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Isolated lumbar disk resorption as a cause of nerve root canal stenosis.

In established isolated disk resorption at the lumbo-sacral junction, nerve root canal stenosis affects predominantly the S1 nerve which becomes obstructed between the inner margin of the superior facet of S1 and the buckled ligamentum flavum behind and by the ridge of the remaining annular fibers in front. However, in addition, there may also be an intervertebral foramen stenosis involving the L5 nerve at this level. Accordingly, in planning the surgical treatment of this condition where bilateral buttock and leg pain has become intractable or frequently recurrent, and where back pain is not major concomitant of the symptom complex, the surgeon must remove the inner and superior margins of the S1 facet together with the whole of the ligamentum flavum, thereby decompressing both L5 and S1 nerve roots. The operation involves a partial facetectomy only at the affected level and spinal stability is not impaired.

Bone Resorption↗

Effect of immediate calcium hydroxide treatment and permanent root-filling on periodontal healing in contaminated replanted teeth.

The effect of immediate permanent root-filling and immediate intracanal calcium hydroxide treatment on experimentally contaminated and necrotized periodontal membranes (PDM) in avulsed and subsequently replanted monkey teeth was studied. Almost the entire root surface in the non-endodontically treated control teeth were covered with inflammatory resorption. A significant shift towards ankylosis not associated with root resorption (greater than 80% of the total root surface area) was noted following calcium hydroxide treatment. About two thirds of the root surfaces from the teeth with permanent root fillings showed surface resorptions or ankylosis preceded by root resorption. The root surface area which would have been covered by inflammatory resorption, unless endodontic treatment had been implemented, were instead predominantly covered by either surface resorption (permanent root filling) or ankylosis (calcium hydroxide treatment). Ankylosis compared with surface resorption may in the long term lead to progressive loss of root substance due to replacement resorption. It was concluded that calcium hydroxide may be an excellent initial intracanal treatment in teeth with healthy PDM, but care should be taken not to risk unnecessary development of ankylosis by prolonged treatment of teeth with compromised PDM.

Alveolar Process↗

Resorption of incisors after ectopic eruption of maxillary canines: a CT study.

The purpose of the study was to analyze the extent and prevalence of resorption of maxillary incisors after ectopic eruption of the maxillary canines in a sample of subjects referred to an orthodontic specialist clinic for consultation. The subjects consisted of 107 children, 39 boys and 68 girls, between 9 and 15 years of age (mean 12.5 years), with 156 ectopically and 58 normally erupting maxillary canines. All children were subjected to a basic clinical and intraoral radiographic investigation. These radiographs were supplemented with computerized tomography (CT) of the upper alveolar bones in order to get more precise information on the positions and relationships between the maxillary canines and adjacent incisors and to evaluate resorptions on the roots of the incisors. The results showed that, relative to the roots of the adjacent incisors, the crowns of 21% the ectopically positioned canines were located to the buccal, 18% to the distobuccal, 27% to the lingual, 23% to the distolingual, 5% apically and 6% between the central and lateral incisors. Ninety-three percent of the ectopically positioned canines were in contact with the roots of the adjacent lateral incisor and 19% were in contact with the central incisor. The corresponding figures for the normally erupting canines were 49%. Resorptions on the roots of the incisors adjacent to the ectopically positioned canine occurred in 38% of the laterals and in 9% of the centrals. The resorptions were graded and tended to be extensive. Among the 58 resorbed lateral incisors, resorptions were slight in 31%, moderate in 9%, and severe with pulpal involvement in 60%. The corresponding figures for the 14 resorbed centrals were 36%, 21%, and 43%, respectively. About 60% of the resorptions involved the middle and apical thirds, the tip of the apex not included. On the sides with normally erupting canines, 3 lateral maxillary incisors were slightly or moderately resorbed distally. In all, 51 of the 107 subjects with ectopically erupting maxillary canines (48%) had resorbed maxillary incisors during the eruption of the maxillary canines. There were statistically significant correlations between ectopic eruption of the maxillary canine, contacts between the teeth and resorptions on the adjacent incisors. It was concluded that resorption on maxillary incisors after ectopic eruption of the maxillary canines is a more common phenomenon than previously reported and has to be considered in all cases with seriously diverging eruption of maxillary canines. It was also concluded that the resorptions of the roots of the incisors were caused by pressure during the eruption of the adjacent, aberrant canine. Finally, it was shown that CT scanning substantially increased the detection of root resorptions on incisors adjacent to ectopically erupting maxillary canines (about 50%). The sensitivity of intraoral films was low when diagnosing the resorptions, being calculated to 0.68.

