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Wear of composite resin veneering materials and enamel in a chewing simulator.
OBJECTIVES: The purpose of this in vitro study was to evaluate the wear of six composite resins for the veneering of crowns compared with the wear of human and bovine enamel, tested in a dual-axis chewing simulator. METHODS: Eight specimens of six different composite resins (Targis I+II, Solidex, BelleglassHP, Estenia, Solidex) and of human and bovine enamel were prepared. Steatite ceramic balls served as antagonistic specimens. Specimens were dynamically loaded in a dual-axis chewing simulator with 49 N up to 1,200,000 loading cycles with additional thermal cycling between 5 and 55 degrees C. After 120,000, 240,000, 480,000, 840,000 and 1,200,000 loading cycles, an impression of the specimens' surface and the antagonistic specimen was taken using a polyvinylsiloxane impression material. The substance loss at the surface was measured with computer-aided laser profilometry. Data were analyzed using ANOVA and the Tukey test. RESULTS: The wear of the ultra fine compact filled composite resins Solidex and BelleglassHP was not statistically significantly different from that of human enamel. The other composite resins and bovine enamel showed a wear statistically significantly higher than human enamel. SIGNIFICANCE: Comparing six composite resins for the veneering of crowns, ultra fine compact filled composite resins BelleGlassHP and Solidex showed a wear not significantly different from the wear of human and bovine enamel.
Later Middle Pleistocene human remains from the Almonda Karstic system, Torres Novas, Portugal.
Later Middle Pleistocene archeological deposits of the Galeria Pesada (Gruta da Aroeira), Almonda Karstic System, Torres Novas, Portugal, yielded two archaic human teeth, a mandibular canine and a maxillary third molar. The C(1)presents moderate and asymmetrical shoveling with a stout root. The slightly worn M(3)exhibits at least four cusps with a large hypocone, three roots with large radicular plates, and an absence of taurodontism. They are moderately large for later Middle Pleistocene humans in their buccolingual crown diameters, although the M(3)mesiodistal diameter is modest. The C(1)exhibits labial calculus and multiple linear hypoplastic defects, but the M(3)is lesion free. Both teeth are morphologically similar to those of other Middle Pleistocene European humans and reinforce a pattern of dental hypertrophy among these archaic Homo.
Dental microwear and diets of African early Homo.
Conventional wisdom ties the origin and early evolution of the genus Homo to environmental changes that occurred near the end of the Pliocene. The basic idea is that changing habitats led to new diets emphasizing savanna resources, such as herd mammals or underground storage organs. Fossil teeth provide the most direct evidence available for evaluating this theory. In this paper, we present a comprehensive study of dental microwear in Plio-Pleistocene Homo from Africa. We examined all available cheek teeth from Ethiopia, Kenya, Tanzania, Malawi, and South Africa and found 18 that preserved antemortem microwear. Microwear features were measured and compared for these specimens and a baseline series of five extant primate species (Cebus apella, Gorilla gorilla, Lophocebus albigena, Pan troglodytes, and Papio ursinus) and two protohistoric human foraging groups (Aleut and Arikara) with documented differences in diet and subsistence strategies. Results confirmed that dental microwear reflects diet, such that hard-object specialists tend to have more large microwear pits, whereas tough food eaters usually have more striations and smaller microwear features. Early Homo specimens clustered with baseline groups that do not prefer fracture resistant foods. Still, Homo erectus and individuals from Swartkrans Member 1 had more small pits than Homo habilis and specimens from Sterkfontein Member 5C. These results suggest that none of the early Homo groups specialized on very hard or tough foods, but that H. erectus and Swartkrans Member 1 individuals ate, at least occasionally, more brittle or tough items than other fossil hominins studied.
Microwear and morphology: functional relationships between human dental microwear and the mandible.
Microscopic pits and scratches form on teeth during chewing, but the extent to which their formation is influenced by mandibular morphology is unknown. Digitized micrographs of the base of facet nine of the first, second, and third mandibular molar were used to record microwear features from an archaeological sample of modern humans recovered from Semna South in northern Sudan (n=38; 100 BC to AD 350). Microwear patterns of the molar row are correlated with mandibular corpus width and depth, and with mandibular length. Variations in shear and compression at the base of facet nine during chewing were inferred. It may be that some correlations between microwear and mandibular morphology are predictable, reflecting similar aspects of masticatory loading, though the full extent of the relationship remains to be resolved.
Dental microwear texture analysis: technical considerations.
