Molar Position Research Articles

Prediction of Residual Alveolar Bone Height in the Posterior Maxilla After Dental Extractions

After tooth extraction in the posterior maxilla, bone resorption often limits implant placement unless additional grafting procedures are performed. However, it is difficult to predict the amount of bone that will remain after extraction based on current evidence. The purpose of this study was to develop a method for predicting the postextraction alveolar bone height in the posterior maxilla. The authors conducted a retrospective cohort study that included all patients who were treated for the extraction and replacement of a maxillary first molar with a dental implant from 2008 to 2019. Potential predictor variables included thirteen pre-extraction radiographic measurements obtained via cone-beam computed tomography. The outcome variable was having more than 6mm of bone height from the alveolar crest to the sinus floor after extraction. Decision tree analyses were used to search for the best predictors of this outcome using random forest analysis with a maximum of 3 randomly chosen covariates in each candidate tree. A total of 63 patients were included in the study; 55.6% were women, and the mean age was 57.6±14.5years. In this study population, having a bone height from the furcation to the maxillary sinus floor of <6.7mm had a 7.1% chance of having >6mm of bone height postoperatively, whereas those patients with ≥6.7mm at the same position preoperatively had a 61.9% chance of having >6mm of bone height postoperatively (P<.001). This study suggests that patients with <6.7mm of bone from the furcation to the sinus are at increased risk of having insufficient bone to support a dental implant without additional grafting at the maxillary first molar position. When treating these patients, the surgeon should consider performing a procedure at the time of extraction to increase bone height or explain additional bone grafting is expected for ideal implant placement.

The Performance of Abutment Material and Finish Line Configuration on the Stress Distribution and Fracture Resistance of Implant-Supported Zirconia Fixed Partial Dentures When Loaded in a Bio-Faithful Model.

This computational study analyzed the strain magnitude and distribution within trabecular bone structure around different materials and finish line (FL) configurations of implant abutments loaded axially. Differences in fracture resistance of these abutments were also assessed. Sixteen endosseous screw vent implants were embedded in eight bio-faithful mandibular simulators resembling D2 and D3 bone density (n = 4 models per bone type) in the second premolar and second molar positions. These models were further subdivided into eight subgroups with different FL configurations and abutment materials. Strain gauges were mounted adjacent to the implants, and the superstructures were successively placed on the abutments. A universal dynamometrical testing apparatus was used for a static compression load. Finally, all samples were subjected to load until fracture. Three-way analysis of variance for strain analysis showed a significant overall interaction between the three variables (bone type, FL configuration, and abutment materials; P < .001), while the analysis for fracture resistance showed significant two-way interactions between bone type and FL configuration (P < .001) and between bone type and abutment material (P < .001). The implant abutment material, the FL configuration of the abutment, and the bone type can influence the mechanical behavior of the abutment used. Zirconia abutments with anatomical FL configurations possess better fracture resistance than zirconia and titanium abutments with circular FL configurations in D2 bone density.

Long-term evaluation of maxillary molar position after distalization using modified C-palatal plates in patients with and without second molar eruption

The purpose of this study was to analyze the treatment effects after molar distalization using modified C-palatal plates with and without secondmolar eruption and to evaluate the three-dimensional position of the molars during long-term retention using cone-beam computed tomography. The study sample comprised 74 third molars in 42 patients. Twenty-seven adolescent patients (mean age, 12.6years) having 48 maxillary third molars were divided into 2 groups according to the eruption of their secondmolars: 15 patients with secondmolar eruption (group 1) and 12 patients without secondmolar eruption (group 2). Pretreatment, posttreatment, and long-term data (mean, 5.2years) from cone-beam computed tomography were scanned and compared with control groups. There was less tipping movement of the first and secondmolars (0.94° and 3.22°) and distal tipping movement of the third molars (8.91°) in group 1 than in group 2 (4.36°, 7.39°, and 3.08°, respectively), but the treatment time was shorter and the positional change of the third molars was insignificant in group 2. In the long-term, the secondmolars fully erupted after distalization in group 2, and there was no difference in the third molar position between group 1, group 2, and the control group, except for the vertical position of the third molars in group1. In the long-term, the secondmolars fully erupted after distalization, and the third molars were in a favorable position. Therefore, these findings suggest that clinicians do not need to extract developing third molars before distalization in adolescents.

