Repair or Observation of Resin Margin Defects: Clinical Trial After Five Years.

OBJECTIVE: To assess the effectiveness of repair/resealing of stained composite margins as an alternative to controlled observation without treatment in a randomized clinical trial after five years. METHODS AND MATERIALS: Each patient recruited had from one to three composite restorations with visible margin discoloration. Initially, the characteristics of each defect were recorded with direct vision through a surgical microscope at 20× magnification. Clinical evaluation was done by two independent examiners using modified USPHS criteria for color, margin discoloration, and margin adaptation. Each restoration was then randomly assigned to a control or treatment group. Control restorations were observed yearly for the presence of recurrent caries; treatment restorations were resealed by exposing the margin with a » round bur, removing all interfacial stain, acid etching, placing an adhesive bonding agent, and a flowable composite to restore margin integrity. There were 152 patients recruited, with 360 restorations (180 control and 180 treatment). RESULTS: At five years, 104 patients were recalled (68%) with 271 restorations (76%): 136 untreated control and 135 resealed restorations. At that time, 61 restorations had been lost or replaced for nonrelated reasons. Clinical evaluation of the remaining 210 restorations determined penetrating discoloration (control = 81%, resealed = 46%) and margin crevice formation (control = 21%, resealed = 11%). Recurrent caries was diagnosed cumulatively in only six control and five treatment restorations (<5%). Microscopically, 49 control restorations (49%) and 36 resealed restorations (33%) had crevice formation. Discoloration was distributed as follows: 9% vs 47% with no discoloration, 30% vs 33% in the composite, 49% vs 18% in the interface, and 12% vs 2% in tooth structure. CONCLUSIONS: Resealing of restorations with margin discoloration reduced the occurrence of penetrating stain from 81% in controls to 46% in resealed margins and crevicing from 21% to 11% after five years. Both controlled observation and resealing of margins resulted in a similar very low incidence (<6%) of recurrent caries.

Gingival Health of Porcelain Laminate Veneered Teeth: A Retrospective Assessment.

STATEMENT OF PROBLEM: The long-term effect of the presence of porcelain laminate veneers (PLVs) on the health of the surrounding gingival issues is not available in the restorative literature. PURPOSE: To assess the long-term effect of PLVs on the health of the surrounding gingival tissues. A secondary aim was to correlate gingival crevicular fluid (GCF) scores with clinical parameters used for gingival health assessment in teeth treated with PLVs. METHODS AND MATERIALS: Patients who received PLVs placed at the Graduate Restorative Clinic within a seven- to 14-year period were recalled for clinical evaluations. Periodontal measurements including gingival index (GI), periodontal pocket depth (PPD), gingival recession (GR), and clinical attachment level (CAL) were measured using a standard probe and indices. Gingival Crevicular Fluid (GCF) was measured with a Periotron machine (Periotron 8000, Oraflow Inc), using Periopaper (Periopaper Gingival Fluid Collection Strip, Oraflow Inc.) for fluid collection. Photographs of any observed clinical defect were taken. Data were tabulated using Excel 2010 (Microsoft Corp). Statistical analysis for all descriptive statistics was performed using SPSS 21 (SPSS Software, IBM Corp.) and Stata SE 13 (Stata Software, StataCorp). Repeated-measures analysis of variance (ANOVA) was done to test for statistical significance of the mean pocket depths between the restored and unrestored surfaces of the veneered teeth. The significance level for all tests was p<0.05. Pearson's correlation coefficient was performed for testing statistical significance between GCF and GI and between GCF and PPD. RESULTS: The frequency distribution of the GI included 47 PLVs (43%) with normal gingiva, 16 (15%) with mild inflammation, and 46 (42%) with moderate inflammation and bleeding on probing. The average PPD on the facial surface of the maxillary and mandibular PLVs was 2.17 mm and 2.16 mm, respectively. On the lingual surface, the average PPD was 2.10 mm for maxillary and 2.22 mm for mandibular PLVs. Gingival recession was seen in 27% of the evaluated PLVs. The repeated-measures ANOVA revealed p≥0.136, showing no statistical difference in the mean pocket depths between restored facial and unrestored lingual surfaces of the veneered teeth. A moderate correlation (r=0.407) was found between GCF and GI, which was significant at p<0.001. No correlation (r=0.124) was found between GCF and PPD, which was not significant at p=0.197. CONCLUSIONS: Gingival response to the evaluated PLVs was in the satisfactory range, with overall GI scores ranging between normal and moderate inflammation, pocket depths ranging from 1 to 2 mm, and recession present in 27% of the evaluated PLVs. No statistically significant difference was found between the mean pocket depths of the restored and unrestored surfaces of veneered teeth (p≥0.136). A moderate correlation was found between GCF and GI.

