OBJECTIVE: The aims of this study were to use a 3-dimensional (3D) system to compare molar relationship assessments performed from the buccal and lingual aspects, and to measure differences in occlusal contact areas between Class II and Class I molar relationships. METHODS: Study casts (232 pairs from 232 subjects, yielding a total of 380 sides) were evaluated from both the buccal and lingual aspects, so that molar relationships could be classified according to the scheme devised by Liu and Melsen. Occlusal contact areas were quantified using 3D digital models, which were generated through surface scanning of the study casts. RESULTS: A cusp-to-central fossa relationship was observed from the lingual aspect in the majority of cases classified from the buccal aspect as Class I (89.6%) or mild Class II (86.7%). However, severe Class II cases had lingual cusp-to-mesial triangular fossa or marginal ridge relationships. Mean occlusal contact areas were similar in the Class I and mild Class II groups, while the severe Class II group had significantly lower values than either of the other 2 groups (p < 0.05). CONCLUSIONS: Buccal and lingual assessments of molar relationships were not always consistent. Occlusal contact areas were lowest for the Class II-severe group, which seems to have the worst molar relationships - especially as seen from the lingual aspect.
Molar

Background: The inclinations and movements of teeth after premature loss of second primary molar cause narrowing in the space of second permanent premolar. Objectives: (1) To evaluate the degree of space loss after premature loss of second primary molar due to teeth inclinations and movements. (2) To assess the effectiveness of the fixed space maintainer and fixed space regained. Subjects and method: This was a prospective trial study. Records of patients were analyzed to evaluate degree of the space loss due to teeth inclinations and movements, fixed space maintainer was used for cases have adequate space and fixed space regain for cases do not have. Results:Loss of space was 6.42% \xb1 0.62 mm and 3.78 \xb1 0.71 mm when second primary molar was extracted before and after first permanent molar erupt, respectively. In maintaining space, 92.9% of excellent results, 7.1% of good and 0% of failure. In regaining space, 88% of excellent results, 8% of good and 4% of failure. Conclusion: After premature loss of second primary molar, adjacent teeth incline and move resulting in loss of space, the degree of space loss depended on timing of tooth extraction. The study shows the effectiveness of fixed space maintainer and fixed space regain in maintaining and regaining spaces.
Molar ;

The purpose of this study was to investigate the stress distribution and intensity derived from the transpalatal lingual arch in the investing bone composed of photoelastic material(PL-3). The transpalatal lingual arch wire was deflected in the horizontal and vertical direction to give the various conditions. The two-dimensional photoelastic stress analysis was performed, and the stress distrebution was recored by photofraphy. The results were as follows: 1. In bilateral expansion, as horizontal deflection was singly applied, the stress was more concentrated on the root apex in square free end than round. In square free end, as vertical deflection was increased gradually, the black line meaning center of rotation moced inferiorly togerher with the increment of whole fringes. 2. In application of vertical deflection on anchorage side for unilateral expansion, the stress distribution that expansive force leaned to expansion side was observed. As vertical deflection increased, the extruding stress was obesrved on molar of expansion side. And as horisontal deflection increased, the tipping stress on the molar of anchorage side was observed. 3. In unilateral rotation with the asymmetric toe-in, the fringe appeared on the distal aspect of root apex.
Molar

OBJECTIVES: The purpose of the present study was to compare the mean preparation times and frequency with which Reciproc and Reciproc Blue instruments reached the full working length in mandibular molars, with or without glide path preparation. MATERIALS AND METHODS: Previously untreated mesiobuccal and mesiolingual canals with completely formed apices were randomly divided into 6 groups (n = 50) depending on the usage of Reciproc (RC; VDW), Reciproc Blue (RC Blue; VDW), C-Pilot (CP; VDW), and R-Pilot (RP; VDW) files: RC, RC Blue, RC + C-Pilot (RC-CP), RC-Blue + C-Pilot (RC Blue-CP), RC+R-Pilot (RC-RP), and RC Blue + R-Pilot (RC Blue-RP). A glide path was prepared using the hand-operated C-Pilot or the machine-operated R-Pilot instruments, respectively. The χ2 test, analysis of variance, and the Tukey post hoc test were used for statistical comparisons. RESULTS: No statistically significant differences were observed in the distribution of the frequency of reaching the full working length in the RC (94%), RC Blue (88%), RC-CP (94%), RC Blue-CP (90%), RC-RP (96%), and RC Blue-RP (92%) groups (p > 0.05). CONCLUSIONS: Preparation of a glide path did not have a significant effect on reaching the full working length using these systems.
Molar

