Clinical Management Protocol for Dental Implants Inserted in Patients with Active Lichen Planus. Part II 4-Year Follow-Up.

PURPOSE: To evaluate marginal bone loss (MBL) of dental implants inserted in active lichen planus patients. MATERIALS AND METHODS: The study included 59 subjects divided into 3 groups depending on their lichen planus diagnosis and administration of a low dose of corticosteroids: 17 healthy individuals, 20 controlled lichen planus patients controlled using low doses of systemic corticosteroids, and 22 noncontrolled lichen planus patients. During 4-year follow-up sessions MBL was evaluated, and biopsies were collected from lichen planus patients and examined. Two-way ANOVA was used to analyze the data (α = 0.05). RESULTS: There was no statistically significant difference in MBL between healthy and controlled patients; however, noncontrolled patients exhibited increased MBL (F = 1309, p < 0.001) which reached 2.53 mm after 4 years. There were significant interactions between state of the disease (F = 1309, p < 0.001), evaluation time (F = 317, p < 0.001), and interaction between state of the disease and observation time (F = 159, p < 0.001). Histopathologic examination of collected biopsies revealed healthy tissue architecture of the controlled patients, while inflammatory cellular infiltration and signs of classical destructive tissue were observed for noncontrolled patients. CONCLUSIONS: Lichen planus patients receiving dental implants should be controlled on a low-dose of corticosteroids to prevent accelerated MBL and to reduce remission of clinical manifestations.

Clinical Management Protocol for Dental Implants Inserted in Patients with Active Lichen Planus.

PURPOSE: To propose a treatment protocol for management of implant candidates suffering from active lichen planus. MATERIALS AND METHODS: Twenty-three patients who were diagnosed with active lichen planus were referred to a dental practice seeking dental implants. Patients received dental implants using open flap technique and sequential osteotomy. After a healing time of 6 weeks, implants were put into occlusal contact using interim prostheses. Of the 55 inserted implants, 42 failed after a short clinical service time (7 to 11 weeks). Failed implants were surgically removed, and osteotomy sites were carefully cleaned using manual curettes and scrubbing of osteotomy walls. CD4/CD8 cell count and gingival biopsies were collected from the surgical sites. Patients were put on an ascending dose (5 mg/10 days) of oral corticosteroids until a daily dose of 20 mg/day was achieved and maintained for 2 weeks. All patients received ten sessions of low-energy soft tissue laser irradiation at the implant insertion sites to assess soft tissue healing through improving blood circulation, reduction of inflammation, and sterilization of the osteotomy region. After approximately 8 weeks, a new set of 42 implants was placed, and definitive restorations were cemented using early loading technique. Marginal bone levels around inserted implants were periodically evaluated every 3 months using digital periapical radiographs (α = 0.05). RESULTS: Primary blood tests revealed a high CD8 cell count, while soft tissue biopsies revealed infiltration of inflammatory cells at the epithelium soft tissue interface of the examined tissue. Repetition of immunological investigations after administration of the oral corticosteroids and soft tissue laser irradiation revealed reduction of CD8 cell counts and disappearance of inflammatory cell infiltration of the examined soft tissue biopsy. Patients reported marked improvement of the oral mucosa after treatment. All implants (n = 42) were functional after 3 years of clinical observation. There was an initial reduction in marginal bone level after 3 months from insertion time, after which it remained constant during the following observation periods. CONCLUSION: Active lichen planus should be managed with oral corticosteroids and soft tissue laser irradiation before insertion of dental implants.

Influence of ceramic color and translucency on shade match of CAD/CAM porcelain veneers.

