Faculty Bibliography

The periodontal ligament has the potential to regenerate a complete periodontal connective tissue attachment, starting with the deposition of cementum, on pathologically exposed root surfaces as well as several materials including titanium oxide. However, most commonly used dental materials result in a fibrous encapsulation or a chronic inflammatory response after periodontal wound healing rather than the formation of a periodontal connective tissue attachment. Recently, an extract of porcine enamel matrix (Emdogain(R), EMD) has been reported inductive of cementum formation in both in vivo and in vitro studies. The aim of this study was to determine the effect of EMD, when applied to materials previously reported not supportive of periodontal connective tissue formation, on the periodontal connective tissue-material interface obtained with these materials in vivo. Bilateral osteotomies were performed on the mandible of a Yucatan minipig exposing the buccal root surface of four premolars. A series of four preparations were placed in each root surface that were subsequently filled with calcium hydroxide, gutta percha, mineral trioxide aggregate (MTA), or left unfilled. One side, in addition, received an application of EMD prior to surgical closure. A bioabsorbable surgical barrier membrane was placed over the osteotomy sites to exclude gingival connective tissue from the wound-healing environment. The mucoperiosteal flaps were then readapted and sutured in position. The animal was euthanized 10 weeks after the procedure, block sections obtained and prepared for light microscopy. Results demonstrated complete regeneration of alveolar bone and periodontal ligament in all four teeth from the EMD-treated side. Fibers from the periodontal ligament were observed to insert into a mineralized matrix consistent with cementum on all four root preparations. In contrast, massive root resorption without regeneration of alveolar bone was found on all teeth from the side not treated with EMD. The results of this pilot study suggest that the application of EMD to material surfaces that normally do not support periodontal connective tissue attachment formation can alter the type of periodontal connective tissue interface obtained with these materials.

Cells within the periodontal ligament have the potential to regenerate a periodontal connective tissue attachment on pathologically exposed root surfaces as well as on several material surfaces including titanium. However, rather than a periodontal connective tissue attachment, a fibrous encapsulation or chronic inflammatory response has been reported at the material connective tissue interface for most dental materials. Cementum is the first tissue of the periodontal connective tissue attachment to develop and the secretion of enamel matrix related proteins on the newly mineralized dentin surface precedes and is thought to induce cementum formation. Enamel matrix-related proteins may also function in the adult because the application of an acid extract of porcine enamel protein matrix (Emdogain(R), EMD) on pathologically exposed root surfaces has been shown to result in cementum regeneration. Therefore, the objective of the present study was to determine whether the application of EMD to materials that do not normally support cementogenesis in vivo would alter the in vitro phenotype of periodontal ligament (PDL) cells including the synthesis of cementum-associated extracellular matrix proteins. Primary PDL cells were established from 21-day-old Sprague-Dawley rats, and were cultured on four materials commonly encountered in dental practice (gutta percha, calcium hydroxide, amalgam, and super EBA cement) with and without the application of EMD. After 7 or 14 days of culture, total-DNA content, collagen synthesis, alkaline phosphatase activity, and the synthesis of a 42-kDa cementum-associated extracellular matrix protein were determined. PDL cells cultured on all materials had decreased total DNA content. The application of EMD further decreased total DNA content. PDL cells cultured on gutta percha and calcium hydroxide with the application of EMD had similar levels of collagen synthesis and alkaline phosphatase activity but also expressed a 42-kDa cementum extracellular matrix-associated protein when compared to the other groups. These results suggest that EMD can alter the phenotype of PDL cells when cultured on these dental materials.

Endodontic (root canal) therapy is required when the pulp of a tooth becomes necrotic due to a bacterial infection or trauma. A proportion of patients who receive endodontic therapy subsequently have periapical (around the tooth root) lesions detected by radiolucency. Currently, there are no means to identify susceptible patients. Although tissue from periapical lesions has been described as inflammatory, inflammatory cell types and their functions have been poorly characterized. For example, T lymphocytes were identified using pan specific anti-CD3 mAb, which recognizes both alphabeta and gammadeltaT cells. Using the current model of gammadeltaT cells as immunoregulatory cells; gammadeltaT cells can mediate protective or destructive milieus. We postulated that patients who have a periapical lesion, as identified by radiographic bone loss, mount a gammadeltaT cell response. We collected specimens removed by surgery from both periapical lesions and other oral tissues, generated total RNA and performed reverse-transcriptase polymerase chain reaction to identify rearranged delta genes. Results were confirmed with semi-nested polymerase chain reaction. In addition, we demonstrate that these lesions contain a population of CD3+ cells that are alphabetaT cell receptor negative, implying that these cells are gammadeltaT cells. Here we show that 36/37 of periapical lesions and only 2/11 of other lesions contain gammadeltaT cells (P<0.0001). Vdelta2+ T cells were the most common subtype identified (30/36) in these samples. This is the first report in the literature of the presence of gammadeltaT cells in human periapical lesions

