Pulp reactions to different preparation techniques on teeth exhibiting periodontal disease

Analysis of the Pulpal Blood Flow Microdynamics during Prosthetic Tooth Preparation Using Diamond Burs with Different Degrees of Wear

Pulpal modifications taking place during prosthetic tooth preparation using worn-out burs may represent a risk for the vitality of the dental pulp. The aim of this in vivo study was to evaluate whether the wear of diamond burs has an influence on the vascular microdynamics at the level of the dental pulp, during vertical preparation for zirconia crowns. The study was performed with a split-mouth design and included 32 vital permanent monoradicular teeth (20 maxillary and 12 mandibular), from six subjects, aged between 20 and 50 years. The teeth were randomly assigned to two study groups of 16 teeth each. For prosthetic preparation, new burs were used in the first group, and burs at their 5th use were used in the second group. Four consecutive determinations of the pulpal blood flow by Laser Doppler flowmetry (LDF-laser Doppler MoorLab instrument VMS-LDF2, Moor Instruments Ltd., Axminster, UK) were taken for each tooth included in the study: before the preparation (control values), immediately, at 24 h, and at 7 days after the prosthetic preparation. A four-way ANOVA statistical analysis was applied to analyze the effect of four considered factors (bur wear degree, time of measurement, tooth number, and tooth location) on the pulpal blood flow (PBF). A significant increase in pulpal blood flow compared to the baseline was recorded immediately after preparation (p < 0.01), at 24 h (p < 0.01), and at 7 days (p < 0.05) in both groups, but more pronounced in the case of burs at the 5th use. The blood flow was significantly higher in upper jaw teeth, irrespective of the measurement time. In conclusion, the use of worn-out diamond burs produces lasting modifications in the pulpal blood flow of teeth that undergo prosthetic crown preparation. ISRCTN registry: ISRCTN49594720.

Variations in the configuration of pulp chambers subjacent to protostylids

PURPOSE

This study aimed to clarify the positional relationship between the crown contour and pulp chamber of protostylids using three-dimensional reconstructed images.

METHODS

Fourteen molars with protostylids from Japanese subjects were subjected to micro-computed tomography. The external surface configurations of the teeth and pulp chambers were reconstructed. Hard tissue thicknesses in appointed buccal areas were measured on the reconstructed images.

RESULTS

Well-developed protostylids exhibited pulp-prominences above or at the cervical line level. Those that were moderately developed exhibited bulges of the pulp chamber subjacent to the protostylids. Ten of the 14 teeth had prominences in the crown pulp above or at the cervical line level. In addition, 13 teeth exhibited pulp chamber bulges surrounding the lower tooth trunk. No significant differences were apparent in the buccal horizontal thickness of the hard tissue between the protostylids with pulp chamber prominences and the protostylids without pulp chamber prominences at the cervical line level.

CONCLUSION

Pulp chamber configurations subjacent to protostylids vary based on the development of the traits of the protostylids. Minimum possible taper should be applied during standard vital tooth preparations, as reduced residual dentin thickness is predicted in well- and moderately developed protostylids.

Noninvasive Quantitative Evaluation of the Dentin Layer during Dental Procedures Using Optical Coherence Tomography

A routine cavity preparation of a tooth may lead to opening the pulp chamber. The present study evaluates quantitatively, in real time, for the first time to the best of our knowledge, the drilled cavities during dental procedures. An established noninvasive imaging technique, Optical Coherence Tomography (OCT), is used. The main scope is to prevent accidental openings of the dental pulp chamber. Six teeth with dental cavities have been used in this ex vivo study. The real time assessment of the distances between the bottom of the drilled cavities and the top of the pulp chamber was performed using an own assembled OCT system. The evaluation of the remaining dentin thickness (RDT) allowed for the positioning of the drilling tools in the cavities in relation to the pulp horns. Estimations of the safe and of the critical RDT were made; for the latter, the opening of the pulp chamber becomes unavoidable. Also, by following the fractures that can occur when the extent of the decay is too large, the dentist can decide upon the right therapy to follow, endodontic or conventional filling. The study demonstrates the usefulness of OCT imaging in guiding such evaluations during dental procedures.

