Apical limit of root canal instrumentation and obturation, part 2. A histological study

The results of an in vivo histological study involving apical and periapical tissues following root canal therapy after different observation periods demonstrated the most favourable histological conditions when the instrumentation and obturation remained at or short of the apical constriction. This was the case in the presence of vital or necrotic pulps, also when bacteria had penetrated the foramen and were present in the periapical tissues. When the sealer and/or the gutta-percha was extruded into the periapical tissue, the lateral canals and the apical ramifications, there was always a severe inflammatory reaction including a foreign body reaction despite a clinical absence of pain.

Incomplete calcium hydroxide removal from the root canal: a case report

This case demonstrates failure of root canal treatment of a maxillary central incisor following incomplete mechanical removal of a Ca(OH)2 intracanal dressing and subsequent resorption of the material from the apical portion of the root canal. Retreatment some 4 years later involved the removal of the contents of the root canal and permanent obturation by lateral condensation of cold gutta-percha with a sealer. Follow-up showed complete periradicular bone healing with a lamina dura evident. An explanation of the processes involved is offered, based upon histopathological and microbiological evidence in the literature.

Periradicular curettage

Periradicular curettage is a part of the treatment procedure of periradicular surgery. Its main purpose is to remove pathological periradicular tissues for visibility and accessibility to facilitate the treatment of the apical root canal system, or sometimes for the removal of harmful foreign materials present in the periradicular area. Inflammatory periradicular lesions (granuloma and cysts) are the responses of the periradicular tissues to irritants from the root canal and not from the periradicular area unless medicaments and/or filling materials have been forced through the apical foramina or perforations into the periodontium. Histologically, the inflammatory periradicular lesion is similar to healing granulation tissue, which is composed of cells which have natural and specific immunological defence capability and cooperate by means of cytokines to amplify the protective mechanisms of the host. Accordingly, it is not necessary to completely curette out all the inflamed periradicular tissues during surgery, since this granulation-like tissue will be incorporated into the new granulation tissue as part of the healing process. To control the source of irritants in the root canal is far more important than to remove all periradicular tissues affected by the irritants. The successful removal of all irritants from the root canal system results in resolution of pulpally induced periradicular lesions. In the case where the periradicular lesion is caused by endodontic instruments or cytotoxic filling materials placed in the periradicular tissues, removal of these foreign objects is required for resolution of the lesion.

Long-term follow-up on C-shaped mandibular molars

Three cases of mandibular second molars with C-shaped root canal morphology are described. Two of these molars did not radiographically show the usual anatomic configuration of two separated roots, but rather had a single conical root. Only two root canals orifices were observed in the pulp chamber floor: a mesial-lingual orifice in its normal position and a buccal C-shaped fissure that was continuous from the normal location of the mesiobuccal canal to that of the distal canal. The fissure became smaller in the apical third, ending in a distal direction. The third case, a second molar extracted because of severe periodontal involvement showed, after sectioning, a C-shaped root with connections between all three canals.

Tissue reaction to endodontic materials: methods, criteria, assessment, and observations

The purpose of this study was to develop methods and criteria for the testing of the biocompatibility of endodontic materials. One hundred twenty-one teeth from 12 baboons (Papio anubis) were used to test three sealers: AH26, Kerr pulp canal sealer, and Kloroperka N.O. Gutta-percha cones were used as solid core in all cases. Under disinfected conditions, access preparation was performed, and with working length approximately 1.0 mm short of the foramen, the instrumentation of the root canal was started, using sodium hypochlorite (1%) for irrigation. After the root canals were cleaned and shaped, they were obturated with gutta-percha cones and the sealer, and by lateral condensation technique. Histologic periapical reactions were evaluated at 1, 7, 30, 365, 730, and 1095 days. The methods and criteria used were adequate for ranking of the biocompatibility of the tested materials in the short and long periods. At short observation periods (1 to 7 days) AH26 caused severe reactions, and Kerr pulp canal sealer and Kloroperka N.O., moderate and mild reactions, respectively. At 2- and 3-year observation periods the ranking was AH26, mild; Kerr pulp canal sealer, moderate; and Kloropercha N.O., severe.

