Time Efficiency of Immediate Loading of Full-arch Implant Reconstructions Using Prefabricated Prostheses Located by an Anchor Pin: a Pilot Study.

OBJECTIVE: To investigate the time efficiency of prefabricated prostheses located by an anchor pin stereolithographic attachment system for immediate loading implant reconstruction of completely edentulous jaws and compare it with the conventional protocol. METHODS: Edentulous patients were recruited and randomly assigned into two groups: the full digital workflow group (digital group) and the conventional workflow group (conventional group). In the digital group, a provisional prosthesis was fabricated before surgery using a fully digital workflow and delivered immediately after implant placement. The positioning of the provisional prosthesis was guided precisely by the anchor pin attachment system. In the conventional group, the provisional prosthesis was fabricated after implant placement using a conventional procedure. Clinical and laboratory time efficiency were recorded, and clinician and patient satisfaction were evaluated. RESULTS: Six patients were enrolled in this pilot study and 57 implants were placed following the guided surgery protocol. Of these, 54 were immediately loaded. The total clinical chair time in the digital workflow group was significantly less than that in the conventional workflow group (digital 60.0 ± 13.2 minutes; conventional 106.7 ± 24.7 minutes) (P = 0.045). The total post-surgery procedure took significantly less time in the digital group than the conventional group (digital 202.5 ± 22.5 minutes; conventional 403.7 ± 55.4 minutes) (P = 0.004). The patients' and clinicians' satisfaction with the provisional prostheses was similar in both groups. CONCLUSION: Time efficiency in immediate loading of implant-supported full-arch fixed restorations was improved with prefabricated prostheses located by the anchor-pin-attachment system. Less postoperative chair time was required in the digital group than in the conventional group.

Occlusal Rehabilitation in a Patient with Oligodontia and Microdontia using Implants and Full-Ceramic Restorations: A Clinical Report.

Oligodontia is the agenesis of six or more permanent teeth, excluding the third molars. Multidisciplinary dental treatments should be performed sequentially due to the restoration requirements for good oral function, aesthetics and self-confidence of patients. In this study, we report a case using dental implants and full-ceramic prostheses to restore the absent and malformed teeth in a patient with agenesis of 18 permanent teeth and with some primary teeth retained. The dental sequential treatments began when she was 16 years old, and she wore removable partial dentures for 4 years with unsatisfying restoration outcome. When she became an adult, dental implants and full-ceramic prostheses were used to restore the absent and malformed teeth. Finally, the patient was very satisfied with the functional and aesthetic outcomes of the prosthetic treatment.

Association between EDAR Polymorphisms and Non-Syndromic Tooth Agenesis in the Chinese Han Population.

OBJECTIVE: To explore the relationship between single nuclear polymorphisms (SNPs) in ectodysplasin A receptor (EDAR) and EDAR-associated death domain (EDARADD) genes and non-syndromic tooth agenesis. METHODS: Ten putative SNPs in EDAR and EDARADD were selected, and a case-control study was conducted in 112 subjects with non-syndromic tooth agenesis and 112 normal control subjects. DNA was obtained from peripheral blood samples. Genotyping was performed by Sanger sequencing. RESULTS: Three SNPs (rs3749098, rs3749099, and rs10432616) in EDAR exhibited significant differences in the alleles and/or genotype frequencies between the case group (individuals with non-syndromic tooth agenesis) and control group (normal individuals). The T allele was identified in the SNP rs3749098 in 99.1% of the case group and in 96.0% of the control group (P = 0.0326). Regarding the SNP rs3749099, the C allele was identified in 99.1% of the case group and in 96.0% of the control group (P = 0.0326). Regarding the SNP rs10432616, the C allele was identified in 97.8% of the case group and in 100.0% of the control group (P = 0.0245). CONCLUSION: Our results suggested that SNPs in EDAR could be a pathogenic factor for non-syndromic tooth agenesis. Furthermore, EDAR can be regarded as a marker gene for the risk of tooth agenesis.

Simultaneous Occurence of an Autosomal Dominant Inherited MSX1 Mutation and an X-linked Recessive Inherited EDA Mutation in One Chinese Family with Non-syndromic Oligodontia.

