A finite element analysis on the indication for extracting partially impacted mandibular third molars considering mandibular trauma.

BACKGROUND: Patients presenting with partially impacted lower third molars (M3) have a higher likelihood of experiencing angle fractures while simultaneously decreasing the risk of condylar fractures. However, the specific biomechanical mechanism responsible for this occurrence remains unclear. Moreover, there is an ongoing debate regarding whether the removal of M3s might actually increase the risk of condylar fractures. This study aimed to evaluate how the presence of M3s influences mandibular fractures resulting from blows to the symphysis and lateral mandibular body, and to determine the indication for extracting M3s in such cases. METHODS: Models of the mandible with a partially M3-impacted model (M3I), M3-extracted model (M3E), and M3-absent model (M3A) were generated using a computer. A traumatic blown force of 2000 N was applied to the symphysis and the right body of the mandible. Von Mises and principal stresses were analyzed, and failure indexes were determined. Two cases of mandibular linear fractures were chosen for model verification and interpretation. RESULTS: When force was applied to the symphysis, the condylar region exhibited the highest stress levels, while stress in the mandibular angle region was much less regardless of the M3 state. On applying the force to the right mandibular body, stress in the condylar region decreased while stress in the mandibular body increased, especially in the blown regions. Impacted tooth or cavity formation post-M3 extraction led to uneven stress distribution on the blown side of the mandible, increasing the risk of mandibular angle fractures. In cases where M3 was absent or the extraction socket had healed, stress from lateral traumatic blown force was evenly distributed along both the inner and outer oblique lines of the mandible, thereby reducing the risk of mandibular fractures. CONCLUSIONS: The reduced risk of condylar fractures in patients with partially impacted lower M3s and mandibular angle fractures is mainly due to lateral blows on the mandible, which generate less stress in the condylar region than blows on the mandibular symphysis, rather than being caused by the M3 itself. Extraction of the lower M3 can decrease the risk of mandibular fractures, with a minor influence on condylar fractures.

Effect of various Er:YAG laser conditioning energies on dentin surface: micromorphological investigation and dentin-resin shear bond strength test.

The aim of this study is to assess the influence of various Er:YAG laser energies on dentin surface micromorphology and dentine-resin shear bond strength (SBS). Eighty dentin specimens were prepared and divided randomly into ten groups: control group (CG), phosphoric acid-etched group (AG), four laser-conditioned groups treated with various pulse energies of 40, 60, 80, and 100 mJ (L40, L60, L80, L100), and four laser-conditioned acid-etched groups (LA40, LA60, LA80, LA100). Two specimens from each group underwent scanning electron microscopy examination, while the remaining six were subjected to the dentin-resin SBS test. Statistical analyses included Welch's analysis of variance (ANOVA), followed by post hoc Tamhane's T2 multiple comparisons test, Pearson's correlation, and Fisher's exact test. Pulse energies of 60, 80, and 100 mJ fully exposed the dentin tubule orifices, although 100 mJ lead to microcracks. Laser-conditioned surfaces exhibited smaller tubule diameters compared to acid-etched surfaces, and tubule diameters positively correlated with dentin-resin SBS. Laser-conditioned groups showed lower SBS values, while laser-conditioned acid-etched groups demonstrated higher SBS values. No significant relationship was observed between dentin surface roughness and SBS. The range of laser energies used for dentin conditioning had limited effects on SBS or failure modes. Laser conditioning with energies ranging from 40 to 100 mJ effectively removes the smear layer from the dentin surface. However, to enhance dentin-resin bond strength, further acid etching of the laser-conditioned surface is necessary.

A systematic review and network meta-analysis of virtual reality, audiovisuals and music interventions for reducing dental anxiety related to tooth extraction.

