Maxillary Four Implant-retained Overdentures via Locator® Attachment: Intermediate-term Results from a Retrospective Study Feng Wang, DDS, MS;* Alberto Monje, DDS;† Wei Huang, DDS, MS;# Zhiyong Zhang, DDS;# Guomin Wang, DDS, MD;‡ Yiqun Wu, DDS, MD#
ABSTRACT Background: Maxillary overdentures have been utilized to restore oral function in scenarios where limited bone structure represents a drawback for financial issues and for cases where oral hygiene is uncertain. Purpose: The aim of this study was to evaluate the intermediate-term clinical outcome of four locator attachment retaining maxillary overdentures and to test their reliability. Materials and Methods: A retrospective study was conducted from January 2007 to October 2013. After the placement of four maxillary dental implants and a healing period of approximately 3 months, all the implants were restored with locator-retained overdentures with partial palatal coverage. Subjects and implant characteristics, implant position (anterior vs posterior maxilla), bone quality, and opposing dentition were recorded. Peri-implant clinical parameters and marginal bone loss (MBL) were evaluated after delivery of the final prosthesis and annually thereafter. The performance of locator components and the prosthetic restoration were also recorded at follow-up. Results: A total of 104 implants were placed in 26 subjects (11 women, 15 men; mean age, 64 years; age range, 55–76 years). One implant failed before loading. One subject dropped out of the study during a mean follow-up period of 46 months (range: 7–73 months), achieving an overall survival rate of 95.2%. Clinical parameters revealed healthy tissues around most of the implants, with low scores of plaque and bleeding indices. At the last follow-up evaluation, the mean MBL was 1.7 1 1.1 mm (0.4–2.6 mm). Regression model analysis indicated that MBL for implants in the posterior maxilla was significantly higher than that for implants in the anterior maxilla (p = .0487). Overall, 26 technical and prosthetic complications were reported. Conclusion: Within the limitations of this study, maxillary four implant-retained overdentures via Locator attachment seem to be a predictable alternative for oral rehabilitation. KEY WORDS: dental implants, edentulous maxilla, overdenture, survival rate
*Assistant Professor, Department of Oral Implantology, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, Shanghai, China; †Resident, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI, USA; # Professor, Department of Oral Implantology, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, Shanghai, China; ‡Professor, Center for Cleft Lip and Palate, Department of Oral and Cranio-Maxillofacial Science, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, Shanghai, China
School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, 200011, Shanghai, China; e-mail: [email protected]. Professor Yiqun Wu, Department of Oral Implantology, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, 200011, Shanghai, China; e-mail: [email protected] Disclosure: The authors do not have any financial interests, either directly or indirectly, in the products or information listed in the paper. © 2015 Wiley Periodicals, Inc.
Corresponding Authors: Professor Guomin Wang, Center for Cleft Lip and Palate, Department of Oral and Cranio-Maxillofacial Science,
DOI 10.1111/cid.12335
1
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Clinical Implant Dentistry and Related Research, Volume *, Number *, 2015
INTRODUCTION In patients lacking stability and retention of their full denture, implant-retained overdenture often offers significant improvements. Implant-retained overdentures in the mandible have demonstrated survival rates equivalent to those determined for implant-supported fixed prostheses.1–4 Moreover, numerous publications have shown no differences in marginal bone loss (MBL) around implants retaining mandibular overdentures relative to the implant type or attachment design.5,6 However, in comparison with the edentulous mandible, implant-retained overdenture therapy for the maxilla is often compromised by a reduced bone quantity and quality, which is also subjected to higher biomechanical forces.7–10 The number of implants as well as their positions and degrees of parallelism influence potentially the maxillary overdenture design and hence, the subjective selection of the attachment system.7 Maxillary bar-retained overdenture has been studied extensively, and a high implant survival rate (SR) ranging from 96.3% to 98.2% per year has been reported in previous studies.10 However, for implant-retained unsplinted overdentures, a consensus or a treatment concept is lacking despite their consideration as a favorable treatment with easy maintenance and lesser sensitive technique.11,12 The Locator® (Zest Anchors, Escondido, CA, USA) attachment system was introduced as a new resilient option for the overdenture retention in 2001.13 It consists of a titanium matrix and a nylon-coated matrix, and it is available for certain implant systems. The limited vertical height, self-alignment, and ability to compensate for divergent implant axes have been cited as advantages of the system.13 A limited number of studies have reported a positive clinical outcome for locator attachment overdentures, and no firm conclusions regarding the most preferable treatment strategy with respect to neither the number of implants nor the distribution of this attachment system have been drawn from recent literature.14,15 Moreover, in the vast majority of the studies, the type of opposing dentition was not described, although it is hypothesized that it may affect the survival of implants due to differences in the type of occlusion by means of bite force and occlusal adjustment.14–16 Therefore, the aim of this study was to test the intermediate-term clinical outcome of four maxillary
