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Biomedical subjects

Angelo A Caputo

Publications and source records attributed to Angelo A Caputo.

At least 19 recordsLinked to original sources
PubMed2005

Composite resin bond strength to primary dentin prepared with Er, Cr:YSSG laser.

This in vitro study evaluated the shear bond strength of a hybrid composite resin bonded to primary dentin prepared with an Er, Cr:YSGG hydrokinetic laser compared to conventional bur prepared primary dentin. The results suggest that primary dentin surfaces treated with the Er, Cr:YSGG laser, with or without etching, may provide comparable or increased composite resin bond strengths depending upon bonding agent used.

Acrylic Resins↗
PubMed2005

Thickness and stiffness characteristics of custom-made mouthguard materials.

OBJECTIVES: The purpose of this investigation was to determine the thickness of different types of custom-made mouthguards after processing and the deformational changes after simulated occlusal loading. MATERIALS AND METHODS: Ten mouthguards were fabricated for the same dental arch using the following materials and processing techniques: Group I: vacuum-formed (4 mm), Colored Mouthguard; Group II: vacuum-formed (4 mm), Proform; and Group III: pressure-laminated (3 + 3 mm), Drufosoft. After processing, the thickness was measured in three places: lingual cusps of the first molar, distal marginal ridge of the first premolar; and facial of central incisor. The stiffness of each group was determined by applying a simulated clenching force to the first molar lingual cusp areas on an Instron test machine with a blunt probe. The corresponding penetration was measured with a dial gauge. Thickness and force-deflection measurements of the different mouthguard groups were compared using analysis of variance and post hoc tests. RESULTS: The mean thicknesses at the molar for Groups I and II were 1.55 and 1.52 mm, respectively, and were significantly smaller then the corresponding thickness for Group III (3.48 mm). The mean thicknesses at the facial of the incisors for Groups I and II were similar (2.05 and 2.06 mm, respectively), and were significantly smaller than the corresponding thickness for Group III (3.29 mm). Groups I and II demonstrated similar stiffness that was significantly higher than that for Group III. CONCLUSION: These results show that vacuum-formed mouthguards produced smaller thicknesses than the pressure-laminated mouthguards. The pressure-laminated mouthguards produced material thicknesses that were previously shown to be adequate to protect athletes from trauma.

Analysis of Variance↗
PubMed2004

Effects of various irrigation solutions on microleakage of Class V composite restorations.

STATEMENT OF THE PROBLEM: Irrigation solutions used in the preparation of composite restorations have been reported to contain potential contaminants that may interfere with, and compromise, composite bonding. PURPOSE: The purpose of this in vitro study was to evaluate microleakage of Class V composite restorations after irrigation of acid conditioner with various solutions. MATERIAL AND MENTODS: Standardized Class V preparations (5 mm wide, 4 mm high and 2 mm deep) were made at the cemento-enamel junction on available buccal, lingual, mesial, and distal surfaces of extracted human posterior teeth. The prepared teeth, separated into 7 groups (n=10), were etched for 10 seconds with a 37% phosphoric acid gel. Each group was irrigated with 1 of the following solutions: (1) tap water, (2) sterile water, (3) sodium chloride solution, (4) filtered water, (5) chlorhexidine, (6) sodium hypochlorite, and (7) distilled water. Each preparation was treated with a bonding agent (Opti-Bond Solo) and then restored with a hybrid composite (Herculite XRV). The restorations were polished with Soflex polishing disks and then thermal cycled for 1000 cycles between 5 degrees C and 55 degrees C with a 20-second dwell time. Assessment of microleakage was performed by application of a dye penetrant, sectioning of the teeth, and examination at original magnification x 20. The nonparametric Kruskal-Wallis test (alpha=.05) was used for statistical analysis. RESULTS: Microleakage ranging from 10% to 30% was observed in all groups tested. Tap water exhibited the highest incidence of leakage, sterile water the least, with the other irrigation solutions leading to intermediate leakage. However, there was no significant difference in microleakage resulting from any of the irrigation solutions tested. CONCLUSION: The effect of irrigation solutions used in this in vitro study was not significant.

