C.M. Kreulen

Bacterial Counts in Carious Dentine under Restorations: 2–Year in vivo Effects

Little is known about the long–term effects of fluoride–releasing materials on carious dentine in vivo. The aim was to investigate the 2–year influence of a resin–modified glass ionomer cement (RM–GIC) and amalgam on the bacteriological counts of carious dentine that remained under class I restorations. To enable a split–mouth design, 33 molar pairs in 33 patients (mean age 15.1 years, SD 1.4) were selected, based on clinically and radiographically diagnosed occlusal dentine caries. The enamel of the carious molars was removed, and the carious dentine was sampled under aseptic conditions just beneath the dentinoenamel junction. The molars were alternately restored with RM–GIC or amalgam without further removal of carious dentine. The samples were processed for microbiological determination of total viable counts (TVC), mutans streptococci (MS), and lactobacilli (LB). The molar pairs of 25 patients were reevaluated after 2 years using the same clinical techniques and were permanently restored after complete caries removal. Both materials showed a substantial decrease in numbers of TVC and LB of the carious dentine after the 2–year period. Compared to amalgam, the decrease in the numbers of LB was significantly more pronounced for RM–GIC. No microorganisms were detected in only 11 molars (6 RM–GIC and 5 amalgam) after the 2–year period. Based on this study, we suggest that complete removal of carious dentine is still the best conservative treatment, irrespective of the restorative material used.

Five-year survival of 3-unit fiber-reinforced composite fixed partial dentures in the anterior area

OBJECTIVES The purpose of this clinical study was to evaluate the long-term outcome of 3-unit anterior fixed partial dentures (FPDs) made of fiber-reinforced resin composite (FRC), and to identify design factors influencing the survival rate. METHODS 52 patients (26 females, 26 males) received 60 indirectly made FRC FPDs, using pre-impregnated unidirectional glass fibers, requiring manual wetting, as framework material. FPDs were surface (n=48) or hybrid (n=12) retained and mainly located in the upper jaw. Hybrid FPDs had a combination of retainers; i.e. crown at one and surface retention at the other abutment tooth. Surface FPDs were either purely adhesively retained (n=29) or with additional mechanical retention (n=19). Follow-up period was at minimum 5 years, with check-ups every 1-2 years. Six operators were involved, in three centers in the Netherlands, Finland and Sweden. Survival rates, including repairable defects of FPDs, and success rates were determined. RESULTS Kaplan-Meier survival rate at 5 years was 64% (SE 7%). For the level of success, values were 45% (SE 7%) and the estimated median survival time 58 (SE 10.1) months. For surface FPDs, additional mechanical retention did not improve survival significantly. There was a trend towards better survival of surface FPDs over hybrid FPDs, but differences were not significant. Main failure modes were fracture of the FPD and delamination of veneering composite. SIGNIFICANCE A success rate of 45% and a survival rate of 64% after 5 years was found. Fracture of the framework and delamination are the most prevalent failure modes, especially for surface FPDs.

Clinical studies of fiber-reinforced resin-bonded fixed partial dentures: a systematic review

In the past decade, follow-up studies on fiber-reinforced composite fixed partial dentures (FRC FPDs) have been described. Combining the results of these studies to draw conclusions about the effectiveness of FRC FPDs is challenging. The objective of this systematic review was to obtain survival rates of FRC FPDs and to explore the relationships between reported survival rates and risk factors. In a literature-selection procedure on the clinical performance of FRC FPDs, 15 studies, reporting on 13 sets of patients, were analyzed. The Kaplan-Meier estimate of the overall survival, based on the data from all sets of patients (n = 435) was 73.4% (69.4-77.4%) at 4.5 yr. Converted survival rates at 2 yr of follow-up showed substantial heterogeneity between studies. It was not possible to build a reliable regression model that indicated risk factors. The technical problems most commonly described were fracture of the FPD and delamination of the veneering composite.