implant-retained unsplinted overdentures in terms of survival rate, bone-level changes, and related risk factors (i.e., implant position, implant diameter/length, bone quality, and opposing dentition type). MATERIALS AND METHODS Screening Process The patients included in the study were evaluated according to the following parameters using the patient records: age (upon placement of the implant) and gender, health status, general illnesses and medications, smoking habits, anatomical position of the implant, characteristics of the implants (implant length, width and surface treatment), implant primary stability, bone quality at the site of implant insertion, bone grafting procedures, and type of opposing dentition. This study protocol was approved by the ethics committee of the Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, School of Medicine. Inclusion Criteria Medical charts of patients who had been treated in the Department of Oral Implantology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University, School of Medicine, between January 2007 and October 2013, were reviewed. Subjects were selected to participate if their clinical condition met the following inclusion criteria: (1) subjects treated with four implant and locator abutment-supported maxillary overdentures; (2) an absence of severe systemic or bone metabolic disease, which may compromise the surgery or trigger postoperative complications; (3) subjects with natural dentition/fixed prosthesis/removable partial denture with controlled periodontal disease; (4) no drug or alcohol abuse; (5) no history of head or neck radiation. Exclusion Criteria Patients were excluded from the study on one or more of the following conditions: (1) systemic status that was likely to affect bone metabolism (unbalanced hormonal condition, previous irradiation of the head and neck region, uncontrolled diabetes mellitus); and (2) active smoker subjects (>10 cigarettes/day). Surgical Stage Placement of the implant was planned based on the clinical and radiographic evaluation including pan-
Maxillary Overdenture with Locator Attachment
oramic radiograph and/or cone beam computed tomography (Orthophos XG 3D, Sirona, Bensheim, Germany). A surgical template was fabricated by duplicating the existing complete maxillary denture of each patient. Each patient was treated under local anesthesia. The four implants were placed according to a standard procedure defined by the manufacturer. A bone substitute material (Bio-Oss, Geistlich AB, Basel, Switzerland) was used to assist implant placement in patients with an insufficient maxillary bone volume. Primary stability, implant position, and bone type (according to the classification of Lekholm and Zarb)17 during placement were recorded by the surgeons (Y.W., W.H.). Submerged healing was only applied for the grafted sites. One standardized long cone periapical radiograph was obtained immediately after implant placement. After surgery, amoxicillin (Xinya Co., Shanghai, China; 500 mg, 4 times a day for 7 days) and metronidazole (Xinyiwanxiang, Shanghai, China; 400 mg, 3 times a day for 7 days) were prescribed. A chlorhexidine oral rinse (0.12%) was also prescribed (60 s, 5–6 times a day for 7 days). Sutures were removed 7 to 10 days after surgery. Patients were allowed to wear dentures 2 to 4 weeks after implant placement. At the location of the implant placement, space was left to allow for the placement of a resilient base denture liner to avoid disrupting the process of implant osseointegration. Furthermore, patients were provided with instructions to maintain their oral health during this period. Prosthetic Stage At 3 to 6 months postimplant placement, the prosthesis fabrication procedures were initiated. All of the patients were provided with Locator (Zest Anchors)-retained overdentures. At the first restorative appointment, a periapical radiograph was obtained to evaluate the bone level of the installed implants. After making the custom tray, an open-tray impression with four implant impression copings was obtained using silicone. The impression was then shipped to the laboratory for pouring and mounting. The record base and wax rim were fabricated in the laboratory and then used in the clinic to obtain the vertical dimensions and centric occlusion relationship records of the patient. The master cast was then mounted on the articulator with the occlusal records. The height of the Locator attachment was dependent on the implant position; in the case of an implant that was not on the same level, a different locator abutment with
3
