Laser light passage through restored and carious posterior teeth.

Laser Doppler flowmetry (LDF) has been used to investigate pulpal blood flow as a means of pulp vitality testing. Transmission of laser light from the tooth surface to the pulp space may be influenced by caries and restorations. One hundred and twenty-two first and second molars that had caries into dentine, restorations or significant loss of coronal tissue were sectioned in half axio-bucco-lingually. The two sections were illuminated with a laser from their buccal and lingual aspects 2 mm coronal to the amelocemental junction. Light reaching the pulp space was recorded. Buccal and lingual illumination sites were equally effective for 67 teeth (55%). Buccal sites alone were effective for 35 teeth (29%), despite over one-third of these surfaces being restored or featuring enamel or dentine caries. A lingual position alone was effective for 20 teeth (16%). Caries affected light transmission, but for over half the teeth, the pulp could be illuminated from all four probe positions. No effect was found when the influence of mesial and distal restorations on transmission into the corresponding tooth section was examined. The pulp spaces of most (84%) restored, and carious posterior teeth could be illuminated by laser light from their buccal aspect and these teeth could potentially be vitality tested using LDF.

Influence of clinical experience on the radiographic determination of endodontic working length.

AIM: To determine the influence of clinical experience on the accuracy and consistency of estimation of radiographic working length (WL) for the root canal treatment of single-rooted teeth. METHODOLOGY: Forty conventional WL periapical radiographs that included variations in file length were selected. They were digitally scanned and arranged in PowerPoint presentations on CDs. These were distributed to three assessor groups; fourth-year undergraduates at two stages of training (Groups 1 and 2) and endodontic postgraduates (Group 3). Participants were asked to determine the adjustment needed in millimetres to position the file tip at the correct WL for each image. A gold standard file position was provided by three experienced endodontists. For inter-group comparison of scores, the Kruskal-Wallis, ANOVA and post hoc Bonferroni tests were used. Evaluation of intra-examiner consistency was with the Kappa test. To evaluate intra-group consistency, the Wilcoxon signed rank test was used to compare the frequency of weighted correct scorings. RESULTS: File adjustments of Group 3 were significantly more accurate than those of Group 1 (P = 0.006). The scores of Group 3 were also better than those of Group 2, although the difference was not significant. When the scores of the undergraduate groups were compared, the difference was not statistically significant. The consistency of the groups was not affected by a 2-week pause between assessments, and no definite pattern could be detected across any of the groups with the Kappa test. CONCLUSION: Clinical experience after graduation influenced the accuracy of estimating the adjustments needed for correct radiographic WL of single-rooted teeth. The most experienced group was significantly more accurate than the other groups.

Effect of restorations on pulpal blood flow in molars measured by laser Doppler flowmetry.

AIM: To: (i) compare laser Doppler pulpal blood flow (PBF) signals from restored and unrestored first molar teeth, (ii) investigate PBF in teeth with large and small restorations, and (iii) to relate PBF to pulp chamber dimensions on radiographs. METHODOLOGY: Bitewing radiographs of young adults with restored first molars were obtained and pulp chamber dimensions measured. Subjects were divided into 2 groups: group A with a restored tooth and an unrestored contralateral (43 subjects) and group B, those with a molar with a small (usually occlusal) restoration whilst the contralateral tooth had an extensive occlusal restoration (or restorations) or restored proximal surface(s) and/or cuspal overlay (31 subjects). The 148 teeth responded to electric pulp testing, and their PBF was recorded using a laser Doppler flowmeter. Data were analysed using Student's t-test. RESULTS: In group A the PBF in the restored teeth was significantly lower than in unrestored contralaterals (P = 0.028) and the total pulp chamber area and that in the clinical crown were smaller (P = 0.039 and 0.021 respectively). The group B molars with large restorations had significantly lower PBF than contralaterals with small restorations (P = 0.001), and their total pulp chamber area and pulp chamber width at cervix were reduced significantly (P = 0.003 and 0.032 respectively). CONCLUSIONS: In molars the size of the pulp chamber was influenced by the presence of restorations and the PBF was reduced when restorations were present. Size and extent of restorations had a significant effect on PBF.

