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Experimental investigation of the aesthetic effect of various tooth positions after loss of an incisor tooth.
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[Bad news for tooth restoration. Comment on J. Würz, M. Johner and O. Pohler's "Tooth rebuilding with nonprecious metal-containing screws and posts" (Schweiz, Mschr. Zahnheilk. 89: 1162, 1979)].
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[January 1940, Volume 50/No. 1, Schweizerische Monatsschrift für Zahnheilkunde: The question of tooth extraction in the treatment of tooth arrangement anomalies. By Rudolf Hotz].
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[A study on tooth marks--on the reproducibility and identification of tooth marks by means of a three-dimensional measuring instrument].
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[Effect of the tooth contour on gingival health. 1. Buccal contour and overlap of the natural tooth].
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[Bridge preparation for the front tooth: morphological structure and formation of abutment tooth].
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A clinical investigation of the efficacy of a tooth-whitening gel.
The objective of this randomized, controlled, examiner-blind, parallel-group clinical study was to determine whether a tooth-whitening gel (Colgate Simply White Night Clear Whitening Gel) can significantly lighten teeth when used once daily at night, as compared with a commercially available dentifrice. Following a baseline tooth shade evaluation using the VITA Shade Guide, qualifying adult male and female subjects from the Buffalo, New York area were randomized into 2 treatment groups, which were balanced for baseline VITA Shade Guide scores, gender, and age. The treatment groups were: (1) a commercially available dentifrice only; and (2) a tooth-whitening gel in addition to a commercially available dentifrice. Subjects assigned to the 2 groups were given the dentifrice and a soft-bristled toothbrush. In addition, subjects in one of the groups were given the tooth-whitening gel. All subjects were instructed to brush their teeth for 1 minute twice daily (morning and evening) with the dentifrice. The subjects in the group also using the tooth-whitening gel were further instructed to apply the gel once daily at night, as per manufacturer instructions. Evaluations of tooth shade for each subject were repeated after 2 weeks, and again after 3 weeks of product use. In addition, evaluations of tooth shade for subjects using the tooth-whitening gel were later conducted at 6 months after product use. Seventy-five subjects complied with the protocol and completed the study. At the 2-week and 3-week examinations, subjects using the tooth-whitening gel and dentifrice exhibited statistically significant (P < .05) tooth shade lightening relative to baseline tooth shade. Furthermore, at the 2-week and 3-week examinations, subjects using the tooth-whitening gel exhibited statistically significant (P < .05) tooth shade lightening relative to subjects using only the dentifrice. In addition, the 6-month-postuse examination showed that subjects using the tooth-whitening gel exhibited statistically significant (P < .05) tooth shade lightening relative to baseline, thereby maintaining the tooth shade lightening that was evident at 3 weeks. The results of this clinical study indicate that after once-daily use at night for 2 or 3 weeks, the tooth-whitening gel provided statistically significant tooth shade lightening relative to baseline tooth shade for up to at least 6 months and also provided statistically significant tooth shade lightening relative to a commercially available dentifrice after 2 and 3 weeks of product use.
Tooth wear patterns in the deciduous dentition.
Tooth wear is common in the deciduous dentition. A recent study suggests that tooth wear in the deciduous dentition is related to subsequent tooth wear in adults, so that early identification of factors related to tooth wear could be of long-term benefit. The purposes of this study were to describe patterns of tooth wear in the deciduous dentition and to relate tooth wear to occlusal characteristics and longitudinal dietary patterns. Data were collected as part of a longitudinal study of a cohort of children recruited at birth from Iowa hospitals. Stone casts were obtained in the deciduous dentition stage, and 355 children, 4 to 5 years old, met the selection criteria. Tooth wear was categorized for each tooth as none, mild, moderate, or severe, and related to occlusal characteristics and longitudinal data on fruit juice and soft drink consumption. All children exhibited some tooth wear on at least 1 tooth, and nearly 16% of them had at least 1 tooth with severe wear. Tooth wear was generally more severe in the maxillary arch and the anterior teeth. Severe tooth wear on the molars was significantly related to posterior crossbites, but severe tooth wear on the incisors was related to Class III canine relationships. There were no statistically significant relationships between tooth wear and soft drink or fruit juice consumption. Based on our results, we concluded that mild tooth wear is universal in the deciduous dentition, but only a few occlusal factors are related to severe tooth wear. Tooth wear was not related to any dietary patterns we investigated.
[A study of root resorption of deciduous teeth in dogs. Influence of successional tooth germ and occlusal force].
