Parathyroid hormone and its effects on dental tissues

Hormone and implant osseointegration: Elaboration of the relationship among function, preclinical, and clinical practice

As clusters of peptides or steroids capable of high-efficiency information transmission, hormones have been substantiated to coordinate metabolism, growth, development, and other physiological processes, especially in bone physiology and repair metabolism. In recent years, the application of hormones for implant osseointegration has become a research hotspot. Herein, we provide a comprehensive overview of the relevant reports on endogenous hormones and their corresponding supplementary preparations to explore the association between hormones and the prognosis of implants. We also discuss the effects and mechanisms of insulin, parathyroid hormone, melatonin, vitamin D, and growth hormone on osseointegration at the molecular and body levels to provide a foothold and guide future research on the systemic conditions that affect the implantation process and expand the relative contraindications of the implant, and the pre-and post-operative precautions. This review shows that systemic hormones can regulate the osseointegration of oral implants through endogenous or exogenous drug-delivery methods.

Effects of teriparatide on bone formation in rats with experimentally induced premaxillary expansion

Objective:

This study aimed to evaluate the effects of systemic teriparatide on sutural bone formation after premaxillary suture expansion in rats.

Material and Methods:

Twenty Wistar male rats (8-10 weeks old) were randomly divided into two groups, namely, control (C, n=10) and teriparatide (T, n=10). An expansion force was applied to the maxillary incisors using helical spring for a seven-day expansion period, for both groups. On the eighth day, the rats were kept for a seven-day consolidation period, and then 60 µg/kg teriparatide (once a day) was administered to group T subcutaneously for seven days. Then, all the rats were sacrificed, and histological sections were stained with hemotoxylin-eosin for examination. Anti-osteonectin, anti-osteocalcin, anti-Vascular endothelial growth factor (VEGF) and anti-transforming growth factor beta (TGF-β) were evaluated by immunohistochemical analysis in the midpalatal suture area.

Results:

Histologically, the newly formed bone tissue was observed to be larger in group T than in group C. The number of immunoreactive osteoblasts for osteonectin, osteocalcin and VEGF antibodies was significantly higher in group T than in group C (p = 0.0001). The TGF-β antibody showed a mild reaction in group T, but did not reach significance in comparison with group C (p ˃ 0.05).

Conclusion:

Systemic teriparatide application following the premaxillary expansion of the suture area may stimulate bone formation and add to the consolidation of the expansion in rats by regulating osteonectin, osteocalcin and VEGF.

Effects of Drugs and Chemotherapeutic Agents on Dental Implant Osseointegration: Narrative Review

BACKGROUND

Dental implants have been one of the most popular treatments for rehabilitating individuals with single missing teeth or fully edentulous jaws since their introduction. As more implant patients are well-aged and take several medications due to various systemic conditions, clinicians should be mindful of possible drug implications on bone remodeling and osseointegration.

OBJECTIVE

The present study aims to study and review some desirable and some unwelcomed implications of medicine on osseointegration.

METHODS

A broad search for proper relevant studies were conducted in four databases, including Web of Science, Pubmed, Scopus, and Google Scholar.

RESULTS

Some commonly prescribed medicines such as nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), anticoagulants, metformin, and chemotherapeutic agents may jeopardize osseointegration. On the contrary, some therapeutic agents such as anabolic, anti-catabolic, or dual anabolic and anti-catabolic agents may enhance osseointegration and increase the treatment's success rate.

CONCLUSION

Systemic medications that enhance osseointegration include mineralization promoters and bone resorption inhibitors. On the other hand, medications often given to the elderly with systemic problems might interfere with osseointegration, leading to implant failure. However, to validate the provided research, more human studies with a higher level of evidence are required.

Parathyroid Hormone 1 Receptor Signaling in Dental Mesenchymal Stem Cells: Basic and Clinical Implications

Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) are two peptides that regulate mineral ion homeostasis, skeletal development, and bone turnover by activating parathyroid hormone 1 receptor (PTH1R). PTH1R signaling is of profound clinical interest for its potential to stimulate bone formation and regeneration. Recent pre-clinical animal studies and clinical trials have investigated the effects of PTH and PTHrP analogs in the orofacial region. Dental mesenchymal stem cells (MSCs) are targets of PTH1R signaling and have long been known as major factors in tissue repair and regeneration. Previous studies have begun to reveal important roles for PTH1R signaling in modulating the proliferation and differentiation of MSCs in the orofacial region. A better understanding of the molecular networks and underlying mechanisms for modulating MSCs in dental diseases will pave the way for the therapeutic applications of PTH and PTHrP in the future. Here we review recent studies involving dental MSCs, focusing on relationships with PTH1R. We also summarize recent basic and clinical observations of PTH and PTHrP treatment to help understand their use in MSCs-based dental and bone regeneration.

