Abstract
Introduction
The Dental Apical Inflammation Score (DAIS) is a semi-quantitative histopathological score used to categorise apical inflammatory lesions. This score has shown clinical potential for assessment of wound-healing and infection risk in post-apical lesions.
Objective
This retrospective study aimed to investigate whether periapical lesion volume measurements obtained using manual segmentation on cone-beam computed tomography (CBCT) scans were related to the DAIS categorisation. In addition, the correlations of periapical lesion volume with treatment, anatomical sites, and histological diagnosis criteria were explored.
Material and methods
CBCT scans and histopathological findings of specimens from a cohort of 153 patients were used in this study. Volumetric measurement of the apical lesions was performed using MeVisLab© software. Fisher’s exact test and Kruskal–Wallis H-test were performed to examine the relationship between lesion volume and different factors.
Results
Lesions with a DAIS of 4 showed a significantly larger mean volume than those with a DAIS of 2 (p-value of 0.0377). Lesion volumes also showed a significant difference (p-value of 0.0157) in relation to the histological diagnosis types, with diagnosis based on the presence of radicular cysts being associated with a larger mean lesion volume than that based on the proportion of radicular cysts.
Discussion/conclusions
The volume of the preoperative periapical lesion correlates with both the DAIS category and histological diagnosis and can be used to assess inflammatory infiltrations, facilitating clinical decision-making and treatment-plan optimisation.
Abbreviations
AI
Artificial intelligence
CBCT
Cone-beam computed tomography
DAIS
Dental Apical Inflammation Score
1
Introduction
The Dental Apical Inflammation Score (DAIS) is a semi-quantitative, staged histopathological score that is obtained using a dual-assessment mode and can classify apical inflammatory infiltrations as either acute or chronic, detect bone tissue, identify and characterise foreign material deposits, and detect cyst epithelium [ ]. The DAIS also assesses the bone tissue and characteristics of osteitis using the Histopathological Osteomyelitis Evaluation Score and categorises the findings into four combinations of tissue with inflammation infiltration on the basis of infiltrate quality and quantity: DAIS 1 (acute inflammation = low, chronic inflammation = low), DAIS 2 (acute inflammation = low, chronic inflammation = high), DAIS 3 (acute inflammation = high, chronic inflammation = low), and DAIS 4 (acute inflammation = high, chronic inflammation = high). This score can help determine wound-healing and the risk of further infections after apical lesions.
Periapical lesions are caused by inflammation of the apical periodontium as a result of infection or necrosis of the root canal system [ ]. Endodontic diseases are estimated to affect between 7 % and 86 % of the population [ ] and are the most common cause of pain of odontogenic origin [ , ]. Periapical lesions can be caused by vital or endodontically treated teeth and are mostly categorised as dental granulomas, periradicular cysts, or abscesses [ ]. Condensing osteitis is another entity caused by chronically inflamed pulp tissue and subsequent chronic apical periodontitis and shows a distinct radiographic appearance [ , ]. The biological and therapeutic aims of endodontic treatment are to prevent apical lesions or create optimal conditions for healing, based on the removal of infection and elimination of bacteria from the root canal system and prevention of reinfection [ ]. Most periapical lesions heal after careful non-surgical endodontic treatment [ ]. After a period of time, apical lesions appear as a radiolucent field in the periapical bone in comparison with the surrounding healthy tissue structures [ , ].
Currently, cone-beam computed tomography (CBCT) imaging is the standard method for obtaining more precise insights into the shape and volume of a periapical granuloma, abscess, or cyst. However, radiological differential diagnosis of different entities is still difficult. This raises the question of whether volume size can provide information regarding the histological diagnosis of apical lesions.
Periapical lesions contain various populations of acutely and chronically inflammatory cells [ , ]. Histologically, these lesions are characterised by fibrous connective and granulation tissue, proliferating epithelium, and various inflammatory cell types [ , ]. Regardless of the differences in the causal pathogeneses, all apical lesions show inflammatory infiltration with local tissue destruction. Although histopathological assessment of apical granulomas and radicular cysts is a widely used routine diagnostic procedure, standardised diagnostic assessment procedures in the form of a score to assess these inflammatory infiltrations are currently unavailable. Previous studies have investigated the volume of periapical lesions using CBCT for various research purposes. One study [ ] investigated the sphericity of periapical lesions and its relationship with the CBCT periapical volume index, while another studied the correlation between the periapical index and lesion volume in CBCT imaging [ ]. The influence of the size and volume of periapical lesions on the outcome of endodontic microsurgery has also been explored using CBCT scans [ ]. In another study [ ], CBCT-based volumetric measurement was performed to determine the predictive factors influencing healing and to assess the outcome of non-surgical root canal treatment performed for the management of large cyst-like periapical lesions. Furthermore, CBCT has been used in intraoral periapical radiography to detect simulated external inflammatory root resorption [ ] and periapical bone loss [ ] and to calculate preoperative cystic jaw lesion volume [ ].
However, to the best of our knowledge, the relationship between the periapical lesion volume determined using CBCT scans and the DAIS has not yet been investigated. Thus, this retrospective study primarily aimed to clarify whether the periapical lesion volume measured from manually drawn segmentations in CBCT scans was correlated with the corresponding DAIS categorisations. Additionally, we investigated whether the periapical lesion volume was correlated with treatment outcomes (endodontically treated or untreated), anatomical sites (upper and lower jaws), and histological diagnosis types (proportion of radicular cysts and presence of radicular cysts).
