Abstract
BackgroundThis study aimed to determine the degree of taper and total occlusal convergence angles (TOC) for all-ceramic bonded crown preparations carried out by private practitioners in Dubai, UAE.Material and MethodsA convenience sample of all-ceramic crown preparations carried out by private dental practitioners were scanned (Carestream CS 3500) from casts and the digital images assessed. The degree of taper was measured on the axial walls of each crown preparation and the bucco-lingual and mesio-distal convergence angles subsequently calculated.ResultsA total of 154 dentists prepared a total of 206 crown preparations (72 anterior, 134 posterior). The mean convergence angles mesio-distally for all preparations was 24.6° (sd 11.8º), and for the bucco-lingual it was 32.6° (sd 15.3°). The mean TOC was 28.6°. In anterior preparations, the mean bucco-lingual convergence angle was 38.8° (sd 12.2°) compared to 29.3° (sd 15.5°) for posterior preparations (p<0.001). Mean mesio-distal convergence anteriorly was 20.6° (sd 10.18°) compared to 26.7° (sd 12.16°) posteriorly (p<0.001). Distal and buccal taper were significantly greater on posterior teeth (<0.001) compared to anteriors whereas lingual taper was greater on anterior teeth (p<0.001). Mesial taper was not different. Premolars had significantly lower convergence values compared to other teeth.ConclusionsBucco-lingual and mesio-distal convergence angles significantly exceeded the clinically acceptable convergence angle of between 10° and 22°. Greater axial taper is recommended for resin bonded all-ceramic crowns but reliance on adhesion in such preparations rather than parallelism may reduce retention and have increased biologic cost to pulp health. Key words:All-ceramic crown preparations, convergence angles, axial taper.
Highlights
The retention of a single crown relies on several factors, such as the height of the preparation, surface texture, the method of placement, the closeness of fit, and the axial taper of the preparation walls
This study aimed to determine the degree of taper and total occlusal convergence angle on casts of teeth prepared for all-ceramic crowns by private practitioners in Dubai, UAE
154 dentists prepared a total of 206 crown preparations
Summary
The retention of a single crown relies on several factors, such as the height of the preparation, surface texture, the method of placement (cemented or bonded), the closeness of fit, and the axial taper of the preparation walls. Three studies assessed the quality of metal-ceramic crown preparations provided privately in the Middle East and found that the TOC angles were higher than recommended with the highest recorded value being 38.2° for mesio-distal convergence on molars [13,14,15]. This study aimed to determine the degree of taper and total occlusal convergence angle on casts of teeth prepared for all-ceramic crowns by private practitioners in Dubai, UAE. This study aimed to determine the degree of taper and total occlusal convergence angles (TOC) for all-ceramic bonded crown preparations carried out by private practitioners in Dubai, UAE. The degree of taper was measured on the axial walls of each crown preparation and the bucco-lingual and mesio-distal convergence angles subsequently calculated. Greater axial taper is recommended for resin bonded all-ceramic crowns but reliance on adhesion in such preparations rather than parallelism may reduce retention and have increased biologic cost to pulp health
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