Effects of root contact length on the failure rate of anchor screw.

PURPOSE: This study aimed to evaluate the causal relationship between root contact and root contact length of orthodontic miniscrew implants (miniscrews), and assessed factors for implant failure through cone-beam computed tomography (CBCT) images. METHODS: First, a logistic regression analysis was performed to investigate the most relevant factors for implant failure based on sex, age, vertical skeletal pattern, horizontal skeletal pattern, and presence of root contact in 59 patients (mean age: 21.2, age range: 13-54 years) who had miniscrew implants. Next, 38 miniscrews (1.6 mm in diameter and 8.0 mm in length) with root contact were investigated in the patients. Root contact length was measured using CBCT taken after miniscrew implant placement. RESULTS: The results showed that root contact was the most critical risk factor for failure of miniscrew implants in patients. Logistic regression analysis showed that the risk approximately doubled as the root contact length increased by 1.0 mm. CONCLUSION: Avoiding proximity to the root during miniscrew implant placement is essential to prevent implant failure.

Comparison of cerebral cortex activation induced by tactile stimulation between natural teeth and implants.

BACKGROUND: The purpose of this study was to assess the cortical-level sensory differences between natural teeth with a periodontal membrane and dental implants. MATERIAL AND METHODS: We used functional near-infrared spectroscopy (fNIRS) to measure brain activity in the cerebral cortex of 12 patients who had both natural teeth and dental implants in the lower molar region. Painless vibratory tactile stimulation was performed on both the natural teeth and the dental implants. RESULTS: Activation was seen in the somatosensory cortex during stimulation of both natural teeth and dental implants. A comparison of cortical activation showed no significant differences between natural teeth and dental implants. CONCLUSIONS: These results indicate the possible existence of sensory input to the cerebral cortex via dental implants as well as natural teeth, and thus suggest that may not only the periodontal membrane be involved in the signaling pathway. The data from this experiment may help us for understanding the neural mechanisms underlying natural teeth and dental implants. Key words:fNIRS, natural teeth, implants, brain activity, somatosensory cortex.

Mechanical and frictional properties of aesthetic orthodontic wires obtained by hard chrome carbide plating.

BACKGROUND/PURPOSE: Although aesthetic wire coating has been increasing in demand, it has problems that changes in mechanical properties and increase in frictional force. The aim of this study was to evaluate the coating of the wire, as characterized by aesthetics, in terms of low and constant friction and mechanical properties. MATERIALS AND METHODS: Hard chrome carbide-plated (HCCP) wires (HCCP group), commercially available polymer-coated wires (P group), rhodium-coated wires (R group), and uncoated wires (control group) were used. For all wire types, a stainless steel wire of dimensions 0.017 inch × 0.025 inch was used. They were evaluated by three-point bending, friction testing, surface observation, and colorimetric testing. RESULTS: The HCCP group was not significantly different from the control group in terms of flexural strength (σ) and flexural modulus (E) (σ: p = 0.90, E: p = 0.35). However, it was significantly inferior compared to the three other groups in terms of the maximum static and kinetic frictional forces under both dry and wet conditions (p < 0.05). In the surface observation, scratches were observed on the wire after the friction test. In the colorimetric test, no significant difference was observed between the HCCP group and the R group (p > 0.05). CONCLUSION: The mechanical properties of the HCCP wire were not significantly different compared to the control group. The frictional force of the HCCP wire was significantly lower than the other group. Therefore, the HCCP wire was suggested to increase the efficiency of tooth movement in clinics.

Simple Myofunctional Therapy Using Ready-made Mouthpiece Device before and after Orthodontic Treatment.

The present report describes myofunctional therapy using a ready-made training device, the T4A, in patients with permanent dentition and its effect on the prevention of relapse. The buccinator mechanism maintains the inner pressure of the tongue muscle equivalent to the outer pressure of the perioral soft tissues, such as the orbicular muscles, including the cephalopharyngeus and buccinator muscles. Training is performed so that patients learn to place their tongue and lips in the appropriate resting positions. The shape of the T4A and tongue guard supports the tongue from the bottom, allowing formation of the correct resting tongue position. However, the use of T4A for a long period of time may cause the teeth movement; therefore, caution is required. Use of the T4A is effective for the correction of oral habits, myofunctional therapy and for teaching the correct resting tongue position during the daytime and for the correction of oral habits, teaching correct resting tongue position during sleep.

Effect of Melamine Sponge on Tooth Stain Removal.

OBJECTIVES: To investigate the stain removal ability of melamine sponge before aesthetic tooth whitening in extracted teeth. METHODS: Melamine sponge of thickness 40 mm was compressed and the destruction of the partition wall structure during the compression process was examined under a stereoscopic microscope. An extracted human tooth was cleaned by normal polishing or with melamine sponge for 90 s. To evaluate the stain level, the tooth surfaces were photographed under a stereoscopic microscope at 0, 30, 60 and 90 s. The residual stained region was traced in a high-magnification photograph, and the stain intensity was presented as a change, relative to the intensity before the experiment (0 s). RESULTS: Mechanical cleaning by toothbrushing produced polishing scratches on the tooth surface, whereas use of the melamine sponge resulted in only minimal scratches. As the compression level increased, the stain-removing effect tended to become stronger. CONCLUSION: Melamine sponge can remove stains from the tooth surface more effectively and less invasively compared to a conventional toothbrush. As no new scratches are made on the tooth surface when using a melamine sponge brush, the risk of re-staining is reduced. Cleaning using a melamine sponge brush can be easily and effectively performed at home and in a dental office.

