Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MOLAR”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed1978

A cephalometric evaluation of high-pull molar headgear and face-bow neck strap therapy.

The effects of two different extraoral appliances were evaluated over a 1-year period. Of the thirty-seven cases selected for study, twenty were treated with a face-bow neck strap and seventeen were treated with a high-pull molar headgear. Patients ranged in age from 10.10 to 16.6 years and averaged 13.4 years. The appliances exerted less than 600 Gm. of force per side and were worn for 12 to 16 hours per day. All cases were fully banded, and extraction and nonextraction treatment were included. An analysis of pretreatment data revealed a high degree of selection. Patients selected for high-pull treatment generally exhibited larger anterior face heights, steeper mandibular plane angles, and a greater amount of tooth eruption of the upper first molars than the patients selected for neck strap therapy. A control group of ten untreated subjects was matched to each treatment group to permit assessment of the impact of treatment on growth. Relative to normal growth, treatment with face-bow neck strap traction tended to direct the maxilla and mandible downward and backward. The palatal plane was lowered anteriorly and point A was retracted. The maxillary molars were extruded, and concomitantly an increase in anterior face height and mandibular plane angle was observed. On the other hand, the high-pull molar headgear traction resulted only in increased mandibular molar eruption. However, there was also a nonsignificant tendency for point A to be held back and for lower anterior face height to increase. The comparison of the two treatment samples revealed that the functional occlusal plane was tipped down at the back as the maxillary molars were more extruded in the neck strap sample. In the high-pull sample, the functional occlusal plane was unchanged and the mandibular molars were more extruded than they were in the neck strap group.

Adolescent↗
PubMed1983

Ectopic eruption of the maxillary first permanent molar: etiologic factors.

For clinical handling, it is important to determine whether any etiologic factors, alone or in combination, are of more importance than others in causing ectopic eruption of a maxillary first permanent molar. Etiologic factors involved in ectopic eruption of maxillary first permanent molars were investigated in 129 children with a mean age of 8.6 years. Ninety-two children (fifty-eight boys and thirty-four girls) had ectopic eruption and thirty-seven children served as controls and were matched by age and sex. Two types of ectopic eruption could be distinguished: a reversible type in which the permanent molar frees itself and an irreversible type in which the permanent molar remains in a locked position. Measurements were made on lateral head films, orthopantomograms, and dental casts. For 104 subjects all variables could be measured. Data was analyzed by discriminant analysis. Children with irreversible ectopic eruption had significantly larger permanent molars and a more pronounced mesial angle of eruption. A tendency toward a shorter maxilla was also found. No significant difference was found between sides with reversible ectopic eruption and sides with normal eruption. From the discriminant analysis between groups and all variables investigated, 90.7 percent of the cases could be correctly classified into groups. This study indicates that sufficient space may be gained for the premolars if the mesial tipping of the first molar is corrected, despite the tendency toward a shorter maxilla and larger than normal permanent molars.

Cephalometry↗
PubMed1984

Organ culture study of effect of vitamin-A-deficiency on rat third molar development.

A culture procedure for rat third molars suitable for nutritional-developmental studies is described. Unerupted third molars from 12-day-old rats were cultured in BGJb media containing 20 per cent rat serum and supplemented with 25 mM HEPES buffer, 25 mg ascorbic acid, 20 mg L-glutamine, 12 mg penicillin G and 10 mg streptomycin sulphate per 100 ml of media. Molars were cultured at the liquid-gas interphase using a 50 per cent O2, 45 per cent N2, 5 per cent CO2 gas mixture at 10 lb-psig (pounds per square inch guage). Molar cultures were maintained successfully for 9-14 days without evidence of necrosis, although they developed at a slower rate than in vivo. Molars cultured in 50 per cent O2 compared to those cultured in 21 per cent O2 for periods of 2, 4, 6 and 8 days had higher values for protein, alkaline phosphatase (AP), Ca, P and Ca/P. Vitamin-A-deficiency gave lower values for AP, Ca, P, Ca/P, 45Ca, 35S and [14C]-proline uptake. Histologically, A - molars had atrophic ameloblasts, some foci of squamous metaplasia and abnormal keratin formation. Thus, deficiency of vitamin A imposed during in-vitro development of rat third molars retarded dentinogenesis and interfered with early mineralization of enamel and dentine.

