Influence of luting strategies on dentin bond performance of self-adhesive resin luting cement in combination with a universal adhesive.

OBJECTIVES: This study aimed to evaluate the dentin bond performance of various resin luting cement (RLC) systems combined with universal adhesives in different luting strategies. MATERIALS AND METHODS: Three self-adhesive resin luting cements (SRLCs) were used with universal adhesives as primers. Twelve specimens per group were prepared to measure shear bond strength (SBS) under distinct luting strategies in etch-&-rinse and self-etch modes. Regarding luting strategies, the bonded specimens were categorized into four groups based on tooth primer application and the curing mode of the SRLC paste: (i) with light irradiation of the tooth primer (wL) + dual-cure mode (DC) of the SRLC paste, (ii) wL + self-cure mode (SC) of the SRLC paste, (iii) without light irradiation of the tooth primer (woL) + DC mode of the SRLC paste, and (iv) woL + SC mode of the SRLC paste. Specimens were also subjected to different storage conditions: 24 h in water (baseline condition) and 10,000 cycles of thermal cycling. RESULTS: Luting strategy, storage condition, and SRLC system type significantly influenced dentin SBS values in both etching modes. Notably, certain SRLCs exhibited significantly higher dentin SBS when the primer was light-irradiated compared with no primer irradiation. CONCLUSION: Most SRLCs demonstrated higher dentin bond strength with light-irradiated primers, suggesting potential enhancement of dentin bond performance via primer light irradiation.

Influence of etching mode on bonding performance of self-adhesive flowable resin composites to bovine teeth.

This study aimed to evaluate the bonding performance of self-adhesive flowable resin composites (SARs) to bovine teeth. Three SARs, one experimental, and two commercially available products, were used. The study parameters were shear bond strength (SBS), microleakage, and scanning electron microscopy (SEM) evaluation of bonding interfaces. The SBS of the materials was 14.1-15.1 MPa to enamel, 22.2-23.2 MPa to etched enamel, and 7.4-10.7 MPa to dentin. Specimens with pre-etching showed lower microleakage scores than those without pre-etching. SEM images of the interfaces of the materials showed excellent adaptation regardless of the substrate or etching mode. The study results indicate that enamel pre-etching can improve the bonding performance of SARs.

Treatment of saliva contamination of resin core foundation before adhesive luting.

This study aimed to evaluate the influence of surface pretreatment on the shear bond strength of resin luting cement to saliva-contaminated resin core foundation. The surface free energy (γS) of the adherent surfaces was examined. The two-way analysis of variance revealed that the surface pretreatment and storage conditions had a significant effect on the strength of the bond to resin core foundation. The γS values of the saliva-contaminated group were significantly lower than those of the other groups, and they tended to improve after surface pretreatment. The tendency of improvement in γS values differed depending on the type of pretreatment agents. Surface treatment with solutions containing functional monomers is effective in removing saliva contaminants from the resin core foundation surfaces and in creating an effective bonding surface for the resin luting cement.

Modified Lengthening Temporalis Myoplasty Using an Intraoral Approach.

BACKGROUND: Lengthening temporalis myoplasty (LTM) is a unique and definite facial reanimation procedure that involves inserting the whole temporal tendon directly into the nasolabial fold. However, the nasolabial fold incision remains one of the difficulties of this procedure, particularly in young or female patient. To avoid the need for this incision, the authors developed an intraoral approach to manipulate the temporal muscle tendon toward the nasolabial fold. in this study, we describe the details of this procedure. METHOD: The authors performed their intraoral approach procedure in 5 patients with established complete facial paralysis. instead of making an incision at the nasolabial fold to approach the coronoid process, the authors made the incision at the buccal mucosa. The results were evaluated both subjectively and objectively. RESULTS: The authors achieved facial reanimation without leaving any obvious scar on the face or neck and the effect of static reconstruction is obvious, even immediately after the surgery. All the patients obtained good facial movement within 4 months (2.5 months in average), and improved all evaluated parameters postoperatively. No infections or other major complications were reported following surgery; however, 1 patient developed a slight dimple that required revision. DISCUSSION: The authors could advance temporal tendon toward nasolabial fold firmly obtaining sufficient surgical field similar to that of nasolabial fold incision, and achieved fairly good results without an obvious scar on the face.Establishing LTM without nasolabial fold incision, we could expand the indication of LTM more widely, and it could be more familiar procedure for smile reanimation in all generation.

Prevention of acidic attack on tooth enamel surfaces using polishing paste containing ion-releasing filler.

The purpose of this study was to investigate the ability of polishing paste containing surface pre-reacted glass-ionomer (S-PRG) filler to prevent acidic attack on tooth enamel surfaces. Resin composites were filled in the standardized cavities and finished with silicon carbide paper. These specimens were divided into three groups: the unpolished "control" group, the "PRG" group polished with S-PRG paste, and the "DDP" group polished with diamond-containing polishing paste. Following polishing, the specimens were immersed in a lactic acid buffer solution for 28 days. Optical coherence tomography (OCT) signals were measured to obtain the signal intensity and width at 1/e2 at selected locations on the enamel surface adjacent to the restoration. Although signal intensity significantly increased in all groups, widths at 1/e2 did not change significantly in the PRG group. For both the control and DDP groups, signal intensity and width at 1/e2 increased and decreased over time, respectively.

Effect of light irradiation and primer application on polymerization of selfadhesive resin cements monitored by ultrasonic velocity.