extended height was used to help equalize the level differences. Individual attachments were screwed into their respective implants using torque wrenches as recommended by the manufacturers. All of the overdentures consisted of a horseshoe-shaped metal framework with an acrylic base, which incorporated the locator male, denture caps, and acrylic teeth (Figure 1). When the antagonistic occlusal situation was a complete denture, the prosthesis was positioned in the bilaterally balanced occlusion. When the natural teeth were in the antagonistic jaw, the prosthesis was positioned without interference in the lateral protrusive excursions. Patients were instructed regarding hygiene procedures associated with the attachment and the overdentures, and were arranged for recall in the first 3 months and every 1 year thereafter. Recall Protocol All of the patients were clinically and radiographically followed up once a year after prosthesis delivery. For the most recent follow-up, peri-implant condition of the implant-supported overdenture, MBL around the implant, and implant survival rate were evaluated. Peri-implant Clinical Parameters (1) Modified Plaque Index (mPI) was measured at four points around the implants according to the following scale: 0, no plaque; 1, plaque on probing; 2, visible plaque; and 3, abundant plaque. For each implant, one mPI value was calculated based on the average of the four obtained values.18 (2) The Modified Sulcus Bleeding Index (mSBI) was measured at four surfaces around the implants. The mSBI was scored as follows: 0 = no bleeding when a periodontal probe was passed along the gingival margin adjacent to the implant; 1 = visible, isolated bleeding spots; 2 = blood formed a confluent red line on the margin; and 3 = heavy or profuse bleeding. For each implant, one mSBI value was calculated based on the average of the four obtained values.18 (3) Pocket probing depth (PPD) was measured in millimeters around the implants and was evaluated at six sites for each implant (total of 24 sites per patient), and the mean and highest values at each implant were documented.
4
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2015
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
Figure 1 A, Preoperative panoramic radiograph showing limited bone available in posterior maxilla. B, Intraoral view of maxilla 1 month after teeth extraction. C, Four implants placed in edentulous maxilla. D, Panoramic radiograph taken after implant placement. E, The record base and wax rim with resin teeth in the articulator after obtaining the vertical dimension and the centric relation occlusion record of the patient in clinic. F, Observing the soft tissue height in the model. G, The height of the Locator attachment is dependent on the thickness of soft tissue and occlusal plane of opposing dentition. H, Different abutment height helps to equalize the level differences of inserted implants. I and J, Individual attachments are screwed into their respective implants. K, Intraoral view of four Locator abutments in maxilla with opposing denture. L, Frontal view of final dentures. M, Clinical parameters evaluation on the day of denture delivery. N, Denture with partial palatal coverage design. O, Lateral profile of patient with final overdenture. P, Frontal view of patient with final overdentures. Q, Panoramic radiograph taken immediately after denture delivery. R, Periapical radiographs taken on the day the impression was taken. S, Periapical radiographs taken at 3-year follow-up.
MPI, mSBI, and PPD measurements were recorded by an experienced clinician using a plastic probe with a standardized probing force of 0.2 N (Click-Probe, KerrHawe SA, Bioggio, Switzerland). Peri-implant MBL MBL was recorded by comparing standardized long cone periapical radiographs. All of the images were scanned
and transferred to a computer with an image analysis program (GE Healthcare Centricity@ v3.0, Pittsburgh, PA, USA). MBL was documented on the radiograph viewer with the aid of fourfold magnification. The radiographic linear distance from the implant shoulder to the first bone-to-implant contact was used to calculate the MBL. The location of the MBL in relation to the implant shoulder was assessed at the mesial and the
Maxillary Overdenture with Locator Attachment
distal aspects at the time of implant insertion, prosthesis loading, and at the last follow-up radiograph. Radiographic assessments were conducted by two assistants. Prosthodontic Maintenance The number of technical and prosthetic complications was recorded, including prosthesis fracture, damage or loss of the Locator male and denture caps, and denture relining at follow-up. Statistical Analysis
5
TABLE 2 Implant Position and Bone Quality in the Site Implant Position (FDI Classification) Bone Quality
A B C D Total
15-14 Area
12–22 Area
24–25 Area
(Posterior)
(Anterior)
(Posterior)
Total
0 11 13 2 26
0 32 20 0 52
0 13 12 1 26
0 56 45 3 104
Statistical analysis was conducted using the SAS statistical package (SAS 9.3, SAS Institute Inc., Cary, NC, USA). Descriptive statistical analyses of peri-implant hygienic parameters and MBL were performed using the mean of the distribution, the standard deviation, the minimum and the maximum. Cohen’s kappa test was used to measure the interexaminer reliability. The Mann– Whitney U test was used to compare the mPI and mSBI. In addition, a logistic regression model was used to evaluate the influence of the implant diameter, implant length, implant position (anterior or posterior), bone quality, and opposing dentition on MBL. Multiple implants within patients were accounted for using a mixed model. The level of statistical significance was set at p 2 .05.