Aging↗
PubMed1991

Third molar eruption among rural Nigerians.

Times of eruption of third molars were studied in rural Nigerian adolescents--125 males and 133 females. Results of this study showed that the average age for the initial eruption of third molars was 15 years in male subjects and 13 years for female subjects. The incidence of eruption showed a steep rise after the age of 16 years for male subjects and 14 years for female subjects. By the age of 19 years, all third molars had erupted into the oral cavity. The eruption of lower third molars was generally ahead of the upper third molars for all age groups. The results of this study suggest that (1) the timing of third molar eruption is strongly influenced by the availability of mandibular trigone space, (2) the attrition and shrinkage of the dental arch, probably as the result of nonrefined highly fibrous diets, produce larger mandibular trigone spaces, and (3) the early eruption of third molars observed in the present study may be due to the nature of the diet used and the vigorous employment of the masticatory apparatus (from infancy) by the subjects examined.

Adolescent↗
PubMed1993

Third molars as an acute problem in Finnish university students.

The study was carried out to determine the risk of acute disease of third molars in young adult patients. The subjects in this case-control study were 100 consecutive university students who complained of third molar problems when making an appointment. The third molars were mostly mandibular, partly erupted, and distoangularly oriented. Severity of discomfort and interference with daily activities were graded by the patients on average as 5.0 (SD +/- 2.7) and 3.6 (SD +/- 2.9), on a scale from 0 through 10. Distoangular lower third molars caused the most discomfort and interfered most with activities of patients. The risk of acute disease in patients with distoangularly oriented third molars was 3.6 times that in other patients. Bivariate analysis showed that if the follicle of a distoangular third molar were enlarged, the risk of acquiring acute disease was 44 times that in other patients. It was concluded that early removal of partially erupted and distoangularly oriented lower third molars is recommended, especially when they are associated with an enlarged follicle.

Acute Disease↗
PubMed1995

Are mandibular third molars a risk factor for angle fractures? A retrospective cohort study.

PURPOSE: Anecodotal reports suggest that the presence of mandibular third molars predispose the mandible to angle fractures. The purpose of this study was to evaluate mandibular third molars as risk factors for angle fractures in a patient sample with fractured mandibles. MATERIALS AND METHODS: The medical records and panoramic radiographs of a patient cohort with mandible fractures was retrospectively reviewed. Data were collected for the following variables: age, sex, race, mechanism of injury, number and location of mandible fractures, and the presence and position of the mandibular third molars. RESULTS: Of the 73 patients with mandibular third molars, 30 (41.1%) had angle fractures. Of the 28 patients without mandibular third molars, 3 (10.7%) had angle fractures (P = .004). CONCLUSION: The results of this study demonstrate that patients with fractured mandibles and mandibular third molars are 3.8 times more likely to have an angle fracture than patients without mandibular third molars.

Adult↗
PubMed2004

Distal movement of mandibular molars in adult patients with the skeletal anchorage system.

The skeletal anchorage system (SAS) consists of titanium anchor plates and monocortical screws that are temporarily placed in either the maxilla or the mandible, or in both, as absolute orthodontic anchorage units. Distalization of the molars has been one of the most difficult biomechanical problems in traditional orthodontics, particularly in adults and in the mandible. However, it has now become possible to move molars distally with the SAS to correct anterior crossbites, maxillary dental protrusion, crowding, and dental asymmetries without having to extract premolars. This study evaluated the treatment and posttreatment changes during and after distalization of the mandibular molars. In 15 adult patients (12 women and 3 men), a total of 29 mandibular molars were successfully distalized with SAS. The amount of distalization and relapse and the type of tooth movement were analyzed with cephalometric radiographs and dental casts. The average amount of distalization of the mandibular first molars was 3.5 mm at the crown level and 1.8 mm at the root level. The average amount of relapse was 0.3 mm at both the crown and root apex levels. Of 29 mandibular molars, 9 were tipped back, and the others were translated distally in accordance with the established treatment goals. SAS is a viable modality to move mandibular molars for distally correcting anterior crossbites, malocclusions characterized by mandibular anterior crowding, and dental asymmetries.

