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American Journal of Orthodontics and... May 2020This study aimed to compare the 3-dimensional force system produced by transpalatal arch (TPA) mechanics with that produced by a continuous arch (CA) on the expansion of...
INTRODUCTION
This study aimed to compare the 3-dimensional force system produced by transpalatal arch (TPA) mechanics with that produced by a continuous arch (CA) on the expansion of maxillary first molars.
METHODS
A patient's model with 2 molars in 4-mm crossbite had orthodontic appliances bonded to all teeth. The first and the second molars were connected to two 3-dimensional load cells to compare the forces in the transverse and anteroposterior planes (Fx and Fy) and the rotational moments (Mz) produced in both molars by the expanded TPA and by 0.016-in nickel-titanium CA. The data were evaluated using 6 independent t tests, and the net moment at the molar's center of resistance was also calculated.
RESULTS
All forces and moments were different at both molars. At the first molar, CA produced Fx of 2.60 N, Fy of -0.08 N, Mz of -5.16 N·mm, and Net Mz of -5.68 N·mm, whereas the TPA produced Fx of 2.87 N, Fy of -0.60 N, Mz of -22.08 N·mm, and Net Mz of -25.09 N·mm. At the second molar, the TPA did not produce significant forces and moments, whereas the CA produced Fx of -1.00 N, Mz of 3.95 N·mm, Fy of -0.84 N, and Net Mz of -0.67 N·mm.
CONCLUSIONS
Based on our findings in a clinical set up with the specific horseshoe TPA and archwire tested, with the TPA used only on the first molars and the CA used from one second molar to the other, the mechanics produced different expansion forces at the first molar. The TPA produced a larger rotational side effect on the first molar, whereas the CA produced side effects on the second molar.
Topics: Dental Arch; Humans; Malocclusion; Molar; Orthodontic Appliance Design; Orthodontic Appliances; Tooth Movement Techniques
PubMed: 32354434
DOI: 10.1016/j.ajodo.2019.05.017 -
The Angle Orthodontist Jan 2022To assess the changes in alveolar bone of the mandibular second molars following molar protraction and investigate the factors associated with the alveolar bone changes.
OBJECTIVES
To assess the changes in alveolar bone of the mandibular second molars following molar protraction and investigate the factors associated with the alveolar bone changes.
MATERIALS AND METHODS
Cone-beam computed tomography of 29 patients (mean age 22.0 ± 4.2 years) who had missing mandibular premolars or first molars and underwent molar protraction were reviewed. Alveolar bone level was measured as the distance from the cementoenamel junction at six points, buccal, lingual, mesiobuccal (MB), mesiolingual (ML), distobuccal (DB), and distolingual (DL), of the second molars at pretreatment (T0) and after molar protraction (T1). Factors associated with alveolar bone changes at the distal and mesial of the second molars were assessed.
RESULTS
Mean alveolar bone changes ranged from -1.2 mm (bone apposition) to 0.8 mm (bone resorption). The presence of a third molar impaction at T0 (P < .001), third molar angulation at T0 (P < .001), and Nolla's stage of third molar at T0 (P = .005) were significantly associated with alveolar bone level changes distal to the second molars. Treatment duration (P = .028) was significantly associated with alveolar bone level changes mesial to the second molar.
CONCLUSIONS
Patients with impacted third molars, third molars at an earlier stage of development, and mesially angulated third molars at pretreatment may have less alveolar bone resorption distal to the second molars following protraction. Patients with increased treatment time may have reduced alveolar bone resorption mesial to the second molars.
Topics: Adolescent; Adult; Bicuspid; Cone-Beam Computed Tomography; Humans; Mandible; Molar; Molar, Third; Tooth, Impacted; Young Adult
PubMed: 34587241
DOI: 10.2319/022321-147.1 -
Odontology Jan 2022The shaping outcomes after instrumentation with rotary and reciprocating glide path and shaping systems were evaluated through micro-computed tomography (Micro-CT)....
