Influence of the orthodontic bonding procedure on biofilm formation.

INTRODUCTION: In orthodontics, white spot lesions are a persistent and widespread problem caused by the demineralization of buccal tooth surfaces around bonded brackets. The remaining adhesive around the brackets leads to surface roughness, which might contribute to demineralization. The present in vitro study aimed to compare a conventional and a modern adhesive system (APC Flash-Free technology) for orthodontic brackets with regard to the adhesion of Streptococcus sobrinus, a leading caries pathogen. METHODS: This in vitro study included 20 premolar teeth and compared 10 APC Flash-Free adhesive-coated ceramic brackets (FF)with 10 conventionally bonded (CB) ceramic clarity brackets. Specimens were incubated in an S. sobrinus suspension for 3 h. To evaluate the bacterial formation, samples were analysed with a scanning electron microscope (SEM). Imaging software was used to quantify and statistically compare percentage values of colonization (PVC) in both groups' adhesion and transition areas. RESULTS: We found a significant difference in biofilm formation between the groups for the adhesive and transition areas. PVC in the adhesive area was approximately 10.3-fold greater for the CB group compared with the FF group (median: 3.2 vs 0.31; P < 0.0001). For the transition area, median PVC was approximately 2.4-fold greater for the CB group compared with the FF group (median: 53.17 vs 22.11; P < 0.01). CONCLUSIONS: There was a significantly lower level of S. sobrinus formation around the FF bracket system than there was surrounding the conventionally bonded group. This study suggests that the FF adhesive bracket system can help reduce the occurrence of bacterial growth around orthodontic brackets.

Mediterranean diet component oleic acid increases protective lipid mediators and improves trabecular bone in a Porphyromonas gingivalis inoculation model.

AIM: Therapeutic modulation of bacterial-induced inflammatory host response is being investigated in gingival inflammation and periodontal disease pathology. Therefore, dietary intake of the monounsaturated fatty acid (FA) oleic acid (OA (C18:1)), which is the main component of Mediterranean-style diets, and saturated FA palmitic acid (PA (C16:0)), which is a component of Western-style diets, was investigated for their modifying potential in an oral inoculation model of Porphyromonas gingivalis. MATERIALS AND METHODS: Normal-weight C57BL/6-mice received OA- or PA-enriched diets (PA-ED, OA-ED, PA/OA-ED) or normal standard diet for 16 weeks and were inoculated with P. gingivalis/placebo (n = 12/group). Gingival inflammation, alveolar bone structure, circulating lipid mediators, and in vitro cellular response were determined. RESULTS: FA treatment of P. gingivalis-lipopolysaccharide-incubated gingival fibroblasts (GFbs) modified inflammatory activation, which only PA exacerbated with concomitant TNF-α stimulation. Mice exhibited no signs of acute inflammation in gingiva or serum and no inoculation- or nutrition-associated changes of the crestal alveolar bone. However, following P. gingivalis inoculation, OA-ED improved oral trabecular bone micro-architecture and enhanced circulating pro-resolving mediators resolvin D4 (RvD4) and 4-hydroxydocosahexaenoic acid (4-HDHA), whereas PA-ED did not. In vitro experiments demonstrated significantly improved differentiation in RvD4- and 4-HDHA-treated primary osteoblast cultures and reduced the expression of osteoclastogenic factors in GF. Further, P. gingivalis infection of OA-ED animals led to a serum composition that suppressed osteoclastic differentiation in vitro. CONCLUSIONS: Our results underline the preventive impact of Mediterranean-style OA-EDs by indicating their pro-resolving nature beyond anti-inflammatory properties.

Effects of reducing excess dental adhesive on bacterial adhesion in the bracket periphery.