A comparative evaluation of dentinal hypersensitivity and microleakage associated with composite restorations in cavities preconditioned with air abrasion - An ex vivo study

Background and Objective:

Enormous advances have been made in adhesives; however, the problem of post-operative sensitivity has dragged along. Enough literature exists on the effect of air abrasion over bond strength of composites. However, not much is reported on its relation with microleakage and post operative sensitivity. Therefore, the aim of the study was to compare and evaluate dentinal hypersensitivity and microleakage associated with composite restorations in cavities preconditioned with air abrasion.

Study Design:

Fifteen patients were selected for the study who had to undergo extractions of both maxillary first premolars. On each patient, occlusally placed Class V cavities were made using rotary burs on both the premolars. On the right side premolar, restoration was done using total etch technique. On the left side premolar, restoration was done in similar way after preconditioning of the cavity with air abrasion. Sensitivity levels were recorded on a modified visual analogue scale preoperatively and post operatively at 1 week and one month time period. Following extraction, dye penetration test was done and 1 sample each from one group was subjected to Scanning Electron Microscope for evaluation of tooth restoration interface.

Results:

Clinically significant difference was there in post operative sensitivity levels after one month between the two groups. Increase in sensitivity was less in teeth restored after preconditioning with air abrasion. Dye penetration was also less in teeth restored after preconditioning with air abrasion. However, penetration at the gingival wall was more than the occlusal wall in both the groups.

Conclusion:

The study consolidates the fact that microleakage and post operative sensitivity are linked directly. It also proves that air abrasion can help in reducing the post operative sensitivity to a level; however, a larger sample size would be needed to obtain more robust results with stronger validation.

In vitro evaluation of microleakage of various types of dental cements

Introduction. Microleakage is defined as the clinically undetectable seepage of oral fluids containing bacteria and debris between cement layer and tooth restoration. Objective. This in vitro study investigated the effect of different dental cements (zinc-phosphate, polycarboxylate, glass-ionomer and resin cement) on microleakage in different ceramic crown systems (metal ceramic crown, metal ceramic crown with a porcelain margin, Empress 2 and In Ceram all-ceramic crowns) fixed on extracted human teeth. Methods. One hundred and sixty intact human premolars were randomized to four groups of forty teeth each, according to the different ceramic crown systems. They were prepared in a standardized manner for metal-ceramic and all-ceramic crowns. Crowns were made following a standard laboratory technique, and each group of crowns were divided into four groups according to the different cement agents and cemented on their respective abutments. The specimens were subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco-oral and meso-distal direction. The microleakage in the area of tooth-cement interface was defined as linear penetration of methylene blue and was determined with a microscope to assign microleakage scores using a five-point scale. Results. A significant association was found between a cement type and degree of microleakage (p=0.001). No statistically significant differences were found among the different ceramic crown systems luted with the same dental cement. The smallest degree of microleakage was observed in specimens luted with resin cement (X=1.73), followed by glass-ionomer cement (X=2.45) and polycarboxylate cement (X=3.20). The greatest degree of microleakage was detected in the crowns fixed with zincphosphate cement (X=3.33). Conclusion. The investigated dental cements revealed different sealing abilities. The use of resin cement resulted in the percentage of 0 microleakage scores. Due to this feature, the resin cement is to be recommended in everyday clinical practice.

An immunohistochemical evaluation of cell adhesion molecules in human dental pulp after tooth preparation and application of temporary luting cements

OBJECTIVE

The aim of this study was to determine if temporary luting cements used with provisional restorations alter the expression of cell adhesion molecules (CAMs) in human dental pulp.

STUDY DESIGN

Twenty-five healthy human premolars and third molars scheduled to be extracted for orthodontic reasons were randomly assigned to 5 experimental groups. Group 1 included untreated teeth as negative control. In groups 2-5, provisional crowns were cemented to the prepared teeth with either eugenol-containing or eugenol-free temporary cement and extracted 24 or 48 h after the treatment. Expression ratio and staining intensity of CAMs, including E-selectin, P-selectin, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and platelet endothelial cell adhesion molecule 1 (PECAM-1), was investigated in the pulp samples. The assessment of immunohistochemical reactions was performed by 2 independent observers using a semiquantitative scale.

