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PubMed1997

A 5-year evaluation of ceramic inlays (CEREC).

The intention of this study was to evaluate the clinical function of porcelain inlays made with the Cerec technique after 5 years. 115 inlays were produced in 46 patients and of these were 51 inlays evaluated. Epoxy models were made from impressions and the gap width and depth was measured in a microscope. SEM pictures were also produced to illustrate the ditching. The measured marginal defects showed a mean width and depth of (SD) 373 (147) and 111 (67) microns respectively. No significant differences of the ditchings could be detected between molars and premolars. Only 3 inlays were found to be fractured of all inlays produced.

Bicuspid↗
PubMed1996

A comparison of the dimensional stability of three inlay pattern materials.

This study investigates the dimensional stability of 3 inlay pattern materials stored for different periods of time. Three indices were formulated to assess changes. These were: deviation and area change which both indicate a proportional contraction or expansion, and ratio which shows distortion. A brass master model was constructed to represent a cavity with 4 intersecting reference lines on the base, which were transferred to the bottom of the inlay pattern. The materials tested were Kerr's Type II blue inlay casting wax, Duralay (an autopolymerizing acrylic resin) and Modilux (a light-curing resin). Ten inlay patterns were prepared from each material in the brass master model cavity. Measurements of pre-determined points on the reference lines were recorded with a reflex microscope immediately after removal of the inlay patterns and then repeated at intervals of 1 hour and 24 hours. These measurements were compared to corresponding measurements on the brass master model and then converted into the three indices previously mentioned. Analysis of data showed that none of the materials distorted and that all the patterns underwent a proportional contraction, with wax contracting more than Duralay and Modilux. Significantly more contraction occurred at 24 hours than between onset (0 hour) and 1 hour. As contraction only occurred after 1 hour and wax contracted the most, it is recommended that Duralay or Modilux be used as the pattern material, especially if a delay in investing is anticipated.

Analysis of Variance↗
PubMed2005

Arthroscopic reconstruction of the posterior cruciate ligament using tibial-inlay and double-bundle technique.

Biomechanical research has suggested that the double-bundle and tibial inlay technique is superior to the single-bundle and the transtibial tunnel method for posterior cruciate ligament (PCL) reconstruction. A combination the posterior tibial inlay and femoral double-bundle technique is thought to be an ideal method for PCL reconstruction. Recently, we successfully performed arthroscopic PCL reconstruction using the tibial-inlay and double-bundle technique. Achilles tendon-bone allograft is used and the bone plug for the arthroscopic tibial inlay fixation is designed in a cylindrical shape and perpendicular to the fiber texture of the Achilles tendon. Achilles tendon is manually split into deep and superficial layers to reconstruct anterolateral and posteromedial bundles as the natural insertion of PCL. The intra-articular lengths of each bundle between tibial tunnel and 2 femoral tunnels are measured to achieve fixation of the graft to the original PCL attachment. After tibial bone plug fixation with an absorbable interference screw and additional suture anchoring, the anterolateral bundle is fixed in a reduction position with the knee in 90 degrees of flexion and the posteromedial bundle is fixed nearly in extension. This procedure makes it possible not only to reproduce the original concept of PCL tibial inlay graft arthroscopically without posterior arthrotomy, but also to achieve a more anatomic PCL reconstruction of the 2 bundles.

Achilles Tendon↗
PubMed2005

Inlay butterfly cartilage tympanoplasty in children.

