Influence of third molar space on angulation and dental arch crowding

Effect of mandibular third molars on crowding of mandibular teeth in patients with or without previous orthodontic treatment: a systematic review and meta-analysis

OBJECTIVES

To assess the scientific evidence related to the role of the mandibular third molars on the late crowding of the lower anterior teeth in patients with or without previous orthodontic treatment. The secondary outcomes included changes in mandibular arch width and arch length.

MATERIALS AND METHODS

The databases PubMed, Scopus, ProQuest, and Google Scholar were searched from inception until April 2022. The included papers were studies evaluating the role of mandibular third molars on crowding of mandibular anterior teeth in patients of any age and gender, with mandibular third molars impacted or semi-impacted or erupted. Predetermined and prepiloted data collection forms were used to record the necessary information.

RESULTS

Thirteen observational studies were included in the present systematic review. Most of them were assigned an overall risk of bias of moderate risk while the rest of them were at high risk. Four studies found an association between the presence of mandibular third molar and mandibular incisor crowding. Finally, seven studies were included in the quantitative analysis. Three different meta-analyses were conducted: for patients (a) with or (b) without previous orthodontic treatment and (c) in combination for patients with and without previous orthodontic treatment. According to the pooled results of all three meta-analyses, random effects model yielded a significant benefit for those without third molars compared to those with third molars regarding crowding, mean Little's irregularity index and mean arch length.

CONCLUSIONS

Lower third molars may contribute to mandibular crowding and lower arch constriction. Further prospective research of high quality is needed to clarify the impact of third molars on anterior mandibular crowding.

Three-dimensional relationship between the degree of bilateral impacted mandibular third molars angulation and the mandibular dental arch parameters: a cross-sectional comparative study

OBJECTIVE

The purpose of this study was to three-dimensionally evaluate the relationship between the degree of bilateral impacted mandibular third molar (IM3M) angulation and the mandibular dental arch parameters in normal skeletal and dental malocclusion patients.

MATERIALS AND METHODS

In this retrospective cross-sectional comparative study, 120 adult subjects' cone-beam computed tomography (CBCT) images were three-dimensionally analyzed. The sample included 120 adults aged 20-30 years, with a gender distribution of 51 male and 69 female participants. The sample was divided into 100 adults with bilateral IM3M (study group) and 20 adults with normal bilateral erupted M3M (control group). The study group was sub-divided into three groups according to the degree of IM3M buccolingual angulation (BL°): group A, < 12° on the center of the ridge (N = 30), group B, 12-24° off-center of the ridge (N = 40), group C, > 24° off-center of the ridge (N = 30). The study group was also sub-divided into two groups according to IM3M mesiodistal angulation (MD°): group 1 from 10 to 45° (N = 36), group 2 > 45° (N = 64). Comparison within and between groups was performed using one-way ANOVA followed by Tukey's post hoc test. The correlation between IM3M, BL, and MD angulation and the mandibular arch parameter was calculated using Pearson's correlation coefficient.

RESULTS

Statistically significant differences (P < 0.001) were found between the IM3M BL° and anterior teeth inclination, arch length (AL), and inter-second molar width (inter 2nd MW) as well as between the IM3M MD° with anterior crowding and the arch length (P < 0.001). A significant positive correlation was found between IM3M BL° and anterior teeth inclination and between IM3M MD° and anterior teeth crowding and inter 2nd MW. A significant negative correlation was observed between IM3M BL° and inter 1st MW and 2nd MW.

CONCLUSION

The degree of buccolingual and mesiodistal angulation of the impacted mandibular third molars was related with mandibular dentoalveolar changes. Increased buccolingual angulation is generally associated with increased anterior teeth inclination and decreased 1st and 2nd inter-molar width. The increase in mesiodistal angulations was generally related with increased anterior teeth crowding and 2nd inter-molar width.

CLINICAL RELEVANCE

Assessment of the relationship between the impacted mandibular third molars and the degree of arch discrepancy, and the position of mandibular incisors in the three planes of space might help in the decision-making process for the extraction of the impacted third molars in adult patients.

