Cell Homing for Pulp Tissue Engineering with Endogenous Dentin Matrix Proteins.

INTRODUCTION: Compelling evidence pinpoints that pulp tissue engineering after the transplantation of stem cells is possible. Although intriguing, severe problems regarding clinical feasibility remain. Cell homing has been proposed as a viable alternative in which dentin-derived growth factors in a conducive scaffold may attract resident cells to form pulplike tissue. In this study, an ectopic animal model for in situ dental pulp tissue engineering was developed to evaluate whether pulplike tissue formation in empty root canals after the attraction of stem cells was possible and whether this could be enhanced by dentin-derived growth factors. METHODS: Three types of fibrin (custom-made fibrin, fibrin sealant, and plasma rich in growth factors [PRGF]) as well as a self-assembling peptide were evaluated in vivo in a modified tooth root model using human teeth. Root canal dentin was conditioned with EDTA, tooth roots were filled with growth factor-laden scaffolds, and dental pulp stem cells in collagen were placed at the root tip. Constructs were implanted into immunocompromised mice for 4 weeks and subsequently analyzed histologically. Differential interference contrast and second harmonic generation imaging were performed for selected sections. RESULTS: For custom-made fibrin and fibrin sealant with dentin matrix proteins, migration into the roots and the formation of a pulplike tissue were observed, whereas the peptide-based scaffold appeared less suitable. PRGF supported tissue formation regardless of the addition of dentin matrix proteins. In the test groups with dentin matrix proteins and EDTA conditioning, differentiated odontoblastlike cells extended cellular processes into the dentinal tubules, which coincided with the deposition of the newly formed collagenous dentin matrix. CONCLUSIONS: This new cell homing model provides evidence that fibrin derivatives make applicable scaffolds and that dentin-derived proteins induce chemotaxis and pulplike tissue formation.

Continued root maturation despite persistent apical periodontitis of immature permanent teeth after failed regenerative endodontic therapy.

Three immature permanent teeth with pulp necrosis and apical periodontitis were treated with regenerative endodontic therapy (RET), which included root canal disinfection with sodium hypochlorite irrigation, intra-canal medication with calcium hydroxide paste, 17% EDTA rinse, induction of periapical bleeding into the canal, collagen matrix and MTA coronal seal, and composite resin restoration of access cavities. After different periods of follow-up, it was observed that continued root maturation, especially apical closure occurred despite persistent apical periodontitis of immature permanent teeth after failed RET. This finding is of interest as the secondary goal of further root maturation occurred despite failure of the primary goal of elimination of clinical symptom/sign and periapical inflammation. The possible biological mechanisms that could allow for further root maturation to occur in spite of persistent root canal infection of immature permanent teeth are discussed. Based on these observations, the biology of wound healing of immature permanent teeth after injury is not fully understood and should be further investigated. This case report demonstrates that whilst further root maturation is considered a successful outcome for teeth treated with RET, the primary objective must be the resolution of the signs and symptoms of apical periodontitis.

Effects of corticopuncture (CP) and low-level laser therapy (LLLT) on the rate of tooth movement and root resorption in rats using micro-CT evaluation.

The aim of this study was to compare the rate of tooth displacement, quantity of root resorption, and alveolar bone changes in five groups: corticopuncture (CP), low-level laser therapy (LLLT), CP combined with LLLT (CP + LLLT), control (C), and negative control (NC). A total of 60 half-maxilla from 30 male Wistar rats (10 weeks old) were divided randomly into five groups: three (CP, LLLT, and CP + LLLT) test groups with different stimulation for accelerated-tooth-movement (ATM), one control (C) group, and one negative control (NC) group with no tooth movement. Nickel-titanium coil springs with 50 g of force were tied from the upper left and right first molars to micro-implants placed behind the maxillary incisors. For the CP and CP + LLLT groups, two perforations in the palate and one mesially to the molars were performed. For the LLLT and CP + LLLT groups, GaAlAs diode laser was applied every other day for 14 days (810 nm, 100 mW, 15 s). The tooth displacements were measured directly from the rat's mouth and indirectly from microcomputer (micro-CT) tomographic images. Bone responses at the tension and compression sites and root resorption were analyzed from micro-CT images. The resulting alveolar bone responses were evaluated by measuring bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular thickness (TbTh). Root resorption crater volumes were measured on both compression and tension sides of mesial and distal buccal roots. The tooth displacement in the CP + LLLT group was the greatest when measured clinically, followed by the CP, LLLT, and control groups (C and NC), respectively (p <0.05). The tooth movements measured from micro-CT images showed statistically higher displacement in the CP and CP + LLLT groups compared to the LLLT and control groups. The BMD, BV/TV, and TbTh values were lower at the compression side and higher at the tension side for all three test groups compared to the control group. The root resorption crater volume of the distal buccal root was higher in the control group, followed by CP, LLLT, and CP + LLLT, mostly at the compression site. Combining corticopuncture and low-level laser therapy (CP + LLLT) produced more tooth displacement and less root resorption at the compression side. The combined technique also promoted higher alveolar bone formation at the tension side.

