Background and objectives: Impacted third molars (ITM) are the most commonly-impacted teeth. There is a risk for ITM to cause a number of pathological conditions, and external root resorption (ERR) of adjacent teeth is one of the most prevalent. Retaining or prophylactic extraction of ITM is a polemic topic. External root resorption of adjacent teeth is one of possible indications for prophylactic removal of ITM. The aim of this study was to assess the relationship between external root resorption (ERR) on the distal aspect of second molars’ roots and positional parameters of ITM. Methods: Cone beam computed tomography scans of 109 patients (41 males, 68 females; mean age 26.4 ± 7.9 years) with 254 ITM (131 in the maxilla and 123 in the mandible) were retrospectively analyzed. Positional parameters of ITM (mesio-distal position, angulation, impaction depth, and available eruption space) were evaluated. The presence, location, and depth of ERR of adjacent second molars were assessed. Results: Analysis showed a relationship between ITM impaction depth, mesial inclination angle, and the presence of ERR. Mesial inclination angle of more than 13.6° increased the odds of ERR occurrence by 5.439 (95% CI, 2.97–9.98). ITM presence at the level of ½ of roots of the adjacent second molar or more apically increased the odds of ERR occurrence by 2.218 (95% CI, 1.215–4.048). No significant correlation was detected between the occurrence of ERR and patient age, gender, or the available eruption space in the mandible. Depth of ERR did not depend on its location. Conclusions: Incidence of ERR in second molars is significantly associated with mesial inclination and a deep position of ITM.

The objective of this study was to evaluate whether the calcification stages of maxillary canine, mandibular second molar, and mandibular third molar can be used for assessment of growth phase. The study group consisted of 274 subjects. Pre-treatment digital panoramic and lateral cephalometric radiographs of the patients were analysed. The patients’ age was ranging from 7 to 19 years. Right maxillary canine, mandibular second molar and third molar were used as a sample. The teeth mineralization was assessed using modification of Gleiser and Hunt method. The skeletal maturation was assessed by the cervical vertebrae maturation (CVM) method. A significant association was found between CVM stage 2 and maxillary canine (UC) stage 4, mandibular second molar (LM2) stage 4, and mandibular third molar (LM3) stage 1. CVM stage 3 corresponded with UC stage 5, LM2 stage 5, LM3 stage 2. CVM stage 4 matched with UC stage 5, LM2 stage 6 and LM3 stage 3. The highest correlations between CVM and calcification stages were in the group of the maxillary canine ( r = 0.812, P < 0.01) and mandibular second molar ( r = 0.824, P < 0.01). Limitation of our study was that the study sample was not very big and the distribution value in the groups was very high, so it was impossible to check more statistical parameters. The calcification stages of UC, LM2, and LM3 as indicators of skeletal maturity could be clinically used with caution, until this method is verified with a larger sample group.

Background and Objectives: The aim of this systematic review was to summarize currently available data of published articles that have investigated the post-treatment status of impacted maxillary central incisors (ICI) treated by the surgical-orthodontic approach. Materials and Methods: MEDLINE, Scopus, Cochrane Oral Health Group’s Trials Register, and ScienceDirect electronic databases were systematically searched with no publication date restrictions up to January 2021. Data assessing the status of ICI after combined surgical-orthodontic treatment and forced eruption duration were extracted, and the quality of the studies was evaluated. Results: In total, 7074 studies were identified, of which 42 articles were assessed for eligibility through full-text evaluation. Seven included studies (five retrospective studies, one randomized clinical trial, and one prospective clinical trial) met the inclusion criteria, representing 211 patients with unilaterally impacted maxillary incisors. The risk of bias ranged from moderate to high. The results show that the root length of immature ICIs increased significantly but remained shorter than that of homonym teeth at post-treatment. Periodontal parameters of treated ICIs were in a clinically acceptable range. Measurements of the alveolar bone showed a reduction of bone thickness and support. The average forced eruption duration ranged from 8.0 ± 4.5 to 14.41 ± 4.03 months. Conclusions: Based on existing evidence, it is reasonable to conclude that the surgical-orthodontic treatment affected the post-treatment status of ICI; however, the current literature is insufficient to draw concrete conclusions. Further well-conducted multi-center randomized studies with a large sample are needed to confirm this statement.

To assess the genetic and environmental influences on the variability of human third molar (M3) root mineralization stages via a twin study. The study sample consisted of 162 same-sex twins (66 dizygotic and 96 monozygotic, mean age: 17.9 years) with normal growth and development. Panoramic radiographs were evaluated to assess root mineralization stages of the upper and lower third molars, using the method of Demirijian et al. (1973). Zygosity was established using 15 specific DNA markers. Females developed their third molar roots earlier in life than males. Monozygotic twins (MZ) demonstrated higher intra-pair correlations for M3 root development stages than did DZ twins. An ACE model with additive genes, as well as common and specific environmental factors, provided the best explanation of variation in M3 root development. The mineralization of M3 roots showed highly additive genetic determination, varying from 60 to 63%, whereas a common environment contributed from 25 to 27%, and a specific environment only accounted 14% of the total variation, at most. A considerable proportion of the total variability of the third molar root mineralization rate can be attributed to additive genetic effects, while common and specific environmental effects have a smaller, yet significant, impact.

The purpose of this investigation was to determine the impact of heritability on third molar agenesis in twins. The study sample consisted of 284 same sex twins (172 monozygotic and 112 dizygotic), whose mean ages were 19.7 ± 4.3 and 18.9 ± 4.8 years, respectively. The monozygotic group consisted of 36.3% males and 63.7% females, while the dizygotic group consisted of 50.1% males and 49.9% females. The zygosity of the twins was established using 15 specific DNA markers. The prevalence of third molar agenesis in monozygotic twins was 19.6%, which was higher than in the dizygotic twins group (15.50%) (p = 0.004). In both groups, third molar agenesis was more frequent in the maxilla than in the mandible (p = 0.000). Agenesis of the maxillary third molars was mostly affected by additive genetic factors (62–63%), with the common environment and the specific environment accounting for up to 25% and 13%, respectively. In contrast, agenesis of the lower third molars was associated with a higher additive genetic determination (81–83%), with the specific environment accounting for 17% to 19%. The study’s conclusion is that the formation of the third molars follicle is strongly controlled by additive genetic factors.