Effect of Abutment Height on Marginal Bone Loss Around Dental Implants: A Systematic Review.

PURPOSE: To analyze the influence of abutment height (AH) on marginal bone loss (MBL). MATERIALS AND METHODS: A literature search was performed for human studies (RCTs, prospective and retrospective cohorts) reporting on AH and MBL. The data obtained-including clinical outcomes, treatment covariates, and patient characteristics-were analyzed. Meta-regression was performed on the effect size of the differences between the shorter and larger AHs on the MBL of each study. The estimation was done using the restricted maximum likelihood method. RESULTS: The initial screening and full-text analysis resulted in 7,936 and 46 articles, respectively. Finally, 14 articles were included in the systematic review, reporting a total of 1,606 implants. An overall high-to-moderate risk of bias was determined among the included investigations. Meta-regression analysis revealed that AH had a significant effect on MBL (b = -1.630, P < .003), demonstrating that longer abutments were correlated with less MBL. No effects were observed for the study type (P = .607), the number of stages (P = .510), or the elapsed time (P = .491). CONCLUSIONS: The height of the abutment has a significant impact on MBL. As such, increased AH is related to less MBL. Nevertheless, the role of confounding variables remains to be studied and determined.

Effect of Abutment Height on Marginal Bone Loss Around Dental Implants: A Systematic Review.

PURPOSE: To analyze the influence of abutment height (AH) on marginal bone loss (MBL). MATERIALS AND METHODS: A literature search was performed for human studies (randomized controlled trials, prospective and retrospective cohorts) reporting on the AH and MBL. The data obtained-including clinical outcomes, treatment covariates and patient characteristics-were analyzed. Meta-regression was performed on the effect size of the differences between the shorter and larger AHs on the MBL of each study. The estimation was done using the restricted maximum likelihood method. RESULTS: The initial screening and full-text analysis resulted in 7,936 and 46 articles, respectively. Finally, 14 articles were included in the systematic review, reporting a total of 1,606 implants. An overall high-to-moderate risk of bias was determined among the included investigations. Meta-regression analysis revealed that AH had a significant effect on MBL (b = - 1.630, P < .003), demonstrating that longer abutments were correlated with less MBL. No effects were observed for the study type (P = .607), the number of stages (P = .510), or the elapsed time (P = .491). CONCLUSION: The height of the abutment has a significant impact on MBL. As such, increased AH is related to less MBL. Nevertheless, the role of confounding variables remains to be studied and determined.

Effect of different concentrations of commercially available mouthwashes on wound healing following periodontal surgery: a randomized controlled clinical trial.

OBJECTIVES: The purpose of this study was to evaluate the effect of chlorhexidine and essential oils containing mouth rinses on oral wound healing after periodontal flap surgery. MATERIALS AND METHODS: Eighty subjects participated in the study and were randomly assigned to use water, 0.12% chlorhexidine (CHX), essential oils (EO), 5% CHX, and 10% EO. Subjects were examined at 1, 2, and 3 weeks postoperatively. Plaque index (PI) and the modified gingival index (GI) were recorded, while wound epithelialization was measured to evaluate the healing process. Numerical data were analyzed with parametric test for multiple comparisons (ANOVA) with Bonferroni correction. Categorical data were analyzed using Chi-square test/fisher exact test. RESULTS: All groups demonstrated a gradual GI reduction from first to third visit. Patients in the CHX group presented statistically significant lower PI scores than patients in the water group at the all-time points of the study. Wound epithelialization analysis demonstrated that 100% of the sites in the CHX group were healing by secondary intention at visit 1. This finding was statistically significant. CONCLUSION: Full strength concentrations of CHX and EO did not show any detrimental effects on healing after traditional periodontal surgery at the end of the observation period. CLINICAL RELEVANCE: The use of chlorhexidine and EO containing mouthwashes does not appear to delay wound healing. Diluting these commercial mouthwashes may present an approach that could possibly reduce the adverse effects (such as tooth staining) associated with their use, while maintaining their antibacterial properties.

