Search PubMed⌕ Search

Biomedical subjects

I A Mjör

Publications and source records attributed to I A Mjör.

At least 19 recordsLinked to original sources
PubMed2003

The repair of direct composite restorations: an international survey of the teaching of operative techniques and materials.

This article reports the findings of a study on the aspects of the teaching of repair as a conservative alternative to the replacement of failing direct composite restorations (DCRs) in primary dental degree curricula in the UK and Ireland, Germany and Scandinavia. Data on teaching, including operative techniques applied in the repair of DCRs, were collected by means of a questionnaire sent to 58 dental schools in the surveyed countries. Based on the overall response rate of 83%, the findings indicate that the majority (59%) of the schools in the countries surveyed may be found to teach the repair of DCRs. However, marked variations were observed in respect of this teaching and the expected longevity of repaired DCRs. Where the repair of DCRs was not taught, views differed as to the intentions, if any, to include this teaching in the curriculum. It is concluded that the teaching of DCRs may be found to be widespread in dental schools in the UK and Ireland, Germany and Scandinavia, with this teaching being subjected to considerable variation within and between countries.

Composite Resins↗
PubMed2003

Remaining dentine thickness and human pulp responses.

AIM: To evaluate pulp responses as a function of remaining dentine thickness (RDT) of 98 class V cavity preparations in 49 teeth of 31 patients aged 10-16 years. METHODOLOGY: Shallow cavities were restored with amalgam, deeper cavities or pulp exposures were restored with amalgam lined with calcium hydroxide or with zinc oxide eugenol. Teeth were extracted after 3-89 days for orthodontic reasons. Following processing for light microscope analysis, the number of odontoblasts, pulp inflammation, and repair was recorded. RESULTS: In comparison with independent odontoblasts, the numbers of odontoblasts were reduced by 13.6% beneath a RDT of 2.5-0.5 mm, 33.7% beneath a RDT of 0.5-0.01 mm and 99.0% beneath pulp-exposed cavities. Reparative dentine was observed following pulp exposure and reactionary dentine was observed with a mean RDT of 0.77 mm (2.5-0.01 mm). Reactionary dentine secretion was influenced by RDT and restorative materials. Pulp inflammation was not influenced by RDT in the present study. CONCLUSIONS: Cavity RDT mediates a powerful influence on underlying pulp tissue vitality but it has little effect on reactionary dentine secretion and inflammatory activity. Gross tissue injury explains the poor pulp capping prognosis following exposure and underlies the need to avoid this type of injury. Following restoration, a RDT of 0.5 mm or greater is necessary to avoid evidence of pulp injury.

Adolescent↗
PubMed2002

Influence of the method of funding on the age of failed restorations in general dental practice in the UK.

OBJECTIVE: This study examined the effect of the method of funding treatment on the age of restorations at the time of replacement. METHOD: A group of general dental practitioners were recruited to take part in the study. Each participant was asked to record the reason for placement and replacement of restorations. The age and class of the restoration being replaced was also recorded, together with details of the material being used and the material being replaced. Details of the method of payment of the failed restoration were recorded. RESULTS: Details of the reason for placement/replacement were received for 3,196 restorations from 32 GDPs. Of the restorations placed, 54% were amalgam, 32% composite, 8% compomer and 7% glass ionomer. The age of restorations at the time of replacement was significantly associated with the method of payment for the restoration, with restorations placed in the Armed Forces having been in service significantly longer at the time of their replacement than restorations placed under NHS regulations. CONCLUSION: Statistical analysis indicated that restorations placed within the NHS regulations were replaced at a significantly lower age than restorations placed under the other funding arrangements investigated.

Age Factors↗
PubMed2001

Bonding of all-porcelain crowns: structural characteristics of the substrate.

OBJECTIVES: The aim of this in vitro study was to evaluate the morphology of dentin in teeth prepared for single-unit all-porcelain crowns (SUAPC) in terms of tubule orientation, density and increase in surface area after etching. METHODS: Twenty anterior and 20 posterior teeth from adults were prepared 1mm below the cemento-enamel junction (CEJ) for SUAPC. The samples were divided into groups based on type of tooth (anterior or posterior) and bonding system employed. The teeth were processed for evaluation of morphology of the substrate, hybrid layer thickness and resin tag formation. The observations were subdivided according to location in the preparation and tubule density was calculated. RESULTS: The observations revealed the variability in tubule density and orientation in different areas within any one preparation. The morphology of the cervical margin was less predictable with the presence of cementum and an ill-defined cemento-dentinal junction. Statistically significant differences in the density of tubules were found depending on location. Groups 2, 3, 5 and 6 samples showed that the hybrid layer thickness and resin tag morphology depended on the density and direction of tubules. In those sectors with parallel and oblique tubule orientation and with a low density of tubules, the hybrid layer was significantly thinner than in areas with cross-sectioned tubules. SIGNIFICANCE: The cementum and the peripheral intertubular dentin surface area are likely to be responsible for the bond strength after acid etching of crown preparations, but not all areas exhibited equal responses to etching. In particular, the bonding substrate at the gingival margins may contribute little in terms of micromechanical retention.

