Maxillary Second Molars Research Articles

Improvement of cheek retractor for clinical dental photograph of dental profession

Objective To measure Chinese occlusion cast and skull lateral projection to acquired height, depth and arch of normotopia and lateral position, so as to obtain the data of national people for improvement of dental retracter and enhancing photography quality. Methods From May 2008 to May 2010 in Department of Orthodontics Peking University School and Hospital of Stomatology, a total of 247 cases were selected by convenient sampling method. The patients selected completed nonextraction treatment and had all permanent teeth without loss of tooth and second accessional teeth dentia already, and their molar relationship was neutral, and their overbite and overlap were normal. After treatment, we ensured fang′s point, molar point, subspinable, supramentale, maxillary second molar distal to the surface profile and mandibular second molar distal to the neck point by deposit model and skull lateral projection. The dental retracter height and depth of normotopia and lateral position, and we compared the measurement values of dental retracter between existed retracter and retracter model by X-ray. Results The model and X-ray measured depth of normotopia and lateral position, which were (39.54±4.29) mm and (36.18±3.26) mm compared with a similar size 39.20 mm and 34.41mm of existed retracter (P>0.05). The model and X-ray measured the height of model′s normotopi, which was (12.41±2.67) mm and was smaller than 16.13 mm of existed one (P<0.01); the model and X-ray measured the height of lateral position, which was (39.54±4.29) mm and bigger than the existed one (31.16 mm) (P<0.01). Conclusions The national dental retracter depth of normotopia and height of lateral position are discrepant with existed dental retracter, so it requires to design material retracter for clinical use, and compare with traditional retracter′s surface of image to find out the shortages and improve. Key words: Orthodontics; Retractor; Medical photography

Root and Root Canal Morphology in Maxillary Second Molar with Fused Root from a Native Chinese Population

IntroductionRoot fusion is an anatomic variation in maxillary second molars (MSMs); however, the nature of this canal morphology as it relates to its root anatomy has not been fully clarified. The purpose of this study was to investigate the relationship between features of fused roots and root canal anatomy in MSMs using micro–computed tomographic imaging. MethodsOne hundred eighty-seven extracted MSMs were scanned with the μCT50 (Scanco Medical, Bassersdorf, Switzerland), and their root and canal morphology was classified and analyzed using the classifications proposed by Yang and Vertucci. The number and position of canals that merged were recorded and compared among different root fusion types. ResultsOne hundred eight (57.75%) MSMs had 3 separate roots, and 79 (42.25%) had fused roots. Of the 79 fused roots, 22 showed partial canal merging, and 6 had complete canal merging. Canal merging was found with teeth with 3-root fusion more often than in those with 2-root fusion (P < .05). Of 28 merged canals, 16 occurred between mesiobuccal and distobuccal canals and 9 among mesiobuccal, distobuccal, and palatal canals. ConclusionsMSMs with fused roots may present a complicated root canal system as a result of canal merging.

Evaluation of the prevalence of the maxillary molars with two palatal roots by cone-beam CT

To investigate the characteristic of the maxillary molars with two palatal roots and its prevalence by cone-beam computered tomography. Cone-beam CT (CBCT) images of dentitions were collected retrospectively from 528 patients comprising 1957 maxillary molars. The characteristic and prevalence of maxillary molars with two palatal roots was analyzed. The tooth position, sex and unilateral and bilateral occurrence were recorded. The prevalence of two palatal roots was 0.72%(14/1957). Maxillary second molar with two palatal roots was detected in 1.12%(11/979), which showed a statistically higher prevalence than maxillary first molar 0.31%(3/978). This prevalence did not differ with sex or the side(P > 0.05). The mean distance of interorifice from the mesiolpalatal canal to the distopalatal canal was (2.84 ± 0.50) mm, and the angle between two palatal roots was on average (34.6 ± 16.1) °,which were significantly greater than the mean distance of interorifice from the two buccal roots (2.15 ± 0.82) mm and the angle between the two roots was (21.3 ± 12.2) °. The prevalence of maxillary second molars with two palatal roots was higher than that of the first malars. The angle between the two palatal roots brings difficulty to root canal therapy, so the consciousness of double palatal roots of maxillary molars was helpful for clinical operation.

