Evaluation of the Accuracy of Solid Implant Casts

Purpose Materials used to fabricate the most dimensionally accurate implant casts have not been identified experimentally. The purpose of this investigation was to examine the dimensional accuracy of implant casts fabricated with different materials. Measurements of linear horizontal dimensional change and strain produced on a master framework were evaluated and correlated. Materials and Methods A master framework was fabricated to fit an aluminum five-implant model. Forty polyether implant impressions of the aluminum model were randomly grouped and poured in either Vel-mix, Die Keen, Resin Rock, or Low Fusing Alloy. A digital veneer caliper was used to measure linear distance between the most distal abutments on each of the experimental implant casts and the master model. In addition, strain values were recorded from strain gauges bonded in the mesiodistal axis of the framework, which was secured by prosthetic retaining screws torqued to 10 Ncm. Results A one-way ANOVA showed a significant difference among the four die materials in dimensional change of the experimental casts (p= .0001). A post-hoc Duncan's multiple-range test (p < .05) showed that casts fabricated with Low Fusing Alloy had the least linear dimensional change from the master cast, but the material exhibited the greatest dimensional variability. A MANOVA (Wilks' Lambda) showed significant differences in strain on the framework based upon die material (p= .015). A post-hoc Duncan's multiple-range test (p < .05) showed that Resin Rock casts induced significantly less strain on the framework than the other materials. Negligible correlation was found between the linear horizontal dimensional change and the total absolute strain on the framework. Conclusion Experimental implant casts made of Resin Rock minimized strain on the master framework and decreased the amount of framework distortion on casts of this material. Low Fusing Alloy yielded accurate casts, but highly variable linear dimensional changes in the horizontal dimension may preclude its clinical benefit.     

Biocompatibility of dentin bonding agents

Abstract Dentin bonding agents were introduced to enhance the bonding of composite resins to dentin. Many commercial brands of bonding agents are now available for clinical use, and they are getting more and more popular. The third generation of dentin bonding agents seems to be more effective than earlier generations, although more complex to use. Dentin bonding agents have different chemical compositions, different mechanisms of actions, and different clinical application procedures and, conceivably, different biological effects on the pupal tissues are expected. The reported biological effects of dentin bonding agents ranged from none to severe, depending on several factors. Opinsion varied whether the inflammatory reactions associated with some bonding agents were due to the tooth restoration interface, or due to a combination of both factors.     

Oxidation of two high-palladium PFM alloys

Formation of an oxide layer at the alloy surface is important as to porcelain/alloy bonding. In this study the influence of oxygen pressure as well as oxidation temmperature and time on the oxide formation of 2 high-palladium PFM alloys was investigated. Tested were OL (Pd, Cu, Ga, In, Sn and Au) and OS (Pd, In, Sn, Cu, Ga and Co). After oxidation (1–10 min, vacuum/air, 940–1020°C) the oxides were removed selectively by means of leaching in 37% HCl. Concentrations of the metallic parts of the oxide layers were determined by means of an emission spectrometer. Oxygen in the oxide layer and the alloy were computed from weight changes during oxidation and leaching. PdO content decreased with increasing oxidation time. Higher oxidation temperatures gave less PdO in case of OL. These phenomena may be explained on the basis of the relatively low decomposition temperature of PdO. The components In and Ga oxidize preferentially. In both cases approximately twice as much as oxide is found in the oxide layer compared to a non-preferential oxidation model. Copper and tin oxide formation is 30–40% less in comparison with the non-preferential situation. In case of OS Co is oxidized preferentially 2.5 times the amount computed for the non-preferentially oxidizing alloy. The Influence of Co on the oxide formation is such that it suppresses the oxide formation of Cu relative to Ga, as well as the formation of SnO₂.     

