Elaine L. Davis

Oral health of patients with intellectual disabilities: A systematic review

A systematic review of original studies was conducted to determine if differences in oral health exist between adults who have intellectual disabilities (ID) and the general population. Electronic searching identified 27 studies that met the inclusion criteria. These studies were assessed for strength of evidence. People with ID have poorer oral hygiene and higher prevalence and greater severity of periodontal disease. Caries rates in people with ID are the same as or lower than the general population. However, the rates of untreated caries are consistently higher in people with ID. Two subgroups at especially high risk for oral health problems are people with Down syndrome and people unable to cooperate for routine dental care. Evidence supports the need to develop strategies to increase patient acceptance for routine care, additional training for dentists to provide this care, and the development of more effective preventive strategies to minimize the need for this care.

Reliability and accuracy of four dental shade-matching devices

STATEMENT OF PROBLEM There are several electronic shade-matching instruments available for clinical use, but the reliability and accuracy of these instruments have not been thoroughly investigated. PURPOSE The purpose of this in vitro study was to evaluate the reliability and accuracy of 4 dental shade-matching instruments in a standardized environment. MATERIAL AND METHODS Four shade-matching devices were tested: SpectroShade, ShadeVision, VITA Easyshade, and ShadeScan. Color measurements were made of 3 commercial shade guides (Vitapan Classical, Vitapan 3D-Master, and Chromascop). Shade tabs were placed in the middle of a gingival matrix (Shofu GUMY) with shade tabs of the same nominal shade from additional shade guides placed on both sides. Measurements were made of the central region of the shade tab positioned inside a black box. For the reliability assessment, each shade tab from each of the 3 shade guide types was measured 10 times. For the accuracy assessment, each shade tab from 10 guides of each of the 3 types evaluated was measured once. Differences in reliability and accuracy were evaluated using the Standard Normal z test (2 sided) (alpha=.05) with Bonferroni correction. RESULTS Reliability of devices was as follows: ShadeVision, 99.0%; SpectroShade, 96.9%; VITA Easyshade, 96.4%; and ShadeScan, 87.4%. A significant difference in reliability was found between ShadeVision and ShadeScan (P=.008). All other comparisons showed similar reliability. Accuracy of devices was as follows: VITA Easyshade, 92.6%; ShadeVision, 84.8%; SpectroShade, 80.2%; and ShadeScan, 66.8%. Significant differences in accuracy were found between all device pairs (P<.001) for all comparisons except for SpectroShade versus ShadeVision (P=.033). CONCLUSIONS Most devices had similar high reliability (over 96%), indicating predictable shade values from repeated measurements. However, there was more variability in accuracy among devices (67-93%), and differences in accuracy were seen with most device comparisons.

Effects of composite restorations on resistance to cuspal fracture in posterior teeth.

A clinically acceptable MOD cavity preparation was used instead of a jig-mounted slot preparation in this investigation. Each preparation was proportional to the tooth dimension. The design of the testing instrument ensured that forces applied to the specimens were applied to tooth structure and not to the restorative material. Prepared unrestored teeth were weaker than restored teeth. No significant difference was noted in fracture resistance between teeth restored with amalgam and with composite resin. The method used in this study is replicable, allowing the possibility of comparison studies by using identical procedures. Future research will focus on issues of polymerization method and modulus of elasticity and their effects on fracture resistance of remaining tooth structure.

Defining a natural tooth color space based on a 3-dimensional shade system

STATEMENT OF PROBLEM The natural tooth color space reported by a manufacturer may not represent the comprehensive spectrum of natural teeth for all population groups. PURPOSE The purpose of this study was to define a natural tooth color space within the Greater Buffalo, New York population and to compare that to the color space determined by a manufacturer. MATERIAL AND METHODS Nine hundred and thirty-three maxillary central incisors (501 patients) were measured with a shade-taking device (Vita Easyshade). For each tooth, L*, a*, b* values, chroma, hue, and the closest shade (Vita 3D-Master) were recorded. A linear regression analysis was performed to determine how well the manufacturers values predict actual values for L*, a*, and b*. Color differences (DeltaE*) between the Buffalo population and the closest shade were also calculated. A 1-sample t test was used to determine whether the color differences seen in the sample were statistically different from the perceptibility threshold, DeltaE*=3.7 (alpha=.05). RESULTS All 3 attributes of the Buffalo population displayed a broader range than those from the shade guide. However, the regression analysis revealed a significantly positive relationship between the L*, a*, and b* values of the 2 methods (P<.001). The 1-sample t test revealed a significant DeltaE* (mean DeltaE*=6.15) difference from the perceptibility threshold of DeltaE*=3.7 (P<.001). CONCLUSIONS Color differences between the Buffalo population and the shade guide were frequently above published perceptibility thresholds, but within the range of acceptability. The Buffalo population tooth color space encompassed the manufacturers color space.

