Bespoke video vignettes - an approach to enhancing reflective learning developed by dental undergraduates and their clinical teachers

This study explores the selective use of video as a medium to support reflective processes as related to dental undergraduate learning. With the objective of developing and enhancing high-quality adult dental care, the use of compiled video materials created in an undergraduate clinical setting was investigated. Video cameras were used to capture elements of reflection-in-action and reflection-on-action typically found during everyday clinical practice. 'Gold standard' or 'textbook outcomes' are rarely, if ever, fully achieved in dental practice. Real-life clinical experiences offer challenges and opportunities for both teachers and students to engage with reflective learning processes. The materials generated allowed for an experience of individual reflective learning and the creation of a data bank or archive with potential use for the benefit of a wider student cohort. Various aspects of the students' views and comments on the process of reflection were reported and explored by means of a semi-structured focus group moderated by a linked educational advisor.

Outreach clinical dental education: the Portsmouth experience - a 4-year follow-up study

BACKGROUND

The Portsmouth Dental Academy (UPDA) was opened in September 2010 and was a development from the highly successful School of Professionals Complementary to Dentistry (2004-2010). The aim of the Academy was to provide integrated team education for all dental professionals in a primary care setting. The dental students are on outreach from King's College London, and the dental care professional students are registered at the University of Portsmouth.

OBJECTIVES

To evaluate the dental students response to the residential outreach educational experience at the UPDA.

METHODS

A 49-item questionnaire divided into nine domains that provided both qualitative data and quantitative data were administered at the end of the longitudinal 10-week placement, to four successive cohorts of students in 2010-2014.

RESULTS

A 95% return rate was achieved. Students valued highly the quality of the clinical teaching. Through their experience, they felt they understood fully the role of the dentist in care planning in primary care and felt well prepared for dental foundation training. This educational success is unpinned with successful maintenance factors including a well-organised induction period and giving the students a sense of belongingness, empowerment and autonomy for their personal development as new graduates.

CONCLUSION

Within the limitations of the questionnaire study over the 4-year period, the students were very positive about all the aspects of this residential outreach education at the UPDA but particularly valued the immersion in clinical dentistry and the bridging from dental school to their dental foundation training.

Micro-invasive interventions for managing proximal dental decay in primary and permanent teeth

BACKGROUND

Proximal dental lesions, limited to dentine, are traditionally treated by invasive (drill and fill) means. Non-invasive alternatives (e.g. fluoride varnish, flossing) might avoid substance loss but their effectiveness depends on patients' adherence. Recently, micro-invasive approaches for treating proximal caries lesions have been tried. These interventions install a barrier either on top (sealing) or within (infiltrating) the lesion. Different methods and materials are currently available for micro-invasive treatments, such as sealing via resin sealants, (polyurethane) patches/tapes, glass ionomer cements (GIC) or resin infiltration.

OBJECTIVES

To evaluate the effects of micro-invasive treatments for managing proximal caries lesions in primary and permanent dentition in children and adults.

SEARCH METHODS

We searched the following databases to 31 December 2014: the Cochrane Oral Health Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via OVID, EMBASE via OVID, LILACs via BIREME Virtual Health Library, Web of Science Conference Proceedings, ZETOC Conference Proceedings, Proquest Dissertations and Theses, ClinicalTrials.gov, OpenGrey and the World Health Organization (WHO) International Clinical Trials Registry Platform. We searched the metaRegister of Controlled Trials to 1 October 2014. There were no language or date restrictions in the searches of the electronic databases.

SELECTION CRITERIA

We included randomised controlled trials of at least six months' duration that compared micro-invasive treatments for managing non-cavitated proximal dental decay in primary teeth, permanent teeth or both, versus non-invasive measures, invasive means, no intervention or placebo. We also included studies that compared different types of micro-invasive treatments.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, extracted data and assessed the risk of bias. We used standard methodological procedures expected by Cochrane to evaluate risk of bias and synthesise data. We conducted meta-analyses with the random-effects model, using the Becker-Balagtas method to calculate the odds ratio (OR) for lesion progression. We assessed the quality of the evidence using GRADE methods.

MAIN RESULTS

We included eight trials, which randomised 365 participants. The trials all used a split-mouth design, some with more than one pair of lesions treated within the same participant. Studies took place in university or dental public health clinics in Brazil, Colombia, Denmark, Germany, Thailand, Greenland and Chile. Six studies evaluated the effects of micro-invasive treatments in the permanent dentition and two studies on the primary dentition, with caries risk ranging from low to high. Investigators measured caries risk in different studies either by caries experience alone or by using the Cariogram programme, which combines eight contributing factors, including caries experience, diet, saliva and other factors related to caries. The follow-up period in the trials ranged from one to three years. All studies used lesion progression as the primary outcome, evaluating it by different methods of reading radiographs. Four studies received industry support to carry out the research, with one of them being carried out by inventors of the intervention.We judged seven studies to be at high overall risk of bias, primarily due to lack of blinding of participants and personnel. We evaluated intervention effects for all micro-invasive therapies and analysed subgroups according to the different treatment methods reported in the included studies.Our meta-analysis, which pooled the most sensitive set of data (in terms of measurement method) from studies presenting data in a format suitable for meta-analysis, showed that micro-invasive treatment significantly reduced the odds of lesion progression compared with non-invasive treatment (e.g fluoride varnish) or oral hygiene advice (e.g to floss) (OR 0.24, 95% CI 0.14 to 0.41; 602 lesions; seven studies; I(2) = 32%). There was no evidence of subgroup differences (P = 0.36).The four studies that measured adverse events reported no adverse events after micro-invasive treatment. Most studies did not report on any further outcomes.We assessed the quality of evidence for micro-invasive treatments as moderate. It remains unclear which micro-invasive treatment is more advantageous, or if certain clinical conditions or patient characteristics are better suited for micro-invasive treatments than others.

AUTHORS' CONCLUSIONS

The available evidence shows that micro-invasive treatment of proximal caries lesions arrests non-cavitated enamel and initial dentinal lesions (limited to outer third of dentine, based on radiograph) and is significantly more effective than non-invasive professional treatment (e.g. fluoride varnish) or advice (e.g. to floss). We can be moderately confident that further research is unlikely to substantially change the estimate of effect. Due to the small number of studies, it does remain unclear which micro-invasive technique offers the greatest benefit, or whether the effects of micro-invasive treatment confer greater or lesser benefit according to different clinical or patient considerations.

