Lateral incisor root resorption and active orthodontic treatment in the early mixed dentition.

AIM: To evaluate the presence of root resorption in the lateral incisor after active orthodontic treatment in the early mixed dentition. METHODS: Twenty-six children treated at the Children's Clinic of the Schulich School of Medicine and Dentistry at the University of Western Ontario were examined radiographically for lateral incisors root resorption before and after early active treatment to align upper incisors (2 x 4 appliance). In addition, canine inclinations to the midline and to the long axis of the lateral incisor as well as the most medial position of the canine crown were measured as potential risk factors for root resorption. RESULTS: 8% (4) of the lateral incisors exhibited root resorption and the mean crown-to-root ratio of these teeth was significantly higher than that for lateral incisors not exhibiting root resorption. Similarly, mean canine inclinations to the midline and to the long axis of the lateral incisor were also significantly higher for the root resorption group. No association could be found between the most medial position of the canine crown and root resorption in the lateral incisor. CONCLUSION: This study showed that active orthodontic treatment in the early mixed dentition does not increase the risk for root resorption in the lateral incisors as long as the clinician takes into consideration canine inclinations and their potential effect on root resorption. Limitations inherent to radiographic assessment are acknowledged.

A treatment decision-making model for infraoccluded primary molars.

The objective of this paper is to clarify the literature's findings and provide guidelines for decision-making during the long-term treatment planning of infraoccluded primary molars. This paper presents a synopsis of findings concerning prevalence, aetiology, diagnostic methods, diagnostic criteria and treatment options. Treatment decisions are mainly guided by the clinical assessment of the presence or absence of succedaneous tooth, evaluation of onset, time of diagnosis, resorption rate, rate of progression of infraocclusion, risk of adverse effects over time, and predictive clinical patterns of infraoccluded primary molars. These models are a result of a comprehensive review of the literature and presents a compilation of findings in a format that is of practical use to the clinician.

Microleakage of three sealants following conventional, bur, and air-abrasion preparation of pits and fissures.

OBJECTIVES: The aim of this study was to compare the microleakage of a filled sealant with a drying agent (UltraSeal XT plus), a filled sealant (Prismashield) and an unfilled sealant (Delton), after conventional, bur, and air-abrasion tooth preparation techniques. SETTING: The study was completed in a clinical setting at the Simulated Practice Environment Clinic, School of Dentistry, University of Western Ontario, London, Ontario, Canada. SAMPLE AND METHODS: One hundred and eighty extracted teeth were cleaned and divided randomly into three groups. Group 1 was prepared using acid etch only. Group 2 was prepared with a 1/4 round bur in a low-speed handpiece followed by acid etching. Group 3 was prepared with high speed (120PSI) microabrasion using 27 microm alpha-alumina particles in a Midwest Airtouch unit. The teeth in each group were randomly assigned to one of the three subgroups according to the sealant applied. Subgroup A was sealed with a filled sealant with drying agent, B with a filled sealant only, and C with an unfilled sealant. All teeth were stored in artificial saliva for 7 days at 37 degrees C. After this, the teeth were coated with nail varnish 1 mm from the sealant and immersed in 1% methylene blue dye for 48 h at 37 degrees C. Each tooth was sectioned at four locations buccolingually and a total of 665 sections were ranked (0-3) for microleakage. Statistical analysis was completed using the Chi-squared test and Fisher's exact test. RESULTS: UltraSeal XT plus, the filled sealant with drying agent, showed significantly less microleakage than the other two sealants (P < 0.05). Delton, the unfilled sealant, showed significantly less microleakage than Prismashield, the filled sealant (P < 0.05). Air abrasion with acid etch showed significantly less microleakage than either bur with acid etch or acid etch alone. There was however, no significant difference between the bur and acid etch tooth preparations (P < 0.05). CONCLUSIONS: UltraSeal XT plus was the most effective sealant for preventing microleakage in this study. The most successful method of preparation was air abrasion with acid etch.

The safety and efficacy of treatment with air abrasion technology.

