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PubMed1994

The effect of restorative materials on the wear of human enamel.

The wear of human dental enamel against amalgam, Concise composite, SR-Isosit Inlay/Onlay composite, Vitadur-N glazed porcelain, unglazed IPS Empress ceramic, and enamel (control) was investigated by use of a modified stress cycling machine. Testing was carried out in water and in citric acid (pH 4) and the enamel-material couples were subjected to 25,000 cycles of wear with a maximum load of 40 N. Tooth profile reduction was measured at baseline and at 5000 cyclic intervals with a computer image analysis program. The depth of the wear scars on material specimens was analyzed with a profilometer. All materials produced increased enamel wear in acid. Vitadur-N glazed porcelain was found to be the most destructive to human dental enamel, and this was closely followed by Empress and enamel.

Acrylic Resins↗
PubMed1999

The influence of cyclic loading on the wear of a dental composite.

The load applied to a tooth surface during mastication is not a constant force and the objective of the research reported in this paper was to evaluate the impact of variable masticatory loads on the mechanisms involved in the wear of a dental composite. A new wear testing machine has therefore been developed, which incorporates a sine cam mechanical system to generate an alternating sine curve load at the wear surfaces to simulate the loading produced by masticatory process. The basic wear pattern is generated by positioning a disc shaped specimen against a rotating cylindrical ring with a normal load applied to the upper surface of the specimen. This approach allows different combinations of static and sine curve loads to be applied, thereby facilitating the study of different wear situations. It was found that the wear behaviour associated with variable loading patterns differed from that of static loading.

Composite Resins↗
PubMed2006

Night splinting does not increase ankle range of motion in people with Charcot-Marie-Tooth disease: a randomised, cross-over trial.

QUESTION: What is the effect of wearing splints at night to stretch the plantarflexors on dorsiflexion range of motion (ROM) in people with Charcot-Marie-Tooth disease? DESIGN: Randomised, assessor-blinded, cross-over trial. PARTICIPANTS: 14 people (1 dropout) aged 7 to 30 years with Charcot-Marie-Tooth disease Type 1A and with < or = 15 degrees dorsiflexion range of motion (ROM). INTERVENTION: A splint holding the ankle in maximum dorsiflexion was worn nightly on one leg for 6 weeks followed by the opposite leg for the subsequent 6 weeks. OUTCOME MEASURES: The primary outcome was dorsiflexion ROM; secondary outcomes were eversion ROM, and dorsiflexion, eversion, and inversion strength, measured before and after splinting, and three months later. RESULTS: There was no significant difference between the experimental and the control intervention in terms of ROM or strength. Wearing the splint at night increased dorsiflexion ROM by 1 degree (95% CI -3 to 4; p = 0.72) and eversion ROM by 1 degree (95% CI -1 to 3; p = 0.28) compared to not wearing the splint. Wearing the splint increased dorsiflexion strength by 41 N (95% CI -53 to 135; p = 0.38), reduced eversion strength by 6 N (95% CI -112 to 101; p = 0.92) and reduced inversion strength by 8 N (95% CI -110 to 95; p = 0.88) compared to not wearing the splint. CONCLUSION: Wearing night splints does not increase ankle ROM or strength in people with Charcot-Marie-Tooth disease Type 1A.

Adolescent↗
PubMed2002

Tongue piercing: impact of time and barbell stem length on lingual gingival recession and tooth chipping.

BACKGROUND: The increasing popularity of tongue piercing has prompted several case reports documenting oral complications of this practice. However, there are no studies assessing potentially significant parameters. The purpose of this study was to evaluate the effect of time (years of wear) and tongue barbell size (stem length) on gingival recession and tooth chipping. METHODS: Fifty-two adults (mean age 22) with tongue piercings were examined for gingival recession on the lingual aspect of the 12 anterior teeth and for tooth chipping anywhere in the mouth. Subjects were grouped according to years of wear (0 to 2, 2 to 4, and 4+ years) and barbell stem length (long > or =1.59 cm, or short <1.59 cm). Data analysis was based on binomial test and non-parametric tests. RESULTS: No subject with a tongue piercing <2 years (group 0-2) exhibited lingual recession or tooth chipping. Lingual recession was found on mandibular central incisors in 50% of subjects wearing long barbells for 2 or more years. Tooth chipping was found on molars and premolars in 47% of subjects with a tongue piercing for 4+ years. CONCLUSIONS: Tongue piercing is associated with lingual recession of mandibular anterior teeth and chipping of posterior teeth. Long-term use of a tongue barbell increases the prevalence of these complications. Barbell stem length appears to differentially affect prevalence of recession and chipping. Since the overwhelming majority of subjects with tongue piercings are young adults, cessation efforts are needed to target this population.

