[Digital Concepts for the Care of Newborns with Craniofacial Anomalies]. / Digitale Konzepte für die Versorgung von Neugeborenen mit kraniofazialen Anomalien.

The treatment of newborns with craniofacial abnormalities such as cleft lip and/or palate poses special challenges for healthcare providers. Often, the collaboration of an interdisciplinary team of pediatricians, orthodontists, and oral and maxillofacial surgeons is necessary. Therapy using feeding or stimulation plates can improve feeding and strengthen orofacial muscle tone. The treatment of patients with cleft lip and palate using conventionally manufactured feeding plates as well as the treatment of patients with reduced orofacial muscle tone through stimulation plates therapy are established and widely used methods. The conventional production of these plate appliances can lead to serious complications such as swallowing of impression material and airway obstruction due to aspiration. Through an innovative, entirely digital workflow using computer-assisted design and manufacturing of the appliances in a 3D printer, risks can be minimized and time and costs can be saved. This article aims to explain the digital workflow of treating newborns with 3D CAD/CAM feeding and stimulation plates through two case studies.

Age-related changes in the midpalatal suture: Comparison between CBCT staging and bone micromorphology.

The age-related maturation of the human midpalatal suture is challenging to predict, but critical for successful non-surgical rapid maxillary expansion (RME). While cone-beam computed tomography (CBCT) can be used to categorize the suture into stages, it remains unclear how well the stages predict the actual micromorphology of the palate. To address this clinically relevant question, we used CBCT together with three-dimensional micro-computed tomography (µCT) analysis on 24 human palate specimens from individuals aged 14-34 years. We first classified the specimens into stages (A-E) using CBCT images and then correlated the results with our comprehensive µCT analysis. Our analysis focused on several factors, including bone volume fraction (BV/TV), sutural width, volume, interdigitation, ossification, and their associations with age, CBCT stage, and sex. Our µCT analysis revealed a decrease in sutural width and volume after the age of 20 years, accompanied by sutural closure beginning in the palatal segment. The overall rate of ossification remained low but increased after the age of 20 years. No significant differences were found between males and females. Importantly, we also found no correlation between individual age and CBCT stages. Furthermore, there was no association between CBCT stages and patalal suture volume, ossification and interdigitation. Taken together, our findings cast doubt on the reliability of CBCT stage as a means of predicting skeletal maturity of the palatal suture, as it appears to lack the precision required to accurately assess the true micromorphology of the palatal suture. Future investigations should explore whether alternative CBCT parameters may be more useful in addressing the challenging question of whether RME requires surgical bone weakening.

[Association of oral health literacy and behaviour with physical oral health. What role can dental education play?] / Zusammenhang von Mundgesundheitskompetenz und -verhalten mit physischer Mundgesundheit. Welche Rolle kann die zahnmedizinische Ausbildung spielen?

BACKGROUND: Oral health is an essential component of a person's general health and well-being. It is influenced by many factors. These include individual aspects such as oral health literacy and oral health behaviour. The aim of this study was to investigate the association between oral health literacy and behaviour with physical oral health. METHODS: In this population-based cross-sectional study, data of 5510 subjects enrolled in the Hamburg City Health Study (HCHS) from 2016 to 2018 with a mean age of 62.1 years and 50.7% women were evaluated. Physical oral health was assessed using the 14-item Physical Oral Health Index (PhOX). A newly developed 10-item questionnaire based on the Oral Health Literacy Adult Questionnaire and the 5th German Oral Health Study were used to determine oral health literacy and behaviour. RESULTS: The sum score of the 10 questions related to oral health literacy and behaviour significantly correlated with the PhOX sum score (r = 0.23; p < 0.001). An increase of one point in the total score of oral health literacy and behaviour was associated with an increase in the PhOX sum score of 1.45 points on average. This association decreased only marginally after integrating potential confounders such as age and education. CONCLUSION: Higher oral health literacy and better oral health behaviour are associated with better physical oral health. Oral health literacy and behaviour should be important targets in dental education to efficiently and sustainably improve the oral health of the general population.