The role of successional tooth germ and occlusal force in root resorption of mandibular second deciduous molars was studied in 24 beagle dogs by means of radiographic and histologic evaluations. 70 days after birth their mandibular right third permanent premolar germs were surgically removed, and in 10 of the dogs the maxillary right and left second deciduous molars were extracted to decrease the occlusal force on the mandibular second deciduous molars. 1) When successional tooth germs were present, whether the occlusal force was normal or decreased, the alveolar bone and deciduous tooth adjacent to the tooth germ were resorbed, accompanied by eruption of the permanent tooth. After the resorption of the deciduous tooth reached half of the root, many odontoclasts were observed in the dental pulp of the deciduous tooth. The root resorption was hastened by internal resorption. 2) When successional tooth germs were removed, whether the occlusal force was normal or decreased, the root resorption was delayed. The resorption from the root surface progressed very slowly, but shortly after this resorption reached the pulp, internal resorption occurred and the deciduous tooth was resorbed in short time. 3) When the occlusal force was decreased, in the deciduous teeth in which successional tooth germs were present, the tooth resorption tended to delay to a later time. However in the deciduous teeth from which the successional tooth germs were removed, the processes of tooth resorption was very different in individuals, the difference between tooth resorption in normal occlusal force and in decreased occlusal force was not clear. 4) In all groups, shallow resorption on the deciduous root surface was observed before the successional tooth started to erupt, and this resorption was apart from the tooth germ. By repeating resorptive periods and resting periods, this resorption progressed according to the increase in age, and in the resting period, resorption was repaired by new deposits of cementum.
Tissue-engineered hybrid tooth and bone.
Tooth loss accompanied by alveolar bone resorption presents a significant clinical problem. We have investigated the utility of a tissue-engineering approach to provide corrective therapies for tooth-bone loss. Hybrid tooth-bone tissues were bioengineered as follows. Tooth implants were generated from pig third molar tooth bud cells seeded onto polyglycolide (PGA) and polyglycolide-colactide (PLGA) scaffolds, and grown for 4 weeks in the omenta of adult rat hosts. Bone implants were generated from osteoblasts induced from bone marrow progenitor cells obtained from the same pig, seeded onto PLGA fused wafer scaffolds, and grown for 10 days in a rotational oxygen-permeable bioreactor system. The tooth and bone implants were harvested, sutured together, reimplanted, and grown in the omenta for an additional 8 weeks. Histological and immunohistochemical analyses of the excised hybrid tooth-bone constructs revealed the presence of tooth tissues, including primary and reparative dentin and enamel in the tooth portion of hybrid tooth-bone implants, and osteocalcin and bone sialoprotein-positive bone in the bone portion of hybrid tooth-bone constructs. Collagen type III-positive connective tissue resembling periodontal ligament and tooth root structures were present at the interface of bioengineered tooth and bone tissues. These results demonstrate the utility of a hybrid tooth-bone tissue-engineering approach for the eventual clinical treatment of tooth loss accompanied by alveolar bone resorption.
The potential prognostic value of some periodontal factors for tooth loss: a retrospective multilevel analysis on periodontal patients treated and maintained over 10 years.
BACKGROUND: The great challenge in clinical periodontology is assigning a prognosis to a periodontally affected patient. Many different factors can affect the long-term maintenance of periodontally compromised teeth. The main questions usually considered by the periodontist are: 1) Will a tooth lose more bone in the future? 2) Will the tooth itself be lost in the future? The purpose of this retrospective study was to evaluate the value of some clinical, genetic, and radiographic variables in predicting tooth loss in periodontal patients (aged 40 to 60 years) treated and maintained for 10 years. METHODS: Sixty consecutive non-smoking patients (aged 46.77 +/- 4.96 years) with moderate to severe chronic periodontitis (CP) were treated with scaling and root planing (SRP). Some patients also underwent additional surgical treatments. All patients were maintained in the same private practice for 10 years. The frequency of recall appointments was 3.4 +/- 1.0 months. At baseline (T(0)) and 10 years later (T(2)) the following clinical variables were evaluated: the number of teeth, probing depths (PD), tooth mobility (TM), and presence of prosthetic restorations (PR). In addition, radiographic measurements were taken of the mesial and distal distances from the cemento-enamel junction (CEJ) to the bottom of the defect (BD), to the bone crest (BC), and to the root apex (RA). At T(2), a genetic test to determine the IL-1 genotype and genetic susceptibility for severe periodontal disease was performed for all 60 patients, and they were classified as IL-1 genotype positive (G+) or negative (G-) according to the test results. Tooth loss was used as the outcome variable. Different predictor variables were then tested using a two-level statistical model (patient and tooth levels). At the patient level, these were: age, gender, mean bone loss (mean CEJ-BD)(T0), the interleukin-1 (IL-1) genotype, the interaction between mean bone loss, and IL-1 genotype (mean CEJ-BD(T0) x IL-1 genotype). At the tooth level, the variables were: TM(T0), prosthetic restorations (PR)(T0), molar teeth (MT)(T0), the infrabony component of the defect (BC-BD)(T0), PD(T0), bone level (CEJ-BD)(T0), and residual supporting bone (BD-RA)(T0). RESULTS: Among the considered predictor variables, the following were significantly associated with the outcome variable: 1) MT(T0) (P <0.0001); 2) BC-BD(T0) (P = 0.0377); and 3) BD-RA(T0) (P <0.0001). MT(T0) were found to be more prone to loss and the amount of BD-RA(T0) prognostic for tooth loss: the lower the residual amount of supporting bone, the higher the probability of tooth loss. Conversely, the BC-BD(T0)was associated with a reduced probability of future tooth loss: the greater the infrabony component, the lower the probability of tooth loss. None of the other considered predictors proved predictive for tooth loss. CONCLUSIONS: Within the scope of this study, many traditional prognostic factors were ineffective in predicting future tooth loss and, therefore, were of no prognostic value. Conversely, a few specific factors at the tooth level emerged as viable prognostic factors. The use of these factors may be of great value to practitioners as predictors of tooth loss when assigning a prognosis.
Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth.
STATEMENT OF PROBLEM: A restored endodontically treated tooth is less likely to fracture when there is axial tooth structure between the core base and preparation finish line. However, an accurate prognosis requires knowing whether fracture resistance depends on a complete circumferential distribution of tooth structure or tooth structure in a specific location related to the applied force. PURPOSE: This in vitro study investigated the fracture resistance of restored endodontically treated teeth when residual axial tooth structure was limited to one half the circumference of the crown preparation. MATERIAL AND METHODS: Fifty extracted maxillary anterior teeth were sectioned 18 mm from their apices, endodontically treated, and divided into 5 groups of 10 teeth each. Four groups were prepared with full shoulder crown preparations having axial wall heights of 2 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, one half of the axial tooth structure was removed, palatally, labially, or proximally, and groups were identified according to the site of retained coronal tooth structure. For the fifth group, all axial tooth structure was removed to the level of the preparation shoulder. Thus, in 1 group the axial walls were circumferential, 360 degrees around the preparations (Complete group), in 3 groups the axial walls were continuous for 180 degrees (Palatal, Labial, and Proximal groups), and the last group had no retained coronal tooth structure incisal to the finish line (Level group). All 50 prepared teeth were then restored with quartz fiber posts (Bisco), composite resin (Bisco) cores, and metal crowns. A universal testing machine compressively loaded the tooth specimens from the palatal at a crosshead speed of 0.5 cm/min at an angle of 135 degrees to the long axis of teeth until failure occurred. A survival analysis was conducted using a log-rank test followed by Holm-Sidak pairwise tests (alpha=.05) to detect significant differences in median failure load between groups. The mode of failure was determined by visual inspection of all specimens. RESULTS: The median failure load (P<.001) was 607 N, 782 N, 358 N, 375 N, and 172 N for the Complete, Palatal, Labial, Proximal, and Level groups, respectively. The predominant mode of failure was an oblique palatal to facial root fracture for the groups with remaining coronal tooth structure. In the Level group, post debonding was the predominant mode of failure. CONCLUSION: For restored endodontically treated teeth that do not have complete circumferential tooth structure between the core and preparation finish line, the location of the remaining coronal tooth structure may affect their fracture resistance.
Dentition and tooth replacement pattern in Chalcides (Squamata; Scincidae).