Dental anomalies associated with malocclusion among 13 year old Kurdish students

The aim of this national oral health survey was to determine the prevalence of malocclusions due to some anomalies in the dentition among the 13 years old Kurdish students in sulaimani intermediate school. Materials and methods: The total sample was 950 (455 males and 495 females) which assessed by diagnostic set and special instrument. The clinical examination was mainly based on the definitions of Bjork et al. Some variables were recorded as present or absent sometimes denoting the tooth or the teeth involved in malocclusion and their distribution according to the whole sample. Results: The results showed that 1)The most common extracted tooth was the mandibular first molar (2.9%). 2) At this age group the most common partially erupted tooth was the maxillary canine (4.2%). 3) The most common unerupted tooth was the maxillary second molars. 4) The most common retained deciduous tooth was the maxillary canine (6.8%), then the maxillary second molars (5.4%).5) Hypodontia as judged clinically was found in 2.1% of the sample affecting one or more permanent teeth. The most common congenitally missing tooth was the maxillary lateral incisor (0.9%), mandibular second premolars (0.4%), and then maxillary second premolar (0.2%). 6) 29.2 % of the sample had one or more rotated teeth. The most common rotated tooth was the mandibular second premolars (5.3%). 7). The sample showed 30.4% with one or more displaced teeth. The most common displaced tooth was the maxillary lateral incisor (8.8%), then the maxillary canine (7.2%). Conclusion: At the age of 13 both males and females show large range of dental anomalies that are better to be

Clinical effects of pendulum and straight wire technology in patients with fully erupted maxillary second molar

Objective To investigate the clinical effect of pendulum and straight wire technology in patients with fully erupted second molar.Methods Patients with Angle class Ⅱ malocclusion were chosen.Control group included patients without erupted second molar.Experimental group included patients with completely erupted second molar.Pendulums were used in two groups to distalize maxillary molars.Then straight wire orthodontic treatment had been performed until treatment was over.Cephalograms of each stage were analyzed.Results In the experimental group,mesiobuccal cusp of first molar was distalized for 4.62 mm,geometric center was distalized for 3.75 mm,about 81 percent of the movement of mesiobuccal cusp.In control group,mesiobuccal cusp of first molar was dis talized for 5.78 mm,geometric center was distalized for 3.20 mm,about 55 percent of the movement of mesiobuccal cusp.It turned out first molar was distalized in both groups,but more rotation took place in control group than that in the experimental group.Conclusions Pendulum can distalize maxillary first and second molars in patients with completely erupted second molar.The pendulum and straight wire technology can treat these patients successfully. Key words: Angle class Ⅱ malocclusion; Pendulum; Maxillary second molar

Strategic maxillary second-molar extraction in Class II malocclusion

Maxillary second-molar extraction in Class II malocclusion is a controversial issue in orthodontics. This treatment protocol is rigorous and not routine. In this case report, we present the orthodontic treatment of a patient with a Class II malocclusion, maxillary crowding, and no mandibular first molars, treated with extraction of the maxillary second molars. The mechanotherapy and indications of maxillary second-molar extraction are discussed.

Efficiency of noncompliance simultaneous first and second upper molar distalization: a three-dimensional tooth movement analysis.

Objective of this prospective study was the three-dimensional (3D) analysis of tooth movements after the noncompliance simultaneous distalization of the first and second maxillary molars. Ten patients (five girls and five boys; mean age: 13.2 years) with bilateral Class II molar relationships were treated with a noncompliance, fixed intraoral appliance. Upper second molars had already erupted in all cases. Dental casts and lateral cephalometric radiographs were taken immediately before placement and after removal of the appliance. The casts were 3D digitized and superimposed on a predefined area in the palate. The resulting holograms, as well as the cephalometric radiographs, were digitized and analyzed by means of customized cephalometric software. The whole procedure was repeated after a two- to four-week interval to estimate the error of both methods. The cast assessment of 3D sagittal and vertical tooth movements was more reliable than the cephalometric record. The average maxillary first molar distal movement was 2.8 mm. Anchorage loss was expressed by a 1.9-mm proclination of the central incisors. A substantial variation among patients and among the right and left side in the same patient was observed. Noncompliance simultaneous distalization of the first and second maxillary molars can be an efficient treatment option for the correction of Class II molar relationship. However, anchorage loss and individual variation have to be seriously considered. Bilaterally symmetrical effectiveness should not be relied upon.

