The problems caused by proximal contact loss(PCL)of dental implants have been a mainstream research topic in recent years,and scholars are unanimously committed to analyzing their causes and related factors,aiming to identify solutions to the problems related to PCL.The effects of the anterior component of force(ACF),the lifelong re-molding of the adult craniofacial jaw and alveolar socket,and the osseointegration characteristics of dental implants are the main causes of PCL.On the one hand,the closing movement of the mandible causes the ACF of the tooth to move through the posterior molar cusp.Moreover,drifting between the upper and lower posterior teeth and mandibular anteri-or teeth can cause the anterior teeth of the upper and lower jaws to be displaced labially.On the other hand,reconstruc-tion of the jaw,alveolar socket and tooth root,the forward horizontal force of the masticatory muscles,the dynamic com-ponent of the jaw and the forward force generated by the oblique plane of the tooth cusp can cause the natural tooth to experience near-middle drift.Additionally,natural teeth can shift horizontally and vertically and rotate to accommodate remodeling of the stomatognathic system and maintain oral function.Nevertheless,the lack of a natural periodontal mem-brane during implant osseointegration,the lack of a physiological basis for near-medium drift,the small average degree of vertical motion and the integrated silence of dental implants without the overall drift characteristics of natural teeth increases the probability of PCL.The high incidence of PCL is clearly associated with the duration of prosthesis delivery and the mesial position;but it is also affected by the magnitude of the bite force,occlusion,the adjacent teeth,restora-tion design,implant location,jaw,and patient age and sex.PCL has shown a significant correlation with food impaction,but not a one-to-one correspondence,and did not meet the necessary and sufficient conditions.PCL is also associated with peri-implant lesions as well as dental caries.PCL prevention included informed consent,regular examinations,se-lection of retention options,point of contact enhancement,occlusal splints,and the application of multipurpose digital crowns.Management of the PCL includes adjacent contact point additions,orthodontic traction,and occlusal adjust-ment.Existing methods can solve the problem of food impaction in the short term with comprehensive intervention to seek stable,long-term effects.Symmetric and balanced considerations will expand the treatment of issues caused by PCL.

Objective: To explore the relationship between MSX1 gene detection and tooth loss in a Van der Woude syndrome (VWS) family Methods : DNA was extracted from the venous blood of 2 patients with dental hy⁃podontia in the 9th family of Van der Woude syndrome (VWS) families and 62 controls with complete dentition. Primers were designed for the MSXl gene. The coding regions of exons 1 and 2 of the MSX1 gene were amplified by PCR. The purified products of exons 1 and 2 of the MSX1 gene were sequenced and analyzed by sequence alignment Results: The ivs2+68 C>T polymorphism in the MSX1 gene was found in the VWS9 members with tooth loss, and the VWS pa⁃tients with IRF6 gene mutations had increased tooth loss Conclusion Congenital tooth loss in the patients with con⁃genital missing teeth in VWS family 9 may be related to the ivs2 + 68 C> T polymorphism of the MSX1 gene.

Objective: To investigate the clinical effect of concentrated growth factor (CGF) applied in guided bone regeneration (GBR) for severe bone deficiency in the anterior maxilla. Methods : Forty patients with bone defects in the anterior maxilla were chosen to be treated with GBR, 20 patients were treated with CGF applied in GBR as the observation group, and the other 20 patients were treated only with GBR as the control group. The evaluation of wound healing was performed after the operation, and bone augmentation was evaluated half a year after the operation. Results: The first-stage healing rate of soft tissue wounds in the observation group was 100% and 75% in the control group, and the primary healing rate in the observation group was better than that in the control group (P=0.017). The changes in bone width of the observation group were （3.70 ± 0.28） mm, and those of the control group were （2.96 ± 0.16） mm. The bone augmentation in the observation group was higher than that in the control group (P=0.000). Conclusion CGF applied in GBR has a good effect on bone augmentation for severe bone deficiency in the anterior maxilla.

Objective:To compare the maxillary sinus mucosa's stress distribution when elevated by three lift materials.Methods:Three Finite element models of maxillary sinus mucosa with 0.3 mm thickness elevated by implant,grafting autogenous cancellous bone and hydroxyapatite respectively were established in the specific units.ANSYS finite element analysis software was used to evaluate maxillary sinus mucosa deformation by the simulated closed sinus lift surgery.Differences of Von Mises stress values of mucosa surface were calculated when maxillary sinus mucosa lift height was increased from 1 mm to 5 mm according to the a large deformation theory. Results:The Von Mises stress values on membrane surface elevated by implant,grafting autogenous cancellous bone and hydroxyapa-tite bone substitute materials showed no difference within 5 mm elevation.Conclusion:Closed maxillary sinus floor lifting operation with implant elevating the maxillary sinus membrane directly is a simple and minimally invasive way for sinus floor elevation.