Regenerative potential of immature permanent non-vital teeth following different dentin surface treatments.

This study evaluates the regenerative potential of immature permanent non-vital teeth following different dentin surface treatments in dogs. Periapical lesions and necrotic pulps were induced in 288 roots of 144 teeth in twelve dogs. Teeth were randomly divided into 3 equal groups according to the evaluation period. Each group was subdivided into 8 subgroups according to the treatment modalities including; blood clot, blood clot and collagen, blood clot and Ethylenediaminetetraacetic acid (EDTA), blood clot, collagen and EDTA, blood clot and Mixture Tetracycline Citric Acid and Detergent (MTAD), blood clot, collagen and MTAD, positive control and negative control. Apart from control subgroups, all infected root canals were cleaned with sodium hypochlorite solution and triple antibiotics paste before different treatment protocols. After different treatments, the root length, thickness and apical diameter were evaluated by radiographic examination. Histopathological examination was carried out to evaluate the inflammation, bone/root resorption, tissue in-growth in pulp space, new hard tissue formation and apical closure. Using EDTA solution as a surface modifier showed significantly higher levels of tissue in-growth in the pulp space after 6 weeks and 3 months. Addition of collagen as a scaffold caused significantly more bone/root resorption than the other subgroups while EDTA caused significantly lower inflammatory cell counts only after 2 weeks. Final rinse with 17% EDTA solution before blood clot induction has positive impact on tissue interaction along dentinal walls without modification of the cell type. Moreover, the use of collagen as a scaffold material and MTAD as a surface modifier did not improve the quality of the regenerative process.

The effects of ageing on the biomechanical properties of root dentine and fracture.

OBJECTIVES: Knowledge of the mechanical behaviour of root dentine can facilitate better understanding of spontaneous vertical root fracture (VRF), an age-related disease initiated mainly at the root apex. We tested the hypothesis that the biomechanical properties of root dentine change with ageing. METHODS: Sixteen human premolars were divided into "old" (17-30 years) and "young" (50-80 years) groups. The elastic modulus, nano-hardness, micro-hardness, elemental contents, tubular density/area of root dentine in cervical, middle and apical root regions were evaluated using atomic force microscopy-based nano-indentation, Knoop indentation, scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. RESULTS: The apical dentine showed a lower nano-hardness, a lower elastic modulus, a lower calcium content, a lower calcium-to-phosphorus ratio and a smaller tubular density/area than the cervical dentine in both age groups, whereas spatial differences in micro-hardness were observed only in old roots. Compared with young dentine, old dentine showed a greater hardness, a higher elastic modulus, a greater mineral content and a smaller tubular size in the cervical portion, whereas the age-induced changes in tubular density were insignificant. Finite element analysis revealed that due to its higher elastic modulus, old apical dentine has a higher stress level than young dentine. CONCLUSIONS: The intrinsic material properties of root dentine have spatial variations, and they are altered by ageing. The higher stress level in old apical dentine may be one reason, if not the most important one, why spontaneous VRFs are more likely to occur in the elderly population.

A comparative study of temperature elevation on human teeth root surfaces during Nd:YAG laser irradiation in root canals.

The purpose of this study was to evaluate the temperatures on the root surfaces during Nd:YAG laser irradiation in root canals using pulse durations of 180 and 320 µs. Thirty extracted human teeth were used in this study. The teeth were enlarged up to ISO 40 (multi-rooted) or up to ISO 60 (single-rooted) by conventional technique using K-files. Then the teeth were placed into a water bath with a constant temperature of 37 °C and then irradiated with an Nd:YAG laser having an output power of 1.5 W, a frequency of 15 Hz, using an optic fiber of 200 µm diameter. The temperature on the root surface was measured by means of attaching thermocouples in three areas (coronal, mesial, and apical regions) of the root canals. The thermographic study showed that the average temperature elevation for both pulse durations on the root surfaces was less than 9 °C. There was no significant difference in the observed temperatures in coronal and mesial areas. Though a higher increase of temperature was observed in the apical region when the pulse length of the Nd:YAG laser was 320 µs. The results of the study showed that the temperature rises during Nd:YAG laser irradiation with parameters used in this study minimal to cause damage on bone and periodontal tissues. Moreover, it was suggested that in order to have lower temperature in the apical region, an Nd:YAG laser with a pulse length of 180 µs is preferred than one with a pulse length of 320 µs.

Regenerative endodontic treatment (revascularization) for necrotic immature permanent molars: a review and report of two cases with a new biomaterial.

