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PubMed2003

Anatomic crown width/length ratios of unworn and worn maxillary teeth in white subjects.

STATEMENT OF PROBLEM: Dimensions of teeth have been available for a century. Some significant and clinically relevant aspects of dental esthetics, however, such as the crown width/length ratios, have not been presented in tooth morphology sources until recently. PURPOSE: The purpose of this study was to analyze the anatomic crowns of 4 tooth groups (central incisors, lateral incisors, canines, and first premolars) of the maxillary dentition with respect to width, length and width/length ratios and determine how these parameters are influenced by the incisal edge wear. MATERIAL AND METHODS: Standardized digital images of 146 extracted human maxillary anterior teeth from white subjects (44 central incisors, 41 lateral incisors, 38 canines, 23 first premolars) were used to measure the widest mesiodistal portion "W" (in millimeters) and the longest inciso-cervical/occluso-cervical distance "L" (in millimeters). The width/length ratio "R" (%) was calculated for each tooth. A 1-way analysis of variance was used to compare the mean values of W, L, and R for the different groups ("unworn" and "worn" subgroups, except for premolars). Multiple least significant difference range tests (confidence level 95%) were then applied to determine which means differed statistically from others. RESULTS: There was no influence of the incisal wear on the average value of W (width) within the same tooth group. The widest crowns were those of central incisors (9.10 to 9.24 mm) > canines (7.90 to 8.06 mm) > lateral incisors (7.07 to 7.38 mm). Premolars (7.84 mm) had similar width as canines and worn lateral incisors. The L-value was logically influenced by incisal wear (worn teeth were shorter than unworn teeth) except for lateral incisors. The longest crowns were those of unworn central incisors (11.69 mm) > unworn canines (10.83 mm) and worn central incisors (10.67 mm) > worn canines (9.90), worn and unworn lateral incisors (9.34 to 9.55 mm), and premolars (9.33 mm). Width/length ratios also showed significant differences. The highest values were found for worn central incisors (87%) and premolars (84%). The latter were also similar to worn canines (81%), which constituted a homogeneous group with worn lateral incisors (79%) and unworn central incisors (78%). The lowest ratios were found for unworn canines and unworn lateral incisors (both showing 73%). CONCLUSIONS: Along with other specific and objective parameters related to dental esthetics, average values for W (mesiodistal crown dimension), L (inciso-cervical crown dimension), and R (width/length ratio) given in this study for white subjects may serve as guidelines for treatment planning in restorative dentistry and periodontal surgery.

Analysis of Variance↗
PubMed2001

Evaluation of effect of 3D video glasses on perceived pain and unpleasantness induced by restorative dental treatment.

Previous studies on modulation of anxiety, pain and unpleasantness have documented a positive effect of video glasses (I-Glasses, Virtual i-O, Seattle, USA) on the perceived pain and unpleasantness under different laboratory and clinical conditions. The aim of this study was to evaluate whether distraction induced by video glasses also had an effect on the perceived intensity of pain and unpleasantness during dental treatment. Pain and unpleasantness was evoked by the preparation (drilling) of a minor dental cavity (class I). Twenty-three patients (17 female and six male, age range 20-49 years) with a need for an occlusal dental restoration in two homologous teeth participated in the study. In this split-mouth design, the patient received the dental treatment wearing 3D video glasses and without video glasses (control situation) in a randomized order. The tooth cavities were prepared in accordance with conventional techniques after mounting the video glasses. The patient rated the intensity of pain and unpleasantness on 100 mm visual analogue scales (VASs) after preparation of the first cavity; immediately after, the opposite tooth was prepared and again the volunteer rated the intensity of pain and unpleasantness. The cavities were then filled using a routine composite technique. Eventually, the patient indicated whether she would prefer video glasses or not if she were to have another filling and what the expectations of the effect had been. Differences in VAS ratings in the video and control situation were tested by Student's t-test. There was no statistically significant effect on the perceived pain (p=0.90) or unpleasantness (p=0.39), but the majority (74%) of the patients would still prefer to wear video glasses if they were to have another dental filling, and 73% had expected a positive effect of the video glasses. These findings suggest that perceived intensity of dental pain is resistant to a simple distraction technique.

