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PubMed1994

Effect of increasing cement space on cementation of artificial crowns.

In this study, the effect of cement space on cementation with an artificial crown and machined die was investigated. Spacing was varied in increments of 10 microns, and the dies were cemented in the crown by a force of 25 N with either zinc phosphate cement or a silicone fluid. Separation of the artificial crown and die was measured relative to complete seating without cement. A silicone fluid of 10.6 Pa seconds viscosity was used first with seating times from 168 seconds (SD 8.8 seconds) with no spacing to 2.1 seconds (SD 0.07 second) with 50 microns spacing. Unless 40 microns of spacing was used, the zinc phosphate cement did not allow the artificial crown to seat to less than 30 microns seating discrepancy, and it was suggested that particles in the cement caused this effect. The seating discrepancy ranged from 368 microns (SD 10 microns) without spacing to 29 microns (SD 1 micron) with 50 microns spacing. It was concluded that providing cement space substantially facilitated seating of crowns during cementation.

Cementation↗
PubMed1994

Tightening characteristics for screwed joints in osseointegrated dental implants.

The significance of tightening abutment screws and gold cylinders to osseointegrated fixtures with the correct torque is demonstrated, and a simple relationship between applied torque and screw preload is derived by use of mechanical engineering principles. The principles of a number of tightening methods are outlined and assessments made of their accuracy. The difference between optimum and design torque is highlighted. The necessity and means of achieving optimum torque to ensure a reliable joint in clinical practice is discussed.

Dental Abutments↗
PubMed1994

Biomechanical considerations when combining tooth-supported and implant-supported prostheses.

The force distribution of multiple tooth-supported and implant-supported prostheses is completely different. A direct correlation exists between the degree of flexion at the site of loading and the amount of force distribution to other members of the prosthesis. Micromovement produced by the periodontal fibers facilitates force distribution to all the root surfaces of the natural tooth abutments. The rigidity of the implant/abutment/prosthesis configuration concentrates the force at the crestal bone at the site of loading with limited distribution to the remaining implants. Differential mobility concentrates the force distribution to the bone support of the most rigid members of splinted natural teeth or to the implants when they are united with natural teeth in a combined prosthesis. Implants always support the natural teeth and never the other way around. Therefore a nonrigid attachment is recommended between a tooth-supported prosthesis and an implant-supported prosthesis when they are combined. However, when implants are interspersed with natural teeth in the same prosthesis, the restoration will be implant borne. This requires special force distribution analysis to prevent implant overload.

Alveolar Process↗
PubMed1994

Maxillary and mandibular reconstruction using calvarial bone grafts and Branemark implants: a preliminary report.

A review of 24 patients reconstructed with calvarial bone grafts and 93 Branemark implants (Nobelpharma, Chicago, IL) revealed an overall success rate of 91.4%. Two grafting techniques were used. A vertical grafting technique with delayed implant placement had an 86% success rate in 13 patients who had 50 implants placed. The average follow-up for this group was 31 months. A horizontal grafting technique with immediate implant placement had a success rate of 98%. This group included 13 patients who had 43 implants placed at the time of their bone grafting procedure. Two patients had a combination of grafting techniques. The average follow-up for this group was 18 months. A patient questionnaire revealed a high percentage and degree of satisfaction.

Adult↗
PubMed1994

Nerve transposition and implant placement in the atrophic posterior mandibular alveolar ridge.

The results obtained with a modified surgical technique for transposition of the inferior alveolar nerve followed by immediate placement of endosseous implants in mandibles with moderate to severe atrophy are presented. Ten transpositions of the inferior alveolar nerve together with the installation of 21 implants were performed in six patients. The mean postoperative follow-up time was 23 months, with a range of 12 to 46 months. All implants with functioning pontics remained stable, with no mobility nor signs or symptoms of pain and infection during the follow-up period. Postoperative radiographic evaluation disclosed no pathologic bone loss around the implants. Neurosensory evaluation was performed using the two-point discrimination test. One patient with unilateral transposition had objective neurosensory dysfunction at 12 months postoperative, although all the nerve function were reported as normal by the patients. Strict patient selection criteria are necessary, with full awareness by the patient of the possibility of long-term or even permanent nerve paresthesia, when this procedure is contemplated.

