Is there a relationship between the presence of external root resorption in second molars adjacent to impacted mandibular third molars with awake bruxism and masticatory muscle activity?

OBJECTIVES: This study aimed to assess whether awake bruxism and masticatory muscle activity could be related to external root resorption (ERR) in second molars adjacent to impacted mandibular third molars. MATERIALS AND METHODS: Sixty patients, with requests for a cone-beam, computed tomography, were divided into two groups: ERR (patients with ERR in the second molar, n = 30), and control group (n = 30). Awake bruxism was assessed through the Oral Behaviors Checklist (OBC) and an ecological momentary assessment (EMA). Surface electromyography (EMG) was used to assess the masseter and anterior temporal muscle function. Normality and homogeneity of variances were demonstrated. Descriptive analysis was performed, using the T-test and Chi-square test to compare the characteristics of the groups. A multiple regression model was performed. RESULTS: The ERR group presented more non-functional oral activities related to awake bruxism than the control group, according to OBC (p = 0.027) and EMA (p = 0.035). In addition, the ERR group had higher EMG activity than the control group in rest and isotonic protocols (p < 0.05). CONCLUSIONS: Awake bruxism and greater masticatory muscle activity seem to be related to the presence of ERR in second molars adjacent to impacted mandibular third molars. CLINICAL RELEVANCE: The results of the present study can reinforce the theory that triggering ERR in the second molars adjacent to impacted mandibular third molars may be related to mechanical forces coming from the masticatory function.

Factors associated with spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction.

INTRODUCTION: This study aimed to identify significant factors affecting the spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction. Temporary skeletal anchorage devices in the missing mandibular first molar (ML-6) or missing deciduous mandibular second molar (ML-E) with missing succedaneous premolar spaces provided traction. METHODS: Forty-one mandibular third molars of 34 patients (10 male and 24 female; mean age 18.3 ± 3.7 years) that erupted after second molar protraction were included in this study. They were classified into upright (U) and tilted (T) groups. Linear and angular measurements were performed at the time of treatment initiation (T1) and of ML-6 or ML-E space closure (T2). Regression analyses were used to identify significant factors related to third molar uprighting. RESULTS: Nolla stage (odds ratio [OR] 4.1), sex (OR 0.003 for male), third molar angulation at T1 (OR 1.1), missing tooth space (OR 0.006), rate of third molar eruption (OR 23.3), and rate of second molar protraction (OR 0.2) significantly affected third molar uprighting. Age, third molar angulation at T1, rate of third molar eruption, and rate of second molar protraction were significant factors for predicting third molar angulation at T2. CONCLUSIONS: Available space for third molar eruption before and after second molar protraction is not associated with uprighting of erupting third molars. Older patients whose third molars are in greater Nolla stage, are in a more upright position at T1, and have a greater eruption rate have a greater chance for third molar uprighting. Alternatively, an increase in second molar protraction rate results in mesial tipping of the third molars.

Relationship between the Position of Impacted Third Molars and External Root Resorption of Adjacent Second Molars: A Retrospective CBCT Study.

BACKGROUND AND OBJECTIVES: Impacted third molars (ITM) are the most commonly-impacted teeth. There is a risk for ITM to cause a number of pathological conditions, and external root resorption (ERR) of adjacent teeth is one of the most prevalent. Retaining or prophylactic extraction of ITM is a polemic topic. External root resorption of adjacent teeth is one of possible indications for prophylactic removal of ITM. The aim of this study was to assess the relationship between external root resorption (ERR) on the distal aspect of second molars' roots and positional parameters of ITM. Methods: Cone beam computed tomography scans of 109 patients (41 males, 68 females; mean age 26.4 ± 7.9 years) with 254 ITM (131 in the maxilla and 123 in the mandible) were retrospectively analyzed. Positional parameters of ITM (mesio-distal position, angulation, impaction depth, and available eruption space) were evaluated. The presence, location, and depth of ERR of adjacent second molars were assessed. Results: Analysis showed a relationship between ITM impaction depth, mesial inclination angle, and the presence of ERR. Mesial inclination angle of more than 13.6° increased the odds of ERR occurrence by 5.439 (95% CI, 2.97-9.98). ITM presence at the level of ½ of roots of the adjacent second molar or more apically increased the odds of ERR occurrence by 2.218 (95% CI, 1.215-4.048). No significant correlation was detected between the occurrence of ERR and patient age, gender, or the available eruption space in the mandible. Depth of ERR did not depend on its location. Conclusions: Incidence of ERR in second molars is significantly associated with mesial inclination and a deep position of ITM.