Adult↗
PubMed2004

Dentoskeletal effects induced by rapid molar distalization with the first class appliance.

The purpose of this study was to evaluate the treatment effects of the first class appliance (FCA; Leone, Firenze, Italy), a new intraoral device for unilateral or bilateral rapid molar distalizaton. A retrospective study was conducted to compare the predistalization and postdistalization cephalograms of 17 patients (10 male, 7 female) with Class II malocclusions treated with the FCA. Mean age at the start of treatment was 13 years 4 months. The FCA produced rapid molar distalization, and the bilateral Class II molar relationship was corrected in 2.4 months, on average. Maxillary molar distalization contributed to 70% of the space created anterior to the first molars; 30% of the space was due to reciprocal anchorage loss of the maxillary second premolars. The maxillary first molars showed a significant distalization of 4.0 mm, associated with a significant distal axial incline of 4.6 degrees and a significant extrusion of 1.2 mm. As for anchorage loss, the second premolars exhibited a significant mesial movement of 1.7 mm, associated with a significant mesial axial incline of 2.2 degrees and a nonsignificant extrusion of 1.0 mm. In the anterior region, a significant mesial movement of the maxillary incisor of 1.3 mm was associated with a significant incisor proclination (2.6 degrees ) and a significant increase in overjet (1.2 mm). No significant changes in either sagittal or vertical skeletal relationships were observed. The results suggest that the FCA is an efficient and reliable device for distalizing the maxillary permanent first molars.

Adolescent↗
PubMed2005

A comparison of two intraoral molar distalization appliances: distal jet versus pendulum.

INTRODUCTION: This study compared the dentoalveolar and skeletal effects on Class II malocclusions of the distal jet with concurrent full fixed appliances and the pendulum appliance both followed by fixed appliances. METHODS: The 2 samples each consisted of 32 subjects (19 girls and 13 boys) with mean ages at the start of treatment of 12 years 3 months in the distal jet group and 12 years 6 months in the pendulum group. The durations of the distalization phase of treatment were 10 months in the distal jet group and 7 months in the pendulum group, and the durations of the second phase of treatment with fixed appliances were 18 months in the distal jet group and 24 months in the pendulum group. Lateral cephalograms were analyzed at 3 observation times: before treatment, after distalization, and after orthodontic treatment. RESULTS: During molar distalization, the pendulum subjects showed significantly more distal molar movement and significantly less anchorage loss at both the premolars and the maxillary incisors than the distal jet subjects. The distal jet used simultaneously with fixed appliances and the pendulum were equal in their ability to move the molars bodily. Very little change occurred in the inclination of the mandibular plane at the end of the 2-phase treatment (less than 1 degrees ) in both groups. At the end of comprehensive treatment, the maxillary first molars were 0.6 mm mesial to their original positions in the distal jet group and 0.5 mm distal in the pendulum group. Nevertheless, total molar correction was identical in the 2 groups (3.0 mm), and both appliances were equally effective in achieving a Class I molar relationship. Simultaneous edgewise orthodontic treatment during molar distalization in the distal jet group shortened the overall treatment time but produced significant flaring of both maxillary and mandibular incisors at the end of treatment. The impact on the soft tissue profile was minimal with both appliances.

Adolescent↗
PubMed2005

Relationship between the presence of unerupted mandibular third molars and fractures of the mandibular condyle.

Previous studies have shown that the presence of unerupted mandibular third molars predisposes the mandible to angle fractures. This study attempted to relate the presence of unerupted mandibular third molars with the incidence of condyle fractures. The authors compared the proportion of fractures in 439 patients who had unerupted third molars or no unerupted third molars. Fractures at the condylar region showed a significantly higher incidence in patients without unerupted third molars than in those patients with unerupted third molars. This study provides solid clinical evidence to suggest that the removal of unerupted mandibular third molars predisposes the mandible to condyle fractures.