AIMS: To evaluate patient and operator exposure to respirable particulates following the use of air abrasion in tooth preparation, and to compare the microleakage of pit and fissure sealants after conventional, bur and air abrasion preparation of the pits and fissures. METHODS: To examine air abrasion safety, sampling data were collected using a physical model of the upper torso of a patient. Previously extracted bovine incisors were prepared using an air abrasion instrument. Patient and operator exposure samples were collected. The variables examined included the size of the alumina oxide particles, the speed of particle delivery and the method of dust collection. To assess the efficacy of air abrasion, 36 extracted human molars were divided into three groups. The groups were prepared by conventional acid etching, opening the pits and fissures with a round bur, or by air abrasion. To simulate oral conditions, sealed teeth were immersed in artificial saliva and thermocycled. Teeth were immersed in a 1% solution of methylene blue and sectioned to assess the microleakage associated with each sealant. CONCLUSIONS: (1) Dust from the KCP 1000 is insufficient to be a health hazard to patients or operators, (2) chair-side suction can be used as an alternative to the KCP 1000 suction, (3) superior sealants were obtained when tooth surfaces were prepared by a bur, compared to air abrasion and conventionally prepared surfaces, and (4) air abrasion tooth surfaces demonstrated less microleakage than conventionally prepared tooth surfaces.

Microleakage of sealants after conventional, bur, and air-abrasion preparation of pits and fissures.

PURPOSE: The aim of this study was to compare the microleakage of unfilled and filled sealants after conventional, bur, and air-abrasion tooth preparation. METHODS: Seventy-two extracted molars were randomly divided into three groups. In group 1, 24 teeth were prepared by pumicing and acid etching with 37% phosphoric acid. In group 2, 24 teeth were prepared with a 1/4-round bur in a low-speed handpiece and then acid etched. In group 3, 24 teeth were prepared by high-speed (160 PSI) microabrasion using 50 mu alpha alumina particles in a KCP 2000 machine. In each group, 12 teeth were sealed with a filled sealant and 12 teeth with an unfilled sealant. All the teeth were stored in artificial saliva for 7 days and thermocycled for 2000 cycles. Teeth were then sealed apically and coated with nail varnish 1 mm from the margins and stained in 1% methylene blue for 24 h. Each tooth was sectioned in three locations and ranked (0-3) for microleakage. RESULTS: There were 216 sections and 66% showed no leakage. CONCLUSIONS: Chi-square statistical analysis of the data led to the following conclusions: 1) superior results were obtained when the tooth surfaces were prepared by a bur, 2) conventionally and KCP 2000-prepared tooth surfaces yielded similar results, and 3) the unfilled sealant was superior to the filled sealant.

Glass ionomer materials as a rechargeable fluoride-release system.

It is well established that glass ionomers (GI) release fluoride (F). The degree of F released depends on the physical and chemical properties of the product. In the present study the fluoride release and the capacity of the GI to be recharged with fluoride was tested for five different brands: XR Ionomer (Kerr), Vitrebond (3M), GC Fuji Lining (G.C. Dental Industries Corp.), Baseline VLC (Dentsply) and Zinomer (Dent. Mat.). Fifteen test specimens were prepared for each brand. The specimens were immersed in deionized water. The F released was measured once a day for 11 days. Refluoridation of the test specimens was done with solutions of 0.02%, 0.04% and 0.2% NaF for 5 minutes on days 11, 16, 21 and 26. The F released from recharged specimens was measured daily until day 32. There was a positive correlation between the amount of F in the GI and the ability to release F. The five materials became 'recharged' with F following repeated F exposure in solution, the 0.2% solution being the most effective. XR ionomer released significantly more fluoride than any other material and showed the greatest ability to be recharged. Zinomer released significantly less fluoride than any other material and showed the least ability to be recharged. The present results indicate that GI serves as a F reservoir and can act as a prolonged slow-release system for at least 32 days.

Remineralization of natural carious lesions with a glass ionomer cement.