Pulp size in molars: underestimation on radiographs.

The aim was to determine whether radiographs provide a clinically useful indication of pulp size in diseased/restored human first molar teeth, and to investigate accessibility of pulp tissue for diagnostic testing using laser Doppler flowmetry (LDF). Extracted teeth of known age were collected. Restorative materials were removed and teeth with evidence of pulp exposures excluded. Fifty-six teeth were radiographed from buccal and mesial aspects, and then their crowns were sectioned axiobuccolingually and photographed. Images were digitally scanned and measurements made of the total pulp area (above a line across the most superior part of the pulpal floor) and the pulp area in the clinical crown (superior to a line between the amelocemental junctions). The pulp width at the cervix and the highest point of the pulp were also recorded. Data were analysed using Pearson correlations. Pulp areas within the clinical crowns were significantly larger than indicated by radiographs, by 23% in the case of the clinically attainable buccal view (P < 0.05). Pulps may be more accessible to flowmeter testing than they appear. Absence of pulp tissues in the crown was recorded in equal numbers of teeth on radiographs and sections, but with agreement for only one tooth. Sixteen per cent of the teeth had no pulp area in the clinical crown when sectioned, but might still be suitable for testing using LDF.

The bitewing radiograph as an assessment tool in fixed prosthodontics.

Molar crown preparations, as described in the literature, have standard forms dictated by the demands of retention, resistance and the physical properties of materials. Standard designs may not be appropriate for all patients because of ethnic variations in tooth shape, pulp size and dentine thickness. Accurate data on these features could assist clinicians to minimize the risk of accidental pulpal injury. The aim of this study was to compare the first molar crown and pulp dimensions between Asian (Chinese, Korean, Malay) and other ethnic groups, using measurements from the bitewing radiographs of 121 subjects. Comparisons revealed the following significantly different features of Asian first molars: larger total pulp areas in uppers (P < 0.0005); shorter crowns (P < 0.0005); narrower upper teeth at the cervix (P < 0.0005); wider pulps at the cervix of lowers (P < 0.02); more bulbous crowns (P < 0.0005 for uppers; P < 0.01 for lowers), and finally significantly thinner dentine interproximally at the cervix (P=0.001 for uppers; P=0.011 for lowers). Preparations with wide shoulders could pose hazards to the pulps in Asian subjects. This study emphasizes the value of bitewing films in assessing crown and pulp size and shape before making crown preparations. The experienced practitioner may intuitively include tooth and pulp morphology in treatment planning, but this appears not to be taught or documented in textbooks.

Coronal pulp size in molars: a study of bitewing radiographs.

AIM: To: (i) study coronal pulp dimensions in human first molar teeth; (ii) investigate the effects of restorations on pulp size; (iii) determine differences in dimensions between teeth of Mongoloid patients and teeth of other ethnic groups; and (iv) record the presence of pulp stones. METHODOLOGY: Bitewing radiographs of 121 subjects (mean age, 20.9 years) were taken under standardized conditions. The films were digitally scanned and nine measurements were made from the image of each first molar. The data were analysed in terms of presence or absence of restorations and in terms of racial group. Differences were examined using Student's t-test, Pearson correlations and Levene's test. RESULTS: A total of 445 teeth were analysed. Large crowns were correlated to large pulps. Teeth restored with occlusal and proximal restorations had significantly smaller pulps (P = 0.044 and 0.004, respectively), but no difference was found in pulp area in the clinical crown between the restoration types. Mongoloid crowns were shorter and more bulbous. Pulp areas of maxillary molars and pulp widths at the cervix of mandibular molars were significantly larger in Mongoloids. The pulp area in the clinical crown correlated to pulp horn height for Mongoloids and others and for maxillary and mandibular teeth. No differences were found between the heights of pulp horns in the Mongoloid and other teeth. Four of the pulp measurements demonstrated sexual dimorphism. Stones were present in almost 10% of the subjects, representing 4% of the tooth pulps examined. CONCLUSION: Even teeth with shallow occlusal restorations had reduced pulp spaces. There were significant differences in pulp and crown dimensions between the teeth of Mongoloid patients and those of other patients.

