Administration of the bisphosphonate zoledronic acid during tooth development inhibits tooth eruption and formation and induces dental abnormalities in rats

Root resorption of primary molars and dental development of premolars in children with Osteogenesis Imperfecta medicated with bisphosphonates, grouped according to age and gender

BACKGROUND

Osteogenesis imperfecta (OI) is an inherited disorder characterized by bone fragility and skeletal alterations. The administration of bisphosphonates (BPs) to patients with OI reduces pain, thereby improving their quality of life. The main mechanism of action of BPs is the inhibition of osteoclast action. In the oral cavity of children with OI during growth and development, physiological processes that require the function of osteoclasts occur. The aim of this investigation was to study the dental development of premolars and the root resorption of primary molars in children with OI medicated with BPs according to age and sex.

METHODS

An observational and analytical study was designed. The study sample consisted of 26 6- to 12-year-old children with a confirmed diagnosis of OI treated with BPs with available panoramic radiographs. The control group consisted of 395 children with available panoramic radiographs. Both groups were divided into subgroups according to sex and age. The third quadrant was studied, focusing on the first left temporary molar (7.4), the second left temporary molar (7.5), the first left permanent premolar (3.4) and the second left permanent premolar (3.5). The Demirjian method was used to study the dental development of 3.4 and 3.5, and the Haavikko method was used to study the root resorption of 7.4 and 7.5. The Mann‒Whitney U test was used for comparisons, and p < 0.05 indicated statistical significance.

RESULTS

The mean chronological age of the 421 patients was 9.21 years (95% CI 9.05-9.37). The sample was reasonably balanced by sex, with 52.5% (221 patients) boys versus 47.5% (200 patients) girls. Delayed exfoliation and tooth development were described in children with OI (p = 0.05). According to sex, the root resorption of primary molars and tooth development were significantly lower in boys in both groups and in girls in the OI group, but the differences between the age groups were not significant.

CONCLUSIONS

Children with OI treated with BPs exhibit delayed dental development of the premolars and delayed root resorption of the primary molars. Boys exhibited delays in both variables, but the differences by age subgroup were not significant. These clinical findings support the importance of clinically and radiographically monitoring the dental development and root resorption of primary teeth in children with OI treated with BPs to avoid alterations of the eruptive process.

Influence of zoledronic acid and pamidronate on tooth eruption in children with osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) is a congenital disease comprising a heterogeneous group of inherited connective tissue disorders. The main treatment in children is bisphosphonate therapy. Previous animal studies have shown that bisphosphonates delay tooth eruption. The aim of this study is to determine whether patients with OI treated with pamidronate and/or zoledronic acid have a delayed eruption age compared to a control group of healthy children.

METHODS

An ambispective longitudinal cohort study evaluating the age of eruption of the first stage mixed dentition in a group of children with OI (n = 37) all treated with intravenous bisphosphonates compared with a group of healthy children (n = 89). Within the study group, the correlation (Pearson correlation test) between the type of medication administered (pamidronate and/or zoledronic acid) and the chronology of tooth eruption is established, as well as the relationship between the amount of cumulative dose received and tooth eruption.

RESULTS

The age of eruption of the study group was significantly delayed compared to the age of eruption of the control group for molars and lateral incisors (p < 0.05). Patients who received higher cumulative doses had a delayed eruption age compared to those with lower cumulative doses (p < 0.05). There is a high positive correlation between age of delayed tooth eruption and Zoledronic acid administration.

CONCLUSION

Patients with OI have a delayed eruption of the 1st stage mixed dentition compared to a control group of healthy children. This delayed eruption is directly related to the cumulative dose of bisphosphonates and the administration of zoledronic ac.

Effects of antiresorptive medications on tooth root formation and tooth eruption in paediatric patients

Tooth eruption is a pivotal milestone for children's growth and development. This process involves with the formation of the tooth root, the periodontal ligament (PDL) and the alveolar bone, as the tooth crown penetrates the bone and gingiva to enter the oral cavity. This review aims to outline current knowledge of the adverse dental effects of antiresorptive medications. Recently, paediatric indications for antiresorptive medications, such as bisphosphonates (BPs), have emerged, and these agents are increasingly used in children and adolescents to cure pathological bone resorption associated with bone diseases and cancers. Since tooth eruption is accompanied by osteoclastic bone resorption, it is expected that the administration of antiresorptive medications during this period affects tooth development. Indeed, several articles studying human patient cohorts and animal models report the dental defects associated with the use of these antiresorptive medications. This review shows the summary of the possible factors related to tooth eruption and introduces the future research direction to understand the mechanisms underlying the dental defects caused by antiresorptive medications.

Interleukin-17 plays a role in dental pulp inflammation mediated by zoledronic acid: a mechanism unrelated to the Th17 immune response?

OBJECTIVE

To evaluate the influence of RORγT inhibition by digoxin on inflammatory changes related to interleukin-17 (IL-17) in the pulp of rats treated with zoledronate (ZOL).

METHODOLOGY

Forty male Wistar rats were divided into a negative control group (NCG) treated with saline solution, a positive control group (PCG) treated with ZOL (0.20 mg/kg), and three groups treated with ZOL and co-treated with digoxin 1, 2, or 4 mg/kg (DG1, 2, and 4). After four intravenous administrations of ZOL or saline solution in a 70-day protocol, the right molars were evaluated by histomorphometry (number of blood vessels, blood vessels/µm2, cells/µm2, total blood vessel area, and average blood vessel area) and immunohistochemistry (IL-17, TNF-α, IL-6, and TGF-β). The Kruskal-Wallis/Dunn test was used for statistical analysis.

