A comparative study based on the mandibular movement track and the movement parameters of the virtual articulator in simulating occlusal adjustment / 华西口腔医学杂志

OBJECTIVES@#This study aimed to compare the effects of virtual adjustment on occlusal interferences in mandibular posterior single crown and three-unit bridge restorations by using the mandibular movement track and the movement parameters of a virtual articulator.@*METHODS@#Twenty-two participants were recruited. Digital casts of the maxillary and mandibular arches were obtained using an intraoral scanner, and the jaw registration system was used to record the data of the mandibular movement track and the movement parameters of the articulator. Four kinds of restorations with 0.3 mm occlusal interferences were designed with dental design software. In particular, single crowns were designed for teeth 44 and 46, whereas three-unit bridges were designed for teeth 44-46 and 45-47, and the corresponding natural teeth were virtually extracted. Virtual adjustment of the restorations was performed using two dynamic occlusal recordings, namely, the mandibular movement track and the movement parameters of the virtual articulator. A reverse-engineering software was used to measure the root-mean-square of the three-dimensional deviation of the occlusal surfaces between natural teeth and the adjusted restorations. The differences between the two methods of virtual-occlusion adjustment were compared and analyzed.@*RESULTS@#For the same group of restorations, the three-dimensional deviation of the mandibular movement track group were lower than those of the virtual articulator group, and the differences were statistically significant (P<0.05). For the four groups of restorations adjusted by the same method, the three-dimensional deviation of the 46-tooth single crown was the largest and the smallest three-dimensional deviation was that of the 44-tooth single crown. Statistical differences existed between the 44-tooth single crown and the other groups (P<0.05).@*CONCLUSIONS@#For the occlusal design of posterior single crown and three-unit bridge, the mandibular movement track could be a more effective approach to virtual occlusal adjustment than the movement parameters of the virtual articulator.

A comparative study to measure the sagittal condylar inclination using mechanical articulator, virtual articulator and jaw tracking device

PURPOSE@#. To compare the sagittal condylar inclination (SCI) in dentate individuals measured by the different methods with mechanical articulator (MA), virtual articulator (VA), and a jaw tracking device (JTD) system. @*MATERIALS AND METHODS@#. A total of 22 healthy dentate participants were enrolled in this study. For MA workflow, the SCI was obtained by a semi-adjustable articulator with protrusive interocclusal records. The SCI was also set on a VA by aligning intraoral scan (IOS) with cone beam computed tomography (CBCT) and facial scan (FS), respectively. These virtual workflows were conducted in a dental design software, namely VAIOS-CBCT and VAIOS-FS . Meanwhile, a JTD system was also utilized to perform the measurement. Intraclass correlation was used to assess the repeatability within workflows. The bilateral SCI values were compared by Wilcoxon matched-pairs signed rank test for each workflow, and Kruskal-Wallis test and post hoc p-value Bonferroni correction were used to compare the differences among four workflows. The agreement of VAIOS-CBCT , VAIOS-FS , and JTD compared with MA was evaluated by Bland-Altman analysis. @*RESULTS@#. Intraclass correlation of the SCI revealed a high degree of repeatability for each workflow. There were no significant differences between the left and right sides (P > .05), except for VAIOS-CBCT (P = .028). Significant differences were not found between MA and VAIOS-FS (P > .05). Bland-Altman plots indicated VAIOS-CBCT , VAIOS-FS , and JTD were considered to substitute MA with high 95% limits of agreement. @*CONCLUSION@#. The workflow of VAIOS-FS provided an alternative approach to measure the SCI compared with MA.

Promotion effect of TGF-β-Zfp423-ApoD pathway on lip sensory recovery after nerve sacrifice caused by nerve collateral compensation / 国际口腔科学杂志·英文版

Resection of oral and maxillofacial tumors is often accompanied by the inferior alveolar nerve neurectomy, resulting in abnormal sensation in lower lip. It is generally believed that spontaneous sensory recovery in this nerve injury is difficult. However, during our follow-up, patients with inferior alveolar nerve sacrifice showed different degrees of lower lip sensory recovery. In this study, a prospective cohort study was conducted to demonstrate this phenomenon and analyze the factors influencing sensory recovery. A mental nerve transection model of Thy1-YFP mice and tissue clearing technique were used to explore possible mechanisms in this process. Gene silencing and overexpression experiments were then conducted to detect the changes in cell morphology and molecular markers. In our follow-up, 75% of patients with unilateral inferior alveolar nerve neurectomy had complete sensory recovery of the lower lip 12 months postoperatively. Patients with younger age, malignant tumors, and preservation of ipsilateral buccal and lingual nerves had a shorter recovery time. The buccal nerve collateral sprouting compensation was observed in the lower lip tissue of Thy1-YFP mice. ApoD was demonstrated to be involved in axon growth and peripheral nerve sensory recovery in the animal model. TGF-β inhibited the expression of STAT3 and the transcription of ApoD in Schwann cells through Zfp423. Overall, after sacrificing the inferior alveolar nerve, the collateral compensation of the ipsilateral buccal nerve could innervate the sensation. And this process was regulated by TGF-β-Zfp423-ApoD pathway.

