Temperature variation in the pulp during Nd-YAG laser irradiation at tooth cervical protion in vitro / 实用口腔医学杂志

Objective:To observe the temperature vaxiation in the pulp chamber during Nd-YAG laser irradiation at tooth cervical portion.Methods:60 extracted permanent teeth were divided into 3 groups (anterior teeth,premolars and molars,n =20).The teeth in each group were further divided into 4 subgroups according to the laser power setting (0.4 W,0.8 W)and interval time(1 0 s,20 s)(n =5).After canal preparation the teeth were fixed and filmed using the parallel projection technique.the thickness of the buccal pulp chamber wall was measured by graphic analyzing software.The buccal cervical portion of the teeth was irradiated through 200 μm optical fiber,Temperature in the pulp was measured by K type thermo-electric couples fixed to the pulp chamber wall.Re-sults:The temperature inside the chamber increased with the higher power setting(P <0.01 ),under the same power setting,longer irradiation duration caused higher temperature rise(P <0.01 ).Greater chamber wall thickness was associated with lower temperature rise.Conclusion:The temperature rise in the pulp chamber during laser irradiation is correlated with laser power setting and the thickness of the irradiated tooth tissue.

Root canal treatment of two-rooted three-canal maxillary first premolar: a case report / 华西口腔医学杂志

According to literature, the incidence of three-canal maxillary first premolar is between 0.5% and 7.5%. The two types of three-canal maxillary premolars are two-rooted and three-rooted three-canal maxillary premolars. Most case reports in Chinese literature focus on three-rooted three-canal maxillary premolars. To our knowledge, no domestic case report on two-rooted three-canal maxillary premolar has been published. In this study, we describe the root canal treatment of a two-rooted three-canal maxillary premolar.

Fracture of the separated nickel titanium instruments during ultrasonic removal: an experimental study / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This in vitro study is to evaluate the effect of ultrasonic power settings and cooling methods on fracture behavior of the separated nickel titanium instruments during ultrasonic removal.</p><p><b>METHODS</b>40 discarded and 10 new nickel titanium instruments were used to establish the separated instrument removal model. The discarded instruments were divided into four groups according to two ultrasonic power settings(6 or 10) and different cooling methods (using water coolant or without using water coolant), and all the new instruments were put into the group in which ultrasonic vibration was used at a higher power setting (10) without using water coolant. The time required for fracture of the separated instruments was recorded.</p><p><b>RESULTS</b>The time was longer with statistical significance at a lower power setting compared with that at a higher power setting regardless of the use of water coolant. The time was longer with statistical significance by the use of water coolant compared with that without using coolant regardless of power settings (6 or 10). The time required for fracture of the new instruments was longer than that of the discarded instruments with statistical significance.</p><p><b>CONCLUSION</b>During ultrasonic removal of separated nickel titanium instruments, water coolant could decrease the occurrence of fracture. When removing separated nickel titanium instruments with ultrasonic vibration, an attempt without coolant shouldn't be made at a higher power setting.</p>

The clinical study on the use of diode laser irradiation in the treatment of periodontal-endodontic combined lesions / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the adjunctive effect of diode laser irradiation for the treatment of periodontal-endodontic combined lesions.</p><p><b>METHODS</b>30 cases with periodontal-endodontic combined lesions were selected. All cases were randomly divided into experimental group and control group (n=15). In the control group, patients were treated with root canal therapy and conservative periodontal treatment (scaling and root planning), and patients in the experimental group were treated with root canal therapy and conservative periodontal treatment followed by diode laser irradiation. Clinical measurements including pocket probing depth (PPD), clinical attachment level (CAL), modified bleeding index (mBI), periapical index (PAI) were taken before treatment (baseline). Three and six months after the treatment, the adjunctive effects of diode laser in the treatment of periodontal-endodontic combined lesions were evaluated.</p><p><b>RESULTS</b>Three months after the treatment, the average PPD, CAL and mBI levels were reduced significantly in both groups. But the average PPD reduction in the experimental group was significantly greater (P<0.05) than in control group. However the average CAL and mBI reduction were not significantly different between two groups. Six months after the treatment, the average PPD, CAL and mBI levels were further reduced in the experiment group, but not in the control group. The average PAI levels were reduced significantly in both groups, but the PAI reduction was not significantly different between two groups.</p><p><b>CONCLUSION</b>The use of diode laser as an adjunct procedure in the treatment of periodontal-endodontic combined lesions can aid in achieving success.</p>

Clinical study of the three mesial root canals of mandibular first molars / 实用口腔医学杂志

Objective:To investigate the clinical incidence of the three mesial root canals of mandibular first molars. Methods: Incidence and morphology of the three mesial root canals of mandibular first molars were determined by probing the fissure or grooves between the mesiobuccal and mesiolingual root canal orifices and X-ray analysis. Results: Of the 222 mandibular first molars, 13 of the molars had three mesial root canals. The incidence rate was 5.85 %. Conclusion: Although the incidence rate of the three mesial root canals of mandibular first molars was very low, the dental operative microscope was helpful for the diagnosis.