Objective To study the impact of the number of functional natural teeth (FNT) and different oral restoration behaviors on well-being of the elderly.Methods The elderly residents of Guangzhou Haizhu District were acted as respondent,WHO-5 Scale was the measurement instrument of well-being.Analysis of covariance was used to correct confounding factors and analyze the corrected data,and then it was compared by LSD Test.Resuits (1) The results of analysis of covariance showed that,average scores on WHO-5 Scale were not all the same among different groups which were divided by different number of FNT or different oral restoration behaviors (Respectively:F=21.547,P＜0.001 ; F=141.219,P＜0.001).(2) The results of LSD Test showed that,although there were no statistical differences in corrected average scores between group with 5-9 FNT and group with 10-14 FNT (LSD-t=-0.536,P=0.593),differences had statistical senses between other groups(P＜0.01).All scores were ordered from the least to the most number of FNT,and they were (11.786±5.270),(15.724±4.036),(15.934±3.957),(18.941±2.616) and (23.390±6.951) respectively.It also showed that,there were no statistical differences in corrected average scores between the perfect oral restoration behavior group,the imperfect oral restoration behavior group and the no oral restoration behavior group(respectively:(23.056±4.772),(20.647±2.660),(14.872±7.313) ; P＜0.01).Statistical differences were also found in corrected average scores between the imperfect oral restoration behavior group and the abnormal oral restoration behavior group (respectively:(20.647 ±2.660),(14.565±2.914);LSD-t=13.108,P＜0.01).No statistical differences were found in corrected average scores between the no oral restoration behavior group and the abnormal oral restoration behavior group(respectively:(14.872±7.313),(14.565±2.914) ; LSD-t=-0.696,P＜0.01).The differences in corrected average scores between the needless oral restoration behavior group and the perfect oral restoration behavior group also showed no statistical significance (respectively:(22.848± 8.068),(23.056± 4.772) ; LSD-t =-0.340,P =0.734).Conclusion Well-being of the elderly may be associated with number of FNT and oral restoration behaviors.

OBJECTIVETo photoelastically investigate the difference in load distribution of Tension More (TM) implants with different conical angle designs.

METHODSThe following five groups of implants of different conical angles were designed: cylinder implant, upper 1/3 TM implant (taper length of 3 mm); 1/2 TM implant (taper length of 5 mm); lower 1/3 TM implant (taper length of 7 mm); and bottom TM implant (taper length of 10 mm). The implants were centrally located in individually photoelastic models consisting of a simulated trabecular bone and a 1 mm-thick layer of cortical bone. Vertical and 45° oblique static loads were applied at the center of the superstructures. The resulting stresses were monitored photoelastically and recorded photographically. RESULTS With vertical loading, the cylinder implant showed higher stress levels in the cortical bone and trabecular bone than the upper 1/3 TM implant, 1/2 TM implant, and lower 1/3 TM implant. The four groups of TM implants showed lower stress levels in the cortical bone than the cylinder implant under oblique loads. The least favorable stress concentration in cortical bone was observed in the upper 1/3 TM implant under vertical and oblique loads.

CONCLUSIONTM implants of rational conical angle designs seem to be effective in stress distribution. For all designs and load directions, the upper 1/3 TM implant is the most favorable around the crest.

Bone and Bones ; Dental Implants ; Stress, Mechanical

OBJECTIVETo explore the effect of preoperative anxiety level on postoperative pain sensation in partially edentulous patients undergoing surgery for implant denture.

METHODSEighty partially edentulous patients receiving implant denture were examined for preoperative anxiety level using State Trait Anxiety Inventory (STAI) and Modified Dental Anxiety Scale (MDAS) questionnaires before implantation surgery. The Visual Analogue Scale (VAS) and Present Pain Intensity (PPI) Questionnaire were used to assess the pain sensation in patients immediately after the operation. The correlations of preoperative state anxiety, trait anxiety, and dental anxiety with postoperative VAS score were analyzed. According to the assessment results of STAI, the patients were divided into little or no (score range 20-37) anxiety group (L group), moderate (38-44) anxiety group (M group), and high (45-80) anxiety group (H group) to analyze the effect of state anxiety and trait anxiety levels on postoperative pain sensation.

RESULTSSignificantly positive correlations were found between preoperative state anxiety, trait anxiety and dental anxiety among the patients (P<0.01). Postoperative VAS score was positively correlated with trait anxiety score (P<0.01) and differed significantly between different trait anxiety groups (P<0.01). Compared with the patients in M and L groups, those in H group showed a significantly higher VAS score after the operation (P<0.05).

