Association between arch perimeter management and the occurrence of mandibular second molar eruption disturbances

To investigate the association between the management of mandibular arch perimeter during development of the dentition and its effects on second permanent molar (M2) eruption.

Seven electronic databases were searched without restrictions up to June 2020. Assessment was performed using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool for non-randomized clinical trials (non-RCT). Odds ratio (OR) with 95% confidence intervals was calculated from random-effects meta-analyses. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool was used to assess the certainty of the evidence.

Five non-RCTs, with serious to moderate risk of bias, were included. A low certainty of evidence indicated that individuals undergoing mandibular arch perimeter management by controlling the position of the first molar had a high prevalence of M2 eruption difficulties. The odds of eruption disorders was 7.5 times higher (OR: 7.57, [3.72, 15.41], P < .001) in treated individuals. Subgroup analysis revealed that appliances that increased the arch perimeter lead to a greater chance of eruption disorders compared to appliances that only maintained the perimeter. The predictive factors for the M2 eruption difficulty were its previous mesioangulation in relation to the first molar (>24°) and the treatment time (>2 years).

Mandibular arch perimeter management during development of the dentition leads to an increase in the occurrence of M2 eruption difficulties. The identification of possible risk factors as well as the choice of the appropriate appliance type and the monitoring of these individuals seems to be essential to avoid undesirable effects with this therapy.