Aged↗
PubMed1996

Ten years' clinical evaluation of three luting cements.

OBJECTIVE: The aim of the present clinical longitudinal study was to observe, over 10 years, the prognosis of abutment teeth restored with fixed prostheses retained by glass ionomer luting cements and one conventional zinc phosphate cement. METHODS: Three dentists prepared 135 abutment teeth in 61 patients to retain 81 fixed prostheses. The prostheses were retained by two glass ionomer luting cements (Ketac-Cem, Fuji Ionomer), or a conventional zinc phosphate cement (De Trey Zinc Zement Improved). The patients were examined yearly for 10 years. RESULTS: Post-operative hypersensitivity occurred in five teeth restored with glass ionomer luting cement. The prevailing reason for abutment tooth failure was secondary caries (n = 21) and pulp necrosis (n = 5). Non-parametric survival estimates indicated that 80-85% of the abutment teeth remained intact after 5 years and 71-81% after 10 years. CONCLUSIONS: The 10-year results indicate that the prognosis of abutment teeth restored with fixed prostheses is good, regardless of whether a glass ionomer or a zinc phosphate luting cement is used.

Dental Abutments↗
PubMed2004

Resistance form in tooth preparation.

Theoretical and clinical studies of resistance form are reviewed, supporting the basic prosthodontic principle that resistance form is an essential element in preparation design. Concepts of the"on-off" nature of resistance form, its application in guidelines for minimally acceptable preparation taper, and the controversy over whether there is a relationship with clinical success or failure are discussed. It is more challenging to obtain resistive molar preparations than resistive anterior preparations, and uneven preparation margins can make parallel 0 degree taper preparations lack resistance form. The usefulness of grooves, especially in molar preparations with uneven margins, is illustrated. The Lewis and Zuckerman techniques for evaluating resistive areas of a preparation are shown to be consistent with each other but not with the Weed method.

Crowns↗
PubMed2005

Monitoring of implant stability in grafted bone using resonance frequency analysis. A clinical study from implant placement to 6 months of loading.

The aim of this prospective study was to compare implants placed in grafted and normal non-grafted maxilla by means of resonance frequency analysis (RFA), clinical stability and implant failure. Twenty-nine patients with severe atrophy of the edentulous maxilla were treated with autogenous bone grafts as onlay (24 patients) or as interpositional grafts in conjunction with a Le Fort I osteotomy (five patients) 6 months prior to placement of 222 implants. Ten non-grafted patients treated with 75 Brånemark implants in the edentulous maxillae served as a control group. RFA was performed at implant placement, abutment connection and after 6 months of bridge loading. Seventeen (8%) implants were lost in the grafted bone and one (1%) in normal bone. RFA revealed a similar pattern in both grafted and normal maxillae, i.e. increasing resonance frequency (RF) with time (Wilcoxon Signed Rank test for paired data). Twenty implants that were rotation mobile (low primary stability) at the time of insertion showed a significantly lower value at implant placement according to RFA (Mann-Whitney U-test, P = 0.020). The RF for the failed implants revealed a tendency towards lower values (Mann-Whitney U-test, P = 0.072), compared to the successful implants. It is concluded that implants placed in grafted bone when using a two-stage technique achieve a stability similar to that of implants placed in normal non-grafted bone.

Aged↗
PubMed2006

Osseointegration of oxidized and turned implants in circumferential bone defects with and without adjunctive therapies: an experimental study on BMP-2 and autogenous bone graft in the dog mandible.