In this study, we investigated the effect of light irradiation and primer/adhesive application on the polymerization reaction and elastic modulus (E) of self-adhesive resin cement (SAC) through ultrasonic velocity (V) measurements. The V values of longitudinal and shear waves were determined based on the transit time through the specimens and specimen thicknesses, and were used to calculate the E values. Analysis of variance and Tukey tests revealed that V increased rapidly, reaching a plateau at 2,700-2,900 m/s, when the SACs were light-irradiated. However, the increasing rate of V was retarded for the non-irradiated SACs. In addition, when the primer/adhesive was applied, higher E values were obtained after 24 h. Finally, the polymerization behavior of the SACs was affected by light irradiation and primer application, and the use of prime/adhesive might improve mechanical properties. In clinical situations, use of primer/adhesive is recommended for getting proper adhesion.

Comparison of enamel bond fatigue durability between universal adhesives and two-step self-etch adhesives: Effect of phosphoric acid pre-etching.

The effect of phosphoric acid pre-etching on enamel bond fatigue durability of universal adhesives and two-step self-etch adhesives was investigated. Four universal adhesives and three two-step self-etch adhesives were used. The initial shear bond strengths and shear fatigue strengths to enamel with and without phosphoric acid pre-etching using the adhesives were determined. SEM observations were also conducted. Phosphoric acid pre-etching of enamel was found to increase the bond fatigue durability of universal adhesives, but its effect on two-step self-etch adhesives was material-dependent. In addition, some universal adhesives with phosphoric acid pre-etching showed similar bond fatigue durability to the two-step self-etch adhesives, although the bond fatigue durability of universal adhesives in self-etch mode was lower than that of the two-step self-etch adhesives. Phosphoric acid pre-etching enhances enamel bond fatigue durability of universal adhesives, but the effect of phosphoric acid pre-etching on the bond fatigue durability of two-step self-etch adhesives was material-dependent.

Ultrasonic monitoring of the setting of silicone elastomeric impression materials.

This study used an ultrasonic measurement device to monitor the setting behavior of silicone elastomeric impression materials, and the influence of temperature on setting behavior was determined. The ultrasonic device consisted of a pulser-receiver, transducers, and an oscilloscope. The two-way transit time through the mixing material was divided by two to account for the down-and-back travel path; then it was multiplied by the sonic velocity. Analysis of variance and the Tukey honest significant difference test were used. In the early stages of the setting process, most of the ultrasonic energy was absorbed by the elastomers and the second echoes were relatively weak. As the elastomers hardened, the sonic velocities increased until they plateaued. The changes in sonic velocities varied among the elastomers tested, and were affected by temperature conditions. The ultrasonic method used in this study has considerable potential for determining the setting processes of elastomeric impression materials.

Effectiveness of platysma muscle flap in preventing Frey syndrome and depressive deformities after parotidectomy.

BACKGROUND: Frey syndrome (FS) or depressive deformity (DD) occurring after parotidectomy significantly reduces a patient's quality of life. However, there seems to be no effective treatment strategy against these complications. In this study, we report our experience of using platysma muscle flap (PMF) to prevent the development of FS and DD after parotidectomy, and evaluate its effect subjectively and objectively. METHODS: Superficial parotidectomy was performed for eight cases of parotid gland tumor, and a PMF was transferred to cover the site. The incidence of FS and DD were evaluated subjectively, using a questionnaire to the patients and board-certified reconstructive surgeons, and objectively, using Minor's starch-iodine test. RESULTS: In seven patients, the defect could be completely covered with PMF, and none of them developed FS or obvious DD. However, in one patient, the defect could be only partially covered, and the patient developed complications in the exact site that the flap did not cover. Overall scores from the questionnaire were high in relation to both cosmetic and functional perspectives from most of the patients and all the surgeons. No patients had major postoperative complications requiring revision. CONCLUSIONS: PMF can be useful to cover the defect and prevent complications after parotidectomy. PMF is relatively easy to perform with fewer complications; however, a complete coverage of the defect should be ensured to obtain optimal results.

Assessment of T-shape double fascia graft for lower lip deformity from facial paralysis: A questionnaire survey.

INTRODUCTION: There are two main methods to treat lower-lip deformity (LLD) in facial paralysis. The first method is surgical intervention on the side of the paralysis, and the second involves denervating the depressor muscles on the healthy side. It is sometimes difficult for patients to ethically accept the denervating healthy tissue; therefore, we performed the T-shape double fascia graft (TSDFG), which reportedly restores symmetry. In this study, we report our experience with TSDFG and evaluation of the outcomes including the patient questionnaires. METHODS: Two fascia strips from the thigh, 7 × 70 mm in size, were used; one was grafted horizontally at the lower lip to correct the static position, and the other was grafted obliquely at the lateral side by folding and crossing the horizontal fascia. A total of nine patients were treated by this procedure; three procedures were performed individually and six were performed in combination with another static or reanimation procedure. A questionnaire containing a five-point scoring system for facial appearance in multiple situations and other problems was sent to each patient at least 6 months after the surgery. RESULT: From the physicians' point of view, all patients achieved an improvement in symmetry of the lower lip, particularly when opening of the mouth; however, assessments from the patients demonstrated much less satisfaction. The main reason for the dissatisfaction was the slight bulkiness of the red lip. There was one comment that noted that with more treatment, the expectations were higher, and, as a result, the patient could not admit satisfaction at the end. DISCUSSION: TSDFG is a simple and effective procedure for LLD; however, slight modifications may be required. In addition, there were some gaps in the perception of the results between the physicians and patients, and we need to consider these when planning to treat LLD.