This study was undertaken as a prerequisite to investigations on tooth differentiation in a squamate, the Canarian scincid Chalcides. Our main goal was to determine whether the pattern of tooth replacement, known to be regular in lizards, could be helpful to predict accurately any stage of tooth development. A growth series of 20 laboratory-reared specimens, aged from 0.5 month after birth to about 6 years, was used. The dentition (functional and replacement teeth) was studied from radiographs of jaw quadrants. The number of tooth positions, the tooth number in relation to age and to seasons, and the size of the replacement teeth were recorded. In Chalcides, a single row of pleurodont functional teeth lies at the labial margin of the dentary, premaxillary, and maxillary. Whatever the age of the specimens, 16 tooth positions were recorded, on average, in each quadrant, suggesting that positions are maintained throughout life. Replacement teeth were numerous whatever the age and season, while the number of functional teeth was subject to variation. Symmetry of tooth development was evaluated by comparing teeth two by two from the opposite side in the four jaw quadrants of several specimens. Although the relative size of some replacement teeth fitted perfectly, the symmetry criterion was not reliable to predict the developmental stage of the opposite tooth, whether the pair of teeth compared was left-right or upper-lower. The best fit was found when comparing the size of successive replacement teeth from the front to the back of the jaw. Every replacement tooth that is 40-80% of its definitive size is followed, in the next position on the arcade, by a tooth that is, on average, 20% less developed. Considering teeth in alternate positions (even and odd series), each replacement tooth was a little more developed than the previous, more anterior, one (0.5-20% when the teeth are from 10-40% of their final size). The latter pattern showed that tooth replacement occurred in alternate positions from back to front, forming more or less regular rows (i.e., "Zahnreihen"). In Chalcides, the developmental stage of a replacement tooth in a position p can be accurately predicted provided the developmental stage of the replacement tooth in position p-1 or, to a lesser degree, in position p-2 is known. This finding will be particularly helpful when starting our structural and ultrastructural studies of tooth differentiation in this lizard.
Morphological variations in a tooth family through ontogeny in Pleurodeles waltl (Lissamphibia, Caudata).
Most nonmammalian species replace their teeth continuously (so-called polyphyodonty), which allows morphological and structural modifications to occur during ontogeny. We have chosen Pleurodeles waltl, a salamander easy to rear in the laboratory, as a model species to establish the morphological foundations necessary for future molecular approaches aiming to understand not only molecular processes involved in tooth development and replacement, but also their changes, notably during metamorphosis, that might usefully inform studies of modifications of tooth morphology during evolution. In order to determine when (in which developmental stage) and how (progressively or suddenly) tooth modifications take place during ontogeny, we concentrated our observations on a single tooth family, located at position I, closest to the symphysis on the left lower jaw. We monitored the development and replacement of the six first teeth in a large growth series ranging from 10-day-old embryos (tooth I1) to adult specimens (tooth I6), using light (LM), scanning (SEM), and transmission electron (TEM) microscopy. A timetable of the developmental and functional period is provided for the six teeth, and tooth development is compared in larvae and young adults. In P. waltl the first functional tooth is not replaced when the second generation tooth forms, in contrast to what occurs for the later generation teeth, leading to the presence of two functional teeth in a single position during the first 2 months of life. Larval tooth I1 shows dramatically different features when compared to adult tooth I6: a dividing zone has appeared between the dentin cone and the pedicel; the pulp cavity has enlarged, allowing accommodation of large blood vessels; the odontoblasts are well organized along the dentin surface; tubules have appeared in the dentin; and teeth have become bicuspidate. Most of these modifications take place progressively from one tooth generation to the next, but the change from monocuspid to bicuspid tooth occurs during the tooth I3 to tooth I4 transition at metamorphosis.
Tooth structure removal associated with various preparation designs for anterior teeth.
STATEMENT OF PROBLEM: The conservation of sound tooth structure helps preserve tooth vitality and reduce postoperative sensitivity. Innovative preparation designs, like those for porcelain laminate veneers, are much less invasive than conventional complete-coverage crown preparations. However, no study has quantified the amount of tooth structure removed during these preparations. PURPOSE: The purpose of this study was to quantify and compare the amount of tooth structure removed when various innovative and conventional tooth preparation designs were completed on different teeth. MATERIAL AND METHOD: . A new comprehensive tooth preparation design classification system was introduced. Typodont resin teeth representing the maxillary left central incisor, maxillary left canine, and mandibular left central incisor were prepared with the following designs: partial (V1), traditional (V2), extended (V3), and complete (V4) porcelain laminate veneer preparations; resin-bonded retainer preparation with grooves (A1) and with wing/grooves (A2); all-ceramic crown preparation with 0.8 mm axial reduction and tapering chamfer finish line (F1), all-ceramic crown preparation with 1.0 mm axial reduction and rounded shoulder finish line (F2), and metal-ceramic crown with 1.4 mm axial reduction and facial shoulder finish line (F3). After tooth preparations (10 per group), the crown was separated from the root at the CEJ. The removed coronal tooth structure was measured with gravimetric analysis. Means and standard deviations for tooth structure removal with different preparation designs were calculated and analyzed with analysis of variance at a significance level of P<.05. RESULTS: Significant differences in the amount of tooth structure removal were noted between preparation designs. Ceramic veneers and resin-bonded prosthesis retainers were the least invasive preparation designs, removing approximately 3% to 30% of the coronal tooth structure by weight. Approximately 63% to 72% of the coronal tooth structure was removed when teeth were prepared for all-ceramic and metal-ceramic crowns. For a single crown restoration, the tooth structure removal required for an F3 preparation (metal-ceramic crown) was 4.3 times greater than for a V2 preparation (porcelain laminate veneer, facial surface only) and 2.4 times greater than for a V4 preparation (more extensive porcelain laminate veneer). CONCLUSION: Within the limitations of this study, tooth preparations for porcelain laminate veneers and resin-bonded prostheses required approximately one-quarter to one-half the amount of tooth reduction of conventional complete-coverage crowns.