Does an Association Exist Between the Presence of Lower Third Molar and Mandibular Angle Fractures?: A Meta-Analysis.

PURPOSE: The current data suggest that the presence of lower third molars predisposes the patient to a greater risk of mandibular angle fracture. Thus, the present review sought to determine whether an association exists between the presence of a lower third molar and the occurrence of a mandibular angle fracture in adults and to assess the influence of third molar position according to the Pell and Gregory classification. MATERIALS AND METHODS: The present study was a systematic review and meta-analysis of analytical observational studies. The present review included all reports of the relationship between mandibular angle fractures and lower third molars. No restriction regarding year, language, or publication status was used. The review protocol was registered at the PROSPERO database (registration no. CRD42016047057). Electronic searches unrestricted for publication period and language were performed in the PubMed, Scopus, SciELO, and Latin American and Caribbean Health Sciences databases. Google Scholar and OpenGrey databases were used to search the "gray literature," avoiding selection and publication biases. The entire search was performed by 2 eligibility reviewers. Association and proportion meta-analyses were planned for the studies with sufficient data. The primary predictor variable was the relationship between the presence of a lower third molar and the development of mandibular angle fractures. The secondary outcome variables were the vertical and horizontal positions of the lower third molar, according to the Pell and Gregory classification and their relationship to the susceptibility to developing a mandibular angle fracture. RESULTS: The search strategies resulted in 411 studies, from which 16 were selected for qualitative and quantitative review. The association meta-analysis included all the selected studies and showed that patients with lower third molars are 3.16 times more likely to develop mandibular angle fractures. The proportion meta-analysis included 5 studies and showed that the overall rate of mandibular angle fractures was 51.58% and that positions III and C are more likely to result in fracture, with a rate of 59.84 and 63.67%, respectively. CONCLUSIONS: The results of the present study have shown that the presence of impacted third molars increases by 3.16 times the risk of mandibular angle fractures in adults, with the greatest risk present when third molars are classified as IIIC according to Pell and Gregory. The available evidence is not sufficiently robust to determine whether third molar presence or the level of impaction is the main causative factor for the occurrence of mandibular angle fractures.

Orthodontic uprighting of a horizontally impacted third molar and protraction of mandibular second and third molars into the missing first molar space for a patient with posterior crossbites.

A 22-year-old woman came with a unilateral missing mandibular first molar and buccal crossbite. The open space was closed by protraction of the mandibular left second molar and uprighting and protraction of the horizontally impacted third molar using temporary skeletal anchorage devices, and her buccal crossbite was corrected with modified palatal and lingual appliances. The total active treatment time was 36 months. Posttreatment records after 9 months showed excellent results with a stable occlusion.

The effect of headgear on upper third molars: a retrospective longitudinal study.

OBJECTIVES: To investigate the effects of orthodontic non-extraction treatment with or without headgear on the position of and the space available for upper third molars in growing children with class II malocclusions. MATERIALS AND METHODS: The sample consisted of pre- and post-treatment panoramic radiographs and lateral cephalograms of 294 class II orthodontic patients; 160 were treated with headgear and 134 were treated without headgear. The space available for the upper third molar was measured on the lateral cephalogram as the distance from pterygoid vertical (PTV) to the distal surface of the upper first molar crown (PTV-M1). Angulation, vertical position and tooth development stage of the upper third molars were evaluated on panoramic radiographs. All measurements were evaluated statistically. RESULTS: In both groups PTV-M1 increased, but the increase in PTV-M1 was significantly higher for patients treated without headgear. A linear model for repeated measures revealed that this difference was still significant after correction for age, gender and molar occlusion. Further, there is no evidence that the change in angulation, vertical position and development stage of the upper third molars during orthodontic treatment is influenced by headgear therapy. CONCLUSION: This study indicates that the use of headgear in growing patients significantly affects the space available for upper third molars. However, orthodontic treatment with headgear does not influence the angulation, vertical position and development stage of upper third molars. It is therefore important to always take into account third molars during treatment planning.

