Age Related Senescence, Apoptosis, and Inflammation Profiles in Periodontal Ligament Cells from Canine Teeth.

OBJECTIVE: The periapical tissues, including periodontal ligament cells (PDLCs) play an important role in repairing the surrounding tissue of the teeth. A decrease in the regenerative potentiality of resident stem cells (PDLCs) has been suggested to be attributed to the decline of pulp regeneration. Therefore, examining the functional changes in periodontal tissue and cells that occur during the aging process is necessary. METHODS: The changes in the cementum extract (CE) and PDLCs isolated from young and aged dog teeth were evaluated. PDLCs growth rate, senescence markers, p16 and p21, and proinflammatory cytokines, IL-6, IL-1ß, and TNF-α, were analyzed by RT-PCR. Bax, an apoptosis marker, Bcl-2, a marker for cell survival, and IL-6 were examined by Western blot analyses to detect their variance expression in the CE. RESULTS: Our results demonstrated that aged PDLCs exhibit a low growth rate and an increased expression of p16; however, no change has been demonstrated in the expression of p21. The chronic inflammatory molecules, IL-6 and TNF-α, were significantly upregulated compared to young PDLCs. Western blot analyses showed decreased expression of Bcl-2 in the CE of the aged tooth (p < 0.001). CONCLUSION: Taken together, aging influences the functional changes of PDLCs and CE and increases senescence, chronic inflammation, and apoptosis markers. As a result, donor age is a key factor influencing the utilization of PDLCs for tooth regeneration.

In Vitro Assessment of Enamel Permeability in Primary Teeth with and without Early Childhood Caries Using Laser Scanning Confocal Microscope.

OBJECTIVE: To compare the permeability of the enamel of primary teeth from individuals free of Early Childhood Caries (ECC) with that from individuals affected with ECC by assessment of dye penetration using Laser Scanning Confocal Microscope (LSCM). STUDY DESIGN: Experimental in vitro study. Exfoliated primary maxillary anterior teeth (n = 44) were collected and divided into two groups (n=22 per group): samples with ECC (Group 1) and without ECC (Group 2). The samples were immersed in Rhodamine B dye solution for 1 day, cut longitudinally into 3 sections, observed using LSCM. Dye penetration depths in the incisal, middle, cervical thirds and on labial, lingual surfaces were recorded. Data were analyzed by the Mann-Whitney test (α = 5%, p < .005). RESULTS: The overall mean penetration depth for group 1 (100.6 µm ± 58.48 µm) was significantly higher than that of group 2 (31.55 µm ± 23.40 µm, p < .000). Mean penetration depth in the incisal, middle, and cervical thirds and on the labial and lingual surfaces of group 1 also presented significantly higher scores than in group 2 (p < .005). CONCLUSION: There was significantly more dye penetration in the ECC group than in the non-ECC group. This could be related to a higher level of enamel permeability in teeth affected with ECC.

Does Orthodontic Treatment Affect the Alveolar Bone Density?

Few studies involving human participants have been conducted to investigate the effect of orthodontic treatment on alveolar bone density around the teeth. Our previous study revealed that patients who received 6 months of active orthodontic treatment exhibited an ∼24% decrease in alveolar bone density around the teeth. However, after an extensive retention period following orthodontic treatment, whether the bone density around the teeth can recover to its original state from before the treatment remains unclear, thus warranting further investigation.The purpose of this study was to assess the bone density changes around the teeth before, during, and after orthodontic treatment.Dental cone-beam computed tomography (CBCT) was used to measure the changes in bone density around 6 teeth in the anterior maxilla (maxilla central incisors, lateral incisors, and canines) of 8 patients before and after orthodontic treatment. Each patient underwent 3 dental CBCT scans: before treatment (T0); at the end of 7 months of active orthodontic treatment (T1); after several months (20-22 months) of retention (T2). The Friedman test was applied to evaluate the changes in the alveolar bone density around the teeth according to the 3 dental CBCT scans.From T0 to T1, a significant reduction in bone density was observed around the teeth (23.36 ±â€Š10.33%); by contrast, a significant increase was observed from T1 to T2 (31.81 ±â€Š23.80%). From the perspective of the overall orthodontic treatment, comparing the T0 and T2 scans revealed that the bone density around the teeth was relatively constant (a reduction of only 0.75 ±â€Š19.85%). The results of the statistical test also confirmed that the difference in bone density between T0 and T2 was nonsignificant.During orthodontic tooth movement, the alveolar bone density around the teeth was reduced. However, after a period of bone recovery, the reduced bone density recovered to its previous state from before the orthodontic treatment. However, the bone density around ∼10% of the teeth in this region could not recover to 80% of its state from before the orthodontic treatment.