Loss of the mandibular first molar often leads to the overeruption of the opposing maxillary first molar, resulting in inadequate interocclusal space. In this report, two miniscrews were placed into the buccal and palatal region of the upper first molar to correct the overerupted teeth using power chains. Progress of treatment was evaluated every two weeks for five months. The clinical results showed significant intrusion while maintaining periodontal health, tooth vitality, and root length.
Molar

Impacted mandibular third molars are located between the second mandibular molar and mandibular ramus. However, ectopic mandibular third molars with heterotopic positions are reported in the subcondylar or pterygomandibular space. The usual cause of malposition is a cyst or tumor, and malposition without a pathology is rare. This case report described an impacted mandibular third molar in the pterygomandibular space without any associated pathology.
Molar ; Molar, Third*

Intracanal separation of the rotary files is a serious concern in modern endodontic practice. The objective of this study was to compare the life span and fracture patterns of three NiTi rotary files in molar teeth. Mesiobuccal roots of upper molar (n = 150) and mesial roots of lower molar (n = 150) were divided into three groups and each group was prepared with Profile, ProTaper, and K3 respectively. Every file was used until separation and/or deterioration of the cutting blade was happened, and then the number of canals to separation and/or unwinding were recorded. Radiographs and Scanning electon microscope (SEM) photographs were taken to evaluate the patterns of separation. The results were as follows : 1. There were no significant differences in numbers of canals to separation and/or unwinding among the groups. 2. Comparing between flaring files, K3 showed significant lower numbers of canals to separation and/or unwinding (p < 0.05), and there was no significant difference between shaping files 3. Separations of instruments were occurred at the midpoint of curvatures within the canals. 4. In SEM observations, ductile fractures were seen in most of cases, characterized by shallow dimples. Additional researches is needed to provide a new guideline that informs the appropriate number of times to use NiTi files.
Molar* ; Tooth

The purpose of this study is to evaluate the effects of surface treatment and composition of reinforcement material on fracture strength of fiber reinforced composite inlay bridges. The materials used for this study were I-beam, U-beam TESCERA ATL system and ONE STEP(Bisco, IL, USA). Two kinds of surface treatments were used; the silane and the sandblast. The specimens were divided into 11 groups through the composition of reinforcing materials and the surface treatments. On the dentiform, supposing the missing of Maxillary second pre-molar and indirect composite inlay bridge cavities on adjacent first pre-molar disto-occlusal cavity, first molar mesio-occlusal cavity was prepared with conventional high-speed inlay bur.The reinforcing materials were placed on the proximal box space and build up the composite inlay bridge consequently. After the curing, specimen was set on the testing die with ZPC. Flexural force was applied with universal testing machine (EZ-tester; Shimadzu, Japan). at a cross-head speed of 1 mm/min until initial crack occurred. The data wasanalyzed using one-way ANOVA/Scheffes' post-hoc test at 95% significance level. Groups using I-beam showed the highest fracture strengths (p < 0.05) and there were no significant differences between each surface treatment (p > 0.05). Most of the specimens in groups that used reinforcing material showed delamination. 1. The use of I-beam represented highest fracture strengths (p < 0.05). 2. In groups only using silane as a surface treatment showed highest fracture strength, but there were no significant differences between other surface treatments (p > 0.05). 3. The reinforcing materials affect the fracture strength and pattern of composites inlay bridge. 4. The holes at the U-beam did not increase the fracture strength of composites inlay bridge.
Inlays* ; Molar

No abstract available.
Molar* ; Tooth*

OBJECTIVES: The aim of this study was to assess the influence of operator experience level on the lifespan of the WaveOne Primary file (Dentsply Maillefer, Ballaigues, Switzerland) in extracted teeth. MATERIALS AND METHODS: Moderately curved canals of extracted maxillary and mandibular molars were randomly distributed into 2 groups: experienced and inexperienced operators. Ten files were allocated to each group (n = 10). Each canal was prepared until the working length was reached, and the same file was used to prepare additional canals until it separated. The number of canals prepared before file separation was recorded. The fragment length of each file was measured, and the location of the fragment in the canal was determined. Data were statistically analysed using the independent 2-sample t-test. RESULTS: The 2 operators prepared a total of 324 moderately curved canals of maxillary and mandibular molars. There was no significant intergroup difference in the mean number of canals prepared (p = 0.27). The average lifespan of the WaveOne Primary file was 17.1 and 15.3 canals, and the longest lifespan was 25 and 20 canals, when used by experienced and inexperienced operators, respectively. There were no statistically significant intergroup differences in separated fragment length and location. CONCLUSIONS: Within the limitations of this study, operator experience level appears to have no effect on the lifespan of the WaveOne Primary file in preparation of moderately curved canals. Single teeth with multiple canals can be prepared safely even by a novice operator by using a single file.
Molar ; Tooth*