Adult↗
PubMed2006

Assessment of oral health-related quality of life before and after third molar surgery.

PURPOSE: This study was designed to further our understanding of recovery after third molar surgery by using 2 instruments to measure quality of life outcomes, the more global Oral Health Impact Profile (OHIP-14), and the condition-specific Health-Related Quality of Life (HRQOL) instrument. PATIENTS AND METHODS: Clinical and quality of life data pre- and postsurgery from 63 patients with all 4 third molars below the occlusal plane, treated with topical minocycline during third molar surgery to reduce the incidence of delayed clinical healing, were available for analyses. Each patient was given 2 questionnaires to complete; the more global OHIP-14 and the HRQOL instrument designed to assess recovery after third molar surgery. Prevalence, Extent, and Severity of the OHIP-14 scores were calculated presurgery and for postsurgery days (PSD) 1, 7, 14. The percentage of patients reporting clinically relevant responses detrimental to quality of life from the condition-specific HRQOL instrument were reported for the same time frame. RESULTS: Study patients were most likely female, less than 25 years old, and Caucasian. Most (72%) had bone removed from both lower third molars. Median surgery time was 27 minutes (interquartile range [IQ], 20, 40 minutes.). Median surgeons' estimate of overall difficulty was 14 of a possible 28 (IQ 10, 18), and the median degree of difficulty for lower third molars was 8 of 14 (IQ 6, 10). Few patients (only 10%) had delayed clinical healing. Prevalence for all OHIP-14 items, percent of patients reporting items "fairly often" or "very often," were increased from presurgery on PSD 1 and then decreased on PSD 7 and PSD 14. OHIP-14 Severity scores, the sum of OHIP-14 responses, followed the same pattern as the Prevalence scores. OHIP-14 Severity scores on PSD 1 were 27 (IQ 16, 34), decreasing to 8 (IQ 3, 13) by PSD 7, and 1 (IQ 0, 5) by PSD 14. Recovery for outcomes addressed by both instruments followed a similar pattern and time course. However, each instrument also assessed distinctly different outcomes, adding information that could not be obtained by 1 instrument alone. CONCLUSION: Complementary instruments to measure quality of life outcomes provide a broader understanding of recovery after third molar surgery.

Adult↗
PubMed2003

Finite element analysis of stresses in molars during clenching and mastication.

STATEMENT OF PROBLEM: During physiological functions of the masticatory system such as swallowing and chewing, teeth are subjected to variations in force application. Most in vitro analyses of stress have not analyzed the combined forces acting on teeth. PURPOSE: The purpose of this study was to analyze the stresses induced in a mandibular molar during clenching and chewing of morsels with various elastic moduli. MATERIALS AND METHODS: The investigation was performed by means of finite element analysis with the use of contact elements. Two-dimensional models of the mandibular first molar and the crown of the opposing maxillary molar were created. The computerized simulation evaluated the clenching and chewing of 4 morsels with different elastic moduli (similar to hard gum, tough meat, bone, and combination of hard gum and bone). The movement of the studied teeth was simulated in the frontal plane. Teeth models crushed morsels and closed into the maximal intercuspation position. The values of stresses in the mandibular molar were calculated during these situations. RESULTS: The study revealed that clenching of molars and chewing morsels of high elastic moduli resulted in maximal equivalent stresses within occlusal enamel. During mastication of morsels of low elastic moduli the stress concentration was located in the cervical region of the lingual side of the mandibular molar. Masticating a low-elasticity morsel containing a fragment of bone caused the highest equivalent stresses in the lingual wall and high tensile stresses in enamel near the central intercuspal fissure of the tooth studied. CONCLUSION: During mastication of various morsels, maximal equivalent stresses occurred in occlusal enamel and in the cervical region of the lingual wall of the first mandibular molar. The more unfavorable and highest stresses were exerted during mastication of nonhomogeneous morsels.

Bite Force↗
PubMed2005

Risk of periodontal defects after third molar surgery: An exercise in evidence-based clinical decision-making.