Adolescent↗
PubMed2001

Reversed palatal perforation by upper incisors in ageing blind mole-rats (Spalax ehrenbergi).

Blind mole-rats (Spalax ehrenbergi) are fossorial solitary rodents that present striking morphological, physiological and behavioural adaptations to the subterranean environment in which they live. Previous studies have shown that mole-rats are specialised in tooth-digging. The rapid eruption-rate of their incisors has evolved to compensate for their excessive wear by excavation. Males use their incisors more than females for digging and fighting, and their rate of incisor eruption is significantly more rapid than in females. Since mole-rats use their incisors for digging throughout the year, we suggest that continuous mechanical pressure on their oral tissues concentrated at the apical sites of the upper incisors leads to cell and tissue fatigue. We provide evidence for 5 stages of palatal perforation by the upper incisors at their apical sites, with maximum perforation characterising aged males. Interspecies comparisons with 7 other fossorial and semi-fossorial rodent species, and with beavers, which expose their incisors to enormous mechanical pressure, revealed that this palatal perforation is unique to the male mole-rat. We suggest that while the fast eruption rate of incisors in the mole-rat compensates for the rapid wear resulting from digging, evolutionary adaptation to continuous tooth-digging is still ongoing, since the physical pressure of digging at the apical sites of the upper incisors leads to tissue destruction, breakage of the palatal bone and possibly to death, as a result of maxillary inflammation.

Aging↗
PubMed1985

A method to determine the loss of substance of dental restorations.

A method is described for quantitative in vivo wear measurements on Class I and II composite restorations. Class I gold inlays were made in an acrylic premolar and molar. Over the occlusal parts of the teeth cast silver caps were made after releasing the surface of the inlay with tinfoil. Wear on the restorations was simulated by grinding away some gold from the inlay. Silicon impressions of the teeth were made with the caps both before and after this simulation. The volume and the average thickness of the removed gold was measured from the weight of the enclosed impression material in the cap before and after the wear simulations, the density of the tinfoil and the impression material as well as thickness and the weight of the tinfoil-release. Values expected for the volume and the average thickness of the removed gold were calculated from the weight of the restored acrylic teeth before and after the wear simulation, the weight, the density and the thickness of the tinfoil and the density of the gold used for the inlays. Measured and expected values are linearly correlated (r = 0.97). An average wear thickness of the occlusal surface of a particular tooth of at least 30 micron can be detected. Because of its simplicity, inexpensiveness and accuracy the wear measurement method is highly productive and suitable for large scale and long-term clinical research on the wear behaviour of posterior composites.

Acrylic Resins↗
PubMed2006

Incidence of noncarious cervical lesions and their relation to the presence of wear facets.

PROBLEM: Noncarious cervical lesions are characterized by loss of tooth structure in the cervical area, compromising its integrity and resulting in esthetic problems for the patient. PURPOSE: The purpose of this study was to assess noncarious cervical lesions in young patients in an attempt to establish a possible relationship to the presence of wear facets. MATERIALS AND METHODS: First-year dental students of Bauru Dental School were studied to verify the prevalence of noncarious cervical lesions and their relationship to the presence of wear facets. After 3 years, the students were examined again to verify the incidence of new lesions, trying to establish a correlation to the previous existence of wear facets. RESULTS: Of the 1,131 teeth analyzed, 129 had noncarious cervical lesions. Twenty-nine of the 40 students had at least one tooth with one lesion. After 3 years, the incidence of new lesions was 57. Mandibular first molars (22.3%), mandibular first premolars (13.2%), mandibular second premolars (13.2%), and maxillary first molars (12.4%) showed the highest prevalence of lesions. On final analysis, 86.8% of all teeth presenting lesions showed wear facets. The identification of new lesions associated with the presence of wear facets identified during the first exam 3 years earlier was statistically significant (p < 0.01). CONCLUSIONS: The patterns of wear facets found in the study population examined were associated with an increased occurrence of noncarious cervical lesions. CLINICAL SIGNIFICANCE: Occlusal factors, especially the presence of wear facets, should be considered in the management of noncarious cervical lesions.