OBJECTIVE: To investigate the influence of translucency of CAD/CAM ceramic milling blocks on the final color of porcelain veneer cemented using resin cement with two different opacities. MATERIALS AND METHODS: A standardized incisal lap preparation was made on a maxillary right central incisor that was duplicated using composite resin material (Z250, A4, 3M ESPE). The resin dies were individually laser scanned (Bluecam, Sirona) in order to build a 3D model of the porcelain veneer on the CAD software (Cerec 3D). Three types of milling blocks were used to fabricate the required restorations: multichromatic, high translucency, and low translucency milling blocks (IPS Empress CAD, A1 Vita shade tab). The milled veneers were polished, glazed, and bonded on the resin dies using high opacity and low opacity resin cements (Panavia F2.0). A digital shade guide device (Easyshade Advance, Vita) was used to measure color parameters (CIE Lab values) at the incisal, middle, and cervical third of each cemented restoration. ΔE values of the cemented veneers were calculated against the target color (A1). RESULTS: Cementation of porcelain veneers resulted in significant color change of the resin die (A4) as ΔE values ranged between 8.9 and 13.7. However, the type of milling block did not have an observable effect on final color as the measured ΔE values, against original die color, were very close for the multichromatic block (ΔE = 10.7 ± 0.1), high translucency (ΔE = 9.7 ± 0.09), and low translucency blocks (ΔE = 13.4 ± 0.11). The opacity of the used resin cement did not affect the final shade match, as the observed ΔE values using either high opacity and low opacity resin cement were less than 2 for the three used ceramic blocks. The greatest color difference was observed between the incisal third of multichromatic veneers (ΔE = 8.9) and the cervical third of low translucency veneers (ΔE = 13.7), while for the rest of the test groups this shift was not clinically observable (ΔE < 2.5). CONCLUSION: Within the limitations of this study, the shade match of CAD/CAM porcelain veneers was not influenced by the translucency of used milling block or the opacity of the resin cement.

Simulation of cumulative damage associated with long term cyclic loading using a multi-level strain accommodating loading protocol.

OBJECTIVE: To assess step by step the associated cumulative damage introduced in zirconia veneered restorations after long term cyclic loading using a new multi-level strain accommodating loading protocol. METHODS: 40 zirconia veneered crowns received thermal and cyclic loading (3.5 million cycles at maximum load of 25 kg representing 70% of the critical load of the veneer ceramic). The used loading protocol allowed for reproduction of the combined damping action of the periodontal ligament, food substance, jaw deformation, and free movement of the mandibular joint. Speed of load application and release was obtained from the chewing cycle of adult patients. Principles of fractographic analysis were used to study the behavior and origin of critical crack and associated structural damage. RESULTS: The multi-level strain damping effect prevented generation of cone cracks and contact damage under the loading indenter commonly associated with fracture strength tests. 29 specimens (73%) survived 3.5 million cycles without fracture, 9 specimens (22%) demonstrated cohesive fracture of the veneer ceramic and limited axial fracture of the framework was observed in two specimens (5%). Of all fractured specimens, 2 restorations (5%) failed after 500,000 cycles while the rest survived at least 3 million cycles before fracture was observed. Fractographic analysis revealed initial wear and abrasion below the loading area, subsurface micro-cracking of the glass matrix followed by slow crack growth that traveled in a stepping pattern till deflection at zirconia veneer interface. SIGNIFICANCE: Cyclic loading using multi-level strain accommodating model can reproduce clinical failure. With exception to manufacturing errors, zirconia veneered restoration survived a simulated 7-year service time without fracture.

Internal adaptation, marginal accuracy and microleakage of a pressable versus a machinable ceramic laminate veneers.

