Supragingival calculus formation in a group of young adults

The presence of calculus was assessed on the lingual surfaces of the mandibular anterior teeth in a randomly selected group of 63 young adults. The rate of regrowth of calculus after professional prophylaxis was also observed. Twenty-two individuals had supragingival calculus on the mandibular lingual surfaces of their teeth at baseline. Eleven of these individuals demonstrated regrowth of calculus by the end of the study, in spite of repeated professional prophylaxis. Thus, 17.5% of subjects exhibited rapid regrowth of calculus on the mandibular lingual surfaces of their teeth within 2 weeks of professional prophylaxis.     

A study of anterior guidance

PURPOSE: This study focuses on the curvature and inclination of the lingual surfaces of the maxillary anterior teeth from the transition point on the cingulum to the incisal edge. MATERIALS AND METHODS: On 32 sets of mounted casts, 768 measurements were made of the curvature of the lingual surfaces utilizing radius gauges. The inclination of the lingual surface relative to the occlusal plane was recorded. The relationship of the incisal edge of the mandibular teeth to the transition point on the cingulum of the maxillary teeth was determined. Centric occlusion contact was noted on each tooth. RESULTS: Significant differences were found between the measured areas of any one tooth and between the types of teeth. The average radius ranged from 20.5 mm on the mesial ridge of the canine to 5.3 mm in the fossa of the central. The average inclination of the lingual surfaces was 46 degrees. In centric occlusion, 97% of the canines and 59% of the centrals and laterals were in contact with the opposing teeth. These contacts occurred 2.8 mm incisal to the transition point. The centrals contracted two opposing teeth (45%), and canines contacted one opposing tooth (53%). CONCLUSIONS: The function and curvature of the incisor teeth vary considerably from those of the canines. Overcontouring the lingual surfaces of the maxillary incisors to gain contact is not normal and may be detrimental.     

Testing for carcinogenicity of pharmaceuticals

When two-layered artificial teeth are used, acrylic resin occlusal parts can be removed from base parts and used directly as resin patterns for casting, which facilitates fabrication of metal occlusal surfaces. Because these teeth were made of acrylic resin, it was easy to modify occlusal morphology before converting to metal. Application of two-layered artificial teeth to achieve lingual contact occlusion brought about sufficient masticatory forces and denture stability and resulted in patient satisfaction.     

Anterior crowns in re-establishing vertical dimension of occlusion: overcoming fear of heights

The rejuvenation of this dentition is initiated with the placement of six anterior crowns. Re-establishing the vertical dimension has allowed the restoration of pleasing proportions to the centrals. This has led to the re-assertion of the dominance of the centrals and thus corrected the reverse smile line. The restoration of these teeth demands harmonious accommodation of the requirements of esthetics, phonetics and function. These considerations are inseparable and are in fact, determinants of each other. Esthetics and phonetics help determine the degree of vertical opening and incisal edge placement. This location influences anterior guidance, lingual and labial contours, the pitch of the anterior teeth and proper lip support. The principles of proportion, so important in esthetics, allow us, to calculate incisor length. Thus, function, phonetics and esthetics are intimately intertwined and enhance one another in the restoration of vertical dimension of occlusion.     

Recent research on calculus

This paper discusses the different types of calcium phosphate in calculus and the role of plaque pH in controlling calcium phosphate precipitation (calculus) or dissolution (caries). There is great site-specificity of deposition of supragingival but not subgingival calculus, with highest amounts of the former being present on the lingual aspects of the mandibular anterior teeth. This may be because the plaque there is most alkaline as that region has the highest salivary film velocity and the lowest salivary sugar concentration during consumption of sugar-containing food and drinks. The importance of calculus removal for good gingival health is emphasised.     

Root caries in a sample of elderly persons

With the anticipated increase in the aged adult population and the associated gingival recession, the prevalence of root caries is expected to increase. The purpose of this study was to determine the experience and distribution of root caries in a group of aged adults living in Kayelitsha. All non-institutionalized elderly black adults participating in a community geriatric programme were examined. Root caries was recorded using visual and tactile criteria and expressed as the root caries index (RCI) rate. The mean age of the subjects was 65.2 years, the mean number of teeth present was 17.3 and the mean RCI rate was 2.2 per cent. All subjects had gingival recession while only 23.8 per cent had root caries. No surfaces with restored root caries lesions were found. In the maxilla the highest RCI rate was observed on the interproximal surfaces of the posterior teeth (4.4 per cent) but in the mandible the buccal surfaces of the posterior teeth had the highest RCI rate (4.2 per cent). In both the maxilla and the mandible the lingual surfaces of the anterior teeth showed no root caries. Maxillary teeth did not have a significantly higher root caries attack rate than mandibular teeth. Root caries does not appear to be a public health problem in the sampled population.     