The aim of the study was to compare the integration and implant stability of turned and oxidized titanium implants when placed in experimental bone defects with autogenous bone graft, BMP-2 or without adjunctive therapy. Four defects were prepared on each side of the mandible of 12 mongrel dogs five months after tooth extractions. Implants with turned and oxidized surfaces were placed in the defects. The circumferential gaps were filled with either autogenous bone grafts, a BMP-allogeneic dog mixture in a thermoplastic carrier, carrier alone or left without any treatment (control). There were no statistically significant differences between control and treated sites, neither for turned nor for oxidized implants with regard to histomorphometric measurements in ground sections and to implant stability as measured with resonance frequency analysis (RFA) after 4 and 12 weeks of healing. However, oxidized implants showed a significantly higher stability after 4 weeks and a tendency (p < 0.1) of that after 12 weeks. Histomorphometry showed more bone contacts for oxidized than for turned implants. It is concluded that oxidized implants gain stability more rapidly and integrate with more bone contacts than implants with a turned surface when placed in bone defects.

Animals↗
PubMed2005

Bonding of fibre-reinforced composite post to root canal dentin.

OBJECTIVE: The aim of this study was to determine bonding properties of two types of fibre-reinforced composite (FRC) posts cemented into root canals of molars. Serrated titanium posts served as reference. METHODS: Prefabricated carbon/graphite FRC posts with cross-linked polymer matrix and individually formed glass FRC posts with interpenetrating polymer network (IPN) polymer matrix were compared. The crowns of extracted third molars were removed and post space (diameter: 1.5mm) was drilled, etched and bonded. The posts were treated with dimethacrylate adhesive resin, light-polymerized and cemented with a dual-polymerizing composite resin luting cement. After thermocycling (6000x) the samples were cut into discs of thicknesses: 1, 2 and 4mm (n=12/group). Push-out force was measured by pushing the post from one end. Assessment of failure mode was made under a stereomicroscope (1, adhesive failure between post and cement; 2, cohesive failure of post-system; 3, adhesive failure between cement and dentin). RESULTS: The push-out force increased with increased height of dentin disc in all groups (ANOVA, p<0.001). In the 4mm thick dentin discs the individually formed glass FRC posts showed highest push-out force and the difference to that of the titanium posts was significant (ANOVA, p<0.001). The other differences were not statistically significant. None of the individually formed glass FRC posts showed adhesive failures between the post and the cement. CONCLUSIONS: Contrary to the other posts, there were no adhesive (post-cement) failures with the individually formed glass FRC posts, suggesting better interfacial adhesion of cement to these posts.

Adhesiveness↗
PubMed2006

Axial-wall inclination angle and vertical height interactions in molar full crown preparations.

OBJECTIVE: This study has been designed to evaluate the interaction of axial wall heights with inclination angles in full crown tooth preparations. The interaction of these parameters was related to the resulting preparation surface area. MATERIALS AND METHODS: A right regular pyramid was used to simulate a single mandibular molar preparation with known convergence angles and vertical heights. Various combinations of these two variables allowed the calculation of surface areas with a formula for the area of a pyramid and right triangles through trigonometric manipulations. The pyramidal model system had a 9-mm square base with vertical heights from 3- to 5-mm and single-side inclination angles from 2 to 25 degrees. The occlusal surface was a flat, square or rectangular surface and was included in the total area. RESULTS: A percentage of surface area lost or gained served as the dependent variables. The significance levels were set at 10.0% or greater magnitude of loss/gain in a surface area compared to the ideal 2 degree-level. Significant area loss was demonstrated in all alpha-level comparisons. The largest change was found in the 5-mm height grouping compared to the 3-mm height grouping, -36.6% difference between groups at the 2 degree-level. CONCLUSIONS: Axial single-side inclination angles greater than 10 degrees in 3- and 4-mm height-molars are detrimental to maximum surface area in full crown restorations. The 5-mm axial wall height with < or = 10 degree single wall has been shown to maximize the luting agent surface area between restoration and tooth structure.

