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Ceramic single crowns
and maxillary sinus, increased patient comfort, shorter treatment time, and reduced cost. The results achieved with a 6-mm short implant and a single implant system (the Straumann 6-mm tissue-level micro-rough dental implant) were evaluated. Methods.—The search of PubMed and a hand search identified studies published between January 1987 and August 2011 that reported on Straumann 6 mm implants placed in human jaws with data on survival rate and time of failure. The follow-up period had to be at least 12 months (range 1 to 8 years). Implant survival and time of failure were the principal outcome measures. The data from the 12 methodologically acceptable studies included 690 implants. A meta-analysis was also performed. Results.—The cumulative survival rate percentage (CSR%) at 4 months was between 81.3% and 100.0% for all but two studies. These two, which reported 75.0% and 47.6%, had relatively small sample sizes. Pooled CSR was 93.7%. Of the 266 implants placed in the maxilla and 364 in the mandible, 25 implants were lost. Overall failure rate for maxillary implants was 5.3% and for the mandible was 1.4%. Most failures occurred early (76%), with 20% delayed and 4% late failures. Discussion.—It was initially hypothesized that most failures with the 6-mm Straumann implants would occur early, and the results confirmed this view. Failure was more likely in maxillary compared to mandibular sites.
However, overall these short implants performed well and had favorable survival rates.
Clinical Significance.—Short implants are usually placed in less-than-ideal sites or those with compromised alveolar situations, which may account for the common finding that implants of standard length tend to have better survival data than short implants. However, no statistical correlation has been noted between implant length and its effect on implant survival or success. Implant diameter has actually been shown to be more important in dissipating forces than implant length. Straumann 6-mm short implants have a micro-rough surface that may contribute to its success. Most failures occurred within the first 4 months after placement and before loading. Future prospective randomized clinical investigations are needed to provide confirmatory evidence for these findings.
Srinivasan M, Vazquez L, Rieder P, et al: Survival rates of short (6 mm) micro-rough surface implants: A review of literature and meta-analysis. Clin Oral Impl Res 25:539-545, 2014 Reprints available from M Srinivasan, Dept of Gerodontology and Removable Prosthodontics, School of Dental Medicine, Rue Barthelemy-Menn 19, Geneva 1205, Switzerland; fax: þ41 22 379 4052; e-mail: [email protected]
Fixed Prosthodontics Ceramic single crowns Background.—Ceramic restorations offer improved esthetics, soft tissue biocompatibility, chemical resistance to biodegradation, and reduced plaque accumulation compared to more conventional materials. However, they still have low fracture resistance and brittleness that must be overcome. Factors that contribute to fracture include complex geometry, choice of luting agent, choice of ceramic system, and location in the arch. The 5-year survival rate for ceramic single crowns is estimated to be around 90% in various studies, with a fracture rate of about 4%. Most fractures to the core occur early in the crown’s life. Whether the opposing dentition or gender of the patient influence clinical performance of ceramic
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Dental Abstracts
single crowns is currently unknown. The long-term practice-based clinical performance of various ceramic crown restorations was evaluated, along with factors that may alter that performance. Methods.—The ceramic single crowns were placed at the Mayo Clinic and had been in function since 2005. Restorations were evaluated clinically, radiographically, and via photographs. Both bilayer and monolayer ceramic systems were assessed. Results.—The 59 patients (mean age 55 years, range 16 to 85 years) had a total of 226 single ceramic crowns on 183
A natural opposing dentition was present in 43% of the patients. The fracture risk of ceramic crowns opposing natural teeth differed significantly from that when the crown was opposite fixed tooth or implant-retained restorations. Seventy-four percent of the fractures occurred when the opposing dentition was a fixed tooth or implant-retained restoration. The complications in 7% of the ceramic crowns could be repaired without replacing the existing crown.
