A Systematic Review of Screw- versus Cement-Retained Implant-Supported Fixed Restorations Sami Sherif, BDS, DMSc,1,2 Harlyn K. Susarla, DMD, MPH,1 Theodoros Kapos, DMD, MMSc,1,2 Deborah Munoz, DMD, MMSc,1,3 Brian M. Chang, DDS, FACP,4 & Robert F. Wright, DDS, FACP5 1
Harvard School of Dental Medicine, Boston, MA Private Practice, London, United Kingdom 3 Private Practice, Boston, MA 4 Department of Maxillofacial Prosthodontics, Cleveland Clinic, Cleveland, OH 5 Department of Prosthodontics, University of North Carolina School of Dentistry, Chapel Hill, NC 2
Keywords Systematic review; implant failure; crown failure; screw loosening; decementation; porcelain fracture; screw-retained restorations; cement-retained restorations. Correspondence Robert F. Wright, UNC School of Dentistry, 335 Brauer Hall, Campus Box 7450, Chapel Hill, NC 27599-7450. E-mail: [email protected] The authors deny any conflicts of interest. Accepted August 21, 2013 doi: 10.1111/jopr.12128
Abstract Purpose: To systematically evaluate the survival and success of screw- versus cement-retained implant crowns. Materials and Methods: The authors performed an electronic search of nine databases using identical MeSH phrases. Systematic evaluation and data extraction of the articles from 1966 through 2007 were completed by three reviewers and two clinical academicians. The major outcome variable was implant or crown loss, and the minor outcome variables were screw loosening, decementation, and porcelain fracture. Random effects Poisson models were used to analyze the failure and complication rates. Results: The initial search produced 26,582 articles. Of these, 577 titles and subsequently 295 abstracts were available for evaluation, with 81 full texts meeting the criteria for review. Data were extracted from 23 level one and two research studies. Fleiss’ kappa interevaluator agreement ranged from almost perfect to moderate. Major failures included 0.71 screw-retained and 0.87 cement-retained failures per 100 years. Minor failures included 3.66 screw loosenings, 2.54 decementations, and 0.46 porcelain fractures per 100 years. Conclusion: There is no significant difference between cement- and screw-retained restorations for major and minor outcomes with regard to implant survival or crown loss. This is important data, as clinicians use both methods of restoration, and neither is a form of inferior care.
The early modern era of endosseous implant therapy was dominated by the screw-retained restoration. Such rehabilitations, which were initially intended for the edentulous patient, were mostly of a full-arch nature. The initial “ad modem Branemark” protocol called for an edentulous patient to be treated with four to six 3.75 mm external hex implants placed in the anterior mandible. The anterior mandible was selected for several reasons. As the lower anterior teeth are usually the last to be lost, a greater volume of bone exists in this area. This increased volume allows for the use of longer implants, ultimately providing more bicortical stabilization. The intraforaminal placement of the implants in the anterior mandible also avoids the inferior alveolar nerve in addition to reducing the effects of mandibular flexion, which occurs mostly in the posterior mandible up to a magnitude of 800 µm upon opening.1 The implants were covered for 4 to 6 months, and subsequently restored with a screwretained gold bar overlaid with pink acrylic and denture teeth.
Screw-retained crowns were chosen because they arguably offer more reliable retrieval, have a decreased space requirement, and result in healthier soft tissues, as no cement cleanup is necessary.2-4 The use of acrylic denture teeth not only simplifies maintenance of the prosthesis, but is also thought to provide a dampening force on the implants from occlusal trauma. As the scope of implant therapy was increased to include treating the partially edentulous patient, the cement-retained restoration gradually became more popular. The 1988 introduction of the UCLA custom abutment, which permitted the retention of a prosthesis directly on the implant without the use of a transmucosal abutment, allowed for smaller interocclusal space requirements.5 Telescopic crowns were then fabricated on these abutments. Subsequently, the introduction of a screw-retained abutment with a cemented restoration, Cera One (Nobel Biocare, Yorba Linda, CA), enhanced the success of implant therapy.6 Cement-retained crowns offered the
C 2013 by the American College of Prosthodontists Journal of Prosthodontics 23 (2014) 1–9
1
Screw- versus Cement-Retained Implant-Supported Fixed Restorations
Sherif et al
Figure 1 Publications retained at title, abstract, and full-text review stages.