OBJECTIVES: The aim of this study was to evaluate the internal adaptation and marginal properties of ceramic laminate veneers fabricated using pressable and machinable CAD/CAM techniques. MATERIALS AND METHODS: 40 ceramic laminate veneers were fabricated by either milling ceramic blocks using a CAD/CAM system (group 1 n=20) or press-on veneering using lost wax technique (group 2 n=20). The veneers were acid etched using hydrofluoric acid, silanated, and cemented on their corresponding prepared teeth. All specimens were stored under water (37 °C) for 60 days, then received thermocycling (15,000 cycles between 5 and 55 °C and dwell time of 90 s) followed by cyclic loading (100,000 cycles between 50 and 100 N) before immersion in basic fuchsine dye for 24 h. Half of the specimens in each group were sectioned in labio-lingual direction and the rest were horizontally sectioned using precision cutting machine (n=10). Dye penetration, internal cement film thickness, and vertical and horizontal marginal gaps at the incisal and cervical regions were measured (α=0.05). RESULTS: Pressable ceramic veneers demonstrated significantly lower (F=8.916, P<0.005) vertical and horizontal marginal gaps at the cervical and incisal margins and lower cement film thickness (F=50.921, P<0.001) compared to machinable ceramic veneers. The inferior marginal properties of machinable ceramic veneers were associated with significantly higher microleakage values. CONCLUSIONS: Pressable ceramic laminate veneers produced higher marginal adaptation, homogenous and thinner cement film thickness, and improved resistance to microleakage compared to machinable ceramic veneers. CLINICAL SIGNIFICANCE: The manufacturing process influences internal and marginal fit of ceramic veneers. Therefore, dentist and laboratory technicians should choose a manufacturing process with careful consideration.

Partial-retainer design considerations for zirconia restorations.

OBJECTIVE: Bond strength limitations of adhesive zirconia restorations have stood as a barrier against their widespread use. Selective infiltration etching is a new surface treatment that enhances bonding to zirconia-based materials. Beside bond strength, the performance of adhesive zirconia restorations could be affected by other variables. The aim of this study was to evaluate the influence of partial-retainer design on the failure load of selective infiltration-etched zirconia restorations. METHOD AND MATERIALS: Cantilever selective infiltration-etched zirconia restorations consisting of a pontic, a connector, and a single partial retainer were bonded to resin teeth (Filtek Z250, 3M ESPE). Four designs were tested: lingual, mesiolingual, buccal, and inlay retainers. A full-crown retainer was used as a control. The inner surface of each retainer received selective infiltration-etching surface treatment, and the specimens were bonded using a resin cement (Panavia F 2.0, Kuraray). Half of the cemented restorations were subjected to an artificial aging program (n = 10). The failure load and type of the bonded restorations were evaluated by applying axial load to the pontic. Two-way ANOVA and Tukey S post hoc tests were used to analyze the data (alpha = 0.05). RESULTS: The partial-retainer design had a significant influence on the failure load of the tested restorations (F = 19.24, P < .001), with the lingual design being the weakest. No significant difference was found between the full-crown, inlay, and buccal retainers. Artificial aging did not influence failure load of the tested restorations. SEM examination revealed that all specimens failed cohesively by fracture of the supporting tooth. The lingual design and the full-crown restorations were associated with complete coronal fracture of the supporting tooth, while minor coronal fractures were observed for the other three partial-retainer designs. CONCLUSIONS: The design of the partial retainer significantly influences the failure load and type of selective infiltration-etched zirconia restorations. The design of the partial retainer could affect the clinical performance of these restorations.

Surface topography of zirconia implants does not alter action potentials of isolated rat sciatic nerves.

The purpose of this study was to explore the effects of airborne-particle abrasion and selective infiltration etching of a yttrium-partially stabilized tetragonal zirconia polycrystal (Y-TZP) implant surfaces on nerve conduction. Particle-abraded Y-TZP (P/Y-TZP), selective infiltration etched Y-TZP (SIE/Y-TZP), and commercially pure titanium (CP-Ti) were used in the study (n = 5).The compound action potentials of the right and left sciatic nerves of eight sacrificed rats were quantified at the in vitro level. The implants were brought into intimate contact with the nerves and the time required for initiation of compound action potentials (TcAP), depolarization (Dp), repolarization (Rp), and amplitude of evoked compound action potentials (cAPs) were recorded before and after contact with the implants. The difference in cAPs between the basal response and after contact with CP-Ti implant was significant (p < 0.05). Time-dependent changes in cAPs of P/Y-TZP and SIE/Y-TZP groups and their basal nerve responses were similar (p > 0.05). Within- and between-subject comparisons revealed that TcAP, Dp, and Rp values for all groups were similar (p > 0.05). Particle-abraded and selective infiltration-etched zirconia implant surfaces do not alter nerve conduction beyond physiologic limits.