A functional evaluation of fixed and removable bridgework

Removable and fixed prosthetic appliances were constructed for each of twenty subjects in order to replace a missing first molar. (In two cases the second bicuspid was also restored.) Masticatory performance tests with soft and tough foods were made before, immediately after, and one and two weeks following the insertion of the appliance. The degree of pulverization before swallowing and the time and chewing strokes required per mouthful were obtained for each subject at each period.The insertion of either fixed or removable appliances caused a statistically significant increase in masticatory performance with both hard and soft foods. The two appliances were about equivalent in their effect. Masticatory performance was generally higher after appliances were in place for a two-week period, indicating that individuals learned to use both fixed and removable appliances more efficiently within this time. The duration of this learning period has not been determined.Subjects with a diminished masticatory capacity swallowed larger particles of food than did those with a normal or superior masticatory performance. Upon the insertion of fixed and removable appliances, most individuals immediately used fewer strokes to pulverize their food finer at the swallowing point. After two weeks of usage, the patients required seven fewer masticatory strokes and six seconds less time per mouthful and at the same time achieved 16 units greater pulverization than they did previous to the insertion of the partial appliances.     

总义齿、覆盖义齿和种植覆盖义齿修复后咀嚼效率和下颌运动型的比较

目的　比较总义齿 (completedenture ,CD )、覆盖义齿 (completeoverdenture ,COD )和种植覆盖义齿 (implant supportedoverdenture ,IOD)修复后患者的咀嚼效率和下颌运动轨迹的差异。 方法　分别选取CD、COD和IOD修复后患者各 14名 ,在义齿正常戴用半年后测量患者的咀嚼效率和下颌运动轨迹。对下颌运动轨迹从规则程度、末端集中性、额状面的分型和咀嚼运动中的接触滑动4个方面进行评价 ,测试用食物为杏仁和小枣。结果　IOD组患者咀嚼枣和杏仁的效率均显著高于CD组 (P <0 0 1) ;COD组患者咀嚼杏仁的效率显著高于CD组 (P <0 0 1)。COD组患者咀嚼枣的效率高于CD组 ,且IOD组患者咀嚼枣和杏仁的效率高于COD组 ,但其间差异无显著性。IOD组患者下颌运动轨迹的规则程度显著优于CD组 (P <0 0 5 ) ,末端轨迹集中性也显著优于CD组 (P <0 0 1)。结论　IOD和COD修复有利于提高无牙颌患者或口内只保留个别残根患者的咀嚼效率。IOD修复患者较CD修复患者具有更加规则的下颌运动型。     

利用压膜式活动矫治器压入下颌第一、第二磨牙1例

本文报道1例左上颌第一、第二磨牙缺失较长时间后对第一、第二磨牙伸长,因修复间隙不足而采用压膜式活动矫治器配合正畸橡皮圈持续施轻力进行左下颌第一、第二磨牙的压低,从而获得足够的间隙完成种植牙修复,建立良好稳定的咬合关系。     

Influence of length of food platform on masticatory performance in patients missing unilateral mandibular molars with distal extension removable partial dentures

Reduction of the size of food platform of a distal extension removable partial denture has been recommended to decrease functional load on the abutment teeth and residual ridges. The purpose of this study was to investigate the influence of shortening food platform on masticatory performance. Eight subjects unilaterally missing mandibular molars participated in the study. A unilateral design was used for the denture framework. The length of the food platform was changed as follows. Initially, (A) was adjusted so that the distal end of the platform was in accordance with the distal end of maxillary second molar. Next, the platform was shortened successively to 15 mm (B) and 10 mm (C). Subjects were asked to masticate 2-colored wax cubes to evaluate masticatory performance. Mixing Ability Index was calculated from the color mixture and the form of masticated cubes. Repeated measures one-way ANOVA indicated significant difference of Mixing Ability Index among platforms (P < 0.0001). The Dunnett's test indicated no significant difference between A (1.27 +/- 0.29) and B (1.36 +/- 0.29), and a significant difference between A and C (0.89 +/- 0.30), (P < 0.001). Masticatory performance decreased significantly when the length of food platform was shortened to 10 mm.     

