Resinous perforation-repair materials inhibit the growth,attachment, and proliferation of human gingival fibroblasts

The choice of repair material is one of the important factors in the prognosis of the endodontically treated tooth with a perforation defect. The cytotoxicity of perforation-repair materials must be investigated to ensure a safe biological response. The aim of this in vitro study was to evaluate the effect of resin-modified, glass-ionomer cement, compomer, and resin on human-gingival fibroblasts. Human gingival fibroblasts from crown lengthening surgery were cultured by using an explant technique with the consent of the patient. Cytotoxicity was judged by using an assay of tetrazolium bromide reduction. The results showed that resin-modified, glass-ionomer cement Fuji II LC, compomer Compoglass, and resin SpectrumTPH (TPH) were cytotoxic to primary human gingival fibroblast cultures by inhibiting cell growth and proliferation. TPH alone had an effect on cell attachment. It was found that TPH was the most cytotoxic repair material among those tested in all cultures. The toxicity decreased in the order of TPH>FLC>CG.     

Characterization of treponemes isolated from human and non-human primate periodontal pockets

Treponemes were isolated from ligature induced periodontal pockets of non-human primates, and from humans with periodontitis. Approximately 39% of the microscopic count were spirochetes from humans, while 65% of the microscopic microbiota was accounted for by spirochetes from non-human primates. Metabolically, the human treponemal isolates grew on trypticase-yeast extract based media while the non-human primate isolates grew only on pectin, glucuronic or galacturonic acids. The end-products of glucose fermentation by the human treponemes were acetate and propionate, while acetate was produced by the non-human primate treponemes from pectin. All of the human isolates were indole positive, hemolyzed blood, required serum for growth, but did not require thiamine pyrophosphate (TPP). The non-human primate treponemes were indole negative, were inhibited in their growth by blood, grew in the absence of serum, and required TPP for growth. PAGE analysis of whole cell proteins revealed three categories of treponemal isolates: (i) human isolates similar to Treponema denticola ; (ii) human isolates of small size; and (iii) non-human primate isolates similar to the pectinolytic treponemes. Serologically, the human treponemal isolates were similar to T. denticola , while the non-human primate isolates were similar to the pectinolytic treponemes. Four human, 4 non-human primate, and 4 reference treponemes exhibited a Mol% G + C of their DNA of 40.0-43.1. The metabolic differences between the human and non-human primate treponemal isolates may be a reflection of ecological differences in the periodontium of the pathological entities which exist in human and non-human primates.     

Craniofacial pattern of Class III deciduous dentition.

The purpose of this study was to investigate the morphological characteristics of the cranio-dento-facial complex of children with deciduous dentition and Class III malocclusion. Forty Chinese children in Taiwan with normal occlusion and 40 with Class III malocclusion in deciduous dentition were selected for cephalometric analysis. Mandibular length was significantly greater and the mandible was situated farther forward in the Class III group. The maxilla was also slightly backward in this group, perhaps in association with the shorter maxillary length. The mandibular incisors were tipped lingually to compensate for the intermaxillary skeletal dysplasia and the maxillary incisors were tipped lingually by the retroinclined mandibular incisors.     

A retrospective analysis of peri-implant tissue responses at immediate load/provisionalized microthreaded implants

PURPOSE: The aim of this retrospective study was to examine the peri-implant tissue status at immediately provisionalized anterior maxillary implants 12 to 30 months following tooth replacement. MATERIALS AND METHODS: This is a retrospective study of 43 microthreaded, TiO2 grit-blasted implants placed in healed ridges and immediate extraction sockets to restore maxillary anterior and premolar teeth in 28 patients. The cortical bone position relative to the implant reference point was evaluated at implant placement and 6 to 30 months following restoration. Radiographs were assessed using 7x magnification. The distance from the reference point to the cortical bone was measured to +/- 0.1 mm. The relationship of the peri-implant mucosa to the incisal edge of the definitive prosthesis was recorded. RESULTS: Four implants in 3 individuals failed during the first 6 weeks following placement and provisional loading. Cortical bone adaptation from the time of implant placement up to 30 months following restoration ranged from 0.0 mm to 1.5 mm (average, 0.33 +/- 0.40 mm mesially and 0.28 +/- 0.37 mm distally). The mean radiographic measurements from the interproximal crestal bone to the contact point were 4.53 +/- -0.91 mm (mesial) and 4.06 +/- 0.98. Maintenance and growth of papilla was observed in this group of immediate provisionalized single-tooth implants. Definitive abutment or abutment screw loosening was not observed. DISCUSSION: The linear clinical and radiographic measures of peri-implant tissue responses suggest that proper implant placement is followed by supracrestal biological width formation along the abutment and preservation of toothlike tissue contours. This may influence buccal peri-implant tissue dimensions. CONCLUSIONS: Generalized maintenance of crestal bone and the increased soft tissue dimension with maintenance of peri-implant papilla were identified as expected outcomes for immediate loading/provisionalization of microthreaded, TiO2 grit-blasted implants. Control of peri-implant tissues can be achieved to provide predictable and esthetic treatment for anterior tooth replacement using dental implants.     

Control of apatite crystal growth by the co-operative effect of a recombinant porcine amelogenin and fluoride

Recently, we used native amelogenins extracted from developing pig enamel to examine the combined effect of fluoride and amelogenins on the growth of octacalcium phosphate (OCP) and apatite crystals. The purpose of the present study was to investigate this combined effect using a highly purified recombinant amelogenin. We applied porcine amelogenin (rP172) and fluoride in a dual-membrane system as a model for tooth enamel formation. The combination of rP172 and fluoride in this system resulted in the formation of rod-like apatite crystals. On the other hand, without fluoride, rod-like OCP crystals of a comparable size were formed, and rather large hexagonal prisms of mixed crystals of OCP and apatite grew without amelogenins. Thus, highly purified and homogeneous recombinant amelogenin, in co-operation with F, regulated the mineral phase, habit, and size of crystals in the same manner as the extracted heterogeneous porcine amelogenins. We suggest that in both cases the control over the crystal phase and morphology was a direct effect of amelogenin protein serving as a scaffold for apatite mineralization.     