Adolescent↗
PubMed2000

Adhesive luting of indirect restorations.

PURPOSE: To describe the potential of adhesive luting procedures with respect to (1) material characteristics and classifications, (2) film thickness, (3) overhang control, (4) bonding to different inlay materials, (5) adhesion to tooth substrates and the problem of hypersensitivities, (6) wear of luting composites, and (7) clinical performance. MATERIALS AND METHODS: A literature review of relevant studies of various in vitro and in vivo studies enables an overview of possibilities and limitations of adhesively luted indirect restorations. RESULTS: (1) Resin-based composites are the material of choice for adhesive luting. Both material properties and wear behavior of fine particle hybrid-type resin-based composites are superior to other materials. The use of compomers is questionable due to hygroscopic expansion and possible crack formation as proven for IPS Empress caps in vitro and in vivo. (2) Recent luting cements exhibit excellent flow characteristics with mean film thicknesses ranging between 8 microm and 21 microm. The ultrasonic insertion technique is recommended for viscous luting composites or conventional restorative composites utilizing their thixotropic properties. (3) For successful overhang control, good fit of the restoration (during luting) and high radiopacity of the cement (after luting) are indispensable. Overhang control is estimated easier when the ultrasonic insertion technique is applied. (4) The pre-treatments of ceramic inlays using hydrofluoric acid or silica coating result in effective bonding; for pre-treatment of resin-based composite inlays, silica coating is promising as well. (5) Bonding to enamel and dentin is proven clinically acceptable, but it should be performed with multi-step systems providing separate primers and bonding agents producing a perfect internal seal with almost no hypersensitivities. Dual-cured multi-step bonding agents provide the most promising potential. (6) The viscosity and filler content of the resin composite used for luting does not influence the wear characteristics within the marginal luting area in vivo. However, the ultrasonic insertion technique involving high viscosity materials provides enhanced handling characteristics for luting of tooth-colored inlays. (7) Clinical results with tooth-colored inlays and veneers are promising over periods of up to 10 yrs, including use in severely destroyed teeth.

Acid Etching, Dental↗
PubMed1986

Epithelial differentiation at the edentulous alveolar ridge in man. A stereological study.

The epithelial lining of the mucosa of the edentulous, maxillary alveolar ridge was subjected to an ultrastructural and stereological analysis. Four biopsies collected from the non-inflamed crest, i.e., the center over former tooth sockets, in non-denture-wearing female patients 30 to 55 years of age were processed for light and electron microscopy. At the light-microscopic level, epithelial thickness was determined histometrically. Electron micrographs were sampled at two levels of magnification, from five strata in regions of epithelial ridges and from three strata over connective tissue papillae. Standardized stereological point-counting techniques were employed to analyze a total of 990 electron micrographs. Observations and data revealed that at the alveolar ridge the oral epithelium is truly keratinizing and comprises four strata including a 40 +/- 5 micron-thick stratum corneum, which displays the oral keratin pattern. The histo- and cytodifferentiation were peculiar: (1) Compared to the neighbouring gingival and hard palate epithelium, that of the alveolar crest was markedly thicker, with elongated rete ridges indicating acanthosis. (2) The cytoarchitecture was identical neither to the gingival nor to the hard palate epithelium but revealed a mixture of features typical for either of these two epithelia. Reasons for this are explained on the basis of factors, possible genetic, inherent in epithelial cells that are possibly derived from both the gingival and the palatal environment.

Adult↗
PubMed1976

Attrition: possible mechanisms of compensation.

Attrition, or wear of the occlusal surfaces of the teeth, may not only be physiologically normal, but necessary for function. Since occlusal wear must lead to reduction in tooth length, significant dimensional changes in facial morphology are inevitable unless mechanisms exist to compensate for attrition. Secondary dentine formation, alveolar growth, and adaptive changes in the masticatory muscles can provide this compensation, and may be part of a complex system by which an effective level of masticatory function is maintained even when attrition is extreme.

Adult↗
PubMed1980

Flow rate, sodium and potassium concentration in mixed saliva of complete denture-wearers.