RESULTS

PCG showed an increase in total blood vessel area (p=0.008) and average blood vessel area (p=0.014), and digoxin treatment reversed these changes. DG4 showed a reduction in blood vessels/µm2 (p<0.001). In PCG odontoblasts, there was an increase in IL-17 (p=0.002) and TNF-α (p=0.002) immunostaining, and in DG4, these changes were reversed. Odontoblasts in the digoxin-treated groups also showed an increase in IL-6 immunostaining (p<0.001) and a reduction in TGF-β immunostaining (p=0.002), and all ZOL-treated groups showed an increase in IL-17 (p=0.011) and TNF-α (p=0.017) in non-odontoblasts cells.

CONCLUSION

ZOL induces TNF-α- and IL-17-dependent vasodilation and ectasia, and the classical Th17 response activation pathway does not seem to participate in this process.

Prevalence of dental alterations in patients under bisphosphonates therapy: a systematic review

This systematic review aimed to estimate the prevalence and describe dentoalveolar lesions associated with bisphosphonates therapy. A systematic review of the literature was conducted using the following databases: PubMed, Embase, Cochrane, CINAHL, Scopus, Web of Science, Lilacs, SciElo, and Grey Literature. Quality of individual studies analysis was performed by using Newcastle-Ottawa Scale. Certainty of cumulative evidence was achieved by applying Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. The software R Statistics version 4.0.5 (The R Foundation) was used for proportion estimations per study and corresponding confidence intervals were estimated through the Clopper-Pearson method. Four articles were included for the qualitative synthesis. Two studies were considered of good quality, one of fair, and one of poor quality. A total of 231 patients were encompassed. Widening of the periodontal ligament space (22.2-39.7%), periradicular radiolucencies (20-22.9%), and pulp calcifications (33.3-69.2%) were the most frequent alterations. Certainty of evidence was rated as very low. Based on limited evidence, this systematic review reports a variety of dentoalveolar alterations in patients under bisphosphonate therapy. These features might impact on dental clinical practice. However, the level of evidence is considered very low due to important limitations.

Craniofacial Characteristics and Orthodontic Treatment of Diamond Blackfan Syndrome: Two Case Reports

Diamond Blackfan anemia (DBA) is a chronic congenital form of erythrocytic hypoplasia in which erythroid precursor cell levels are low. DBA reflects ribosomal dysfunction and is accompanied by hematopoietic cell apoptosis, anemia, and various somatic symptoms. We report the characteristic symptoms of the craniofacial region and the orthodontic treatments of two DBA cases. Case 1 was a 12-year-old female. The typical physical and facial characteristics of DBA were lacking. On initial examination, she exhibited a skeletal Class II jaw and end to end molar relationships and a large overjet. An edgewise appliance was placed after extraction of the first maxillary premolars. After 3 years and 11 months, an appropriate overjet and overbite, rigid intercuspation, and an acceptable profile were evident without any clinical adverse effects. Case 2 was a 13-year-old female. She exhibited a skeletal Class I jaw relationship, a spaced dental arch, the maxillofacial dysplasia characteristic of Binder syndrome, hypoplasia of the right mandibular condyle, and labial protrusions of the maxillary and mandibular incisors. We placed an edgewise appliance and after 1 year and 7 months, the occlusion was optimal in the absence of any adverse effects. Our two DBA cases exhibited a broad spectrum of physical and dentofacial symptoms. Patients with DBA are often prescribed combined steroid/bisphosphonate therapies. Both agents are likely to affect alveolar bone remodeling after tooth extraction and orthodontic tooth movement. Careful consideration of medication with reference to various dentofacial characteristics is necessary.

High doses of zoledronic acid induce differential effects on femur and jawbone microstructure

OBJECTIVES

The aim of this study is to investigate the long-term effects on jaw and femur bone induced by oncologic doses of zoledronic acid in a young rat model.

MATERIAL AND METHODS

Six 12-week-old male Wistar rats received zoledronic acid (0.6 mg/kg) and six control rats received saline solution in the same volume. Compounds were administered intraperitoneally in five doses every 28 days. Euthanasia was performed 150 days after therapy onset. After animal sacrifice, their mandibles and femurs were scanned ex vivo using a high-resolution (14 μm) micro-computed tomography. Morphometric bone parameters were calculated using CT-Analyzer (Bruker, Belgium) between the first and second mandibular molars and in the distal femur metaphysis and epiphysis.

RESULTS

The treatment group as compared to the controls showed a significantly (p < .05) increased bone quantity (↑BV/TV, ↓Po[Tot], ↑Tb.Th), bone density (↑TMD, ↑BMD), and osteosclerosis of the trabecular bone (↓Tb.Sp, ↓Conn.Dn, ↓Tb.Pf, ↓SMI) in all anatomical sites. Bone remodeling suppression due to zoledronic acid treatment was more pronounced (p < .05) in the femoral metaphysis relative to the mandible and epiphysis. The exploratory linear discriminant analysis showed that for the mandible, it was mainly the bone quantity-related morphometric indices (BV/TV and Tb.Th), while for the femoral epiphysis and metaphysis, it was bone structure-related (Tb.Pf and Tb.N), which are of primary importance to study the treatment effect.

CONCLUSION

High doses of bisphosphonates can differently affect the bone quantity, density, and structure in long bones and jawbones. In the metaphysis, bone changes were primarily concentrated in the region of the growth plate. Future studies may consider the use of bone morphometric indices to evaluate the effect of bisphosphonates.

