Sahng G. Kim

Effects of Local Anesthetics on Pulpal Blood Flow in Dogs

Effects of 2% lidocaine with epinephrine (1 :100,000) administered by the various local anesthetic techniques - i.e., infiltration, mandibular block, and intraseptal injection - on pulpal blood flow in dogs were determined using the 15 μm radioisotope-labeled microsphere injection method. The pulpal blood flow decreased significantly with all three techniques; however, the most drastic reduction occurred in the molar teeth with the intraseptal injection. When 2% lidocaine without epinephrine was used in the intraseptal injection, pulpal blood flow increased significantly.

Decreasing intradental nerve activity in the cat with potassium and divalent cations

Nerve activity was recorded from deep dentinal cavities in the canine teeth to assess the possible influence of potassium and divalent cations in decreasing this activity in hypersensitive teeth. The decreased activity after the topical application of 0.756 mol/l KCl to the cavity was primarily due to the cation. KCl elicited a biphasic response from intradental nerves, an initial transient excitatory response followed by a prolonged inhibitory period. During the inhibitory period 3 mol/l NaCl, an effective excitatory stimulus, failed to evoke intradental nerve activity. However, with time the response to 3 mol/l NaCl eventually recovered to its previous control level. Close, intra-arterial injection of KCl showed the same biphasic response and time-course of intradental nerve activity as with topical application. Therefore, whether KCl was applied topically or injected its effectiveness in altering the nerve activity was similar. Pretreatment of the dentinal cavity with CaCl2, MgCl2 or SrCl2 greatly reduced the response of intradental nerves to KCl. Therefore these divalent cations seem to have a depressant action on pulpal nerve fibres. The mechanism of action of KCl seems to be an alteration of K+ concentration immediately surrounding the intradental nerves which presumably depolarizes the nerve fibre membrane and elicits an initial firing of action potentials. Because of the persisting high levels of extracellular potassium a sustained depolarized state occurs that results in an inactivation of the action potential. Divalent cations appear to depress the excitability of the nerve cell membrane without altering membrane potential. Such ionic agents could be used in conjunction with KCl as a possible treatment for hypersensitive teeth.

Regenerative Endodontic Treatment of Permanent Teeth after Completion of Root Development: A Report of 2 Cases

INTRODUCTION Clinical regenerative endodontic treatment has been focused on immature necrotic teeth, but it should be extended to mature teeth as an alternative to conventional endodontic treatment. There have been no clinical reports to attempt to revascularize pulp in the entire root canals of mature necrotic teeth. The present report describes the treatment of mature, necrotic, permanent incisors with apical periodontitis by using regenerative endodontic therapy. METHODS In this case report, modified regenerative endodontic procedures were used to enhance the probability of pulp revasuclarization in mature necrotic teeth. At the first appointment, the root canals were mechanically instrumented to the apices with a large apical size by using the step-back technique and irrigated copiously with antimicrobial solution. Intracanal medicaments (calcium hydroxide or ciprofloxacin) were placed in the root canals. At the following appointment, the root canals were irrigated with antimicrobial solution, and bleeding was induced into the root canals by passing hand files beyond apices. Collagen membranes were placed in the canals as a matrix against which mineral trioxide aggregate was placed. Glass ionomer was used to restore the teeth. The resolution of apical radiolucency and regression of clinical signs and symptoms were observed at recall appointments. CONCLUSIONS The present report presents modified regenerative endodontic procedures for mature necrotic permanent teeth. Further clinical studies with a large number of cases are needed to investigate the outcome of regenerative endodontic therapy for mature necrotic teeth.

Comparison of pulpal blood flow in dog canine teeth determined by the laser Doppler and the 133xenon washout methods

Pulpal blood flow measurements by laser Doppler flowmetry were compared with those made simultaneously and on the same teeth by the 133Xe washout method. Pulpal method flow in the resting state was 82.4 ml/min per 100 g as calculated from the fast component of the 133Xe washout, whereas laser Doppler flowmetry recorded 263 mV. The close intra-arterial (i.a.) injection of the vasoconstrictor norepinephrine (10(-2)-10(-1) micrograms/kg) caused a reduction of pulpal blood flow by 20.2% with the 133Xe washout and by 9.7% with the laser Doppler flowmetry in 6 observations in 4 dogs. The laser Doppler flowmetry measurements of these norepinephrine-induced changes correlated significantly with changes measured by the 133Xe washout method as analysed by linear regression (p = 0.004).

Regenerative Endodontics: Barriers and Strategies for Clinical Translation

Regenerative endodontics has encountered substantial challenges toward clinical translation. The adoption by the American Dental Association of evoked pulp bleeding in immature permanent teeth is an important step for regenerative endodontics. However, there is no regenerative therapy for most endodontic diseases. Simple recapitulation of cell therapy and tissue engineering strategies that are under development for other organ systems has not led to clinical translation in regeneration endodontics. Recent work using novel biomaterial scaffolds and growth factors that orchestrate the homing of host endogenous cells represents a departure from traditional cell transplantation approaches and may accelerate clinical translation.

