Short-term evaluation of photobiomodulation therapy on the proliferation and undifferentiated status of dental pulp stem cells.

The aim of this in vitro study was to analyze the effect of photobiomodulation therapy (PBMT) on the proliferation and undifferentiating status of stem cell from human exfoliated deciduous teeth (SHEDs). PBMT was carried out with an aluminum gallium indium phosphide (InGaAlP) diode laser in contact and punctual mode (continuous wave, 660 nm, 20 mW, 0.028 cm2, and average energy densities of 1 (1 s), 3 (4 s), 5 (7 s), 10 (14 s), 15 (21 s), or 20 (28 s) J/cm2 per point). The immunoprofile of the SHEDs was analyzed using flow cytometry. Cell proliferation was assessed by the MTT reduction assay. Gene expressions of mesenchymal stem cell markers (OCT4, Nestin, CD90, and CD105) were assessed by RT-qPCR 48 h after PBMT. Data were compared by analysis of variance (ANOVA) and Tukey's test (p ≤ 0.05). Cells cultured under nutritional deficit and treated with PBMT at 5 J/cm2 presented similar cell growth than those of positive control group. Cell growth was significantly higher than those of other groups. Mesenchymal stem cell gene markers were still expressed after PBMT at 5 J/cm2. In a short-term analysis, PBMT increases the number of stem cells with no interference in the undifferentiated state of the irradiated cells, which opens wide possibilities for application in tissue regeneration.

Laser treatment contributes to maintain membrane integrity in stem cells from human exfoliated deciduous teeth (shed) under nutritional deficit.

This study aimed to analyze the effects of laser irradiation on the membrane integrity and viability of stem cells from human exfoliated deciduous teeth (SHED) that were kept in serum starvation. Nutritional deficit was used to mimic the cellular stress conditions of SHED isolation for regenerative dental approaches, where laser therapy could be beneficial. SHED were cultured under serum starvation (MEMα + 1%FBS) for 1 or 24 h pre-irradiation (protocols A and B, respectively). Then, cells received low-level laser therapy (LLLT; 660 nm) at 2.5 J/cm2 (0.10 W; groups I and V), 5.0 J/cm2 (0.20 W; groups II and VI), 7.5 J/cm2 (0.30 W; groups III and VII), or remained non-irradiated (groups IV and VIII). During irradiation, cells were maintained in 1% FBS (groups I-IV) or 10% FBS (normal culture conditions; groups V-VIII). Membrane integrity was evaluated by quantifying lactate dehydrogenase (LDH) release (immediately after irradiation), and cell viability was assessed by the MTT assay (24, 48, and 72 h post-irradiation). Serum starvation did not alter LDH release by non-irradiated SHED, while LDH release decreased significantly in groups irradiated in 1% FBS (I and III), but not in groups irradiated in 10% FBS (V-VII), regardless the pre-irradiation conditions (protocols A/B). Cell viability was significantly higher 24 h after irradiation, in most protocol A groups. In contrast, cell viability remained mostly unaltered in protocol B groups. LLLT contributed to maintain membrane integrity in SHED subjected to nutritional deficit before and during irradiation with 0.10 or 0.30 W. Short serum starvation before irradiation improved SHED viability at 24 h post-irradiation.

Intrastriatal transplantation of stem cells from human exfoliated deciduous teeth reduces motor defects in Parkinsonian rats.