[iMED DENT-First in place model curriculum in dentistry in Germany]. / Der erste Modellstudiengang Zahnmedizin in Deutschland ­ iMED DENT.

October 2019 saw the launch of iMED DENT, the first model study program in dentistry in Germany. The launch was preceded by a development process lasting several years in which European locations, among others, with innovative dental study programs were initially visited. The central reform objective of the model study program was then defined: the development, implementation, and ongoing optimization of an interdisciplinary curriculum with a scientific focus that integrates theoretical and practical dental content. Further steps were the development of the study program objectives and the modular study structure. The latter consists of the three parts: "Normal Function," "From Symptom to Disease," and "Therapy." In the curriculum, the central area of dentistry is flanked by basic and clinical medical subjects. This article reports on the important development steps of the model study program, its structure, and quality assurance measures. First evaluations of the achievement of study program objectives and the need for optimization in the current curriculum are presented.

Mechanical-induced bone remodeling does not depend on Piezo1 in dentoalveolar hard tissue.

Mechanosensory ion channels are proteins that are sensitive to mechanical forces. They are found in tissues throughout the body and play an important role in bone remodeling by sensing changes in mechanical stress and transmitting signals to bone-forming cells. Orthodontic tooth movement (OTM) is a prime example of mechanically induced bone remodeling. However, the cell-specific role of the ion channels Piezo1 and Piezo2 in OTM has not been investigated yet. Here we first identify the expression of PIEZO1/2 in the dentoalveolar hard tissues. Results showed that PIEZO1 was expressed in odontoblasts, osteoblasts, and osteocytes, while PIEZO2 was localized in odontoblasts and cementoblasts. We therefore used a Piezo1floxed/floxed mouse model in combination with Dmp1cre to inactivate Piezo1 in mature osteoblasts/cementoblasts, osteocytes/cementocytes, and odontoblasts. Inactivation of Piezo1 in these cells did not affect the overall morphology of the skull but caused significant bone loss in the craniofacial skeleton. Histological analysis revealed a significantly increased number of osteoclasts in Piezo1floxed/floxed;Dmp1cre mice, while osteoblasts were not affected. Despite this increased number of osteoclasts, orthodontic tooth movement was not altered in these mice. Our results suggest that despite Piezo1 being crucial for osteoclast function, it may be dispensable for mechanical sensing of bone remodeling.

Effects of Infantile Hypophosphatasia on Human Dental Tissue.

Hypophosphatasia (HPP) is an inherited, systemic disorder, caused by loss-of-function variants of the ALPL gene encoding the enzyme tissue non-specific alkaline phosphatase (TNSALP). HPP is characterized by low serum TNSALP concentrations associated with defective bone mineralization and increased fracture risk. Dental manifestations have been reported as the exclusive feature (odontohypophosphatasia) and in combination with skeletal complications. Enzyme replacement therapy (asfotase alfa) has been shown to improve respiratory insufficiency and skeletal complications in HPP patients, while its effects on dental status have been understudied to date. In this study, quantitative backscattered electron imaging (qBEI) and histological analysis were performed on teeth from two patients with infantile HPP before and during asfotase alfa treatment and compared to matched healthy control teeth. qBEI and histological methods revealed varying mineralization patterns in cementum and dentin with lower mineralization in HPP. Furthermore, a significantly higher repair cementum thickness was observed in HPP compared to control teeth. Comparison before and during treatment showed minor improvements in mineralization and histological parameters in the patient when normalized to matched control teeth. HPP induces heterogeneous effects on mineralization and morphology of the dental status. Short treatment with asfotase alfa slightly affects mineralization in cementum and dentin. Despite HPP being a rare disease, its mild form occurs at higher prevalence. This study is of high clinical relevance as it expands our knowledge of HPP and dental involvement. Furthermore, it contributes to the understanding of dental tissue treatment, which has hardly been studied so far.