Acid Etching, Dental↗
PubMed2001

Influence of patient factors on age of restorations at failure and reasons for their placement and replacement.

OBJECTIVE: This study examined the reasons given by a selected group of dental practitioners for placement and replacement of restorations and correlated the data provided with patient factors, such as patients' age and gender, caries risk, occlusal function and oral hygiene, with restoration longevity. METHOD: A group of general dental practitioners (GDPs) were recruited to take part in the study. Each participant was asked to record the reason for placement or replacement of restorations from a list of potential reasons. The age and Class of the restoration being replaced was also recorded, as also was the material being used and the material being replaced. RESULTS: Details of reason for placement/replacement was received on 3196 restorations from 32 GDPs. Of the restorations placed, 54% were amalgam, 32% composite, 8% compomer and 7% glass ionomer. The reasons for placement/replacement of the restorations were principally primary caries (28%), secondary caries (29%), margin fracture (10%), tooth fracture (7%), and non-carious defects (6%). Overall, the mean age of restorations at failure was 7.1 years. Of the patients who received glass ionomer restorations, 29% were rated as having poor oral hygiene, compared with 18% of the patients who received amalgam restorations, 18% of the patients who received composite restorations and 23% of the patients who received compomer restorations. Of the patients who received glass ionomer restorations, 35% were rated as having high caries susceptibility, compared with 27% of those receiving amalgam restorations, 21% of those receiving composite restorations and 30% of those receiving compomer restorations. CONCLUSION: Primary caries was the principal reason for initial restorations. Secondary caries was the most prevalent reason for replacement of restorations. The results also indicate a selective application of different materials for different patients.

Adolescent↗
PubMed2001

The structure of dentine in the apical region of human teeth.

AIM: To study the structure of the apical region of human teeth with emphasis on dentinal tubules and their branches. METHODOLOGY: This descriptive histological study employed demineralized stained sections for light microscopy, demineralized unstained sections for scanning electron microscopy, and undemineralized, acid-etched specimens for confocal tandem scanning microscopy. RESULTS: The apical portion of human teeth showed marked variations in structure, including accessory root canals, areas of resorption and repaired resorptions, occasional attached, embedded and free pulp stones, varied amounts of irregular secondary dentine, and even cementum-like tissue lining the apical root canal wall. The apex often deviated from the long axis of the root canal. Primary dentinal tubules were irregular in direction and density. Some areas were devoid of tubules. CONCLUSIONS: The irregular and variable structure of the apical region of human teeth represent special challenges during endodontic therapy. Obturation techniques based on the penetration of adhesives into dentinal tubules are unlikely to be successful and adhesive techniques must depend on impregnation of a hybrid layer.

Adult↗
PubMed2001

An overview of reasons for the placement and replacement of restorations.

AIM: Surveys on reasons for the placement and replacement of restorations have been conducted in various countries. The purpose of this paper is to bring together and review the data of 10 such surveys with similar methodology. METHOD: The studies reviewed are all based on the protocol described by Mjör in 1981. RESULTS: The surveys reviewed provide data on the reasons for the placement and replacement of a total of 32,777 restorations. Notwithstanding differences between countries, different groups of practitioners and minor variations in methodology, the data included in the selected surveys indicate that everyday clinical practice in Scandinavia, UK and USA during the 1980s and 1990s has involved more replacement than initial restorations, with the ratio of initial to replacement restorations ranging from 1:1.1 to 1:2.4 for amalgam and 1:1.1 to 1:3.8 for composite materials. Primary caries has been consistently found to be the principal reason for the provision of initial restorations of amalgam and composite. The principal reason for the replacement of restorations of amalgam and composite has remained secondary caries as diagnosed clinically. Material failures (marginal degradation, discoloration, bulk fracture and loss of anatomic form) accounted for the replacement of more restorations of composite than amalgam. Recent surveys have reported secondary caries as the principal cause of failure of restorations of glass-ionomer cements and related materials. CONCLUSIONS: The clinical diagnoses of caries may continue to be found to account for the placement and replacement of most intracoronal restorations. Surveys of the type reviewed provide valuable insight into patterns of provision of dental care and highlight research priorities in relation to direct restorations.

Composite Resins↗
PubMed2001

Pulp-dentin biology in restorative dentistry. Part 1: normal structure and physiology.