Frequency and Severity of Second Molar External Root Resorption Due to the Adjacent Third Molar and Related Factors: A Cone-Beam Computed Tomography Study.

Objective: This study sought to assess the frequency and severity of second molar external root resorption (ERR) due to the adjacent third molar and its correlation with the position of third molar and other related factors using cone-beam computed tomography (CBCT). Materials and Methods: This cross-sectional study evaluated 320 second molars and their adjacent impacted third molars on CBCT scans of patients over 16 years, retrieved from the archives of Azad University Radiology Department. Presence/absence of second molar ERR, its location and severity (if present), and position of adjacent third molar were determined on CBCT scans, and recorded in a checklist. Data were analyzed using a logistic regression model. Results: The frequency of second molar ERR was 33.4% in the mandible and 14% in the maxilla. The severity of ERR was significantly correlated with the involved jaw (P=0.001) but had no correlation with age, gender, or depth of impaction of adjacent third molar (P>0.05). The mesioangular and horizontal positions of impacted third molars had a significant correlation with the frequency of second molar ERR (P<0.006). Conclusion: According to the results of this study, ERR occurring in second molars adjacent to third molars is common, especially in the mandible. Mesially inclined third molars have a greater potential of being associated with ERR in second molars.

Evaluation of the effect of impaction on the mineralization of mandibular third molars and forensic age estimation in a sample of south Indian children.

Assessment of third molar mineralization is a basic forensic odontological method available for age estimation in children and adolescents. Due to their protracted development into the late adolescence, their development has become the subject of interest and acquired great forensic importance. It is clearly evident in the literature that impaction factor has an influence on the rate of maturation of the third molars. In this regard, the present study was undertaken to test the relationship between impaction and its concomitant effect on the mineralization of the third molar and forensic age estimation. A total of 520 digital orthopantomograms (OPG) of 260 males and 260 females of south Indian origin were assessed retrospectively. Maturation of the third molars (I3M) was assessed using the method of Cameriere et al. (Int J Leg Med 122 (6):493-497, 2008). Impaction status was determined according to the position of lower right and left third molars in relation to the long axis of the second molars. Out of the total sample, 68.1% of lower left third molars and 71.2% of lower right molars were impacted. Statistical measures for I3M were calculated in the males and females for both impacted and non-impacted third molars. It was ascertained that the mean age and I3M values were higher in impacted third molars, indicating the slower rate of maturation than non-impacted ones. The sensitivity and specificity of the test (I3M < 0.08) was 96.2% and 72.4% for non-impacted third molars and 46.2% and 87% for impacted third molars, respectively. Our findings indicate that the cut-off value of I3M < 0.08 resulted in greater number of age misclassifications (false negatives) for impacted molars, highlighting the need for new cut-off value of I3M to meet the legal standards. It was concluded that the mineralization of impacted third molars was slower compared to non-impacted ones in south Indian males and females. Further studies are warranted to validate these findings among a larger and more diverse sample.

270 A Retrospective Analysis of The Impaction Status of Mandibular Third Molars as A Risk Factor for Fractures of Angle or Condylar Region of The Mandible

Abstract Background the position and angulation of mandibular third molars have both been found to influence the angle and condylar fractures. Objective: To identify whether there is an association between the depth and angulation of third molar impaction and the relative risk of fracture of the mandibular angle and condyle. Method Four-hundred and eighty-two panoramic dental radiographs were assessed for the period from January 2012 to June 2020. The study variables included the presence of mandibular third molars, position and angulation. The outcome variables were angle and condylar fractures. Results the mean age was 28.5 years (range 15-89) and 93.2% (n = 499) were male. Angle fractures were significantly more frequent with an impacted wisdom tooth (M3) ( p = 0.023) whereas condylar fractures were more commonly associated with a fully erupted M3. The highest incidence of angle fractures was observed with wisdom teeth classified as class II ( p = 0.026) and position B ( p = 0.05). In contrast, class I wisdom molars were more frequently associated with condylar fractures. With regards to the angulation of wisdom teeth, angles between 80 o – 100 o were highly correlated with angle fractures ( p = 0.020) whereas M3 angulations of 60 o – 80 o were related to condylar injuries (p = 0.025). Conclusions fractures of the mandibular angle were significantly associated with Class II and position B wisdom teeth whereas class I third molars were associated with fracture of the condyles. The likelihood of angle and condylar fractures almost doubled when M3 angulations were (80-100) and (60-80) respectively.