Retrospective investigation of the 3D effects of the Carriere Motion 3D appliance using model and cephalometric superimposition.

OBJECTIVES: Carriere Motion 3D™ appliance (CMA) represents a method for molar distalization and correction of class II malocclusion. The aim was to investigate the 3D effects of the CMA by superimposing digital models and cephalometric X-rays. MATERIALS AND METHODS: We retrospectively examined 16 patients treated with CMA in combination with class II elastics. We compared digitized models and cephalometric X-rays of records taken before therapy and after the removal of CMA. The records were superimposed to assess the skeletal and dentoalveolar changes. The results of the cephalometric X-ray analysis were compared to an untreated age- and gender-matched sample. RESULTS: Class II occlusion was corrected after 11.85 ± 4.70 months by 3.45 ± 2.33 mm. The average distalization of the upper first molars was 0.96 ± 0.80 mm. The analysis of the cephalometric X-rays confirmed a distalization of the upper first molars with distal tipping and revealed a mesialization of the lower first molars of 1.91 ± 1.72 mm. Importantly, CMA resulted in a mild correction of the skeletal class II relationship (ANB: - 0.71 ± 0.77°; Wits: - 1.99 ± 1.74 mm) and a protrusion of the lower incisors (2.94 ± 2.52°). Compared to the untreated control group, there was significant distalization of the upper first molars and canines with mesialization and extrusion of the lower first molars. CONCLUSION AND CLINICAL RELEVANCE: CMA is an efficient method for treating class II malocclusions. However, the class II correction is only partially caused by a distalization of the upper molars.

Early enzyme replacement therapy prevents dental and craniofacial abnormalities in a mouse model of mucopolysaccharidosis type VI.

Mucopolysaccharidosis VI (MPS VI) is a hereditary lysosomal storage disease caused by the absence of the enzyme arylsulfatase B (ARSB). Craniofacial defects are common in MPS VI patients and manifest as abnormalities of the facial bones, teeth, and temporomandibular joints. Although enzyme replacement therapy (ERT) is the treatment of choice for MPS VI, the effects on the craniofacial and dental structures are still poorly understood. In this study, we used an Arsb-deficient mouse model (Arsb m/m ) that mimics MPS VI to investigate the effects of ERT on dental and craniofacial structures and compared these results with clinical and radiological observations from three MPS VI patients. Using micro-computed tomography, we found that the craniofacial phenotype of the Arsb m/m mice was characterized by bone exostoses at the insertion points of the masseter muscles and an overall increased volume of the jaw bone. An early start of ERT (at 4 weeks of age for 20 weeks) resulted in a moderate improvement of these jaw anomalies, while a late start of ERT (at 12 weeks of age for 12 weeks) showed no effect on the craniofacial skeleton. While teeth typically developed in Arsb m/m mice, we observed a pronounced loss of tooth-bearing alveolar bone. This alveolar bone loss, which has not been described before in MPS VI, was also observed in one of the MPS VI patients. Interestingly, only an early start of ERT led to a complete normalization of the alveolar bone in Arsb m/m mice. The temporomandibular joints in Arsb m/m mice were deformed and had a porous articular surface. Histological analysis revealed a loss of physiological cartilage layering, which was also reflected in an altered proteoglycan content in the cartilage of Arsb m/m mice. These abnormalities could only be partially corrected by an early start of ERT. In conclusion, our results show that an early start of ERT in Arsb m/m mice achieves the best therapeutic effects for tooth, bone, and temporomandibular joint development. As the MPS VI mouse model in this study resembles the clinical findings in MPS VI patients, our results suggest enzyme replacement therapy should be started as early as possible.

Mandibular condyle morphology among patients with mucopolysaccharidosis: An observational study of panoramic radiographs.