BACKGROUND: This study explored the neural differentiation and therapeutic effects of stem cells from human exfoliated deciduous teeth (SHED) in a rat model of Parkinson's disease (PD). METHODS: The SHED were isolated from fresh dental pulp and were induced to differentiate to neurons and dopamine neurons by inhibiting similar mothers against dpp (SMAD) signaling with Noggin and increase conversion of dopamine neurons from SHED with CHIR99021, Sonic Hedgehog (SHH) and FGF8 in vitro. The neural-primed SHED were transplanted to the striatum of 6-hydroxydopamine (6-OHDA)-induced PD rats to evaluate their neural differentiation and functions in vivo. RESULTS: These SHED were efficiently differentiated to neurons (62.7%) and dopamine neurons (42.3%) through a newly developed method. After transplantation, the neural-induced SHED significantly improved recovery of the motor deficits of the PD rats. The grafted SHED were differentiated into neurons (61%), including dopamine neurons (22.3%), and integrated into the host rat brain by forming synaptic connections. Patch clamp analysis showed that neurons derived from grafted SHED have the same membrane potential profile as dopamine neurons, indicating these cells are dopamine neuron-like cells. The potential molecular mechanism of SHED transplantation in alleviating motor deficits of the rats is likely to be mediated by neuronal replacement and immune-modulation as we detected the transplanted dopamine neurons and released immune cytokines from SHED. CONCLUSION: Using neural-primed SHED to treat PD showed significant restorations of motor deficits in 6-OHDA-induced rats. These observations provide further evidence that SHED can be used for cell-based therapy of PD.

Low-level laser irradiation induces in vitro proliferation of stem cells from human exfoliated deciduous teeth.

The aim of this study was to evaluate the effect of low-level laser irradiation (LLLI) on the proliferation and viability of stem cells from human exfoliated deciduous teeth (SHED). Cells were irradiated or not (control) with an InGaAlP laser diode (660 nm, 30 mW, continuous action mode) using two different energy densities (0.5 J/cm2-16 s; 1.0 J/cm2-33 s). Irradiation was performed at 0 and 48 h, with the laser probe fixed at a distance of 0.5 cm from the cells. Cell proliferation was analyzed at 0, 24, 48, and 72 h by the Trypan blue exclusion method and MTT assay. Cell cycle and Ki67 expression were analyzed by flow cytometry. Apoptosis-related events were evaluated by expression of annexin V/PI and nuclear morphological changes by staining with DAPI. Differences between groups at each time were analyzed by the Kruskal-Wallis and Mann-Whitney tests, adopting a level of significance of 5% (p < 0.05). The results showed that an energy density of 1.0 J/cm2 promoted an increase in cell proliferation at 48 and 72 h compared to the control and 0.5 J/cm2 groups. Cell cycle analysis revealed a predominance of cells in the S and G2/M phases in the irradiated groups. This finding was confirmed by the increased expression of Ki67. Low positive staining for annexin V and PI was observed in all groups, and no nuclear changes were detected, indicating that cell viability was not affected by the energy densities tested. It can be concluded that the LLLI parameters used (660 nm, 30 mW, 1.0 J/cm2) promote the proliferation of SHEDs and the maintenance of cell viability.

Simple and Integrated Spintip-Based Technology Applied for Deep Proteome Profiling.

Great efforts have been taken for developing high-sensitive mass spectrometry (MS)-based proteomic technologies, among which sample preparation is one of the major focus. Here, a simple and integrated spintip-based proteomics technology (SISPROT) consisting of strong cation exchange beads and C18 disk in one pipet tip was developed. Both proteomics sample preparation steps, including protein preconcentration, reduction, alkylation, and digestion, and reversed phase (RP)-based desalting and high-pH RP-based peptide fractionation can be achieved in a fully integrated manner for the first time. This easy-to-use technology achieved high sensitivity with negligible sample loss. Proteomic analysis of 2000 HEK 293 cells readily identified 1270 proteins within 1.4 h of MS time, while 7826 proteins were identified when 100000 cells were processed and analyzed within only 22 h of MS time. More importantly, the SISPROT can be easily multiplexed on a standard centrifuge with good reproducibility (Pearson correlation coefficient > 0.98) for both single-shot analysis and deep proteome profiling with five-step high-pH RP fractionation. The SISPROT was exemplified by the triplicate analysis of 100000 stem cells from human exfoliated deciduous teeth (SHED). This led to the identification of 9078 proteins containing 3771 annotated membrane proteins, which was the largest proteome data set for dental stem cells reported to date. We expect that the SISPROT will be well suited for deep proteome profiling for fewer than 100000 cells and applied for translational studies where multiplexed technology with good label-free quantification precision is required.

Stem Cells from Human Exfoliated Deciduous Teeth: A Growing Literature.

