Evaluation of new gingival retraction agents.

Current gingival retraction agents are not without undesirable side-effects; there appears to be no ideal gingival retraction agent. Several sympathomimetic amines, capable of producing local vasoconstriction with minimal systemic side-effects, are available as non-prescription nasal decongestants and eye washes. The purpose of this study was to evaluate the efficacy of three of these agents for gingival tissue displacement. Mongrel dogs were used as experimental subjects, in which pulse rate and blood pressure were monitored electronically. Visine (tetrahydrozoline HCl, 0.05%), Afrin (oxymetazoline, 0.05%), and Neosynephrine (phenylephrine HCl, 0.25%) were the commercial products studied as gingival retraction agents. Plain, untreated cord was used as a mechanical control, and as a vehicle for the three experimental agents. Commercially available cords impregnated with both racemic epinephrine (8%) and alum were also used as standard retraction agents with which the test solutions were compared. Visine and Afrin produced tissue displacement greater than that of any of the other agents; Neosynephrine, epinephrine, and alum were more effective than the untreated mechanical control. Cardiovascular changes included a slight increase in systolic pressure in the Neosynephrine group, and a slightly lower mean arterial pressure and pulse rate in all three experimental groups.

Prostaglandin E2 enhances bradykinin-evoked iCGRP release in bovine dental pulp.

Mediators produced during inflammation are responsible for hyperalgesia and expression of neurotransmitters and receptors in the nervous system. The production of bradykinin (BK) and the prostaglandins (PGs) may regulate initiation of pain. This study tested the hypothesis that BK and prostaglandin E2 (PGE2) have a positive interaction in evoking neurosecretion of immunoreactive calcitonin gene-related peptide (iCGRP). Bovine dental pulp was prepared and stimulated by the superfusion method with BK alone and in combination with PGE2. Kinin receptor antagonists to bradykinin-evoked release of iCGRP were also tested. Also tested was the hypothesis that dental pulp contains either the B1 or B2 or both BK receptors. Results showed that PGE2 enhanced BK-evoked iCGRP release by more than 50%. Western immunoblots revealed detectable B2 receptor protein with no detectable B1 receptor protein. We conclude that BK evokes iCGRP release from bovine dental pulp which is enhanced by a positive interaction with PGE2. Neurosecretion is evoked from isolated terminals of dental pulp fibers via the bradykinin B2 receptor-dependent mechanism.

Intrinsic regulation of CGRP release by dental pulp sympathetic fibers.

Neurotransmission from sympathetic and peptidergic afferent fibers participates in the regulation of pulpal blood flow (PBF) via opposing effects. In this study, we directly tested the hypothesis that activation of pulpal sympathetic terminals inhibits exocytosis of immunoreactive calcitonin gene-related peptide (iCGRP) from peptidergic afferents innervating bovine dental pulp. The results demonstrate that norepinephrine inhibits capsaicin-evoked iCGRP release. The application of alpha-adrenergic antagonists (phentolamine or phenoxybenzamine) increased spontaneous release of iCGRP. Moreover, administration of agents that evoke the release of sympathetic neurotransmitters (guanethidine or reserpine) inhibited capsaicin-evoked iCGRP release. Collectively, these results indicate that sympathetic neurotransmission inhibits exocytosis from pulpal peptidergic afferent fibers. Analysis of these data supports the hypothesis that peripheral sympathetic vasomotor control may operate by a direct mechanism (vasoconstriction) as well as by an indirect mechanism (e.g., inhibition of exocytosis from afferent fibers). Since capsaicin-sensitive neurons are nociceptors, it is possible that certain sympathetic neurotransmission may modulate pain.

Leaching of unpolymerized materials from orthodontic bonding resin.

The unpolymerized material extracted from cured orthodontic bonding resin was analyzed by UV spectrophotometry. Under certain conditions, substantial amounts of the material (approximately 14%) were leached from bracketed teeth. The possible carcinogenicity of these unpolymerized materials is discussed.

beta 2-Adrenoceptor regulation of CGRP release from capsaicin-sensitive neurons.

Previous studies have suggested that neurotransmitter substances from the sympatho-adrenomedullary system regulate pulpal blood flow (PBF), in part, by the inhibition of vasoactive neuropeptide release from pulpal sensory neurons. However, no study has evaluated the role of beta-adrenoceptors. We evaluated the hypothesis that activation of beta-adrenoceptors inhibits immunoreactive calcitonin gene-related peptide (iCGRP) release from capsaicin-sensitive nociceptive neurons via in vitro superfusion of bovine dental pulp. Either norepinephrine or epinephrine inhibited capsaicin-evoked iCGRP. The norepinephrine effect was blocked by the selective beta(2)-adrenoceptor antagonist, ICI 118,551, but not by pre-treatment with the selective beta(1)-adrenoceptor antagonist, atenolol. In addition, application of albuterol, a selective beta(2)-adrenoceptor agonist, significantly blocked capsaicin-evoked release of iCGRP. Collectively, these studies demonstrate that activation of beta(2)-adrenoceptors in dental pulp significantly reduces exocytosis of neuropeptides from capsaicin-sensitive nociceptors. This effect may have physiologic significance in regulating PBF. Moreover, since capsaicin selectively activates nociceptors, beta(2)-adrenoceptor agonists may have clinical utility as peripherally acting therapeutics for dental pain and inflammation.