Isolation, Characterization, and Differentiation of Dental Pulp Stem Cells in Ferrets.

INTRODUCTION: The ferret canine tooth has been introduced as a suitable model for studying dental pulp regeneration. The aim of this study was to isolate and characterize ferret dental pulp stem cells (fDPSCs) and their differentiation potential. METHODS: Dental pulp stem cells were isolated from freshly extracted ferret canine teeth. The cells were examined for the expression of stem cell markers STRO-1, CD90, CD105, and CD146. The osteo/odontogenic and adipogenic differentiation potential of fDPSCs was evaluated. Osteogenic and odontogenic marker genes were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR) on days 1, 4, and 8 after osteo/odontogenic induction of fDPSCs including dentin sialophosphoprotein (DSPP), dentin matrix protein-1, osteopontin, and alkaline phosphatase. Human dental pulp cells were used as the control. The results were analyzed using 3-way analysis of variance. RESULTS: fDPSCs were positive for STRO1, CD90, and CD105 and negative for CD146 markers with immunohistochemistry. fDPSCs showed strong osteogenic and weak adipogenic potential. The overall expression of DSPP was not significantly different between fDPSCs and human dental pulp cells. The expression of DSPP in osteo/odontogenic media was significantly higher in fDPSCs on day 4 (P < .01). The overall expression of dentin matrix protein-1, osteopontin, and alkaline phosphatase was significantly higher in fDPSCs (P = .0005). CONCLUSIONS: fDPSCs were positive for several markers of dental pulp stem cells resembling human DPSCs and appeared to show a stronger potential to differentiate to osteoblastic rather than odontoblastic lineage.

Analysis of expression patterns of IGF-1, caspase-3 and HSP-70 in developing human tooth germs.

AIMS: To analyze expression patterns of IGF-1, caspase-3 and HSP-70 in human incisor and canine tooth germs during the late bud, cap and bell stages of odontogenesis. MATERIALS AND METHODS: Head areas or parts of jaw containing teeth from 10 human fetuses aged between 9th and 20th developmental weeks were immunohistochemically analyzed using IGF-1, active caspase-3 and HSP-70 markers. Semi-quantitative analysis of each marker's expression pattern was also performed. RESULTS: During the analyzed period, IGF-1 and HSP-70 were mostly expressed in enamel organ. As development progressed, expression of IGF-1 and HSP-70 became more confined to differentiating tissues in the future cusp tip area, as well as in highly proliferating cervical loops. Few apoptotic bodies highly positive to active caspase-3 were observed in enamel organ and dental papilla from the cap stage onward. However, both enamel epithelia moderately expressed active caspase-3 throughout the investigated period. CONCLUSIONS: Expression patterns of IGF-1, active caspase-3 and HSP-70 imply importance of these factors for early human tooth development. IGF-1 and HSP-70 have versatile functions in control of proliferation, differentiation and anti-apoptotic protection of epithelial parts of human enamel organ. Active caspase-3 is partially involved in formation and apoptotic removal of primary enamel knot, although present findings might reflect its ability to perform other non-death functions such as differentiation of hard dental tissues secreting cells and guidance of ingrowth of proliferating cervical loops.

The relationship of hydrogen peroxide exposure protocol to bleaching efficacy.

