[Cup-shaped tooth wear defects: more than erosive challenges?] / Komvormige defecten in occlusale vlakken van molaren: meer dan alleen erosieve belasting?

The underlying mechanism of the development of cups and grooves on occlusal tooth surfaces is still unclear. The aim of this study was to evaluate factors contributing to in-vitro cup formation, and to elucidate the clinical process. Extracted human molar teeth were exposed to acidic aqueous solutions at pH of 4.8 and 5.5 in combination with different loading conditions: no load (0N, control), 30N or 50N. Before and after 3 months exposure, the samples were scanned using a non-contact profilometer. A statistically significant difference between a loading of 0N and 50N was found at pH 4.8 (p < 0.002). Cup shaped lesions had formed only at pH of 4.8, in the 30N and 50N groups. The study showed that a cup can arise fully in enamel and that this requires simultaneous acidic and mechanical loading.

[Intra-oral restoration and correction of single- and multi-unit dental prostheses]. / Intraorale reparatie en correctie van kronen en bruggen.

In cases of a fracture of the porcelain or non-aesthetic margin of a correctly functioning single- or multi-unit dental prosthesis, an intra-oral restoration or correction using a resin composite can generally be chosen. To establish adhesion to metal, porcelain, resin and composite, macro-mechanical, micromechanical and/or chemical retention methods are available. In order to achieve macro-mechanical retention, the preparation ofpits, grooves and/or undercuts is necessary. Micromechanical retention indicates surface roughening of the prosthodontic material at microscopic level through etching or sand-blasting. For chemical retention methods, special primers are used which may react chemically with the several prosthodontic materials. The treatment of choice is determined by the prosthodontic material and the feasibility of the retention method.

A multifunctional device to simulate oral ageing: the "Rub&Roll".

UNLABELLED: This article describes an in vitro fatigue and/or wear simulator enabling controlled application of force, speed, type of liquids and duration, to mimic challenges representative for the human oral environment. The device consists of a container in which a cylinder with specimen holder is placed which drives another cylinder (rod). The rod rotates in an opposite direction to the rotation of the stirring motor, rolling over the specimens mounted in the cylinder. When the rod contacts the specimen a force is applied to mimic processes in the oral environment. The design, working and construction principles of a new device, the Rub&Roll, and some of the possible applications are described Four different application examples are presented: occlusal wear in an low acidic abrasive slurry; combined erosive and abrasive wear of enamel exposed to apple juice or apple pulp; the wear of sealant material in natural teeth in an abrasive slurry; and the influence of mechanical loading cycles on micro tensile bond strength of an adhesive system to dentin Application of the "Rub & Roll" device showed results which are clinically relevant, reproducible and in accordance with existing literature. CONCLUSIONS: The Rub&Roll enables controlled application of chemical and mechanical loading, allowing variation of force, sliding distance, velocity, number of cycles, and frequency, and a combination with erosive and abrasive challenges representative of those in the oral environment.

Randomized control trial of composite cuspal restorations: five-year results.

The objective of this randomized control trial was to compare the five-year clinical performance of direct and indirect resin composite restorations replacing cusps. In 157 patients, 176 restorations were made to restore maxillary premolars with Class II cavities and one missing cusp. Ninety-two direct and 84 indirect resin composite restorations were placed by two operators, following a strict protocol. Treatment technique and operator were assigned randomly. Follow-up period was at least 4.5 yrs. Survival rates were determined with time to reparable failure and complete failure as endpoints. Kaplan-Meier five-year survival rates were 86.6% (SE 0.27%) for reparable failure and 87.2% (SE 0.27%) for complete failure. Differences between survival rates of direct and indirect restorations [89.9% (SE 0.34%) vs. 83.2% (SE 0.42%) for reparable failure and 91.2% (SE 0.32%) vs. 83.2% (SE 0.42%) for complete failure] were not statistically significant (p = .23 for reparable failure; p = .15 for complete failure). Mode of failure was predominantly adhesive. The results suggest that direct and indirect techniques provide comparable results over the long term (trial registration number: ISRCTN29200848).

[Considerations in the treatment of tooth wear]. / Overwegingen bij de behandeling van gebitsslijtage.