Crowns↗
PubMed2005

Anchoring dental implant in tissue-engineered bone using composite scaffold: a preliminary study in nude mouse model.

PURPOSE: The purpose of this study was to fabricate a tissue-engineered bone graft anchoring dental implant with bone marrow stromal cell (bMSC) seeded coral-implant composite scaffold. MATERIALS AND METHODS: Titanium dental implants (3 mm in diameter) were inserted into the cylinder coral scaffolds (5 mm in diameter and 1 mm in wall thickness). bMSCs were isolated from iliac bone marrow of adult New Zealand White rabbits, induced by dexamethasone and seeded into the composite scaffold at the density of 2 x 10 8 /mL in 200 muL medium. Nine cell coral-implant complexes were incubated in vitro for 5 days. One complex was processed for scanning electronic microscopy. The other 8 complexes, together with 4 coral scaffold without cell acting as control, were implanted subcutaneously into nude mice back. At 1 and 2 months after implantation, 4 specimens from the experiment group and 2 specimens from the control group were harvested respectively. New bone restoration and new bone integration with dental implant were evaluated by gross inspection, manual handling test, radiographic examination, and histologic observation. RESULTS: Specimens harvested at 2 months after implantation were red and similar to native bone. Manual handling test showed that dental implants were fixed in the newly formed bone. Radiographic examination showed that most of the coral scaffold had been absorbed. Bone density x-ray shadow could be observed around the dental implant. Histologic examination showed that large amount of new bone formed around the dental implants and integrated well with the implants in some area. In the control group no bone formation was observed both macroscopically and microscopically. CONCLUSION: The results of the study suggested that the tissue-engineered bone of bMSCs seeded natural coral-implant composite scaffold is promising for dental implant anchoring, which has positive implication for clinical jaw reconstruction.

Animals↗
PubMed2006

Effect of alendronate on endosseous implant integration: an in vivo study in rabbits.

PURPOSE: Alendronate sodium (Fosamax; Merck, Whitehouse Station, NJ) is a second-generation bisphosphonate used widely in osteopenic individuals for decreasing bone resorption and increasing bone density. The ability of alendronate to affect systemic bone remodeling raises natural questions about the drug's influence on dental implant osseointegration. Current knowledge regarding the effect of systemic bisphosphonates, specifically alendronate, on all 3 phrases of osseointegration is incomplete and only a few studies have started to investigate peri-implant bone responses to alendronate-coated implants. The purpose of this study was to determine the effect of systemic alendronate therapy on osseointegration of dental implants based on torque-removal values in rabbits. MATERIALS AND METHODS: Identical titanium dental implants were placed using a standardized surgical protocol in the bilateral distal femur and proximal tibia of 20 New Zealand white rabbits (79 implants total). One week before implant placement, 10 rabbits were given doses of alendronate and continued on weekly dosing for 5 weeks until euthanized. The other 10 rabbits were untreated controls. Torque-removal values were determined using a Tohinichi 15-BTG torque wrench (Tohinichi Mfg Co, Ltd, Tokyo, Japan) for all implants. RESULTS: Analysis of torque data showed no statistical differences between the alendronate and control groups in both femur and tibia sites. A statistically significant difference, however, was noted in torque removal values between femur and tibia sites regardless of drug or non-drug groups. CONCLUSIONS: In summary, orally dosed alendronate administration in rabbits had no significant effect on dental implant torque-removal values 6 weeks after endosseous placement in femur and tibia.

Alendronate↗
PubMed2006

Immediate loading versus immediate provisionalization of maxillary single-tooth replacements: a prospective randomized study with BioComp implants.