Maxillary molar intrusion with fixed appliances and mini-implant anchorage studied in three dimensions.

The intrusion of an overerupted maxillary molar using traditional orthodontic treatment is a real challenge. The aim of this study was to investigate the envelope of intrusive movements of a maxillary molar in cases using mini-implants as anchorage with partial or full-mouth fixed edgewise appliances. The cusp tips of the pretreatment and postintrusion dental casts were recorded by a three-dimensional (3D) digitizer. The 3D data of the serial dental casts were analyzed to distinguish the direction and magnitude of individual tooth movement. The mean intrusive movement of the maxillary first molars was three to four mm, with a maximum of over eight mm. For the adjacent maxillary second molars and second premolars, the amount of intrusion was two mm and 1-2 mm, respectively. This study demonstrated that significant true intrusion of maxillary molars could be obtained in a well-controlled manner by using fixed appliances with titanium mini-implants as bony anchorage.

Ectopic eruption of the maxillary first permanent molar: characteristics and occurrence in growing children.

The purpose of this study was to determine the characteristics and occurrence of the ectopic eruption of the maxillary first permanent molar in a sample of growing Spanish children. A descriptive, observational, retrospective study was done using the radiographs of 509 consecutive patients, who were in the first phase of mixed dentition. A method was designed to evaluate the amount of pathologic resorption of the second maxillary primary molar and the impaction of the first permanent molar measured in millimeters. Statistical analysis of the studied variables was done using chi-square, analysis of variance, and Pearson correlation coefficient. The frequency of occurrence was 4.3% with no differences in both sexes. Of these, 36.4% were unilateral and 63.6% bilateral with a right:left relation of 3:1. Of the 36 ectopic molars, 69.4% self-corrected spontaneously. In such cases, the pathological resorption of the root of the second maxillary primary molar and its adverse clinical implications were persistent. The relation between self-correction and impaction was 2.27:1. The average impaction on the right side was 2.91 mm and 1.6 mm on the left side. Correlation between the magnitude of resorption and grade of impaction was not observed. Although resorption was found on grades I and II, spontaneous self-correction could occur without arch length loss. However, on grade III or more, therapeutic intervention has to be done. The benefit of early diagnosis and treatment of the maxillary first permanent molar is the prevention of the premature loss of second maxillary deciduous molar and the resulting malocclusion.

A comparative analysis of maxillary tooth movement produced by cervical headgear and pend-x appliance.

The purpose of this study was to compare the effects of cervical headgear and pend-x on the maxillary first molar, second molar, first premolar, and upper incisors. Cephalometric radiographs were obtained at the start of treatment (T1) and after molar distalization was completed (T2) for 13 patients in a pend-x group and 13 patients in a cervical headgear group. The changes of the maxillary teeth were measured on maxillary superimpositions. Nonparametric Mann-Whitney U-test was used to compare the mean differences between the two groups. The mean amount of distalization for the headgear group was 3.15 +/- 1.94 mm and that for the pend-x group was 3.81 +/- 2.25 mm. The second molar teeth were also distalized to a mean amount of 2.27 +/- 1.33 mm in the headgear group and 2.04 +/- 2.15 mm in the pend-x group. The mean treatment time for distalization was 11.38 +/- 3.18 months for the headgear group and 7.31 +/- 4.09 months for the pend-x group. During distalization, the maxillary molars tipped distally in both groups, but intergroup differences were not significant. The anterior inclinations of the first premolar and upper incisor increased significantly in the pend-x group (P < .01). Maxillary molars showed no vertical movement in the pend-x group but extruded in the headgear group (P < .01). The anchorage loss of the pend-x appliance as well as the necessary patient compliance and greater treatment time with the cervical headgear should be taken into consideration.