The purpose of this study was to compare two in-office bleaching methods with respect to tooth color change and level of hydrogen peroxide penetration into the pulp cavity and to evaluate relationships between penetration level and color change. Eighty extracted canines were exposed to two different bleaching regimens (conventional vs sealed bleaching technique). After exposure to 38% hydrogen peroxide gel for one hour, hydrogen peroxide amount was estimated spectrophotometrically. Color change was measured per Commission Internationale de l'Eclairage methodology. Linear regression was used to evaluate factors affecting color change, including bleaching technique. The conventional and sealed bleaching groups showed no difference for any color change parameters (ΔL, Δa, Δb, ΔE); however, there was significantly greater hydrogen peroxide penetration in the conventional bleaching group (p<0.05). Linear modeling of the change in lightness (ΔL) showed that the increase in lightness tended to be greater for teeth with lower initial L* values (r=-0.32, p<0.05). After adjustment for initial L*, there was no evidence that ΔL differed with hydrogen peroxide penetration levels (p>0.05) or bleaching technique (mean group difference in ΔL=0.36; p>0.05).

Permanent tooth mineralization in bonobos (Pan paniscus) and chimpanzees (P. troglodytes).

The timing of tooth mineralization in bonobos (Pan paniscus) is virtually uncharacterized. Analysis of these developmental features in bonobos and the possible differences with its sister species, the chimpanzee (P. troglodytes), is important to properly quantify the normal ranges of dental growth variation in closely related primate species. Understanding this variation among bonobo, chimpanzee and modern human dental development is necessary to better contextualize the life histories of extinct hominins. This study tests whether bonobos and chimpanzees are distinguished from each other by covariance among the relative timing and sequences of tooth crown initiation, mineralization, root extension, and completion. Using multivariate statistical analyses, we compared the relative timing of permanent tooth crypt formation, crown mineralization, and root extension between 34 P. paniscus and 80 P. troglodytes mandibles radiographed in lateral and occlusal views. Covariance among our 12 assigned dental scores failed to statistically distinguish between bonobos and chimpanzees. Rather than clustering by species, individuals clustered by age group (infant, younger or older juvenile, and adult). Dental scores covaried similarly between the incisors, as well as between both premolars. Conversely, covariance among dental scores distinguished the canine and each of the three molars not only from each other, but also from the rest of the anterior teeth. Our study showed no significant differences in the relative timing of permanent tooth crown and root formation between bonobos and chimpanzees.

[Gene clone and expression of Barx1 in different tooth of the mini-pig at embryonic day 40].

OBJECTIVE: To partially clone and compare the quantitative expression of tooth development-related gene Barx1 in different teeth of the mini-pig embryo at embryonic day 40, and to investigate the relationship between Barx1 spatial quantitative expression and tooth morphogenesis. METHODS: The mini-pig Barx1 genes was partially cloned and the mRNA sequences of human Barx1 genes was aligned with expressed sequence tags (EST) of pig by basic local alignment search tool (BLAST), which were assembled with DNAman v5.2.2. With designed primers, Barx1 was partially cloned in use of reverse transcription polymerase chain reaction (PCR), and tested by BLAST with all the species in NCBI database and confirmed as one part of target gene. Laser capture microdissection was used to collect tooth samples from frozen sections which were prepared before in -80°C freezer. Real-time PCR was carried out to analyze quantitative expression in different teeth. RESULTS: Partial mini-pig Barx1 gene of 698 bp was cloned. Real-time PCR showed that, glyceraldehyde-3-phosphate dehydrogenase used as loading control, the figures of 2(-ΔCT) of lower deciduous incisor, canine, the third premolar and molar were 0.000 249, 0.000 715, 0.026 096 and 0.112 656, respectively. There was a trend of increasing expression from anterior to posterior teeth. CONCLUSIONS: Barx1 gene could be related to the number or differentiation of tooth cusps.

Long-term changes of mercury levels in ringed seal (Phoca hispida) from Amundsen Gulf, and beluga (Delphinapterus leucas) from the Beaufort Sea, western Canadian Arctic.