RADIOGRAPHIC EVALUATION OF THE EFFECT OF IMPLANT SUPPORTED AND IMPLANT RETAINED DISTAL EXTENSION REMOVABLE PARTIAL DENTURES ON THE SUPPORTING STRUCTURES

Objective: To evaluate and compare the effect of implant supported versus implant retained removable partial denture restoring Kennedy's class I cases on the supporting structures by measuring marginal bone loss and bone density around implant. Subjects and Methods: Twelve patients were selected from the outpatient clinic, Prosthodontics Department, Faculty of Dentistry, Minia University. Both groups were classified into two equal groups; according to the implant superstructures either dome shaped abutment -and-ball and socket attachment. Each Patient of both groups had two implants in second molar position and received removable partial denture of the same design. Patients were followed up for one year radiographicaly regarding marginal bone loss and bone density around each implant. Group I: Six patients received RPD supported by dome shaped short abutments. Group II six patients received RPD retained by ball and socket attachments. Results: Results revealed that there was Significant increase in marginal bone loss in group II implant retained with ball abutment than group I implant supported with dome shaped abutment and Significant increase in bone density in group I (implant supported) than group II (implant retained) Conclusion: The use of dome shaped abutment produce less marginal bone loss and increase of bone density than the use of ball abutment.

Third molar impaction position in Peruvian adults

Objective. To determine the position of the third molars in patients treated in a diagnostic imaging center in Lima during the period 2017-2020. Methodology. An observational, descriptive, cross-sectional and retrospective research was carried out; which consisted of a sample of 253 panoramic radiographs of patients treated in a private radiological center. The position of the lower third molars, the depth of impact, and their impaction position in relation to the mandibular ramus were evaluated using the Pell and Gregory classification; as well as the Winter classification. The data were analyzed in the statistical package SPSS vs. 26. Outcome. It was observed that the vertical and mesioangular position were the most common with 14.6% and 13.2%; respectively. Type I and II according to Pell and Gregory was the most common with values of 15.4% and 14.4%; as well as, class B with 15.4%. Conclusion. The vertical and mesioangular impaction position, type B and class II were the most frequent for the lower third molars.

Changes in third molar position after Class II subdivision malocclusion treatment with asymmetric extractions.

This study aimed to assess the changes in third molars angulation and their available space after Class II subdivision malocclusion treatment with asymmetric premolar extractions. The sample consisted of 37 patients (17 male, 20 female and mean age 13.18±1.99years) in group 1 (Type 1 Class II subdivision) and 25 (10 male, 15 female, mean age 13.56±2.46years) in group 2 (Type 2 Class II subdivision). In group 1, extractions were performed in the two maxillary quadrants and in the Class I mandibular quadrant. In group 2, extraction was performed in the Class II maxillary quadrant. Panoramic radiographs were used to evaluate third molar angulations and their available space pre- and post-treatment. Radiographic measurements were performed with Dolphin® Imaging 11.9. Paired t tests were used for intragroup comparison between stages and sides. In Type 1, there were similar improvements in third molar angulations and increases in the space available on the extraction quadrants in the maxillary arch. In the mandibular arch, there was significantly greater improvement in angulation and greater space availability in the extraction quadrant after treatment. In Type 2, there was significantly greater improvement in angulation and available space for the maxillary third molar on the extraction quadrant. In the mandibular arch, there was a similar improvement in the available space for the third molars. After treatment, both groups presented better angulation and significantly greater space for third molar eruptions on the extraction quadrants, when compared to the homologous non-extraction quadrants.