OBJECTIVES: White spot lesions are one of the most common side effects of orthodontic therapy with a multibracket appliance and may indicate a preliminary stage of caries, also known as initial caries. Several approaches may be utilized to prevent these lesions, such as reducing bacterial adhesion in the area surrounding the bracket. This bacterial colonization can be adversely affected by a number of local characteristics. In this context, the effects of excess dental adhesive in the bracket periphery were investigated by comparing a conventional bracket system with the APC flash-free bracket system. MATERIALS AND METHODS: Both bracket systems were applied to 24 extracted human premolars, and bacterial adhesion with Streptoccocus sobrinus (S. sobrinus) was performed for 24 h, 48 h, 7 d, and 14 d. After incubation, bacterial colonization was examined in specific areas by electron microscopy. RESULTS: Overall, significantly fewer bacterial colonies were found in the adhesive area around the APC flash-free brackets (n = 507 ± 13 bacteria) than the conventionally bonded bracket systems (n = 850 ± 56 bacteria). This is a significant difference (**p = 0.004). However, APC flash-free brackets tend to create marginal gaps with more bacterial adhesion in this area than conventional bracket systems (n = 265 ± 31 bacteria). This bacterial accumulation in the marginal-gap area is also significant (*p = 0.029). CONCLUSION: A smooth adhesive surface with minimal adhesive excess is beneficial for reducing bacterial adhesion but also poses a risk of marginal gap formation with subsequent bacterial colonization, which can potentially trigger carious lesions. CLINICAL RELEVANCE: To reduce bacterial adhesion, the APC flash-free bracket adhesive system with low adhesive excess might be beneficial. APC flash-free brackets reduce the bacterial colonization in the bracket environment. A lower number of bacteria can minimize white spot lesions in the bracket environment. APC flash-free brackets tend to form marginal gaps between the bracket adhesive and the tooth.

GDF15 Promotes the Osteogenic Cell Fate of Periodontal Ligament Fibroblasts, thus Affecting Their Mechanobiological Response.

Periodontal ligament fibroblasts (PdLFs) exert important functions in oral tissue and bone remodeling following mechanical forces, which are specifically applied during orthodontic tooth movement (OTM). Located between the teeth and the alveolar bone, mechanical stress activates the mechanomodulatory functions of PdLFs including regulating local inflammation and activating further bone-remodeling cells. Previous studies suggested growth differentiation factor 15 (GDF15) as an important pro-inflammatory regulator during the PdLF mechanoresponse. GDF15 exerts its effects through both intracrine signaling and receptor binding, possibly even in an autocrine manner. The extent to which PdLFs are susceptible to extracellular GDF15 has not yet been investigated. Thus, our study aims to examine the influence of GDF15 exposure on the cellular properties of PdLFs and their mechanoresponse, which seems particularly relevant regarding disease- and aging-associated elevated GDF15 serum levels. Therefore, in addition to investigating potential GDF15 receptors, we analyzed its impact on the proliferation, survival, senescence, and differentiation of human PdLFs, demonstrating a pro-osteogenic effect upon long-term stimulation. Furthermore, we observed altered force-related inflammation and impaired osteoclast differentiation. Overall, our data suggest a major impact of extracellular GDF15 on PdLF differentiation and their mechanoresponse.

Shear bond strength after using sealant before bonding: a systematic review and meta-analysis of in vitro studies.

OBJECTIVES: Decalcification during orthodontic treatment is significantly increased. To prevent this negative impact, new treatments with sealants before bonding brackets are commonly been used. This systematic review discusses current knowledge on shear bond strength when using sealant before bonding. MATERIALS AND METHODS: A systematic review and meta-analysis were performed to identify studies that address shear bond strength after using a sealant before bonding brackets. The search was carried out using common electronic databases in addition to individual searches. Both screening and study eligibility analysis were performed according to PRISMA and Cochrane Guidelines for systematic reviews. Several terms describing shear bond strength after using a sealant before bonding brackets were searched. Particular attention was paid to bond failure and bracket loss. For the statistical outcome, all results were shown in a forest plot based on standardized mean differences (SMD) with a random-effects model to respect heterogeneity of these studies. To assess the heterogeneity of the different trials, I2-value and the Q-Test were performed. RESULTS: The initial search identified 416 studies. After a thorough selection process, a total of 15 articles met the inclusion criteria. All 15 articles reported results of in vitro studies. Papers were divided into four subgroups according to their used product: ProSeal, Transbond bonding, the combination of Transbond bonding and ProSeal and Clearfil Protect Bond. The results of this review demonstrate a high heterogeneity of the studies. The SMD of the examined 15 articles show nearly no difference between the control and the intervention groups in shear bond strength (p < 0.0001; OR - 0.12; Cl - 0.47-0.23). Forest plots for comparison of the subgroups depict no difference in shear bond strength as well. CONCLUSIONS: This meta-analysis concludes that there is no additive benefit for shear bond strength when using sealant before bonding. However, additional randomized controlled studies should be performed to analyze impact of sealants on bonding strength and bracket loss in more detail. CLINICAL RELEVANCE: Using sealants before orthodontic bonding does not reduce shear bond strength.