OBJECTIVE: To assess the results of inlay butterfly cartilage tympanoplasty in children. STUDY DESIGN: Before-and-after trial; follow-up duration, 26.6 +/- 19.9 months (mean +/- standard deviation). SETTING: Tertiary referral center. PATIENTS: Fifty-nine pediatric cases of tympanic membrane perforation. INTERVENTION: Inlay butterfly cartilage tympanoplasty was performed under general anesthesia according to the technique originally described by Eavey and modified by Lubianca-Neto (i.e., without any associated split-thickness skin graft). MAIN OUTCOME MEASURES: Percentage of perforation closures, surgical complications, preoperative and postoperative puretone hearing thresholds; the results of inlay butterfly cartilage tympanoplasty were compared with those obtained in a retrospective series of 29 underlay fascia temporalis myringoplasties. RESULTS: The 71% "take rate" of inlay butterfly cartilage tympanoplasty was not significantly different from the 83% take rate obtained with underlay fascia temporalis tympanoplasty (p = 0.23, chi test). The anatomic results were improved when the graft diameter was at least 2 mm larger than the size of the perforation (81% take rate) (p = 0.009, chi test). No iatrogenic cholesteatoma was observed. Pure-tone hearing thresholds were improved at 0.5, 1, and 2 kHz, and stable at 4 kHz. Hearing levels were not different from those obtained with underlay fascia temporalis tympanoplasty. CONCLUSION: Inlay butterfly cartilage tympanoplasty is a safe, efficient, time-saving, and easy technique of tympanoplasty in children. Anatomic results may be improved by associating a split-thickness skin graft and/or by trimming a tragal graft much larger than the size of the perforation.

Adolescent↗
PubMed2003

Volume maintenance of inlay bone grafts in the craniofacial skeleton.

Although the clinical use of inlay bone grafts is widespread in craniofacial surgery, the dynamics of inlay bone grafting to the craniofacial skeleton have never been well characterized. Previous work demonstrated that volume maintenance of bone grafts in the onlay position is a consequence of their microarchitectural features, rather than their embryological origins. The purpose of this study was to investigate whether the properties determining the volume maintenance of bone grafts in the onlay position in the craniofacial skeleton could be extended to bone grafts in the inlay position. It was hypothesized that volume maintenance of an inlay bone graft could be better explained on the basis of the microarchitectural features of the graft (cortical versus cancellous composition), rather than its embryological origin (membranous versus endochondral), and that the primary determinant of bone graft behavior is the interaction between the microarchitectural features of the bone graft and the local mechanical environment in which the bone graft is placed. Cortical and cancellous bone grafts were harvested from the iliac crest (endochondral origin) of 25 New Zealand white rabbits, and cortical bone was harvested from the mandible (membranous origin) of each rabbit. Four 7-mm trephine holes were made in the cranium of each rabbit, posterior to the coronal suture. Each defect was filled with endochondral cortical bone, endochondral cancellous bone, or membranous cortical bone or was left as an ungrafted control specimen. Animals were killed at 3, 8, or 16 weeks. Crania were subjected to micro-computed tomographic and histological assessments. Micro-computed tomographic analysis demonstrated significant increases in actual bone volume from time 0 to the time of death for all types of grafts. Cortical bone demonstrated significant increases in space-occupying volume at all time points. By 16 weeks, no statistically significant difference in either the actual bone volume or the space-occupying volume according to graft type could be detected. There was no resorption of the inlay bone grafts; in fact, all bone types exhibited increased volume. Cancellous bone demonstrated the greatest capacity to increase actual bone volume. All bone graft types seemed to reach a steady-state bone volume, as if controlled by a local regulator. The regulator is likely the local mechanical environment in which the grafts were placed, as corroborated by the findings that the bone grafts seemed to recapitulate the characteristics of the bone in which they were placed, rather than maintaining their native characteristics.

Animals↗
PubMed2004

Posterior cruciate ligament reconstruction using single-bundle patella tendon graft with tibial inlay fixation: 2- to 10-year follow-up.