Alternation of the magnetic resonance signals characteristic of mandibular condyles during growth.

In a previous study, we named the magnetic resonance imaging (MRI) signal that is characteristic of mandibular condyles in growing children the "double contour-like structure" (DCLS). In the current study, we evaluated the alternating appearance and disappearance of the DCLS in children as they grow to elucidate the significance of the DCLS. In 11 subjects who were 9-14 years old at the time of the first examination, MRI characteristics of mandibular condyles were sought from fast spin-echo intermediate-weighted images; 2 or 3 years later, repeat MRI were obtained from the same subjects. At the second examination, 10 of the 16 DCLSs detected at the first examination had disappeared. A significant relationship was found between the alternation of the DCLS and the bone marrow conversion from red to yellow in mandibular condyles. Alternation of the DCLS tended to coincide with eruption of the permanent maxillary second molars. The DCLS was also shown to appear as a hypersignal on T2-weighted images. Double contour-like structure signals in mandibular condyles appeared and disappeared as children grew, and these signal alternations may be useful as a criterion for the staging of mandibular condyle development in children. Possible constituents of the DCLS may be hypervascular loose fibrous tissue and a proliferation of cartilage.

Comparison of dental arch and alveolar widths of patients with Class II, division 1 malocclusion and subjects with Class I ideal occlusion.

This study evaluates dental arch and alveolar widths of patients with Class II, division 1 malocclusion. Thirty female patients with Class II, division 1 malocclusion were compared with 30 female subjects with Class I ideal occlusion. Patients with posterior crossbites even in a single tooth were excluded from the study. According to our results, arch widths measured between maxillary second premolars and maxillary first molars were found narrower in the Class II, division 1 group, and mandibular intercanine widths were narrower in the Class I group. Interalveolar widths showed no difference between the groups. These results suggested that transverse discrepancy in Class II, division 1 patients originated from upper posterior teeth and not from the maxillary alveolar base. Therefore, slow maxillary expansion rather than rapid maxillary expansion may be considered before or during the treatment of Class II, division 1 patients.

Analysis of divergent angle and length of CEJ to furcation entrance in extracted molars

The purposes of this study were to investigate the furcation entrance angle (FEA) and the distance between cemento-enamel junction (CEJ) and furcation entrance (FE) of the extracted maxillary and mandibular molars. Assay teeth comprised 89 maxillary molars and 93 mandibular molars. All the FEAs and CEJ-FEs of the molars were measured by a stereomicroscope at 2.5 x equipped with a Bioscan OPTIMAS Image Analyzer (BOIA). The results were summarized as follows: (1) The mean FEAs in the buccal, mesial and distal furcations were 96.3 +/- 10.0, 103.8 +/- 9.7, and 107.2 +/- 12.2 degrees in the maxillary molars, and 91.6 +/- 11.7, 101.7 +/- 11.5, and 97.1 +/- 10.7 degrees in the maxillary second molars, respectively. At the buccal and lingual furcations of mandibular first and second molars, they measured 100.5 +/- 9.7/102.7 +/- 8.5, and 93.3 +/- 11.5/91.7 +/- 10.8 degrees, respectively. (2) The mean distance of CEJ-FEs at the buccal, mesial and distal furcations of maxillary molars were 3.42 +/- 1.5mm, 3.55 +/- 0.97 mm, and 3.69 +/- 0.98mm for the first molars, and 3.01 +/- 1.04mm, 4.04 +/- 1.58mm and 3.00 +/- 1.14mm for the second molars. At the buccal and lingual furcations of the mandibular first and second molars, they were recorded as 1.90 +/- 0.08mm and 2.90 +/- 0.07mm, and 2.82 +/- 1.34mm and 3.46 +/- 1.03mm, respectively. It was concluded that buccal FEA of maxillary 2nd molar was the smallest (91.56 +/- 9.68 degrees) as compared to the mesial and distal FEAs; whereas the mean distance of CEJ-FEs at the buccal surface was the smallest (1.90mm +/- 0.08mm) when compared to the others.