Adult stem cells research has been considered the most advanced sort of medical-scientific research, particularly stem cells from human exfoliated deciduous teeth (SHED), which represent an immature stem cell population. The purpose of this review is to describe the current knowledge concerning SHED from full-text scientific publications from 2003 to 2015, available in English language and based on the keyword and/or abbreviations 'stem cells from human exfoliated deciduous teeth (SHED)', and individually presented as to the properties of SHED, immunomodulatory properties of SHED and stem cell banking. In summary, these cell populations are easily accessible by noninvasive procedures and can be isolated, cultured and expanded in vitro, successfully differentiated in vitro and in vivo into odontoblasts, osteoblasts, chondrocytes, adipocytes and neural cells, and present low immune reactions or rejection following SHED transplantation. Furthermore, SHED are able to remain undifferentiated and stable after long-term cryopreservation. In conclusion, the high proliferative capacity, easy access, multilineage differentiation capacity, noninvasiveness and few ethical concerns make stem cells from human exfoliated deciduous teeth the most valuable source of stem cells for tissue engineering and cell-based regenerative medicine therapies.

Zinc Up-Regulates Insulin Secretion from ß Cell-Like Cells Derived from Stem Cells from Human Exfoliated Deciduous Tooth (SHED).

Stem cells from human exfoliated deciduous tooth (SHED) offer several advantages over other stem cell sources. Using SHED, we examined the roles of zinc and the zinc uptake transporter ZIP8 (Zrt- and irt-like protein 8) while inducing SHED into insulin secreting ß cell-like stem cells (i.e., SHED-ß cells). We observed that ZIP8 expression increased as SHED differentiated into SHED-ß cells, and that zinc supplementation at day 10 increased the levels of most pancreatic ß cell markers-particularly Insulin and glucose transporter 2 (GLUT2). We confirmed that SHED-ß cells produce insulin successfully. In addition, we note that zinc supplementation significantly increases insulin secretion with a significant elevation of ZIP8 transporters in SHED-ß cells. We conclude that SHED can be converted into insulin-secreting ß cell-like cells as zinc concentration in the cytosol is elevated. Insulin production by SHED-ß cells can be regulated via modulation of zinc concentration in the media as ZIP8 expression in the SHED-ß cells increases.

Influence of contact points on the performance of caries detection methods in approximal surfaces of primary molars: an in vivo study.

This in vivo study aimed to evaluate the influence of contact points on the approximal caries detection in primary molars, by comparing the performance of the DIAGNOdent pen and visual-tactile examination after tooth separation to bitewing radiography (BW). A total of 112 children were examined and 33 children were selected. In three periods (a, b, and c), 209 approximal surfaces were examined: (a) examiner 1 performed visual-tactile examination using the Nyvad criteria (EX1); examiner 2 used DIAGNOdent pen (LF1) and took BW; (b) 1 week later, after tooth separation, examiner 1 performed the second visual-tactile examination (EX2) and examiner 2 used DIAGNOdent again (LF2); (c) after tooth exfoliation, surfaces were directly examined using DIAGNOdent (LF3). Teeth were examined by computed microtomography as a reference standard. Analyses were based on diagnostic thresholds: D1: D 0 = health, D 1 ­D 4 = disease; D2: D 0 , D 1 = health, D 2 ­D 4 = disease; D3: D 0 ­D 2 = health, D 3 , D 4 = disease. At D1, the highest sensitivity/specificity were observed for EX1 (1.00)/LF3 (0.68), respectively. At D2, the highest sensitivity/ specificity were observed for LF3 (0.69)/BW (1.00), respectively. At D3, the highest sensitivity/specificity were observed for LF3 (0.78)/EX1, EX2 and BW (1.00). EX1 showed higher accuracy values than LF1, and EX2 showed similar values to LF2. We concluded that the visual-tactile examination showed better results in detecting sound surfaces and approximal caries lesions without tooth separation. However, the effectiveness of approximal caries lesion detection of both methods was increased by the absence of contact points. Therefore, regardless of the method of detection, orthodontic separating elastics should be used as a complementary tool for the diagnosis of approximal noncavitated lesions in primary molars.

