Safe Removal of a Broken Abutment Screw with Customized Drill Guide and Rotary Instrument: A Clinical Report.

This clinical report introduces a method for safe retrieval of a broken implant abutment screw. A reverse-tapping rotary instrument has been introduced in the market and is widely used to retrieve broken screws; however, it is difficult to use the rotary instrument unless an access hole for engagement of the rotary instrument is positioned directly on the center of the top of the broken screw remnant. Poor visibility is another limitation to make an access hole. To keep the position of the rotary instrument at the center of the broken screw, a customized drill guide was fabricated, modifying an implant impression coping with self-cured acrylic resin, all easily found in daily practice. The broken screw was easily removed, not damaging the internal threads of the implant. This technique could be applied to most implant systems when a specific removal kit for each implant system is not prepared.

Restoration of immediately loaded implants in a minimal number of appointments: a retrospective study of clinical effectiveness.

PURPOSE: The purpose of this study was to assess the clinical effectiveness of an experimental technique versus the conventional method for the fabrication of implant-supported fixed complete dentures. MATERIALS AND METHODS: Between January 2005 and June 2010, edentulous patients who had received rehabilitation by means of nonsegmented fixed implant-supported complete dentures were identified from the pool of individuals treated at Eastman Institute for Oral Health, University of Rochester. Data collection consisted of a chart review and recording of treatment variables in a customized database. Variables of interest included number of implants per patient, time of implant placement, number of appointments required to complete prosthesis fabrication, type of appointments, manufacturing process used for creation of the framework, and fit of the framework. The number of appointments for conventional and experimental protocols was evaluated for statistical significance using two-way analysis of variance. Presence or absence of clinically acceptable prosthesis fit with the two techniques was evaluated using the Fisher exact test and exact logistic regression analysis. RESULTS: Forty-two patients (48 arches) were included. When the experimental technique was used, prosthesis fabrication and delivery required an average of 4 appointments, whereas the conventional technique required an average of 7.8 appointments to deliver the definitive prosthesis. The prostheses fabricated with the experimental technique showed clinically passive fit on the implants in 17 of 18 arches. The frameworks fabricated with the conventional technique achieved clinically passive fit in 18 of 30 arches. CONCLUSIONS: The experimental technique significantly reduced the number of appointments required to fabricate a nonsegmented fixed implant-supported prosthesis. Moreover, this experimental technique provided clinically acceptable fit of the prosthesis in a significantly greater number of cases compared to a conventional implant elastomeric impression technique.

Development of a contemporary animal model of Candida albicans-associated denture stomatitis using a novel intraoral denture system.

Denture stomatitis (DS) is a fungal infection characterized by inflammation of the oral mucosa in direct contact with the denture and affects up to 50% of denture wearers. Despite the prevalence, very little is known about the role of fungal or host factors that contribute to pathogenesis. Recently, we developed a novel intraoral denture system for rodent research. This denture system consists of custom-fitted fixed and removable parts to allow repeated sampling and longitudinal studies. The purpose of this study was to use this denture system to develop a clinically relevant animal model of DS. To establish DS, rats were inoculated with pelleted Candida albicans, which resulted in sustained colonization of the denture and palate for 8 weeks postinoculation. Biofilm formation on the denture was observed by week 4 and on the palate by week 6 postinoculation. Rats were monitored for clinical signs of disease by assigning a clinical score after macroscopic examination of the palate tissue according to Newton's method. By week 4 postinoculation, the majority of inoculated rats with dentures exhibited a clinical score of 1 (pinpoint erythema). By week 6 and week 8 postinoculation, increasing percentages of rats exhibited a clinical score of 2 (diffuse erythema/edema). Histological analysis of palate tissue demonstrated progressively increasing inflammatory cell recruitment throughout the time course of the infection. Palatal biofilm formation was commensurate with development of palatal erythema, which suggests a role for biofilm in the inflammatory response.

Fracture resistance of composite resin restorations and porcelain veneers in relation to residual tooth structure in fractured incisors.