Computed Tomography-Based Investigation on the Effects of Intravenous Bisphosphonate Administration on Tooth Growth in a Minipig Animal Model

Background and Objectives: The objective of this study was to evaluate the effects of bisphosphonate (BP) administration on tooth growth, using CT-data of a minipig animal model investigation. Materials and Methods: Tooth growth was evaluated in minipigs, with eight animals receiving weekly zoledronate (ZOL) and three animals serving as the control group. Tooth growth was evaluated at the right 2nd molar (M2) in the maxilla. A computed tomography-based measuring method was applied to evaluate tooth growth in the coronal-apical, buccal-oral and mesial-distal axis. Results: ZOL-administration was found to impact tooth growth in all evaluated measuring axes, with the highest effect observed in the coronal-apical axis. Conclusions: Detrimental effects of BP administration on growing teeth have been reported by a number of investigators. The results of this investigation demonstrate that intravenous ZOL affects the growth of the whole tooth within a short period of administration. With BPs being administered to a growing number of pediatric patients, further studies should be conducted to qualify and quantify the effects of BPs on developing teeth.

The Critical Role of MMP13 in Regulating Tooth Development and Reactionary Dentinogenesis Repair Through the Wnt Signaling Pathway

Matrix-metalloproteinase-13 (MMP13) is important for bone formation and remodeling; however, its role in tooth development remains unknown. To investigate this, MMP13-knockout (Mmp13^−/−) mice were used to analyze phenotypic changes in the dentin–pulp complex, mineralization-associated marker-expression, and mechanistic interactions. Immunohistochemistry demonstrated high MMP13-expression in pulp-tissue, ameloblasts, odontoblasts, and dentin in developing WT-molars, which reduced in adults, with human-DPC cultures demonstrating a >2000-fold increase in Mmp13-expression during mineralization. Morphologically, Mmp13^−/− molars displayed critical alterations in the dentin-phenotype, affecting dentin-tubule regularity, the odontoblast-palisade and predentin-definition with significantly reduced dentin volume (∼30% incisor; 13% molar), and enamel and dentin mineral-density. Reactionary-tertiary-dentin in response to injury was reduced at Mmp13^−/− molar cusp-tips but with significantly more dystrophic pulpal mineralization in MMP13-null samples. Odontoblast differentiation-markers, nestin and DSP, reduced in expression after MMP13-loss in vivo, with reduced calcium deposition in MMP13-null DPC cultures. RNA-sequencing analysis of WT and Mmp13^−/− pulp highlighted 5,020 transcripts to have significantly >2.0-fold change, with pathway-analysis indicating downregulation of the Wnt-signaling pathway, supported by reduced in vivo expression of the Wnt-responsive gene Axin2. Mmp13 interaction with Axin2 could be partly responsible for the loss of odontoblastic activity and alteration to the tooth phenotype and volume which is evident in this study. Overall, our novel findings indicate MMP13 as critical for tooth development and mineralization processes, highlighting mechanistic interaction with the Wnt-signaling pathway.

Dental phenotype in an adolescent with osteogenesis imperfecta type XII

Mutation in SP7, encoding the osteoblast-specific transcription factor SP7 (also known as osterix), has been described to cause osteogenesis imperfecta (OI) type XII. However, the exact dental phenotype has not been well described. We report the detailed dental manifestation of a boy known to have OI type XII, presented with impacted dentition, necessitating combined oral and maxillofacial surgical and orthodontic treatment. This case also highlighted the need of multidisciplinary team assessment in this group of children.

Missing and unerupted teeth in osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) is a genetic disorder characterized by bone fragility and craniofacial and dental abnormalities such as congenitally missing teeth and teeth that failed to erupt which are believed to be doubled in OI patients than normal populations and were associated with low oral health quality of life. However, the etiology of these abnormalities remains unclear. To understand the factors influencing missing and unerupted teeth, we investigated their prevalence in a cohort of OI patients as a function of the clinical phenotype (OI type), the genetic variant type, the tooth type and the onset of bisphosphonate treatment.

METHOD

A total of 144 OI patients were recruited from The Shriners Hospital, Montreal, Canada, between 2016 and 2017. Patients were evaluated using intraoral photographs and panoramic radiographs. Missing teeth were evaluated in all patients, and unerupted teeth were assessed only in patients ≥15 years old (n = 82).

RESULTS

On average, each OI patient had 2.4 missing teeth and 0.8 unerupted teeth, and the most common missing and unerupted teeth were the premolars and the upper second molars, respectively. These phenomena were more prominent in OI type III and IV than in OI type I, and were not sex or age-related. Missing teeth were significantly more common in patients with C-propeptide variants than all other variants (p-value <0.05). Unerupted teeth were significantly more common in patients with α1 and α2 glycine variants or substitutions than in those with haploinsufficiency variants. Early-onset of bisphosphonate treatment would significantly increase the risk of unerupted teeth in patients with OI types III and IV (OR = 1.68, 95% CI (1.15-1.53)).

CONCLUSION

The prevalence of missing and unerupted teeth at the tooth type level in OI patients varies according to the nature of the collagen variants and the OI type. These findings highlight the role of collagen in tooth development and eruption.

