Bilateral maxillary fused second and third molars: a rare occurrence / 国际口腔科学杂志·英文版

This case report describes the diagnosis and endodontic therapy of maxillary fused second and third molars, using cone-beam computed tomography (CBCT). A 31-year-old Chinese male, with no contributory medical or family/social history, presented with throbbing pain in the maxillary right molar area following an unsuccessful attempted tooth extraction. Clinical examination revealed what appeared initially to be a damaged large extra cusp on the buccal aspect of the distobuccal cusp of the second molar. However, CBCT revealed that a third molar was fused to the second molar. Unexpectedly, the maxillary left third molar also was fused to the second molar, and the crown of an unerupted supernumerary fourth molar was possibly also fused to the apical root region of the second molar. Operative procedures should not be attempted without adequate radiographic investigation. CBCT allowed the precise location of the root canals of the right maxillary fused molar teeth to permit successful endodontic therapy, confirmed after 6 months.

Diagnostic test study of dental operating microscope used for locating the second mesiobuccal canal orifice in maxillary first molars / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To estimate the diagnostic potential of the dental operating microscope used for locating the second mesiobuccal canal (MB2) orifice in maxillary first molars.</p><p><b>METHODS</b>120 extracted maxillary first molars were used, all the access cavities were prepared and fixed on the dental study model. MB2 orifices were examined with naked eye and under a dental operating microscope (DOM). The examination was repeated by another dentist with the same methods. Then Indian ink was injected into the pulp chamber and all the teeth were treated to be transparent to determine if it had a real MB2.</p><p><b>RESULTS</b>The sensitivity and accuracy of the DOM group were 0.78 and 0.76, higher than 0.61 and 0.65 of the naked eye group (P<0.05). The correspondency of Kappa index between observers by naked eye and DOM was 0.701 and 0.819, respectively.</p><p><b>CONCLUSION</b>The use of DOM can increase the detection rate of MB2.</p>

Investigation of root canal curvature of human maxillary first premolar in buccolingual directions / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate root canal curvatures of human maxillary first premolars in buccolingual directions.</p><p><b>METHODS</b>One hundred extracted permanent maxillary first premolars were used. After access preparation, a K-file was inserted into the canals and gently advanced until it reached the apical foramen. Then standardized periapical radiovisiography (RVG) images were taken from mesiodistal direction. The angle of curvature was determined according to the method described by Schneider. The radiu of curvature and length of the curved part of the root canal were calculated.</p><p><b>RESULTS</b>1) The total 50.00% (88/176) of root canal curves were in buccolingual directions, and 53 curves were showed in apical 1/3 of root region. 11.93% (21/176) of S-shaped canals were detected, and the first curves were mostly showed in middle 1/3 of root region, the secondary curves were totally showed in apical 1/3 of root region. 2) There was no difference of curvatures between buccal and lingual root canals, but the secondary curves of S-shaped canals were more complicated than other root canals. 3) There was no correlation between the angle of curvature and the radius of curvature (r=0.002, P>0.05), but significantly correlation between the angle of curvature and length of the curved part of the root canal (r=0.489, P<0.01).</p><p><b>CONCLUSION</b>The occurrence of curved root canals in buccolingual directions may be high in human maxillary first premolars, and the curvatures of S-shaped canals were more complicated than others.</p>