Effects of mandibular odontogenic keratocyst surgery and removable partial prostheses on masticatory performance

STATEMENT OF PROBLEM: Surgical treatment of odontogenic keratocysts often results in tooth loss. However, information about the effects of different surgical methods and postoperative prosthetic therapy on masticatory performance is lacking. PURPOSE: The purpose of this study was to compare tooth loss following odontogenic keratocyst treatment by enucleation, segmental mandibulectomy with reconstruction, or marsupialization, and the resultant effect on masticatory performance with and without removable partial dentures (RPDs). MATERIAL AND METHODS: Patients with odontogenic keratocysts of the mandible were treated with either enucleation (n=33), segmental mandibulectomy and immediate autogenous bone reconstruction (n=18), or marsupialization in combination with secondary enucleation (n=9). Clinical and radiographic examinations were used to assess the number of teeth with cyst involvement preoperatively and the number of teeth lost following cyst treatment. Masticatory performance with peanuts was measured after cyst treatment both with and without an RPD. The differences in the number of the teeth involved preoperatively and lost postoperatively were compared among the 3 groups with a chi square test for trend. The absorbance value (reflecting masticatory performance) difference among the 3 groups preprosthesis and postprosthesis was analyzed using a 1-way analysis of variance (ANOVA), respectively. The pre- and postprosthetic comparison was made within each group, and a paired t test was used. Age was compared using 1-way ANOVA among 3 groups. Gender was compared using the chi square test (alpha=.05). RESULTS: Although the average number of teeth involved preoperatively with the cyst was similar among the 3 treatment groups, the number of teeth lost following marsupialization was significantly less than the number lost following enucleation or segmental mandibulectomy. Prior to provision of an RPD, mean masticatory performance (mean absorbance value of 0.36+/-0.08) in subjects receiving segmental mandibulectomy was significantly lower than for subjects receiving enucleation (0.52+/-0.15) or marsupialization (0.89+/-0.12) (P<.01). Provision of an RPD significantly increased masticatory performance in subjects who were treated by enucleation or segmental mandibulectomy (P<.01). CONCLUSION: Masticatory performance following odontogenic keratocyst surgery is related to the number of lost teeth, which is a function of the operative method used. Restoration with an RPD postoperatively may improve masticatory function when multiple teeth are lost following enucleation or segmental mandibulectomy.     

Preparation and management of full coverage restorations for combination fixed removable prostheses

The understanding of the theories and applications of fixed prosthodontics utilized in conjunction with intracoronally attached removable partial dentures is vital to full-mouth combined reconstructions. Required objectives of fixed full coverage retainers include elimination of pathology, restoration of form and function, as well as enhancement of aesthetics. These topics are discussed in terms of design of full-coverage preparations and tissue management.     

Survival analysis of metal crowns versus restorations in primary mandibular molars

Background

The effectiveness of stainless steel crowns (SSCs) versus direct restorations when placed in primary mandibular molars (teeth nos. L and S) is uncertain. The authors evaluated effectiveness by gauging longevity of treatment.

Furcation topography of the maxillary and mandibular first molars

The objective of the present study was to describe the topography of the furcation area of the maxillary and mandibular first molars. By using a photogrammetric method, the furcation areas of extracted teeth were plotted to obtain 3-dimensional contour maps. By comparing the individual 10 drawings of the maxillary and mandibular first molars, respectively, some morphological characteristics of the furcation areas could be described. Accordingly, the study showed the complexity of the furcation areas with presence of a number of small ridges, peaks and pits forming a mixture of convexities and concavities.     

Articaine infiltration for anesthesia of mandibular first molars

A randomized, controlled trial of 31 healthy volunteers compared 4% articaine with 1:100,000 epinephrine buccal infiltration to buccal plus lingual infiltration of the same dose of drug in achieving pulpal anesthesia of mandibular first molar teeth. Data were compared with efficacy of an inferior alveolar nerve block using 2% lidocaine 1:80,000 epinephrine in a cohort of 27 of the volunteers. Anesthesia was determined using electronic pulp testing. Buccal and buccal plus lingual infiltrations of articaine with epinephrine did not differ in efficacy in obtaining pulpal anesthesia for mandibular permanent first molars (p = 0.17). Efficacy of 4% articaine with epinephrine infiltrations for first molar pulp anesthesia was similar to that of an IANB using lidocaine with epinephrine over a 30-minute study period (96 and 80 episodes of no response to maximal stimulation respectively, p = 0.097). Subjective tooth numbness was more common after IANB than buccal infiltration (p = 0.005). The discomfort of buccal infiltration with articaine was volume dependent (p = 0.017) and similar to that of an IANB.     