Abnormalities in Tooth Formation after Early Bisphosphonate Treatment in Children with Osteogenesis Imperfecta

Treatment with intravenous bisphosphonate (BP) in children and adolescents with osteogenesis imperfecta (OI) started in Sweden in 1991. No human studies on the role of BP therapy in development of disturbances in tooth mineralization or tooth morphology have been published. The study cohort comprised 219 individuals who were divided into four groups: group 1, BP treatment onset before 2 years of age (n = 22); group 2, BP treatment onset between 2 and 6 years of age (n = 20); group 3, BP treatment onset between 6 and 10 years of age (n = 13); and a control group of patients with OI who had not received BP therapy (n = 164). The chi-square test was used in between-group comparisons of the prevalence of tooth agenesis. The prevalence of tooth agenesis was significantly higher in children who began BP treatment before the age of 2 years (group 1; 59%,) compared to the controls (10%; p < 0.001) and to children who had begun BP therapy between ages 2 and 6 years (group 2; 10%; p = 0.009) or between ages 6 and 10 years (group 3; 8%; p = 0.003). Different types of disturbances in the enamel formation were seen in 52 premolars, where 51 were seen in those who began BP treatment before the age of 2 years. To conclude, starting BP treatment before the age of 2 years increases the risk of abnormalities in tooth formation manifesting as morphological aberrations, tooth agenesis, and enamel defects.

Effects of systematic bisphosphonate use in patients under orthodontic treatment: a systematic review

BACKGROUND

Bisphosphonates are a class of drugs prescribed for several osseous related disorders owing to their ability to regulate bone turnover, which could in turn affect orthodontic treatment outcomes.

OBJECTIVE

To examine the effect of bisphosphonate (BP) use on orthodontic patients through clinical and radiographic measurements.

SEARCH METHODS

Systematic and unrestricted search of 17 databases complemented with additional hand-searches were performed up to March 2019.

SELECTION CRITERIA

Articles reporting on human patients with a history of BPs administration that received orthodontic treatment were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Data regarding the medical profile of the patients, the specific type of malocclusion and the performed treatment plan, as well as the clinical and radiographic outcomes were extracted. Quality assessment was performed by the ROBINS-I tool for the cohort studies and by a slightly modified checklist from the original one proposed by Agbabiaka et al. for the case reports.

RESULTS

7 articles (1 retrospective cohort study and 6 case reports) were eventually included in the present review including 122 subjects (29 patients and 93 controls) reporting on the clinical and radiographic changes following orthodontic treatment of patients during or after BPs use. BPs seem to have a controversial effect on the clinical and patient-reported variables, even though the majority of the included patients presented with compromised treatment results and a rather slow rate of tooth movement. Most radiographic findings revealed mild root resorption, widened periodontal ligament spaces and sclerotic changes on the surrounding alveolar bone. However, these results should be interpreted with caution, due to the limited number of the eligible articles and their limitations.

LIMITATIONS

The included studies were of rather low quality due to study design and incomplete reporting.

CONCLUSIONS AND IMPLICATIONS

BP administration seems to be associated with compromised clinical outcomes, prolonged treatment time, and moderate changes on the roots and surrounding tissues of orthodontic patients.

REGISTRATION

Non-registered.

FUNDING

None.

Alterations in odontogenesis and tooth eruption resulting from exposure to hexavalent chromium in suckling animals

BACKGROUND

Heavy metals including Cr VI are present in inadequately treated effluents that contaminate drinking water. Hence, Cr VI exposure can affect children through intake of breast milk from an exposed mother or bottle-feeding formula prepared with contaminated water. To date, there are no reports on the effects of Cr VI exposure on tooth formation processes concomitant to tooth eruption.

AIM

To study the effect of Cr VI exposure on tooth tissue formation in suckling Wistar rats by assessing dental tissues at different stages of tooth eruption.

DESIGN

Experimental animals received 12.5 mg/kg body weight/day of a potassium dichromate solution by gavage; control animals were similarly administered an equivalent volume of saline solution. Each group was divided into three subsets according to age at euthanasia: 9, 15, and 23 days. Dental formation was analysed histologically and histomorphometrically.

STATISTICAL ANALYSIS

Student's t test; P < .05.

RESULTS

Cr VI-exposed animals showed a delay in mineralized crown and root tissue formation. These findings are directly associated with the observed delay in tooth eruption.

CONCLUSION

Our findings show the importance of monitoring drinking water levels of toxic substances, since exposure during early childhood can alter tooth formation, growth, and development.

Dental alterations on panoramic radiographs of patients with osteogenesis imperfecta in relation to clinical diagnosis, severity, and bisphosphonate regimen aspects: a STROBE-compliant case-control study

OBJECTIVE

This study aimed to assess the prevalence of dental findings on panoramic radiographs (PRs) of patients with osteogenesis imperfecta (OI) and correlate these results with epidemiologic and medical data.

STUDY DESIGN

A case-control study was conducted with 24 patients with OI and 48 sex- and age-matched controls. Demographic, clinical, and bisphosphonate regimen-related data were recorded. The outcome variables were the presence or absence of dental alterations in PRs. Mann-Whitney U test, Pearson's χ² test, and multinomial logistic regression analysis (95% confidence interval) were used (significance level of 5%).

RESULTS

OI type 4 demonstrated a high prevalence (62.5%), followed by type 1 (37.5%). With regard to prevalence associated with severity, the moderate form was the most prevalent (P = .028). The mean time of intravenous pamidronate regimen was 6.6 ± 4.4 years. Dentinogenesis imperfecta was observed in 75% of patients with OI, and this group showed a high prevalence of dental abnormalities in comparison with controls (P < .05). Bisphosphonate therapy was associated with ectopic teeth (P = .007) and tooth impaction (P = .033). Pulp obliteration was significant with bisphosphonate treatment over a period of 7 years (P = .026).