Long-term sealing efficacy of four root surface sealing materials used in endodontic leakage studies

Fifty extracted human maxillary anterior teeth were biomechanically instrumented and divided into five equal groups, four experimental and a control. The teeth in the experimental groups had their root surface coated with one of four sealants; epoxy, casting resin, sticky wax, or nail polish. The roots of the remaining teeth were not coated and served as controls. All of the teeth were mounted in the caps of scintillation vials. Five microliters of [3H]uridine were deposited in the root canal space and disintegration counts were obtained over time periods of 1, 4, 8, 12, and 36 wk. At the conclusion of the experiment, sticky wax was demonstrated to provide a superior seal (p < 0.0001).     

薄板铸机开浇冷齿形成的分析与解决

本钢炼钢厂薄板坯连铸机在开浇初期,特别是在低碳钢的生产时,结晶器内几乎每个浇次开浇时都会产生冷齿,由于薄板坯铸机拉速高,冷齿现象极易产生漏钢的事故,并产生7m左右的废坯,增加了生产成本。因此主要对能够引起冷齿的生产和设备各种相关的因素进行分析,并通过生产实践的方法找出最佳的解决办法。     

Preservation of alveolar bone in extraction sockets using bioabsorbable membranes

The purpose of this study was to evaluate the clinical effectiveness of a bioabsorbable membrane made of glycolide and lactide polymers in preserving alveolar ridges following tooth extraction using a surgical technique based on the principles of guided bone regeneration. Sixteen patients requiring extractions of 2 anterior teeth or bicuspids participated in the study (split-mouth design). Following elevation of buccal and lingual full-thickness flaps and extraction of teeth, experimental sites were covered with bioabsorbable membranes; control sites did not receive any membrane. Titanium pins served as fixed reference points for measurements. Flaps were advanced in order to achieve primary closure of the surgical wound. No membrane became exposed in the course of healing. Reentry surgeries were performed at 6 months. Results showed that experimental sites presented with significantly less loss of alveolar bone height, more internal socket bone fill, and less horizontal resorption of the alveolar bone ridge. This study suggests that treatment of extraction sockets with membranes made of glycolide and lactide polymers is valuable in preserving alveolar bone in extraction sockets and preventing alveolar ridge defects.     

A morphometric analysis of the furcation region of mandibular molars

This study examined furcation dimensions and morphology in first and second mandibular molar teeth. One hundred thirty-four extracted human mandibular molars with divergent roots were selected. Teeth were viewed at 7X magnification on a dissecting microscope interfaced with a computer equipped with a state-of-the-art histomorphometry software program. Various aspects of furcation anatomy were measured and recorded. Data were examined by using analysis of variance for all paired comparisons. For nonparametric data, the Kruskal Wallis test was used. Results indicated that 61.94% of buccal and 50.75% of lingual molar surfaces presented with cervical enamel projections (CEPs), with the highest frequency noted in second molars. CEPs ranged from 0.98 mm to 1.33 mm, whereas root trunk heights varied between 2.23 mm and 2.93 mm. Generally, lingual molar surfaces had longer root trunks when compared to buccal surfaces. Root separation increased by approximately 0.5 mm at each 1-mm increment apical to the furcal roof. This study provides new information regarding the furcal anatomy of mandibular molar teeth and supplements previous reports that suggest the CEP is a common problem which must be addressed by clinicians when treating molar teeth.     

A new correction procedure for calibrating dental caries frequency

The incisors and canines and the premolars and molars show differential resistance to cariogenic factors. The anterior teeth have a lower caries frequency than the posterior teeth. However, these tooth classes are lost differentially in postmortem stages due to their anatomical structures. This differential postmortem tooth loss distorts proportions between the anterior and posterior tooth classes. The disproportionality can affect the calculation of total caries prevalence. In this paper, we propose a new calibration procedure which removes this disproportionality and call it the proportional correction factor. For this procedure, the caries rates of anterior and posterior teeth are corrected by multiplying the anterior teeth by three-eighths and the posterior teeth by five-eighths. These fractions are derived from the human dental formula which contains three anterior and five posterior teeth by side. The correction factor is more effective if the proportion of anterior to the posterior teeth is extremely distorted. When this procedure is used with the caries correction factor, it provides a useful way to approach to an almost true caries prevalence.     

