Abnormal tooth size and morphology in subjects with cleft lip and/or palate in the north of England.

The aim of this study was to investigate tooth size and morphology in subjects with unilateral cleft palate (UCLP), bilateral cleft palate (BCLP), and isolated cleft palate (ICP) living in the north of England and to compare these with a control group. The measurements were undertaken retrospectively using dental study casts. To assess tooth size, the mesiodistal and buccolingual dimensions of each fully erupted permanent tooth were measured using digital Vernier callipers. The following morphological features of the teeth were assessed: upper incisor shovelling and crown form, the presence of Carabelli's tubercle on the upper molars, molar cusp number, and lower molar fissure pattern. Multilevel regression analysis was used to determine differences in tooth size, while chi-square tests and analysis of variance were used to assess differences in tooth morphology between the groups. Tooth size was reduced in all cleft groups in both jaws, with the smallest teeth being found in the ICP group. Upper lateral incisors on the cleft-affected side in UCLP and BCLP patients showed the greatest reduction in size. The upper central and lateral incisors on the cleft-affected side in the UCLP and BCLP groups were frequently hypoplastic or peg-shaped. Molar morphology in all the cleft groups was similar to that in the control group. Reduced tooth dimensions were found in both jaws in subjects with all types of clefts, suggesting a shared genetic basis. Additionally, the upper incisors were abnormal in morphology in UCLP and BCLP subjects with or without a cleft palate, suggesting shared local aetiological factors.

Dental arch dimensions in oligodontia patients.

INTRODUCTION: The aim of this study was to compare the dental arch sizes in a group of oligodontia patients with a group of age- and sex-matched untreated Class I control patients. METHODS: Dental casts were measured of 50 oligodontia patients and 50 untreated Class I patients between 8 and 16 years old. For each subject, dental arch length and width parameters were measured in the maxillary and mandibular arches with digital calipers. The various dental arch parameters were compared between the 2 groups by using ANOVA. RESULTS: The mean age of the subjects was 12.5 years. The average number of teeth missing in the oligodontia group was 11. The mean maxillary and mandibular arch lengths in the oligodontia group were reduced by 4.40 and 2.80 mm, respectively, when compared with the control group. The intercanine widths were reduced in the oligodontia group compared with the control group by 2.82 mm in the maxillary arch and 2.70 mm in the mandibular arch. The intermolar widths of the maxillary and mandibular arches in the oligodontia group were reduced by 3.40 and 1.80 mm, respectively, compared with the control group. These differences were statistically significant (P<0.01). CONCLUSIONS: The findings indicate that arch length and width are reduced in oligodontia patients; this should be taken into account when planning orthodontic treatment.

Fluoride release for restorative materials and its effect on biofilm formation in natural saliva.

This study investigated the influence of natural saliva of varying pH on surface biofilm formation of restorative materials and how this influenced fluoride release. Columnar specimens of glass ionomer cement (GIC), resin modified glass ionomer cement (RMGIC), compomer, giomer and composite, were prepared, matured for 24 h at 37 degrees C and 100% humidity, lapped and then placed in natural stimulated saliva with a pH of 3.8 or 7.1. Fluoride release was determined daily using an ion-selective electrode. The surfaces of selected specimens were observed using Confocal Laser Scanning Microscopy in conjunction with a fluorescent dye. The surface biofilm formation and bacterial growth was most dominant under neutral conditions and on the surfaces of GICs compared with other materials. GICs released significantly higher amounts of fluoride than other materials. The results suggest that the increased fluoride release of GICs did not reduce the amount of bacterial growth and biofilm formation on the surfaces of these materials when stored in natural saliva.

A method for producing controlled fluoride release from an orthodontic bracket.

The aim of this study was to manufacture and test, in vitro, a novel modification to provide fluoride-releasing orthodontic brackets. Thirty-two orthodontic brackets were drilled to produce a recess (approximately 1.3 mm in diameter and 0.7 mm in depth) at the centre of the bracket base. Four materials, with and without the addition of sodium fluoride, a glass ionomer cement (Ketac Cem micro), a resin-modified glass ionomer cement (RMGIC; GC Fuji Ortho LC), a zinc phosphate (Zinc Cement Improved), and a resin (Transbond XT) were used to fill the recess in the bracket base. Fluoride release was measured daily during the first week and then weekly for 10 weeks. An ion chromatograph with suppressed conductivity was used for free fluoride ion determination. Statistical analysis to determine the amount of flouride release was undertaken using analysis of variance and Tukey's test. During the first 2 weeks, the resin group, with the addition of 38 per cent sodium fluoride added, released significantly more free fluoride (P < 0.05), but after 2 weeks the fluoride release markedly decreased. After 5 weeks, the RMGIC group, with 15 per cent added sodium fluoride, had significantly higher (P < 0.05) daily fluoride release than the other groups. The findings demonstrated that an appropriate fluoridated material can be used as a fluoride-releasing reservoir in a modified orthodontic bracket to enable it to release fluoride over the period of fixed appliance treatment.

Micro-tensile bond strength to surface and subsurface enamel.