Catecholamines may play an important role in the control of intrapulpal pressure as mediators of vasoconstriction. A baseline level of catecholamines (dopamine, epinephrine, and norepinephrine) in the uninflamed human dental pulp was previously reported using high-performance liquid chromatography. The purpose of this study was to compare the level of catecholamines present in the inflamed human dental pulp with the baseline level established in virgin teeth. Twelve uninflamed pulps were analyzed as a control and to validate previous findings. Pulp tissue was obtained from 10 vital and inflamed teeth requiring endodontic treatment. Selective criteria for each patient included: absence of systemic disease, medications, and allergies; a vital response to ice, heat, and electric pulp tests; and periodontal probing < or = 3 mm. A prior history of pain associated with the tooth was an additional criterion for inflamed pulps. To avoid the presence of an exogenous catecholamine, local anesthesia without epinephrine was administered. Dopamine, epinephrine, and norepinephrine were chemically extracted and analyzed by high-performance liquid chromatography with ultraviolet detection. Catecholamine levels found to be present in the pulp during inflammation were greater than the baseline level established in uninflamed pulp tissue

While a gutta-percha system is most commonly used by practitioners for canal obturation, there is no agreement on how best to close the chamber of an endodontically treated tooth. Some materials used in restorative dentistry may have endodontic applications. Restorative materials of particular interest to endodontists are those used as subgingival restorations. Their properties include insolubility in oral fluids, adhesiveness, dual-cure capabilities, radiopacity, hardness and fluoride release, low cure shrinkage and a low coefficient of thermal expansion. The purpose of this in vitro study was to test three products that could be used to seal pulp chambers of endodontically treated teeth to prevent bacterial infiltration. A bacteriological assay system was used to determine the efficacy of three commercially available restorative materials to prevent penetration of Streptococcus salivarius from the pulp chambers into the prepared canals. The materials evaluated were: Geristore two-paste system with Tenure Quik with fluoride, Dispersalloy with Tenure Quik with fluoride, and Marathon posterior composite with Tenure Quik with fluoride. During the sixty days of the study, the analysis indicated that the Geristore two-paste system with Tenure Quik with fluoride provided a statistically significant improved seal when compared to the Marathon posterior composite and Dispersalloy amalgam with Tenure Quik with fluoride

One hundred seventeen patients with posterior teeth requiring endodontic treatment were studied. Specific clinical findings were recorded, including pulp, vitality, preoperative pain, sensitivity to percussion, and the presence of a periradicular radiolucency. Excluded from the study were teeth with restorations to be maintained, greater than class I mobility, pocket depths > 5 mm, endodontic retreatments, and patients taking pain altering medications. Teeth were randomly assigned to 1 of 3 groups: (i) total occlusal reduction, (ii) simulated occlusal reduction (nonfunctional cusp reduction), or (iii) control (occlusion untouched). After canal instrumentation, a questionnaire was used by patients to record pain responses over a 48-h post-operative period. Responses were tabulated using a chi(2) test (p = < 0.05), and a statistically valid profile of patients most likely to benefit from occlusal reduction was developed. Occlusal reduction should prevent postoperative pain in those patients whose teeth initially exhibit pulp vitality, percussion sensitivity, preoperative pain, and/or the absence of a periradicular radiolucency.

Recent studies have demonstrated that periodontal ligament-derived (PDL) cells have the potential to regenerate a complete periodontal connective tissue attachment apparatus on both root and artificial substrates. To study the characteristics of endodontic materials conducive to periodontal regeneration, we have established an experimental model using PDL cell cultures that express a 42 kDa protein (CP42) associated with cementum extracellular matrix. In this report, the effect of gutta percha, dental amalgam, composite and calcium hydroxide on PDL cell proliferation, collagen and noncollagen protein synthesis, alkaline phosphatase activity, and CP42 expression are presented. While all substrates supported PDL cell attachment and proliferation, highest levels of alkaline phosphatase activity, collagen and noncollagen protein synthesis were observed in control cultures. Lowest levels of the above parameters were observed with gutta percha while amalgam, composite and calcium hydroxide had intermediate levels. Only control PDL cultures demonstrated CP42 expression. These data suggest that culture substrate can markedly influence periodontal extracellular matrix gene expression in vitro and provide an experimental model to select and develop endodontic materials compatible with periodontal regeneration in vivo.

Successful root canal therapy is dependent upon obturating the root canal system. A critical component of the filling procedure is sealer placement. This in vitro study investigated the efficacy of six methods of sealer placement using clear plastic blocks with simulated curved canals instrumented to the apex using a step-back technique. After sealer placement and setting, the blocks were cross-sectioned at 2 mm intervals from mid-canal to apex. The sections were evaluated with a stereo operating microscope at x6 magnification for placement of an evenly distributed layer of sealer around the prepared canal walls. The lentulo spiral and the Max-i-Probe Delivery System were the most effective means of sealer placement, followed by ultrasonic and sonic files. The least effective methods were the paper point and the K file

Post designs may have a direct effect on fracture resistance of endodontically treated teeth. This in vitro study compared the resistance of three prefabricated threaded post systems with lateral shearing forces. After endodontics were completed, prefabricated posts were inserted according to the manufacturer's instructions. A silver amalgam core was placed, and extracted human teeth were prepared to a standard size with a 1 mm gingival chamfer finished on sound dentino A cast was fabricated and cemented, and the specimens were thermocycled. The test samples were secured to an Instron testing machine and loaded until failure. Fracture patterns were recorded, fractured surface areas were measured, and compressive stresses were calculated. However, there were no statistically significant differences among threaded posts in each test group