Comparison of the effects of intra-arterial and locally applied vasoactive agents on pulpal blood flow in dog canine teeth determined by laser doppler velocimetry

The vasoactive agents norepinephrine, 5-hydroxytryptamine, isoproterenol and bradykinin, at concentrations which changed local arterial pressure without changing systemic arterial pressure significantly, were injected intra-arterially (i.a.) into the maxillary artery or applied directly in a deep dentinal cavity on the buccal surface of canine teeth. The probe of a laser Doppler velocimeter was placed in the cavity to monitor pulpal blood flow. Bolus i.a. injections of the vasoconstrictors norepinephrine and 5-hydroxytryptamine produced a statistically significant (p less than 0.05) reduction in pulpal blood flow, 21.1 +/- 3.7 and 30.7 +/- 15.2%, and the local arterial pressure from the lateral nasal artery increased with norepinephrine but decreased with 5-hydroxytryptamine. The i.a. injections of the vasodilators isoproterenol and bradykinin were found to decrease both local arterial pressure and pulpal blood flow, 17.7 +/- 6.0 and 22.7 +/- 4.2%, respectively (p less than 0.05). However, local application of isoproterenol and bradykinin caused a biphasic response: an increase in pulpal blood flow, 8.6 +/- 1.6 and 9.4 +/- 1.1% (p less than 0.05), followed by a decrease, 19.1 +/- 11.9 and 5.3 +/- 2.1% (p greater than 0.005). Local application of norepinephrine and 5-hydroxytryptamine caused a decrease in pulpal blood flow, 23.7 +/- 5.2% (p less than 0.05) and 9.3 +/- 5.2% (p less than 0.05), respectively. These findings were in accordance with those from other reliable methods, such as injections of radioisotope-labelled 15 microns microspheres and the 133Xe washout technique, making laser Doppler flowmetry a reliable alternative. In addition, the biphasic response to the locally applied vasodilators and the reduction of pulpal blood flow after i.a. injection of vasodilators suggest that regulation of pulpal blood flow is determined by the combined effects of the low compliance environment and the stealing of perfusion to the pulp by the neighbouring tissues.

Tooth regeneration: a revolution in stomatology and evolution in regenerative medicine.

A tooth is a complex biological organ and consists of multiple tissues including the enamel, dentin, cementum and pulp. Tooth loss is the most common organ failure. Can a tooth be regenerated? Can adult stem cells be orchestrated to regenerate tooth structures such as the enamel, dentin, cementum and dental pulp, or even an entire tooth? If not, what are the therapeutically viable sources of stem cells for tooth regeneration? Do stem cells necessarily need to be taken out of the body, and manipulated ex vivo before they are transplanted for tooth regeneration? How can regenerated teeth be economically competitive with dental implants? Would it be possible to make regenerated teeth affordable by a large segment of the population worldwide? This review article explores existing and visionary approaches that address some of the above‐mentioned questions. Tooth regeneration represents a revolution in stomatology as a shift in the paradigm from repair to regeneration: repair is by metal or artificial materials whereas regeneration is by biological restoration. Tooth regeneration is an extension of the concepts in the broad field of regenerative medicine to restore a tissue defect to its original form and function by biological substitutes.

Cost-effectiveness of Endodontic Molar Retreatment Compared with Fixed Partial Dentures and Single-tooth Implant Alternatives

INTRODUCTION One of the most challenging situations in dentistry is a failed root canal treatment case. Should a failed root canal-treated tooth be retreated nonsurgically or surgically, or should the tooth be extracted and replaced with an implant-supported restoration or fixed partial denture? These four treatment alternatives were compared from the perspective of cost-effectiveness on the basis of the current best available evidence. METHODS The costs of the four major treatment modalities were calculated using the national fee averages from the 2009 American Dental Association survey of dental fees. The outcome data of all treatment modalities were retrieved from meta-analyses after electronic and manual searches were undertaken in the database from MEDLINE, Cochrane, ISI Web of Knowledge, and Scopus up to April 2010. The treatment strategy model was built and run with TreeAge decision analysis software (TreeAge Software, Inc, Williamstown, MA). RESULTS Endodontic microsurgery was the most cost-effective approach followed by nonsurgical retreatment and crown, then extraction and fixed partial denture, and finally extraction and single implant-supported restoration. CONCLUSIONS The cost-effectiveness analysis showed that endodontic microsurgery was the most cost-effective among all the treatment modalities for a failed endodontically treated first molar. A single implant-supported restoration, despite its high survival rate, was shown to be the least cost-effective treatment option based on current fees.

The Influence of 5-Hydroxytryptamine (Serotonin) on Blood Flow in the Dog Pulp

The effect of intra-arterial injection of 5-hydroxytryptamine (5-HT) on pulpal blood flow of the dog was determined using the 15-μm radioisotope-labeled microsphere injection method. Pulpal blood flow was significantly reduced following the 5-HT injection. This decrease in blood flow appeared to be due to vasoconstriction as determined by an increase in pulpal vascular hindrance. However, our findings do not preclude the possibility that blood flow was reduced as a result of passive compression of venules produced by vasodilation in a low-compliance environment.

Biphasic pulp blood-flow response to substance P in the dog as measured with a radiolabelled, microsphere injection method

A dose of the vasoactive substance P (SP), affecting local circulation only (0.0001-0.001 micrograms/kg body weight) when given by a close injection into the maxillary artery, caused a biphasic flow response in pulpal blood flow (PBF), as measured by a radioisotope-labelled 15 micron microsphere injection technique. Immediately after the SP injection, PBF increased some 66 per cent (p less than 0.02) and vascular hindrance (Z) decreased to 40 per cent against control values (p less than 0.02), indicating vasodilation. Thirty seconds after the SP injection, PBF decreased by 53 per cent (p less than 0.05), and pulpal Z increased 139 per cent against control values (p less than 0.02), indicating decreased blood flow. This biphasic flow response may be due to the active vasodilation of arterioles by SP, which causes a compression of venules and hence a reduction of PBF in what is a low-compliance system.