Determining the quality of life after removing of impacted lower wisdom tooth using the principal component analysis method.

The main objective of this study was to determine to what extent a detailed oral instruction about treatment after surgical removal of a lower wisdom tooth affects postoperative quality of life (QoL). The research on QoL after removal of a lower wisdom tooth was conducted with 108 patients. Depending on the type of information given to each respondent individually, the examinees were divided into two groups: a test group which was given detailed written and oral instructions, and a control group which received only written instructions about treatment after the surgery. In this research the QoL was examined using modified Oral Health Impact Profile-14 (OHIP-14) criterion four, seven and thirty days after the operation depending on the type of information previously provided to the respondents. In order to reduce the dimensionality of the obtained data sets, as well as in order to explain the relationship between the examined variables that are interrelated the principal component analysis (PCA) was applied. Both groups expressed satisfaction with the postoperative period for the individual variables investigated in modified OHIP-14 questionnaire, with the intensity and the order of the major components of satisfaction determined by the PCA differing between the two groups of the patients. On the fourth postoperative day, the test group expressed the highest level of satisfaction with sleep, physical appearance and the ability to eat. In the later postoperative period the test group (on the seventh and thirtieth day) had the highest level of satisfaction with the absence of discomfort during removal of sutures, satisfaction with performed treatment, and the ability to eat. Detailed preoperative oral instructions to patients can significantly improve the quality of life after operative removal of a lower wisdom tooth.

[Influence of the mandibular second premolar extraction on the angulation of the mandibular third molar].

OBJECTIVE: To compare the angular changes in the developing mandibular third molars in the mandibular second premolar extraction and non-extraction cases and to determine whether the mandibular second premolar extraction causes favorable rotational changes in the angulations of the developing mandibular third molars and benefits its later eruption. METHODS: Pretreatment and posttreatment panoramic radiographs were taken from 45 subjects who had been treated by the extraction of the mandibular second premolars and 48 subjects who had been treated without extraction. The horizontal reference plane was used to measure and compare the changes in the angulations of the developing mandibular third molars. RESULTS: The mean uprighting of the mandibular third molars seen in the extraction group was (5.9±2.5) degrees on the right side and (8.0±3.4) degrees on the left side following treatment. For the nonextraction group the mean uprighting was (1.8±2.4) degrees on the right side and (1.5±2.1) degrees on the left side. There was a statistically significant difference between the groups (P<0.05). CONCLUSION: Mandibular second premolar extraction might be a helpful procedure on the angulations of the developing mandibular third molars.

The influence of impaction on the rate of third molar mineralisation in male black Africans.

One of the main criteria used in dental age diagnostics in living adolescents and young adults is assessment of the mineralisation stage of the third molars. In the case of Europid populations, it has been established that impaction status has an influence on the rate of mineralisation of the third molars. In view of this, a study was undertaken to determine whether the chronological process of wisdom tooth mineralisation is dependent upon impaction status in black Africans too. Orthopantomograms (553) of 437 male and 116 female black South Africans with verified birth dates in the age group between 10 and 26 years were studied. Mineralisation stage and impaction status were determined for all third molars. Statistical measures were calculated for the mandibular wisdom teeth at stages F, G and H and for the maxillary wisdom teeth at stage H in the male gender for both impacted and non-impacted third molars. It was ascertained that the minimum age in persons with impacted third molars, depending on the wisdom tooth observed, was 0.19-2.57 years higher than in those with non-impacted wisdom teeth. Test persons with impacted mandibular wisdom teeth at stage F or G were on average between 0.32 and 1.88 years older than those with non-impacted mandibular wisdom teeth. The 50 % probability values of impacted wisdom teeth at stage H were 1.85-3.31 years higher than those in non-impacted wisdom teeth. The conclusion was drawn that in male black Africans, impacted mandibular wisdom teeth mineralise more slowly than non-impacted lower third molars. The presence of impacted mandibular wisdom teeth in mineralisation stage H in male black Africans does not, however, furnish proof of completion of the 18(th) year of life beyond reasonable doubt.