Pleiotropic deficiencies of the laccase-derepressed mutant lah-1 are caused by constitutively increased expression of the cross-pathway control gene cpc-1 in Neurospora crassa

PURPOSE: To estimate gamma-ray doses received by Hiroshima atomic bomb survivors using electron spin resonance (ESR) of tooth enamel and to compare the results with cytogenetic data. MATERIALS AND METHODS: Tooth enamel ESR was performed for 100 teeth donated from 69 Hiroshima survivors, and conventional cytogenetic examinations were conducted for 61 of the tooth donors. To evaluate possible contamination from dental X-ray exposure, which primarily affects the tooth's buccal surface, each tooth was divided into buccal and lingual parts for subsequent independent enamel isolation and ESR measurement. RESULTS: Almost 20 teeth showed considerably larger buccal doses than lingual doses, but most of these discrepant teeth were incisors and canines. The results are probably attributable to solar light exposure. In contrast, the buccal and lingual doses found in molars were similar. Conventional translocation data of lymphocytes and ESR-estimated doses of 40 donors of molars showed the dose-response for translocations to be almost the same as that expected from in vitro gamma-ray irradiation experiments. CONCLUSIONS: Both tooth enamel ESR and lymphocyte cytogenetics are useful measures for individual biodosimetry of acute radiation exposure, even half a century after the exposure occurred.     

Occlusal interference of lingual appliances: advantages or inconvenience

Lingual orthodontics presents a few technical problems; when practicing it, it reveals a considerable amount of advantages. The occlusal interference of the lingual maxillary bite plane with the mandibular incisors generate contact forces. A moment of corono-vestibulary version will weight upon the upper incisor independently from teeth position. Actions regarding the mandibulary incisors are depending on their position according to the bite plane. An incisor axe in perpendicular position to the plan generates intrusion. A lingual position generates a moment of lingual version and vice versa. These actions have to be considered. They might be, according to clinical situation, beneficial or not.     

The aesthetic composite bridge

New developments are constantly introduced in the search for the optimal treatment modality to restore a single anterior tooth. The patient attention has shifted to aesthetics of the restoration, biocompatibility of the dental materials utilized, conservative preparation of the teeth to be restored, and the retention of intact adjacent dentition. The learning objective of this article is to review the methods currently utilized and to present a recently introduced treatment modality--the two-component bridge, which combines the strength and resiliency of composite resin with the aesthetic advantages of porcelain. The technology of the material is reviewed, the predominantly lingual tooth preparation procedures are outlined, and the bridge try-in is described. The advantages of the two-component bridge are presented along with the contraindications and suggestions of careful case selection. Three cases with congenitally missing maxillary lateral incisors in youthful patients are presented to supplement the theoretical outline and to describe and illustrate the clinical procedure.     

Efficacy of chewing gum in preventing extrinsic tooth staining

The purpose of this six-week clinical study was to determine the efficacy of sugar-free chewing gum versus no chewing on preventing Peridex (0.12% chlorhexidine)-associated stain. One-hundred and fifty healthy adult subjects, categorized by tea or coffee intake and smoking, were randomly assigned to a chewing or no chewing gum group. All subjects were given Peridex and an ADA-approved toothbrush and fluoride toothpaste to use twice a day. Gum was chewed for 20 minutes five times each day, after toothbrushing and Peridex rinse in the morning and evening, and after each meal. At baseline, all subjects received a professional cleaning to remove all supragingival deposits and extrinsic strain. At three and six weeks, safety and stain intensity and area were monitored on the anterior teeth and posterior Ramfjord teeth using the Lobene stain scoring method. Seventy-two subjects in each group completed the study. Attrition was unrelated to product use. No untoward reactions were reported or observed at any time in the study. At the six-week evaluations, the chewing gum group exhibited significantly lower (p < 0.05-0.001) total stain scores on both anterior and posterior areas evaluated compared to the no chewing group scores. In addition to the stain evaluations, a randomly selected subset of 60 subjects was evaluated for gingivitis at baseline prior to cleaning, and at three and six weeks, on the buccal and lingual surfaces of the Ramfjord teeth. Both the chewing gum and no chewing gum subset subjects had a significant decrease in gingivitis scores from baseline to three weeks (p < 0.001) and from baseline to six weeks (p < 0.05-0.001). There were no significant statistical differences between the two groups at anytime during the study on gingivitis levels. Chewing gum, after product use, did not reduce the efficacy of chlorhexidine on gingivitis scores.     

Historical development of whiteners: clinical safety and efficacy

Trimming composite restorations includes gross removal of excess material, contouring, and finishing. Many surfaces such as the lingual surface of anterior teeth or the occlusal surfaces of posterior teeth require the use of rigid rotating instruments. The purpose of our study was to assess the suitability of eight finishing diamonds, five tungsten carbide finishing burs, and one ceramically coated finishing instrument for trimming a small-particle hybrid composite material. A total of 70 specimens of Herculite XRV were treated with the different finishing instruments under simulated practice conditions, and surface roughness was recorded quantitatively using an optical laser pick-up. The resulting surfaces were examined qualitatively with the help of scanning electron microscopy (SEM). Cutting efficiency of the diamonds and burs was evaluated at a constant pressure of 2.5 N using 42 additional specimens of Herculite XRV. Significant differences were calculated using one-way ANOVA and pairwise contrasts by Tukey's multiple range test. The results showed that finishing diamonds were characterized by high cutting efficiency and relatively rough corresponding composite surfaces, whereas tungsten carbide finishing burs led to smooth composite surfaces but had little cutting efficiency. For gross removal and contouring of composite restorations, a 15-40 microns finishing diamond is recommended followed by a tungsten carbide bur for finishing the restoration.     

