Chapter 8 : Experimental Studies of Root Canal Therapy for Infected Nonvital Permanent Teeth with Incompletely Formed Apices

A total of 160 root canals in 90 teeth with incompletely formed roots of puppies were prepared for infected root canal therapy. The experimental group was treated with Vitapex and the control group was treated with calcium hydroxide-CMCP paste root canal filling material. Histopathological sections from decalcified specimens were prepared after observation periods of 30, 60, 120 and 180 days. In addition, 24 root canals in 16 teeth were treated with Vitapex on the opposite side with sound teeth and subjected to tetracycline administration. Observations were carried out by contact microradiography and tetracycline labeling and resulted in the following conclusions. 1: Almost no root growth was observed using both root canal filling materials, and the addition of newly-formed hard tissue was observed close to the root apical foramen involved. 2: The addition of hard tissue after root canal filling was thought to be primarily by cementum. 3: A greater amount of hard tissue formation resulting in closure of the apex and a more favorable outcome was observed in the control group than in the experimental group. 4: The control group had a higher percentage of hard tissue formation outside the root apex close to the root tip than did the experimental group. 5: The experimental group showed good results in each observation period. The control group showed better results with a shorter observation period than did the experimental group, but in longer observation periods, tended to decrease in cases with poor results. 6: Undecalcified specimens were examined using contact microradiography and tetracycline labeling. In the experimental group, the addition of newly-formed hard tissue was observed close to the apical foramen near the root tip formed during the course of treatment. Normal root formation in the dental arch was observed in all samples in the experimental and control groups.Editor, Toshiyuki KawakamiLanguage Editor, David M Carlsonviii, 232 p. ill. (some col.

Chapter 6 : Histopathological Studies of Pulpectomy in the Deciduous Teeth of Dogs

A study was performed to examine the impact of resorbable root canal filling material, Vitapex, containing calcium hydroxide and iodoform, on the physiological resorption of its roots, succedaneous permanent tooth buds and periodontal tissues. A total of 14 puppies aged 2-5 months were used; teeth were anesthetized, pulps were extirpated and immediate root canal filling was performed. These procedures were carried out in 53 deciduous teeth with 81 root canals, and contralateral intact teeth were used as controls. The animals were bred for 5 to 60 days and were tracked with radiographical and histological examinations. Results obtained were the following: 1: The form of healing observed after the experimental procedures was divided into 2 groups: those healed either by remaining vital pulp tissue or by the periodontal ligament, with 17 and 29 cases, respectively. 2: The resorption of root canal filling material and the physiological root resorption were almost the same in the majority of cases. 3: The rate of physiological root resorption in the experimental group was slightly delayed compared to that of the control group. 4: The remaining pulp tissue lesions, either in short or long term cases, comprised 5 cases of congestion, 3 cases of hemorrhage, 5 cases of mild inflammation, 11 cases of purulent inflammation, and 1 case of atrophy. 5: Periapical lesions, either in short or long term cases, comprised 6 cases with congestion, 12 cases with mild inflammation, 17 cases with purulent inflammation and 7 cases with pathological alveolar bone resorption. 6: In most cases, the lesions did not significantly affect the permanent tooth buds, except for 6 of 81 cases. 7: Pathological grades obtained in this experiment, in a total of 81 cases, were good in 41 cases (50.6%), fair in 20 cases (24.7%) and a failure in 20 cases (24.7%). 8: The best pathological grades after the experimental procedure were obtained in cases in which the root canal filling material was limited within the canal itself (flush) and in those cases which were underfilled. Overextension of root canal filling should be avoided as much as possible. 9: The relationship between root status and pathological grades showed a slightly lower incidence and favorable results with physiological root resorption compared to those without physiological root resorption. 10: In this study, the use of Vitapex for immediate root canal filling after pulp extirpation in canine deciduous teeth produced good results. Vitality of the remaining pulp and periodontal tissue was restored with subsequent physiological root resorption and without adverse effect on succedaneous permanent tooth buds.Editor, Toshiyuki KawakamiLanguage Editor, David M Carlsonviii, 232 p. ill. (some col.