CONCLUSIONS

This study found a significant prevalence of dental alterations in patients with OI, and certain alterations were associated with bisphosphonate therapy, indicating its influence on the dentin-related physiopathology.

Genetically-achieved disturbances to the expression levels of TNFSF11 receptors modulate the effects of zoledronic acid on growing mouse skeletons

Zoledronic acid (ZOL), a nitrogen bisphosphonate (N-BP), is currently used to treat and control pediatric osteolytic diseases. Variations in the intensity of the effects and side effects of N-BPs have been reported with no clear explanations regarding their origins. We wonder if such variations could be associated with different levels of RANKL signaling activity in growing bone during and after the treatment with N-BPs. To answer this question, ZOL was injected into neonate C57BL/6J mice with different genetically-determined RANKL signaling activity levels (Opg^+/+\Rank^Tg-, Opg^+/+\Rank^Tg+, Opg^+/-\Rank^Tg-, Opg^+/-\Rank^Tg+, Opg^-/-\Rank^Tg- and Opg^-/-\Rank^Tg+ mice) following a protocol (4 injections from post-natal day 1 to 7 at the dose of 50 μg/kg) that mimics those used in onco-pediatric patients. At the end of pediatric growth (1 and half months) and at an adult age (10 months), the bone morphometric and mineral parameters were measured using μCT in the tibia and skull for the different mice. A histologic analysis of the dental and periodontal tissues was also performed. At the end of pediatric growth, a delay in long bone and skull bone growth, a blockage of tooth eruption, some molar root alterations and a neoplasia-like structure associated with incisor development were found. Interestingly, the magnitude of these side effects was reduced by Opg deficiency (Opg^-/-) but increased by Rank overexpression (Rank^Tg). Analysis of the skeletal phenotype at ten months confirmed respectively the beneficial and harmful effects of Opg deficiency and Rank overexpression. These results validated the hypothesis that the RANKL signaling activity level in the bone microenvironment is implicated in the modulation of the response to ZOL. Further studies will be necessary to understand the underlying molecular mechanisms, which will help decipher the variability in the effects of N-BPs reported in the human population. SIGNIFICANT STATEMENTS: The present study establishes that in mice the RANKL signaling activity level is a major modulator of the effects and side-effects of bisphosphonates on the individual skeleton during growth. However, the modulatory actions are dependent on the ways in which this level of activity is increased. A decrease in OPG expression is beneficial to the skeletal phenotype observed at the end of growth, while RANK overexpression deteriorates it. Far removed from pediatric treatment, in adults, the skeletal phenotypes initially observed at the end of growth for the different levels of RANKL signaling activity were maintained, although significant improvement was associated only with reductions in OPG expression.

Paradoxical side effects of bisphosphonates on the skeleton: What do we know and what can we do?

Bisphosphonates are considered the most effective drugs for controlling adult and pediatric osteolytic diseases. Although they have been used successfully for many years, several side effects, such as osteonecrosis of the jaw, delayed dental eruption, atypical femoral fracture, and alterations to the bone growth system, have been described. After an overview of nitrogenous bisphosphonate, the purpose of this article is to describe their mechanisms of action and current applications, review the preclinical and clinical evidence of their side effects in the skeleton ("what we know"), and describe current recommendations for preventing and managing these effects ("what we can do"). Finally, promising future directions on how to limit the occurrence of these side effects will be presented.

Hypercementosis Associated with ENPP1 Mutations and GACI

Mineralization of bones and teeth is tightly regulated by levels of extracellular inorganic phosphate (P_i) and pyrophosphate (PP_i). Three regulators that control pericellular concentrations of P_i and PP_i include tissue-nonspecific alkaline phosphatase (TNAP), progressive ankylosis protein (ANK), and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1). Inactivation of these factors results in mineralization disorders affecting teeth and their supporting structures. This study for the first time analyzed the effect of decreased PP_i on dental development in individuals with generalized arterial calcification of infancy (GACI) due to loss-of-function mutations in the ENPP1 gene. Four of the 5 subjects reported a history of infraocclusion, overretained primary teeth, ankylosis, and/or slow orthodontic tooth movement, suggesting altered mineral metabolism contributing to disrupted tooth movement and exfoliation. All subjects had radiographic evidence of unusually protruding cervical root morphology in primary and/or secondary dentitions. High-resolution micro-computed tomography (micro-CT) analyses of extracted primary teeth from 3 GACI subjects revealed 4-fold increased cervical cementum thickness ( P = 0.00007) and a 23% increase in cementum density ( P = 0.009) compared to age-matched healthy control teeth. There were no differences in enamel and dentin densities between GACI and control teeth. Histology revealed dramatically expanded cervical cementum in GACI teeth, including cementocyte-like cells and unusual patterns of cementum resorption and repair. Micro-CT analysis of Enpp1 mutant mouse molars revealed 4-fold increased acellular cementum thickness ( P = 0.002) and 5-fold increased cementum volume ( P = 0.002), with no changes in enamel or dentin. Immunohistochemistry identified elevated ENPP1 expression in cementoblasts of human and mouse control teeth. Collectively, these findings reveal a novel dental phenotype in GACI and identify ENPP1 genetic mutations associated with hypercementosis. The sensitivity of cementum to reduced PP_i levels in both human and mouse teeth establishes this as a well-conserved and fundamental biological process directing cementogenesis across species (ClinicalTrials.gov NCT00369421).

Effects of pamidronate administration on tooth eruption and mandibular growth in new born rats

Purpose:

Bisphosphonates are commonly used drugs in pediatric patients in the treatment of osteoporotic diseases and various types of cancers. The purpose of this study was to evaluate the effects of pamidronate administration on mandibular growth and tooth eruption in new born rats.