BACKGROUND: Tooth extraction is a common procedure performed by oral and maxillofacial surgeons or dentists, often resulting in dental fear and anxiety. The use of relaxing music, audiovisuals, and virtual reality (VR) technologies has been employed to reduce dental anxiety. This network meta-analysis (NMA) aimed to assess the comparative effectiveness of relaxing music, audiovisuals, and VR in reducing dental anxiety associated with tooth extraction. METHODS: Four electronic databases were searched up to March 8, 2023, to identify randomized controlled trials (RCTs) evaluating different multimedia interventions, including the application of using relaxing music, audiovisuals, and VR technologies for dental anxiety. Studies utilizing various anxiety scales for tooth extraction were considered eligible. The pooled standard mean difference (SMD) and 95% confidence interval (CI) of anxiety scale scores were analyzed using Bayesian NMA. RESULTS: A total of 11 RCTs were included in this NMA. The Bayesian NMA results demonstrated that relaxing music (SMD = -0.64, 95% CI: -1.04, -0.25) and VR (SMD = -0.54, 95% CI: -1.08, -0.02) were associated with a reduction in dental anxiety, while audiovisuals (SMD = -0.34, 95% CI: -0.97, 0.33) required further consideration. Ranking probabilities indicated that relaxing music might be the most acceptable method for individuals with dental anxiety. The frequentist NMA yielded consistent rankings in a sensitivity analysis. CONCLUSIONS: Relaxing music shows the greatest potential for reducing dental anxiety related to tooth extraction when compared to other multimedia interventions.

Long non-coding RNA ZFY-AS1 represses periodontitis tissue inflammation and oxidative damage via modulating microRNA-129-5p/DEAD-Box helicase 3 X-linked axis.

A large number of studies have manifested long non-coding RNA (lncRNA) is involved in the modulation of the development of periodontitis, but the specific mechanism has not been fully elucidated. The purpose of this study was to explore the biological function and latent molecular mechanism of lncZFY-AS1 in periodontitis. The results clarified lncZFY-AS1 and DEAD-Box Helicase 3 X-Linked (DDX3X) were up-regulated, but microRNA (miR)-129-5p was down-regulated in periodontitis. Knockdown of lncZFY-AS2 or overexpression of miR-129-5p decreased macrophage infiltration and periodontal membrane cell apoptosis, increased cell viability, repressed inflammatory factors and nuclear factor kappa B activation, reduced oxidative stress, but promoted nuclear factor-E2-related factor 2/heme oxygenase 1 expression. LncZFY-AS1 elevation further aggravated periodontitis inflammation, oxidative stress, and apoptosis. LncZFY competitively adsorbed miR-129-5p to mediate DDX3X expression. Knockdown lncZFY's improvement effect on periodontitis was reversed by depressive miR-129-5p or enhancive DDX3X. In conclusion, these data suggest lncZFY-AS1 promotes inflammatory injury and oxidative stress in periodontitis by competitively binding to miR-129-5p and mediating DDX3X expression. LncZFY-AS1/miR-129-5p/DDX3X may serve as a novel molecular target for treatment of periodontitis in the future.

Effect of humic acid as a photosensitizer combined with low-energy laser on orthodontic tooth movement in rats.

BACKGROUND/PURPOSE: Humic acid (HA) could promote light conversion reaction, and lasers accelerate orthodontic tooth movement. We investigated the effect of HA, as a photosensitizer, combined with low-energy laser on orthodontic tooth movement in rats. MATERIALS AND METHODS: An orthodontic tooth movement model was established, and the upper left first molar was moved mesially by a nickel-titanium tension spring with a 50-g force. HA was injected into the rats' abdominal cavity (80 mg/kg once daily). The periodontal tissue of the upper left upper first molar on the pressure side was irradiated (50 s once every 2 days) using a semiconductor laser (wavelength, 650 nm; power, 50 mV). Distance moved by the upper left first molar was measured at different time points, and the tissue of the first molar was sectioned and scanned by micro-computed tomography to evaluate the alveolar bone density. Tartrate-resistant acidic phosphatase staining was used to observe the osteoclast number, alveolar bone, and periodontal tissue. RESULTS: HA alone did not significantly affect orthodontic tooth movement, alveolar structure density, or periodontal tissue remodeling (P > 0.05). HA combined with a low-energy laser accelerated orthodontic tooth movement. The number of bone absorption lacunae and osteoclasts on the alveolar bone's pressure side increased significantly (P < 0.05), while the density decreased significantly (P < 0.05); however, no root absorption was observed. CONCLUSION: HA can improve the conversion rate of low-energy lasers, enhance the low-energy laser effect, and promote orthodontic tooth movement and periodontal tissue reconstruction on the pressure side in rats, without causing root resorption.

In vitro evaluation of the effectiveness of bleaching agents activated by KTP and Nd:YAG laser.