Since the origin of tooth wear (attrition, abrasion and erosion) is multi-factorial, its diagnosis is complicated but vital. The so-called Tooth Wear Evaluation System, introduced earlier, makes a systematic diagnostic approach possible. The system consists of various modules, which can be used by the practitioner depending on the goal. Two new modules have been added to the Tooth Wear Evaluation System. The Therapy Start Module can be used to determine which one of the possible treatment modalities (counseling, monitoring, or restorative treatment) should be chosen. The Level of Difficulty Module gives the practitioner indications of the level of difficulty that may be encountered during a restorative treatment.

Surface roughness of etched composite resin in light of composite repair.

OBJECTIVES: In search for clinically effective composite repair protocols, the effect of various etching protocols on the surface roughness of composite resins with different filler composition were investigated. METHODS: Of two composite resins (hybrid-filled Clearfil AP-X; nano-filled Filtek Supreme XT) specimens of 3mm thick with a diameter of 7 mm were prepared (n=24). The top surface was polished with 4000-grit SiC-abrasive paper and subjected to one of eight surface treatments: (n=3): negative control (NC), 37% phosphoric acid for 20s (37PA-20s), 3% hydrofluoric acid for 20s (3HF-20s), for 120 s (3HF-120 s), 9.6% hydrofluoric acid for 20s (9.6HF-20s), for 120 s (9.6%HF-120 s), 37PA-20s followed by 9.6%HF for 120 s (37PA-20s/9.6HF-120 s) and 9.6%HF for 120 s followed by 37PA-20s (9.6HF-120s/37PA-20s). Roughness (S(a)) was measured using a 3D noncontact optical interferometer (WYKO) and surface topography imaged by SEM. Multilevel models were used to estimate the variances within a sample and between samples in each group. Using the resulting overall variances and the means for each group, the eight groups were compared consecutively using t-tests (p<0.05). RESULTS: The hybrid-filled composite resin demonstrated a significantly rougher surface than the nano-filled (p<0.05). For both composites 9.6%HF-120 s, 37PA-20s/9.6HF-120 s and 9.6%HF-120 s/37PA-20s resulted in a large increase in roughness compared to the other groups (p<0.05). For the hybrid-filled, the succeeding groups (37PA-20s, 3HF-20s, 3HF-120 s and 9.6HF-20s) resulted in a statistically significant increase in surface roughness (p<0.02). For the nano-filled only a statistically significant increase in roughness was found between 3HF-20s and 3HF-120 s (p<0.001) and between 9.6HF-20s and 9.6HF-120 s (p<0.001). SEM surface characterization revealed that the hybrid-filled composite resin was much more affected by etching than the nano-filled. SIGNIFICANCE: Composite resins should not be seen as a group of materials having identical properties when it comes to repair. The effect of etching will depend on the composition of the filler particles.

Is there one optimal repair technique for all composites?

OBJECTIVES: The aim of this study was to investigate the effectiveness of a variety of techniques to bond new composite to artificially aged composite of different compositions. METHODS: Composite resin blocks were made of five different commercially available composites (n=30) (Clearfil AP-X, Clearfil PhotoPosterior, Photo Clearfil Bright, Filtek Supreme XT and HelioMolar). After aging the composite blocks (thermo-cycling 5000×), blocks were subjected to one of 9 repair procedures: no treatment (control), diamond bur, sandblasting alumina particles, CoJet™, phosphoric acid, 3% hydrofluoric acid 20s or 120s, 9.6% hydrofluoric acid 20s or 120s. In addition, the cohesive strength of the tested composites was measured. Two-phase sandwiches ('repaired composite') were prepared using each of the 9 repair protocols, successively followed by silane and adhesive (OptiBond FL) treatment, prior to the application of the same composite. Specimens were subjected to micro-tensile bond strength testing. Data were analyzed using ANOVA and Tukey's HSD (p<0.05). RESULTS: For all composites the lowest bond strength was obtained when no specific repair protocol (control) was applied; the highest for the cohesive strength. Compared to the control for the microhybrid composite (Clearfil AP-X) five repair techniques resulted in a significantly higher repair strength (p<0.05), whereas for the nano-hybrid composite (Filtek Supreme XT) and hybrid composite containing quartz (Clearfil PhotoPosterior) only one repair technique significantly increased the bond strength (p<0.01). SIGNIFICANCE: None of the surface treatments can be recommended as a universally applicable repair technique for the different sorts of composites. To optimally repair composites, knowledge of the composition is helpful.

