Mandibular lip bumper treatment and second molar eruption disturbances

Second molar eruption disturbances in borderline extraction orthodontic patients

INTRODUCTION

Nonextraction treatment is associated with a greater prevalence of third molar impactions, whereas data on second molars are lacking. This study investigated whether there is a difference in the prevalence of second molar eruption disturbances when crowding is treated with or without extractions.

METHODS

Patients were grouped by maxillary and mandibular crowding, including mild crowding (<5 mm) without extractions, borderline crowding (5-9 mm) without extractions, and borderline crowding with extractions. The 535 evaluated arches were from 346 patients aged 10-15 years with unerupted second molars at treatment start. The frequency and severity of second molar eruption disturbances were scored in final records using a severity classification based on a modified Archer system, a hybrid Archer Pell-Gregory system, and a partial impaction scale. Pretreatment panoramic radiographs were scored for impaction-risk indicators. Fisher exact test was used.

RESULTS

In the maxilla, 20.0% of nonextraction patients with borderline crowding had second molar eruption disturbances compared to 5.2% of extraction patients with borderline crowding (P = 0.010). In the mandible, 27.6% of nonextraction borderline crowding patients had second molar eruption disturbances compared to 7.1% of extraction patients with borderline crowding (P = 0.006). There was no difference in the frequency of eruption disturbances between mild crowding without extractions and borderline crowding without extractions. The prevalence of impactions was higher in the maxilla when molars were apically positioned and in the mandible when molars were mesially angulated or had insufficient space pretreatment.

CONCLUSIONS

In patients with borderline crowding, extraction treatment reduces the risk of second molar eruption disturbances; however, nonextraction treatment does not increase the risk when compared with patients with mild crowding. When considering extractions for crowding, providers should evaluate second molar impaction-risk indicators on pretreatment radiographs.

Short-term dentoalveolar effects of aesthetic lip bumper appliance: A longitudinal cases-series and pilot study

Background

To investigate the short-term dentoalveolar effects on the mandibular arch of a modified, aesthetic lip bumper (ALBAa). The study sample comprised 23 patients (13 boys and 10 girls, with a mean age of 9.5 ± 1.8 years) in mixed dentition, with no previous orthodontic treatment. For each patient, a scan of the mandibular arch was digitally acquired pre-treatment (T0), and at 3 months (T1), 6 months (T2) and 9 months (T3) post-treatment. Linear intra-arch measurements, Little's irregularity index of the amount of mandibular anterior crowding, and the crown tipping values on all mandibular teeth were measured and compared statistically between time points. ANOVA and subsequent post-hoc tests were performed, considering a p-value of < 0.05 as significant.

Results

Linear intra-arch distances and crown tipping values on the mandibular teeth increased between the following time points: T0vsT1, T1vsT2, T0vsT2 and T0vsT3 (p < 0.05), although in the last three months of observation (T2vsT3) they only reached statistical significance at the lower incisors and lower left premolar concerning crown tipping values. There was a statistically significant decrease in anterior crowding throughout the observational period (p < 0.05), and this effect was equally distributed across the different time points investigated.

Conclusions

ALBAa therapy led to an increase in both linear intra-arch distances and crown tipping values, with a reduction in Little's index. The distribution of the effects reported across the observational period depended on the mechanism of action (mechanical vs. functional).

Torqued and conventional cantilever for uprighting mesially impacted molars: A 3-dimensional finite element analysis

INTRODUCTION

The objective of this study was to evaluate the effects of the torqued cantilever (TC) and conventional tip-back cantilever (CC) made of stainless steel (SS) and titanium-molybdenum alloy (TMA) on the uprighting of mesially impacted mandibular molars using three-dimensional finite element analysis.

METHODS

The 3-dimensional mandibular model included part of the mandible with mesially tipped and impacted mandibular second molar, periodontal ligament (PDL), molar tube, mini-implant, and cantilevers. Four finite element method models (TC-SS, TC-TMA, CC-SS, and CC-TMA) were created to simulate different skeletally anchored uprighting mechanics. CC mechanics involved a known 0.019 × 0.025-in helical cantilever acting on a buccal molar tube. TC mechanics included a 0.019 × 0.025-in cantilever capable of producing mesial root torque by acting on a tube positioned on the molar disto-occlusal surface with the slot in a buccolingual direction. Three-dimensional molar displacement and stress distribution on the molar PDL were recorded.