Adult↗
PubMed1979

The effect of wear on the cheek teeth and associated dental tissues of the lizard Uromastix aegyptius (Agamidae).

Serial coronal sections of the teeth and their surrounding tissues in the agamid lizard, Uromastix aegyptius, were examined with the light microscope in order to determine how these structures change as the teeth wear. Because new teeth are added only at the posterior end of the tooth row and older teeth are not replaced, the series of sections included the youngest as well as the oldest teeth. Two types of changes occur as the teeth become older: bone under the teeth changes from cancellous to compact, and the pulp chamber of the tooth is obliterated. Although the labial surface of the dentary lacks a periosteal covering and some of the bone lacks any covering at all, it remains functional throughout the life of the animal.

Animals↗
PubMed2004

Minimizing prion risk without compromising the microbial composition of biofilms grown in vivo in a human plaque model.

AIMS: To determine whether the stringency of sterilization procedures for biological components of in vivo dental plaque-generating devices based on enamel can be increased to minimize prion risk without compromising natural biofilm composition. METHODS AND RESULTS: The composition of in vitro biofilms, grown on hypochlorite-treated and untreated autoclaved enamel surfaces, was determined using culture-based methods and checkerboard DNA: DNA hybridization analysis. No differences were found between biofilms recovered from either substrate. SIGNIFICANCE: Several in situ models allow generation of plaque in the oral cavity, followed by recovery of intact biofilms for experimentation. Approaches allowing plaque formation on natural tooth surfaces are most valuable, but present a possible infection risk to volunteers wearing plaque-collecting devices, particularly with respect to prions. Hypochlorite treatment of biological material, as an adjunct to autoclaving, reduces infection risk without compromising biofilm composition and should be adopted in all future studies using plaque-generating devices incorporating enamel, where there is a potential prion threat, and further investigated in other biological hard tissues.

Bacteria↗
PubMed1994

Mesio-occlusodistal amalgam restorations: quantitative in vivo data up to 4 years. A data base for the development of amalgam substitutes.

Wear and marginal quality of 14 mesio-occlusodistal amalgam restorations (Dispersalloy) were quantitatively analyzed in this in vivo study. Wear rates, measured as maximum vertical loss of substance in the occlusal contact area, were 41, 50, 57, 79, 82, 123, 165, and 215 microns after 1, 2, 3, 6, 9, 24, 36, and 48 months, respectively. In the contact-free occlusal area an expansion of 2 to 9 microns was recorded. The micromorphology of the tooth-amalgam interface significantly changed within the first 9 months after restoration placement. The percentages of marginal opening increased from 91% to 100%, marginal restoration fracture from 49% to 89% and underfilled margin from 50% to 78%. Amalgam restorations have clinically proved successful despite their poor marginal adaptation and their inferior wear resistance compared to enamel. Thus, the wear resistance of amalgam substitutes, preferably metal-free, tooth-colored restorative materials, would not necessarily have to exceed that of amalgam to replace it. The wear data generated may serve as guiding figures in the development of amalgam substitutes.

Adult↗
PubMed1992

Vertical dimension increases in the adult rhesus monkey: a pilot study.

Tooth impaction, increased muscle activity, and histologic changes in the bone of the temporomandibular joint have been reported following attempts to increase the vertical dimension of occlusion. The purpose of this research was to study the effects of increases in the vertical dimension of occlusion on bone density at five levels of the mandible in the adult rhesus monkey, and to assess dentoalveolar changes by lateral cephalometric radiographs and mounted diagnostic casts. Mandibular cobalt chromium splints measuring 3 mm in height at the first molar, providing even occlusal contact to the maxillary anterior and posterior teeth, were cemented in place on two monkeys. Five similar monkeys without splints were used as controls. Computed tomograms were completed to evaluate bone density bilaterally at five levels of the mandible after 3 months of splint wear. Pretreatment and posttreatment lateral cephalometric radiographs and mounted diagnostic casts were completed to assess tooth impaction. Periodontal ligament (PDL) thickening and mobility of molars and premolars were evaluated before splint placement and after splint removal. There was no statistically significant difference in the bone density levels of the animals with splints compared with the controls. Minimal dentoalveolar changes were observed.