Acid Etching, Dental↗
PubMed2004

Stress transfer of four mandibular implant overdenture cantilever designs.

STATEMENT OF PROBLEM: The influence of implant number and cantilever design on stress distribution on bone has not been sufficiently assessed for the mandibular overdenture. PURPOSE: The purpose of this simulation study was to measure, photoelastically, the biologic behavior of 2 or 3 implants retaining different designs of cantilevered bar mandibular overdentures and to compare load characteristics. MATERIALS AND METHODS: Two photoelastic models of a human edentulous mandible were fabricated having 2 or 3 screw-type implants (Nobel Biocare, 3.75 x 10mm) embedded in the parasymphyseal area. Bar frameworks using a 7-mm cantilever were fabricated for both models. A clip-retained and a plunger-retained (SwissLoc) prosthesis were fabricated as superstructures for each framework. Vertical loads of 15 and 30 pounds were applied unilaterally to the first molar and 15 pounds to the first premolar on each of the 4 standardized overdenture prostheses. The cantilever was removed from the 2-implant framework and the clip-retained prosthesis was loaded similarly on the first molar with 25 pounds. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically. RESULTS: While all 4 prostheses demonstrated low stress transfer to the implants, the plunger-retained prosthesis caused more uniform stress distribution to the ipsilateral terminal abutment compared to the clip-retained prosthesis and provided retention security under tested loads. The plunger-retained prosthesis retained by 2 implants provided better load sharing from the ipsilateral edentulous ridge than the clip-retained prosthesis retained by 3 implants, and lower resultant stresses were seen on the implants. CONCLUSIONS: Under load, all prosthetic designs demonstrated a low stress transfer to the ipsilateral abutment and to the contralateral side of the arch. The plunger-retained prosthesis retained by 2 implants demonstrated a more uniform stress transfer to the ipsilateral terminal abutment than the clip-retained prosthesis retained by 3 implants and provided more retention, given the implant configuration, prosthetic design and arch form.

Compressive Strength↗
PubMed2004

Photoelastic analysis of the effect of palatal support on various implant-supported overdenture designs.

STATEMENT OF PROBLEM: The effect of palatal support on various types of implant-supported maxillary overdenture designs has not been sufficiently assessed. PURPOSE: The purpose of this study was to photoelastically evaluate the palatal support of 3 designs of maxillary implant-supported overdentures. MATERIAL AND METHODS: A photoelastic model of an edentulous maxilla was fabricated with four 3.75 x 13-mm 3i implants. Three maxillary overdenture designs were fabricated: a splinted Hader bar incorporating 2 distal ERA attachments with anterior clips; non-splinted Zaag 4-mm direct abutments and attachments; and nonsplinted Locator 2-mm direct abutments and attachments. All restorative components and attachments were fitted and observed for passivity of fit and alignment. The overdentures were first tested with complete palatal coverage. Unilateral 25-lb loads were applied at the left and right first molars and the incisive papilla area. The photoelastic effects were monitored and recorded photographically. The palatal area was removed from the 3 overdentures and the loading regimens were repeated. RESULTS: The highest stresses under central loading were seen with the splinted Hader bar and complete palatal coverage, followed by similar levels of stress with either Zaag or Locator attachments. After removal of the palate, the center load demonstrated greater differences between designs. The highest stresses were observed with the Hader bar, followed by the Zaag and then Locator attachments. Lack of palatal coverage demonstrated higher levels of stress around implants and visible supporting tissues. The unilateral load produced the highest stress for the splinted Hader bar, followed by Locator, and then Zaag. CONCLUSIONS: Removal of the palatal support produced a greater effect and more concentrated stress difference for maxillary overdentures than differences between the attachment designs tested.