PURPOSE: Reconstruction of the posterior cruciate ligament (PCL) using the tibial inlay fixation has been reported as an alternative to the transtibial tunnel technique. Previous failures in PCL reconstruction and early reports raising potential biomechanical and clinical advantages have spurred interest in this technique. The purpose of this study was to evaluate the minimum 2-year results of PCL reconstruction using a single-bundle bone-patellar tendon-bone graft and tibial inlay fixation. METHODS: The authors prospectively studied 44 patients having isolated or combined PCL reconstruction using the direct tibial inlay fixation technique. The study period was from 1991 to 2001. Two-year minimum follow-up was 93% (41/44) and averaged 39.4 months. These 41 patients comprised the study group. Thirty-one patients were male and 10 patients were female; average age was 28 years. There were 35 primary and 6 revision reconstructions. Surgery was performed in the acute or subacute setting (<8 weeks) in 34% (14/41) and chronic setting in 66% (27/41). Combined reconstructions involving the posterolateral corner, anterior cruciate ligament (ACL), or medial collateral ligament (MCL) were done in 85% (35/41). In all patients, preoperative posterior drawer (PD) examination demonstrated greater than 12 mm posterior translation. All PCL reconstructions were performed with bone-patellar tendon-bone graft, which was 12 to 18 mm in width (16 autograft; 25 allograft). Wider tendon grafts were prepared from the allografts and tubularized to fit through an 11-mm tunnel. All patients were evaluated with preoperative and postoperative examination and x-rays. Final follow-up International Knee Documentation Committee (IKDC) subjective evaluation, final follow-up IKDC objective evaluation, and final follow-up Telos stress radiography were performed in all patients. RESULTS: Postoperative PD examination demonstrated the following: 0 (normal) in 9 patients, 1+ in 25 patients, 2+ in 7 patients, and none >2+, as compared to preoperative PD 3+ or greater in all patients in this report. No patient had <12 mm PD preoperatively. Mean improvement in PD was >2 grades of translation as compared to preoperative exam. Forty of forty-one demonstrated a solid endpoint on clinical PD testing. Final follow-up Telos stress radiography with 25 kg posterior load applied at 80 degrees to 90 degrees of flexion demonstrated average side-to-side difference of 4.11 mm (-2 to 10 mm). Average flexion loss was 4 degrees (0-15 degrees ). None lost extension. Preoperative IKDC objective evaluation rated all knees as severely abnormal based on instability. Final follow-up objective IKDC evaluation distribution was as follows: A, 4 knees; B, 24 knees; C, 11 knees; and D, 2 knees, as compared to all 41 D preoperatively. Average final follow-up IKDC subjective score was 75.1 (20-100). When assessing final follow-up stability with Telos stress radiography, primary cases were significantly more stable than revision cases (P <.05). There was no difference in stability when comparing allograft versus autograft, but improved IKDC scores were seen with allograft (P <.05). There was a trend for combined reconstructions to be more stable than isolated reconstructions. All patients evaluated their knee as improved or greatly improved and would repeat the procedure. CONCLUSIONS: Reconstruction of the PCL-deficient knee with severe posterior laxity is a challenging surgical problem, as combined instability patterns frequently coexist (85% in this study). When appropriate combined reconstructions or primary repair is used, PCL reconstruction with autologous or allograft bone-patellar tendon-bone graft using tibial inlay fixation was shown to be a successful technique at 2- to 10-year follow-up. Based on their initial experience with this technique and previous experience with open and arthroscopic techniques using a transtibial tunnel, the authors continue to use the tibial inlay technique as their preferred technique for isolated or combined reconstruction of the PCL.

Adolescent↗
PubMed1995

[Nonelastic deformations of polyethylene inlays in hemiprostheses].

In most models of hip prosthesis, the inlay is formed by a layer of polyethylene. The attrition of polyethylene results from two components, wear and nonelastic deformation. Former studies analysed total attrition. The aim of this trial was to measure solely the non elastic deformation. Nonelastic deformation was investigated using two different types of bipolar hemiprostheses to exclude influences of different shaped metal caps. The bipolar hemiprostheses were tested with a hydraulic pulser. 1 x 10(6) cycles of a halfsinewave with a stress of 4600 N at a frequency of 8 Hz were used. The whole procedure was carried out in isotonic saline solution. Stress was applied along a single axis to prevent any wear. After the test, the inner surface of the polyethylene inlay was analysed with a touchpeg. As the inlays had different inner diameters, the analysis of the surface was defined along radials of 5 degrees, 25 degrees and 45 degrees. The nonelastic deformation in the direction of the main stress at 45 degrees was higher than at the lateral areas. The nonelastic deformation measured was between 0.2 and 0.6 mm/a, i.e. 5 to 30% of total attrition. There was a significant difference between the two types of inlays. The model with several pegs and edges for a complicated snap mechanism had a significant higher nonelastic deformation (alpha = 0.05) than the smooth shaped inlay.