Fig 2.—Fracture through core of the maxillary first molar ceramiclayered crown. (Courtesy of Dhima M, Paulusova V, Carr AB, et al: Practice-based clinical evaluation of ceramic single crowns after at least five years. J Prosthet Dent 111:124-130, 2014.)
natural teeth and 43 implants. Mean follow-up was 6.1 years (range 5.1 to 12.9 years). The most common location was the anterior or posterior maxilla, and most teeth had no foundation material. Custom zirconia was used for most implant crown abutments. Luting-bonding agents were resin-modified glass ionomer cement in the majority of cases, with glass ionomer cement the next most common choice. None of the patients required endodontic therapy after the crown was placed. Fractures were most likely at the incisal edge of the anterior teeth, the distal marginal ridge, and the functional cusp. Twelve percent of the restorations fractured, with 63% extending to the core (Fig 2), requiring replacement. Posterior teeth developed fractures in 7.4% of cases. None of the implant-supported crowns fractured. Fractures were more common when the opposing dentition was a fixed metal ceramic and resin metal restoration. Choice of ceramic system did not correlate with any differences in fracture data. Three restorations had margins showing tactile and visual evidence of an opening. Eighty-seven percent of the ceramic crowns had no wear evident, but 4% had wear that extended to the core. These latter crowns were alumina core restorations in areas consistent with contact with the opposing dentition. Wear and type of opposing dentition showed no statistical correlation. However, a significant difference in wear of the ceramic crowns was found between the anterior and posterior positions. Posterior teeth had significantly less wear than anterior teeth.
Seven percent of the ceramic crowns demonstrated soft tissue recession, usually on the labial surface of the anterior maxillary and mandibular teeth. Anterior crowns had significantly more recession than posterior crowns. Nine percent of the ceramic crowns had erythema, with a third of these having erythema surrounding the entire tooth. The replacement-free survival rate was 99.1% 1 year after insertion of the crown, with rates of 96.7%, 95.1%, 92.8%, and 92.8% 3, 5, 7, and 10 years after insertion, respectively. Just 6% of the crowns had to be replaced, with mean replacement time 3.3 years after insertion (range 0.1 to 6.1 years). One implant-supported crown required replacement to resolve symptomatic periapical pathology measuring more than 5 mm. Discussion.—The survival rates of these ceramic single crowns were 95.1% at 5 years and 92.8% at 10 years. The most common reason for replacement was fracture to the core of the ceramic crowns. This occurred most often in posterior teeth.
Clinical Significance.—These ceramic crowns have good clinical performance after 5 and 10 years and can be used in all areas of the mouth. Most of the fractures occurred within the first few years after insertion and affected layered ceramic crowns in posterior regions. Monolithic ceramic systems may perform better for posterior locations.
Dhima M, Paulusova V, Carr AB, et al: Practice-based clinical evaluation of ceramic single crowns after at least five years. J Prosthet Dent 111:124-130, 2014 Reprints available from M Dhima, Mayo Clinic, Dept of Dental Specialties, 200 First St SW, Rochester, MN 55905; e-mail: [email protected]
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However, overall these short implants performed well and had favorable survival rates.
Clinical Significance.—Short implants are usually placed in less-than-ideal sites or those with compromised alveolar situations, which may account for the common finding that implants of standard length tend to have better survival data than short implants. However, no statistical correlation has been noted between implant length and its effect on implant survival or success. Implant diameter has actually been shown to be more important in dissipating forces than implant length. Straumann 6-mm short implants have a micro-rough surface that may contribute to its success. Most failures occurred within the first 4 months after placement and before loading. Future prospective randomized clinical investigations are needed to provide confirmatory evidence for these findings.