Dental Abutments↗
PubMed2004

Influence of attachment systems on load transfer of an implant-assisted maxillary overdenture.

PURPOSE: This photoelastic study compared the load transfer characteristics of 2 retention mechanisms in an implant-assisted overdenture prosthesis. MATERIALS AND METHODS: Four implants were incorporated into a photoelastic model of a moderately resorbed edentulous human maxilla. Two retention mechanisms were studied by changing components on the same model and the palateless overdenture. The retention mechanisms studied were bar splint with anterior clip and distal resilient attachments, and solitary ball/O-ring attachments. Loads, ranging from 1.4 to 14.4 kg, were applied to the palatal incline of central incisors and buccal incline of premolars with and without balancing contacts. Stresses developed around all the implants under each loading condition were photographed in the field of a circular polariscope. RESULTS: With both retention mechanisms, protrusive and laterotrusive loads without balancing contacts caused instability of the overdenture, producing minimal stress around the implants in the supporting structure. High intensity stresses indicating intrusion of the posterior implants were noted when the bar/distal resilient attachment overdenture had balancing contacts for protrusive and laterotrusive loads. The posterior implants of ball/O-ring attachment overdenture exhibited high intensity stresses indicating not only intrusion, but also bending, when the occlusion was balanced. CONCLUSIONS: Balanced occlusion was required in both retention mechanisms for stability of the implant-assisted overdenture when clinically acceptable loads were applied. The protrusive and laterotrusive loads were not distributed equitably in either mechanism, since highest stresses occurred at the posterior implants.

Compressive Strength↗
PubMed2004

Biomechanical comparison of straight and staggered implant placement configurations.

The effect of buccolingual staggered implant placement on stress distribution within the supporting structure was examined photoelastically. Two photoelastic models of a human mandible, edentulous distal to the canine, were fabricated. Three screw-type implants were embedded into the edentulous region of each model. The implants were placed in a straight line in one model and in a buccolingual staggered configuration in the other. Vertical and lateral loads were applied to a fixed partial denture superstructure. No clear biomechanical advantage to a staggered 1.5 mm buccal and lingual offset placement configuration was observed.

Birefringence↗
PubMed2004

Effects of incremental curing on contraction stresses associated with various resin composite buildups.

OBJECTIVE: The purpose of this study was to photoelastically evaluate contraction stresses associated with various resin composite build-up procedures, including incremental curing and the use of flowable composite for pulpless molars. METHOD AND MATERIALS: Life-sized photoelastic models of an endodontically treated molar were fabricated. The cavity represented a conservative access preparation and included four lateral walls. The following materials were used for buildup: dual-cured hybrid composite (Cleafil DC Core [DC], BIS-CORE [BC]); light-cured flowable composite (AELITEFLO LV [ALV]); and chemical-cured flowable composite (CORE-FLO [CF]). The photoelastic models were built up with the following techniques: bulk-cured (BDd [dual-cured DC], BDc [chemically-cured DC], BBd [dual-cured BC], and BC [CF]); and incremental-cured (1 mm gingivally + 3.5 mm occlusally; IAB [ALV + BC], ICB [CF + BC], and IBB [BC + BC]). Isochromatic fringes developed in the models were recorded photographically in the field of a circular polariscope, and maximum fringe order was determined. Five specimens were tested for each condition. RESULTS: Stress intensity of the build-up methods fell into two categories: high (BDd, BBd, BC, and IAB) and low (BDc, ICB, and IBB). The difference between high and low groups was statistically significant, except between BC and ICB. The maximum fringe order was developed around the point angles at the cavity floor for all the conditions tested. CONCLUSIONS: Type and setting mechanism of resin composite build-up technique had considerable influence on contraction stress. Incremental buildup using composites with low elastic modulus did not reduce contraction stress intensity compared with bulk-cured techniques.