Clinical Evaluation of the Effect of Implant-Supported and Implant Retained Distal Extension Removable Partial Dentures on the Supporting Structures

Objective: To evaluate and compare the effect of implant supported versus implant retained removable partial denture restoring Kennedy's class I cases on the supporting structures by measuring modified gingival index and probing depth for abutment teeth and implants.&#x0D; Subjects and Methods: Twelve patients; who had Kennedy class I mandibular partially edentulous ridge extending distal to the first or second premolar, were selected from the outpatient clinic, Prosthodontics Department, Faculty of Dentistry, Minia University. The patients were classified into two equal groups; according to the implant superstructures either dome shaped abutment or ball and socket attachment. Each Patient of both groups had two implants in second molar position (one in each side) and received removable partial denture of the same design. Patients were followed up for one year clinically. Group I: Six patients received RPD supported by dome shaped short abutments. Group II six patients received RPD retained by ball and socket attachments.&#x0D; Results: Results revealed that, there was no statistically significant difference between the two groups regarding modified gingival index and probing depth around the abutment teeth and implant abutment.&#x0D; Conclusion: The use of dome shaped abutment or ball and O-ring attachment have the same effect on gingival index and probing depth around natural abutments and implants in Kennedy class I mandibular situations.

Assessment of Anchorage Loss with Conventional versus Contemporary Method of Intraoral Anchorage: A Prospective Clinical Study

Background: Anchorage control is a major concern in the design of orthodontic treatment planning. Even the best known methods to reinforce the anchorage result in taxing of the anchor unit. Control of anchorage is primarily important in “critical anchorage” situations where no anchor loss is acceptable. Temporary anchorage devices (TADs) offer to solve one of our greatest dilemmas of “anchorage control” and have been compared in this study with conventional intraoral anchorage in situ. Materials and Methods: The study involved a total of 60 subjects; 26 males and 34 females with a mean age of 16.7 years having Angle's Class I malocclusion with severe crowding who were divided randomly into two groups; Group A - TADs and Group B - Nance palatal button (NPB) for anchorage preparation. Amount of anchor loss was determined at maxillary first molar using the pre- and post-treatment lateral cephalograms. Results: The mean range of difference between pre- and post-values of the maxillary molar position in Group A was 0.02–0.09 mm (P = 0.005) and in Group B was 1.18–1.26 mm (P = 0.0001). Hence, the anchorage loss during the initial phase of leveling and alignment was approximately 1.22 mm with the use of NPB and minimal when TADs were placed and engaged before leveling and alignment. Conclusion: Minimal mesial movement of the maxillary first molars was observed when TADs were placed and engaged before leveling and alignment, thus proving their efficacy in maximum anchorage situations.

Does a preoperative cone beam CT reduce complication rates in the surgical removal of complex lower third molars? A retrospective study including 486 cases

BackroundThis study was designed to analyse the value of preoperative Cone Beam CTs (CBCT) prior to the surgical removal of complex lower third molars. Furthermore, the aim was to assess injuries to the inferior alveolar nerve (IAN) bundle and postoperative neurological disorders depending on the position of the lower third molar and the inferior alveolar nerve bundle.MethodsIn this retrospective examination preoperative Cone Beam CTs and Orthopantomographs (OPT) of 324 patients were analysed concerning the location of the lower third molars in relation to the mandible and the inferior alveolar nerve bundle. Surgery protocols of all patients who underwent the surgical removal of at least one complex lower third molar were analysed concerning patient data, length of surgery, intraoperative haemorrhage, intraoperative exposure of the inferior alveolar nerve bundle, postoperative swelling and postoperative neurological disorders. The data was then compared to data from international studies.ResultsIn all 324 patients a permanent neurological damage was not found. Temporary neurological damage was recorded in 13 cases (2.6%). A caudal nerve position with no measurable distance to the root of the lower third molar was associated with the highest risk of a temporal neurological damage. A vestibular touching nerve route also correlated with postoperative sensitivity impairment. If a mesioangulation (Winter) or a Pell and Gregory Type IIIC appears in the OPT, risk of neurological damage is at its highest.ConclusionsThree-dimensional radiographic imaging, in our patient group, does not significantly affect the risk for complications during the surgical removal of complex lower third molars. Therefore, it should only be utilized for risk assessment, especially in cases of symptom-free lower third molars.A preoperative orthopantomogram still can be accepted as standard for radiographic imaging.An intraoperative exposure of the IAN bundle does not necessarily predict simultaneous neurological damage. Exposure of the IAN bundle is no indication for a discontinuation of the surgery.