Age-dependent impaired neurogenic differentiation capacity of dental stem cell is associated with Wnt/ß-catenin signaling.

Two kinds of dental stem cells (DSCs), dental pulp stem cells (DPSCs) and stem cells from human-exfoliated deciduous teeth (SHED), have been identified as novel populations of mesenchymal stem cells that can be induced to differentiate into osteoblasts, chondrocytes, adipocytes, and neuron-like cells in vitro. As we know, both of them originate from the neural crest, but have distinct characteristics and functions in vitro and in vivo. The regeneration potential of DSCs declines with advanced age; however, the mechanism of the impaired potential in DSCs has not been fully explored. In this study, we investigated whether declined neurogenic differentiation capacity is associated with an altered expression of Wnt signaling-related proteins in vitro. We compared stem cells isolated from human dental pulp in two age groups: the exfoliated deciduous teeth (5-12 years), and the third permanent teeth (45-50 years). We found that the expression levels of neuron markers, such as ßIII-tubulin, microtubule-associated protein 2(MAP2), tyrosine hydroxylase (TH), and Nestin were lower in the DPSCs group compared with that in the SHED group; however, in supplementation with human recombinant Wnt1 in the medium, the DPSCs were prone to neural differentiation and expressed higher levels of neurogenic markers. In summary, our study demonstrated that Wnt/ß-catenin signaling may play a vital role in the age-dependent neural differentiation of DSCs. Therefore, DSCs may provide an ideal source of stem cells that can further extend their therapeutic application in nerve injury and neurodegenerative diseases.

Stem Cells from Human Exfoliated Deciduous Teeth Modulate Early Astrocyte Response after Spinal Cord Contusion.

The transplantation of stem cells from human exfoliated deciduous teeth (SHED) has been studied as a possible treatment strategy for spinal cord injuries (SCIs) due to its potential for promoting tissue protection and functional recovery. The aim of the present study was to investigate the effects of the early transplantation of SHED on glial scar formation and astrocytic reaction after an experimental model of SCI. Wistar rats were spinalized using the NYU Impactor. Animals were randomly distributed into three groups: control (naive) (animal with no manipulation); SCI (receiving laminectomy followed by SCI and treated with vehicle), and SHED (SCI rat treated with intraspinal SHED transplantation, 1 h after SCI). In vitro investigation demonstrated that SHED were able to express mesenchymal stem cells, vimentin and S100B markers, related with neural progenitor and glial cells, respectively. The acute SHED transplantation promoted functional recovery, measured as from the first week after spinal cord contusion by Basso, Beattie, and Bresnahan scale. Twenty-four and 48 h after lesion, flow cytometry revealed a spinal cord vimentin+ cells increment in the SHED group. The increase of vimentin+ cells was confirmed by immunofluorescence. Moreover, the bioavailability of astrocytic proteins such as S100B and Kir4.1 shown to be increased in the spinal cord of SHED group, whereas there was a glial scar reduction, as indicated by ELISA and Western blot techniques. The presented results support that SHED act as a neuroprotector agent after transplantation, probably through paracrine signaling to reduce glial scar formation, inducing tissue plasticity and functional recovery.

Partial expression of Papillon-Lefèvre Syndrome.

Papillon- Lefèvre Syndrome (PLS) is a rare autosomal recessive trait, which is transmitted with an estimated frequency of one to four per million individuals. It is characterized by palmar plantar keratosis and severe early-onset periodontitis affecting both deciduous and permanent dentition. In this report, we present clinical, microbiological and leukocyte function test findings of a thirty-five year-old patient with symptoms typical of Papillon-Lefèvre Syndrome except for premature loss of deciduous and permanent dentition. The patient exhibited palmar plantar keratosis and an isolated, moderately deep periodontal pocket in the third quadrant. No anaerobic bacteria were isolated from the plaque culture. The neutrophil function test revealed defective chemotaxis and phagocytosis while intracellular killing and respiratory burst were normal.