AIM: To compare two different laser sources, a KTP laser with a wavelength of 532 nm and a Nd:YAG laser with a wavelength of 1064 nm, to investigate the relation between laser source and bleaching gel during laser irradiation. METHODS: Extracted human teeth were stained and randomly divided into six groups. Two in-office bleaching gels, Beyond and Opalescence Boost, were applied to stained teeth and then irradiated at either 532 nm or 1064 nm. The temperature change of pulp chamber was measured. The color change (ΔE*) was evaluated at the following time points: immediately after bleaching, 7, 14 and 30 days after the end of bleaching. RESULTS: Boost irradiated by KTP laser showed the higher temperature increase when compared with Beyond irradiated KTP and Nd:YAG. Boost irradiated by Nd:YAG presented lower temperature increase than by KTP. All groups showed a certain color change. After bleaching, Nd:YAG laser irradiation did not increase the ΔE* value significantly compared with gels without laser (p >  0.05). At each time point, Boost activated by KTP laser showed higher ΔE* value compared with other groups (p < 0.05), but decreased significantly 15 days after the end of bleaching. The other groups showed a relatively small change in ΔE* value after 30 days (p > 0.05). CONCLUSIONS: KTP laser achieved better results than the Nd:YAG laser regarding tooth color change when associated with the Opalescence Boost bleaching gels.

Comamonas granuli sp. nov., isolated from granules used in a wastewater treatment plant.

A Gram-negative, motile, rod-shaped, non-spore-forming bacterial strain, designated as Ko03(T), was isolated from microbial granules, and was characterized, using a polyphasic approach, in order to determine its taxonomic position. The isolate was positive for catalase and oxidase, but negative for gelatinase and beta-galactosidase. Phylogenetic analyses using the 16S rRNA gene sequence showed that the strain formed a monophyletic branch towards the periphery of the evolutionary radiation occupied by the genus Comamonas, its closest neighbors being Comamonas koreensis KCTC 12005(T) (95.9% sequence similarity), Comamonas nitrativorans DSM 13191(T) (95.7%), and Comamonas odontotermitis LMG 23579(T) (95.7%). Strain Ko03(T) had a genomic DNA G+C content of 68.4 mol% and the predominant respiratory quinone was Q-8. The major fatty acids were C(16:1) omega7c (44.7%), C(16:0) (28.1%), C(18:1) (16.1%), and C(10:0) 3-OH (3.5%). These chemo-taxonomic results supported the affiliation of strain Ko03(T) to the genus Comamonas. However, low 16S rRNA gene sequence similarity values and distinguishing phenotypic characteristics allowed genotypic and phenotypic differentiation of strain Ko03(T) from recognized Comamonas species. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Ko03(T) represents a novel species of the genus Comamonas, for which the name Comamonas granuli sp. nov. is proposed. The type strain is Ko03(T) (=KCTC 12199(T)=NBRC 101663(T)).

Dyadobacter ginsengisoli sp. nov., isolated from soil of a ginseng field.

A Gram-negative, aerobic, non-motile, non-spore-forming and rod-shaped bacterium, strain Gsoil 043(T), was isolated from soil from a ginseng field in Pocheon province, South Korea. The novel isolate was characterized in order to determine its taxonomic position. On the basis of 16S rRNA gene sequence similarity, strain Gsoil 043(T) was shown to belong to the family 'Flexibacteraceae' and was related to Dyadobacter fermentans (96.7 %), Dyadobacter crusticola (96.3 %) and Dyadobacter hamtensis (95.8 %). The 16S rRNA gene sequence similarity of the novel strain to other recognized species within the family 'Flexibacteraceae' was less than 87.0 %. The G+C content of genomic DNA was 48 mol%. Phenotypic and chemotaxonomic data (major menaquinone, MK-7; major fatty acids, C(16 : 1)omega7c, iso-C(15 : 0) and C(16 : 0)) supported the affiliation of strain Gsoil 043(T) to the genus Dyadobacter. The results of physiological and biochemical tests enabled strain Gsoil 043(T) to be differentiated genotypically and phenotypically from the three Dyadobacter species with validly published names. The novel isolate therefore represents a novel species for which the name Dyadobacter ginsengisoli sp. nov. is proposed, with the type strain Gsoil 043(T) (=KCTC 12589(T)=LMG 23409(T)).