Materials and Methods:

Forty Sprague Dawley rats were included in the study and divided into four groups as; 14th day pamidronate group, 30th day pamidronate group, 14th day control group and 30th day control group. Pamidronate groups were daily injected with 1.25 µg/g pamidronate disodium subcutaneously whereas control groups were injected with sterile saline. Eruption levels of lower incisor and molar teeth were assessed macroscopically. Mandibular growth was assessed by measuring reference points in cone beam tomography. Histological and histomorphometric examinations were performed under light microscope to evaluate tooth morphology and number of osteoclasts.

Results:

Retardation in mandibular growth, decrease in number of osteoclasts, delay in tooth eruption, degeneration in both tooth morphology and structure were observed in the pamidronate groups compared to control groups.

Conclusion:

Pamidronate administration during growth and development stage may adversely affect tooth eruption and mandibular growth in new born rats.

Immune cell profile of dental pulp tissue treated with zoledronic acid

AIM

To characterize the pulp immune cell profile in the teeth of rats treated with zoledronic acid (ZA).

METHODOLOGY

Male Wistar rats (n = 6 per group) received four intravenous infusions of ZA at doses of 0.04, 0.20 or 1.00 mg kg^-1 ZA or saline (control). On the 70th experimental day, they were euthanized. The first right molar was examined microscopically and submitted to toluidine blue reaction and immunohistochemical for CD68, tumour necrosis Factor (TNF)-α, interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), nuclear factor kappa B (NF-kB) and IL-18 binding protein (IL-18 bp). The presence of ectasic/dilated vessels and inflammatory cells was analysed, and mast cells and mononuclear CD68-positive cells were counted along with the intensity of immunostaining (0-3) for inflammatory markers in odontoblasts and nonodontoblasts pulp cells. The Kruskal-Wallis/Dunn's test (scores or quantitative data) and the chi-squared test (categorical data) were used (GraphPad Prism 5.0, P < 0.05).

RESULTS

There was no differences in the number of animals exhibiting dilated/ectasic blood vessels (P = 0.242) and inflammatory cells (P = 0.489) or in the number of mast cells (P = 1.000). However, there was an increase in mononuclear CD68-positive cells (P = 0.026), immunostaining of TNF-α (P = 0.020), IL-1β (P = 0.027) and iNOS (P = 0.001) in odontoblasts, and IL-1β (P = 0.013) in nonodontoblast pulp cells dose-dependently. NFkB (nucleus and cytoplasm) and IL-18 bp did not differ between groups.

CONCLUSION

ZA modified the immune cell profile in the dental pulp, increasing the number of macrophages and expression of pro-inflammatory markers independent of NFkB.

Timing of dental development in osteogenesis imperfecta patients with and without bisphosphonate treatment

Bisphosphonates have established their role as medical therapy for pediatric osteogenesis imperfecta (OI) patients. Since bisphosphonates have also been shown to delay tooth development in animal models, we aimed to assess whether the medication has a similar effect on children with OI. In this cross-sectional study, bisphosphonate-treated OI patients of whom dental panoramic tomograph was taken between 3 and 16years of age formed the study group. The patients, 22 in total, had been treated with pamidronate, zoledronic acid or risedronate for at least one year before the radiography. Developmental stage of the permanent teeth, resorption of the deciduous teeth, and number of the erupted permanent teeth were radiographically assessed in the left mandibular quadrant. Dental panoramic tomographs of 50 OI patients, naïve to bisphosphonates, and of 50 healthy individuals of the same age were used as controls. The dental development was statistically significantly accelerated in the OI group naïve to bisphosphonates showing median advancement of dental age by 0.63years from chronological age and median increase in the number of erupted teeth by 0.31 as compared to Finnish norms. Bisphosphonate-treated OI patients displayed, however, age-appropriate dental development. The OI patients not treated with bisphosphonates also showed statistically significantly faster resorption of the deciduous teeth than the treated ones, and displayed an altered interrelationship between the resorption stage of an individual primary tooth and the developmental stage of the succedaneous permanent tooth, unlike the OI patients treated with bisphosphonate. No correlation between either cumulative bisphosphonate dose or between treatment length and any measured component of the dental development was found. To conclude, OI itself was found to lead to advanced dental development. Bisphosphonate treatment had a delaying effect in all the three aspects studied, resulting in a rate of dental development indistinguishable from normal.

Effects of Pamidronate on Dental Enamel Formation Assessed by Light Microscopy, Energy-Dispersive X-Ray Analysis, Scanning Electron Microscopy, and Microhardness Testing

The aim of the present work was to investigate birefringence and morphology of the secretory-stage enamel organic extracellular matrix (EOECM), and structural and mechanical properties of mature enamel of upper incisors from adult rats that had been treated with pamidronate disodium (0.5 mg/kg/week for 56 days), using transmitted polarizing and bright-field light microscopies (TPLM and BFLM), energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM) and microhardness testing. BFLM showed no morphological changes of the EOECM in pamidronate and control groups, but TPLM revealed a statistically significant reduction in optical retardation values of birefringence brightness of pamidronate-treated rats when compared with control animals (p0.05). The present study indicates that pamidronate can affect birefringence of the secretory-stage EOECM, which does not seem to be associated with significant changes in morphological and/or mechanical properties of mature enamel.