Compressive force strengthened the pro-inflammatory effect of zoledronic acid on il-1ß stimulated human periodontal fibroblasts.

OBJECTIVES: The number of patients in dentistry taking bisphosphonates (BP) increases every year. There are only little data about the influence of biomechanical stress due to orthodontic treatment and periodontal inflammation in BP patients. This study focused on the effects of the induced inflammation by IL-1ß in compressed human periodontal ligament fibroblasts (HPdLF) exposed to the nitrogen-containing BP zoledronate in vitro. MATERIALS AND METHODS: HPdLF were incubated with 5 µmol/l zoledronate and 10 ng/ml IL-1ß for 48 h. In the last 3 h, cells were exposed to a compressive, centrifugal force of 34.9 g/cm2. Cell viability was analyzed directly after the compressive force by MTT assay. Gene expression of COX-2 and IL-6 was investigated using quantitative qRT-PCR. PGE-2 and IL-6 protein secretion were measured via ELISA. RESULTS: The cell viability of HPdLF was not affected. Without inflammatory pre-stimulation, COX-2 expression was increased by compression and zoledronate. IL-6 expression was increased under compression. On secretion level, the combination of compression and zoledronate induced a slightly increase of IL-6 secretion. In contrast, inflammatory pre-stimulation strengthened the compressive upregulation of COX-2, as well as induced a higher PGE-2 secretion. Further addition of zoledronate to pre-stimulated cells additionally strengthened the compression-induced upregulation of COX-2 and IL-6 expression as well as protein secretion compared to all other groups. CONCLUSIONS: Biomechanical stress might trigger a pro-inflammatory potential of BP further enhanced in the presence of an inflammatory pre-stimulation. CLINICAL RELEVANCE: To prevent excessive host inflammatory responses, occlusal overloading and mechanical stress due to orthodontic treatment should be avoided in BP patients with untreated periodontitis.

GDF15 Supports the Inflammatory Response of PdL Fibroblasts Stimulated by P. gingivalis LPS and Concurrent Compression.

Periodontitis is characterized by bacterially induced inflammatory destruction of periodontal tissue. This also affects fibroblasts of the human periodontal ligaments (HPdLF), which play a coordinating role in force-induced tissue and alveolar bone remodeling. Excessive inflammation in the oral tissues has been observed with simultaneous stimulation by pathogens and mechanical forces. Recently, elevated levels of growth differentiation factor 15 (GDF15), an immuno-modulatory member of the transforming growth factor (TGFB) superfamily, were detected under periodontitis-like conditions and in force-stressed PdL cells. In view of the pleiotropic effects of GDF15 in various tissues, this study aims to investigate the role of GDF15 in P. gingivalis-related inflammation of HPdLF and its effect on the excessive inflammatory response to concurrent compressive stress. To this end, the expression and secretion of cytokines (IL6, IL8, COX2/PGE2, TNFα) and the activation of THP1 monocytic cells were analyzed in GDF15 siRNA-treated HPdLF stimulated with P. gingivalis lipopolysaccharides alone and in combination with compressive force. GDF15 knockdown significantly reduced cytokine levels and THP1 activation in LPS-stimulated HPdLF, which was less pronounced with additional compressive stress. Overall, our data suggest a pro-inflammatory role for GDF15 in periodontal disease and demonstrate that GDF15 partially modulates the force-induced excessive inflammatory response of PdLF under these conditions.

Hyperlipidemic Conditions Impact Force-Induced Inflammatory Response of Human Periodontal Ligament Fibroblasts Concomitantly Challenged with P. gingivalis-LPS.

In obese patients, enhanced serum levels of free fatty acids (FFA), such as palmitate (PA) or oleate (OA), are associated with an increase in systemic inflammatory markers. Bacterial infection during periodontal disease also promotes local and systemic low-grade inflammation. How both conditions concomitantly impact tooth movement is largely unknown. Thus, the aim of this study was to address the changes in cytokine expression and the secretion of human periodontal ligament fibroblasts (HPdLF) due to hyperlipidemic conditions, when additionally stressed by bacterial and mechanical stimuli. To investigate the impact of obesity-related hyperlipidemic FFA levels on HPdLF, cells were treated with 200 µM PA or OA prior to the application of 2 g/cm2 compressive force. To further determine the additive impact of bacterial infection, HPdLF were stimulated with lipopolysaccharides (LPS) obtained from Porphyromonas gingivalis. In mechanically compressed HPdLF, PA enhanced COX2 expression and PGE2 secretion. When mechanically stressed HPdLF were additionally stimulated with LPS, the PGE2 and IL6 secretion, as well as monocyte adhesion, were further increased in PA-treated cultures. Our data emphasize that a hyperlipidemic condition enhances the susceptibility of HPdLF to an excessive inflammatory response to compressive forces, when cells are concomitantly exposed to bacterial components.