Basic fibroblast growth factor regulates phosphate/pyrophosphate regulatory genes in stem cells isolated from human exfoliated deciduous teeth.

BACKGROUND: Basic fibroblast growth factor (bFGF) regulates maintenance of stemness and modulation of osteo/odontogenic differentiation and mineralization in stem cells from human exfoliated deciduous teeth (SHEDs). Mineralization in the bones and teeth is in part controlled by pericellular levels of inorganic phosphate (Pi), a component of hydroxyapatite, and inorganic pyrophosphate (PPi), an inhibitor of mineralization. The progressive ankylosis protein (gene ANKH; protein ANKH) and ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1/ENPP1) increase PPi and inhibit mineralization, while tissue-nonspecific alkaline phosphatase (ALPL; TNAP) is a critical pro-mineralization enzyme that hydrolyzes PPi. We hypothesized that regulation by bFGF of mineralization in SHEDs occurs by modulation of Pi/PPi-associated genes. METHODS: Cells were isolated from human exfoliated deciduous teeth and characterized for mesenchymal stem cell characteristics. Cells were treated with bFGF, and the osteogenic differentiation ability was determined. The mRNA expression was evaluated using real-time polymerase chain reaction. The mineralization was examined using alizarin red S staining. RESULTS: Cells isolated from primary teeth expressed mesenchymal stem cell markers, CD44, CD90, and CD105, and were able to differentiate into osteo/odontogenic and adipogenic lineages. Addition of 10 ng/ml bFGF to SHEDs during in vitro osteo/odontogenic differentiation decreased ALPL mRNA expression and ALP enzyme activity, increased ANKH mRNA, and decreased both Pi/PPi ratio and mineral deposition. Effects of bFGF on ALPL and ANKH expression were detected within 24 h. Addition of 20 mM fibroblast growth factor receptor (FGFR) inhibitor SU5402 revealed the necessity of FGFR-mediated signaling, and inclusion of 1 µg/ml cyclohexamide (CHX) implicated the necessity of protein synthesis for effects on ALPL and ANKH. Addition of exogenous 10 µm PPi inhibited mineralization and increased ANKH, collagen type 1a1 (COL1A1), and osteopontin (SPP1) mRNA, while addition of exogenous Pi increased mineralization and osterix (OSX), ANKH, SPP1, and dentin matrix protein 1 (DMP1) mRNA. The effects of PPi and Pi on mineralization could be replicated by short-term 3- and 7-day treatments, suggesting signaling effects in addition to physicochemical regulation of mineral deposition. CONCLUSION: This study reveals for the first time the effects of bFGF on Pi/PPi regulators in SHEDs and implicates these factors in how bFGF directs osteo/odontogenic differentiation and mineralization by these cells.

Cellular Hypoxia Promotes Heterotopic Ossification by Amplifying BMP Signaling.

Hypoxia and inflammation are implicated in the episodic induction of heterotopic endochondral ossification (HEO); however, the molecular mechanisms are unknown. HIF-1α integrates the cellular response to both hypoxia and inflammation and is a prime candidate for regulating HEO. We investigated the role of hypoxia and HIF-1α in fibrodysplasia ossificans progressiva (FOP), the most catastrophic form of HEO in humans. We found that HIF-1α increases the intensity and duration of canonical bone morphogenetic protein (BMP) signaling through Rabaptin 5 (RABEP1)-mediated retention of Activin A receptor, type I (ACVR1), a BMP receptor, in the endosomal compartment of hypoxic connective tissue progenitor cells from patients with FOP. We further show that early inflammatory FOP lesions in humans and in a mouse model are markedly hypoxic, and inhibition of HIF-1α by genetic or pharmacologic means restores canonical BMP signaling to normoxic levels in human FOP cells and profoundly reduces HEO in a constitutively active Acvr1(Q207D/+) mouse model of FOP. Thus, an inflammation and cellular oxygen-sensing mechanism that modulates intracellular retention of a mutant BMP receptor determines, in part, its pathologic activity in FOP. Our study provides critical insight into a previously unrecognized role of HIF-1α in the hypoxic amplification of BMP signaling and in the episodic induction of HEO in FOP and further identifies HIF-1α as a therapeutic target for FOP and perhaps nongenetic forms of HEO. © 2016 American Society for Bone and Mineral Research.