The Effect of Third Molars on the Mandibular Anterior Crowding Relapse-A Systematic Review

The present systematic review updates the evidence on wisdom teeth contributing to lower incisor crowding following orthodontic treatment. Relevant literature was searched on online databases, namely Pubmed, Scopus, and Web of Science, up to December 2022. Eligibility criteria were formulated using the PICOS approach and PRISMA guidelines. Eligible research included original clinical studies involving patients previously being treated orthodontically with permanent dentition at the end of treatment, regardless of sex or age. The initial search yielded 605 citations. After considering eligibility criteria and removing duplicates, only 10 articles met the criteria for inclusion. The risk of bias of eligible studies was evaluated using the Cochrane Handbook for Systematic Reviews and Interventions tool. The majority were highly biased, mainly regarding allocation concealment, group similarity, and assessment blinding. The vast majority did not report statistically significant associations between the presence of third molars and crowding relapse. However, a minor effect has been suggested. Seemingly, there is no clear connection between mandibular third molars and incisor crowding after orthodontic treatment. The present review did not find adequate evidence to advocate preventative removal of the third molars for reasons of occlusal stability.

Kinesio Taping as an Adjunct Therapy in Postoperative Care after Extraction of Impacted Third Lower Molars—A Randomized Pilot Study

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly administered according to protocol for the management of complications such as pain, swelling, and trismus following the removal of the third impacted lower molar; however, treatment with NSAIDs may result in multiple adverse effects. The aim of this study was to compare the effectiveness of kinesio taping (KT) and the use of NSAIDs in the treatment of postoperative complications after extraction of an impacted third lower molar. Material and methods: The study comprised a group of 30 patients, randomly divided into the test group (with KT, n = 15) or the control group (without KT, n = 15). The surgery was performed according to standard procedures. In the test group, KT was applied immediately after surgery. Pain, swelling, and trismus were assessed. The VAS scale was used to assess pain. Swelling was measured based on six reference points on the face using a tailor’s meter, and a caliper was used to measure the distance between the upper and lower medial incisors of the upper and lower teeth to determine the extent of trismus. Measurements were performed three times: on the day of the surgery, on the second day following the surgery, and on the 7th day after the surgery. Results: Pain intensity (day of procedures), maximum mouth opening (on the seventh day after the surgery), and the use of NSAIDs (day of surgery) were significantly lower (p < 0.05) in the test group than in the control group. Conclusions: Kinesio taping in addition to NSAIDs was found to be more effective than NSAIDs alone in increasing the degree of jaw opening, decreasing pain intensity, and reducing the non-steroid anti-inflammatory dosage in patients after impacted mandibular wisdom teeth surgery.

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.

The role of impacted third molar angulation on the anterior crowding

Objectives:

The aim of this study was to assess the role of impacted third molar angulation on the severity of anterior crowding.

Materials and Methods:

Panoramic radiographs and three-dimensional (3D) digital models of 45 patients satisfying the following inclusion criteria were selected for this study. To calculate the irregularity index of Little, the sum of the contact point displacements from the anatomical contact point to the contact point among the lower canine teeth was measured on 3D digital models. Little’s irregularity index was used to classify patients as having mild, moderate, or severe crowding. For intragroup variance, comparisons T test was used. The Spearman single rank correlation coefficients were used to analyze any correlation among degree of crowding and (a) third molar inclination to base of mandible, (b) third molar inclination to occlusal plane, and (c) third molar inclination to second molar inclination respectively.

Results:

There were no statistical differences found in all tested parameters (i.e., third molar inclination to mandibular plane, inclination of the third molars to occlusal plane, and inclination of the third molars to second molars) among three groups (P > 0.005).

Conclusion:

It can be deduced that no relationship obtains among the third molar inclination to base of mandible, third molar inclination to occlusal plane, third molar inclination to second molar inclination, and the level of anterior crowding.

Incidence of hypercementosis in mandibular third molars determined using cone beam computed tomography

PURPOSE

This study was conducted to investigate the incidence and predictors of hypercementosis in mandibular third molars using cone beam computed tomography.

METHODS

Using a retrospective approach, 1,160 cone beam computed tomography image sets were analyzed. Two oral radiologists independently evaluated the image sets based on four severity grades: 0, no hypercementosis around the root; 1, hypercementosis surrounding less than half of the root surface; 2, hypercementosis surrounding more than half of the root surface; and 3, hypercementosis surrounding the entire root surface. Hypercementosis was identified as a dark or light layer. Statistical analyses of relationships between hypercementosis incidence and possible predictors (e.g. age, sex, impaction, and occlusion) were performed using chi-square test or Fisher's exact test; logistic regression was used for multivariate analysis.

RESULTS

The severity of hypercementosis increased with age, and the incidences were as follows: ≤19 years, 0%; 20-24 years, 14.1%; 25-29 years, 57.7%; 30-39 years, 83.0%; 40-49 years, 92.7%; 50-59 years, 93.4%; and ≥60 years, 96.8%.