Zygomatic Implants: The Impact of Zygoma Bone Support on Biomechanics

Maxillectomy and severely resorbed maxilla are challenging to restore with provision of removable prostheses. Dental implants are essential to restore esthetics and function and subsequently quality of life in such group of patients. Zygomatic implants reduce the complications associated with bone grafting procedures and simplify the rehabilitation of atrophic maxilla and maxillectomy. The purpose of this study was to compare, by means of 3-dimensional finite element analysis, the impact of different zygomatic bone support (10, 15, and 20 mm) on the biomechanics of zygomatic implants. Results indicated that maximum stresses within the fixture were increased by 3 times when bone support decreased from 20 to 10 mm and were concentrated at the fixture/bone interface. However, stresses within the abutment screw and the abutment itself were not significantly different regardless of the bone support level. Supporting bone at 10 mm sustained double the stresses of 15 and 20 mm. Fixture's deflection was decreased by 2 to 3 times when bone support level increased to 15 mm and 20 mm, respectively. It was concluded that zygomatic bone support should not be less than 15 mm, and abutment screw is not at risk of fracture regardless of the zygomatic bone support.

Replacement versus repair of defective restorations in adults: resin composite

BACKGROUND

Composite filling materials have been increasingly used for the restoration of posterior teeth in recent years as a tooth-coloured alternative to amalgam. As with any filling material composites have a finite life-span. Traditionally, replacement was the ideal approach to treat defective composite restorations, however, repairing composites offers an alternative more conservative approach to the tooth structure where restorations are partly still serviceable. Repairing the restoration has the potential of taking less time and may sometimes be performed without the use of local anaesthesia hence it may be less distressing for a patient when compared with replacement.

OBJECTIVES

To evaluate the effects of replacing (with resin composite) versus repair (with resin composite) in the management of defective resin composite dental restorations in permanent molar and premolar teeth.

SEARCH METHODS

For the identification of studies relevant to this review we searched the Cochrane Oral Health Group's Trials Register (to 24 July 2013); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 6); MEDLINE via OVID (1946 to 24 July 2013); EMBASE via OVID (1980 to 24 July 2013); BIOSIS via Web of Knowledge (1969 to 24 July 2013); Web of Science (1945 to 24 July 2013); and OpenGrey (to 24 July 2013). Researchers, experts and organisations known to be involved in this field were contacted in order to trace unpublished or ongoing studies. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

Trials were selected if they met the following criteria: randomised controlled trial (including split-mouth studies), involving replacement and repair of resin composite restorations in adults with a defective molar restoration in a permanent molar or premolar teeth.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed titles and abstracts for each article identified by the searches in order to decide whether the article was likely to be relevant. Full papers were obtained for relevant articles and both review authors studied these. The Cochrane Collaboration statistical guidelines were to be followed for data synthesis.

MAIN RESULTS

The search strategy retrieved 298 potentially eligible studies, after de-duplication. After examination of the titles and abstracts, full texts of potentially relevant studies were retrieved but none of the retrieved studies met the inclusion criteria of the review.

AUTHORS' CONCLUSIONS

There are no published randomised controlled trials relevant to this review question. There is therefore a need for methodologically sound randomised controlled trials that are reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement (www.consort-statement.org/). Further research also needs to explore qualitatively the views of patients on repairing versus replacement and investigate themes around pain, anxiety and distress, time and costs.

Replacement versus repair of defective restorations in adults: amalgam

BACKGROUND

Amalgam is a common filling material for posterior teeth, as with any restoration amalgams have a finite life-span. Traditionally replacement was the ideal approach to treat defective amalgam restorations, however, repair offers an alternative more conservative approach where restorations are only partially defective. Repairing a restoration has the potential of taking less time and may sometimes be performed without the use of local anaesthesia hence it may be less distressing for a patient when compared with replacement. Repair of amalgam restorations is often more conservative of the tooth structure than replacement.

OBJECTIVES

To evaluate the effects of replacing (with amalgam) versus repair (with amalgam) in the management of defective amalgam dental restorations in permanent molar and premolar teeth.

SEARCH METHODS

For the identification of studies relevant to this review we searched the Cochrane Oral Health Group's Trials Register (to 5 August 2013); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 7); MEDLINE via OVID (1946 to 5 August 2013); EMBASE via OVID (1980 to 5 August 2013); BIOSIS via Web of Knowledge (1969 to 5 August 2013); Web of Science (1945 to 5 August 2013) and OpenGrey (to 5 August 2013). Researchers, experts and organisations known to be involved in this field were contacted in order to trace unpublished or ongoing studies. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

Trials were selected if they met the following criteria: randomised controlled trial (including split-mouth studies), involving replacement and repair of amalgam restorations in adults with a defective restoration in a molar or premolar tooth/teeth.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed titles and abstracts for each article identified by the searches in order to decide whether the article was likely to be relevant. Full papers were obtained for relevant articles and both review authors studied these. The Cochrane Collaboration statistical guidelines were to be followed for data synthesis.

MAIN RESULTS

The search strategy retrieved 201 potentially eligible studies after de-duplication. After examination of the titles and abstracts, full texts of the relevant studies were retrieved but none of these met the inclusion criteria of the review.

AUTHORS' CONCLUSIONS

There are no published randomised controlled trials relevant to this review question. There is therefore a need for methodologically sound randomised controlled trials that are reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement (www.consort-statement.org/). Further research also needs to explore qualitatively the views of patients on repairing versus replacement and investigate themes around pain, distress and anxiety, time and costs.

Extrasinus zygomatic implant placement in the rehabilitation of the atrophic maxilla: three-dimensional finite element stress analysis

Placement of zygomatic implants lateral to the maxillary sinus, according to the extrasinus protocol, is one of the treatment options in the rehabilitation of severely atrophic maxilla or following maxillectomy surgery in patients with head and neck cancer. The aim of this study was to investigate the mechanical behavior of a full-arch fixed prosthesis supported by 4 zygomatic implants in the atrophic maxilla under occlusal loading. Results indicated that maximum von Mises stresses were significantly higher under lateral loading compared with vertical loading within the prosthesis and its supporting implants. Peak stresses were concentrated at the prosthesis-abutments interface under vertical loading and the internal line angles of the prosthesis under lateral loading. The zygomatic supporting bone suffered significantly lower stresses. However, the alveolar bone suffered a comparatively higher level of stresses, particularly under lateral loading. Prosthesis displacement under vertical loading was higher than under lateral loading. The zygomatic bone suffered lower stresses than the alveolar bone and prosthesis-implant complex under both vertical and lateral loading. Lateral loading caused a higher level of stresses than vertical loading.

