Micro-morphometric study of the resected root surface after endoscope-supported apicoectomy

Endoscopy combined with subsequent digital image analysis makes it possible to survey quantitative characteristics of clinical findings in dentistry. The aim of this study was to provide a quantitative description of diagnostic parameters of the resected root surface (RRS) during apicoectomy. In a general group, the analogue video recordings of 237 apicoectomies in 191 patients (84 men, 107 women, with an average age of 40.7 years) at the Department of Oral and Maxillofacial Surgery of UMG were digitised and subsequently evaluated. 71 apicoectomies on 47 patients fulfilled the quality criteria of a complete representation of RRS without artefacts immediately after root end resection and were selected for the study cohort (n=71). Evaluation was carried out in3 steps: (1) Descriptive analysis of the interventions according to demographic parameters and location in the dental arch. (2) Assessment of findings at the RRS and correlation with parameters for age, tooth location, presence of root posts and location per root segments. (3) Micromorphometric analysis using Image J, with description of the relative length of craze lines and cracks and relative area of root canals, frosted dentine and sealing gaps. The complete RRS and root canal served as references. The results were correlated with age, location of tooth and presence of root posts. The distribution of interventions for the study cohort related to demographic parameters and to anatomical location, and were tested using the Chi-squared test. For comparisons between proportions of segments per finding, exact two-sided 95% confidence intervals (Clopper–Pearson) were calculated and the null hypotheses were tested with the Chi-squared test. For the micro-morphometric analysis, descriptive tables were presented. In the study cohort there was no gender-specific distribution (p = 0.466) and the interventions were made mainly in the age group between 40 and 64 years (51.1%). Interventions were performed more frequently in the maxilla (p=0.01), posterior areas dominated in the maxilla (p=0.02) and in the mandible (p 0.05). The presence of a root post seemed to have an impact on the occurrence of the frosted dentine (p = 0.06). The observation of craze lines/cracks and frosted dentine was 7.1% and 64.4% of total segments respectively, mainly in the buccal segment (11.3% and 84.5% respectively). The observation of sealing gaps was 9.2% of total segments, mainly distally (11.3%). In the micromorphometric analysis, the relative length of craze lines was 43% and that of cracks was 65% in relation to the extent of dentine along craze lines or cracks respectively. The minimal width of craze line and crack was 1 and 2.5 pixels respectively. The relative area of frosted dentine, root canal and sealing gap in relation to the total area of RRS was 26%, 5.8% and 1.6% respectively. Borderline results arose for the length of cracks and craze lines depending on the age of the patient (p=0.05), the presence of a root post (p = 0.05), but not on the type of tooth location (p>0.05). The frosted dentine area had an influence on the length of craze lines and cracks (p=0.008). The present evaluation intended to provide an improvement for the description of clinical findings at the RRS during periapical surgery by means of endoscopic imaging and subsequent digital image analysis. Morphometric analysis shows, that frosted dentine appears to be a very common phenomenon with a high incidence and variability mostly in the buccal segment. Craze lines and cracks show significantly different extension relative to the dentine thickness at their locations. The minimal thickness of craze line lies at the limits of the image resolution and requires further improvement of the visualisation tools. Quantification of sealing gap defects may be used as an instrument of quality control for further studies.