Influence of clodronate and compressive force on IL-1ß-stimulated human periodontal ligament fibroblasts.

OBJECTIVES: The aim of this study was to investigate in vitro the effect of clodronate on interleukin-1ß (IL-1ß)-stimulated human periodontal ligament fibroblasts (HPdLFs) with the focus on inflammatory factors of orthodontic tooth movement with and without compressive force. MATERIALS AND METHODS: HPdLFs were incubated with 5 µM clodronate and 10 ng/mL IL-1ß. After 48 h, cells were exposed to 3 h of compressive force using a centrifuge. The gene expression of cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), matrix metalloproteinase 8 (MMP-8), and the tissue inhibitor of MMP (TIMP-1) was analyzed using RT-PCR. Prostaglandin E2 (PGE-2), IL-6, and TIMP-1 protein syntheses were quantified via ELISA. RESULTS: Compressive force and IL-1ß induced an overexpression of COX-2 gene expression (61.8-fold; p < 0.05 compared with control), diminished by clodronate (41.1-fold; p < 0.05 compared with control). Clodronate slowed down the compression and IL-1ß induced IL-6 gene expression (161-fold vs. 85.6-fold; p < 0.05 compared with control). TNF-α was only slightly affected without statistical significance. Clodronate reduced IL-1ß-stimulated MMP-8 expression with and without compressive force. TIMP-1 on gene and protein level was downregulated in all groups. Analyzing the MMP-8/TIMP-1 ratio, the highest ratio was detected in IL-1ß-stimulated HPdLFs with compressive force (21.2-fold; p < 0.05 compared with control). Clodronate diminished IL-1ß-induced upregulation of MMP-8/TIMP-1 ratio with (11.5-fold; p < 0.05 compared with control) and without (12.5-fold; p < 0.05 compared with control) compressive force. CONCLUSION: Our study demonstrates a slightly anti-inflammatory effect by clodronate under compressive force in vitro. Additionally, the periodontal remodeling presented by the MMP-8/TIMP-1 ratio seems to be diminished by clodronate. CLINICAL RELEVANCE: Reduction of pro-inflammatory factors and reduction of periodontal remodeling might explain reduced orthodontic tooth movement under clodronate intake.

Craniofacial venous malformations treated by percutaneous sclerotherapy using polidocanol: a single-center experience.

BACKGROUND: Percutaneous therapy with various sclerosants is an established treatment of venous malformations in general. We investigated the safety and effectiveness of polidocanol in the craniofacial region. PURPOSE: To present and evaluate our subjective and objective mid- and long-term results of patients with craniofacial venous malformations (CFVM) after percutaneous sclerotherapy using polidocanol. MATERIAL AND METHODS: Twenty patients with CFVM treated by percutaneous sclerotherapy were followed up and asked to fill in a questionnaire comparing levels of the following CFVM-related symptoms before and after treatment: pain; functional impairment; cosmetic deformities; and impairment in daily life. Additionally, both size reduction as well as procedural-related complication rates were analyzed. RESULTS: Evaluation of the questionnaire revealed an improvement or complete relief of CFVM-related symptoms with significant reduced impairment in daily life after percutaneous sclerotherapy. Eighteen (90%) patients noticed a post-sclerotherapy improvement of at least one of their corresponding symptoms and expressed satisfaction with regard to their treatment. For 13 patients, a > 50% size reduction of the CFVM could be observed, while seven exhibited a < 50% size reduction. One minor complication was encountered in 56 treatment sessions (1.8%). CONCLUSION: Percutaneous sclerotherapy using polidocanol is a well-tolerated treatment for CFVM with a low complication rate. Size reduction and positive results with improvement of different clinical symptoms can be achieved.

Mechanical loading increases pro-inflammatory effects of nitrogen-containing bisphosphonate in human periodontal fibroblasts.

