Removable thermoplastic appliances modified by incisal cuts show altered biomechanical properties during tipping of a maxillary central incisor.

BACKGROUND: The present study aimed to evaluate the force delivery of removable thermoplastic appliances (RTAs), modified by different sized incisal cuts, during tipping of a maxillary central incisor in palatal and vestibular direction. METHODS: Forty-five RTAs from three different materials (Biolon®, Erkodur®, Ideal Clear®) of the same thickness (1 mm) were used. Analysis was performed on a separated maxillary central incisor which was part of a resin model with a complete dentition. In 15 RTAs, of different material, a cut was inserted at the incisal edge of tooth 11. In 15 other appliances, the cut was extended to teeth 12 and 21. Fifteen aligners remained uncut. The experimental tooth was tipped starting from the zero position in 0.05° steps to a maximal deflection of ± 0.42° of the incisal edge in vestibular and palatal direction, after positioning the RTA onto the model. RESULTS: The horizontal (Fx) and the vertical (Fz) force components were decreased by approximately half with increasing cut size. Fz values changed during palatal tipping from a weak intrusive force, for aligners without cut, to an extrusive force with increasing cut size. Compared to both other materials used (Erkodur® and Ideal Clear®), the Biolon® aligners showed significantly higher Fx and Fz values (p < 0.0001, respectively). CONCLUSIONS: RTAs modified by different sized incisal cuts show altered biomechanical properties and an inversion of the vertical force component, during tipping of a maxillary central incisor.

Osteoblast-like cells with different embryologic origins behave differently in increasing zoledronic acid concentrations: a pilot study in pigs.

OBJECTIVE: We compared the intraindividual effects of increasing zoledronic acid (ZA) concentrations on osteoblast-like cells with different embryologic origins. STUDY DESIGN: Cultured osteoblast-like cells from mandible and iliac crest bone samples of domestic pigs were exposed to increasing concentrations of ZA (0, 10-8, 10-6, and 10-4 M). Proliferation was assessed by cell counting. Receptor activator of nuclear factor kB ligand and osteoprotegerin (OPG) messenger RNA expression were assessed at 0, 1, 4, 7, and 10 days. RESULTS: The OPG expression level was higher in the iliac crest than in the mandible. Neither ZA concentration nor the cells' origin affected the expression of receptor activator of nuclear factor kB ligand. At 10-6 M, OPG expression from both locations reached the same level after 7 days of cultivation, as OPG expression increased to a greater extent in the mandible in comparison to the iliac crest. CONCLUSION: Cultured mandibular osteoblast-like cells reacted more sensitively to high ZA concentrations than did osteoblast-like cells from the iliac crest.

Primary stability and osseointegration of dental implants in polylactide modified bone - A pilot study in Goettingen minipigs.

The present study aimed to evaluate primary stability (PS) and osseointegration of dental implants in polylactide [70/30 poly(l-lactide-co-d, l-lactide); (PLDLA)] modified bone in 30 Goettingen minipigs. Each animal received three implants per jaw quadrant. In a split-mouth design, one side of the maxilla and mandible was randomly allocated to the experimental treatment (PLDLA applied into the drill hole before implantation), while the contralateral sides served as intraindividual controls (no PLDLA applied). The required insertion torque and the implant stability quotient (ISQ) were measured during implantation. ISQ, volume density (VD) of new bone formation (NBF), and the bone-implant contact (BIC) were evaluated at the end of the observation period (1, 3, 6, 12, and 24 months, respectively) in six animals each. Across all study groups, the PLDLA treatment resulted in a) a comparable insertion torque, b) an equivalent ISQ, c) a reduced BIC, and d) a reduced VD of NBF, as opposed to the untreated controls. In conclusion, the PLDLA treatment did not affect the PS, but rather led to an impaired osseointegration, which was particularly strong in the compact mandibular bone, and decreased in the spongious maxillary bone. PLDLA induced anchoring in spongious bone should be evaluated in further investigations.

Connexin subtype expression during oral carcinogenesis: A pilot study in patients with oral squamous cell carcinoma.

Gap junctional intercellular communication (GJIC) and connexin (Cx) expression were reported in association with carcinogenesis in various types of tumours. In an earlier histomorphometric study, the protein levels of Cx subtypes 26, 43 and 45 were differentially expressed in oral squamous cell carcinoma (OSCC), corresponding lymph node metastases and dysplasia-free oral mucosa. Moreover, membrane Cx43 acted as an independent prognostic marker in OSCC tissues. This study aimed to confirm the expression of described Cx subtypes at the mRNA level. Hence, a reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis of Cx26, Cx43 and Cx45 gene expressions was performed in paired carcinoma and mucosa samples of 15 OSCC patients. Additionally, we assessed the interaction between Cx subtype expression and clinicopathological routine parameters. The RT-qPCR analysis revealed that Cx26 was downregulated in OSCC (P=0.01), while Cx43 was marginally upregulated in cancer tissue (P=0.04). Cx45 was significantly overexpressed in OSCC tissue compared with the intraoral mucosa controls (P<0.01), and remained unchanged at different tumour stages. No significant interactions between differential Cx subtype expression and clinicopathological routine parameters were observed. In conclusion, Cx regulation at the transcriptional level appears to be an early event during the initiation and development of OSCC, and is maintained during further progression. However, the mRNA-protein correlation is variable. This may be indicative of post-transcriptional, translational and degradation regulations being associated with the determination of Cx protein concentration during oral carcinogenesis.