Prediction and diagnosis of clinical outcomes affecting restoration margins.

The longevity of dental restorations is largely dependent on the continuity at the interface between the restorative material and adjacent tooth structure (the restoration margin). Clinical decisions on restoration repair or replacement are usually based upon the weakest point along that margin interface. Physical properties of a restorative material, such as polymerisation shrinkage, water sorption, solubility, elastic modulus and shear strength, all have an effect on stress distribution and can significantly affect margin integrity. This review will focus on two aspects of margin deterioration in the oral environment: the in vitro testing of margin seal using emersion techniques to simulate the oral environment and to predict clinical margin failure and the relationship between clinically observable microleakage and secondary caries. The many variables associated with in vitro testing of marginal leakage and the interpretation of the data are presented in detail. The most recent studies of marginal leakage mirror earlier methodology and lack validity and reliability. The lack of standardised testing procedures makes it impossible to compare studies or to predict the clinical performance of adhesive materials. Continual repeated in vitro studies contribute little to the science in this area. Clinical evidence is cited to refute earlier conclusions that clinical microleakage (penetrating margin discoloration) leads to caries development and is an indication for restoration replacement. Margin defects, without visible evidence of soft dentin on the wall or base of the defect, should be monitored, repaired or resealed, in lieu of total restoration replacement.

Adhesive resin induces apoptosis and cell-cycle arrest of pulp cells.

The application of an adhesive resin near or directly over the pulp was shown to induce pulp inflammation and lack of dentin regeneration. We hypothesize that the absence of dentin bridging is due to adhesive-resin-induced apoptosis of cells responsible for pulp healing and dentin regeneration. Mouse odontoblast-like cells (MDPC-23), undifferentiated pulp cells (OD-21), or macrophages (RAW 264.7) were exposed to SingleBond polymerized for 0-40 seconds. Annexin V and propidium iodide assays demonstrated that SingleBond induced apoptosis of MDPC-23, OD-21, and macrophages. The proportion of apoptotic cells was dependent on the degree of adhesive resin polymerization. Adhesive-resin-induced death of pulp cells was associated with activation of the pro-apoptotic cysteine protease Caspase-3. Interestingly, most cells exposed to adhesive resin that did not undergo apoptosis showed cell-cycle arrest. We conclude that an adhesive resin induces apoptosis and cell-cycle arrest of cells involved in the regeneration of the dentin-pulp complex in vitro.

A clinical evaluation of air-abrasion treatment of questionable carious lesions. A 12-month report.

BACKGROUND: The efficacy of treating questionable incipient lesions early with air abrasion, a modality used by many practitioners, has not been adequately demonstrated. METHODS: The authors enrolled 223 teeth, each with a questionable incipient pit-and-fissure carious lesion, from 93 dental patients in a projected five-year randomized clinical trial. Caries was defined as softness, decalcification or cavitation at the base of a pit or fissure or radiographic evidence of caries. Each tooth was randomly assigned to either a treatment group (n = 113 teeth) or a control group (n = 110 teeth) (which was observed but left untreated until the definition of caries was met). Each tooth in the treatment group was air-abraded and restored with a flowable resin-based composite. The authors re-examined teeth in both groups every six months; they evaluated the restorations using a modified set of Ryge criteria and inspected teeth for caries using radiographs, mirrors and standardized explorers. RESULTS: Of the 113 teeth with questionable incipient carious lesions air-abraded in the treatment group, 50 had caries extending into dentin. After 12 months of clinical service, there were three sealants that exhibited a partial loss of sealant which did not require any re-treatment. Two restorations with penetrating staining were re-treated. In the control group at the end of 12 months, only nine of the 86 recalled teeth were diagnosed with pit-and-fissure caries and were treated with air abrasion and restored with flowable resin-based composite. There was no statistically significant difference between the volume of the treatment and control preparations. CONCLUSION: After 12 months of clinical service, two preventive resin-based composite restorations in the treatment group required re-treatment. Fewer teeth than expected in the control group were diagnosed as having caries and were treated. CLINICAL IMPLICATIONS: The merit of treating questionable incipient pit-and-fissure carious lesions early with air abrasion has not been demonstrated after 12 months in this clinical study.