Remineralization of carious lesions at the histological level is of great benefit since this will arrest lesion progression. The ability of glass ionomer cement (GIC) to (1) release fluoride it originally contains and (2) release "loosely bound" fluoride acquired from its surroundings have been previously demonstrated. This in vitro study examined the potential for caries remineralization if the lesion was placed near a GIC. Sixteen mesiodistal sections were cut through extracted deciduous molars exhibiting approximal white spot lesions. Sections were "linked" to a plastic tooth restored with a GIC to simulate the abutting surfaces of adjacent teeth. Lesions were photographed in water under polarized light initially and after one- and two-week exposures to artificial saliva. The photographs were digitized, lesion body outlined, and the area corresponding to the body of the lesion was determined to provide a comparison over time. Sixty-two percent of the sections showed a quantitative reduction in lesion body size by an average of 43% after the first week and an additional 14% reduction after the second week. All but two sections demonstrated a qualitative change thereby illustrating that a reduction in pore volume size of the lesion body had also occurred. Therefore, fluoride released from a GIC has the potential to enhance remineralization of the early carious lesion in vitro. The greatest remineralization occurred during the first week of artificial saliva exposure.

A fluoride release-adsorption-release system applied to fluoride-releasing restorative materials.

This investigation compared the initial fluoride release and release following refluoridation of three resin-modified glass-ionomer cements (Photac-Fil Applicap, Vitremer, and Fuji II LC) and a new polyacid-modified resin composite material (Dyract). After daily flouride release was measured for 8 days, specimens were refluoridated in 1,000-ppm solutions of fluoride ion for 10 minutes and fluoride release was measured for 5 days. Two further 5-day refluoridation-release periods were carried out. All materials released fluoride initially. Photac released the most; Dyract released the least. Initial release was greatest over the first few days. All materials released significantly more fluoride for 24 to 48 hours after refluoridation. Less fluoride was released with each successive refluoridation for the three glass-ionomer cements. The release from the Dyract compomer remained at a comparatively constant and significantly lower level following each refluoridation.

Fluoride release from glass ionomer cement in vivo and in vitro.

The aims of this study were to investigate in vivo the release of fluoride from three glass ionomer cements (GICs) Vitrebond, Ketac-Fil and ChemFil II into the saliva of preschool children for a 1-year period and also to study in vitro the release-absorption-release of fluoride from the same GICs for 16 weeks. In the first part of the study, glass ionomer restorations were placed in primary teeth in preschool children. Unstimulated saliva was collected and the fluoride in the saliva was measured before placement of the restorations, immediately after, after 3 weeks, after 6 weeks, and after 1 year. In the second part of the study, test specimens of GICs were placed in deionized water and the release of fluoride was measured weekly for 16 weeks. At week 12, samples were exposed to fluoride toothpaste. The concentration of fluoride in saliva was 0.04 ppm before placement of the restorations. After three weeks it had increased to 0.8 ppm and the level remained as high as 0.3 ppm even after 1 year. In the laboratory study the tested glass ionomer cements showed a capacity to absorb fluoride from the fluoride toothpaste and then release it. It is concluded that glass ionomer cement can act as a rechargeable slow release fluoride device.

Glass ionomer cements as a fluoride release system in vivo.

Fluoride release to saliva from three glass ionomer cements, Vitrabond, Ketac-Fil, and ChemFil II, was followed for six weeks in vivo. Colony forming units (CFU) of S. mutans present in saliva before and after placement of glass ionomer restorations were analysed. Thirty-six children received 1-6 glass ionomer cement restorations of one of the three materials. Unstimulated saliva was collected and analysed before insertion of restorations (baseline measurement), immediately after treatment, after 3 weeks and after 6 weeks. The fluoride concentration was measured according to a method slightly modified from Ekstrand (1977) and Duckworth et al. (1987). Baseline concentration of fluoride was between 0.038 and 0.050 ppm. Immediately after placement of GIC restorations, fluoride concentrations increased to 0.8 for ChemFil II and 1.2 ppm for Ketac-Fil and Vitrabond. After 3 weeks, concentrations of released fluoride decreased about 35% for all three materials, and after 6 weeks, concentrations decreased another 30%. However, still after 6 weeks, the fluoride concentrations of unstimulated saliva was 10 times higher than the baseline values. The more restored teeth surfaces the higher was the saliva fluoride concentration found. The prevalence of S. mutants in saliva decreased after placement of the GIC restorations.