RESULTS

Significant reductions were recorded in the expression ratio and/or the staining intensity of E-selectin, ICAM-1, and VCAM-1 in samples removed 48 h after treatment with eugenol-containing cement compared with intact teeth. This reduction was significant only for ICAM-1 for 48-h eugenol-free samples. Moreover, the eugenol-free cement group indicated considerably higher E-selectin, ICAM-1, and VCAM-1 expression compared with the eugenol-containing group (P < .005) 48 h after the application. The PECAM-1 reactivity was similar for all of the experimental groups.

CONCLUSION

Application of temporary luting cements after tooth preparation for full crown causes alterations in the expression of endothelial CAMs in the dental pulp.

Comparison of human pulp response to total-etch and self-etch bonding agents

OBJECTIVE

To compare the pulp reactions in terms of pulp inflammation, leakage involving bacteria and reactionary dentin formation to total-etch adhesive, Prime & Bond NT and self-etch adhesive, Xeno III in 2 mm deep class V cavities prepared in human teeth.

STUDY DESIGN

2 mm deep class V cavities were prepared on buccal surface of 40 human premolars. The teeth were randomly divided into two groups based on the application of a total-etch adhesive system, Prime and Bond NT after acid etching or a self-etching adhesive system, Xeno III. The teeth were extracted after 7 and 30 days and prepared according to routine histological techniques.

RESULTS

All teeth were asymptomatic. Both the adhesives showed moderate to severe inflammatory reactions in few cases initially at seven days, but the response was generally minimal at 30 days. Leakage involving bacteria was detected in 42.5% of restorations and 40% of the specimens were associated with various grades of pulp inflammation. The cavity remaining dentin thickness influenced the grade of inflammatory activity. A significant correlation was detected between inflammatory cell response and the presence of bacteria. Pulp response to self-etching adhesive, Xeno III was minimally different from that of the total-etch adhesive, Prime & Bond NT (p < .05).

CONCLUSIONS

A self-etching adhesive system, Xeno III showed similar pulp response and leakage involving bacteria to a total-etch adhesive, Prime & Bond NT. Both adhesives showed an acceptable biological compatibility with human pulps at 30 days.

Adhesion to porcelain and metal

Some compelling clinical benefits of porcelain and metal adhesion are presented. Current concepts for metal adhesion are reviewed, including modifications of metal surface and resin chemistry. Porcelain adhesion is reviewed, including little-known methods that use silane but no hydrofluoric acid etching. Clinical protocols for use of metal and porcelain adhesives are presented.

Immunohistochemical evaluation of endothelial cell adhesion molecules in human dental pulp: effects of tooth preparation and adhesive application

OBJECTIVE

Studies have demonstrated that restorative procedures can initiate pulpal inflammation. Adhesion molecules on endothelial cells mediate the leukocyte-endothelium interaction, which is the fundamental event of inflammation. The aim of this study was to evaluate possible changes in the endothelial cell adhesion molecules (CAMs) of human dental pulp with tooth preparation, and after the application of one-step self-etch adhesive.

MATERIALS AND METHODS

Twenty healthy human premolars and third molars scheduled to be extracted for orthodontic reasons were randomly assigned to four experimental groups. Group 1 involved sound intact teeth representing the controls. In group 2, teeth were prepared for full crown and extracted within 2h. Groups 3 and 4 comprised the teeth coated with one-step self-etch adhesive, iBond Gluma inside following the preparation and extracted after 24 and 48h, respectively. Tissue distribution and staining intensity of CAMs including E-selectin, P-selectin, ICAM-1, VCAM-1 and PECAM-1 was investigated in the pulp samples using monoclonal antibodies and the streptavidin-biotin-horse-radish immunoperoxidase procedure. The assessment of immunohistochemical reactions was performed by two independent observers using a semi-quantitative scale.

RESULTS

All the CAMs evaluated were expressed by the healthy pulp tissues. Significant alterations in the distribution and staining intensity of CAMs were detected following tooth preparation. One-step self-etch adhesive tested in the present study induced inflammatory reactions in the pulp (P<0.05, Mann-Whitney U-test).