OBJECTIVE: To describe the simultaneous occurence of an autosomal dominant inherited MSX1 mutation and an X-linked recessive inherited EDA mutation in one Chinese family with nonsyndromic oligodontia. METHODS: Clinical data of characteristics of tooth agenesis were collected. MSX1 and EDA gene mutations were detected in a Chinese family of non-syndromic oligodontia. RESULTS: Mild hypodontia in the parents and severe oligodontia in the son was recorded. A novel missense heterozygous mutation c.517C>A (p.Arg173Ser) was detected in the MSX1 gene in the boy and the father. A homozygous missense mutation c.1001G>A (p.Arg334His) was detected in the EDA gene in the boy and the same mutant occurred heterozygously in the mother. CONCLUSION: Simultaneous occurence of two different gene mutations with different inheritence patterns, which both caused oligodontia, which occurred in one subject and in one family, was reported.

Prosthodontic Treatment for Severe Oligodontia with Long-term Follow-up.

OBJECTIVE: To express the early prosthodontic treatment strategies for severe oligodontia patients with or without a syndrome and to share details of their experiences of the long-term follow-up. METHODS: Patients with severe oligodontia (excluding the third molars, and with six or more congenitally missing permanent teeth) who had finished prosthetic rehabilitation between 2001 and 2014 and who had undergone at least 1-year follow-up at the Department of Prosthodontics, Peking University School of Stomatology were included in the study. The general and oral characteristics were determined and examined, interdisciplinary plans were provided, and the prosthodontic treatment conditions were described and evaluated. RESULTS: In total 26 subjects were included. Twenty males and six females, whose first dental visit occurred between the ages of 2 years and 9 months old, and 31 years old were recorded, of which, 12 (46.2%) subjects had non-syndromic oligodontia and 14 (53.8%) had oligodontia with different syndromes. The number of congenitally missing teeth (excluding the third molars) was between 7 to 28 (mean = 18), with 14 and 21 teeth in the non-syndromic and syndromic oligodontia patients, respectively. Most of the patients accepted conventional prostheses and two had implant-supported crowns or bridges. The age of the first prosthesis delivery ranged from 3.5 to 31 years old. The follow-up period ranged from 15 months (1 year and 3 months) to 162 months (13.5 years), with a mean of 108 months (9 years). CONCLUSION: Early treatment for young patients and long-term follow-up greatly benefits patients. Interdisciplinary treatment ensures more satisfactory results.

Prevalence of tooth agenesis in adolescent Chinese populations with or without orthodontics.

OBJECTIVE: To determine the prevalence of hypodontia in the general population and orthodontic population in adolescent Chinese Hans. METHODS: Two groups named the general population (6015 subjects) and the orthodontic population (2781 subjects) were investigated, respectively. The former came from the students of three general universities in North China and the latter came from patients coming to the Department of Orthodontics, Peking University School and Hospital of Stomatology for orthodontic consulting during the summer and winter holidays in 2008. The prevalence and average missing number of hypodontic teeth was investigated in the two groups. The distribution of missing teeth was analysed between jaw positions and between genders. RESULTS: The prevalence of tooth agenesis was found to be 5.89% for the general population group and 7.48% for orthodontic subjects. Tooth agenesis was more frequently found in females than in males in both of the two groups and showed a statistically significant difference (P < 0.01). Tooth agenesis was found more frequently in the mandible than in the maxilla in the general population but had no difference in the orthodontic population. The prevalence and the number of missing teeth were higher in the orthodontic population than in the general population. Tooth agenesis showed different characteristics in the two populations. The congenital absence of the second mandibular premolars and the maxillary lateral incisors increased in the orthodontic population. Gender difference in hypodontia expressed an opposite effect in the two groups. Although tooth agenesis was more frequently found in females than in males, males missed more teeth than females in the orthodontic population. CONCLUSION: Tooth agenesis showed different characteristics between the general and orthodontic adolescent Chinese populations.

[Precision of digital impressions with TRIOS under simulated intraoral impression taking conditions].

OBJECTIVE: To evaluate the precision of digital impressions taken under simulated clinical impression taking conditions with TRIOS and to compare with the precision of extraoral digitalizations. METHODS: Six #14-#17 epoxy resin dentitions with extracted #16 tooth preparations embedded were made. For each artificial dentition, (1)a silicone rubber impression was taken with individual tray, poured with type IV plaster,and digitalized with 3Shape D700 model scanner for 10 times; (2) fastened to a dental simulator, 10 digital impressions for each were taken with 3Shape TRIOS intraoral scanner. To assess the precision, best-fit algorithm and 3D comparison were conducted between repeated scan models pairwise by Geomagic Qualify 12.0, exported as averaged errors (AE) and color-coded diagrams. Non-parametric analysis was performed to compare the precisions of digital impressions and model images. The color-coded diagrams were used to show the deviations distributions. RESULTS: The mean of AE for digital impressions was 7.058 281 µm, which was greater than that of 4.092 363 µm for the model images (P<0.05). However, the means and medians of AE for digital impressions were no more than 10 µm, which meant that the consistency between the digital impressions was good. The deviations distribution was uniform in the model images,while nonuniform in the digital impressions with greater deviations lay mainly around the shoulders and interproximal surfaces. CONCLUSION: Digital impressions with TRIOS are of good precision and up to the clinical standard. Shoulders and interproximal surfaces scanning are more difficult.