Influence of restoration adjustments on prefrontal blood flow: A simplified NIRS preliminary study.

OBJECTIVE: The aim of this study was to examine, after setting several restorations, the influence of adjusted occlusal interference during gum chewing on blood flow in the prefrontal area as determined using near-infrared spectroscopy. MATERIAL AND METHODS: The physiological rate was assessed using a visual analog scale (VAS) questionnaire. We selected 16 patients who desired prosthetic restorative treatment on the lateral dentition, and eight healthy volunteers. Subjects were divided into three eight-person groups. One group received restorations on the premolar area (PA), another group received restorations on the molar area (MA), and the control group (CT) received no prosthetic restorations. The spectroscope was fastened to the frontal region of the head after placement of the final restoration, but before adjustment. RESULTS: Pre-adjustment (first gum chewing for CT) blood flow in the prefrontal cortex was measured during gum chewing. Blood flow was again measured during gum chewing after the restoration (second gum chewing for CT) had been adjusted in accordance with the subjective assessment of the patient while wearing the device. The VAS provided quantification of comfort during gum chewing before and after restoration adjustment. For the PA and MA groups, adjusting restorations decreased discomfort significantly during gum chewing. Moreover, in the MA group, prefrontal blood flow was significantly reduced, and blood flow correlated with discomfort. CONCLUSIONS: Activation of the prefrontal area may provide an objective criterion for judging the functionality of occlusion after prosthetic occlusal reconstruction and/or orthodontics.

Effects of mandibular retrusive deviation on prefrontal cortex activation: a functional near-infrared spectroscopy study.

The objective of this study was to evaluate occlusal condition by assessing brain activity in the prefrontal cortex, which is associated with emotion. Functional near-infrared spectroscopy (fNIRS) was used to detect changes in cerebral blood flow in the prefrontal cortex of 12 healthy volunteers. The malocclusion model was a custom-made splint that forced the mandible into retrusion. A splint with no modification was used as a control. The cortical activation during clenching was compared between the retrusive position condition and the control condition. A visual analog scale score for discomfort was also obtained during clenching and used to evaluate the interaction between fNIRS data and psychiatric changes. Activation of the prefrontal cortex was significantly greater during clenching in the mandibular retrusive condition than during clenching in the control condition. Furthermore, Spearman rank-correlation coefficient revealed a parallel relation between prefrontal cortex activation and visual analog scale score for discomfort. These results indicate that fNIRS can be used to objectively evaluate the occlusal condition by evaluating activity in the prefrontal cortex.

Medical-grade collagen peptide in injectables provides antioxidant protection.

Medical-grade collagen peptide is used as an additive agent in pharmaceutical formulations; however, it is unknown as to whether the compound exerts antioxidant effects in vitro. In this study, we evaluated the antioxidant effects of medical-grade collagen peptide on reactive oxygen species such as hydroxyl radical, superoxide anion radical and singlet oxygen using electron spin resonance and spin trapping. We confirmed that medical-grade collagen peptide directly inhibited hydroxyl radical generated by the Fenton reaction or by ultraviolet irradiation of hydrogen peroxide, and singlet oxygen. In addition, an antioxidant effect of medical-grade collagen peptide on singlet oxygen was observed in peptide fractions 12-22. The total amount of antioxidant amino acids (Gly, Hyp, Glu, Ala, Cys, Met and His) constituted more than half of the total amino acids in these fractions. These results suggest that the observed antioxidant properties of medical-grade collagen peptide are due to the compound containing antioxidant amino acids. Medical-grade collagen peptide, which is used in pharmaceuticals, and especially in injectables, could provide useful antioxidant properties to protect the active ingredient from oxidation.

Vertical facial height and its correlation with facial width and depth: Three dimensional cone beam computed tomography evaluation based on dry skulls.

INTRODUCTION: The aim of the present study was to evaluate how vertical facial height correlates with mandibular plane angle, facial width and depth from a three dimensional (3D) viewing angle. METHODS: In this study 3D cephalometric landmarks were identified and measurements from 43 randomly selected cone beam computed tomography (CBCT) images of dry skulls from the Weisbach collection of Vienna Natural History Museum were analyzed. Pearson correlation coefficients of facial height measurements and mandibular plane angle and the correlation coefficients of height-width and height-depth were calculated, respectively. RESULTS: The mandibular plane angle (MP-SN) significantly correlated with ramus height (Co-Go) and posterior facial height (PFH) but not with anterior lower face height (ALFH) or anterior total face height (ATFH). The ALFH and ATFH showed significant correlation with anterior cranial base length (S-N), whereas PFH showed significant correlation with the mandible (S-B) and maxilla (S-A) anteroposterior position. CONCLUSIONS: High or low mandibular plane angle might not necessarily be accompanied by long or short anterior face height, respectively. The PFH rather than AFH is assumed to play a key role in the vertical facial type whereas AFH seems to undergo relatively intrinsic growth.