OBJECTIVES: There is increasing evidence that inflammation and biomechanical loading can influence the effects of bisphosphonates (BP). The aim of this study was to investigate the influence of tensile strain application combined with IL-1ß and clodronate or zoledronate on human periodontal ligament fibroblasts (HPdLF) in vitro. MATERIALS AND METHODS: HPdLF were cultured with 10 nM IL-1ß and 5 µM clodronate or zoledronate for 48 h. Cells were applied to cyclic tensile strain (CTS; 3% elongation) for 12 h in vitro. Cell number was analyzed directly after CTS by MTT assay. Gene expression of receptor activator of cyclooxygenase-2 (COX-2) was investigated using real-time PCR. MMP-8, TIMP-1, and PGE2 were measured by ELISA. Statistics were performed with SPSS (ANOVA, p < 0.05). RESULTS: Zoledronate reduced the cell number of HPdLF (60.3 vs. 100%), which was significant when combined with IL-1ß. Combined with 3% CTS, this effect was voided and cell number increased over the level of the control cells. IL-1ß led to a 10-fold increase of COX-2 gene expression. Combined with CTS and zoledronate, this increase was enhanced to a gene expression 70-fold that of control cells with related PGE2 synthesis. Clodronate neither reduce the cell number nor enhanced the COX-2 gene expression. CTS increased MMP-8 protein synthesis. Combined with BP, this increase was voided. TIMP-1 protein synthesis was increased at all conditions under CTS. CONCLUSIONS: Mechanical loading might activate cell metabolism and abolish BP- and inflammation-induced reduction of viability. Combination of mechanical loading, inflammation, and nitrogen-containing bisphosphonates can cause pro-inflammatory effects. CLINICAL RELEVANCE: Periodontal inflammation should be treated initially before BP intake to prevent decreased cell viability of the periodontium and increased inflammation, which might be enhanced by the addition of mastication forces.

Diabetes and hyperglycemia as risk factors for postoperative outcome in maxillofacial surgery.

BACKGROUND: Aim of this study was to investigate the frequency of complications in maxillofacial surgery in-patients in correlation to diabetes mellitus or a pathologically altered glucose metabolism. MATERIALS AND METHODS: All patients' electronic health records were analyzed retrospectively. Diabetes mellitus anamnesis, the treatment regime, blood glucose levels, and the duration of inpatient treatment were recorded. Glucose readings ≥200 mg/dL measured at any time and fasting glucose levels of ≥110 mg/dL were defined as hyperglycemic. Noted complications were infection, dehiscence, swelling, and necrosis. RESULTS: 8.7% out of 1374 patients had a known diabetes diagnosis. 13.0% had high fasting glucose and 11.4% aberrant maximum glucose readings. Complications did not occur more often in patients with a previously known diabetes but more often in patients with high maximum blood glucose levels. Of these patients, only 56.3% were known diabetics. CONCLUSIONS: Diabetes mellitus does not necessarily lead to higher frequency of complications in surgical patients. Moreover, patients with well-controlled diabetes seem to have a similar outcome compared to nondiabetics. Hyperglycemia however has an important impact on treatment outcome.

Hydrocephalus in vein of Galen malformation: etiologies and therapeutic management implications.

BACKGROUND: Up to now, only little is known about hydrocephalus (HC) in vein of Galen malformation (VGM). We want to present the different etiologies and our long-term experience (1992-2015) in the management of HC. METHODS: Out of 44 treated children with VGM, we retrospectively reviewed all cases with HC. We analyzed the etiologies, our treatment results and complications. RESULTS: Twenty-one children (48 %) presented either with HC or developed it over time. In 21 % of those cases, high venous pressure was presumably the sole cause. Until 2009, seven of them received ventriculoperitoneal (VP) shunting; six of those resulted in severe postoperative complications. The remaining children have been treated successfully by endovascular embolization. Five out of the 44 children (11 %) developed HC after intraventricular hemorrhage. In four cases, those children were treated with positive results by using transient external ventricular drainages. In one case a VP shunt with highest valve pressure was inserted. Another four children (9 %) presented with aqueductal stenosis-related HC caused by either dilated venous outflow or space-occupying coil masses after embolization. The latter case was successfully treated by ventriculocisternostomy, whereas endovascular treatment decreased the venous outflow in size and thus resolved the HC in the other cases. In the remaining cases (7 %), atrophy due to melting brain syndrome led to HC ex vacuo. CONCLUSIONS: HC in VGM is a common phenomenon with several etiologies requiring different treatments. In most cases, embolization of the VGM as sole treatment is completely sufficient in order to decrease high venous pressure. However, certain other causes of HC should be treated in an interdisciplinary setting by specialized neurosurgeons.