Influence of selective caries excavation on marginal penetration of class II composite restorations in vitro

Selective caries excavation may support pulp preservation. This in vitro study investigated the influence of selective removal of demineralized dentin on marginal integrity of composite restorations as determined by dye penetration. Dentinal caries-like lesions were produced in the approximal surfaces of 40 extracted human molars (ethylenediaminetetraacetate, 0.5 M, 96 h). The following test procedures were established: complete excavation, selective excavation, and caries-free control. Two class II cavities with enamel at the cervical margins were prepared per tooth and demineralization volume was determined by micro-computed tomography for the purpose of a stratified distribution to receive complete excavation or selective excavation. After complete or selective excavation (30 cavities each), adhesive composite restorations were placed. Cavities without demineralized dentin (20 cavities) served as control. The marginal integrity of restorations was evaluated by dye penetration with and without thermocycling or mechanical loading. Results were analyzed by non-parametrical statistical tests (Mann-Whitney U Test) with an α = 0.05 level of significance. Dye penetration did not differ significantly among completely excavated, selectively excavated, or undemineralized teeth, but was increased by thermocycling and mechanical loading in all experimental groups. Selective caries removal did not increase marginal penetration in class II restorations. The presence of remaining demineralized dentin surrounded by sound dentin did not impair marginal integrity of restorations with margins placed in sound enamel.     

Comparison of Number and Mean Charge Between Dental Sealants and One-surface Restorations

An important concern of the insurer is how sealants, if a covered benefit, will affect the premium. Important factors that may have an influence on determining the premium include the decline in caries rate coupled with the long-term cost to an insurer for sealants vs one-surface restorations. In this study of more than 1 million dentally insured children (aged 5-15), the mean charge ($) for sealants and one-surface restorations was determined, along with the frequency of these procedures, by patient age. For this group of children, 43 percent of one-surface restorations occurred between ages 12-14, whereas 32 percent of the patients received sealants at either 7 or 8 years of age. States varied substantially in the number of sealants as a percentage of the number of restorations. Only three states had more sealants placed than one-surface, posterior restorations. Three states had an annual increase in the ratio of sealant to restoration charge, while 13 states had an annual decrease. With the exclusion of a few states with a minimum number of sealants and restorations in 1988, the highest ratio of the cost of sealants to the cost of one-surface restorations was observed in New York (.60) and New Jersey (.56) and the lowest observed in Kansas and Utah (.37). The ratios for both New York and New Jersey were lower in 1988 than in the previous two years. The ratio of the number of one-surface, posterior restorations to the population served was approximately the same for each NIDR region in the contiguous United States. Alaska and Hawaii had a higher proportion.     

Attitudes of two groups of dentists towards dental hygienists

The purpose of the study was to assess whether cooperation with a dental hygienist was based on pursuit of financial gain or on aspirations to improve patient care. To this end a questionnaire was sent to 972 dentists. 412 dentists replied, of whom 178 had patients treated by a dental hygienist. Questions were asked regarding practice profile, preventive orientation and dentists' opinion about the material and immaterial value of cooperation with a dental hygienist. Discriminant analysis showed that the main distinguishing factor between dentists who did and dentists who did not cooperate with dental hygienists was their opinion about the quality of the dental hygienists' work in relation to the non-financial costs for patients, insurance companies, and dentists. The difference in the dentists' opinions about the direct profitability of dental hygienists was not significant. The conclusion can be drawn that the orientation of Dutch dentists towards care for their patients plays a more important role in a dentist's decision to cooperate with a dental hygienist than is usually presumed.     

Influence of surface wetness on bonding effectiveness of universal adhesives in etch‐and‐rinse mode

The purpose of this study was to evaluate whether surface wetness would influence the bonding effectiveness of universal adhesives in etch‐and‐rinse mode. All‐Bond Universal (AB), G‐Premio Bond (GP), Prime & Bond Active (PB), and Scotchbond Universal Adhesive (SU) were evaluated. Initial bond strengths and bond‐fatigue strengths of universal adhesives to both wet and dry enamel and dentin in etch‐and‐rinse mode were determined. Scanning electron microscopy observations of the adhesive interfaces were also conducted. The bond‐fatigue durability of universal adhesive to enamel in etch‐and‐rinse mode was influenced by the surface wetness, unlike that to dentin. The bond fatigue durability of AB and GP to dentin in etch‐and‐rinse mode was different depending on the surface wetness, unlike that of PB and SU. The thicknesses of the adhesive or hybrid layer of resin–dentin interfaces were not influenced by the surface wetness, but the length of resin tags in the wet group was longer than in the dry group. Some universal adhesives with the addition of specific components and optimization of water content can achieve stable bonds regardless of surface wetness, but the surface wetness of dentin is still a significant factor for universal adhesive bonding in etch‐and rinse mode, unlike that of enamel.     