Bond strength and durability of glass ionomer cements used as bonding agents in the placement orthodontic brackets

One potential risk of orthodontic treatment is the development of surface decalcification in association with use of brackets and bands. A bonding agent that could render tooth structure more resistant to the caries process clearly would reduce the negative iatrogenic outcomes of orthodontic therapy and thereby benefit the patient. Glass ionomer cement (GIC) bonds chemically to both enamel and dentin. In addition its high fluoride content makes enamel more resistant to caries. The purpose of this study was to evaluate the bond strength and durability of GIC when used as a bonding agent in the placement of orthodontic brackets. The materials tested were three GICs (Ketac-Fil, Ketac-Cem, and Chelon) and a standard bonding agent currently in widespread use (Rely-A-Bond). Brackets were attached to the facial surface of 96 premolar specimens and half the specimens for each bonding agent were thermocycled. Bond shear strength was determined with an Instron testing device by applying a load to the occlusal margin of each bracket to the point of failure. A two-way ANOVA indicated a significant bonding agent by thermocycling interaction (F = 4.78, p less than 0.01). Thermocycling decreased bond strength significantly for all materials, but had the greatest impact on Rely-A-Bond. However, Rely-A-Bond provided the strongest bond with and without thermocycling. Although bond strength for the standard orthodontic bonding agent deteriorates significantly under thermal stress, these results suggest that it is still greater than the bond strength provided by GIC materials.

COMPARISON OF ACCURACY BETWEEN COMPRESSION- AND INJECTION-MOLDED COMPLETE DENTURES

STATEMENT OF PROBLEM A clinically significant incisal pin opening may occur after processing complete dentures if a compression molding technique is used. To recover the proper vertical dimension of occlusion, a time-consuming occlusal adjustment is necessary that often destroys the anatomy of the artificial teeth. A new injection molding process claims to produce dentures that require few, if any, occlusal adjustments in the laboratory after processing. PURPOSE This laboratory study compared incisal pin opening, dimensional accuracy, and laboratory working time for dentures fabricated by this new injection system with dentures constructed by the conventional compression molding technique. MATERIAL AND METHODS Two groups of 6 maxillary and 6 mandibular dentures were evaluated as follows: group 1 (control), Lucitone 199, compression molded with a long cure cycle; and group 2, Lucitone 199, injection molded with a long cure. Incisal pin opening was measured with a micrometer immediately after deflasking. A computerized coordinate measuring machine was used to measure dimensional accuracy of 3-dimensional variations in selected positions of artificial teeth in 4 stages of denture fabrication. Analysis of variance (ANOVA) and t tests were performed to compare the groups. RESULTS A significant difference was found in pin opening between groups (t test). Horizontal dimensional changes evaluated with repeated measures ANOVA revealed no significant differences between groups. However, analysis of vertical dimensional changes disclosed significant differences between the groups. There was no appreciable difference in laboratory working time for flasking and molding denture bases between the injection and compression molding techniques when polymethyl methacrylate resin was used. CONCLUSION The injection molding method produced a significantly smaller incisal pin opening over the standard compression molding technique. The injection molding technique, using polymethyl methacrylate, was a more accurate method for processing dentures. There were no appreciable differences in laboratory working time between the injection and compression molding techniques.

Clinical wear study of three commercially available artificial tooth materials: Thirty-six month results

STATEMENT OF PROBLEM Excessive wear of artificial resin teeth has been a concern to both the patient and the dentist because of unfavorable associated sequelae. The search for a more wear resistant resin tooth material resulted in the development of modified resin teeth that displayed acceptable wear resistance. PURPOSE This study compared clinical wear of a new modified resin tooth material with two other commercially available modified resin materials over a period of 36 months. Differences in wear by gender, cuspal anatomy, arch, individual tooth type, and chewing side preference were also evaluated. MATERIAL AND METHODS A total of 67 patients were randomized into one of three treatment groups in this double-blind study; group 1, Ivoclar-Vivodent and Orthotyp; group 2, Dentsply-Trublend SLM; and group 3, Dentsply-Bioblend IPN. Tooth wear was determined by measuring vertical heights of contacting points at baseline and 36 months with a computerized coordinate measuring machine and computer-controlled positioning stages. Measurements were completed at 36 months for 55 patients who remained in the study. RESULTS Repeated measures analysis of variance revealed no significant difference in total wear by gender or tooth material at 36 months. There was also no significant difference by chewing side preference or cuspal anatomy. However, there was a significant difference in individual tooth wear (canine, premolar, molar) and by arch. CONCLUSION New modified resin teeth have displayed clinically acceptable wear resistance for most patients.