Dental workforce development as part of the oral health agenda for Brunei Darussalam

BACKGROUND

Brunei Darussalam is a Sultanate with a Malay Islamic monarchy. There are high levels of dental disease among its 406,200 population. The population's oral health needs require an integrated blend of primary and specialist care, together with oral health promotion.

PROCESS AND OUTCOMES

This paper describes the planning and measures taken to address these needs. In accordance with an oral health agenda published and launched in 2008, focusing on access, health promotion and prevention, and the education and training of the dental workforce, the Brunei Darussalam Ministry of Health is seeking to improve oral health status and reduce the burden of oral disease. It also seeks to transform the country's oral health services into a preventatively orientated, high-quality, seamless service underpinned by the concept of 'teeth for life'. In the process of effecting this transition, the Brunei Darussalam Ministry of Health is developing a dental workforce fit for future purpose, with an emphasis on a modern approach to skill mix. An important element of this programme has been the development of a highly successful Brunei Darussalam Diploma in Dental Therapy and Dental Hygiene.

CONCLUSION

It is concluded that the Brunei Darussalam oral health agenda and, in particular, the forward-looking programme of dental workforce development is a model for other countries facing similar oral health challenges.

The impact of fractured endodontic file removal on vertical root fracture resistance: three-dimensional finite element analysis

This study investigated by means of finite element analysis the influence of fractured file removal on root fracture resistance in an endodontically-treated canine. A 4mm fragment of an endodontic file was deliberately fractured in the apical third of an upper canine root and removed by ultrasonic tips. Micro-computed tomography scans were carried out before and after fractured file removal on the same tooth. Two 3D-FE models (before and after file removal) were subjected to 100N loading. Results indicate that the fractured file removal increased von Mises stresses by 55%. Peak stresses were located around the root filling/dentine interface prior to file removal. Following file removal, peak stresses were concentrated at the buccal root surface/bone interface that might initiate vertical root fracture buccolingually.

Antibiotic prophylaxis in dentistry: part II. A qualitative study of patient perspectives and understanding of the NICE guideline

BACKGROUND

The National Institute for Health and Clinical Excellence (NICE) recommendations in 2008 for antibiotic prophylaxis before dental treatment contradict previous practice. There is a potential difficulty in explaining the new guidance to patients who have long believed that they must receive antibiotics before their dental treatment.

AIM

This study investigated the patient-related barriers and facilitating factors in implementation of the NICE guidance.

METHODS

In-depth interviews were conducted with nine patients concerning their views about barriers and factors that could influence the implementation of the NICE guidance on antibiotic prophylaxis before dental treatment. Data were analysed using framework analysis.

RESULTS

For patients the rationale for the NICE guidance was unclear. They understood that at the population level the risk of infective endocarditis was less than the risk of adverse reaction to antibiotics. However, on an individual level they felt that the latter risk was negligible given their previous experience of antibiotics. They were aware that standards of care change over time but were concerned that this may be an example where a mistake had been made. Patients felt that the characteristics of the person advising them about the new guidance were important in whether or not they would accept them - they wished to be advised by a clinician that they knew and trusted, and who was perceived as having appropriate expertise.

CONCLUSIONS

Patients generally felt that they would be most reassured by information provided by a clinician who they felt they could trust and who was qualified to comment on the issue by respecting their autonomy. The implications of the findings for the development of patient information are discussed.

Replacement versus repair of defective restorations in adults: amalgam

BACKGROUND

Amalgam is a common filling material for posterior teeth, as with any restoration amalgams have a finite life-span. Traditionally replacement was the ideal approach to treat defective amalgam restorations, however, repair offers an alternative more conservative approach where restorations are only partially defective. Repairing a restoration has the potential of taking less time and may sometimes be performed without the use of local anaesthesia hence it may be less distressing for a patient when compared with replacement.

OBJECTIVES

To evaluate the effectiveness of replacement (with amalgam) versus repair (with amalgam) in the management of defective amalgam dental restorations in permanent molar and premolar teeth.

SEARCH STRATEGY

For the identification of studies relevant to this review we searched the Cochrane Oral Health Group Trials Register (to 23rd September 2009); CENTRAL (The Cochrane Library 2009, Issue 4); MEDLINE (1950 to 23rd September 2009); EMBASE (1980 to 23rd September 2009); ISI Web of Science (SCIE, SSCI) (1981 to 22nd December 2009); ISI Web of Science Conference Proceedings (1990 to 22nd December 2009); BIOSIS (1985 to 22nd December 2009); and OpenSIGLE (1980 to 2005). Researchers, experts and organisations known to be involved in this field were contacted in order to trace unpublished or ongoing studies. There were no language limitations.

SELECTION CRITERIA

Trials were selected if they met the following criteria: randomised or quasi-randomised controlled trial, involving replacement and repair of amalgam restorations.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed titles and abstracts for each article identified by the searches in order to decide whether the article was likely to be relevant. Full papers were obtained for relevant articles and both review authors studied these. The Cochrane Collaboration statistical guidelines were to be followed for data synthesis.

MAIN RESULTS

The search strategy retrieved 145 potentially eligible studies, after de-duplication and examination of the titles and abstracts all but three studies were deemed irrelevant. After further analysis of the full texts of the three studies identified, none of the retrieved studies met the inclusion criteria and all were excluded from this review.

AUTHORS' CONCLUSIONS

There are no published randomised controlled clinical trials relevant to this review question. There is therefore a need for methodologically sound randomised controlled clinical trials that are reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement (www.consort-statement.org/). Further research also needs to explore qualitatively the views of patients on repairing versus replacement and investigate themes around pain, distress and anxiety, time and costs.