Dental microwear analysis is commonly used to infer aspects of diet in extinct primates. Conventional methods of microwear analysis have usually been limited to two-dimensional imaging studies using a scanning electron microscope and the identification of apparent individual features. These methods have proved time-consuming and prone to subjectivity and observer error. Here we describe a new methodological approach to microwear: dental microwear texture analysis, based on three-dimensional surface measurements taken using white-light confocal microscopy and scale-sensitive fractal analysis. Surface parameters for complexity, scale of maximum complexity, anisotropy, heterogeneity, and textural fill volume offer repeatable, quantitative characterizations of three-dimensional surfaces, free of observer measurement error. Some results are presented to illustrate how these parameters distinguish extant primates with different diets. In this case, microwear surfaces of Cebus apella and Lophocebus albigena, which consume some harder food items, have higher average values for complexity than do folivores or soft fruit eaters.
Correlation between buccolingual inclination and wear of mandibular teeth in ancient and modern Japanese.
This study compared the correlation between the buccolingual inclination and the wear score of the mandibular teeth in Jomon (one of the ancestors of modern Japanese who lived from 5000 to 300 BC) and modern Japanese. Data were obtained from 40 modern male Japanese and 39 male Jomon skulls housed in the University Museum of the University of Tokyo and National Science Museum, Tokyo. For each specimen, three computed tomograms of coronal sections of the mandibular body were available. The second premolar, first molar and second molar of Jomon stood more vertically than those of modern Japanese. There were significant correlations between tooth wear and the buccolingual inclination of mandibular molars. When ancient and modern populations were compared, tooth wear was significantly greater and buccolingual tooth inclination was more vertical in the ancient people, who probably applied stronger masticatory forces than modern people. The results suggest that the mandibular molar orientation is more buccal and there is greater tooth wear in the first and second molars of people with strong masticatory function.
Extreme bilateral molar rotation in Monodelphis domestica (Marsupialia: Didelphidae).
Rotation of a tooth around an axis perpendicular to the occlusal plane through angles approaching 180 degrees is a rare anomaly found in the mammalian dentition. A specimen of Monodelphis domestica was found to show such extreme rotation of both lower last molars, with consequent disruption of normal occlusion and wear. A review of the literature discovered 41 other reported cases of extreme rotation, from four different orders of mammals. The distribution of extreme rotation within the dentition can be summarized as follows. It is found only in isolated teeth or in contralateral pairs of teeth. Bilateral rotation is far more common than would be expected based on the chance of the independent occurrence of two rotations. Extreme rotation has a significantly higher frequency in upper rather than lower teeth, in premolars rather than other teeth, and on the left- rather than the right--hand side. The incidence of extreme rotation across mammals was estimated to be approx. 1 in 5850.
Experimental studies of human dentine wear.
Previous in-vitro studies have described the relation between rates of enamel wear and variables such as applied load and lubricant pH. The aim here was to extend understanding of tooth-wear processes by considering the rate of wear in human dentine. Enamel was removed from extracted third molar teeth that had been sectioned mesiodistally. Moisture fluctuation within dentine was minimized by conducting all procedures under copious irrigation or in sealed containers of lubricant at pH 7.0. Specimens were subjected to wear using a purpose-built apparatus at loads of 6.2, 9.95 and 13.2 kg. All experiments were done with a unidirectional wear stroke of 3 mm at a rate of 80 cycles/min for 75 min and repeated for 75 min. Dentine wear was assessed by specimen weight loss. At pH 7.0, wear rates ranged from 0.50 mg/10(3) cycles at a load of 6.2 kg to 0.77 mg/10(3) cycles when a load of 13.2 kg was applied. At higher loads, dentine wear rates were similar to those of enamel. Increasing load is thus associated with a progressive increase in the rate of dentine wear. This relation differs significantly from that for enamel, reflecting fundamental differences in the composition and structure of these tissues.
Removable occlusal overlay splint in the management of tooth wear: a clinical report.
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Clinical assessment of high-strength all-ceramic crowns.