Animals↗
PubMed2006

Inferring parrotfish (Teleostei: Scaridae) pharyngeal mill function from dental morphology, wear, and microstructure.

Morphology, occlusal surface topography, macrowear, and microwear features of parrotfish pharyngeal teeth were investigated to relate microstructural characteristics to the function of the pharyngeal mill using scanning electron microscopy of whole and sectioned pharyngeal jaws and teeth. Pharyngeal tooth migration is anterior in the lower jaw (fifth ceratobranchial) and posterior in the upper jaw (paired third pharyngobranchials), making the interaction of occlusal surfaces and wear-generating forces complex. The extent of wear can be used to define three regions through which teeth migrate: a region containing newly erupted teeth showing little or no wear; a midregion in which the apical enameloid is swiftly worn; and a region containing teeth with only basal enameloid remaining, which shows low to moderate wear. The shape of the occlusal surface alters as the teeth progress along the pharyngeal jaw, generating conditions that appear suited to the reduction of coral particles. It is likely that the interaction between these particles and algal cells during the process of the rendering of the former is responsible for the rupture of the latter, with the consequent liberation of cell contents from which parrotfish obtain their nutrients.

Animals↗
PubMed2001

A comparison of the wear resistance and hardness of indirect composite resins.

STATEMENT OF PROBLEM: Various new, second-generation indirect composites have been developed with claimed advantages over existing tooth-colored restorative materials. To date, little independent research has been published on these materials, and the properties specified in the advertising materials are largely derived from in-house or contracted testing. PURPOSE: Four second-generation indirect composites (Artglass, belleGlass, Sculpture, and Targis) were tested for wear resistance and hardness against 2 control materials with well-documented clinical application. Human enamel was also tested for comparison. MATERIAL AND METHODS: Twelve specimens of each material were fabricated according to the manufacturers' directions and subjected to accelerated wear in a 3-body abrasion, toothbrushing apparatus. Vickers hardness was measured for each of the tested materials, and energy dispersive x-ray (EDX) spectroscopy was performed to determine the elemental composition of the composite fillers. The statistical tests used for wear and hardness were the Kruskal-Wallis 1-way ANOVA test with Mann-Whitney tests and 1-way ANOVA with multiple comparisons (Tukey HSD). The Pearson correlation coefficient was used to determine the existence of a relationship between the hardness of the materials and the degree to which they had worn. The level of statistical significance chosen was alpha=.05. RESULTS: The control material Concept was superior to the other composites in wear resistance and hardness and had the lowest surface roughness. Significant relationships were observed between depth of wear and hardness and between depth of wear and average surface roughness. Enamel specimens were harder and more wear resistant than any of the composites. EDX spectroscopy revealed that the elemental composition of the fillers of the 4 new composites was almost identical, as was the composition of the 2 control composites. CONCLUSION: The differences in wear, hardness, and average surface roughness may have been due to differences in the chemistry or method of polymerization of the composites. Further research in this area should be encouraged. It was also apparent that the filler present in the tested composites did not exactly fit the manufacturers' descriptions.

Acrylic Resins↗
PubMed1999

Two-body sliding wear of a direct-filling silver alternative to amalgam.

OBJECTIVE: This study investigated the wear resistance of a mercury-free silver direct-filling material and a dental amalgam. METHOD AND MATERIALS: A precipitated silver powder was rinsed with dilute fluoboric acid and consolidated into a cohesive solid. For tooth cavity restoration and flexural testing, the silver was consolidated with a dental amalgam plugger at a load of 15 N. For wear testing, because of the relatively large specimen size, the silver was pressed at a pressure of 150 MPa, yielding a density similar to that obtained by hand consolidation. RESULTS: The silver had a flexural strength twice that of amalgam. Pin-on-disk wear resulted in a smooth surface and hardening in silver, as measured by indentation inside the wear tracks, in contrast to the damage that was found in amalgam. The wear track cross-sectional area (n = 12) at 10(6) revolutions was not statistically significantly different among amalgam, polished silver, and burnished silver. CONCLUSION: The consolidated silver exhibited work hardening and surface densification during wear and, as a result, was more resistant to wear-induced damage than amalgam.