Chapter 9 : Clinical and Radiographic Observation of Permanent Teeth with Incompletely Formed Roots after Root Canal Therapy

A total of 33 teeth with 66 root canals were clinically diagnosed as irreversible pulpitis, and 38 teeth with 53 canals were diagnosed as apical periodontitis. Those 71 teeth had 119 root canals, with incompletely formed roots, and they underwent root canal therapy and filling using a formulation of calcium hydroxide and iodoform called Vitapex and were clinically observed for 30 to 1312 days. The following are the results and conclusions. 1: After root canal therapy, the condition of the root canal filling material was determined by radiograph In 66 root canals with irreversible pulpitis, 16 cases were overfilled, 11 cases were flush and 39 cases were underfilled. In 53 cases with apical periodontitis, 28 cases were overfilled, 10 cases were flush and 15 cases were underfilled. 2: Clinical discomfort was experienced in 10 cases with irreversible pulpitis and in 3 cases with apical periodontitis. However, most of the discomfort was of a mild degree and disappeared within a week. 3: At the last observation, a high frequency of closure of the root apex was observed by radiograph. Cases with apical periodontitis tend to have a slight delay in inducing closure of the root apex compared with cases with irreversible pulpitis. However, after 540 days, closure of the root apex was observed in all cases. 4: Clinical and radiographic findings show that in 33 cases with irreversible pulpitis, 23 cases were good, 9 cases were fair and 1 case was poor. On the other hand, in 38 cases with apical periodontitis, 35 cases were good, 2 cases were fair and 1 case was poor.Editor, Toshiyuki KawakamiLanguage Editor, David M Carlsonviii, 232 p. ill. (some col.

Chapter 7 : Clinical and Radiographic Examinations of Pulpectomy in Deciduous Teeth

Clinical and radiographic examinations were done on 163 deciduous teeth treated with a root canal filling material called Vitapex, which contains calcium hydroxide and iodoform. Anesthesia was administered, followed by pulp extirpation and immediate root canal filling, with observation for 5 to 1307 days. The following results were obtained. 1: Excessive bleeding during pulp extirpation seemed to adversely affect the overall clinical and radiographic results. The poor clinical condition of the pulp resulted in a higher incidence of poor results based on radiographs. 2: Deciduous teeth are susceptible to overfilling after a certain period due to root resorption. A higher incidence of good pathological scores was obtained when the root canal filling was flush, not overfilled. Radiographs confirmed resorption of excess root canal filling material in all cases. 3: During the observation period, root canal filling materials were in a stable condition and only few roots exhibited resorption. Root resorption occurred earlier or at the same time as the resorption of root canal filling material. 4: During the observation period, eruption of the succeeding permanent teeth was observed in 18 cases. In 12 out of 18 cases, eruption of the succeeding tooth did not occur at the same time as on the contralateral side (control). In 6 out of 12 cases, eruption of the succeeding permanent tooth was earlier than on the contralateral side but in 4 out of 12 cases, a delay in the replacement was observed. Also, 2 cases were replaced almost immediately. 5: During the observation period, pathological root resorption was observed in cases where root canal filling material was rapidly resorbed. 6: Until the last observation day, 127 out of 163 cases (77.9%) showed no clinical discomfort or adverse radiographic findings and only 36 out of 163 cases (22.1%) showed some discomfort. 7: Signs and symptoms observed in the study were the following: 5 cases of spontaneous pain, 3 cases of pain during mastication, 10 cases of pain on percussion, 3 cases of gingival swelling, 1 case of redness, 1 case of tenderness, 3 cases of fistula and 3 cases of drainage. Discomfort was felt from the 1st to 3rd day after treatment and was mostly of a mild degree. 8: Radiographic findings of those with clinical discomfort were the following: 2 cases with loss of lamina dura, 12 cases with incomplete resorption, 8 cases with root resorption and 5 cases with pathological lesion. 9: In 36 cases with clinical discomfort and adverse radiographic findings, 12 cases (33.3%) had clinical discomfort only, 17 cases (47.2%) had clinical discomfort associated with adverse radiographic findings and 7 cases (19.5%) were asymptomatic but with adverse radiographic findings. Adverse radiographic findings were observed in 13 out of 91 cases (14.3%) in anterior and 23 out of 72 cases (31. 9%) in posterior teeth. The clinical diagnosis of cases with adverse radiographic findings was observed in the most infectious pulpitis particularly acute suppurative pulpitis and chronic hyperplastic pulpitis. 10: The overall clinical and radiographic results obtained in the study were the following: out of 163 cases, 127 obtained good results (77.9%) and 25 cases were fair (15.3%) for a total of 93. 2% had satisfactory results. Only 11 cases had poor results (6. 8%). In 151 cases with stable periodontal tissue condition from the radiograph, 117 cases obtained good results (77. 5%), 23 cases were fair (15. 2%) and 11 cases were poor (7. 3%). Resorption of about 1/4 to 2/3 of the root occurred in 12 cases, in which 10 cases obtained good results (83.3%), 2 cases were fair (16.7%) and none of the cases was classified as poor. Root canal filling immediately after anesthesia and pulp extirpation in cases with advanced root resorption was thought to be significant. 11: There was no change in the condition of the root in 92 cases until the last observation day. In 92 cases, 72 cases obtained good results (78.3%), 9 cases were fair (9.8%) and 11 cases were poor (11. 9%). The remainder of the 59 cases with root resorption became stable within the observation period. In 59 cases, 45 cases obtained good results (76.3%), 14 cases were fair (23.7%) and no case was classified as poor. Vitapex employed in root canal filling of deciduous teeth mostly did not induce clinical signs and symptoms, and adverse radiographic findings as well as affecting physiological root resorption confirming that this is an excellent root canal filling material.Editor, Toshiyuki KawakamiLanguage Editor, David M Carlsonviii, 232 p. ill. (some col.