Bisphosphonates: Pharmacokinetics, bioavailability, mechanisms of action, clinical applications in children, and effects on tooth development

Bisphosphonates (BPs) avidly bind to calcium crystals and inhibit osteoclastic bone resorption, making them useful for treatment of skeletal disorders such as osteoporosis, Paget's disease, osteogenesis imperfecta and metastatic bone diseases. BPs therapeutically act by causing toxic effects on osteoclasts or interfering with specific intracellular pathways in those cells. BPs that possess nitrogen in their composition are called nitrogen-containing BPs (NBPs) and include alendronate, pamidronate, risedronate, ibandronate, and zoledronate. Simple BPs or non-NBPs do not have nitrogen in their composition, include etiodronate and clodronate, and were the first to be tested in animals and clinically used. Because BPs may be administered to pregnant women or children during deciduous and permanent teeth development, it is expected that they might disturb tooth eruption and development. A review of current literature on pharmacokinetics, bioavailability, mechanisms of action, and clinical applications of BPs in children, and their effects on tooth eruption and development is presented.

Bone resorption: an actor of dental and periodontal development?

Dental and periodontal tissue development is a complex process involving various cell-types. A finely orchestrated network of communications between these cells is implicated. During early development, communications between cells from the oral epithelium and the underlying mesenchyme govern the dental morphogenesis with successive bud, cap and bell stages. Later, interactions between epithelial and mesenchymal cells occur during dental root elongation. Root elongation and tooth eruption require resorption of surrounding alveolar bone to occur. For years, it was postulated that signaling molecules secreted by dental and periodontal cells control bone resorbing osteoclast precursor recruitment and differentiation. Reverse signaling originating from bone cells (osteoclasts and osteoblasts) toward dental cells was not suspected. Dental defects reported in osteopetrosis were associated with mechanical stress secondary to defective bone resorption. In the last decade, consequences of bone resorption over-activation on dental and periodontal tissue formation have been analyzed with transgenic animals (RANK^Tg and Opg^−∕− mice). Results suggest the existence of signals originating from osteoclasts toward dental and periodontal cells. Meanwhile, experiments consisting in transitory inhibition of bone resorption during root elongation, achieved with bone resorption inhibitors having different mechanisms of action (bisphosphonates and RANKL blocking antibodies), have evidenced dental and periodontal defects that support the presence of signals originating bone cells toward dental cells. The aim of the present manuscript is to present the data we have collected in the last years that support the hypothesis of a role of bone resorption in dental and periodontal development.

Preclinical evidence of potential craniofacial adverse effect of zoledronic acid in pediatric patients with bone malignancies

High doses of zoledronic acid (ZOL), one of the most potent inhibitors of bone resorption, are currently evaluated in phase III clinical trials in Europe for the treatment of malignant pediatric primary bone tumors. The impact of such an intensive treatment on the craniofacial skeleton growth is a critical question in the context of patients with actively growing skeleton; in particular, in light of our previous studies evidencing that endochondral bone formation was transiently disturbed by high doses of ZOL. Two protocols adapted from pediatric treatments were developed for newborn mice (a total of 5 or 10 injections of ZOL 50μg/kg every two days). Their impact on skull bones and teeth growth was analyzed by X-rays, microCT and histology up to 3months after the last injection. ZOL administrations induced a transient delay of skull bone growth and an irreversible delay in incisor, first molar eruption and root elongation. Other teeth were affected, but most were erupted by 3months. Root histogenesis was severely impacted for all molars and massive odontogenic tumor-like structures were observed in all mandibular incisors. High doses of ZOL irreversibly disturbed teeth eruption and elongation, and delayed skull bone formation. These preclinical observations are essential for the follow-up of onco-pediatric patients treated with ZOL.

The use of bisphosphonates in children: review of the literature and guidelines for dental management

Bisphosphonates are inhibitors of osteoclastic bone resorption with therapeutic benefit in a variety of bone disorders in both adults and children. While these agents have been routinely used in adults for the past three decades, their more recent introduction into paediatric medicine means there is a paucity of data on long-term safety and effects on dental development. There is uncertainty regarding the dental management of children treated with bisphosphonates, particularly when invasive dental procedures, such as extractions and oral surgical procedures, are required. There are limited data with which to make recommendations about the dental management of patients treated with bisphosphonates, and there are no published recommendations that specifically address paediatric patients. This paper aims to outline paediatric uses and adverse effects of bisphosphonates and present recommendations on the dental management of children receiving bisphosphonates.

Feasibility and dose discovery analysis of zoledronic acid with concurrent chemotherapy in the treatment of newly diagnosed metastatic osteosarcoma: a report from the Children's Oncology Group

AIM

Patients with metastatic osteosarcoma (OS) have a poor outcome with conventional therapies. Zoledronic acid (ZA) is a third-generation bisphosphonate that reduces skeletal-related events in many adult cancers, and pre-clinical data suggest a possible benefit in OS. This study assessed the maximum tolerated dose (MTD) and the feasibility of ZA when combined with chemotherapy in patients with metastatic OS.

PATIENTS AND METHODS

Patients with a histological diagnosis of OS were eligible if they were <40 years of age, had initially metastatic disease and met organ function requirements. Treatment combined surgery and a conventional chemotherapy regimen. ZA was given concurrent with chemotherapy for a total of eight doses over 36 weeks. Three dose levels of ZA were tested: 1.2 mg/m(2) [max 2 mg], 2.3 mg/m(2) [max 4 mg] and 3.5 mg/m(2) [max 6 mg]. The MTD was determined during induction. Six patients were to be treated at each dose level, with an additional six patients treated with the MTD to help assess post-induction feasibility.