Replacement versus repair of defective restorations in adults: resin composite

BACKGROUND

Composite filling materials have been increasingly used for the restoration of posterior teeth in recent years as a tooth coloured alternative to amalgam. As with any filling material composites have a finite life-span. Traditionally, replacement was the ideal approach to treat defective composite restorations, however, repairing composites offers an alternative more conservative approach where restorations are partly still serviceable. Repairing the restoration has the potential of taking less time and may sometimes be performed without the use of local anaesthesia hence it may be less distressing for a patient when compared with replacement.

OBJECTIVES

To evaluate the effectiveness of replacement (with resin composite) versus repair (with resin composite) in the management of defective resin composite dental restorations in permanent molar and premolar teeth.

SEARCH STRATEGY

For the identification of studies relevant to this review we searched the Cochrane Oral Health Group Trials Register (to 23rd September 2009); CENTRAL (The Cochrane Library 2009, Issue 4); MEDLINE (1950 to 23rd September 2009); EMBASE (1980 to 23rd September 2009); ISI Web of Science (SCIE, SSCI) (1981 to 22nd December 2009); ISI Web of Science Conference Proceedings (1990 to 22nd December 2009); BIOSIS (1985 to 22nd December 2009); and OpenSIGLE (1980 to 2005). Researchers, experts and organisations known to be involved in this field were contacted in order to trace unpublished or ongoing studies. There were no language limitations.

SELECTION CRITERIA

Trials were selected if they met the following criteria: randomised or quasi-randomised controlled trial, involving replacement and repair of resin composite restorations.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed titles and abstracts for each article identified by the searches in order to decide whether the article was likely to be relevant. Full papers were obtained for relevant articles and both review authors studied these. The Cochrane Collaboration statistical guidelines were to be followed for data synthesis.

MAIN RESULTS

The search strategy retrieved 279 potentially eligible studies, after de-duplication and examination of the titles and abstracts all but four studies were deemed irrelevant. After further analysis of the full texts of the four studies identified, none of the retrieved studies met the inclusion criteria and all were excluded from this review.

AUTHORS' CONCLUSIONS

There are no published randomised controlled clinical trials relevant to this review question. There is therefore a need for methodologically sound randomised controlled clinical trials that are reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement (www.consort-statement.org/). Further research also needs to explore qualitatively the views of patients on repairing versus replacement and investigate themes around pain, anxiety and distress, time and costs.

Effect of Distance from Curing Light Tip to Restoration Surface on Depth of Cure of Composite Resin

Aims

While light-activating composite resins, the light tip may not always be close to the surface of the restoration. This may be intentional in an attempt to create a ramp cure. The aim of this study was to determine the effect of a range of separation distances between the light tip and the restoration surface on the depth of composite cure for different types of light-curing units with a broad range of outputs.

Methods

Three halogen light units, one plasma arc-curing (PAC) light unit and two light-emitting diode (LED) curing lights in clinical use were tested, and a total of 570 restorations cured in a two-part human tooth model at separations ranging from 0 to 15 mm. The tooth was disassembled and depth of cure determined using the scrape test ISO 4049. Light intensity was also measured at each separation distance for each light.

Results

The depth of cure was generally found to decrease as the separation distance increased for all lights at the various cure times. However, the effect of increasing the separation distance was less than anticipated. The depth of cure was also related to the light output.

Conclusions

Depth of composite cure was directly related to intensity and duration of light exposure and inversely related to distance of the light source from the surface for halogen and plasma lights. However, the effect of increasing the separation distance up to 15 mm was less than expected. Altering the separation distance in order to modify the polymerisation characteristics is unlikely to be effective.

Clinical performance of Rochette bridges used as immediate provisional restorations for single unit implants in general practice

A retrospective clinical audit of the role and survival of 69 Rochette bridges used as immediate provisional restorations for single tooth, implant-retained crowns was carried out over the period between February 1991 and May 2001. In each case the extracted tooth was immediately temporised using a Rochette bridge with a single wing and pontic and cemented to the abutment tooth without any tooth preparation (Phase I). This bridge was removed at the time of implant placement and recemented (Phase II). At the implant exposure stage the bridge was removed and discarded. In Phase I, 15.9% of the bridges required recementation and 27.5% of the bridges required recementations in phase 2; 7.2% of the bridges required recementations in both phases. An 80% probability of survival was noted after an interval of 200 days for phase I and a 78% probability of survival over the same time interval was observed for Phase II. A significant debond rate was observed when the retainer was a canine in comparison to the other bridges in Phase I. In Phase I the spring cantilever debond rate was significantly higher than that observed on the other bridges. More debondings were observed in males (25.8%) compared with females (7.9%) in Phase I. More debondings were noted in the maxilla than in the mandible in Phase II. The performance characteristics of the metal acrylic Rochette bridge observed in this report supports the conclusion that this type of restoration is an effective means of immediate temporisation for patients undergoing single tooth implant retained restorations.

The effect of infection-control barriers on the light intensity of light-cure units and depth of cure of composite

AIM

Dental curing lights are vulnerable to contamination with oral fluids during routine intra-oral use. This controlled study aimed to evaluate whether or not disposable transparent barriers placed over the light-guide tip would affect light output intensity or the subsequent depth of cure of a composite restoration.

METHODS

The impact on light intensity emitted from high-, medium- and low-output light-cure units in the presence of two commercially available disposable infection-control barriers was evaluated against a no-barrier control. Power density measurements from the three intensity light-cure units were recorded with a radiometer, then converted to a digital image using an intra-oral camera and values determined using a commercial computer program. For each curing unit, the measurements were repeated on ten separate occasions with each barrier and the control. Depth of cure was evaluated using a scrape test in a natural tooth model.

RESULTS

At each level of light output, the two disposable barriers produced a significant reduction in the mean power density readings compared to the no-barrier control (P<0.005). The cure sleeve inhibited light output to a greater extent than either the cling film or the control (P<0.005). Only composite restorations light-activated by the high level unit demonstrated a small but significant decrease in the depth of cure compared to the control (P<0.05).

CONCLUSION

Placing disposable barriers over the light-guide tip reduced the light intensity from all three curing lights. There was no impact on depth of cure except for the high-output light, where a small decrease in cure depth was noted but this was not considered clinically significant. Disposable barriers can be recommended for use with light-cure lights.