Predicting tooth loss during a population-based study: role of attachment level in the presence of other dental conditions.
BACKGROUND: Our objectives were to quantify: 1) the association between incident tooth loss and prior periodontal attachment level; and 2) the contribution to tooth loss made by non-periodontal conditions in increasingly periodontally involved teeth. METHODS: The Florida Dental Care Study was a prospective cohort study of persons who at baseline had at least 1 tooth and were 45 years or older. In-person interviews and clinical examinations were conducted at baseline, and at 24 and 48 months, with telephone interviews at 6-month intervals in between. A regression model was used to simultaneously quantify tooth-specific predictors of tooth loss, with person-level factors taken into account. RESULTS: Of the 687 persons who participated for a 48-month clinical examination, 36% lost 1 or more teeth during follow-up, and 5.0% of all teeth were lost. Attachment level up to 2 years before tooth loss was strongly predictive of incident tooth loss, with increases in risk for each millimeter in attachment loss. Certain other tooth-specific conditions (tooth mobility, bulk restoration fracture, decayed surfaces, filled surfaces, tooth type and arch location, root fragment) were strongly and independently associated with increased risk for tooth loss, while others were not (prosthetic crown coverage, cusp fracture, root surface defect). Propensity to choose extraction over other treatment alternatives, as reported by participants at baseline, was also strongly predictive of tooth loss. CONCLUSIONS: Increasingly severe attachment level was consistently associated with an increased risk for tooth loss in this sociodemographically diverse sample, with or without other tooth-specific conditions taken into account.
Tooth quality in dental fluorosis genetic and environmental factors.
Dental fluorosis (DF) affects the appearance and structure of tooth enamel and can occur following ingestion of excess fluoride during critical periods of amelogenesis. This tooth malformation may, depending on its severity, influence enamel and dentin microhardness and dentin mineralization. Poor correlation between tooth fluoride (F) concentration and DF severity was shown in some studies, but even when a correlation was present, tooth fluoride concentration explained very little of DF severity. This fact calls into question the generally accepted hypothesis that the main factor responsible for DF severity is tooth fluoride concentration. It has been shown previously that genetic factors (susceptibility to DF) play an important role in DF severity although DF severity relates to individual susceptibility to fluoride exposure (genetics), tooth fluoride concentration relates to fluoride ingestion (environmental). The objective of this study was to investigate the correlation between tooth fluoride concentration, DF severity, and tooth mechanical and materials properties. Three strains of mice (previously shown to have different susceptibility to DF) at weaning were treated with four different levels of F in their water (0, 25, 50, and 100 ppm) for 6 weeks. Mice teeth were tested for fluoride by instrumental neutron activation analysis (INAA), DF severity determined by quantitative light-induced fluorescence [QLF], and tooth quality (enamel and dentin microhardness and dentin mineralization). Tooth fluoride concentration (environment factor) correlated positively with DF severity (QLF) (rs=0.608), fluoride treatment group (rs=0.952). However, tooth fluoride concentration correlated negatively with enamel microhardness (rs=-0.587), dentin microhardness (rs=-0.268) and dentin mineralization (rs=-0.245). Dental fluorosis (genetic factor) severity (QLF) correlated positively with fluoride treatment (rs=0.608) and tooth fluoride concentration (rs=0.583). DF severity correlated negatively with enamel microhardness (rs=-0.564) and dentin microhardness (rs=-0.356). Genetic factors (DF severity) and the environmental factor (fluoride concentration in tooth structure) have similar influence on tooth biomechanical properties, whereas only the environmental factor has an influence on tooth material property (mineralization).