clinician improved occlusal accuracy, enhanced esthetics, increased chances of achieving a passive fit, and decreased instances of retention loss. They were more akin to conventional fixed prosthodontics and were less costly to fabricate.7 Though there is an abundance of retrospective and prospective studies evaluating placement of screw- and cement-retained restorations, there is a dearth of systematic assessments of their outcomes. As such, the purpose of this review is to systematically evaluate the outcomes of screw- and cement-retained implant restorations.
function of time, these outcomes measures were represented as exposure time in months. Failures of implant fixtures preloaded with definitive restorations were excluded. Minor outcome factors were classified as those requiring clinician intervention that immediately threatened survival of the restorations. Included in this category were screw loosening, decementation and subsequent total loss of retention, porcelain fractures that did not necessitate replacement of the prosthesis, bone loss per month, strain, and marginal gap discrepancies. Search strategy
Materials and methods Systematic search design and article selection
The search strategy was designed to identify level 1 and level 2 evidence of the outcomes of screw- and cement-retained restorations in healthy patients with partial edentulism treated with fixed prosthodontic implant therapy. Interventions were broadly classified into two groups: screw-retained or cementretained restorations. To be included, eligible studies must have had a follow-up period of at least 12 months. The outcomes of interest were classified as major and minor outcomes. Major outcomes included those factors leading to restoration failure (i.e., failure of the prosthesis, thus requiring replacement). These included abutment fracture, esthetic failure, severe prosthesis fracture, and implant failure. As a 2
The search strategy (Fig 1) began with an electronic search of publications from 1966 to 2007. This search was performed using the following electronic databases: MEDLINE (1966 to December 2007), EMBASE (1980 to December 2007), the Cochrane Oral Health Group Trials Register, and the Cochrane Central Register of Controlled Trials (CENTRAL). The search included only English language articles published in peerreviewed journals. The keywords used for the search were combinations of the following: 1. 2. 3. 4. 5.
“Dental implant” “Screw-retained crown OR prosthesis” “Cement-retained crown OR prosthesis” “implant crown esthetics” “implant crown satisfaction”
C 2013 by the American College of Prosthodontists Journal of Prosthodontics 23 (2014) 1–9
Sherif et al
Screw- versus Cement-Retained Implant-Supported Fixed Restorations
Table 1 Inclusion and exclusion criteria Inclusion criteria Randomized clinical trials (including preference RCTs) Prospective and retrospective cohort studies with patient recall Written in English Minimum 12 months of functional loading Including healthy patients Method of intervention: Screw- or cement-retained restoration Exclusion criteria Immediate restoration Clinical reports Technique articles Mean functional loading time less than 12 months Data not divisible into screw- and cement-retained cohorts Acrylic veneering of prosthesis∗ Cantilevers∗ Screw-retained crowns not having an objective torque control method. Hand tightening was excluded∗ Lingual set screws∗ ∗
Not a strict criterion for exclusion, provided that data that pertained to cantilevers or acrylic veneering materials could be separated from relevant included data. If this data could not be separated, the study was excluded.
case series or case reports were excluded. Three independent evaluators assessed the studies produced from the database searches. After each step in the process of deletions (by title, abstract, and full text), a Kappa statistic was calculated to evaluate interexaminer agreement. The evaluators viewed the authors or titles. Studies that included insufficient information in the title were marked to be retrieved for abstract review. From these abstracts, articles with insufficient information to merit their exclusion were retrieved for full-text review. Two clinical academicians reviewed all studies set to be included at each. We defined clinical academicians as full-time faculty members. Those studies selected for inclusion then underwent validity assessment and data retrieval. Validity assessment was completed to ascertain the quality of the study and was done primarily on the basis of followup and allocation concealment. Follow-up was assessed by thoroughness and completeness and any explanation for loss to follow-up (selection bias). Allocation concealment was assessed as described in the Cochrane Handbook for Systematic Reviews of Interventions (v4.2.5), and was categorized as adequate, unclear, or inadequate. Finally, those studies accepted were grouped according to bias: 1) low risk of bias and 2) high risk of bias (including preference randomized clinical trials). Data retrieval and analysis
6. “mean plaque index OR MPI” 7. “sulcular bleeding index OR SBI” 8. “ceramic fracture” All selected articles contained well-defined inclusion and exclusion criteria (Table 1). Following the electronic search, all nondental articles or those that used evidence from either
Data retrieval: For each study, the date of publication, author, journal implant hex type, retention method, cement type, number of implants and prosthesis, major and minor factors listed above, and demographic details were recorded. Exposure and outcome variables per implant were taken including how and at what time points they were assessed.