Dimensionality of dental anxiety measurements

A survey among 620, 30-40-yr-olds, was carried out in order to measure dental anxiety with Corah's DAS, Weiner's AALC, and some other questions on anxiety, among which was the duration of psychophysiologic responses prior to a dental appointment. The data were analyzed with a Non Metric Components analysis. The DAS turned out to be unidimensional. The AALC on the other hand appeared to contain four components. A second stage analysis comprising the DAS component, the four AALC components, and the remaining variables revealed a two-dimensional structure, of which only the first component is dentistry related. This component showed better differentiation of the respondents than with DAS or AALC alone. Part of AALC's questions and a question about anxiety in daily life proved to be superfluous for measuring dental anxiety. It is concluded that dental anxiety and anxiety in general have to be measured with questions covering different aspects.     

The Economic Contribution of Dental Hygienists'' Activities to Dental Practice: Review of the Literature

This article reviews studies of dental practice and essays on practice management that have included information on the economic contributions of oral hygiene services. Several studies found that these services were less remunerative than other services and recommended that dentists delegate these functions when possible. However, one study noted that performance time, as well as delegation, influenced practice productivity and also reflected the practice's concept of care. Some practice management authors indicated that poorly managed practices without an excess of patients do not benefit economically from hiring a hygienist; but for practices with good management capabilities and an excess of patients, a hygienist may be able to make a major contribution to practice productivity. The lower remuneration for hygiene services and the high percentage of practice time required to provide a complete prophylaxis once or twice a year to each patient led several authors to doubt that dentists would or could provide these services themselves. The data in the reported studies, however, are insufficient to support firm conclusions about the profitability of hygienists' activities in dental practice.     

A path analysis of the utilization of dental services

In this paper Andersen's model of health services utilization is applied to the use of dental visits. This analysis builds on previous work by including clinical oral health indicators rather than self-reports as measures of need by using a path model to analyze the dynamics of predisposing, enabling and need factors on dental utilization. The sample consisted of 287 volunteers who were employees of a university health center. The path analysis using ordinary least squares found that sex was the most important variable affecting use of services. Men tended to have higher number of visits due to higher need and women more visits regardless of need. A surprising result was that income had no significant effect on volume of dental visits, which contradicts much of the literature in the area. Finally, the analysis suggests that because of the nature of clinical oral health indicators cross-sectional analysis of dental service utilization may not be appropriate.     

Prevalence of dental caries and quality of restorations among new immigrants to Israel

The purpose of the present investigation was to gather information on the prevalence of dental caries and the quality of restorations of new immigrants to Israel, and to compare those two categories among immigrants from different regions of origin. New immigrants, residents of four absorption centers in Israel, were included in the study. Altogether, 1,031 immigrants (417 Eastern European, 338 Western European/North American and 276 South American) were examined. The results indicate that new immigrants to Israel from Eastern Europe are affected with more carious teeth (D), are missing more teeth (M), and have received quantitatively less treatment (F) than immigrants from Western Europe/North American and South America. The South America are an intermediate group. A similar distribution was found between the groups by their respective ages. The quality of dental restoration was found to be statistically higher among immigrants from Western European/North American and South American origins with the latter group exhibiting an intermediate level of quality of dental restorations.     

Shear fatigue strength of resin composite bonded to dentin at physiological frequency

The purpose of this study was to examine the shear fatigue strengths of a resin composite bonded to dentin. Three adhesive systems – a two‐step self‐etch adhesive (OptiBond XTR; Kerr) and two universal adhesives [Scotchbond Universal (3M ESPE) and G‐Premio Bond (GC)] – were used in self‐etch mode to bond a resin composite to dentin at a physiologic frequency of 2 Hz over 50,000, 100,000, and 1,000,000 cycles. A staircase method of fatigue testing was used. Twenty specimens were used for each test condition. There was no significant difference in shear fatigue strength across the cycling periods for the three individual adhesives. Differences in shear fatigue strength were found among the three adhesives within each cycling period. Regardless of the adhesive used in self‐etch mode for bonding a resin composite to dentin, shear fatigue strength was not influenced by the number of cycles used for testing.     