Effect of variable light intensity on composite shrinkage.

STATEMENT OF PROBLEM: Polymerization shrinkage is a critical limitation of dental composites and may contribute to postoperative pain, tooth fracture, microleakage, and secondary caries. Polymerization with high-intensity light sources has been related to increased depth of cure and improved mechanical properties. However, high-intensity light initiation has also been associated with greater polymerization shrinkage. PURPOSE: The purpose of this study was to investigate the effect of sequentially increasing light intensity on the polymerization shrinkage of 2 composites, a hybrid and a microfil. A Knoop hardness test was used to evaluate effectiveness of the cure with each intensity increase. MATERIAL AND METHODS: Four groups of 12 samples were measured for polymerization shrinkage by using a linometer. Light intensity curing sequences were as follows: full-intensity control (100% intensity for 40 seconds), low-intensity control (25% intensity for 40 seconds), test group 1 (25% intensity for 20 seconds, 50% for 10 seconds, 100% for 10 seconds), and test group 2 (25% intensity for 10 seconds, 50% for 10 seconds, 100% for 20 seconds). Statistical comparisons were made using a 1-factor ANOVA and a Tukey multiple comparisons test within each material. RESULTS: Results showed a significant difference (P<. 05) in mean linear shrinkage between the full-intensity control group and the other 3 sequences for both composites. No difference existed within the other 3 groups for either composite. Knoop hardness was similar for the full-intensity control and test group 2. The low-intensity control group and test group 1 were also similar but significantly lower. CONCLUSION: Curing composites for 10 seconds at 25% intensity, 10 seconds at 50%, and 20 seconds at 100% significantly reduced polymerization shrinkage while not compromising depth of cure.

Effectiveness of sealant treatment over five years in an insured population.

BACKGROUND: The authors analyzed an insurance claim database to evaluate the use and effectiveness of placing sealants on first and second permanent molars of children in private dental practices. METHODS: A retrospective study was conducted using an insured population with sealant coverage at 70 percent of the usual fee in a preferred provider organization than that limited reapplication to once every three years. Children were selected who were eligible for sealant benefits from July 1, 1990, to June 30, 1991. Two groups were selected for analysis, based on age, as determined by permanent molar eruption dates. Children who received sealants were compared with those who did not to determine post-sealant restorative outcomes after five years. RESULTS: During the full year of coverage, sealants were used in only 16.3 percent of first permanent molars and 11.6 percent of second permanent molars. The five-year incidence of an occlusal restoration having been placed was 13.7 percent and 20.8 percent, respectively, on nonsealed first and second molars and 6.5 percent and 10.4 percent, respectively, on sealed first and second molars. From years three to five, sealant placement provided only nominal additional preventive effect. CONCLUSIONS: In the population selected, both the incidence of occlusal caries and the use of sealants were lower than expected for both age groups. However, within these groups, molar occlusal surfaces were only half as likely to have been restored in sealed teeth than in nonsealed teeth after five years. CLINICAL IMPLICATIONS: Based on the five-year data from a population with a low incidence of caries, the authors found that 15 sealed first permanent molars or 10 sealed second permanent molars prevented placement of one occlusal restoration. Therefore, sealants are more effective when placed in patients with risk factors for occlusal caries.

Evaluation of custom occlusal matrix technique for posterior light-cured composites.