UNLABELLED: Testing of bond strength to enamel has been undertaken on both surface and subsurface enamel on the assumption that it is the same substrate. Over recent years, the micro-tensile method has become widely used for the evaluation of dental adhesives. However, there have been no micro-tensile bond strength studies comparing surface and subsurface enamel using orthodontic adhesives. It has been proposed that the bond strength to subsurface enamel is greater than that to surface enamel. OBJECTIVE: The micro-tensile bond strength (MTBS) of Transbond (light activated paste, 3 M Unitek, USA) to surface and subsurface enamel was investigated. METHODS: Ten sound freshly extracted lower human first molars were divided into two groups of five each. Surface enamel of the first group was removed with 500-grit silicone carbide paper, whilst in the second group it was left intact. Gelatin capsules filled with Transbond composite paste were bonded perpendicular to the enamel using light cure adhesive Primer (Transbond XT, 3 M Unitek, USA) in both groups, and stored in distilled water at 37 degrees C for 24 h. Crowns of all specimens were sectioned bucco-lingually into vertical slabs of approximately 0.6 mm thickness. Slabs in each group were prepared into an hourglass shape of 1mm width and 0.6 mm thickness. Micro-tensile bond strength was determined using a mini tensile testing machine (COMPACT Gauge, DILLON). RESULTS: Mean values of MTBS were: 31.2 MPa (SD14.5) for surface enamel and 47.9 (SD15.0) for subsurface enamel. SIGNIFICANCE: There was a significant difference between the two groups P = 0.001. It was concluded that subsurface enamel has significantly higher bond strength than surface enamel. This has implications for bonding in restorative dentistry and orthodontics.

Auto-transplantation in the restorative management of traumatized anterior teeth: a case report.

UNLABELLED: Auto-transplantation can be used to replace missing anterior teeth following traumatic injuries. This technique has the advantage (over other forms of treatment) of maintaining alveolar bone height which allows orthodontic and further restorative intervention by way of implants later in life. Careful restorative management of transplanted teeth is vital to their long-term survival as inadequate maintenance post transplant may result in root resorption and eventual tooth loss. This paper describes the restorative management of two cases following transplantation. CLINICAL RELEVANCE: Dental practitioners should be aware of the option to auto-transplant teeth as part of an overall treatment plan and the subsequent interventions often required.

Effect of impression technique on bond strength.

If the effects of surface preparation (eg, acid etching, laser preparation, crystal growth) are to be investigated on the same tooth from which the bond strength is recorded, a method of surface replication is required that does not affect the subsequent bond. This study investigated the effect of 2 different methods of taking impressions on bond strength. Three groups of 11 mandibular incisors were used. The labial enamel was etched with 37% phosphoric acid for 30 seconds. Group A (control) had no impression taken; in group B (silicone), impressions were taken with silicone impression material before bonding; in group C (polyether), an impression was taken with polyether before bonding. After the impressions were taken, GAC brackets (A Company, San Diego, Calif) were bonded to the labial surfaces of the etched enamel with Transbond XT light-cured composite (3M Unitek, Monrovia, Calif). Teeth with bonded brackets were stored in water at 37 degrees C for 24 hours, and then bond strength was measured on a testing machine. The adhesive remnant index (ARI) was also recorded. The lowest bond strength was found after silicone replication (mean [standard deviation]: 8.6 [1.7] MPa) and the highest in the control group (21.2 [4.0] MPa). There was no significant difference between the control group and the polyether replication group (19.1 [4.7] MPa). The surface detail replications of polyether and silicone were found to be identical. It was concluded that polyether had no significant effect on bond strength and was suitable for surface replication before bonding. Polyether allows replication of the enamel surface without a significant effect on bond strength, and this technique could be used to examine the relationship between enamel preparation techniques and subsequent bond strength between composite and enamel.

Comparison of in vivo and in vitro shear bond strength.

Much of the research into composite adhesives suggests that these materials will deteriorate in the oral environment, but most of these claims are made on the basis of extrapolation from in vitro experiments; relatively little in vivo research has been conducted into the mechanical properties of composite adhesives. For this study, we recruited 20 volunteers to wear removable appliances containing orthodontic brackets bonded to enamel slabs for 12 weeks. Each appliance carried 3 brackets bonded with Transbond (3M Unitek UK; Bradford, United Kingdom) and 3 brackets bonded with Heliosit (Ivoclar-Vivadent; Leicester, United Kingdom). The bond strengths were tested at intervals of 4, 8, and 12 weeks. Control specimens were stored in sterile water at 37 degrees C and were debonded at the same time intervals. Transbond specimens debonded after 4 weeks in vivo had significantly (P <.05) lower bond strengths (9.78 megapascals [MPa]) than did the controls (14.34 MPa). In vivo, specimens bonded with Heliosit had significantly (P <.05) lower bond strengths after 4 weeks (8.16 MPa vs 10.96 MPa) and 8 weeks (9.96 MPa vs 13.61 MPa) than did the controls. These results indicate differences between bond strength testing in vitro and in vivo. Further research is required into the effects of the oral environment on bond strength.

The relationship between acid-etch patterns and bond survival in vivo.

The aim of this study was to investigate the relationship between acid-etch quality and bond survival in vivo. The subjects were 29 orthodontic patients. High-resolution silicone impressions were taken of the buccal tooth surfaces after etching for 30 seconds with 37% phosphoric acid. The impressions were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A 4-point classification system and histometric techniques were used to evaluate etch patterns on the enamel surfaces where orthodontic brackets were to be bonded. After impressions were made, all teeth (including first molars) were bonded with 0.022-in Andrews' prescription brackets ("A" Company, San Diego, Calif) and Right-On composite (TP Orthodontics, Leeds, England). The first date of bond failure for each tooth was recorded; it varied from 1 to 806 days. An ideal etch pattern was found on less than 5% of the orthodontic bonding area; type C pattern (pitted enamel surface) occupied the greatest area. Overall, the failure rate was 55.8% over 26 months; the greatest failure rate occurred in first molars. Multiple regression analysis revealed a positive and statistically significant relationship between the area occupied by ideal etch type and the length of survival of the bond (P <.001).