Association between eruption state of the third molar and the occurrence of mandibular angle fractures.

BACKGROUND/AIM: Fractures of the mandible, especially the mandibular angle, are one of the most frequent types of injuries of the facial skeleton. In many cases, a retained third molar can be found in the line of the fracture. However, it remains unclear whether a relationship between third molars and mandibular angle fractures exists. MATERIALS AND METHODS: Patients with isolated or combined fractures of the lower jaw between January 2001 and December 2007 were analyzed retrospectively. Electronic health records were investigated regarding the types of mandibular fractures, and panoramic radiographs were reviewed concerning the existence of third molars. In addition, a systematic review was performed to compare the findings of this study with existing data. RESULTS: Six hundred and thirty-two patients were treated for mandibular fractures within the time frame. Two hundred and sixty-seven had a mandibular angle fracture. In 461 patients, panoramic radiographs were available, of which 45.6% did not have a third molar. About 3.8% were edentulous. There is a significant relationship between the existence of unerupted third molars and the occurrence of mandibular angle fractures (P < 0.001). No correlation exists for erupted third molars. CONCLUSIONS: Fractures of the mandibular angle are more likely to appear in patients with retained third molars which might be due to the reduced bone mass. Once the wisdom teeth have erupted, the bone structure is more solid and more resistant to external forces and the development of fractures.

Cranial Doppler ultrasound in Vein of Galen malformation.

INTRODUCTION: Vein of Galen malformation (VGM) is the severest paediatric neurovascular disease usually requiring multiple staged embolisations. In the high-risk group of children with high-flow arteriovenous shunts, timing of treatment is uncertain. Low Doppler resistance index (RI) is known to be associated with adverse outcome in hypoxic-ischaemic brain injury in children. In this study, we want to present our long-term results of cranial transfontanellar Doppler ultrasound in children with VGM. METHODS: We identified and retrospectively analysed 264 transfontanellar Doppler measurements in 19 endovascular-treated true VGM (five females, 14 males) between 2000 and 2013. The recordings were obtained from the internal carotid arteries (ICA), the anterior cerebral arteries (ACA) and the basilar arteries (BA). Maximal systolic velocity (Vs), end-diastolic velocity (Ved) and the RI were measured before and after embolisation. RESULTS: Untreated, nearly all cases showed pathologic high systolic (up to >1.0 m/s), very high diastolic velocities (up to >0.5 m/s) and low RI (<0.6). There were statistically significant differences (p = 0.012) between the pre-embolisation RI and the post-embolisation RI with pathologic low RI before and nearly normal RI after successful shunt reduction. CONCLUSION: Successful endovascular shunt reduction in VGM leads to significant changes of cranial Doppler RI from pathologic low values to normal values. We propose cranial Doppler ultrasound as an adjunctive technique to other screenings in the management of VGM. Further research is warranted to evaluate the role of the RI in the treatment timing decision.

Effectiveness of maxillary protraction using facemask with or without maxillary expansion: a systematic review and meta-analysis.

OBJECTIVES: Class III therapy using a face mask is a common approach for treatment of a deficient maxilla and reverse overbite. Usually, maxillary protraction is combined with transverse palatal expansion using intraoral appliances. The purpose of this study was to systematically review the effectiveness of face mask therapy in combination with concepts of palatal expansion and compression. MATERIAL AND METHODS: A systematic review and meta-analysis were performed to identify studies that address class III treatment using a face mask. The search was carried out using common electronic databases as well as hand search. Both screening and study eligibility analysis were performed with consideration of PRISMA and Cochrane Guidelines for systematic reviews. Several terms describing class III face mask treatment were searched. Particular attention was paid to new strategies of enhancing maxillary protraction. RESULTS: The initial search identified 2048 studies. After a thorough selection process, a total of 22 articles met the inclusion criteria. After assessment of the individual quality scoring of each article, eight studies were provided for meta-analysis of the cephalometric parameters. The statistical analysis of treatment changes advocates a positive influence on sagittal maxillary development, which is not primarily influenced by transverse expansion. Dental side effects are more distinct when no expansion was carried out. For the concept of alternating activation/deactivation of the expansion appliance (alt-RAMEC), two articles of high methodological scoring were identified. They indicate an enhancement of face mask treatment. CONCLUSIONS: The findings are consistent with results of previous literature studies regarding the efficiency of class III face mask treatment. A further need for more randomized controlled studies was identified especially with regard to the new concept of alternating maxillary expansion and compression, which showed a positive influence on the maxillary protraction based on two studies. CLINICAL RELEVANCE: Class III therapy using extraoral face mask anchorage is effective for maxillary protraction. The recently discussed new protocols potentially improve this treatment.