The value of extended-setting-time amalgam in pre-clinical practice in undergraduate dental training

This is a single-blind controlled study investigating the advantages of extended-setting time dental amalgam compared to a standard amalgam in the training of undergraduate dental students. 50 dental students were randomly assigned 1 of the 2 alloys for each restoration placed in the study. Each student placed class I and class II restorations in extracted human teeth mounted in typodont arches. 449 completed restorations were available for assessment, 228 restorations in the experimental group and 221 restorations in the control group. The test restorations were overall marginally inferior to those of the control group. There appears to be no advantage in using extended-setting time dental amalgam in undergraduate training.     

Epidemiologic study of idiopathic enamel hypomineralization in permanent teeth of Swedish children

In the late seventies an increasing number of children showing extensive and severe idiopathic hypomineralization of the enamel of incisors and permanent first molars was reported within the Public Dental Services in Sweden. An epidemiologic study was initiated to analyze the prevalence, extension and severity in Swedish children born in 1970 and in the years before and after. 2252 children born in 1966-74 were examined according to well defined criteria on enamel hypomineralization. It was found that 15.4% of the children born in 1970 showed such changes. The corresponding figures for children born in 1966, 1969, 1971, 1972 and 1974 were 6.3, 7.3, 7.1, 5.2 and 4.4, respectively.     

Influence of X-ray beam angulation upon the radiographic image of proximal carious lesions

Abstract Twenty-two extracted human molars and premolars with a total of34 initial proximal carious lesions were radiographed in 16 different views varying the horizontal angulation of the X-ray beam in steps of 2.5° The radiographs were read simultaneously by three observers. Clinical and radiographic diagnoses were compared. When utilizing all 16 views the concordance was 95%. All proximal surfaces were scored using four scoring classes. Surfaces without radiolucencies were scored 0, and carious surfaces were scored according to the extent of the radiolucencies. Nine sound and 12 carious surfaces were assigned identical scores in all 16 views, while 22 (65%) of the carious surfaces were assigned two, three or four different scores. Deviations from a direction of the X-ray beam tangential to the proximal surface eliciting a radiographic image belonging to a different score were measured. In 71% of the cases a deviation of 7.5° or less elicited a different score. Projectional circumstances should be taken into consideration in interpreting proximal radiolucencies.     

Galvanic series of some dental alloys

abstract – Galvanic series for different metals in different electrolytes have been published, but never for dental alloys in artificial saline solution. The material classes studied are amalgam, gold alloy, nickel alloy, chromium cobalt casting alloy and temporary crown form. The electrogalvanic potentials were measured and determined in reference to a hydrogen electrode (H₂/H⁺) arbitrarily defined as zero. A galvanic series of the tested materials was arranged in order of their potentials.     

Plaque-removing effect of dental floss and toothpicks in children 12–13 years of age

The aim of the present study was to assess the cleaning effect of dental floss and toothpicks on interproximal surfaces. The plaque situation was assessed in a group of children 12-13 years of age by the Patient Hygiene Performance Index (PHPI). It was found that dental floss has a greater plaque-removing effect of the interproximal areas than toothpicks, predominantly on the mesial surfaces of the teeth.     

A longitudinal study of multiple approaches to dental health education

An evaluation was made of the separate effects on oral hygiene of token reward treatments, discovery (project) learning, and plaque staining feedback demonstrations with children in the first through fifth grades. Both short- and long-term effects were assessed in an open classroom setting. Twenty classrooms were non-randomly assigned to treatment and control groups. Plaque scores were recorded according to the Podshadley Patient Hygiene Performance Index (PHP) at time T0, before initiation of any of the educational interventions; and again at times T1, T2, and T3; 7 days, 74 days and 255 days, respectively, following cessation of the educational interventions. The combination of dental health interventions at this school had short-range effects at every grade level, and those effects persisted for 9 months among the third and fourth graders. It was not possible to identify which of the various treatments produced the observed differences, although the project learning method was generally less effective. A linear regression analysis was used to evaluate the shifts in oral hygiene behavior, a method not previously used in studies of this type.