Variations in maxillary second molar position of untreated subjects with normal occlusions: A long-term observational study.

The purpose of the present study was to evaluate the long-term variations in maxillary second molar position in untreated subjects with normal occlusion. A sample of 39 subjects (18 females and 21 males) selected from the University of Michigan Growth Study (UMGS) was followed longitudinally with digital dental casts at 3 observation times: T1, when the maxillary permanent second molars were fully erupted, T2, last observation available in the longitudinal series (38 subjects), and T3, at least 20years after T2 (12 subjects). Digital measurements were recorded with an open-source software. Outcome variables were sagittal and transverse inclinations of the upper second molars. Two mixed-effect models were performed. The maxillary second molars had a distolingual inclination at T1, T2 and T3. Sagittal and transverse inclination showed progressive significant uprighting from T1 through T3 (P<.001). From T1 to T2, the adjusted difference in sagittal crown inclination was 8.0° (95% CI from 6.5° to 9.6°; P<.001). From T2 to T3, the adjusted difference was 5.5° (95% CI from 3.0° to 8.1°; P<.001). From T1 to T2, the adjusted difference in transverse crown inclination was 1.9° (95% CI from 0.4° to 3.5°; P=.011). From T2 to T3, the adjusted difference was 6.0° (95% CI from 3.4° to 8.5°; P<.001). Along with age, maxillary second molars showed a progressive significant uprighting with a decrease in the distal and lingual inclinations.

Análise da movimentação de dentes de próteses totais polimerizadas com energia de microondas em função da sorção de água: influência da pressão e temperatura

The processing of denture base resins may originate dimensional changes that can alter the occlusal position of artificial teeth of the concluded prosthesis. The polymerization method and the water sorption property of the acrylic resin may cause these changes. Pressure, temperature, and time of water sorption may also have influence on the previous alterations. The aim of this research was to verify the alteration of buccal cusps position of first molars on marillary dentures, polymerized by water bath (9 hours at 76ºC) and microwave energy (3 min at 500W), regarding water sorption under different conditions of time, pressure, and temperature of water storage. Sixty dentures were waxed onto metal die simulating an edentulous maxilla and divided into 4 groups (GI, GII, GIII, and GIV) of 15 samples each. Four different treatments, as follows, were applied to these samples: processing by water bath and stored in water under environmental pressure for 30 days at 37±2ºC (control -GI); processing by water bath and stored in water under 40 pounds for 1 hour at 60±2ºC (Gll): processing br microrwawe energy and stored in water under environmental pressure for 30 days at 37±2ºC(GIII): and processing by microware enerrgy and stored in water under 40 pounds for 1 hour at 60±2ºC (GIV). The degree diferences obtained between the pre and post water sorption were 0.65 for GI; 0.55 for GII; 0.83 for GIII, and -0.57 for GIV (p&gt;0.05). There was significant alteration in the positioning of the artificial firth maxillary molars among the control and the treated storage groups, when cured by microwave energy or water bath.

Retrospective Analysis on Inferior Third Molar Position by Means of Orthopantomography or CBCT: Periapical Band-Like Radiolucent Sign

Background: Orthopantomography (OPG) is usually used as a primary diagnostic radiological exam in the planning of third molar surgery because it is deeply available in dental clinics and has lower radiation doses compared to Cone-beam computed tomography (CBCT). The OPG provides a bi-dimensional image, but several radiological signs have been proposed to study the position of the lower third molar and to predict surgical risks. Methods: Patients were divided into two groups, the OPG with a radiolucent area (D-group) and the OPG without any sign (C-group) in correspondence of inferior wisdom tooth roots. Results: The mean distance between the inferior third molar root and the lingual cortical mandibular bone was −1.09 ± 1.5 mm. The nearness of the root that is less than 1 mm was more frequent in the D-group (84.85%) compared to the C-group (14.58%) with statistical significance (Odd ratio: 32.8) using the Chi-square test. Conclusions: When the root of the impacted inferior third molar is impacted into the lingual cortical plate, a periapical band-like radiolucent sign may appear in the OPG image. It could be useful for the prediction of root position and surgical risks.