A 3-year longitudinal, controlled clinical study of a gallium-based restorative material

AIM

The aim of this three-year longitudinal controlled study was to compare the clinical performance of Galloy versus a high copper, mercury based Dispersalloy filling material.

METHODS

Moderate to large class I and class II cavities or replacement restorations were selected and 25 Galloy restorations and 25 Dispersalloy controls were placed in 14 adult patients by a single operator. Restorations were photographed and a silicone impression recorded at baseline, 6 months, 1 year, 2 years and 3 years.

RESULTS

At 3 years all 22 Dispersalloy restorations but only 4 Galloy restorations were still in situ. Three Dispersalloy restorations were lost to follow-up. Tooth fracture was observed in 15 (60%) of the Galloy restorations by the end of the 3 years, compared to one (4%) Dispersalloy restoration, which failed due to tooth fracture. A further six Galloy restorations had to be removed due to complaints of persistent pain. Four teeth restored with Galloy required endodontic treatment but none of the Dispersalloy restored teeth required endodontics. Of the four Galloy restorations remaining in situ, three were relatively small restorations and the fourth a moderate sized restoration required a marginal repair.

CONCLUSION

The clinical performance of Galloy restorations was so grossly inferior to the Dispersalloy controls that Galloy cannot be recommended for clinical use in moderate to large or multi-surface cavities.

Efficacy and safety of desensitization to allopurinol following cutaneous reactions

OBJECTIVE

To evaluate the long-term efficacy and safety of slow oral desensitization in the management of patients with hyperuricemia and allopurinol-induced maculopapular eruptions.

METHODS

A retrospective evaluation of an oral desensitization regimen using gradual dosage-escalation of allopurinol in 32 patients (30 with gout and 2 with chronic lymphocytic leukemia) whose therapy was interrupted because of a pruritic cutaneous reaction to the drug.

RESULTS

Twenty-one men and 11 women with a mean age of 63 years (range 17-83 years), a mean serum urate level of 618 micromoles/liter (range 495-750) (or, mean 10.4 mg/dl [range 8.3-12.6]), and a mean serum creatinine level of 249 micromoles/liter (range 75-753) (or, mean 2.8 mg/dl [range 0.8-8.5]) were studied. Desensitization failed in 4 patients because of unmanageable recurrent rash. Twenty-eight patients completed the desensitization procedure to a target allopurinol dosage of 50-100 mg/day, 21 without deviation from the protocol for a mean of 30.5 days (range 21-56 days) and 7 requiring dosage adjustments because of a recurrent rash over 53.8 days (range 40-189 days). Seven of these 28 patients developed late cutaneous reactions 1-20 months postdesensitization, 4 responding to dosage modification and 3 discontinuing the drug. Twenty-five of the 32 patients (78%) continued to take allopurinol; their mean duration of followup was 32.6 months (range 3-92 months) and the mean postdesensitization serum urate level was 318 micromoles/liter (range 187-452) (or, mean 5.3 mg/dl [range 3.0-7.5]).

CONCLUSION

The study confirms the long-term efficacy and safety of slow oral desensitization to allopurinol in patients with maculopapular eruptions, particularly in those with gout, who cannot be treated with uricosurics or other urate-lowering drugs. Although pruritic skin eruptions may recur both during and after desensitization, most of these cutaneous reactions can be managed by temporary withdrawal of allopurinol and dosage adjustment.

Dental post-operative sensitivity associated with a gallium-based restorative material

INTRODUCTION

This study forms part of a 2-year longitudinal clinical trial to compare the performance of a gallium-based restorative material (Galloy) with a high copper, mercury based (Dispersalloy) control material.

METHOD

Following Ethical Committee approval, 25 galloy restorations and 25 Dispersalloy controls were placed in 14 adult patients, by a single operator. The cavities were of moderate size, indicating the use of amalgam as the restorative material. All restorations were polished within 1 week of placement, photographed and a silicone impression of the tooth and restoration recorded. In addition, a visual analogue scale (VAS), indicating the extent of any post-operative sensitivity, was completed by each patient for each restoration, immediately prior to polishing. A score of 0 indicated no sensitivity, while a score of 10 indicated the greatest possible sensitivity. At 6-month recall, the VAS scores, silicone impressions and photographs were repeated.

RESULTS

The mean sensitivity scores for the galloy and Dispersalloy restorations at 1 week were 5.1 (+/- 3.4) and 1.0 (+/- 1.5), respectively and at 6 months, 1.8 (+/- 3.0) and 0.2 (+/- 0.1) respectively. The differences between these means at 1 week and at 6 months were significant (P < 0.01).

CONCLUSION

Galloy restorations were associated with a much greater severity of post-operative sensitivity than Dispersalloy restorations.

A comparison of the shear bond strength of composite resin bonded by a fourth and a fifth generation dental adhesive to bovine teeth

AIM

This study compared the shear bond strengths, to bovine enamel and dentine, of composite resin bonded using an established bonding agent (Syntac) and the more recent Syntac SC.

METHOD

A total of 24 adult bovine incisors were divided into two equal groups and prepared by roughening the enamel surfaces with a medium-grit, high-speed diamond. The enamel was etched and 24 x 5 mm diameter composite discs were light-cured and bonded using Syntac and 24 using Syntac SC, following the manufacturer's instructions. The samples were shear tested 72 hours later at a crosshead speed of 50 mm/min using a Howden Universal Testing Machine. The labial enamel and 1 mm of dentine were removed and the experiment was repeated.

RESULTS

The mean shear bond strengths (MPa) for the Syntac and Syntac SC bonded composite to enamel were 10.9 +/- 4.5 and 8.9 +/- 5.7, and to dentine 6.4 +/- 3.2 and 5.5 +/- 3.1, respectively. The differences between the values for each material on enamel and between each material on dentine were not significant (P > 0.01). However, nine (19%) Syntac SC bonded composite discs debonded during build-up and had to be remade, prior to testing.

CONCLUSION

When a bond between composite and resin was achieved, no significant difference was found between the mean shear bond strengths of Syntac and Syntac SC bonded composite to either enamel or dentine. However, lack of composite adherence to the Syntac SC was noted during the preparation of specimens.

In vitro study of the number of surface defects in monophase and two-phase addition silicone impressions

STATEMENT OF PROBLEM

Monophase addition-cured silicone impression materials in stock trays are considered to be alternatives to two-phase systems used with custom trays.