STATEMENT OF PROBLEM: All-ceramic crowns are being used extensively. Little data are available on their clinical performance. PURPOSE: This study evaluated the clinical performance of In-Ceram (Vita Zahnfabrik) crowns. MATERIAL AND METHODS: Forty-one patients (16 men, 25 women; mean age 47.3 years, range 18 to 77 years) were examined with a total of 80 In-Ceram all-ceramic crowns fabricated at the University of Iowa College of Dentistry from 1994 to 1997. The percentage distribution for crowns included: 67% anterior single crowns, 26% posterior single crowns, 6% anterior implant crowns, and 1% posterior implant crowns. This study documented the integrity of the junction between crown and tooth, color match to adjacent teeth, secondary dental caries, wear of crown and opposing dentition, and visible cracks in the crown. Alpha, Bravo, and Charlie ratings were assigned with a modified USPHS criteria. The patients were also surveyed with respect to oral hygiene and satisfaction of treatment. Estimations of 4-year success rates and corresponding confidence intervals were calculated by fitting a constant hazard function model with the SAS procedure GENMOD. RESULTS: Marginal integrity for 88% of artificial crowns was rated Alpha or Bravo. Shade match for 99% was Bravo or better. Only 1% of the crowns were carious, and 1 crown exhibited occlusal wear. One premolar crown had a small fracture of veneering porcelain. One molar crown was remade after core fracture. All patients (100%) expressed satisfaction with their crowns. The estimated 4-year success rates (Alpha or Bravo), with 95% confidence intervals in parentheses were calculated as: 83.5% (65.7%-94.6%) for marginal integrity, 95.8% (82.9%-99.8%) for shade match, and 95.5% (81.6%-99.7%) for secondary caries, 100% (88%-100%) for wear, and 100% (88%-100%) for cracks.
Tooth wear treated with direct composite restorations at an increased vertical dimension: results at 30 months.
STATEMENT OF PROBLEM: Severe tooth wear localized to the anterior maxillary or mandibular teeth with loss of interocclusal space is difficult to manage. PURPOSE: This study evaluated the outcome of composite restorations placed at an increased vertical dimension of occlusion in such patients. METHODS AND MATERIAL: Sixteen patients were restored with 104 restorations in 2 groups. In group A, Durafill composite and Scotchbond Multipurpose dentine adhesive system were used to place direct anterior restorations (N = 52). In group B, Herculite XRV composite and Optibond dentine bonding agent was used (N = 52). The restorations were placed at an increased vertical dimension of occlusion creating a posterior disclusion of 1 to 4 mm. RESULTS: Clinical follow-up showed that the posterior occlusion remained satisfactorily restored after a mean duration of 4.6 months (range 1 to 11 months). Mean follow-up of 30 months has shown a combined success rate of 89.4% for both groups with 93 of the restorations remaining in service. Maintenance in group A was high with 33 failures, but low in group B with 6 failures. Patient satisfaction was reported as good. CONCLUSION: Direct composite restorations may be a treatment option for localized anterior tooth wear.
Clinical evaluation of resin-bonded gold alloy veneers.
STATEMENT OF PROBLEM: Clinical performance of resin-bonded alumina-abraded type III cast gold alloy veneers has not been reported. PURPOSE: This retrospective study evaluated the survival of such restorations for the management of tooth wear and other restorative problems. MATERIAL AND METHOD: This clinical study evaluated 25 patients between 14 and 60 years of age treated with a total of 158 cast gold veneers cemented with Panavia Ex cement. Restorations placed between January 1990 and February 1996 (mean age 48 months) were evaluated. Factors, including age, gender, operator, site, design, the extent of dentin exposure, the presence of previous restorations, dynamic and static occlusion, rubber dam, cause, and methods of interocclusal space creation, were evaluated with Cox regression. Survival probability was evaluated with Kaplan-Meier analyses. Significance was taken as P <.05. RESULTS: Failures occurred for 7.6% of restorations in 28% of patients. Alumina-abraded gold alloys cemented with Panavia Ex cement had an estimated 89% survival probability at 60 months using Kaplan-Meier analyses. The only variable to statistically influence survival was operator (P <.0001). Operator differences were due to a single operator who placed only 2 restorations in the same patient, both of which failed unusually quickly. CONCLUSION: Resin-bonded alumina-abraded type III cast gold alloys can be successfully used to restore both anterior and posterior teeth and were associated with an estimated 89% survival probability at 60 months.
Fabrication of multiple posts and cores using a thermoplastic material and an indirect technique: a clinical report.
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Wear of enamel and veneering ceramics after laboratory and chairside finishing procedures.