The aim of the present study was to investigate whether there is a direct correlation between the amount of residual tooth structure in a fractured maxillary incisor and the fracture resistance of composite resin restorations or porcelain veneers after cyclic loading. Sixty human-extracted maxillary central and lateral incisors were mounted in an acrylic block with the coronal aspect of the tooth protruding from the block surface. The teeth were assigned to two groups: 2-mm incisal fracture and 4-mm incisal fracture. Then, the teeth were further divided into two different restoration subgroups, porcelain laminate veneer and composite resin restoration, therefore obtaining four groups for the study (n=15). The specimens were subjected to 1000 cycles of thermocycling and were mechanically tested with a custom-designed cyclic loading apparatus for 2×106 cycles or until they failed. The specimens that survived the cyclic loading were loaded on the incisal edge along the long axis of the tooth with a flat stainless steel applicator until they fractured using a universal testing machine to measure the failure load. Two-way anova was used to assess the significance of restoration, amount of fracture, and interaction effect (α=0.05). During the cyclic loading, for the composite resin group, two specimens with 2-mm fracture and three specimens with 4-mm fracture failed. For the porcelain veneer group, two specimens with 2-mm fracture and one specimen with 4-mm fracture failed. The 2-way anova did not show statistical significance for restoration (P=0.584), amount of fracture (P=0.357), or interaction effect (P=0.212). A composite resin restoration and a porcelain veneer could perform similarly for replacing a fractured incisor edge up to 4mm. Other factors such as esthetic and/or cost would be considerations to indicate one treatment over the other.

The influence of verification jig on framework fit for nonsegmented fixed implant-supported complete denture.

PURPOSE: The purpose of this retrospective study was to assess if there was a difference in the likelihood of achieving passive fit when an implant-supported full-arch prosthesis framework is fabricated with or without the aid of a verification jig. MATERIALS AND METHODS: This investigation was approved by the University of Rochester Research Subject Review Board (protocol #RSRB00038482). Thirty edentulous patients, 49 to 73 years old (mean 61 years old), rehabilitated with a nonsegmented fixed implant-supported complete denture were included in the study. During the restorative process, final impressions were made using the pickup impression technique and elastomeric impression materials. For 16 patients, a verification jig was made (group J), while for the remaining 14 patients, a verification jig was not used (group NJ) and the framework was fabricated directly on the master cast. During the framework try-in appointment, the fit was assessed by clinical (Sheffield test) and radiographic inspection and recorded as passive or nonpassive. RESULTS: When a verification jig was used (group J, n = 16), all frameworks exhibited clinically passive fit, while when a verification jig was not used (group NJ, n = 14), only two frameworks fit. This difference was statistically significant (p < .001). CONCLUSIONS: Within the limitations of this retrospective study, the fabrication of a verification jig ensured clinically passive fit of metal frameworks in nonsegmented fixed implant-supported complete denture.

Prospective observation of CAD/CAM titanium-ceramic-fixed partial dentures: 3-year follow-up.

PURPOSE: There is lack of knowledge about the clinical performance of computer-aided design/computer-aided manufacturing (CAD/CAM) titanium-ceramic-fixed partial dentures (FPDs). The purpose of this study was to evaluate CAD/CAM titanium-ceramic FPDs after 3 years in function. MATERIALS AND METHODS: Thirty-one FPDs were fabricated for 23 patients. The Ti frameworks were completely fabricated using CAD/CAM technology, and the low-fusing porcelain was veneered. After confirming there were no mechanical or biological complications, the FPDs were cemented using zinc phosphate cement. The patients were recalled at 12, 24, and 36 months after cementation to examine for the presence of any mechanical complications, such as fractures of the veneering porcelain or the supportive framework, or biological complications, including caries, gingivitis, or periodontitis. The periodontal condition was measured using probing depth (PD), bleeding on probing (BOP), and plaque index (PI). Success and survival rates were estimated using the Kaplan-Meier analysis. RESULTS: There were four cohesive and three adhesive porcelain fractures, but no framework fractured. The Kaplan-Meier cumulative success rate of the CAD/CAM titanium-ceramic crown with regard to mechanical complications was 76.4%, and the cumulative survival rate was 96.8% after 3 years of use. One patient developed caries, but the condition was not associated with marginal discrepancy. No other biological complications were reported. The periodontal parameters demonstrated a tendency that slightly increased up to 24 months and was maintained by 36 months. At the end of the follow-up, PD was 2.86 mm, percentile of surface with BOP was 23.5, and PI was 0.45. CONCLUSION: The CAD/CAM titanium-ceramic FPDs survived in the mouths of patients without major complications for 3 years, although the risk of porcelain fracture appeared to be relatively high.