A novel non-stop mutation in MSX1 causing autosomal dominant non-syndromic oligodontia.

Oligodontia, which is the congenital absence of six or more permanent teeth, excluding the third molars, may contribute to masticatory dysfunction, speech alteration, aesthetic problems and malocclusion. Msh homeobox 1 (MSX1) was the first gene identified as causing non-syndromic oligodontia. In this study, we identified a novel heterozygous non-stop mutation (c.910_911dupTA, p.*304Tyrext*48) in MSX1 in a Chinese family with autosomal dominant non-syndromic oligodontia. This novel mutation substitutes the stop codon with a tyrosine residue, potentially adding 48 amino acids to the C-terminus of MSX1. Further in vitro study found that mutant MSX1 could be expressed but had lost its ability to enter the nucleus. This is the first report indicating that a non-stop mutation in MSX1 is responsible for oligodontia. This study broadens the mutation spectrum for MSX1 and provides a new way to clarify the mechanism of MSX1 in tooth agenesis.

[Association between AXIN2 polymorphism and oligodontia].

OBJECTIVE: To explore the association between AXIN2 polymorphism and oligodontia in Chinese population. METHODS: We employed 97 individuals diagnosed with sporadic non-syndromic oligodontia and 200 healthy control subjects. Their DNA was obtained from the whole blood or buccul swap samples and the genotyping was performed by polymerase chain reaction (PCR). RESULTS: Significant differences were observed in the allele and genotype frequencies of rs145353986 of AXIN2. Distributions of genotypes GG, GC and CC of rs145353986 polymorphism were significantly different between the case group and the control group (P = 0.011) and C allelic frequency was higher in the case group (P=0.002). CONCLUSION: These data demonstrate an association between rs145353986 of AXIN2 and non-syndromic oligodondia in the Chinese population. Furthermore, AXIN2 can be regarded as a marker gene for the risk of tooth agenesis.

[Effects of wearing dentures on sleep breathing among edentulous people: a preliminary study].

OBJECTIVE: To investigate the effects of wearing dentures on sleep breathing among edentulous people. METHODS: Nine edentulous people were recruited to participate in this selfcontrolled case series clinical study. Polysomnogram (PSG) was carried out on two consecutive nights, on one night the patients slept wearing dentures, and on the other without dentures. The indexes such as apnea and hypopnea index (AHI), L-SpO2, and morning blood pressure etc. were compared. RESULTS: Among the nine edentulous people, eight showed a higher AHI when they slept with dentures, and only one showed a lower AHI. The average AHI of the nine edentulous people was 8.82 without dentures and 11.72 with dentures, which meant that AHI was significantly higher when the edentulous people slept with dentures in their mouths (P<0.05). While no significant differences were found in the score of L-SpO2 and morning blood pressures (P>0.05). CONCLUSION: Wearing dentures might lead to an increase of AHI during sleep among edentulous people.

[Fracture reliability of zirconia all-ceramic crown according to zirconia coping design].

OBJECTIVE: To study the fracture resistance and characteristics of the bi-layer zirconia all ceramic crowns according to the zirconia coping design using various experimental methods and to compare the results of the in vitro test with the clinical evaluation. METHODS: The bi-layer zirconia all ceramic crowns were fabricated by the same method as used in clinical practice. Two different coping designs with/without zirconia marginal collar were used. All the samples were cemented onto corresponding resin dies. All the specimens were tested in the 2 groups with/without zirconia collar. The fracture load test was performed on 10 crowns from each group. Fracture strength was tested with a universal testing machine. The fracture modes and features of the failed crowns were observed with an integrated microscope and a field emission scanning electron microscope. RESULTS: The zirconia collar group showed higher fracture load than the group without zirconia collar. All the zirconia crowns failed with porcelain failure and without zirconia coping broken. The porcelain fracture modes were crack, chipping and delamination. The distribution of the different fracture modes in the groups was the same. CONCLUSION: The bi-layer zirconia crown with 2 mm zirconia marginal collar showed more fracture strength under once load. The fracture modes of the test specimens were the same as the clinical fracture bi-layer zirconia crowns, showing porcelain chipping and delamination.