Posterior composite restorations are difficult to contour and polish due to their occlusal anatomy and opposing occlusion. Recently a new technique utilizing a clear custom occlusal matrix showed promise in reducing the chair time necessary to place posterior composite restorations. Sixty specially molded plastic mandibular right second molar teeth with a mesio-occlusal composite preparation were restored with a light-cured composite in a typodont, using either the custom occlusal matrix (experimental) or the standard technique (control) as taught at the University of Michigan School of Dentistry. The times necessary to complete the procedures were recorded. The teeth were evaluated in a blind manner by two evaluators using a modified Ryge criteria. The times to place and finish the control and experimental restorations were subjected to a t-test. The evaluations of surface smoothness, margin adaptation, occlusal anatomy, and axial form were compared using a Fisher exact test. The custom occlusal matrix significantly reduced placement and finishing time and improved surface smoothness of mesio-occlusal posterior composite restorations placed in vitro. Due to the time needed to construct the custom occlusal matrix, there was no significant difference in total mean time of the two procedures.

Resistance to fracture of three all-ceramic systems.

All-ceramic restorations have become an attractive alternative to porcelain-fused-to-metal crowns, but their strength is still an important issue. The purpose of this study was to compare the in vitro fracture resistance of three all-ceramic systems: IPS Empress, In-Ceram, and Procera AllCeram. Thirty dies were replicated from a master die using high filler resin with a modulus of elasticity similar to dentin. Ten cores each of In-Ceram and Procera were fabricated to a thickness of 0.5 mm. The remaining porcelain was applied using a sculpting device to produce a crown with a final thickness of 1.0 mm axially and 2.5 mm occlusally. Ten IPS Empress crowns were mixed to the same dimensions and were pressed by the manufacturer. The internal surfaces of all the crowns were etched and silanated prior to cementation with a resin cement (Panavia 21). The cemented samples were loaded in an Instron machine until fracture. The mean fracture loads were: IPS Empress, 222.45 (+/- 49) kg; In-Ceram, 218.8 (+/- 36) kg; Procera AllCeram, 194.20 (+/- 37) kg. Tukey's test showed no statistically significant differences among the three all-ceramic systems at p < .05.

Shear bond strength of a resin cement to densely sintered high-purity alumina with various surface conditions.

Procera Sandvik AB is now manufacturing a densely sintered high-purity alumina core for an all-ceramic crown designed for anterior and posterior restorations. Whereas the material holds promise on the basis of in vitro strength tests, the ability to alter the surface and use conventional bonded resin cements has not been reported previously in the literature. Samples of the core were treated by means of one of four methods routinely used for all ceramic restorations, and then a commercially available resin cement was bonded to the surface. A shear bond test of the adhesion showed that the highest shear bond strengths of 11.99 +/- 3.12 MPa were obtained with air abrasion at 80 psi and 50-microm alumina particles.

Fluoride release and re-uptake in direct tooth colored restorative materials.

OBJECTIVES: Glass ionomers may be "recharged" through topical fluoride (F-) treatments; however, this reported "recharging," may be attributed to surface changes after F- treatment. This study examined differences in F- release and re-uptake among dual-cured and chemically-cured glass ionomers, and a photo-cured F- releasing composite. A secondary goal was to determine if tensile strength or surface roughness changed due to F- release, or F- re-uptake and re-release. METHODS: In Phase 1, initial surface roughness and diametral tensile strength were measured. F- release was measured for 30 days. Strength and roughness were then remeasured. In Phase 2, surface roughness was measured, then materials were treated with a 5000 ppm neutral F- gel, the same gel without F-, or phosphoric acid. F- release was measured for 30 days, then final surface roughness and strength were determined. RESULTS: Significant differences were found in amount and rate of F- release, and F- re-uptake and re-release among study materials and enamel controls (p < 0.001). The amount and rate of F- re-release after NaF treatment differed significantly from F- release after acid treatment in glass ionomers, although both groups showed increased F- release after surface treatment (p < 0.001). There were no significant changes in tensile strength or surface roughness after F- release or F- re-uptake and re-release as determined by ANOVA. SIGNIFICANCE: The results of this in vitro study indicate that applications of neutral 5000 ppm F- gel to aged glass ionomer restorations results in a significant fluoride uptake and subsequent release. The data suggest that the application of neutral fluoride gel to glass ionomer restorations in situ may result in increases in oral fluoride concentrations, without affecting the restoration's surface roughness or tensile strength.

Dentin bonding: SEM comparison of the dentin surface in primary and permanent teeth.