CONCLUSION

It seems evident that tooth preparation for full crown and application of one-step self-etch adhesive on prepared teeth had a potential to interfere with the inflammatory response.

Analysis of pulpal reactions to restorative procedures, materials, pulp capping, and future therapies

Every year, despite the effectiveness of preventive dentistry and dental health care, 290 million fillings are placed each year in the United States; two-thirds of these involve the replacement of failed restorations. Improvements in the success of restorative treatments may be possible if caries management strategies, selection of restorative materials, and their proper use to avoid post-operative complications were investigated from a biological perspective. Consequently, this review will examine pulp injury and healing reactions to different restorative variables. The application of tissue engineering approaches to restorative dentistry will require the transplantation, replacement, or regeneration of cells, and/or stimulation of mineralized tissue formation. This might solve major dental problems, by remineralizing caries lesions, vaccinating against caries and oral diseases, and restoring injured or replacing lost teeth. However, until these therapies can be introduced clinically, the avoidance of post-operative complications with conventional therapies requires attention to numerous aspects of treatment highlighted in this review.

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.

Bacterial microleakage and pulp inflammation associated with various restorative materials

OBJECTIVES

Many restorative materials are claimed to be successful in preventing bacterial microleakage and minimizing pulp inflammation. However, information regarding the in vivo performance of materials in comparison with each other is limited. The aim of this study was to evaluate and compare the pulp response of nine restorative materials when placed in non-exposed monkey cavities.

METHODS

279 standardized non-exposed Class V cavities, were prepared into buccal dentin. Cavities were restored with a number of materials in the following categories: Zinc oxide eugenol (ZnOE), Calcium hydroxide [Ca(OH)(2)], zinc phosphate (ZP), Resin-modified glass ionomer (RMGI), Composite resin (CR), Bonded amalgam (BA), Gutta-percha (GP), Compomer and Silicate. Pulp tissues were collected and evaluated at short, intermediate and long-term intervals according to ISO guidelines; employing histomorphometric analysis, Spearman's rho and ANOVA statistics. Pulp responses were categorized according to FDI, ISO and ADA standards. Bacteria were detected using McKay stains.

RESULTS

Pulp inflammation was found to be correlated to bacterial microleakage around the restoration (p < or =0.0001). The frequency of bacterial microleakage was found to vary between restorative materials (p < or =0.0001). In rank order of preventing bacterial microleakage from best to the worst; RMGI (100%), BA (88%), ZnOE (86%), CR (80%), GP (64%), Ca(OH)(2) (58%), compomer (42%), silicate (36%) and ZP (0%).

SIGNIFICANCE

The most effective restorative materials to prevent bacterial microleakage and pulp injury from inflammatory activity were RMGI, BA, ZnOE and CR restorations.

Secondary caries in crowned teeth: correlation of clinical and radiographic findings

STATEMENT OF PROBLEM

The diagnostic value of radiographs for interproximal caries detection on nonrestored teeth is well investigated. However, little is known about the use of radiographs in the diagnosis of secondary caries localized at crown margins.

PURPOSE

The aim of this study was to correlate clinical findings with regard to secondary caries with the findings of a radiographic evaluation.

MATERIALS AND METHODS

One hundred randomly selected patients who underwent restorations with fixed prostheses and were exhibiting at least one secondary carious lesion were included in the study. A total of 820 restorations (test group, 730 interproximal surfaces of 365 single crowns and 910 interproximal surfaces of 455 fixed partial denture retainer crowns) and 1024 interproximal surfaces of 512 nonrestored teeth (control group) were investigated clinically, with the use of modified California Dental Association criteria, and radiographically for interproximal carious lesions. The extension of the lesions was rated to be initial (with no cavitation), early (with cavitation limited to orthodentin), or deep (with cavitation). The data were statistically analyzed for normal distribution, and the frequency of the findings was calculated in absolute numbers and as a percentage. Statistically significant differences were determined by use of the chi(2) test (P<.05). A linear regression model was applied for the correlation between the percentage of secondary caries and the duration of the crowns in situ.

RESULTS

Secondary caries was diagnosed clinically in 11.2% of 1640 interproximal surfaces but only in 8.3% radiographically. In contrast, the frequency of interproximal carious lesions diagnosed clinically in nonrestored teeth increased with the use of radiographs from 3.3% to 4.1%.

