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 in vitro study was to determine the effects of dental fluorosis on the tensile bond strength of metal brackets bonded to human teeth and to evaluate the changes in the tooth enamel surface after debonding. The study sample consisted of 68 recently extracted human upper premolars, which were divided into 2 groups: the fluorosis group (34 fluorosed teeth) and the control group (34 healthy teeth). Identical premolar metal brackets were bonded on the buccal surfaces of the teeth. Both groups were submitted to a tension test using a universal testing machine. The number and length of the enamel microcracks in the buccal surface of each tooth were determined before bracket bonding and after debonding using a stereomicroscope. The percentage adhesive remnant index (PARI) was calculated after debonding. The results showed that the tensile bond strength (TBS) of brackets bonded to fluorosed teeth was 21.08% lower than that of brackets bonded to healthy teeth (p < 0.0001). The length of the enamel microcracks on fluorosed teeth increased by 47.4% after debonding, whereas the control group showed an increase of only 12.6%. The PARI showed lower values for fluorosed teeth in comparison to the control group (p = 0.047). In conclusion, dental fluorosis has a negative impact on tensile bond strength and the length of microcracks formed after bracket debonding.

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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.

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.