INTRODUCTION: Revascularization is a valuable treatment in immature necrotic teeth that allows the continuation of root development. In this article we describe successful revascularization treatment of 2 necrotic immature first mandibular molars. METHODS: The clinical and radiographic examinations showed extensive coronal caries, immature roots, and periapical radiolucencies in mandibular first molars of a 9-year-old boy and an 8-year-old girl. The exam findings suggested revascularization treatment in both cases, which was started with irrigation of the canals by using NaOCl 5.25% for 20 minutes, followed by 3 weeks of triple antibiotic (metronidazole, ciprofloxacin, and minocycline) paste dressing. Next, the antibiotic paste was removed, bleeding was induced in the canals, and calcium enriched mixture (CEM) cement was placed over blood clots. RESULTS: In radiographic and clinical follow-ups both cases were asymptomatic and functional, periapical radiolucencies were healed, and roots continued to develop. CONCLUSIONS: Revascularization is a realistic treatment in immature necrotic molars. In addition, placing CEM cement as a new endodontic biomaterial over the blood clot formed inside the canals provided good seal and favorable outcomes.

Cleaning of the root canal using Nd:YAP laser and its effect on the mineral content of the dentin.

OBJECTIVE: To compare the efficacy of root canal cleanliness with and without Nd:YAP laser and to assess the effect of the laser on the mineral content of the dentin. BACKGROUND DATA: A high degree of cleanliness of the canal when using Nd:YAG laser has been shown while the laser had been in contact with the canal wall. A new Nd:YAP laser has been studied recently, which is considered to be superior to Nd:YAG with regard to antibactericidal ability due to its 1.34-mu wavelength, which is in the infra red range. This wavelength is absorbed better in water that of Nd:YAG. MATERIALS AND METHODS: Fourteen extracted single rooted premplars were divided into two groups. In group 1, canals were cleaned, instrumented and shaped with K files. In group 2, initial preparation was done using K files and completed with a Nd:YAP laser. Teeth were then split longitudinally and submitted to SEM. RESULTS: The cleanliness of the laser treated teeth was significantly greater than teeth treated with K files alone (p<0.05). No difference in Ca and P content was detected when the use of K files was compared to the use of laser. CONCLUSIONS: It appears that Nd:YAP laser improves the cleanliness of the root canal. However, since Nd:YAP laser serves as an addition to K files, its clinical value for replacing conventional root canal instrumentation remains to be determined.

Cleaning of the root canal using Nd:YAP laser and its effect on the mineral content of the dentin.

OBJECTIVE: The aim of this study was to compare the efficacy of root canal cleanliness with and without Nd:YAP laser and to assess the effect of the laser on the mineral content of the dentin. BACKGROUND DATA: A high degree of cleanliness of the canal when using the Nd:YAG laser has been shown while the laser is in contact with the canal wall. A new Nd:YAP laser has been studied recently, which is considered to be superior to the Nd:YAG with regard to antibactericidal ability due to its 1.34 micro m wavelength, which is in the infra-red range. This wavelength is absorbed better in water than that of Nd:YAG. MATERIALS AND METHODS: Fourteen extracted single rooted premplars were divided into two groups. In group 1, canals were cleaned, instrumented, and shaped with K files. In group 2, initial preparation was done using K files and completed with a Nd:YAP laser. Teeth were then split longitudinally and submitted to scanning electron microscopy. RESULTS: The cleanliness of the laser-treated teeth was significantly greater than teeth treated with K files alone (p < 0.05). No difference in Ca and P content was detected when the use of K files was compared to the use of laser. CONCLUSION: It appears that the Nd:YAP laser improves the cleanliness of the root canal. However, since the Nd:YAP laser serves as an addition to K files, its clinical value for replacing conventional root canal instrumentation remains to be determined.

[Clinical studies on the use of hyperbaric oxygen in replantation of young permanent teeth].

OBJECTIVE: To investigate the treatment effects of hyperbaric oxygen(HBO) in replantation of young permanent teeth. METHODS: A total of 138 luxation injuries to young permanent teeth undergoing treatment. The teeth were replanted and then divided into 2 groups. The HBO group was exposed to 0.25 MPa pure oxygen 40 x 2 minutes each day for 10 days continuously while the control group were compared. RESULTS: The total effective rates of the HBO group and the control group were 97.26% and 70.77% respectively, and showed significant difference (P < 0.05); respective frequencies of missing tooth after 1 year were 1.37% and 18.46%, and provided a statistical significance (P < 0.001). CONCLUSION: HBO used in replantation of luxated young permanent teeth could promote the recovery of periodontal membrane, pulp, and prevent resorption of root.

Strength of roots before and after endodontic treatment and restoration.

The resistance to fracture of mandibular premolar roots before and after endodontic and restorative procedures was tested. Seven treatment groups were evaluated. A Universal testing machine was used to apply vertical and lateral (45-degree) forces. Overall, the untreated roots showed the highest resistance to fracture. Factors of importance to prevent fracture were found to be (a) the amount of remaining tooth structure; (b) strength of post and core; and (c) bonding between core material and dentin. These factors suggest that a composite core following the use of EDTA to remove the smear layer may be a successful treatment when sufficient tooth structure remains.