CONCLUSION

The observed incidences of hypercementosis were relatively higher than in previous studies, and the incidence was significantly lower for occluded teeth than for non-occluded teeth.

Craniofacial Growth in Adolescence and its Influence on the Mandibular Incisor Crowding

Background

To analyze craniofacial growth during adolescence from the ages of 12 to 21 years and its relation to late mandibular incisor crowding.

Material and Methods

The study included 61 orthodontically untreated subjects (49% males). Lateral cephalograms were used to assess the jaw growth and inclination of the incisors. Little's Irregularity Index and the anterior mandibular dental arch depth of mandibular dentition were measured.

Results

A reduction of the skeletal class angle (ANB) was observed in both genders, although it was significant only in males (η2=0.188; p=0.015). The growth of the mandible was more prominent compared to that of the maxilla, and it was more prominent in males than in females. The skeletal vertical dimension, however, demonstrated a significant reduction in both genders (η2=0.527-0.593, p<0.001). The mandibular incisors tended to retrocline in both genders, while the maxillary ones tended to procline in males, and slightly retrocline in females. A decrease in the mandibular dental arch depth occurred in both genders (η2=0.259; p<0.05). An increase in the irregularity of incisors for 1.8±1.7 mm on average (95% CI 1.3-2.2; η2=0.520; p<0.001) was observed in both genders. A logistic regression revealed that less sagittal growth of maxilla (increase of SNA angle ≤2°) and reduction of convexity in skeletal sagittal interjaw relationship (reduction of ANB ≥1°) were significant predictors of the occurrence of crowding (Δ Little Irregularity Index ≥1mm) yielding odds ratios of 4.9 and 4.8.

Conclusions

The differential growth of the maxilla and mandible is related to the occurrence of late crowding, mostly in smaller amounts in maxillary sagittal growth compared to the mandible.

Comparative analysis of the gonial angle on lateral cephalometric radiographs and panoramic radiographs

We measured the gonial angle (GA) on panoramic radiography (PR) and analyzed the correlation between the GA on PR and lateral cephalometric radiography (LCR). In total, 49 PR films and LCR films from dentate young adults were evaluated. Orthodontists plotted four points (articulare, menton, posterior gonion, and lower gonion) on the PR and carefully traced them. Using a protractor, two radiologists measured the GA on LCR images. A simultaneous experimental study of two dry skulls was performed to compare the GA on LCR and PR. The GA was slightly smaller on the PR of the dry mandible than on the LCR and tended to decrease continuously with magnitude toward the Frankfort horizontal plane. The mean GA was 115.1 ± 5.2° on PR and 122.2 ± 6.4° on the LCR. The values were highly correlated (Pearson product-moment correlation coefficient, 0.801). The GA on PR was nonsignificantly smaller than that measured on LCR. The difference may be due to head position, the inclination angle of the mandibular body, and/or the direction of the incident X-ray beam.

Role of third molars in orthodontics

The role of third molars in the oral cavity has been extensively studied over the years. Literature includes numerous diagnostic and treatment alternatives regarding the third molars. However, an issue that has not been discussed at the same level is their involvement in orthodontic therapy. The aim of this study is to present a review of the contemporary literature regarding the most broadly discussed aspects of the multifactorial role of third molars in orthodontics and which are of general dental interest too.

Third molars and dental crowding: different opinions of orthodontists and oral surgeons among Italian practitioners

BACKGROUND

The role of third molars as a cause of incisor crowding, especially in the lower arch, continues to be controversial. The aim of this work is to compare opinions of Italian oral surgeons and orthodontists on this topic.

METHODS

One hundred ninety-three Italian practitioners of the Society of Orthodontics (SIDO) and the Italian Society of Oral Surgery (SICOI) were asked to fill out an online questionnaire made up of six questions. Practitioners were asked to express their opinion on the relation between upper and lower third molar eruption and anterior crowding.

RESULTS

One hundred sixty-six members of both societies completed the online research survey; response rate (RR) was 86%. There were no statistically significant differences between the two groups (P > 0.005). Both agree not to believe that third molars create a force responsible for anterior crowding in the upper (82.5% orthodontists, 83.8% surgeons) and in the lower arch (52.6% orthodontists, 63.8% surgeons). Both agree also not to consider the upper (89.7% orthodontists, 82.1% surgeons) and lower (58.8% orthodontists, 63.2% surgeons) third molar extraction useful to prevent crowding.

CONCLUSIONS

Italian orthodontists and oral surgeons have the same opinion on the role of the third molar in causing anterior crowding. The majority of both groups of clinicians do not consider their preventive extraction useful in order to prevent anterior crowding.