Axonal Degeneration in Dental Pulp Precedes Human Primary Teeth Exfoliation.

The dental pulp in human primary teeth is densely innervated by a plethora of nerve endings at the coronal pulp-dentin interface. This study analyzed how the physiological root resorption (PRR) process affects dental pulp innervation before exfoliation of primary teeth. Forty-four primary canine teeth, classified into 3 defined PRR stages (early, middle, and advanced) were fixed and demineralized. Longitudinal cryosections of each tooth were stained for immunohistochemical and quantitative analysis of dental pulp nerve fibers and associated components with confocal and electron microscopy. During PRR, axonal degeneration was prominent and progressive in a Wallerian-like scheme, comprising nerve fiber bundles and nerve endings within the coronal and root pulp. Neurofilament fragmentation increased significantly during PRR progression and was accompanied by myelin degradation and a progressive loss of myelinated axons. Myelin sheath degradation involved activation of autophagic activity by Schwann cells to remove myelin debris. These cells expressed a sequence of responses comprising dedifferentiation, proliferative activity, GAP-43 overexpression, and Büngner band formation. During the advanced PRR stage, increased immune cell recruitment within the dental pulp and major histocompatibility complex (MHC) class II upregulation by Schwann cells characterized an inflammatory condition associated with the denervation process in preexfoliative primary teeth. The ensuing loss of dental pulp axons is likely to be responsible for the progressive reduction of sensory function of the dental pulp during preexfoliative stages.

Ultrastructure of transganglionic degeneration in brain stem trigeminal nuclei during normal primary tooth exfoliation and permanent tooth eruption in the cat.

Electron microscopy is used to study changes in the axons and terminals in the cat brain stem trigeminal nuclei, main sensory, and partes interpolaris and caudalis, during the process of natural tooth shedding. Areas previously showing light optical argyrophilic degeneration products and adjacent areas lacking this degeneration are included. Various types of alteration occur early during tooth loss, including increased presumed glycogen, increased cytoplasmic density, flocculence, lucency, and neurofilamentous hyperplasia. By the stage of maximum exfoliation, terminals and axons of marked density become prominent in areas showing argyrophilia, whereas nondense forms occur elsewhere. By late eruption ages, all forms of degenerated terminals and axons are rare, but phagocytes are heavily laden with similar forms of debris. The sequence of ultrastructural events is discussed in light of recent studies of transganglionic degeneration, their correlation with light microscopic findings, and the potential implications for central plasticity in this system.

A histological study of the exfoliation of human deciduous teeth.

For clarification of the histological details of the shedding of human deciduous teeth, exfoliated and extracted deciduous teeth were examined by light and electron microscopy. After the roots were completely resorbed, the dentogingival junction migrated along the inner resorbing surface and finally reached the pulpal surface of the crown. At the same time, the gingival epithelium also proliferated and migrated under the crown of the deciduous tooth in such a way that part of it lined the residue of the pulp and another part lined the surface overlying the erupting successional tooth. This phenomenon took place from various sides of the tooth surface. Therefore, just before exfoliation, the migrated gingival epithelium formed narrow necks of tissue, and the crown was only superficially attached to the gingiva by them. The final shedding of the tooth appeared to occur by a tearing of these narrow tissue regions. The results of the present study suggest that the dento-gingival junction as well as gingival epithelium play important roles in the process of exfoliation of human deciduous teeth.

An ultrastructural study of tooth resorption in the kitten.