The first permanent molars and palatal or mandibular variations

101 children, each of them with two teleradiographies, were selected. The first X-ray was taken at the time of the mixed dentition, the second one, when the permanent dentition was established. The purpose of the research is to show the oscillations of the palatine and mandibular planes, and their link to the movements of the first permanent molars. The palatine plane is found to swing between -7 degrees and +5 degrees with an average of -0.97 degree. The posterior part of that plane rocks downwards in 51% of the children. The limits are -7 degrees and -1 degree, with an average of -3.2 degrees. In 22%, the plane rocks upwards between +1 degree and +5 degrees with an average of +3.1 degrees. In 27% it moves parallel to itself. The posterior part of the mandibular plane varies between -6 degrees and +5 degrees, with an average of -1.1 degrees. It rocks downwards in 48% of the cases, between -6 degrees and -1 degree with an average of -3.9 degrees. In 22% of the children, this plane rocks upwards between +1 degree and +5 degrees with an average of +2.5 degrees. In 30%, it moves parallel to itself. The overall result is that the more the posterior part of the palate, or of the mandible moves downwards, the more the first permanent molars get straight or move forwards.     

Concurrent relationship between additional canals of mandibular first molars and maxillary first molars using cone-beam computed tomography

Objective

To investigate the bilateral concurrence and relationships between distolingual (DL) roots and DL canals of the mandibular first molars and second mesiobuccal (MB2) canals of the maxillary first molars using cone-beam computed tomography (CBCT).

Methods

A total of 150 CBCT images showing all mandibular and maxillary first molars were retrospectively investigated in a South Korean subpopulation. The patient age, sex, positions of first molars, and presence of roots and canals were assessed. The frequency, bilateral concurrence of DL roots, DL canals, and MB2 canals, and concurrent relationship of DL roots or DL canals with MB2 canals were investigated. Data were analyzed using Fisher’s exact test and odds ratios from binary logistic regression.

Results

The prevalences of DL roots, DL canals, and MB2 canals were 24.7, 42.7, and 56.0 %, respectively, and showed significant bilateral concurrence. A concurrent relationship between DL roots and MB2 canals was not demonstrated, whereas the presence of a DL canal was significantly correlated with the presence of an MB2 canal on the same side.

Conclusions

The presence of a DL root of the mandibular first molar, a strong ethnic characteristic, could not predict the presence of an MB2 canal of the maxillary first molar. The correlation between DL canals and MB2 canals on the same side and the significant bilateral concurrence, whether present or absent, of DL roots, DL canals, and MB2 canals can aid clinicians in the prediction of additional canals in the first molars.     

下颌第一恒磨牙远舌根的临床分析

目的调查下颌第一恒磨牙远舌根的发生率及根管治疗情况。方法临床收集378颗下颌第一恒磨牙根管治疗的完整病例,包括病历记录和术前、术中、术后X线片,记录下颌第一恒磨牙的牙根数目、根管数目及根管治疗情况。结果在378颗下颌第一恒磨牙中,远舌根的发生率为26.98％（102/378）,男、女患者和左、右侧远舌根的发生率均无统计学差异（P>0.05）。在根管治疗中,远舌根根管器械分离、侧穿和欠填的发生率高于其他根管（P<0.05）。结论远舌根在下颌第一恒磨牙中的发生率较高,发生器械分离、根管侧穿以及欠填的比例也高于其他根管。     

Descriptive classification of variations in primary mandibular first molars

Variability in tooth morphology can play a significant role in the achievable results of restorative treatment. This study identified the variations of morphology of the primary mandibular first molar (Type I and II coronal outline and Type A-F cusp alignment.) Type I coronal outline was found more frequently (86 percent) than Type II (14 percent). 93 percent of the primary mandibular first molars comprise four cusps, 5 percent comprise five cusps, and 2 percent comprise 3 cusps (F). Among the four-cusp group, 70 percent had an oblique transverse ridge (C), 25 percent had a poorly developed transverse ridge (A). Among the five-cusp-group, 67 percent had a distal cusp (E), and 33 percent had a fifth lingual cusp (D). The most frequent combination of coronal outline and cusp alignment was Type I-C (60 percent), and followed by Type I-B (22 percent), II-C (5 percent), and II-A (4 percent).     

下颌第一磨牙远舌根的研究进展

远舌根是位于下颌恒磨牙远中舌侧的一个部分或完全独立的额外牙根,常见于下颌第一磨牙。远舌根通常细短弯曲,它的出现增大了下颌第一磨牙根管治疗的难度。充分认识和识别远舌根,对于提高下颌第一磨牙根管治疗的成功率有重要意义。近年来,随着大家对下颌第一磨牙解剖的认识日益重视,对远舌根的研究日趋深入。下面就国内外学者对于远舌根的解剖研究作一回顾。