Biomechanical Phenomena↗
PubMed2026

Clinical performance of two lithium disilicate CAD/CAM materials in posterior Class II inlay restorations: A 48-month randomised split-mouth clinical trial.

OBJECTIVES: To compare the clinical performance of Amber Mill (AM) and IPS e.max CAD (EM) lithium disilicate computer-aided design/computer-aided manufacturing (CAD/CAM) materials in posterior Class II inlay restorations and characterise their baseline properties. METHODS: Thirty-four adults received paired AM and EM posterior Class II inlays (68 restorations) in a triple-blind randomised split-mouth trial followed for 48 months. Restorations were evaluated at baseline and annually using revised World Dental Federation (FDI) criteria, with fracture and retention as the primary endpoint. Baseline characterisation included flexural strength, shear bond strength, translucency parameter, and scanning electron microscopy. McNemar, Wilcoxon signed-rank, Friedman, one-way analysis of variance, Tukey post hoc, and inter-rater agreement analyses were used. RESULTS: At 48 months, 18 paired participants were available for primary analysis. Failures occurred in 2 of 18 AM restorations and in 3 of 18 EM restorations, corresponding to success rates of 88.9% and 83.3%, respectively, with no significant between-material difference (McNemar p = 1.000). No catastrophic bulk ceramic fracture was observed. Secondary FDI scores remained mostly within the clinically acceptable range; marginal staining deteriorated over time in both groups (p < .001) without significant between-material differences. Baseline material testing showed significant material- and translucency-dependent differences in flexural strength, shear bond strength, and translucency. CONCLUSIONS: Within the limitations of the 48-month follow-up and the tested Class II inlay indication, AM showed clinical performance comparable to EM. Observed clinical complications were related to retention or marginal/interface behaviour. CLINICAL SIGNIFICANCE: For posterior Class II lithium disilicate CAD/CAM inlays, medium-term complications were mainly retention/interface-related, suggesting adhesive-interface durability may be as important as baseline ceramic strength.

Humans↗
PubMed2001

Effect of surface treatment on fatigue behaviour between Tetric Ceram inlays and Variolink luting composite.

The effect of pre-treatment of composite inlays on bonding performance between a resin composite inlay and a luting composite has not been fully studied. The aim of the present study was to evaluate the influence of three different pre-treatment modes on fatigue bond strength and marginal adaptation. One hundred twenty resin composite discs (Tetric Ceram) were made as simulated inlays and randomly assigned to four groups (n=30): Without treatment (WT), hydrofluoric acid etching for 15 s + silanating (HF), roughening with a silicon carbide bur (SC), and silica coating + silanating (CO). Luting composite cylinders (Variolink II low) were bonded to the discs using Heliobond, and after 24 h in water at 37 degrees C, quasistatic shear bond strengths (n=l) and fatigue bond strengths (n=20; 5,000 cycles) were measured. Thirty-two third molars received occlusomesial Class II cavities (n=8), and direct resin composite inlays were luted with identical methods and materials. Before and after thermomechanical loading (100,000x50 N, 2,500 x +5 degrees C/+55 degrees C), replicas were made and examined (SEM, x200). CO and SC exhibited significantly higher bond strengths and adhesive fatigue limits than HF and WT (P<0.05). After thermomechanical loading, CO (98% continuous margin) and SC (95% continuous margin) demonstrated that they provide significantly more fatigue resistance than HF (88%).