Analysis of Variance↗
PubMed1998

Cytotoxicity evaluation of 43 metal salts using murine fibroblasts and osteoblastic cells.

Metallic biomaterials are generally used for replacement of structural components of the human body such as bones, joints, and tooth roots. When they are implanted inside a body, metallic biomaterials may corrode and/or wear, releasing metal ions and debris which may have toxic effects on tissues and organs. Since it is important for biomaterials to have no toxicity against a living body, a systematic and quantitative evaluation of the cytotoxicity of metallic elements is required for the development of new metallic biomaterials with superior biocompatibility. In this study, the cytotoxicity of 43 metal salts were evaluated by the colony formation method using two kinds of cultured cells. The effects of the difference in valence numbers of metallic elements in the salts on cytotoxicity were examined. The cytotoxicity of the salts of metallic elements' oxo acids was also investigated. As a result, the intensity of metal salts' cytotoxicity tends to be quite similar between MC3T3-E1 and L929 (the correlation coefficient of metal salts' IC50s is 0.82). The intensity of metal salts' cytotoxicity depends on the kinds of metallic elements, their chemical states, and concentrations. The IC50 of the highest toxic salt is 1.36 x 10(-6) mol L-1, which differs four orders of magnitude from the IC50 of the lowest toxic salt. K2Cr2O7, CdCl2, VCl3, AgNO3, HgCl2, SbCl3, BeSO4, and InCl3 are high toxic salts in which IC50s are smaller then 10(-5) mol L-1 for both or either of the cell lines. HgCl, Tl(NO3)3, GaCl3, CuCl2, MnCl2, CoCl2, ZnCl2, NiCl2, SnCl2, IrCl4, TlNO3, CuCl, RhCl3, Pb(NO3)2, Cr(NO3)3 and Bi(NO3)3 are relatively high toxic salts in which IC50s are smaller than 10(-4) mol L-1 for both or either cell lines.

Animals↗
PubMed1994

Enamel thickness and the helicoidal occlusal plane.

In the present study 38 unworn maxillary molars (M1 = 16, M2 = 12, M3 = 10) of modern humans from a Slavic necropolis were sectioned through the mesial cusps in a plane perpendicular to the cervical margin of the crown. Five slightly worn M1s and one slightly worn M3 were also used thus increasing the total sample to 44, but measurements made on the worn areas were coded as missing values. Seven measurements of enamel thickness as well as the heights of the protocone and the paracone dentine horns were recorded in order to analyze whether changes in these dimensions in anteroposterior direction can be related to the helicoidal occlusal plane. Uni- and multivariate analyses revealed that the distribution of enamel thickness within and between maxillary molars corresponds to a helicoidal occlusal wear pattern. Enamel thickness along the occlusal basin increases from anterior to posterior, which may lead to rapid development of a reverse curve of Monson in first molars when compared to posterior teeth. However, although these overall differences together with the serial, especially delayed eruption pattern of human molars, contribute to the marked expression of the helicoidal occlusal plane in Homo, differences in enamel patterning between molars indicate that a helicoidal plane is a structural feature of the orofacial skeleton. In contrast to first upper molars, second and third molars show absolutely and relatively thicker enamel under the Phase I wear facet of the paracone, i.e., the lingual slope of the paracone, than under the Phase II facet of the protocone, i.e., the buccal slope of that cusp. These proportional differences are most pronounced in M3, as evidenced by uni- and multivariate statistics. It thus appears that the pattern of enamel thickness distribution from M1 to M3 follows a trend towards providing additional tooth material in areas that are under greater functional demands, that is, corresponding to a lingual slope of wear anteriorly and to a flat or even buccal one posteriorly. In addition, the heights of the dentine horns in anteroposterior direction change in a way that lends support to the hypothesis that the axial inclination of teeth could be one of the most important factors for the development of the helicoidal occlusal plane. Finally, the changes in morphology and enamel thickness distribution from first to third upper molars found in this study suggest that molars could be "specialized" in their function, i.e., from performing proportionally more shearing anteriorly to increased crushing and grinding activities posteriorly.