The shaping outcomes after instrumentation with rotary and reciprocating glide path and shaping systems were evaluated through micro-computed tomography (Micro-CT). Thirty extracted maxillary first molars were selected. Mesio-buccal canals were randomized into two groups (n = 15): rotary system ProGlider and ProTaper Next X1, X2 (PG-PTN) and reciprocating system WaveOne Gold Glider and WaveOne Gold Primary (WOGG-WOG). Specimens were micro-CT scanned before, after glide path and after shaping. Increase in canal volume and surface area, percentage of removed dentin from the inner curvature, centroid shift and canal geometry variation through ratio of diameter ratios (RDR) and ratio of cross-sectional areas (RA) were measured in the apical and coronal levels and at the point of maximum curvature. The number of pecking motions needed to reach the working length (WL) was recorded. One-way ANOVA and post hoc Turkey-Kramer tests were used (p < 0.05). Post-glide path analysis revealed that in the coronal third, RDR was more favorable to PG and centroid shift was lower for WOGG in the apical third. Post-shaping analysis showed a reduced removal of dentin and a more favorable RA for PTN at point of maximum curvature. The number of pecking motions up to WL resulted in different between groups both for glide path and shaping phases. Despite a higher dentin removal for reciprocating instruments at the point of maximum curvature, both systems seemed to produce well-centered glide path and shaping outcomes. Rotary and reciprocating systems seemed able to respect the original canal anatomy.
Topics: Dental Pulp Cavity; Equipment Design; Gold; Molar; Root Canal Preparation; X-Ray Microtomography
PubMed: 34173078
DOI: 10.1007/s10266-021-00631-2 -
Hua Xi Kou Qiang Yi Xue Za Zhi = Huaxi... Jun 2021With a case of mesial impaction of maxillary first and second molar, the mechanical analysis and clinical applications of a self-made helical spring for the uprighting...
With a case of mesial impaction of maxillary first and second molar, the mechanical analysis and clinical applications of a self-made helical spring for the uprighting treatment of mesial impacted molars was introduced.
Topics: Humans; Mandible; Maxilla; Molar; Molar, Third; Tooth Movement Techniques; Tooth, Impacted
PubMed: 34041888
DOI: 10.7518/hxkq.2021.03.018 -
Laboratory Animals Aug 2018Rat molar eruption and occlusion data were compiled from several studies but several inconsistencies were found, rendering the planning of eruptional studies difficult...
Rat molar eruption and occlusion data were compiled from several studies but several inconsistencies were found, rendering the planning of eruptional studies difficult and imprecise. Our aim was to measure eruption and occlusion days, as well as eruption velocity, in the upper and lower three molars from infancy to end of adolescence in the rat. A total of 19 male and female Wistar rats were scanned daily by micro-computed tomography (CT) from day 15 to 70. We measured the eruption of all maxillary and mandibular molars with reference points at the hard palate and mandibular canal at three stages: pre-emergent, pre-occlusal, and functional. Statistical analysis was performed with a mixed-model analysis of variance (ANOVA) and a Sidak post hoc test. The first molar erupts on average on day 17, the second molar on day 20, and the third molar on day 33. The eruption velocity of the first molar was the highest at 90.9 microns/day (standard error (se) = 12.80), followed by the second molar at 65.9 microns/day (se = 5.80), and the lowest was the third at 47.0 microns/day (se = 3.28), ( p < 0.001). On average, the pre-occlusal phase had the highest velocity at 97.2 microns/day (se = 1.72), the pre-emergent was lower at 84.9 (se = 2.29), and the functional was the lowest at 21.7 (se = 0.45), ( p < 0.001). The eruption rate decreased from the first to third molar and was also different between phases: the pre-occlusal phase had the highest rate, closely followed by the pre-emergent phase while the functional eruption rate was significantly lower than the other phases.
Topics: Animals; Female; Longitudinal Studies; Male; Molar; Rats; Rats, Wistar; Time Factors; Tooth Eruption; X-Ray Microtomography
PubMed: 29316852
DOI: 10.1177/0023677217750410 -
Current Medical Imaging 2020To evaluate impacted mandibular third molar tooth region and obtain linear measurements using CBCT images and to assess the relationship between the impacted third molar...