Acid Etching, Dental↗
PubMed2006

Proximal direct composite restorations and chairside CAD/CAM inlays: marginal adaptation of a two-step self-etch adhesive with and without selective enamel conditioning.

The aim of this study was to evaluate the marginal adaptation of CEREC ceramic inlays, CEREC composite inlays and direct composite restorations in unbeveled proximal slot cavities under artificial aging conditions. Two groups of each restoration type were prepared (n = 6), one group with a self-etch adhesive, the other group with H(3)PO(4) enamel etching before the self-etch adhesive application. Replicas were generated before and after long-term thermo-mechanical loading under dentinal fluid simulation and margins were evaluated at x200 magnification in the scanning electron miscroscope (SEM). Statistically, significant differences were found before and after loading with respect to the percentages of "continuous margins", the direct composite filling with H(3)PO(4) enamel etching giving the lowest percentages of "continuous margins" after loading (p < 0.05). The highest percentage of "continuous margin" was attained by composite inlays without H(3)PO(4) enamel etching. However, these results were not significantly different from ceramic inlays after stressing. Polymerization shrinkage is still one critical property of composite restorative materials. The marginal adaptation of indirect adhesive proximal slot restorations without enamel bevels both fabricated out of composite and ceramic is better than that of directly placed composite restorations.

Acid Etching, Dental↗
PubMed1997

Clinical evaluation of heat-pressed glass-ceramic inlays in vivo: 2-year results.

In the present study, the 2-year clinical and scanning electron microscope (SEM) results for heat-pressed ceramic inlays are reported. In a selected patient population, 51 cavities were restored with all-ceramic inlays. All margins were located within the enamel. The inlays were luted to the cavities with a high-viscosity, dual-cure luting composite. After 2 days, 1 year, and 2 years, the restorations were evaluated clinically, using the modified USPHS criteria. Quantitative margin analysis was performed in the SEM on the replicas fabricated at the recall times. The data were tested for significant differences, using the chi-square test for the clinical evaluation and the Mann-Whitney U-test for the margin analysis. After 2 years, the clinical evaluation of the margin adaptation revealed Bravo ratings for 14 restorations (27.5%); 37 restorations (72.5%) were rated Alfa. Compared to the baseline data, this difference was statistically significant (p < or = 0.5). SEM analysis revealed that the ceramic-composite interface exhibited significantly (p < or = 0.01) more gap formation than the enamel-composite interface at all times of evaluation. Wear of the luting composite could be determined along 50% of the restoration interface during the first year, 53% during the second year. The inlay restorations controlled in this study perform well after a period of 2 years.

Adult↗
PubMed1997

One-year clinical evaluation of composite fillings and inlays in posterior teeth.

In the course of a prospectively designed long-term clinical trial, composite fillings and inlays were evaluated for clinical acceptability as restorative materials in one, two or more surface cavities of posterior teeth over a 1-year period. In 45 patients, 88 restorations were placed by nine student operators, under the supervision of an experienced dentist, to compare the two half sides using the composite resins Tetric (Vivadent), blend-a-lux (Blend-a-med), and Pertac-Hybrid Unifil (Espe). The first clinical follow-up check took place within a time period of 11-13 months after placement of the restorations using modified USPHS criteria. The interpretation of the clinical criteria showed satisfactory results over this time period: more than 85% of the inlays and direct fillings were rated "alpha" or "bravo", using the parameters of assessment defined in this study. Only three restorations (two fillings, one inlay), all in molars, were rated "delta", i.e., unacceptable. The reasons for their replacement were marginal opening, secondary caries, and loss of sensitivity. For the criteria "surface texture", "anatomical form of the surface", and "occlusion", composite inlays were significantly better than composite fillings. These results indicate that posterior composite restorations provide acceptable and excellent clinical service, even if they are placed by relatively inexperienced student operators.

Adult↗
PubMed1999

Longevity of cast gold inlays and partial crowns--a retrospective study at a dental school clinic.