RESULTS

The SS cantilever produced almost twice as much molar displacement as the TMA. TC mechanics showed more evident mesial displacement of the molar root apexes. CC mechanics had greater molar rotation. TC uprighting moment produced greater molar mesial extrusion and greater intrusion of the distal root apex. The dual deflection system of the TC mechanics induced the lowest stress on the PDL, regardless of the metallic alloy.

CONCLUSIONS

TC delivered a more efficient uprighting moment to the molar with less unwanted tooth movement and stress on the PDL and a more accessible site for bonding the molar tube.

Does arch length preservation in mixed dentition children affect mandibular second permanent molar eruption? A systematic review and meta-analysis

BACKGROUND

Arch length preservation strategies utilize leeway space or E-space in the mixed dentition to resolve mild to moderate mandibular incisor crowding. The purpose of this systematic review of the literature was to analyze the effects of arch length preservation strategies in on mandibular second permanent molar eruption.

METHODS

A search for relevant articles published from inception until May 2020 was performed using PubMed/Medline, Cochrane databases, Clinicaltrials.gov, Google scholar and journal databases. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were adopted for the conduct of the systematic review. Using RevMan 5.3 software, the most pertinent data were extracted and pooled for quantitative analysis with 95% confidence intervals. Heterogeneity was analyzed by using Cochran Q test and I squared statistics.

RESULTS

A total of 5 studies involving 855 mixed dentition patients with arch length preservation therapy were included in the qualitative analysis. Pooled estimate of the data from two studies revealed 3.14 times higher odds of developing mandibular second molar eruption difficulty due to arch length preservation strategies using lingual holding arch (95% CI; OR 1.10-8.92). There was no heterogeneity found in the analysis. The certainty levels were graded as very low.

CONCLUSIONS

This systematic review demonstrates that arch length preservation strategies pose a risk for development of mandibular second molar eruption disturbances, but the evidence was of very low quality. Registration number: CRD42019116643.

Mini-implant Supported Lip Bumper

Patients with a skeletal class II malocclusion are usually associated with a prognathic maxilla with orthognathic mandible or a retrognathic mandible with orthognathic maxilla or a combination of both. Patients with severe prognathic maxilla are usually associated with increased overjet which results in a lower lip trap. The lip trap should be managed the earliest as it will lead to further proclination of the upper anterior teeth and also hinder the normal growth of the mandible. To overcome the limitations of a conventional lip bumper, we arrived at an idea of fixed lip bumper supported using mini-implants.

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

OBJECTIVES

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Surgical uprighting of impacted mandibular second molar: a narrative review

Early diagnosis of impacted mandibular second molar (MM2) is critical since treatment at a later stage can be complicated. It often requires a multidisciplinary approach. Surgical uprighting of impacted MM2 appears to be a safe, effective, and a reliable alternative to conventional orthodontic mechanics with minimal risk of morbidity or pulpo-periodontal problems. Timely diagnosis is critical and factors affecting treatment outcomes must be assessed for a successful outcome. Although surgical uprighting or repositioning is the most commonly prescribed option for MM2 management, there isn't a review of literature that discusses the etiology, assessment, and surgical management of impacted MM2 with an emphasis on surgical uprighting technique and comparing various factors that affect the outcome.

Effects of lip bumper therapy on the mandibular arch dimensions of children and adolescents: A systematic review

INTRODUCTION

The aim of this systematic review was to identify, evaluate, and provide a synthesis of the available literature on the effects of lip bumper (LB) therapy on the mandibular dental arch of children and adolescents.

METHODS

MEDLINE, Scopus, Web of Science, Cochrane Library, and Lilacs were systematically searched without restrictions up to May 2019. Risk-of-bias assessment was performed using Cochrane's tool for randomized controlled trials (RCTs) and the Risk of Bias in Nonrandomized Studies of Interventions tool for non-RCTs. The Grading of Recommendations, Assessment, Development and Evaluation tool was used to assess the quality of the evidence.