Missense Pathogenic variants in KIF4A Affect Dental Morphogenesis Resulting in X-linked Taurodontism, Microdontia and Dens-Invaginatus.

The etiology of dental anomalies is multifactorial; and genetic and environmental factors that affect the dental lamina have been implicated. We investigated two families of European ancestry in which males were affected by taurodontism, microdontia and dens invaginatus. In both families, males were related to each other via unaffected females. A linkage analysis was conducted in a New Zealand family, followed by exome sequencing and focused analysis of the X-chromosome. In a US family, exome sequencing of the X-chromosome was followed by Sanger sequencing to conduct segregation analyses. We identified two independent missense variants in KIF4A that segregate in affected males and female carriers. The variant in a New Zealand family (p.Asp371His) predicts the substitution of a residue in the motor domain of the protein while the one in a US family (p.Arg771Lys) predicts the substitution of a residue in the domain that interacts with Protein Regulator of Cytokinesis 1 (PRC1). We demonstrated that the gene is expressed in the developing tooth bud during development, and that the p.Arg771Lys variant influences cell migration in an in vitro assay. These data implicate missense variations in KIF4A in a pathogenic mechanism that causes taurodontism, microdontia and dens invaginatus phenotypes.

Enhancement of MicroRNA-200c on Osteogenic Differentiation and Bone Regeneration by Targeting Sox2-Mediated Wnt Signaling and Klf4.

MicroRNA (miR)-200c functions in antitumorigenesis and mediates inflammation and osteogenic differentiation. In this study, we discovered that miR-200c was upregulated in human bone marrow mesenchymal stromal cells (hBMSCs) during osteogenic differentiation. Inhibition of endogenous miR-200c resulted in downregulated osteogenic differentiation of hBMSCs and reduced bone volume in the maxilla and mandible of a transgenic mouse model. Overexpression of miR-200c by transfection of naked plasmid DNA (pDNA) encoding miR-200c significantly promoted the biomarkers of osteogenic differentiation in hBMSCs, including alkaline phosphatase, Runt-related transcription factor 2, osteocalcin, and mineral deposition. The pDNA encoding miR-200c also significantly enhanced bone formation and regeneration in calvarial defects of rat models. In addition, miR-200c overexpression was shown to downregulate SRY (sex determining region Y)-box 2 (Sox2) and Kruppel-like factor 4 by directly targeting 3'-untranslated regions and upregulate the activity of Wnt signaling inhibited by Sox2. These results strongly indicated that miR-200c may serve as a unique osteoinductive agent applied for bone healing and regeneration.

MicroRNA-200c Attenuates Periodontitis by Modulating Proinflammatory and Osteoclastogenic Mediators.

This study tested whether microRNA (miR)-200c can attenuate the inflammation and alveolar bone resorption in periodontitis by using an in vitro and a rat model. Polyethylenimine (PEI) was used to facilitate the transfection of plasmid DNA encoding miR-200c into primary human gingival fibroblasts (HGFs) and gingival tissues of rats. We first analyzed how proinflammatory and osteoclastogenic mediators in HGFs with overexpression of miR-200c responded to Porphyromonas gingivalis lipopolysaccharide (LPS-PG) challenge in vitro. We observed that overexpression of miR-200c significantly reduced interleukin (IL)-6 and 8 and repressed interferon-related developmental regulator-1 (IFRD1) in HGFs. miR-200c also downregulated p65 and p50. In a rat model of periodontitis induced by an LPS injection at the gingival sulcus of the second maxillary molar (M2), we analyzed how the mediators in rat gingiva and alveolar bone resorption responded to miR-200c treatment by a local injection of PEI-plasmid miR-200 nanoplexes. We observed that the local injection of miR-200c significantly upregulated miR-200c expression in gingiva and reduced IL-6, IL-8, IFRD1, and the ratio of receptor activator of nuclear factor kappa-B ligand/osteoprotegerin. Using micro-computed tomography analysis and histomorphometry, we further confirmed that local treatment with miR-200c effectively protected alveolar bone resorption in the rat model of periodontitis by reducing the distance between the cemento-enamel junction and the alveolar bone crest and the inter-radicular space in the upper maxilla at M2. These findings imply that miR-200c may serve as a unique means to prevent periodontitis and associated bone loss.

