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The various proposed etiologies for root intrusion in tooth-implant combination cases are discussed. Clinical examples of root intrusion are illustrated. Advantages and disadvantages of nonrigid connector and coping/suprastructure techniques are presented.
Balancing the extraction of primary teeth is a procedure advocated to maintain symmetry of the developing dentition by encouraging symmetrical drift of teeth mesial and distal to the extraction sites on each side of the dental arch. Current opinion about this procedure expressed in standard reference works is confused and occasionally contradictory. Whilst some authorities cite specific situations where balancing extractions should be performed, others are less precise with their advice, and at least one considers that there is little justification for the procedure. Scientific evidence supporting the procedure is tenuous. The one study carried out specifically to compare dental centre line shift following unilateral or bilateral extraction of primary teeth showed greater shift in cases of unilateral (unbalanced) extractions. Other studies do not directly address the issue and such information as they offer is imprecise. Although the procedure of balancing extractions is strongly advocated by many clinicians, it is not based on definitive experimental evidence.
Recent publications have described a common belief, held in rural areas in Africa, that unerupted primary canines cause diarrhoea, vomiting and fever in infants. To relieve these symptoms a traditional native healer extracts these tooth buds. The emigration of Ethiopian Jews to Israel in 1991 allowed an investigation of this practice among this community. A group of 59 children (27 boys and 32 girls) aged 3-12 years were examined clinically and radiographically. Evidence was found of extraction of 63 primary canine buds in 35 (59%) of the children. Extraction of one canine was found in 16 children, two in 13 children and three in three children, and three children had all four canines extracted. Forty-six (74%) mandibular compared to only 16 (26%) maxillary canines had been extracted; the extractions were equally divided between both sides of the jaws. Another 19 primary canines had hypoplastic defects, probably the result of unsuccessful extractions. Associated dental abnormalities included hypoplasia of the permanent successors and adjacent primary and permanent teeth, displacement of permanent teeth, midline shift to the extraction side, missing primary lateral incisors (probably accidentally extracted) and distal eruption of permanent lateral incisors, leaving their primary predecessors retained. Parental enquiry revealed that the practice is more common in rural rather than urban areas and still exists in the Ethiopian community in Israel. The findings of this survey should urge the authorities to take steps to stop this practice.
Traumatic events at an early age may lead to developmental dental anomalies and ectopic tooth eruption. A case is reported in which a traumatic injury at two months of age resulted in the development of supernumerary teeth in the upper right premaxillary region. The maxillary canine ectopically erupted or transposed into the space left by the missing central incisor and eliminated the need for a prosthesis in this region.
Denture reduction in formal orthodontic treatment does not appear to prevent the impaction of lower third molars. The extraction of premolar teeth is best carried out as close as possible to the eruption time of the cuspids. The posterior part of the mandibular arch should be evaluated by the study of lateral oblique roentgenograms and one of several options regarding treatment should then be adopted.
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By using only a portion of the dental arch, rather than some geometric construction that conforms to the dental arch, more pertinent information can be gathered regarding the sequelae of some event or insult to the arch. The measurement, D E Space, has been explained and utilized to describe the effectss of unattended dental caries on arch form. Only caries which become severe have a significant effect on the dental arch--a reduction in D E Space, which can be interpreted as relative arch length (depth) and is significant only for the year after its exfoliation. This occurs one year early and is also significant.
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The results of this study show that positional changes occur in the mandibular third molar at least until 20 years of age. A significant number of mandibular third molars in young adults in positions of mesio-angular impaction attain an upright position in a year. A significant relationship exists between the initial age of the patient and the amount of change in the inclination of the third molar. Initial inclination is closely related to the change in inclination in mandibular third molars.
The laser reflexion method, a direct contactless measuring technique with a high accuracy, has been applied for clinical purposes. A prototype has been tested using a laser beam to illuminate a patient's tooth fixed to the equipment by an impression plate. The reflected patterns were thrown onto a screen with a coordinate system and photographically recorded, and the movement of the tooth has been geometrically calculated. The relapse tendency after orthodontic treatment of a patient with periodontal disease and parafunctions was studied by repeated measurements of the left medial upper incisor. By use of the method, it was possible to observe that the velocity of the studied tooth was highest during the 1st day and, besides the horizontal movement, a rotation of the tooth began at the end of the measuring period.
Histologic sections from six autopsy cases which from a clinical point of view fitted into the criteria of periodontosis were examined with the aim at evaluating the role of subgingival plaque in the etiology of the loss of attachment in this condition. The following pertinent observations were made: 1. The subgingival plaque in most instances was not calcified to form calculus. 2. The thickness of the subgingival plaque varied between 20 and 200 mu (0.02-0.2 mm). 3. Where loss of attachment had taken place, the distance from the most apical part of the subgingival plaque to the most apical point of the epithelial cuff varied between 0.2 and 1.1 mm; this distance was never found to be more than 1.1 mm. This would indicate a cause and effect relationship, the plaque being the obvious cause. 4. There was very severe chronic inflammation in the soft tissue bordering upon the plaque with resulting collagenolysis. 5. The cellular infiltration and the collagenolysis may be limited to a zone of 1 to 2 mm in the immediate vicinity of the plaque. Between the inflamed area and the surface of the gingivae buccally and lingually there may be a fairly wide zone of healthy tissue which hides the symptoms of inflammation from being observed on a clinical examination. In turn this could leave the clinician with the impression that attachment has been lost and bone resorbed because of degenerative changes. The following conclusions can be made: In these six cases of "alveolar bone loss vastly out of proportion to what one would expect from the local etiologic factors in the patient at that age" there was no morphologic evidence that degenerative changes were responsible for the loss of attachment. On the contrary inflammatory changes induced by the subgingval plaque dominated the histopathologic picture.
1. The subjective separation of the normal and the diseased periodontium for splinting purposes is artificial. With the exception of cases of secondary trauma from occlusion, the diseased periodontium should be treated in the same manner as the normal periodontium with regards to splinting. 2. Retionales for stabilization found to be valid are: I. Prevention of mobility A. Post acute trauma. B. In occlusal therapy. II. Prevention of drifting A. Replacement of missing teeth. B. Postorthodontics. III. In treatment of secondary trauma for occlusion. A. For functional stability. B. With unknown effects on the progression of periodontitis. 3. The relationship of trauma from occlusion and periodontitis is unclear at this time. 4. A need exists for a clinical test correlating histologic signs of trauma from occlusion and clinical findings. 5. Temporary splinting generally is not indicated during the initial or surgical phase of treatment of the periodontal patient, because mobility short of secondary trauma from occlusion does not impair healing.
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The purpose of this study was to investigate expression of type I collagen and bone sialoprotein (BSP) mRNAs in the alveolar bone accompanied with tooth movement. The right side of the upper jaw of the rat was used for orthodontic tooth movement, and the left side was used for physiological tooth movement. After the proper number of days of movement, histological specimens were decalcified and sliced into paraffin sections. The expression of mRNAs was examined by the in situ hybridization method. In the samples of physiological tooth movement, a high level of expression in both mRNAs was observed in osteoblasts along the mineralization front and adjacent osteocytes in the interradicular septum (IRS). In contrast, a low level of mRNA expression was observed on the opposite side of the IRS. In the specimens of experimental tooth movement, a high level of expression was detected in the osteoblasts on the tension side of IRS, but negligible reaction in those on the compression side. These results suggest that BSP gene expression as well as that of collagen are related not only to mineralization in physiological bone remodeling but also to the process by activated osteoblasts induced by orthodontic force. In addition, response to the artificial force was observed in osteocytes in IRS.