Winner 2003 - The IADR.CED Visiting Scholar Stipend

Maciej Zarow

The IADR – CED Visiting Scholar Stipend Support Report

Professor Paul Brunton is currently Head of Department of Operative Dentistry at the University of Leeds and retains an Honorary Senior Lecturer appointment at the University of Manchester. I therefore visited both of these institutions to study the research techniques used in our project investigating Fibre Reinforced Composite Fixed Partial Dentures. The first part of the study was due to start in Poland in 2003, but was delayed because of problems in the supply of materials.  This, coupled with recruitment difficulties early in the study, resulted in a slow start to the clinical evaluation and final SEM evaluation performed in Manchester.

Krakow, Poland

The present study was designed to evaluate fibre-reinforced composite fixed partial dentures (FRCFPD).  The reconstructions were used to replace one missing permanent tooth, with the study designed to demonstrate if there was any value in preparing teeth for FRCFPD and whether a cantilever or fixed-fixed design was to be recommended. 

Professor Brunton acted as coordinating investigator for the design and conduct of the study, and was responsible for standardizing clinical procedures at both centres.

The study was a randomised controlled trial of FRCFPDs, when used to replace one missing permanent tooth.  The study was of one year’s duration in the first instance, with the option to extend the study, subject to the performance of the materials under investigation.

The aim of this randomized, controlled clinical trial was to evaluate the clinical performance of FRCFPDs.

The agreed start date for the evaluation was 1st July 2004. All baseline evaluations were completed between one week and one month after placement of the restorations. In-service reviews were completed at 6 months and one year. Prof. Brunton visited Krakow several times between 2004 and 2006) and together we evaluated restorations clinically according to UPSHS criteria. Triple tray polivinylosiloxane impressions, which included each test restoration, were taken, together with a photographic record.

Leeds, UK

During my visit to Leeds Dental Institute I undertook a literature review related to the present study and to the mechanical behaviour of endodontically treated teeth.  This review will form part of my future scientific research. The literature review allowed me to summarize current data about FRCFPD. I also observed 4th and 5th year students’ treating patients under supervision. I prepared photographic documentation on  clinical guidelines for an article about “the resin glass ionomer sandwich technique” related to previous research collaboration between the Universities of Krakow and Leeds.

Manchester, UK

The literature reviewed at the University of Leeds allowed me to understand the procedures applied during SEM assessment being performed at the University of Manchester.  

SEM Assessment

Replicas of the restorations were obtained by pouring the impressions with a self-cured epoxy resin material (Stycast 1266, ICI Belgium Westerlo, Belgium). The poured impressions were vibrated for 120s to ensure that no air bubbles remained in the resin material and, in particular, at the resin/impression interfaces and then left for 24h to ensure complete set of the resin at room temperature (20ºC). The set replicas were carefully trimmed and inspected for imperfections in and around the restoration. Any replica found to be defective was excluded and a new replica made, starting with a new impression. The completed replicas were washed in 70% Isopropyl Alcohol BP (IPA, Adams Healthcare, Leeds, UK) in the ultrasonic bath (Transonic T310, CAMLAB Ltd, Cambridge, UK) for 5 min to ensure that all debris in and around the restoration margins was removed. The replicas were then stored separately in labelled plastic bags. The resin replicas were carefully handled to prevent contamination or damage to the restoration margins and surfaces. Disposable latex-free examination gloves (Micro-Touch Ultra, Micro-Touch Technology, Malaysia) were used to pick up and hold the replicas by the buccal and palatal surfaces only.

The washed resin replicas were separately mounted on aluminium SEM stubs using silver dag. Once mounted, each replica was left two hours to allow the silver dag to fully dry. Specimens were identified by marking the side of the stubs using a felt tip permanent marker pen (Lumocolor).

The mounted specimens were sputter-coated with gold in a Gold-Sputter Coater Unit (Em Scope-SC 500, Biorad, UK) to an approximate thickness of 20nm. The gold-coated specimens were subsequently stored in a sealed container at room temperature (20ºC).

The specimens were examined in a Cambridge 360 SEM (Cambridge Instruments Ltd., Cambridge, UK) as follows:

The specimens were placed on the specimen stage in the specimen chamber and imaged using I-Scan digital imaging software (ISS, Manchester, UK). All specimens were placed and oriented in a standardised manner under the examination field.

The margins of each restoration were examined at X10 – X1500 magnification. The features of the margins of the restorations and adjacent enamel were assessed in terms of marginal qualities, marginal opening, quality of preparation margins, and restoration margin quality. Areas of interest were examined at high magnification (X300- X1500). To facilitate the assessment, the margins of both abutments were divided into the following 7 sections: occlusal, linguocclusal, linguomesial (or -distal), linguogingival, buccocclusal, buccomesial

(or -distal), buccogingival. The assessments were made using the codes and criteria appropriate  to SEM analysis.

A total of 29 samples were studied under SEM. The statistical analyses of the assessments will be undertaken in Krakow, Poland.

We have submitted one abstract for oral presentation at the IADR-CED meeting in Dublin, Ireland (Fibre-reinforced composite fixed partial dentures – a clinical study.

Zarow M, Brunton P. )

This presentation will report the 12 months’ clinical evaluation of  FRCFPD.

I also plan to submit a paper this year on the 12 month clinical and SEM evaluation of FRCFPDs in both English-language and Polish-language dental journals.      

0532 Stress distribution associated with indirect composite restorations, an FEA study

M. ZAROW¹, J. KRUPINSKI¹, G. MILEWSKI¹, and P. BRUNTON², ¹ Jagiellonian University, Krakow, Poland, ² University Dental Hospital of Manchester, United Kingdom

The design of the preparation for composite inlays/onlays could influence the prognosis of the restoration.

Objective: This study was carried out to determine the tensile stresses in different cases of cavity preparation for composite inlay/onlays, which develop at marginal area when subjected to vertical and horizontal loads.

Methods: Finite element models of upper first molar with different type of preparation were generated. As a composite material for indirect restoration Sculpture (Jeneric Pentron) was used. The load of 100 N was applied.vertically. The following three exercises with FEM (Ansys 5,3 Software) were studied: - inlays with different width of remaining vestibular/palatal walls (1,5mm and 3,0mm), - onlays with different type of cusp coverage (shoulder 0,75mm; shoulder1,5mm), - inlays with different preparation of occlusal margin (coincide or not coincide with occlusal contacts). Results: In case of inlays with 3,0mm width of remaining walls the maximal recorded tensile stress was 31,5 MPa and in case of 1,5mm width – 34,2 MPa. In case of onlays with 0,75mm shoulder, maximal tensile stress of 34 MPa was recorded and in case of 1,5mm shoulder – 15,6MPa. In case of inlays, where occlusal margin coincided with occlusal contacts maximal tensile stress of 20,7 Mpa was recorded and in case of no occlusal contacts – 13,6 Mpa.

Conclusions: The restoration margins should not coincide with occlusal contacts. In case of unsufficient width of remaing walls, cuspal coverage should be taken into consideration. In case of cuspal coverage, shoulder preparation should be sufficiently thick.

Joint Meeting of the Continental European, Israeli, and Scandinavian (NOF) Divisions of the IADR (August 25 - 28, 2004)