Colorectal Cancer-Associated Genes Are Associated with Tooth Agenesis and May Have a Role in Tooth Development.

Previously reported co-occurrence of colorectal cancer (CRC) and tooth agenesis (TA) and the overlap in disease-associated gene variants suggest involvement of similar molecular pathways. Here, we took an unbiased approach and tested genome-wide significant CRC-associated variants for association with isolated TA. Thirty single nucleotide variants (SNVs) in CRC-predisposing genes/loci were genotyped in a discovery dataset composed of 440 individuals with and without isolated TA. Genome-wide significant associations were found between TA and ATF1 rs11169552 (P = 4.36 × 10-10) and DUSP10 rs6687758 (P = 1.25 × 10-9), and positive association found with CASC8 rs10505477 (P = 8.2 × 10-5). Additional CRC marker haplotypes were also significantly associated with TA. Genotyping an independent dataset consisting of 52 cases with TA and 427 controls confirmed the association with CASC8. Atf1 and Dusp10 expression was detected in the mouse developing teeth from early bud stages to the formation of the complete tooth, suggesting a potential role for these genes and their encoded proteins in tooth development. While their individual contributions in tooth development remain to be elucidated, these genes may be considered candidates to be tested in additional populations.

Effectiveness of Two Different Lingual Flap Advancing Techniques for Vertical Bone Augmentation in the Posterior Mandible: A Comparative, Split-Mouth Cadaver Study.

Vertical ridge augmentation in the posterior mandible is a technique-sensitive procedure that requires adequate anatomical knowledge and precise surgical skills to minimize the risk of complications. One of the most important but also challenging aspects of the surgical technique is proper flap management to allow for passive flap closure and reduce the chances of postoperative complications affecting deep anatomical spaces. This article presents a detailed description of a novel lingual flap advancement technique and its validation via a split-mouth, comparative study using a cadaver model. A total of 12 fresh cadaver heads presenting bilateral posterior mandibular edentulism were selected. Sides were randomized to receive a classic lingual flap release technique (control) or the modified technique presented here, which involves the intentional preservation of the mylohyoid muscle attachment to the mandible. Vertical flap release was measured at three different zones using standard forces. The mean difference between the test and control group in zones I (retromolar pad area), II (middle area), and III (premolar area) was 8.273 ± 1.794 mm (standard error of the mean [SEM] = 0.5409 mm), 10.09 ± 2.948 mm (SEM = 0.8889 mm), and 10.273 ± 2.936 mm (SEM = 0.8851 mm), respectively, reaching very strong statistical significance (P < .0001) in all three zones.

Irx1 regulates dental outer enamel epithelial and lung alveolar type II epithelial differentiation.

The Iroquois genes (Irx) appear to regulate fundamental processes that lead to cell proliferation, differentiation, and maturation during development. In this report, the Iroquois homeobox 1 (Irx1) transcription factor was functionally disrupted using a LacZ insert and LacZ expression demonstrated stage-specific expression during embryogenesis. Irx1 is highly expressed in the brain, lung, digits, kidney, testis and developing teeth. Irx1 null mice are neonatal lethal and this lethality it due to pulmonary immaturity. Irx1-/- mice show delayed lung maturation characterized by defective surfactant protein secretion and Irx1 marks a population of SP-C expressing alveolar type II cells. Irx1 is specifically expressed in the outer enamel epithelium (OEE), stellate reticulum (SR) and stratum intermedium (SI) layers of the developing tooth. Irx1 mediates dental epithelial cell differentiation in the lower incisors resulting in delayed growth of the lower incisors. Irx1 is specifically and temporally expressed during developmental stages and we have focused on lung and dental development in this report. Irx1+ cells are unique to the development of the incisor outer enamel epithelium, patterning of Lef-1+ and Sox2+ cells as well as a new marker for lung alveolar type II cells. Mechanistically, Irx1 regulates Foxj1 and Sox9 to control cell differentiation during development.