Treatment effects of the mandibular anterior repositioning appliance on patients with Class II malocclusion.

The mandibular anterior repositioning appliance (MARA) is a tooth-borne functional appliance for use in patients with Class II malocclusions; it positions the mandible forward into a Class I occlusion. The aim of this study was to investigate the MARA's dental and skeletal effects on anterior, posterior, and vertical changes in 30 Class II patients. The treatment group consisted of 12 boys with an average age of 11.2 years and 18 girls with an average age of 11.3 years. A pretreatment cephalometric radiograph was taken 2 weeks before treatment, and a posttreatment cephalometric radiograph was taken 6 weeks after removal of the MARA, with an average treatment time of 10.7 months. The mean and standard deviation were calculated for each cephalometric variable, and Student t tests were performed to determine the statistical significance of the changes. The results of the study showed that the MARA produced measurable treatment effects on the skeletal and dental elements of the craniofacial complex. These effects included a considerable distalization of the maxillary molar, a measurable forward movement of the mandibular molar and incisor, a significant increase in mandibular length, and an increase in posterior face height. The effects of the MARA treatment were then compared with those of the Herbst and Fr?nkel appliances. The treatment results of the MARA were very similar to those produced by the Herbst appliance but with less headgear effect on the maxilla and less mandibular incisor proclination than observed in the Herbst treatment group.     

Fluoride varnish concentration gradient and its effect on enamel demineralization

PURPOSE: Two of the 4 fluoride varnishes available on the American market today are sold in 10-mL tubes of 5% NaF varnish (Duraphat and Duraflor). Pilot studies have shown that a separation of contents within these tubes exists. The purpose of the current study was 4-fold: (1) to measure the fluoride concentration gradient in 10-mL tubes of fluoride varnish, based on resting position of the tube prior to use; (2) to compare and contrast fluoride concentration gradients of Duraphat, Duraflor, and CavityShield; (3) to compare this gradient to the ability to inhibit caries in an artificial caries environment; and finally, (4) to determine if quantitative light fluorescence (QLF) can detect differences in lesions developed when exposed to an artificial caries environment and fluoride varnish. METHODS: Human teeth specimens were subjected to a caries challenge and treated with a sample of fluoride varnish from 1 of 5 categories: Duraphat stored horizontally and vertically for 1 week, Duraflor stored horizontally and vertically for 1 week, or a CavityShield 0.4 mL "unidose." All specimens were then analyzed with the QLF system and with confocal microscopy. RESULTS: Results showed no significant fluoride ppm differences exist between groups (P=.29). It was shown that the order in which Duraflor varnish was dispensed from tubes significantly affected the fluoride concentration (P<.05). The order effect was not significant for Duraphat (P=.99). QLF data analysis showed there was no significant difference (P>.05) in the amount of remineralization obtained by using any varnish stored in any position. CONCLUSIONS: These results indicate that all 3 brands of fluoride varnish are able to remineralize incipient in vitro carious lesions, regardless of what part of the 10-mL tube the varnish is taken from. However, a fluoride concentration gradient exists in tubes of Duraflor. Also, QLF is able to detect demineralized and remineralized incipient lesions.     

Characterization of treponemes isolated from human and non-human primate periodontal pockets

Treponemes were isolated from ligature induced periodontal pockets of non-human primates, and from humans with periodontitis. Approximately 39% of the microscopic count were spirochetes from humans, while 65% of the microscopic microbiota was accounted for by spirochetes from non-human primates. Metabolically, the human treponemal isolates grew on trypticase-yeast extract based media while the non-human primate isolates grew only on pectin, glucuronic or galacturonic acids. The end-products of glucose fermentation by the human treponemes were acetate and propionate, while acetate was produced by the non-human primate treponemes from pectin. All of the human isolates were indole positive, hemolyzed blood, required serum for growth, but did not require thiamine pyrophosphate (TPP). The non-human primate treponemes were indole negative, were inhibited in their growth by blood, grew in the absence of serum, and required TPP for growth. PAGE analysis of whole cell proteins revealed three categories of treponemal isolates: (i) human isolates similar to Treponema denticola ; (ii) human isolates of small size; and (iii) non-human primate isolates similar to the pectinolytic treponemes. Serologically, the human treponemal isolates were similar to T. denticola , while the non-human primate isolates were similar to the pectinolytic treponemes. Four human, 4 non-human primate, and 4 reference treponemes exhibited a Mol% G + C of their DNA of 40.0-43.1. The metabolic differences between the human and non-human primate treponemal isolates may be a reflection of ecological differences in the periodontium of the pathological entities which exist in human and non-human primates.     