Three-dimensional analysis of the outcome of different scanning strategies in virtual interocclusal registration

PURPOSE@#. The purpose of this in vitro study was to assess whether scanning strategies of virtual interocclusal record (VIR) affect the accuracy of VIR during intraoral scanning. @*MATERIALS AND METHODS@#. Five pairs of reference cubes were added to the digital upper and lower dentitions of a volunteer, which were printed into resin casts. Subsequently, the resin casts were articulated in the maximal intercuspal position in a mechanical articulator and scanned with an industrial computed tomography system, of which the VIR was served as a reference VIR. The investigated VIR of the upper and lower jaws of the resin master cast were recorded with an intraoral scanner according to 9 designed scanning strategies.Then, the deviation between the investigated VIRs and reference VIR were analyzed, which were measured by the deviation of the distances of six selected reference points on the upper reference cubes in each digital cast to the XY-plane between the investigated VIRs and reference VIR. @*RESULTS@#. For the deviation in the right posterior dentitions, RP group (only scanning of right posterior dentitions) showed the smallest deviation. Besides, BP group (scanning of bilateral posterior dentitions) showed the smallest deviation in the left posterior dentitions. Moreover, LP group (scanning of left posterior dentitions) showed the smallest deviation in the anterior dentitions. For the deviation of full dental arches, BP group showed the smallest deviation. @*CONCLUSION@#. Different scanning strategies of VIR can influence the accuracy of alignment of virtual dental casts. Appropriate scanning strategies of VIR should be selected for different regions of interest and edentulous situations.

Activation of mitogen-activated protein kinases in satellite glial cells of the trigeminal ganglion contributes to substance P-mediated inflammatory pain / 国际口腔科学杂志·英文版

Inflammatory orofacial pain, in which substance P (SP) plays an important role, is closely related to the cross-talk between trigeminal ganglion (TG) neurons and satellite glial cells (SGCs). SGC activation is emerging as the key mechanism underlying inflammatory pain through different signalling mechanisms, including glial fibrillary acidic protein (GFAP) activation, phosphorylation of mitogen-activated protein kinase (MAPK) signalling pathways, and cytokine upregulation. However, in the TG, the mechanism underlying SP-mediated orofacial pain generated by SGCs is largely unknown. In this study, we investigated whether SP is involved in inflammatory orofacial pain by upregulating interleukin (IL)-1β and tumour necrosis factor (TNF)-α from SGCs, and we explored whether MAPK signalling pathways mediate the pain process. In the present study, complete Freund's adjuvant (CFA) was injected into the whisker pad of rats to induce an inflammatory model in vivo. SP was administered to SGC cultures in vitro to confirm the effect of SP. Facial expression analysis showed that pre-injection of L703,606 (an NK-1 receptor antagonist), U0126 (an inhibitor of MAPK/extracellular signal-regulated kinase [ERK] kinase [MEK] 1/2), and SB203580 (an inhibitor of P38) into the TG to induce targeted prevention of the activation of the NK-1 receptor and the phosphorylation of MAPKs significantly suppressed CFA-induced inflammatory allodynia. In addition, SP promoted SGC activation, which was proven by increased GFAP, p-MAPKs, IL-1β and TNF-α in SGCs under inflammatory conditions. Moreover, the increase in IL-1β and TNF-α was suppressed by L703, 606, U0126 and SB203580 in vivo and in vitro. These present findings suggested that SP, released from TG neurons, activated SGCs through the ERK1/2 and P38 pathways and promoted the production of IL-1β and TNF-α from SGCs, contributing to inflammatory orofacial pain associated with peripheral sensitization.

Minimal invasive microscopic tooth preparation in esthetic restoration: a specialist consensus / 国际口腔科学杂志·英文版

By removing a part of the structure, the tooth preparation provides restorative space, bonding surface, and finish line for various restorations on abutment. Preparation technique plays critical role in achieving the optimal result of tooth preparation. With successful application of microscope in endodontics for >30 years, there is a full expectation of microscopic dentistry. However, as relatively little progress has been made in the application of microscopic dentistry in prosthodontics, the following assumptions have been proposed: Is it suitable to choose the tooth preparation technique under the naked eye in the microscopic vision? Is there a more accurate preparation technology intended for the microscope? To obtain long-term stable therapeutic effects, is it much easier to achieve maximum tooth preservation and retinal protection and maintain periodontal tissue and oral function health under microscopic vision? Whether the microscopic prosthodontics is a gimmick or a breakthrough in obtaining an ideal tooth preparation should be resolved in microscopic tooth preparation. This article attempts to illustrate the concept, core elements, and indications of microscopic minimally invasive tooth preparation, physiological basis of dental pulp, periodontium and functions involved in tool preparation, position ergonomics and visual basis for dentists, comparison of tooth preparation by naked eyes and a microscope, and comparison of different designs of microscopic minimally invasive tooth preparation techniques. Furthermore, a clinical protocol for microscopic minimally invasive tooth preparation based on target restorative space guide plate has been put forward and new insights on the quantity and shape of microscopic minimally invasive tooth preparation has been provided.

