A Comparative Assessment of Three Mandibular Retention Protocols: A Prospective Cohort Study

PURPOSE

Fixed retainers have been advocated for the prevention of anterior mandibular crowding after orthodontic treatment. However, limited data is available to help clinicians choose a retention protocol that is acceptable in terms of stability, emergencies, and side effects in the long term. It was the aim of this study to assess survival and alignment stability of the 0.016" x 0.022" stainless steel wire compared to more common protocols.

MATERIALS AND METHODS

Three different mandibular fixed retention protocols were compared in 600 consecutive patients: 1. 0.0215" multistrand wire (MW) with separate curing of resin and composite; 2. 0.016" x 0.022" stainless-steel wire with simultaneous curing of resin and composite (SS1C); and 3. 0.016" x 0.022" stainless-steel wire with separate curing of resin and composite (SS2C). The hazard rate for detachment across wire groups was assessed with a Cox frailty model.

RESULTS

Incisor alignment was maintained with all retention wires. One incisor with unexpected torque change was observed in group MW. The average annual emergency rate was below 2% for all three protocols. Fewer emergency visits were found in patients with solid steel wires than with multistrand wires. Detachment of the wire is the most common cause of emergency visits with no difference between wire types. Multistrand wires were more often damaged than were solid steel wires. There was no evidence that direct application of the composite on the uncured primer influenced retainer adhesion to the enamel.

CONCLUSIONS

The mandibular anterior teeth can be predictably stabilised with a 0.016" x 0.022" stainless steel wire..

Evaluation of the effect of ultraviolet light polymerized clear adhesive on shear and tensile bond strength of heat cure denture base resin to the cobalt-chromium retentive minor connector: An in vitro study

Aim:

The aim of this study is to evaluate the efficacy of new material ultraviolet (UV) light polymerized clear adhesive on shear and tensile bond strength of heat cure denture base resin (Polymethylmethacrylate (PMMA)) to cobalt-chromium (Co-Cr) retentive minor connector.

Setting and Design:

Comparative evaluation- In-vitro study.

Materials and Methods:

Sixty samples of Co-Cr plates mimicking minor connectors were fabricated. Thirty samples were coated with new material UV light polymerized clear adhesive and cured under UV light source for 10 min. In gun-metal flask, metal plates were placed in the lower compartment over it. Heat cure acrylic resin was packed in the dough stage with the help of clamps and processed according to the manufacturer's instructions. Samples were kept in artificial saliva for 90 days. Shear and tensile bond strengths were calculated of each sample with a Universal testing machine, and results were statistically analyzed. Type of bond failure was observed for each sample under stereomicroscope.

Statistical Analysis Used:

Unpaired t test.

Results:

Tensile bond strength, as well as shear bond strength, showed that 0.93 N and 1.64 N respectively for without application of new adhesive was more as compared to that of samples with the application of new adhesive which is 0.75 N and 1.54 N respectively. Bond failure was found to be an adhesive failure in resin–metal interface.

Conclusions:

Excellent bonding seen between the new adhesive and acrylic interface but limited effect on the metal interface. To increase bond strength between metal and resin interface, some surface treatment with the metal surface is needed to increase the bonding of the new adhesive to the metal surface.

In-vitro investigation to evaluate the flexural bond strengths of three commercially available ultra low fusing ceramic systems to Grade II Titanium

BACKGROUND

This in-vitro investigation was designed to compare the flexural bond strengths of three commercially available ultra low fusing ceramic systems to Grade II Titanium and evaluate the type of bond failure through Scanning Electron Microscopy (SEM) and Energy Dispersion X ray Spectrum (EDS).

MATERIALS & METHODS

Sixty patterns of auto polymerizing resin of dimensions 25.1 mm X 3.1mm X 0.6mm each were fabricated from a stainless steel die. Titanium casting for all the samples was done in a Titanium casting machine. Ten samples were allotted to each of three groups randomly. Ceramic build up was done step by step using the manufacturers' instructions. Flexural Bond strength tests for the samples were performed by using a 3-point bending test on a Universal testing machine in compliance with Deutsches Institut für Normung (DIN) 13.927 draft. After the tests were completed, three samples, one from each group were selected randomly for the subsequent Scanning Electronic Microscopy (SEM) studies to characterize the type and morphology of the fracture in representative specimens.

RESULTS

The maximum load to fracture the porcelain was recorded for each specimen. All the means of the three groups were compared by one-way Analysis of Variance (ANOVA) and it was found that Group I & Group III had significantly higher bond strength values as compared with the Group II (P< 0.001). All the 10 samples of Group I & III gave bond strength values above the standard values of 25 MPa. There was statistically significant difference in the bond strengths between Group I & Group III (t = 2.76 and P< 0.05), between Group I & II (t = 5.09 and P< 0.001) and between Group II & Group III (t = 13.28 and P< 0.001). SEM studies revealed occurrence of cohesive type fractures in the ceramic body of samples belonging to Groups I & III, while there was adhesive failure at ceramo-metal junction of samples belonging to Group II. EDS Analysis supported the findings of SEM studies.

CONCLUSION

All the three ceramic systems fared better than the minimal recommended values stated by ISO 9693:1999 of 25MPa of which Orotig TiKrom was rated the best with values of 54.69 MPa. Vita TitanKeramik ranked second with values of 45.12MPa and the least values were obtained with Noritake Ti-22 with values of 27.76. The bond failure was predominantly cohesive in nature in case of Vita TitanKeramik and Orotig TiKrom; whereas adhesive failure was noticed in case of Noritake Ti-22. How to cite this article: Mabrurkar V, Habbu N, Hashmi SW, Musani S, Joshi N. In-vitro investigation to evaluate the flexural bond strengths of three commercially available ultra low fusing ceramic systems to Grade II Titanium. J Int Oral Health 2013;5(5):101-7.