Catalase/peroxidase activity in dental pulp.

Extrinsic stains on vital teeth are bleached with 30% hydrogen peroxide (H2O2) or carbamide peroxide, H2O2 greatly inhibits the activity of several enzymes. Free H2O2 and carbamide peroxide readily enter the pulp through the coronal wall of the tooth. Nevertheless, adverse effects have been remarkably rare. This study was undertaken to determine whether dental pulp exhibits any catalase or peroxidase activity that might protect it from damage during vital bleaching procedures. Pulpal tissue from healthy human teeth was assayed for catalase and glutathione peroxidase activity. A phosphate buffer extract of the tissue served as the source of the enzymes. The rate of breakdown of H2O2 by the tissue extract was measured and the rate constant for catalase was determined. The catalase activity, defined as microM H2O2 broken down/min/mg wet tissue, was determined and found to be only 2 x 10(-2), which is very low. The fibrous pulpal tissue was found to exhibit virtually no glutathione peroxidase activity.

An in vitro method to evaluate regulation of neuropeptide release from dental pulp.

Although pulpal neuropeptides such as calcitonin gene-related peptide and substance P may mediate neurogenic inflammation, little is known about the regulation of neuropeptide release from dental pulp. This article describes an in vitro method for superfusing dental pulp which permits the study of mechanisms regulating the release of immunoreactive CGRP (iCGRP). Tissue extracts from bovine dental pulp dilute in parallel to authentic calcitonin gene-related peptide and substance P peptide standards when assayed by radioimmunoassay. Pulpal levels of iCGRP were 17-fold greater than levels of immunoreactive substance P. Administration of a potassium pulse evoked a significant release of iCGRP from dental pulp (155 +/- 21 fmol/g/9 min) as compared with iCGRP spontaneously released from concurrent control chambers (18 +/- 11 fmol/g/9 min). The in vitro superfusion of pulp tissue may serve as a useful method for identifying peripherally acting drugs which modulate nociceptor secretory activity and for determining their mechanisms of action.

Penetration of the pulp chamber by carbamide peroxide bleaching agents.

Hydrogen peroxide readily penetrates the pulp chamber of freshly extracted teeth. This study was undertaken to determine whether carbamide peroxide also penetrates the pulp chamber. Freshly extracted teeth were sectioned 2 to 3 mm apical to the cementoenamel junction and the coronal pulpal tissue was removed. Acetate buffer was placed in the pulp chamber to absorb and stabilize any peroxide that might penetrate. The coronal portion of each tooth was immersed in either carbamide peroxide gel or gelled hydrogen peroxide at various concentrations for 15 min at 37 degrees C. The buffer was removed, leukocrystal violet was added, and the optical density of the resulting blue solution was determined spectrophotometrically. Amounts of peroxide found in the pulp chamber after 15 min ranged from 3.3 +/- 0.38 micrograms for the 10% sample to 40.4 +/- 3.51 micrograms for the 30% sample.

Evaluation of functional GABA(B) receptors in dental pulp.

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that is elevated in inflamed human dental pulp. Because GABA agonists are antihyperalgesic in other tissue, it is possible that GABA agonists have similar effects in dental pulp assuming that this tissue contains GABA receptors. We tested the hypothesis that dental pulp contains functional GABA(B) receptors using a GTPgamma35S binding assay. This is a functional assay because GTPgamma35S will be bound to cell membranes only when activation of metabotropic receptors has lead to binding and activation of their associated G(alpha)-proteins via release of GDP and binding of the GTPgamma35S. Baclofen, a GABA(B) agonist, evoked GTPgamma35S binding in both human and bovine dental pulp. This was mediated by the GABA(B) receptor because it was blocked by the selective antagonist phaclofen in both tissues. The presence of GABA and its receptor, GABA(B), suggests that this system may be relevant in the production or management of endodontic pain.

Evaluation of the combination of flurbiprofen and tramadol for management of endodontic pain.