RESULTS

Twenty-four patients (median age 13.5 years [range, 7-22]; 16 females) were treated. Five patients experienced dose-limiting toxicities (DLTs) during induction, including three patients treated with 3.5 mg/m(2). DLTs included hypophosphatemia, hypokalemia, hyponatremia, mucositis, limb pain and limb oedema. There were no reports of excessive renal toxicity or osteonecrosis of the jaw. The MTD was defined as 2.3 mg/m(2) (max 4 mg).

CONCLUSIONS

ZA can be safely combined with conventional chemotherapy with an MTD of 2.3 mg/m(2) (max 4 mg) for patients with metastatic osteosarcoma.

Reduced RANKL expression impedes osteoclast activation and tooth eruption in alendronate-treated rats

The creation of the eruption pathway requires the resorption of the occlusal alveolar bone by osteoclasts and signaling events between bone and dental follicle are necessary. The aim of the present study has been to evaluate the effect of alendronate on osteoclastogenesis and the expression of the regulator proteins of osteoclast activation, namely RANK, RANKL and OPG, in the bone that covers the first molar germ. Newborn Wistar rats were treated daily with 2.5 mg/kg alendronate for 4, 8, 14, 21 and 28 days, whereas controls received sterile saline solution. At the time points cited, maxillae were fixed, decalcified and processed for light and electron microscopic analysis. TRAP histochemistry was performed on semi-serial sections and the osteoclasts in the occlusal half of the bony crypt surface were counted. TUNEL analysis was carried out on paraffin sections. The occlusal bone that covers the upper first molar was removed in additional 4- and 8-day-old alendronate-treated and control rats in which the expression of RANK, RANKL and OPG was analyzed by SDS-polyacrylamide gel electrophoresis and Western blotting. TRAP-positive osteoclasts were more numerous in the alendronate group at all time points, despite their unactivated phenotype and the presence of apoptotic cells. RANKL expression in the alendronate specimens was inhibited at all time points, unlike in controls. Our findings indicate that the expression of RANKL in the occlusal portion of the bony crypt is unrelated to osteoclast recruitment and differentiation but is crucial to their activation during the creation of the eruption pathway.

The effect of bone morphometric changes on orthodontic tooth movement in an osteoporotic animal model

Objective:

To elucidate the effect of bone morphometric changes on orthodontic tooth movement (OTM) in zoledronic acid–treated ovariectomized rats.

Materials and Methods:

Twenty-one 10-week-old female Wistar rats were divided into ovariectomy (OVX), OVX with zoledronic acid administration (OVX + ZOL), and sham operation (control) groups. Two weeks after OVX, ZOL administration was initiated. Twelve weeks after OVX, a nickel-titanium closed-coil spring of 25-g force was applied mesially to the maxillary left first molar. In vivo micro–computed tomography (CT) of the left proximal tibia was performed for bone morphometric analysis every 2 weeks after OVX. In addition, OTM was investigated using micro-CT at 0, 12, and 14 weeks after OVX.

Results:

There were significant differences in the bone mineral content (BMC), bone volume (BV), BMC to tissue volume ratio (BMC/TV), and BV to TV ratio of trabecular bone between the control and OVX groups and also between the OVX + ZOL and OVX groups. In the OVX + ZOL group, increased BMC and BV in the cortical bone and increased bone mineral density (BMD) in the trabecular bone were observed. Interestingly, OTM in the OVX group was almost two times more than that in the control and OVX + ZOL groups. Moreover, OTM was correlated with BMD, BMC, BV, and BMC/TV in the trabecular bone.

Conclusions:

OVX accelerated OTM, while ZOL suppressed it. OTM demonstrated a significant negative relationship with trabecular bone mass.

Common dental disorders of the degu (Octodon degus)

Dental disease is prevalent in the captive degu (Octodon degus), yet little has been documented on the variety of disorders in this species. In this internet-based study, dental cases presented over a 7-year period were collated, analyzed, and grouped. Of the 137 total cases, the most common dental disorder of the degu was found to be molar malocclusion (42.3 %). Other disorders documented included enamel decoloration (13.1%), molar elodontoma (8.0%), enamel hypoplasia (6.6%), incisor tooth fracture (6.6%), incisor malocclusion (3.6%), oral abscess (2.2%), and impacted molar teeth (0.7%). Details of each condition, pathogenesis, and clinical signs are described. Age was found not to be a significant predictor of dental disease in the degu.

Tooth dentin defects reflect genetic disorders affecting bone mineralization

Several genetic disorders affecting bone mineralization may manifest during dentin mineralization. Dentin and bone are similar in several aspects, especially pertaining to the composition of the extracellular matrix (ECM) which is secreted by well-differentiated odontoblasts and osteoblasts, respectively. However, unlike bone, dentin is not remodelled and is not involved in the regulation of calcium and phosphate metabolism. In contrast to bone, teeth are accessible tissues with the shedding of deciduous teeth and the extractions of premolars and third molars for orthodontic treatment. The feasibility of obtaining dentin makes this a good model to study biomineralization in physiological and pathological conditions. In this review, we focus on two genetic diseases that disrupt both bone and dentin mineralization. Hypophosphatemic rickets is related to abnormal secretory proteins involved in the ECM organization of both bone and dentin, as well as in the calcium and phosphate metabolism. Osteogenesis imperfecta affects proteins involved in the local organization of the ECM. In addition, dentin examination permits evaluation of the effects of the systemic treatment prescribed to hypophosphatemic patients during growth. In conclusion, dentin constitutes a valuable tool for better understanding of the pathological processes affecting biomineralization.