OBJECTIVE: The object of this study was to apply evidence-based principles to answer the question, What is the risk of having periodontal defects on the distal aspect of the mandibular second molar (M2) following third molar (M3) removal? STUDY DESIGN: To identify relevant articles for review, we completed a computerized literature search of Medline. The inclusion criteria for articles included prospective cohort studies or randomized clinical trials with follow-up periods of 6 months or more, and preoperative and postoperative measurements of periodontal probing depths (PDs) or attachment levels (ALs). RESULTS: Eight articles met the inclusion criteria. Overall, the reported mean changes in ALs or PDs on the distal of M2 6 months after M3 removal were clinically insignificant, ie, less than 2 mm. Six months after M3 removal, 52% to 100% of subjects had no change or improvement in ALs or PDs. Given periodontal disease present preoperatively, the number needed to treat (NNT) ranged from 3 to 10. Given healthy periodontal status preoperatively, 48% had worsening of their periodontal measures after M3 removal and the number needed to harm (NNH) was 2. CONCLUSION: Commonly, the second molar periodontal probing depth or attachment levels either remain unchanged or improve after third molar removal. For subjects with healthy second molar periodontium preoperatively, the indication for third molar removal needs to be evaluated carefully as these subjects have an increased risk for worsening of probing depths or attachment levels after third molar removal.

Alveolar Bone Loss↗
PubMed2006

Panoramic radiographic predictors of mandibular third molar eruption.

OBJECTIVE: Third molar (M3) eruption can be problematic. According to some orthodontic surgeons, the teeth are capable of aggravating the average crowding level in the dental arch. The question is whether it might be possible to give a prognosis for ultimate M3 position in the arch and make an early decision to extract or retain them. The purpose of the study was to determine which measurements made on panoramic tomograms might facilitate prognosis for M3 position in the dental arch over the years. STUDY DESIGN: The investigation involved 64 patients who had been enrolled to the study group 10 years earlier, ie, in 1993, when an analysis had been carried out regarding M3 effect on dental arch crowding. At that time panoramic tomograms had been taken, and dental casts made. The procedures were repeated in 2003. The following measurements were taken at baseline (1993) and at the end of the study (2003): (1)/the retromolar space to lower third molar crown width, (2) third molar angulation to the base of the mandible, and (3) third molar to second molar inclination. RESULTS: At some defined values of the Ganss ratio, and M3 inclination to mandibular base and second molar, it is possible to predict potential lower third molar alignment in the dental arch using a panoramic radiograph.

Adolescent↗
PubMed2002

Age-related and site-specific changes in the pulpodentinal morphology of rat molars.

The rat molars are frequently used as experimental models in endodontic research, but there is little systematic information available on the influence of age on the pulpodentinal organ in Wistar rat molars and it is often difficult to evaluate more subtle changes following experimental interventions. The aim here was to describe changes with age in first upper Wistar rat molars with specific reference to the pulpodentinal organ. Animals were perfused with glutaraldehyde at 19 days, 1, 3, 6, 8, 12, 16, or 24 months of age. First upper molars from 56 animals were demineralized in EDTA, embedded in Epon, and processed for light and transmission electron microscopy. Substantial variation in the structure of the dentine and odontoblasts was observed within the root canals and the coronal pulp chamber. In general, odontoblasts changed from a tall, columnar morphology in the coronal pulp chamber to a more cuboidal or flattened shape near the apex, particularly towards the interradicular space. Secondary dentine formation was more pronounced along the mesial aspect of the root chamber and corresponding to the bottom of fissures. Local tertiary dentine formation was layered in the upper pulp chamber, corresponding to occlusal attrition of the cusp. In several molars a local formation of irregular tertiary dentine was observed cervically in the mesial pulp chamber. After 1 year, a distinct protrusion of irregular dentine extended into the mesiocervical pulp, apparently corresponding to a denudation of cervical root dentine. Experimental pulp-capping studies frequently use first upper rat molars with perforations made through the mesial aspect of the crown; such perforations might be close to the irregular dentine in the mesiocervical region. In conclusion, this study identifies age-associated and regional changes of pulpodentinal morphology in first upper rat molars. Therefore, evaluation of morphological alterations following vital-pulp experiments should be done in specific age groups and at specific sites in the pulp.