Considerable knowledge has accumulated over the years on the structure and function of the dental pulp and dentin. Some of this knowledge has important clinical implications. This review, which is the first of seven articles, will be limited to those parts of the normal structure and physiology of the pulp and dentin that have been shown to result in, or are likely lead to, tissue reactions associated with the clinical treatment of these tissues. Although certain normal structures will be highlighted in some detail, a basic knowledge of pulpal and dentinal development and structure is a prerequisite for an understanding of this text.

Biology↗
PubMed2001

Pulp-dentin biology in restorative dentistry. Part 3: Pulpal inflammation and its sequelae.

Physiologic and histopathologic experimental studies over the last 30 to 40 years have demonstrated that the healing of the dental pulp is comparable to that of connective tissue elsewhere, despite its location in the low-compliance pulp chamber. The greatest difficulty from a clinical point of view is to assess cellular changes and vitality of the pulp. If it is vital, the potential for repair is present, especially in young individuals.

Animals↗
PubMed2001

Pulp-dentin biology in restorative dentistry. Part 4: Dental caries--characteristics of lesions and pulpal reactions.

The infectious disease dental caries results in lesions that may affect enamel, dentin, pulp, and cementum. If a caries lesion has progressed to the stage at which it requires restorative intervention, it is important that the clinician understand the tissue changes in the dentin that are likely to have taken place during lesion development. Until the present, no major distinction between the restorative treatment of active (rapidly progressing) and arrested (slowly progressing) lesions has been made, despite the fact that the two conditions exhibit major differences in tissue changes in the pulp-dentin complex. Intratubular changes and tertiary dentin formation will affect the outcome of the restorative treatment. In unaffected dentin and in rapidly progressing lesions, permeable tubules persist, and when the preparation of carious teeth results in the opening of unaffected dentin, greater care must be taken in all phases of the restorative procedures than if the dentin is impermeable. An active, deep lesion can be changed to an arrested lesion by a two-step excavation approach. Optimal assessment of the prevailing clinical conditions can only be made on the basis of thorough knowledge of the biology of the pulp-dentin organ.

Dental Caries↗
PubMed2000

The teaching of Class I and Class II direct composite restorations in European dental schools.

OBJECTIVES: The purpose of this descriptive study was to provide updated data on the teaching of Class I and Class II direct composite restorations in Europe as part of a survey of this aspect of the primary dental curriculum in Europe and North America. METHODS: Data on the teaching of posterior composite restorations and related matters were collected by means of a postal questionnaire sent to 185 dental schools known to exist in Europe. Non-respondents were sent a second questionnaire after two months. Further information pertaining to student requirements was sought after six months from all respondents. RESULTS: The response ranged from 92% for dental schools in Scandinavia to 40% from dental schools in Southern Europe with an overall response of 56%. All but four of the 104 participating schools were found to teach the use of composites in Class I and Class II, two-surface situations in at least premolar teeth. Contraindications and techniques taught for posterior composites varied within and between the country groupings of Northern and Central Europe. Scandinavia, Southern Europe and Eastern Europe. However, certain consensus views were identified. The experience of adverse biological reactions to the use of resin-based restoratives in European dental schools was found to be limited. CONCLUSIONS: Notwithstanding the variation in the response from the four geographic regions investigated and the relatively low overall response to the questionnaire, it is concluded that the data reported indicates that most dental schools in Europe teach the use of composites in selected Class I and Class II situations. However, considerable variation exists both within and between the regions investigated in relation to this teaching. Further research and consensus conferences should be planned to reduce variability across Europe in relation to the contraindications and techniques taught for posterior composites.

Composite Resins↗
PubMed2000

Reasons for placement and replacement of restorations in student clinics in Manchester and Athens.

Data on reasons for the placement and replacement of restorations provide insight into patterns of clinical practice. This study investigated reasons for the provision of restorations in student clinics at the Universities of Manchester and Athens. Using the methods first described by Mjör, data were collected in relation to all initial and replacement restorations placed in adult patients in the main teaching clinics in the 2 schools over a 3-month period. The principal reason for intervention was recorded, according to approved treatment plans. Data were collected on 2620 restorations, 1431 (55%) of which were placed in Manchester. Primary caries was the main reason for the placement of initial restorations: 82% in Athens and 48% in Manchester (p<0.001). The principal reason for restoration replacement was secondary caries, accounting for 54% in Manchester and 33% in Athens (p<0.001). Other differences between the schools, included the ratio of initial placement to replacement restorations (Manchester 1:1.1; Athens 1:0.6: p<0.01) and significantly more 2-surface class II restorations having been placed in Manchester (p<0.001). Class III and IV restorations predominated in Athens. It is concluded, despite the acknowledged limitations of the methods employed, that the patterns of placement and replacement of restorations and the use of materials differ between the dental schools of Manchester and Athens. The differences are considered to relate more to local patterns of dental disease and patient selection for student clinics than to any differences in teaching philosophy. Subsequent studies of the type reported, despite acknowledged limitations would provide insight into the impact on patient care of the teaching of new materials, techniques and treatment philosophies.