The influence of incisal veneering porcelain thickness of two metal ceramic crown systems on failure resistance after cyclic loading.

STATEMENT OF PROBLEM: In some clinical situations, the length of either a prepared tooth or an implant abutment is shorter than ideal, and the occlusal clearance to be restored by a porcelain crown is large. Incisal thickness of the coping and the veneering porcelain should be considered to prevent mechanical failure of the crown. PURPOSE: The purpose of this study was to investigate the influence of incisal veneering porcelain thickness of metal ceramic systems on failure resistance after cyclic loading. MATERIAL AND METHODS: With a standardized technique, 60 metal ceramic anterior crowns with 2 different incisal thicknesses of porcelain veneer (2.0 and 4.0 mm) and 2 different metal alloys (Pisces Plus (B), base metal, and Leo (N), high noble metal) were fabricated to fit a custom abutment and divided into 4 groups (B20, B40, N20, N40) (n=15). The crowns were then cemented using resin cement (PANAVIA 21) and thermal cycled and mechanically cycle loaded (49-N load) for 2,000,000 cycles. The specimens were evaluated for cracks and/or bulk fracture with an optical stereomicroscope (x10) and assigned a score of success, survival, or failure. The specimens without bulk fracture after cyclic loading were loaded along the long axis of the tooth, on the incisal edge, in a universal testing machine at a crosshead speed of 1.5 mm/min until fracture. The fracture strength value (N) was recorded. The exact logistic regression and Fisher's exact test were used to study the effect of different alloys and porcelain incisal thicknesses on the success and survival rates after cycle loading. The forces at failure (fracture) of different groups were compared using the rank transform-based nonparametric 2-way ANOVA (alpha=.05). RESULTS: According to exact logistic regression, crowns of the high noble alloy group showed significantly higher success rates (P=.002) than those of the base metal group after cyclic loading. The success rate of the crowns with 2 mm of incisal veneering porcelain was significantly higher (P<.001) than that of the crowns with 4 mm of incisal veneering porcelain. For crowns with a 4-mm incisal thickness, N40 showed a significantly higher success rate than B40 (P=.04, Fisher's exact test). As for survival rate, the exact logistic regression indicated that neither metal type (P=.11) nor thickness (P=.60) had a significant effect. The 2-way ANOVA showed a significant effect of thickness (P=.001) and no significant effect of metal type (P=.08) on the failure load. CONCLUSIONS: The high noble metal ceramic crowns demonstrated a significantly higher success rate after cyclic loading than the base metal ceramic crowns. Crowns with a porcelain incisal thickness of 2 mm showed, for both metal ceramic systems, a greater success rate than those with a 4-mm incisal thickness.

Prospective observation of CAD/CAM titanium ceramic single crowns: a three-year follow up.