The literature suggest differences between primary and permanent teeth regarding the composition and morphology of the dentin. The purpose of this study was to compare the effect of two dentin conditioners on the micromorphology of the dentin surface of primary and permanent teeth. Human extracted and noncarious molars were divided into four groups and conditioned with either 10% phosphoric acid (All-Bond 2) or 10% maleic acid (Scotchbond Multi-Purpose) for different time periods. SEM photomicrographs (1500x) were taken from the conditioned dentin and evaluated blindly by three calibrated examiners. The results indicate that the smear layer was removed more easily from primary teeth than from permanent teeth (P = 0.0001), which suggests greater reactivity to acidic dentin conditioners. We also found that the longer the time of application of dentin conditioner the more smear layer is removed (P = 0.0094). In comparing primary and permanent dentin, the results of this study indicate that less time is required for appropriate acid conditioning of primary dentin surfaces. Such a differentiated protocol for bonding to primary tooth dentin results in surface morphological characteristics similar to those found in conditioned permanent teeth.

Effect of adding opaque porcelain on the final color of porcelain laminates.

STATEMENT OF PROBLEM: Increasing the opacity of porcelain laminates is one of the techniques most commonly used to mask the color of darkly stained teeth. PURPOSE OF STUDY: Two different brands of porcelain (Fortune and Optec) disks that contained various amounts of modifying porcelains to alter opacity were cemented with untinted resin cement to a dark colored substrate. MATERIAL AND METHODS: The color of the substrate was measured before and after cementation and the change in color was calculated. RESULTS: Fortune porcelain showed a progressive increase in the amount of change produced as the modifying porcelain was increased, whereas Optec porcelain showed a decrease in the amount of change as modifying porcelain was increased. CONCLUSION: A progressive increase of yellow was exhibited in the samples as the amount of opacity is increased.

A survey of failure modes in composite resin restorations.

This study was undertaken as a first step in identifying opportunities to decrease the need for replacement of class 3, 4, and 5 composite resin restorations. Data regarding the reasons for original placement or replacement of a restoration, the age of restorations at the time of replacement, and patient/doctor factors that may be associated with a decision to place or replace a restoration were recorded by use of a cross-sectional survey. During a 2-week period 108 dentists recorded reasons for placing or replacing 1360 restorations. Of the 1360 restorations, 42.8% were classified as primary placement and 57.2% as replacement restorations. Of the primary placements 80% were categorized as being due to caries; 9.1% fracture of tooth; 8.4% other (erosion lesions were specified 94% of the time). By class, caries was the dominant cause for class 3 (96.2%); caries and other (erosion) for class 5 (77.3% and 16.4%); fracture of tooth and caries (48.9% and 40.2%) for class 4 restorations.

Dentin bonding: SEM comparison of the resin-dentin interface in primary and permanent teeth.

Previous studies have suggested minor differences between primary and permanent teeth in terms of dentin composition and morphology. Other reports indicated lower bond strengths of resin composites to dentin of primary teeth compared with dentin of permanent teeth; however, no information is available regarding differences in the micromorphology of the resin-dentin interface that may explain these lower bond strengths. Therefore, the purpose of the present study was to compare primary and permanent teeth in terms of the thickness of the hybrid layer developed with two bonding systems. Our hypothesis was that bonding differences previously reported between primary and permanent dentin would be reflected in hybrid layer differences observable in SEM analyses. Twenty human extracted and non-carious teeth were divided into 4 groups: 5 primary and 5 permanent teeth restored with All-Bond 2/Bisfil P system; and 5 primary and 5 permanent teeth restored with Scotchbond Multi-Purpose/Z100. The sample area available on each tooth was divided for the two dentin conditioning times (7 and 15 sec). Measurements of hybrid layer thickness were performed by means of SEM at x13,000. The results of this study indicated that the hybrid layer produced is significantly thicker in primary than in permanent teeth (p = 0.0001), suggesting that primary tooth dentin is more reactive to acid conditioning. No difference was observed in the hybrid layers produced by the two adhesive systems (p = 0.7920). The increased thickness of the hybrid layer in primary teeth (25 to 30%) and the subsequent lack of complete penetration of adhesive resin into previously demineralized dentin may contribute to the lower bond strengths to primary dentin reported in the literature. If a narrower hybrid layer more uniformly infused with resin is the goal of dentin bonding, it is concluded that a differentiated protocol for bonding to primary dentin (with shorter time for dentin conditioning) can be used as a means to reproduce the hybrid layer thickness seen in permanent teeth.