CONCLUSION

Within the limits of this study, the results confirm that radiographs improve the diagnostic sensitivity for interproximal caries in nonrestored teeth. However, for the diagnosis of secondary caries in crowned teeth, the clinical examination is more reliable than the radiographic evaluation.

Saving pulps--a biological basis. An overview

AIM

Cavity preparation and restoration variables have an uncertain relationship to pulp injury and repair responses. The purpose of this paper is to determine the importance of cavity preparation and restoration variables, by ranking them according to their effect on pulp injury (odontoblast survival) and pulp repair (reactionary dentine secretion).

METHOD

The seven studies reviewed are all based on the protocols described by Murray, Smith and colleagues in 2000 and 2001.

RESULTS

The studies reviewed provide new perspectives on the importance of cavity preparation and restoration variables in mediating pulp activity.

CONCLUSIONS

The onset of post-operative complications may be most productively minimised by focusing practitioner attention to aspects of treatment highlighted in this review.

The effect of etching on bacterial microleakage of an adhesive composite restoration

OBJECTIVES

The incidence of bacterial microleakage, pulp inflammation and necrosis associated with dentine etching treatments prior to restoration are not known. Consequently, to resolve some of the controversy surrounding the effects and importance of vital dentine etching, the authors investigated these factors.

METHODS

110 standardised class V cavities were cut into buccal dentine, without exposing the pulp of teeth scheduled for extraction for orthodontic reasons. Cavities were either left unetched, or etched with the non-equivalent treatments of phosphoric acid gel for 60s or Ethylenediaminetetraacetic acid (EDTA) for 30s, prior to placement of composite resin. Teeth were collected and pulp responses were evaluated according to ISO guidelines, using pathohistomorphometric analysis and ANOVA statistics.

RESULTS

Etching was found to be correlated to bacterial microleakage (p=0.0001) and tertiary dentine formation (p=0.0023). Bacterial microleakage was correlated to inflammatory activity (p=0.0001). The frequency of bacterial microleakage was: no etching (65%), EDTA (51%) and phosphoric acid (PA) (20%).

SIGNIFICANCE

Vital dentine etching treatment is of extreme importance for the placement of RC to minimise bacterial microleakage. PA etching proved to be more effective at preventing bacterial microleakage than non-etching, and etching with EDTA.

The effect of cavity restoration variables on odontoblast cell numbers and dental repair

OBJECTIVES

Dentinal repair following cavity restoration is dependent on several parameters including the numbers of surviving odontoblasts. The purpose of this study was to examine the effects of cavity cutting and restoration treatments on post-operative odontoblast numbers.

METHODS

353 Standardised non-exposed rectangular Class V cavities, were cut into the buccal dentin of intact 1st or 2nd premolar teeth of 165 patients, aged between nine and 25 years of age. Composite cavity restorations with various etching treatments were compared with resin-modified glass ionomer cements, enamel bonding resins, as well as polycarboxylate, calcium hydroxide, and zinc oxide eugenol materials. Following tooth extraction (20-381 days) for orthodontic reasons, the area of the reactionary dentine and the area of the odontoblasts was measured histomorphometrically.

RESULTS

Odontoblast numbers and dentine repair activity were found to be influenced more by cavity restoration variables, than the choice of cavity filling materials or patient factors. The most important cavity preparation variable was the cavity remaining dentine thickness (RDT); below 0.25mm the numbers of odontoblasts decreased by 23%, and minimal reactionary dentine repair was observed.

CONCLUSIONS

Odontoblast injury increased as the cavity RDT decreased. In rank order of maintaining odontoblast numbers beneath restored cavities with a RDT below 0.5mm, and using calcium hydroxide for comparison; calcium hydroxide (100%), polycarboxylate (82.4%), zinc oxide eugenol (81.3%), composite (75.5%), enamel bonding resin (49.5%) and RMGIC (42.8%). The vitality and dentine repair capacity of the pulp is dependent on odontoblast survival. Variations in the extent of odontoblast injury caused during operative procedures, may be the major underlying reason for the success or failure of restorative treatments.