Dental resin curing blue light induced oxidative stress with reactive oxygen species production.

Dental resin curing blue light has been used in the treatment of tooth bleaching and to restore teeth with resin-based composite fillings. However, there has been little consideration of its effect on oral tissues such as dental pulp and oral mucosa. The aim of this study was to investigate whether dental resin curing blue light irradiation affects the dental pulp, especially the blood vessels that are known as the first target of reactive oxygen species (ROS), which play an important role in vascular reactivity. We found that blue light irradiation increased the level of lipid peroxidation in isolated rat aorta blood vessels by measuring malondialdehyde. Furthermore, cell proliferative activity was decreased in a time-dependent manner and apoptosis of human aorta vascular smooth muscle cells (VSMCs) was induced. These results indicated that (ROS) such as hydrogen peroxide and hydroxyl radicals were generated in VSMCs by irradiation with blue light, and they induced cytotoxicity associated with oxidative stress, which increased lipid peroxidation and apoptosis. In addition, N-acetyl-l-cysteine, which is a typical intracellular antioxidant, protected VSMCs against cytotoxicity associated with oxidative stress. These findings suggested that antioxidants may be used to prevent oxidative stress in dental pulp by repeated and/or multiple treatments with blue light irradiation in future dental treatments.

The amount of TMJ displacement correlates with brain activity.

The aim of this functional magnetic resonance imaging (fMRI) study was to investigate the correlation between the severity of malocclusion and brain activation. The fMRI was used to measure blood-oxygenation- level-dependent (BOLD) signals of twelve healthy human subjects while they clenched in two different ways to simulate two types of malocclusion. In each malocclusion model, a custom-made splint forced the mandible to each of two retrusive positions (0.5 mm, 0.7 mm). A no-modification splint provided the control. We compared the BOLD signals measured at each clenching position with those measured during the corresponding resting conditions. The BOLD signals were significantly stronger in the amygdala and the prefrontal area (PFA) when subjects clenched in the two retrusive positions compared during clenching in the control position. In addition, the BOLD signal in the PFA increased as the simulated malocclusion became more severe. These results indicate that we may be able to objectively assess the severity of malocclusion via focus on the brain activity.

Chewing-induced regional brain activity in edentulous patients who received mandibular implant-supported overdentures: a preliminary report.

PURPOSE: We used functional magnetic resonance imaging (fMRI) to investigate the change in brain regional activity during gum chewing when edentulous subjects switched from mandibular complete dentures to implant-supported removable overdentures. METHODS: Four edentulous patients (3 males and 1 female, aged 64 to 79 years) participated in the study. All subjects received a set of new maxillary and mandibular complete dentures (CD), followed by a maxillary complete denture and a new mandibular implant-supported removable overdentures (IOD). A 3-T fMRI scanner produced images of the regional brain activity for each subject that showed changes in the blood-oxygenation-level-dependent (BOLD) contrast in the axial orientation during gum-chewing with CD and IOD. RESULTS: Region-of-interest analysis showed that IOD treatment significantly suppressed chewing-induced brain activity in the prefrontal cortex. The chewing-induced brain activities in the primary sensorimotor cortex and cerebellum tended to decrease with IOD treatment, however they did not reach to significance level. There was no change in brain activity in the supplementary motor area, thalamus and insula between gum chewing with CD and IOD. Group comparison using statistical parametrical mapping further showed that, within the prefrontal cortex, the neural activity of the frontal pole significantly decreased during gum-chewing with IOD when compared to that with CD (P<0.05). CONCLUSION: Despite the limitation of a small sample size, these results suggest that the gum-chewing task in elderly edentulous patients resulted in differential neural activity in the frontal pole within the prefrontal cortex between the 2 prosthodontic therapies-mandibular CD and IOD.

Effects of mandibular deviation on brain activation during clenching: an fMRI preliminary study.

Using functional magnetic resonance imaging (fMRI) in eight healthy human subjects, the present study measured blood oxygenation level-dependent (BOLD) signals during clenching in a malocclusion model, using a custom-made splint that forced the mandible to a retrusive position and a splint of no modification for control, and compared the results to the BOLD signals during the corresponding resting conditions. An individual visual analog scale (VAS) score was also examined during clenching to evaluate the interactions between fMRI data and psychiatric changes. During both clenchings, activations in four brain regions (premotor cortex, prefrontal cortex, sensorimotor cortex, and insula) were seen. However, clenching in the malocclusion model, with psychological discomfort, increased additionally BOLD signals in the anterior cingulate cortex and the amygdala. Furthermore, there was a parallel relationship between BOLD signal intensities and VAS scores in these two regions. The findings may suggest the involvement of clenching with malocclusal conditions in the emotion and/or pain-related neural processing in the brain.