PURPOSE

This study compared the number of surface defects in addition-cured silicone impressions recorded with monophase materials in stock trays and two-phase impressions in custom trays.

METHODS

The number of voids visible on the surface of impressions recorded in vitro were counted. Two monophase impression materials. (President Monobody system 75, Bayer Cutter) in stock trays were compared with impressions recorded with two-phase addition silicone materials (President Plus light-body/regular-body and Zhermack Elite light-body/medium-body) in custom trays. A total of 200 automixed impressions, 50 with each material, were recorded of 50 dentoform molar teeth prepared for full veneer crowns. Impressions were examined for surface voids anywhere on the prepared part of the tooth by a trained examiner.

RESULTS

Mean number of voids observed for the monophase impressions were 3.0 +/- 2.2 for President Monobody system and 3.4 +/- 2.0 for Bayer Cutter system. Mean number of voids for the two-phase materials were 0.8 +/- 1.0 for President Plus, and 1.0 +/- 1.1 for Zhermack Elite. No significant differences were observed for number of voids between the monophase materials or between the two-phase systems (ANOVA and Neuman-Keuls p > 0.05). However, both two-phase materials in custom trays had significantly fewer surface voids than the two-monophase materials (ANOVA and Neuman-Keuls, p < 0.001) used in stock trays.

CONCLUSION

Monophase addition-cured impression materials in stock trays carries an increased risk of void formation on the surface of the impression when compared with two-phase addition silicone materials in custom trays.

Preliminary investigation of a novel retentive system for hydrofluoric acid etch-resistant dental ceramics

STATEMENT OF PROBLEM

A potential limitation to clinical use of In-Ceram and In-Ceram Spinell dental ceramics has been the inability to etch fit surfaces.

PURPOSE

This study investigated a novel retentive system for In-Ceram and In-Ceram Spinell ceramics.

MATERIAL AND METHODS

The system, Bateman etch retention system, relies on incorporation of plastic chips on the surface of a specimen. The plastic chips were subsequently burnt-out to leave pits on the fitting surface of the ceramic restoration. The effect of these surface pits on flexural strength of test specimens was compared with unetched and sandblasted samples. Shear bond strengths between clean and saliva contaminated samples and Panavia TC resinous cement were also determined.

RESULTS

The Bateman etch retention system significantly reduced the flexural strength of both In-Ceram and Spinell ceramic specimens compared with unetched and sandblasted samples (p < 0.05). No significant differences were discovered between shear bond strengths of uncontaminated Bateman etch retention system and sandblasted samples. However, mean shear bond strengths of saliva-contaminated Bateman etch retention system In-Ceram samples were substantially greater than those of saliva contaminated sandblasted samples (p < 0.05).

CONCLUSION

The Bateman etch retention system method should be the subject of additional investigation.

Current materials and techniques for direct restorations in posterior teeth. Part 2: Resin composite systems

This paper, the second in a two-part review of direct materials and techniques for intracoronal restorations in posterior teeth, deals with resin composite systems. Based on a consensus view on appropriate applications for composites in posterior teeth, consideration is given to the selection of composite systems, indications for posterior composites in different populations, principles for cavity preparation, placement techniques, clinical performance and the use of posterior composites in the context of the changing pattern of dental disease and the need to expand existing knowledge. It is concluded that posterior composites have a place in everyday clinical practice, albeit relatively limited and that the time has come to actively pursue and realise the opportunities afforded by these materials.

Current materials and techniques for direct restorations in posterior teeth. Part 1: Silver amalgam

This paper, the first of two reviewing materials and techniques for direct intracoronal restorations in posterior teeth, deals with the use of silver amalgam. Based on a consensus view on appropriate applications and contraindications for silver amalgam, the toxicity of amalgam and competing materials, financial implications and international legislation, consideration is given to the continued use of this material. It is concluded that silver amalgam still has a place in everyday practice, albeit restricted in comparison to its former use. Amalgam should only be used where it offers clear advantages over other materials. This requirement for use of silver amalgam will continue until true substitutes are developed and evaluated, alternative materials are optimised and dentists are fully trained in the use of adhesive techniques.

The effect of a surface wetting agent on void formation in impressions

STATEMENT OF PROBLEM

Impressions free from voids are important for the fabrication of accurate restorations. Any material or technique that reduces the incidence of bubbles is welcome.

PURPOSE

The aim of this study was to determine whether the use of a surfactant designed for clinical use (Hydrosystem) reduced the number of visible air bubbles on the surface of a range of impression materials.

MATERIAL AND METHODS

The surfactant was used before impressions were recorded with one of the following: a putty-wash condensation silicone, four polyvinyl siloxane materials, a polyether, a polysulfide, and an irreversible hydrocolloid impression material. Impressions recorded without the use of Hydrosystem acted as controls. Impressions were made of two prepared acrylic resin teeth in vitro and examined for surface voids by an examiner who was blind to whether the surfactant was used.

RESULTS

Hydrosystem surfactant significantly reduced the number of surface voids when it was used with low-viscosity addition-cured silicone material but not when used with irreversible hydrocolloid, polysulfide, a hydroactive monophase addition-cured silicone, or a putty-wash condensation silicone.

CONCLUSION

The use of Hydrosystem surfactant may result in a clinically significant improvement in impression quality.

Assessment of a prototype battery operated wax-knife for domiciliary and surgery use

The aims of this study were to examine a prototype battery operated wax-knife, assess the extent to which manufacturer's claims have been achieved and determine its potential for clinical use. The mean time required for the wax-knife to achieve an operating temperature of 150 degrees C was 20.2(+/-4.3) s. The mean operating temperature of the ceramic blade was 155.4(+/-3.9) degrees C, range 150 degrees C to 162 degrees C. The mean usage time following full battery recharge was 42 (+/-2) minutes. The wax-knife provided a direct heating tool which retained many of the characteristics of the traditional wax-knife and was suitable for use in the surgery and in domiciliary situations.

