among those with a PPD of 7 mm or more. CONCLUSIONS: Cracks occurred mainly in molar teeth, and were commonly found in intact teeth with no restoration. Patients with cracked teeth were most frequently aged 50-59 years. Cracked teeth showing a PPD of more than 4 mm were more likely to show pulp necrosis.

Predicting extension of cracks to the root from the dimensions in the crown: A preliminary in vitro study.

BACKGROUND: In this study, the authors investigated whether extension of a tooth crack into the root can be predicted by the appearance of the crack in the crown in vitro. METHODS: The authors obtained 22 cracked teeth from 22 patients who underwent extraction, and they scanned the teeth using microcomputed tomography. The length and width of the crack on the occlusal surface (LOS and WOS, respectively) and the length of the crack on the proximal surface (LCPS) were measured on 3-dimensional reconstruction images. The pulp chamber roof was penetrated and removed. A crack line visible under the microscope only on the access cavity wall rather than extending to the bottom of the pulp chamber was termed a "nonroot crack." A crack seen at the bottom of the pulp chamber or root wall was termed a "root crack." The authors analyzed the data using Pearson correlation coefficients and receiver operating characteristic curves. RESULTS: There was a significant correlation between the LOS and LCPS (correlation coefficient, 0.782; P < .001) and between the WOS and LCPS (correlation coefficient, 0.651; P < .05). The LCPS increased by 1.195 millimeters for every 1-mm increase in the LOS. The area under the receiver operating characteristic curve was 0.839 (95% confidence interval, 0.659 to 1.000) for LOS and 0.760 (95% confidence interval, 0.557 to 0.964) for WOS. CONCLUSIONS: The extent of a crown crack may indicate how far the crack extends to the root. Both the LOS and WOS may be valuable for assessing whether a crack involves the root, although the LOS seems to be more useful. PRACTICAL IMPLICATIONS: The dimensions of a crack in a crown provide a helpful approach for predicting the depth of the crack and its likely prognosis.

The management of cracked tooth syndrome in dental practice.

Cracked tooth syndrome is a commonly encountered condition in dental practice which frequently causes diagnostic and management challenges. This paper provides an overview of the diagnosis of this condition and goes on to discuss current short and long-term management strategies applicable to dental practitioners. This paper also covers the diagnosis and management of this common condition and aims to inform clinicians of the current thinking, as well as to provide an overview of the techniques commonly used in managing cracked tooth syndrome.

Cracked tooth syndrome mimicking trigeminal autonomic cephalalgia: A report of four cases.

BACKGROUND: This report describes four cases of cracked tooth syndrome secondary to traumatic occlusion that mimicked trigeminal autonomic cephalalgias. All patients were referred by general practitioners to the Orofacial Pain Clinic at Nihon University Dental School for assessment of atypical facial pain. CLINICAL PRESENTATION: Case 1: A 51-year-old woman presented with severe pain in the maxillary and mandibular left molars. Case 2: A 47-year-old woman presented with sharp, shooting pain in the maxillary left molars, which radiated to the temple and periorbital region. Case 3: A 49-year-old man presented with sharp, shooting, and stabbing pain in the maxillary left molars. Case 4: A 38-year-old man presented with intense facial pain in the left supraorbital and infraorbital areas, which radiated to the temporoparietal and maxillary regions. All cases mimicked trigeminal autonomic cephalalgias, a group of primary headache disorders characterized by unilateral facial pain and ipsilateral cranial autonomic symptoms. Trigeminal autonomic cephalalgias include cluster headache, paroxysmal hemicrania, hemicrania continua, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing/short-lasting neuralgiform headache attacks with cranial autonomic features. Pulpal necrosis, when caused by cracked tooth syndrome, can manifest with pain frequencies and durations that are unusual for pulpitis, as was seen in these cases. CONCLUSION: Although challenging, differentiation of cracked tooth syndrome from trigeminal autonomic cephalalgias is a necessary skill for dentists.

Three-Dimensional Analysis of Enamel Crack Behavior Using Optical Coherence Tomography.

The aim of this study was to nondestructively analyze enamel crack behavior on different areas of teeth using 3D swept source-optical coherence tomography (SS-OCT). Ten freshly extracted human teeth of each type on each arch ( n = 80 teeth) were inspected for enamel crack patterns on functional, contact and nonfunctional, or noncontact areas using 3D SS-OCT. The predominant crack pattern for each location on each specimen was noted and analyzed. The OCT observations were validated by direct observations of sectioned specimens under confocal laser scanning microscopy (CLSM). Cracks appeared as bright lines with SS-OCT, with 3 crack patterns identified: Type I - superficial horizontal cracks; Type II - vertically (occluso-gingival) oriented cracks; and Type III - hybrid or complicated cracks, a combination of a Type I and Type III cracks, which may or may not be confluent with each other. Type II cracks were predominant on noncontacting surfaces of incisors and canines and nonfunctional cusps of posterior teeth. Type I and III cracks were predominant on the contacting surfaces of incisors, cusps of canines, and functional cusps of posterior teeth. Cracks originating from the dental-enamel junction and enamel tufts, crack deflections, and the initiation of new cracks within the enamel (internal cracks) were observed as bright areas. CLSM observations corroborated the SS-OCT findings. We found that crack pattern, tooth type, and the location of the crack on the tooth exhibited a strong correlation. We show that the use of 3D SS-OCT permits for the nondestructive 3D imaging and analysis of enamel crack behavior in whole human teeth in vitro. 3D SS-OCT possesses potential for use in clinical studies for the analysis of enamel crack behavior.

Cracked Teeth: Distribution, Characteristics, and Survival after Root Canal Treatment.

INTRODUCTION: The aims of this study were to analyze the distribution and characteristic features of cracked teeth and to evaluate the outcome of root canal treatments (RCTs) for cracked teeth. The prognostic factors for tooth survival were investigated. METHODS: Over the 5-year study period, 175 teeth were identified as having cracks. Data were collected regarding the patients' age, sex, tooth type, location and direction of cracks, probing depth, pulp vitality, type of restoration, cavity classification, opposing teeth, and previous endodontic treatment history. Cracked teeth were managed via various treatment methods, and the 2-year survival rate after RCT was analyzed using the Kaplan-Meier method in which significance was identified using the log-rank test. Possible prognostic factors were investigated using Cox multivariate proportional hazards modeling. RESULTS: One hundred seventy-five teeth were diagnosed with cracks. Most of the patients were aged 50-60 years (32.0%) or over 60 (32.6%). The lower second molar was the most frequently (25.1%) affected tooth. Intact teeth (34.3%) or teeth with class I cavity restorations (32.0%) exhibited a higher incidence of cracks. The 2-year survival rate of 88 cracked teeth after RCT was 90.0%. A probing depth of more than 6 mm was a significant prognostic factor for the survival of cracked teeth restored via RCT. The survival rate of root-filled cracked teeth with a probing depth of more than 6 mm was 74.1%, which is significantly lower than that of teeth with probing depths of less than 6 mm (96.8%) (P = .003). CONCLUSIONS: Cracks were commonly found in lower second molars and intact teeth. RCT was a reliable treatment for cracked teeth with a 2-year survival rate of 90.0%. Deep probing depths were found to be a significant clinical factor for the survival of cracked teeth treated with RCT.