Study of Dental Caries and PTH Gene

Parathyroid hormone (PTH) is essential for calcium and phosphate homeostasis in odontogenesis-related cells. Therefore, the present study aimed to investigate the association between single nucleotide polymorphisms in the gene encoding PTH, and dental caries in Brazilian children. Three hundred and fifty-three children (170 boys and 183 girls, age ranging from 8 to 11 years old) were included in this study. The International System for Detection and Assessment of Carious Lesions (ICDAS) was used for diagnosis of dental caries. Visible biofilm was also evaluated during the clinical examination. Genomic DNA was extracted from saliva for real-time PCR to evaluate the single nucleotide polymorphisms rs6256, rs307247 and rs694 in PTH gene. Dental caries was classified in ICDAS0 vs. ICDAS1−6 or ICDAS1−2 vs. ICDAS3−6. Chi-square test, binary logistic regression adjusted by biofilm and haplotype analyses were performed (p < 0.05). Biofilm was associated with dental caries (p < 0.05). There were no associations between dental caries and rs6256, rs307247, rs694 in none of the analyses performed (p > 0.05). In conclusion, the present study supports that the single nucleotide polymorphisms rs6256, rs307247, and rs694 in the PTH-encoding gene are not associated with dental caries in Brazilian children.

Locally administrated single-dose teriparatide affects critical-size rabbit calvarial defects: A histological, histomorphometric and micro-CT study

OBJECTIVE

The aim of this study was to evaluate the effect of teriparatide (PTH 1-34, rhPTH) on a rabbit defect model with local xenogen grafts histomorphometrically and radiologically.

METHODS

For this purpose, two 10 mm diameter critical-size defects were created in the calvaria of 16 rabbits. In the control group, the defect area was filled with a xenogen graft, while in the teriparatide group (PTH 1-34), a xenogen graft combination with 20 mcg teriparatide was used. For both 4 - week and 8 - week study groups, new bone, residual graft, and soft tissue areas were evaluated as well as bone volume histomorphometrically and radiologically.

RESULTS

Histomorphometrically, there was a significant difference in new bone area values at the 8th week (p < 0.05), but there was no significant difference between the 4 - week values (p > 0.05). There was no statistically significant difference between the groups at both 4 and 8 weeks (p > 0.05). In the radiologically measured total bone volume values, PTH1-34 group values were found to be significantly higher for both 4 - and 8 - weeks values compared to the control groups (p < 0.05).

CONCLUSION

In this study, rhPTH, which is used locally in defect areas to be repaired with bone grafts, increases both new bone volume and total bone volume.

Cranio-Maxillofacial and Dental Findings in Albright's Hereditary Osteodystrophy and Pseudohypoparathyroidism

INTRODUCTION

The clinical phenotype of pseudohypoparathyroidism (PHP) is caused by Albright's Hereditary Osteodystrophy (AHO). Often, "round face" the only facial clinical sign reported in the literature. The aim of this study was to highlight various cranio-maxillofacial clinical findings associated with AHO.

RESULTS

Four patients presented with PHP type 1a. Only one patient exhibited the classical round face. All patients exhibited dental anomalies, class III malocclusion with maxillary retrusion, and a copper beaten appearance of the skull. One suffered from craniosynostosis.

CONCLUSION

The frequency of craniofacial and dental features associated with malocclusion should prompt careful follow-up, particularly during facial growth, in patients with AHO.

Early effects of parathyroid hormone on vascularized bone regeneration and implant osseointegration in aged rats

The decreased bone mass and impaired osteogenesis capacities that occur with aging may influence the outcome of dental implants. Parathyroid hormone (PTH) (1-34) is an anabolic agent for the treatment of osteoporosis. However, little is known about its effects and mechanisms on vascularized bone regeneration and implant osseointegration in aging. In current study, we adopted both in vivo and in vitro approaches to explore the mechanisms of early actions of PTH (1-34) on the angiogenic and osteogenic microenvironment to enhance implant osseointegration in aged rats. Daily subcutaneous injections of 30 μg/kg PTH (1-34) were given to female rats aged 20 months beginning on next day of implantation and lasting for 5 weeks. Radiological and histological analysis confirmed that PTH (1-34) improved new bone formation, angiogenesis and implant osseointegration in aged rats in the early stage. The osteogenic potential of aged bone mesenchymal stem cells (BMSCs) was enhanced, while their adipogenesis capacity was attenuated. Furthermore, PTH (1-34) was shown to promote angiogenesis directly via endothelial cell migration and blood vessel formation in vitro. Meanwhile, PTH (1-34) stimulated more osteoclasts participation in bone remodeling by secreting angiogenic and osteogenic growth factors to induce early vascularization and stimulate the migration or differentiation of BMSCs indirectly. Together, these results demonstrate mechanistic insight into how PTH (1-34) regulates the angiogenic and osteogenic microenvironment to result in more active bone remodeling and new bone formation, making it an excellent potential therapeutic agent for rapid vascularized bone regeneration and implant osseointegration in the aged population.