Hydrofluoric acid on dentin should be avoided.

UNLABELLED: Hydrofluoric acid can be used for intra-oral repair of restorations. Contamination of tooth substrate with hydrofluoric acid cannot always be avoided. OBJECTIVES: To investigate the bonding effectiveness to hydrofluoric acid contaminated dentin by, micro-tensile bond strength testing, SEM and TEM. METHODS: For this study, 15 molar teeth were used of which dentin surfaces were subjected to five, different etching procedures. Group A, 37.5% phosphoric acid (Kerr Gel) (control group); group B, 37.5% phosphoric acid followed by 3% hydrofluoric acid (DenMat); group C, 37.5% phosphoric acid, followed by 9.6% hydrofluoric acid (Pulpdent); group D, 3% hydrofluoric acid followed by 37.5%, phosphoric acid; group E, 9.6% hydrofluoric acid followed by 37.5% phosphoric acid. After the bonding procedure (OptiBond FL, Kerr) a composite resin build-up (Clearfil AP-X, Kuraray), was made. After 1 week storage, specimens were prepared for micro-tensile bond testing, SEM- and, TEM-analysis. Data were analyzed using ANOVA and post hoc Tukey's HSD (p<0.05). RESULTS: In the control group (solely phosphoric acid), the mean microTBS was 53.4+/-10.6 MPa, which was, significantly higher than any hydrofluoric acid prepared group (group A versus groups B-E, p<0.001). No, significant differences in microTBS were found between the 3% and 9.6% hydrofluoric acid groups: group B versus group C (13.5+/-5.5 MPa and 18.7+/-4.3 MPa, respectively) or group D versus group E (19.9+/-6.8 MPa and 20.3+/-4.1 MPa, respectively). SIGNIFICANCE: Due to its adverse effect on the bond strength of composite to dentin, contact of hydrofluoric acid to dentin should be avoided.

[Cariology and restorative dentistry: old and new risks]. / Cariologie en restauratieve tandheelkunde oude en nieuwe risico's.

Complaints concerning restorative treatments at disciplinary tribunals are relatively rare. The nature of the complaints, the judgements, and the implicit view on caries management are, however, a cause of concern. Usually, the complaints are on alleged negligence because lesions were not or were too late restored. Modern caries management concentrating on disease control rather than on damage repair and its minimally invasive nature could be reasons of complaints concerning perceived negligence. As usual, careful documentation of findings, diagnostics, risk assessment, and monitoring decisions and good patient communication are decisive in preventing complaints. However, post-graduate education of dentists in caries detection, diagnosis, and management is needed to reduce the variability of caries care provided.

Restoration techniques and marginal overhang in Class II composite resin restorations.

OBJECTIVES: The objective of the study was to compare in vitro interproximal overhang formation of Class II composite resin restoration when using different matrix systems. METHODS: 240 lower left molar phantom head teeth with an MO-preparation were divided into 12 groups (n=20). In six groups a circumferential matrix (Tofflemire X-thin matrix, HaweNeos 1001-c, SuperCap) was used, combined with either a hand-instrument (PFI49 or OptraContact) or separation ring (Composi-Tight Gold). In the other six groups two sectional matrix systems were used (flexible and dead-soft), with three separation rings (Composi-Tight Gold, Contact Matrix, Palodent BiTine). Matrices were secured with wooden wedges and preparations were restored with composite resin Clearfil AP-X (Kuraray) placed and polymerized in increments. After matrix removal overhang was measured on a standardized digital macroscopic image in mm(2). For analysis a multiple linear regression model was used. RESULTS: Use of circumferential matrices resulted in less overhang than sectional matrices (-0.85 mm2, p<0.001). A flexible matrix led to less overhang than dead-soft matrices (-0.54mm2, p<0.001), and no difference was found between straight and pre-contoured matrices (p=0.945). The insertion of the OptraContact resulted in a much increased overhang of 2.54 mm2 (p<0.001). The Composi-Tight Gold and the Contact Matrix System rings resulted in less overhang, -0.69 and -0.68 mm(2), respectively (both p<0.001), whereas the Palodent BiTine ring did not. CONCLUSIONS: Use of circumferential matrices or sectional flexible matrices resulted in the least marginal overhang when combined with a Contact Matrix separation ring or a Composi-Tight Gold ring.