Adolescent↗
PubMed2000

Age of restorations at replacement in permanent teeth in general dental practice.

The ages of 6,761 restorations replaced in permanent teeth, 6,088 in adults > or =19 years of age and 673 in adolescents < or =18 years, were available for analyses. The results showed that the median age of amalgam restorations in adults was 11 years and that of resin-based composite restorations 8 years. This difference in longevity was significant (P = 0.000 l). The median age of failed conventional glass ionomer restorations in adults was 4 years and for resin-modified glass ionomer 2 years. In adolescents, the median longevity of failed amalgam restorations was 5 years and that of composite restorations 3 years, while both types of glass ionomers had a median longevity of 2 years. The data were subdivided based on clinician gender and practice setting. The results showed that the median age of amalgam and composite restorations replaced Its male clinicians was higher than that for female clinicians irrespective of clinical setting. The median age of amalgam and composite restorations replaced by salaried dentists was significantly lower than that by private practitioners. Minor differences were noted in longevity of restorations between male and female patients. The age of replaced restorations was shortest for the group of clinicians with the least clinical experience and highest for those that graduated > or = 30 years ago.

Adolescent↗
PubMed2000

Reasons for replacement of restorations in permanent teeth in general dental practice.

OBJECTIVE: The analysis of reasons for the replacement of 9,805 amalgam, composite, glass ionomer, resin modified glass ionomer and 'other' restorations in permanent teeth in general dental practice. DESIGN: The data were subdivided on the bases of age and gender of the patients, the types of restorations and the clinicians' gender, experience and practice setting. RESULTS: The clinical diagnosis of secondary caries was the main reason for replacement of all types of restorations studied, followed by fracture of restorations, especially bulk fracture, irrespective of patient's age. Bulk discoloration was the third most common reason for replacement of resin based materials in adults, but it rarely occurred in adolescents 18 years and younger. The reasons for replacement of restorations were not associated with the gender of the patients. Subgroupings based on the clinicians' gender showed that female clinicians diagnosed secondary caries more often than male clinicians. Otherwise, the reasons for replacements were similar for both genders of clinicians. Subdivision of restorations based on the years since graduation of the clinicians resulted in small groups. The youngest group of clinicians diagnosed relatively more secondary caries both for amalgam and composite restorations than the most experienced group. CONCLUSION: The clinical diagnosis secondary caries was the main reason for replacement of all types of restorations studied.

Adolescent↗
PubMed2000

Teaching of posterior composite restorations in Japanese dental schools.

AIM: This study was conducted to assess the teaching programmes for Class I and II composite restorations in Japanese dental schools to obtain an overview of what is being taught, the relative teaching volume, the criteria for the provision of posterior composite restorations and the placement techniques taught. DESIGN: Questionnaire forms mailed to the operative dentistry teaching departments in all 29 Japanese dental schools. RESULTS: The response rate was 93 per cent, with replies from 27 of the 29 dental schools. Twenty-five (93 per cent) responding schools taught the use of Class I and two schools stated that they did not teach the use of posterior composite restorations. One of the two schools had no plan to teach posterior composites within the next five years. The other school did not answer this question. Most schools anticipated that the proportion of teaching time devoted to posterior composite restorations would increase within the next five years. Diversities and similarities between teaching programmes were noted between Japanese, North American and European dental schools, the Japanese programmes being closer to those in Europe than those in North America. CONCLUSION: The diversities in the teaching of posterior composite restorations in Japanese dental schools are as great as in other parts of the world. Such diversities must affect the overall quality of restorations in general practice.

Bicuspid↗
PubMed2000

Secondary caries: a literature review with case reports.

The clinical diagnosis of secondary caries is by far the most common reason for replacement of restorations, but the scientific basis for the diagnosis is meager. The purpose of this article is to review the literature on secondary (recurrent) caries and present case reports to document the problems encountered in the clinical diagnosis of secondary caries. The literature on secondary caries was critically reviewed and subdivided into clinical diagnosis, location of secondary lesions, histopathology, microleakage, and microbiology. The case reports included restorations that were scheduled to be replaced because of secondary caries or stained margins of composite restorations. The lesions were photographed preoperatively and postoperatively. Based on the limited literature available, secondary caries appears to be a localized lesion similar or identical to primary caries. It is most often localized gingivally on restorations. Narrow gaps, crevices, ditches, and "microleakage" do not lead to secondary caries, but wide voids may. Secondary caries is difficult to diagnose clinically. Consistency or hardness and discoloration of dentin and enamel are the best parameters. Secondary caries is the same as primary caries located at the margin of a restoration.

Dental Caries↗