patients with two-implant supported overdentures; five patients with four-implant supported overdentures; 1 patient with three-implant supported overdentures), and the other eight patients had mandibular removable partial dentures. Two patients with five sites received guided bone regeneration (GBR) simultaneous with implant placement. The mean interval between implant placement to final overdenture delivery was 4.3 months (range: 3.7–8.4 months). The mean follow-up time was 46 months (range: 7–73 months). Two patients did not attend recall examinations, resulting in a follow-up incidence rate of 92.9%.
RESULTS
Implant and Prosthetic Characteristics
Study Population
One hundred and four tissue-level ITI-implants (Straumann AG, Waldenburg, Switzerland) were placed in the 26 patients assessed. All of the implants displayed the same surface modifications (sand-blasted, large-grit, acid-etched, SLA). Table 1 shows the characteristics of the implants. Implant distribution according to the bone quality and location is reported in Table 2. Among the 104 Locator abutments, 36 had a height of 1 mm, 45 had an extended height of 2 mm, and the remaining 23 had an extended height of 3 mm. Blue denture caps, which had a retention force of 1.5 lbs, were used for 86 implants; and pink denture caps, with a retention force of 3 lbs, were used for 18 implants.
A total of 104 implants were placed in 26 patients (11 women, 15 men; mean age, 64 years; age range, 55–76 years) (Table 1). Four patients were under routine medication for cardiovascular problems, five patients had controlled diabetes, and eight patients smoked
ABSTRACT Background: Maxillary overdentures have been utilized to restore oral function in scenarios where limited bone structure represents a drawback for financial issues and for cases where oral hygiene is uncertain. Purpose: The aim of this study was to evaluate the intermediate-term clinical outcome of four locator attachment retaining maxillary overdentures and to test their reliability. Materials and Methods: A retrospective study was conducted from January 2007 to October 2013. After the placement of four maxillary dental implants and a healing period of approximately 3 months, all the implants were restored with locator-retained overdentures with partial palatal coverage. Subjects and implant characteristics, implant position (anterior vs posterior maxilla), bone quality, and opposing dentition were recorded. Peri-implant clinical parameters and marginal bone loss (MBL) were evaluated after delivery of the final prosthesis and annually thereafter. The performance of locator components and the prosthetic restoration were also recorded at follow-up. Results: A total of 104 implants were placed in 26 subjects (11 women, 15 men; mean age, 64 years; age range, 55–76 years). One implant failed before loading. One subject dropped out of the study during a mean follow-up period of 46 months (range: 7–73 months), achieving an overall survival rate of 95.2%. Clinical parameters revealed healthy tissues around most of the implants, with low scores of plaque and bleeding indices. At the last follow-up evaluation, the mean MBL was 1.7 1 1.1 mm (0.4–2.6 mm). Regression model analysis indicated that MBL for implants in the posterior maxilla was significantly higher than that for implants in the anterior maxilla (p = .0487). Overall, 26 technical and prosthetic complications were reported. Conclusion: Within the limitations of this study, maxillary four implant-retained overdentures via Locator attachment seem to be a predictable alternative for oral rehabilitation. KEY WORDS: dental implants, edentulous maxilla, overdenture, survival rate
*Assistant Professor, Department of Oral Implantology, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, Shanghai, China; †Resident, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI, USA; # Professor, Department of Oral Implantology, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, Shanghai, China; ‡Professor, Center for Cleft Lip and Palate, Department of Oral and Cranio-Maxillofacial Science, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, Shanghai, China
School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, 200011, Shanghai, China; e-mail: [email protected]. Professor Yiqun Wu, Department of Oral Implantology, School of Medicine, Shanghai Key Laboratory of Stomatology, Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, 200011, Shanghai, China; e-mail: [email protected] Disclosure: The authors do not have any financial interests, either directly or indirectly, in the products or information listed in the paper. © 2015 Wiley Periodicals, Inc.