Mercury (Hg) concentrations were determined in the canine teeth of ringed seals (Phoca hispida) harvested during the 13th-14th, late 19th and early 21st Centuries in Amundsen Gulf, Northwest Territories, Canada. Most historical and pre-industrial teeth contained undetectable Hg levels (i.e. <1.0 ng/g DW), whereas samples from 2001-03 contained up to 12 ng/g DW in an age-dependent pattern. Assuming a median [Hg] value in 13th-14th Century teeth of half the detection limit (i.e. 0.5 ng/g DW), geometric means of Hg in modern teeth were 9-17 times those of seals in the 14th Century, equivalent to an anthropogenic input of 89-94% of total Hg in modern seals. These results corroborate a previous study of beluga (Delphinapterus leucas) in the nearby Beaufort Sea. While the seals' trophic position (inferred from delta(15)N values) did not change over time, modern delta(13)C values were lower by about 2 per thousand than in the 14th and 19th Centuries. This could be due to increased dissolution of anthropogenically derived CO(2) in the ocean from the atmosphere, but could also indicate more offshore pelagic feeding by modern seals, which might be a factor in their Hg exposure. New tooth [Hg] data are also presented for the Beaufort Sea beluga, using recently-discovered museum samples collected in 1960/61, which showed that most of the anthropogenic contribution to beluga Hg had already taken effect by 1960 (reaching approximately 75% of total Hg). Taken together, the long-term seal and beluga data indicate that whereas Hg levels in the marine ecosystems of the western Canadian Arctic were probably unchanged from pre-industrial times up to the late 19th Century, there was a significant, many-fold increase in the early to mid-20th Century, but little or no change after about the early 1960s.

Prenatal growth acceleration in maxillary deciduous canines of children with Down syndrome: histological and chemical composition study.

Previous studies have reported that the abnormal development of the second deciduous molar in Down syndrome and cerebral palsy begins before birth. In view of these results we have turned our attention to the earlier stages of dental development in utero, represented by the primary canine, in order to see if we can identify more precisely the origin and timing of developmental insults in these conditions. The study was carried out on exfoliated or extracted maxillary primary canines of children with Down syndrome (DS) and cerebral palsy (CP) and they were compared to a control group of children with no adverse medical history. Thin sections were made through the mid-sagittal bucco-palatinal axis. Using a light microscope, the width of prenatal enamel and postnatal enamel, defined by the neonatal line was measured on each section at a standardized location. The chemical composition of the enamel was then measured at three different locations using an energy dispersive spectrophotometer (ESR) in a high vacuum mode. The total enamel width in DS and controls was similar and greater than that of CP canines. Significantly more enamel was laid down prenatally in DS teeth than in controls or CP and it was more highly mineralized. These results for DS canines differ from those previously published for the later developing second primary molars. They support the hypothesis of accelerated growth in the early stages of intra-uterine development, prior to the establishment of reduced growth trajectories in the later stages. The results for CP teeth showed that more prenatal enamel was laid down prenatally than in controls. Mineralization in CP was poor during the first two trimesters and improved significantly during the last trimester. While this approach is retrospective, we propose that it may aid in identifying the onset of developmental anomalies of unknown etiology that are expressed in later life.

Spatial distribution of lead in the roots of human primary teeth.

Lead remains one of the most hazardous metals in our environment. The concentrations of lead in coronal dentine and enamel have previously been reported but limited information is available regarding lead levels in radicular dentine and cementum. This study reports the distribution of lead in 26 roots of 16 human maxillary primary teeth from seven individuals. In addition, calcium and phosphorous concentrations were also measured to detect any variations in the degree of mineralization in different regions of the roots. The mean lead concentration in these roots was 1.67 +/- 1.43 microg/g, which is comparable to other studies. In all cases there were higher lead concentrations in the apices of non-resorbed roots of primary maxillary teeth relative to middle and cervical regions. The findings reported here are of potential significance during the process of physiological root resorption whence periapical tissue may be exposed to higher levels of lead.

Determination of lidocaine in dental pulp by high-performance liquid chromatography.