Flow rate, sodium and potassium concentrations in stimulated mixed saliva obtained from eleven elderly (mean age 63) inexperienced denture-wearers, were determined. Salivary samples were collected at four different dental stages: 1. Before tooth extraction. 2. After tooth extraction. 3. Three weeks after wearing newly constructed complete dentures. 4. Following one year of denture wearing. Plasma electrolytes were included for comparison. The salivary sodium and potassium concentrations varied from stage to stage without showing corresponding variations in sodium and potassium in the blood. This points to selective action and an active transport system in the salivary cells. The mean flow rate and salivary electrolyte concentration showed a definite significant rise following the wearing of new complete dentures as compared with the previous dentulous and edentulous stages (Period A, non-denture-wearers). The mean flow rate was 2 ml/min after denture-wearing compared to 0.75 ml/min at the dentulous and edentulous stage (Period A). The stimulant effect represented by the dentures was found to be even more pronounced after one year. Mean sodium and potassium concentration at Period A were at levels of 5.50 and 13.67 mequiv./l respectively, as compared to levels of 23.72 and 19.40 mequiv./l respectively, after insertion of dentures. The difference was significant at a level of P less than 0.005. Although sodium concentration correlated well with flow rate, potassium concentration did not show any correlation with variations during secretion, following the wearing of dentures.

Adult↗
PubMedDate not supplied

Salivary proteins: protective and diagnostic value in cariology?

Saliva is essential for a lifelong conservation of the dentition. Various functions of saliva are implicated in the maintenance of oral health and the protection of our teeth: (i) The tooth surface is continuously protected against wear by a film of salivary mucins and proline-rich glycoprotein. (ii) The early pellicle proteins, proline-rich proteins and statherin, promote remineralization of the enamel by attracting calcium ions. (iii) Demineralization is retarded by the pellicle proteins, in concert with calcium and phosphate ions in saliva and in the plaque fluid. (iv) Several salivary (glyco)proteins prevent the adherence of oral microorganisms to the enamel pellicle and inhibit their growth. (v) The salivary bicarbonate/carbonate buffer system is responsible for rapid neutralization of acids. An overview is presented on the major antimicrobial systems in human saliva. Not only the well-known major salivary glycoproteins, including mucins, proline-rich glycoprotein and immunoglobulins, but also a number of minor salivary (glyco)proteins, including agglutinin, lactoferrin, cystatins and lysozyme, are involved in the first line of defense in the oral cavity. Besides, small cationic antimicrobial peptides, e.g. defensins, cathelicidin and the histatins, have come into focus. These are potentially suited as templates for the design of a new generation of antibiotics, since they kill a broad spectrum of microorganisms, while hardly evoking resistance, in contrast to the classical antibiotics.

Antimicrobial Cationic Peptides↗
PubMed1990

Nightguard vital bleaching: effects on enamel surface texture and diffusion.

A recently reported technique for bleaching vital discolored teeth involves the use of a mouthguard and 10% carbamide peroxide without preoperative etching or postoperative polishing of the enamel. This in vitro study evaluated the effects of the bleaching agent on the surface texture of the enamel. Thirty-three extracted teeth were subjected to 10% carbamide peroxide for a period equivalent to 5 weeks of nighttime wear. A control area on each tooth had been covered and sealed. All discolored teeth experienced lightening, but there was no difference in color between the treated and control areas; the color-changing effects apparently extend to portions of the tooth not in direct contact with the solution. Epoxy replicas of the teeth were examined under a scanning electron microscope. No etching was apparent, and no difference in surface texture between treated and control areas was detected.

Bicuspid↗
PubMed1992

Composite-resin materials and techniques in dentistry.

Important features to consider when selecting composite resins are filler size and amount, radiopacity, and fluoride content. Submicron particles provide the best polishability, and heavily filled resins demonstrate better wear resistance. The radiopacity of the composite resin should slightly exceed that of enamel to allow visualization of the restoration and recurrent decay. Fluoride added to the matrix may arrest the progression of caries. Properly cured composite resins should not cause chronic pulpal irritation; however, infection of the cervical contraction gap resulting from poor bonding to root surfaces may cause pulpal irritation. Techniques to improve curing include incremental build-up, reflective matrices and wedges, and controlling the direction of light vectors. A surface sealant is highly recommended to reduce wear, especially in the posterior region. Porcelain veneers perform better clinically than do composite-resin veneers. Class I and II composite-resin restorations reinforce weakened tooth structure; however, problems with cervical leakage and wear prevent the recommendation of these materials for larger posterior restorations that involve occlusal contacts or that require bonding to root surfaces.