The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

PURPOSE: To measure the surface loss of dental restorative zirconia and the short-term bond strength between an indirect composite resin (ICR) and zirconia ceramic after various sandblasting processes. MATERIALS AND METHODS: Three hundred zirconia bars were randomly divided into 25 groups according to the type of sandblasting performed with pressures of 0.1, 0.2, 0.4 and 0.6 MPa, sandblasting times of 7, 14 and 21 seconds, and alumina powder sizes of 50 and 110 microm. The control group did not receive sandblasting. The volume loss and height loss on zirconia surface after sandblasting and the shear bond strength (SBS) between the sandblasted zirconia and ICR after 24-h immersion were measured for each group using multivariate analysis of variance (ANOVA) and Least Significance Difference (LSD) test (alpha=.05). After sandblasting, the failure modes of the ICR/zirconia surfaces were observed using scanning electron microscopy. RESULTS: The volume loss and height loss were increased with higher sandblasting pressure and longer sandblasting treatment, but they decreased with larger powder size. SBS was significantly increased by increasing the sandblasting time from 7 seconds to 14 seconds and from 14 seconds to 21 seconds, as well as increasing the size of alumina powder from 50 microm to 110 microm. SBS was significantly increased from 0.1 MPa to 0.2 MPa according to the size of alumina powder. However, the SBSs were not significantly different with the sandblasting pressure of 0.2, 0.4 and 0.6 MPa. The possibilities of the combination of both adhesive failure and cohesive failure within the ICR were higher with the increases in bonding strength. CONCLUSION: Based on the findings of this study, sandblasting with alumina particles at 0.2 MPa, 21 seconds and the powder size of 110 microm is recommended for dental applications to improve the bonding between zirconia core and ICR.

Erratum: The effect of various sandblasting conditions on surface changes of dental zirconia and shear bond strength between zirconia core and indirect composite resin

On page 219, there was an error in the Fig. 5.

Nitric oxide and prostaglandin E2 secretion in osteocytes induced by intermittent cyclic compressive force / 生物医学工程学杂志

This paper is aimed to investigate the effect of rest-inserted loading on the mechanosensitivity of osteocytes. In the investigation, cultured MLO-Y4 osteocyte-like cells were strained on cyclic compressive force (CCF) by the self-made compressive loading device. Then we observed the effect of different rest periods-inserted loading (5 s, 15 s, 30 s, respectively) on the mechanosensitivity of osteocytes. We then determined the levels of secreted nitric oxide (NO) and prostaglandin E2 (PGE2) by Griess method and enzyme linked immunosorbent assay (ELISA), respectively. We then stained the cytoskeleton F-actin using immunofluorescence. We found that the expressions of NO and PGE2 in rest-inserted strained groups (> 15 s) were significantly increased compared to those in the continuous strained group. And rest-inserted loading promoted the parallel alignment of stress fibers. It indicates that rest-inserted loading could promote the mechanosensitivity of osteocytes, and this might be related to the parallel alignment of stress fibers.

Effects of intracellular osmolality changes on the voltage-gated sodium channels currents of trigeminal ganglion neuron / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the biomechanical effects of intracellular changes on the voltage-gated sodium channels (VGSCs) on trigeminal ganglion neuron (TRGN).</p><p><b>METHODS</b>TRGN cells were acutely isolated from the neonatal SD rats. The voltage-dependent currents of the VGSCs on these neurons were elicited and analyzed by whole-cell patch-clamp recordings and the intracellular anisotonicity stimuli was established by adjusting the content of pipette solution. The effects of hypo-(260 mOsm) and hypertonic (350 mOsm) osmolarity on the activation and inactivation kinetics of VGSCs on TRGN were evaluated, compared with the normal intracellular environment.</p><p><b>RESULTS</b>The results demonstrated that intracellular hypotonic stimuli could influence both the activation and inactivation characteristics of VGSCs currents, including the membrane potential at half inactivation (V0.5) of the G-V and inactivation curves had obvious statistics significance (P<0.05) between hypotonicity (260mOsm) and isotonicity (306mOsm). However, only inactivation properties changed under intracellular hypertonic effects, including inactivation rate and k value.</p><p><b>CONCLUSION</b>It suggests that the kinetics of VGSCs on TRGN can be modulated both by intracellular hypo- and hypertonic with different characteristics.</p>

Construction of three-dimensional finite element models of the first mandibular molar restored with three post and core systems / 实用口腔医学杂志

Objective:To establish three-dimensional(3D) finite element models of the first mandibular molar restored with three post and core systems.Methods:Three 3D finite element models of the restored first mandibular molars were constructed by using CT image reconstruction technique.Then MIMICS software was used to separate the areas and to finish 3D calculation.GEOMAGIC software was applied to modify and generate a NURBS surface in each patch.All components of the models were assembled under the ANSYS preprocessor.Specific materials parameters were selected to simulate the various restoration and dentin status.Results:The 3D finite element models of restored first mandible molars were successfully established,which were consistent to the situation observed in the clinical environment.Conclusion:It is a practical and accurate method to establish three-dimensional finite element models by CT image reconstruction technique and reverse engineering software MIMICS and GEOMAGIC.