Rudy C. Melfi

An in vitro comparison of the efficacy of the stepback technique versus a step-back/ultrasonic technique in human mandibular molars

This study compared the effect of the step-back preparation versus a step-back/ultrasound preparation on the tissue removal from the mesial root canals of 60 extracted human mandibular molars. The step-back/ultrasound preparation significantly cleaned isthmuses at both levels and canals at the 1-mm level more effectively than the step-back preparation. Statistical analysis indicated no significant difference, in canal cleanliness at the 3-mm level, between the step-back and the step-back/ ultrasound groups. There were no significant differences demonstrated in isthmus cleaning ability when comparing the step-back group with the control group, at both the 1- and 3-mm levels. At the 1-mm level, operator 1 significantly cleaned canals in the step-back group more effectively than operator 2. However, in the step-back/ultrasound group, no significant differences were demonstrated between operators in their ability to clean canals at this level. In both experimental groups, operator comparisons indicated no significant differences in isthmus cleanliness at the 1-mm level.

Pulpal response to vital bleaching procedures

The application of heat ranging from 115 to 124 F and a 35% solution of hydrogen peroxide to intact human premolars causes a mild superficial inflammation (graded 0.5 to 1.0) in a significant number of pulps. Peroxide alone, or heat with saline solution, was judged to be less irritating since it did not cause a significant number of inflammatory responses.

Induced apical closure of permanent teeth in adult primates using a resorbable form of tricalcium phosphate ceramic.

Conditions of an open apex were simulated in four Cynalmolgus monkeys by extirpating the vital pulps and by preparing the root canals through the apex. The apical 3 mm of 20 teeth was treated with a tricalcium phosphate resorbable ceramic. The periapical tissues of the treated teeth showed a minimal inflammatory response. The periodontal ligament tended to regenerate. Formation of mineralized tissue within the root canal occurred, but bridging was incomplete.

Direct pulp capping of permanent teeth in primates using a resorbable form of tricalcium phosphate ceramic

A resorbable ceramic was placed over 22 surgically created pulpal exposures in an experiment. Histological evidence showed that formation of a dentinal bridge took place by direct apposition on the pulpal tissues that were treated with a ceramic form of tricalcium phosphate. Formation of a dentinal bridge appears to be predictable. The bridge is contiguous and thick, pulpal inflammation is minimal, and odontoblasts ore observed directly under and in contact with the bridge. The ceramic form of tricalcium phosphate appears to enhance the formation of a dentinal bridge in contrast with the calcium hydroxide that was used as the control.

A histopathologic evaluation of tissue reactions to the minimum effective doses of some endodontic drugs.

Abstract Minimal doses (0.0025 c.c.) of Cresatin, camphorated parachlorophenol, and formocresol were placed on cotton pellets in 10 mm. polyethylene tubes and implanted into the subcutaneous connective tissues in the backs of rats to determine the tissue reactions. Empty tubes and saline-filled tubes were used as controls. Microscopic slides were made of the tissues of animals killed at 3, 7, 14, and 30 days and examined. Formocresol produced the most severe reaction at 3, 7, and 14 days, but the tissues had recovered and were nearly normal at 30 days. Camphorated parachlorophenol produced moderate reactions at 3 and 7 days, with recovery to normal at 14 and 30 days with tissue growing into the tube openings. Cresatin produced an unexplained severe reaction at 7 days, with no reaction noticeable at 3, 14, or 30 days.

An ultrastructural study of dentinal innervation in the adult human tooth

Abstract The odontoblastic process and the intradentinal nerve in the pulpal third of the dentin from permanent teeth was investigated with the electron microscope. Three types of nerve structure were observed within the predentin and dentin: bare nonmyelinated fibers, Schwann cell-sheathed fibers, and myelinated fibers. In addition, structures suggestive of synaptic or attachment sites were observed. Some structural changes were noted within the odontoblastic process themselves when certain types of nerve fiber were associated with them.

A study of freeze-dried (lyophilized) dentin used as an apical barrier in adult monkey teeth

Thirty-two fully formed vital teeth of four adult cynomolgus monkeys were endodontically prepared to simulate conditions of an open apex. The apical 2 to 5 mm. of 24 teeth were filled with freeze-dried dentin. The eight remaining teeth received no implant material and served as controls. All the teeth were obturated with gutta-percha. The monkeys were sacrificed at 6, 13, 23, and 27 week periods, and the specimens were prepared for histologic examination. The early specimens showed acute inflammation apically; later specimens showed osseous healing. Some experimental teeth had partial cementum bridging against the implant material. Freeze-dried dentin was found to be a biocompatible material which can be used effectively as a substitute barrier against which gutta-percha can be condensed in mechanically prepared open-apexed monkey teeth.

The histologic effect of topically applied acetylsalicylic acid on bone healing in rats

Abstract The fate of topically applied therapeutic agents and the healing of the bone they contact are basic problems related to the repair process. Twelve albino rats were used, with twelve matched littermates as controls. A mucoperiosteal flap was raised and a lesion made in the crest of the maxillary ridge with a No. 2 bur. Powdered aspirin was placed in the lesion, and the flap was replaced and sutured. Sacrifice times were at 1 hour and 1, 4, 7, 15, and 30 days. The inflammatory response was of greater intensity and duration in those lesions containing aspirin. The osteoclastic activity around the aspirin-containing sites was of greater intensity than around the control sites in all 4- and 7-day specimens. The aspirin-containing sites showed much less bone repair within the lesions at 15 days; yet both were completely filled at 30 days.

An in vitro autoradiographic study comparing the apical seal of uncatalyzed dycal to Grossman's sealer†

This in vitro autoradiographic study compared the seal of uncatalyzed Dycal and laterally condensed gutta-percha to Grossmans sealer and laterally condensed gutta-percha. The results showed that the teeth obturated with gutta-percha and no sealer had significantly greater leakage than either uncatalyzed Dycal or Grossmans sealer at all five levels. There was no significant difference in leakage between uncatalyzed Dycal and Grossmans sealer at the 1-mm level. Grossmans sealer showed significantly greater leakage at the 2-, 3-, 4-, and 5-mm levels when compared with uncatalyzed Dycal.

Mast Cells and Basophils in the Mandibular Alveolar Connective Tissue and Bone Marrow of Germfree Albino Rats

Mast cells and basophils decreased in numbers in older germfree rats. Degranulation of mast cells increased in older animals. It is possible that aging is related to increasing degranulation and the release of pharmacologically active substances such as heparin. The release of heparin might play a role in bone loss.