Adolescent↗

Healing following devitalization of sites within the periodontal ligament by ultralow temperatures.

Healing of specific rat periodontal ligament (PDL) sites following freezing injury was monitored histologically to evaluate repair potentials of this tissue. Buccal alveolar plates supporting the first mandibular molar in 15 adult rats were surgically exposed. The coronal 3 mm of plate covering the buccal surface of the mesiobuccal root and underlying periodontal ligament and cementum were subjected to ultralow temperature using a gas expansion micro/cryoprobe, diameter 2 mm, cooled to -81 degrees C for 5 seconds. Tissues were repositioned and sutured in layers. Animals were sacrificed at 1, 24 and 72 hours and at 2, 5 and 7 weeks following surgery and mandibles removed for histologic analysis. Microscopic evaluation of 24-hour specimens showed loss of cellular vitality in the PDL, adjacent bone and cementum at experimental sites. Cellularity of the gingiva coronal to the crest, and of the PDL apical to the experimental zone, appeared to be within normal limits. Transition between experimental and nonexperimental sites was abrupt. After 72 hours cells from the PDL and gingiva appeared to migrate into and repopulate the noncellular PDL. Few capillaries surrounded by mesenchymal cells and limited polymorphonuclear neutrophil infiltration were observed within the injured PDL site. Marginal gingival inflammation was minimal. At 14 days, collagen lysis, resorption of alveolar bone and root resorption were evident. In the PDL space, nonfunctionally oriented, cellular connective tissue elements were abundant. At 5 and 7 weeks, root resorption was marked. At this time interval, osteogenesis at seams of nonvital bone, repair cementum at sites of root resorption, and at times, ankylosis, were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Process↗

Hypothermic insult to the periodontium: a model for the study of aseptic tooth resorption.

The aim of the current investigation was to define an animal model for the study of hard tissue resorption by examining the responses of the periodontal ligament (PDL) to both single and multiple episodes of hypothermic injury to the crowns of rat teeth. A group of 12 male rats weighing 200-250 g were anesthetized, and pellets of dry ice (CO2) were applied once to the crowns of the right first maxillary molars for continuous periods of 10 or 20 min. Animals were sacrificed at 2, 7, 14 and 28 days and tissues were processed for routine histological examination. A second group of eight animals and a third group of 12 animals were subjected to three applications of dry ice over a period of 1 week and sacrificed at 2 and 14 days respectively after the final application. In addition to thermal insult, the periodontium of teeth from a fourth group of six rats was subjected to mechanical trauma. Examination of the sections from the group undergoing a single freezing episode revealed that, by 1 week, shallow resorption lacunae had appeared on the root surface. These became more extensive after 14 days. At the same time hyaline degeneration was evident in the PDL. Within this group, teeth subjected to the longer 20-min application times generally showed more extensive injuries. By 28 days, evidence of repair was observed with reparative cementum beginning to line the resorption lacunae in the root dentin. Sections from animals subjected to multiple episodes of thermal trauma and those subjected to additional mechanical insult showed more extensive external root resorption than those from single-injury animals. It was concluded that low temperature stimuli applied to the crowns of rat molars were capable of eliciting a sterile degenerative response in the PDL which, in turn, resulted in external root resorption. Furthermore, the degree of this tissue injury was commensurate with the duration and number of exposures to the trauma. The results also indicated that progression of the resorptive process required periodic exposure to the injury, in the absence of which repair to the damaged root occurred.