Mechanical loading influences the effects of bisphosphonates on human periodontal ligament fibroblasts.

OBJECTIVES: There is increasing evidence that bisphosphonates affect orthodontic tooth movement. The object of the study was to investigate the changes produced by tensile strain on human periodontal ligament fibroblasts (HPdLFs) treated with clodronate or zoledronate. MATERIALS AND METHODS: HPdLF were cultured with 5 and 50 µM clodronate or zoledronate for 48 h and applied to tensile strain (TS) (5 and 10 %) for 12 h in vitro. Viability was verified by MTT assay and apoptosis rate via caspase 3/7 assay. Gene expression of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) was investigated using real-time PCR. OPG was also analyzed by ELISA and RANKL by immunocytochemical staining. RESULTS: Zoledronate (50 µM) reduced the viability of HPdLF (76 vs 100 %) and combined with 5 % TS to 53 %. TS of 10 % and clodronate reduced viability to 79 % with increased caspase 3/7 activity. Clodronate (5 µM) led to a slight increase of OPG gene expression, zoledronate (5 µM) to a slight decrease. Combined with 5 % TS, both increased OPG gene expression (2-3-fold) and OPG synthesis. Zoledronate increased gene expression of RANKL (4-fold). Combined with 5 % of TS, this increase was abolished. TS of 10 % in combination amplified increase of RANKL ending up with a 9-fold gene expression by clodronate and high RANKL protein synthesis. CONCLUSIONS: This study shows for the first time that mechanical loading alters the effects of bisphosphonates on viability, apoptosis rate, and OPG/RANKL system of HPdLF dependent on the applied strength. Low forces and bisphosphonates increase factors for bone apposition, whereas high forces combined with bisphosphonates stimulate osteoclastogenesis. CLINICAL RELEVANCE: Mechanical loading of periodontal ligament with high strengths should be avoided during bisphosphonate therapy.

Induction of IL-6 and MMP-8 in human periodontal fibroblasts by static tensile strain.

OBJECTIVES: Mechanical loading is a potential activator of inflammation and able to stimulate factors for periodontal and alveolar bone destruction. Aim of this study was to investigate the inflammatory response and synthesis of proteinases by human periodontal ligament fibroblast (HPdLF) dependent on different strengths of static tensile strain (STS). MATERIALS AND METHODS: HPdLFs were loaded with different STS strengths (1, 5, and 10 %) in vitro. Gene expressions of cyclooxygenase (COX)-2 and interleukin (IL)-6 were analyzed by quantitative real-time polymerase chain reaction. Production of IL-6, prostaglandin E2 (PGE2), matrix metalloproteinase (MMP)-8, and tissue inhibitors of matrix metalloproteinase (TIMP)-1 were measured by enzyme-linked immunosorbent assay. Receptor activator of nuclear factor-kappa ligand (RANKL) synthesis was detected by immunocytochemical staining. RESULTS: Ten percent STS led to an increased gene expression of IL-6 and COX-2 (34.4-fold) in HPdLF, and 1 and 5 % STS slightly reduced the gene expression of IL-6. Synthesis of IL-6 was significantly reduced by 1 % STS and stimulated by 10 % STS. Ten percent STS significantly induced PGE2 production. RANKL was not detectable at any strength of STS. MMP-8 synthesis showed significantly higher values only at 10 % STS, but TIMP-1 was stimulated by 5 and 10 % STS, resulting into highest TIMP-1/MMP-8 ratio at 5 % STS. CONCLUSIONS: High-strength STS is a potent inducer of periodontal inflammation and MMP-8, whereas low-strength STS shows an anti-inflammatory effect. Moderate-strength STS causes the highest TIMP-1/MMP-8 ratio, leading to appropriate conditions for reformation of the extracellular matrix. CLINICAL RELEVANCE: Furthermore, this study points out that the strength of force plays a pivotal role to achieve orthodontic tooth movement without inducing periodontal inflammation and to activate extracellular matrix regeneration.

GDF15 Contributes to the Regulation of the Mechanosensitive Responses of PdL Fibroblasts through the Modulation of IL-37.