Clinical, radiographic, and histologic study of endodontic treatment failures

One hundred fifty cases of endodontic treatment failures were studied clinically, radiographically, and histologically. Fifty-seven percent of the teeth were asymptomatic. Pain alone and/or associated with swelling was present in 21% of the teeth. There was no correlation between the size of periradicular rarefaction and the occurrence or severity of clinical signs and/or symptoms. Stainable bacteria were demonstrated in 69% of the teeth and were present mostly in the canal. The severity of periradicular inflammation was related to presence of stainable bacteria in the canal. Swelling and pain or a draining sinus tract was often associated with stainable bacteria inside the canal. The development of a radicular cyst associated with an endodontically treated tooth that has failed is not necessarily the cause of endodontic treatment failure.

Prevalence of previous endodontic treatment, technical standard and occurrence of periapical lesions in a randomly selected adult, general population

A random sample of 967 subjects selected from the total population in a Swedish county were examined radiographically regarding prevalence and quality of endodontic treatment and occurrence of periapical lesions. The relationship between the technical standard of endodontic treatment and the occurrence of periapical lesions was also analyzed. Of the selected individuals, 95% attended examination (751 dentate and 169 edentulous individuals). Of the 17,430 teeth examined, 1,492 (8.6%) were endodontically treated. Approximately 70% of the treated root canals were inadequately obturated; 10% showed excess of root filling beyond the apex. The prevalence of periapical lesions was 2.9%, and 24.5% of the endodontically treated roots demonstrated periapical lesions. Root fillings ending more than 2 mm from apex had a significantly lower frequency of periapical lesions than root fillings ending within 2 mm of the apex. No difference in the frequency of periapical lesions was found between properly and improperly obturated root canals. Excess of root filling material beyond the apex was related to a significantly higher frequency of periapical lesions.

Root canal dentinal tubule disinfection

Dentinal tubules of the root canal walls of human teeth were infected in vitro with a known bacterial isolate. The roots were exposed to either calcium hydroxide or iodine potassium-iodide for various periods of time and the viability of microorganisms was determined by incubation of entire root samples in a culture medium. The effects of the two agents on microbial viability were evaluated and compared. Iodine potassium-iodide disinfected dentin effectively. In contrast, bacteria remained viable in the dentin after relatively extended periods of calcium hydroxide treatment.

[Pulpal-periapical response to canal medication with Ca(OH)2]

This study consisted of biopsies of teeth and root tips removed after Ca(OH)2 therapy. The teeth were clinically intact or exposed to caries, trauma, and/or iatrogenesis. Following the therapy most of the canal walls were clean, but the canals contained varying amounts of pulp tissues, debris and Ca(OH)2 particles. In one case microrganisms were present in the apical part of the canal, but not beyond the foramen. The Ca(OH)2 therapy was efficient for its purpose.

Traumatically injured primary incisors: a clinical and histological study

World-wide epidemiological studies state that from 8 percent to 30 percent of children up to 7 years of age sustain injury to primary incisors, including crown fracture, root fracture, tooth avulsion, and dental displacement, which result in malformation of permanent incisors depending upon their state of development. In this study, traumatized primary incisors were evaluated clinically and radiographically, with the following data recorded: exact or approximate time-interval of traumatic episode(s) and extraction, mobility, color change, sensitivity to percussion/palpation, swelling, sinus tract, caries, crown/root fracture, periodontal/periapical lesions, external/internal root resorption, mineralization, and obturation. Based upon the local damage and developmental age, 138 teeth were extracted, fixed in 10 percent formalin, and processed for histological evaluation according to routine methodology. Histologic findings were: the presence of varying extent of necrosis, bacteria in the area of necrosis--not in all cases--neutrophilic leukocytes, chronic inflammatory cells, pulpal calcifications, resorption/apposition, and circulatory changes. The blood pigment distinguished hemorrhage due to extraction from pathologic circulatory changes. All the described reactions varied in intensity and extent with the time interval and the assumed force of the original trauma. Physical trauma to primary teeth caused pulpal damage, which could involve periapical tissue, depending on the extent of the initial damage.

Dens evaginatus: a case report

A case of bilateral dens evaginatus is presented. The difficulty of clinical diagnosis and the limited value of pulp testing in cases of dens evaginatus are discussed.