Barium Compounds↗
PubMed2003

Photoelastic stress analysis of implant-tooth connected prostheses with segmented and nonsegmented abutments.

STATEMENT OF PROBLEM: There is some question about whether implant abutment selection affects the transfer of load between connected implants and natural teeth. PURPOSE: The purpose of this study was to compare stress transfer patterns with either 1 or 2 posterior implants connected to a single anteriorly located simulated natural tooth with either 1 or 2 segmented and nonsegmented implant abutments under relevant functional loads by use of the photoelastic stress analysis technique. MATERIAL AND METHODS: A model of a human left mandible, edentulous posterior to the first premolar, with two 3.75-mm x 13-mm screw-type implants embedded within the edentulous area, was fabricated from photoelastic materials. The implants were in the first and second molar positions. Two fixed partial denture prosthetic restorations were fabricated with either segmented conical abutments or nonsegmented UCLA abutments. Vertical occlusal loads were applied at fixed locations on the restorations. The photoelastic stress fringes that developed in the supporting mandible were monitored visually and recorded photographically. The stress intensity (number of fringes), stress concentrations (closeness of fringes), and their locations were subjectively compared. RESULTS: Loading on the restoration over the simulated tooth generated apical stresses of similar intensity (fringe order) at the tooth and the first molar implant for both abutment types. Low-level stress was transferred to the second molar implant. Loading directed on the implant-supported region of the restoration demonstrated low transfer of stress to the simulated tooth. Nonvertical stress transfer with slightly higher intensity was observed for the nonsegmented abutment. CONCLUSION: Within the limitations of this simulation study, stress distribution and intensity for the 2 implant conditions was similar for segmented and nonsegmented abutment designs. Magnitude of stresses observed for both abutment designs was similar for the single implant condition. Vertical loading produced more nonaxial stresses away from the force applied for the 1 implant condition with the nonsegmented abutment. Direct loading results were similar for both abutment designs. Specific recommendations for selection of implant abutment and application should be based on clinical criteria.

Adult↗
PubMed2003

Fracture toughness of nine flowable resin composites.

STATEMENT OF PROBLEM: Flowable composite is used in a variety of clinical applications; however, the capacity of these materials to resist crack propagation is not well understood. PURPOSE: The purpose of this investigation was to compare the resistance to crack propagation of 9 flowable composites as measured by the fracture toughness. MATERIAL AND METHODS: The composites studied include AeliteFlo, Crystal Essence, Flow-it, FloRestore, Permaflo, Revolution, Tetric Flow, VersaFlo, and Wave. Ten specimens of each composite were formed with a brass mold with a 3-mm preformed notch. The final dimensions of each specimen were 2 x 4.2 x 20 mm. All specimens were light-polymerized to manufacturer specifications and stored in air for 24 hours. The fracture toughness value, K(IC) (MNm(-3/2)), for each specimen was measured by use of a 3-point bending mode and a single-edge notched beam at a crosshead speed of 0.125 mm/min until fracture. The data were analyzed statistically by use of 1-way analysis of variance, t tests (P<.05), and regression analysis. RESULTS: The flowable composites tested showed a spectrum of fracture toughness values ranging from 1.15 +/- 0.10 MNm(-3/2) for Wave to 1.65 +/- 0.13 MNm(-3/2) for Permaflo (significantly different, P<.05). The remaining materials formed 1 group with intermediate K(IC) values not different from each other (P>.05) but significantly different from Wave and Permaflo. Comparisons of fracture toughness to the filler content by volume of each composite revealed no correlation. CONCLUSION: This in vitro study concluded that there was no significant difference among 7 of the 9 composites tested in their resistance to fracture. Permaflo showed the greatest resistance to crack propagation. There was no correlation between the filler content by volume and the fracture toughness of these flowable composites.

Air↗
PubMed2003

Contraction stress of composite resin build-up procedures for pulpless molars.