During orthodontic tooth movement (OTM), areas of compressive and tensile forces are generated in the periodontal ligament (PdL), a mechanoreactive connective tissue between the teeth and alveolar bone. Mechanically stimulated PdL fibroblasts (PdLFs), the main cell type of PdL, express significantly increased levels of growth differentiation factor 15 (GDF15). In compressed PdL areas, GDF15 plays a fundamental role in modulating relevant OTM processes, including inflammation and osteoclast activation. However, the specific function of this factor in tensile areas has not yet been investigated. Thus, the aim of this study was to investigate the role of GDF15 in the mechanoresponse of human PdLFs (hPdLFs) that were exposed to biaxial tensile forces in vitro. Using siRNA-mediated knockdown experiments, we demonstrated that GDF15 had no impact on the anti-inflammatory force response of elongated hPdLFs. Although the anti-inflammatory markers IL1RN and IL10, as well as the activation of immune cells remained unaffected, we demonstrated an inhibitory role of GDF15 for the IL-37 expression. By analyzing osteogenic markers, including ALPL and RUNX2, along with an assessment of alkaline phosphatase activation, we further showed that the regulation of IL-37 by GDF15 modulates the osteogenic differentiation potential of hPdLFs. Despite bone resorption in tensile areas being rather limited, GDF15 was also found to positively modulate osteoclast activation in those areas, potentially by adjusting the IL-37 levels. In light of our new findings, we hypothesize that GDF15 modulates force-induced processes in tissue and bone remodeling through its various intra- and extracellular signaling pathways as well as interaction partners. Potentially acting as a master regulator, the modulation of GDF15 levels may hold relevance for clinical implications.

GDF15 Modulates the Zoledronic-Acid-Induced Hyperinflammatory Mechanoresponse of Periodontal Ligament Fibroblasts.

Orthodontic tooth movement (OTM) is thought to be impeded by bisphosphonate (BP) therapy, mainly due to increased osteoclast apoptosis and changes in the periodontal ligament (PdL), a connecting tissue between the alveolar bone and teeth. PdL cells, mainly fibroblasts (PdLFs), are crucial regulators in OTM by modulating force-induced local inflammatory processes. Recently, we identified the TGF-ß/BMP superfamily member GDF15 as an important modulator in OTM, promoting the pro-inflammatory mechanoresponses of PdLFs. The precise impact of the highly potent BP zoledronate (ZOL) on the mechanofunctionality of PdLFs is still under-investigated. Therefore, the aim of this study was to further characterize the ZOL-induced changes in the initial inflammatory mechanoresponse of human PdLFs (hPdLFs) and to further clarify a potential interrelationship with GDF15 signaling. Thus, two-day in vitro treatment with 0.5 µM, 5 µM and 50 µM of ZOL altered the cellular properties of hPdLFs partially in a concentration-dependent manner. In particular, exposure to ZOL decreased their metabolic activity, the proliferation rate, detected using Ki-67 immunofluorescent staining, and survival, analyzed using trypan blue. An increasing occurrence of DNA strand breaks was observed using TUNEL and an activated DNA damage response was demonstrated using H2A.X (phosphoS139) staining. While the osteogenic differentiation of hPdLFs was unaffected by ZOL, increased cellular senescence was observed using enhanced p21Waf1/Cip1/Sdi1 and ß-galactosidase staining. In addition, cytokine-encoding genes such as IL6, IL8, COX2 and GDF15, which are associated with a senescence-associated secretory phenotype, were up-regulated by ZOL. Subsequently, this change in the hPdLF phenotype promoted a hyperinflammatory response to applied compressive forces with an increased expression of the pro-inflammatory markers IL1ß, IL6 and GDF15, as well as the activation of monocytic THP1 cells. GDF15 appeared to be particularly relevant to these changes, as siRNA-mediated down-regulation balanced these hyperinflammatory responses by reducing IL-1ß and IL-6 expression (IL1B p-value < 0.0001; IL6 p-value < 0.001) and secretion (IL-1ß p-value < 0.05; IL-6 p-value < 0.001), as well as immune cell activation (p-value < 0.0001). In addition, ZOL-related reduced RANKL/OPG values and inhibited osteoclast activation were enhanced in GDF15-deficient hPdLFs (both p-values < 0.0001; all statistical tests: one-way ANOVA, Tukey's post hoc test). Thus, GDF15 may become a promising new target in the personalized orthodontic treatment of bisphosphonatepatients.