BACKGROUND: Mucopolysaccharidoses (MPS) are a group of rare metabolic diseases characterized by a wide spectrum of symptoms including progressive condylar resorption. AIM: The aim of this study was to quantify the severity of condylar involvement in MPS I individuals in comparison with a group of non-MPS individuals and to describe how condylar changes may vary among the different types of MPS. DESIGN: Fifty panoramic radiographs of MPS patients (13.4 ± 6.2 years) with MPS I (n = 14), MPS II (n = 2), MPS IV (n = 8) and MPS VI (n = 2) were compared with forty panoramic radiographs of non-MPS individuals. The severity of condylar resorption was evaluated using a qualitative score (grades 0-3) and using the ratio of condylar height to ramus height (CH: RH). RESULTS: All MPS I and VI individuals showed pronounced bilateral degenerative condylar resorption. In contrast, individuals with MPS II and IV exhibited heterogeneous findings. The quantification of condylar height to ramus height revealed that CH: RH was significantly decreased in MPS I as compared to that of non-MPS individuals (P < .001). In contrast, the CH: RH ratios of MPS II and IV showed great variability. CONCLUSION: Mucopolysaccharidoses subtypes differ with regard to the severity of condylar resorption.

Role of c-Fos in orthodontic tooth movement: an in vivo study using transgenic mice.

OBJECTIVES: The transcription factor c-Fos controls the differentiation of osteoclasts and is expressed in periodontal ligament cells after mechanical stimulation in vitro. However, it is unclear how c-Fos regulates orthodontic tooth movement (OTM) in vivo. The aim of this study was therefore to analyse OTM in transgenic mice with overexpression of c-Fos. MATERIALS AND METHODS: We employed c-Fos transgenic mice (c-Fos tg) and wild-type littermates (WT) in a model of OTM induced by Nitinol tension springs that were bonded between the left first maxillary molars and the upper incisors. The unstimulated contralateral side served as an internal control. Mice were analysed by contact radiography, micro-computed tomography, decalcified histology and histochemistry. RESULTS: Our analysis of the unstimulated side revealed that alveolar bone and root morphology were similar between c-Fos tg and control mice. However, we observed more osteoclasts in the alveolar bone of c-Fos tg mice as tartrate-resistant acid phosphatase (TRAP)-positive cells were increased by 40%. After 12 days of OTM, c-Fos tg mice exhibited 62% increased tooth movement as compared with WT mice. Despite the faster tooth movement, c-Fos tg and WT mice displayed the same amount of root resorption. Importantly, we did not observe orthodontically induced tissue necrosis (i.e. hyalinization) in c-Fos tg mice, while this was a common finding in WT mice. CONCLUSION: Overexpression of c-Fos accelerates tooth movement without causing more root resorption. CLINICAL RELEVANCE: Accelerated tooth movement must not result in more root resorption as higher tissue turnover may decrease the amount of mechanically induced tissue necrosis.

Accelerated tooth movement in Rsk2-deficient mice with impaired cementum formation.

Coffin-Lowry-Syndrome (CLS) is a X-linked mental retardation characterized by skeletal dysplasia and premature tooth loss. We and others have previously demonstrated that the ribosomal S6 kinase RSK2, mutated in CLS, is essential for bone and cementum formation; however, it remains to be established whether RSK2 plays also a role in mechanically induced bone remodeling during orthodontic tooth movement (OTM). We, therefore, performed OTM in wild-type (WT) mice and Rsk2-deficient mice using Nitinol tension springs that were fixed between the upper left molars and the incisors. The untreated contralateral molars served as internal controls. After 12 days of OTM, the jaws were removed and examined by micro-computed tomography (µCT), decalcified histology, and immunohistochemistry. Our analysis of the untreated teeth confirmed that the periodontal phenotype of Rsk2-deficient mice is characterized by alveolar bone loss and hypoplasia of root cementum. Quantification of OTM using µCT revealed that OTM was more than two-fold faster in Rsk2-deficient mice as compared to WT. We also observed that OTM caused alveolar bone loss and root resorptions in WT and Rsk2-deficient mice. However, quantification of these orthodontic side effects revealed no differences between WT and Rsk2-deficient mice. Taken together, Rsk2 loss-of-function accelerates OTM in mice without causing more side effects.