Morinda citrifolia Leaf Extract Enhances Osteogenic Differentiation Through Activation of Wnt/β-Catenin Signaling

Morinda citrifolia (Noni) leaf is an herbal medicine with application in the domestic treatment of a broad range of conditions, including bone fracture and luxation. However, the basic mechanism underlying the stimulation of osteogenic differentiation by Noni leaf extract remains poorly understood. This study aimed to examine the effect of this extract on osteogenic differentiation and the mechanism by which Noni leaf extract enhances osteogenic differentiation. Aqueous extract of Noni leaves was prepared, and rutin and kaempferol-3-O-rutinoside were identified to be two of its major components. C2C12 and human periodontal ligament (hPDL) cells were used to study the effect of Noni. Noni did not show cytotoxicity at a concentration range of 0.015%-1.0% (w/v%) and significantly enhanced the activity of alkaline phosphatase (ALP) and expression levels of osteoblast differentiation markers, including Runx2, ALP, osterix, and osteocalcin, bone morphogenetic protein 2, Wnt3a, and β-catenin. In addition, Noni enhanced the matrix mineralization of hPDL cells. In the signaling pathways, Noni increased the phosphorylation levels of Akt and GSK3β and nuclear translocation and transcriptional activity of β-catenin, which were attenuated by the addition of Dkk-1, a Wnt inhibitor, or LY294002, a PI3K inhibitor. These results suggest that Noni leaf extract enhances osteogenic differentiation through the PI3K/Akt-dependent activation of Wnt/β-catenin signaling. Noni leaf extract might be a novel alternative medicine for bone and periodontal regeneration in patients with periodontal diseases.

The local administration of parathyroid hormone encourages the healing of bone defects in the rat calvaria: Micro-computed tomography, histological and histomorphometric evaluation

OBJECTIVE

To evaluate the effect of a single-dose local administration of PTH on bone healing in rat calvarial bone defects by means of micro-computed tomography, histological and histomorphometric analysis.

DESIGN

Critical-size cranial osteotomy defects were created in 42 male rats. The animals were randomly divided into 3 groups. In the C Group, the bone defect was only filled with a blood clot. In the S Group, it was filled with a collagen sponge and covered with bovine cortical membrane. In the PTH Group, the defect was filled with a collagen sponge soaked with PTH and covered with bovine cortical membrane. The groups were further split in two for euthanasia 15 and 60days post-surgery. Data was statistically analyzed with t-tests for independent samples or the nonparametric Mann-Whitney test when applicable. Intragroup comparisons were analyzed with paired t-tests (p<0.05).

RESULTS

Micro-CT analysis results did not demonstrate statistically significant intergroup differences. At 15days post-surgery, the histomorphometric analysis showed that the PTH Group exhibited a significantly higher percentage of bone formation compared with the S Group. At 60days post-surgery, a higher percentage of new bone was observed in the PTH group.

CONCLUSION

The results suggest that the local administration of PTH encouraged the bone healing in critical-size calvarial defects in rats.

Upper alveolar ridge in edentulous patients and caldwell luc surgery

The aim of this study is to understand the upper alveolar ridge changes and its impact on Caldwell Luc surgery, in a patient papulation from a Medical College Hospital. We undertook a study to measure the thickness of upper alveolar ridge in edentulous and edentulous patients, to know the difference between the two and its effects on Caldwell Luc surgery. The finding of the study led us to conclude that the upper alveolar ridge is quite thin in edentulous patients and requires care while scraping the unhealthy mucosa from the floor of the maxillary sinus in Caldwell Luc surgery.

Teriparatide - Indications beyond osteoporosis

Osteoporosis is a condition of impaired bone strength that results in an increased risk of fracture. The current and most popular pharmacological options for the treatment of osteoporosis include antiresorptive therapy, in particular, oral bisphosphonates (alendronate, risedronate, ibandronate). Anabolic agents like teriparatide have widened our therapeutic options. They act by directly stimulating bone formation and improving bone mass quantity and quality. Two forms of recombinant human parathyroid hormone (PTH) are available : full-length PTH (PTH 1-84; approved in the EU only) and the 1-34 N-terminal active fragment of PTH (teriparatide, US FDA approved). This review aims to discuss the benefits of teriparatide beyond the currently licensed indications like fracture healing, dental stability, osteonecrosis of jaw, hypoparathyroidism, and hypocalcemia.