Adaptation, Physiological↗
PubMed1993

Longitudinal study on occlusal force distribution in lower distal-extension removable partial dentures with conus crown telescopic system.

The purpose of this study was to examine longitudinal changes of the occlusal force distribution in lower distal-extension removable partial dentures with the conus crown telescopic system. Occlusal force applied to the denture and forces transmitted to the retainers were measured on several separate occasions from the insertion of new dentures to about 3 months after. The occlusal force distribution ratio to the retainers was calculated when a load of 20 N was applied to the denture. The results are summarized as follows: (i) The more posterior the loading point of occlusal force, the smaller was the ratio. When the occlusal force was applied to the most anterior artificial tooth, the ratio was 65-100% of the occlusal force. (ii) As the denture wearing time proceeded, the ratio was decreased. The smaller the ratio, the greater was the rate of its decrease.

Aged↗
PubMedDate not supplied

In search of a gold standard.

This is a review article of relevant research to offer best-practice advice to the practitioner regarding the choice of intracoronal indirect restorative materials. The paper reviews the use of cast gold, a variety of porcelain materials and indirect composite resin materials as inlay materials. Subjects reviewed are the effects on tooth strength, the effect of bonding the material on tooth strength, stress analysis on teeth using different restorative material choice of luting material, wear of the material and its antagonist surface and clinical research outcomes and conclusions.

Composite Resins↗
PubMed2004

Comparative evaluation of clinical efficacy of gallium and amalgam alloys in primary molars.

The present study was conducted to compare the clinical efficacy (marginal integrity and bulk fracture) of two alloys--Galloy (gallium based) and Aristaloy (amalgam based) in primary molars. 90 primary molars with initial caries formation were selected. 45 were restored with Galloy and 45 with Aristaloy in Class I and II preparations. They were evaluated at two-month intervals for 6 months. The results showed that Galloy performed at par with Aristaloy with regards to marginal integrity and bulk fracture. Hence Galloy can be considered as an interesting substitute in Pedodontic practice.

Adolescent↗
PubMed1975

Molar tooth attrition in a selected group of Nigerians.

A study of the degree and gradient of attrition was undertaken on 352 molar teeth of 88 selected Nigerian subjects. A method for the quantification of attrition experience per molar tooth is described. There is a close correlation between age and the degree of attrition of the first molar. This finding may be of value in age determination in forensic odontology. The wear on the first molar is about two stages ahead of that on the second and third molars. It is suggested that the degree of tooth attrition may be an index of masticatory activity.

Adult↗
PubMed1999

Additive contour of porcelain veneers: a key element in enamel preservation, adhesion, and esthetics for aging dentition.

Esthetics and function are equal concerns when restoring the anterior dentition. Modern concepts in restorative dentistry have brought new solutions through bonded porcelain veneers that are stress distributors and involve the crown of the tooth as a whole in supporting occlusal force and masticatory function. This recovery of the original biomechanics of the intact tooth, the biomimetic principle, is particularly valuable when considering the restoration of an aging dentition. Both function and appearance are affected by the senescent changes of the aging teeth. Erosion and surface wear lead to a progressive thinning of enamel, ultimately leading to increased crown flexibility and higher surface strains. It appears therefore that the restoration of tooth volume will not only re-establish the original and youthful appearance of the smile but will also allow the biomimetic recovery of the crown. The final treatment outcome strongly depends on the therapeutic approach chosen, the driving force of which should be the preservation of the thin remaining enamel. While a number of preparation techniques will expose dentin to a great extent, the principle of enamel preservation can still be fulfilled by the use of a specific approach. This article describes a treatment method which includes the use of a diagnostic template. This type of work strategy, documented with clinical cases, integrates additive wax-ups and acrylic mock-ups. The latter will provide a significant amount of diagnostic information and economy of tooth substrate, the importance of which cannot be overestimated in the completion, functionality, and longevity of the final restoration.

Acrylic Resins↗