[Change to a new composite with low shrinkage not sensible at this point]. / Overstap naar een nieuwe composiet met geringe krimp nu nog onverstandig.

In dentistry much research focuses on the development of procedures and materials with the aim of preventing negative effects of polymerisation shrinkage stress of composite resin. The clinical implications of shrinkage stress seem to be limited as long as correct restorative procedures are precisely followed. With the introduction of a silorane-based composite resin exhibiting a low-shrinkage behaviour the dentist is confronted with some uncertain factors. Long-term clinical studies are needed before applying these materials on a large scale.

The effect of proximal contour on marginal ridge fracture of Class II composite resin restorations.

OBJECTIVES: To compare the marginal ridge fracture strength of Class II composite resin restorations placed with a straight or contoured matrix band using composite resins with different modulus of elasticity. METHODS: In 60 artificial first molars standardized MO-preparations were ground. Two matrix systems were used: (1) A straight matrix (Standard Tofflemire Matrix, KerrHawe) in Tofflemire retainer (Produits Dentaire). (2) A contoured matrix (Standard matrix, Palodent, Dentsply). In both groups, a wooden wedge and separation ring (Composi-Tight Gold, GDS) were placed and the matrix was burnished against the adjacent tooth. Three composite resins together were used (Filtek Supreme: e-modulus 13.3 GPa (3M ESPE), Clearfil AP-X: 16.6 GPa (Kuraray) and Clearfil Majesty Posterior: 22.0 GPa (Kuraray)), resulting in six groups (n=10). Teeth were mounted into a MTS servo hydraulic testing machine (Mini Bionix II, MTS, USA) with stylus placed on the marginal ridge. Samples were loaded at a crosshead speed of 1.0mm/min until fracture occurred. Fracture resistance data were statistically analyzed using ANOVA and Scheffé's post hoc test for multiple comparison of groups (p<0.05). RESULTS: Contoured proximal surfaces (365.5+/-87.6N) resulted in significant stronger marginal ridges compared to straight surfaces (290.5+/-64.2N) (p<0.001). Clearfil AP-X (378.1+/-94.63N) provided a higher resistance to fracture than Filtek Supreme (301.4+/-67.3N) (p=0.001) and Clearfil Majesty Posterior (304.5+/-70.6N) (p=0.002). No differences were found between Filtek Supreme and Clearfil Majesty Posterior (p=0.890). CONCLUSION: Within the limitations of this in vitro study it was shown that use of a contoured matrix results in a stronger marginal ridge of a Class II composite resin restoration.

A clinical study on interdental separation techniques.

The effect of interdental separation of a special separation ring and wooden wedge was investigated. In a split-mouth design, 27 patients were randomly assigned to one of two groups (W or S). In 11 patients, an interdental wooden wedge (Hawe-Neos) was placed (group W), and in 16 patients, a separation ring (Composi-Tight Gold) was placed at the contact between teeth 4/5 and 5/6. Simultaneously, in both groups, a wooden wedge, combined with a separation ring (Composi-Tight Gold), was placed on the contact between teeth 4/5 and 5/6 (reference group W+S). To measure proximal contact tightness, frictional forces were recorded at the removal of a 0.05 mm thick metal matrix band inserted between adjacent teeth. Contact tightness was measured at contacts 4 and 5 and at 5 and 6 in the third and fourth quadrant using the Tooth Pressure Meter prior to applying separation devices (TO) five minutes after application (T1) and five minutes after removal of the devices (T2). The effect of separation was determined by calculating the differences between contact tightness before application and contact tightness with the devices in situ (T1-T0). Interdental recovery was calculated by the difference in contact tightness before application and after removal of the devices (T2-T0). To assess the presence of statistically significant differences between these measurement times, paired t-tests were applied. With each patient, either a comparison between W and W+S or S and W+S was made. For both W versus W+S and S versus W+S, paired t-tests were applied to compare differences (T1-T0 and T2-T0) between the separation devices. Within a patient, groups W and S could not be compared, therefore, to compare separation achieved between these two devices, unpaired t-tests were used. The increase in contact tightness measured at contact 4 and 5 for group W (0.98 +/- 0.26 N) was statistically significantly less compared to the increase in group S (5.48 +/- 0.88 N) (p < 0.001) or group W+S (4.62 +/- 0.68 N) (p = 0.02). No significant differences were found between groups S and W+S (p = 0.77). For all groups, five minutes after removal of the devices, the contact tightness at contact 4 and 5 and at contact 5 and 6 were still significantly weaker compared to the tightness at baseline (p < 0.02). When separation is required for restorative procedures, such as at placement of a Class II resin composite restoration, special separation rings may be more useful than wooden wedges.