Stresses at the dentinoenamel junction of human teeth--a finite element investigation.

A three-dimensional, linear, elastic finite element model of a maxillary first premolar from longitudinal ground sections was developed to investigate stress variation in the enamel and dentin adjacent to the dentinoenamel junction (DEJ). The effect of regional variation in the contour of the DEJ on the stress patterns for enamel and dentin was also analyzed. The normal (compressive or tensile) and shear stresses in the dentin and enamel surfaces of the DEJ were computed for a vertical load of 170 N acting on the entire occlusal surface of the model. The normal stresses in dentin and enamel were maximum on the occlusal surface of the model and diminished along the buccal and lingual surfaces of the DEJ. However, the magnitude of the normal stresses increased at the cervical enamel, which also showed increased values for shear stress distribution. The normal and shear stresses were markedly affected by the contour of the DEJ and the thickness of enamel in the occlusal third on the buccal and lingual surfaces. The results suggested that because the mechanical interlocking between enamel and dentin in the cervical region is weaker than in other regions of the DEJ, enamel in this region may be susceptible to belated cracking that could eventually contribute to the development of cervical caries.     

Microbiologic and immunologic characteristics of periodontal disease in Hispanic americans with type 2 diabetes

BACKGROUND: The microbiology of periodontitis in type 1 diabetes has been reported, but less is known about type 2 diabetes. Moreover, these data have not linked microbial colonization, host response, and clinical presentation in type 1 or type 2 diabetes. The objectives of this study were to relate periodontal status, periodontal microorganisms, and host-response characteristics in Hispanic Americans with type 2 diabetes. METHODS: Plaque and serum samples were obtained from 63 Hispanic American subjects with and without type 2 diabetes. The microbiology of subgingival plaque samples was evaluated using DNA checkerboard hybridization, and serum antibody to a battery of oral microorganisms was determined using an enzyme-linked immunosorbent assay. RESULTS: In general, similar pathogens were present in periodontitis sites from subjects with and without type 2 diabetes, although the periodontitis sites in diabetes showed a higher frequency of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans), and Campylobacter spp. Serum antibody to Campylobacter rectus was elevated in type 2 diabetes, whereas antibody to P. gingivalis and C. rectus were elevated in subjects with periodontitis, irrespective of diabetes status. Stratification of the population based upon antibody to P. gingivalis or C. rectus suggested a linkage between elevated antibody to P. gingivalis, increased frequency of diabetes, and significantly worse periodontitis. CONCLUSION: The increased severity of periodontal disease with type 2 diabetes may reflect an alteration of the pathogenic potential of periodontal bacteria and/or a modification of the characteristics of the host's inflammatory response that may contribute to a breakdown in the homeostasis of the periodontium.     

Root contact during insertion of miniscrews for orthodontic anchorage increases the failure rate: an animal study

OBJECTIVES: Miniscrews and miniplates are increasingly being used for absolute anchorage during orthodontic treatment. However, potential problems of damaging adjacent roots and their consequences during mini-implant placement in the alveolar process have not been clearly described. MATERIALS AND METHODS: Animal experiments were used to evaluate the stability of miniscrews placed with intentional root contact. The root repair was evaluated after screw removal. Seventy-two miniscrews were surgically placed in the mandibular alveolar bone of six adult mongrel dogs with metabolic bone labeling at 3-week intervals. Miniscrews of the experimental group were placed so that they contacted the root of the adjacent teeth, were retained for different time durations, and were then removed. The insertion torque, clinical measurements, removal torque, and histological findings were analyzed. RESULTS: (1) miniscrews contacting the roots showed a significantly higher insertion torque than those without contact; (2) there was a significant difference in the removal torque measurements based on the mobility of miniscrews and the state of root contact; and (3) miniscrews contacting the root were at greater risk of failure. CONCLUSIONS: During placement of miniscrews in the aveolar process, increased failure rates were noticed among those contacting adjacent roots. Failed miniscrews appeared to be surrounded with a greater volume of soft tissue. When more inflammation was present, the adjacent roots seemed to experience more resorption. Nevertheless, the created lesion was repaired with a narrow zone of mineralized tissue deposited on the root surface, which was likely cellular cementum, and was mainly filled with alveolar bone, with the periodontal ligament space being maintained.     

Wnt/beta-catenin inhibits dental pulp stem cell differentiation

Dental pulp stem cells (DPSCs) are a unique precursor population isolated from postnatal human dental pulp and have the ability to regenerate a reparative dentin-like complex. Canonical Wnt signaling plays a critical role in tooth development and stem cell self-renewal through beta-catenin. In this study, the regulation of odontoblast-like differentiation of DPSCs by canonical Wnt signaling was examined. DPSCs were stably transduced with canonical Wnt-1 or the active form of beta-catenin, with retrovirus-mediated infection. Northern blot analysis found that Wnt-1 strongly induced the expression of matricellular protein osteopontin, and modestly enhanced the expression of type I collagen in DPSCs. Unexpectedly, Wnt-1 inhibited alkaline phosphatase (ALP) activity and the formation of mineralized nodules in DPSCs. Moreover, over-expression of beta-catenin was also sufficient to suppress the differentiation and mineralization of DPSCs. In conclusion, our results suggest that canonical Wnt signaling negatively regulates the odontoblast-like differentiation of DPSCs.