An in vivo study of a clinical surfactant used with poly(vinyl siloxane) impression materials

The aim of this study was to determine whether the use of a topical surfactant (Hydrosystem), designed for clinical use, improved the quality of the impression surface of two poly(vinyl siloxane) materials used in vivo. Before impressions were taken, Hydrosystem was applied to the maxillary left or right premolar teeth, allocated at random, in 50 subjects. The untreated side acted as a control for each subject. The impressions were examined for quality of reproduction and number of surface defects. Hydrosystem was found to significantly improve the quality of reproduction.

A survey of dental airlines and an examination of tooth-drying techniques

The aims of this study were: 1. To assess the prevalence and severity of water and oil contamination in 20 dental airlines in clinical use, using a commercial test kit, LP Aerotest. 2. To determine the effect, in vitro, of such contamination on the shear bond strengths to etched bovine enamel, of composite resin and a dedicated bonding agent. The enamel was dried using either an oil-and-water-contaminated 3-in-1 syringe, a warm-air tooth-dryer, silica gel-dried air or blotting paper, prior to bonding. A total of 11 (5 mm diameter) composite discs were bonded in each group. The samples were shear tested 72 hours later at a cross-head speed of 50 mm/min. All airlines had > 100 mg/m3 water and traces of oil (< 0.5 mg/m3) were present in 50% of samples. The mean shear bond strengths (MPa) for the 3-in-1 syringe, tooth-dryer, dried air and blotting paper-dried teeth were 14.5 +/- 3.8, 19.0 +/- 2.6, 19.6 +/- 4.2 and 19.7 +/- 1.9 respectively. The differences between the values for the tooth dryer, dry air and blotting paper were not significant (P > 0.01) but a significant difference (P < 0.01) was observed between these and the 3-in-1 syringe.

A survey of the effectiveness of dental light-curing units and a comparison of light testing devices

The aims of this study were to: 1. survey the light output from 49 light-curing units in clinical use; 2. measure the effect on depth of cure of composite resin caused by a range of light outputs; 3. assess the relationship between radiometer meter readings and depth of cure of composite resin in a human tooth model and a Heliotest. The mean meter reading produced by the 49 lights surveyed using a lampChecker radiometer was 4.4 (+/-2.4 SD), range 0.3 to 10.0. The manufacturer of the radiometer considers optimal light output to provide a meter reading within the range 5.0 to 7.0. Lights of very low output (0.7 +/- 0.1 SD) were found to be capable of curing, after 20 seconds, a 1.9 (+/-0.3 SD) mm thickness of composite resin. However, only approximately 50% of this thickness can be considered fully cured. Increasing the cure time from 20 seconds to 60 seconds increased the mean depths of cure by a factor of approximately 1.4. The mean depths of cure of composite resin placed in the Heliotest were greater than those observed in the natural tooth model, by a factor of approximately 1.3. Correlation coefficients of meter readings and depth of cure were greater for the Efos Cure Rite and Demetron 100 radiometers than the lampChecker unit.

Diagnosis and management of the dry mouth: Part 1

Dry mouth is a relatively common problem, often neglected by patients and dentists alike. This article reviews the symptoms, causes and treatment of xerostomia and provides guidelines for recognizing the condition at an early stage.

Caries inhibition by a resin-modified and a conventional glass ionomer cement, in vitro

OBJECTIVES

The aim of this study was to compare inhibition, in vitro, of a resin-modified and a conventional glass ionomer cement.

METHODS

Standardized Class V cavities were prepared in extracted human molar teeth and restored with Fuji II LC (n = 14) or Chemfil II (n = 14) according to manufacturers' guidelines. The teeth were submerged in an acid gel (lactic acid, gelatin, thymol, pH 4.5) for 14 days and resin embedded. Photomicrographs of ground sections were examined for enamel surface lesions, dentine surface lesions, wall lesions and evidence of caries inhibition.

RESULTS

There was no significant difference between the depths of enamel or dentine surface lesions between the two materials. No wall lesions were found.

CONCLUSIONS

Fuji II LC proved more acid resistant than Chemfil II and both materials inhibited caries in vitro.

A comparison of three wetting agents used to facilitate the pouring of dies

This study compared the effect of a clinical surfactant and one of three laboratory surfactants used before pouring dies from elastomeric impression materials. A total of 154 impressions were recorded. Hydrosystem surfactant was used before the recording of 78 of these impressions. A total of 154 dies were poured with Wax-mate, Tensilab, or Hydrosystem surfactants and examined for surface voids by an examiner who was unaware which wetting agent was used. Six dies were grossly defective and discarded. When the Hydrosystem surfactant had not been used during impression recording there was no significant difference between Hydrosystem (mean 10.2 +/- 8.8 voids, n 25), Wax-mate (mean 13.1 +/- 14.4 voids, n 25), and Tensilab (mean 14.9 +/- 11.6 voids, n 21) surfactants when the dies were poured. When Hydrosystem surfactant was used during impression recording, there was no significant difference between the number of voids on dies produced with Hydrosystem (mean 3.8 +/- 3.9 voids, n 26), Wax-mate (3.9 +/- 3.3 voids, n 25), or Tensilab (3.7 +/- 4.9 voids, n 26) surfactants. However, each of the groups in which Hydrosystem surfactant was used before impression recording resulted in dies with significantly fewer voids than when it had not been used, independent of the surface wetting agent used in the pouring of dies (p < 0.05). To reduce the number of voids in laboratory dies, this in vitro study suggested that a topical surfactant should be used before an impression is recorded.

An in vitro investigation into the shear bond strengths of two dentine-bonding agents used in the reattachment of incisal edge fragments

This in vitro study investigated the shear bond strengths of sectioned bovine incisal edge fragments reattached using Gluma 2000 and Scotchbond 2. Teeth were sectioned 3 mm from the incisal edge using an Acutome with a 0.5 mm diamond wheel running at 90 degrees to the mesial or distal surface of the tooth. Twenty four incisal fragments were rebonded with each of the dentine bonding agents; a further 24 intact incisors were used as a control group. The control group required a mean fracture force of 940(+/- 144) N which was significantly greater (p < 0.01) than that required to fracture fragments rebonded using GLUMA 2000 (609 +/- 116) N and Scotchbond 2 (393 +/- 97) N. The mean force required to fracture incisal fragments rebonded with GLUMA 2000 was significantly greater (p < 0.01) than that required to fracture incisal fragments rebonded with Scotchbond 2.

