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Maxillary First Molars (maxillary + first_molar)
Selected AbstractsThe three-dimension finite element analysis of stress in posterior tooth residual root restored with postcore crownDENTAL TRAUMATOLOGY, Issue 1 2010Gang Fu Some researchers have analyzed the stress of the anterior teeth after postcore crown restoration, but the stress of the posterior teeth after such restoration has not been reported. We used three-dimension finite element methods to analyze the stress magnitude and distribution of remaining dentin in posterior tooth residual root restored with postcore crown. The binding material, loading direction, number, length and material of posts were studied. Methods:, The models of residual root of maxillary first molar restored with postcore crown were created by CT scanning, mimics software and abaqus software. Different number, length and material of posts were used in the modeling. The posts were cemented with zinc-phosphate cement or composited resin. A load of 240 N was applied to the occlusal surface in four directions and tensile, shear, and von Mises stresses were calculated. Result:, (i) The maximum stress on remaining dentin changed irregularly as the number and length of posts changed. (ii) The maximum stress on remaining dentin decreased slightly as elastic modulus of the material of posts increased. (iii) The maximum stress on bonding layer and remaining dentin was lower when bonded with resin luting agent than with zinc-phosphate cement. (iv) The maximum stress on remaining dentin increased markedly as loading angle increased. Conclusion:, The number, length, material of posts, bonding material and loading angle all have influence on the magnitude and distribution of stress. The influence of loading angle is most apparent. [source] A six-canal maxillary first molar: case reportINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2002F. Maggiore No abstract is available for this article. [source] Frequency and type of canal isthmuses in first molars detected by endoscopic inspection during periradicular surgeryINTERNATIONAL ENDODONTIC JOURNAL, Issue 3 2005T. Von Arx Abstract Aim, To analyse the occurrence of canal isthmuses in molars following root-end resection. Methodology, The material consisted of 56 mandibular and 32 maxillary first molars subjected to periradicular surgery. Based on radiographic, clinical, as well as intraoperative status, only roots with associated pathological lesions were treated. In total, 124 roots were resected (80 mandibular and 44 maxillary molar roots). The cut root faces were inspected with a rigid endoscope following apical root-end resection. The number of canals as well as the presence and type of canal isthmuses were recorded. Results, In maxillary first molars, 76% of resected mesio-buccal roots had two canals and an isthmus, 10% had two canals but no isthmus, and 14% had a single canal. All disto-buccal and palatal roots had one canal. In mandibular first molars, 83% of mesial roots had two canals with an isthmus. In 11%, two canals but no isthmus were present, and 6% demonstrated a single canal. Sixty-four per cent of distal roots had a single canal and 36% had two canals with an isthmus. Conclusions, This clinical study during periradicular surgery and intraoperative endoscopic examination of first permanent molars found a high frequency of canal isthmuses at the resection level. Endoscopic inspection also demonstrated that none of the isthmuses were filled, emphasizing the difficulty of orthograde instrumentation and root filling of canal isthmuses. [source] An evaluation of .06 tapered gutta-percha cones for filling of .06 taper prepared curved root canalsINTERNATIONAL ENDODONTIC JOURNAL, Issue 2 2005M. P. J. Gordon Abstract Aim, To compare the area occupied by gutta-percha, sealer, or void in standardized .06 tapered prepared simulated curved canals and in mesio-buccal canals of extracted maxillary first molars filled with a single .06 gutta-percha point and sealer or lateral condensation of multiple .02 gutta-percha points and sealer. Methodology, Simulated canals in resin blocks with either a 30° curve and radius of 10.5 mm (n = 20) or a 58° curve and 4.7 mm radius (n = 20) and curved mesio-buccal canals of extracted maxillary first molars (n = 20) were prepared using .06 ProFiles® in a variable tip crown-down sequence to an apical size 35 at 0.5 mm from the canal terminus or apical foramen. Ten 30° and 58° curved resin canals and 10 canals in the extracted teeth group were obturated with .02 taper gutta-percha cones and AH 26 sealer using lateral condensation. The time required to obturate was recorded. The remaining canals were obturated with a single .06 taper gutta-percha cone and AH 26 sealer. Excess gutta-percha was removed from the specimens