Table 2 Articles selected for inclusion in systematic review First author Andersson6 Becker8 Duncan9 Heckmann10 Jemt11 Karl12 Karl13 Karl14 Keith15 Krenmeir16 Levine17 Levine18 Levine19 Mericske-Stern20 Norton21 Priest22 Scheller23 Schropp24 Schwarz-Arad25 Singer26 Vigolo27 Weber28 Zitzmann29
Journal
Year
Research design
Level of evidence
IJP JPD JOMI COIR IJP JOMI JPD JPD JOMI JOMI JOMI JOMI JOMI COIR JOMI JOMI JOMI J Clinical Perio JP JOMI JOMI COIR JPD
1998 1995 2003 2006 2000 2006 2007 2008 1999 2002 1999 2002 2007 2001 2006 1999 1998 2005 1999 1996 2004 2006 2000
Prospective cohort Prospective cohort Prospective cohort In vitro/vivo Prospective cohort In vitro In vitro In vitro/vivo In vitro Retrospective cohort Retrospective cohort Retrospective cohort Retrospective cohort Prospective cohort Retrospective cohort Retrospective cohort Prospective cohort RCT Retrospective cohort Retrospective cohort Retrospective cohort Prospective cohort Prospective cohort
2 2 2 2 2 2 2 2 2 2 2 2 1b 2 2 2 2 2
C 2013 by the American College of Prosthodontists Journal of Prosthodontics 23 (2014) 1–9
3
Screw- versus Cement-Retained Implant-Supported Fixed Restorations
Sherif et al
Table 3 Major outcome failures, by study
Study
Implants
Exposure time (Years)
Andersson-c 1998 Becker-s 1995 Duncan-s 2003 Duncan-c 2003 Jemt-s 2000 Krenmeir-s 2002 Krenmeir-c 2002 Levine-s 1999 Levine-c 1999 Levine-s 2002 Levine-c 2002 Levine-c 2007 Norton-c 2006 Priest-s 1999 Priest-c 1999 Scheller-c 1998 Schropp-s 2005 Schropp-c 2005 Schwarz-Arad-c 1999 Singer-c 1996 Vigolo-s 2004 Vigolo-c 2004 Weber-s 2006 Weber-c 2006 Zitzmann-s 2000 Total Summary
60 22 37 37 159 22 93 81 76 71 600 500 173 51 61 77 2 43 72 225 62 125 93 59 81 2882
279 63.5 111 111 477 65.6 277.5 162 152 126 1065 958 533.4 509.5 610 358 3.00 64.5 143.5 298.4 407 868.3 279 177 258.7 8357.9
Major failures
Mean exp. time
5.00 1.00 0.00 0.00 10.00 1.00 4.00 0.00 0.00 0.00 6.00 1.00 13.00 1.00 2.00 9.00 0.00 0.00 2.00 3.00 4.00 1.00 0.00 0.00 2.00 65.00
4.7 2.9 3.0 3.0 3.0 3.0 3.0 2.0 2.0 1.8 1.8 1.9 3.1 10.0 10.0 4.6 1.5 1.5 2.0 1.3 6.6 6.9 3.0 3.0 3.2 2.9
Test
Failure rate (per 100 years)
95% CI (lower)
95% CI (upper)
3.3 0.8 1.3 1.3 5.7 0.8 3.3 1.9 1.8 1.5 12.6 11.5 6.4 6.1 7.3 4.3 0.1 0.8 1.7 3.6 4.9 10.4 3.3 2.1 3.1 100
1.79 1.57 0.00 0.00 2.10 1.52 1.44 0.00 0.00 0.00 0.56 0.10 2.44 0.20 0.33 2.51 0.00 0.00 1.39 1.01 0.98 0.12 0.00 0.00 0.77 0.81
0.29 0.28 0.00 0.00 0.37 0.27 0.31 0.00 0.00 0.00 0.12 0.02 0.53 0.03 0.06 0.04 0.00 0.00 0.27 0.19 0.17 0.02 0.00 0.00 0.14 0.00
10.1 8.97 0.08 0.10 11.95 8.58 6.68 0.14 0.13 0.07 2.61 0.48 11.29 1.20 1.69 15.42 0.00 0.00 7.19 5.18 5.53 0.53 0.06 0.09 4.41 6.85
Coefficient
S.E.