PURPOSE: The aim of this prospective randomized study was to evaluate the clinical outcome of immediately loaded solid plasma sprayed (TPS) BioComp (BioComp Industries BV, Vught, The Netherlands) implants versus immediate provisionalized but non-loaded BioComp implants in the anterior and premolar region of the maxilla. MATERIALS AND METHODS: Forty-eight patients (31 females and 17 males) with a mean age of 42.3+/-13.1 years (range 19 to 78 years) were included in the study. Fifty threaded TPS implants were placed and provisionalized within 24 hours after surgery. The patients were randomly assigned to 2 groups. In the immediate loaded (IL) group (n=24) the occlusion of the provisional was designed with normal contacts in centric relation and at lateral excursions, while in the non-immediate loaded (IP) group (n=24) the provisional restoration was adjusted to clear all occlusal contacts or contacts at lateral excursions. Patients were instructed to eat a soft diet and to avoid placing food in the area of the provisional crown during the first 6 weeks. Regular clinical and radiographic controls were performed and the survival rate and implant stability quotient (ISQ) values were evaluated at delivery of the definitive restoration at 6 months. At 1 year, radiographic coronal bone defects and gingival esthetics between the 2 groups were assessed. RESULTS: Of the IL group, 2 fixtures were lost, while 3 implants were lost in the IP group. The failing implants showed increasing mobility at 2 to 3 weeks after insertion, and were removed. The remaining 45 implants were stable at every subsequent follow-up examination, and 6 months after implant placement, ISQ values were measured. The mean ISQ value in the IL group was 63.7+/-5.8 versus 63.2+/-4.3 for the IP group (P=.78). The mean mesial marginal bone loss after 12 months in the IL group was 0.27+/-0.2 mm versus 0.28+/-0.22 mm in the IP group (P=.9). The mean distal marginal bone loss after 12 months in the IL group was 0.19+/-0.15 mm versus 0.2+/-0.11 mm in the IP group (P=.87). All implants of the IL group had an ideal gingival buccal margin, versus 91% of the IP group. Full regeneration of the mesial interdental papilla was observed in 70% of the IL group versus 91% of the IP group, while full regeneration of the distal papilla was observed in 91% of both the IL and IP implants. CONCLUSION: No significant differences in ISQ mean values in radiographic bone loss and gingival esthetics were found between immediate non-loaded provisionalization and immediately loaded BioComp implants in the maxilla.

Adult↗
PubMed2004

Development of implant movement checker for determining dental implant stability.

Noninvasive and nondestructive mobility assessment of dental implants is very important and useful for dental implantation diagnostic-aids. The development of implant movement (IM) checker based on microcontroller is presented in this paper. Data acquisition system and bender-type piezoelectric probe were used to improve measurement quality to the original tooth mobility (TM) tester. The adoption of a microcontroller and the use of a dental drill-sized measuring probe were sufficient in the reproducibility and reliability of the IM checker. When the implant was subjected to a constant force and amplitude, the acceleration of the model was detected using the measuring probe. The data acquisition system controlled for obtaining the appropriate acceleration signals based on the preload detection during measurement. Dental implant models of Molteno and Rigolac were made at different stiffness and were used to verify the reliability and validity of measurements. The values of measurements obtained by the IM checker were reliable and precise. The maximum error for perpendicular measurements was less than 12% measured by a new operator and decreased to 2% by an experienced operator. The IM checker was applied to monitor the stability of dental implantation, which compared the relative IM score of the new 5[see text] implant with the adjacent old 6 [see text] implant that had been used functionally for 3 years.

Dental Implants↗
PubMed2003

Finite element analysis to determine implant preload.