Obstructive sleep apnea and craniofacial appearance in MPS type I-Hurler children after hematopoietic stem cell transplantation.

OBJECTIVES: Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal storage disorder characterized by severe multi-systemic organ manifestations including obstructive sleep apnea syndrome (OSAS). Hematopoietic stem cell transplantation (HSCT) is the treatment of choice in severe MPS I (MPS IH, Hurler syndrome). However, the effect of HSCT on OSAS in MPS IH still remains unclear. The purpose of this study was to analyze respiratory patterns during sleep following HSCT in MPS IH children and to relate these findings to craniofacial abnormalities. METHODS: Overnight polysomnographies of nine MPS IH children (mean age: 8.2 years) previously treated with HSCT were retrospectively analyzed. Magnetic resonance images of the head were assessed with regard to soft and hard tissue abnormalities of the upper respiratory tract. RESULTS: The mean apnea hypopnea index (AHI) was 5.3 events/h (range, 0.3-12.2), and the majority of apnea/hypopneas were obstructive. Whereas two patients had severe OSAS (AHI > 10) and two moderate OSAS (5 > AHI < 10), five patients had no evidence of OSAS (AHI < 2.0). Donor cell chimerism was significantly lower in MPS IH patients with OSAS as compared to patients without OSAS (p < 0.001). The upper airway space and the maxilla were significantly smaller and the adenoids larger in MPS IH patients with OSAS as compared to those of non-OSAS patients. CONCLUSION: OSAS was only observed in MPS IH patients with graft failure or low donor cell chimerism. Conversely, successful HSCT seems to ameliorate adenoid hyperplasia and maxillary constriction in MPS IH patients and thereby minimizes the risk of OSAS at least at younger ages.

Surface Characteristics of Esthetic Nickel⁻Titanium and Beta-Titanium Orthodontic Archwires Produced by Plasma Electrolytic Oxidation (PEO)-Primary Results.

BACKGROUND/AIM: There is continuing interest in engineering esthetic labial archwires. The aim of this study was to coat nickel-titanium (NiTi) and beta-titanium (ß-Ti), also known as titanium molybdenum (TMA), archwires by plasma electrolytic oxidation (PEO) and to analyze the characteristics of the PEO-surfaces. MATERIALS AND METHODS: PEO-coatings were generated on 0.014-inch NiTi and 0.19 × 0.25-inch ß-Ti archwires. The surfaces were analyzed by scanning electron microscopy and stereomicroscopy. Cytocompatibility testing was performed with ceramized and untreated samples according to EN ISO 10993-5 in XTT-, BrdU- and LDH-assays. The direct cell impact was analyzed using LIVE-/DEAD-staining. In addition, the archwires were inserted in an orthodontic model and photographs were taken before and after insertion. RESULTS: The PEO coatings were 15 to 20 µm thick with a whitish appearance. The cytocompatibility analysis revealed good cytocompatibility results for both ceramized NiTi and ß-Ti archwires. In the direct cell tests, the ceramized samples showed improved compatibility as compared to those of uncoated samples. However, bending of the archwires resulted in loss of the PEO-surfaces. Nevertheless, it was possible to insert the ß-Ti PEO-coated archwire in an orthodontic model without loss of the PEO-ceramic. CONCLUSION: PEO is a promising technique for the generation of esthetic orthodontic archwires. Since the PEO-coating does not resist bending, its clinical use seems to be limited so far to orthodontic techniques using straight or pre-bent archwires.

[Reform efforts in dentistry - national and international approaches]. / Reformbemühungen in der Zahnmedizin ­ nationale und internationale Ansätze.