The purpose of this study was to develop a method for lidocaine detection in dental pulp by high-performance liquid chromatography. The amounts of lidocaine in dog pulps were quantitated after local injection to evaluate lidocaine recovery from pulp tissue with this technique. Comparison was also made between the amount of lidocaine found in upper and lower canines. The high-performance liquid chromatography system was shown to be a reliable and reproducible tool for lidocaine determination. Lidocaine extraction from the tissue showed recovery of 90%. The amount of lidocaine recovered from the upper canine (0.21 microg/mg) was higher than the lower canine (0.17 microg/mg).

Avaliaçäo da resistência adesiva à dentina de materiais à base de ácidos polialcenóicos e polímeros resinosos: efeito da variaçäo morfológica do substrato dentinário / Evaluation of the bond strength to dentin of polyalcenoic acids and resinous polymers: effect of the morphological variation of the dentin substrate

Dentre os inúmeros fatores que podem influenciar a qualidade adesiva de sistemas restauradores à dentina, destaca-se a variaçäo morfológica regional desse substrato. Embora o assunto seja alvo de constantes estudos com os sistemas adesivos resinosos, os materiais híbridos de cimento de ionômero de vidro e resina composta carecem de informaçäo específica a respeito. O presente estudo avaliou a influência das diferenças morfológicas da dentina na resistência de uniäo proporcionada por 2 cimentos de ionômero de vidro modificados por resinas Vitremer [VT], (3M) e Fuji II LC [FLC], (GC) e uma resina composta modificada por poliácidos Dyract [DY], (Dentsply). Caninos humanos extraídos receberam um desgaste, de aproximadamente 1,5 mm de espessura, realizado por pontas diamantadas na face vestibular, estendendo-se da borda incisal até próximo do ápice radicular. A superfície de dentina exposta foi dividida em quatro regiöes: radiculares apical, média e cervical, e regiäo coronária. Os sistemas restauradores foram aplicados de acordo com as recomendaçöes dos respectivos fabricantes sobre toda a extensäo da dentina, armazenados por 24 horas e secionados tranversalmente ao longo-eixo do dente em várias fatias de aproximadamente 1,0 mm de espessura cada. Os grupos de seçöes obtidos eram separados de acordo com a regiäo dentinária de origem e cada espécime recebia um desgaste bilateral na interface adesiva, reduzindo a área adesiva para aproximadamente 0,6 mm². Os espécimes, em número de 20 para cada regiäo dentinária, para cada material, foram fixados em um dispositivo Bencor Multi-T e a resistência adesiva testada em traçäo numa máquina de ensaios Kratos a uma velocidade de 0,5mm/min. Os valores médios de resistência adesiva (MPa) para o material DY foram nas distintas regiöes: radicular/apical 36,3ñ17,08, radicular/média 36,2ñ16,14, radicular/cervical 33,4ñ10,9 e coronária 33,6ñ7,41, radicular/média 15,9ñ5,10, radicular/cervical 19,8ñ9,66 e coronária 24,5ñ8,5. A análise de variância a dois critérios demonstrou haver diferenças estatisticamente significantes somente entre materiais (p<0,05). Os materiais mostraram-se insensíveis às variaçöes morfológicas do substrato dentinário (p>0,05). O DY apresentou valores médios de resistência adesiva superiores ao FLC e ao VT, em todas as regiöes dentinárias

Glucose retention on the surfaces of primary teeth in 3- and 4-yr-old children.

Glucose retention was determined in 38 kindergarten children ages 3-4 yr. The children rinsed their mouths with 10 ml of a 0.5 mol/l glucose solution for 15 s and then spat out. Three minutes after they put the solution in their mouths, a small paper-point was used to collect samples of saliva from the labial and buccal surfaces of the maxillary and mandibular primary teeth. The concentration of glucose in the small amount of saliva collected was measured with an immobilized enzyme system. Glucose retention was highest on the maxillary central primary incisor, second highest on the maxillary first primary molar and third highest on the maxillary lateral primary incisor. An intermediate value was seen on the maxillary and mandibular second primary molars, the mandibular first primary molar and the maxillary primary canine. A lower value was observed on the mandibular primary canine and the lowest on the mandibular incisors. It was concluded that there were site differences in glucose retention on primary teeth of 3- and 4-yr-old children.