Corresponding Authors: Professor Guomin Wang, Center for Cleft Lip and Palate, Department of Oral and Cranio-Maxillofacial Science,
DOI 10.1111/cid.12335
1
2
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2015
INTRODUCTION In patients lacking stability and retention of their full denture, implant-retained overdenture often offers significant improvements. Implant-retained overdentures in the mandible have demonstrated survival rates equivalent to those determined for implant-supported fixed prostheses.1–4 Moreover, numerous publications have shown no differences in marginal bone loss (MBL) around implants retaining mandibular overdentures relative to the implant type or attachment design.5,6 However, in comparison with the edentulous mandible, implant-retained overdenture therapy for the maxilla is often compromised by a reduced bone quantity and quality, which is also subjected to higher biomechanical forces.7–10 The number of implants as well as their positions and degrees of parallelism influence potentially the maxillary overdenture design and hence, the subjective selection of the attachment system.7 Maxillary bar-retained overdenture has been studied extensively, and a high implant survival rate (SR) ranging from 96.3% to 98.2% per year has been reported in previous studies.10 However, for implant-retained unsplinted overdentures, a consensus or a treatment concept is lacking despite their consideration as a favorable treatment with easy maintenance and lesser sensitive technique.11,12 The Locator® (Zest Anchors, Escondido, CA, USA) attachment system was introduced as a new resilient option for the overdenture retention in 2001.13 It consists of a titanium matrix and a nylon-coated matrix, and it is available for certain implant systems. The limited vertical height, self-alignment, and ability to compensate for divergent implant axes have been cited as advantages of the system.13 A limited number of studies have reported a positive clinical outcome for locator attachment overdentures, and no firm conclusions regarding the most preferable treatment strategy with respect to neither the number of implants nor the distribution of this attachment system have been drawn from recent literature.14,15 Moreover, in the vast majority of the studies, the type of opposing dentition was not described, although it is hypothesized that it may affect the survival of implants due to differences in the type of occlusion by means of bite force and occlusal adjustment.14–16 Therefore, the aim of this study was to test the intermediate-term clinical outcome of four maxillary
implant-retained unsplinted overdentures in terms of survival rate, bone-level changes, and related risk factors (i.e., implant position, implant diameter/length, bone quality, and opposing dentition type). MATERIALS AND METHODS Screening Process The patients included in the study were evaluated according to the following parameters using the patient records: age (upon placement of the implant) and gender, health status, general illnesses and medications, smoking habits, anatomical position of the implant, characteristics of the implants (implant length, width and surface treatment), implant primary stability, bone quality at the site of implant insertion, bone grafting procedures, and type of opposing dentition. This study protocol was approved by the ethics committee of the Ninth People’s Hospital Affiliated with Shanghai Jiao Tong University, School of Medicine. Inclusion Criteria Medical charts of patients who had been treated in the Department of Oral Implantology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University, School of Medicine, between January 2007 and October 2013, were reviewed. Subjects were selected to participate if their clinical condition met the following inclusion criteria: (1) subjects treated with four implant and locator abutment-supported maxillary overdentures; (2) an absence of severe systemic or bone metabolic disease, which may compromise the surgery or trigger postoperative complications; (3) subjects with natural dentition/fixed prosthesis/removable partial denture with controlled periodontal disease; (4) no drug or alcohol abuse; (5) no history of head or neck radiation. Exclusion Criteria Patients were excluded from the study on one or more of the following conditions: (1) systemic status that was likely to affect bone metabolism (unbalanced hormonal condition, previous irradiation of the head and neck region, uncontrolled diabetes mellitus); and (2) active smoker subjects (>10 cigarettes/day). Surgical Stage Placement of the implant was planned based on the clinical and radiographic evaluation including pan-