The Study of dentistry in Germany is in need of reform. The actual regulation on licensing dentists in Germany is from 1955, with the last changes made in 1993. Recently there have been different initiatives related to reform: a national catalogue of competency-based learning objectives in dental education (NKLZ), changes and stipulations in the respective rules relating to undergraduate curriculum in dental medicine, and an initiative of the Germany Ministry of Health to tackle and reorganize dental education in Germany.This article presents and reflects on these reform efforts in the context of actual teaching in Germany, Europe, and the United States.The reform process is an opportunity for dental education in German faculties of medicine. New dentistry programs are allowed at all faculties with model educational programs in medicine. Therefore, an example of actual reform efforts are presented based on the experiences of Hamburg. Research on dental educational programs revealed interesting approaches in dental education in other European faculties of medicine. Selected faculties were visited. These experiences led to the formulation of five main goals of reform: interdisciplinary study, problem- and symptom-based learning, early patient contact, science-based education, and communication training. The main goal is a dental education program designed along science-based, prevention-oriented, multidisciplinary, and individualized dental care that contributes to the life-long oral health of patients.

Inhibition of bone resorption by bisphosphonates interferes with orthodontically induced midpalatal suture expansion in mice.

OBJECTIVES: Craniofacial sutures are important growth sites for skull development and are sensitive to mechanical stress. In order to determine the role of bone resorption in stress-mediated sutural bone growth, midpalatal suture expansion was performed in mice receiving alendronate, an anti-resorptive bisphosphonate. MATERIALS AND METHODS: The midpalatal sutures of 8-week-old C57BL/6 mice were expanded by orthodontic wires over the period of 2 weeks. Mice with maxillary expansion without drug treatment as well as untreated animals served as controls. Skulls were analyzed with micro-computed tomography (micro-CT), immunohistochemistry and histology. RESULTS: Maxillary expansion in mice without drug treatment resulted in an increase of TRAP-positive osteoclasts. In contrast, no increase in osteoclasts was observed in expanded sutures of mice with bisphosphonate treatment. Double calcein labeling demonstrated rapid bone formation on the oral edges of the expanded sutures in mice without bisphosphonate treatment. Less bone formation was observed in bisphosphonate-treated mice after expansion. Histology revealed that the sutural architecture was reestablished in expanded sutures of mice without bisphosphonate treatment. In contrast, the sutural architecture was disorganized and the cartilage had an irregular form, following expansion in bisphosphonate-treated mice. Finally, micro-CT imaging demonstrated that the total amount of maxillary expansion was significantly lower in mice with bisphosphonate treatment as compared to those of mice without drug treatment. CONCLUSIONS: In conclusion, our results indicate that osteoclast-mediated bone resorption is needed for maxillary suture expansion and reorganization of sutural architecture. CLINICAL SIGNIFICANCE: Orthodontic palatal expansion can be complicated in patients with inherited or drug-induced diseases of osteoclast dysfunction.

Differences in maxillomandibular morphology among patients with mucopolysaccharidoses I, II, III, IV and VI: a retrospective MRI study.

OBJECTIVE: The aims of this study were to analyze the maxillomandibular morphology of patients with mucopolysaccharidosis (MPS) type I, II, III, IVa and VI and to evaluate the craniofacial effect of hematopoietic stem cell transplantation (HCST) in MPS I. MATERIALS AND METHODS: One hundred head magnetic resonance images were retrospectively analyzed from 41 MPS and 27 control individuals. The width, height and length of the maxilla and mandible were plotted against age and the means of controls, MPS I, MPS II and MPS III were statistically compared. To determine the effect of HSCT in MPS I, jaw morphology was compared between MPS I patients with full donor chimerism versus patients with mixed/no donor chimerism. RESULTS: Maxillary dimensions were not statistically different between the MPS types. The height and length of the mandible were clearly smaller in MPS I as compared to those in controls, MPS II and MPS III. This was associated with progressive resorption of the mandibular condyles in MPS I, which was also observed in MPS II and VI, but not in MPS III or IVa. Whereas the success of HCST did not affect these changes, mandibular width was significantly smaller in MPS I individuals with full donor chimerism. CONCLUSION: MPS I individuals have a smaller mandible as compared to control, MPS II and MPS III individuals due to progressive condylar degeneration. These abnormalities are also evident following successful HSCT. CLINICAL RELEVANCE: Clinicians should be aware of specific differences in mandibular morphology and condylar involvement among the MPS subtypes.