RESULTS

After examination of the full texts, 6 studies were included. One RCT presented unclear risk of bias, and 5 non-RCTs presented serious to moderate risk of bias. LB therapy resulted in a buccal inclination of the incisors, distalization of the permanent first molars, and distal inclination of the permanent first molars, which increased perimeter and arch length. An increase in the arch width with greater gain in the interpremolar and/or deciduous molar distance and less gain in intercanine and intermolar distances was also reported. LB therapy increased the risk of second molar impaction with inclination >30° and the risk of ectopic eruption when treatment time was >2 years. The level of the evidence was graded as very low for variable arch length and second molar eruption disturbances. All other outcomes were graded as having low level of evidence.

CONCLUSIONS

Owing to the low level of certainty identified, the conclusions should be considered cautiously. Increase in arch perimeter and width was attributed to the proclination of the incisors, buccalization of the deciduous molar and premolar areas, and distal inclination of the molars. However, there was an increased chance of impaction and ectopic eruption of permanent second molar after treatment with LB.

Three-dimensional measurement and analysis of mandibular characteristics in subjects with impacted mandibular second molars

OBJECTIVE

To investigate the morphological characteristics of the mandible in subjects with impacted mandibular second molars by measuring and analysing the mandible in three dimensions.

SETTING AND SAMPLE POPULATION

In this retrospective study, the data of a total of 52 609 subjects who underwent cone-beam computed tomography (CBCT) for diagnosis and treatment were reviewed. According to the inclusion and exclusion criteria, 183 subjects with impacted mandibular second molars and 176 age- and sex-matched controls were included.

METHODS

A retrospective case-control study was designed. The 183 subjects were divided into two groups: group 1 (G1) comprised 120 patients with unilaterally impacted mandibular second molars, and group 2 (G2) comprised 63 patients with bilaterally impacted mandibular second molars. Group 3 (G3) contained 176 age- and sex-matched controls. The mandible was reconstructed with nineteen landmarks using Mimics software. Twelve linear lengths and 3 angles were measured.

RESULTS

The bilateral germination gap, mandibular body width and gonion width in G1 were significantly lower than those in G3 (P < .05), while the gnathion angle and first molar width values in G1 were significantly higher than those in G3 (P < .05). The results in G2 were similar to those in G1, but the differences between G2 and G3 were greater than those between G1 and G3. There were no significant differences in the other measurements among the groups.

CONCLUSION

The mandibles of the subjects with impacted second molars were constricted in terms of the sagittal length and transverse width.

[Three-dimensional analysis of the mandible with impacted mandibular second molar]

OBJECTIVE

To study the developmental and morphological characteristics of the mandible in patients with impacted mandibular second molar and to predict the possible trend of mandibular development via three-dimensional (3D) measurement and analysis.

METHODS

A total of 88 cases of impacted group and 88 cases of control group were screened out. 3D measurements were performed by using Mimics software. A total of 23 landmark points and 17 measurements were determined. The measurements were analyzed by t-test.

RESULTS

The mandible length, the space between the first molars, the space between mandibular angles, and the width between the first molars in the impacted group were lower than those in the control group (P<0.05). Moreover, the value of the submandibular angle was higher than that in the control group (P<0.05).

CONCLUSIONS

The impacted mandible of patients with mandibular second molar showed lack of sagittal and width development, and the impacted mandibular second molar was a manifestation of its degeneration.

The influence of mandibular third molar germectomy on the treatment time of impacted mandibular second molars using brass wire: a prospective clinical pilot study

The brass wire ligature is an efficient method to correct a moderately mesially impacted mandibular second molar (MM2). The aim of this prospective clinical pilot study was to evaluate the influence of mandibular third molar (MM3) germectomy on the treatment time for this procedure and to determine its impact on oral health-related quality of life (OHRQoL) using the short-form Oral Health Impact Profile (OHIP-14). The STROBE guidelines were followed. Impacted MM2 were assigned randomly to receive brass wire ligature treatment either with germectomy (group A) or without germectomy (group B). Descriptive statistics and the Student t-test were used in the statistical analysis; significance was set at P≤0.05. One thousand and thirty patients were assessed. Fourteen subjects with 20 mesially angulated (range 25-40°) impacted MM2 were identified. Paired comparisons of groups A and B showed no statistically significant difference in treatment time (171days for group A and 174days for group B; P=0.440), but a statistically significant difference in OHIP-14 values at the 3- (P=0.017) and 7-day (P=0.002) follow-up. The brass wire technique can be used effectively in moderately impacted MM2, but the combined use of MM3 germectomy does not influence the treatment time and shows a negative impact on OHRQoL.