Ectopic Eruption of Maxillary First Permanent Molars: Preliminary Results of Prevalence and Dentoskeletal Characteristics in Spanish Paediatric Population.

The ectopic eruption of the maxillary first permanent molar (EEM) is a local alteration of dental eruption with a multifactorial aetiology. The aims of our study were to determine the prevalence of the EEM in children and to analyse whether there is a relationship between EEM and dento-skeletal characteristics. A total of 322 children were analysed with the Ricketts cephalometric study and descriptive and analytical statistical analysis was carried out. The prevalence of EEM was 8.7%, with no statistically significant differences regarding gender or location, but a higher prevalence in the 7-year-old age group (18.8%) and bilateral EEM was more prevalent than unilateral EEM (p < 0.05). The most frequent findings were a shortened anterior cranial base, a retroposition of the maxilla and a distal position of the upper permanent first molar in relation to the pterygoid vertical in children with EEM. No statistically significant differences were found regarding the cephalometric parameters except a decreased palatal plane in the bilateral EEM group and a distal upper incisor position in the EEM group (p < 0.05). In conclusion, the prevalence of the EEM was 8.7%, more frequently bilateral, and significantly in seven-year-old patients. Children with bilateral EEM have decreased palatal plane values and a more posterior position of the upper incisor.

Evaluation of anatomical references for locating the course of the posterior superior alveolar artery for dental implant surgery

This retrospective cohort study aimed to identify the best anatomical reference for predicting the posterior superior alveolar artery (PSAA) location. Computed tomographic images of 90 maxillary sinuses were evaluated. We studied five references, including the alveolar crest, maxillary sinus floor, zygomatoalveolar crest, hard palate and soft palate, and measured the distances between them and the PSAA. Variations in the distance were evaluated by the standard deviation and coefficient of variation (CV). The zygomatoalveolar crest was an unstable reference, owing to its high standard deviation and CV. The smallest CV was for the distance between the alveolar crest and PSAA, although the distance was smaller in edentulous jaws than dentulous jaws. The distance between the sinus floor and PSAA was larger in male and edentulous patients. The PSAA was detected in 40.0%, 44.4%, 54.4% and 56.7% of the sinus walls at the first and second premolar and the first and second molar positions, respectively. At these tooth positions, the respective heights above the hard palate were 11.2 ± 4.9, 8.2 ± 4.9, 6.2 ± 2.8 and 8.1 ± 2.9 mm. The hard palate was the most stable reference for predicting the location of the PSAA, irrespective of sex, age and dentition.

Evaluation of strategic uprighting of the mandibular molars using an orthodontic miniplate and a nickel-titanium reverse curve arch wire: Preliminary cephalometric study

ObjectiveTo evaluate the overall treatment effects in terms of the amount of uprighting with changes in the sagittal and vertical positions of mandibular molars after applying an orthodontic miniplate with a nickel-titanium (NiTi) reverse curve arch wire (biocreative reverse curve [BRC] system).MethodsA total of 30 female patients (mean age, 25.99 ± 8.96 years) were treated with the BRC system (mean BRC time, 10.3 ± 4.07 months). An I-shaped C-tube miniplate (Jin Biomed) was placed at the labial aspect for the alveolar bone of the mandibular incisors. A 0.017 × 0.025-inch NiTi reverse curve arch wire was engaged at the C-tube mini-plate anteriorly and the first and second premolars and molars posteriorly in the mandibular arch. Pre- and post-BRC lateral cephalograms were analyzed. A paired t-test was used to analyze the treatment effects of BRC.ResultsThe mandibular second molars were intrusively uprighted successfully by the BRC system. Distal uprighting with a controlled vertical dimension was noted on the first molars when they remained engaged in the BRC and the distal ends of the arch wire were laid on the second molars. The mandibular first and second premolars showed a slight extrusion. The changes in the mandibular incisors were unremarkable, while the mandibular molar angulation improved significantly. The lower occlusal plane rotated counterclockwise (MP-LOP 1.13° ± 2.60°).ConclusionsThe BRC system can provide very effective molar uprighting without compromising the position of the mandibular anterior teeth.

