Does mandibular third molar have an impact on dental mandibular anterior crowding? A literature review

Factors influencing the efficacy of invisalign in molar distalization and tooth movement

Introduction: The work aims to establish and analyze the factors influencing the efficacy of Invisalign in molar distalization and tooth movement. Objectives of the study: 1) identify factors contributing to molar distalization and tooth movement; 2) analyze the effectiveness of Invisalign technology in molar distalization and tooth movement. Methods: The study was conducted in 2020-2022 in Baoding (PRC) based on Baoding's first central hospital. Forty patients (mean age 28.5 ± 1.5 years, 18-35 years; 20 women and 20 men) participated in the study. Results: All patients had mild to moderate degrees of tooth crowding, with an angle class II malocclusion, as well as maxillary third molars. Before and after the therapy, the condition of the alveolar bone, soft tissues, and facial height were measured. Fixation of the anterior teeth was performed. Calculations of the distal molar movement were performed. For orthodontic procedures, the second M of the upper jaw were moved, and then the first molars were moved. Discussion: Distalization of the upper molars was found to be an effective movement, with an efficiency of about 83% when vertical rectangular attachments were used. The first molar was moved distally by 2.85 mm without significant tilt or movement in the vertical plane.

External Root Resorption of Second Molars Due to Impacted Mandibular Third Molars during Orthodontic Retention

Whether there is a relationship between impaction of the third molars and the onset of crowding remains to be determined, and extraction of third molars after orthodontic treatment is left to the judgement of the practitioner. This report describes a case where a third molar caused external root resorption (ERR) of the mandibular second molar after orthodontic treatment. As ERR of the mandibular second molar was detected after non-extraction orthodontic treatment, the affected tooth was extracted and substituted with the third molar. External root resorption of the second molar occurred despite being determined as low risk given the state of the impacted third molar as observed on a panoramic radiograph obtained at the end of active treatment. The present results indicate that in cases where the mandibular third molar is present, the corpus length is short, and non-extraction treatment has been performed, it is necessary to obtain X-ray images on a regular basis or preventively extract the third molar to avoid ERR of the second molars.

Clinical Indications to Germectomy in Pediatric Dentistry: A Systematic Review

Germectomy is a procedure often required in patients at developmental age. It is defined as the surgical removal of the third molar at a very specific stage of development. The aim of this study was to systematically analyze the literature in terms of clinical indications for germectomy in patients at developmental age. Literature searches were performed using PubMed, Google Scholar, Cochrane Library and Scopus from 1952 to 30 June 2021. The study protocol was registered after the screening stage (PROSPERO CRD42021262949). The search strategy identified 3829 articles: 167 from PubMed, 2860 from Google Scholar, 799 from Cochrane Library and 3 from Scopus. Finally, eight full-text papers were included into the qualitative analysis. Based on the included studies, clinical indications for germectomy were mainly related to orthodontic causes, infectious and cariogenic causes and prophylaxis. Based on these results, it is not possible to present evidence-based clinical indications for germectomy in patients at developmental age. Clinical trials on this subject focused specifically on patients at developmental age are awaited.

Presence and Maturation Dynamics of Mandibular Third Molars and Their Influence on Late Mandibular Incisor Crowding: A Longitudinal Study

The objective of this study was to investigate the relationship between the absence, presence and dynamics of mandibular third molar development and the occurrence and amount of late mandibular incisor crowding. Dental plaster casts and panoramic radiographs of 72 orthodontically untreated subjects from the Nittedal growth study, Norway were analyzed. The subjects were recalled for a checkup at 12, 15, 18 and 21 years of age. Mandibular incisor crowding was assessed using Little's irregularity index and dental maturation of the third molars by the Cameriere's index. The majority of the subjects (64%) had ≥1 mm increase in irregularity; 22% experienced an increase of 0.1-0.9 mm and 14% had unchanged or decreased irregularity. Incisor irregularity increased with age, regardless of absence or presence of third molars. The amount of change in incisor irregularity from 12 to 21 years did not differ significantly between subjects with hypodontia of third molars, extraction and those with third molars present. No differences were observed between erupted, unerupted or impacted third molars. No correlation was found between the amount of change in irregularity and maturation of the third molars. In conclusion, occurrence and amount of mandibular late incisor crowding is not significantly influenced by the presence of mandibular third molars or their development dynamics.

Influence of orthodontic treatment with premolar extraction on the spatial position of maxillary third molars in adult patients: a retrospective cohort cone-bean computed tomography study

Background

Based on low-dose radiation Cone-bean computed tomography (CBCT) images, This study aims to establish a space coordinate system, which offers more precise and comparable evaluation on changes of maxillary third molars influenced by orthodontic treatment with premolar extraction in adults. The system suggests promising application prospect in future studies related to CBCT superimposition and evaluation for its feasibility and efficiency.

Methods

Forty-nine maxillary third molars from 27 patients (mean age, 20.78 years) were included. CBCT images were obtained before and after orthodontic treatment with premolars extracted (mean treatment duration, 31.47 months). The changes in the position, angulation, and rotation of the third molars were evaluated with a space coordinate system using four landmarks: anterior nasal spine (ANS), posterior nasal spine (PNS), left and right orbitales.

Results

After orthodontic treatment, the third molars moved forward (adjusted mean, 1.44 mm) (p < 0.001) and downward (adjusted mean, 2.87 mm) (p < 0.001) accompanied by outward rotation of the crowns (adjusted mean, 5.38°) (p = 0.001), while changes in angulation were insignificant.

Conclusions

This was the first study to systematically investigate the spatial position change of maxillary third molars in adult patients who received orthodontic treatment with premolar extraction. During the process, maxillary third molars moved downward and forward accompanied by outward rotation of the crowns. Orthodontists should take tooth movement potential into consideration when making extraction plans.

Evaluation of the influence of mandibular third molars on mandibular anterior crowding relapse

Objective: To evaluate the influence of mandibular third molars on relapse of mandibular anterior crowding in orthodontically treated patients.Material and Methods: Sample included orthodontic records of 108 patients: Group 1: 72 patients (39 female; 33 male) with third molars present in the postretention evaluation stage. Group 2: 36 patients (18 female; 18 male) who did not present the third molars in the postretention evaluation stage. Panoramic radiographs and dental models were evaluated at three different stages: pre-treatment; posttreatment and postretention. Panoramic radiographs showed the presence or absence of third molars in the 3 evaluated stages and on the dental models, overbite and mandibular anterior crowding was measured by the Little Irregularity Index. For intergroup comparisons, t-tests and a multifactorial regression analysis were used.Results: There was no statistically significant difference in the relapse of mandibular anterior crowding among the groups with and without mandibular third molars at the postretention stage.Conclusion: The presence or absence of mandibular third molars did not influence the relapse of mandibular anterior crowding in orthodontically treated patients.