Eleven kittens of various ages were used to obtain teeth in situ at differing stages of exfoliation. The teeth were processed by routine techniques for examination by light and transmission electron microscopy. The dental hard tissues were eroded by odontoclasts supported by numerous blood vessels, fibroblasts, and macrophages. No evidence of intracellular collagen was found within any of these cells, indicating that helper cells are not required to remove the collagenous component of dentin and cementum. The loss of periodontal ligament during shedding involved the removal of cells and extracellular material. Two forms of fibroblastic cell death were identified: One, apoptotic cell death, involved condensation, and its occurrence suggests that exfoliation of deciduous teeth is a programmed physiological event; the other occurred in cells containing many profiles of collagen and involved the selective disruption of the mitochondria and eventual dissolution of cytosol. This form of cell death has not been previously described and is significantly different from necrotic cell death, which was not observed during exfoliation. Some fibroblasts maintained a normal morphology. These various cellular responses suggest that phenotypically different populations of fibroblasts may exist in the periodontal ligament. Collagen removal was an extracellular occurrence which did not seem to involve increased phagocytotic activity by fibroblasts.

Early-onset periodontitis associated with Weary-Kindler syndrome: a case report.

Weary-Kindler syndrome is a rare and poorly understood genetic disorder that has manifestations of both epidermolysis bullosa and poikiloderma congenitale. There are approximately 70 cases documented in the past 40 years but no cases appear in the dental literature, although dental findings have been discussed superficially in dermatological and pediatric publications. This case reports on the periodontal findings and treatment for a 16-year-old female diagnosed with the syndrome. Early exfoliation of deciduous teeth, severe periodontal bone loss around many permanent teeth, and fragile bleeding gingiva were key features. Microbiological testing revealed an absence of Actinobacillus actinomycetemcomitans and low levels of other commonly accepted periodontal pathogens. Tests for inflammation, including AST and elastase, were positive prior to therapy and greatly decreased after mechanical root instrumentation. A beneficial effect of non-surgical periodontal therapy was observed in the short-term follow-up.

A long-term survey of tooth loss in 600 treated periodontal patients.

1. Six hundred patients in a private periodontal practice were reexamined an average of 22 years after their active treatment and the patterns of tooth loss were observed. 2. During the post-treatment period, 300 patients had lost no teeth from periodontal disease, 199 had lost one to three teeth, 76 had lost 4 to 9 teeth and 25 had lost 10 to 23 teeth. 3. Of 2,139 teeth that originally had been considered of questionable prognosis, 666 were lost. Of these, 394 were lost by one sixth of the patients and only 272 by the other five-sixths. 4. Of 1,464 teeth which originally had furcation involvements, 460 were lost, 240 of them by one-sixth of the patients who deteriorated most. 5. The mortality of teeth which were treated with periodontal surgery was compared with that of teeth which did not have surgery. Tooth retention seemed more closely related to the case type than the surgery performed. 6. In general, periodontal disease is bilaterally symmetrical and there is a predictable order of likelihood of tooth loss according to position in the arch.

A histological study of root-resected and root-transected rat incisors when eruption ceases, shortly before they are exfoliated from the socket.

Resection of the odontogenic region or root transection of normal (impeded) rat lower incisors showed that eruption ceased from 1 to 13 weeks when the base of the resected teeth (87.5%) or of the distal segment of the transected ones (86%) reached the alveolar-crest region. When the operated teeth reached the crestal region, the enamel-related periodontal tissues were absent and the periodontal ligament (PDL) was the only periodontal tissue that remained. The PDL of the crestal region may be considered as mature PDL, showing a length of approx. 5-6 6 mm at the mesial face of the tooth, 4-5 mm at lingual face and 1 mm at distal face; from these limits towards the apical end of the socket the PDL becomes gradually immature. The mature PDL seems not to have a role in the process of tooth eruption. Several factors can be suggested to explain the more frequent retention, at the crestal region of the socket, of impeded rather than unimpeded incisors submitted to the same procedures. The connective tissue that develops between the base of the tooth and the bone that fills the alveolus may have more time to organize itself in impeded than in unimpeded teeth, which erupt at a faster rate; this tissue could support and retain the impeded operated teeth longer than the unimpeded ones. The decrease in the mechanical properties of the PDL in the unimpeded condition may ease the traumatic effects and lead to exfoliation. Eruption might be stopped by the increase in occlusal forces, per unit area of root surface, as the root becomes shorter; this effect is likely to be greater in impeded than unimpeded teeth.