Furcation entrance dimension, divergent angle and length of CEJ to furcation entrance relate to periodontal therapy

In previous studies we have investigated the furcation entrance dimension (FED), furcation entrance angle (FEA) and the distance between cementoenamel junction and furcation entrance (CEJ-FE) of the first and second molars and compared the Chinese with the Caucasians. The aim of the present study was to relate the FED, FEA, and distance of CEJ-FE to the clinical significance of periodontal therapy of molar furcations. All the FEDs, FEAs, and distance of CEJ-FEs of the molars were measured by a stereomicroscope equipped with a Bioscan OPTIMAS Image Analyzer and statistically analyzed by Student's paired t-test, multiple regression of ANOVA and correlation analysis. The results are summarized below. (1) There is a significant relationship between FEA and location of buccal, mesial, and distal furcations of maxillary first and second molars (16& 26, p < 0.001; 17&27, p < 0.01). (2) There exists a significant relationship between FEA and FED in the mandibular first and second molars. (3) There exists a significant relationship between FED and FEA in the mandibular second molar (r = 0.370, p < 0.05). (4) The prevalence of mean FED and FEA (type D, FED < or = 0.75 mm and FEA < or = 90 degree) of the maxillary first molar (45%) is twice as high as the maxillary first molar (24%). (5) The prevalence of type D of the buccal (32%) and lingual (37%) furcations on the mandibular second molar is markedly higher than the first molar (buccal = 12%; lingual = 4%, respectively). These results reveal that those topographics of the FED, FEA, and distance of CEJ-FE in second molars have poor prognosis in periodontal therapy when compared with first molars.

The study of molar furcation involvements in adult periodontitis. II. Age, sex, location and prevalence

The purposes of the study were as follows: (1) to evaluate the molar furcation involvement and number of molar correlated with age and sex; and (2) to study the relationship between the means of alveolar bone loss and associated factors of molar furcation involvements (FIs). 1102 molars (703 males and 399 females) were measured in 219 individuals (136 males and 83 females) for the alveolar bone loss and associated factors of molar furcation involvements. Based on the results, we conclude the following: (1) the higher prevalence of FI was in the mandibular first molar (94.6%), whereas the lowest prevalence of FI was in maxillary second molar; (2) except for the mandibular first molar, the prevalence of molar FI markedly increased with an increased age group (16 & 26, r = 0.335, p < 0.01; 17 & 27, r = 0.345, p < 0.01; 37 & 47, r = 0.239, p < 0.01); (3) the prevalence of molar FI was significantly higher in males than in females (p < 0.05); (4) the mean number of molar FI was significant greater in males (mean = 3.45) than in females (mean = 2.69); (5) factors such as age (r = 0.222, p < 0.01), sex, (r = 0.145, p < 0.05), number of remaining teeth (r = -0.330, p < 0.01) and molar FI (r = 0.471, p < 0.01) are strongly associated with the mean alveolar bone loss of molars.

Remodeling mechanisms of transseptal fibers during and after tooth movement.

The remodeling mechanisms of transseptal fibers during and after tooth movement were investigated histologically. An autoradiographic study was conducted to assess the synthetic response. One hundred fifty male Wistar strain growing rats were divided into three groups--one control and two experimental groups. Animals in the experimental groups were subjected to tooth movement with 25 g and 150 g of force. Maxillary first and second molars were separated and retained mechanically. Transseptal fibers were stretched in proportion to the amount of force applied for up to 2 days. Dynamic remodeling with proliferation of fibroblasts during tooth movement and slow rearrangement during retention periods occurred in both experimental groups. Collagen phagocytosis within the fibroblasts was observed ultrastructurally during the experimental periods. The number of silver grains in fibroblasts in the collagen fibers increased 160% the first day and 206% during the first 3 days. Proliferating fibroblasts remodeled the transseptal fibers through the synthesization and degradation of collagen fibers.