Aging↗
PubMed2002

A three-dimensional analysis of enamel distribution patterns in human permanent first molars.

The morphology of the enamel cap and the thickness of the enamel of human molars are regarded as closely related to function. Previously, enamel thickness has been studied in specific sections only, not the distribution patterns of the entire crown. Here, the three-dimensional distribution pattern of the enamel of human permanent first molars was examined with a newly developed system. A distinctive pattern of enamel thickness common to all the individuals examined was found, regardless of the variation in absolute enamel thickness among individuals. It was confirmed that the lingual faces of upper molars and the buccal faces of lower molars have thicker enamel than the other crown faces. Moreover, in lower molars, enamel was significantly thicker at the hypoconid than at the protoconid crown face. The distal face tended to exhibit thicker enamel than either mesial or lingual faces, owing to the thicker hypoconulid enamel. It is suggested that the gradients of thickness within a molar are not necessarily manifested according to direction, but are the result of cusp-specific patterning. The distribution of enamel in the occlusal fovea was found to correspond to the morphology of the outer enamel surface, with the exception of the distinctly thin enamel at and near the tip of the mesiobuccal cusps in both upper and lower molars. The thickness of the enamel in that region might therefore be related to developmental timing or the topography of the enamel-dentine junction, rather than to functional demand. When viewed from a whole-crown, three-dimensional perspective, enamel thickness patterns are in part, but not entirely, explained as an adaptation to functional demand.

Child↗
PubMed1999

Third molar management: a case against routine removal in adolescent and young adult orthodontic patients.

In the nearly two decades since the National Institutes of Health conference, controversy and uncertainty have continued with respect to the diagnosis and treatment of impacted, nondiseased third molars in adolescents and young adults. Articles published over the past 10 years have studied the issue from the vantage point of risk management. Those who favor prophylactic removal justify this action on three premises: 1. All impacted third molars are potentially pathologic; therefore, prophylactic removal reduces or eliminates risk of future disease. 2. The presence of third molars can cause late crowding. 3. Removal during adolescence and young adulthood reduces risks of operative and postoperative complications compared with older patients. Those who favor conservative management offer three counter arguments: 1. Although impacted third molars do pose a risk of a pathologic condition, the risk is relatively small in comparison with the risks of operative and postoperative complications and the costs of unnecessary removal. 2. Although some investigators have shown a statistical association of third molars and late anterior crowding, the association is not strong enough to allow prediction of patients at risk. This is due principally to the high degree of individual variability, suggesting that many other factors interact in the development of postadolescent crowding. 3. Although studies have shown that morbidity is reduced when impacted, nondiseased third molars are removed during adolescence or young adulthood, the cost-risk-benefit data do not justify routine removal. Proponents of prophylactic removal argue that the benefits outweigh the risks. Proponents of conservative management argue that the scientific evidence is inconclusive in support of prophylactic removal. Unfortunately, much of the clinical research has been flawed. This has led to contradictory interpretations that have not fully clarified the relative risks and benefits of early intervention. Untrustworthy data have served only to fuel the debate and controversy concerning proper protocols. However, careful analyses of the published research show that routine removal of impacted or unerupted, disease-free third molars cannot be justified. A case-by-case management protocol that requires monitoring development represents the consensus of most researchers in this field.

Adolescent↗
PubMed1990

Late lower arch crowding: the effect of second molar extraction.

Mesial drift and change in crowding over a 5-year period were compared in 30 subjects whose lower second molars were extracted between ages 11 and 17 years and 30 subjects whose lower second molars were not extracted. Significant differences were found. The nonextraction subjects showed an average forward movement of first molars and an increase in crowding. The extraction group showed slight distal movement of first molars and a decrease in crowding. It is concluded that lower second molar extraction reduces the tendency to forward movement of buccal segments and increased crowding by relieving eruptive pressure from third molars and that the presence of a developing lower third molar with insufficient space can be one cause of late lower arch crowding.

Adolescent↗