PURPOSE: The purpose of this study was to photoelastically evaluate contraction stresses associated with various resin composite build-up procedures for pulpless molars. MATERIALS AND METHODS: Photoelastic models of endodontically treated mandibular molars were fabricated to simulate a preparation for a full-cast crown. The model configuration included three lateral walls, but no post space. The buildups were made with dual-curing resin composite using the following procedures: 1) bulk dual cure, 2) bulk chemical cure, 3) horizontal two increments, dual cure, and 4) indirect. Five specimens were fabricated for each condition. The stresses developed in the models were recorded photographically in the field of a circular polariscope. RESULTS: The build-up procedures tested generated widely different stress distributions and intensities. The highest stresses were seen with the bulk dual-cure method. The slower polymerization chemical-cure group developed distributions similar to the bulk dual-cure group with a significantly lower fringe order. The two horizontal increments dual-cure techniques developed an individual group of fringes for each layer. Compared with the bulk dual-cure group, stresses around the occlusal margin were reduced by incrementalization, while fringes were more closely spaced at the line angles with a slightly lower fringe order. The indirect method demonstrated the lowest stress which extended over the smallest area. CONCLUSION: Contraction stress in resin composite buildups varied significantly depending upon the procedures of fabrication. The bulk dual-cure method developed the most severe contraction stresses, while the indirect technique resulted in significantly lower contraction stresses than the other techniques tested.

Analysis of Variance↗
PubMed2002

Effect of irrigation solutions on dentin bonding agents and restorative shear bond strength.

STATEMENT OF PROBLEM: The presence of irrigation solution prior to the application of dentin bonding agents may be one source of contamination and may adversely affect bond strength. PURPOSE: The purpose of this in vitro investigation was to evaluate the effect of irrigation solutions of different purity levels on the shear bond strength of a hybrid composite to dentin. MATERIAL AND METHODS: Forty extracted, intact human molars were hand-scaled. All soft tissue was removed, and the teeth were stored in room-temperature tap water for 1 week. Subsequently, each tooth was embedded in autopolymerizing acrylic resin with the coronal portion exposed. After complete polymerization of the resin, the dentin surfaces were exposed, and the crown was cut longitudinally on all 4 sides to produce flat dentin surfaces for bonding. The prepared specimens were assigned to 4 groups of irrigation solutions: tap water (control), sterile water, 0.9% NaCl irrigation solution, and filtered water. Within each irrigation group were 4 dentin bonding agent subgroups: Prime & Bond NT, One-Step, Single Bond Adhesive, and OptiBond Solo. The dentin surfaces (n = 10 per irrigation/bonding agent pair) were etched with 37% phosphoric acid, rinsed with the assigned irrigation solution for 15 seconds, and then dried. Plastic cylinders (3 mm long x 3 mm inner diameter) were filled with a hybrid composite (Herculite XRV) and bonded to the dentin. Specimens were loaded in a universal testing machine, and shear force was applied to the base of the composite cylinders, parallel to the dentin surfaces, at a crosshead speed of 0.05 in/min until fracture. Failure loads were recorded. Bond strength data were compared with analysis of variance (P<.05). Post-hoc comparisons of means were performed with t tests and P values adjusted for multiple comparisons (Bonferroni method). RESULTS: Tap water irrigation (control) produced no significant difference in bond strengths for all dentin bonding agents tested. When other irrigation solutions were used, One-Step consistently produced significantly lower bond strengths than other dentin bonding agents (P<.05). No preferential choice of irrigation solution could be made for Prime & Bond or Single Bond Adhesive. However, when One-Step or Solo was used, irrigation with normal saline significantly reduced bond strengths (P<.05). CONCLUSION: Within the limitations of this study, the bond strength to dentin of a hybrid composite irrigated with different solutions was dependent on the dentin bonding agent used.

Acid Etching, Dental↗
PubMed2002

Effect of splinting and interproximal contact tightness on load transfer by implant restorations.