OBJECTIVES
To evaluate impacted mandibular third molar tooth region and obtain linear measurements using CBCT images and to assess the relationship between the impacted third molar and the mandibular canal.
METHODS
CBCT scans of 351 patients (208 females, 143 males) were assessed. Age, gender, and impaction site were recorded for each patient. The relationship of third molars with the vertical axis of second molars, 2nd molar resorption and the relationship between third molar apices and the mandibular canal were assessed. In addition, the distance between ramus and second molar, mesiodistal width of the third molar, the angle between third molar and second molar, and width of the third molar capsule were measured. Binary Logistic Regression, Chi-Square Test, and General Linear Model were used for statistical analysis.
RESULTS
The highest percentage of impaction was found for mesioangular followed by transversal and vertical. The transversal impacted third molars revealed a significant association with adjacent second molar root resorption (p<0.001). There was a statistical significance between the second molar resorption and distance between ramus and second molar (p<0.001). The mesioangular impacted third molars revealed significant relation with the mandibular canal (p<0.05). The most frequent variation found was the dental canal followed by the retromolar canal. In general, higher measurement values were obtained for men when compared to women (p<0.05).
CONCLUSION
CBCT assessment of the third molar region provided useful information regarding impacted mandibular third molar surgery operations.
Topics: Cone-Beam Computed Tomography; Female; Humans; Male; Mandible; Molar; Molar, Third; Tooth, Impacted
PubMed: 33135608
DOI: 10.2174/1573405616666200103094611 -
Journal of Oral and Maxillofacial... Apr 2018This study aimed to investigate the prevalence of juxta-apical radiolucency (JAR), assessing its association with third molar status and describing its radiologic...
PURPOSE
This study aimed to investigate the prevalence of juxta-apical radiolucency (JAR), assessing its association with third molar status and describing its radiologic features through panoramic radiography.
MATERIALS AND METHODS
We evaluated 1,050 radiographs (1,830 third molars) for the presence of JAR. The JAR and control groups were classified according to the third molar's angulation, impaction, and root development. The presence of radiographic signs of proximity between the mandibular canal and third molar and the imaging features of JAR also were recorded.
RESULTS
JAR was identified in 116 patients (11%) and 130 third molars (7.1%), being significantly associated with female patients and with the second and third decades of life. There also was an association with teeth with a vertical angulation and complete root formation. Radiographic signs of proximity to the mandibular canal were absent in 66.2% of JAR cases. In most cases, there was lamina dura in the juxta-apical area that appeared to overlap the mandibular canal and to have a cortical outline.
CONCLUSIONS
JAR is not a rare imaging finding. Given its possible relationship with nerve injuries and its differential diagnostic possibilities, knowing the characteristics of JAR is important to assist professionals in treatment planning and making the correct diagnosis.
Topics: Adult; Female; Humans; Male; Molar, Third; Prevalence; Radiography, Dental; Radiography, Panoramic; Tooth Extraction; Tooth, Impacted; Trigeminal Nerve Injuries; Young Adult
PubMed: 29247624
DOI: 10.1016/j.joms.2017.11.023 -
Medicina (Kaunas, Lithuania) Mar 2021Endodontic microsurgery is a highly predictable treatment option in most cases when conventional endodontic treatment is not feasible. Nevertheless, mandibular molars... (Review)
Review
Endodontic microsurgery is a highly predictable treatment option in most cases when conventional endodontic treatment is not feasible. Nevertheless, mandibular molars are still considered by clinicians to be the most difficult type of teeth, with the lowest success rate. In recent years, endodontic microsurgery has been attempted more frequently with the emergence of modern cutting-edge technologies such as dental operating microscopes, various microsurgical instruments, and biocompatible materials, and the success rate is increasing. This review describes the current state of the art in endodontic microsurgical techniques and concepts for mandibular molars. Notably, this review highlights contemporary equipment, technology, and materials.