The long-term effect of a composite resin restoration on proximal contact tightness.

OBJECTIVE: The aim of this study was to investigate changes in proximal contact tightness up to 6 months after the restorative treatment. MATERIALS AND METHODS: In a randomised clinical trial Class II composite resin restorations were placed in 52 patients. Proximal contact tightness was measured before, directly after, and 6 months after treatment. These data were analysed statistically using linear regression and t-tests. RESULTS: Proximal contacts, that increased in tightness as result of the treatment tend to loose tightness after a 6-months period but remain tighter than before treatment. Proximal contacts, that decreased after treatment hardly change after 6 months. CONCLUSIONS: A change in contact tightness after restorative treatment will not always remain stable over time.

Comparison of proximal contacts of Class II resin composite restorations in vitro.

This study investigated the tightness of the proximal contact when placing posterior resin composite restorations with circumferential and sectional matrix systems in an in vitro model using a special measuring device (Tooth Pressure Meter). A manikin model was used with an artificial first molar in which an MO-preparation was ground, simulating the clinical situation of an amalgam replacement. This preparation was duplicated, resulting in 160 identically prepared teeth. These teeth were divided into 8 groups (n=20). In 2 groups, circumferential matrix bands (flat or contoured) in a Tofflemire retainer were applied. In the remaining 6 groups, 3 different separation rings were combined with 2 types of sectional matrix bands. All the cavities were restored using Clearfil Photo Bond and Clearfil AP-X. The tightness of the proximal contact was measured using the Tooth Pressure Meter. Data were statistically analyzed using SPSS 12. ANOVA was used to find differences in proximal contact tightness between the groups. Tukey tests were used to find differences between the homogeneous subgroups. The use of sectional matrices combined with separation rings resulted in tighter proximal contacts compared to when circumferential systems were used (p<0.001). The use of these devices is therefore recommended when posterior resin composite restorations are placed.

A comparison of fatigue resistance of three materials for cusp-replacing adhesive restorations.

OBJECTIVES: To investigate the fatigue resistance and failure behaviour of cusp-replacing restorations in premolars using different types of adhesive restorative materials. METHODS: A class 2 cavity was prepared and the buccal cusp was removed in an extracted sound human upper premolar. By using a copy-milling machine this preparation was copied to 60 human upper premolars. In groups of 20 premolars each, direct resin composite restorations, indirect resin composite restorations and ceramic restorations were made. All restorations were cusp replacements made in standardized shape and with adhesive techniques. Cyclic load (5 Hz) was applied starting with a load of 200 N (10,000 cycles) followed by stages of 400, 600, 800 and 1000 N at a maximum of 50,000 cycles each. Samples were loaded until fracture or to 2,10,000 cycles maximum. In case of fracture, the failure mode was recorded. RESULTS: No differences were seen in fracture strength between the three groups (Wilcoxon P = 0.16). No differences were observed with regard to failure mode above or below the cemento enamel junctions (chi2 P = 0.63). The indirect resin composite and ceramic restorations showed significantly more combined cohesive and adhesive fractures than the direct resin composite restorations, which showed more adhesive fractures (chi2 P = 0.03 and 0.002). CONCLUSIONS: The results of this study suggest that ceramic, indirect resin composite and direct resin composite restorations provide comparable fatigue resistance and exhibit comparable failure modes in case of fracture, although the indirect restorations tend to fracture more cohesively than the direct restorations.

