Effects of loupes and microscope on laminate veneer preparation / 北京大学学报(医学版)

OBJECTIVE@#To assess and compare the effects of loupes and microscope on laminate veneer preparation of the first practitioner from the aspects of efficiency, quality and accuracy of preparation, and preference.@*METHODS@#Twenty young prosthodontists from the Department of Prosthodontics, Peking University School and Hospital of Stomatology were recruited into this study, which was prospective, single blind, self-control trials. The participants had no experience of using dental magnification devices. They prepared laminate veneers in the artificial dental model, under routine visual field (control group), 2.5× headwear loupes (loupes group), and 8× operating microscope (microscopic group) by turning. The time for tooth preparation was recorded. Thereafter, subjective assessments of efficiency, quality of preparation and preference were performed by themselves using visual analogue score (VAS). Expert assessments of quality and accuracy of preparation were performed by two professors using stereomicroscope and digital technique respectively.@*RESULTS@#In terms of efficiency, the subjective scores for the control group, loupes group and microscopic group were 7.15±1.73, 8.10±0.91 and 5.40±2.04, respectively. There was significant difference between the loupes group and microscopic group (P<0.05). The time of tooth preparation for the control group, loupes group and microscopic group was (430.10±163.04) s, (393.90±157.27) s and (441.95±164.18) s, respectively. There was significant difference between the loupes group and microscopic group (P<0.05). The loupes group was more efficient than the microscopic group. In terms of the quality of preparations, the subjective scores for the control group, loupes group and microscopic group were 6.55±2.09, 7.85±0.99 and 6.25±1.77, respectively. There was significant difference between the loupes group and microscopic group (P<0.05). The expert evaluations for the control group, loupes group and microscopic group were 12.20±1.67, 12.50±1.70 and 11.35±2.60, respectively. There was significant difference between the loupes group and microscopic group (P<0.05). The loupes group had higher quality than the microscopic group. In terms of the accuracy of preparations, the control group, loupes group and microscopic group of incisal 1/3 were (0.107±0.097) mm, (0.142±0.118) mm and (0.123±0.087) mm, respectively, of middle 1/3 were (0.128±0.073) mm, (0.113±0.105) mm and (0.125±0.077) mm, respectively, and of cervical 1/3 were (0.075±0.054) mm, (0.068±0.044) mm and (0.058±0.047) mm, respectively. There was no significant difference among the three groups (P>0.05). In terms of the preference, the subjective scores for the control group, loupes group and microscopic group were 6.55±2.31, 8.60±1.10 and 5.80±2.07, respectively. There was significant difference between the loupes group and microscopic group (P<0.05). The participants had the highest preference for loupes.@*CONCLUSION@#For the first practitioners, loupes is better than microscope for laminate veneer preparation.

Influence of implants prepared by selective laser melting on early bone healing / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the influence of the rough surface of dental implants prepared by selective laser melting (SLM) on early bone healing around titanium implants.@*METHODS@#A total of sixteen titanium implants were involved in our research, of which eight implants were prepared by SLM (TIXOS Cylindrical, Leader-Novaxa, Milan, Italy; 3.3 mm×10 mm, internal hex) and the other eight were sandblasted, large-grit and acid-etched (SLA) implants (IMPLUS Cylindrical, Leader-Novaxa, Milan, Italy; 3.3 mm×10 mm, internal hex). All of the dental implants were inserted into the healed extraction sockets of the mandible of two adult male Beagle dogs. Half of the dental implants were designed to be healed beneath the mucosa and the other half were intended to be healed transgingivally and were immediately loaded by acrylic resin bridge restoration. Three types of tetracycline fluorescent labels, namely calcein blue, alizarin complexone and calcein, were administered into the veins of the Beagle dogs 2, 4, and 8 weeks after implant placement respectively for fluorescent evaluation of newly formed bone peri-implant. Both Beagle dogs were euthanized 12 weeks after implant insertion and the mandible block specimens containing the titanium implants and surrounding bone and soft tissue of each dog were carefully sectioned and dissected. A total of 16 hard tissue slices were obtained and stained with toluidine blue for microscopic examination and histomorphometric measurements. Histological observation was made for each slice under light microscope and laser scanning confocal microscope (LSCM). Comparison on new bone formation around titanium implants of each group was made and mineral apposition rate (MAR) was calculated for each group.@*RESULTS@#Dental implants prepared by selective laser melting had achieved satisfying osseointegration to surrounding bone tissue after the healing period of 12 weeks. Newly formed bone tissue was observed creeping on the highly porous surface of the SLM implant and growing into the pores of surface structure. Higher MAR values were shown for SLM implants compared with SLA implants (P<0.01).@*CONCLUSION@#Dental implants prepared by selective laser melting could promote early bone healing and improve mineral apposition rate.

Correlation between the phenotype and genotype of tooth agenesis patients by tooth agenesis code / 中国医学科学院学报

<p><b>OBJECTIVE</b>To analyze the correlation between the phenotype and genotype of tooth agenesis using the tooth agenesis code (TAC) and the traditional descriptor for missing teeth.</p><p><b>METHODS</b>Patients with isolated hypodontia caused by PAX9 or MSX1 mutation reported before May 2007 were enrolled. The teeth missing rate and TAC code were recorded. The missing teeth patterns caused by the two mutations were compared.</p><p><b>RESULTS</b>The teeth missing rates in each teeth positions were significantly different between maxillary and mandibular except maxillary central incisor, lateral incisor and mandibular canine, first molar (P<0.05, P<0.001). MSX1 gene mutation often led to the loss of maxillary first premolar, maxillary second premolar, and mandibular second premolar, while PAX9 gene mutation often led to the loss of the first, second, and third molars. The results were similar when analyzed either by TAC code analysis or by traditional descriptor.</p><p><b>CONCLUSIONS</b>PAX9 and MSX1 gene mutation can cause different phenotypes of tooth agenesis. The TAC code can be used in the analysis of the correlation between phenotype and genotype of the missing teeth patients.</p>