STATEMENT OF PROBLEM: The nature of the forces used to clamp implant components together, and how they are generated and sustained, is lacking in the literature. PURPOSE: This study examined the dynamic nature of developing the preload in an implant complex using finite element analysis. METHODS: The implant complex was modeled in accordance with the geometric designs for the Nobel Biocare implant systems. A thread helix design for the abutment screw and implant screw bore was modeled to create the geometric design for these units of the implant systems. Using the software programs HyperWorks and LS3D-Dyna, 2 3-dimensional finite element models of (1) a Branemark System 3.75 x 10-mm titanium Mark III implant, a CeraOne titanium abutment, a Unigrip gold alloy abutment screw, and (2) a Replace Select System 4.30 x 10-mm titanium implant, a Straight Esthetic titanium abutment, and a TorqTite titanium abutment screw were created. Modeling the threads to the machining specifications permitted simulation of screw tightening. The abutment screws were subjected to a tightening torque in increments of 1 Ncm from 0 to 64 Ncm using ABAQUS software. Using these models, the effect of the coefficient of friction on the development of preload amount in the implant complex during and after abutment screw tightening was determined. In the first experiment, the coefficient of friction was set to 0.20 between the titanium bearing surface of the abutments and the implant bearing surfaces, and 0.26 between the gold abutment screw and the titanium implant screw bore. In the second experiment, the coefficient of friction was varied; the titanium implant and titanium abutment bearing surfaces were set to a coefficient of friction of 0.20, whereas the Mark III gold and the Replace Select titanium abutment screws and their respective titanium screw bores in the implants were set to 0.12. The preload amount (N) was determined from the finite element analysis. RESULTS: The stress distribution pattern clearly demonstrated a transfer of preload force from the screw to the implant during tightening. A preload of 75% of the yield strength of the abutment screw was not established using the recommended tightening torques. CONCLUSION: Using finite element analysis, a torque of 32 Ncm applied to the abutment screws in the implant assemblies studied in the presence of a coefficient of friction of 0.26 resulted in a lower than optimum preload for the abutment screws. To reach the desired preload of 75% of the yield strength, using a torque of 32 Ncm applied to the abutment screws in the implant assemblies studied, the coefficient of friction between the implant components should be 0.12.

Dental Abutments↗
PubMed2004

In vitro fracture resistance of posterior metal-ceramic and all-ceramic inlay-retained resin-bonded fixed partial dentures.

STATEMENT OF PROBLEM: Inlay-retained resin-bonded fixed partial dentures (RBFPDs) are conservative prosthetic restorations; however, their resistance to fracture is not clear. PURPOSE: The purpose of this study was to compare fracture loads of posterior complete coverage metal-ceramic restorations with all-ceramic inlay-retained RBFPDs. MATERIAL AND METHODS: Thirty-two posterior ceramic RBFPD restorations were divided into 4 groups (n=8): (1) Complete metal-ceramic fixed partial dentures (MC-FPDs) fabricated of Ni-Cr-based alloy (Wirolloy) and veneered with a ceramic (IPS d.SIGN) as the control group; (2) inlay-retained metal-ceramic (MC RBFPDs) with the same materials as the control; (3) inlay-retained lithium disilicate (LD) glass-ceramic (IPS Empress 2) RBFPDs; and (4) inlay-retained zirconia-based (Z) ceramic (Cercon) RBFPDs. Control specimens were prepared to receive conventional complete MC-FPDs designed to include a 1.3-mm-circumferential, 90-degree flat shoulder with rounded angles. Inlay-retained RBFPD specimens were prepared with 2-mm occlusal reduction but without bevels at the occlusal or gingival margins. Specimens were loaded and fracture loads (N) measured at fracture with a universal testing machine at a crosshead speed of 1.0 mm/min and 250 kgf load cell. Data were analyzed with 1-way ANOVA and Duncan test (alpha=.001). RESULTS: Fracture loads (mean +/- SD) were greatest for control specimens (1318.43 +/- 211.00 N) and Z-RBFPD (1247.70 +/- 262.51 N) specimens as compared to MC-RBFPD or LD-RBFPD (P < .001). MC-RBFPD exhibited the next highest fracture loads (958.01 +/- 194.29 N), and LD-RBFPD exhibited the significantly lowest values (303.23 +/- 92.54 N) of the materials tested (P < .001). CONCLUSION: Inlay-retained zirconia-based ceramic RBFPDs demonstrated the greatest fracture resistance among all inlay-retained restorations tested.

Ceramics↗