Remake Rates for Single‐Unit Crowns in Clinical Practice: Findings from The National Dental Practice‐Based Research Network

Thomson³

et al. 2020

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Purpose: In-laboratory assessment by laboratory technicians may offer insight to increase clinical success of dental crowns, and research in this area is lacking. Materials and Methods: Dentists in the National Dental Practice-Based Research Network enrolled patients in a study about single-unit crowns; laboratory technicians evaluated the quality of tooth preparations and impressions. The primary outcome for each crown was clinical acceptability (CAC), as judged by the treating dentist. A secondary outcome was "Goodness of Fit (GOF)," a composite score of several aspects of clinical fit, also judged by the study dentist. A mixed-effects logistic regression was used to analyze associations between laboratory technician ratings and the CAC and GOF. Results: Dentists (n = 205) evaluated 3731 crowns. Technicians ranked the marginal detail of impressions as good or excellent in 92% of cases; other aspects of the impression were ranked good or excellent 88% of the time. Regarding tooth preparation, about 90% of preparations were considered adequate (neither excessive nor inadequate reduction). Factors associated with higher CAC were more preparation taper, and use of optical imaging. Factors associated with better GOF were higher impression quality, greater occlusal reduction, more preparation taper, and optical imaging.Conclusions: Overall quality of preparations and impressions was very high, as evaluated by laboratory technicians. Several clinical parameters were associated with higher CAC and GOF. Clinicians who struggle with crown remakes might consider less conservative tooth preparation, as well as using digital impression technology.Despite careful attention to detail and the use of current techniques and materials, dentists still must remake crowns that do not fit clinically; the remake rate approaches 4%. 1 Such remakes require additional time and effort from the dentist, patient, and laboratory. It is often difficult to know why one particular crown must be remade, yet the next one-fabricated using the same laboratory and techniques-may fit nicely on the next patient. Possible sources of error which could cause a crown to be clinically unacceptable include (1) inadequate detail in the impression; (2) insufficient occlusal reduction; (3) insufficient axial reduction; (4) distorted impressions; (5) poor mounting in laboratory, or incorrect interocclusal record; (6) improper preparation design; (7) poor laboratory work; and (8) unknown factors.The quality of impressions submitted to dental laboratories has been criticized in the literature, with as many as 90% of impressions having an error. 2 One study of 1157 impressions found that 86% of impressions had at least one error, with over half having to do with the preparation finish line. 3 Errors were caused by tissue over the finish line, voids in the impression,

Section: Methodsmentioning

confidence: 99%

“…Despite careful attention to detail and the use of current techniques and materials, dentists still must remake crowns that do not fit clinically; the remake rate approaches 4% . Such remakes require additional time and effort from the dentist, patient, and laboratory.…”

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confidence: 90%

Laboratory Technician Assessment of the Quality of Single‐Unit Crown Preparations and Impressions as Predictors of the Clinical Acceptability of Crowns as Determined by the Treating Dentist: Findings from the National Dental Practice‐Based Research Network

McCracken

Thomson³

et al. 2020

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“…Questions from the survey considered in this manuscript focused on techniques for making impressions, such as the use of different materials, retraction techniques, and tray types. Other questions from the survey focused on treatment recommendations, 55 material choices, and crown preparation techniques.…”

Section: Clinical Techniques Questionnaire Contentmentioning

confidence: 99%

Impression Techniques Used for Single‐Unit Crowns: Findings from the National Dental Practice‐Based Research Network

McCracken

Louis

et al. 2017

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Purpose To: (1) determine which impression and gingival displacement techniques practitioners use for single-unit crowns on natural teeth; and (2) test whether certain dentist and practice characteristics are significantly associated with the use of these techniques. Materials and Methods Dentists participating in the National Dental Practice-Based Research Network were eligible for this survey study. The study used a questionnaire developed by clinicians, statisticians, laboratory technicians, and survey experts. The questionnaire was pre-tested via cognitive interviewing with a regionally diverse group of practitioners. The survey included questions regarding gingival displacement and impression techniques. Survey responses were compared by dentist and practice characteristics using ANOVA. Results The response rate was 1777 of 2132 eligible dentists (83%). Regarding gingival displacement, most clinicians reported using either a single cord (35%) or dual cord (35%) technique. About 16% of respondents preferred an injectable retraction technique. For making impressions, the most frequently used techniques and materials are: poly(vinyl siloxane), 77%; polyether, 12%; optical/digital, 9%. A dental auxiliary or assistant made the final impression 2% of the time. Regarding dual-arch impression trays, 23% of practitioners report they typically use a metal frame tray, 60% use a plastic frame, and 16% do not use a dual-arch tray. Clinicians using optical impression techniques were more likely to be private practice owners or associates. Conclusions This study documents current techniques for gingival displacement and making impressions for crowns. Certain dentist and practice characteristics are significantly associated with these techniques.

“…1,2 The indications for crowns are diverse, and may include factors such as endodontic treatment, cracks and fractures of the tooth, large restorations, esthetic shortcomings, or significant caries. 1,3,4 When planning crowns, there is variation among dentists in…”

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confidence: 99%

“…3,4 In fact, evidence suggests recommendations for crowns may be influenced by factors unrelated to tooth and patient variables. 1 Dentists must make a variety of clinical decisions when fabricating crowns for their patients. Depending on the restorative material, historic guidelines suggest an optimal design for tooth preparation based on fundamental principles for predictable successful prosthodontic treatment.…”

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confidence: 99%

Preparation Techniques Used to Make Single‐Unit Crowns: Findings from The National Dental Practice‐Based Research Network

Minyé¹,

Gilbert

et al. 2018

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Purpose: To: (1) determine which preparation techniques clinicians use in routine clinical practice for single-unit crown restorations; (2) test whether certain practice, dentist, and patient characteristics are significantly associated with these techniques. Methods: Dentists in the National Dental Practice-Based Research Network participated in a questionnaire regarding preparation techniques, dental equipment used for single-unit crown preparations, scheduled chair time, occlusal clearance determination, location of finish lines, magnification during preparation, supplemental lighting, shade selection, use of intraoral photographs, and trimming dies. Survey responses were compared by dentist and practice characteristics using ANOVA. Results: Of the 2132 eligible dentists, 1,777 (83%) responded to the survey. The top two margin configuration choices for single-unit crown preparation for posterior crowns were chamfer/heavy chamfer (65%) and shoulder (23%). For anterior crowns, the most prevalent choices were the chamfer (54%) and the shoulder (37%) configurations. Regarding shade selection, a combination of dentist, assistant, and patient input was used to select anterior shades 59% of the time. Photographs are used to communicate shade selection with the laboratory in about half of esthetically demanding cases. The ideal finish line was located at the crest of gingival tissue for 49% of respondents; 29% preferred 1 mm below the crest; and 22% preferred the finish line above the crest of tissue. Average chair time scheduled for a crown preparation appointment was 76 ± 21 minutes. Practice and dentist characteristics were significantly associated with margin choice including practice type (p < 0.0001), region (p < 0.0001), and years since graduation (p < 0.0001). Conclusions: Network dentists prefer chamfer/heavy chamfer margin designs, followed by shoulder preparations. These choices were related to practice and dentist characteristics.