An in vitro study of the characteristics of a computer-aided radiographic evaluation (CARE) system for longitudinal assessment of density changes

In recent years, several systems for computerized analysis of radiographs have been introduced, most of which use digital conversion of the image followed by subtraction of consecutive images to assess changes. This paper introduces a computer-based qualitative and quantitative radiographic evaluation system based on the CADIA algorithm. Problems associated with computerized radiographic analysis are discussed and evaluation criteria for this type of system are suggested. These criteria include evaluation of system noise and threshold setting, reproducibility, and establishment of the system working curve (validity). The CARE system noise ranged from a - 10 to + 10 CADIA value and the threshold was set on 13 for all measurements. The reproducibility was high, both for the radiographic technique and for repeated measurements. The working curve was established and showed the system's ability to detect small density changes of 0.048 O.D. which corresponds to 0.27 mm of aluminum thickness or compact bone equivalent. The linear range of the curve was between 0.7 and 1.8 O.D. By controlling the exposure parameters it was possible to work within the linear range of the curve. Based on these evaluation criteria, the CARE system can be used to quantitatively evaluate small density changes on sequential radiographs for early detection of caries and periodontal disease.     

The Effect of Fatigue Damage on the Force Required to Remove a Restoration in a Cement-Retained Implant System

PURPOSE: To evaluate the luting agents and retentive forces before and after mechanical stressing. MATERIALS AND METHODS: Sample size N was 12 for each group, and 12 Cera-One closed-end gold cylinders were cemented with three types of luting cements (ImProv, UltraTemp, and TempBond). The force required to remove the gold cylinders from the abutments was determined with an MTS testing machine. After cleaning and recementing the cylinders, the samples were placed in the housings of an Alabama-type three-body wear machine and load of 110 N was applied to the gold cylinders at a frequency of 80 cycles/min for 50,000 cycles. Then each cylinder was pulled from its abutment and the force at which the failure occurred was recorded. The procedure was repeated with 300,000 cycles. RESULTS: Statistical analysis arising from two-way ANOVA found that the forces required to remove the abutments were significantly different. The most retentive cement was ImProv. Before cyclic loading, on average, ImProv produced a retentive value 85% higher than that yielded by TempBond, and 25% higher than that of UltraTemp. The three cements were significantly different at each of the three cycle levels. CONCLUSIONS: These results might suggest TempBond luting agent as the material of choice for provisional cementation because it allows easier removal of the prosthesis and maintains enough retention to prevent loosening of the restoration. The clinical implication is that the effect of cyclic load on the strength of the cements is different, an important factor in selection of a cement. ImProv had the highest retentive value before and after the two cycles, and TempBond had the lowest. UltraTemp had the highest percentage of retentive value lost. TempBond had no significant loss under loading even though initially it was the weakest.     

Dental caries experience and association to risk indicators of remote rural populations

Background.  Dental caries continues to be the most common infectious disease of childhood; however, it is no longer pandemic, but endemic in specific sectors of populations. Therefore, it is important to identify and target patients at risk of developing caries in order to develop specific preventive measures.
Aim.  This study aims to test dental caries risk indicators for significant associations with caries severity.
Design.  Five separate, small, isolated rural villages in Mexico with varying degrees of caries prevalence were selected for this observational study. A total of 248 children were examined. Risk indicators were assessed via questionnaire and water and salt fluoride analysis. Caries severity was measured by the International Caries Detection and Assessment System (ICDAS-I).
Results.  Prevalence of caries ranged from 95% to 100% for the five villages. Mean total DMFS (decayed, missing, or filled surfaces–permanent teeth) and dmfs (decayed, missing, or filled surfaces–primary teeth) scores ranged from 2.5 to 5.0 and from 11.3 to 16.9, respectively. Multivariable models showed age and drinking soda between meals to be significantly associated with DMFS, and drinking juice and being female were significantly associated with dmfs.
Conclusion.  DMFS and dmfs were high in each village, significantly different between villages, and associated with specific risk indicators.     

Irradiance effects on the mechanical properties of universal hybrid and flowable hybrid resin composites.

OBJECTIVES: A potential problem with high-intensity lights might be failure of polymer chains to grow and cross-link in a desired fashion, thereby affecting the structure and properties of the polymers formed. The purpose of this study was to evaluate mechanical properties of resin composites polymerized using four different light-curing units. METHODS: A conventional quartz-tungsten-halogen (QTH) light, a soft-start light, an argon-ion laser, and a plasma-arc curing light were used to polymerize disk-shaped (9.0mm diameter x 1.0 mm high) and cylinder-shaped (4mm diameter x 8 mm high) specimens of a universal hybrid and a flowable hybrid composite. Biaxial flexure strength, fracture toughness, hardness, compressive strength, and diametral tensile strength were determined for each composite. RESULTS: The use of the plasma-arc curing light, a high-intensity light, resulted in significantly lower hardness for the universal hybrid composite compared with the hardness obtained using the conventional QTH and the soft-start units. Hardness was the only mechanical property that was adversely affected by the use of a high-intensity light. SIGNIFICANCE: High-intensity lights might affect some resin composite mechanical properties, but this effect cannot be generalized to all resin composites and all properties.