Maxillary Overdenture with Locator Attachment
oramic radiograph and/or cone beam computed tomography (Orthophos XG 3D, Sirona, Bensheim, Germany). A surgical template was fabricated by duplicating the existing complete maxillary denture of each patient. Each patient was treated under local anesthesia. The four implants were placed according to a standard procedure defined by the manufacturer. A bone substitute material (Bio-Oss, Geistlich AB, Basel, Switzerland) was used to assist implant placement in patients with an insufficient maxillary bone volume. Primary stability, implant position, and bone type (according to the classification of Lekholm and Zarb)17 during placement were recorded by the surgeons (Y.W., W.H.). Submerged healing was only applied for the grafted sites. One standardized long cone periapical radiograph was obtained immediately after implant placement. After surgery, amoxicillin (Xinya Co., Shanghai, China; 500 mg, 4 times a day for 7 days) and metronidazole (Xinyiwanxiang, Shanghai, China; 400 mg, 3 times a day for 7 days) were prescribed. A chlorhexidine oral rinse (0.12%) was also prescribed (60 s, 5–6 times a day for 7 days). Sutures were removed 7 to 10 days after surgery. Patients were allowed to wear dentures 2 to 4 weeks after implant placement. At the location of the implant placement, space was left to allow for the placement of a resilient base denture liner to avoid disrupting the process of implant osseointegration. Furthermore, patients were provided with instructions to maintain their oral health during this period. Prosthetic Stage At 3 to 6 months postimplant placement, the prosthesis fabrication procedures were initiated. All of the patients were provided with Locator (Zest Anchors)-retained overdentures. At the first restorative appointment, a periapical radiograph was obtained to evaluate the bone level of the installed implants. After making the custom tray, an open-tray impression with four implant impression copings was obtained using silicone. The impression was then shipped to the laboratory for pouring and mounting. The record base and wax rim were fabricated in the laboratory and then used in the clinic to obtain the vertical dimensions and centric occlusion relationship records of the patient. The master cast was then mounted on the articulator with the occlusal records. The height of the Locator attachment was dependent on the implant position; in the case of an implant that was not on the same level, a different locator abutment with
3
extended height was used to help equalize the level differences. Individual attachments were screwed into their respective implants using torque wrenches as recommended by the manufacturers. All of the overdentures consisted of a horseshoe-shaped metal framework with an acrylic base, which incorporated the locator male, denture caps, and acrylic teeth (Figure 1). When the antagonistic occlusal situation was a complete denture, the prosthesis was positioned in the bilaterally balanced occlusion. When the natural teeth were in the antagonistic jaw, the prosthesis was positioned without interference in the lateral protrusive excursions. Patients were instructed regarding hygiene procedures associated with the attachment and the overdentures, and were arranged for recall in the first 3 months and every 1 year thereafter. Recall Protocol All of the patients were clinically and radiographically followed up once a year after prosthesis delivery. For the most recent follow-up, peri-implant condition of the implant-supported overdenture, MBL around the implant, and implant survival rate were evaluated. Peri-implant Clinical Parameters (1) Modified Plaque Index (mPI) was measured at four points around the implants according to the following scale: 0, no plaque; 1, plaque on probing; 2, visible plaque; and 3, abundant plaque. For each implant, one mPI value was calculated based on the average of the four obtained values.18 (2) The Modified Sulcus Bleeding Index (mSBI) was measured at four surfaces around the implants. The mSBI was scored as follows: 0 = no bleeding when a periodontal probe was passed along the gingival margin adjacent to the implant; 1 = visible, isolated bleeding spots; 2 = blood formed a confluent red line on the margin; and 3 = heavy or profuse bleeding. For each implant, one mSBI value was calculated based on the average of the four obtained values.18 (3) Pocket probing depth (PPD) was measured in millimeters around the implants and was evaluated at six sites for each implant (total of 24 sites per patient), and the mean and highest values at each implant were documented.