P-value
− 0.51 − 22.82 0.5 − 1.5
0.82 1.62 0.87 0.84
0.54
Harvard School of Dental Medicine, Boston, MA Private Practice, London, United Kingdom 3 Private Practice, Boston, MA 4 Department of Maxillofacial Prosthodontics, Cleveland Clinic, Cleveland, OH 5 Department of Prosthodontics, University of North Carolina School of Dentistry, Chapel Hill, NC 2
Keywords Systematic review; implant failure; crown failure; screw loosening; decementation; porcelain fracture; screw-retained restorations; cement-retained restorations. Correspondence Robert F. Wright, UNC School of Dentistry, 335 Brauer Hall, Campus Box 7450, Chapel Hill, NC 27599-7450. E-mail: [email protected] The authors deny any conflicts of interest. Accepted August 21, 2013 doi: 10.1111/jopr.12128
Abstract Purpose: To systematically evaluate the survival and success of screw- versus cement-retained implant crowns. Materials and Methods: The authors performed an electronic search of nine databases using identical MeSH phrases. Systematic evaluation and data extraction of the articles from 1966 through 2007 were completed by three reviewers and two clinical academicians. The major outcome variable was implant or crown loss, and the minor outcome variables were screw loosening, decementation, and porcelain fracture. Random effects Poisson models were used to analyze the failure and complication rates. Results: The initial search produced 26,582 articles. Of these, 577 titles and subsequently 295 abstracts were available for evaluation, with 81 full texts meeting the criteria for review. Data were extracted from 23 level one and two research studies. Fleiss’ kappa interevaluator agreement ranged from almost perfect to moderate. Major failures included 0.71 screw-retained and 0.87 cement-retained failures per 100 years. Minor failures included 3.66 screw loosenings, 2.54 decementations, and 0.46 porcelain fractures per 100 years. Conclusion: There is no significant difference between cement- and screw-retained restorations for major and minor outcomes with regard to implant survival or crown loss. This is important data, as clinicians use both methods of restoration, and neither is a form of inferior care.
The early modern era of endosseous implant therapy was dominated by the screw-retained restoration. Such rehabilitations, which were initially intended for the edentulous patient, were mostly of a full-arch nature. The initial “ad modem Branemark” protocol called for an edentulous patient to be treated with four to six 3.75 mm external hex implants placed in the anterior mandible. The anterior mandible was selected for several reasons. As the lower anterior teeth are usually the last to be lost, a greater volume of bone exists in this area. This increased volume allows for the use of longer implants, ultimately providing more bicortical stabilization. The intraforaminal placement of the implants in the anterior mandible also avoids the inferior alveolar nerve in addition to reducing the effects of mandibular flexion, which occurs mostly in the posterior mandible up to a magnitude of 800 µm upon opening.1 The implants were covered for 4 to 6 months, and subsequently restored with a screwretained gold bar overlaid with pink acrylic and denture teeth.
Screw-retained crowns were chosen because they arguably offer more reliable retrieval, have a decreased space requirement, and result in healthier soft tissues, as no cement cleanup is necessary.2-4 The use of acrylic denture teeth not only simplifies maintenance of the prosthesis, but is also thought to provide a dampening force on the implants from occlusal trauma. As the scope of implant therapy was increased to include treating the partially edentulous patient, the cement-retained restoration gradually became more popular. The 1988 introduction of the UCLA custom abutment, which permitted the retention of a prosthesis directly on the implant without the use of a transmucosal abutment, allowed for smaller interocclusal space requirements.5 Telescopic crowns were then fabricated on these abutments. Subsequently, the introduction of a screw-retained abutment with a cemented restoration, Cera One (Nobel Biocare, Yorba Linda, CA), enhanced the success of implant therapy.6 Cement-retained crowns offered the
C 2013 by the American College of Prosthodontists Journal of Prosthodontics 23 (2014) 1–9
1
Screw- versus Cement-Retained Implant-Supported Fixed Restorations
Sherif et al
Figure 1 Publications retained at title, abstract, and full-text review stages.
clinician improved occlusal accuracy, enhanced esthetics, increased chances of achieving a passive fit, and decreased instances of retention loss. They were more akin to conventional fixed prosthodontics and were less costly to fabricate.7 Though there is an abundance of retrospective and prospective studies evaluating placement of screw- and cement-retained restorations, there is a dearth of systematic assessments of their outcomes. As such, the purpose of this review is to systematically evaluate the outcomes of screw- and cement-retained implant restorations.