Cytotoxic interactive effects of dentin bonding components on mouse fibroblasts.

Previous studies have shown a wide range of pulpal reactions to dentin bonding systems and a poor correlation between in vitro and in vivo toxicity of dentin bonding agents. Because dentin bonding agents are composed of multiple components which may diffuse through dentin, we hypothesized that these components may cause cytotoxicity through interactive (synergistic) effects. We investigated the cytotoxicities of four dentin bonding components--HEMA, Bis-GMA, TEGDMA, and UDMA--and interactive effects for three binary combinations of the dentin bonding components--HEMA and Bis-GMA, Bis-GMA and TEGDMA, and TEGDMA and UDMA. Cytotoxicities to Balb/c 3T3 mouse fibroblasts were measured by the MTT assay. Concentrations which caused 50% toxicity compared with controls (TC50 values) were compared, and the interactive effects were determined by evaluation of the differences between observed and expected MTT activities of the cells. The ranks of toxicity of the dentin bonding components in terms of TC50 values were as follows: Bis-GMA > UDMA > TEGDMA >>> HEMA (least toxic) after 24- and 72-hour exposures. As binary combinations, the three combinations of dentin bonding components interacted in three ways--synergism, additivism, and antagonism--which were influenced by the concentrations of both components. The longer period of exposure resulted in a significant increase in the cytotoxicity of the dentin bonding components and combinations. The findings indicate that both exposure time and the interactions between the dentin bonding components may be important parameters in determining the cytotoxicity of dentin bonding agents in vivo.

The effect of pulpal fluid flow on tensile bond strength of a glass-ionomer cement: an in vivo and in vitro comparison.

Previous studies of the bonding capabilities of glass-ionomer cements have concentrated on the use of in vitro testing conditions. Since early moisture contamination appears to have adverse effects on the physical properties of glass-ionomer cements, and with the probability of pulpally derived dentinal fluid being present under in vivo conditions, the objective of this study was to compare in vivo tensile bond strength with in vitro tensile bond strength of a glass-ionomer cement to dentin utilizing the same teeth under similar test conditions. A glass-ionomer lining cement was placed on freshly exposed labial dentin of the maxillary incisor on 10 Rhesus monkeys. Immediately following placement, an orthodontic button was placed over the cement and left undisturbed for 1 hour. The teeth were then extracted and stored in 100% relative humidity for 23 hours. An Instron testing machine was used to register in kilograms the force required to cause tensile bond failure of the cement. Identical methodology was then used on the same teeth for in vitro testing. The concluding results indicate that a statistically significant difference (P < or = 0.05) exists between in vivo and in vitro tensile bond strengths of the glass-ionomer lining cement and that the bond failure was cohesive in character for all cases both in vivo and in vitro. These findings suggest that clinically, tensile bond strengths of glass-ionomer cements to cut dentin can be expected to be weaker in vital teeth than in devital teeth.

Physical properties and repair bond strength of direct and indirect composite resins.

Use of composite resins now includes indirect curing methods. Surface chemistry, repair bond strength, plus location of failure and five physical properties of two direct and three indirect composite resins were determined. There were statistically significant differences in flexural strength of materials and in hardness values. Repair bond strength failures were not significantly different; failures occurred primarily at the interface. Multiple internal reflection spectroscopy confirmed the presence of unpolymerized material after cure in all products. Indirect cure of the direct composite resin increased the degree of cure.

Evaluating tooth eruption on sealant efficacy.

For patients aged 5 to 9 and 11 to 14, 100 occlusal surfaces on newly erupting permanent molars were treated with a self-curing pit and fissure sealant. All teeth were categorized according to stage of eruption and sealant thickness of the coating applied. After 36 months, 75 surfaces were examined for a final evaluation; 52 surfaces (70%) did not need retreatment. Of the 23 surfaces retreated as a result of sealant loss or marginal deterioration, 18 were retreated only once in the six recall evaluations. Those molars treated originally with the operculum covering the distal marginal ridge of the occlusal surface had twice the probability for retreatment as teeth not treated until the entire marginal ridge was exposed. The thickness of the sealant coating did not affect the early signs of sealant failure.