Predictive model of third molar eruption after second molar extraction.

INTRODUCTION: Extraction of second permanent molars is an option for providing space in orthodontic treatment. Although many articles have described its impact on the outcome, there are few data on the prognosis of the eruption of the adjacent third molars. The aims of this investigation were to provide predictive models of eruption of third molars after second permanent molar extraction and to validate them. METHODS: A total of 48 patients (ages, 11-23 years) who had 128 second permanent molars (54 maxillary, 74 mandibular) extracted during orthodontic treatment were followed until eruption of the third molars was complete. RESULTS AND CONCLUSIONS: A lineal regression model predicted the final angle of the third molars with the permanent first molar by using the variables of initial angle, jaw, and the developmental stage of the third molar. A logistic regression model predicted the probability of correct eruption by using the variables of initial angle, jaw, sex, age, and the developmental stage of the third molar.

Clinical study of frontal chewing patterns in various crossbite malocclusions.

INTRODUCTION: The purpose of this study was to clarify the frontal chewing patterns of various crossbite malocclusions. METHODS: A mandibular kinesiograph was used to record the masticatory movements of 106 subjects (ages, 12-35 years) with crossbite malocclusion and 22 subjects (ages, 16-30 years) with normal occlusion. The chewing patterns were classified into 8 chewing types according to the cycle shape of the frontal incisor point movement. The crossbite subjects were divided into 5 groups by the anteroposterior position of the crossbite, and then the subjects with posterior crossbite were divided into 3 groups by the transverse position of the crossbite. The Mann-Whitney U test was used to compare the frequency of each chewing type between any crossbite group and the control group; and between the various crossbite groups. RESULTS: In the crossbite groups, normal chewing occurred much less often than in subjects with normal occlusion. In the posterior crossbite group, reverse chewing was greater (P = 0.002), and normal chewing was less frequent (P = 0.001) compared with the anterior crossbite group. When accompanied by mandibular shift, mandibular prognathism, arch crossbite, in the crossbite or shift side, reverse type, and reverse-crossing type occurred more often than in contralateral side. CONCLUSIONS: In the frontal plane, patients with posterior crossbite might have more abnormal chewing types than those with anterior crossbite, and posterior crossbite could contribute to the high frequency of reverse and reverse-crossing chewing types, especially when accompanied by mandibular shift, mandibular prognathism, or arch crossbite.

Effects of orthodontic treatment and premolar extractions on the mandibular third molars.

BACKGROUND: The space available for an unerupted mandibular third may depend on the choice of premolar extracted. AIMS: To investigate the effects of orthodontic treatment and premolar extractions on the inclinations of the mandibular third molars and the space available for their eruption, and to compare these changes with a nonextraction group. METHODS: The pre- and post-treatment panoramic radiographs of 54 subjects (20 males, 34 females) were used. Eighteen of these subjects had the four first premolars extracted, 16 subjects had four second premolars extracted and 20 subjects were treated nonextraction. Changes in the inclinations and spaces available for the unerupted third molars were compared. RESULTS: In the nonextraction group the third molars uprighted approximately 1 degree and in the second premolar extraction group the third molars uprighted 10 degrees. The spaces available for the third molars increased significantly in the first and second premolar extraction groups as compared with the space available in the nonextraction group. CONCLUSIONS: Orthodontic treatment and extraction of the second premolars improved the inclinations of unerupted third molars and the space available for their eruption into the arch. The changes in inclination and eruption space were less marked following first premolar extractions.

Unusual cause of tooth mobility.