A review of the bioactivity of hydraulic calcium silicate cements.

OBJECTIVES: In tissue regeneration research, the term "bioactivity" was initially used to describe the resistance to removal of a biomaterial from host tissues after intraosseous implantation. Hydraulic calcium silicate cements (HCSCs) are putatively accepted as bioactive materials, as exemplified by the increasing number of publications reporting that these cements produce an apatite-rich surface layer after they contact simulated body fluids. METHODS: In this review, the same definitions employed for establishing in vitro and in vivo bioactivity in glass-ceramics, and the proposed mechanisms involved in these phenomena are used as blueprints for investigating whether HCSCs are bioactive. RESULTS: The literature abounds with evidence that HCSCs exhibit in vitro bioactivity; however, there is a general lack of stringent methodologies for characterizing the calcium phosphate phases precipitated on HCSCs. Although in vivo bioactivity has been demonstrated for some HCSCs, a fibrous connective tissue layer is frequently identified along the bone-cement interface that is reminiscent of the responses observed in bioinert materials, without accompanying clarifications to account for such observations. CONCLUSIONS: As bone-bonding is not predictably achieved, there is insufficient scientific evidence to substantiate that HCSCs are indeed bioactive. Objective appraisal criteria should be developed for more accurately defining the bioactivity profiles of HCSCs designed for clinical use.

[Effect of early-loaded small diameter implants retained mandibular overdentures on masticatory performance].

OBJECTIVE: To evaluate the clinical effect and masticatory efficiency of two early loaded Small Diameter Implants (SDI) retained mandibular overdentures. METHODS: Eight mandibular edentulous patients received two SDIs insertion between mental foramina. The mandibular overdentures were connected with implants for early loading in the period of 2-4 weeks following implant insertion. The data of visual analogue scale (VAS) of denture satisfaction and masticatory ability were collected at baseline, two weeks, three months and six months following overdenture loading. Masticatory efficiency was evaluated before surgery and six months after overdenture loading. RESULTS: Within the period of six months following overdenture loading, all the 16 implants remained stable. Compared with the baseline, the VAS data of denture satisfaction,stability, masticatory and poltophagy ability two weeks, three months and six months after overdenture loading were significantly improved with 30 degree (P<0.01), especially the masticatory and poltophagy ability of hard and crisp food. The value of masticatory efficiency improved considerably six months after overdenture loading (P<0.01). CONCLUSION: Mandibular overdentures retained by two SDIs can significantly improve patients' denture satisfaction and masticatory efficiency, and provide more rational diet.

[Esthetic evaluation of Cerec 3D anterior crowns].

OBJECTIVE: To observe the short-term effect of clinical application of Cerec 3D anterior crowns. METHODS: A total of 16 patients were restored with 31 Cerec 3D anterior crowns. All restorations were stained before cementation. The evaluation started 1 week after luting. The restorations were examined in accordance with the modified US Public Health Service (USPHS) criteria at baseline and every 6 - 12 months. RESULTS: The observation period of 31 Cerec 3D anterior crowns varied from 8 to 33 months. The mean observation period was 22 months. All restorations scored A or B by modified USPHS standard. And 22 out of 31 restorations scored A for all criteria while 8 restorations scored B in color matching. Slight differences of translucency and chroma could be observed. Between baseline and follow-up examinations, insignificant shift from A-to B-rating occurred. CONCLUSION: Cerec 3D anterior crowns may achieve favorable short-term esthetic effects.

[Short-term clinical observation of modified resin-bonded fixed partial denture utilizing tooth undercuts].