Radiopacity of posterior composite resins, composite resin luting cements, and glass ionomer lining cements

The radiopacities of seven posterior composite resins, seven composite resin luting cements, and six glass ionomer lining cements were studied. The purpose was to obtain an indication of radiopacity values of different brands within each of these three groups of materials and to show differences in radiopacities of composite resin inlay materials and their accompanying luting cements. On radiographs, the optical densities of standardized samples were determined and radiopacity values of the materials were expressed in millimeter equivalent aluminum. The composite resins observed displayed higher radiopacities than aluminum. A luting cement and a glass ionomer cement were shown to be less radiopaque than aluminum. Generally the radiopacity of composite resins appeared to be higher than their accompanying luting cements. If materials with substantial differences in radiopacity are used in combined applications for the restorative treatment of teeth, lower radiopacity can interfere with the diagnosis of caries and the detection of gaps near the restoration.

In vivo cariostatic effect of resin modified glass ionomer cement and amalgam on dentine

Fluoride-releasing materials have been reported to be bactericidal in vitro. This may be of benefit to modern dentistry, which is directed to the preservation of tooth tissue during restorative treatment. Little is known about in vivo effects. The aim is to investigate the influence of a resin-modified glass ionomer cement (RM-GIC) on carious dentine that remains under restorations, compared to amalgam. Using a split month design, 40 molar pairs in 40 patients (mean age 14.9 years) were selected, based on clinically and radiographically diagnosed occlusal dentine caries. Under aseptic conditions, the enamel was removed and the carious dentine was sampled just beneath the dentino-enamel junction using a round bur. Without further removal of carious dentine, the molars of a pair were alternately restored with RM-GIC or amalgam. The colour and the consistency of the carious dentine were assessed. The samples were processed for microbiological determination of total viable counts (TVC), mutans streptococci (MS), and lactobacilli (LB). After 6 months the molars were reopened, similarly sampled and evaluated, and then permanently restored after complete caries removal. For both materials a substantial decrease in the numbers of TVC, MS and LB was found after the 6-month period. Also a positive effect was observed on the colour and the consistency of the remaining carious dentine, which was comparable for the two materials. RM-GIC showed a significantly larger decrease in counts of MS and LB than amalgam, but not for TVC. Since in only few cavities the number of bacteria decreased under the level of detection, it is still considered essential to remove all carious dentine during restorative treatment.

Fiber-reinforced dental composites in beam testing

OBJECTIVES The purpose of this study was to systematically review current literature on in vitro tests of fiber-reinforced composite (FRC) beams, with regard to studies that followed criteria described in an International Standard. The reported reinforcing effects of various fibers on the flexural strength and elastic modulus of composite resin beams were analyzed. SOURCES Original, peer reviewed papers, selected using Medline from 1950 to 2007, on in vitro testing of FRC beams in comparison to non-reinforced composite beams. Also information from conference abstracts (IADR) was included. DATA With the keywords (fiber or fibre) and (resin or composite) and (fixed partial denture or FPD), the literature search revealed 1427 titles. Using this strategy a broad view of the clinical and non-clinical literature on fiber-reinforced FPDs was obtained. Restricting to three-point bending tests, 7 articles and 1 abstract (out of 126) were included. Finally, the data of 363 composite beams were analyzed. The differences in mean flexural strength and/or modulus between reinforced and unreinforced beams were set out in a forest plot. Meta-regression analyses were performed (single and multiple regression models). CONCLUSIONS Under specific conditions we have been able to show that fibers do reinforce resin composite beams. The flexural modulus not always seems to increase with polyethylene-reinforcement, even when fibers are located at the tensile side. Besides, fiber architecture (woven vs. unidirectional) seems to be more important than the type of fiber for flexural strength and flexural modulus.

Replacement risk of amalgam treatment modalities: 15-year results

OBJECTIVES This paper reports on the replacement risk of different treatment modalities for Class II amalgam restorations in a clinical trial of 15 years duration. METHODS The performance of 1117 conventional Class II amalgam restorations in a controlled, longitudinal study were analysed using logistic regression with a random component. Primary variables regarding replacement risk were the treatment modality (cavity wall treatments) and alloy (conventional versus high copper). Secondly, the operator, type of tooth and type of restoration (MO/DO vs MOD) were considered. RESULTS Over 15 years, 17% of the restorations were replaced (true failures). The application of copalite varnish or silver suspension and the type of alloy did not reduce the replacement risk. Reduced risks were observed by providing a 90-degree cavosurface angle combined with a cavity wall finish. The operator and the type of restoration determine replacement risk to a significant extent. CONCLUSIONS Additional treatment modalities do not necessarily reduce replacement risks of Class II amalgam restorations within 15 years, while clinical variables affect the risk of replacement to a certain degree.