STATEMENT OF PROBLEM: To circumvent the difficulty of achieving a passive framework fit, some authors have suggested that multiple adjacent implants be restored individually. This protocol requires that each unit be able to withstand mastication forces. Non-splinted restorations have numerous interproximal contacts that require adjustments prior to placement, with an unknown outcome relative to load transfer. PURPOSE: This in vitro simulation study examined the effect of splinting and interproximal contact tightness on passivity of fit and the load transfer characteristics of implant restorations. MATERIAL AND METHODS: A photoelastic model of a human partially edentulous left mandible with 3 screw-type implants (3.75 x 10 mm) was fabricated. For non-splinted restorations, individual crowns were fabricated on 3 custom-milled titanium abutments. After the units were cemented, 5 levels of interproximal contact tightness were evaluated: open, ideal (8 microm shim stock drags without tearing), light (ideal +10 microm), medium (ideal + 50 microm), and heavy (ideal + 90 microm). For splinted restorations, five 3-unit fixed partial dentures were fabricated, internally adjusted with silicone disclosing material, and cemented to the model. Changes in stress distribution under simulated non-loaded and loaded conditions (6.8 kg) were analyzed with a polariscope. RESULTS: In the simulated alveolar structures, non-splinted restorations with heavier interproximal contacts were associated with increased tensile stresses between implants; occlusal loads tended to concentrate around the specific loaded implant. Splinted restorations shared the occlusal loads and distributed the stresses more evenly between the implants when force was applied. The load-sharing effect was most evident on the center implant but also was seen on the terminal abutments of the splinted restorations. CONCLUSION: The results of this in vitro study suggest that excessive contact tightness between individual crowns can lead to a non-passive situation. In this experiment, splinted restorations exhibited better load sharing than non-splinted restorations.

Birefringence↗
PubMed2002

Effects of aging on the dimensional stability of custom-made mouthguards.

OBJECTIVE: The purpose of this investigation was to assess the effects of aging on the dimensional stability of vacuum-formed, pressure-formed, and pressure-laminated custom-made mouthguards. METHOD AND MATERIALS: A master model representing the dental arch was fabricated in acrylic resin. Two ethylene vinyl acetate thermoplastic materials were tested: Essix (regular) and Proform (prelaminated). The model was benchmarked in five places along the curvature of the arch. The model was used to fabricate 10 specimens for each of the following groups: 1 = vacuum-formed (3-mm) Essix; 2 = vacuum-formed (4-mm) Proform; 3 = pressure-formed (3-mm) Essix; 4 = pressure-formed (4-mm) Proform; 5 = pressure-laminated (3-mm + 2-mm) Essix; 6 = pressure-laminated (3-mm + 3-mm) Essix. Die stone was poured into the newly made specimens and measured. Aging of the specimens was simulated by reproducing cleaning cycles (48 hours' soaking in water at 60 degrees F and brushing 100 times with a soft denture brush in soapy water at 140 degrees F for 20 minutes). Die stone was poured into the aged specimens and measured. Initial and postaging measurements were compared. RESULTS: All specimens showed dimensional changes post-aging, mainly decreases. Pressure-laminated specimens showed the best dimensional stability. CONCLUSION: Aging induced various dimensional changes in mouthguards, depending on the materials and processing techniques used. Most of the dimensional change for all mouthguards occurred at the central incisor region, the most important area for the protection of the anterior teeth and the premaxilla. Pressure-laminated mouthguard specimens showed the smallest range of changes at the central incisor region, suggesting potentially improved fit, comfort, and protection.

Analysis of Variance↗
PubMedDate not supplied

Accuracy of mechanical torque-limiting devices for implants.