CONCLUSIONThe preoperative trait anxiety level is associated with postoperative pain sensation in partially edentulous patients receiving implant denture, suggesting the necessity of preoperative anxiety intervention in clinical practice.

Adult ; Aged ; Anxiety ; epidemiology ; Dental Implantation ; psychology ; Dentition ; Female ; Humans ; Male ; Middle Aged ; Pain Measurement ; Pain, Postoperative ; epidemiology ; Surveys and Questionnaires ; Tooth Diseases ; psychology

Objective To photoelastically investigate the difference in load distribution of Tension More (TM) implants with different conical angle designs. Methods The following five groups of implants of different conical angles were designed: cylinder implant, upper 1/3 TM implant (taper length of 3 mm); 1/2 TM implant (taper length of 5 mm); lower 1/3 TM implant (taper length of 7 mm); and bottom TM implant (taper length of 10 mm). The implants were centrally located in individually photoelastic models consisting of a simulated trabecular bone and a 1 mm-thick layer of cortical bone. Vertical and 45° oblique static loads were applied at the center of the superstructures. The resulting stresses were monitored photoelastically and recorded photographically. Results With vertical loading, the cylinder implant showed higher stress levels in the cortical bone and trabecular bone than the upper 1/3 TM implant, 1/2 TM implant, and lower 1/3 TM implant. The four groups of TM implants showed lower stress levels in the cortical bone than the cylinder implant under oblique loads. The least favorable stress concentration in cortical bone was observed in the upper 1/3 TM implant under vertical and oblique loads. Conclusion TM implants of rational conical angle designs seem to be effective in stress distribution. For all designs and load directions, the upper 1/3 TM implant is the most favorable around the crest.

Objective To explore the effect of preoperative anxiety level on postoperative pain sensation in partially edentulous patients undergoing surgery for implant denture. Methods Eighty partially edentulous patients receiving implant denture were examined for preoperative anxiety level using State Trait Anxiety Inventory (STAI) and Modified Dental Anxiety Scale (MDAS) questionnaires before implantation surgery. The Visual Analogue Scale (VAS) and Present Pain Intensity (PPI) Questionnaire were used to assess the pain sensation in patients immediately after the operation. The correlations of preoperative state anxiety, trait anxiety, and dental anxiety with postoperative VAS score were analyzed. According to the assessment results of STAI, the patients were divided into little or no (score range 20-37) anxiety group (L group), moderate (38-44) anxiety group (M group), and high (45-80) anxiety group (H group) to analyze the effect of state anxiety and trait anxiety levels on postoperative pain sensation. Results Significantly positive correlations were found between preoperative state anxiety, trait anxiety and dental anxiety among the patients (P<0.01). Postoperative VAS score was positively correlated with trait anxiety score (P<0.01) and differed significantly between different trait anxiety groups (P<0.01). Compared with the patients in M and L groups, those in H group showed a significantly higher VAS score after the operation (P<0.05). Conclusion The preoperative trait anxiety level is associated with postoperative pain sensation in partially edentulous patients receiving implant denture, suggesting the necessity of preoperative anxiety intervention in clinical practice.

Objective To explore the effect of preoperative anxiety level on postoperative pain sensation in partially edentulous patients undergoing surgery for implant denture. Methods Eighty partially edentulous patients receiving implant denture were examined for preoperative anxiety level using State Trait Anxiety Inventory (STAI) and Modified Dental Anxiety Scale (MDAS) questionnaires before implantation surgery. The Visual Analogue Scale (VAS) and Present Pain Intensity (PPI) Questionnaire were used to assess the pain sensation in patients immediately after the operation. The correlations of preoperative state anxiety, trait anxiety, and dental anxiety with postoperative VAS score were analyzed. According to the assessment results of STAI, the patients were divided into little or no (score range 20-37) anxiety group (L group), moderate (38-44) anxiety group (M group), and high (45-80) anxiety group (H group) to analyze the effect of state anxiety and trait anxiety levels on postoperative pain sensation. Results Significantly positive correlations were found between preoperative state anxiety, trait anxiety and dental anxiety among the patients (P<0.01). Postoperative VAS score was positively correlated with trait anxiety score (P<0.01) and differed significantly between different trait anxiety groups (P<0.01). Compared with the patients in M and L groups, those in H group showed a significantly higher VAS score after the operation (P<0.05). Conclusion The preoperative trait anxiety level is associated with postoperative pain sensation in partially edentulous patients receiving implant denture, suggesting the necessity of preoperative anxiety intervention in clinical practice.