OBJECTIVE: To observe a short-term clinical result of modified resin-bonded fixed partial denture(MRBFPD) utilizing tooth undercuts. METHODS: One hundred and twenty-nine patients received restoration and totally 196 missing teeth were restored with 148 MRBFPD. According to the positions of abutments in the dental arch, all the MRBFPD were divided into three groups, namely anterior prostheses (40), posterior prostheses (95) and prostheses spanning anterior and posterior (13). The prostheses were examined at 2 weeks, 1 month, 3 months, 6 months, and every year after denture delivery. Retention and marginal integrity of MRBFPD, sensibility, secondary caries and gingival bleeding index were clinically evaluated. The evaluation results were graded as good, acceptable, and bad according to modified United States Public Health service (USPHS) criteria. Survival in this study was defined at two levels: "complete" survival (survival without any debonding), and "functional" survival (survival including loss of retention on one occasion and successful rebonding of the original MRBFPD without further debonding). RESULTS: The average follow-up period was 26 months. Fifteen prostheses failed and were rated as bad with USPHS criteria, and ten prostheses were evaluated as "acceptable" because the gingival bleeding index has been rated as 3 or more at one appointment but reduced to 1 or 0 after treatment. The results of the other 123 prostheses were evaluated as "good". The "complete" survival rates were 80% (32/40) for anterior prostheses, 11/13 for prostheses spanning anterior and posterior, and 95% (90/95) for posterior prostheses, while the "functional" survival rates were 80% (32/40), 11/13 and 99% (93/95) respectively. The "complete" survival rate of posterior prostheses was statistically higher than that of anterior prostheses (χ(2) = 5.433, P < 0.05). The "functional" survival rate of posterior prostheses was not only higher than that of anterior prostheses (χ(2) = 13.179, P < 0.01)but also higher than that of prostheses spanning anterior and posterior (χ(2) = 4.143, P < 0.05) statistically. CONCLUSIONS: The results of this preliminary study suggest that short term survival rate of MRBFPD in posterior area was statistically better than that in anterior area. The outstanding advantage of MRBFPD is the minimum need of dental tissue reduction. However, their long-term success needs further investigation.

[Adoption of the condyle position of patients with extensive tooth wear during occlusal rehabilitation].

OBJECTIVE: To evaluate the adoption of the condyle position of patients with extensive tooth wear during occlusal rehabilitation, and the correlation between increased vertical dimensions and the changes of joint spaces. METHODS: Twenty-seven patients (five from Beifang hospital, others from Peking University School and Hospital of Stomatology) with extensive tooth wear were selected and received occlusal rehabilitation treatment. The radiographs of standard Schüllers position were taken before treatment (stage 1), 1 month following delivery of temporary restoration (stage 2), and 1 month following delivery of permanent restoration (stage 3). RESULTS: The superior, anterior and posterior joint spaces were (3.24 ± 0.16), (2.06 ± 0.11), (1.89 ± 0.13) mm at stage 1; (3.61 ± 0.15), (1.94 ± 0.10), (2.52 ± 0.11) mm at stage 2; (3.49 ± 0.19), (1.93 ± 0.10), (2.40 ± 0.13) mm at stage 3. The posterior joint spaces at stage 2 and stage 3 were significantly larger than that at stage 1(P < 0.01). The superior spaces at stage 2 were significantly larger than that at stage 1 (P < 0.05). No correlations between the increased vertical dimensions and the changes of joint spaces were found in the three stages (P > 0.05). CONCLUSIONS: The condyle positions in the patients with extensive tooth wear changed after occlusal rehabilitation.

[Inhibition of retinoblastoma binding protein 2 promotes osteogenic differentiation of human adipose-derived stromal cells].

OBJECTIVE: To explore the effect of retinoblastoma binding protein 2 (RBP-2), a histone H3K4 demethylase, on osteogenic differentiation of human adipose-derived stromal cell (hASC). METHODS: According to the GenBank sequence information of RBP-2, four different small interfering RNAs (siRNA) targeting RBP-2 gene were designed and the corresponding short hairpin RNAs (shRNA) were cloned into pLL 3.7 lentivirus RNA interference vector. The lentivirus with RBP-2-siRNA was packaged in 293T cells. The effective sequence was examined and selected by Western blotting and real-time PCR. The lentiviruses with efficient knockdown effects were used to infect hASC. On the 14th day after osteogenic differentiation, alkaline phosphatase (ALP) activities of hASC were quantitatively tested and at the same time, ALP staining and alizarin red staining were performed to assess the difference of osteogenic differentiation between the knockdown group and the control group. RESULTS: The recombinant lentivirus siRNA targeting RBP-2 was successfully constructed and the expression of RBP-2 mRNA and protein were dramatically suppressed by infection with RBP-2-siRNA lentivirus. On the 14th day after osteogenic induction, ALP activity of hASC in the knockdown group [(299.2 ± 22.7), (224.3 ± 17.7) U/g] was much stronger than that in the control group [(129.9 ± 12.9) U/g, P < 0.05] and the same result was achieved for the ALP staining and alizarin red staining. CONCLUSIONS: The constructed RBP-2-siRNA lentivirus could markedly decrease the expression of RBP-2 and promote osteogenic differentiation of hASC. It indicated that RBP-2 can repress the osteogenic differentiation of hASC.