Paste technique re-treatment study: a clinical, histopathologic, and radiographic evaluation of 50 cases

This study correlated clinical, radiographic, and histopathologic aspects of 50 endodontic failures involving the paste technique. All clinical and radiographic findings were recorded. The teeth were re-treated with gutta-percha/Kloroperka and lateral condensation. Subsequently, periapical surgery, including retrograde amalgam filling, was performed for the removal of material in the periapical tissue. The resulting biopsy specimens were processed for histologic evaluation. Although neutrophilic leukocytes predominated in some cases, all types of inflammatory cells were present. Macrophages and foreign body cells contained paste particles. The blood pigment distinguished hemorrhage due to surgery from pathologic circulatory changes. There was resorption/apposition of bone and root fragments. Epithelial strands and parts of cyst walls were observed. There was a correlation between a periapical radiolucency and inflammation but no correlation between amounts and types of inflammatory cells and pain. Paste placed beyond the foramen caused tissue damage and reduced prognosis.

An evaluation and comparison of the pulpal response to gold foil and indium alloy

All teeth restored with gold foil had pulpal changes marked by persistent hemorrhage, destruction of odontoblasts, and inflammation. Bacteria were found more frequently on cavity walls of teeth restored with gold foil and with increasing frequency for all materials as the observation period became longer. The presence or absence of bacteria could not be related to the pulpal response for either indium alloy or gold foil. Because this and previous studies indicated that gold foil in direct contact with prepared dentin surfaces produces pulpal injury, a base to protect the pulp is indicated. Indium alloy or another appropriate base could be used for the required pulpal protection.

The pulpal effect of freezing temperatures applied to monkey teeth

When temperatures below -80 degrees C, are applied to intact monkey teeth via a liquid nitrogen probe for 1, 2, or 3 minutes, an increasing degree of pulpal damage occurs, but all pulps remain vital. The lesion appears to be predictable and is characterized by a distinct layer of coronal secondary dentin with cellular inclusions, odontoblast destruction, and microvascular injury. The root pulp remains essentially healthy and uninflamed. Periodontal and root tissue damage was also observed.

Pulpal and radicular response to maxillary osteotomy in monkeys

The purpose of this study was to examine the pulpal and radicular response to total maxillary osteotomy. The osteotomy was performed on four adult Macaca irus monkeys. Monkeys were killed after a postsurgical observation period of 150 days. Tissue blocks of the maxilla with teeth were cut and examined histologically. The pulp of the majority of the teeth from experimental animals showed cellular and circulatory pathologic changes, even in the presence of collateral circulation.

Predominant microflora associated with human dental periapical abscesses

The microflora of periapical abscesses of teeth free of periodontal disease was studied. Permucosal aspiration of abscess contents and anaerobic cultural, microscopic, and biochemical techniques indicated a mixed but somewhat specific and relatively limited facultative and obligate anaerobic flora with Fusobacterium nucleatum and Streptococcus mitis as a frequent pair.

Capping of monkey pulps with Dycal and a Ca-eugenol cement

Capping of 120 teeth in four monkeys was performed with Dycal or with a calcium-eugenol cement. The observation periods were 8 days or 90 days. The monkeys were killed, and the teeth were examined histologically. After 8 days, the pulp-tissue reactions were basically the same in the two groups. The tissue adjacent to the exposure site was characterized by varying amounts of necrotic tissue, inflammatory cells, and extravasated erythrocytes. Capping material and dentin chips were displaced into the pulp tissue. Particles from the capping materials were found in vessels, macrophages, and foreign body cells. After 90 days, more hard-tissue formation occurred in the Dycal group than in the Ca-eugenol cement group. The hard tissue was formed by either fibroblasts or the original odontoblasts.

Pain: a poor parameter of evaluation in dentistry

In summary, we must be aware of the limitations of our instruments for determining success. A diagnosis is achieved by developing a composite picture through a keen gathering of all factors leading to the disease. Pain must surely be considered in patient management and patient-dentist rapport, but to allow our judgment to be swayed by pain alone is no more rational than to hinge our diagnosis upon a single other test. It is of paramount importance that we realize that, pulpally, periodontally, and periapically, there is no correlation between amount of destruction and reported presence or absence of pain. Pain is a poor parameter of evaluation.