Topics: Humans; Microsurgery; Molar
PubMed: 33809673
DOI: 10.3390/medicina57030270 -
The British Journal of Oral &... Oct 2016To find out whether the angulation of mandibular third molars is associated with the thickness of the bone at the site of impaction, and if so, which particular...
To find out whether the angulation of mandibular third molars is associated with the thickness of the bone at the site of impaction, and if so, which particular angulation affects the protective mechanism of the nerve, we retrospectively studied the thickness of lingual bone at the sites of impaction of 200 mandibular third molars in 149 patients using coronal, sagittal, and axial slices of cone-beam computed tomograms (CT). We measured the bone at the cementoenamel junction of the mandibular second molar, at the mid-root of the third molar, and at the apex of the root. Bone less than 1mm thick was defined as "thinning". We correlated these measurements with the angulation of the tooth based on the position of the second molar and the occlusal plane in 3 dimensions: vertical, mesiobuccal, and buccolingual. The primary outcome was the thickness of the bone around the third molar. A total of 102 teeth were on the left (51%), and 125 were angulated with an occlusal plane of <85° (63%). The mean (SD) thickness of bone at the cementoenamel junction of the second molar was 1.40 (0.87) mm, at mid-root 1.07 (1.03) mm, and at the apex 1.07 (1.30) mm. When the horizontal and mesioangular angulations of teeth were <85°, the thickness of bone at the mid-root differed significantly from that when the vertical and distoangular angulations were 85° or more (p<0.001). Correlations between the thickness of the bone and the buccolingual angulations were significantly associated with perforation of the bone at mid-root and apex (p<0.003). The bone around horizontal and mesioangular impactions was 3.6 times more likely to be "thin" than that at mid-root of vertical and distoangular third molars. A buccolingual angulation was also associated with perforation of the lingual cortex (p<0.003). As the bone was thinner at the mid-root of horizontally and mesioangularly impacted teeth, it seemed to compromise the integrity of the lingual plate, which is the natural protective barrier of the lingual nerve. These findings could be of prognostic value.
Topics: Humans; Hyoid Bone; Mandible; Molar; Molar, Third; Tooth, Impacted
PubMed: 27381746
DOI: 10.1016/j.bjoms.2016.06.005 -
Nigerian Journal of Clinical Practice Jun 2023The aim of this clinic study was to investigate the effect of piezoincision on the rate of mandibular molar mesialization using clinical, radiological, and biochemical... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND AND AIM
The aim of this clinic study was to investigate the effect of piezoincision on the rate of mandibular molar mesialization using clinical, radiological, and biochemical methods.
MATERIALS AND METHODS
Twenty-one patients requiring mandibular first molar extraction and second molar mesialization were included in the study which was designed as split-mouth study. Piezoincision was performed on the buccal surface of alveolar bone following regional alignment to the randomly selected side. 150 g of force was applied to the second molar teeth using mini-screw-supported anchorage after the piezoincision. Cone beam computed tomography (CBCT), gingival crevicular fluid (GCF) and digital model records of the patients were obtained. Two- and three-dimensional measurements were performed and compared on the CBCT images in a study which lasted 24 weeks.
RESULTS
According to the model analysis, the canine-second molar distance was consistently reduced and a greater decrease was measured on the experimental group (p < 0.05). Second molar mesial rotations increased in both groups (p < 0.001). Two-dimensional measurements on CBCT images showed increased mesial and buccal tipping of second molars in experimental group (p < 0.001). There was a significant increase in mesialization measurements of experimental group (p < 0.001). Three-dimensional measurements on the CBCT images showed a decrease of root length in both groups (p < 0.001), and a greater decrease was found in the experimental group (p < 0.001). When intra-group changes in GCF results were examined, it was observed that there was no significant change in osteoprotegerin (OPG) values over time in experimental group (p = 0.148).
CONCLUSION
The piezoincision technique provided acceleration of mandibular molar mesialization and did not cause further damage to the buccal alveolar bone. Piezoincision can be used as a safe method in the mandibular molar region.
Topics: Mandible; Molar; Tooth; Face; Cone-Beam Computed Tomography
PubMed: 37470644
DOI: 10.4103/njcp.njcp_657_22