Organizational considerations for an electronic curriculum. Part II: A multimedia approach to dental education in general and to prosthodontics in particular.

STATEMENT OF PROBLEM: In using multimedia electronic knowledge-transfer as a tool in dental education, an overriding concern has centered on how to devise an organizational model that will accommodate the vast and diverse arrays of information involved, yet be sufficiently simple to provide students with a rational and consistent means of accessing the information they require. PURPOSE: This article presents a model that adopts the Natural History of Dental Diseases as the organizing principle. This article also encourages a mindset in prosthodontics that focuses on the dynamics of energy-dispersal through the supporting structures, in an attempt to provide learners with a deeper cognitive dimension for problem solving and to facilitate their empowerment as life-long learners.

Organizational considerations for an electronic curriculum. Part I: A rational nosology for concept management in dentistry.

STATEMENT OF PROBLEM: With the use of multimedia electronic knowledge as a tool in dental education, an overriding concern has centered on how to devise an organizational model that will accommodate the vast and diverse arrays of information involved, yet be sufficiently simple enough to provide students with a rational and consistent means of accessing the information they require. By adopting the natural history of the diseases dentists are called on to address as a common organizing principle, it becomes possible to link all concepts that relate to individual problem areas through a technique of retro-mapping. PURPOSE: The purpose of this article is to introduce learners to a cognitive "scaffolding" that will assist them in achieving a deeper cognitive dimension for problem solving.

Minimizing biomechanical overload in implant prostheses: a computerized aid to design.

Implant-supported prostheses must be able to withstand the load capabilities of individual patients to overload them. The gold alloy screw in the Brånemark system is by intention the weakest component. Therefore, if cantilever lengths can be designed so that occlusal forces distributed to individual fixtures are limited to the gold screws' ability to accept them, breakage-free performance may be assured. Models, such as that of Skalak, are capable of developing the required analytical processes to provide the information necessary to achieve this design. Unfortunately, the overt mathematical complexity of the Skalak model has militated against its routine use in the operatory. Its computational aspects are, however, eminently suited to computerization and indeed provide the basis for the computer program that is described in this article. This program is simple to apply clinically and, when used in conjunction with available load parameters of gold screw performance, can provide the clinician with a routine and scientific basis for rational implant prosthesis design.

Computerized expert system for the diagnosis of pulp-related pain.

A major problem in the correct diagnosis of pulpal pain is that the associated clinical signs do not predictably correlate with the underlying pathological process. Using conditional probabilities of various pulp conditions from published data, Bayesian Statistical Inference provides the means for deriving a composite probability of the presence of a disease from a multiple set of symptoms. A computer program that can infer a diagnosis for pulpal pain from any combination of 17 clinical symptoms has been developed. From the data, the program provides the computed relative probabilities of a healthy pulp, a saveable pulp, an unsaveable pulp, and a necrotic pulp being present.

Management of loading forces on mandibular distal-extension prostheses. Part II: Classification for matching modalities to clinical situations.

When a mandibular distal-extension removable partial denture is planned, consideration should be given to the capacity of the supporting structures to accept the functional loading of the prosthesis. To prescribe a treatment modality that will not cause their breakdown, an analysis should be made of the relative strength and weakness of the ridges and abutment teeth. This judgment can be visualized by classifying partially edentulous jaws into one of the four categories that are possible when the two key factors of ridge resistance and abutment teeth are combined.

Management of loading forces on mandibular distal-extension prostheses. Part I: Evaluation of concepts for design.

The viscoelastic reaction of ridge mucosa and abutment teeth, by virtue of their periodontal ligaments, is a necessary dimension in the evaluation of design concepts for removable partial dentures for patients with distal-extension ridges. The possible modalities are (1) removable partial dentures with flexible denture bases (stressbreakers), (2) use of a floating denture base impression technique, (3) use of a mucofunctional impression technique to relate the denture base to the framework, and (4) use of an endosseous implant. An evaluation of each modality has been made.