4
Clinical Implant Dentistry and Related Research, Volume *, Number *, 2015
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Figure 1 A, Preoperative panoramic radiograph showing limited bone available in posterior maxilla. B, Intraoral view of maxilla 1 month after teeth extraction. C, Four implants placed in edentulous maxilla. D, Panoramic radiograph taken after implant placement. E, The record base and wax rim with resin teeth in the articulator after obtaining the vertical dimension and the centric relation occlusion record of the patient in clinic. F, Observing the soft tissue height in the model. G, The height of the Locator attachment is dependent on the thickness of soft tissue and occlusal plane of opposing dentition. H, Different abutment height helps to equalize the level differences of inserted implants. I and J, Individual attachments are screwed into their respective implants. K, Intraoral view of four Locator abutments in maxilla with opposing denture. L, Frontal view of final dentures. M, Clinical parameters evaluation on the day of denture delivery. N, Denture with partial palatal coverage design. O, Lateral profile of patient with final overdenture. P, Frontal view of patient with final overdentures. Q, Panoramic radiograph taken immediately after denture delivery. R, Periapical radiographs taken on the day the impression was taken. S, Periapical radiographs taken at 3-year follow-up.
MPI, mSBI, and PPD measurements were recorded by an experienced clinician using a plastic probe with a standardized probing force of 0.2 N (Click-Probe, KerrHawe SA, Bioggio, Switzerland). Peri-implant MBL MBL was recorded by comparing standardized long cone periapical radiographs. All of the images were scanned
and transferred to a computer with an image analysis program (GE Healthcare Centricity@ v3.0, Pittsburgh, PA, USA). MBL was documented on the radiograph viewer with the aid of fourfold magnification. The radiographic linear distance from the implant shoulder to the first bone-to-implant contact was used to calculate the MBL. The location of the MBL in relation to the implant shoulder was assessed at the mesial and the
Maxillary Overdenture with Locator Attachment
distal aspects at the time of implant insertion, prosthesis loading, and at the last follow-up radiograph. Radiographic assessments were conducted by two assistants. Prosthodontic Maintenance The number of technical and prosthetic complications was recorded, including prosthesis fracture, damage or loss of the Locator male and denture caps, and denture relining at follow-up. Statistical Analysis
5
TABLE 2 Implant Position and Bone Quality in the Site Implant Position (FDI Classification) Bone Quality
A B C D Total
15-14 Area
12–22 Area
24–25 Area
(Posterior)
(Anterior)
(Posterior)
Total
0 11 13 2 26
0 32 20 0 52
0 13 12 1 26
0 56 45 3 104
Statistical analysis was conducted using the SAS statistical package (SAS 9.3, SAS Institute Inc., Cary, NC, USA). Descriptive statistical analyses of peri-implant hygienic parameters and MBL were performed using the mean of the distribution, the standard deviation, the minimum and the maximum. Cohen’s kappa test was used to measure the interexaminer reliability. The Mann– Whitney U test was used to compare the mPI and mSBI. In addition, a logistic regression model was used to evaluate the influence of the implant diameter, implant length, implant position (anterior or posterior), bone quality, and opposing dentition on MBL. Multiple implants within patients were accounted for using a mixed model. The level of statistical significance was set at p 2 .05.
patients with two-implant supported overdentures; five patients with four-implant supported overdentures; 1 patient with three-implant supported overdentures), and the other eight patients had mandibular removable partial dentures. Two patients with five sites received guided bone regeneration (GBR) simultaneous with implant placement. The mean interval between implant placement to final overdenture delivery was 4.3 months (range: 3.7–8.4 months). The mean follow-up time was 46 months (range: 7–73 months). Two patients did not attend recall examinations, resulting in a follow-up incidence rate of 92.9%.
RESULTS
Implant and Prosthetic Characteristics
Study Population
One hundred and four tissue-level ITI-implants (Straumann AG, Waldenburg, Switzerland) were placed in the 26 patients assessed. All of the implants displayed the same surface modifications (sand-blasted, large-grit, acid-etched, SLA). Table 1 shows the characteristics of the implants. Implant distribution according to the bone quality and location is reported in Table 2. Among the 104 Locator abutments, 36 had a height of 1 mm, 45 had an extended height of 2 mm, and the remaining 23 had an extended height of 3 mm. Blue denture caps, which had a retention force of 1.5 lbs, were used for 86 implants; and pink denture caps, with a retention force of 3 lbs, were used for 18 implants.
A total of 104 implants were placed in 26 patients (11 women, 15 men; mean age, 64 years; age range, 55–76 years) (Table 1). Four patients were under routine medication for cardiovascular problems, five patients had controlled diabetes, and eight patients smoked