2
Material and Methods
2.1
Patient data collection
This study evaluated a cohort of 153 patients (74 female and 79 male patients; median age, 56 years; range, 9–89 years) who were recruited between January 2021 and November 2023 at the Center for Maxillofacial Surgery at Danube Private University (Krems an der Donau, Austria). The patients underwent surgical removal of a cyst or granuloma, and the resected tissue samples underwent routine histopathological assessment followed by DAIS categorisation, as described in the next section. Before each intervention, preoperative CBCT scans of the complete maxilla and mandible were obtained using Orthophos SL 3D (Sirona Dental Systems, Wals, Austria) in high-definition mode at 57–273 μSv and a field of view of 11 × 10 cm at Danube Private University. The scans were anonymised, exported as DICOM files, and subsequently imported into the created network from MeVisLab© (MeVis Research, Bremen, Germany) software for retrospective examination. The Central Ethical Review Board of the Federal State of Lower Austria approved the study protocol (approval number GS4-EK-4/451–2021). Informed consent was not required because patient-specific information was anonymised.
2.2
Histopathological processing and analysis
Histopathological processing of tissue samples involved macroscopic gross examination, tissue sampling, decalcification, paraffin processing, histopathological staining, and microscopic diagnosis with classification by a pathologist. Soft and osseous tissues were fixed in 4 % buffered formalin for at least 24 h and embedded in cassettes up to 30 × 15 × 5 mm. The adhering soft tissue was removed for tooth-adhering cysts. The tooth tissue was described, but not further processed. Macroscopically identifiable bone was separated from the soft tissue and decalcified with Osteomoll® (4 % formaldehyde and 10 % hydrogen chloride) at room temperature for at least 6 h. Decalcified tissue is cartilaginous or rubbery and does not show strong resistance; therefore, the endpoint was determined by periodically checking the softness of the bone. The soft tissue and the decalcified bone were processed (drained and degreased) overnight in automated systems (Sakura Finetek VIP6AI®, Leica Biosystems ASP300S®, Sanova VIP5®, or Histocom ExcelsiorAS®) and placed in liquid paraffin the next day. After cooling and hardening of the paraffin, tissue sections with a thickness of 2–3 μm were obtained and placed on microscopy slides. The slides were stained with haematoxylin and eosin by using automated systems (Sakura Finetek TissueTek Prisma+®) and automated covering. The use of closed systems with barcode-tracking ensured high-quality, consistent, and reproducible results. Examinations with special stains or immunohistochemical assessments were requested by the pathologist, if necessary, for diagnosis of bacterial infections after evaluation of the haematoxylin and eosin-stained slides, especially in cases showing bacterial colonisation. Material deposits in the tissue were observable in the polarisation. After the final histological diagnosis, the apical lesions were scored as DAIS 1 (acute inflammation = low; chronic inflammation = low), DAIS 2 (acute inflammation = low; chronic inflammation = high), DAIS 3 (acute inflammation = high; chronic inflammation = low), or DAIS 4 (acute inflammation = high; chronic inflammation = high).
2.3
Volumetric measurements
Volumetric measurements of the apical lesions were performed using MeVisLab, a powerful development platform for medical image computing research. In dentistry, this software has been previously used for applications such as three-dimensional reconstruction and assessment of tooth and root canal morphology [ , ], endodontic access cavity preparation [ ], different types of root canal instrumentation techniques [ ], and the development of a tool for bone density assessment [ ]. In this study, manual segmentation of apical lesions was performed on a specific viewing monitor in a darkened room by two experienced dentists with clinical knowledge. To verify the segmentation results for the proposed mesh, segmentation was performed using a solid body in the form of an implant imaged using CBCT and the resultant volume was compared with the manufacturer’s specifications. No deviations were observed, confirming the accuracy of the volume measurements.
The measured volumetric data were divided into groups corresponding to DAIS I, II, III, and IV, endodontically treated/non-treated teeth, localisation in the upper/lower jaw, and different histological diagnosis types (proportion of radicular cysts and presence of radicular cysts, follicular cysts, and periapical granulomas).
2.4
Experimental design
The focus of this study was to investigate the potential relationship between periapical lesion volume on CBCT scans and the corresponding DAIS scores. Owing to the unbalanced distribution of patient data among the different DAIS classes, we applied two different categorisation strategies to achieve a sufficient amount of data and their distribution among the different groups, which are prerequisites for statistical analysis. In the first strategy, we combined the cases with DAIS 1 and 2 into group 1 and those with DAIS 3 and 4 into group 2. In the second strategy, we considered the cases with DAIS 2 as group 1 and those with DAIS 4 as group 2 which was related to low acute inflammation and high acute inflammation, respectively. In both strategies, the periapical lesion volume was compared between groups 1 and 2. We also investigated whether the periapical lesion volume was correlated with different treatment outcomes (endodontically treated or not), anatomical sites (upper and lower jaws), and histological diagnosis types (proportion of radicular cysts and presence of radicular cysts). An illustration of this study’s research questions is presented in Fig. 1 .