Srinivasan M, Vazquez L, Rieder P, et al: Survival rates of short (6 mm) micro-rough surface implants: A review of literature and meta-analysis. Clin Oral Impl Res 25:539-545, 2014 Reprints available from M Srinivasan, Dept of Gerodontology and Removable Prosthodontics, School of Dental Medicine, Rue Barthelemy-Menn 19, Geneva 1205, Switzerland; fax: þ41 22 379 4052; e-mail: [email protected]
Fixed Prosthodontics Ceramic single crowns Background.—Ceramic restorations offer improved esthetics, soft tissue biocompatibility, chemical resistance to biodegradation, and reduced plaque accumulation compared to more conventional materials. However, they still have low fracture resistance and brittleness that must be overcome. Factors that contribute to fracture include complex geometry, choice of luting agent, choice of ceramic system, and location in the arch. The 5-year survival rate for ceramic single crowns is estimated to be around 90% in various studies, with a fracture rate of about 4%. Most fractures to the core occur early in the crown’s life. Whether the opposing dentition or gender of the patient influence clinical performance of ceramic
44
Dental Abstracts
single crowns is currently unknown. The long-term practice-based clinical performance of various ceramic crown restorations was evaluated, along with factors that may alter that performance. Methods.—The ceramic single crowns were placed at the Mayo Clinic and had been in function since 2005. Restorations were evaluated clinically, radiographically, and via photographs. Both bilayer and monolayer ceramic systems were assessed. Results.—The 59 patients (mean age 55 years, range 16 to 85 years) had a total of 226 single ceramic crowns on 183
A natural opposing dentition was present in 43% of the patients. The fracture risk of ceramic crowns opposing natural teeth differed significantly from that when the crown was opposite fixed tooth or implant-retained restorations. Seventy-four percent of the fractures occurred when the opposing dentition was a fixed tooth or implant-retained restoration. The complications in 7% of the ceramic crowns could be repaired without replacing the existing crown.
Fig 2.—Fracture through core of the maxillary first molar ceramiclayered crown. (Courtesy of Dhima M, Paulusova V, Carr AB, et al: Practice-based clinical evaluation of ceramic single crowns after at least five years. J Prosthet Dent 111:124-130, 2014.)
natural teeth and 43 implants. Mean follow-up was 6.1 years (range 5.1 to 12.9 years). The most common location was the anterior or posterior maxilla, and most teeth had no foundation material. Custom zirconia was used for most implant crown abutments. Luting-bonding agents were resin-modified glass ionomer cement in the majority of cases, with glass ionomer cement the next most common choice. None of the patients required endodontic therapy after the crown was placed. Fractures were most likely at the incisal edge of the anterior teeth, the distal marginal ridge, and the functional cusp. Twelve percent of the restorations fractured, with 63% extending to the core (Fig 2), requiring replacement. Posterior teeth developed fractures in 7.4% of cases. None of the implant-supported crowns fractured. Fractures were more common when the opposing dentition was a fixed metal ceramic and resin metal restoration. Choice of ceramic system did not correlate with any differences in fracture data. Three restorations had margins showing tactile and visual evidence of an opening. Eighty-seven percent of the ceramic crowns had no wear evident, but 4% had wear that extended to the core. These latter crowns were alumina core restorations in areas consistent with contact with the opposing dentition. Wear and type of opposing dentition showed no statistical correlation. However, a significant difference in wear of the ceramic crowns was found between the anterior and posterior positions. Posterior teeth had significantly less wear than anterior teeth.
Seven percent of the ceramic crowns demonstrated soft tissue recession, usually on the labial surface of the anterior maxillary and mandibular teeth. Anterior crowns had significantly more recession than posterior crowns. Nine percent of the ceramic crowns had erythema, with a third of these having erythema surrounding the entire tooth. The replacement-free survival rate was 99.1% 1 year after insertion of the crown, with rates of 96.7%, 95.1%, 92.8%, and 92.8% 3, 5, 7, and 10 years after insertion, respectively. Just 6% of the crowns had to be replaced, with mean replacement time 3.3 years after insertion (range 0.1 to 6.1 years). One implant-supported crown required replacement to resolve symptomatic periapical pathology measuring more than 5 mm. Discussion.—The survival rates of these ceramic single crowns were 95.1% at 5 years and 92.8% at 10 years. The most common reason for replacement was fracture to the core of the ceramic crowns. This occurred most often in posterior teeth.
Clinical Significance.—These ceramic crowns have good clinical performance after 5 and 10 years and can be used in all areas of the mouth. Most of the fractures occurred within the first few years after insertion and affected layered ceramic crowns in posterior regions. Monolithic ceramic systems may perform better for posterior locations.
Dhima M, Paulusova V, Carr AB, et al: Practice-based clinical evaluation of ceramic single crowns after at least five years. J Prosthet Dent 111:124-130, 2014 Reprints available from M Dhima, Mayo Clinic, Dept of Dental Specialties, 200 First St SW, Rochester, MN 55905; e-mail: [email protected]
Volume 60
Issue 1
2015
45