Crown vs. composite for post-retained restorations: A randomized clinical trial

OBJECTIVES This randomized clinical trial compared the survival of composite resin restorations and metal-ceramic crowns on endodontically treated teeth that received a glass fiber post using 2 different cementation methods. METHODS Forty-seven patients (age 42.5 ± 11.5) with fifty-seven endodontically treated teeth with extensive coronal damage but always with one intact surface were randomly allocated according to the type of coronal restoration: metal-ceramic crown or composite resin. In case of crown restoration, a core buildup was performed with microhybrid composite resin. The dentin bonding agent and composite resin used were the same for both direct and indirect restorations. Descriptive analysis was performed using FDI clinical criteria and survival of restorations/teeth analyzed using Kaplan-Meier statistics and log-rank tests. RESULTS 57 restorations (30 composite resin and 27 crowns) were made in 47 patients. The recall rate was 100% and follow up time ranged between 1 and 5 years. One tooth was extracted 11 months post-restoration due to root fracture (composite group). Eight composite restorations and one crown had reparable failures, all due to secondary caries or restoration fracture. The overall annual failure rate (AFR) was 0.92% after 50 months for success of the restorations, with 1.83% for the composite group and 0.26% for the metal-ceramic crown group. The log-rank test showed no difference for survival according to the type of restoration (p=0.344). However, for success rates, metal-ceramic crowns demonstrated better performance (p=0.022). CONCLUSIONS Indirect restorations provided higher acceptable clinical performance and lower need for re-intervention, but both types of restorations presented good survival rates. (NCT01461239). CLINICAL SIGNIFICANCE When endodontically treated teeth with at least one intact surface must be restored, composite resin restorations and metal-ceramic crows are acceptable alternatives to achieve good survival and success rates.

THE ANALYSIS OF RESTORATION SURVIVAL DATA IN SPLIT-MOUTH DESIGNS

OBJECTIVE To report methodological difficulties with restoration survival data in controlled clinical trials on Class II amalgam restorations using a split-mouth design. The advantages and disadvantages of different ways of handling these data are described. METHODS Three statistical methods (Kaplan-Meier estimation, logistic regression with random component and Friedmans statistic) are compared using data from a controlled clinical trial in which cavosurface angle (regular or non-standard) and cavity wall finish (applied or not applied) determine four treatment modalities of New True Dentalloy restorations. RESULTS In this study logistic regression with a random component yields the best interpretable results. Cavity wall finish in combination with a regular cavosurface angle is indicated as the worst and cavity wall finish in combination with a non-standard cavosurface angle as the best treatment when the criterion is replacement or not within 15 years. CONCLUSIONS The dependency between restorations within a patient needs to be taken into account. Logistic regression with a random component may be a valuable alternative to very advanced statistical survival modelling when restricting the research question to replacement within a certain time interval is not a major problem.

Fiber-reinforced composites in fixed prosthodontics-Quo vadis?

Fiber-reinforced composite (FRC) materials were introduced to dentistry more than five decades ago and they were first indicated as a reconstruction material for fixed dental prostheses (FDP). Understanding the need for preserving dental hard tissue during the preparation of abutments became essential and progress in adhesive and FRC technology enabled the development of the concept of minimally invasive FDP’s using FRC materials that could be utilized in the lab or at chairside. Based on research and experience of 25 yeras, the following benefits of FRC fixed dental prostheses have been identified: 1. FRC materials allows for following the Dynamic Treatment Concept), 2. minimal invasiveness, 3. profitable and affordable treatment options. From the patient perspective, the most significant reasons for selecting FRC FDPs seem to be: 1. possibility of receiving the FDP in a single-visit, 2. being less expensive and painless treatment and 3. possibility of avoiding removable devices. Understanding and managing the risk factors dictate the successful use of direct or indirect FRC FDP treatment modalities. Based on the present knowledge and experience, with sufficient inter-occlusal space, correct framework design and precise application of adhesive techniques, FRC FDPs could provide definitive fixed prosthodontic solutions, with expected survival time of at least five to six years, high patient satisfaction, and postpone other invasive and costly treatments.