Effective management of endodontic pain represents a continuing challenge. In this study, we evaluated the efficacy of flurbiprofen and a novel centrally acting analgesic, tramadol, alone and in combination, for reducing pain in endodontic emergency patients. Patients (n = 49) were administered a local anesthetic and underwent pulpectomy. They were then administered, on a double-blind basis, either: (i) placebo (one capsule to start and then every 6 h); (ii) flurbiprofen (100 mg loading dose and then 50 mg every 6 h); (iii) tramadol (100 mg loading dose and then 100 mg every 6 h); or (iv) the combination of flurbiprofen and tramadol (as above). Pulpectomy combined with placebo medication resulted in a 50% reduction in pain by 24 h (p < 0.01). Patients treated with flurbiprofen and tramadol reported less pain, compared with placebo treatment at 6 and 24 h (p < 0.01 for both). These results suggest that a nonsteroidal anti-inflammatory drug/opiate combination, together with endodontic therapy, may be useful in the management of endodontic pain.

Bradykinin levels in dental pulp by microdialysis.

Bradykinin is a potent mediator of pain and inflammation. To examine extracellular levels of bradykinin in human dental pulp, CMA/20 microdialysis probes were inserted into the pulp tissue of 22 teeth diagnosed with normal pulp or with irreversible pulpitis before their extraction or endodontic therapy. Probes were perfused with a modified Locke-Ringer's buffer and bradykinin levels in the dialysate evaluated using a radioimmunoassay. Mean extracellular levels of bradykinin within pulp tissue diagnosed with irreversible pulpitis were significantly higher (262.26 +/- 83.79 fmol/ml) than that found within normal pulp (19.41 +/- 6.47 fmol/ml). Highest levels of bradykinin were detected in pulp tissue diagnosed with irreversible pulpitis when the patient had reported pain in the past, compared with patients who were in pain just before their visit. These observations suggest that the bradykinin system is activated during pulpitis and may contribute to pain and inflammation.

Reevaluation of submerged vital roots.

A total of eight vital roots were submerged and retained under complete dentures in two patients. Within two to three years, each patient experienced problems of pain, re-exposure, and inflammation, resulting in the removal of the roots. Histologic evaluation showed evidence of chronic inflammation of the pulpal tissue. Because of alveolar resorption and perhaps super-eruption of the submerged roots, the likelihood of exposure and abscess is a distinct disadvantage to the procedure. Therefore, some doubt remains as to the long-term success with this technique.

Abrasive particles in tobacco products: a possible factor in dental attrition.

Tobacco products are known to cause oral soft-tissue lesions, but they may also directly affect the teeth. Abrasive particles contained in tobacco products may contribute to dental attrition. We studied tobacco samples from 16 brands of cigars, eight brands of snuff, four brands of chewing tobacco and several unprocessed tobacco leaves used as cigar wrappers. Insoluble particulate matter made up about 0.5 percent of the weight of an average tobacco sample.

Skin tumors may imitate infectious processes.

A small nodule on the middle finger of the right hand of a right-handed dentist was removed and found to be benign. The lesion recurred and showed increased collagen deposition and vascularity; it was diagnosed as a dermatofibroma. In the absence of a specific incidence of trauma, the cause of such a lesion is a matter of speculation. Such lesions can develop as local tissue reactions to wounds that are the result of routine operatory procedures. This points to the need for careful handling of sharp instruments. Because of the serious consequences of a malignancy or infection from HIV, nodules and other lesions of unknown etiology that appear suddenly should not be ignored.

Antimicrobial properties and dentin bonding strength of magnesium phosphate cements.

The main objective of this work was to assess the antimicrobial properties and the dentin-bonding strength of novel magnesium phosphate cements (MPC). Three formulations of MPC, consisting of magnesium oxide and a phosphate salt, NH4H2PO4, NaH2PO4 or a mixture of both, were evaluated. As a result of the setting reaction, MPC transformed into either struvite (MgNH4PO4·6H2O) when NH4H2PO4 was used or an amorphous magnesium sodium phosphate when NaH2PO4 was used. The MPC had appropriate setting times for hard tissue applications, high early compressive strengths and higher strength of bonding to dentin than commercial mineral trioxide aggregate cement. Bacteriological studies were performed with fresh and aged cements against three bacterial strains, Escherichia coli, Pseudomonas aeruginosa (planktonic and in biofilm) and Aggregatibacter actinomycetemcomitans. These bacteria have been associated with infected implants, as well as other frequent hard tissue related infections. Extracts of different compositions of MPC had bactericidal or bacteriostatic properties against the three bacterial strains tested. This was associated mainly with a synergistic effect between the high osmolarity and alkaline pH of the MPC. These intrinsic antimicrobial properties make MPC preferential candidates for applications in dentistry, such as root fillers, pulp capping agents and cavity liners.

Endodontic and implant algorithms.

Dental professionals are often faced with challenges when formulating a treatment plan for patients presenting with a compromised tooth. A common dilemma involves the decision between tooth retention using endodontic treatment with crown restoration, and extraction and an implant-borne restoration. In this article the authors evaluate the 2 treatment modes, and observe that because outcomes are similar with both treatments, decisions should be based on the patient's informed decision concerning restorability, costs associated with the procedures, esthetics, potential adverse outcomes, and ethical factors.