From 1963 to 1993, 890 patients were treated with 3518 cast gold restorations by students and postgraduate dentists. The longevity of these restorations was studied retrospectively using the patient files. Longevity was calculated using the method described by Kaplan and Meier. After the observation period, 111 (3.2%) of the examined restorations were not in place anymore. The most frequent reasons for failure were caries (33.7%), lack of retention (32.7%), endodontic treatment (29.6%), insufficient marginal adaptation (3.1%) and extraction (1%). The cumulative survival rate and a 95% interval of confidence was calculated for all restorations and for each of the locations and surfaces included in the trial. The 10-year survival rate for occlusal inlays was, 76.1% (12.1) for MO inlays 88.3% (4.2), for DO inlays 83.4% (4.6), for MOD inlays 87.5% (2.4), for partial crowns 86.1% (3.3) and 85.7% (1.7) for all restorations. Based on the statistical method used, the cast gold restorations demonstrated satisfactory longevity results.

Adult↗
PubMed1993

Wear of ceramic inlays, their enamel antagonists, and luting cements.

The wear of ceramic inlay materials and antagonist enamel cups was measured in vitro. Per group, six MOD inlays were adhesively cemented in extracted molars. Castable glass ceramic, pressed glass ceramic, and feldspathic porcelain were used as inlay materials. A microfilled and a fine hybrid composite served as luting agents. The restorations were exposed to an in vitro wear test that corresponds to approximately 5 years of clinical service. The wear in the occlusal contact area was quantified during and at the end of the test with a three-dimensional scanner. Final wear measurements on the inlays (mean +/- SD) ranged from 21.8 +/- 8.8 microns for pressed glass ceramic to 59.0 +/- 37.9 microns for castable glass ceramic. The mean wear of the enamel antagonists ranged from 74.6 +/- 32.9 microns for pressed glass ceramic to 153.2 +/- 61.5 microns for feldspathic porcelain. The wear of the luting composites at the end of the test ranged from 4.9 +/- 5.1 microns for microfilled to 12.3 +/- 6.3 microns for fine hybrid.

Aluminum Silicates↗
PubMed1992

The plane of fracture and shear bond strength of three composite inlay systems.

Composite inlays have been introduced to overcome some of the problems encountered with direct placement techniques. However, some doubt has been expressed about the strength of the bond between the inlay surface and the composite luting cement due to the decreased number of C = C bonds remaining following supercuring of the inlay. This study investigated the bond strength of three composite inlay systems to etched bovine enamel and recorded the plane of fracture of the samples. The bond strength of one system was significantly greater than that of the other groups and was increased by the application of an unfilled resin enamel bonding agent. Unfilled resin application did not significantly alter the other systems tested. In only one of the systems tested was the inlay/composite cement bond found to be the weak link in the bonding procedure. In this group, the application of the manufacturer's specially formulated bond enhancer did not lead to an increase in bond strength.

Acrylates↗
PubMed2005

Ceramic inlays bonded with two adhesives after 4 years.

OBJECTIVE: The aim of the present study was to clinically evaluate the effect of two different adhesive/resin composite combinations for luting of IPS Empress inlays. METHODS: Ninety-four IPS Empress restorations were placed in 31 patients in a controlled prospective clinical split-mouth study. The restorations were luted with EBS Multi/Compolute (3M Espe) or with Syntac/Variolink II low (Ivoclar Vivadent) without lining. At baseline and after 0.5, 1, 2, and 4 years, the ceramic restorations were examined according to modified USPHS codes and criteria. RESULTS: Two patients including four restorations missed the 4 years recall (drop out). After 4 years of clinical service, four restorations in two patients (three luted with Compolute, one with Variolink II) had to be replaced due to hypersensitivities, 90 inlays and onlays were acceptable (failure rate 4%; Kaplan-Meier survival analysis). Between the five recalls, a statistically significant deterioration was found for the criteria marginal adaptation and inlay fracture (Friedman 2-way ANOVA; p < 0.05). Between the adhesives no statistical difference was found. At baseline, 95% of the restorations revealed luting composite overhangs. After 4 years, 55% of cases had overhangs and 38% showed marginal ditching. No differences were found for surface roughness, color matching, integrity tooth, proximal contact, hypersensitivity, and satisfaction (p > 0.05). CONCLUSION: For luting of ceramic inlays, no difference between the two luting systems was detectable. The overall failure rate after 4 years was 4%.

