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.     

Relationship between enamel bond fatigue durability and surface free‐energy characteristics with universal adhesives

The relationship between enamel bond fatigue durability and surface free‐energy characteristics with universal adhesives was investigated. The initial shear bond strengths and shear fatigue strengths of five universal adhesives to enamel were determined with and without phosphoric acid pre‐etching. The surface free‐energy characteristics of adhesive‐treated enamel with and without pre‐etching were also determined. The initial shear bond strength and shear fatigue strength of universal adhesive to pre‐etched enamel were higher than those to ground enamel. The initial shear bond strength and shear fatigue strength of universal adhesive to pre‐etched enamel were material dependent, unlike those to ground enamel. The surface free‐energy of the solid (γ_S) and the hydrogen‐bonding force () of universal adhesive‐treated enamel were different depending on the adhesive, regardless of the presence or absence of pre‐etching. The bond fatigue durability of universal adhesives was higher to pre‐etched enamel than to ground enamel. In addition, the bond fatigue durability to pre‐etched enamel was material dependent, unlike that to ground enamel. The surface free‐energy characteristics of universal adhesive‐treated enamel were influenced by the adhesive type, regardless of the presence or absence of pre‐etching. The surface free‐energy characteristics of universal adhesive‐treated enamel were related to the results of the bond fatigue durability.     

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.     

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.     

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.     

Pulpal response to dental amalgams

Abstract – The pulpal reactions to amalgams with relatively high Cu content were compared with a conventional amalgam placed in unlined cavities prepared in intact monkey teeth. After a 1-week observation period the pulpal responses from one of the Cucontaining amalgams and the conventional amalgam were of the same magnitude, whereas the two other amalgams gave more pronounced reactions. After observation periods of 1 and 2 months only one o( the amalgams with high Cu content caused more pronounced reactions than the conventional amalgam.     

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.     

Dental Public Health for the 21st Century: Implications for Specialty Education and Practice

A panel of public health practitioners sponsored by the Health Resources and Services Administration met December 6–8, 1994, to examine current roles and responsibilities for dental public health workers and to recommend changes in education and training to meet challenges posed by an evolving health care system. Overall, at least the same number, if not more, dental public health personnel will be needed in the future. While some new roles were identified, the panel felt that only small numbers of personnel will be needed to fill these new roles. Not all of these roles necessarily require a dental degree. The panel felt that a need exists for more academicians for dental schools, schools of public health, dental public health residencies, and dental hygiene programs; oral epidemiologists and health services researchers; health educators; and specialists in utilization review/outcomes assessment, dental informatics, nutrition, program evaluation, and prevention. To meet these personnel needs: (1) dental public health residency programs should be structured to meet the educational needs of working public health dentists with MPH degrees through on-the-job residency programs; (2) the standards for advanced specialty education programs in dental public health should be made sufficiently flexible to include dentists who have advanced education and the requisite core public health courses; (3) flexible MPH degree programs must be available because of the rising debt of dental students and the decreased numbers of graduating dentists; (4) loan repayment should be available for dentists who have pursued public health training and are working in state or local health departments; and (5) standards for advanced education in dental public health should be developed for dental hygienists.     

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.     

A simplified dental examination for detection of cavitated carious lesions in school setting

Objective:  The objective of the study was to compare a simplified dental examination involving the use of a wooden spatula and a toothpick (TS examination) with the conventional dental mirror and probe examination (MP examination) for detection of cavitated carious lesions in schoolchildren.
Methods:  The study involved three groups of caries-positive schoolchildren aged 4–5, 9–10 and 13–14 years with 179, 188 and 202 children, respectively. All children were examined by a trained and calibrated examiner using a wooden spatula and a toothpick under natural light. After a week the same examiner examined the three groups of children by a dental mirror and a Community Periodontal Index (CPI) probe. 'Teeth' were considered as units of measurement for data analysis. The WHO recommended criteria (2) for decayed, missing and filled teeth were followed for recording dental caries on a specially designed recording form. The sensitivity, specificity, positive predictive value, negative predictive value, false-positive rate and false-negative rate of TS examination were calculated using MP examination as the standard method.
Results:  The specificity of TS examination was well above 95% in three types of dentition. Although the sensitivity of this type of examination in deciduous and mixed dentitions was almost comparable with that of MP examination, it was the lowest for permanent dentition but still within the acceptable limits.
Conclusion:  The TS examination can provide an alternative to traditional MP examination to undertake regular check-ups of schoolchildren for dental caries.     

Dental anxiety, the parental family and regularity of dental attendance

A survey was carried out among 25-yr-old inhabitants of Amsterdam in order to study the relationship between regularity of dental attendance on the one hand and dental anxiety, dental upbringing of the respondents, dental behavior of the parents, education, sex, and the interactions between these independents, on the other. The data were analyzed hierarchically with regression analysis, the logistic approach. Dental anxiety, sex, dental upbringing and the interaction between education and anxiety, in that order, were found to be of importance for the prediction of regularity of dental attendance. Two other terms, though lacking substantial standardized regression coefficients, namely education and the interaction between education and dental upbringing, are also present in the model found. The prediction of one being a regular attender is satisfactory, but the classification of the irregular attenders is disappointing. The effect is discussed of the rather large non-response and attention is given to the effect of dental upbringing in regard to coping resources in the dental situation. It has to be concluded that other factors must be included to achieve an improvement of the classification of the irregular attenders. Dental anxiety, although of importance, cannot account for an adequate differentiation between regular and irregular attenders.     

Dental behavior management problems in Swedish children

Abstract – 4505 Swedish children aged 4-11 yr were surveyed regarding dental behavior management problems (BMP) and dental health. Dental charts were retrieved from clinics in the Public Dental Service in Göteborg. and data were then compiled regarding BMP, action against BMP, caries, fillings, use of local anesthetics, and number of missed appointments. Behavior management problems were found in 10.5% of the children, and were more common in the younger children, among children who missed appointments, and in children who received restorative treatment without local anesthetics. The BMP children had more carious and fewer filled surfaces. In 43.4% of the cases with BMP the strategy chosen was postponement of dental treatment or no measure taken.     

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.     

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.     

Dental hygienists''influence on the patients''knowledge, motivation, self-care, and perception of change

The purpose of this study was to assess the success of the dental hygienist in the dental health education of dental patients in general dental practice. Special emphasis was laid on health education in the field of periodontics. The answers on a questionnaire of 159 dental patients who visited a dental hygienist were compared with the answers of 302 dental patients who had never visited a dental hygienist. The comparison was done by means of t-test and regression analysis on specially developed scales with regard to knowledge, motivation, self-care, and perception of change. On all scales the dental patients who visited a dental hygienist scored better. This difference remained when social demographic variables and the dentist's influence were taken into account. This indicates that the dental hygienist is successful in the behavioral aspect of her work.