PURPOSE: This in vitro study compared the wear of enamel against 3 types of ceramics with high esthetic potential (designed for layering techniques): feldspathic porcelain (Creation), aluminous porcelain (Vitadur alpha), and low-fusing glass (Duceram-LFC). Laboratory finishing (glazing/polishing) and chairside polishing with a Dialite kit were simulated to compare their respective effects on wear. METHODS: Tooth-material specimen pairs were placed in an artificial mouth using closed-loop servohydraulics. Constant masticatory parameters (13.5 N occlusal force, 0.62 mm lateral excursion; 0.23 second cuspal contact time) were maintained for 300, 000 cycles at a rate of 4 Hz. The occlusal surface of each pair was mapped and digitally recorded before and after each masticatory test. Quantitative changes were measured in terms of depth and volume of wear. Quantitative wear characteristics were assessed by SEM. RESULTS: Significant differences were observed (2-factor ANOVA, P <.05). Duceram-LFC generated increased volume loss of enamel (0.197 mm(3)) compared with Creation (0.135 mm(3)) and Vitadur alpha (0.153 mm(3)). Creation exhibited the lowest ceramic wear and lowest combined volume loss (0.260 mm(3); the sum of the data for enamel and the opposing material) compared with Duceram-LFC (0.363 mm(3)) and Vitadur alpha (0.333 mm(3)). The most significant differences among materials were observed in volume loss, not in depth of wear. For all 3 ceramic systems, qualitative SEM evaluation revealed an abrasive type of wear. Wear characteristics of chairside polished specimens were similar to those of laboratory finished specimens (glazed and polished). CONCLUSION: Duceram-LFC was the most abrasive ceramic for the antagonistic tooth. Creation ceramic was the least abrasive material and most resistant to wear. Defects, brittleness, and the possibly insufficient toughness of LFC may explain its increased abrasiveness. Laboratory and chairside finishing procedures generated similar results.
Three-body wear associated with three ceramics and enamel.
STATEMENT OF PROBLEM: Wear of human enamel is a clinical concern whenever opposing teeth need to be restored using ceramic restorations. PURPOSE: This in vitro study investigated wear of human enamel and 3 dental ceramics: a conventional porcelain (Vitadur Alpha), a low-fusing hydrothermal ceramic (Duceram-LFC), and a machinable ceramic (Vita Mark II) in a 3-body wear test. MATERIAL AND METHODS: Thirty pairs of tooth-ceramic specimens were tested in a dental wear machine, under a standard load (40 N), rate (80 cycles/minute), and for 25,000 cycles in a simulated food slurry medium. Amount of wear was determined by measuring the height loss of the tooth and depth of wear track of the ceramic materials. Analysis of variance (ANOVA) was used to analyze the data, followed by Bonferroni multiple comparisons method to produce sets of simultaneous 95% confidence intervals. RESULTS: ANOVA revealed significant differences between the groups for both enamel wear (P =. 002) and ceramic wear (P <.001). Further comparisons (95% CI significance level) revealed that the difference in enamel wear produced by Alpha porcelain and Duceram-LFC ceramic material was not statistically significant, whereas that produced by Vita Mark II ceramic was significantly less. Vita Mark II ceramic was significantly more resistant to wear than Alpha porcelain and Duceram-LFC ceramic. Furthermore, Alpha porcelain was significantly more resistant to wear than Duceram-LFC ceramic. CONCLUSION: The abrasiveness of Alpha porcelain and Duceram-LFC ceramic was similar, yet both were significantly more abrasive than Vita Mark II ceramic. In addition, Vita Mark II was the most wear-resistant ceramic and Duceram-LFC ceramic the least resistant.
Occlusal rehabilitation of a patient with dentinogenesis imperfecta: a clinical report.
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In vitro investigation of the wear of human enamel by dental porcelain.
STATEMENT OF PROBLEM: Metal ceramic systems are advocated when both esthetics and strength are required. A major drawback to many porcelains is their wear and destruction of opposing natural dentition. PURPOSE: This study evaluated the wear of enamel opposing 1 traditional and 2 recently introduced low-fusing feldspathic dental porcelains. MATERIAL AND METHODS: Six blocks of Ceramco II, Finesse, and Omega 900 feldspathic porcelain materials were fabricated and fired according to manufacturer recommendations. Porcelain blocks were polished through 0.25 microm diamond polishing paste. Thirty-six enamel specimens were obtained and milled to a 2 mm (+0.5 mm) diameter. Enamel specimens were attached to an offset cam motor operating at 60 Hz. Enamel specimens were in constant contact with the stationary porcelain blocks under a load of 600 g and traversed a distance of 8 mm. Diameter and height of enamel specimens were measured at times of 0, 6, 12, 24, and 48 hours and subsequent determination of enamel volume loss recorded. Profilometric surface roughness of the ceramic blocks was also measured for the corresponding times. RESULTS: Statistical analysis revealed that both Finesse and Omega 900 feldspathic porcelains caused significantly less enamel volume loss when compared with Ceramco II porcelain at all time intervals. Surface roughness revealed no consistent significant differences among porcelains. CONCLUSION: Both Finesse and Omega 900 porcelains were not as destructive to human tooth structure as Ceramco II porcelain. These results suggest an advantage of the new, lower-fusing porcelains in conditions where natural dentition wear is a concern.