Exponential behavior of a quantum system in a macroscopic medium

An exponential behavior at all times is derived for a solvable dynamical model in the weak-coupling, macroscopic limit. Some implications for the quantum measurement problem are discussed, in particular in connection with dissipation.Comment: 8 pages, report BA-TH/94-17

A Coherent Understanding of Solvable Models for Quantum Measurement Processes

By making use of Schwinger's oscillator model of angular momentum, we put forward an interesting connection among three solvable Hamiltonians, widely used for discussions on the quantum measurement problem. This connection implies that a particular macroscopic limit has to be taken for these models to be physically sensible.Comment: 10 pages, report BA-TH/93-14

Macroscopic limit of a solvable dynamical model

The interaction between an ultrarelativistic particle and a linear array made up of $N$ two-level systems (^^ ^^ AgBr" molecules) is studied by making use of a modified version of the Coleman-Hepp Hamiltonian. Energy-exchange processes between the particle and the molecules are properly taken into account, and the evolution of the total system is calculated exactly both when the array is initially in the ground state and in a thermal state. In the macroscopic limit ($N \rightarrow \infty$), the system remains solvable and leads to interesting connections with the Jaynes-Cummings model, that describes the interaction of a particle with a maser. The visibility of the interference pattern produced by the two branch waves of the particle is computed, and the conditions under which the spin array in the $N \rightarrow \infty$ limit behaves as a ^^ ^^ detector" are investigated. The behavior of the visibility yields good insights into the issue of quantum measurements: It is found that, in the thermodynamical limit, a superselection-rule space appears in the description of the (macroscopic) apparatus. In general, an initial thermal state of the ^^ ^^ detector" provokes a more substantial loss of quantum coherence than an initial ground state. It is argued that a system decoheres more as the temperature of the detector increases. The problem of ^^ ^^ imperfect measurements" is also shortly discussed.Comment: 30 pages, report BA-TH/93-13

Emergence of a Wiener process as a result of the quantum mechanical interaction with a macroscopic medium

We analyze a modified version of the Coleman-Hepp model, that is able to take into account energy-exchange processes between the incoming particle and the linear array made up of $N$ spin-1/2 systems. We bring to light the presence of a Wiener dissipative process in the weak-coupling, macroscopic ($N \rightarrow \infty$) limit. In such a limit and in a restricted portion of the total Hilbert space, the particle undergoes a sort of Brownian motion, while the free Hamiltonian of the spin array serves as a Wiener process. No assumptions are made on the spectrum of the Hamiltonian of the spin system, and no partial trace is computed over its states. The mechanism of appearance of the stochastic process is discussed and contrasted to other noteworthy examples in the literature. The links with van Hove's ``$\lambda^2 T$ limits are emphasized.Comment: 20 pages, LaTeX, no figure

Reflection and Transmission in a Neutron-Spin Test of the Quantum Zeno Effect

The dynamics of a quantum system undergoing frequent "measurements", leading to the so-called quantum Zeno effect, is examined on the basis of a neutron-spin experiment recently proposed for its demonstration. When the spatial degrees of freedom are duely taken into account, neutron-reflection effects become very important and may lead to an evolution which is totally different from the ideal case.Comment: 26 pages, 6 figure