Composite Resins↗
PubMed2004

In vitro wear of nano-composite denture teeth.

PURPOSE: Few laboratory tests have been able to substantiate and quantify the wear resistances of polymeric denture teeth. This study evaluated the relative wear resistance of several types of denture teeth using an in vitro wear testing device. MATERIAL AND METHODS: Four different types of denture teeth [nano-filled (Veracia) and micro-filled composites (SR-Orthosit, Endura, Duradent, Surpass), cross-linked acrylic (SR-Postaris, Genios-P, Creapearl, Vitapan Physiodens, Premium 8, Integral), and a conventional acrylic (Biotone)] were used. The flattened buccal surface of each denture tooth was subjected to the evaluation of Knoop hardness (n=5) and localized wear for 100,000 cycles (n=10). Wear values were determined in micrometers using a profilometer. The data for the hardness, wear depth, and worn surface areas were individually analyzed by one-way ANOVA. RESULTS: Knoop hardness values (KHN) ranged from 28.2 to 29.8 for micro-filled composite, 18.9 to 21.6 for cross-linked acrylic, 22.7 for nano-composite, and 18.6 for conventional acrylic teeth. All micro-filled composite teeth were significantly harder than other teeth (p <0.0001). The wear depth values were 90.5 microm for the nano-composite, 69.8 to 93.0 microm for the micro-filled composite, 80.8 to 104.0 microm for the cross-linked acrylic, and 162.5 microm for conventional acrylic teeth. The worn surface areas were 5.1 mm2 for the nano-composite, 2.6 to 3.6 mm2 for the micro-filled composite, 4.4 to 5.7 mm2 for the cross-linked acrylic, and 10.1 mm2 for conventional acrylic teeth. The wear values of the acrylic control were significantly different from all other denture teeth (p <0.001). CONCLUSION: The nano-composite tooth was harder and more wear resistant than the acrylic teeth but not significantly different from most of the cross-linked and micro-filled composite teeth tested.

Acrylic Resins↗
PubMed1975

Relation of the alveolus to the cemento-enamel junction following attritional wear in aboriginal skulls. An enquiry into normality of cementum exposure with aging.

With tooth attrition, the height of the alveolar crest does not increase to keep pace with active tooth eruption and the cemento-enamel junction-alveolar crest distance increases slightly with age in aboriginal skulls. But there is no atrophy of the alveolar bony margin. Some decrease in interalveolar height does occur. This does not necessarily mean that passive eruption with exposure of cementum is normal. Rather it is postulated that the epithelial attachment proliferates onto cementum, inhibiting alveolar crest addition, while the base of the gingival sulcus remains at the cemento-enamel junction. During the course of this investigation, it was found that the distance between the cemento-enamel junction and alveolar crest increased more rapidly with advancing wear in the lower molar region than in the upper. In the lower first molar region, the lingual distance was significantly greater than that between cemento-enamel junction and alveolar crest on the buccal aspect during each stage of wear. The size of the tooth, as reflected in the robustness index, had no influence on the processes or rate of active eruption, bone deposition at the alveolar crest, or measurements taken between cemento-enamel junction and alveolar crest.

Aging↗
PubMed2007

Mutual wear evaluation of resin composites when opposing enamel and dentin.

Mutual wear rates of resin composites and both superficial and deep layers of enamel and dentin were investigated by means of an in vitro wear test. Occlusal surfaces of extracted molars were ground flat to respective layers of enamel and dentin. Hemispherical-shaped styli (n = 8) made of microfilled and microhybrid composites were placed perpendicular to the finished tooth surface (600 grit) in the presence of tap water, and a two-body wear test (75 N load and 1.2 Hz) was performed for 100,000 cycles. The wear depths on both tooth and composite specimens were determined, and the data were statistically analyzed by two-way ANOVA and Boneferroni test (p < 0.05). The values of deep and superficial dentin specimens against Esthet-X (530.2 +/- 213.0 microm and 717.4 +/- 309.6 microm) were significantly greater than those against Epic-TMPT (34.1 +/- 17.6 microm and 29.3 +/- 10.8 microm). The values of Esthet-X against dentin were the smallest (2.4-2.6 microm), followed by those of the same material against enamel (5.5-6.1 microm), and those of Epic-TMPT against enamel (7.2-7.9 microm). It was concluded that the wear rates of dentin varied with the type of composite used while those of enamel showed the consistency.

Composite Resins↗