Adult↗
PubMed2006

In vitro biological response to a light-cured composite when used for cementation of composite inlays.

OBJECTIVE: To define the cytotoxicity of a photo-cured composite when used as a bonding system under a composite inlay. METHODS: Composite specimens were photo-cured with or without a 2 mm composite inlay interposed between them and the light source. Samples were extracted in complete cell culture medium and the obtained eluates applied to primary cultures of human pulp and gingival fibroblasts. After 72 h of incubation, cell viability was evaluated by MTT assay. Survival rates were calculated with respect to negative controls. RESULTS: Both shielded and unshielded composite samples were cytotoxic to pulp and gingival cells. The inlay shielded composite samples reached a significantly higher level of cytotoxicity compared to the unshielded ones. SIGNIFICANCE: The results suggested that the cytotoxicity of a light-cured composite resin used as a bonding system for indirect composite restorations may be significantly increased as a result of an inlay light-shielding effect.

Cells, Cultured↗
PubMed2005

The effect of box preparation on the strength of glass fiber-reinforced composite inlay-retained fixed partial dentures.

STATEMENT OF PROBLEM: Nonstandardized box dimensions for inlay-retained fixed partial dentures (FPDs) may result in uneven distribution of the forces on the connector region of such restorations. PURPOSE: The objective of this in vitro study was to evaluate the effect of box dimensions on the initial and final failure strength of inlay-retained fiber-reinforced composite (FRC) FPDs. MATERIAL AND METHODS: Twenty-one inlay-retained FPDs were prepared using FRC (everStick) frameworks with unidirectional fiber reinforcement between mandibular first premolars and first molars. Boxes were prepared using conventional inlay burs (Cerinlay), and small and large ultrasonic tips (SONICSYS approx). Box dimensions were measured after preparation with a digital micrometer. All restorations were subjected to thermal cycling (6000 cycles, 5 degrees C-55 degrees C). Fracture testing was performed in a universal testing machine (1 mm/min). Acoustic emission signals were monitored during loading of the specimens. Initial and final fracture strength values (2-way ANOVA, Bonferroni post hoc tests, alpha =.05) and failure types (Fisher exact test) were statistically compared for each group. RESULTS: Significant differences (P =.0146 and P =.0086) were observed between the groups in the dimensions of the boxes prepared using conventional burs buccolingually (2.8-3.0 mm in molars, 3.1-4.3 mm in premolars) and the small size (2.5-2.9, 2.9-3.8 mm) or large size (2.6-3.8, 3.2-4.9 mm) ultrasonic tips for the premolars and the molars, respectively. No significant differences were found at the initial and final failures between the conventionally prepared group (842 +/- 267 N, 1161 +/- 428 N) and those prepared with either small (1088 +/- 381 N, 1320 +/- 380 N) or large ultrasonic tips (1070 +/- 280 N, 1557 +/- 321 N), respectively. The failure analysis demonstrated no significant difference in failure types but predominant delamination of the veneering resin (85%) in all experimental groups. According to acoustic emission tests, a higher energy level was required for final failure of the FRC FPDs with boxes finished using small ultrasonic tips. CONCLUSION: Standardized box dimensions showed no significant effect on fracture strength at either initial or final failure of the fiber-reinforced FPDs. The FRC FPDs with boxes refined with small ultrasonic burs required a greater energy level before failure. The type of failure observed after the fracture tests was primarily delamination of the veneering resin.

Acoustics↗