STATEMENT OF PROBLEM: Computer-aided design/computer-aided manufacturing (CAD/CAM) titanium ceramic restorations were developed with the potential for replacing expensive, high noble metal ceramic restorations. However, there is a lack of information about the clinical performance of CAD/CAM titanium ceramic single crowns. PURPOSE: The purpose of this study was to evaluate CAD/CAM titanium ceramic single crowns after 3 years in function. MATERIAL AND METHODS: A total of 41 crowns were fabricated for 21 patients. The titanium copings were CAD/CAM milled (Everest CAD/CAM system) with an even thickness of 0.5 mm, and low-fusing veneering porcelain (Vita Titanium Porcelain) was added incrementally. The crowns were cemented using zinc phosphate cement after confirming that there were no mechanical and biological complications. The patients were recalled at 12, 24, and 36 months after cementation to examine the presence of any complications and measure periodontal parameters such as probing depth (PD), bleeding on probing (BOP), and plaque index (PI). The success and survival rates were estimated using the Kaplan-Meier analysis. RESULTS: The success rate of CAD/CAM titanium ceramic crowns with regard to mechanical complications was 82.3% (95% confidence interval: 71.2% to 95.1%). The cumulative survival rate of the crowns was 94.9% (95% confidence interval: 88.3% to 100%) after 3 years. No biological complications were observed. At the end of the follow up, PD was 2.93 mm, percentile of surface with BOP was 29.2, and PI was 0.31. CONCLUSIONS: The clinical performances of the CAD/CAM titanium ceramic crowns for 3 years were acceptable, with no biologic complications and a high cumulative survival rate.

Ring liner and burn-out temperature affect the clinical time required to fit a cast post.

STATEMENT OF PROBLEM: A cast post that is made with an unlined metal casting ring may exhibit anisotropic shrinkage which could result in distortion and consequently require more chair time for fitting in the root canal. PURPOSE: The purpose of this study was to investigate whether the presence of a ring liner and the burn-out temperature of the investment material affect the clinical time required to fit a cast post. MATERIAL AND METHODS: Sixty identical post patterns were fabricated from a customized stainless steel root form. They were divided into 3 groups (n=20) as follows: group LH used a cellulose ring liner and a final burn-out temperature of 815 degrees C; group NH used no liner with the same temperature; group NL used no liner with a final burn-out temperature of 600 degrees C. All groups were invested in stainless steel casting rings with the same phosphate-bonded investment (Hi Temp) and cast with same alloy (Protocol). Two blinded investigators, with different levels of experience, adjusted and placed the posts in the experimental root form until a subjective acceptable fit was achieved. Each investigator fit 10 cast posts for each group, and the time required to achieve a subjective acceptable fit was measured in seconds. Two-way ANOVA was used to test the significance of the investigator, group, and their interaction. One-way ANOVA and a post hoc Tukey HSD test were used to find significant differences among the groups (alpha=.05). RESULTS: The 2-way ANOVA showed a significant effect of the investigator (P=.001) and group (P<.001), but not interaction (P=.15). The 1-way ANOVA showed significant differences among the 3 groups (P<.001), and the Tukey HSD test showed significant differences between the following pairs: LH and NH (P=.009), and LH and NL (P<.001). NH and NL did not demonstrate a significant difference. CONCLUSIONS: Investing a post pattern without a ring liner and setting the final burn-out temperature at 600 degrees C allow the fabrication of cast posts that require significantly less adjustment time for clinical placement than those invested with a ring liner and burned out at 815 degrees C.

The influence of veneering porcelain thickness of all-ceramic and metal ceramic crowns on failure resistance after cyclic loading.