Animals↗

Analysis of the healing response to gutta-percha and Diaket when used as root-end filling materials in periradicular surgery.

AIM: To analyse the healing response to gutta-percha and Diaket when used as root-end filling materials in periradicular surgery. METHODOLOGY: Periradicular surgery was completed using the mandibular second, third and fourth premolar teeth from nine male mongrel dogs. The six roots on one side of the mouth were randomly allocated to one of the following groups: group A: a resected root end and a burnished gutta-percha root filling; group B: cavities were prepared to a depth of 4.0 mm, using ultrasonic root-end preparation and filled with Diaket. The response was evaluated histologically at 55 (nine specimens) and 150 (three specimens) days post operatively. RESULTS: The data for the 55-day period was analysed statistically using Wilcoxon's Signed Ranks test. No statistical analysis was carried out on the 150-day group due to the small number of specimens. The level of significance was set at P < 0.05. No statistical significance was observed in the healing response between Diaket and gutta-percha in the following categories at 55 days: inflammatory response, angiogenesis, root-end resorption, and cementum deposition. Statistically significant differences were observed in the healing categories: bone apposition (P < 0.05) and periodontal ligament formation (P < 0.05). CONCLUSIONS: At both time intervals, Diaket had a better healing response that was characterized by hard tissue formation adjacent to the root-end filling material bordered by occasional multinucleated giant cells. The nature of both the hard tissue formation and the adjacent cells, however, remains undetermined. Diaket displayed the best healing of either material used in this study.

Animals↗

The effect of citric acid treatment on periodontal healing after replantation of permanent teeth.

The aim of this study was to evaluate the effect of surface demineralization on the healing of 120 replanted teeth in fifteen 8- to 16-month-old dogs. Replanted teeth were divided into two groups (A and B). In group A, teeth were replanted following planing of the entire root surface. In group B, teeth were replanted following planing and surface demineralization with citric acid. Replanted teeth were splinted for 7 days, and observation periods were 3, 14 and 56 days. A total of 95 teeth and their surrounding tissues were examined histologically under a light microscope. Histological examination of specimens 3 days after replantation revealed that initial reunion between the root and the alveolar periodontal ligament fibres was via a fibrin-like network in both groups. Fourteen days after replantation histological observations showed superior healing in group B with regard to epithelial condition, periodontal ligament fibre reattachment to the root surface, resorption and functional arrangement of the periodontal ligament fibres. By 56 days after replantation, healing was superior in group A; group B was characterized by severe inflammatory and replacement resorption. These results indicated that surface demineralization had an initial positive effect, but later led to impaired healing.

Animals↗

Three-dimensional finite element analysis and comparison of stress distribution in overdentures supported with bar attachments and telescopic crowns.

OBJECTIVE: To determine which one of the overdenture (OD) retainers was more beneficial to the abutments--the bar or the telescopic crown--and if a tooth could be used as an OD abutment when the supporting bone decreased to half of the root. MATERIALS AND METHODS: The three-dimensional finite element method was used to investigate the stress distribution in a mandible with an overdenture supported by the roots of two canines. The two teeth were either connected with a bar attachment or restored with telescopic crowns, and were then restored with a complete overdenture. For each type of superstructure, the influence of bone height around the roots (no alveolar resorption and resorption to half of the root length) was analyzed under three loading conditions. RESULTS: The most extreme stress values were located at the alveolar ridge crest of the bone around the root of the abutment. In the case of anterior loading, the largest compressive stress (LCS) in telescopic crown overdenture (TOD) was lower. When loaded posteriorly there was no obvious difference between bar attachment overdenture (BOD) and TOD. At the alveolar ridge crest around the root of the abutment, the stress value in the model with decreased bone level was higher than in the model with normal bone level, but the range was not significant. CONCLUSION: 1. In terms of stress in the alveolar bone, complete overdenture over telescopic crowns is more convenient than over bar attachments. 2. Stress increases as the height of the bone around the roots decreases, but the increment is less than 30%. It is important for an abutment with bone resorption to perform root amputation to obtain an acceptable crown/root ratio.

Alveolar Bone Loss↗