We describe a case of a 71-year-old otherwise healthy man who presented to the dental clinic with the chief complaint of mobility involving his upper left molar teeth. The patient was a febrile, and clinical oral examination revealed localised grade II mobility and absence of gingival swelling, erythema or sinus tract. Orthopantogram revealed a poorly defined radiolucency involving the upper left second and third molar teeth. Surgical exploration of the involved area was performed and revealed the presence of a 'jelly like' brown tissue that fragments easily. Pathological examination confirmed the diagnosis of diffuse large B cell lymphoma.

Rotational drift of mandibular third molar teeth: a series of four cases.

Rotational drift of mandibular third molar teeth is a challenge for clinicians to predict and manage. Evidence on the incidence and degree of rotation is sparse. As the factors influencing rotation are not defined, prediction is impossible. A series of four cases with lower third molar rotation are presented and discussed. Significant rotation can alter the degree of difficulty for an extraction. A lack of well-documented cases has hindered investigation of this phenomenon. Further research is required to identify the aetiology, incidence and increase in risk factors caused by such rotational drift.

Opinions of American and Swedish orthodontists about the role of erupting third molars as a cause of dental crowding.

OBJECTIVE: To compare the opinions of Swedish orthodontists and American orthodontists regarding the association between third molar eruption and dental crowding. MATERIALS AND METHODS: A survey was distributed to Swedish orthodontists (n = 230) asking their views on the force exerted by erupting third molars, its relationship to crowding, and their recommendations for prophylactic removal. Results were compared with those from a similar study conducted in the United States. Chi square analysis was used to determine differences in responses to questions between Swedish and American orthodontists. P < or = .05 was considered significant. RESULTS: Both Swedish and American orthodontists believed that lower third molars were more likely than upper third molars to cause force (65% and 58% for Swedish and American orthodontists, respectively) and crowding (42% and 40%, respectively). No statistically significant differences were seen between the answers of American and Swedish orthodontists regarding the role of upper and lower third molars in causing crowding. Although only 18% of Swedish orthodontists "generally" or "sometimes" recommended prophylactic removal of mandibular third molars, 36% of American orthodontists "generally" or "sometimes" recommended removal (P < .0001). CONCLUSIONS: Most orthodontists in the United States and Sweden do believe that erupting lower third molars exert an anterior force; however, they also believe that these teeth "rarely" or "never" cause crowding of the dentition. The reason that more American orthodontists recommend prophylactic removal of mandibular third molars remains unexplained.

Craniodental Allometry, Prenatal Growth Rates, and the Evolutionary Loss of the Third Molars in New World Monkeys.

A growing body of literature demonstrates that genetic patterning mechanisms underlie the relative proportions of the mammalian postcanine dentition with the third molar being key to understanding variation within the molar row. With this relatively recent insight, there has been renewed interest in mammalian taxa that have lost the third molars. Within platyrrhines, the marmosets and tamarins (Callitrichidae family) are characterized by small body size, claw-like nails, twinning, and reduced molar number. Small body size is hypothesized to have resulted in the third molar being crowded out of the jaws leading to its evolutionary loss in this family. To further explore this hypothesis, we measured the cranium and dentition of 142 individuals spanning all five platyrrhine families. These data reveal that callitrichids have a significantly smaller proportion of mandibular postcanine tooth row length relative to other platyrrhines, refuting the "crowding out" hypothesis. However, postcanine tooth row length is significantly correlated with mandibular length and cranial length (P < 0.01) across all platyrrhines providing evidence for a strong allometric association between postcanine tooth row length and body size more generally. The small body size that characterizes callitrichids results in part from slower prenatal growth rates. Given the allometric relationship between postcanine tooth row length and body size, reported here and in previous studies, we hypothesize that the evolutionary loss of the third molars in callitrichids results from the inhibition of third molar development as a consequence of the slower prenatal growth rates associated with small body size in this family. Anat Rec, 302:1419-1433, 2019. © 2018 Wiley Periodicals, Inc.

Dislocation of an upper third molar by an ossifying fibroma--case report.