Multiple-tooth receptive fields of single human periodontal mechanoreceptive afferents

1. Single-unit impulse activity from 25 mechanoreceptive afferents was recorded in the human inferior alveolar nerve using tungsten microelectrodes. All of these afferents were considered to originate in periodontal receptors because they showed responses to mechanical stimulation of one or more teeth but not to stimulation of the gingiva. 2. For each afferent isolated, forces with "ramp-and-hold"-shaped profiles of similar magnitudes (261 +/- 21 mN, mean +/- SD) were applied to the incisors, the canine, and the first premolar on the recording side, and the contralateral central incisor in four horizontal directions: lingual, labial, mesial, and distal. For a few of the afferents, forces were also applied in the axial directions (up and down). Both static and dynamic response components were analyzed. 3. For about one half of the tested afferents, the receptive fields were restricted to a single tooth. The remainder (52%) responded to stimulation of a group of teeth (on average 3.1 teeth), which typically showed contact between their crowns. 4. Afferents responding to loading of multiple teeth showed their strongest responses to forces applied to a particular tooth, with a gradual decline in the responsiveness to the adjacent teeth. 5. The stimulation directions eliciting the strongest afferent responses for the most sensitive tooth were approximately evenly distributed over the four stimulation directions, except for some bias toward the lingual direction. In contrast, loading of the adjacent teeth most often showed the strongest responses in the mesial or distal directions, in most cases toward the most sensitive tooth.(ABSTRACT TRUNCATED AT 250 WORDS)     

Histochemical studies on the mucins of the vertebrate tongues. VIII. Histochemical analysis of mucosubstances in the tongue of the turtle

The tongue of the fresh-water turtle, Geomyda trijuga, was investigated histochemically to determine the localization and nature of mucosubstances in it. The results were considered in comparison with the lingual mucosubstances of other vertebrates. A heterogenous distribution of neutral mucosubstances, sulphomucins, sialomucins and hyaluronic acid in various lingual sites was noted. The anterior half of the lingual surface was keratinized, whereas on the posterior half numerous broad papillae and three types of goblet cells were found. The lingual salivary glands were absent from the turtle tongue. The importance of lingual histology in establishing the phylogeny of vertebrates and the possible functional significance of mucosubstances in the physiology of gustation are discussed.     

Strain profiles in molars restored with posterior composite resins: effect of cavity size & restorative technique

The objective of the study was to quantitatively compare peak strain in buccal & lingual aspects of human molar teeth restored with composite res in polymers as a function of: 1) cavity size, 2) restorative material, 3) restorative technique. Two composite resin materials were investigated: Herculite (sub micron filler particle) & P 50 (supra micron filler particle). Performance was compared to two different types of high copper amalgams. A total of 48 freshly extracted human molar teeth free from cracks or caries were used. MOD cavities were prepared with three different cavity sizes: 1 mm, 2.5 mm & 5 mm. Rectangular rosette strain gauges were applied centrally on the buccal & lingual surfaces of the prepared teeth. Strain measurements were recorded during subsequent cavity restoration procedures and curing cycles. A comparison of peak strains in the amalgam vs composites using bulk-pack technique showed significantly higher strain in the composite series. Highest strains were noted in the largest cavity size (5 mm). Slot preparation following restoration reduced strains in the composite materials. Subsequent re-filling of the slot increased strain, but still less than the initial value.     

Peripherally administered sufentanil inhibits pain perception after postpartum tubal ligation

A retrospective questionnaire survey of 111 retention-period adult patients was performed to examine discomfort that may be caused by bonded lingual orthodontic appliances. Despite instructions to avoid or relieve the discomfort, 57% to 76% of patients complained of tongue soreness, difficulty in chewing fibrous food, difficulty in pronouncing the s and t sounds, and difficulty in tooth brushing after the bonding of lingual appliances; the levels were significantly higher than those undergoing edgewise labial treatment. Twenty percent to 44% of patients experienced high levels of the aforementioned discomfort. Although this discomfort decreased gradually with time, 20% to 46% of patients felt discomfort until after the removal of the lingual appliances. The ratio of tongue soreness and speech difficulty caused by upper lingual bracket application to lower lingual bracket application was almost equal. Rank correlation analyses revealed two things: the deeper the bite, the greater the level of tongue soreness, teeth pain and difficulty in chewing tough food; and the larger the overjet, the greater the level of tongue soreness.