function of time, these outcomes measures were represented as exposure time in months. Failures of implant fixtures preloaded with definitive restorations were excluded. Minor outcome factors were classified as those requiring clinician intervention that immediately threatened survival of the restorations. Included in this category were screw loosening, decementation and subsequent total loss of retention, porcelain fractures that did not necessitate replacement of the prosthesis, bone loss per month, strain, and marginal gap discrepancies. Search strategy
Materials and methods Systematic search design and article selection
The search strategy was designed to identify level 1 and level 2 evidence of the outcomes of screw- and cement-retained restorations in healthy patients with partial edentulism treated with fixed prosthodontic implant therapy. Interventions were broadly classified into two groups: screw-retained or cementretained restorations. To be included, eligible studies must have had a follow-up period of at least 12 months. The outcomes of interest were classified as major and minor outcomes. Major outcomes included those factors leading to restoration failure (i.e., failure of the prosthesis, thus requiring replacement). These included abutment fracture, esthetic failure, severe prosthesis fracture, and implant failure. As a 2
The search strategy (Fig 1) began with an electronic search of publications from 1966 to 2007. This search was performed using the following electronic databases: MEDLINE (1966 to December 2007), EMBASE (1980 to December 2007), the Cochrane Oral Health Group Trials Register, and the Cochrane Central Register of Controlled Trials (CENTRAL). The search included only English language articles published in peerreviewed journals. The keywords used for the search were combinations of the following: 1. 2. 3. 4. 5.
“Dental implant” “Screw-retained crown OR prosthesis” “Cement-retained crown OR prosthesis” “implant crown esthetics” “implant crown satisfaction”
C 2013 by the American College of Prosthodontists Journal of Prosthodontics 23 (2014) 1–9
Sherif et al
Screw- versus Cement-Retained Implant-Supported Fixed Restorations
Table 1 Inclusion and exclusion criteria Inclusion criteria Randomized clinical trials (including preference RCTs) Prospective and retrospective cohort studies with patient recall Written in English Minimum 12 months of functional loading Including healthy patients Method of intervention: Screw- or cement-retained restoration Exclusion criteria Immediate restoration Clinical reports Technique articles Mean functional loading time less than 12 months Data not divisible into screw- and cement-retained cohorts Acrylic veneering of prosthesis∗ Cantilevers∗ Screw-retained crowns not having an objective torque control method. Hand tightening was excluded∗ Lingual set screws∗ ∗
Not a strict criterion for exclusion, provided that data that pertained to cantilevers or acrylic veneering materials could be separated from relevant included data. If this data could not be separated, the study was excluded.
case series or case reports were excluded. Three independent evaluators assessed the studies produced from the database searches. After each step in the process of deletions (by title, abstract, and full text), a Kappa statistic was calculated to evaluate interexaminer agreement. The evaluators viewed the authors or titles. Studies that included insufficient information in the title were marked to be retrieved for abstract review. From these abstracts, articles with insufficient information to merit their exclusion were retrieved for full-text review. Two clinical academicians reviewed all studies set to be included at each. We defined clinical academicians as full-time faculty members. Those studies selected for inclusion then underwent validity assessment and data retrieval. Validity assessment was completed to ascertain the quality of the study and was done primarily on the basis of followup and allocation concealment. Follow-up was assessed by thoroughness and completeness and any explanation for loss to follow-up (selection bias). Allocation concealment was assessed as described in the Cochrane Handbook for Systematic Reviews of Interventions (v4.2.5), and was categorized as adequate, unclear, or inadequate. Finally, those studies accepted were grouped according to bias: 1) low risk of bias and 2) high risk of bias (including preference randomized clinical trials). Data retrieval and analysis
6. “mean plaque index OR MPI” 7. “sulcular bleeding index OR SBI” 8. “ceramic fracture” All selected articles contained well-defined inclusion and exclusion criteria (Table 1). Following the electronic search, all nondental articles or those that used evidence from either
Data retrieval: For each study, the date of publication, author, journal implant hex type, retention method, cement type, number of implants and prosthesis, major and minor factors listed above, and demographic details were recorded. Exposure and outcome variables per implant were taken including how and at what time points they were assessed.