BACKGROUND: The occurrence of ossifying fibromas (OFs) in childhood and adolescence has been described in the literature, along with different courses of the disease due to different growth rates. CASE REPORT: In the case of the 15-year-old female patient presented here, an OF resulted in displacement of a maxillary third molar far into the maxillary sinus. It is assumed that the tumour originated coronal to the affected tooth 18. Radiographs document an initial rapid growth of this tumour over a period of 2 years, while its growth almost completely ceased in the next 2 years immediately prior to diagnosis and surgical treatment. The operation was complicated by unexpected profuse bleeding from the tumour tissue. CONCLUSION: The peculiarity of the OF in the case presented here is its similarity, in terms of clinical and radiological appearances, with a follicular cyst, its unusual place of origin that resulted in the migration of the tooth 18 into the maxillary sinus, its different growth dynamics, and the pronounced haemorrhage encountered as the tumour was surgically removed.

Radiographic study of the positional changes and eruption of impacted third molars in young adults of an Asian Indian population.

PURPOSE: The aim of the study was to assess changes in the angular position and eruption status of third molars in students of an Asian Indian population during a 4-year follow-up period. PATIENTS AND METHODS: The series consisted of 43 students (11 males, 32 females). Standardized panoramic radiographs were taken at baseline (mean age, 19.1 +/- 0.7 years) and at the end of study (mean age 23.1 +/- 0.7 years). Angulation and degree of impaction of third molars were determined by their sagittal relationship to the adjacent second molar and eruption to the occlusal plane. Root formation was also assessed. RESULTS: During the 4-year follow-up period, 11 of 72 of the mandibular teeth (15%) and 17 of 74 of the maxillary teeth (23%) changed their sagittal inclination. Thirty-one of 118 impacted teeth (26%; level B + C) achieved level A eruption more so in the mandible, ie, 15 of 52 (29%), than in the maxilla, ie, 16 of 66 (24%). In the mandible, 9 of 24 impacted vertical teeth (37.5%), 3 of 6 distoangular teeth (50%), and 3 of 22 mesioangular impacted teeth (13.6%) erupted to the occlusal plane. In the maxilla, 9 of 36 impacted vertical teeth (25%) and 7 of 27 distoangular teeth (26%) erupted to the occlusal plane during the follow-up. The number of teeth with complete root formation increased in mandible from 61% to 93% and in maxilla from 62% to 94.5%. CONCLUSIONS: Unpredictable changes in the position and angulation of teeth continued to occur even after the age of 19 years, more so in vertical and distoangular teeth than in mesioangular teeth.

The impact of retained third molars on the deployed airman.

Dental emergencies can significantly affect the mission of the deployed unit. As many as 22% of all emergency department visits at a deployed Expeditionary Medical Support facility can be attributed to dental problems and many of these problems are caused by impacted third molar teeth. Currently, there is no reliable method of predicting when asymptomatic, partially erupted third molar teeth will become painful. Therefore, it is imperative that Air Force dental providers carefully consider the consequences of giving patients a clean bill of health when asymptomatic, partially erupted third molar teeth are present in the oral cavity. Recommendations for future study are presented.

Does the angulation of the mandibular third molar influence the fragility of the mandibular angle after trauma to the mandibular body? A three-dimensional finite-element study.

The relationship between mandibular third molar (M3) angulation and mandibular angle fragility is not well established. The aim of this study was to evaluate the impact of M3 angulation on the mandibular angle fragility when submitted to a trauma to the mandibular body region. A three-dimensional (3D) mandibular model without M3 (Model 0) was obtained by means of finite-element analysis (FEA). Four models were generated from the initial model, representing distoangular (Model D), horizontal (Model H), mesioangular (Model M) and vertical (Model V) angulations. A blunt trauma with a magnitude of 2000 N was applied perpendicularly to the sagittal plane in the mandibular body. Maximum principal stress (Pmax) (tensile stress) values were calculated in the bone. The lowest Pmax stress values were noted in Model 0. When the M3 was present extra stress fields were found around marginal bone of second molar and M3. Comparative analysis of the models with M3 revealed that the highest level of stress was found in Model V, whereas Model D showed the lowest stress values. The angulation of M3 affects the stress levels in the mandibular angle and has an impact on mandibular fragility. The mandibular angle becomes more fragile in case of vertical impaction when submitted to a trauma to the mandibular body region.