A randomized clinical trial on proximal contacts of posterior composites.

OBJECTIVE: The objective of this study was to investigate clinical changes in proximal contact strength inserting Class II composite resin restorations according to one of three randomly assigned protocols. MATERIALS AND METHODS: Seventy-one Class II restorations (MO/DO) were placed by two calibrated operators. Restorations were randomly assigned to one of three groups: one using a circumferential and two a sectional matrix system with separation rings. Proximal contacts were measured by one independent observer with a Tooth Pressure Meter immediately before treatment, and directly after finishing the restoration. RESULTS: Compared to the situation before treatment groups with a sectional matrix system resulted in a statistical significant stronger mean proximal contact strengths (p<0.05), whereas the use of a circumferential matrix system with hand-instrument resulted in a lower proximal contact strength (p<0.05). CONCLUSION: Class II posterior composite resin restorations placed with a combination of sectional matrices and separation rings resulted in a stronger proximal contact than when a circumferential matrix system was used.

The amalgam-free dental school.

OBJECTIVES: To review the change in teaching of Restorative Dentistry at Nijmegen dental school over the period 1986 to the present. KEY POINTS: In 1986, class I and II resin composite restorations were included in the pre-clinical program. However, these courses still started with class I and II amalgam restorations. From 1990 on, the number of amalgam restorations placed in the clinic gradually decreased while the number of resin composite restorations increased. Meanwhile, resin composite had become the first choice for treatment of primary caries (class I and class II) lesions. Finally in 1994, the pre-clinical training started with resin composite restorations before dental amalgam was taught and the advantage of a minimal preparation was further emphasized. Since 2001 the teaching of dental amalgam ceased at the dental school. This was not an abrupt change but the result of a long transitional stage during which it was gradually substituted by resin composite. This step-by-step introduction allowed the acceptance of composite resin by the staff as an alternative for dental amalgam in posterior restorations. As in 2001 students placed only 2.5 amalgam restorations before graduation, it was decided to stop with the pre-clinical training program. CONCLUSIONS: The introduction of resin composites meant an important change in teaching restorative dentistry at Nijmegen dental school. It was not just a change in materials and techniques but also a change in treatment philosophy. The reduced need for preparation and the strengthening effect on the remaining tooth were the principal reasons for the shift from dental amalgam to adhesive dentistry with resin composite at Nijmegen dental school.

Five-year clinical performance of posterior resin composite restorations placed by dental students.

OBJECTIVES: To investigate the survival over a five-year period of posterior resin composite restorations placed by students. METHODS: Class I and II resin composite restorations placed by second-fourth year dental students were evaluated. Patients attended the dental school every 6 months for a regular check-up during which all restorations were checked on their clinical acceptability. In case of replacement or repair of a restoration, this was registered in the patient's record. From each record the survival time and reasons for failure of resin composite restorations were gathered. RESULTS: Seven-hundred three posterior resin composite restorations in 382 patients (49% female and 51% male, age 22-78) were evaluated. At 5 years 560 of the 703 restorations were still considered to be "clinically acceptable". Forty-nine restorations were considered as "functionally present", of which 44 were restored with a crown and four had received a new restoration adjacent to the existing restoration without its removal. Ninety-four restorations had failed. The main reasons for failure were restoration fracture, caries, endodontic treatment, defective margin and lack of proximal contact. The survival rate of the restorations was 87% at 5 years, resulting in an annual failure rate of 2.8%. CONCLUSIONS: Dental students are able to place resin composite restorations in posterior teeth with an acceptable mean annual failure rate.

[Restoring the occlusion by direct techniques]. / Occlusieopbouw met directe restauraties.

Today, extensive and generalized tooth wear is often a reason for restoring the occlusion. Adhesive techniques and direct composite restorations can reduce the need for more expensive indirect restorations. In this article the advantages and disadvantages of the direct and indirect techniques are discussed. Furthermore, the treatment sequence for direct restorations is described and illustrated by some case-reports.