STATEMENT OF PROBLEM: In some clinical situations, the length of either a prepared tooth or an implant abutment is shorter than ideal, and the thickness of a porcelain crown must be increased. Thickness of the coping and the veneering porcelain should be considered to prevent mechanical failure of the crown. PURPOSE: The purpose of this study was to investigate the influence of veneering porcelain thickness for all-ceramic and metal ceramic crowns on failure resistance after cyclic loading. MATERIAL AND METHODS: All-ceramic and metal ceramic crowns (n=20) were fabricated on an implant abutment (RN Solid Abutment) for the study. Two different framework designs with 2 different incisal thicknesses of veneering porcelain (2 mm and 4 mm) were used for each all-ceramic and metal ceramic crown system, resulting in 4 experimental groups (n=10) with identically shaped crowns. The all-ceramic crown consisted of alumina (Procera AllCeram) frameworks and veneering porcelain (Cerabien), while metal ceramic crowns were made of high noble metal (Leo) frameworks and veneering porcelain (IPS Classic). All crowns were cemented on the corresponding abutments using a resin cement (Panavia 21). They were subjected to 1000 cycles of thermal cycling (5 degrees C and 55 degrees C; 5-second dwell time). The crowns were tested with a custom-designed cyclic loading apparatus which delivered simultaneous unidirectional cyclic loading at 135 degrees, vertically, at an rpm of 250, with a load of 49 N. Each specimen was loaded for 1.2 x 106 cycles or until it failed. The specimens were thoroughly evaluated for cracks and/or bulk fracture with an optical stereomicroscope (x10) and assigned a score of success, survival, or failure. The specimens without bulk fracture after cyclic loading were loaded along the long axis of the tooth, on the incisal edge, in a universal testing machine at a crosshead speed of 1.5 mm/min, until fracture. Fisher's exact test was used to compare the success and survival rate between the 2 different materials (alpha=.05). Two-way ANOVA was used to analyze data in terms of material, porcelain thickness, and interaction effect. Also, a 2-sample t test was performed to compare between 2 thicknesses within the same material (alpha=.05). RESULTS: According to the Fisher's exact test, the all-ceramic group showed significantly higher success (P=.003) and survival rates (P=.001) than the metal ceramic group. For the failure load, the 2-way ANOVA showed significant effects for material (P<.001) and porcelain thickness (P=.004), but not a significant interaction effect (P=.198). For the metal ceramic groups, crowns with a 2-mm porcelain thickness showed a significantly greater failure load than crowns with a 4-mm porcelain thickness (P=.004). However, all-ceramic groups did not show a significant difference between the 2 different thicknesses of veneering porcelain (P=.198). CONCLUSIONS: The all-ceramic crowns showed significantly higher success and survival rates after cyclic loading, but lower failure loads than metal ceramic crowns. The thickness of the veneering porcelain affected the failure load of the metal ceramic crowns, but not that of the all-ceramic crowns.

The accuracy of implant impressions: a systematic review.

STATEMENT OF PROBLEM: Various implant impression techniques, such as the splint, pick-up, and transfer techniques, have been introduced, and some techniques may be more accurate than others. Also, clinically, some factors, including the angulation or depth of implants, may affect the accuracy of the implant impressions. PURPOSE: The purposes of this review were to: (1) investigate the accuracy of published implant impression techniques, and (2) examine the clinical factors affecting implant impression accuracy. MATERIAL AND METHODS: An electronic search was performed in June 2008 of MEDLINE, EMBASE, and Cochrane Library databases with the key words implant, implants, impression, and impressions. To be included, the study had to investigate the accuracy of implant impressions and be published in an English peer-reviewed journal. In addition, a hand search was performed to enrich the results for the time period from January 1980 to May 2008. After executing the search strategies, 41 articles were selected to be included in the review process. RESULTS: All of the selected articles were in vitro studies. Of the 17 studies that compared the accuracy between the splint and nonsplint techniques, 7 advocated the splint technique, 3 advocated the nonsplint technique, and 7 reported no difference. Fourteen studies compared the accuracy of pick-up and transfer impression techniques, and 5 showed more accurate impression with the pick-up techniques, 2 with the transfer technique, and 7 showed no difference. The number of implants affected the comparison of the pick-up and splint techniques. Eleven studies compared the accuracy of polyether and vinyl polysiloxane (VPS), and 10 of 11 reported no difference between the 2 materials. Four studies examined the effect of implant angulation on the accuracy of impressions. Two studies reported higher accuracy with straight implants, while the other 2 reported there was no angulation effect. CONCLUSIONS: The review of abutment level or implant level internal connection implants indicated that more studies reported greater accuracy with the splint technique than with the nonsplint technique. For situations in which there were 3 or fewer implants, most studies showed no difference between the pick-up and transfer techniques, whereas for 4 or more implants, more studies showed higher accuracy with the pick-up technique. Polyether and VPS were the recommended materials for the implant impressions.