using heat and the warm mass vertically condensed. Horizontal sections were cut at 0.5, 1.5, 2.5, 4.5, 7.5 and 11.5 mm from the canal terminus or apical foramen. Colour photographs were taken using an Olympus 35 mm camera attached to a stereomicroscope set at ×40 magnification, and then digitized using a flatbed scanner. The cross-sectional area of the canal contents was analysed using Adobe PhotoShop®. The percentage of gutta-percha, sealer or voids to the total root canal area were derived and data analysed using unpaired Student's t -test and the Mann,Whitney U -test. Results, In the 30° curved canals the levels had between 94 and 100% of the area filled with gutta-percha with no significant difference (P > 0.05) between the lateral condensation and single cone techniques. In the 58° curved canals the levels had 92,99% of the area filled with gutta-percha, with the single cone technique having significantly (P < 0.05) more gutta-percha fill at the 2.5 mm level only. In the mesio-buccal canals of the teeth the levels had between 72 and 96% of the area filled with gutta-percha with no significant difference (P > 0.05) between the lateral condensation and single cone technique. The time for obturation was significantly (P < 0.05) greater for lateral condensation compared with the single cone technique in all groups. Conclusions, The .06 taper single cone technique was comparable with lateral condensation in the amount of gutta-percha occupying a prepared .06 tapered canal. The .06 single cone technique was faster than lateral condensation. [source] Masseter muscle thickness as a predictive variable in treatment outcome of the twin-block appliance and masseteric thickness changes during treatmentORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2010S Kiliaridis To cite this article: Kiliaridis S, Mills CM, Antonarakis GS: Masseter muscle thickness as a predictive variable in treatment outcome of the twin-block appliance and masseteric thickness changes during treatment Orthod Craniofac Res 2010;13:203,213 Structured Abstract Authors,,, Kiliaridis S, Mills CM, Antonarakis GS Objectives,,, To estimate the association of initial masseter muscle thickness with treatment outcomes using functional appliances and the effect of treatment on masseter muscle thickness. Material and Methods,,, Twenty-two children, aged 8,12, with skeletal and dental class II relationships and increased overjet were treated with twin-block appliances for 9,17 months, until a class I molar relationship and decreased overjet was achieved. Dental casts, lateral cephalograms, and ultrasonographic measurements of the masseter muscle were performed before and after treatment. Twenty-two children, aged 8,12, without immediate need for orthodontic treatment, served as controls. They were observed for 11,17 months, and ultrasonographic masseter muscle measurements were taken before and after the observation period. Results,,, Masseter muscles in treated children were thinner at the end of treatment, while untreated controls showed an increase in thickness. Treated children with thinner pre-treatment muscles showed greater mandibular incisor proclination, distalisation of maxillary molars, and posterior displacement of the cephalometric A point during treatment. Conclusion,,, Treatment of a dental class II relationship with functional appliances leads to mild atrophy of the masticatory muscles, possibly because of their decreased functional activity. The initial condition of the muscles may be associated with mandibular incisor proclination, and the position of maxillary first molars and A point. [source] Dentin strain induced by laser irradiationAUSTRALIAN ENDODONTIC JOURNAL, Issue 2 2010Satoshi Watanabe dds Abstract The purpose of this study was to investigate the strain and temperature change in dentin induced by laser irradiation of human root canals with or without water cooling. Twenty-eight palatal roots of extracted human maxillary first molars were used. The strain in dentin was measured using strain gauges fixed on the apical third of the buccal root surface. The temperature change of the root dentin was monitored using thermocouples embedded into dentin near the apex. The root canal was irradiated with Er:YAG or Nd:YAG laser at an output of 1 W (100 mJ, 10 pps) for 5 s. The tip of the irradiation fibre was located 2.0 mm from the root apex. With water cooling, the mean maximum strain induced by Er:YAG laser was significantly lower than that by Nd:YAG laser (P < 0.05). However, without water cooling, no significant difference between the two lasers (P > 0.05) was found. The results suggest that the strain induced by Er:YAG laser irradiation in dentin with water cooling may be minimal, but there still might be a risk of root micro-fracture if cooling is not sufficient. [source] | ||||||||||