Examination of tooth-drying techniques: evaluation in-vitro of a prototype warm-air tooth dryer

A prototype, rechargeable, warm-air tooth dryer is evaluated and its capabilities compared with those of an established mains electricity powered dryer (Handi-Dri). The evaluation includes warm-up cycle, maximum temperature and constancy of temperature of air output, battery discharge profile, time required to dry etched enamel, ability to dry wet filter paper, flow rate and pressure of air output, convenience and ease of use. Selected tests were also applied to a dental 3-in-1 syringe. Alternative methods of drying the tooth surface are also reviewed. The prototype was found to be suitable for tooth drying; it was considered safer and more convenient than the Handi-Dri and offered advantages over other methods.

An in vitro study of a surface wetting agent for addition reaction silicone impressions

The aims of this study were to determine whether the use of a topical surfactant (Hydrosystem) reduced the number of air bubbles visible on the surface of polyvinyl siloxane impressions and stone dies. The impressions exhibited a mean of 1.4 +/- 2.1 bubbles when Hydrosystem wetting agent was used, which was significantly less (p < 0.001) than when it was not used (mean 5.5 +/- 4.7 bubbles). Dies prepared with Hydrosystem surfactant contained a mean of 0.4 +/- 0.8 bubbles, which was significantly (p < 0.001) less than when Wax-Mate surface agent was used (mean 3.5 +/- 5.2 bubbles). In conclusion, in vitro use of Hydrosystem surfactant reduced the number of air bubbles on the surface of silicone impressions and stone dies.

A longitudinal study of the clinical performance of porcelain veneers

A total of 315 porcelain labial veneers were fitted in 96 patients in two teaching hospitals, between July 1986 and October 1991, and were evaluated after a period of up to 63 months. During the evaluation period 53 (17%) restorations in 31 (32%) patients presented with a problem at review. Of these, 25 (8%) were of a minor nature and the veneer remained in use while 34 (11%) debonded or were removed. Increased problem and failure rates were associated with veneers placed on existing restorations, where tooth surface loss had occurred prior to treatment, and where inappropriate luting agents were employed. Age, gender, fabrication technique (platinum foil or refractory die), use of rubber dam and year of bonding were not significant factors.

Topical guanethidine relieves dentinal hypersensitivity and pain

The topical application of guanethidine solution to the affected teeth has been successful in relieving natural and clinically induced dentinal pain and hypersensitivity in 13 of 14 dental patients in a pilot study. The mechanism of this analgesia was unclear but probably involved anti-noradrenergic block as there was no evidence of local anaesthesia. Further studies may generate new ideas about the cause of the excruciating pain and hypersensitivity often associated with the acute exposure of tooth dentine and lead to new ways of managing the discomforts of dental conservation and restoration.

The use of topical guanethidine in the relief of dentine hypersensitivity: a controlled study

After a pilot study had indicated that the topical application of guanethidine might be of value in the treatment of tooth dentine hypersensitivity, a double-blind study was undertaken to investigate whether guanethidine was more effective than a distilled water control in alleviating dentinal pain. In 39 adult subjects, who had complained of dentine hypersensitivity, a 1 sec blast of air from a dental 3-in-1 syringe was directed onto sensitive root dentine at an angle of 90 degrees from a distance of 1 cm. The severity of the resulting pain was indicated by the subject on a 10 cm visual analogue scale (VAS). One droplet of either 1% guanethidine monosulphate (Ismelin, Ciba-Geigy) or distilled water, allocated at random, was applied to the dentine for 1 min. The tooth was re-tested with the standardised air blast and a second VAS was marked by the subject. In total, 19 patients received guanethidine and 20 received water. VAS scores before treatment in the 2 groups treated with either guanethidine or water (means: 6.5 +/- 2.2 and 6.0 +/- 2.5, respectively) were not significantly different (Mann-Whitney, P = 0.48) whereas the VAS scores in the 2 groups after treatment with guanethidine or water (means: 2.7 +/- 2.4 and 4.8 +/- 2.9, respectively) were significantly different (Mann-Whitney, P < 0.02). It was concluded that guanethidine reduced dentinal hypersensitivity more effectively than distilled water.(ABSTRACT TRUNCATED AT 250 WORDS)

A longitudinal study of the clinical performance of resin bonded bridges and splints

A total of 382 resin bonded bridges and splints were fitted, in 309 patients, in a teaching hospital. The restorations were evaluated after a period ranging from 5 months to 8 years. During the evaluation period 125 restorations (33%) debonded of which 69 (55%) were rebonded. The survival rates of the rebonded restorations at first, second, third or fourth rebond, where necessary, did not differ from the survival rate of the same restorations up to the first debond. Restorations constructed using the Rochette design had a significantly higher debond rate than the other designs. However, since they also exhibited a high rebond rate Rochette restorations continued to perform well over the study period. Splints had a higher debond rate as did restorations placed in patients in the age group 11 to 20 years, restorations involving more than two abutment teeth, and restorations containing more than one tooth pontic.

The limitation of visual perception in restorative dentistry

Accurate judgement of size, depth and angle is required in the practice of restorative dentistry. Most assessments are made simply by visual examination, and these judgements are therefore often subjective; the limitation of visual perception renders such judgements inaccurate and subject to variation. The use of standardized objects to allow size or angle judgement by direct comparison improves accuracy, and their routine use may improve the quality of restorative treatment.

The removal of carbon particles from the buccal surface of upper incisors and canines (by saliva and mechanical movement)

Clearance time of carbon particles from the buccal surfaces of upper incisor and canine teeth was measured, and its possible relationship with plaque accumulation and gingival inflammation was assessed. The average clearance time observed was 20.75 minutes. Factors influencing particle removal were found to be significantly related to the severity of gingival inflammation but not to differences in plaque accumulation. Thus the factors involved in particle clearance may modify the gingival response to plaque. Alternatively, small changes in gingival contour as a result of the inflammatory process may alter significantly the ability of these factors to remove particulate matter.

Evaluation of the use of colour transparencies for scoring gingivitis

The effects of altering exposure, angle at which the exposure was made, magnification, type of flash, and the method of viewing, on scoring gingivitis from colour transparencies were evaluated. The results of this study suggest that, by using a standardised photographic technique, the scoring of gingivitis from colour transparencies is a valid procedure. However, many practical drawbacks arose, indicating that this method is not entirely satisfactory.