Oral rehabilitation of a 12-year-old patient diagnosed with a central giant cell granuloma using a fibula graft and an implant-supported prosthesis: a clinical report.

This clinical report describes the oral rehabilitation of a 12-year-old boy with a central giant cell granuloma of the mandible. He underwent en bloc resection of a central giant cell granuloma, free vascularized fibula reconstruction, implant placement, and prosthesis fabrication. The multidisciplinary approach successfully restored function and esthetics. Considerations regarding the extensive surgical and prosthetic rehabilitation of a young adult with remaining growth are discussed.

Effect of subgingival depth of implant placement on the dimensional accuracy of the implant impression: an in vitro study.

STATEMENT OF PROBLEM: In some instances, an implant needs to be placed deep subgingivally, which may result in a less accurate impression of the implant. PURPOSE.: The purpose of this study was to evaluate the effect of subgingival depth of implant placement on the accuracy of implant impressions. MATERIAL AND METHODS: A stone master model was fabricated with 5 implant analogs (RN synOcta analog), embedded parallel to each other, at the center (E) and the 4 corners (A, B, C, and D). The vertical position of the shoulders of the implants was intentionally different among the implants: A and E were flush with the top surface of the model; B was 2 mm below, and C and D were 4 mm below the surface. The horizontal distances of implants A, B, C, and D from E were measured with a measuring microscope. A cross-shaped metal measuring bar was then fabricated and connected to E, with the arms of the casting designed to be 2 mm above the top surface of the model and incorporating a reference mark. With the measuring bar connected to E, the vertical distances from the apical surface of A, B, C, and D to the measuring reference marks were measured with a digital micrometer. The body of the impression coping for implant D was modified by adding 4 mm of additional impression coping, while standard impression copings were used for all other implants. Open tray impressions were made using medium-body polyether material (Impregum Penta) or a combination of putty and light-body vinyl polysiloxane (VPS) material (Elite HD+) (n=15). Then casts were poured with type IV dental stone. The vertical and horizontal distances of the casts were measured with the methods outlined above for the master model. The distortion values that were determined as differences between the measurements of the master model and those of the casts were collected for statistical analysis. Two-way and 1-way repeated measures ANOVA followed by Tukey's HSD test were performed to compare the distortion values (alpha=.05). RESULTS: For vertical measurements, 2-way repeated measures ANOVA showed no significant depth (P=.36), material (P=.24), or interaction effects (P=.06). However, it showed significant depth effect for horizontal measurements (P=.01). Within the polyether group, 1-way repeated measures ANOVA showed significant differences in horizontal measurements among the implants with different depths (P=.03). The post hoc Tukey's test showed that the impression of 4-mm-deep implants with normal impression copings (C) was significantly less accurate than impressions of 0-mm-deep implants (A) (P=.02). Within the VPS group, there was no significant difference among the implants with different depths (P=.09). CONCLUSIONS: There was no effect of implant depth on the accuracy of the VPS group. However, for the polyether group, the impression of an implant placed 4 mm subgingivally showed a greater horizontal distortion compared to an implant placed more coronally. Adding a 4-mm extension to the retentive part of the impression coping eliminated this difference.

Oral rehabilitation of a completely edentulous epidermolysis bullosa patient with an implant-supported prosthesis: a clinical report.

This clinical report describes the rehabilitation of a completely edentulous 29-year-old man diagnosed with recessive dystrophic epidermolysis bullosa (EB). Four implants were placed in each arch, and metal-resin implant fixed complete dentures were fabricated for both arches. This treatment option appears to be favorable for EB patients, compared to other options involving removable prostheses, in that it causes less mechanical irritation to the oral mucosa.