Influence of synthetic polyethylene glycol hydrogels on new bone formation during mandibular augmentation procedures in Goettingen minipigs.

Polyethylene glycol hydrogels (PEG) have been used as slow release carrier for osteoinductive growth factors in order to achieve a retarded delivery. However, there have been concerns about negative effects on bone regeneration. This study aims to test whether PEG hydrogels themselves affect new bone formation (NBF), when used as a carrier during mandibular augmentation procedures. In a randomized split-mouth design, bilateral mandibular bone defects were surgically created in 12 Goettingen minipigs, and subsequently augmented, using PEG hydrogel on one side of the mandible. The contralateral sides, without PEG, served as controls. After 4 and 12 weeks, bone formation was evaluated in six animals each. A comparison of the data, using a three-way analysis of variance (ANOVA), revealed a significant effect of the healing time and the region of the graft on the distribution and enhancement of NBF (P < .0001, respectively). Although a 0.3% (95%-CI [-5.5; 4.8]) lower volume density of newly formed bone could be observed over all PEG hydrogel sections, in contrast to the contralateral controls, the analysis revealed no clinically significant effects of the PEG hydrogel treatment on the total level (P = 0.90), and the distribution of NBF (P = 0.54). In conclusion, PEG hydrogels do not affect NBF when used as a carrier for osteoinductive growth factors during mandibular augmentation procedures.

Reduced somatosensory impairment by piezosurgery during orthognathic surgery of the mandible.

PURPOSE: This clinical trial aimed to test the hypothesis that piezosurgery causes reduced nerval irritations and, thus, reduced somatosensory impairment when used in orthognathic surgery of the mandible. METHODS: To this end, 37 consecutive patients with Angle Class II and III malocclusion were treated using bilateral sagittal split osteotomies (BSSO) of the mandible. In a split mouth design, randomized one side of the mandible was operated using a conventional saw, while a piezosurgery device was used on the contralateral side. In order to test the individual qualities of somatosensory function, quantitative sensory testings (QSTs) were performed 1 month, 6 months and 1 year after surgery. RESULTS: A comparison of the data using a two-way analysis of variance (ANOVA) revealed a significant reduction in postoperative impairment in warm detection threshold (WDT) (P = 0.046), a decreased dynamic mechanical allodynia (ALL) (P = 0.002) and a decreased vibration detection threshold (VDT) (P = 0.030) on the piezosurgery side of the mandible as opposed to the conventionally operated control side. In the remaining QSTs, minor deviations from the preoperative baseline conditions and a more rapid regression could be observed. CONCLUSIONS: Piezosurgery caused reduced somatosensory impairment and a faster recovery of somatosensory functions in the present investigation.

Sinus floor augmentation with recombinant human growth and differentiation factor-5 (rhGDF-5): a pilot study in the Goettingen miniature pig comparing autogenous bone and rhGDF-5.

AIM: The aim of this study was to test the hypothesis that recombinant human growth and differentiation factor-5 (rhGDF-5) in combination with a beta-tricalcium phosphate (beta-TCP) scaffold material results in superior bone formation in sinus floor augmentations in miniature pigs compared with a particulated autogenous bone graft combined with the scaffold material. MATERIAL AND METHODS: Six adult female Goettingen minipigs underwent a maxillary sinus floor augmentation procedure. In a split-mouth design, the sinus floors were augmented with beta-TCP mixed with autogenous cortical bone chips, in a ratio of approximately 1 : 1, on one side. The contralateral test site was augmented using beta-TCP coated with two concentrations of rhGDF-5 (400 microg rhGDF-5/g beta-TCP or 800 microg rhGDF-5/g beta-TCP; three animals in each case). Simultaneously, one dental implant was inserted into each sinus floor augmentation. After 12 weeks, a histological and histomorphometric assessment of non-decalcified histological specimens was made. RESULTS: There were significantly higher mean values of volume density of newly formed bone using beta-TCP coated with two concentrations of rhGDF-5 (400 microg: 32.9%; 800 microg: 23.9%) than with the corresponding control (autogenous bone/beta-TCP) (14.6%, 12.9%) (P=0.012, P=0.049). The bone-to-implant contact rates (BIC) were significantly enhanced in test sites (400 microg: 84.2%; 800 microg: 69.8%) compared with the corresponding control sites (24.8%, 40.8%) (P=.027, P=.045). CONCLUSION: rhGDF-5 delivered on beta-TCP significantly enhanced bone formation compared with beta-TCP combined with autogenous bone in sinus lift procedures in miniature pigs.

CPA6, FMO2, LGI1, SIAT1 and TNC are differentially expressed in early- and late-stage oral squamous cell carcinoma--a pilot study.

To identify novel genes that could be involved in oncogenesis of oral squamous cell carcinoma a microarray-based gene-expression analysis was performed using tumour samples from patients with low-stage (n=4) and high-stage (n=4) disease in a pilot study. Genes (601) were found to be significantly regulated in cancer tissue compared to adjacent intraindividual mucosa controls. Genes (25) were identified with differences in their regulation comparing samples from early-stage cancer with those from advanced disease. The gene expression pattern of 5 of 7 genes examined by real-time-PCR verified the results received from the microarray-experiment. Among these, FMO2, CPA6, TNC and SIAT1 were significantly upregulated in early disease stages. LGI1 gene expression was significantly enhanced in normal adjacent mucosa of patients with early-stage disease without showing a differential expression in carcinoma biopsies. With this pilot study several novel genes were identified, which could be related to early and late stage disease. Hypotheses from these findings are discussed and have to be confirmed in a larger study sample.