Table 2 Articles selected for inclusion in systematic review First author Andersson6 Becker8 Duncan9 Heckmann10 Jemt11 Karl12 Karl13 Karl14 Keith15 Krenmeir16 Levine17 Levine18 Levine19 Mericske-Stern20 Norton21 Priest22 Scheller23 Schropp24 Schwarz-Arad25 Singer26 Vigolo27 Weber28 Zitzmann29
Journal
Year
Research design
Level of evidence
IJP JPD JOMI COIR IJP JOMI JPD JPD JOMI JOMI JOMI JOMI JOMI COIR JOMI JOMI JOMI J Clinical Perio JP JOMI JOMI COIR JPD
1998 1995 2003 2006 2000 2006 2007 2008 1999 2002 1999 2002 2007 2001 2006 1999 1998 2005 1999 1996 2004 2006 2000
Prospective cohort Prospective cohort Prospective cohort In vitro/vivo Prospective cohort In vitro In vitro In vitro/vivo In vitro Retrospective cohort Retrospective cohort Retrospective cohort Retrospective cohort Prospective cohort Retrospective cohort Retrospective cohort Prospective cohort RCT Retrospective cohort Retrospective cohort Retrospective cohort Prospective cohort Prospective cohort
2 2 2 2 2 2 2 2 2 2 2 2 1b 2 2 2 2 2
C 2013 by the American College of Prosthodontists Journal of Prosthodontics 23 (2014) 1–9
3
Screw- versus Cement-Retained Implant-Supported Fixed Restorations
Sherif et al
Table 3 Major outcome failures, by study
Study
Implants
Exposure time (Years)
Andersson-c 1998 Becker-s 1995 Duncan-s 2003 Duncan-c 2003 Jemt-s 2000 Krenmeir-s 2002 Krenmeir-c 2002 Levine-s 1999 Levine-c 1999 Levine-s 2002 Levine-c 2002 Levine-c 2007 Norton-c 2006 Priest-s 1999 Priest-c 1999 Scheller-c 1998 Schropp-s 2005 Schropp-c 2005 Schwarz-Arad-c 1999 Singer-c 1996 Vigolo-s 2004 Vigolo-c 2004 Weber-s 2006 Weber-c 2006 Zitzmann-s 2000 Total Summary
60 22 37 37 159 22 93 81 76 71 600 500 173 51 61 77 2 43 72 225 62 125 93 59 81 2882
279 63.5 111 111 477 65.6 277.5 162 152 126 1065 958 533.4 509.5 610 358 3.00 64.5 143.5 298.4 407 868.3 279 177 258.7 8357.9
Major failures
Mean exp. time
5.00 1.00 0.00 0.00 10.00 1.00 4.00 0.00 0.00 0.00 6.00 1.00 13.00 1.00 2.00 9.00 0.00 0.00 2.00 3.00 4.00 1.00 0.00 0.00 2.00 65.00
4.7 2.9 3.0 3.0 3.0 3.0 3.0 2.0 2.0 1.8 1.8 1.9 3.1 10.0 10.0 4.6 1.5 1.5 2.0 1.3 6.6 6.9 3.0 3.0 3.2 2.9
Test
Failure rate (per 100 years)
95% CI (lower)
95% CI (upper)
3.3 0.8 1.3 1.3 5.7 0.8 3.3 1.9 1.8 1.5 12.6 11.5 6.4 6.1 7.3 4.3 0.1 0.8 1.7 3.6 4.9 10.4 3.3 2.1 3.1 100
1.79 1.57 0.00 0.00 2.10 1.52 1.44 0.00 0.00 0.00 0.56 0.10 2.44 0.20 0.33 2.51 0.00 0.00 1.39 1.01 0.98 0.12 0.00 0.00 0.77 0.81
0.29 0.28 0.00 0.00 0.37 0.27 0.31 0.00 0.00 0.00 0.12 0.02 0.53 0.03 0.06 0.04 0.00 0.00 0.27 0.19 0.17 0.02 0.00 0.00 0.14 0.00
10.1 8.97 0.08 0.10 11.95 8.58 6.68 0.14 0.13 0.07 2.61 0.48 11.29 1.20 1.69 15.42 0.00 0.00 7.19 5.18 5.53 0.53 0.06 0.09 4.41 6.85
Coefficient
S.E.
P-value
− 0.51 − 22.82 0.5 − 1.5
0.82 1.62 0.87 0.84
0.54