Three-dimensional evaluation of maxillary second molar position in untreated patients with normal occlusion : Implications for preadjusted appliance prescriptions.

The study was aimed at evaluating the sagittal and transversal inclinations of upper second molars in untreated adolescents with normal occlusion. Asample of 41subjects (16females, 25males) was selected from the University of Michigan Growth Study (UMGS). Digital dental casts with fully erupted second molars in occlusion were chosen (mean age 14.9 ± 1.3years). Digital measurements were recorded with the open source software 3DSlicer ( www.slicer.org ). The digital measurements of the UMGS sample were compared with the manual measurements collected by Andrews from his sample of untreated classI subjects with normal overbite and overjet. Two mixed effect models (sagittal and transversal inclinations) were performed. The "random effect" was represented by the subjects, while the "fixed effects" were the two compared groups, the side of the arch (right and left), and the group × side interaction. Outcome variables were sagittal and transversal inclinations of the upper second molars. The UMGS group showed asignificantly greater distal crown angulation (-18.9°) with respect to the Andrews sample (0.4°, P < 0.0001). As for the transversal inclination, the UMGS group exhibited significantly greater lingual crown inclination (-10.6° versus -8.0°, P = 0.0118). Fully erupted maxillary second molars in asample of adolescent subjects with normal occlusion showed significantly greater distal and lingual inclinations when compared with Andrews' values. The finding of adistal crown inclination in contrast with Andrews' observation of amesial crown inclination suggests that revision in tip prescription for preadjusted brackets may be considered.

Radiographic Position of Impacted Mandibular Third Molars and Their Association with Pathological Conditions.

Objectives This study aimed to assess the radiographic position of impacted mandibular third molars (IMTMs) and their association with pathological conditions. Materials and Methods The impaction depth, relationship with ramus, and angulation of 1600 IMTMs and their association with 2nd molar distal caries and root resorption, pathological conditions, and proximity to the mandibular canal were evaluated on panoramic radiographs. The IMTM position was determined based on the depth of impaction according to the Pell and Gregory classification, relationship with ramus according to the Pell and Gregory classification, and angulation according to the Winter's classification. The classical and Bayesian logistic regressions were applied to analyze the effect of IMTM position on the associated complications using the odds ratio (OR) and 95% confidence interval (credible interval for Bayesian models). Two-tailed P value < 0.05 was considered statistically significant. Results Of 1600 IMTMs evaluated in this study, 195 (12.2%), 252 (15.8%), and 119 (7.4%) had caused second molar distal caries, second molar root resorption, and pathological lesions, respectively, and 872 (54.5%) had contact with the mandibular canal. Impaction angulation was a risk factor for second molar distal caries (maximum OR = 5.01, 95% CI: 3.12–8.18). Changed angulation and greater impaction depth were the risk factors for second molar root resorption (minimum OR = 1.64, 95% CI: 0.58–4.02). Decreased distance between the ramus and distal side of the second molar was a risk factor for associated pathological lesions (minimum OR = 2.73, 95% CI: 1.79–4.25). Mesioangular and horizontal angulations and greater impaction depth were the risk factors for contact with the mandibular canal (maximum OR = 3.44, 95% CI: 2.6–4.57 and minimum OR = 1.3, 95% CI: 094–1.8). Conclusions The frequency of complications associated with IMTMs was low, but considerable. The occurrence of these conditions might be affected by the impaction position. Thus, regular follow-ups are recommended in order to be able to surgically intervene when the first signs of pathologies arise.