Effects of incremental versus bulk fill technique on resistance to cuspal fracture of teeth restored with posterior composites

Posterior resin placed with an incremental technique produces greater resistance to cuspal fracture than posterior resin placed with a bulk technique. P-30 composite placed by either a bulk fill or incremental technique produces greater resistance to cuspal fracture than Ful-fil composite.

Effect of two connector designs on the fracture resistance of all-ceramic core materials for fixed dental prostheses

STATEMENT OF PROBLEM Most all-ceramic fixed dental prostheses (FDPs) fail at the connectors. PURPOSE The purpose of this study was to determine the effect of 2 connector designs on the fracture resistance of core materials used for all-ceramic FDPs. MATERIAL AND METHODS Three materials were tested: (1) heat-pressed lithium disilicate glass ceramic (IPS e.max Press (Press)), (2) milled lithium disilicate glass ceramic (IPS e.max CAD (CAD)), and (3) milled yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP) (IPS e.max ZirCAD (ZirCAD)). Specimens were made into 30 x 4 x 4-mm bars to represent 3-unit FDPs. Two connector designs, round (0.60 +/-0.01-mm radius of curvature) and sharp (0.06 +/-0.001-mm radius of curvature), with a 3.00 +/-0.05-mm cross-section for each connector, were studied (n=5). Each specimen was loaded to fracture in a universal testing machine with a crosshead speed of 0.1 mm/min. Data were analyzed with a 2-way univariate ANOVA and Tukey HSD test (alpha=.05). RESULTS Mean (SD) failure loads for round connector designs were 684.2 (70.1) N for ZirCAD, 260 (7.8) N for CAD, and 172.9 (35.5) N for Press. Mean (SD) failure loads for sharp connector designs were 386.3 (51.5) N for ZirCAD, 87.9 (7.0) N for CAD, and 125.1 (15.1) N for Press. The 2-way univariate ANOVA indicated statistically significant differences (P<.005) for material and connector design, and, also, a significant interaction between material and connector design. Higher maximum failure loads were found for the round connector design when compared to the sharp connector design, for ZirCAD and CAD. However, this difference was not statistically significant for the Press groups. SEM subjective assessment of the fractured specimens revealed that the fracture initiated from the gingival surface (tensile) of the connector toward the pontic (central loading point). CONCLUSIONS Fracture resistance of ceramic core materials is affected by fabrication technique and connector design. Connector design affected fracture resistance of the milled ceramic, but not the pressed ceramic.

Survey of Ethical Issues in Dental Research

The American Association for Dental Research (AADR) surveyed its leaders to determine their perceptions of the prevalence of problematic research practices and the possible roles AADR should play in promoting scientific integrity. Seventy-six of the 98 program chairs and Association officers (1990-1995) surveyed responded. In general, these respondents did not think that serious misconduct or sloppy science occurred more often in AADR than in other scientific disciplines. Overall, respondents rated practices that undermine the trustworthiness of science (falsifying or fabrication of research data, retaliation, failure to present negative results, failure to disclose involvement with commercial enterprises, failure to maintain research records, etc.) as more serious, but less prevalent, than practices considered disrespectful of the work of others (gift authorship, citing sources without reading them, dividing a project into many small units, etc.). All respondents said that they had observed each of the less serious problematic practices one or more times, whereas 10% reported having observed retaliation, 30% reported having observed falsification, and 54% reported having observed plagiarism one or more times. AADR leaders had observed many more instances of misconduct and other problematic research practices than had faculty surveyed by Swazey et al. (1993), supporting conclusions by Greenberg and Goldberg (1994) that status and years of experience are associated with more frequent observations of misconduct. With respect to the possible roles the AADR might play in promoting research integrity, 88% thought that AADR should develop ethics cases and materials for educational use, 78% thought that AADR should create a process for addressing allegations of misconduct, 72% thought that the Association should develop an ethics committee or consultation service, 55% thought it should create a yearly ethics symposium, and 45% thought that the AADR should develop a more specific code of ethics to complement the general code recently developed by the IADR.