The role of the multidisciplinary health care team in the management of patients with Marfan syndrome.

Marfan syndrome (MFS) is a rare, severe, chronic, life-threatening disease with multiorgan involvement that requires optimal multidisciplinary care to normalize both prognosis and quality of life. In this article, each key team member of all the medical disciplines of a multidisciplinary health care team at the Hamburg Marfan center gives a personal account of his or her contribution in the management of patients with MFS. The authors show how, with the support of health care managers, key team members organize themselves in an organizational structure to create a common meaning, to maximize therapeutic success for patients with MFS. First, we show how the initiative and collaboration of patient representatives, scientists, and physicians resulted in the foundation of Marfan centers, initially in the US and later in Germany, and how and why such centers evolved over time. Then, we elucidate the three main structural elements; a team of coordinators, core disciplines, and auxiliary disciplines of health care. Moreover, we explain how a multidisciplinary health care team integrates into many other health care structures of a university medical center, including external quality assurance; quality management system; clinical risk management; center for rare diseases; aorta center; health care teams for pregnancy, for neonates, and for rehabilitation; and in structures for patient centeredness. We provide accounts of medical goals and standards for each core discipline, including pediatricians, pediatric cardiologists, cardiologists, human geneticists, heart surgeons, vascular surgeons, vascular interventionists, orthopedic surgeons, ophthalmologists, and nurses; and of auxiliary disciplines including forensic pathologists, radiologists, rhythmologists, pulmonologists, sleep specialists, orthodontists, dentists, neurologists, obstetric surgeons, psychiatrist/psychologist, and rehabilitation specialists. We conclude that a multidisciplinary health care team is a means to maximize therapeutic success.

Mannose 6-phosphate-dependent targeting of lysosomal enzymes is required for normal craniofacial and dental development.

Mucolipidosis II (MLII) is a severe systemic genetic disorder caused by defects in mannose 6-phosphate-dependent targeting of multiple lysosomal hydrolases and subsequent lysosomal accumulation of non-degraded material. MLII patients exhibit marked facial coarseness and gingival overgrowth soon after birth, accompanied with delayed tooth eruption and dental infections. To examine the pathomechanisms of early craniofacial and dental abnormalities, we analyzed mice with an MLII patient mutation that mimic the clinical and biochemical symptoms of MLII patients. The mouse data were compared with clinical and histological data of gingiva and teeth from MLII patients. Here, we report that progressive thickening and porosity of calvarial and mandibular bones, accompanied by elevated bone loss due to 2-fold higher number of osteoclasts cause the characteristic craniofacial phenotype in MLII. The analysis of postnatal tooth development by microcomputed tomography imaging and histology revealed normal dentin and enamel formation, and increased cementum thickness accompanied with accumulation of storage material in cementoblasts of MLII mice. Massive accumulation of storage material in subepithelial cells as well as disorganization of collagen fibrils led to gingival hypertrophy. Electron and immunofluorescence microscopy, together with (35)S-sulfate incorporation experiments revealed the accumulation of non-degraded material, non-esterified cholesterol and glycosaminoglycans in gingival fibroblasts, which was accompanied by missorting of various lysosomal proteins (α-fucosidase 1, cathepsin L and Z, Npc2, α-l-iduronidase). Our study shows that MLII mice closely mimic the craniofacial and dental phenotype of MLII patients and reveals the critical role of mannose 6-phosphate-dependent targeting of lysosomal proteins for alveolar bone, cementum and gingiva homeostasis.