PURPOSE: To examine the accuracy of 3 mechanical torque wrenches. MATERIALS AND METHODS: The torque outputs of the Nobel Biocare, Straumann ITI, and DynaTorq ITL mechanical torque-limiting devices were determined using a special setup on an Instron test machine. The devices were held in the test setup and oriented so that activation of the drivers caused a pure torsion effect. RESULTS: Significant differences generally existed between individual units and the target torque levels for the Nobel Biocare torque controller. DISCUSSION: The mean torque values of the ITI and ITL devices were within 10% of their respective target torque levels. Knowledge of applied torque levels to the screws that retain implant abutments and their attached prostheses is necessary to achieve optimal preload. The ITI and ITL devices tested in this study were capable of providing consistent torque at or near their respective targets. CONCLUSION: The torque output of each individual device deviated in varying degrees from target torque values.

Analysis of Variance↗
PubMedDate not supplied

Removal torque of immediately loaded transitional endosseous implants in human subjects.

PURPOSE: Transitional implants were designed to support provisional restorations and to allow for load-free osseointegration of conventional implants while a patient was provided with immediate esthetics and function. The purpose of this study was to evaluate the removal torque values of immediately loaded transitional implants in human subjects. MATERIALS AND METHODS: Thirty-one 1.8-mm-diameter transitional implants were placed in 4 patients to support provisional restorations and were subjected to immediate loading. Removal torque values were recorded using a modified ITI torque driver, which was calibrated on an Instron test machine. Torque values were subjected to analysis of variance and post hoc comparisons of means (P < .05). RESULTS: Twenty-six implants were removed intact with torque values between 10.5 and 22.9 Ncm, while 5 fractured at the bone crest at values between 27.1 and 35.4 Ncm. Mean torque values increased with time in function. These values were significantly lower in the maxilla (16.1 +/- 4.8 Ncm) than in the mandible (24.0 +/- 7.3 Ncm). DISCUSSION: Results suggest that these transitional implants may be safely removed from the maxilla after 7 to 15 months, but there is a risk of implant fracture during removal from the mandible after 10 months. CONCLUSION: Removal torque levels for these implants indicate varying degrees of integration even though they were subjected to immediate loading.

Aged↗
PubMedDate not supplied

Bicortically stabilized implant load transfer.

PURPOSE: Questions exist as to the potential advantages of bicortical stabilization of implants in the mandible through engagement of the lingual cortical plate. The purpose of this investigation was to determine photoelastically the effect of lingual cortical plate engagement on implant load transfer. MATERIALS AND METHODS: Composite photoelastic models of an edentulous posterior segment of a mandible were fabricated using plastics of different modulus to simulate cortical and trabecular bone. One model included a 3.75 x 15-mm threaded implant that engaged the simulated lingual cortical plate, while in the other model the implant was centrally located within the simulated trabecular bone. A metal superstructure was cast using an abutment cylinder. Simulated vertical occlusal loads were applied to the superstructure over the implant and at fixed buccal cantilever lengths. Stresses that developed within the model were monitored photoelastically and recorded photographically. Peri-implant defects were then formed in the models and the loading and recording procedures were repeated. RESULTS: Lingual cortical plate engagement generated the highest stresses at the lingual cortical plate and the buccal crestal cortical layer at the implant neck. Stress intensity within the buccal plate at the implant neck was lower than that in the centrally placed implant. In the presence of a peri-implant defect, for all load conditions, more load was borne by the trabecular bone. Increasing cantilever lengths caused asymmetric load transfer with higher maximum stresses. DISCUSSION: For both implant placements, a large portion of the applied load was taken by the crestal cortical bone simulant. Engagement of the lingual cortical plate reduced maximum stress in the crestal cortical bone by approximately 25%. With peri-implant defects, the simulated trabecular bone provided the main support of the applied load. Longer buccal cantilever lengths increased maximum stresses for all placement and crestal bone conditions. CONCLUSIONS: The results of this investigation do not indicate a clear load transfer advantage to apical engagement of the lingual cortical plate in this model.

Alveolar Process↗