Second molar impaction associated with lip bumper therapy

INTRODUCTION:

Although lip bumpers (LBs) provide significant clinical gain of mandibular arch perimeter in mixed-dentition patients, orthodontists are reluctant to use them due to the possibility of permanent second molar eruptive disturbances.

OBJECTIVE:

The present study was conducted to assess second molar impaction associated with the use of LBs, and to investigate how they can be solved.

MATERIAL AND METHODS:

Lateral and panoramic radiographs of 67 patients (34 females and 33 males) were assessed prior (T₁) and post-LB treatment (T₂). LB therapy lasted for approximately 1.8 ± 0.9 years. Concomitant rapid palatal expansion (RPE) was performed in the maxilla at LB treatment onset. Impaction of mandibular second molars was assessed by means of panoramic radiographs in relation to the position of first mandibular molars. Horizontal and vertical movements of first and second molars were assessed cephalometrically on lateral cephalometric radiographs based on mandibular superimpositions.

RESULTS:

Eight (11.9%) patients had impacted second molars at the end of LB therapy. Two patients required surgical correction, whereas five required spacers and one patient was self-corrected. Mandibular first molar tip and apex migrated forward 1.3 mm and 2.3 mm, respectively. Second molar tip showed no statistically significant horizontal movement.

CONCLUSION:

Although LB therapy increased the risk of second molar impaction, impactions were, in most instances, easily solved.

Etiological factors in second mandibular molar impaction

OBJECTIVES

The impaction of the second mandibular molar (MM2) has recently become more prevalent. Several etiological hypothesis have been proposed to investigate the association between skeletal features and impaction of MM2. The aims of this study were to analyze the skeletal features in patients with MM2 impaction and the association between arrested eruption of MM2 and the presence of the third mandibular molar (MM3).

STUDY DESIGN

In this retrospective study 48 subjects from 3,530 Caucasian orthodontic patients with MM2 impaction were included in a study group (SG) and compared to a control group (CG) of 200 subjects without MM2 impaction. Panoramic radiographs evaluated the presence or absence of the MM3 germ. Cephalometric analysis was performed to evaluate linear and angular skeletal values. For the statistical analysis, descriptive statistics, Student's t-test, χ2 test and odds ratio (OR) were used.

RESULTS

The paired comparisons between SG and CG showed in cephalometric analysis both a reduced mandibular gonial angle (ArGoMe) and lowered Jarabak's polygon value with a statistically significant difference (P≤ 0.05). MM3 was statistically significant associated (P≤ 0.05) with MM2 impaction but it is not a risk factor (OR 0.817).

CONCLUSIONS

Subjects with MM2 impaction show a vertical condylar growth direction. MM3 is not a risk factor for MM2 impaction. Key words:Impacted mandibular second molar, skeletal features, orthodontic.

Impaction of permanent mandibular second molar: a retrospective study

OBJECTIVE

To determine the prevalence of impacted mandibular second molar (MM2) and the association between MM2 impaction and crowding. The clinical significance of the angle between first and second mandibular molar and of the space between the first mandibular molar (MM1) and the anterior margin of mandibular ramus in MM2 impaction were also evaluated.

MATERIAL AND METHODS

In this retrospective study , from the dental records of 2,945 caucasian young orthodontics patients , 40 subjects with MM2 impaction were included in a study group (SG) and compared with a control group (CG) of 200 subjects without MM2 impactions. The crowding , the angle of inclination of MM2, the distance between MM1 and mandibular ramus, the canine and molar relationships, and the lower centre line discrepancy were measured. For the statistical analysis , descriptive statistics and t-Student for independent sample groups were used.

RESULTS

The prevalence of impacted MM2 was 1.36%. The independent-Samples t-Test between SG and CG showed: the presence of crowding (P ≤ 0.001), an higher angle values of MM2 inclination (P ≤ 0.001) and a smaller distance between MM1 and the anterior margin of mandibular ramus (P ≤ 0.001) in the SG.

CONCLUSION

The impaction of MM2 is a relatively rare occurrence in orthodontic caucasian populations. The crowding, a higher angle values of MM2 inclination and a reduced distance between MM1 and the anterior margin of mandibular ramus, at the time of one third of MM2 root formation (T1), characterize MM2 impaction.